WO2012008427A1 - Low-reflective film, method for formation thereof and low-reflective member equipped therewith, and coating solution for formation of low-reflective film, method for preparation thereof and low-reflective member equipped therewith - Google Patents

Abstract

[Problem] To provide a low-reflective film to be formed on a transparent base material and a method for forming the low-reflective film. Specifically, to provide a low-reflective film which can have a low refractive index and a low reflectance when prepared in the form of a single-layered film and can be formed so as to have a large surface area in a simpler manner, a method for forming the low-reflective film, and a low-reflective member equipped with the low-reflective film. [Solution] A low-reflective film and a process for producing the low-reflective film, said low-reflective film characterised by comprising silica microparticles and at least one metal oxide selected from a group consisting of tungsten oxide, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, tin oxide, aluminum oxide, hafnium oxide, chromium oxide, cerium oxide, molybdenum oxide and lanthanum oxide as a binder in an amount of 5 to 40 mass% inclusive relative to the amount of the silica microparticles, and by having a refractive index of 1.20 to 1.40 inclusive.

Description

LOW REFLECTIVE FILM, METHOD FOR FORMING THE SAME, LOW REFLECTIVE MEMBER USING THE SAME, LOW REFLECTIVE FILM FORMING COATING LIQUID, METHOD FOR PREPARING THE SAME, AND LOW REFLECTIVE MEMBER USING THE SAME

The present invention relates to a low reflection film, a method for forming the same, a low reflection member using the same, a coating liquid for forming a low reflection film, a method for preparing the same, and a low reflection member using the same. Specifically, the present invention relates to a solar cell cover glass, an automobile glass, or a protective member for a lighting fixture as a low reflective member having a low reflective film formed on the surface of a transparent substrate, and particularly to a solar cell cover glass. .

The low-reflection film prevents the surface reflection of the substrate, eliminates the loss of light transmittance due to surface reflection (hereinafter sometimes referred to simply as transmittance), and increases the transmittance of a transparent substrate such as glass or transparent plastic. In order to improve, it is formed on the substrate surface.

The low reflection film is formed on the surface of the cover glass for solar cells, the surface of lenses for optical devices such as still cameras, video cameras, and liquid crystal projectors, image display surfaces such as cathode ray tubes and liquid crystal display devices, or copying machines, It is formed on the surface of an imaging tube, an LED display element, illumination, an organic EL, a window or a showcase, a reflector member of an automobile headlamp, or the like.

When solar cells are used outdoors, the solar cells are constantly exposed, so that they are required to have weather resistance such as heat resistance, water resistance and wear resistance, which is resistant to differences in temperature and wind and rain, and preferably as a protective member Of solar cell cover glass. The cover glass for a solar cell is required to have transparency and low reflectivity in order to obtain high light receiving efficiency in the solar cell and not to reduce the conversion efficiency. Therefore, since the glass plate is used as the substrate and the low reflection film is formed on the surface of the glass plate, a solar cell cover glass is commercially available because it is hardly deteriorated and can maintain the performance over a long period of time. By forming a low reflection film on the surface, if the substrate is transparent, the transmittance increases without loss due to surface reflection. For example, a solar cell cover glass with a low-reflection film formed on the surface has a higher transmittance as the refractive index of the low-reflection film is lower, and the solar cell has better light reception efficiency and energy conversion from light to electricity. Increases efficiency.

Still cameras, video cameras, and the like use a plurality of lenses in a multi-group for correcting aberrations. If surface reflection is not suppressed, resolution is lowered and flare and ghost are caused. Therefore, it is important to form a low reflection coating on the lens surface, in other words, a low reflection film. In a display device, a showcase, or the like, unless the surface reflection is reduced by the low reflection film, the visibility deteriorates due to reflection of the reflected image.

Conventionally, for optical lenses and prisms, a multilayer film in which thin films having different refractive indexes and thicknesses are superimposed on a transparent substrate, that is, a multi-coat has been often used. If the reflective film has a multilayer structure, reflection can be prevented in a wide wavelength range. However, when forming a plurality of thin films by vacuum deposition or the like, it is necessary to precisely control the thickness of each thin film in order to achieve low reflection. Furthermore, in order to perform multi-coating on a large plate glass, a large-sized vacuum film forming apparatus is required, which is technically difficult and expensive.

Therefore, recently, development of a single-layer and low-refractive-index low-reflecting film that is advantageous for producing a low-reflection member having a large area easily at low cost has been desired. A single-layer low-reflection film is easier to form on the surface of a substrate than a multilayer film, and can be used for a solar cell cover glass to improve light-receiving efficiency and, in turn, light-to-electricity conversion efficiency. . Further, it is suitably used for preventing reflection of automobile glass, particularly windshields, and for improving illuminance when used for protective members of lighting fixtures such as cover glasses and transparent plastics.

In a single-layer low-reflection film, a method of reducing the refractive index of the film by incorporating air having a refractive index of 1 as microvoids (voids) or metapores into the film formed on the substrate surface is attempted. It has been. For example, it has been studied to form a low reflection film comprising a porous silica film or a silica film using hollow silica fine particles on the substrate surface.

A porous silica film is formed by applying a raw material liquid obtained by mixing a silica sol and a surfactant or a high boiling point solvent to a substrate, and then forming a mesopore in the silica film by forming a film by a sol-gel method. It is obtained by. In addition, the sol-gel method means that a sol composed of silicon alkoxide and colloidal silica obtained by dehydrating and condensing it is gelled after being applied to the surface of the body, and then heated and fired to obtain amorphous, polycrystalline, etc. This is a technique for forming a relatively hard film.

The hollow silica fine particles are silica fine particles containing fine voids or mesopores by using an alkoxysilane having a specific alkyl group or the like and aggregating and condensing the same. A film formed on the substrate using these hollow silica fine particles has voids or mesopores derived from the hollow silica fine particles, and becomes a low reflection film by the air contained in the voids or mesopores.

However, the hollow silica fine particles have a problem that the production process is complicated. Therefore, it is difficult to adopt as a cover glass for solar cells, a protective member for lighting equipment, and an automobile glass, which are general-purpose products.

For example, in Patent Document 1, porous composite oxide particles composed of silica and an inorganic oxide other than silica are coated with a porous silica-based inorganic oxide layer having a thickness of 0.5 nm to 20 nm. Disclosed is a fine particle characterized in that By forming a film containing the fine particles on the surface of the substrate, it is said that a substrate with a film having a low refractive index and excellent adhesion to a resin, strength, antireflection ability, etc. can be provided. .

Patent Document 2 includes silica, Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , Ce ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , MoO ₃ , and WO _3. A composite oxide sol in which a composite oxide colloidal particle having an average particle size of 5 nm to 300 nm and an inorganic oxide other than silica selected is dispersed in water and / or an organic solvent, the colloidal particle comprising: A composite in which a part of an element other than silica constituting the inorganic oxide is removed and the particle surface is coated with a silica coating, and the refractive index is in the range of 1.36 to 1.44. An oxide sol is disclosed. The composite oxide sol can be used to provide a substrate for low reflection in which a coating film having a low refractive index is formed.

Specifically, the surface of the particles from which a part of the inorganic oxide has been removed and voids are formed are hollow silica fine particles coated with a silica film, and the composite oxide colloidal particles as the hollow silica fine particles are converted into water and / or an organic solvent. It is a dispersed complex oxide sol.

However, the composite oxide sol described in Patent Document 1 or Patent Document 2 has a process of removing a part of the inorganic oxide and a process of coating the surface of the colloidal particles with silica in its production, and the process is complicated. There is a problem that there is a problem, and it is difficult to employ it as a protective member for solar cell cover glass, automobile glass and lighting equipment.

International Patent Publication No. WO00 / 37359 JP 2006-117526 A

Up to now, when forming a silica film containing silica fine particles, the silica fine particles can be easily filled in a spherical shape, and if the particle size distribution of the silica fine particles is uniform, it is possible to increase the packing density. The obtained silica film can ensure a packing density of 70% or more by closest packing. However, even if a binder is used, spherical silica fine particles are bonded together with a narrow contact area. If a shear force acts between the fine particles under external stress, they are brittle and easily broken, and the formed silica film There was a problem of poor wear resistance.

On the other hand, the rod-like silica fine particles are bulky particles having a large aspect ratio, and the rod-like silica fine particles are three-dimensionally entangled to form a three-dimensional bridge structure. Therefore, the obtained silica film is bulky and has a large porosity. Become. The silica film is porous, rich in air layer, and exhibits an excellent low reflection performance with an apparent refractive index of 1.25 or less, but the friction strength is extremely brittle, and it can be easily peeled off with light friction and can withstand practical use. There was a problem that was not.

It is an object of the present invention to provide a low reflection film that solves the above problems, a method for forming the same, and a low reflection member using the same.

Another object of the present invention is to provide a low reflection member having excellent heat resistance, wear resistance and antifouling properties. It is another object of the present invention to provide a low reflection film having a low refractive index and low reflectance in a single layer film.

Furthermore, an object of the present invention is to provide a method for forming a low-reflection film that allows easy formation of a large-area low-reflection film on the surface of a substrate by a simpler method.

Furthermore, the present invention can form a film with a large area by a simpler method for use in improving the light receiving efficiency of a solar cell, preventing reflection of an automobile windshield, and improving illuminance as a protective member of a lighting fixture. An object of the present invention is to provide a low reflection film, a method for forming the same, and a low reflection member using the same.

Further, as a further problem, a coating solution using colloidal silica is used for a plastic hard coat film, etc., but colloidal silica is hydrolyzed and aggregated in the coating solution to precipitate a solid, gelling, etc. There was a problem. In addition, the desired hardness, acid resistance, and alkali resistance cannot be obtained due to gelation, and there is a problem that it must be discarded after use for a certain period. Therefore, if the stability of the coating solution is not so high, the life of the solution cannot be obtained. For example, it is technically possible to obtain a silica film by industrially continuously coating a large plate having a meter angle (1 m × 1 m) or more. There was also a problem that it was difficult economically. In particular, the water concentration in the coating solution was severely controlled, and operation was performed so that water would not enter as much as possible.

The present invention solves the above-mentioned further problems, has a low refractive index and a low reflectance in a single layer film, and is superior in liquid stability to give a large-area low reflection film on the substrate surface in a simpler manner, An object of the present invention is to provide a coating liquid for forming a low reflection film having an excellent liquid life.

In addition, the present invention uses a coating solution for forming a low reflection film having excellent liquid stability and a long liquid life, thereby improving the light receiving efficiency of solar cells, preventing reflection of automobile windshields, and a protective member for lighting equipment. An object is to efficiently obtain a low-reflecting member that is excellent in weather resistance such as heat resistance, heat resistance that can withstand outdoor use, wear resistance, and antifouling property, which is used for improving illuminance and the like.

In particular, the present invention provides a coating solution for forming a low reflection film that gives a low reflectance to a solar cell cover glass, which is a protective member of a solar cell, and gives a high light receiving efficiency and conversion efficiency to the solar cell, and a method for preparing the same It aims at providing the used low reflection member.

As a result of intensive studies in view of the above problems, the following first and second viewpoints were obtained.
"First view"

According to the first aspect, the present invention uses a specific metal oxide as a binder that binds silica fine particles when formed into a film, so that the film strength is low and the weather resistance is poor and is easily deteriorated. A low reflection film having a low refractive index has been solved.

Furthermore, the present invention finds a low reflection film having excellent optical performance such as low reflection performance and excellent friction strength by coexisting silica fine particles having different shapes of rod-like silica particles and spherical silica fine particles in the low reflection film. It is a thing.

In particular, in the present invention, a low-reflection film formed by forming a low-reflection film on a transparent substrate such as a glass plate by coexisting silica fine particles having different shapes and a metal oxide as a binder for joining the silica fine particles in a low-reflection film. The optical characteristics and the friction strength of the reflecting member were suitable for the cover glass application of the solar cell.

In the present invention, the rod-like silica fine particles refer to elongated silica fine particles, which may be beaded or curved. In addition, the spherical silica fine particles are round silica fine particles, and may be a perfect ellipsoid or a distorted ellipsoid. The maximum diameter of the silica fine particles is referred to as a long diameter in the case of rod-shaped silica fine particles, and is referred to as a particle diameter in the case of spherical silica fine particles. Further, the minimum diameter of the rod-like silica fine particles is referred to as the short diameter. The same applies to rod-shaped colloidal silica and spherical colloidal silica. The fine particles are particles having a maximum diameter of approximately 100 nm or less. Colloidal silica is a colloid in which silicon oxide or its hydrate is agglomerated, and is usually obtained by dehydration condensation using alkoxysilane (tetraethoxysilane or the like) as a raw material or by ion exchange from alkali silicate. The colloid is obtained by removing the alkali component.

Further, the binder means what is bonded, and the metal oxide joins the silica fine particles at the interface of the silica fine particles.

In the present invention, the low reflection film is a film having a low refractive index (refractive index (nD) measured by an ellipsometer (nD) = 1.40 or less) formed on the surface of the substrate to prevent reflection of light on the surface of the substrate. is there.

In the present invention, the refractive index is a measured value obtained by spectroscopic ellipsometry measurement using an ellipsometer, and the average transmittance and average reflectance are measured using a spectrophotometer in the wavelength range of light, 380 nm to 1200 nm. This is a value obtained by measuring the transmittance and the reflectance of the light and calculating the average transmittance and the average reflectance in the wavelength region. The transmittance curve is a curve obtained by continuously plotting measured values of transmittance with a spectrophotometer in a certain wavelength region.

In the low reflection film of the present invention, the binder of silica fine particles is selected from tungsten oxide, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, tin oxide, aluminum oxide, hafnium oxide, chromium oxide, molybdenum oxide, cerium oxide, and lanthanum oxide. By using at least one metal oxide selected from the group, a low reflective film excellent in frictional strength and free from strength reduction was formed on the substrate surface due to heat firing, wetting and aging.

In particular, tungsten compounds, niobium compounds, and tantalum compounds are hard when they become particles, and the friction strength such as wear resistance is improved. In addition, the optical characteristics can be adjusted by including the low reflection film.

That is, the present invention is the low reflection film of the inventions 1 to 4 below.

[Invention 1]
At least one selected from the group consisting of silica fine particles and tungsten oxide, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, tin oxide, aluminum oxide, hafnium oxide, chromium oxide, molybdenum oxide, cerium oxide, and lanthanum oxide. A binder composed of a metal oxide is contained, and the content ratio of the binder composed of the metal oxide to the silica fine particles is 5% by mass or more and 40% by mass or less, and the refractive index is 1.20 or more and 1.40 or less. A low reflective film characterized by the above.

[Invention 2]
Silica fine particles are rod-shaped silica fine particles having a major axis of 5 nm or more and 100 nm or less, and spherical silica having a particle size of 5 nm or more and 50 nm or less as observed with a scanning electron microscope (hereinafter abbreviated as SEM). The low reflective film of invention 1 characterized by comprising mainly fine particles.

[Invention 3]
The low reflection film according to invention 2, wherein the mass ratio of the rod-like silica particles and the spherical silica particles is rod-like silica particles: spherical silica particles = 20: 80 to 80:20.

[Invention 4]
The low reflection film according to any one of inventions 1 to 3, wherein the metal oxide is at least one metal oxide selected from the group consisting of tungsten oxide, niobium oxide and tantalum oxide.

The transparent substrate forming the low reflection film of the present invention includes a transparent resin plate such as a glass plate, a polycarbonate plate, an acrylic plate, and polyethylene terephthalate. However, a glass plate is a preferable material because it is hard and hardly scratched and has excellent heat resistance and weather resistance. In particular, the low-reflection film of the present invention can provide a highly durable low-reflection member even when a glass plate is used as the substrate, and can be particularly preferably used for a solar cell cover glass.

By forming the low reflection films of the inventions 1 to 4 on the surface of the transparent substrate, the low reflection members of the inventions 5 and 6 were obtained.

[Invention 5]
A low reflection member comprising the transparent substrate surface on which the low reflection film of the inventions 1 to 4 is formed.

[Invention 6]
The low reflection member according to invention 5, wherein the transparent substrate is a glass plate, and the average transmittance in a light wavelength range of 380 nm to 1200 nm is 95% or more.

Usually, the peak position indicating the maximum value of the transmittance curve of the low reflection member having a low reflection film made only of silica is around 500 nm, but by adding a metal oxide to the low reflection film formed on the surface, When the peak position is shifted to 500 nm or more and 900 nm or less, the transparency of the low reflection film is increased, and the solar cell cover glass is used, the conversion efficiency of the solar cell is increased, and the low reflection is excellent for the solar cell cover glass. A member was obtained.

[Invention 7]
The low reflection member according to invention 5 or 6, wherein the peak of the maximum value of the transmittance curve is in the range of 500 nm or more and 900 nm or less.

The low reflection member described in the inventions 5 to 7 is particularly suitable for use as a solar cell cover glass.

[Invention 8]
A solar cell cover glass comprising the low reflection member of the invention 5-7.

The present invention also relates to a method for forming a low reflection film for forming the low reflection film according to any of the first to fourth aspects of the invention on a substrate.

In the method for forming a low reflection film of the present invention, it is preferable to use a dispersion of colloidal silica, which is a precursor, in order to incorporate silica fine particles in the low reflection film.

In order to allow silica fine particles having different shapes to coexist, it is preferable to use a coating solution for forming a low reflection film having colloidal silica having different shapes as a precursor. The low reflection film forming coating solution is a liquid that is applied to the surface of a substrate to form a low reflection film on the substrate.

In the present invention, a liquid in which colloidal silica and a specific metal compound are dispersed is applied to a substrate as a coating liquid for forming a low reflection film, and then heated and fired, whereby colloidal silica is made into silica fine particles, and the metal compound is made into a metal oxide, A low reflective film in which silica fine particles were bonded using a metal oxide as a binder was obtained.

In the method for forming a low reflection film of the present invention, in addition to the dispersion of colloidal silica on the substrate, selected from the group consisting of tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, molybdenum, cerium and lanthanum By using the dispersion liquid of at least one kind of metal compound, a low reflection film excellent in frictional strength was formed on the surface of the substrate without any decrease in adhesion strength due to heating, baking, wetting or aging.

In particular, tungsten, niobium and tantalum compounds are themselves hard when they become particles, and it is considered that frictional strength such as wear resistance is improved by containing them in a low reflection film.

Inventions 9 to 12 show methods for forming a low reflection film of the present invention.

[Invention 9]
A dispersion containing a metal compound of at least one metal selected from the group consisting of tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, molybdenum and rare earth is added to the dispersion containing colloidal silica. A coating solution for forming a low reflection film is applied to a substrate to form a coating film, and then heated and fired to form colloidal silica as silica fine particles and a metal compound as a metal oxide to form a low reflection film. Method.
The method of the invention 9 is, for example, a method of forming the low reflection film of the invention 1 on a substrate.

[Invention 10]
Colloidal silica is a rod-shaped colloidal silica having a major axis of 5 nm or more and 100 nm or less and a spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less as observed by SEM, and 90% or more of the total number of the colloidal silica. The method of Invention 9, wherein the compound content is 5% by mass or more and 40% by mass or less in terms of oxide.
The method of the invention 10 is, for example, a method of forming the low reflection film of the invention 2 on a substrate.

[Invention 11]
The method according to invention 10, wherein the mass ratio of the rod-shaped colloidal silica to the spherical colloidal silica is rod-shaped colloidal silica: spherical colloidal silica = 20: 80 to 80:20 in terms of oxide.
The method of the invention 11 is, for example, a method of forming the low reflection film of the invention 3 on a substrate.

[Invention 12]
The method of inventions 9 to 11, wherein the metal compound is a metal compound of at least one metal selected from the group consisting of tungsten, niobium and tantalum.
The method of the invention 12 is, for example, a method of forming the low reflection film of the invention 4 on a substrate.

[Invention 13]
A low reflection member obtained by forming a low reflection film having a refractive index of 1.20 or more and 1.40 or less on the surface of a transparent substrate by the method of inventions 9-12.

[Invention 14]
The low reflection member according to invention 13, wherein the transparent substrate is a glass plate, and the average transmittance in the light wavelength range of 380 nm to 1200 nm is 95% or more.

[Invention 15]
The low reflection member according to invention 13 or 14, wherein the maximum peak of the transmittance curve is in the range of 500 nm or more and 900 nm or less.

[Invention 16]
A solar cell cover glass comprising the low reflection member according to any one of Inventions 13 to 15.

"Second viewpoint"
According to a second aspect, the present invention comprises the following inventions 17 to 29.

[Invention 17]
A coating solution for forming a low reflection film on a substrate, comprising a tungsten compound and colloidal silica, wherein the tungsten compound is 5 masses in terms of oxide relative to the mass of the colloidal silica. A coating solution for forming a low reflection film, comprising a dispersion liquid contained in a range of from 50% to 40% by weight.
As the colloidal silica, at least two kinds of colloidal silicas having different shapes are preferably used, for example, rod-shaped colloidal silica and spherical colloidal silica.

[Invention 18]
The coating liquid for forming a low reflection film according to the invention 17, characterized in that a rod-like colloidal silica having a major axis of 5 nm or more and 100 nm or less and a spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less are used for the colloidal silica as observed with a scanning electron microscope. .

[Invention 19]
The coating solution for forming a low reflection film according to Invention 17 or Invention 18, wherein the mass ratio of rod-shaped colloidal silica: spherical colloidal silica is 20:80 to 80:20.

[Invention 20]
The tungsten compound is W (OR ¹ ) _6-n X _n (n is 1 ≦ n ≦ 6. R ¹ is independently a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n- Butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, An ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom).

[Invention 21]
Tungsten compound is W (OR ² ) _6-n Cl _n (n is 1 ≦ n ≦ 6, R ² is each independently a thiol group, ethyl group, n-propyl group, i-propyl group, n-butyl) Or a s-butyl group, an i-butyl group, a t-butyl group, an n-amyl group, an i-amyl group, or an s-amyl group.) Coating liquid for forming.

[Invention 22]
The coating liquid for forming a low reflection film according to any one of Inventions 17 to 21, wherein water is contained in an amount of 1 to 50% by mass with respect to the total mass of the coating liquid for forming a low reflection film.

[Invention 23]
A cover glass for a solar cell, on which a low reflection film using the coating liquid for forming a low reflection film of the inventions 17 to 22 is formed.

[Invention 24]
A method for preparing a coating liquid for forming a low reflection film for forming a low reflection film on a substrate, comprising mixing a dispersion containing a tungsten compound and a dispersion containing colloidal silica. 22: A method for preparing a coating solution for forming a low reflection film.
Specifically, colloidal silica includes at least two types of silica having different shapes.

[Invention 25]
Tungsten compound is the following reaction WCl ₆ + 5Na (OR ² ) → W (OR ² ) ₅ Cl + 5NaCl in a solvent of i-propanol (also known as isopropyl alcohol, 2-propanol, hereinafter abbreviated as IPA).
(R ² is each independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group or s-amyl group). W (OR ² ) ₅ Cl synthesized in the above method.

Moreover, since the low reflection film by the coating liquid for forming a low reflection film of the present invention has a very low reflectance even in a single layer film, a high transmittance can be obtained when it is formed on one or both sides of a transparent substrate.

The present inventors apply the above-described coating solution for forming a low reflection film onto a substrate such as a glass plate, and then heat and calcinate, tungsten alkoxide becomes tungsten oxide (hereinafter referred to as WO ₃ ), and colloidal silica is dehydrated. A low-reflection film obtained by bonding the condensed and cured silica fine particles as a binder with WO ₃ was obtained.

[Invention 26]
The present invention is a method for forming a low reflection film in which the above-described coating solution for forming a low reflection film is applied to a substrate and then heated and fired to obtain a low reflection film.

The coating solution for forming a low reflection film of the invention 17 to 22 is applied to a substrate to form a coating film, and then heated and fired to cure the coating film by using colloidal silica as silica fine particles and tungsten compound as tungsten oxide. And a tungsten oxide is contained, and the low reflective film having a refractive index of 1.20 or more and 1.40 or less is obtained on the substrate, with the tungsten oxide content in the silica fine particles in the range of 5 mass% to 40 mass%. A method for forming a low reflection film.

In the method for forming a low reflection film of the present invention, the silica fine particles fired by the colloidal silica are bonded with WO _{3 formed} by firing the tungsten alkoxide, so that the fine particles have a small void and are dense and hard. A reflective film was obtained. Low-reflective film having a lower refractive index (refractive index of 1.20 or more and 1.40 or less) than a simple silica coat (refractive index of 1.46) due to air having a refractive index of 1 taken into the film as a void. was gotten.

Further, due to the effect of containing WO ₃ , a hydrophilic film was obtained, and the antifouling property was obtained as compared with the silica-only film.

In this way, a low reflection film having a refractive index of 1.20 or more and 1.40 or less is obtained. For example, when the low reflection film is formed on the surface of a colorless transparent glass plate having a thickness of 3 mm as a substrate, A visible light transmittance of 98% was obtained on the glass substrate with a low reflection film, which is a low reflection member. Note that the visible light transmittance of the glass plate is about 90%, and in the case of a normal silica coat film having no voids, the visible light transmittance is 92%.

[Invention 27]
A low-reflection member characterized in that an average transmittance of a low-reflection film formed on a glass substrate by a method for forming a low-reflection film of the invention 26 is 95% or more.
The average transmittance is a value calculated by measuring the transmittance of light in the wavelength range of 380 nm to 1200 nm using a spectrophotometer.

[Invention 28]
The peak of the maximum transmittance of the transmittance curve is in the range of 500 nm or more and 900 nm or less.
The transmittance curve is a curve obtained by continuously plotting measured values of transmittance with a spectrophotometer in a certain wavelength range.

[Invention 29]
A cover glass for a solar cell, comprising the low reflection member of the invention 27 or the invention 28.

According to a second aspect, the present invention further comprises the following inventions 30 to 42.

[Invention 30]
A coating solution for forming a low reflection film on a substrate, comprising a niobium compound and colloidal silica, wherein the niobium compound is 5 masses in terms of oxide relative to the mass of the colloidal silica. A coating solution for forming a low reflection film, comprising a dispersion liquid contained in a range of from 50% to 40% by weight.
As the colloidal silica, at least two kinds of colloidal silicas having different shapes are preferably used, for example, rod-shaped colloidal silica and spherical colloidal silica.

[Invention 31]
The coating for forming a low-reflective film according to invention 30, wherein rod-like colloidal silica having a major axis of 5 nm or more and 100 nm or less and spherical colloidal silica having a particle size of 5 nm or more and 50 nm or less are used for colloidal silica as observed with a scanning electron microscope It is a liquid.

[Invention 32]
The coating solution for forming a low reflection film according to Invention 30 or Invention 31, wherein the mass ratio of rod-shaped colloidal silica: spherical colloidal silica is 20:80 to 80:20.

[Invention 33]
The niobium compound is Nb (OR ¹ ) _5-n X _n (n is 1 ≦ n ≦ 5, and R ¹ is independently a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n- Butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, An ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom).

[Invention 34]
The niobium compound is Nb (OR ² ) _5-n Cl _n (n is 1 ≦ n ≦ 5, R ² is independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group) , S-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, or s-amyl group. 30 to 32 coating liquid for forming a low reflection film.

[Invention 35]
The coating liquid for forming a low reflection film according to inventions 30 to 34, comprising 1% by mass or more and 50% by mass or less of water based on the total mass of the coating liquid for forming a low reflection film.

[Invention 36]
A cover glass for a solar cell, on which a low reflection film using the coating liquid for forming a low reflection film according to inventions 30 to 35 is formed.

[Invention 37]
A method for preparing a coating solution for forming a low-reflection film for forming a low-reflection film on a substrate, comprising mixing a dispersion containing a niobium compound and a dispersion containing colloidal silica. A method for preparing a coating solution for forming a low reflection film of 35 to 35.
Specifically, colloidal silica includes at least two types of silica having different shapes.

[Invention 38]
A niobium compound is reacted in the following reaction in a solvent of i-propanol (also known as isopropyl alcohol, 2-propanol, hereinafter abbreviated as IPA) NbCl ₅ + 4Na (OR ² ) → Nb (OR ² ) ₄ Cl + 4NaCl
R ² is independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, or n-amyl group. I-amyl group or s-amyl group. The method of the invention 37, which is Nb (OR ² ) ₄ Cl synthesized in ( ₄ ).

Moreover, since the low reflection film by the coating liquid for forming a low reflection film of the present invention has a very low reflectance even in a single layer film, a high transmittance can be obtained when it is formed on one or both sides of a transparent substrate.

The present inventors apply the above-described coating solution for forming a low reflection film to a substrate such as a glass plate, and then heat and calcinate, and niobium alkoxide becomes niobium oxide (hereinafter referred to as Nb ₂ O ₅ ), and colloidal silica. Thus, a low-reflective film obtained by bonding silica fine particles obtained by dehydration condensation and bonding with Nb ₂ O ₅ as a binder was obtained.

The present invention is a method for forming a low reflection film in which the above-described coating solution for forming a low reflection film is applied to a substrate and then heated and fired to obtain a low reflection film.

[Invention 39]
The coating liquid for forming a low reflection film according to inventions 30 to 35 is applied to a substrate to form a coating film, and then heated and fired to cure the coating film using colloidal silica as silica fine particles and niobium compound as niobium oxide, thereby producing silica fine particles. And a niobium oxide content in the range of 5% by mass to 40% by mass with a refractive index of 1.20 or more and 1.40 or less on the substrate. A method for forming a low reflection film.

In the method for forming a low reflection film of the present invention, the fine silica particles fired by colloidal silica are bonded with Nb ₂ O ₅ obtained by firing niobium alkoxide, so that they have minute voids and are dense and hard. A low reflection film was obtained. Low-reflective film having a lower refractive index (refractive index of 1.20 or more and 1.40 or less) than a simple silica coat (refractive index of 1.46) due to air having a refractive index of 1 taken into the film as a void. was gotten.

Further, due to the effect of containing Nb ₂ O ₅ , a hydrophilic film was obtained, and the antifouling property was obtained and deteriorated as compared with the silica-only film.

In this way, a low reflection film having a refractive index of 1.20 or more and 1.40 or less is obtained. For example, when the low reflection film is formed on the surface of a colorless transparent glass plate having a thickness of 3 mm as a substrate, A visible light transmittance of 98% was obtained on the glass plate with a low reflection film, which is a low reflection member. Note that the visible light transmittance of the glass plate is about 90%, and in the case of a normal silica coat film having no voids, the visible light transmittance is 92%.

[Invention 40]
A low reflection member, wherein a low reflection film is formed on a glass substrate by the method for forming a low reflection film of the invention 39, and the average transmittance in the light wavelength region of 380 nm to 1200 nm is 95% or more.
The average transmittance is a value calculated by measuring the transmittance of light in the wavelength range of 380 nm to 1200 nm using a spectrophotometer.

[Invention 41]
The peak of the maximum transmittance of the transmittance curve is in the range of 500 nm to 900 nm.
The transmittance curve is a curve obtained by continuously plotting measured values of transmittance with a spectrophotometer in a certain wavelength range.

[Invention 42]
A cover glass for a solar cell, comprising the low reflection member of the invention 40 or the invention 41.

According to the second aspect, the present invention further comprises the following inventions 43 to 55.

[Invention 43]
A coating liquid for forming a low reflection film on a substrate, which comprises a tantalum compound and colloidal silica, and the tantalum compound is 5 masses in terms of oxide with respect to the mass of the colloidal silica. A coating solution for forming a low reflection film, comprising a dispersion liquid containing the composition in a range of not less than 40% and not more than 40% by mass.
As the colloidal silica, at least two kinds of colloidal silicas having different shapes are preferably used, for example, rod-shaped colloidal silica and spherical colloidal silica.

[Invention 44]
The coating liquid for forming a low reflection film according to the invention 43, characterized in that a rod-shaped colloidal silica having a major axis of 5 nm or more and 100 nm or less and a spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less are used for the colloidal silica as observed with a scanning electron microscope. It is.

[Invention 45]
The coating solution for forming a low reflection film according to Invention 43 or Invention 44, wherein the mass ratio of rod-shaped colloidal silica: spherical colloidal silica is 20:80 to 80:20.

[Invention 46]
The tantalum compound is Ta (OR ¹ ) _5-n X _n (where n is 1 ≦ n ≦ 5 and R ¹ is independently methyl, ethyl, n-propyl, i-propyl, n- Butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, An ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom.) The coating solution for forming a low reflection film according to inventions 43 to 45, wherein:

[Invention 47]
The tantalum compound is Ta (OR ² ) _5-n Cl _n (n is 1 ≦ n ≦ 5, R ² is independently methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group) S-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group or s-amyl group). Coating liquid.

[Invention 48]
The coating liquid for forming a low reflection film according to inventions 43 to 48, comprising 1% by mass or more and 50% by mass or less of water with respect to the total mass of the coating liquid for forming a low reflection film.

[Invention 49]
A cover glass for a solar cell on which a low reflection film using the coating liquid for forming a low reflection film according to the inventions 43 to 48 is formed.

[Invention 50]
A method for preparing a coating solution for forming a low reflection film for forming a low reflection film on a substrate, comprising mixing a dispersion containing a tantalum compound and a dispersion containing colloidal silica. 48. A method for preparing a coating solution for forming a low reflection film.
Specifically, colloidal silica includes at least two types of silica having different shapes.

[Invention 51]
The following reaction TaCl ₅ + 4Na (OR ² ) → Ta (OR ² ) ₄ Cl + 4NaCl in a tantalum compound in a solvent of i-propanol (also called isopropyl alcohol, 2-propanol, hereinafter abbreviated as IPA)
R ² is independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, or n-amyl group. I-amyl group or s-amyl. The method of Invention 50, which is Ta (OR ₂ ) ₄ Cl synthesized in ( ₁ ).

Moreover, since the low reflection film by the coating liquid for forming a low reflection film of the present invention has a very low reflectance even in a single layer film, a high transmittance can be obtained when it is formed on one or both sides of a transparent substrate.

The present inventors apply the above-described coating solution for forming a low reflection film to a substrate such as a glass plate, and then heat and calcinate, so that tantalum alkoxide becomes tantalum oxide (hereinafter referred to as Ta ₂ O ₅ ), and colloidal silica. A low-reflective film obtained by bonding silica fine particles cured by dehydration with Ta ₂ O ₅ as a binder was obtained.

The present invention is a method for forming a low reflection film in which the above-described coating solution for forming a low reflection film is applied to a substrate and then heated and fired to obtain a low reflection film.

[Invention 52]
The coating solution for forming a low reflection film of Inventions 43 to 48 is applied to a substrate to form a coating film, and then heated and fired to cure the coating film using colloidal silica as silica fine particles and tantalum compound as tantalum oxide, thereby producing silica fine particles. And a tantalum oxide, and a low reflection film having a refractive index of 1.20 or more and 1.40 or less is obtained on the substrate. A method for forming a low reflection film.

In the method for forming a low-reflection film of the present invention, these fine silica particles fired by colloidal silica are joined with Ta ₂ O _{5 formed} by firing tantalum alkoxide, so that they have minute voids and are dense and hard. A low reflection film was obtained. Low-reflective film having a lower refractive index (refractive index of 1.20 or more and 1.40 or less) than a simple silica coat (refractive index of 1.46) due to air having a refractive index of 1 taken into the film as a void. was gotten.

Further, due to the effect of containing Ta ₂ O ₅ , a hydrophilic film was obtained, and the antifouling property was obtained as compared with the silica-only film.

In this way, a low reflection film having a refractive index of 1.20 or more and 1.40 or less is obtained. For example, when the low reflection film is formed on the surface of a colorless transparent glass plate having a thickness of 3 mm as a substrate, A visible light transmittance of 98% was obtained on the glass substrate with a low reflection film, which is a low reflection member. The visible light transmittance of the glass plate is about 90%, and the visible light transmittance is 92% in a glass substrate on which a normal silica coat film having no voids is formed.

[Invention 53]
A low-reflection member, wherein the low-reflection film is formed on a glass substrate by the method for forming a low-reflection film of the invention 52, and the average transmittance in the light wavelength region of 380 nm to 1200 nm is 95% or more.
The average transmittance is a value calculated by measuring the transmittance of light in the wavelength range of 380 nm to 1200 nm using a spectrophotometer.

[Invention 54]
The peak of the maximum value of the transmittance curve of the transmittance curve of the invention 52 is in the range of 500 nm or more and 900 nm or less, The low reflection member of the invention 11.
The transmittance curve is a curve obtained by continuously plotting measured values of transmittance with a spectrophotometer in a certain wavelength range.

[Invention 55]
A cover glass for a solar cell, comprising the low reflection member of invention 53 or invention 54.

According to the present invention, a low reflection film as a single layer film capable of forming a large area by a simple method, a method for forming the same, and a low reflection member using the same are provided. The low reflection member in which the low reflection film is formed on the transparent substrate surface by the low reflection film forming method of the present invention has a high average transmittance.

According to the present invention, a low reflection film having a sufficiently low reflection effect with a single layer film can be obtained, and a method for forming a low reflection film that can be easily formed over a large area is obtained. The low reflection member obtained by the method is suitably used for a solar cell cover glass, an automotive glass (particularly a windshield), or a protective member for a lighting fixture.

In addition, the low reflection film obtained from the coating liquid for forming a low reflection film of the present invention is a single layer film, which can provide a sufficiently low reflection effect and can be easily formed on a large area.

That is, the coating solution for forming a low reflection film of the present invention can be applied to a large area by various methods, and a low reflection film having a very low refractive index was obtained as a single layer film. A low reflection member having a low reflection film formed on the surface of a transparent substrate using the coating liquid for forming a low reflection film of the present invention has a high transmittance in a wide wavelength range.

Further, according to the present invention, a coating solution for forming a low reflection film, which is excellent in liquid stability and stable even when water is added to 50% by mass, is obtained.

The low reflection film obtained by the coating liquid for forming a low reflection film of the present invention is a dense film containing fine voids sufficient to lower the refractive index, and colloidal silica fine particles are made of WO ₃ , Nb ₂ O ₅ or When Ta ₂ O ₅ is bonded as a binder, it has a low refractive index (1.20 or more and 1.40 or less) with respect to a normal silica film due to the effect of an air layer having a refractive index of 1 taken in as microvoids. A low reflection film was obtained. In addition, the low reflection film is hydrophilic because it contains a metal oxide, and is hardly contaminated and has antifouling properties.

Further, the low reflection film obtained by the coating liquid for forming a low reflection film of the present invention is excellent in durability such as heat resistance and abrasion resistance to withstand outdoor use, in addition to antifouling property.

It is a drawing substitute SEM photograph of the glass substrate with a low reflective film using tungsten alkoxide regarding 1st Embodiment. It is a transmittance | permeability curve of the glass substrate with a low reflection film using tungsten alkoxide regarding 1st Embodiment. It is a drawing-substitute SEM photograph of the glass substrate with a low reflective film using niobium alkoxide regarding 1st Embodiment. It is a transmittance | permeability curve of the glass substrate with a low reflection film using niobium alkoxide regarding 1st Embodiment. It is a drawing-substitute SEM photograph of the glass substrate with a low reflection film using tantalum alkoxide regarding 1st Embodiment. It is a transmittance | permeability curve of the glass substrate with a low reflection film using the tantalum alkoxide regarding 1st Embodiment. It is a drawing substitute SEM (scanning electron microscope) photograph of the glass substrate with a low reflection film using tungsten alkoxide regarding 2nd Embodiment. It is the transmittance | permeability curve of the glass substrate with a low reflection film using tungsten alkoxide regarding 2nd Embodiment. It is a drawing substitute SEM (scanning electron microscope) photograph of the glass substrate with a low reflection film using niobium alkoxide regarding 2nd Embodiment. It is the transmittance | permeability curve of the glass substrate with a low reflection film using niobium alkoxide regarding 2nd Embodiment. It is a drawing substitute SEM (scanning electron microscope) photograph of the glass substrate with a low reflection film using a tantalum alkoxide regarding 2nd Embodiment. It is the transmittance | permeability curve of the glass substrate with a low reflection film using the tantalum alkoxide regarding 2nd Embodiment.

"I. First embodiment" (Embodiment of the present invention from the first viewpoint)

1. First, the low reflection film of the present invention will be described.
The present invention is selected from the group consisting of silica fine particles and tungsten oxide, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, tin oxide, aluminum oxide, hafnium oxide, chromium oxide, molybdenum oxide, cerium oxide and lanthanum oxide. A binder comprising at least one metal oxide is contained, the content ratio of the binder comprising the metal oxide to the silica fine particles is 5% by mass or more and 40% by mass or less, and the refractive index is 1.20 or more. The low reflection film is 40 or less. The refractive index is preferably as low as possible, more preferably 1.35 or less, and still more preferably 1.30 or less.

Furthermore, the present invention is characterized in that the silica fine particles are mainly rod-like silica fine particles having a major axis of 5 nm to 100 nm and spherical silica fine particles having a particle size of 5 nm to 50 nm as observed by SEM. This is the low reflection film. “Mainly” means 90% or more of the total number of colloidal silica, and the rest are silica fine particles having a shape not satisfying the above range.

The present invention is also the above low reflection film, wherein the mass ratio of the rod-like silica particles and the spherical silica particles is rod-like silica particles: spherical silica particles = 20: 80 to 80:20.

The present invention is also the above low reflection film, wherein the metal oxide is at least one metal oxide selected from the group consisting of tungsten oxide, niobium oxide and tantalum oxide.

In the low reflection film of the present invention, the content of the metal oxide in the low reflection film is 5% by mass or more and 40% by mass with respect to the mass of the silica (solid mass) of the rod-like silica fine particles and the spherical silica fine particles. % Or less. If it is less than 5% by mass, the resulting film is inferior in frictional strength, and if it is more than 40% by mass, the refractive index of the resulting film will be high and a low reflection film will not be obtained. Preferably, they are 10 mass% or more and 30 mass% or less.

Further, in the low reflection film of the present invention, containing a metal oxide in the silica film has an effect of shifting the peak of the maximum value of the transmittance curve to the long wavelength side. Further, since the metal oxide itself is hard, there is an effect of improving the wear resistance.

At this time, since the metal oxide does not fill the voids of the silica fine particles, the metal oxide exists in the film as fine particles having substantially the same particle diameter of 5 nm or less and 50 nm or more, or the metal oxide is present. At the grain boundary of the silica fine particles, it is required that the silica fine particles are bonded to give strength to the low reflection film, and that the metal oxide does not change due to a high temperature environment, water adhesion and ultraviolet irradiation.

Such metal oxides include tungsten oxide (WO ₃ , refractive index 1.75), niobium oxide (niobium pentoxide: Nb ₂ O ₅ , refractive index 1.9), tantalum oxide (tantalum pentoxide: Ta _2). O ₅ , refractive index 2.0), titanium oxide (TiO ₂ , refractive index 2.2), zirconium oxide (zirconia: ZrO ₂ , refractive index 1.85), tin oxide (SnO ₂ , refractive index 1.7), Aluminum oxide (alumina: Al ₂ O ₃ , refractive index 1.65), hafnium oxide (hafnia: HfO ₂ , refractive index 1.90), chromium oxide (Cr ₂ O ₃ , refractive index 2.1), molybdenum oxide ( MoO ₂ , MoO ₃ , refractive index 1.80), cerium oxide (ceria: CeO ₂ , refractive index 1.8) and lanthanum oxide (La ₂ O ₃ , refractive index 1.75).

The low reflection film of the present invention is obtained by joining silica fine particles having different shapes as a binder with a metal oxide as a binder, and obtaining a low refractive index by air having a refractive index of 1 taken into a minute void (gap). According to observation, it is preferable that the major axis of the rod-like silica fine particles is 5 nm or more and 100 nm or less. If the major axis is smaller than 5 nm or larger than 100 nm, it is difficult to form minute voids in the film. In this case, the aspect ratio of the rod-like silica fine particles, that is, the major axis / minor axis is preferably 2 or more and 10 or less. When the major axis / minor axis is smaller than 2 and larger than 10, it is difficult to form minute voids made of air in the film.

On the other hand, the spherical silica fine particles preferably have a particle size of 5 nm or more and 50 nm or less. If the particle size is smaller than 5 nm or larger than 50 nm, it is difficult to form minute voids in the film.

In the present invention, among all the silica particles including rod-like silica particles and spherical silica particles, 90% or more of the total number of silica particles having a shape falling within the above range is necessary when observed by SEM. The rest are silica fine particles having a shape that does not satisfy the above range. The inclusion of more than 10% out of the range is not preferable because there is a problem in forming minute voids.

In the low reflection film of the present invention, the mass ratio of the rod-like silica fine particles to the spherical silica fine particles is rod-like silica fine particles: spherical silica fine particles = 80: 20 to 20:80. In other ranges, void formation is small and it is difficult to obtain a low reflection film, and the adhesion strength of the low reflection film to a substrate, particularly a glass plate, is poor.

The preferred film thickness on the substrate surface of the low reflection film of the present invention is 20 nm or more and 500 nm or less. If the film thickness is thinner than 20 nm, the wear resistance is inferior and film formation is difficult. On the other hand, if it is thicker than 500 nm, the film thickness becomes non-uniform and it is difficult to form a film. Preferably, they are 50 nm or more and 150 nm or less. In order to obtain a low reflectance with respect to visible light, the thickness is preferably 100 nm or more and 120 nm or less.

The low reflection film of the present invention is a film containing a large number of microvoids. Specifically, voids are formed by joining silica particles of different shapes as a binder with a metal oxide, and due to the effect of air having a refractive index of 1 taken into the voids, a low refractive index ( A low reflection film of 1.20 or more and 1.40 or less) was obtained. In addition, a hard film can be obtained by including a metal oxide in the low reflection film, and it is hydrophilic with good adhesion to the substrate, is conductive, and is not easily charged with static electricity. The formed low reflection member is difficult to get dirty.

Specifically, as observed by SEM, 90% or more of the total number of silica fine particles is rod-like silica fine particles having a major axis of 5 nm or more and 100 nm or less, and spherical silica fine particles having a particle diameter of 5 nm or more and 50 nm or less. The low reflection film of the present invention containing at least one metal oxide selected from niobium or tantalum in a range of 5% by mass to 40% by mass with respect to all silica fine particles, in addition to antifouling property, Excellent heat resistance, durability to withstand outdoor use, and wear resistance. Moreover, by including a metal oxide, it is hydrophilic and conductive, is hardly charged with static electricity, and has excellent antifouling properties.

2. Method for Forming Low Reflective Film Next, a method for forming the low reflective film of the present invention which gives the above low reflective film will be described.
That is, the present invention provides at least one metal compound selected from the group consisting of tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, molybdenum, cerium and lanthanum in a dispersion containing colloidal silica. A coating solution for forming a low reflection film comprising a dispersion liquid containing a coating material is applied to a substrate to form a coating film, and then heated and fired to colloidal silica as silica fine particles and a metal compound as a metal oxide to be cured. This is a method for forming a low reflection film.

Further, according to the present invention, the colloidal silica is 90% or more of the total number of colloidal silica, as observed by SEM, when the colloidal silica having a long diameter of 5 nm or more and 100 nm or less and the spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less. In the above method, the metal compound content relative to the colloidal silica is 5% by mass or more and 40% by mass or less in terms of oxide.

The present invention is also the above method, wherein the mass ratio of the rod-shaped colloidal silica to the spherical colloidal silica is rod-shaped silica colloidal silica: spherical colloidal silica = 20: 80 to 80:20.

The present invention is also the above method, wherein the metal compound is a metal compound of at least one metal selected from the group consisting of tungsten, niobium and tantalum.

In the method for forming a low reflection film of the present invention, when forming a low reflection film on a substrate, a coating liquid for forming a low reflection film in which a dispersion of colloidal silica and a specific metal compound are dispersed is used.

In the method for forming a low reflection film of the present invention, the content of the metal compound in the coating solution for forming the low reflection film is the mass of colloidal silica, which is a combination of rod-shaped colloidal silica and spherical colloidal silica (mass of solid content, hereinafter the same). ) In terms of oxide, it is in the range of 5 mass% or more and 40 mass% or less. Preferably it is the range of 10 mass% or less and 30 mass% or more. If it is less than 5% by mass, the resulting film is inferior in abrasion resistance, and if it is more than 40% by mass, the refractive index of the obtained film is high and it is difficult to form a low reflection film. Preferably, they are 10 mass% or more and 30 mass% or less.

Assuming the film formation mechanism in the method for forming a low reflection film of the present invention, the coating liquid for forming a low reflection film in which colloidal silica having different shapes coexisted was coated on the substrate, so that the colloidal silica in the liquid was coated. In the film formed by heating and baking the coating film, the coating is formed in a state where the spherical silica particles are trapped in the gap formed by the Brownian motion, in which the rod-shaped colloidal silica having a large aspect ratio is entangled and joined in a bridge shape It is considered that a film having a low refractive index, that is, a low reflection film was formed by the effect that air having a refractive index of 1 was taken into the gaps in the microvoids.

Specifically, in the drying process of the coating film, the solvent filled by capillarity in the gaps between the rod-shaped colloidal silica and the spherical colloidal silica has the effect of strongly bonding the contact points between them, and as the solvent evaporates, the rod-shaped It is considered that fine spherical colloidal silica is trapped in the gaps between the colloidal silicas, and shrinks and dries while rearranging so that silicas of different shapes are adjacent to each other at more contacts. In this way, by using two types of colloidal silica having different shapes, a denser film than when only rod-shaped colloidal silica is used, and a coarser porosity film than when only spherical colloidal silica is used, and It is presumed that a porous film having many contacts and stronger bonding and excellent in friction strength is formed.

However, if a porous film composed of two types of silica fine particles having different shapes and air is formed on the surface of the transparent substrate, it exhibits excellent low reflectivity with respect to visible light having a wavelength of about 500 nm to 550 nm. When forming a low-reflection film on a cover glass for a solar cell, it has been difficult to control the transmittance over a wide range of wavelengths from 380 nm to 1200 nm in order to improve the conversion efficiency. For this purpose, it is preferable to add a metal compound as a refractive index adjusting material, hydrolyze it, and then condense it.

In the method for forming a low reflection film of the present invention, the coating liquid for forming the low reflection film is dispersed in a dispersion containing colloidal silica having different shapes, such as tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, A dispersion containing at least one metal compound selected from the group consisting of molybdenum, cerium and lanthanum was added to obtain a coating solution for forming a low reflection film. In addition, the simple substance of these metals is hydrophobic, and even if it makes it fine particle, it is difficult to disperse | distribute it in a coating liquid. These metal oxides or hydrates, like the fine particles of simple metals, generally have poor dispersibility when used as a coating solution and tend to be inferior in stability, such as precipitation of crystals and solids, Often there is a problem with the liquid life.

Therefore, in the method for forming a low reflection film of the present invention, a metal alkoxide is preferably used as the metal compound. In particular, an alkoxide of tungsten, niobium or tantalum provides a coating solution for forming a low reflection film having excellent liquid stability and excellent liquid life.

In the tungsten compound, silicotungstic acid (SiO ₂ · 12WO ₃ · 26H ₂ O) may be used, and silicotungstic acid is soluble in water and alcohol, and is excellent in liquid stability and liquid life.

In the formation of a low reflection film, for example, tetraethoxysilane (hereinafter abbreviated as TEOS) is cured to form a film unless the content of colloidal silica in the coating solution is 5 mass% or less. However, for example, tungsten alkoxide, niobium alkoxide, or tantalum alkoxide can be contained in an arbitrary ratio with respect to colloidal silica.

Thus, the metal compound is made of tungsten oxide (WO ₃ , refractive index 1.75), niobium oxide (niobium pentoxide: Nb ₂ ) by heating and baking the coating solution for forming a low reflection film on the substrate surface. O ₅ , refractive index 1.9), tantalum oxide (tantalum pentoxide: Ta ₂ O ₅ , refractive index 2.0), titanium oxide (TiO ₂ , refractive index 2.2), zirconium oxide (zirconia: ZrO ₂₎ , Refractive index 1.85), tin oxide (SnO ₂ , refractive index 1.7, aluminum oxide (alumina: Al ₂ O ₃ , refractive index 1.65), hafnium oxide (hafnia: HfO ₂ , refractive index 1.90) , Chromium oxide (Cr ₂ O ₃ , refractive index 2.1), molybdenum oxide (MoO ₂ , MoO ₃ , refractive index 1.80), cerium oxide (ceria: CeO ₂ , refractive index 1.8) or lanthanum oxide ( la ₂ O _3, the refractive index .75), and as a binder to bond the silica fine particles.

In the present invention, the inclusion of the metal oxide in the low reflection film has the effect of shifting the peak of the maximum transmittance curve to the long wavelength side, and the wear resistance of the low reflection member on which the low reflection film is formed. It is thought that it brought about the effect of improving. When the metal compound in the coating liquid for forming the low reflection film becomes a metal oxide in the film, the silica fine particles were adhered as a binder at the grain boundary of the silica fine particles to give strength to the low reflection film. The metal oxide is required not to change at high temperatures and ultraviolet rays.

In view of the above points, at least one metal compound selected from the group consisting of tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, molybdenum, cerium, and lanthanum was selected. In particular, tungsten, niobium and tantalum compounds such as tungsten, niobium and tantalum alkoxides or silicotungstic acid are excellent. Due to the effect of adding these metal compounds to the coating solution for forming a low reflection film, the adhesion strength to the glass plate is improved when a low reflection film is formed.

Further, in the method for forming a low reflection film of the present invention, a low reflection film forming coating solution having a specific colloidal silica having a different shape and a specific metal compound is heated and fired to form a metal having silica fine particles as a binder. A low reflective film bonded with an oxide is obtained. At this time, in order to obtain a low refractive index by air having a refractive index of 1 taken into microvoids (gap), a rod-like colloidal silica having a major axis of 5 nm or more and 100 nm or less and a particle diameter of 5 nm or more are observed by SEM. The rod-shaped colloidal silica of 50 nm or less is preferably 90% or more of the total number of colloidal silica. If the major axis is smaller than 5 nm or larger than 100 nm, the above-mentioned effects are not obtained, and the above-mentioned minute voids are hardly formed in the film. When the aspect ratio of the rod-shaped colloidal silica, that is, the major axis / minor axis is smaller than 2 or larger than 10, the above-mentioned effects are not obtained, and the above-mentioned minute voids are hardly formed in the film. In spherical colloidal silica, if the particle size is smaller than 5 nm or larger than 50 nm, minute voids are hardly formed in the film. In order to obtain minute voids, it is necessary that the colloidal silica having a shape falling within the above range as observed by SEM is 90% or more of the total number. The inclusion of more than 10% out of the range is not preferable because there is a problem in forming minute voids.

As observed by SEM, the major axis is 5 nm or more and 100 nm or less, the major axis / minor axis = 2 or more and 10 or less is rod-shaped colloidal silica, and the spherical colloidal silica having a particle size of 5 nm or more and 50 nm or less is the total number of colloidal silica. By using a coating solution for forming a low reflection film that is 90% or more and is made of a dispersion containing the above metal compound, voids can be easily generated.

In the method for forming a low reflection film of the present invention, by using colloidal silica that gives silica particles having different shapes as described above, silica particles having different shapes and tungsten oxide, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, Refractive index of 1.20 or more and 1.40 or less comprising at least one metal oxide selected from the group consisting of tin oxide, aluminum oxide, hafnium oxide, chromium oxide, molybdenum oxide, cerium oxide and lanthanum oxide A low reflection film was obtained. More preferably, it is a low reflective film comprising at least one metal oxide selected from the group consisting of tungsten oxide, niobium oxide and tantalum oxide as the metal oxide.

Further, in the method for forming a low-reflection film of the present invention, a rod-shaped colloidal silica in a coating solution for forming a low-reflection film that gives a low-reflection film that easily generates voids and has excellent adhesion strength to a glass plate: The mass ratio is 80:20 to 20:80 in terms of oxide. In other ranges, void formation is small and it is difficult to obtain a low reflection film, and the adhesion strength of the low reflection film to the substrate is inferior.

Specifically, the present invention relates to a rod-shaped colloidal silica having a major axis of 5 nm or more and 100 nm or less, and a major axis / minor axis of 2 or more and 10 or less, as observed by SEM. At least one selected from the group consisting of tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, molybdenum, cerium and lanthanum in a dispersion containing spherical colloidal silica having a diameter of 5 nm or more and 50 nm or less A low-reflective coating solution obtained by adding a dispersion containing a metal compound such as metal alkoxide so that the content of the metal compound relative to colloidal silica is 5% by mass or more and 40% by mass or less in terms of oxide. After being coated onto a coating film, it is heated and fired to convert a metal compound such as a metal alkoxide into a metal oxide. A method of forming a low-reflection film, which is then cured.

In the method for forming a low reflection film of the present invention, a member with a low reflection film having a low reflection film having a refractive index of 1.20 or more and 1.40 or less, that is, a low reflection member is obtained in this way. It was.

For example, when the low reflection film was formed on both surfaces of a 3 mm thick soda lime silicate glass plate as a substrate by a float method, the average transmittance was improved by 8% compared to the case where it was not formed. The average transmittance of the glass plate is about 90%, and the average transmittance when a conventional silica coat film made of colloidal silica and TEOS is formed on both surfaces of the glass plate is about 92%.

In addition, the colloidal silica dispersion and the dispersion of a metal compound, for example, a metal alkoxide, have liquid stability, and therefore, in the colloidal silica dispersion, methanol, ethanol, n-propanol, i-propanol (also known as isopropyl alcohol) are used. Alternatively, an alcohol solvent such as 2-propanol (hereinafter abbreviated as IPA), an ester solvent such as ethyl acetate, or an organic solvent typified by a polar solvent such as acetone is used. In a dispersion of a metal compound, particularly a metal alkoxide. Is preferably an organic solvent typified by alcohol such as methanol, ethanol, n-propanol or IPA, and is preferably used in the method for producing a low reflection film of the present invention.

Usually, when water is added to a dispersion of colloidal silica, the colloidal silica becomes unstable and solid content often precipitates, and although it is not usually added, it is composed of colloidal silica and tungsten, niobium and tantalum. In the coating solution for forming a low reflection film using an alkoxide selected from the group, a solid content hardly precipitates even when water is added up to 50% by mass with respect to the total weight due to the action of the alkoxide. Further, by adding 1% by mass or more of water to the low reflection film forming coating solution, the wettability with the glass plate is improved and the coating is facilitated. In the coating solution for forming a low reflection film used in the method for forming a low reflection film of the present invention, the water content can be arbitrarily adjusted between 1% by mass and 50% by mass with respect to the total mass.

Therefore, in the method for forming a low reflection film of the present invention, it is possible to use a coating solution for forming a low reflection film having a water content of 1% by mass to 50% by mass. Preferably, they are 1 mass% or more and 30 mass% or less. Furthermore, Preferably, they are 1 mass% or more and 10 mass% or less.

The low-reflection film according to the method of forming a low-reflection film of the present invention is a film containing a large number of microvoids, and a refractive index of 1 incorporated into voids formed by joining silica particles having different shapes as binders with metal oxides. Due to the effect of the air layer, the refractive index becomes low.

In the method for forming a low reflection film of the present invention, the low reflection film forming coating solution can be applied to a substrate by a sol-gel method.

For example, in a film forming method in a vacuum such as a vapor deposition method and a sputtering method, it is difficult to obtain a mixed film having several types of compositions by a single film formation on the surface of a substrate, but a wet coating method such as a sol-gel method. Can be easily formed by a single coating on the substrate surface, and is expected to be applied to a wide range of light control films in the ultraviolet, visible and infrared regions. The sol-gel method is suitably used for the production of a protective member, particularly a solar cell cover glass.

Application of the coating solution for forming a low reflection film on a substrate, particularly a substrate, is a spine coater method, a dip-up method, that is, a dip coating method, a spray method, a roller coating method, a flow coating method, a screen printing method, a brush coating, It can be performed by a method such as inkjet.

It is preferable that the coating formed on the substrate by various coating methods is dried at 80 ° C. or higher and 150 ° C. or lower for 10 minutes to 6 hours, and then further heated and fired. The heating temperature is determined according to the heat-resistant temperature of the substrate. Baking is preferably performed in a temperature range in which characteristics such as hydrophilicity can be maintained. In the case of a plastic transparent substrate, it is preferable to treat at approximately 300 ° C. or lower. In addition, the inorganic glass plate can be fired at a high temperature of about 750 ° C. by adjusting the firing time. As a preferred embodiment, a film excellent in abrasion resistance can be obtained by baking at 500 ° C. or higher and 800 ° C. or lower for 2 to 3 minutes, that is, 120 seconds to 180 seconds.

When preparing a coating solution for forming a low reflection film, tungsten, niobium, and tantalum compounds, in particular, alkoxides of these metals and silicotungstic acid can be arbitrarily mixed with colloidal silica.

In particular, in the method for forming a low reflection film according to the present invention, when a coating solution for forming a low reflection film contains a compound of tungsten, niobium, or tantalum, that is, a low-reflection film using an alkoxide or silicotungstic acid of these metals. After applying the coating liquid for forming a reflective film on a glass plate, it is preferably heated and fired to obtain a low reflective member on which a low reflective film is formed. The upper limit is 800 ° C. or lower in consideration of glass deformation, and does not need to be higher than 800 ° C. or higher. After reaching the desired firing temperature, a hard low-reflection film can be obtained by heating and holding for 2 to 3 minutes, that is, 120 to 180 seconds.

In this way, after using a glass plate for the substrate, and applying a coating solution for forming a low reflection film, which is a combination of the colloidal silica and at least one metal compound selected from tungsten, niobium or tantalum, to the substrate by the above method, By heat-firing, a low reflection member excellent in wear resistance was obtained.

3. Dispersion containing colloidal silica Next, a dispersion containing colloidal silica used in the coating liquid for forming a low reflection film in the present invention will be described.

The following are mentioned as a silicon compound for producing | generating colloidal silica for making the low anti-film of this invention contain a silica particle.
For example, the silicon compound is preferably an alkoxide, and is represented by the general formula Si (OR) ₄ , wherein R is independently a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, or a secondary butyl group. , A methoxyethyl group, an ethoxyethyl group or a phenyl group), or a hydrolyzate or partial hydrolyzate thereof, particularly tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, Tetranormal propoxysilane, tetranormalbutoxysilane, tetratertiarybutoxysilane or the like or a hydrolyzate thereof is preferable. Further, the —OR group of the alkoxide may be substituted with a halogen atom such as a chlorine atom, and for example, chlorotriethoxysilane, dichlorodinnormalbutoxysilane, trichloronormalbutoxysilane and the like are used. In the method for producing a low reflection film of the present invention, these silicon compounds are dehydrated and condensed to form a rod-like colloidal silica having a major axis of 5 nm or more and 100 nm or less, a major axis / minor axis of 2 or more and 10 or less, a particle size of 5 nm or more, What was prepared in spherical colloidal silica of 50 nm or less is used as a raw material.

4). Metal Alkoxide Next, various metal alkoxides as metal compounds used in the coating solution for forming a low reflection film in the present invention will be described in order.

[Tungsten alkoxide]
In the present invention, in order to contain tungsten oxide in the low reflection film, it is preferable to use tungsten alkoxide which is excellent in stability without being precipitated in the coating liquid for forming the low reflection film.

Such tungsten alkoxide includes W (OR) ₆ or W (OR) _6-n X _n (n is 1 ≦ n ≦ 5, R is independently a methyl group, an ethyl group, or an n-propyl group) I-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, A methoxypropyl group, an ethoxymethyl group, an ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X represents a halogen atom). Further, calcium tungstate obtained by firing in the presence of inorganic and organic salts such as Ca, Fe, Mn and alkoxide in the tungsten alkoxide, that is, CaWO ₄ , iron tungstate, that is, FeWO ₄ , manganese tungstate, That is, a tungstic acid compound such as MnWO ₄ can be used.

In the low reflection manufacturing method of the present invention, it is particularly preferable to use W (OR) _6-n Cl _n . n is 1 ≦ n ≦ 5, and R is independently methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group or s-amyl group.

Of these, W (OR) ₅ Cl is preferable. R is independently methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, n-amyl, i -Amyl group or s-amyl group.

W (OR) ₅ Cl is useful for the liquid stability of a coating solution for forming a low reflection film, and is used as a dispersion dispersed in methanol, ethanol or IPA, and mixed with a dispersion containing colloidal silica. preferable.

W (OR) ₅ Cl is synthesized by the following reaction in an IPA solvent.
WCl ₆ + 5Na (OR) → W (OR) ₅ Cl + 5NaCl

[Niobium alkoxide]
In the present invention, in order to contain niobium oxide in the low reflection film, it is preferable to use a niobium alkoxide that is excellent in stability without being precipitated in the coating liquid for forming the low reflection film.

Examples of such niobium alkoxide include Nb (OR) ₅ , Nb (OR) _{5 -n} X _n (n is 1 ≦ n ≦ 4, R is independently a methyl group, an ethyl group, an n-propyl group, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, n-amyl, i-amyl, s-amyl, 2-ethylhexyl, methoxyethyl, methoxy A propyl group, an ethoxymethyl group, an ethoxyethyl group, an ethoxypropyl group or a phenyl group, X is a halogen atom) or a mixed alkoxide (Fe, Mn) with Fe and Mn: Nb = 1: 2. is there.

In the present invention, among others, Nb (OR) is preferably used _5-n Cl n. n is 1 ≦ n ≦ 4, and R is independently methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, n-amyl group, i-amyl group or s-amyl group.

Among these, Nb (OR) ₄ Cl is preferable. R is independently methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, n-amyl, i -Amyl group or s-amyl group.

Nb (OR) ₄ Cl is useful for the stability of the coating solution for forming a low reflection film, and is used by mixing with a dispersion containing colloidal silica as a dispersion dispersed in methanol, ethanol or IPA. It is preferable.

Nb (OR) ₄ Cl is under IPA solvent, is synthesized by the following reaction.
NbCl ₅ + 4Na (OR) → Nb (OR) ₄ Cl + 4NaCl

[Tantalum alkoxide]
In the present invention, in order to contain tantalum oxide in the low reflection film, it is preferable to use tantalum alkoxide that is excellent in stability without being precipitated in the coating liquid for forming the low reflection film.

Examples of such tantalum alkoxide include Ta (OR) ₅ , Ta (OR) _{5 -n} X _n (n is 1 ≦ n ≦ 4, R is independently a methyl group, an ethyl group, an n-propyl group, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, n-amyl, i-amyl, s-amyl, 2-ethylhexyl, methoxyethyl, methoxy A propyl group, an ethoxymethyl group, an ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom.) Or a mixed alkoxide with Fe and Mn (Fe, Mn): Ta = 1: 2 Can be mentioned.

In the present invention, among others, Ta (OR) is preferably used _5-n Cl n. n is 1 ≦ n ≦ 4, and R is independently methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, n-amyl group, i-amyl group or s-amyl group.

Of these, Ta (OR) ₄ Cl is preferable, and each R is independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t- A butyl group, an n-amyl group, an i-amyl group or an s-amyl group;

Ta (OR) ₄ Cl is useful for the stability of the coating solution for forming a low reflection film, and is used by mixing with a dispersion containing colloidal silica as a dispersion dispersed in methanol, ethanol or IPA. Is preferred.

Ta (OR) ₄ Cl is synthesized by the following reaction in an IPA solvent.
TaCl ₅ + 4Na (OR) → Ta (OR) ₄ Cl + 4NaCl

[Titanium alkoxides and complexes]
In the present invention, in order to contain titanium oxide in the low reflection film, it is preferable to use a titanium alkoxide that is excellent in stability without being precipitated in the coating solution for forming the low reflection film.

Such a titanium alkoxide has the general formula Ti (OR) ₄ (R is independently methyl group, ethyl group, normal propyl group, isopropyl group, normal butyl group, secondary butyl group, methoxyethyl group, ethoxyethyl) Group or a phenyl group) or a hydrolyzed sol thereof, and tetraethoxytitanium, tetranormalpropoxytitanium, tetraisopropoxytitanium or tetranormalbutoxytitanium is preferably used. In addition, those polycondensation dimer to 10-mer are also used.

The titanium alkoxide may be substituted with —OR in the halogen atom such as a chlorine atom. For example, chlorotriethoxytitanium, dichlorodinormalbutoxytitanium, or trichloronormalbutoxytitanium may be used.

The titanium metal complex is represented by the general formula Ti (OR) _n Y _4-n . In the formula, OR represents an alkoxy group, and Y: represents a chelate. n: represents an integer of 0 to 3. Each R is independently a methyl group, ethyl group, normal propyl group, isopropyl group, normal butyl group, secondary butyl group, methoxyethyl group, ethoxyethyl group or phenyl group.

[Zirconium alkoxide]
In the present invention, in order to contain zirconium oxide in the low reflection film, it is preferable to use a zirconium alkoxide that is excellent in stability without being precipitated in the coating solution for forming the low reflection film.

As such a zirconium alkoxide, the general formula Zr (OR) ₄ , (R is independently methyl group, ethyl group, normal propyl group, isopropyl group, normal butyl group, secondary butyl group, methoxyethyl group, ethoxy And an alkoxy compound thereof or a hydrolysis sol thereof.

As such Zr alkoxide, tetraethoxyzirconium, tetranormalpropoxyzirconium, tetraisopropoxyzirconium or tetranormalbutoxyzirconium and zirconium hydroxide sol which is a hydrolyzate thereof are preferably used.

In addition, Zr alkoxides in which —OR may be substituted with halogen, and examples thereof include chlorotriethoxyzirconium, dichlorodinormalbutoxyzirconium, and trichloronormalbutoxyzirconium.

[Tin alkoxide]
In the present invention, in order to contain tin oxide in the low reflection film, it is preferable to use a tin alkoxide that is excellent in stability without being precipitated in the coating solution for forming the low reflection film.

Examples of such tin alkoxides include tin alkoxides such as tetraethoxytin, tetranormalpropoxytin, tetraisopropoxytin, and tetranormalbutoxytin, or hydrolyzed sols thereof. SnO ₂ is a semiconductor, and imparts an antistatic function to the hydrophilic low reflection film of the hydrophilic low reflection member of the present invention.

[Aluminum alkoxide]
In the present invention, in order to contain aluminum oxide in the low reflection film, it is preferable to use an aluminum alkoxide that is excellent in stability without being precipitated in the coating solution for forming the low reflection film.

Such aluminum alkoxides are represented by the general formula Al (OR) ₃ (where each R is independently methyl, ethyl, isopropyl, normal butyl, secondary butyl, methoxyethyl, ethoxyethyl or phenyl). )), Or hydrolyzed sols thereof, such as triethoxyaluminum, triisopropoxyaluminum, trinormalpropoxyaluminum, or trisecondary butylaluminum, which can be suitably used.

In addition, —OR of aluminum alkoxide may be substituted with a halogen atom such as a chlorine atom, and examples thereof include chlorodiisopropoxyaluminum, chlorodisecondary butylaluminum, dichloroisopropoxyaluminum, and dichlorosecondarybutylaluminum.

The aluminum metal complex is represented by the general formula Al (OR) _n Y _3-n , 1 ≦ n ≦ 3. In the formula, OR represents an alkoxide, and Y: represents a chelate. Here, n represents an integer of 0 to 3. R is each independently a methyl group, an ethyl group, an isopropyl group, a normal butyl group, a secondary butyl group, a methoxyethyl group, an ethoxyethyl group, or a phenyl group. Examples of the chelate include acetylacetone (hereinafter sometimes abbreviated as acac), ethyl acetoacetate, methyl acetoacetate, propyl acetoacetate, trifluoroacetylacetone, hexafluoroacetylacetone, methanesulfonic acid, or trifluoromethanesulfonic acid. In addition, there can be mentioned dimers and trimers obtained by condensation polymerization of aluminum alkoxide and these aluminum metal complexes.

[Hafnium alkoxide]
In the present invention, in order to contain hafnium oxide in the low reflection film, it is preferable to use hafnium alkoxide that is excellent in stability without being precipitated in the coating liquid for forming the low reflection film.

In the method for producing a low-reflection film of the present invention, the hafnium alkoxide for containing hafnium oxide in the low-reflection film includes a general formula Hf (OR) ₄ (R is independently methyl group, ethyl group, normal propyl, Group, isopropyl group, normal butyl group, secondary butyl group, methoxyethyl group, ethoxyethyl group or phenyl group.) Or a hydrolyzed sol thereof.

As such a hafnium alkoxide, tetraethoxyhafnium, tetranormalpropoxyhafnium, tetraisopropoxyhafnium, tetranormalbutoxyhafnium, and a hafnium hydroxide sol which is a hydrolyzate thereof are preferably used.

In addition, the halogen-substituted hafnium alkoxide may be substituted with halogen, and examples thereof include chlorotriethoxyhafnium, dichlorodinormalbutoxyhafnium, and trichloronormalbutoxyhafnium.

[Chromium alkoxides and complexes]
In the present invention, in order to contain chromium oxide in the low reflection film, it is preferable to use a chromium alkoxide that is excellent in stability without being precipitated in the coating solution for forming the low reflection film.

Such chromium alkoxides are represented by the general formula Cr (OR) ₃ (wherein R is independently methyl, ethyl, isopropyl, normal butyl, secondary butyl, methoxyethyl, ethoxyethyl or phenyl). And triethoxypropoxychromium, triisopropoxychromium, trinormalpropoxychrome or trisecondary butylchromium, which are hydrolyzed sols thereof, and can be suitably used.

In addition, chromium acetylacetone is used as a complex, chromium nitrate, chromium chloride, chromium acetate, and chromium phosphate are used as inorganic salts, and octylate and naphthenate are used as organic salts.

[Molybdenum alkoxide]
In the present invention, in order to contain molybdenum oxide in the low reflection film, it is preferable to use molybdenum alkoxide that is excellent in stability without being precipitated in the coating solution for forming the low reflection film.

Molybdenum alkoxide is Mo (OR) ₆ , Mo (OR) _6-n X _n , (1 ≦ n ≦ 5, and R is independently methyl group, ethyl group, normal propyl group, isopropyl group, normal Butyl group, secondary butyl group, t-butyl group, 2-ethylhexyl, methoxyethyl group, methoxypropyl group, ethoxymethyl group, ethoxyethyl group, ethoxypropyl group or phenyl group, X is fluorine atom, chlorine atom, bromine It is an atom or an iodine atom.) The molybdenum alkoxides obtained Ca, Fe, after firing coexist inorganic or organic salts and alkoxides of Mn or the like, calcium molybdate, i.e. CaMoO _4, iron molybdate, i.e. FeMoO _4, molybdenum, manganese, i.e. MnMoO ₄ A molybdate compound such as the above may be used.

[Rare earth alkoxide complex]
In the present invention, in order to contain a rare earth in the low reflection film, it is possible to use a rare earth alkoxide that is excellent in stability without being precipitated in the coating liquid for forming the low reflection film, and use cerium alkoxide or lanthanum alkoxide. Can do.

The rare earth alkoxide is represented by the general formula M (OR) ₃ (M represents a rare earth element: La, Y, Ce, Pr, Nd, Sm or Eu, and R is independently a methyl group, an ethyl group, an isopropyl group, or a normal butyl group. Group, secondary butyl group, methoxyethyl group, ethoxyethyl group or phenyl group). Examples of the cerium alkoxide include triethoxycerium, triisopropoxycerium, and trinormalpropoxycerium. The lanthanum alkoxide includes triethoxy lanthanum, and tri-propoxy yttrium and triethoxy samarium are also used.

In addition, acetylacetone salts as cerium or lanthanum complexes, nitrates, chlorides, acetates and phosphates as rare earth inorganic salts, octylates and naphthenates as organic salts are also used.

[Silica sol]
Silica and metal sols produced by solvent substitution of oxides obtained by hydrolyzing silicon or metal chlorides or alkoxides are commercially available. In the method for producing a low reflection film of the present invention, silica fine particles are used as raw materials. Can be used.

For example, organosilica sol is available from JGC Catalysts & Chemicals Co., Ltd. under the trade names Oscar 1132, Oscar 1232, Oscar 1332, Oscar 1432 or Oscar 1632. -ST-UP, IPA-ST-ZL, EG-ST, NPC-ST-30, DMAC-ST, MEK-ST, commercially available. Organoalumina sols are commercially available from Kawaken Fine Chemical Co., Ltd. under the trade names of Aluminum Sol-CSA55 and Aluminum Sol-CSA110AD.

Further, organic solvent-based antimony oxide sols are commercially available from Nissan Chemical Industries, Ltd. under the trade names Sun Colloid ATL-130 and Sun Colloid AMT-130.

Alternatively, a commercially available sol as an aqueous dispersion can be used after solvent substitution.

Such an aqueous sol is commercially available from Nissan Chemical Industries, Ltd. under the trade name, Snowtex 40, Snowtex O, Snowtex C or Snowtex N, and from JGC Catalysts & Chemicals Co., Ltd. -30H, Cataloid SI-30, Cataloid SN or Cataloid SA are commercially available from Asahi Denka Kogyo Co., Ltd. under the trade names Adelite AT-30, Adelite AT-20N, Adelite AT-20A or Adelite AT-20Q, The trade name, Silica Dole-30, Silica Dole-20A or Silica Dole-20B is commercially available from Nippon Chemical Industry Co., Ltd. The water-based silicon oxide sol is available from Nissan Chemical Industry Co., Ltd. under the trade name, Alumina Sol-100, Alumina Sol 200 or alumina sol-520 is commercially available, water Alumina sol is commercially available from Kawaken Fine Chemical Co., Ltd. under the trade name: Alumina Clear Sol, Aluminum Sol-10, Aluminum Sol-20, Aluminum Sol-SV-102, or Aluminum Sol-SH5. Water-based antimony oxide sol is available from Nissan Chemical Industries, Ltd. Product names A-1550 and A-2550 are commercially available. Aqueous zirconium oxide sols are commercially available from Nissan Chemical Industries, Ltd. NZS-30A and NZS-30B are commercially available. Aqueous tin oxide sols are available from Taki Chemical Co., Ltd. The trade names, Cerames S-8 and Cerames C-10 are commercially available, and water-based titanium oxide sols are commercially available from Taki Chemical Co., Ltd. under the trade names, Tynock A-6, Tynock M-6, and tin oxide and antimony oxide. The water-based sol consisting of is commercially available from Taki Chemical Co., Ltd. under the trade name Cerames F-10. It is.

5. Stability of the coating solution for forming a low reflection film The coating solution for forming a low reflection film applied to a transparent substrate needs to have long-term stability and is preferably stored at room temperature for 30 days or more. When mixing the above hydrolyzable metal alkoxide with the coating solution for forming a low reflection film, it is not possible to reduce the refractive index of the target wavelength in the low reflection film by mixing only one type of metal alkoxide. Needs to be mixed with 2 to 4 metal compounds. In such mixing, even if there is only one kind of metal compound, it can exist as a relatively stable sol, but if the mixed metal compound does not match, gelation, aggregation and precipitation will occur uniformly. It may be difficult to obtain a simple coating film.

In general, the zeta potential is important for the stability of the colloid, and the colloidal particles dispersed in the liquid are often charged positively or negatively due to their own ionicity, dipole characteristics, etc. These colloidal particles are surrounded by charges of the opposite sign in an amount that neutralizes the surface charge, and form an electric double layer composed of a fixed layer and a diffusion layer.

The zeta potential is defined as the “slip surface” potential at which liquid flow starts to occur in the electric double layer formed around the fine particles in the solution. As the zeta potential approaches zero, the repulsive forces of the colloidal particles weaken and eventually aggregate. The zeta potential is an important value in evaluating the properties of the interface. In particular, it is an important index for controlling the stability of colloidal dispersion / aggregation and interaction. In controlling the aggregation and dispersion of colloidal particles, when a plurality of metal alkoxides are mixed and used, it is necessary to carefully select the metal alkoxide to be used in consideration of colloidal stability and pot life.

Colloidal particles are more stable when the surface area is made as small as possible. When the surface area is large, the colloidal particles tend to aggregate. It is presumed that the metal alkoxide exists as very small fine particles in the solution, and the colloidal particles are more dispersed and stabilized by surrounding the relatively large colloidal particles such as colloidal silica.

On the other hand, colloidal particles are charged, and electrostatic repulsion works between the particles. The zeta potential is an indicator of stability such as colloidal dispersion / aggregation and interaction. As the zeta potential approaches zero, the tendency of the colloidal particles to aggregate overcomes the electrostatic repulsion, causing the colloidal particles to aggregate. Conversely, an additive that increases the absolute value of the zeta potential can be adsorbed on the surface of the colloidal particles, and a stable colloid can be obtained by pH control.

In addition, when comparing the stability of metal oxide precursors in sols, such as metal alkoxides, Si-based alkoxides such as alkoxysilanes are slow to hydrolyze and are relatively stable without gelation and solids precipitation over time. However, it is known to those skilled in the art that Al, Zr, Ti, Sn, transition metal, and rare earth alkoxides are unstable.

The coating solution for forming a low reflection film used in the method for forming a low reflection film of the present invention includes colloidal silica having different rod-like and spherical shapes, tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, It is a mixture of at least one metal alkoxide selected from molybdenum or rare earth (lanthanum, cerium) or a hydrolyzate thereof, and in particular, at least one selected from the colloidal silica and tungsten, niobium or tantalum. It has been found that the combination of metal alkoxides is stable for a long time.

6). The low reflection member formed on the surface of the silica coating film made of only the low reflection member silica has a high transmittance at a wavelength of 500 nm. The low reflection member formed on the surface of the low reflection film of the present invention in which silica fine particles having different shapes are bonded to each other using a metal oxide as a binder is presumed to give a transmittance curve having a peak at a wavelength of 500 nm. However, in practice, the peak of maximum transmittance slightly shifts within the range of 500 nm to 900 nm on the long wavelength side, and accordingly, the transmittance in the long wavelength region tends to increase. This is a factor that increases the average transmittance of the low reflection member on which the low reflection film of the present invention is formed.

90% or more of the total number of silica fine particles includes rod-like silica fine particles having a major axis of 5 nm to 100 nm and a major axis / minor axis = 2 to 10 and spherical silica particles having a particle diameter of 5 nm to 50 nm. A dispersion liquid containing at least one metal compound selected from the group consisting of tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, molybdenum, cerium, and lanthanum is mixed with the dispersion liquid. This tendency is conspicuous in the low reflection formed by applying the low reflection film-forming coating liquid on the transparent substrate and then baking by heating to form a low reflection film. In the wavelength region of 500 nm or more and 1200 nm or less, the transmittance Improved. This is due to the inclusion effect of the metal oxide generated by firing the metal alkoxide.

Silica fine particles and metal oxides, that is, tungsten oxide (WO ₃ , refractive index 1.75), niobium oxide (niobium pentoxide: Nb ₂ O ₅ , refractive index 1.9), tantalum oxide (tantalum pentoxide: Ta ₂ O ₅ , refractive index 2.0), titanium oxide (TiO ₂ , refractive index 2.2), zirconium oxide (zirconia: ZrO ₂ , refractive index 1.85), tin oxide (SnO ₂ , refractive index 1.7). , Aluminum oxide (alumina: Al ₂ O ₃ , refractive index 1.65), hafnium oxide (hafnia: HfO ₂ , refractive index 1.90), chromium oxide (Cr ₂ O ₃ , refractive index 2.1), molybdenum oxide (MoO ₂ , MoO ₃ , refractive index 1.80), cerium oxide (ceria: CeO ₂ , refractive index 1.8) or lanthanum oxide (La ₂ O ₃ , refractive index 1.75) are also compatible with each other. Yes, in combination However, when silica fine particles and metal oxides coexist, the combination tends to increase the transmittance in a specific wavelength range. However, when the refractive index of the metal oxide is low, it shifts to a slightly longer wavelength side than the peak showing the maximum value of the transmittance curve of silica alone, and as the refractive index of the metal oxide increases. Furthermore, the peak of the maximum value is shown on the longer wavelength side.

Therefore, using this property, when several kinds of metal oxides having different refractive indexes are mixed with silica fine particles, for example, a metal oxide having a relatively low refractive index has a higher transmittance in the visible region. Higher metal oxides tend to increase the transmittance in a longer wavelength region, so by combining them appropriately, the metal oxides will act as a refractive index adjuster and will increase the transmittance over a wide range of wavelengths. .

For the transparent substrate as the substrate for forming the low reflection film of the present invention, an organic plastic substrate or the like can be used in addition to the inorganic glass substrate. As an example of the inorganic glass substrate, a plate-like material such as soda lime silicate glass, borosilicate glass, aluminosilicate glass, barium borosilicate glass, or quartz glass can be used. Furthermore, these glass substrates also use clear glass products, colored glass products such as green and bronze, functional glass products such as UV and IR cut glass, and safety glass products such as tempered glass, semi-tempered glass, and laminated glass. Can be done. Ceramics are also used for substrates such as Si ₃ N ₄ , SiC, sapphire, Si wafer, GaAs, InP or AlN.

Examples of the plastic substrate include polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), triacetyl cellulose (TAC), and polyimide.

Since the low reflection film of the present invention exhibits an extremely low reflectance even in a single layer film, a low reflection member having a high average transmittance was obtained when formed on one or both surfaces of a transparent substrate.

The low reflection member of the present invention is useful as a cover glass for solar cells. When used as a cover glass for solar cells, high average transmittance and low average reflectance are required, and since solar cells are constantly exposed to sunlight, antifouling properties, water resistance, weather resistance, etc. The material which it has together is desired. As described above, the glass plate with a low reflection film as the low reflection member of the present invention using the colloidal silica having a different shape according to the present invention and at least one metal compound selected from tungsten, tantalum, or niobium is provided. Excellent weather resistance such as dirtiness, heat resistance or wear resistance.

In addition, CIS thin film solar cells and crystalline silicon, which have been developed in recent years, have wide absorption at wavelengths of 400 nm or more and 1200 nm or less, and light in a longer wavelength range than conventional amorphous silicon systems. The absorption peak is in the vicinity of 900 nm. As described above, the low reflection film according to the method of forming a low reflection film of the present invention has high light transmission in the ultraviolet / visible wavelength range, 300 nm to 800 nm, and the near infrared wavelength range, 800 nm to 1200 nm. Therefore, it is suitably used as a cover glass for solar cells having absorption in a long wavelength region as well as amorphous silicon solar cells.

"II. Second Embodiment" (Embodiment of the Present Invention Viewed from Second Viewpoint)

In the present invention, the low-reflection film is a film having a low refractive index (refractive index (nD) measured by an ellipsometer = 1.40 or less) formed on the surface of the substrate to prevent reflection of light on the surface of the substrate. In the present invention, the refractive index is a measured value obtained by spectroscopic ellipsometry measurement using an ellipsometer, and the average transmittance and average reflectance are measured using a spectrophotometer in the wavelength range of light, 380 nm to 1200 nm. This is a value obtained by measuring the transmittance and the reflectance of the light and calculating the average transmittance and the average reflectance in the wavelength region. The transmittance curve is a curve obtained by continuously plotting measured values of transmittance with a spectrophotometer in a certain wavelength region.

The coating liquid for forming a low reflection film is a liquid for coating on the surface of a substrate to form a low reflection film on the substrate. By forming a low reflection film on the surface, if the substrate is transparent, the transmittance increases without loss due to surface reflection. For example, a solar cell cover glass formed with a low-reflection film on the surface has a higher transmittance as the refractive index is lower, the light receiving efficiency of the solar cell is improved, and the energy conversion efficiency from light to electricity is increased. .

Colloidal silica is a colloid in which silicon oxide or its hydrate is agglomerated, and is usually a colloid obtained by dehydration condensation using alkoxysilane as a raw material, or a colloid obtained by removing alkali from an alkali silicate by ion exchange. Is mentioned.

The rod-shaped colloidal silica refers to a long and narrow colloidal silica, and may be on a bead or curved. Further, the spherical colloidal silica refers to a round colloidal silica, and may not be a perfect sphere but a distorted ellipsoid. The maximum diameter of the colloidal silica fine particles is referred to as a long diameter in rod-shaped colloidal silica, and is referred to as a particle diameter in spherical colloidal silica. Moreover, the minimum diameter of rod-shaped colloidal silica is called a short diameter.

The binder means what is bonded. In the present invention, tungsten oxide, niobium oxide or tantalum oxide is present at the interface of the silica fine particles, and the silica fine particles are bonded as a binder.

1. Low Reflective Film Forming Coating Liquid The low reflective film forming coating liquid of the present invention is characterized by comprising a dispersion containing a tungsten compound, a niobium compound or a tantalum compound and colloidal silica. The colloidal silica is preferably at least two types of colloidal silica having different shapes.

When forming a silica film containing silica fine particles, if the silica fine particles are spherical, it is easy to fill, and if the particle size distribution of the silica fine particles is uniform, the packing density can be increased. The film can ensure a packing density of 70% or more by close packing.

However, spherical silica fine particles are bonded to each other by point contact, and if they receive stress from the outside and a shearing force acts between the fine particles, they are brittle and easily broken, and have a poor wear resistance when used as a silica film. was there.

On the other hand, the rod-like silica fine particles are bulky particles having a large aspect ratio, the packing density of the rod-like silica is low, and the rod-like particles are entangled three-dimensionally to form a three-dimensional bridge structure. Has a low filling rate, is bulky and has a high porosity. The silica film is porous, rich in air layer, and exhibits an excellent low reflection performance with an apparent refractive index of 1.25 or less, but the friction strength is extremely brittle, and it can be easily peeled off with light friction and can withstand practical use. There was a problem that was not.

Therefore, it is preferable to use both rod-shaped colloidal silica and spherical colloidal silica in the coating liquid for forming a low reflection film of the present invention.

Assuming that a coating liquid in which colloidal silicas with different shapes coexist is used, the gap formed by the rod-shaped colloidal silica entangled and bonded onto the bridge due to the Brownian motion of the colloidal silica in the liquid when coated on the substrate. In addition, it is considered that a film having a low refractive index, that is, a low reflection film is formed by the effect that the coating film is formed in the state where the spherical silica fine particles are captured and the air having the refractive index of 1 is taken into the gap.

Specifically, in the coating drying process, fine spherical silica particles enter the gap as the solvent evaporates due to capillarity of the voids between the rod-shaped colloidal silica and the spherical colloidal silica, resulting in more silica with different shapes. Therefore, a low-reflective film with excellent frictional strength with more contacts and stronger joints is formed, which is denser using only rod-shaped colloidal silica and coarser porosity using only spherical colloidal silica. it is conceivable that.

However, when colloidal silicas having different shapes coexist, there is a problem that a sol is easily formed and the life of the coating liquid for forming a low reflection film cannot be obtained.

The low-reflection film obtained from the coating liquid for forming a low-reflection film of the present invention has a refraction that is incorporated into microvoids formed by joining silica fine particles having different shapes at the interface with tungsten oxide (WO ₃ ) as a binder. A low refractive index is obtained by air having a refractive index of 1, a rod-shaped colloidal silica prepared in a range of 5 nm to 100 nm in major axis, a spherical colloidal silica prepared in a range of 5 nm to 50 nm in diameter, and tungsten By using the coating liquid for forming a low reflection film in which the compound is dispersed, it is easy to generate microvoids made of air in the low reflection film, and the adhesion strength of the low reflection film to the glass substrate is improved.

In all the colloidal silicas including rod-shaped colloidal silica and spherical colloidal silica contained in the coating solution for forming a low reflection film of the present invention, the colloidal silica is visually observed by a scanning electron microscope (hereinafter abbreviated as SEM). It is preferable that 90% or more of the total number falls within the above range. The remaining portion does not satisfy the above range, in other words, colloidal silica outside the above range, and if more than 10% of colloidal silica outside the above range is contained, it is not preferable because the formation of microvoids is hindered.

In the rod-shaped colloidal silica, if the major axis is shorter than 5 nm, the resulting low reflection film is unlikely to be a film having many minute voids, and if the major axis is longer than 100 nm, minute voids are hardly formed. In spherical colloidal silica, if the particle size is smaller than 5 nm, the resulting low reflection film is unlikely to be a film having many minute voids, and if the particle size is larger than 50 nm, minute voids are not easily formed.

The aspect ratio of the rod-shaped colloidal silica, that is, the major axis / minor axis is preferably 2 or more and 10 or less. When the major axis / minor axis is smaller than 2 or larger than 10, microvoids are hardly formed in the low reflection film.

In the low reflection film obtained by the coating liquid for forming a low reflection film of the present invention, voids are formed by WO ₃ joining silica fine particles having different shapes. When the content of the tungsten compound is less than 5% by mass in terms of WO _{3 with} respect to the mass of the colloidal silica in the coating solution for forming a low reflective film (the mass of the solid, the same applies hereinafter), fewer voids are produced, A film having a low refractive index cannot be obtained. When the content of the tungsten compound is more than 40% by mass in terms of WO ₃ , the resulting film has a high refractive index and is unlikely to be a low reflection film. Preferably, they are 10 mass% or more and 30 mass% or less.

That is, the present invention relates to a low-reflection film-forming coating liquid for forming a low-reflection film on a substrate, particularly a transparent substrate, and comprising a dispersion containing a tungsten compound and colloidal silica. This is a forming coating solution.

The colloidal silica is preferably at least two types of silica having different shapes. Specifically, it is preferable to use rod-shaped colloidal silica having a major axis of 5 nm or more and 100 nm or less and spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less as the colloidal silica having different shapes.

By using the coating liquid for forming a low reflection film of the present invention, the silica fine particles and WO ₃ are bonded, and the content of WO ₃ with respect to the silica fine particles is in the range of 5% by mass or more and 40% by mass or less. A low reflection film having a refractive index of 1.20 or more and 1.40 or less was obtained.

In addition, in the low reflection film by the coating liquid for forming a low reflection film of the present invention, WO ₃ is contained in the range of 5% by mass or more and 40% by mass or less with respect to the silica fine particles. As a result, a low reflection film excellent in durability such as wear resistance and the like that can withstand the load was obtained.

At this time, to the mass of silica, containing a range of WO ₃ is preferably 5 mass% or more, in the range of 40 wt% or less. In the low reflection film of the present invention, voids are formed around the metal oxide. When the content of the metal oxide is less than 5% by mass with respect to the mass of the colloidal silica, a film having a low refractive index cannot be obtained with few voids. When the content of the metal oxide is more than 40% by mass, the resulting film has a high refractive index and does not become a low reflection film. Preferably, it is the range of 10 mass% or less and 30 mass% or more.

In the low reflection film by the coating liquid for forming a low reflection film of the present invention, the low reflection film containing WO ₃ in the range of 5 mass% or more and 40 mass% or less with respect to the silica fine particles is very small in the film. A void is generated and a dense film is formed while being porous, and the refractive index is lowered by taking in air having a refractive index of 1. As described above, the presence of WO ₃ is responsible for increasing the transmittance in a certain wavelength range. By increasing the transmittance in the wavelength range, a film having a low refractive index and extremely transparency was obtained, and the transmittance was improved from the visible light to the infrared light region of the low reflection member formed by the low reflection film. The low reflection base material formed by forming this transparent low reflection film has sufficient low reflection performance even when the low reflection film is a single layer film.

The low reflection film is different silica fine particles in shape by joining the WO ₃ as a binder, while containing microvoids become dense film, silica and WO ₃ at the interface with refractive index 1 taken as the void air Due to the effect of the layer, the refractive index was lowered.

In the coating solution for forming a low reflection film of the present invention, the mass ratio of rod-shaped colloidal silica: spherical colloidal silica, which is easy to generate voids and has excellent adhesion strength to the glass plate, is 20:80 to 80:20. In other ranges, void formation is small and a low reflection film is difficult to obtain, and adhesion strength is poor.

When mass-producing a low reflection member having a low reflection film formed on the substrate surface, the liquid stability of the coating liquid for forming the low reflection film is important. The coating solution for forming a low reflection film of the present invention in which the tungsten compound is dispersed has good liquid stability and is preferably used. Colloidal silica and the tungsten compound are usually synthesized in an organic solvent such as alcohol to form a dispersion, and the coating liquid for forming a low reflection film of the present invention using the tungsten compound may contain water up to a concentration of 50% by mass. It is stable, excellent in safety, and compatible with various application methods.

Normally, when water is added to a dispersion of colloidal silica, the colloidal silica becomes unstable and solids often precipitate, and water is not used, but low reflection using both colloidal silica and the above tungsten alkoxide. In the coating liquid for film formation, the solid content is hardly precipitated even when water is added up to 50 mass% with respect to the total mass of the liquid due to the action of the alkoxide. Further, by adding 1% by mass or more of water to the low reflection film forming coating solution, the wettability with the glass plate is improved. In the low reflection film forming coating solution of the present invention, The content can be arbitrarily adjusted between 1% by mass and 50% by mass. Preferably, they are 1 mass% or more and 30 mass% or less, More preferably, they are 1 mass% or more and 10 mass% or less.

2-a. Tungsten Compound A tungsten compound that is a composition of the coating solution for forming a low reflection film of the present invention will be described.
In the coating solution for forming a low reflection film of the present invention, in order to contain tungsten oxide in the low reflection film, it is preferable to use a tungsten compound that is excellent in liquid stability in the coating solution and has little fear of solid analysis.

Tungsten compounds include halides, hydrates, alkoxides or chelate compounds typified by tungsten chlorides containing W (OR ¹ ) ₆ and WX _{6. In} the present invention, more stable dispersion is possible. It is preferable to use W (OR ¹ ) _6-n X _n that gives a liquid. Here, n is 1 ≦ n ≦ 6, and R ¹ is independently methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t Represents butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, ethoxyethyl group, ethoxypropyl group or phenyl group, and X Is a halogen atom. In addition, the tungsten compound includes calcium tantalate, that is, CaWO ₄ , iron tungstate, that is, FeWO ₄ , manganese tungstate, after the calcination in the presence of inorganic alkoxides such as Ca, Fe, and Mn and alkoxide in the tungsten alkoxide. that like those that generate MnWO tungstate compounds such as _4.

Among these, tungsten chloride and alkoxide, W (OR ² ) _6-n Cl _n are easy to synthesize and are tungsten compounds that are easy to use in the present invention. N is 1 ≦ n ≦ 6, and R ² is independently methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t- A butyl group, an n-amyl group, an i-amyl group or an s-amyl group;

In the coating solution for forming a low reflection film of the present invention, W (OR ² ) ₅ Cl is particularly useful for liquid stability. In the coating solution for forming a low reflection film of the present invention, colloidal is used as a dispersion dispersed in IPA. It is preferable to use a mixture with a silica dispersion. R ² is preferably a methyl group, an ethyl group, an n-propyl group, or an i-propyl group.

W (OR ² ) ₅ Cl can be synthesized in a methanol solvent or an ethanol solvent, but by using IPA as a solvent, it is mixed with a dispersion containing colloidal silica, 1% by mass or more, Even if water is added so as to be 50% by mass or less, a solid content hardly precipitates, and a coating solution for forming a low reflection film having good stability is obtained.

W (OR ² ) ₅ Cl is synthesized by the following reaction in an IPA solvent.
WCl ₆ + 5Na (OR ² ) → W (OR ² ) ₅ Cl + 5NaCl
R ² is independently a methyl group, ethyl group, n-propyl group or i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group. I-amyl group or s-amyl group.

2-b. Niobium Compound A niobium compound that is a composition of the coating solution for forming a low reflection film of the present invention will be described.
In the coating solution for forming a low reflection film of the present invention, in order to contain niobium oxide in the low reflection film, it is preferable to use a niobium compound having excellent liquid stability in the coating solution and less concern for solid analysis. .

The niobium compound, Nb (OR ¹⁾ _5, and Nb (OR ¹⁾ comprising _{NbX 5 5-n X n (} n is ¹ ≦ n ≦ 5.R 1 are each independently a methyl group, an ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, A methoxyethyl group, a methoxypropyl group, an ethoxymethyl group, an ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom). Or the mixed alkoxide (Fe, Mn): Nb = 1: 2 of niobium and Fe or Mn is mentioned.

Among these, Nb (OR ² ) _5-n Cl _n which is a chloride and alkoxide of niobium is a niobium compound that can be easily synthesized and used in the present invention. n is 1 ≦ n ≦ 5, and R ² is independently methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl. Group, n-amyl group, i-amyl group or s-amyl group.

In the coating solution for forming a low reflection film of the present invention, Nb (OR ² ) ₄ Cl is particularly useful for liquid stability. In the coating solution for forming a low reflection film of the present invention, colloidal is used as a dispersion liquid dispersed in IPA. It is preferable to use a mixture with a silica dispersion. R ² is preferably a methyl group, an ethyl group, an n-propyl group, or an i-propyl group.

Nb (OR ² ) ₄ Cl is synthesized by the following reaction in an IPA solvent.
NbCl ₅ + 4Na (OR ² ) → Nb (OR ² ) ₄ Cl + 4NaCl
R ² is independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, or n-amyl group. I-amyl group or s-amyl group.

2-c. Tantalum compound The tantalum compound which is the composition of the coating solution for forming a low reflection film of the present invention will be described.
In the coating solution for forming a low reflection film of the present invention, in order to contain tantalum oxide in the low reflection film, it is preferable to use a tantalum compound that is excellent in liquid stability in the coating solution and has little fear of solid analysis. .

Tantalum compounds include tantalum chlorides, hydrates, alkoxides or chelate compounds. In the present invention, Ta (OR ¹ ) _5-n X _n (where n is ¹ ) which gives a more stable dispersion. ≤ n ≤ 5. R ¹ is independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n An amyl group, an i-amyl group, an s-amyl group, a 2-ethylhexyl group, a methoxyethyl group, a methoxypropyl group, an ethoxymethyl group, an ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom .). Alternatively, a mixed alkoxide (Fe, Mn): Ta = 1: 2 of tantalum and Fe or Mn can be used.

Among these, tantalum chloride and alkoxide Ta (OR ² ) _5-n Cl _n is easy to synthesize and is a tantalum compound easy to use in the present invention. N is 1 ≦ n ≦ 5, and R ² is independently methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t -Butyl group, n-amyl group, i-amyl group or s-amyl group.

In the coating solution for forming a low reflection film of the present invention, Ta (OR ² ) ₄ Cl is particularly useful for liquid stability, and as a dispersion liquid dispersed in isopropyl alcohol in the coating solution for forming a low reflection film of the present invention. It is preferably used by mixing with a dispersion of colloidal silica. R ² is preferably a methyl group, an ethyl group, an n-propyl group or an iso-propyl group.

Ta (OR ² ) ₄ Cl can be synthesized in a methanol solvent or an ethanol solvent, but by using IPA as a solvent, it is mixed with a dispersion containing colloidal silica, 1% by mass or more, Even if water is added so as to be 50% by mass or less, a solid content hardly precipitates, and a coating solution for forming a low reflection film having good stability is obtained.

In the IPA solvent, Ta (OR ² ) ₄ Cl is preferably synthesized by the following reaction.
TaCl ₅ + 4Na (OR ² ) → Ta (OR ² ) ₄ Cl + 4NaCl
R ² is independently a methyl group, ethyl group, n-propyl group or i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group. I-amyl group or s-amyl group.

3. Colloidal silica Next, colloidal silica which is a composition of the coating liquid for forming a low reflection film of the present invention will be described.
The following are mentioned as a silicon compound for producing | generating the colloidal silica for making the coating liquid for low reflective film formation of this invention contain a silica particle.

Preferred silicon compounds include alkoxides, and are represented by the general formula Si (OR) ₄ (wherein R is independently methyl, ethyl, normal propyl, isopropyl, normal butyl, secondary butyl, methoxy Or an hydrolyzate or partial hydrolyzate thereof represented by tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, and the like. Tetranormalpropoxysilane, tetranormalbutoxysilane, tetratertiarybutoxysilane, etc. or a hydrolyzate thereof are preferred. In addition, the alkoxide —OR may be substituted with a halogen atom such as a chlorine atom, and examples thereof include chlorotriethoxysilane, dichlorodinormalbutoxysilane, and trichloronormalbutoxysilane. In the present invention, rod-shaped colloidal silica prepared by dehydrating and condensing these silicon compounds to have a major axis of 5 nm or more and 100 nm or less, and spherical colloidal silica prepared by a particle diameter of 5 nm or more and 50 nm or less are preferably used.

4). The present invention relates to a method for preparing a coating solution for forming a low-reflection film for forming a low-reflection film on a substrate, comprising a dispersion containing a tungsten compound and colloidal silica. It is characterized by mixing the dispersion liquid containing. The colloidal silica is preferably at least two types of colloidal silica having different shapes.

When preparing the coating liquid for forming a low reflection film of the present invention, the colloidal silica dispersion and the tungsten compound dispersion are prepared from methanol, ethanol, An alcohol such as n-propanol or IPA, an ester solvent such as ethyl acetate, or a polar solvent such as acetone is used. In the dispersion of the tungsten compound, an alcohol such as methanol, ethanol, n-propanol or IPA is used. These are mixed and used. Further, pure water may be added.

5. Stability of the coating solution for forming a low reflection film Next, the stability of the coating solution for forming a low reflection film of the present invention will be described in detail below.
When comparing the stability of metal oxide precursors in sols, such as metal alkoxides, Si-based alkoxides such as alkoxysilanes are relatively stable without gelation and solids precipitation over time, but Al-based, It is known to those skilled in the art that Zr-based, Ti-based, and Sn-based alkoxides are unstable.

The coating solution for forming a low reflection film comprising the tungsten compound of the present invention and a dispersion of at least two or more types of colloidal silica having different shapes is prepared such that the water content is in the range of 1% by mass to 50% by mass, Even when water is added, it exhibits excellent liquid stability, and the solid content does not precipitate over a long period of time. Preferably, they are 1 mass% or more and 30 mass%, More preferably, they are 1 mass% or more and 10 mass% or less.

Specifically, the zeta potential is generally important for the stability of colloids, and colloidal particles dispersed in a liquid are often charged positively or negatively due to their ionicity, dipole characteristics, etc. The colloidal particles are surrounded by charges having the opposite sign of the amount that neutralizes the surface charge, and form an electric double layer composed of a fixed layer and a diffusion layer.

The zeta potential is defined as the potential of the “slip surface” where liquid flow begins to occur in the electric double layer formed around the colloidal particles in the colloid. As the zeta potential approaches zero, the repulsive forces of the colloidal particles weaken and eventually aggregate. The zeta potential is an important value in evaluating the interface properties. In particular, it is an important index for controlling the stability of colloidal dispersion / aggregation and interaction. To control the aggregation and dispersion of colloidal particles, when a plurality of metal alkoxides are mixed and used, it is necessary to carefully select the metal alkoxide to be used in consideration of the stability of the colloid and the pot life.

Colloidal particles are more stable when the surface area is made as small as possible. When the surface area is large, the colloidal particles tend to aggregate. It is presumed that the metal alkoxide exists in the solution as extremely small fine particles, and the colloidal particles are more dispersed and stabilized by surrounding the relatively large colloidal particles such as colloidal silica.

On the other hand, colloidal particles are charged, and an electrostatic repulsive force acts between the particles. This repulsive force tends to disperse in the colloidal particles. Since the zeta potential increases in proportion to the magnitude of this electrostatic repulsive force, it becomes an index of the stability of the colloidal particles. When the zeta potential approaches zero, the colloidal particle agglomeration force overcomes the electrostatic repulsive force, and colloidal particle aggregation occurs. Conversely, an additive that increases the absolute value of the zeta potential can be adsorbed on the colloid surface, and a stable colloid can be obtained by pH control.

In addition, when comparing the stability of metal oxide precursors in sols, such as metal alkoxides, Si-based alkoxides such as alkoxysilanes are slow to hydrolyze and are relatively stable without gelation and precipitation of solids over time. However, it is known to those skilled in the art that Al, Zr, Ti, Sn, transition metal, and rare earth alkoxides are unstable.

In addition to tungsten oxide (WO ₃ , refractive index 1.75), titanium oxide (titanium oxide) can be used as a metal oxide that gives a low-reflection film by bonding rod-shaped and spherical silica particles having different shapes as a binder and forming microvoids. (TiO ₂ , refractive index 2.2), zirconium oxide (zirconia: ZrO ₂ , refractive index 1.85), tin oxide (SnO ₂ , refractive index 1.7, aluminum oxide (alumina: Al ₂ O ₃ , refractive index) 1.65), hafnium oxide (hafnia: HfO ₂ , refractive index 1.90), chromium oxide (Cr ₂ O ₃ , refractive index 2.1), cerium oxide (ceria: CeO ₂ , refractive index 1.8), molybdenum oxide (MoO _2, MoO _3, refractive index 1.80), lanthanum oxide (La ₂ O _3, the refractive index 1.75), with the rod-shaped colloidal silica, spherical colloidal silica and the metal Compound by after coating heated baking low reflection film-forming coating solution prepared by dispersing prepared substrate, the low-reflection film.

However, the coating solution for forming a low reflection film is important for long-term stability and is preferably stored at room temperature for 30 days or more. Compared to tungsten oxide, when other metal oxides are used, there are not only some compounds that cannot be stably dispersed in the coating solution for forming a low reflection film, but also solid stability in the liquid deposition. There is a concern that the liquid life is short and the performance of the low reflective film is deteriorated. Moreover, the low reflective film obtained is inferior in hardness and inferior in heat resistance and wear resistance.

The coating liquid for forming a low reflection film of the present invention is a mixture of colloidal silica and a tungsten compound, particularly tungsten alkoxide, and has been found to be stable for a long time in the combination of colloidal silica and tungsten alkoxide. It is.

6). Optical Characteristics of Low Reflective Film and Low Reflective Member Next, optical characteristics of the low reflective member in which the low reflective film is formed on the substrate surface using the coating liquid for forming a low reflective film of the present invention will be described.
When a metal oxide such as silica (refractive index 1.46) and WO ₃ (refractive index 1.75) coexists in the low reflection film, the combination tends to increase the transmittance in a specific wavelength range. . Although the wavelength range cannot be strictly defined, when the refractive index of the metal oxide is low, the peak shifts slightly longer than the peak of the maximum value of the transmittance curve of silica alone. As the refractive index of the metal oxide increases, the peak further appears on the longer wavelength side.

Therefore, in the case of a low reflection film in which WO ₃ having a high refractive index of 1.75 is bonded to silica particles and dispersed in the silica film by utilizing the property that the peak of the maximum value of this transmittance curve is shifted, The presence of WO ₃ increases the transmittance in the long wavelength region of the low reflection member on which the low reflection film is formed, and increases the transmittance in a wide wavelength region.

After applying the coating liquid for forming a low reflection film of the present invention in which a dispersion containing colloidal silica having a different shape is mixed with a dispersion containing tungsten alkoxide, for example, W (OR ² ) ₅ Cl, to a substrate, The low reflection film formed by baking is prominent in this tendency to increase the transmittance in the long wavelength region of the low reflection member on which the low reflection film is formed. In the wavelength region of 800 nm or more and 1200 nm or less, the low reflection film The average transmissivity of the low reflection member formed with was improved.

This is due to the effect of inclusion of WO _{3 in} the low reflection film produced by baking tungsten alkoxide, for example, W (OR ² ) ₅ Cl. R ² is a methyl group, an ethyl group, an n-propyl group or an i-propyl group.

Specifically, the low reflection member formed by forming a silica coat film made only of silica has a high transmittance at a wavelength of 500 nm, and similarly, a low reflection film formed by mixing silica fine particles and WO ₃ is formed. It was estimated that even a low reflection member gives a transmittance curve having a peak at a wavelength of 550 nm, but when actually mixed with WO ₃ , the peak of maximum transmittance shifts between 500 nm and 900 nm on the long wavelength side. As a result, the transmittance in the long wavelength region increases. This is also a factor in increasing the visible light transmittance of the low reflection member on which the low reflection film is formed by the coating liquid for forming a low reflection film of the present invention. In addition, since the peak of maximum transmittance is shifted between 500 nm and 900 nm, the conversion efficiency of the solar cell can be improved by using the low reflection member by the coating solution for forming the low reflection film of the present invention for the cover glass for solar cell. To rise.

In addition, CIS thin film solar cells and crystalline silicon, which have been developed in recent years, have a wide absorption of wavelengths of 400 nm or more and 1200 nm or less, and have a longer wavelength range than conventional amorphous silicon systems. It can absorb light, and its absorption peak is around 900 nm. As described above, the low reflection member formed with the low reflection film by the coating liquid for forming a low reflection film of the present invention has an ultraviolet / visible wavelength range of 300 nm or more and 800 nm or less, and a near infrared wavelength range of 800 nm or more. Since it has high light transmittance at 1200 nm or less, it can be suitably used as a cover glass for solar cells having absorption in a long wavelength region as well as amorphous silicon solar cells.

7. Next, a method for applying the coating solution for forming a low reflection film of the present invention will be described.
It is difficult to form a film having several kinds of compositions on the surface of the substrate by a single film formation in a vacuum film formation method such as a vapor deposition method and a sputtering method, but in a wet coating method such as a sol-gel method, a substrate It is easy to form a film on the surface by a single application. Wet coating methods are expected to have a wide range of applications for low reflection films and light control films for the ultraviolet, visible and infrared regions, starting with the production of cover glass for solar cells, steppers, lasers, organic EL, liquid crystal display elements, LEDs In addition to precision optical equipment such as a lens, a member having a low-reflection film and a light control film such as a lighting fixture, and the like, it is suitably used for the production of general-purpose automotive glass, particularly windshields and lighting fixture protection members.

Moreover, long-term stability is important for a coating solution for forming a low reflection film on a transparent substrate, and it is preferable that the coating liquid can be stored at room temperature for 30 days or more. In particular, the coating solution for forming a low reflection film of the present invention is excellent in long-term stability and is stable even when water is added to 50% by mass or less. Volatility using various organic solvents, viscosity adjustment, solid content concentration Is easy to adjust. Preferably, it is 30 mass% or less, More preferably, it is 1 mass% or more and 10 mass% or less.

Application of the coating solution for forming a low reflection film of the present invention onto a substrate is not only a dip-up method, that is, a dip coating method, but also a spin coating method, a spray coating method, a roller coating method using a reverse roll coater, screen printing, etc. Various coating methods such as coating, brushing, or inkjet are applied.

The coating film formed on the substrate by the coating method is preferably dried at 80 ° C. or higher and 150 ° C. or lower for 10 minutes to 6 hours, and then further heated and fired to form a low reflection film. The heating and firing temperature is determined according to the heat-resistant temperature of the substrate. In the case of a plastic transparent substrate, it is preferable to perform the treatment at about 300 ° C. or less. In addition, the inorganic glass substrate can be heated and fired at a high temperature of about 700 ° C. by adjusting the heating and baking time. As a preferred embodiment, a low reflection film excellent in wear resistance was obtained by baking at 500 ° C. or more and 700 ° C. or less for 2 to 3 minutes, that is, 120 to 180 seconds. In particular, in the combination of a glass plate, colloidal silica, and pre-tungsten alkoxide, a low reflection film excellent in heat resistance and wear resistance was obtained.

8). Low Reflective Film and Low Reflective Member A preferred film thickness on the substrate surface of the low reflective film of the present invention is 20 nm or more and 500 nm or less. If the film thickness is thinner than 20 nm, the wear resistance is inferior and film formation is difficult. On the other hand, if it is thicker than 500 nm, the film thickness becomes non-uniform and it is difficult to form a film. Preferably, they are 50 nm or more and 150 nm or less. In order to obtain a low reflectance with respect to visible light, the thickness is preferably 100 nm or more and 120 nm or less.

In order to obtain a low reflection member, the transparent substrate as a substrate for forming the low reflection film comprising the coating liquid for forming a low reflection film of the present invention includes an inorganic glass substrate, and an organic plastic substrate. Etc. can be used. As an example of the inorganic glass substrate, a plate-like material such as soda lime silicate glass, borosilicate glass, aluminosilicate glass, barium borosilicate glass, or quartz glass can be used. Furthermore, these glass substrates include clear glass products, colored glass products such as green bronze, functional glass products such as UV and IR cut glass, low Fe high transmittance glass, tempered glass, semi-tempered glass or laminated glass. Safety glassware can also be used. Ceramics are also used for substrates such as Si ₃ N ₄ , SiC, sapphire, Si wafer, GaAs, InP or AlN.

Examples of the plastic substrate include polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), triacetyl cellulose (TAC), and polyimide.

Compared with the prior art (Patent Document 1, Patent Document 2), the low reflective film using the coating liquid for forming a low reflective film of the present invention coats the surface of colloidal particles with silica without removing inorganic oxides. Without preparing the composite oxide sol, it is possible to form the low reflection film by directly coating the substrate surface with a single layer film without coating the substrate surface.

In addition, the low reflection member in which the low reflection film is formed by the coating liquid for forming a low reflection film of the present invention is useful as a cover glass for solar cells using a low Fe high-transmission glass substrate whose Fe content is reduced as much as possible. . When used as a cover glass for solar cells, high transmittance and low reflectance are required, and since solar cells are constantly exposed to sunlight, the material has both antifouling properties, water resistance and weather resistance, etc. Is desired. As described above, the glass substrate with a low reflection film produced using the colloidal silica having a different shape according to the present invention and a coating solution for forming a low reflection film using a tungsten compound, particularly tungsten alkoxide, is antifouling and heat resistant. Excellent in wear resistance and wear resistance.

"I. Example of the first embodiment"

Although the low reflective film of this invention, its formation method, and the low reflective member using the same are shown based on an Example, this invention is not limited to a following example.
First, a coating solution for forming a low reflection film for forming a low reflection film on a substrate will be described.

[Coating solution for forming low reflection film using tungsten alkoxide]
A coating solution for forming a low reflection film using two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and tungsten alkoxide having different shapes, and the tungsten alkoxide content relative to the colloidal silica is 14% by mass in terms of oxide. A coating solution for forming a low reflection film (Example 1), a coating solution for forming a low reflection film (Example 2) in which the content of tungsten alkoxide in colloidal silica is 40% by mass in terms of oxide, and tungsten alkoxide in colloidal silica. A coating solution for low reflection film formation (Comparative Example 1) containing 50% by mass in terms of oxide was prepared.
Next, using a rod-shaped colloidal silica and tungsten alkoxide, a coating solution for forming a low reflection film (Example 3) having a tungsten alkoxide content of 20 mass% with respect to the rod-shaped colloidal silica was prepared.
Next, using a spherical colloidal silica and tungsten alkoxide, a coating solution for forming a low reflection film (Example 4) having a tungsten alkoxide content of 20 mass% with respect to the spherical colloidal silica was prepared.

[Coating solution for forming low reflection film using niobium alkoxide]
A coating solution for forming a low-reflection film using two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and niobium alkoxide having different shapes, and the niobium alkoxide content relative to the colloidal silica is 25% by mass in terms of oxide. A coating solution for forming a low reflection film (Example 5), a coating solution for forming a low reflection film having a niobium alkoxide content of 40 mass% in terms of oxide (Example 6), and a niobium alkoxide for colloidal silica. A coating solution for forming a low reflection film (Comparative Example 2) containing 50% by mass in terms of oxide was prepared.
Next, using a rod-shaped colloidal silica and niobium alkoxide, a coating solution for forming a low reflection film (Example 7) having a niobium alkoxide content of 20 mass% with respect to the rod-shaped colloidal silica was prepared.
Next, using a spherical colloidal silica and niobium alkoxide, a coating solution for forming a low reflection film (Example 8) having a niobium alkoxide content of 20 mass% with respect to the spherical colloidal silica was prepared.

[Preparation of coating solution for forming low reflection film using tantalum alkoxide]
A coating solution for forming a low reflection film using two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and tantalum alkoxide having different shapes, and the content of tantalum alkoxide with respect to colloidal silica is 20% by mass in terms of oxide. A coating solution for forming a low reflection film (Example 9), a coating solution for forming a low reflection film (Example 10) in which the content of tantalum alkoxide with respect to colloidal silica is 40% by mass in terms of oxide, and tantalum alkoxide with respect to colloidal silica. A coating liquid for forming a low reflection film (Comparative Example 3) containing 50% by mass in terms of oxide was prepared.
Next, using a rod-shaped colloidal silica and tantalum alkoxide, a coating solution for forming a low reflection film (Example 11) having a tantalum alkoxide content of 20 mass% with respect to the rod-shaped colloidal silica was prepared.
Next, using a spherical colloidal silica and tantalum alkoxide, a coating solution for forming a low reflection film (Example 12) having a tungsten alkoxide content of 20 mass% with respect to the spherical colloidal silica was prepared.

[Coating liquid of comparative example]
Next, a coating solution (Comparative Example 4) using only two types of colloidal silica and not using a metal alkoxide was prepared. Moreover, the coating liquid (Comparative Example 5) using two types of colloidal silica and TEOS was prepared. Also, a coating solution consisting of only tungsten alkoxide (Comparative Example 6), only niobium alkoxide (Comparative Example 7) or tantalum alkoxide (Comparative Example 8) was prepared.

The glass substrate was coated with the coating solution for forming a low reflection film according to Examples 1 to 12 and the coating solution of Comparative Examples 1 to 8 to form a low reflection film, and the physical properties of the obtained glass substrate with the low reflection film were evaluated. . In addition, soda-lime silicate glass by the float process was used for the glass substrate.

The compositions of the coating solutions for forming a low reflection film in Examples 1 to 12 and the coating solutions in Comparative Examples 1 to 8 are summarized in Table 1.

Next, the coating liquid for forming a low reflection film of Examples 1 to 12 and the coating liquid of Comparative Examples 1 to 8 were applied to a colorless and transparent glass substrate having a thickness of 3 mm and a size of 100 mm × 100 mm to obtain a glass substrate with a low reflection film. Obtained. Table 2 shows a method for evaluating physical properties of the obtained glass substrate with a low reflection film.

Hereinafter, Examples 1 to 12 and Comparative Examples 1 to 5 of the present invention will be described in detail.

[Examples 1 to 4, Comparative Example 1 (example using tungsten alkoxide)]
Examples using tungsten alkoxide are shown in Examples 1 to 4 and Comparative Example 2 below.

Example 1

<Preparation of colloidal silica dispersion>
In a three-necked flask with a volume of 1000 ml, a rod-shaped colloidal silica isopropanol (hereinafter abbreviated as IPA) dispersion (manufactured by Nissan Chemical Industries, Ltd., product number, IPA-ST, solid content concentration 30.3 mass%, major axis 10 nm to 20 nm). ) 16.34 g was weighed in and 231.21 g of ethanol was added with stirring. Next, 111.50 g of ethanol was added to 12.28 g of a spherical colloidal silica dispersion (manufactured by JGC Catalysts and Chemicals, product number, OSCAL1432, solid concentration 20.2 mass%, particle size 5 nm to 10 nm) with stirring. Those were mixed to obtain 371.3 g of a colloidal silica dispersion.
The mixing ratio of the rod-shaped colloidal silica and the spherical colloidal silica was 67:33 by mass ratio.

<Preparation of tungsten alkoxide dispersion>
Under a nitrogen stream, 5.86 g of tungsten hexachloride (WCl ₆ ) was collected in a three-necked flask with a capacity of 300 ml, and 79.5 g of IPA cooled to 5 ° C. was added. To this was added 1.70 g of metallic sodium (manufactured by Wako Pure Chemical Industries, Ltd.), then refluxed in a nitrogen atmosphere at 75 ° C. for 24 hours, and cooled to room temperature (about 20 ° C.). Subsequently, pressure filtration was performed, and tungsten alkoxide (W (OCH ₂ (CH ₃ ) ₂ ) ₅ Cl) and NaCl as a by-product were separated by filtration. The concentration of tungsten in the filtrate was 4.22% by mass in terms of WO ₃ . In this way, about 70 g of a dispersion of tungsten alkoxide (W (OCH ₂ (CH ₃ ) ₂ ) ₅ Cl) was obtained.

<Preparation of coating solution for forming low reflection film>
While stirring at room temperature in a nitrogen atmosphere at room temperature in 179.8 g of the colloidal silica dispersion, 13.9 g of the tungsten alkoxide dispersion synthesized above was gradually added dropwise over 3 hours to give a pale brown transparent liquid. Obtained. After mixing, the mixture is further refluxed at 70 ° C. for 6 hours under a nitrogen atmosphere, and the colloidal silica and tungsten alkoxide in terms of mass ratio in terms of oxide are SiO ₂ : WO ₃ = 86: 14, that is, tungsten alkoxide in terms of oxide. A coating solution for forming a low reflection film having a solid concentration of 2.2% by mass was prepared to 14% by mass.

<Production of glass substrate with low reflection film>
The surface of a glass substrate having a thickness of 3 mm and a size of 100 mm × 100 mm was wet-polished with alumina particles, washed with distilled water and then with IPA, and then heated to 100 ° C. and dried. When the contact angle of pure water was measured in order to confirm the surface state, it showed a strong hydrophilic property with a contact angle of 5 ° or less and was clean.
Next, a low reflection film was formed on the surface of the glass substrate by a dip method.
The washed glass substrate was dipped in the low reflection film forming coating solution and pulled upward at a speed of 3.4 mm / sec to apply the low reflection film forming coating solution to both surfaces of the glass substrate. It was dried at 50 ° C. for 30 minutes and further dried at 110 ° C. for 60 minutes. This is put into a baking furnace heated to 750 ° C., held for 150 seconds, taken out, rapidly cooled at room temperature, and formed with a low reflection film having a light blue reflection color on both sides, and a glass with a low reflection film A substrate was obtained.

FIG. 1 shows a drawing-substitute SEM photograph of the surface of a glass substrate with a low reflection film using tungsten alkoxide.
It is an enlarged photograph by SEM of the low reflection film formed on the glass substrate using the coating liquid for low reflection film formation. The ordered particles are silica fine particles, and the silica fine particles are bonded by tungsten oxide serving as a binder and are a porous film containing a microvoid and a hard film.

<Evaluation of glass substrate with low reflection film>
FIG. 2 shows a transmittance curve of a glass substrate with a low reflection film obtained using tungsten alkoxide.
A low reflection film was formed on the surface of the glass substrate by the sol-gel method using the coating liquid for forming the low reflection film. A transmittance curve of 1 is a transmittance curve of a glass substrate with a low reflection film applied to the glass substrate at a lifting speed of 3 mm / sec from the coating tank, and similarly, a transmittance curve of 2 is a lifting speed of 5 mm / sec. The transmittance curve of the glass substrate with a low reflection film is a transmittance curve of the glass substrate with a low reflection film at a pulling rate of 7 mm / sec. As the pulling speed increases, the film thickness increases, and the peak of the maximum transmittance shifts to the long wavelength side. Compared to the transmittance curve (represented by R) of a glass substrate that does not have a reference low-reflection film, the transmittance is improved in the entire wavelength region.

When the physical property values were measured in accordance with the physical property evaluation methods shown in Table 2, the average transmittance of the glass substrate with a low reflection film formed by forming the low reflection film on both surfaces under the above-described pulling speed of 3.4 mm / sec was The average transmittance was 98.0%, and the average transmittance was improved by 7.5% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflection film.

Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 108 nm. Further, when the refractive index n was measured by an ellipsometer, n = 1.298, and satisfactory performance was obtained as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off and the average transmittance was measured to be 97.4%, which was 0.6% lower than that before the test. Moreover, when the contact angle of the pure water was measured, it was 6.5 °, indicating strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days at room temperature (25 ° C.) and 50% relative humidity was measured, it was 9.0 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 2
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Next, the tungsten alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that 40% by mass of tungsten alkoxide in terms of oxide is contained with respect to the mass of the colloidal silica, that is, SiO _2. : WO ₃ = 60: 40 In addition, a coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass was prepared. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 2, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 1 under the condition of a pulling speed of 3.4 mm / sec. The average transmittance was 97.3%, and the average transmittance was improved by 6.8% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 105 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.279, and satisfactory performance was obtained as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 96.6%, which was 0.7% lower than before the test. Moreover, when the contact angle of the pure water was measured, it was 12 °, indicating strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days was measured at room temperature (25 ° C.) and a relative humidity of 50%, it was 5.2 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Comparative Example 1
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Next, the tungsten alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that 50% by mass of tungsten alkoxide is contained in terms of oxide with respect to the mass of the colloidal silica, that is, SiO _2. : WO ₃ = 50: 50 and a coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass was prepared. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 2, the average transmittance of the film-coated substrate formed on both surfaces in the same manner as in Example 1 under the condition of a pulling rate of 3.4 mm / sec, The glass substrate was improved 1.6% from the glass substrate before the film was provided, and was 92.1%, and the desired performance as a glass substrate with a low reflection film was not obtained.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 122 nm. Further, the refractive index of the film was measured with an ellipsometer, and n = 1.362. The refractive index was higher than desired.

This is a result of the content of the tungsten compound with respect to the colloidal silica deviating from the preferable content range of 5% by mass or more and 40% by mass or less in terms of oxide.

Example 3
After the IPA dispersion of rod-shaped colloidal silica used in Example 1 (manufactured by Nissan Chemical Industries, Ltd., product number, IPA-ST, solid content concentration 30.3 mass%, major axis 10 nm to 20 nm) was diluted with ethanol, tungsten alkoxide was used. Is a mass ratio in terms of oxide, SiO ₂ : WO ₃ = 80: 20, that is, a tungsten alkoxide is prepared so as to be 20% by mass in terms of oxide, and a low reflection film having a solid content concentration of 2.0% by mass A forming coating solution was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 2, a low reflective film-coated glass substrate formed by forming low reflective films on both sides in the same manner as in Example 1 under the pulling rate of 3.4 mm / sec. The average transmittance was 97.5%, and the average transmittance was improved by 7.0% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 112 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.292, and the desired performance was obtained as a substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partially peeled, and the frictional strength of the glass substrate with the low reflective film of Example 1 and Example 2 It was inferior compared.

This is a result of forming a film having inferior frictional strength because the colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a different specific particle size shape is not used but only the rod-like colloidal silica is used.

Example 4
After the IPA dispersion of spherical colloidal silica used in Example 1 (manufactured by JGC Catalysts & Chemicals Co., Ltd., product number, OSCAL1432, solid concentration 20.2 mass%, particle size 5 nm to 10 nm) was diluted with ethanol, tungsten alkoxide was obtained. Preparation of SiO ₂ : WO ₃ = 80: 20 by mass ratio in terms of oxide, that is, tungsten alkoxide is 20% by mass in terms of oxide to form a low reflection film having a solid content concentration of 2.0% by mass A coating solution was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 2, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 1 under the condition of a pulling rate of 3.0 mm / sec. The average transmittance was 96.9%, and the average transmittance was improved by 6.4% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 109 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.303, and the desired performance as a low reflection film was obtained.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partially peeled, and the frictional strength of the glass substrate with the low reflective film of Example 1 and Example 2 It was inferior compared.

This is a result of forming a film having inferior frictional strength because only the spherical colloidal silica was used without using colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a specific particle size.

[Examples 5 to 8, Comparative Example 2 (example using niobium alkoxide)]
Examples using niobium alkoxides are shown in Examples 5 to 8 and Comparative Example 2 below.

Example 5

<Preparation of colloidal silica dispersion>
IPA dispersion of rod-shaped colloidal silica (IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid concentration 15.2% by mass, major axis 40 nm to 100 nm) was weighed into a 1000 ml three-necked flask, and IPA 186.6 g was added with stirring. Next, IPA, 194.8 g added to 23.41 g of spherical colloidal silica (manufactured by JGC Catalysts and Chemicals, product number, OSCAL1632, solid content concentration 20.5 mass%, particle size 8 nm to 15 nm) with stirring By mixing, 436 g of colloidal silica dispersion was obtained.
The mixing ratio of the rod-shaped colloidal silica and the spherical colloidal silica was 50:50 by mass ratio.

<Preparation of niobium alkoxide dispersion>
Under a nitrogen stream, 9.76 g of niobium pentachloride (NbCl ₅ ) was collected in a 500 ml three-necked flask, and 205 g of IPA cooled to 5 ° C. was added. To this was added 3.32 g of metallic sodium (manufactured by Wako Pure Chemical Industries, Ltd.) to obtain 218 g of a slurry in which niobium alkoxide (Nb (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl) and by-product NaCl were mixed.
Next, the mixture was refluxed in a nitrogen atmosphere at 75 ° C. for 24 hours and cooled to room temperature (about 20 ° C.). Subsequently, pressure filtration was performed, and niobium alkoxide (Nb (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl) and by-product NaCl were separated by filtration. The concentration of niobium in the filtrate was 2.3% by mass in terms of Nb ₂ O ₅ . This filtrate was used as a dispersion of niobium alkoxide (Nb (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl).

<Preparation of coating solution for forming low reflection film>
While stirring at room temperature in a nitrogen atmosphere at room temperature, the niobium alkoxide dispersion synthesized above, 139.74 g, was gradually added dropwise to the colloidal silica dispersion over 3 hours to obtain a milky white transparent liquid. After mixing, the mixture is further refluxed under a nitrogen atmosphere under 70 for 8 hours. The colloidal silica and niobium alkoxide are in a mass ratio in terms of oxide, SiO ₂ : Nb ₂ O ₅ = 3: 1, that is, niobium alkoxide is converted into oxide. To 25 mass%, and this was used as a coating solution for forming a low reflection film.

<Production of glass substrate with low reflection film>
The surface of a glass substrate having a thickness of 3 mm and a size of 100 mm × 100 mm was wet-polished with alumina particles, washed with distilled water and then with IPA, and then heated to 100 ° C. and dried. When the contact angle of pure water was measured in order to check the surface condition, it showed a strong hydrophilic property with a contact angle of 5 ° or less and was clean.
The washed glass substrate was immersed in the low reflection film forming coating solution, and pulled upward at a speed of 3.0 mm / sec by a dipping method to apply the low reflection film forming coating solution to both surfaces of the glass substrate. It was dried at 50 ° C. for 30 minutes and further dried at 110 ° C. for 60 minutes. This is put into a baking furnace heated to 750 ° C., held for 150 seconds, taken out, rapidly cooled at room temperature, and a low reflection film having a light blue reflection color is formed on both sides. A glass substrate was obtained.

FIG. 3 shows a drawing-substitute SEM photograph of the surface of the glass substrate with a low reflection film using niobium alkoxide.
It is an enlarged photograph by SEM of the low reflection film formed on the glass substrate using the coating liquid for low reflection film formation. The ordered particles were silica, and the silica fine particles were joined by niobium oxide serving as a binder, and became a hard film while being a porous film containing microvoids.

<Evaluation of glass substrate with low reflection film>
FIG. 4 shows a transmittance curve of a glass substrate with a low reflection film using niobium alkoxide.
A low reflection film was formed on the surface of the glass substrate by the sol-gel method using the coating liquid for forming the low reflection film. A transmittance curve of 1 is a transmittance curve of a glass substrate with a low reflection film applied to the glass substrate at a lifting speed of 3 mm / sec from the coating tank. Similarly, a transmittance curve of 2 is a lifting speed of 5 mm / sec. The transmittance curve of the glass substrate with a low reflection film is a transmittance curve of the glass substrate with a low reflection film at a pulling rate of 7 mm / sec. As the pulling speed increases, the film thickness increases, and the peak of the maximum transmittance shifts to the long wavelength side. Compared to the transmittance curve (represented by R) of a glass substrate that does not have a reference low-reflection film, the transmittance is improved in the entire wavelength region.

Subsequently, according to the physical property evaluation method of Table 2, the average transmittance of the glass substrate with a low reflection film formed by forming a low reflection film on both surfaces in the same manner as in Example 5 under the condition of a lifting speed of 3.0 mm / sec. As a result, the average transmittance was 98.2%, and the average transmittance was improved by 7.7% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflection film. . Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 113 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.275, which was satisfactory as a glass substrate with a low reflection film.

The frictional strength of this coating was rubbed back and forth 3000 times with a load of 15 g / cm ^{2 on} the surface of a glass substrate with a low reflection film using a flannel cloth attached to a pad using a flannel abrasion tester. Strength was evaluated. The appearance had a slight haze, but the color tone did not change, and the average transmittance was 97.7%, which was slightly decreased by 0.5% compared to before the test. When the pure water contact angle was measured, it showed a strong hydrophilic property at 6.5 °.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days at 25 ° C. and 50% relative humidity was measured, it was 6.7 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 6
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 5. Next, the niobium alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that the niobium alkoxide is contained in an amount of 40% by mass in terms of oxide based on the mass of the colloidal silica, that is, Nb ₂ A coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass was prepared so that O ₅ : WO ₃ = 60: 40. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods shown in Table 2, a low reflective film-coated glass substrate formed by forming low reflective films on both sides in the same manner as in Example 5 under the condition of a pulling speed of 3.0 mm / sec. The average transmittance was 98.0%, and the average transmittance was improved by 7.5% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 108 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.281, which was a satisfactory performance as a low reflective film glass substrate.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 97.1%, which was 0.9% lower than before the test. Moreover, when the contact angle of the pure water was measured, it was 18 °, indicating strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days at room temperature (25 ° C.) and 50% relative humidity was measured, it was 11.2 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Comparative Example 2
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 5. Next, the niobium alkoxide dispersion prepared in Example 5 is added to the colloidal silica dispersion so that the niobium alkoxide is 50% by mass in terms of oxide with respect to the mass of the colloidal silica. A coating solution for forming a low reflection film having a solid content concentration of 2.0% by mass was prepared so that SiO ₂ : Nb ₂ 0 ₅ = 50: 50. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 3 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 2, the average transmittance of the film-coated substrate formed on both surfaces in the same manner as in Example 5 under the condition of a pulling speed of 3.0 mm / sec is The glass substrate was -0.9% lower than the glass substrate before the film was formed, and it was 89.6%, which was not a glass substrate with a low reflection film.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 115 nm. Further, when the refractive index of the film was measured with an ellipsometer, n = 1.353, and the refractive index was higher than desired.

This is a result of the content of niobium alkoxide with respect to colloidal silica deviating from the preferable content range of 5% by mass or more and 40% by mass or less in terms of oxide.

Example 7
After diluting the IPA dispersion of rod-shaped colloidal silica used in Example 5 (IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration 15.2 mass%, major axis 40 nm to 100 nm) with IPA, niobium alkoxide was obtained. SiO ₂ : Nb ₂ O ₅ = 80: 20 in terms of mass in terms of oxide, that is, niobium alkoxide is prepared so as to be 20% by mass in terms of oxide, and low reflection with a solid content concentration of 2.0% by mass A coating solution for film formation was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods shown in Table 2, a low reflection film was formed on both surfaces under the condition of a pulling speed of 3.0 mm / sec. The average transmittance of the low reflective film-coated glass substrate is 97.2%, and the average transmittance of the glass substrate without the low reflective film is 96.7%, which is 6.7%. % Improved. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 102 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.296, which was satisfactory as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The frictional strength of the low reflective film is cloudy and partially peeled after 3000 reciprocating frictions according to the flannel abrasion test, and compared with the frictional strength of the substrates with the low reflective film of Example 5 and Example 6. It was inferior.

This is a result of forming a film having inferior frictional strength because only spherical colloidal silica was used without using spherical colloidal silica.

Example 8
After the IPA dispersion of spherical colloidal silica used in Example 5 (manufactured by JGC Catalysts and Chemicals Co., Ltd., product number, OSCAL1632, solid concentration 20.5 mass%, particle size 8 nm to 15 nm) was diluted with IPA, niobium alkoxide was obtained. SiO ₂ : Nb ₂ O ₅ = 80 in terms of mass ratio in terms of oxide
: 20, that is, niobium alkoxide was prepared so as to be 20% by mass in terms of oxide, and a coating solution for forming a low reflection film having a solid content concentration of 2.0% by mass was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 2, the average of the glass substrates with low reflection films formed on both surfaces in the same manner as in Example 5 under the condition of a pulling speed of 3.0 mm / sec. The transmittance was 97.6%, and the average transmittance was improved by 7.1% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 117 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.284, which was a satisfactory performance as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partially peeled. It was inferior compared.

This is a result of forming a film having inferior frictional strength because only the spherical colloidal silica was used without using colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a specific particle size.

[Examples 9 to 12, Comparative Example 3 (example using tantalum alkoxide)]
Examples in which tungsten alkoxide is used in Examples 9 to 12 and Comparative Example 3 are shown below.

Example 9
<Preparation of colloidal silica dispersion>
14.28 g of rod-shaped colloidal silica IPA dispersion (manufactured by Nissan Chemical Industries, product number, IPA-ST-UP, solid content concentration 15.2 mass%, major axis 40 nm to 100 nm) is weighed into a three-neck flask with a capacity of 1000 ml. And IPA 106.14 g was added with stirring. Next, IPA 264.2 g was added to spherical colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name, methanol silica sol, solid content concentration 30.2 mass%, particle size 10 nm to 20 nm) with stirring. By mixing, 401 g of colloidal silica dispersion, 401 g, was obtained.
In this way, in the colloidal silica dispersion, the mass ratio in terms of oxide between rod-like colloidal silica and spherical colloidal silica in terms of oxide (SiO ₂ ) is rod-like colloidal silica: spherical colloidal silica = 30: 70. Prepared. The solid content concentration is 1.8% by mass.

<Preparation of tantalum alkoxide dispersion>
Under a nitrogen stream, 8.20 g of tantalum pentachloride was collected in a 500 ml three-necked flask, and 255.10 g of methanol cooled on ice at 5 ° C. was added. To this was added 28% by mass sodium methoxide (Wako Pure Chemical Industries, Ltd.), 17.66 g, and tantalum alkoxide (Ta (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl) and by-product NaCl were mixed. 281 g of slurry was obtained.
Next, the mixture is refluxed at 65 ° C. for 16 hours in a nitrogen atmosphere, cooled to room temperature (about 22 ° C.), and then tantalum alkoxide (Ta (OCH ₂ (CH ₃ ) ₂ ) ₄ by pressure filtration while flowing nitrogen. Cl) and by-product NaCl were filtered off. The concentration of tantalum in the filtrate was 1.8% by mass in terms of Ta ₂ O ₅ .

<Preparation of coating solution for forming low reflection film>
While stirring at room temperature in a nitrogen atmosphere at room temperature in 401 g of the colloidal silica dispersion, 100.3 g of the tantalum alkoxide dispersion synthesized above was gradually added dropwise over 2 hours at room temperature to give a slightly milky white transparent liquid. Obtained. After mixing, the mixture is further refluxed at 60 ° C. for 8 hours under a nitrogen stream, so that colloidal silica and tantalum alkoxide are in a mass ratio in terms of oxide, SiO ₂ : Ta ₂ O ₅ = 80: 20, that is, tantalum alkoxide. Was prepared so as to be 20% by mass in terms of oxide and used as a coating solution for forming a low reflection film.

<Production of glass substrate with low reflection film>
The surface of a glass substrate having a thickness of 3 mm and a size of 100 mm × 100 mm was wet-polished with alumina particles, washed with distilled water and then with IPA, and then heated to 100 ° C. and dried. When the contact angle of pure water was measured in order to check the surface condition, it showed a strong hydrophilic property with a contact angle of 5 ° or less and was clean.
The washed glass substrate was immersed in the low reflection film forming coating solution and coated on both sides by a dipping method at a lifting speed of 4.0 mm / sec. It was dried at 50 ° C. for 30 minutes and further dried at 110 ° C. for 60 minutes. This is put into a baking furnace heated to 750 ° C., held for 150 seconds, taken out, rapidly cooled at room temperature, and a low reflection film having a light blue reflection color is formed on both sides. A glass substrate was obtained.

FIG. 5 shows a drawing-substitute SEM photograph of the surface of the glass substrate with a low reflection film using tantalum alkoxide.
It is an enlarged photograph by the SEM mirror of the low reflection film formed on the glass substrate using the said coating liquid for low reflection film formation. The regularly arranged particles are silica, and the silica fine particles are bonded by a tantalum oxide serving as a binder and are a porous film containing a microvoid and a hard film.

<Evaluation of glass substrate with low reflection film>
FIG. 6 shows a transmittance curve of a glass substrate with a low reflection film using tantalum alkoxide.
A low reflection film was formed on a glass substrate by the sol-gel method using the low reflection film forming coating solution. A transmittance curve of 1 is a transmittance curve of a glass substrate with a low reflection film applied to the glass substrate at a lifting speed of 3 mm / sec from the coating tank, and similarly, a transmittance curve of 2 is a lifting speed of 5 mm / sec. The transmittance curve of the glass substrate with a low reflection film is a transmittance curve of the glass substrate with a low reflection film at a pulling rate of 7 mm / sec. As the pulling speed increases, the film thickness increases, and the peak of the maximum transmittance shifts to the long wavelength side. Compared to the transmittance curve (represented by R) of a glass substrate that does not have a reference low-reflection film, the transmittance is improved in the entire wavelength region.

When the average transmittance of the glass substrate with a low reflection film at the above-described pulling speed of 4.0 mm / sec was measured, the average transmittance was 97.9%, and the average transmittance of the glass substrate without the low reflection film was 90%. Compared to .5%, the average transmittance was improved by 7.4%. Next, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 121 nm. Further, when the refractive index n was measured with an ellipsometer, the refractive index was n = 1.260, which was satisfactory as a glass substrate with a low reflection film.

Next, the frictional strength of this coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. Although the appearance was somewhat haze, the color tone was unchanged, and the average transmittance was measured to be 97.5%, which was 0.4% lower than before the test. Moreover, when the contact angle of the pure water was measured, it was 8.0 ° and showed strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days at 25 ° C. and 50% relative humidity was measured, it was 9.0 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 10
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 9. Then, to the colloidal silica dispersion, a tantalum alkoxide dispersion prepared in Example 1, relative to the weight of the colloidal silica was added as tantalum alkoxide is contained 40 mass% in terms of oxide, i.e., Ta ₂ A coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass was prepared so that O ₅ : WO ₃ = 60: 40. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 9, and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods shown in Table 2, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 9 under the condition of a pulling speed of 3.4 mm / sec. The average transmittance was 97.1%, and the average transmittance was improved by 6.6% compared to the average transmittance 90.5% of the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 109 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.279, which was a satisfactory performance as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 96.5%, which was 0.6% lower than that before the test. Further, when the contact angle of pure water was measured, it was 19.3 ° and showed strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days was measured at room temperature (25 ° C.) and a relative humidity of 50%, it was 3.6 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Comparative Example 3
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 9. Next, the tantalum alkoxide dispersion prepared in Example 5 is added to the colloidal silica dispersion so that the tantalum alkoxide is contained in an amount of 50% by mass in terms of oxide with respect to the mass of the colloidal silica, that is, SiO _2. : Ta ₂ O ₅ = 50: 50, and a coating solution for forming a low reflection film having a solid content concentration of 1.7% by mass was prepared. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 9, and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 2, the average transmittance of the film-coated substrate formed on both surfaces in the same manner as in Example 9 under the condition of a pulling rate of 3.0 mm / sec is The glass substrate was 2.7% higher than the glass substrate before the film was formed, and it was 93.3%, and the desired performance as a glass substrate with a low reflection film could not be obtained.

Next, the film thickness was measured with a stylus type surface shape measuring instrument to be 107 nm. Moreover, when the refractive index of the film was measured with an ellipsometer, it was n = 1.310, and the refractive index was higher than desired.

This is a result of the content of the tantalum compound with respect to the colloidal silica deviating from the preferable content range of 5% by mass or more and 40% by mass or less in terms of oxide.

Example 11
After diluting the IPA dispersion of rod-shaped colloidal silica used in Example 9 (IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration 15.2 mass%, major axis 40 nm to 100 nm) with IPA, tantalum alkoxide was obtained. SiO ₂ : Ta ₂ O ₅ = 80: 20 by mass ratio in terms of oxide, that is, tantalum alkoxide is prepared to be 20% by mass in terms of oxide, and low reflection with a solid content concentration of 2.0% by mass A coating solution for film formation was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 2, the average of the glass substrates with low reflection films formed on both surfaces in the same manner as in Example 9 under the condition of a pulling rate of 3.0 mm / sec. The transmittance was 96.9%, and the average transmittance was improved by 6.5% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 115 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.294, which was a satisfactory performance as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The frictional strength of the low-reflection film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partially peeled. It was inferior compared.

This is a result of forming a film having inferior frictional strength because the colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a different specific particle size shape is not used but only the rod-like colloidal silica is used.

Example 12
The IPA dispersion of spherical colloidal silica used in Example 9 (manufactured by Nissan Chemical Industries, Ltd., trade name, methanol silica sol, solid content concentration 30.2 mass%, particle size 10 nm to 20 nm) was diluted with IPA, and then tantalum. The alkoxide is prepared in such a manner that the alkoxide is in a mass ratio in terms of oxide, SiO ₂ : Nb ₂ O ₅ = 80: 20, that is, the tantalum alkoxide is 20% by mass in terms of oxide. A coating solution for forming a low reflection film was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 9, and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 2, the average of the glass substrates with low reflection films formed on both surfaces in the same manner as in Example 9 under the condition of a pulling rate of 3.0 mm / sec. The transmittance was 97.0%, and the average transmittance was improved by 6.5% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Then, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 113 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.307, which was a satisfactory performance as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partly peeled off, and compared to the glass substrates with the low reflective film of Examples 5 and 6. It was inferior in strength.

This is a result of forming a film having inferior frictional strength because only the spherical colloidal silica was used without using colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a specific particle size.

Comparative Example 4
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film. . Unlike Examples 1 to 12, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.

When the physical property values were measured according to the physical property evaluation method, the average transmittance was 97.4%, which was 7.6% higher than the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.

The glass substrate with a low reflection film of Comparative Example 4 was inferior in film strength, poor in durability, and could not withstand practical use.

Comparative Example 5
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, and TEOS was added so that the mass ratio with respect to the colloidal silica was 20% by mass. After coating on a glass substrate in the same procedure as in Example 1, it was heated and fired to obtain a glass substrate with a low reflection film. Unlike Examples 1 to 12, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.

When the physical property values were measured according to the physical property evaluation method, the average transmittance was 94.6%, which was 4.1% higher than that of the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.

Comparative Example 6
Only the tungsten alkoxide solution prepared in Example 1 was applied to a glass substrate and heated and fired in the same manner as in Example 1 to form a film, thereby obtaining a glass substrate with a tungsten oxide film. A cloudy ground glass substrate having a haze of 46.8% was obtained.

Comparative Example 7
When only the niobium alkoxide solution prepared in Example 5 was applied to a glass substrate and heated and fired in the same manner as in Example 5 to form a film and measured with an ellipsometer to obtain a glass substrate with a niobium oxide film, the film was refracted. The rate was 1.90, and the average transmittance was lower than that of a glass substrate on which a low reflective film was not formed.

Comparative Example 8
Only the tantalum alkoxide solution prepared in Example 9 was applied to a glass substrate and heated and fired in the same manner as in Example 9 to form a film, thereby obtaining a glass substrate with a tantalum oxide film. The refractive index of the film was 1.86, and the average transmittance was lower than that of the glass substrate on which the low reflection film was not formed.

(result)
The evaluation results are shown in Table 3.

The glass substrate with a low reflection film on which the low reflection film of the present invention is formed is excellent in hydrophilicity and antifouling properties, has antistatic properties, and is hardly contaminated. In particular, as shown in Table 3, the low reflective film-coated substrates of Examples 1, 2, 5 and 6 and Examples 9 and 10 show a high average transmittance, and the film strength as a result of the nell abrasion test. Excellent durability without degradation of average transmittance.

The magnifications of the SEM photographs in FIGS. 1, 3, and 5 are the same.

[Addition of water to coating solution]
The coating liquid for forming a low reflection film of Examples 1, 5, and 9, the coating liquid of Comparative Example 4 containing only colloidal silica having a different shape, and the coating liquid of Comparative Example 5 obtained by adding TEOS to a dispersion of colloidal silica having a different shape. Water was added to the coating solution to which water was added, and precipitation of solid content over time was observed.

Specifically, 10.0% by mass of pure water was added to the coating solutions for forming a low reflection film of Examples 1, 5, 9 and Comparative Examples 4, 5, and stored at room temperature (20 ° C.). The presence or absence of white turbidity and solid content was observed.

The low-reflective film-forming coating liquid of Example 1 in which tungsten alkoxide is added to two types of colloidal silicas (rod-shaped colloidal silica + spherical colloidal silica) in different ratios, and niobium alkoxide is added in the low-reflective film of Example 5 The coating solution for forming a low reflection film of Example 9 to which tantalum alkoxide was added as a forming coating solution was added 10.0% by mass of pure water to the coating solution of Comparative Example 4 containing only two types of colloidal silica having different shapes. No change was observed after 90 days.

In comparison, the coating solution of Comparative Example 5 in which TEOS was added to two types of colloidal silica dispersions having different shapes was added with 10% pure water, and after 1 week, it gelled and was not used as a coating solution. It was possible.

Next, 10.0% by mass of pure water was added, and the coating solution for forming a low reflection film prepared in Examples 1, 5 and 9 after 90 days (respectively, Examples 13, 14, and 15) was used. In the same manner as in Examples 1, 5, and 9, coating and film formation were performed on a glass substrate, and physical properties of the obtained glass substrate with a low reflection film were evaluated.

Example 13
A coating solution for forming a low reflection film in which a tungsten alkoxide dispersion is added to a colloidal silica dispersion containing colloidal silica having different shapes is prepared in the same manner as in Example 1, and then pure water is added to the total weight of the liquid. 10.0 mass% was added and it left still for 90 days under room temperature (20 degreeC). The coating solution for forming a low reflection film after standing was applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 2, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 1 under the condition of a pulling speed of 3.4 mm / sec. The average transmittance was 97.7%, and the average transmittance was improved by 7.2% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 112 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.285, and satisfactory performance was obtained as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 96.8%, which was 0.9% lower than that before the test. Further, when the contact angle of pure water was measured, it was 15.2 °, indicating strong hydrophilicity.

Example 14
A coating solution for forming a low reflection film obtained by adding a niobium alkoxide dispersion liquid to a colloidal silica dispersion liquid containing colloidal silica having different shapes was prepared in the same manner as in Example 5, and then pure water was added to the total weight of the liquid. 10.0 mass% was added and it left still for 90 days under room temperature (20 degreeC). The coating solution for forming a low reflection film after standing was applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods shown in Table 2, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 5 under the condition of a pulling rate of 3.0 mm / sec. The average transmittance was 96.8%, and the average transmittance was improved by 6.3% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 108 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.277, and satisfactory performance was obtained as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off and the average transmittance was measured to be 96.1%, which was 0.7% lower than before the test. Further, when the contact angle of pure water was measured, it was 13.6 °, indicating strong hydrophilicity.

Example 15
A coating solution for forming a low reflection film obtained by adding a tantalum alkoxide dispersion liquid to a colloidal silica dispersion liquid containing colloidal silica having different shapes was prepared in the same manner as in Example 9, and then pure water was added to the total weight of the liquid. 10.0 mass% was added and it left still for 90 days under room temperature (20 degreeC). The low reflection film forming coating solution after standing was applied to a glass substrate in the same procedure as in Example 9, and then heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 2, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 1 under the condition of a pulling speed of 3.4 mm / sec. The average transmittance was 96.6%, and the average transmittance was improved by 6.1% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 115 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.264, and satisfactory performance was obtained as a glass substrate with a low reflection film.

Next, the frictional strength of the coating was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to the pad by a wear tester. The friction strength was evaluated. The appearance was slightly scratched and haze was visible, but the film was not peeled off and the average transmittance was measured to be 95.8%, which was 0.8% lower than before the test. Further, when the contact angle of pure water was measured, it was 14.4 ° and showed strong hydrophilicity.

The results are summarized in Table 4. 10.0% by mass of pure water was added to a glass substrate with a low reflection film formed on both surfaces with the low reflection film forming coating liquids of Examples 1, 5, and 9 in which pure water was not added. In addition, the results of physical property evaluation of the glass substrate with a low reflection film formed by forming the low reflection film on both surfaces with the coating liquid for forming the low reflection film of Examples 13, 14, and 15 after 90 days have passed are as follows. No. 9 was a result not inferior to the substrate with a low reflection film.

By adding water, it is easy to adjust the viscosity of the coating solution for forming a low reflection film, and the choice of coating methods that can be handled increases. In addition, the safety against fire tends to increase.

"II. Example of the second embodiment"

"II-1. In the case of tungsten compounds"
Hereinafter, based on an Example and a comparative example, the coating liquid for low reflection film formation of this invention, its preparation method, and the low reflection member using the same are demonstrated.
First, a coating solution for forming a low reflection film for forming a low reflection film on a substrate will be described.

[Coating solution for forming low reflection film]
A coating solution for forming a low reflection film using two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and tungsten alkoxide having different shapes, and the tungsten alkoxide content relative to the colloidal silica is 14% by mass in terms of oxide. A coating solution for forming a low reflection film (Example 1) and a coating solution for forming a low reflection film (Example 2) in which the content of tungsten alkoxide in colloidal silica was 40% by mass in terms of oxide were prepared.
Subsequently, only the rod-shaped colloidal silica and tungsten alkoxide were used, and a coating solution for forming a low reflection film (Example 3) having a tungsten alkoxide content of 20 mass% with respect to the rod-shaped colloidal silica was prepared.
Next, using only spherical colloidal silica and tungsten alkoxide, a coating solution for forming a low reflection film (Example 4) having a tungsten alkoxide content of 20 mass% with respect to the spherical colloidal silica was prepared.

[Coating liquid of comparative example]
A coating solution for forming a low reflection film (Comparative Example 1) in which the content of tungsten alkoxide with respect to colloidal silica was 50% by mass in terms of oxide was prepared.
Next, a coating solution (Comparative Example 2) using only two types of colloidal silica and not using a metal alkoxide was prepared. Moreover, the coating liquid (comparative example 3) using two types of colloidal silica and TEOS was prepared. Moreover, the coating liquid (comparative example 4) which consists only of tungsten alkoxides was prepared.

Table 5 summarizes the compositions of the coating solutions for forming a low reflection film of Examples 1 to 4 and the coating solutions of Comparative Examples 1 to 4.

Next, the coating liquid for forming a low reflection film of Examples 1 to 4 and the coating liquid of Comparative Examples 1 to 4 were colorless and transparent soda lime silicate glass substrates (hereinafter simply referred to as glass substrates) having a thickness of 3 mm and a size of 100 mm × 100 mm. ) To obtain a glass substrate with a low reflection film having a low reflection film formed on the surface, and physical properties of the obtained glass substrate with a low reflection film were evaluated. Table 6 shows the physical property evaluation methods.

Examples 1 to 4 of the present invention and Comparative Examples 1 to 4 will be described in detail.

Example 1
<Preparation of colloidal silica dispersion>
16.34 g of rod-shaped colloidal silica IPA dispersion (manufactured by Nissan Chemical Industries, product number, IPA-ST, solid content concentration 30.3 mass%, major axis 10 nm to 20 nm) was weighed into a 1000 ml three-necked flask, 231.21 g of ethanol was added with stirring. Next, 111.50 g of ethanol was added to 12.28 g of a spherical colloidal silica dispersion (manufactured by JGC Catalysts and Chemicals, product number, OSCAL1432, solid concentration 20.2 mass%, particle size 5 nm to 10 nm) with stirring. Those were mixed to obtain 371.3 g of a colloidal silica dispersion.
The mixing ratio of the rod-shaped colloidal silica and the spherical colloidal silica was 67:33 by mass ratio.

<Preparation of tungsten alkoxide dispersion>
Under a nitrogen stream, 5.86 g of tungsten hexachloride (WCl ₆ ) was collected in a three-necked flask with a capacity of 300 ml, and 79.5 g of IPA cooled to 5 ° C. was added. To this was added 1.70 g of metallic sodium (manufactured by Wako Pure Chemical Industries, Ltd.), then refluxed in a nitrogen atmosphere at 75 ° C. for 24 hours, and cooled to room temperature (about 20 ° C.). Subsequently, pressure filtration was performed, and tungsten alkoxide (W (OCH ₂ (CH ₃ ) ₂ ) ₅ Cl) and NaCl as a by-product were separated by filtration. The concentration of tungsten in the filtrate was 4.22% by mass in terms of WO ₃ . In this way, about 70 g of a dispersion of tungsten alkoxide (W (OCH ₂ (CH ₃ ) ₂ ) ₅ Cl) was obtained.

<Preparation of coating solution for forming low reflection film>
While stirring at room temperature in a nitrogen atmosphere at room temperature in 179.8 g of the colloidal silica dispersion, 13.9 g of the tungsten alkoxide dispersion synthesized above was gradually added dropwise over 3 hours to give a pale brown transparent liquid. Obtained. After mixing, the mixture is further refluxed at 70 ° C. for 6 hours under a nitrogen atmosphere, and the colloidal silica and tungsten alkoxide in terms of mass ratio in terms of oxide are SiO ₂ : WO ₃ = 86: 14, that is, tungsten alkoxide in terms of oxide. A coating solution for forming a low reflection film having a solid concentration of 2.2% by mass was prepared to 14% by mass.

<Production of glass substrate with low reflection film>
The surface of the glass substrate was wet-polished with alumina particles, washed with distilled water and then IPA, and then heated to 100 ° C. and dried. When the contact angle of pure water was measured in order to confirm the surface state, it showed a strong hydrophilic property with a contact angle of 5 ° or less and was clean.
Next, a low reflection film was formed on the surface of the glass substrate by a dip method.
The washed glass substrate was dipped in the low reflection film forming coating solution and pulled upward at a speed of 3.4 mm / sec to apply the low reflection film forming coating solution to both surfaces of the glass substrate. It was dried at 50 ° C. for 30 minutes and further dried at 110 ° C. for 60 minutes. This is put into a baking furnace heated to 750 ° C., held for 150 seconds, taken out, rapidly cooled at room temperature, and formed with a low reflection film having a light blue reflection color on both sides, and a glass with a low reflection film A substrate was obtained.

FIG. 1 shows a drawing-substitute SEM photograph of the surface of a glass substrate with a low reflection film using tungsten alkoxide.
It is an enlarged photograph by SEM of the low reflection film formed on the glass substrate using the coating liquid for low reflection film formation. The ordered particles are silica fine particles, and the silica fine particles are bonded by tungsten oxide serving as a binder and are a porous film containing a microvoid and a hard film.

<Evaluation of glass substrate with low reflection film>
FIG. 2 shows a transmittance curve of a glass substrate with a low reflection film obtained using tungsten alkoxide.
A low reflection film was formed on the surface of the glass substrate by the sol-gel method using the coating liquid for forming the low reflection film. A transmittance curve of 1 is a transmittance curve of a glass substrate with a low reflection film applied to the glass substrate at a lifting speed of 3 mm / sec from the coating tank, and similarly, a transmittance curve of 2 is a lifting speed of 5 mm / sec. The transmittance curve of the glass substrate with a low reflection film is a transmittance curve of the glass substrate with a low reflection film at a pulling rate of 7 mm / sec. As the pulling speed increases, the film thickness increases, and the peak of the maximum transmittance shifts to the long wavelength side. Compared with the transmittance curve (represented by R) of the glass substrate having no reference low reflection film, the transmittance was improved in the entire wavelength region.

Next, when the physical property values were measured according to the physical property evaluation methods shown in Table 6, the average transmission of the low reflective film-coated glass substrate formed on both surfaces with the above-described pulling speed of 3.4 mm / sec. The rate was 98.0%, and the average transmittance was improved by 7.5% compared with the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 108 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.298, and satisfactory performance was obtained as a glass with a low reflection film.

Next, the frictional strength of the low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad by a wear tester. The friction strength of was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off and the average transmittance was measured to be 97.4%, which was 0.6% lower than that before the test. Moreover, when the contact angle of the pure water was measured, it was 6.5 °, indicating strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days at room temperature (25 ° C.) and 50% relative humidity was measured, it was 9.0 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 2
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Next, the tungsten alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that 40% by mass of tungsten alkoxide in terms of oxide is contained with respect to the mass of the colloidal silica, that is, SiO _2. : WO ₃ = 60: 40 In addition, a coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass was prepared. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 6, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 1 under the condition of a pulling rate of 3.4 mm / sec. The average transmittance was 97.3%, and the average transmittance was improved by 6.8% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 105 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.279, and satisfactory performance was obtained as a glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 96.6%, which was 0.7% lower than before the test. Moreover, when the contact angle of the pure water was measured, it was 12 °, indicating strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days was measured at room temperature (25 ° C.) and a relative humidity of 50%, it was 5.2 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 3
After the IPA dispersion of rod-shaped colloidal silica used in Example 1 (manufactured by Nissan Chemical Industries, Ltd., product number, IPA-ST, solid content concentration 30.3 mass%, major axis 10 nm to 20 nm) was diluted with ethanol, tungsten alkoxide was used. Is a mass ratio in terms of oxide, SiO ₂ : WO ₃ = 80: 20, that is, a tungsten alkoxide is prepared so as to be 20% by mass in terms of oxide, and a low reflection film having a solid content concentration of 2.0% by mass A forming coating solution was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods shown in Table 6, the average of the low reflective film-coated glass formed by forming low reflective films on both sides in the same manner as in Example 1 under the pulling speed of 3.4 mm / sec. The transmittance was 97.5%, and the average transmittance was improved by 7.0% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflection film.

Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 112 nm. Moreover, when the refractive index n was measured with the ellipsometer, it was n = 1.292 and the desired performance was obtained as glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partly peeled off, and the frictional strength of the glass substrate with the low reflective film of Example 1 and Example 2 It was inferior.

This is a result of forming a film having inferior friction strength because colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) having a specific shape with a specific particle diameter is not used but only rod-shaped colloidal silica is used.

Example 4
After the IPA dispersion of spherical colloidal silica used in Example 1 (manufactured by JGC Catalysts & Chemicals Co., Ltd., product number, OSCAL1432, solid concentration 20.2 mass%, particle size 5 nm to 10 nm) was diluted with ethanol, tungsten alkoxide was obtained. Preparation of SiO ₂ : WO ₃ = 80: 20 by mass ratio in terms of oxide, that is, tungsten alkoxide is 20% by mass in terms of oxide to form a low reflection film having a solid content concentration of 2.0% by mass A coating solution was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 6, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 1 under the condition of a pulling rate of 3.0 mm / sec. The average transmittance was 96.9%, and the average transmittance was improved by 6.4% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 109 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.303, and the desired performance as a low reflection film was obtained.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partly peeled off, and the frictional strength of the glass substrate with the low reflective film of Example 1 and Example 2 It was inferior compared.

This is a result of forming a film having inferior frictional strength because only colloidal silica was used without using colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a specific particle size.

Comparative Example 1
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Next, the tungsten alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that 50% by mass of tungsten alkoxide is contained in terms of oxide with respect to the mass of the colloidal silica, that is, SiO _2. : WO ₃ = 50: 50 and a coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass was prepared. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 6, the average transmittance of the film-coated substrate formed on both surfaces in the same manner as in Example 1 under the pulling rate of 3.4 mm / sec was It was 1.6% higher than that of the glass substrate before the film was provided, and was 92.1%, and the desired performance as a glass with a low reflection film could not be obtained.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 122 nm. Further, the refractive index of the film was measured with an ellipsometer, and n = 1.362. The refractive index was higher than desired.

This is a result of the content of the tungsten compound with respect to the colloidal silica deviating from the preferable content range of 5% by mass or more and 40% by mass or less in terms of oxide.

Comparative Example 2
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film. . Unlike Examples 1 to 4 and Comparative Example 1, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.
When the physical property values were measured according to the physical property evaluation method, the average transmittance was 97.4%, which was 6.9% higher than the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.
The glass substrate with a low reflection film of Comparative Example 2 was inferior in film strength, poor in durability, and could not withstand practical use.

Comparative Example 3
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, and TEOS was added so that the mass ratio with respect to corodal silica was 20% by mass. After coating on a glass substrate in the same procedure as in Example 1, it was heated and fired to obtain a glass substrate with a low reflection film. Unlike Examples 1 to 4 and Comparative Example 1, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.
When the physical property values were measured according to the physical property evaluation method, the average transmittance was 94.6%, which was 4.1% higher than that of the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.

Comparative Example 4
Only the tungsten alkoxide solution prepared in Example 1 was applied to a glass substrate and heated and fired in the same manner as in Example 1 to form a film, thereby obtaining a glass substrate with a tungsten oxide film. A cloudy ground glass substrate having a haze of 46.8% was obtained.

本発明の反射膜形成用塗布液を用いて表面に低反射膜が形成された低反射膜付きガラス基板は、親水性、防汚性に優れており、帯電防止性能を有し汚れにくい。特に、表７に示す様に、実施例１、２の低反射膜付きガラス基板は、高い平均透過率を示し、ネル磨耗試験の結果、平均透過率が劣化することなく、秀でた耐久性を示した。 (result)
Table 7 shows the evaluation results.

The glass substrate with a low reflection film having a low reflection film formed on the surface thereof using the coating liquid for forming a reflection film of the present invention is excellent in hydrophilicity and antifouling properties, has antistatic properties, and is hardly stained. In particular, as shown in Table 7, the glass substrates with a low reflection film of Examples 1 and 2 showed high average transmittance, and as a result of the Nel abrasion test, the average transmittance was not deteriorated, and excellent durability. showed that.

[Addition of water to coating solution]
Water was added to the coating solution of Comparative Example 3 in which TEOS was added to the coating solution for low reflection film formation of Example 1, the coating solution of Comparative Example 2 containing only colloidal silica having a different shape, and the dispersion of colloidal silica having a different shape. Then, the precipitation of solids over time was observed.

Specifically, 10.0% by mass of pure water is added to the coating solution for forming a low reflection film of Example 1 and the coating solutions of Comparative Example 2 and Comparative Example 3, and stored at room temperature (20 ° C.). The presence or absence of white turbidity and solid content was observed.

Coating solution for forming a low reflection film of Example 1 in which tungsten alkoxide is added to two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica), coating of Comparative Example 2 with only two types of colloidal silica having different shapes The liquid was added with 10.0% by mass of pure water, and no change was observed after 90 days.

In comparison, the coating solution of Comparative Example 3 in which TEOS was added to two types of colloidal silica dispersions having different shapes was added with 10% pure water, and after 1 week, it gelled and was not used as a coating solution. It was possible.

Next, 10.0% by mass of pure water was added, and a glass substrate was prepared in the same manner as in Example 1 using the coating solution for forming a low reflection film (referred to as Example 5) prepared in Example 1 after 90 days. The physical properties of the obtained glass substrate with a low reflection film were evaluated by coating.

Example 5
A coating solution for forming a low reflection film in which a tungsten alkoxide dispersion is added to a colloidal silica dispersion containing colloidal silica having different shapes is prepared in the same manner as in Example 1, and then pure water is added to the total weight of the liquid. 10.0 mass% was added and it left still for 90 days under room temperature (20 degreeC). The coating solution for forming a low reflection film after standing was applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 6, the low reflective film-coated glass formed by forming low reflective films on both sides in the same manner as in Example 1 under the condition of a pulling speed of 3.4 mm / sec. The average transmittance was 97.7%, and the average transmittance was improved by 7.2% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 112 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.285, and satisfactory performance was obtained as a glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 96.8%, which was 0.9% lower than that before the test. Further, when the contact angle of pure water was measured, it was 15.2 °, indicating strong hydrophilicity.

The results are summarized in Table 8. To the glass substrate with a low reflection film formed on both sides with the low reflection film forming coating solution of Example 1 to which pure water was not added, 10.0% by mass of pure water was added, and 90 days passed. The result of physical property evaluation of the glass substrate with a low reflection film formed by forming the low reflection film on both sides with the coating solution for forming the low reflection film of Example 5 after the past is not inferior to the glass substrate with the low reflection film of Example 1. It was a result.

By adding water, it is easy to adjust the viscosity of the coating solution for forming a low reflection film, and the choice of coating methods that can be handled increases. In addition, the safety against fire tends to increase.

"II-2. Niobium compounds"
Hereinafter, based on an Example, the coating liquid for low reflection film formation of this invention, its preparation method, and the low reflection member using the same are demonstrated.
First, a coating solution for forming a low reflection film for forming a low reflection film on a substrate will be described.

[Coating solution for forming low reflection film]
A coating solution for forming a low-reflection film using two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and niobium alkoxide having different shapes, and the niobium alkoxide content relative to the colloidal silica is 25% by mass in terms of oxide. A coating solution for forming a low reflection film (Example 1) and a coating solution for forming a low reflection film (Example 2) in which the niobium alkoxide content relative to colloidal silica was 40% by mass in terms of oxide were prepared.
Next, a coating solution for forming a low reflection film (Example 3) was prepared using only rod-shaped colloidal silica and niobium alkoxide and containing 20% by mass of niobium alkoxide with respect to rod-shaped colloidal silica.
Subsequently, using only spherical colloidal silica and niobium alkoxide, a coating solution for forming a low reflection film (Example 4) having a niobium alkoxide content of 20 mass% with respect to the spherical colloidal silica was prepared.

[Coating liquid of comparative example]
A coating solution (Comparative Example 1) in which the niobium alkoxide content relative to the colloidal silica was 50% by mass in terms of oxide was prepared.
Next, a coating solution (Comparative Example 2) using only two types of colloidal silica and not using a metal alkoxide was prepared. Moreover, the coating liquid (comparative example 3) using two types of colloidal silica and TEOS was prepared. Moreover, the coating liquid (comparative example 4) which consists only of niobium alkoxide was prepared.
A coating solution for forming a low reflection film according to Examples 1 and 2 and a coating solution of Comparative Examples 1 to 6 are coated on a soda lime silicate glass substrate to form a low reflection film, and physical properties of the obtained glass substrate with a low reflection film are evaluated. Went.

Table 9 summarizes the compositions of the coating solutions for forming a low reflection film of Examples 1 to 4 and the coating solutions of Comparative Examples 1 to 4.

Next, the coating liquid for forming a low reflection film of Examples 1 to 4 and the coating liquid of Comparative Examples 1 to 4 were colorless and transparent soda lime silicate glass substrates (hereinafter simply referred to as glass substrates) having a thickness of 3 mm and a size of 100 mm × 100 mm. ) To obtain a glass substrate with a low reflection film having a low reflection film formed on the surface, and physical properties of the obtained glass substrate with a low reflection film were evaluated. Table 10 shows the physical property evaluation methods.

Examples 1 to 4 of the present invention and Comparative Examples 1 to 4 will be described in detail.
Example 1

<Preparation of colloidal silica dispersion>
IPA dispersion of rod-shaped colloidal silica (IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid concentration 15.2% by mass, major axis 40 nm to 100 nm) was weighed into a 1000 ml three-necked flask, and IPA 186.6 g was added with stirring. Next, IPA, 194.8 g added to 23.41 g of spherical colloidal silica (manufactured by JGC Catalysts and Chemicals, product number, OSCAL1632, solid content concentration 20.5 mass%, particle size 8 nm to 15 nm) with stirring By mixing, 436 g of colloidal silica dispersion was obtained.
The mixing ratio of the rod-shaped colloidal silica and the spherical colloidal silica was 50:50 by mass ratio.

<Preparation of niobium alkoxide dispersion>
Under a nitrogen stream, 9.76 g of niobium pentachloride (NbCl ₅ ) was collected in a 500 ml three-necked flask, and 205 g of IPA cooled to 5 ° C. was added. To this was added 3.32 g of metallic sodium (manufactured by Wako Pure Chemical Industries, Ltd.) to obtain 218 g of a slurry in which niobium alkoxide (Nb (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl) and by-product NaCl were mixed.
Next, the mixture was refluxed in a nitrogen atmosphere at 75 ° C. for 24 hours and cooled to room temperature (about 20 ° C.). Subsequently, pressure filtration was performed, and niobium alkoxide (Nb (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl) and by-product NaCl were separated by filtration. The concentration of niobium in the filtrate was 2.3% by mass in terms of Nb ₂ O ₅ . This filtrate was used as a dispersion of niobium alkoxide (Nb (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl).

<Preparation of coating solution for forming low reflection film>
While stirring at room temperature in a nitrogen atmosphere at room temperature, the niobium alkoxide dispersion synthesized above, 139.74 g, was gradually added dropwise to the colloidal silica dispersion over 3 hours to obtain a milky white transparent liquid. After mixing, the mixture is further refluxed under a nitrogen atmosphere under 70 for 8 hours. The colloidal silica and niobium alkoxide are in a mass ratio in terms of oxide, SiO ₂ : Nb ₂ O ₅ = 3: 1, that is, niobium alkoxide is converted into oxide. To 25 mass%, and this was used as a coating solution for forming a low reflection film.

<Production of glass substrate with low reflection film>
The surface of the glass substrate was wet-polished with alumina particles, washed with distilled water and then IPA, and then heated to 100 ° C. and dried. When the contact angle of pure water was measured in order to check the surface condition, it showed a strong hydrophilic property with a contact angle of 5 ° or less and was clean.
Next, a low reflection film was formed on the surface of the glass substrate by a dip method.
The washed glass substrate was immersed in the low reflection film forming coating solution, and pulled upward at a speed of 3.0 mm / sec by a dipping method to apply the low reflection film forming coating solution to both surfaces of the glass substrate. It was dried at 50 ° C. for 30 minutes and further dried at 110 ° C. for 60 minutes. This is put into a baking furnace heated to 750 ° C., held for 150 seconds, taken out, rapidly cooled at room temperature, and a low reflection film having a light blue reflection color is formed on both sides. A glass substrate was obtained.

FIG. 1 shows a drawing-substitute SEM photograph of the surface of a glass substrate with a low reflection film using niobium alkoxide.
It is an enlarged photograph by SEM of the low reflection film formed on the glass substrate using the coating liquid for low reflection film formation. The ordered particles were silica, and the silica fine particles were joined by niobium oxide serving as a binder, and became a hard film while being a porous film containing microvoids.

<Evaluation of glass substrate with low reflection film>
FIG. 2 shows a transmittance curve of a glass substrate with a low reflection film using niobium alkoxide.
A low reflection film was formed on the surface of the glass substrate by the sol-gel method using the coating liquid for forming the low reflection film. A transmittance curve of 1 is a transmittance curve of a glass substrate with a low reflection film applied to the glass substrate at a lifting speed of 3 mm / sec from the coating tank. Similarly, a transmittance curve of 2 is a lifting speed of 5 mm / sec. The transmittance curve of the glass substrate with a low reflection film is a transmittance curve of the glass substrate with a low reflection film at a pulling rate of 7 mm / sec. As the pulling speed increases, the film thickness increases, and the peak of the maximum transmittance shifts to the long wavelength side. Compared with the transmittance curve (represented by R) of the glass substrate having no reference low reflection film, the transmittance was improved in the entire wavelength region.

Next, according to the physical property evaluation method shown in Table 10, the average transmittance of a glass substrate with a low reflection film formed by forming low reflection films on both sides in the same manner as in Example 5 under the condition of a pulling rate of 3.0 mm / sec. As a result, the average transmittance was 98.2%, and the average transmittance was improved by 7.7% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Then, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 113 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.275, and satisfactory performance was obtained as a glass with a low reflection film.

Next, the frictional strength of the low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ^{2 on} the surface of the glass with the low-reflection film by using a flannel cloth attached to the pad using a wear tester. The strength was evaluated. The appearance had a slight haze, but the color tone did not change, and the average transmittance was 97.7%, which was slightly decreased by 0.5% compared to before the test. When the pure water contact angle was measured, it showed a strong hydrophilic property at 6.5 °.

Further, when the surface resistance value of this low reflective film-coated glass after 30 days at 25 ° C. and 50% relative humidity was measured, it was 6.7 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 2
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Next, the niobium alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that the niobium alkoxide is contained in an amount of 40% by mass in terms of oxide with respect to the mass of the colloidal silica. : Nb ₂ O ₅ = 60: 40, and a coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass was prepared. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 10, a low reflective film-coated glass substrate formed by forming low reflective films on both sides in the same manner as in Example 1 under the condition of a lifting speed of 3.0 mm / sec. The average transmittance was 98.0%, and the average transmittance was improved by 7.5% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 108 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.281, which was a satisfactory performance as a glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 97.1%, which was 0.9% lower than before the test. Moreover, when the contact angle of the pure water was measured, it was 18 °, indicating strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days at room temperature (25 ° C.) and 50% relative humidity was measured, it was 18 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 3
After diluting the IPA dispersion of rod-shaped colloidal silica used in Example 1 (IPA-ST-UP, manufactured by Nissan Chemical Industries, Ltd., solid content concentration 15.2 mass%, major axis 40 nm to 100 nm) with IPA, niobium alkoxide was obtained. SiO ₂ : Nb ₂ O ₅ = 80: 20 in terms of mass in terms of oxide, that is, niobium alkoxide is prepared so as to be 20% by mass in terms of oxide, and low reflection with a solid content concentration of 2.0% by mass A coating solution for film formation was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods shown in Table 10, a low reflective film was formed on both surfaces in the same manner as in Example 5 under the condition of a pulling speed of 3.0 mm / sec. The average transmittance of the glass with a low reflection film is 97.2%, and the average transmittance of the glass substrate not provided with the low reflection film is 6.7% compared with 90.5%. Improved.

Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 102 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.296, which was satisfactory as a glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating frictions by the nell cloth abrasion test, partially peeled off, and inferior to the frictional strength of the substrates with the low reflective film of Examples 5 and 6. It was.

This is a result of forming a film having inferior friction strength because colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) having a specific shape with a specific particle diameter is not used but only rod-shaped colloidal silica is used.

Example 4
After diluting the IPA dispersion of spherical colloidal silica used in Example 1 (manufactured by JGC Catalysts and Chemicals Co., Ltd., product number, OSCAL1632, solid concentration 20.5 mass%, particle size 8 nm to 15 nm) with IPA, niobium alkoxide was obtained. SiO ₂ : Nb ₂ O ₅ = 80: 20 in terms of mass in terms of oxide, that is, niobium alkoxide is prepared so as to be 20% by mass in terms of oxide, and low reflection with a solid content concentration of 2.0% by mass A coating solution for film formation was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

According to the physical property evaluation method of Table 2, the physical property value was measured. Under the conditions of a pulling rate of 3.0 mm / sec, a low reflective film with a low reflective film formed on both sides in the same manner as in Example 1 was obtained. The average transmittance was 97.6%, and the average transmittance was improved by 7.1% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 117 nm. Further, when the refractive index n was measured with an ellipsometer, it was n = 1.284, which was a satisfactory performance as a glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partially peeled, and is inferior to the frictional strength of the glass substrate with the low reflective film of Examples 1 and 2. It was.

This is a result of forming a film having inferior frictional strength because only colloidal silica was used without using colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a specific particle size.

Comparative Example 1
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Next, the niobium alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that the niobium alkoxide is 50% by mass in terms of oxide with respect to the mass of the colloidal silica. _{SiO 2: Nb 2 0 5 =} 50: added to a 50 to prepare a solid concentration of 2.0% by weight of the coating solution. The said coating liquid was apply | coated to the glass substrate in the same procedure as Example 1, and it heat-fired and obtained the glass substrate with a film | membrane.

When the physical property values were measured in accordance with the physical property evaluation methods shown in Table 10, the average transmittance of the film-coated substrate formed on both surfaces in the same manner as in Example 1 under the condition of a pulling speed of 3.0 mm / sec is The glass substrate was -0.9% lower than the glass substrate before the film was formed, and it was 89.6%, which was not a glass with a low reflection film.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 115 nm. Further, when the refractive index of the film was measured with an ellipsometer, n = 1.353, and the refractive index was higher than desired.

This is a result of the content of niobium alkoxide with respect to colloidal silica deviating from the preferable content range of 5% by mass or more and 40% by mass or less in terms of oxide.

Comparative Example 2
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film. . Unlike Examples 1 to 4 and Comparative Example 1, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.
When the physical property values were measured according to the physical property evaluation method, the average transmittance was 97.4%, which was 6.9% higher than the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.
The glass substrate with a low reflection film of Comparative Example 2 was inferior in film strength, poor in durability, and could not withstand practical use.

Comparative Example 3
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, and TEOS was added so that the mass ratio with respect to corodal silica was 20% by mass. After coating on a glass substrate in the same procedure as in Example 1, it was heated and fired to obtain a glass substrate with a low reflection film. Unlike Examples 1 to 4 and Comparative Example 1, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.
When the physical property values were measured according to the physical property evaluation method, the average transmittance was 94.6%, which was 4.1% higher than that of the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.

Comparative Example 4
When only the niobium alkoxide solution prepared in Example 1 was applied to a glass substrate and heated and fired in the same manner as in Example 1 to form a film and measured with an ellipsometer to obtain a glass substrate with a niobium oxide film, the film was refracted. The rate was 1.90, and the average transmittance was lower than that of the glass substrate.

(result)
The evaluation results are shown in Table 11.

The glass substrate with a low reflection film having a low reflection film formed on the surface thereof using the coating liquid for forming a low reflection film of the present invention is excellent in hydrophilicity and antifouling properties, has antistatic properties and is hardly stained. In particular, as shown in Table 11, the glass substrates with low reflection films of Examples 1 and 2 showed high average transmittance, and as a result of the nell abrasion test, the average transmittance was not deteriorated, and excellent durability was achieved. showed that.

[Addition of water to coating solution]
The coating liquid for low reflection film formation of Example 1, the coating liquid of Comparative Example 2 containing only a colloidal silica dispersion having a different shape, and the coating liquid of Comparative Example 3 obtained by adding TEOS to a dispersion of colloidal silica having a different shape. Water was added and the precipitation of solids over time was observed.

Specifically, 10.0% by mass of pure water was added to the coating solution for forming a low reflection film of Example 1, the coating solution of Comparative Example 2 and Comparative Example 3, and stored at room temperature (20 ° C.). The presence or absence of white turbidity and solid content was visually observed.

The coating solution for forming a low reflection film of Example 1 in which niobium alkoxide is added to two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and two types of colloidal silica having only different shapes of Comparative Example 2 The coating solution was added with 10.0% by mass of pure water, and no change was observed even after 90 days.

In comparison, the coating solution of Comparative Example 3 in which TEOS was added to two types of colloidal silica dispersions having different shapes was added with 10% pure water, and after 1 week, it gelled and was not used as a coating solution. It was possible.

Next, 10.0% by mass of pure water was added, and the coating solution for forming a low reflection film of Example 1 (referred to as Example 5) after 90 days was used. The physical properties of the obtained glass substrate with a low reflection film were evaluated.

Example 5
A coating solution for forming a low reflection film obtained by adding a niobium alkoxide dispersion liquid to a colloidal silica dispersion liquid containing colloidal silica having different shapes was prepared in the same manner as in Example 1, and then pure water was added to the total weight of the liquid. 10.0 mass% was added and it left still for 90 days under room temperature (20 degreeC). The coating solution for forming a low reflection film after standing was applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods in Table 10, the low reflective film-coated glass was formed by forming low reflective films on both sides in the same manner as in Example 1 under the condition of a pulling rate of 3.0 mm / sec. The average transmittance was 96.8%, and the average transmittance was improved by 6.3% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 108 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.277, and satisfactory performance was obtained as a glass with a low reflection film.

Next, the frictional strength of the low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad by a wear tester. The friction strength of was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off and the average transmittance was measured to be 96.1%, which was 0.7% lower than before the test. Further, when the contact angle of pure water was measured, it was 13.6 °, indicating strong hydrophilicity.

The results are summarized in Table 12. To the glass substrate with a low reflection film formed on both sides with the low reflection film forming coating solution of Example 1 to which pure water was not added, 10.0% by mass of pure water was added, and 90 days passed. The result of physical property evaluation of the glass substrate with a low reflection film formed by forming the low reflection film on both sides with the coating solution for forming the low reflection film of Example 5 after the past is not inferior to the glass substrate with the low reflection film of Example 1. It was a result.

By adding water, it is easy to adjust the viscosity of the coating solution for forming a low reflection film, and the choice of coating methods that can be handled increases. In addition, the safety against fire tends to increase.

"II-3. In the case of tantalum compounds"
Hereinafter, based on an Example, the coating liquid for low reflection film formation of this invention, its preparation method, and the low reflection member using the same are demonstrated.
First, a coating solution for forming a low reflection film for forming a low reflection film on a substrate will be described.

[Coating solution for forming low reflection film]
A coating solution for forming a low reflection film using two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and tantalum alkoxide having different shapes, and the content of tantalum alkoxide with respect to colloidal silica is 20% by mass in terms of oxide. A coating solution for forming a low reflection film (Example 1) and a coating solution for forming a low reflection film (Example 2) in which the content of tantalum alkoxide relative to colloidal silica was 40% by mass in terms of oxide were prepared.
Subsequently, only a rod-shaped colloidal silica and tantalum alkoxide were used, and a coating solution for forming a low reflection film (Example 3) containing 20% by mass of tantalum alkoxide with respect to the rod-shaped colloidal silica was prepared.
Next, using only spherical colloidal silica and tantalum alkoxide, a coating solution for forming a low reflection film (Example 4) having a tantalum alkoxide content of 20 mass% with respect to the spherical colloidal silica was prepared.

[Coating liquid of comparative example]
A coating solution for forming a low reflection film (Comparative Example 1) in which the content of tantalum alkoxide with respect to colloidal silica was 50% by mass in terms of oxide was prepared.
Next, a coating solution (Comparative Example 2) using only two types of colloidal silica and not using a metal alkoxide was prepared. Moreover, the coating liquid (comparative example 3) using two types of colloidal silica and TEOS was prepared. Moreover, the coating liquid which consists only of a tantalum alkoxide (comparative example 6) was prepared.

A glass substrate was coated with the coating solution for forming a low reflection film of Examples 1 to 4 and the coating solution of Comparative Examples 1 to 4 to form a film, and the physical properties of the obtained glass substrate with a low reflection film were evaluated.

Table 13 summarizes the compositions of the coating solutions for forming a low reflection film of Examples 1 to 4 and the coating solutions of Comparative Examples 1 to 4.

Next, the coating liquid for forming a low reflection film of Examples 1 to 4 and the coating liquid of Comparative Examples 1 to 4 were colorless and transparent soda lime silicate glass substrates (hereinafter simply referred to as glass substrates) having a thickness of 3 mm and a size of 100 mm × 100 mm. ) To obtain a glass substrate with a low reflection film having a low reflection film formed on the surface, and physical properties of the obtained glass substrate with a low reflection film were evaluated. Table 14 shows the physical property evaluation methods.

Examples 1 and 2 of the present invention and Comparative Examples 1 to 6 will be described in detail.
Example 1

<Preparation of colloidal silica dispersion>
14.28 g of rod-shaped colloidal silica IPA dispersion (manufactured by Nissan Chemical Industries, product number, IPA-ST-UP, solid content concentration 15.2 mass%, major axis 40 nm to 100 nm) is weighed into a three-neck flask with a capacity of 1000 ml. And IPA 106.14 g was added with stirring. Next, IPA 264.2 g was added to spherical colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name, methanol silica sol, solid content concentration 30.2 mass%, particle size 10 nm to 20 nm) with stirring. By mixing, 401 g of colloidal silica dispersion, 401 g, was obtained.
In this way, in the colloidal silica dispersion, the mass ratio in terms of oxide between rod-like colloidal silica and spherical colloidal silica in terms of oxide (SiO ₂ ) is rod-like colloidal silica: spherical colloidal silica = 30: 70. Prepared. The solid content concentration is 1.8% by mass.

<Preparation of tantalum alkoxide dispersion>
Under a nitrogen stream, 8.20 g of tantalum pentachloride was collected in a 500 ml three-necked flask, and 255.10 g of methanol cooled on ice at 5 ° C. was added. To this was added 28% by mass sodium methoxide (Wako Pure Chemical Industries, Ltd.), 17.66 g, and tantalum alkoxide (Ta (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl) and by-product NaCl were mixed. 281 g of slurry was obtained.
Next, the mixture is refluxed at 65 ° C. for 16 hours in a nitrogen atmosphere, cooled to room temperature (about 22 ° C.), and then subjected to pressure filtration while flowing nitrogen to perform tantalum alkoxide (Ta (OCH ₂ (CH ₃ ) ₂ ) ₄ Cl ) And the by-product NaCl were filtered off. The concentration of tantalum in the filtrate was 1.8% by mass in terms of Ta ₂ O ₅ .

<Preparation of coating solution for forming low reflection film>
While stirring at room temperature in a nitrogen atmosphere at room temperature in 401 g of the colloidal silica dispersion, 100.3 g of the tantalum alkoxide dispersion synthesized above was gradually added dropwise over 2 hours at room temperature to give a slightly milky white transparent liquid. Obtained. After mixing, the mixture is further refluxed at 60 ° C. for 8 hours under a nitrogen stream, so that colloidal silica and tantalum alkoxide are in a mass ratio in terms of oxide, SiO ₂ : Ta ₂ O ₅ = 80: 20, that is, tantalum alkoxide. Was prepared so as to be 20% by mass in terms of oxide and used as a coating solution for forming a low reflection film.

<Production of glass substrate with low reflection film>
The surface of the glass substrate was wet-polished with alumina particles, washed with distilled water and then IPA, and then heated to 100 ° C. and dried. When the contact angle of pure water was measured in order to check the surface condition, it showed a strong hydrophilic property with a contact angle of 5 ° or less and was clean.
Next, a low reflection film was formed on the surface of the glass substrate by a dip method.
The washed glass substrate was immersed in the low reflection film forming coating solution, and pulled upward at a speed of 4.0 mm / sec by a dipping method to apply the low reflection film forming coating solution to both surfaces of the glass substrate. It was dried at 50 ° C. for 30 minutes and further dried at 110 ° C. for 60 minutes. This is put into a baking furnace heated to 750 ° C., held for 150 seconds, taken out, rapidly cooled at room temperature, and a low reflection film having a light blue reflection color is formed on both sides. A glass substrate was obtained.

FIG. 1 shows a drawing-substitute SEM photograph of the surface of a glass substrate with a low reflection film using tantalum alkoxide.
It is an enlarged photograph by the SEM mirror of the low reflection film formed on the glass substrate using the said coating liquid for low reflection film formation. The regularly arranged particles are silica, and the silica fine particles are bonded by a tantalum oxide serving as a binder and are a porous film containing a microvoid and a hard film.

<Evaluation of glass substrate with low reflection film>
FIG. 2 shows a transmittance curve of a glass substrate with a low reflection film using tantalum alkoxide.
A low reflection film was formed on a glass substrate by the sol-gel method using the low reflection film forming coating solution. The transmittance curve of 1 is a transmittance curve of the glass with a low reflection film applied to the substrate at a lifting speed of 3 mm / sec from the coating tank, and similarly, the transmittance curve of 2 is low at a lifting speed of 5 mm / sec. The transmittance curve of the glass with a reflection film is a transmittance curve of the glass with a low reflection film at a pulling rate of 7 mm / sec. As the pulling speed increases, the film thickness increases, and the peak of the maximum transmittance shifts to the long wavelength side. Compared to the transmittance curve (represented by R) of the substrate having no reference low reflection film, the transmittance is improved in the entire wavelength region.

When the average transmittance of the glass with a low reflection film at the aforementioned pulling speed of 4.0 mm / sec was measured, the average transmittance was 97.9%, and the average transmittance of the glass substrate without the low reflection film was 90%. Compared to 0.5%, the average transmittance was improved by 7.4%.

Next, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 121 nm. Further, when the refractive index n was measured with an ellipsometer, the refractive index was n = 1.260, and satisfactory performance was obtained as a glass with a low reflection film.

Next, the frictional strength of the low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad by a wear tester. The friction strength of was evaluated. Although the appearance was somewhat haze, the color tone was unchanged, and the average transmittance was measured to be 97.5%, which was 0.4% lower than before the test. Moreover, when the contact angle of the pure water was measured, it was 8.0 ° and showed strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass after 30 days at 25 ° C. and 50% relative humidity was measured, it was 9.0 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 2
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Next, the tantalum alkoxide dispersion prepared in Example 1 is added to the colloidal silica dispersion so that tantalum alkoxide is contained in an amount of 40% by mass in terms of oxide with respect to the mass of the colloidal silica. Thus, colloidal silica: Ta ₂ O ₅ = 60: 40 was added to prepare a coating solution for forming a low reflection film having a solid content concentration of 1.9% by mass. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 9, and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods shown in Table 14, a low reflective film-coated glass substrate was formed on both surfaces in the same manner as in Example 9 under the condition of a pulling speed of 3.4 mm / sec. The average transmittance was 97.1%, and the average transmittance was improved by 6.6% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Next, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 109 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.279, which was satisfactory as a glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The appearance was slightly scratched and a haze was seen, but the film was not peeled off, and the average transmittance was measured to be 96.5%, which was 0.6% lower than that before the test. Further, when the contact angle of pure water was measured, it was 19.3 ° and showed strong hydrophilicity.

Further, when the surface resistance value of this low reflective film-coated glass substrate after 30 days was measured at room temperature (25 ° C.) and a relative humidity of 50%, it was 3.6 exp10 ⁸ Ω. cm, and it was confirmed that excellent antistatic performance was maintained.

Example 3
The IPA dispersion of rod-shaped colloidal silica used in Example 1 (IPA-ST-UP manufactured by Nissan Chemical Industries, Ltd., solid content concentration 15.2 mass%, major axis 40 nm to 100 nm) was diluted with IPA, and then tantalum alkoxide was obtained. SiO ₂ : Ta ₂ O ₅ = 80: 20 by mass ratio in terms of oxide, that is, tantalum alkoxide is prepared to be 20% by mass in terms of oxide, and low reflection with a solid content concentration of 2.0% by mass A coating solution for film formation was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods shown in Table 14, the average transmission of the glass with a low reflection film formed on both surfaces in the same manner as in Example 9 under the condition of a pulling speed of 3.0 mm / sec. The rate was 96.9%, and the average transmittance was improved by 6.5% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film. Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 115 nm. Further, when the refractive index n was measured by an ellipsometer, it was n = 1.294, which was a satisfactory performance as a glass with a low reflection film.

Next, the frictional strength of this low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad using a wear tester to reduce the low-reflection film. The friction strength of the film was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partially peeled, and is inferior to the frictional strength of the glass substrate with the low reflective film of Examples 1 and 2. It was.

This is a result of forming a film having inferior frictional strength because the colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a different specific particle size shape is not used but only the rod-like colloidal silica is used.

Example 4
After the IPA dispersion of spherical colloidal silica used in Example 1 (manufactured by Nissan Chemical Industries, Ltd., trade name, methanol silica sol, solid content concentration 30.2 mass%, particle size 10 nm to 20 nm) was diluted with IPA, tantalum The alkoxide was prepared in such a way that the oxide ratio in terms of mass ratio was SiO ₂ : Ta ₂ O ₅ = 80: 20, that is, the tantalum alkoxide was 20% by mass in terms of oxide, and the solid content concentration was 2.0% by mass. A coating solution for forming a low reflection film was obtained. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 9, and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured according to the physical property evaluation methods shown in Table 14, the average transmission of the glass with a low reflection film formed on both surfaces in the same manner as in Example 9 under the condition of a pulling speed of 3.0 mm / sec. The rate was 97.0%, and the average transmittance was improved by 6.5% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Then, the film thickness was measured with a stylus type surface shape measuring instrument and found to be 113 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.307, which was satisfactory performance as a glass with a low reflection film.

Next, this low-reflective friction strength was rubbed back and forth 3000 times with a load of 15 g / cm ^{2 on} the surface of the glass substrate with the low-reflective film using a flannel cloth attached to the pad using a wear tester. The friction strength of was evaluated. The frictional strength of the low reflective film is that the appearance after 3000 reciprocating frictions in the flannel cloth abrasion test is cloudy and partially peeled, and is inferior to the frictional strength of the glass substrate with the low reflective film of Examples 1 and 2. It was.

This is a result of forming a film having inferior frictional strength because only the spherical colloidal silica was used without using colloidal silica (rod-like colloidal silica + spherical colloidal silica) having a specific particle size.

Comparative Example 1
A colloidal silica dispersion containing colloidal silica having different shapes was prepared in the same manner as in Example 1. Then, to the colloidal silica dispersion, a tantalum alkoxide dispersion prepared in Example 1, relative to the weight of the colloidal silica was added as tantalum alkoxide is contained 50 mass% in terms of oxide, i.e., SiO ₂ : Ta ₂ O ₅ = 50: 50, and a coating solution for forming a low reflection film having a solid content concentration of 1.7% by mass was prepared. The low reflection film forming coating solution was applied to a glass substrate in the same procedure as in Example 1 and heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods shown in Table 14, the average transmittance of the film-coated substrate formed on both surfaces in the same manner as in Example 9 under the condition of a pulling rate of 3.0 mm / sec is The glass substrate was 2.7% higher than the glass substrate before the film was provided, and it was 93.3%, which was not a glass with a low reflection film.

Next, the film thickness was measured with a stylus type surface shape measuring instrument to be 107 nm. Moreover, when the refractive index of the film was measured with an ellipsometer, it was n = 1.310, and the refractive index was higher than desired.

This is a result of the content of the tantalum compound with respect to the colloidal silica deviating from the preferable content range of 5% by mass or more and 40% by mass or less in terms of oxide.

Comparative Example 2
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film. . Unlike Examples 1 to 4 and Comparative Example 1, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.
When the physical property values were measured according to the physical property evaluation method, the average transmittance was 97.4%, which was 6.9% higher than the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.
The glass substrate with a low reflection film of Comparative Example 2 was inferior in film strength, poor in durability, and could not withstand practical use.

Comparative Example 3
In the same manner as in Example 1, a colloidal silica dispersion containing colloidal silica having a different shape was prepared, and TEOS was added so that the mass ratio with respect to corodal silica was 20% by mass. After coating on a glass substrate in the same procedure as in Example 1, it was heated and fired to obtain a glass substrate with a low reflection film. Unlike Examples 1 to 4 and Comparative Example 1, the low reflection film does not contain a metal oxide.

Subsequently, the glass substrate with a low reflection film was evaluated in the same manner as in Example 1.
When the physical property values were measured according to the physical property evaluation method, the average transmittance was 94.6%, which was 4.1% higher than that of the glass substrate before the low reflective film was provided. The frictional strength of the low reflective film is cloudy in appearance after 3000 reciprocating rubs according to the nell cloth abrasion test, haze is increased by 5.7% compared to before the test, and there is partial peeling and inferior frictional strength. It was.

Comparative Example 4
Only the tantalum alkoxide solution prepared in Example 1 was applied to a glass substrate and heated and fired in the same manner as in Example 9 to form a glass substrate with a tantalum oxide film. The refractive index of the film was 1.86, and the average transmittance was lowered instead.

(result)
The evaluation results are shown in Table 15.

The glass substrate with a low reflection film on which the low reflection film is formed on the surface by the coating solution for forming a low reflection film of the present invention is excellent in hydrophilicity and antifouling properties, has antistatic properties, and is hardly soiled. In particular, as shown in Table 15, the glass substrates with low reflection films of Examples 1 and 2 showed high average transmittance, and as a result of the nell abrasion test, the average transmittance was not deteriorated, and excellent durability was achieved. showed that.

[Addition of water to coating solution]
The coating solution for forming a low reflection film of Example 1, the coating solution of Comparative Example 2 containing only a dispersion of colloidal silica having a different shape, and the coating solution of Comparative Example 3 in which TEOS was added to the dispersion of colloidal silica having a different shape. Water was added to the solid and precipitation of solid content with time was observed.

Specifically, 10.0% by mass of pure water was added to the coating solution for forming a low reflection film of Example 1, the coating solution of Comparative Example 2 and Comparative Example 3, and stored at room temperature (20 ° C.). The presence or absence of white turbidity and solid content was visually observed.

The coating liquid for forming a low reflection film of Example 1 in which tantalum alkoxide is added to two types of colloidal silica (rod-shaped colloidal silica + spherical colloidal silica) and two types of colloidal silica having only different shapes of Comparative Example 4 The coating solution was added with 10.0% by mass of pure water, and no change was observed after 90 days.

In comparison, the coating solution of Comparative Example 3 in which TEOS was added to two types of colloidal silica dispersions having different shapes was added with 10% pure water, and after 1 week, it gelled and was not used as a coating solution. It was possible.

Next, 10.0% by mass of pure water was added, and a glass substrate was prepared in the same manner as in Example 1 using the coating solution for forming a low reflection film (referred to as Example 5) prepared in Example 1 after 90 days. The physical properties of the obtained glass substrate with a low reflection film were evaluated by coating.

Example 5
A coating solution for forming a low reflection film in which a tantalum alkoxide dispersion is added to a colloidal silica dispersion containing colloidal silica having different shapes is prepared in the same manner as in Example 1, and then pure water is added to the total weight of the liquid. 10.0 mass% was added and it left still for 90 days under room temperature (20 degreeC). The coating solution for forming a low reflection film after standing was applied to a glass substrate in the same procedure as in Example 1, and then heated and fired to obtain a glass substrate with a low reflection film.

When the physical property values were measured in accordance with the physical property evaluation methods in Table 14, the low reflective film-coated glass formed by forming low reflective films on both sides in the same manner as in Example 1 under the condition of a pulling speed of 3.4 mm / sec. The average transmittance was 96.6%, and the average transmittance was improved by 6.1% compared to the average transmittance of 90.5% for the glass substrate not provided with the low reflective film.

Subsequently, when the film thickness was measured with a stylus type surface shape measuring instrument, it was 115 nm. Further, when the refractive index n was measured with an ellipsometer, n = 1.264, and satisfactory performance was obtained as a glass with a low reflection film.

Next, the frictional strength of the low-reflection film was rubbed back and forth 3000 times with a load of 15 g / cm ² using a flannel cloth attached to a pad by a wear tester. The friction strength of was evaluated. The appearance was slightly scratched and haze was visible, but the film was not peeled off and the average transmittance was measured to be 95.8%, which was 0.8% lower than before the test. Further, when the contact angle of pure water was measured, it was 14.4 ° and showed strong hydrophilicity.

The results are summarized in Table 16. To the glass substrate with a low reflection film formed on both sides with the low reflection film forming coating solution of Example 1 to which pure water was not added, 10.0% by mass of pure water was added, and 90 days passed. The result of physical property evaluation of the glass substrate with a low reflection film formed by forming the low reflection film on both sides with the coating solution for forming the low reflection film of Example 5 after the past is not inferior to the glass substrate with the low reflection film of Example 1. It was a result.

By adding water, it is easy to adjust the viscosity of the coating liquid for forming a low reflection film, and the choice of coating methods that can be handled increases. In addition, the safety against fire tends to increase.

By the method for forming a low reflection film of the present invention, a low reflection member having a durable low hydrophilic film having a low refractive index formed on the surface thereof was obtained. The low reflection member of the present invention is a cover glass for solar cells, an optical material such as a lens, an image display surface such as a cathode ray tube or a liquid crystal display device, a glass plate or transparent glass such as a window or a showcase, a skylight material, a water heater or a lighting fixture. It can be used in a wide range of fields that require hydrophilicity, antifouling properties, and low-reflection antistatic properties such as plastics. In addition, it is particularly useful as a cover glass for solar cells, because it excels in not only the wavelength range from ultraviolet to visible light but also the near-infrared wavelength range.

Specifically, the low reflection member formed on the surface of the low reflection film of the present invention has an effect of improving the illuminance due to high average transmittance as a protection member for the luminaire, preventing reflection of the windshield, When used for solar cell cover glass, the optical characteristics can be adjusted, the light reception efficiency is improved by improving the average transmittance due to the effect of forming a low reflection film, and in particular, the power generation efficiency is improved. It is used very suitably as a cover glass for solar cells.

In addition, the low reflection member formed with the low reflection film of the present invention is excellent in durability without deterioration of the strength of the low reflection film even when the substrate is a glass plate, and is used as a cover glass for solar cells. Ideal for.

Furthermore, a low reflection film excellent in low refractive index, heat resistance, abrasion resistance and antifouling property is formed by the coating solution for forming a low reflection film of the present invention, a method for preparing the same, and a low reflection member using the same. A low reflection member was obtained. The low reflection member of the present invention is a cover glass for solar cells, an optical material such as a lens, an image display surface such as a cathode ray tube or a liquid crystal display, a window or a showcase, a skylight material, a water heater, a glass plate such as a lighting device, or a transparent glass. It can be used in a wide range of fields that require hydrophilicity, antifouling properties, and low reflection antistatic properties such as plastics. Specifically, the low reflection member having a low reflection film obtained by the coating solution for forming a low reflection film according to the present invention is used as a cover glass for solar cells, glass for automobiles (particularly windshield) or a protective member for lighting equipment. It was used favorably, and special effects such as improving the light receiving efficiency of solar cells, improving the conversion efficiency of power generation, preventing the reflection of windshields, or improving the illuminance by high visible light transmittance as a protective member for lighting fixtures were obtained. .

In addition, the coating liquid for forming a low reflection film of the present invention has no solid content precipitation, has a long liquid life, can contain water, has good wettability with glass, and supports various coating methods. To do.

Further, the peak wavelength of transmitted light can be shifted in accordance with the characteristics of the solar cell to improve the conversion rate of the solar cell, so that it is particularly useful as a cover glass for solar cell.

Usually, the peak of the maximum value of the transmittance of a low-reflection member having a low-reflection film made only of silica is around 500 nm, but by including WO ₃ , the peak shifts to 500 nm to 900 nm, and the cover for solar cells A low reflection member excellent in use as glass was obtained.

The low reflective member of the present invention is particularly suitable for use as a cover glass for solar cells.

Claims (55)

At least one selected from the group consisting of silica fine particles and tungsten oxide, niobium oxide, tantalum oxide, titanium oxide, zirconium oxide, tin oxide, aluminum oxide, hafnium oxide, chromium oxide, molybdenum oxide, cerium oxide, and lanthanum oxide. A binder composed of a metal oxide is contained, and the content ratio of the binder composed of the metal oxide to the silica fine particles is 5% by mass or more and 40% by mass or less, and the refractive index is 1.20 or more and 1.40 or less. A low reflective film characterized by the above. The silica fine particles are mainly rod-like silica fine particles having a major axis of 5 nm to 100 nm and spherical silica fine particles having a particle size of 5 nm to 50 nm as observed with a scanning electron microscope. 2. The low reflection film according to 1. 3. The low reflection film according to claim 2, wherein the mass ratio of the rod-like silica particles and the spherical silica particles is rod-like silica particles: spherical silica particles = 20: 80 to 80:20. 4. The low oxide according to claim 1, wherein the metal oxide is at least one metal oxide selected from the group consisting of tungsten oxide, niobium oxide, and tantalum oxide. 5. Reflective film. A low-reflection member, wherein the low-reflection film according to any one of claims 1 to 4 is formed on a transparent substrate surface. 6. The low reflection member according to claim 5, wherein the transparent substrate is a glass plate, and an average transmittance in a light wavelength region of 380 nm to 1200 nm is 95% or more. The peak of the maximum value of a light transmittance curve is 500 nm or more and 900 nm or less, The low reflection member of Claim 5 or Claim 6 characterized by the above-mentioned. A solar cell cover glass comprising the low reflection member according to claim 5. A dispersion containing at least one metal compound selected from the group consisting of tungsten, niobium, tantalum, titanium, zirconium, tin, aluminum, hafnium, chromium, molybdenum and rare earth is added to the dispersion containing colloidal silica. A coating solution for forming a low reflection film is applied to a substrate to form a coating film, and then heated and fired to form colloidal silica as silica fine particles and a metal compound as a metal oxide to form a low reflection film. Method. Colloidal silica is 90% or more of the total number of rod-shaped colloidal silica having a major axis of 5 nm or more and 100 nm or less and spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less as observed by a scanning electron microscope. The method according to claim 9, wherein the content of the metal compound is 5% by mass or more and 40% by mass or less in terms of oxide. The method according to claim 10, wherein the mass ratio of the rod-shaped colloidal silica to the spherical colloidal silica is rod-shaped silica colloidal silica: spherical colloidal silica = 20: 80 to 80:20. The method according to claim 9, wherein the metal compound is a metal compound of at least one metal selected from the group consisting of tungsten, niobium and tantalum. A low reflection member in which a low reflection film having a refractive index of 1.20 or more and 1.40 or less is formed on the transparent substrate surface by the method according to any one of claims 9 to 12. 14. The low reflection member according to claim 13, wherein the transparent substrate is a glass plate, and an average transmittance in a wavelength range of 380 nm to 1200 nm is 95% or more. The peak of the maximum value of a light transmittance curve is 500 nm or more and 900 nm or less, The low reflection member of Claim 13 or Claim 14 characterized by the above-mentioned. The cover glass for solar cells which consists of a low reflection member of any one of Claim 13 thru | or 15. A coating solution for forming a low reflection film on a substrate, comprising a tungsten compound and colloidal silica, wherein the tungsten compound is 5 masses in terms of oxide relative to the mass of the colloidal silica. A coating solution for forming a low reflection film, comprising a dispersion liquid contained in a range of from 50% to 40% by weight. 18. The low reflection according to claim 17, wherein the colloidal silica is a rod-shaped colloidal silica having a major axis of 5 nm or more and 100 nm or less and a spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less as observed by a scanning electron microscope. Coating liquid for film formation. The coating solution for forming a low reflection film according to claim 17 or 18, wherein the mass ratio of rod-shaped colloidal silica: spherical colloidal silica is 20:80 to 80:20. The tungsten compound is W (OR ¹ ) _6-n X _n (where n is 1 ≦ n ≦ 6 and R ¹ is independently a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n- Butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, 20. The coating solution for forming a low reflection film according to claim 17, wherein the coating solution is an ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom. . The tungsten compound is W (OR ² ) _6-n Cl _n (n is 1 ≦ n ≦ 6, R ² is independently methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl) And a s-butyl group, an i-butyl group, a t-butyl group, an n-amyl group, an i-amyl group, or an s-amyl group. The coating liquid for low reflection film formation of any one of Claims 1. The low reflection according to any one of claims 17 to 21, wherein the low reflection film-forming coating liquid contains 1% by mass or more and 50% by mass or less of water based on the total mass of the coating liquid. Coating liquid for film formation. A solar cell cover glass formed with a low reflective film using the low reflective film forming coating solution according to any one of claims 17 to 22. 18. A method of preparing a coating solution for forming a low reflection film for forming a low reflection film on a substrate, comprising mixing a dispersion containing a tungsten compound and a dispersion containing colloidal silica. A method for preparing a coating solution for forming a low reflection film according to claim 22. The tungsten compound is converted into the following reaction WCl ₆ + 5Na (OR ² ) → W (OR ² ) ₅ Cl + 5NaCl in an isopropyl alcohol solvent.
(R ² is each independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group or s-amyl group.)
The method of claim 24, characterized in that in a synthesized W (OR ²⁾ ₅ Cl. The coating solution for forming a low reflection film according to any one of claims 17 to 22 is applied to a substrate to form a coating film, and then heated and fired to form colloidal silica as silica fine particles, and the tungsten compound is oxidized with tungsten. The coating film is cured as a product, silica fine particles and tungsten oxide are contained, the content of tungsten oxide with respect to the silica fine particles is in the range of 5% by mass or more and 40% by mass or less, and the refractive index is 1.20 or more and 1.40 or less. A method for forming a low reflection film, comprising: obtaining a low reflection film on a substrate. 27. A low reflection member, wherein a low reflection film is formed on a glass substrate by the method for forming a low reflection film according to claim 26, and an average transmittance in a light wavelength region of 380 nm to 1200 nm is 95% or more. The peak of the maximum value of the light transmittance of a light transmittance curve is the range of 500 to 900 nm, The low reflection member of Claim 27 characterized by the above-mentioned. A solar cell cover glass comprising the low reflection member according to claim 27 or 28. A coating solution for forming a low reflection film on a substrate, comprising a niobium compound and colloidal silica, wherein the niobium compound is 5 masses in terms of oxide relative to the mass of the colloidal silica. A coating solution for forming a low reflection film, comprising a dispersion liquid contained in a range of from 50% to 40% by weight. The low-reflection film formation according to claim 30, wherein rod-like colloidal silica having a major axis of 5 nm or more and 100 nm or less and spherical colloidal silica having a particle size of 5 nm or more and 50 nm or less are used for colloidal silica as observed with a scanning electron microscope. Coating liquid. 32. The coating liquid for forming a low reflection film according to claim 30, wherein the mass ratio of rod-shaped colloidal silica: spherical colloidal silica is 20:80 to 80:20. The niobium compound is Nb (OR ¹ ) _5-n X _n (where n is 1 ≦ n ≦ 5 and R ¹ is independently methyl, ethyl, n-propyl, i-propyl, n- Butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, The coating solution for forming a low reflection film according to any one of claims 30 to 32, which is an ethoxyethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom. . The niobium compound is Nb (OR ² ) _5-n Cl _n (n is 1 ≦ n ≦ 5, R ² is independently methyl, ethyl, n-propyl, i-propyl, n-butyl) A s-butyl group, an i-butyl group, a t-butyl group, an n-amyl group, an i-amyl group, or an s-amyl group). The coating liquid for low reflection film formation of any one of Claims 1. 35. The low reflection according to any one of claims 30 to 34, wherein the low reflection film forming coating solution contains 1% by mass or more and 50% by mass or less of water with respect to the total mass of the coating liquid. Coating liquid for film formation. 36. A solar cell cover glass comprising a low reflective film formed using the low reflective film forming coating solution according to any one of claims 30 to 35. A method for preparing a coating solution for forming a low-reflection film for forming a low-reflection film on a substrate, comprising mixing a dispersion containing a diobium compound and a dispersion containing colloidal silica. 37. A method for preparing a coating solution for forming a low reflection film according to claim 30. The niobium compound is converted into the following reaction NbCl ₅ + 4Na (OR ² ) → Nb (OR ² ) ₄ Cl + 4NaCl in an isopropyl alcohol solvent.
(R ² each independently represents a methyl group, ethyl group, n-propyl group or i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group or s-amyl group.)
The method of claim 37, characterized in that in a synthesized Nb (OR ²⁾ ₄ Cl. 36. The coating solution for forming a low reflection film according to any one of claims 30 to 35 is applied to a substrate to form a coating film, and then heated and fired to form colloidal silica as silica fine particles, and the niobium compound is oxidized with niobium. The coating film is cured as a product, silica fine particles and niobium oxide are contained, the niobium oxide content in the silica fine particles is in the range of 5% by mass to 40% by mass, and the refractive index is 1.20 or more and 1.40 or less. A method for forming a low reflection film, comprising: obtaining a low reflection film on a substrate. 40. A low reflection member, wherein a low reflection film is formed on a glass substrate by the method for forming a low reflection film according to claim 39, and the average transmittance in the light wavelength region of 380 nm to 1200 nm is 95% or more. The peak of the maximum value of the light transmittance of a light transmittance curve is the range of 500 nm or more and 900 nm or less, The low reflection member of Claim 40 characterized by the above-mentioned. A cover glass for a solar cell, comprising the low reflection member according to claim 40 or 41. A coating liquid for forming a low reflection film on a substrate, which comprises a tantalum compound and colloidal silica, and the tantalum compound is 5 masses in terms of oxide with respect to the mass of the colloidal silica. A coating solution for forming a low reflection film, comprising a dispersion liquid contained in a range of from 50% to 40% by weight. 44. The low-reflection film formation according to claim 43, wherein the colloidal silica is a rod-shaped colloidal silica having a major axis of 5 nm or more and 100 nm or less and a spherical colloidal silica having a particle diameter of 5 nm or more and 50 nm or less as observed by a scanning electron microscope. Coating liquid. The coating solution for forming a low reflection film according to claim 43 or 44, wherein the mass ratio of the rod-shaped colloidal silica: spherical colloidal silica is 20:80 to 80:20. The tantalum compound is Ta (OR ¹ ) _5-n X _n (n is 1 ≦ n ≦ 5, R ¹ is independently methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl) Group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group, s-amyl group, 2-ethylhexyl group, methoxyethyl group, methoxypropyl group, ethoxymethyl group, ethoxy 46. The coating solution for forming a low reflection film according to any one of claims 43 to 45, which is an ethyl group, an ethoxypropyl group, or a phenyl group, and X is a halogen atom. The tantalum compound is Ta (OR ² ) _5-n Cl _n (n is 1 ≦ n ≦ 5, R ² is independently methyl group, ethyl group, n-propyl group or iso-propyl group, n-butyl group) A s-butyl group, an i-butyl group, a t-butyl group, an n-amyl group, an i-amyl group, or an s-amyl group). The coating liquid for low reflection film formation of any one of Claims 1. The low reflection film according to any one of claims 43 to 47, comprising 1% by mass or more and 50% by mass or less of water with respect to the total mass of the coating liquid for forming the low reflection film. Coating liquid for forming. 49. A cover glass for a solar cell, wherein a low reflection film using the coating liquid for forming a low reflection film according to any one of claims 43 to 48 is formed. 44. A method of preparing a coating solution for forming a low reflection film for forming a low reflection film on a substrate, comprising mixing a dispersion containing a tantalum compound and a dispersion containing colloidal silica. 50. A method for preparing a coating solution for forming a low reflection film according to claim 49. The following reaction TaCl ₅ + 4Na (OR ² ) → Ta (OR ² ) ₄ Cl + 4NaCl in isopropyl alcohol solvent in a tantalum compound
(R ² is each independently a methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, i-butyl group, t-butyl group, n-amyl group, i-amyl group or s-amyl group.)
The method according to claim 50, wherein Ta (OR ² ) ₄ Cl synthesized by the method is used. A coating solution for forming a low reflection film according to any one of claims 43 to 48 is applied to a substrate to form a coating film, and then heated and fired to form colloidal silica as silica fine particles, and a tantalum compound is oxidized with tantalum. The coating film is cured as a product, silica fine particles and tantalum oxide are contained, the content of tantalum oxide with respect to the silica fine particles is in the range of 5% by mass to 40% by mass, and the refractive index is 1.20 or more and 1.40 or less. A method for forming a low reflection film, comprising: obtaining a low reflection film on a substrate. 53. A low reflection member, wherein a low reflection film is formed on a glass substrate by the method for forming a low reflection film according to claim 52, and an average transmittance in a light wavelength region of 380 nm to 1200 nm is 95% or more. 54. The low reflection member according to claim 53, wherein the peak of the maximum value of the light transmittance of the light transmittance curve is in the range of 500 nm to 900 nm. 55. A cover glass for a solar cell, comprising the low reflection member according to claim 53 or claim 54.

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