JP2010181801A - Coating composition, antireflection film using the same, and method for forming antireflection film - Google Patents

Abstract

The present invention provides an antireflection film that achieves both an appearance quality such as less interference unevenness and an excellent antireflection property, and a coating composition used therefor.
The coating composition of the present invention is a coating composition containing inorganic particles and a resin, and measured by viscosity measurement using a rotary viscometer to increase the shear rate. at ° C., the viscosity at a shear rate of 1 × 10 sec ^-1 a, if the viscosity at a shear rate of 1 × 10 ³ sec ^-1 and is B, the viscosity a is 1 to 20 mPa · s, thixotropic coefficient a / B Is 1.001 to 1.400. Moreover, the antireflection film of the present invention includes an antireflection layer formed by using the above coating composition.
[Selection] Figure 1

Description

  The present invention relates to a coating composition, an antireflection film using the coating composition, and a method for producing the antireflection film, and more particularly, to an improvement in the antireflection layer of the antireflection film.

  Development of high-definition and large-screen displays represented by liquid crystal displays and plasma display panels (PDPs) is rapidly progressing. Further, in order to improve the visibility of the display surface of the display, it is necessary to dispose an antireflection layer having an antireflection function for preventing reflection of external light such as a fluorescent lamp on the screen. As a method for forming the antireflection layer, an inorganic metal is vapor-deposited or sputtered on the surface of the display surface of the display, so-called dry coating method, and a low refractive index material or the like is applied to the substrate in a liquid form such as a solution or dispersion, A wet coating method for drying and curing as necessary is known. With the recent increase in size of displays, a roll-to-roll (Roll-to-Roll) wet coating method that is inexpensive and easily accommodates an increase in size is becoming mainstream. As an antireflection film including an antireflection layer formed by a wet coating method, for example, on a transparent substrate film, a hard coat layer for increasing the hardness of the substrate itself, and a single layer or a multilayer refractive index thereon An antireflection film or the like in which layers having different thicknesses of about 100 nm are formed has been proposed (Patent Documents 1 and 2).

  In order to meet the low cost requirements of the market, it has also been proposed to reduce the manufacturing process by using an antireflection layer having a two-layer structure of a hard coat layer and a low refractive index layer (Patent Documents 3 and 4).

  Furthermore, the anti-reflection layer is a two-layer structure of a hard coat layer and a low refractive index layer. An optical film is proposed in which a refractive index layer is sequentially laminated and a hard coat layer is a conductive oxide and needle-like antimony-doped tin oxide, other metal oxides, and a cured product by ionizing radiation (Patent) Reference 5).

JP 2002-200690 A JP 2007-65634 A JP-A-9-145903 JP 2001-318206 A WO04 / 088364

  However, when the wet coating method is used in the production of a conventional antireflection film, uneven thickness of the coating film is likely to occur, and in response to increasing demand for larger size and lower reflection, there is more interference unevenness in terms of appearance quality. It has practical problems such as being noticeable and poor quality. That is, with the increase in size of the antireflection film, as the size increases, there is no actual applicator suitable for the wet coating method, resulting in uneven thickness of the coating film. In addition, the low reflection of the anti-reflection film tends to be more noticeable if the coating film has uneven thickness from the design that increases the refractive index difference of each layer or adopts a multilayer structure with a thin film. There is. In particular, in the coating composition in which metal oxide particles are dispersed in a solvent as in Patent Documents 1 to 5, when the shear rate is frequently changed in the coater part or in the gap between the substrate and the coater part, the coating composition Possible reasons are that the viscous resistance of the material changes non-uniformly, or that the liquid leveling does not catch up due to a sudden increase in viscosity due to the volatilization of the solvent, resulting in a deterioration in thickness unevenness. On the other hand, in Patent Document 2, in order to improve the coating unevenness, the first layer uses a leveling agent to reduce the coating unevenness, and then applies the second layer by laminating. Proposals have been made including a process of removing by heat treatment, etc., but ensuring wettability to the first layer contributes to the reduction of coating unevenness in the second layer, but the process is complicated and economical. It was insufficient in that it was disadvantageous.

  In order to solve the above-described conventional problems, the present invention provides a coating composition having a specific viscosity characteristic, an antireflection film having both an appearance quality such as less interference unevenness formed using the same and an excellent antireflection characteristic, and A method for producing an antireflection film is provided.

The coating composition of the present invention is a coating composition containing inorganic particles and a resin, and the shearing of the coating composition at 25 ° C. measured by viscosity measurement using a rotary viscometer to increase the shear rate. If the viscosity at speed 1 × 10 sec ^-1 was a, the viscosity at a shear rate of 1 × 10 ³ sec ^-1 is B, the viscosity a is 1 to 20 mPa · s, the thixotropic factor a / B 1.001 It is ˜1.400.

  The antireflection film of the present invention includes an antireflection layer formed using the above-described coating composition of the present invention.

The method for producing an antireflection film of the present invention is a method for producing an antireflection film comprising a base material and an antireflection layer formed on one main surface side of the base material, wherein the antireflection layer has a coating composition. The coating composition contains inorganic particles and a resin, and is measured by viscosity measurement using a rotary viscometer to increase the shear rate. the viscosity at a shear rate of 1 × 10 sec ^-1 at 25 ° C. of the coating composition a, when the viscosity at a shear rate of 1 × 10 ³ sec ^-1 and is B, the viscosity a is 1 to 20 mPa · s The thixotropy coefficient A / B is 1.001 to 1.400.

  By using the coating composition of the present invention, it is possible to provide an antireflection film having both appearance quality such as less interference unevenness and excellent antireflection characteristics. In addition, when the coating composition of the present invention is used, it is preferable that a complicated process, for example, a process of removing a specific substance by heat treatment or the like is not required, and appearance quality such as less interference unevenness and excellent antireflection characteristics are obtained. A compatible antireflection film is obtained.

FIG. 1 is a viscosity flow curve of a coating composition used for forming a hard coat layer in an example of the present invention. FIG. 2 is a viscosity flow curve of the coating composition used for forming the low refractive index layer in the examples of the present invention.

The inventors of the present invention determined the coating unevenness in the wet coating method by measuring the viscosity at a shear rate of 1 × 10 sec ⁻¹ at 25 ° C. of the coating composition measured by viscosity measurement using a rotary viscometer to increase the shear rate. When the viscosity at A (hereinafter also referred to as viscosity A) and the viscosity at a shear rate of 1 × 10 ³ sec ⁻¹ is B (hereinafter also referred to as viscosity B), it was found to depend on the thixotropic coefficient A / B. .

  That is, in the coating composition of the present invention, when the thixotropy coefficient A / B is in the range of 1.001 to 1.400, the shear rate is frequently changed in the coater part or in the gap between the substrate and the coater part. Even in this case, the coating composition has uniform viscosity resistance, and it is estimated that uneven coating can be suppressed by quickly transferring to the substrate. Moreover, that the thixotropy coefficient A / B is in the range of 1.001 to 1.100 is also effective for increasing the coating speed.

The viscosity in the present invention is, for example, 1 × 10 sec at 25 ° C. while increasing the shear rate using a rotary viscometer such as Rheostress 600 (manufactured by Eihiro Seiki Co., Ltd.) or Physica MCR301 type (manufactured by Anton Paar). ^The viscosity measured by measuring the viscosity while increasing from ⁻¹ to 1 × 10 ³ sec ⁻¹ .

  In the present invention, the thixotropy coefficient A / B indicates a change in viscosity with an increase in shear rate, and the closer the value is to 1.000, the smaller the change in viscosity with an increase in shear rate. . In the case of a coating composition having a thixotropy coefficient A / B of greater than 1.400 or less than 1.001, if the shear rate is frequently changed in the coater part or between the substrate and the coater part, the viscous resistance It is presumed that uneven coating changes and uneven coating occurs. It should be noted that thixotropy can be achieved by making the content of the components in the coating composition, for example, inorganic particles, resin, organic solvent, etc. appropriate, making the dispersion of the inorganic particles good, and sufficiently dissolving the resin. The coefficient A / B can be in the range of 1.001 to 1.400.

  Furthermore, in this invention, the viscosity A of a coating composition needs to be the range of 1-20 mPa * s. A coating composition having a viscosity A greater than 20 mPa · s tends to have poor fluidity, and when the viscosity A is less than 1 mPa · s, the content of the components of the coating composition is inappropriate, There is a tendency for the antireflection properties to be insufficient.

  Hereinafter, embodiments of the present invention will be described in detail.

<Coating composition>
The coating composition of the present invention contains at least a resin and inorganic particles.

<resin>
The resin is not particularly limited, and in the antireflection film, an ionizing radiation curable resin or a thermosetting resin used for forming an antireflection layer by a wet coating method can be used. Moreover, it is preferable to use ionizing radiation curable resin from the viewpoint of surface hardness. Here, “ionizing radiation curable resin” refers to a resin that is cured by irradiation with ionizing radiation including all electromagnetic waves such as infrared rays, visible rays, ultraviolet rays, X-rays, and electron beams.

  The ionizing radiation curable resin is not particularly limited, and various ionizing radiation curable resins used for forming an antireflection layer by a wet coating method in an antireflection film can be used. For example, a monomer, a prepolymer, an oligomer, or a polymer having a vinyl group, a (meth) acryloyl group, an epoxy group, or an oxetanyl group can be used. From the viewpoint of achieving both productivity and hardness, it is preferable to use a polyfunctional resin. Furthermore, it is preferable to have a large number of bonding groups and functional groups that form hydrogen bonds in the molecule because adhesion is improved. In the present invention, “(meth) acryloyl group” means “acryloyl group” and / or “methacryloyl group”.

  As the ionizing radiation curable resin, specifically, a polyfunctional or monofunctional (meth) acrylate monomer or acrylate oligomer can be used. Further, from the viewpoint of improving scratch resistance, it preferably contains a polyfunctional acrylate having two or more polymerizable unsaturated groups.

The acrylate monomer monofunctional group is a monomer having one (meth) acrylate groups in the molecule, for example, tricyclo [5,2,1,0 _2,6] decane acrylate, isobornyl acrylate, tetrahydrofurfuryl acrylate And phenoxyethyl acrylate. In the present invention, “(meth) acrylate group” means “acrylate group” and / or “methacrylate group”.

  The polyfunctional acrylate monomer is a monomer having 2 or more (preferably 2 to 6) (meth) acrylate groups in the molecule, such as tricyclodecane dimethylol diacrylate, neopentyl glycol diacrylate, Hydroxypivalate neopentyl glycol diacrylate, dioxane glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, bisphenol A type polyethoxylate diacrylate, dipentaerythritol pentaacrylate And dipentaerythritol hexaacrylate.

  Moreover, as an acrylate oligomer, an epoxy acrylate oligomer, a polyester polyacrylate oligomer, a urethane acrylate oligomer etc. are mentioned, for example.

  These polyfunctional or monofunctional (meth) acrylate monomers or oligomers can be used alone or in combination of two or more. Among them, at least one selected from pentaerythritol triacrylate and dipentaerythritol hexaacrylate is preferable from the viewpoint of further improving the scratch resistance.

  The blending ratio of the ionizing radiation curable resin in the coating composition is such that the viscosity A of the coating composition is 1 to 20 mPa · s and the thixotropic coefficient A / B is 1.001 to 1.400. However, it is preferably 10 to 99% by weight, more preferably 15 to 90% by weight, based on 100% by weight of the total weight of the resin and the inorganic particles. This is because the thixotropy coefficient A / B of the coating composition tends to be from 1.001 to 1.400.

<Inorganic particles>
As the inorganic particles, metal oxide particles can be used for adjusting the refractive index. Examples of the metal oxide particles include silica, hollow silica, titanium oxide, zirconium oxide, zinc oxide, cerium oxide, tin oxide, antimony-doped tin oxide (ATO), phosphorus-doped tin oxide (PTO), tin-doped indium oxide (ITO) ), Metal oxide particles such as aluminum-doped zinc oxide, gallium-doped zinc oxide, antimony pentoxide, and zinc antimonate. These metal oxide particles may be used alone or in combination of two or more.

  The coating composition preferably contains conductive oxide particles in order to provide an antistatic function. Here, the “conductive oxide particles” refer to metal oxide particles having conductivity, and are not particularly limited. For example, tin oxide, antimony-doped tin oxide (ATO), phosphorus-doped tin oxide (PTO), tin Examples thereof include metal oxide particles such as doped indium oxide (ITO), aluminum-doped zinc oxide, gallium-doped zinc oxide, antimony pentoxide, and zinc antimonate. Among them, it is preferable to use highly conductive ITO particles, ATO particles, or the like.

  Moreover, the said inorganic particle should just be a particulate form, Although it does not specifically limit, The primary particle diameter has preferable 5-1000 nm. When the primary particle diameter exceeds 1000 nm, the transparency of the coating film comprising the coating composition containing the primary particle diameter tends to decrease. When two or more kinds of metal oxide particles are used in combination, if the particles have the same shape such as a spherical shape or a needle shape, the particles are closely packed in a coating film made of a coating composition containing the particles. It is preferable because it is quick.

  In the present invention, the primary particle diameter of the inorganic particles is obtained by taking an image of the particles using an electron microscope such as a transmission electron microscope at a magnification of 200,000 times. Is measured by calculating the average diameter of the major axis and the minor axis by averaging the two. In addition, the primary particle diameter of the inorganic particles in the antireflection film is measured by cutting the antireflection film with a microtome, and using an electron microscope such as a transmission electron microscope to display the image of the particles in the cut antireflection film cross section. It is used by photographing at a magnification of 200,000 times, measuring the longest diameter of the particles and the longest diameter in the direction orthogonal thereto, and calculating the average diameter of the major and minor axes by averaging both. In addition, the average diameter of the major axis and the minor axis of at least 30 particles is calculated, and the average value thereof is defined as the primary particle diameter of the particles.

  Moreover, the blending ratio of the inorganic particles in the coating composition may be blended so that the viscosity A of the coating composition is 1 to 20 mPa · s and the thixotropy coefficient A / B is 1.001 to 1.400, Although it does not specifically limit, Preferably it is 1 to 90 weight% with respect to the whole weight of resin and an inorganic particle, More preferably, it is 10 to 85 weight%. This is because the thixotropy coefficient A / B of the coating composition tends to be 1.001 to 1.400.

<Organic solvent>
The coating composition of the present invention may further contain an organic solvent capable of dispersing or dissolving the resin. The organic solvent is not particularly limited as long as it is used for forming a coating film by a wet coating method. For example, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and acetyl acetone; ethanol, isopropyl alcohol, isobutyl alcohol , N-butanol, diacetone alcohol and the like; ether group-containing alcohols such as ethyl cellosolve, butyl cellosolve and propylene glycol monomethyl ether; hydroxy esters such as methyl lactate, ethyl lactate and butyl lactate; ethyl acetoacetate, acetoacetate Β-ketoesters such as methyl and butyl acetoacetate; aromatic hydrocarbons such as toluene and xylene are used. These organic solvents may be used alone or in combination of two or more. The amount of the organic solvent added is not particularly limited as long as the viscosity A of the coating composition is 1 to 20 mPa · s and the thixotropy coefficient A / B is 1.001 to 1.400. From the viewpoint of coatability, it is preferable to add such that the content of the resin in the coating composition is about 1 to 50% by weight. Furthermore, from the viewpoint that the thixotropy coefficient A / B of the coating composition is likely to be from 1.001 to 1.400, it is preferable to add so that the resin content in the coating composition is about 1 to 40% by weight. .

<Polymerization initiator>
When an ionizing radiation curable resin is used as the resin, the coating composition of the present invention contains a polymerization initiator. The blending ratio of the polymerization initiator in the coating composition may be blended so that the viscosity A of the coating composition is 1 to 20 mPa · s and the thixotropy coefficient A / B is 1.001 to 1.400. Although not limited, it is preferable that it is 2-20 weight part with respect to 100 weight part of resin, and it is more preferable that it is 3-12 weight part. Scratch resistance can be made suitable. And when hardening the said ionizing radiation curing type resin by ultraviolet irradiation, it is necessary to contain a photoinitiator.

  Examples of the photopolymerization initiator include benzoins such as benzoin ethyl ether, benzoin butyl ether, and benzoin isopropyl ether; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1, Acetophenones such as 1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, N, N-dimethylaminoacetophenone; 2 Thioxanthones such as 1,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone; ketals such as benzyl dimethyl ketal and acetophenone dimethyl ketal; benzophenone There are benzophenones such as methylbenzophenone, 4,4′-bisdiethylamino-benzophenone, 4-benzoyl-4′-methyldiphenyl sulfide; phosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, etc. It can use individually or in combination of 2 or more types.

  In the present invention, the coating composition has a requirement that the viscosity A of the coating composition is 1 to 20 mPa · s and the thixotropy coefficient A / B is 1.001 to 1.400 (hereinafter also referred to as viscosity requirement). In the range satisfying (), various additives such as a polymerization inhibitor, an antioxidant, a dispersant, a surfactant, a light stabilizer and a leveling agent may be included as necessary.

  The coating composition of this invention can be used for formation of the antireflection layer of an antireflection film as follows. In addition, since the antireflection film is located on the outermost surface of the display, it preferably has strength and antifouling property, and the coating composition has a viscosity A of 1 to 20 mPa · s of the coating composition, Silicone-based and fluorine-based additives may be included as long as the thixotropic coefficient A / B satisfies the requirement of 1.001 to 1.400.

<Antireflection film>
The antireflection film of the present invention includes a base material and an antireflection layer disposed on one main surface side on the base material.

<Base material>
The base material is not particularly limited as long as it is a light-transmitting material, and its shape and manufacturing method are not particularly limited. For example, polyester resin, polycarbonate resin, polyacrylic ester resin, alicyclic polyolefin resin, polystyrene resin, polyvinyl chloride resin, polyvinyl acetate resin, polyethersulfone resin, triacetyl cellulose resin, etc. What was processed into the shape can be used. Examples of the method for processing the film or sheet include an extrusion molding method, a calendar molding method, a compression molding method, an injection molding method, and a method in which the resin is dissolved in a solvent and cast. The material used for the substrate 1 may be added with additives such as an antioxidant, a flame retardant, a heat resistance inhibitor, an ultraviolet absorber, a lubricant, and an antistatic agent. Moreover, as said base material, the polyester-type film with favorable balance of heat resistance and a softness | flexibility is preferable, and a polyethylene terephthalate film is more preferable. Moreover, you may provide a primer layer in the main surface of one or both of a base material in order to improve adhesiveness with the layer provided on a base material.

  Although the thickness of the said base material changes with raw materials, it should just be normally 10-500 micrometers, and when using a polyester film, 35-260 micrometers is preferable and 50-200 micrometers is more preferable. When the thickness of the base material is thin, handling properties are poor. On the other hand, when the thickness of the substrate is thick, there is a problem in terms of cost, and flatness due to curling tends to occur when the base material is wound and stored.

<Antireflection layer>
In one embodiment of the antireflection film of the present invention, the antireflection layer includes a hard coat layer and a low refractive index layer that are laminated in order from the substrate side on one main surface side of the substrate.

≪Hard coat layer≫
The hard coat layer is formed using the above coating composition. The method for forming the hard coat layer on the substrate is not particularly limited as long as it is a wet coating method. For example, the above coating composition is applied to one main surface side of the substrate by the wet coating method. Can be formed. The coating method is not particularly limited. For example, reverse roll coating, roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, and the like, gravure printing, screen printing, offset printing, inkjet printing, etc. The printing method can be used.

  The film thickness of the hard coat layer is not particularly limited, but is preferably 0.2 to 10 μm, more preferably 0.9 to 3 μm, and particularly preferably 0.9 to 2 μm. If the thickness of the hard coat layer is less than 0.2 μm, the scratch resistance tends to be inferior. If it is more than 10 μm, not only there is a problem in cost, but also cracks or curls (film warpage) are likely to occur. Become.

  The hard coat layer preferably has a refractive index of 1.45 to 1.75, more preferably 1.50 to 1.70. The product (optical thickness) of the refractive index n of the hard coat layer and the film thickness d (optical thickness) is preferably 435 to 14000 nm, and more preferably 870 to 8750 nm.

  By forming a hard coat layer using the coating composition of the present invention having the viscosity A of 1 to 20 mPa · s and a thixotropic coefficient A / B of 1.001 to 1.400, interference unevenness is small. An antireflection film can be obtained.

≪Low refractive index layer≫
When the antireflection layer has a two-layer structure composed of a hard coat layer and a low refractive index layer as in this embodiment, the low refractive index layer preferably has a refractive index of 1.30 to 1.50. If the optical film thickness, which is the product of the refractive index n and the film thickness d of the low refractive index layer, is designed to be nd = λ / 4, the reflectance will be lower, so the film thickness should be 80 to 150 nm. preferable.

  As the material for forming the low refractive index layer, the above coating composition is used. In that case, in order to adjust the refractive index to 1.30 to 1.50, it is preferable to use inorganic particles having a low refractive index, for example, metal oxide particles such as silica particles and hollow silica particles, as the inorganic particles. Alternatively, a fluorine-based resin or the like may be added. Among these, it is preferable to use hollow silica particles from the viewpoint of refractive index and film cohesion. Moreover, since the primary particle diameter of the hollow silica particles is designed so that the film thickness of the low refractive index is 80 nm to 150 nm, it is preferably 80 nm or less, and more preferably 60 nm or less.

  The void ratio of the hollow silica particles is preferably more than 30% and 50% or less. When the porosity of the hollow silica particles is more than 30% and 50% or less, a sufficient antireflection effect can be obtained. Moreover, the hardness as an inorganic oxide can also be maintained at the time of synthesis | combination of a hollow silica particle. Here, the “void ratio” refers to the ratio of the volume of the void portion to the total volume.

  Further, the blending ratio of the hollow silica particles in the coating composition is such that the refractive index of the low refractive index layer is in the range of 1.30 to 1.50 and the viscosity requirement is satisfied. Although it is not particularly limited, it is preferably 30 to 75 parts by weight when the total weight of the resin and the hollow silica particles is 100 parts by weight.

  In addition, when the low refractive index layer of the antireflection film is located on the outermost surface of the display, from the viewpoint of strength and antifouling properties, silicone-based and fluorine-based additives such as polydimethylsiloxane having a (meth) acryloyl group May be added to the coating composition to the extent that the refractive index is not changed and within a range that satisfies the viscosity requirements. Furthermore, the molecular weight of the polydimethylsiloxane having a (meth) acryloyl group is preferably in the range of 500 to 10,000. When the molecular weight is smaller than 500, the dimethylsiloxane portion is shortened, so that the antifouling effect is not satisfied. When the molecular weight is larger than 10,000, the solubility in the solvent becomes extremely poor, and defects such as repellency frequently occur on the appearance. Defects occur.

  The method for forming the low refractive index layer on the hard coat layer is not particularly limited as long as it is a wet coating method. For example, it is formed by applying the above coating composition on the hard coat layer by the wet coating method. it can. The application method is not particularly limited, and for example, a method similar to the method of forming a hard coat layer on the above-described substrate can be used.

  In another embodiment of the antireflection film, the antireflection layer may include a hard coat layer and a plurality of layers having different refractive indexes that are sequentially laminated on the hard coat layer. Specifically, a hard coat layer, a three-layer structure including a high refractive index layer and a low refractive index layer that are sequentially stacked on the hard coat layer, and a layer that is sequentially stacked on the hard coat layer and the hard coat layer Examples thereof include an antireflection layer having a four-layer structure including a refractive index layer, a high refractive index layer, and a low refractive index layer.

  In the above, the middle refractive index layer has a refractive index of 1.53 to 1.65, more preferably 1.57 to 1.63, and the material is not particularly limited as long as the material has translucency. It is preferable to use the above coating composition. The product (optical thickness) of the refractive index n and the film thickness d of the medium refractive index layer is preferably in the range of 110 to 163 nm, and more preferably in the range of 125 to 150 nm.

  In the above, the high refractive index layer has a refractive index of 1.70 to 1.95, more preferably 1.76 to 1.84, and is not particularly limited as long as the material has translucency, It is preferable to use the above coating composition, and it is more preferable to use a coating composition containing titanium oxide particles having the highest refractive index as inorganic particles. The product nd (optical thickness) of the refractive index n of the high refractive index layer and its thickness d is preferably in the range of 225 nm to 325 nm, and more preferably in the range of 250 to 300 nm.

  Furthermore, in another embodiment, the antireflection film of the present invention is closer to the other main surface side opposite to the main surface on which the antireflection layer of the substrate is formed, by a conventionally known material and method. An infrared absorbing layer can be further formed. Thereby, if the optical film of the present embodiment is arranged on the surface of the PDP, unnecessary near infrared rays emitted when plasma discharge is generated are blocked, and there is no adverse effect on devices using peripheral electronic components. In particular, problems such as malfunctions of remote controls such as televisions and air conditioners can be solved. Further, by integrating the near-infrared absorption layer and the antireflection layer on a single base material, it is possible to reduce the number of members to be bonded to the front plate of the plasma display.

  In the present invention, the visibility reflectance of the antireflection film is preferably 0.05% to 3.0%, and more preferably 0.05 to 2.0%. If the visibility reflectance is 1.5% or less, an excellent antireflection function can be exhibited.

  Hereinafter, based on an Example, this invention is demonstrated more concretely. “Parts” in the examples represents “parts by weight”. The present invention is not limited to the following examples.

  First, the measurement method and the evaluation method used in the examples will be described.

<Viscosity>
In 25 ° C., the rotational viscometer PhysicaMCR301 Model (manufactured by Anton Paar) used, while increasing the shear rate from 1 × 10 sec ^-1 to 1 × 10 ³ sec ^-1, and the viscosity flow curves of the coating composition , Viscosity A, viscosity B, and thixotropy coefficient A / B were calculated.

<Film appearance quality>
The appearance quality of the antireflection film was visually observed under a three-wavelength fluorescent lamp. Judgment evaluated as follows and made B or more into the pass.
A: No interference unevenness B: Interference unevenness occurs slightly, but there is no problem in practical use C: Interference unevenness partially occurs D: Interference unevenness occurs over the entire surface

<Visibility reflectance>
The other principal surface side opposite to the one principal surface side where the antireflection layer of the base material of the antireflection film is formed is painted black with a black oil-based felt pen, and then the spectrophotometer “Ubest V- Using a "570 type" (manufactured by JASCO Corporation), the visibility reflectance was measured with the main surface side on which the antireflection layer was formed as the incident light side.

  Next, the coating composition will be described.

<Coating composition A>
First, a mixture having the following composition was dispersed for 2 hours with a paint conditioner (manufactured by Toyo Seiki Co., Ltd.) using zirconia beads having a diameter of 0.3 mm for stirring and dispersing the liquid, and dispersed with a 0.2 mm metal mesh. After removing the beads, classification was performed with a centrifuge at 14000 G for 30 minutes to remove coarse particles, and the supernatant was collected to obtain dispersion A.
(1) "PCS60" (Nippon Denko's zirconium oxide particles, primary particle diameter 15 nm, specific surface area 65 m ² / g) 11.5 parts (2) "SN100P" (Ishihara Sangyo's conductive oxide particles, Antimony-doped tin oxide, primary particle diameter 20 nm) 14.0 parts (3) “BYK180” (dispersant manufactured by Big Chemie Japan) 2.0 parts (4) 72.5 parts isobutyl alcohol.

Next, after measuring the above dispersion A and the following composition in a beaker and stirring for 60 minutes with a magnetic stirrer, glass fiber filter paper “GFP” (manufactured by Kiriyama Seisakusho, particle size of trapped particles of 0.8 μm or more) Was used for suction filtration to prepare a coating composition A having a refractive index of 1.64. In addition, a refractive index shows not the refractive index of a coating material but the refractive index of the coating film after drying hardening here. The same applies to the following.
(1) Dispersion A 79.8 parts (2) "Aronix M400" (ionizing radiation curable resin, dipentaerythritol hexaacrylate manufactured by Toagosei Co., Ltd.) 5.0 parts (3) "Light acrylate PE-3A" ( Kyoeisha Chemical Co., Ltd. ionizing radiation curable resin, pentaerythritol triacrylate) 2.2 parts (4) “IRGACURE 184” (photopolymerization initiator manufactured by Ciba Specialty Chemicals) 0.7 parts (5) Cyclohexanone 3 parts.

<Coating composition B>
The following composition was measured in a beaker, suction filtered using glass fiber filter paper “GFP” (manufactured by Kiriyama Seisakusho, particle size of trapped particles: 0.8 μm or more) stirred with a magnetic stirrer for 60 minutes, and the refractive index. A coating composition B of 1.58 was prepared.
(1) "Selnax CX-Z210IP-F2" (Nissan Chemical Industries zinc antimonate particles, isopropyl alcohol sol with a solid content of 20% by weight, primary particle size 20 nm) 22.5 parts (2) "Light acrylate PE" -4A "(ionizing radiation curable resin, pentaerythritol tetraacrylate manufactured by Kyoeisha Chemical Co., Ltd.) 25.5 parts (3)" IRGACURE 184 "(photopolymerization initiator manufactured by Ciba Specialty Chemicals) 2.0 parts (4 ) Methyl ethyl ketone 50.0 parts.

<Coating composition C>
Refraction is the same as coating composition B except that 30.0 parts of methyl ethyl ketone is added and 20.0 parts of “UA-510H” (ionizing radiation curable resin, 10-functional urethane acrylate manufactured by Kyoeisha Chemical Co., Ltd.) is added. A coating composition C with a rate of 1.56 was obtained.

<Coating composition D>
The following composition was measured in a beaker, stirred for 60 minutes with a magnetic stirrer, and then filtered with suction using a glass fiber filter paper “GFP” (manufactured by Kiriyama Seisakusho, particle size of trapped particles 0.8 μm or more). A coating composition D having a refractive index of 1.40 was prepared.
(1) Isopropyl alcohol dispersion containing hollow silica particles (Catalyst Chemical Industries, solid content 20% by weight, primary particle size 60 nm) 7.5 parts (2) “Aronix M400” (ionizing radiation curable type manufactured by Toagosei Co., Ltd.) Resin, dipentaerythritol hexaacrylate) 0.5 part (3) “Light acrylate PE-3A” (ionizing radiation curable resin, pentaerythritol triacrylate manufactured by Kyoeisha Chemical Co., Ltd.) 0.5 part (4) “IRGACURE907” ( 0.1 parts (5) “X22-174DX” (methacrylic modified silicone oil made by Shin-Etsu Chemical Co., Ltd.) 0.02 parts (6) 81.38 parts isopropyl alcohol (7) 10.0 parts of ethylene glycol monobutyl ether.

<Coating composition E>
Refractive index is the same as coating composition D except that the hollow silica particle-containing isopropyl alcohol dispersion is 50.0 parts, light acrylate PE-3A is 7.5 parts, and isopropyl alcohol is 31.88 parts. A coating composition E of 1.41 was obtained.

<Coating composition F>
Refractive index was the same as coating composition D, except that the hollow silica particle-containing isopropyl alcohol dispersion was 75.0 parts, light acrylate PE-3A was 10.5 parts, and isopropyl alcohol was 3.88 parts. A coating composition F of 1.47 was obtained.

<Coating composition G>
Coating composition B except that 10 parts of methyl ethyl ketone, 20.0 parts of “KAYARAD DPHA” (Nippon Kayaku Co., Ltd. ionizing radiation curable resin, dipentaerythritol hexaacrylate) and 20.0 parts of cyclohexanone were added. Similarly, a coating composition G having a refractive index of 1.55 was obtained.

<Coating composition H>
Except that the hollow silica particle-containing isopropyl alcohol dispersion was 60.0 parts, light acrylate PE-3A was 8.5 parts, isopropyl alcohol was 8.88 parts, and ethylene glycol monobutyl ether was 22.0 parts. In the same manner as the coating composition D, a coating composition H having a refractive index of 1.40 was obtained.

<Coating composition I>
A coating composition I having a refractive index of 1.61 was obtained in the same manner as in the coating composition A, except that 72.5 parts of methyl ethyl ketone was used in the dispersion A instead of 72.5 parts of isobutyl alcohol.

<Coating composition J>
The hollow silica particle-containing isopropyl alcohol dispersion is 50.0 parts, “Aronix M400” is 5.0 parts, “light acrylate PE-3A” is 5.0 parts, isopropyl alcohol is 9.88 parts, ethylene A coating composition J having a refractive index of 1.44 was obtained in the same manner as the coating composition D, except that 30.0 parts of glycol monobutyl ether was used.

<Coating composition K>
In the dispersion A, a coating composition K having a refractive index of 1.62 was obtained in the same manner as the coating composition A, except that 0.5 part of “BYK180” and 74.0 parts of isobutyl alcohol were used. .

<Coating composition L>
A coating composition L having a refractive index of 1.42 was obtained in the same manner as in the coating composition D, except that 81.38 parts of methyl ethyl ketone was added instead of 81.38 parts of isopropyl alcohol.

  The refractive index, the viscosity A, the viscosity B, and the thixotropy coefficient A / B of the coating compositions A to L are shown in Table 1 below.

  Next, a hard coat layer and a low refractive index layer were formed using the above coating composition.

Example 1
<Base material>
As a substrate, a primer layer made of a silica particle-containing polyester resin is formed only on one main surface of the substrate, and an ultraviolet-cutting polyethylene terephthalate (PET) film having a thickness of 100 μm (refractive index: 1.65, (Total light transmittance: 92.0%) was prepared (hereinafter referred to as “base material A”).

<Formation of hard coat layer>
The main surface of the base material A where the primer layer was not provided was subjected to a corona discharge treatment with a discharge amount of 171.4 W · min / m ² . Next, the coating composition A was applied to the main surface side of the base material A on which the above-mentioned corona discharge treatment was performed using a micro gravure coater (manufactured by Yasui Seiki Co., Ltd.), and then dried. It was. Subsequently, the coating film was irradiated with an integrated light amount of 700 mJ / cm ^{2 in} the atmosphere to cure the coating film, thereby forming a hard coat layer having a thickness of 1.4 μm.

(Example 2)
First, in the same manner as in Example 1, a hard coat layer was formed on the main surface side on which the primer layer on the substrate A was not provided.

<Formation of low refractive index layer>
Next, the coating composition D was applied onto the hard coat layer using the microgravure coater and dried. Then, under a nitrogen purge, the coating film was irradiated with ultraviolet rays with an integrated light amount of 700 mJ / cm ² to cure the coating film to form a low refractive index layer having a thickness of 107 nm to obtain an antireflection film.

(Example 3)
<Base material>
As a base material, a first primer layer made of a silica particle-containing polyester resin is formed on one main surface, and a second primer layer made of a silica particle-containing acrylic resin is formed on the other main surface. A 100 μm ultraviolet-cutting polyethylene terephthalate (PET) film (refractive index: 1.58, total light transmittance: 92.4%) was prepared (hereinafter referred to as substrate B).

<Formation of hard coat layer>
The main surface side of the substrate B on which the first primer layer was provided was subjected to a corona discharge treatment with a discharge amount of 171.4 W · min / m ² . Next, the coating composition B was applied to the main surface side on which the first primer layer of the substrate B subjected to the corona discharge treatment was applied using the microgravure coater, and then dried. Subsequently, the coating film was irradiated with an integrated light amount of 700 mJ / cm ^{2 in} the atmosphere to cure the coating film, thereby forming a hard coat layer having a thickness of 2.8 μm.

Example 4
First, in the same manner as in Example 3, a hard coat layer was formed on the main surface side on which the first primer layer on the substrate B was provided.

<Formation of low refractive index layer>
Next, the coating composition E was applied onto the hard coat layer using the microgravure coater and dried. Then, under a nitrogen purge, the coating film was irradiated with ultraviolet rays with an integrated light amount of 700 mJ / cm ² to cure the coating film to form a low refractive index layer having a thickness of 107 nm to obtain an antireflection film.

(Example 5)
As the substrate, the above-mentioned substrate B was used.

<Formation of hard coat layer>
The main surface side of the base material B on which the first primer layer was provided was subjected to a corona discharge treatment with a discharge amount of 171.4 W · min / m ² . Next, the coating composition G was applied to the main surface provided with the first primer layer of the substrate B subjected to the corona discharge treatment using the microgravure coater, and then dried. Subsequently, the coating film was irradiated with an integrated light amount of 700 mJ / cm ^{2 in} the atmosphere to cure the coating film, thereby forming a hard coat layer having a thickness of 2.8 μm.

(Example 6)
First, in the same manner as in Example 5, a hard coat layer was formed on the main surface side on which the first primer layer on the substrate B was provided.

<Formation of low refractive index layer>
Next, the coating composition H was applied onto the hard coat layer using the microgravure coater and dried. Then, under a nitrogen purge, the coating film was irradiated with ultraviolet rays with an integrated light amount of 700 mJ / cm ² to cure the coating film to form a low refractive index layer having a thickness of 107 nm to obtain an antireflection film.

(Comparative Example 1)
As the substrate, the above-mentioned substrate B was used.

<Formation of hard coat layer>
The main surface side of the base material B on which the first primer layer was provided was subjected to a corona discharge treatment with a discharge amount of 171.4 W · min / m ² . Next, the coating composition C was applied to the main surface side on which the first primer layer of the substrate B subjected to the corona discharge treatment was provided using the microgravure coater, and then dried. Subsequently, the coating film was irradiated with an integrated light amount of 700 mJ / cm ^{2 in} the atmosphere to cure the coating film, thereby forming a hard coat layer having a thickness of 2.8 μm.

(Comparative Example 2)
First, in the same manner as in Comparative Example 1, a hard coat layer was formed on the main surface side on which the first primer layer on the substrate B was provided.

<Formation of low refractive index layer>
Next, the coating composition F was applied onto the hard coat layer using the microgravure coater and dried. Then, under a nitrogen purge, the coating film was irradiated with ultraviolet rays with an integrated light amount of 700 mJ / cm ² to cure the coating film to form a low refractive index layer having a thickness of 107 nm to obtain an antireflection film.

(Comparative Example 3)
As the substrate, the substrate A was used.

<Formation of hard coat layer>
The main surface of the base material A where the primer layer was not provided was subjected to a corona discharge treatment with a discharge amount of 171.4 W · min / m ² . Next, the coating composition I was applied to the main surface side of the base material A on which the above-mentioned corona discharge treatment was performed without using the microgravure coater (manufactured by Yasui Seiki Co., Ltd.), and then dried. It was. Subsequently, the coating film was irradiated with ultraviolet rays with an integrated light amount of 700 mJ / cm ^{2 in} the atmosphere to cure the coating film to form a hard coat layer having a thickness of 1.4 μm.

(Comparative Example 4)
First, in the same manner as in Comparative Example 3, a hard coat layer was formed on the main surface side where the primer layer on the substrate A was not provided.

<Formation of low refractive index layer>
Next, the coating composition J was applied onto the hard coat layer using the microgravure coater and dried. Then, under a nitrogen purge, the coating film was irradiated with ultraviolet rays with an integrated light amount of 700 mJ / cm ² to cure the coating film to form a low refractive index layer having a thickness of 107 nm to obtain an antireflection film.

(Comparative Example 5)
As the substrate, the substrate A was used.

<Formation of hard coat layer>
The main surface of the base material A where the primer layer was not provided was subjected to a corona discharge treatment with a discharge amount of 171.4 W · min / m ² . Next, the coating composition K was applied to the main surface side of the base material A which has been subjected to the corona discharge treatment and not provided with the primer layer, using a micro gravure coater (manufactured by Yasui Seiki Co., Ltd.), and then dried. It was. Subsequently, the coating film was irradiated with ultraviolet light with an integrated light amount of 700 mJ / cm ^{2 in} the atmosphere to cure the coating film to form a hard coat layer having a thickness of 1.4 μm.

(Comparative Example 6)
First, in the same manner as in Comparative Example 5, a hard coat layer was formed on the main surface side on which the primer layer was not provided on the substrate A.

<Formation of low refractive index layer>
Next, the coating composition L was applied onto the hard coat layer using the microgravure coater and dried. Thereafter, the coating film was irradiated with an integrated light amount of 700 mJ / cm ² under a nitrogen purge to cure the coating film to form a low refractive index layer having a thickness of 107 nm. Thus, an antireflection film of Comparative Example 6 was obtained. .

  Appearance quality and visibility reflectance of hard coat layers of Examples 1, 3, 5 and Comparative Examples 1, 3, 5 and Appearance of antireflection films of Examples 2, 4, 6 and Comparative Examples 2, 4, 6 Quality and luminous reflectance were evaluated or measured as described above, and the results are shown in Table 2 below. In Table 2, the hard coat layers of Examples 1 to 6 and Comparative Examples 1 to 6, the types of coating compositions on which the low refractive index layers were formed, viscosity A, viscosity B, and thixotropy coefficient A / B are also shown. Indicated.

  FIG. 1 shows the viscosity flow curves of the coating compositions A and B used in forming the hard coat layer in Examples 1 and 3, respectively. FIG. 2 shows the viscosity flow curves of the coating compositions D and E used for forming the low refractive index layer in Examples 2 and 4, respectively.

  As shown in Table 2 above, in Examples 1 to 6 using a coating composition having a viscosity A of 1 to 20 mPa · s and a thixotropic coefficient A / B of 1.001 to 1.400, A hard coat layer and / or a low refractive index layer having excellent appearance quality with little interference unevenness has been obtained. In Examples 2, 4 and 6 in which the hard coat layer and the low refractive index layer were formed using the coating composition having a thixotropy coefficient A / B of 1.001 to 1.400, the appearance that interference unevenness was small An antireflection film having both quality and excellent antireflection properties has been obtained.

  On the other hand, in Comparative Example 1 using a coating composition having a thixotropy coefficient A / B exceeding 1.400, interference unevenness occurred on the surface of the hard coat layer. Further, in Comparative Example 2 in which the low refractive index layer was formed using a coating composition having a thixotropic coefficient A / B exceeding 1.400, interference unevenness occurred on the surface of the low refractive index layer. In Comparative Example 3 in which the hard coat layer was formed using the coating composition having a viscosity A of less than 1 mPa · s, interference unevenness occurred on the surface of the hard coat layer. In Comparative Example 4 in which the low refractive index layer was formed using a coating composition having a viscosity A exceeding 20 mPa · s, interference unevenness occurred on the surface of the low refractive index layer. Further, in Comparative Example 5 using the coating composition having a thixotropic coefficient A / B of less than 1.001, interference unevenness occurred on the surface of the hard coat layer. In Comparative Example 6 in which the low refractive index layer was formed using a coating composition having a thixotropic coefficient A / B of less than 1.001, interference unevenness occurred on the surface of the low refractive index layer.

  And from the comparison of the data of Examples 2, 4 and 6 of Table 2 and Comparative Examples 2, 4 and 6, hard coating was performed using a coating composition having a thixotropic coefficient A / B of 1.001 to 1.400. The antireflection films of Examples 2, 4 and 6 in which the layers and the low refractive index layers were formed were both in terms of appearance quality and visibility reflectance (antireflection characteristics) than the antireflection films of Comparative Examples 2, 4 and 6. It turns out that it is excellent.

  The antireflection film using the coating composition of the present invention has both an appearance quality such as less interference unevenness and an excellent antireflection property, and is a high definition represented by a liquid crystal display, a plasma display panel (PDP) and the like. And it can be applied as an antireflection film for large screen displays.

Claims (10)

Viscosity at a shear rate of 1 × 10 sec ⁻¹ at 25 ° C. of a coating composition containing inorganic particles and a resin, measured by viscosity measurement using a rotary viscometer to increase the shear rate Is A, and the viscosity at a shear rate of 1 × 10 ³ sec ⁻¹ is B, the viscosity A is 1 to 20 mPa · s, and the thixotropic coefficient A / B is 1.001 to 1.400. A coating composition.   Furthermore, the coating composition of Claim 1 containing an organic solvent.   The coating composition according to claim 1, wherein the resin is an ionizing radiation curable resin.   The coating composition according to claim 1, wherein the inorganic particles are metal oxide particles.   The coating composition according to claim 4, wherein the metal oxide particles include at least conductive oxide particles.   The coating composition according to claim 4, wherein the metal oxide particles are hollow silica particles.   The coating composition as described in any one of Claims 1-6 used for formation of an antireflection layer.   The antireflection film containing the antireflection layer formed using the coating composition as described in any one of Claims 1-7.   The antireflection film according to claim 8, wherein the antireflection layer includes a hard coat layer and a low refractive index layer that are laminated in order from the substrate side on one main surface side of the substrate. A method for producing an antireflection film comprising an antireflection layer formed on one main surface side of a base material and the base material,
The antireflection layer is formed by applying a coating composition to one main surface side of the substrate,
The coating composition contains inorganic particles and a resin, and the viscosity of the coating composition at a shear rate of 1 × 10 sec ⁻¹ at 25 ° C. measured by viscosity measurement using a rotary viscometer to increase the shear rate. Is A, and the viscosity at a shear rate of 1 × 10 ³ sec ⁻¹ is B, the viscosity A is 1 to 20 mPa · s, and the thixotropic coefficient A / B is 1.001 to 1.400. A method for producing an antireflection film.

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