JP2011028185A - Hydrophilic low reflection member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrophilic low reflection member having high light transmittance in a wide region of 400-1,200 nm, strong adhesive strength to a base material, excellent weather resistance, hydrophilicity, antifouling property and antistatic function and inexpensive. <P>SOLUTION: The low reflection member has a transparent substrate and a low reflection film formed on the transparent substrate and the low reflection film is a hydrophilic low reflection material containing magnesium fluoride hydroxide ultrafine particle having 5-500 nm particle diameter. Further by adding a metal oxide as a refractive index adjusting agent, transmissivity in a long wave length region is improved and high transparency is exhibited in the wide wave length region of 400-1,200 nm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydrophilic low reflection member having a transparent substrate (glass plate or the like) and a low reflection film formed on the transparent substrate. Further, the present invention relates to a low reflection member which improves the transmittance of 800 nm to 1200 nm by adding a refractive index adjusting agent and exhibits high transmittance in a wide region of 400 to 1200 nm.

  The low reflection member having hydrophilicity includes a protective film on the surface of a solar cell or an electrophotographic photosensitive member, an optical material such as a lens, an image display surface such as a cathode ray tube or a liquid crystal display, a copying machine, an imaging tube, LED display elements, lighting, organic EL, windows and showcases, digital cameras, liquid crystal projectors, etc., suitable for use in sheet glass, transparent plastics, etc. for antireflection films for lenses for various optical devices, reflectors for automobile headlamps, etc. .

  In general, a low-reflection film for preventing reflection of light on a surface of a base material using the transparency, such as transparent glass and transparent plastic, has been studied for a long time. These surface reflections deteriorate the performance in optical applications such as lenses, and the reflection of electric light or sunlight adversely affects visibility in a display device or a showcase.

  In particular, when used as a surface protection film for solar cells, high light receiving efficiency, that is, high light transmittance and low reflectance is required, and since solar cells are constantly exposed to sunlight, they are resistant to ultraviolet rays and water. A material having both properties and weather resistance is desired. Therefore, from the viewpoint of being able to maintain performance over a long period of time without being deteriorated, an inorganic material is more desirable than an organic material such as a resin.

  The low reflection film is formed on the surface of the substrate to reduce the reflectance. Conventionally, in the production of a low-reflection film, a method of producing a multilayer film composed of a high refractive index film layer and a low refractive film layer on a substrate has been used. It takes a long time, and precise control of the thickness of each thin film is required, and the accuracy may greatly affect the reflectivity, so that there is a disadvantage that it is economically expensive. For this reason, recently, development of a single-layer low-reflection film capable of producing a large area at low cost has been desired.

When obtaining a low reflection effect using thin film interference, the refractive index and thickness of the film are important. When the refractive index of the substrate is n _s , the refractive index of the medium is n ₀ , and the wavelength of light is λ, the refractive index of the film having the lowest reflectance (theoretically 0) is obtained when there is a single low-reflection film. The rate n is represented by n = (n _s × n ₀ ) ^1/2 , and the film thickness d is represented by d = m (nλ / 4) (m = 1, 3, 5,...). When n ₀ is air ≈ 1 and the refractive index n _s of a general base material is 1.4 to 1.7, ideally a very low value of n = 1.18 to 1.30 is obtained. If the low-reflection film is made multilayer, reflection can be prevented over a wide range of wavelengths, but there is a drawback that a sputtering or vapor deposition apparatus is necessary and it is difficult to increase the area, resulting in high cost.

  Therefore, in order to achieve low reflection at a low cost with a single layer, a film as close to the theoretical refractive index as possible with respect to the base material is required.

  Also, in the case of obtaining a low reflection effect by utilizing irregular reflection of light by fine particles (so-called anti-glare film), the refractive index of the fine particles is the same as described above, or the refractive index of the medium (in order to suppress interface reflection with the medium) In the case of air, it is required to be closer to about 1).

For these reasons, magnesium fluoride (MgF ₂ , n = 1.38) having a low refractive index is often used for the antireflection outermost layer as an inorganic material. Magnesium fluoride was mainly formed by vapor deposition, but from the viewpoint of cost and workability, instead of the conventional vapor deposition method, an inexpensive and highly productive coating method suitable for large areas is required. It has become to.

  In order to satisfy these requirements, magnesium fluoride fine particles have been conventionally used as a coating film as an inexpensive antireflection film suitable for a large area. Magnesium fluoride sols include aqueous sols obtained by washing and concentrating magnesium fluoride gel produced by adding an aqueous fluoride solution to an aqueous magnesium salt solution, and organosols obtained by phase-shifting an aqueous sol into an organic solvent. Is known (see Patent Documents 1 and 2). Patent Document 3 describes a method of removing by-products by heating and pressurizing a magnesium fluoride produced in an organic solvent after reaction with an autoclave or the like. Further, Patent Document 4 discloses a support having an abrasion-resistant coating containing magnesium fluoride and a metal oxide. In addition, in the manufacture of magnesium fluoride, there is a disclosure that hydrogen fluoride is unsuitable.

  Further, Patent Document 5 discloses a method for producing a hard-to-charge optical element in which hydrophilicity is introduced by surface modification of a coating layer surface of a substrate coated with a fluoride such as magnesium fluoride by plasma irradiation or the like. It is disclosed. Further, Patent Document 6 discloses an optical body in which water burn is prevented by forming a layer having photocatalytic activity such as titanium dioxide directly under a magnesium fluoride layer in a multilayer antireflection film. The cited document discloses that magnesium fluoride is non-hydrophilic.

  On the other hand, in Non-Patent Document 1, CIS thin-film solar cells and crystalline silicon have a wide absorption region of 400 to 1200 nm, and absorb light in a longer wavelength region than conventional amorphous silicon-based materials. It is disclosed that the absorption peak is around 900 nm.

JP-A-7-69621 JP-A-2-26824 International Patent Publication No. WO2002 / 18982 Special table 2008-501557 gazette JP 2001-147302 A JP 2005-165014 A

Internet <http: // www. showshell-solar. co. jp / solasicis / cis. html [Search June 22, 2009]

  Although it is useful to use magnesium fluoride as a low reflection film as described above, it is described in Patent Document 1 (Japanese Patent Laid-Open No. 7-69621) and Patent Document 2 (Japanese Patent Laid-Open No. 2-26824). In the method, synthesis is carried out in an aqueous system, and by-product salt is washed and concentrated using ultrafiltration, which has problems in terms of productivity and cost. In addition, the method of Patent Document 3 (International Patent Publication WO2002 / 18982) requires complete removal of organic substances produced as a by-product in an autoclave, so that the operation becomes complicated and the removal of organic substances produced as a by-product is sufficient. If not, it is described that the refractive index is not sufficiently lowered. Although the thing of patent document 4 is excellent in the abrasion resistance of a coating film, there exists a problem in the storage stability of the magnesium fluoride which is a chemical | medical solution, and a specific metal oxide precursor liquid mixture.

  In magnesium fluorides used in optical applications as described above, an antireflection function is required by having a low refractive index as shown in Patent Documents 1 to 4, while, as suggested in Patent Document 5, There has been a demand for a method of introducing hydrophilicity in order to prevent charging. However, the hydroxyl group (OH group) generated on the surface of the coating layer by the plasma irradiation or the like of Patent Document 5 has a short life and it is difficult to express long-term hydrophilicity, and equipment such as plasma is necessary for production. Absent.

  The optical body shown in Patent Document 6 satisfies both low emission and antifouling properties due to the hydrophilic combination of magnesium fluoride and titanium oxide, but is troublesome to manufacture because it is a multilayer film. Therefore, a member satisfying low refractive index and hydrophilicity with a single layer film has been demanded.

  On the other hand, as shown in Non-Patent Document 1, the spectral sensitivity of various solar cells is, for example, about 580 nm of visible light in amorphous silicon, and the wavelength region on the long wave side of 800 to 1200 nm in crystal-Si and compound semiconductors. It is necessary to penetrate through the center. For solar cell applications, there is a demand for a low-reflection film that transmits light in a wide range of 400 to 1200 nm, corresponding to not only conventional visible light but also a long wavelength range.

Furthermore, the present invention is not limited to these, and the low reflection film using magnesium fluoride has the following problems.
(1) Dirt on the surface is conspicuous In the case of a low-reflection film that uses optical thin film interference, if organic organic dirt such as sweat or oil adheres, it becomes a thin film, causing optical interference and changing the optical film thickness. Since optical interference occurs, such as appearing colored, dirt will appear more prominently.
(2) Dirt easily adheres In addition, it is very difficult to remove dirt with a thin film made of ultrafine particles, and it takes a lot of labor to remove the dirt, and the antireflection effect utilizing light scattering. Also in the case of the antiglare film for obtaining the surface, since the surface is uneven, the dirt further enters the recess, and the dirt tends to physically adhere to the surface.
(3) It is an insulator and is easy to be charged with static electricity. The reason why these stains are likely to be attached is that the low-reflection film using magnesium fluoride is basically an insulator and is therefore easily charged and hydrophobic. Contaminants are more likely to adhere, especially during the dry season of winter.

For example, a deposited magnesium fluoride film such as glasses or a camera lens has a surface resistance value of 3.9 × 10 ¹² Ω. It is an insulator at cm, and a pure water contact angle of 68 ° is hydrophobic. For this reason, it is obvious that dirt easily adheres due to sweat and dust, and is easily contaminated. Patent Document 5 also describes that the surface of an optical element having a fluoride is easily charged and the transmittance decreases.

Therefore, the low-reflective coating using magnesium fluoride is exposed to wind and rain and ultraviolet rays as well as solar cells, etc., and is always exposed to inorganic and organic matter such as sand dust, bird droppings, and exhaust gas. It is not preferable because the pollutant easily deposits and adheres to the solar light and causes a decrease in power generation efficiency.
(4) Adhesive strength with the substrate is weak.
Since fluoride is not limited to magnesium fluoride, it is chemically stable. Therefore, it is difficult to form a chemical bond with a substrate even if the film is formed on a glass substrate and baked at a certain temperature. Magnesium fluoride has a Mohs hardness of about 6, and the hardness is not so high. Therefore, there is a problem that the abrasion resistance is poor and the film is easily peeled off.

  None of these problems have been solved by known techniques, having high light transmittance and low reflectance, strong adhesion to the substrate, excellent weather resistance, hydrophilic and antifouling properties, There has been a demand for a low-reflective film that has an antistatic function, can be enlarged in area, and is inexpensive in cost. Particularly in recent solar cells using compound semiconductors and crystalline silicon or compound semiconductors, not only the visible light region but also light transmittance in a wide region of 400 to 1200 nm is required. An object of the present invention is to provide such a low reflection film.

  The present applicants have intensively studied to solve such problems, and as a constituent of the low reflection film, water having a hydroxyl group in the molecule is substituted for magnesium fluoride which has low reflectivity but is not hydrophilic. By using magnesium oxyfluoride ultrafine particles, not only has good low reflectivity (refractive index n = 1.2-1.29), but also can exhibit excellent hydrophilicity and antifouling property The present inventors have found that a low reflection film excellent in self-cleaning property and antistatic property can be obtained.

  Furthermore, by mixing a specific metal oxide as a “refractive index modifier” with the magnesium hydroxide fluoride ultrafine particles, the metal oxide can be uniformly dispersed in nanoorder order on the magnesium hydroxide fluoride ultrafine particles. It was found that a colorless and transparent optical thin film having good transparency in a wide range of 400 nm to 1200 nm was obtained, and the present invention was achieved.

Further, by using a metal oxide having antistatic ability such as tin oxide, indium oxide, zinc oxide, antimony oxide, etc. as a refractive index adjusting agent, the surface resistance value is further 1 × 10 ¹⁰ Ω in the hydrophilic low reflection member. . The inventors have found that an antistatic function of cm or less can be imparted, and have reached the present invention.

That is, this invention includes the following inventions 1-11.
"Invention 1"
A low-reflection member having a transparent substrate and a low-reflection film formed on the transparent substrate, wherein the low-reflection film contains hydrophilic magnesium hydroxide fluoride particles having a particle diameter of 5 to 500 nm. A hydrophilic low-reflective member characterized by being expressed.
"Invention 2"
The hydrophilic low reflection member according to the invention 1, wherein the magnesium hydroxide fluoride is MgF2 _-x (OH) _x (x = 0.01 to 0.5).
"Invention 3"
The hydrophilic low reflection member according to invention 1 or 2, wherein the magnesium hydroxide fluoride is MgF _1.89 (OH) _0.11 .
"Invention 4"
Furthermore, the hydrophilic low reflection member in any one of the invention 1 thru | or 3 formed by mixing a metal oxide as a refractive index regulator.
"Invention 5"
The molar ratio of magnesium hydroxide fluoride and metal oxide in the hydrophilic low reflection film is in the range of (10 / 0.5) to (10/30) per 10 moles of magnesium hydroxide fluoride. The hydrophilic low-reflection member according to the invention 4 described above.
"Invention 6"
The metal oxide is one or more selected from SiO ₂ , Al ₂ O ₃ , CeO ₂ , ZrO ₂ , TiO _2, SnO ₂ , In ₂ O ₃ , Sb ₂ O ₅ , La ₂ O _3. The hydrophilic low reflection film according to any one of Inventions 4 to 5, wherein the hydrophilic low reflection film is provided.
"Invention 7"
The hydrophilic low-reflection member according to any one of Inventions 4 to 6, wherein a solution obtained by hydrolyzing magnesium hydroxide fluoride ultrafine particles and a metal compound is formed on a transparent substrate surface.
"Invention 8"
The low reflection member according to any one of Inventions 4 to 7, wherein a difference in average transmittance at a wavelength of 400 to 1200 nm (transmittance after treatment-untransmitted transmittance) is 6% or more.
"Invention 9"
The hydrophilic low reflection member according to any one of inventions 1 to 8, wherein a contact angle with water on the surface of the hydrophilic low reflection film is 30 ° or less.
"Invention 10"
The surface resistance value of the hydrophilic low reflection film surface is 1 × 10 ¹⁰ Ω. The hydrophilic low-reflective member according to any one of Inventions 1 to 8, wherein the hydrophilic low-reflection member is equal to or less than cm.
"Invention 11"
The surface protection member for solar cells using the hydrophilic low reflection member in any one of invention 4 thru | or 9.

  It is possible to obtain a hydrophilic low-reflection member having excellent performance by forming a low-reflection film having ultrafine particles of magnesium hydroxide fluoride fluoride having a low refractive index and excellent hydrophilicity and durability on a transparent substrate. I can do it. Since it has hydrophilicity, it is excellent in antifouling property and can be easily washed away even when dirt adheres. In addition, the low reflection member of the present invention has a wide transmittance up to a long wavelength region of not only visible light but also near infrared light, and is particularly excellent as a transmittance in the 400 to 1200 nm region, and thus is useful as a protective member for solar cells. It is.

Transmission spectrum of the film formed on the glass substrate in Example 1 Transmission spectrum of the film formed on the glass substrate in Comparative Example 2

  The present invention is a low reflection member having a transparent substrate and a low reflection film formed on the transparent substrate, wherein the low reflection film contains magnesium hydroxide fluoride ultrafine particles having a particle diameter of 5 to 500 nm. It is a hydrophilic low reflection member characterized by expressing hydrophilicity.

  Magnesium hydroxide fluoride used in the present invention has a low refractive index (1.22 to 1.29), and also exhibits hydrophilicity by having a hydroxyl group. Therefore, it is “low reflection” and “hydrophilic”. It has a hydrophilic low reflection function. Furthermore, the hydroxyl group can be used as a binding site. When magnesium hydroxide fluoride fine particles are formed on a substrate glass and the transmittance is measured, the optical properties of the optical fiber having a transmittance of about 5 to 8% higher than that of the substrate glass are shown in the ultraviolet to visible region. Was recognized. In particular, it has a low refractive index in the visible light region near 550 nm and provides high transmittance. However, the transmissivity is considerably reduced at long wavelengths in the near infrared (800 to 1200 nm), and is only about 2 to 3% higher than that of untreated glass. This is an improvement for producing a low reflection film in a wide wavelength region. There is room.

  In the present invention, by mixing a specific metal oxide as a refractive index adjusting agent into the magnesium hydroxide fluoride fine particles by the sol-gel method, the long wavelength region of magnesium hydroxide fluoride excellent in transparency from the ultraviolet to the visible region is obtained. The permeability is improved. In mixing, a hydrophilic low-reflection film was constructed utilizing the unique characteristics of magnesium hydroxide fluoride. Details are shown below.

  In general, metal oxides are useful as coating films having optical properties, but their respective refractive indexes are not necessarily low. For example, the refractive index (document value) of a metal oxide single film is 1.45 in order of silica, alumina: 1.61, tin oxide: 1.68, zirconium oxide: 1.86, titanium oxide: 2.15, pentoxide. Tantalum: 2.3. From these values, it seems that metal oxides having a relatively low refractive index, such as silica and alumina, can be applied to optical applications. The coating film of silica alone shows a slightly higher transmittance than the substrate glass at all wavelengths, but does not have a particularly high transmittance in the long wavelength region.

  On the other hand, in the case of a metal compound having a large refractive index, there is a problem in using it as a low reflection film used for optical applications. When a metal oxide having a large refractive index, such as zirconium oxide, tantalum pentoxide, or titanium oxide, is formed alone on a glass substrate, the refractive index is approximately 1.85 to 2 at a theoretical value when baked at a high temperature of 550 ° C. This film shows a higher reflectance (10-20%) than a glass substrate (8%). That is, the low reflection film was not usable at all. When these films were measured by XRD diffraction, crystallization of the metal oxide was observed.

The mixing of two or more of the metal oxides also has a problem in permeability, and a glass substrate coated with a TiO ₂ / SiO ₂ oxidation system has a lower permeability than an untreated glass substrate at 400 to 1200 nm. (See Comparative Example 2).

  As described above, metal oxides having a higher refractive index than glass such as tin oxide, titanium oxide, zirconium oxide, and tantalum pentoxide are inferior in permeability even in a long wavelength region. However, when the present inventors tried to mix several kinds of metal oxides with magnesium hydroxide fluoride as appropriate, depending on the combination, transmission in the long wavelength region was not performed. The rate was found to be high. More surprisingly, it has been discovered that upon firing after deposition, these mixtures exist in an amorphous state in the coating. In fact, when the film after firing was diffracted by XRD, the peak of magnesium hydroxide fluoride was the main component, and the other metal oxides were in an amorphous state with almost no crystals. It is presumed that this amorphous state suppresses the increase in refractive index. This phenomenon was more prominent as the number of metal oxides mixed with magnesium hydroxide fluoride increased.

  That is, in the film formation of a system in which several kinds of magnesium hydroxide fluoride sol and metal oxide sol are appropriately mixed, crystallization is suppressed in the mixed state when the metal oxide sol is mixed at a high temperature, and partly amorphous. It was presumed that the material remained as it was, and the refractive index did not increase.

  In a system that does not contain magnesium hydroxide fluoride, even if it is a metal oxide that crystallizes, it exists in an amorphous state in the presence of magnesium hydroxide fluoride, so the refractive index of the metal oxide is crystallized. It becomes possible to keep it low compared to the case. By this feature, it has been found that even a high refractive index oxide such as zirconium, titanium, or tantalum can be used as a refractive index adjusting agent. This amorphization is one of the major characteristics brought about by using magnesium hydroxide fluoride.

  Based on these findings, the present inventors have mixed a metal oxide as a refractive index adjusting agent with magnesium hydroxide fluoride to optimize the combination that gives high transmittance in a wide wavelength region.

  As described above, the refractive index of magnesium hydroxide fluoride is 1.22-1.29, which is about 0.1 lower than the theoretical value (1.38) of general-purpose magnesium fluoride. Therefore, even when a metal oxide having a high refractive index is added, the allowable range is increased, which is advantageous.

  Further, as described above, since magnesium hydroxide fluoride has a high transmittance at 550 nm, it can be analogized that when mixed with a metal oxide, a transmission curve having a peak at 550 nm is similarly given. When mixed with a product, the peak of the maximum transmittance slightly shifts to the longer wavelength side, and accordingly, the transmittance in the long wavelength region tends to increase. In the case of the oxide alone, especially for alumina (n = 1.61) whose transmittance on the long wavelength side was not high, an improvement in transmittance in the region of 600 to 800 nm was observed.

  In addition, when zirconium oxide (n = 1.68) was formed on a glass substrate, the transmittance was lower than that of the glass substrate at all wavelengths, but in a mixed system of magnesium hydroxide fluoride and zirconium oxide. , An improvement in transmittance was observed in the region of 700 to 900 nm.

  As described above, magnesium hydroxide fluoride and each metal compound have compatibility with each other, and in the combination, a simple average value of the refractive index is not obtained. When a metal oxide is mixed with magnesium hydroxide fluoride, 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 compound is low, the wavelength shifts slightly longer than the peak of the transmittance of magnesium hydroxide fluoride. As the refractive index of the metal oxide increases, the peak further appears on the longer wavelength side.

  Therefore, by utilizing this property, when several types of metal oxides having different refractive indexes are mixed with magnesium hydroxide fluoride, for example, a metal compound having a relatively low refractive index has a higher transmittance in the visible region. Since metal oxides with a high refractive index tend to increase the transmittance in a longer wavelength region, by combining these appropriately, the metal oxide acts as a refractive index adjuster and increases the high transmittance over a wide range of wavelengths. Seem.

  In mixing with magnesium hydroxide fluoride, in order to keep the refractive index low, a metal oxide having a low refractive index can be mixed more than that having a high refractive index. That is, a relatively large amount of low refractive index silica, alumina or the like can be mixed. For example, 0.5 to 8 mol, more preferably 1 to 6 mol can be mixed with respect to 10 mol of magnesium hydroxide fluoride. Medium refractive index tin oxide, yttrium oxide and the like can be mixed in an amount of 0.5 to 7 mol, preferably 1 to 5 mol. In high refractive index zirconia, titanium oxide, tantalum pentoxide and the like, 0.5 to 6 mol, preferably 1 to 4 mol can be mixed. Here, in mixing, it is not always necessary to add a large amount of low refractive index, and it may be appropriately adjusted so that the refractive index of the mixture can be kept low.

  When the addition amount of the metal oxide is large, the refractive index is increased, and the low reflection film is not obtained. On the other hand, when the addition amount is too low, magnesium hydroxide fluoride is the main component, and thus the transmittance increases near 550 nm visible light. However, when the amount is 800 nm or more, the transmittance is significantly reduced, which is not preferable. By adjusting as appropriate, a wide optical matrix film not only for ultraviolet light and visible light but also for a long wavelength region of near-infrared light can greatly increase the transmittance.

  This phenomenon is contrary to the conventional concept of refractive index, and a composite film containing 3 to 5 kinds of elements has an unknown principle, but increases the transmittance in the wavelength range where each element is present as described above. It seems to improve from visible light to infrared light by increasing the transmittance in that wavelength range.

  Although it is impossible to form 3 to 5 types of mixed films at a time by vapor deposition or sputtering, a composite film in which several or more components are mixed can be formed at a time by the sol-gel method (wet coating method). It became possible to realize. This is expected to have a wide range of UV-visible and infrared applications, suggesting that it can be applied to optical devices of all wavelengths such as steppers, lasers, organic EL, liquid crystal display elements, LEDs, lighting fixtures, and lenses. .

  In addition, by mixing these metal oxides, the metal oxides are bonded to the oxides in the substrate, so that the wear resistance is remarkably improved by increasing the film strength.

  In the present invention, the range in which the metal oxide is added with respect to 10 mol of magnesium hydroxide fluoride is expressed by the ratio (molar ratio) with the metal oxide M, (magnesium hydroxide fluoride / M) = (10/0). .5) to (10/30) are preferable, and (10/1) to (10 / 2.5) are particularly preferable. If it is larger than (10 / 0.5), it is not preferable because magnesium hydroxide fluoride is the main component and the film strength is inferior. Moreover, if it is less than (10/30), when mixed with magnesium fluoride, the chemical becomes unstable and gels in several days, which is not preferable.

  Therefore, if the refractive index of the mixture of magnesium hydroxide fluoride and metal oxide is within a range that is within the range of (10 / 0.5) to (10/30), the chemical solution that does not gel. It becomes possible to form a hydrophilic low-reflection film with no problem with the film strength.

  As described above, the main effect of the metal oxide addition is that the refractive index is relatively increased from the visible light to the near-infrared range in order to increase the transmittance in the near-infrared region that cannot be improved by magnesium hydroxide fluoride alone. Although it can be adjusted to a low level, the following effects can be achieved including them.

That is, since the refractive index can be adjusted by adding to [1] magnesium hydroxide fluoride as an effect of adding metal oxide, the optical film thickness can be arbitrarily changed. (Effect as a refractive index adjusting agent)
[2] Change the transmittance. It becomes possible to increase the transmittance in a wide range of wavelengths of not only visible light but also ultraviolet and infrared light. (Adjustment of transmittance)
[3] Increasing coating strength (increasing coating strength)
Since magnesium hydroxide fluoride is not an oxide in nature, it does not bond to a base material such as a glass substrate, and therefore has poor film strength. Here, when a certain amount of metal oxide is added, it is mixed with magnesium hydroxide fluoride and bonded to the base material, so that it has an effect as a binder for increasing the film strength.
[4] By adding a metal oxide, there is a self-cleaning function in which the hydroxyl group of magnesium hydrofluoride is present on the surface layer after the coating is formed, to exert a hydrophilic effect and maintain the hydrophilicity for a long time.
[5] By adding a conductive metal oxide (for example, SnO ₂ , In ₂ O ₃ ) as the metal oxide, the synergistic effect of the hydroxyl group of magnesium hydroxide fluoride and the conductive metal oxide after the coating is formed. The antistatic effect is maintained by the effect, and the antifouling function is maintained for a long time.

  Hereinafter, the magnesium hydroxide fluoride, the manufacturing process of the organosol, and the metal oxide will be described.

The magnesium hydroxide fluoride used in the present invention is a compound having a hydroxyl group. This can be confirmed by X-ray diffraction data, and the X-ray diffraction pattern was found to be consistent with magnesium hydroxide fluoride (MgF _1.89 (OH) _0.11 ) of JCPDS file 54-1272. . Magnesium hydroxide fluoride has amorphous properties and exhibits hydrophilicity as described later.

Such remarkable amorphousness is not described in the preceding examples. The XRD spectrum (FIG. 1 of Patent Document 3) of magnesium fluoride (MgF ₂ · nH ₂ O) having crystal water shown in Patent Document 1 also shows a peak with good crystallinity similar to that of Reference Example 1 above. This is greatly different from the magnesium hydroxide fluoride used in the present invention. XRD shown in Patent Document 1 does not have a JCPD file number and is different from magnesium hydroxide fluoride.

  When the magnesium hydroxide fluoride of the present invention was formed alone on soda lime glass, the refractive index was surprisingly 1.26, which was much lower than the literature value of 1.38. This is presumed to be a film made of a porous material in which magnesium fluoride (refractive index: 1.38) contains a large amount of air layer (refractive index: 1.0). When the density of the coating was determined, it was found that the coating was a bulk body that did not contain a sufficiently densely packed air layer. This is presumed that magnesium hydroxide fluoride has a crystal structure different from conventional magnesium fluoride.

  Magnesium hydroxide fluoride showed a value very close to the theoretical value of 1.22 with respect to the glass substrate. Therefore, even a single layer film has excellent antireflection characteristics with an average visible light reflectance of 0.05% (550 nm) in a wide range of visible light. On the other hand, the compound obtained by adding adhering water to magnesium fluoride described in Patent Document 1 shows a refractive index of 1.37. Therefore, when compared with the same single layer film, the optical characteristics are higher than that of the magnesium hydroxide fluoride of the present invention. Inferior. Judging from the viewpoint of XRD and optical characteristics, it can be said that magnesium hydroxide fluoride and the magnesium fluoride compound described in Patent Document 1 are completely different substances.

  As described above, the magnesium hydroxide fluoride of the present invention has a lower refractive index than magnesium fluoride and is more suitable as a low reflective film material. In addition, it has a stable hydroxyl group in the molecule, unlike the case where adhering water is added, so it exhibits excellent hydrophilicity, exhibits antifouling properties, and can be easily washed away even when dirt is attached. The effect that can be expected.

  Moreover, in order for the film | membrane surface to show hydrophilicity, it is generally desired that the surface is covered with the hydroxyl group. In the present invention, since the ultrafine particles of magnesium hydroxide fluorinated magnesium have a hydroxyl group, the hydroxyl group is exposed on the surface. Further, since the ultrafine particles have a hydroxyl group, adhesion of the ultrafine particles to the base material is improved.

  As a result of examination, the ultrafine particles have fewer hydroxyl groups than simple hydroxides but are sufficiently hydrophilic. Furthermore, since the magnesium hydroxide fluorinated magnesium of the present invention is chemically more stable than a simple hydroxide, the low reflective member having a hydrophilic film made of the ultrafine particles is excellent in reliability for long-term use. Conceivable.

  The fluorinated magnesium hydroxide used in the present invention is obtained by adding a hydrogen fluoride aqueous solution dropwise to a solution in which the magnesium raw material is dispersed, suspended, or dissolved, so that the magnesium raw material is made into ultrafine particles together with the fluorination and hydroxylation of the magnesium raw material. I can do it.

  As the magnesium raw material, inorganic compounds such as magnesium chloride, magnesium oxide and magnesium carbonate are preferably used. It is possible to use organic compounds such as magnesium alkoxide and magnesium carboxylate, but when organic magnesium compounds are used, the viscosity of the resulting magnesium hydroxide sol tends to increase, so inorganic compounds Is preferable, and magnesium chloride and magnesium carbonate are more preferable in terms of removal of by-products described later.

  An organic solvent is preferably used as the solvent used as the dispersion medium. Since an aqueous hydrogen fluoride solution is added during the reaction, a protic polar organic solvent highly compatible with water is more desirable. As such a solvent, alcohols, organic acids and the like can be used. The alcohol is an alcohol having 1 to 10 carbon atoms, preferably an alcohol having 1 to 4 carbon atoms or a glycol ether having 2 to 20 carbon atoms. Examples of alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, isopropanol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, and tert-butyl alcohol, and glycols having 2 to 20 carbon atoms. Examples of ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and dipropylene glycol monomethyl ether. Can be mentioned. Among these, methanol, ethanol, and isopropanol are preferable as alcohols, and diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and the like are preferable as glycol ethers.

  Hereinafter, an organosol containing magnesium hydroxide fluoride ultrafine particles used in the present invention will be described as an example. This manufacturing method includes the following three steps (a), (b), and (c).

(A) A step of gradually producing magnesium hydroxide fluoride ultrafine particles by gradually dropping a solution containing hydrofluoric acid into a solution in which a magnesium compound is dispersed, suspended or dissolved in an organic solvent.
(B) Step of removing by-product or excess hydrogen fluoride (c) Step of solvent substitution or adjustment of solvent concentration of sol obtained in step (b) to form organosol In step (a), the magnesium compound The size of the particles is not particularly limited as long as it can form a dispersion or suspension. For example, particles having an average particle size of 0.1 to 800 μm, preferably 0.3 to 500 μm may be used. The average particle diameter is measured in accordance with JIS K1150 (1994).

  Moreover, content of the magnesium compound in suspension is 0.01-5 mol / L, for example, Preferably, it is 0.05-2 mol / L. If the content is low, the production efficiency of magnesium hydroxide fluoride ultrafine particles tends to be low. On the other hand, if the content is large, gelation occurs instantaneously when the suspension and the solution containing hydrofluoric acid are mixed, and the viscosity of the mixed solution rises rapidly, resulting in a uniform reaction between the magnesium compound and hydrogen fluoride. It is not preferable because it is difficult to proceed.

  The concentration of hydrogen fluoride in the solution containing hydrofluoric acid is 5 to 60% by weight, preferably 10 to 58% by weight. When the concentration of hydrofluoric acid is low, the production efficiency of the magnesium hydroxide fluoride ultrafine particles tends to be low. On the other hand, if the concentration of hydrofluoric acid is high, colloids may be rapidly formed in the reaction system and gelled, which is not preferable because it inhibits the formation of magnesium hydroxide fluoride ultrafine particles.

  Solutions containing hydrofluoric acid include hydrofluoric acid, water, lower alcohols such as methanol, alcohol and isopropanol, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate and isopropyl acetate, diethyl ether and tetrahydrofuran, etc. The ethers can be added as a solvent.

  Even if the ratio of fluorine atoms to magnesium is increased, sufficient hydrophilicity is exhibited. Therefore, in order to impart the characteristics of fluorine atoms, it is preferable to adjust the ratio of fluorine atoms to be high. Therefore, the mixing ratio of the magnesium compound and hydrogen fluoride can be mixed under the condition that all the magnesium compound is consumed. The number of moles of hydrogen fluoride added to the magnesium compound is 1 to 2 times the number of moles of Mg multiplied by the valence number 2, preferably 1 to 1.5 times, more preferably 1 to 1.2 times. Double. When another metal compound (for example, a calcium compound described later) is included as an auxiliary material, the above range is preferable on the basis of the sum of numerical values obtained by multiplying the number of moles of magnesium and each metal compound by the valence. The pH after reaction is adjusted to the range of 1-4.

  The reaction temperature for this reaction is usually from −20 ° C. to the boiling point of the solvent. Specifically, it can be performed at −20 ° C. to 80 ° C., preferably 0 ° C. to 50 ° C. When the reaction temperature is lower than −20 ° C., the reaction rate becomes slow and a cooling device is required, which is not preferable. On the other hand, when the reaction temperature exceeds 80 ° C., the boiling point of hydrogen fluoride is low, so that it volatilizes immediately after the addition and is not used effectively, and hydrogen fluoride gas is generated, which is dangerous. Moreover, the reaction proceeds rapidly immediately after the addition, and the produced colloid becomes a local aggregate or gel, which is not preferable.

  In the reaction, it is also preferable to gradually advance the reaction between the magnesium compound and hydrogen fluoride because of the effect of increasing the uniformity of the organosol. Specifically, the concentration of the dispersoid in the dispersion is low, the addition rate of hydrogen fluoride is slow, the concentration of hydrogen fluoride to be added is low, the diffusion rate of hydrogen fluoride in the organic solvent is slow, and the reaction A method such as reducing the speed is preferred. In carrying out the reaction with a solution, when a solution containing hydrofluoric acid is added rapidly, the reaction advances rapidly, and there is a danger due to sudden heat generation or bumping, which is not preferable.

  The pressure of the reaction system is not particularly limited, but it is convenient to carry out the reaction at around normal pressure. Specifically, it is 0.05-1 MPa, 0.05-0.5 MPa is preferable, and it is enough to perform in the atmospheric pressure state which does not perform pressure adjustment especially.

  By treating the resulting solution in step (b), it is possible to remove by-products or to remove unreacted hydrogen fluoride when hydrogen fluoride is excessively added. That is, holding the reaction solution at an elevated temperature, for example, above the reaction temperature and below the reflux temperature of the organic solvent for about 30 minutes to 100 hours is a low-boiling by-product or an unreacted component such as hydrogen chloride. It is effective for removing hydrogen fluoride, carbon dioxide gas and the like appropriately.

  That is, by stirring the solution at room temperature or under heating or introducing and purging nitrogen gas while refluxing in the vicinity of the boiling point of the solvent, low-boiling by-products or unreacted components such as hydrogen chloride, It is effective for removing hydrogen fluoride, carbon dioxide gas and the like appropriately. In some cases, it may be removed while distillation under reduced pressure. In removing the low-boiling acid, the pH is preferably adjusted to 1 to 4, preferably 2 to 3. By maintaining the pH of the organosol at 1 to 4, by reacting with the alkali metal, earth metal, boric acid, silanol group on the glass surface at the time of coating the substrate, the surface layer is eroded and roughened. Increase the adhesive strength of the coating.

  Further, the remaining acid contributes to the stability of the refractive index adjusting agent such as metal alkoxide and magnesium hydroxide fluoride, and particularly acts as an acid catalyst, so that a stable mixed solution can be prepared.

  In step (c), the concentration of the magnesium hydroxide fluoride fine particle solution obtained in step (b) is adjusted or solvent substitution is performed. In order to increase the fine particle concentration, the solvent may be added to lower the fine particle concentration, such as removal of the organic solvent, for example, distillation or extraction, and the solvent may be the same as or different from the original solvent. Further, depending on the application, the solvent may be converted from a solvent used in the production of the organosol to a different solvent.

  Between step (b) and step (c), a step of crushing the organosol may be included. For pulverization of organosols, those based on impact force and shear force are effective, and gels or sols that are usually obtained as agglomerates of primary particles can be used as primary particle dispersions. Is particularly preferable.

Moreover, it is desirable that the magnesium hydroxide fluorinated magnesium is MgF2 _-x (OH) _x (x = 0.5 to 0.01). By having an OH group, the adhesiveness to the base material and the hydrophilicity will be superior to simple magnesium fluoride. If x exceeds 0.5, the refractive index cannot be kept low, which may cause a problem as a low reflection film. On the other hand, if it is less than 0.01, the number of hydroxyl groups is small, the hydrophilicity becomes small, and the adhesive strength of the film to the substrate may be lowered.

Among these, magnesium hydroxide fluoride MgF _1.89 (OH) _0.11 registered in JCPDS file 54-1272 is preferably used. This compound was observed to be produced even when hydrogen fluoride was dripped more than twice the molar amount of the raw material magnesium compound, leaving MgF _1.89 (OH) _0.11 while leaving hydrogen fluoride in the solution. Can be synthesized. Even if an excessive amount of hydrogen fluoride is added, MgF _1.89 (OH) _0.11 is generated, and it is considered that there is some equilibrium.

  Further, a material containing calcium fluoride fine particles in the magnesium hydroxide fluoride fine particles may be used as a raw material for the low reflection film. Calcium fluoride is prepared by coexisting a precursor material such as an alkoxide compound, halogenated compound, oxyhalogenated compound, and acetic acid compound of calcium with the magnesium raw material when preparing ultrafine particles having fluorinated magnesium hydroxide. It can be obtained through a reaction with an aqueous solution.

  The amount of calcium fluoride introduced is not particularly limited, but the refractive index of calcium fluoride is a value that can be used as a low reflective film material, but is slightly higher than magnesium hydroxide fluoride (n = 1.4 to 1.43) Therefore, when a lower refractive index is required, the introduction amount should be smaller. The hydrophilicity is more preferably 70% by weight or less.

  The average particle size of the ultrafine particles is preferably 5 to 500 nm. If it is less than 5 nm, voids between particles tend to be small, and as a result, the number of exposed hydroxyl groups tends to be small, and hydrophilicity may be lowered. On the other hand, if it exceeds 500 nm, the contact point between the particles and the base material becomes small, and the adhesion of the ultrafine particles to the base material may be reduced.

  By mixing a metal oxide as a refractive index adjusting agent into the organosol prepared as described above, the refractive index in the long wavelength region can be lowered, and as a result, low reflectivity and high transmittance can be realized.

Further, by using a metal oxide having conductivity (for example, SnO ₂ , In ₂ O ₃ containing Sn (ITO) or the like) as the metal oxide, an antistatic function can be imparted. Here, SnO ₂ is a semiconductor and exhibits a function as an antistatic film. Here, in order to develop good conductivity, several percent of Sb is added to SnO ₂ as a co-drug, Zn ₂ is doped with Al ₂ O ₃ , and the same applies to In ₂ O ₃ . Or SnO ₂ is added to

In addition, since fluorine ions can also be an excellent dopant, in the present invention, a good antistatic function can be achieved even in a form in which Sn is doped with F ions or In ₂ O ₃ is doped with F ions from several to 8% each. Was confirmed. Furthermore, it has become possible to realize a long-term stable antistatic function combining both the hydroxyl group of magnesium hydroxide fluoride and the electronic conductivity of the semiconductor. In the present invention, since a conductive metal oxide is used as a refractive index adjusting agent, an antistatic function can be imparted at the same time while maintaining a low refractive index.

  As described above, the refractive index adjusting agent is preferably a metal oxide, and the metal element of the metal oxide may be a metal compound that can finally form an oxide by drying and baking treatment, and titanium. At least one metal oxide selected from silicon, zirconium, iron, tin, aluminum, indium, tin, zinc, antimony, tantalum, lanthanum and the like is preferable. Furthermore, borate, phosphate, etc. can also be used. Among these, when a metal alkoxide, a metal chloride, and its hydrolyzate are used as a raw material, since the intensity | strength and chemical stability of the film | membrane obtained are excellent, it is especially preferable.

  The metal oxide is produced by a so-called sol-gel method. In the sol-gel method, a sol made of a metal compound such as the above-described inorganic salt, organometallic complex, organometallic carboxylate, metal alkoxide and hydrolyzate thereof, or a mixture thereof is used as a raw material. These raw materials (hereinafter sometimes referred to as metal compounds) undergo a reaction such as hydrolysis, dehydration, polycondensation, oxidation, and thermal decomposition in a drying / firing process, whereby a metal oxide is formed by a firing treatment.

  When a base material is coated with a sol containing the above metal compound in the presence of magnesium hydroxide fluoride particles and hydrolyzed, a hydrolysis product of the metal compound is generated. The water required for hydrolysis is supplied from the water in the hydrofluoric acid solution used for preparing the organosol. Since the metal compound sol and the hydrolysis product can react with the hydroxyl groups on the surface of the magnesium hydroxide fluoride fine particles, they have the function of reinforcing the bonds between the particles by polycondensation or bonding the particles to the substrate. Thereafter, the condensation reaction proceeds to improve the mechanical strength of the obtained film. Thereafter, a film is formed through a drying / firing process, and the particles of magnesium hydroxide fluoride can be firmly adhered to the substrate by the action of a so-called binder.

  Below, the main metal compound used as a raw material is illustrated.

The silicon alkoxide as a raw material has a general formula Si (OR) ₄ (wherein R is independently methyl, ethyl, normal propyl, isopropyl, normal butyl, secondary butyl, methoxyethyl, Ethoxyethyl group or phenyl group)) or a hydrolyzate thereof, in particular, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetranormalpropoxysilane, tetranormal Butoxysilane, tetratertiarybutoxysilane or the like or a hydrolyzate thereof is preferable. In addition, a part of -OR may be substituted with a halogen atom such as a chlorine atom, and examples thereof include chlorotriethoxysilane, dichlorodinormalbutoxysilane, and trichloronormalbutoxysilane.

  Inorganic salts such as aluminum chloride, polyaluminum chloride, aluminum hydroxide such as boehmite, anhydrides and hydrates such as aluminum sulfate, aluminum nitrate, aluminum formate, aluminum acetate, aluminum oxalate, and aluminum citrate is there.

  Examples of organic carboxylates include Al salts such as aluminum laurate, aluminum stearate, aluminum naphthenate, aluminum 2-ethylhexanoate, and hydrated salts thereof.

Aluminum alkoxide is represented by the general formula Al (OR) ₃ (wherein R is independently any of methyl group, ethyl group, isopropyl group, normal butyl group, secondary butyl group, methoxyethyl group, ethoxyethyl group or phenyl group) In particular, triethoxyaluminum, triisopropoxyaluminum, trinormalpropoxyaluminum, and trisecondary butylaluminum are preferably used.

  Further, a part of -OR may be substituted with a halogen atom such as a chlorine atom. For example, chlorodiisopropoxyaluminum, chlorodisecondary butylaluminum, dichloroisopropoxyaluminum, dichlorosecondary butylaluminum and the like can be used. .

The aluminum metal complex is represented by the general formula Al (OR) _n Y _3-n . In the formula, OR represents an alkoxide, and Y: represents a chelate. Here, n represents an integer of 0 to 3. R each independently represents 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, trifluoromethanesulfonic acid, and the like. Furthermore, it is also possible to use a 2-trimer obtained by condensation polymerization of aluminum alkoxide and these aluminum metal complexes.

Anhydrous titanium raw materials such as titanium tetrachloride (TiCl ₄ ), titanium trichloride (TiCl ₃ ), titanyl chloride (TiOCl 2), titanium nitrate (Ti (NO ₃ ) ₄ ), titanium oxynitrate (TiO (NO ₃ ) ₂ ) A salt or a hydrate thereof, titanium 2-ethylhexanoate, or an alkoxide. Ti alkoxide is represented by the general formula Ti (OR) ₄ (wherein R is independently methyl group, ethyl group, normal propyl group, isopropyl group, normal butyl group, secondary butyl group, methoxyethyl group, ethoxyethyl group) Or an alkoxy compound represented by any one of phenyl groups), and tetraethoxytitanium, tetranormalpropoxytitanium, tetraisopropoxytitanium, and tetranormalbutoxytitanium are preferably used. Moreover, those polycondensed dimer to dimer are also used.

  Further, a part of -OR may be substituted with a halogen atom such as a chlorine atom. For example, chlorotriethoxytitanium, dichlorodinormalbutoxytitanium, trichloronormalbutoxytitanium, or the like can 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: An integer of 0 to 3 is shown. R each independently represents a methyl group, an ethyl group, a normal propyl 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, methanesulfonic acid, trifluoromethanesulfonic acid, and the like.

  Examples of the mixture of alkoxide and chelate include dibutoxytitanium bisacetylacetonate and isopropoxydititanium bisoctylene glycolate.

Also, zirconium tetrachloride (ZrCl ₄₎ of Zr raw material, zirconium oxychloride _(ZrOCl 2. _8H 2 O), zirconium nitrate _{(Zr (NO 3) 4)} , zirconium oxynitrate (ZrO _{(NO 3) 2} 4 hydrate ), Zr salts such as zirconium stearate, zirconium naphthenate, zirconium 2-ethylhexanoate, zirconium acetylacetonate, etc., or anhydrous and hydrated salts thereof, or a general formula Zr (OR) ₄ (wherein R is independent of each other) And an alkoxy compound represented by a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, a secondary butyl group, a methoxyethyl group, an ethoxyethyl group, or a phenyl group.

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

  Further, -OR may be partially substituted with halogen, and examples thereof include chlorotriethoxyzirconium, dichlorodinormalbutoxyzirconium, and trichloronormalbutoxyzirconium.

Further, Sn raw materials include tin chlorides such as tin dichloride (SnCl ₂ ) and tin tetrachloride (SnCl ₄ ), and tin alkoxides such as tetraethoxytin, tetranormalpropoxytin, tetraisopropoxytin, and tetranormalbutoxytin. Other examples include Sn (OiPr) ₃ (acac), Sn (OnBu) ₃ Cl, BuSnCl ₃ and Bu ₂ Sn (acac) ₂ . Here, SnO ₂ is a semiconductor and is useful as an antistatic film.

  In addition, as described above, metal oxide organosols produced by solvent substitution of oxide fine particles obtained by hydrolyzing basic chlorides and metal alkoxides can be obtained as commercial products, for example, as organosilica sols. , Methanol silica sol, IPA-ST, IPA-ST-UP, IPA-ST-ZL, EG-ST, NPC-ST-30, DMAC-ST, MEK-ST (above, Nissan Chemical Industries, Ltd.), Oscar 1132, Oscar 1232 and Oscar 1332 (catalyst chemical products). Examples of the organoalumina sol include aluminum sol-CSA55 and aluminum sol-CSA110AD (Kawaken Fine Chemicals). Furthermore, there are organic solvent-based antimony oxide sols such as Sun Colloid ATL-130 and Sun Colloid AMT-130 (above, Nissan Chemical Industries products).

  Alternatively, a commercially available sol as an aqueous dispersion can be used after solvent substitution. Examples of such aqueous sols include Snowtex 40, Snowtex O, Snowtex C, Snowtex N (and above, Nissan Chemical Industries), Cataloid S-30H, Cataloid SI-30, Cataloid SN, Cataloid SA ( As described above, Catalyst Chemical Industry Product), Adelite AT-30, Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q (Asahi Denka Kogyo Co., Ltd.), Silica Dole-30, Silica Dole-20A, Silica Dole-20B Water-based silicon oxide sols such as (Nippon Chemical Industrial products); Alumina sol-100, Alumina sol-200, Alumina sol-520 (Nippon Chemical Industrial products), Alumina clear sol, Aluminum sol-10, Aluminum sol-20, Aluminum sol SV- 102, Aluminum sol-SH5 (above Water-based alumina sols such as Kawaken Fine Chemical Products); water-based antimony oxide sols such as A-1550 and A-2550 (Nissan Chemical Industry Products); water systems such as NZS-30A and NZS-30B (Nissan Chemical Industry Products) Zirconium oxide sol; water-based tin oxide sols such as Cerames S-8 and Cerames C-10 (and above, Taki Chemical Products); water-based titanium oxide sols such as Tynock A-6 and Tynock M-6 (and above, Taki Chemical Products); Examples thereof include water-based sol composed of tin oxide and antimony oxide such as Cerames F-10 (above, Taki Chemicals).

  The chemical solution that coats the transparent substrate is important for long-term stability, and it is desirable that it can be stored at room temperature for 30 days or more. When the hydrolyzable metal compound is mixed with the magnesium hydroxide fluoride sol, if the reduction of the refractive index of the target wavelength cannot be achieved by mixing only one kind of metal compound, 2-4 kinds of metal compounds Need to be mixed. In such mixing, even when there is only one kind of metal compound, even if it can exist as a relatively stable sol, there is a possibility of gelation if the compatibility of the mixed metal compound does not match.

  Moreover, when comparing the stability of metal oxide precursors (for example, metal alkoxides) in the sol, Si-based alkoxides such as alkoxysilanes are relatively stable, but Al-based, Zr-based, Ti-based, Sn-based, It is known to those skilled in the art that Ta-based alkoxides are unstable. Patent Document 4 describes a mixed system of magnesium fluoride and an Al-based alkoxide (Patent Document 4; Example 3) and a mixed system of Zr alkoxide (Patent Document 4; Example 4). A transparent sol is gradually produced by using a syringe filter as a complexing agent. When the present inventors made additional trials of Example 3 and Example 4, the chemical solution could only exist stably for one day at room temperature, the viscosity increased rapidly, and it was extremely unsuitable for the coating solution. It was.

Further, referring to the example of Patent Document 4, the stability was confirmed by conducting a supplementary test in a system in which three types of alkoxides of Si alkoxide, Al alkoxide, and Zr alkoxide were added to magnesium fluoride, and the mixture was mixed with MgF ₂ . When the metal oxide sol was mixed with MgF ₂ , the polymerization started rapidly, the viscosity rapidly increased, and after 2 days it was completely gelled, so that it could not withstand practical use and lacked chemical stability.

  It was extremely stable in the mixing of 2 to 4 kinds of the magnesium hydroxide fluoride sol of the present invention and other metal compounds. Moreover, the magnesium hydroxide fluoride used in the present invention had good compatibility with inorganic salts, organic salts, and metal alkoxides.

  In preparation of magnesium hydroxide fluoride sol, the raw material hydrogen fluoride and by-product inorganic acid (for example, HCl) are intentionally left, but the remaining 0.5 to 3% (in terms of F and HCl) acid is a metal. It is considered useful as a peptizer for compounds (for example, metal alkoxides), and long-term stability of 30 days or more at room temperature was confirmed even when 4 to 5 types of metal alkoxides were added.

  In a preferred embodiment, when magnesium chloride is used as the magnesium raw material and HCl is directly reacted with a slight excess of hydrogen fluoride, HCl is produced as a by-product. Hydrogen fluoride and HCl have a high vapor pressure, can be easily removed by heating or bubble ring, and HCl can remain in a few percent.

  As the transparent substrate, an inorganic glass substrate, a plastic substrate, or the like can be used. Examples of inorganic glass substrates include plate-like materials such as soda lime silicate glass, borosilicate glass, aluminosilicate glass, barium borosilicate glass, and quartz glass, especially those manufactured by the float process. Can do. 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 Si3N4, SiC, sapphire, Si wafer, GaAs, InP, and AlN.

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

  Application of the chemical solution onto the substrate can be performed by a spine coater method, a dipping method (dip coating method), a spray method, a roller coating method, a flow coating method, a screen printing method, a brush coating method, an ink jet method or the like.

  The coating film formed by various methods is preferably dried at 80 to 150 ° C. for 10 minutes to 6 hours and further heated and fired. The heating temperature is determined according to the heat-resistant temperature of the substrate. In addition, when taking advantage of the characteristics of magnesium hydroxide fluoride, it is preferable to fire 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 perform the treatment at about 300 ° C. or less. In addition, the inorganic glass substrate can be fired at a high temperature of about 700 ° C. by adjusting the firing time. As a preferred embodiment, a film excellent in wear resistance was obtained by baking at 650 ° C. to 700 ° C. for 150 seconds.

The physical property evaluation method of the antireflection film formed by various methods is shown below.
1. The optical characteristics were measured for transmittance and reflectance with a Hitachi spectrophotometer U-4100.
2. Hydrophilicity was measured with a pure water contact angle measuring device manufactured by Kyowa Interface Science in accordance with JIS R 3257 (1999).
3. The surface resistance value was measured with an insulation resistance measuring instrument (4329A high resistance meter) manufactured by Yokogawa Electric Corporation.
4). The film thickness and the refractive index were measured with an ellipsometer (Mitoshiri Optical Industry Co., Ltd. DVA-FL3: He-Ne laser 633 mm).

  The contact angle is defined from the contact angle between the surface of the coating layer obtained in accordance with JIS R 3257 (1999) and water droplets. As the hydrophilic low-reflection film, it is considered that the higher the wettability, the lower the contact angle is not particularly limited, but it may be, for example, 0.1 ° or more. Since it has hydrophilicity, it is excellent in antifouling property and can be easily washed away even when dirt adheres.

The hydrophilic low reflection member of the present invention has a surface resistance value of 1 × 10 ¹⁰ Ω. Since it is cm or less, it is a hydrophilic low reflection member having an antistatic function.

  These low reflection films are formed on one side or both sides of the transparent substrate. When both surfaces of the transparent substrate are used in contact with a medium having a refractive index close to 1 such as air, a high antireflection effect can be obtained by forming this film on both surfaces of the substrate.

  The hydrophilic low reflection member of the present invention is useful as a surface protection member for solar cells. When used as a surface protection member for solar cells, high light transmittance and low reflectance are required, and since solar cells are constantly exposed to sunlight, antifouling properties, water resistance, weather resistance, etc. The material which has both is desired. As described above, the hydrophilic low reflective film of the present invention containing magnesium hydroxide fluoride is excellent in antifouling property, water resistance and resistance.

  In addition, CIS thin film solar cells and crystalline silicon, which have been developed in recent years, have a wide absorption range of 400 to 1200 nm, and absorb light in the long wavelength range compared to conventional amorphous silicon systems. The absorption peak is in the vicinity of 900 nm. As described above, the hydrophilic low reflection film of the present invention has high light transmissivity in the ultraviolet / visible light region (300 to 800 nm) and the near infrared region (800 to 1200 nm). Of course, it is suitably used as a surface protection member for solar cells having absorption in the long wavelength region as described above.

"Example 1"
Hereinafter, a description will be given based on examples.

  In a 2 L separable flask, 85.91 g (0.902 mol) of reagent-grade magnesium chloride was added, 1820 g of methanol was added, and the mixture was stirred at room temperature for 2 hours to obtain a colorless and transparent magnesium chloride solution. A 55 wt% hydrofluoric acid aqueous solution (72.17 g) (1.98 mol) was intermittently added dropwise to the above magnesium chloride solution at room temperature under stirring conditions (molar ratio: hydrogen fluoride / Mg = 2.20). . After stirring for 3 hours at room temperature, a colorless and transparent sol solution was obtained. When identified by XRD, it was magnesium hydroxide fluoride.

Next, while bubbling dry N ₂ at ₂ L / min into the sol, by-product HCl and excess hydrofluoric acid were degassed and concentrated while heating at about 50 ° C. Bubbling for about 3 hours removed 322 g of methanol, HCl and hydrofluoric acid. As a result of analysis by ion chromatography, the residual acid content was 2.3% as Cl ⁻ ions and 0.9% as F ⁻ ions. In order to adjust the concentration, 350 ml of ethanol was added to adjust the solid content concentration of magnesium hydroxide fluoride to 3.1%.

To this, the reagents Al (OsBu) ₃ : 0.213 mol and Zr (OnBu) ₄ : 0.26 mol were added as metal oxides with stirring, and the reagent Sn (OnBu) ₄ : 0.126 mol was further added for 5 hours. Upon stirring, a light yellow transparent sol solution was obtained. Here, the metal oxide was converted as an oxide after firing.

  The solution was pulled on a general soda lime glass having a thickness of 3 mm by dipping at 5.5 mm / sec and dried at 100 ° C. for 1 hour. The glass substrate was put into an electric furnace at 700 ° C., held for 150 seconds and taken out to obtain a blue transparent film.

  When the light transmittance of 400 to 1200 was measured, it was 97.0% on average, which was greatly improved by 6.5% as compared with 90.5% of the untreated glass substrate.

  The refractive index was n = 1.253 as measured by an ellipsometer (Mizoji Optical Industry DVA-FL3).

  In the appearance inspection after this coating was rubbed 100 times with a load of 300 g with a dry flannel, there was almost no change in the film state. Further, when the contact angle with pure water was measured, it was superhydrophilic at 7.3 °.

  When this film was exposed outdoors at an inclination of 30 °, the pure contact angle was 10.6 ° even after 6 months, showing hydrophilicity, and the change in haze value was + 0.24%. Maintained sex and self-cleaning function.

Further, when the surface resistance value of this film after standing for 1 day in an environment of 25 ° C. and 50% relative humidity was measured, it was 7.2 exp10 ⁸ Ω. The antistatic property of cm was shown.

As a result, the surface resistance of the hydrophilic low reflection film is 7.2 × 10 ⁸ Ω. In cm, this was confirmed to be an excellent hydrophilic antistatic low reflection member.

According to these examples, the hydrophilic low-reflection film of the present invention is excellent in all the effects of low reflection / hydrophilicity and antifouling property, and it becomes possible to obtain a high-performance low-reflection film that is hardly contaminated. Is obvious.
"Example 2"
Into a 2 L separable flask, 43.54 g (0.46 mol) of reagent-grade magnesium chloride and 55.41 g (0.504 mol) of calcium chloride were added, 910 g of methanol and 900 g of ethanol were added, and the mixture was stirred at room temperature for 4 hours. A transparent magnesium chloride / calcium chloride solution was obtained. An amount of 79.63 g (2.09 mol) of a 55 wt% hydrofluoric acid aqueous solution was intermittently added dropwise to the magnesium chloride / calcium chloride solution at room temperature under stirring conditions (molar ratio: hydrogen fluoride / (Mg + Ca) = 2.19). After stirring for 5 hours at room temperature, a milky and colorless transparent sol solution was obtained. When identified by XRD, it was a mixture of magnesium hydroxide fluoride + calcium fluoride.

Next, by-product HCl was degassed and concentrated while heating at about 50 ° C. while bubbling dry N ₂ at ₂ L / min into the sol. After bubbling for about 4 hours, 286 g of methanol / ethanol and HCl were removed. Residual acid content results were analyzed by ion chromatography Cl ^- 2.1% by ions, F ^- was 1.1% as ions. It was 3.1% as hydrochloric acid. To adjust the concentration, 350 ml of ethanol was added, and the solid content concentration of magnesium hydroxide fluoride + calcium fluoride was 3.2%.

To this, the reagents Al (OsBu) ₃ : 0.221 mol and Ti (OnBu) ₄ : 0.246 mol were added as metal oxides with stirring, and further the reagent Bu ₂ Sn (acac) ₂ : 0.124 mol was added. The mixture was stirred for 5 hours to obtain a light yellow transparent sol solution.

  The solution was pulled on a general soda lime glass having a thickness of 3 mm by dipping at 5.5 mm / sec and dried at 100 ° C. for 1 hour. The glass substrate was put into an electric furnace at 700 ° C., held for 150 seconds, and taken out to obtain a light blue transparent film.

  When the light transmittance of 800 to 1200 was measured, the average was 97.2%, which was greatly improved by 6.8% of the increase in transmittance compared with 90.4% of the untreated glass substrate.

  In addition, this film was washed with pure water, dried at 80 ° C. for 1 hour, and the contact angle was measured. As a result, the water droplet spread on the surface of the film, and the contact angle was so small that it could not be measured. I was able to observe something. In addition, after immersing the film in 1 L of water for two days and nights, the contact angle of pure water was measured again. The water droplets spread on the surface of the film, and the contact angle was too small to be measured, and the film was superhydrophilic. Could be observed. This confirms that the hydrophilic film is a durable superhydrophilic low reflection film.

  The film thickness was 181 nm and the refractive index n = 1.298 as measured by an ellipsometer (Mizoji Optical Industry DVA-FL3).

The surface resistance value of the hydrophilic low reflection film is 4.2 × 10 ⁸ Ω. It was cm, and it was confirmed that it was a hydrophilic low reflection member having an excellent antistatic function.

According to these examples, the hydrophilic low-reflection film of the present invention is excellent in all the effects of low reflection / hydrophilicity and antifouling property, and it becomes possible to obtain a high-performance low-reflection film that is hardly contaminated. Is obvious.
"Example 3"
In a 2 L separable flask, 89.41 g (0.94 mol) of reagent-grade magnesium chloride was added, 1850 g of methanol was added, and the mixture was stirred at room temperature for 2 hours to obtain a colorless and transparent magnesium chloride solution. An amount of 72.0 g (1.98 mol) of a 55 wt% hydrofluoric acid aqueous solution was intermittently added dropwise to the above magnesium chloride solution under stirring conditions at room temperature (molar ratio: hydrogen fluoride / Mg = 2.11). . After stirring for 3 hours at room temperature, a colorless and transparent sol solution was obtained. When identified by XRD, it was magnesium hydroxide fluoride.

Next, while bubbling dry N ₂ at ₂ L / min into the sol, by-product HCl and excess hydrofluoric acid were degassed and concentrated while heating at about 50 ° C. Bubbling for about 3 hours removed 289 g of methanol, HCl and hydrofluoric acid. As a result of analysis by ion chromatography, the residual acid content was 1.8% as Cl ⁻ ions and 0.7% as F ⁻ ions. In order to adjust the concentration, 413 ml of ethanol was added, and the solid content concentration of magnesium hydroxide fluoride was 3.22%.

To this, the reagents TEOS: 0.233 mol and Zr (OnBu) ₄ : 0.26 mol were added as metal oxides while stirring, the reagent BuSnCl ₃ : 0.116 mol was added, and 3.5 ml of ethyl acetoacetate was further added. The mixture was stirred for 5 hours to obtain a pale yellow transparent sol solution.

  The solution was pulled up by a dip method at 6.0 mm / sec on a general soda lime glass having a thickness of 3 mm and dried at 100 ° C. for 1 hour. The glass substrate was put into an electric furnace at 700 ° C., held for 150 seconds and taken out to obtain a blue transparent film.

  When the light transmittance of 400 to 1200 was measured, the average was 97.7%, which was greatly improved by 7.2% in increase in transmittance compared to 90.5% of the untreated glass substrate.

  In addition, this film was washed with pure water, dried at 80 ° C. for 1 hour, and the contact angle was measured. As a result, the water droplet spread on the surface of the film, and the contact angle was so small that it could not be measured. I was able to observe something. In addition, after immersing the film in 1 L of water for two days and nights, the contact angle of pure water was measured again. The water droplets spread on the surface of the film, and the contact angle was too small to be measured, and the film was superhydrophilic. Could be observed. This confirms that the hydrophilic film is a durable superhydrophilic low reflection film.

  The film thickness was 182 nm and the refractive index n = 1.287 as measured by an ellipsometer (Mizoji Optical Co., Ltd. DVA-FL3).

The surface resistance value of the hydrophilic low reflection film is 7.8 × 10 ⁸ Ω. It was confirmed that it was a hydrophilic low-reflection member having an excellent antistatic function.

According to these examples, the hydrophilic low-reflection film of the present invention is excellent in all the effects of low reflection / hydrophilicity and antifouling property, and it becomes possible to obtain a high-performance low-reflection film that is hardly contaminated. Is obvious.
Example 4
In a 2 L separable flask, 89.41 g (0.94 mol) of reagent-grade magnesium chloride was added, 1850 g of methanol was added, and the mixture was stirred at room temperature for 2 hours to obtain a colorless and transparent magnesium chloride solution. An amount of 75.27 g (2.07 mol) of a 55 wt% hydrofluoric acid aqueous solution was intermittently added dropwise to the above magnesium chloride solution under stirring conditions at room temperature (hydrogen fluoride / Mg = 2.20). After stirring for 3 hours at room temperature, a colorless and transparent sol solution was obtained. When identified by XRD, it was magnesium hydroxide fluoride.

Next, while bubbling dry N ₂ at ₂ L / min into the sol, by-product HCl and excess hydrofluoric acid were degassed and concentrated while heating at about 50 ° C. Bubbling for about 3 hours removed 208 g of methanol, HCl and hydrofluoric acid. Results residual acid content was analyzed by ion chromatography Cl ^- 2.6% by ions, F ^- was 0.9% as ions. To adjust the concentration, 236 ml of ethanol was added, and the solid content concentration of magnesium hydroxide fluoride was 3.18%.

To this, the reagent TEOS: 0.23 mol and Ti (OnBu) ₄ : 0.23 mol were added as metal oxides while stirring, and the reagent BuSnCl ₃ : 0.116 mol was further added, and 5.0 ml of ethyl acetoacetate was further added. The mixture was stirred for 5 hours to obtain a pale yellow transparent sol solution.

  The solution was pulled up by a dip method at 6.0 mm / sec on a general soda lime glass having a thickness of 3 mm and dried at 100 ° C. for 1 hour. The glass substrate was put into an electric furnace at 700 ° C., held for 150 seconds and taken out to obtain a blue transparent film.

  When the light transmittance at 400 to 1200 nm was measured, the average was 96.7%, and the increase in transmittance was greatly improved by 6.1% compared with 90.6% of the untreated glass substrate. .

  In addition, this film was washed with pure water, dried at 80 ° C. for 1 hour, and the contact angle was measured. As a result, the water droplet spread on the surface of the film, and the contact angle was so small that it could not be measured. I was able to observe something. In addition, after immersing the film in 1 L of water for two days and nights, the contact angle of pure water was measured again. The water droplets spread on the surface of the film, and the contact angle was too small to be measured, and the film was superhydrophilic. Could be observed. This confirms that the hydrophilic film is a durable superhydrophilic low reflection film.

  The film thickness was 177 nm and the refractive index n = 1.324, as measured by an ellipsometer (Mizoji Optical Industry DVA-FL3).

The surface resistance value of the hydrophilic low reflection film is 1.6 × 10 ⁹ Ω. It was confirmed that it was a hydrophilic low-reflection member having an excellent antistatic function.

  These films were not affected by humidity due to the environment and had an antistatic function, and it was confirmed that the film was superhydrophilic and had an antistatic function.

According to these examples, the hydrophilic low-reflection film of the present invention is excellent in all of the effects of low reflection / hydrophilicity, antistatic and antifouling, and it is possible to obtain a high-performance low-reflection film that is resistant to contamination. It is clear that
[Comparative Example 1]
A commercially available magnesium fluoride sol solution was prepared, and without adding a metal oxide, the solution was pulled on a general soda lime glass having a thickness of 3 mm by a dip method at 5.5 mm / sec. Dry for 1 hour. The glass substrate was put into an electric furnace at 700 ° C., held for 150 seconds and taken out to obtain a blue-violet transparent film.

  When the light transmittance of 400 to 1200 nm was measured, the average was 95.6%, and the increase in transmittance was only 4.8% compared with 90.8% of the untreated glass substrate. .

  Further, when this film was immersed in 1 L of water for 2 days and then washed, the film was partially peeled off and the color unevenness was conspicuous, and a good antireflection film could not be obtained.

[Comparative Example 2]
To the 1 L flask, without adding magnesium hydroxide fluoride, the reagent TEOS: 0.12 mol was added to the reagent Ti (OnBu) ₄ : 0.246 mol with stirring, and the mixture was further stirred for 1 hour. A sol solution was obtained. The transparent sol solution was diluted with IPA to prepare a solid concentration of 2.0%. A TiO ₂ / SiO ₂ film was formed on soda lime glass by the same treatment as in Example 1 to obtain a yellow transparent film.

  The film thickness was 86 nm and the refractive index n = 1.899 as measured by an ellipsometer (Mizoji Optical Industry DVA-FL3).

  When the 400 to 1200 light transmittance was measured, the average was 86.7%, and the transmittance was rather inferior to -5.10% compared with 90.8% of the untreated glass substrate. (Figure 2)

  According to the present invention, a substrate having a durable superhydrophilic and low refractive index film formed on the surface and a method for producing the same can be obtained. Therefore, an optical material such as a lens, a cathode ray tube, a liquid crystal display device, etc. In a wide range of fields that require hydrophilicity, antifouling properties, and low anti-reflection antistatic properties such as flat glass and transparent plastics for image display surfaces, windows and showcases, skylight materials, solar cells, water heaters, lighting fixtures, etc. Available. Moreover, since it is excellent not only in the ultraviolet to visible light region but also in the near infrared region, it is particularly useful as a solar cell surface protecting member.

Claims (11)

A low-reflection member having a transparent substrate and a low-reflection film formed on the transparent substrate, wherein the low-reflection film contains hydrophilic magnesium hydroxide fluoride particles having a particle diameter of 5 to 500 nm. A hydrophilic low-reflective member characterized by being expressed. The hydrophilic low-reflection member according to claim 1, wherein the magnesium hydroxide fluoride is MgF2 _-x (OH) _x (x = 0.01 to 0.5). The hydrophilic low reflection member according to claim 1, wherein the magnesium hydroxide fluoride is MgF _1.89 (OH) _0.11 . Furthermore, the hydrophilic low reflection member of any one of Claims 1 thru | or 3 formed by mixing a metal oxide as a refractive index regulator. The molar ratio of magnesium hydroxide fluoride and metal oxide in the hydrophilic low reflection film is in the range of (10 / 0.5) to (10/30) per 10 moles of magnesium hydroxide fluoride. The hydrophilic low reflection member according to claim 4. The metal oxide is one or more selected from SiO ₂ , Al ₂ O ₃ , CeO ₂ , ZrO ₂ , TiO _2, SnO ₂ , In ₂ O ₃ , Sb ₂ O ₅ , La ₂ O _3. The hydrophilic low reflection member according to claim 4 or 5, wherein the hydrophilic low reflection member is provided. The hydrophilic low reflection member according to any one of claims 4 to 6, wherein a film obtained by hydrolyzing magnesium hydroxide fluoride ultrafine particles and a metal compound is formed on the transparent substrate surface. The low reflection member according to any one of Inventions 4 to 7, wherein a difference in (transmittance after double-side treatment-untransmitted transmittance) at a wavelength of 400 to 1200 nm is an average transmittance of 6% or more. The hydrophilic low reflection member according to any one of claims 1 to 8, wherein a contact angle with water on the surface of the hydrophilic low reflection film is 30 ° or less. The surface resistance value of the hydrophilic low reflection film surface is 1 × 10 ¹⁰ Ω. The hydrophilic low-reflective member according to any one of Inventions 1 to 9, wherein the hydrophilic low-reflection member is equal to or less than cm. The surface protection member for solar cells using the hydrophilic low reflection member of any one of Claims 4 thru | or 9.

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