JP2008111964A - Optical film and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film provided with an antireflection layer having low reflectance and high scratch resistance. <P>SOLUTION: A method of manufacturing the optical film comprising a light-transmitting base material, a hard coat film arranged on one main surface side of the light-transmitting base material and a low refractive index film arranged on the hard coat film and having a refractive index smaller than that of the hard coat film includes a low refractive index film forming step for forming the low refractive index film by applying a coating material for forming the low refractive index film which comprises hollow silica fine particles, a curable binder and a polymerization initiator on the hard coat film arranged on one main surface side of the light-transmitting base material to form a coating film on the hard coat film and curing the curable binder in the coating film. The porosity of the hollow fine particle is >30% and ≤50% and the polymerization initiator is incorporated in the quantity of ≥3 pts.wt. and ≤10 pts.wt, per 100 pts.wt. curable binder in the coating material. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical film in which a translucent base material, a hard coat film, and a low refractive index film are laminated in this order, and the hard coat film and the low refractive index film function as an antireflection layer, and a method for producing the same About.

  Development of large-screen displays represented by plasma display panels (PDP) and the like is rapidly progressing. An optical film having an antireflection layer is attached to the display screen in order to prevent reflection of external light. Since the antireflection layer constituting the optical film attached to the display screen is disposed on the outermost surface, the antireflection layer is required to have high scratch resistance.

The antireflection layer is generally composed of a hard coat film formed on a translucent substrate and a low refractive index film disposed on the hard coat film and having a refractive index lower than that of the hard coat film. The In order to further reduce the refractive index of the low-refractive index film and reduce the anti-reflective layer, conventionally, fluorine atoms are introduced into the low-refractive index film by using a fluororesin as a resin component, or hollow silica fine particles It has been proposed to use However, when fluorine atoms are introduced into the low refractive index film and / or hollow silica fine particles are used, the cohesive force of the fluorine atoms is small and / or the content of the curable binder accompanying the use of the hollow silica fine particles is small. Due to the decrease, the film strength is lowered and the scratch resistance is reduced. Therefore, it has been proposed to improve the scratch resistance by curing a curable binder contained in a coating material for forming a low refractive index film in an oxygen concentration atmosphere lower than the oxygen concentration in air (for example, patents). Reference 1).
JP 2006-119599 A

  However, if the curable binder is cured in an atmosphere having an oxygen concentration lower than that in air, a large amount of nitrogen is required, resulting in an increase in manufacturing cost.

  The present invention can realize an optical film including an antireflection layer having a low reflectivity and a high scratch resistance without curing the curable binder in an atmosphere having an oxygen concentration lower than that in air. A method for producing a film and an optical film obtained by the production method are provided.

  The method for producing an optical film of the present invention includes a translucent substrate, a hard coat film disposed on one main surface side of the translucent substrate, and the hard coat film disposed on the hard coat film. A method for producing an optical film comprising a low refractive index film having a smaller refractive index than the hollow silica fine particles on the hard coat film disposed on the one main surface side of the translucent substrate. A coating for forming a low refractive index film containing a curable binder and a polymerization initiator is applied, and after forming a coating film on the hard coat film, the curable binder in the coating film is cured to A low refractive index film forming step of forming a low refractive index film, wherein the void ratio of the hollow silica fine particles is more than 30% and 50% or less, and in the coating material, the polymerization initiator is 100 wt% of the curable binder. 3 parts by weight to 10 parts by weight Characterized in that it contains less.

  The optical film of the present invention is manufactured by the method for manufacturing an optical film of the present invention.

  According to the present invention, an optical film including an antireflection layer having a low reflectance and a high scratch resistance can be realized without curing the curable binder in an atmosphere having an oxygen concentration lower than that in air. The manufacturing method of an optical film and the optical film obtained by this manufacturing method can be provided.

  Hereinafter, the present invention will be described in detail.

(Embodiment 1)
In Embodiment 1, an example of the optical film of the present invention will be described.

  FIG. 1 is a cross-sectional view showing an example of the optical film of the present invention. As shown in FIG. 1, an example of the optical film 1 of the present embodiment includes a translucent substrate 10, a hard coat film 12 directly disposed on one main surface of the translucent substrate 10, And a low refractive index film 15 disposed in contact with the hard coat film 12. Since the refractive index of the low refractive index film 15 is lower than that of the hard coat film 12, the laminate composed of the low refractive index film 15 and the hard coat film 12 functions as the antireflection layer 9.

<Translucent substrate>
The material of the translucent substrate 10 is not particularly limited as long as it has translucency. Examples of the translucent substrate 10 include saturated polyester resins, polycarbonate resins, polyacrylate resins, alicyclic polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyvinyl acetate resins, and triacetyl cellulose. What processed the material, such as a resin, into a film shape can be used.

  Examples of the method for processing into a film include methods such as extrusion molding, calendar molding, compression molding, and injection molding. The thickness of the translucent substrate 10 is usually about 10 to 500 μm. In addition, the translucent base material 10 may further contain additives such as an antioxidant, a flame retardant, a heat resistance inhibitor, an ultraviolet absorber, a lubricant, and an antistatic agent.

  In an example of the optical film 1 of the present embodiment, the total light transmittance is preferably 91% or more. By disposing the antireflection layer 9 on the translucent substrate 10, the total light transmittance of the optical film is higher than the single total light transmittance of the translucent substrate 10. This is because the amount of light incident on the entire optical film 1 is increased by providing the antireflection layer 9.

  In order to set the total light transmittance of the optical film 1 to 91% or more and to make the total light transmittance of the optical film 1 higher than the single total light transmittance of the translucent substrate 10, for example, The thickness of the conductive substrate 10 is 10 μm to 500 μm, and the total light transmittance of the translucent substrate 10 is preferably 85% or more, more preferably 90% or more.

<Low refractive index film>
The low refractive index film 15 includes hollow silica fine particles and a curable binder. The porosity of the hollow silica fine particles needs to be more than 30% and 50% or less. If it is 30% or less, the reflectance of the optical film 1 is not sufficiently low, and if it exceeds 50%, it is difficult to maintain the hardness as an inorganic oxide during the synthesis of the hollow silica fine particles. If the void ratio of the hollow silica fine particles is 35% or more and 45% or less, the reflectance of the optical film 1 can be lowered and the hardness of the hollow silica fine particles is preferable.

  The blending ratio of the hollow silica fine particles contained in the coating material for forming the low refractive index film 15 is preferably 65% by weight or less, more preferably 60% by weight or less of the total weight of the curable binder and the hollow silica fine particles. . The weight of the curable binder remains almost unchanged upon curing. Therefore, the content of the hollow silica fine particles in the low refractive index film 15 is preferably 65% by weight or less and more preferably 60% by weight or less of the total weight of the curable binder (cured) and the hollow silica fine particles. This is because if the content of the hollow silica fine particles is too large, the content of the curable binder in the low refractive index film 15 is lowered, and the scratch resistance of the low refractive index film 15 is lowered. On the other hand, the lower limit of the content of the hollow silica fine particles in the low refractive index film 15 or the lower limit of the mixing ratio of the hollow silica fine particles in the coating material for forming the low refractive index film 15 is from the viewpoint of lowering the reflectance of the optical film. The total weight of the curable binder (cured) and the hollow silica fine particles is preferably 50% by weight or more, and more preferably 55% by weight or more.

  It is preferable that the average particle diameter of the hollow silica fine particles does not greatly exceed the thickness of the low refractive index film 15. On the other hand, if the average particle size is too large, scattering occurs and the haze value increases, such being undesirable. Therefore, the average particle diameter of the hollow silica fine particles is preferably 0.1 μm or less. The average particle size of the hollow silica fine particles is preferably as small as possible because the content of the hollow silica fine particles in the low refractive index film can be increased and the transparency of the low refractive index film is increased.

  In the low refractive index film 15, the optical film thickness nd, which is the product of the refractive index n and the film thickness d of the low refractive index film 15, is preferably 110 nm or more and 163 nm or less, and more preferably 125 nm or more and 150 nm or less. This is because the reflectance of the low refractive index film 15 can be lowered in this case. Regarding the film thickness of the low refractive index film 15 disposed on the hard coat film 12, the optical film thickness, which is the product of the refractive index of the low refractive index film 15 and the above film thickness, is λ / 4 (λ: human eyes). It is preferable to set the wavelength of light having a high visibility to 550 nm in many cases, so that the reflectance becomes lower. The larger the difference between the refractive index of the low refractive index film 15 and the refractive index of the hard coat film 12, the better the antireflection performance is improved. Since one surface of the low refractive index film 15 is also one outermost surface of the optical film of the present embodiment, it is preferable to have strength and antifouling properties.

  The refractive index of the low refractive index film 15 is preferably, for example, less than 1.40, and more preferably 1.38 or less, in order to reduce the reflectance of the optical film 1.

  Examples of the curable binder contained in the coating material for forming the low refractive index film 15 include a thermosetting binder and an ionizing radiation curable binder (ionizing radiation curable resin). As the ionizing radiation curable resin, a compound having a vinyl group, a (meth) acryloyl group, an epoxy group, or an oxetanyl group can be used. The compound may be any of a monomer, a prepolymer, and a polymer. From the viewpoint of improving the scratch resistance, the ionizing radiation curable resin preferably contains a polyfunctional acrylate having at least two polymerizable unsaturated groups.

  Examples of the polyfunctional acrylic compound having two or more unsaturated groups include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,4-cyclohexane diacrylate, Pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) Acrylate, dipentaerythritol hexa (meth) acrylate, 1,2,3-cyclohexanetrimethacrylate, polyurethane polyacrylate, polyester polyacrylate Esters produced from polyhydric alcohol and (meth) acrylic acid such as relate, vinylbenzene such as 1,4-divinylbenzene, 4-vinylbenzoic acid-2-acryloylethyl ester, 1,4-divinylcyclohexanone And derivatives thereof. These may be used alone or in combination of two or more. Of these, at least one selected from pentaerythritol triacrylate and dipentaerythritol hexaacrylate is preferable from the viewpoint of further improving the scratch resistance. Pentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) The acrylate and dipentaerythritol hexa (meth) acrylate are preferable from the viewpoint of increasing the film strength, but since the refractive index is high, it is preferable to use in combination with other polyfunctional acrylic compounds having a refractive index lower than these. .

  However, the refractive index of a polymer of an acrylic compound having two or more polymerizable unsaturated bonds is the refractive index of hollow silica fine particles having a porosity of more than 30% and 50% or less (n = 1.30-1. 40), the refractive index of the low refractive index film 15 increases as the content of the polymer in the low refractive index film 15 increases. Therefore, the content of the polymer in the low refractive index film 15 is determined from the viewpoint of balancing the securing of the strength of the low refractive index film 15 and the suppression of the increase in the refractive index of the low refractive index film 15. The total of the weight of the functional binder) and the hollow silica fine particles is preferably more than 35% by weight and less than 50% by weight, more preferably more than 40% by weight and less than 45% by weight. When the content of the curable binder is within these ranges, an optical film having higher scratch resistance can be realized in combination with the action of the polymerization initiator described later contained in the coating material for forming the low refractive index film 15. .

  Examples of the thermosetting binder include inorganic binders such as silica sol. Examples of the silica sol include a silica sol using a silicon alkoxide and an acid catalyst or an alkali catalyst as starting materials. Examples of the silicon alkoxide include tetramethoxysilane and tetraethoxysilane.

  The coating material for forming the low refractive index film 15 needs to contain a polymerization initiator. The blending ratio of the polymerization initiator in the coating material needs to be 3 parts by mass or more and 10 parts by mass or less with respect to 100 parts by weight of the curable binder, but is preferably 4 parts by mass or more and 8 parts by mass or less. If the amount is less than 3 parts by mass, sufficient scratch resistance cannot be obtained. If the amount exceeds 10 parts by mass, the content of the curable binder in the low refractive index film must be lowered, and the low refractive index film has scratch resistance. It is because it falls.

  In the step of forming the low refractive index film, when the curable binder in the coating film formed on the hard coat film 12 is cured using, for example, ultraviolet rays, the polymerization initiator is a photopolymerization initiator. Use. Examples of the photopolymerization initiator include 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 1-hydroxycyclohexyl phenyl ketone, and 2,2-dimethoxy-2- Phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether , Benzoin ethyl ether, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropane-1-one Thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, etc. These may be used, but these may be used alone or in combination of two or more.

  The solvent contained in the coating material for forming the low refractive index film 15 is not particularly limited as long as it is an organic solvent that can dissolve the curable binder and can stably disperse the hollow silica fine particles. For example, aliphatic hydrocarbon solvents such as hexane and mineral spirits; aromatic hydrocarbon solvents such as benzene, toluene and xylene; ester solvents such as butyl acetate; alcohol solvents such as methanol and butanol; methyl ethyl ketone and isobutylmethyl Examples include ketone solvents such as ketones; aprotic polar solvents such as dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and pyridine. Moreover, although only 1 type of these solvents may be used, you may use in combination of 2 or more type.

  It is preferable that the low refractive index film 15 forming paint contains an antifouling agent so that the low refractive index film 15 has antifouling properties. Examples of the antifouling agent include silicon compounds. The blending amount of the antifouling agent is preferably about 0.01 to 10 parts by mass with respect to 100 parts by mass of the curable binder contained in the coating material for the low refractive index film 15.

  Examples of the silicon-based compound include those having a substituent at the terminal and / or side chain of a compound chain containing a dimethylsilyloxy unit as a repeating unit. More specifically, examples of the silicon compound include polydimethylsiloxane, polyether-modified polydimethylsiloxane, aralkyl-modified polydimethylsiloxane, aralkyl-modified polydimethylsiloxane, fatty acid ester-modified polydimethylsiloxane, and fatty acid amide-modified polydimethylsiloxane. Non-reactive silicone, amino-modified polydimethylsiloxane, epoxy-modified polydimethylsiloxane, carbinol-modified polydimethylsiloxane, carboxyl-modified polydimethylsiloxane, methacryl / acryl-modified polydimethylsiloxane, phenol-modified polydimethylsiloxane, silanol-modified polydimethylsiloxane And reactive silicones such as mercapto-modified polydimethylsiloxane.

  The surface hardness of the low refractive index film 15 is preferably 2H or higher as evaluated by a pencil hardness test specified in JIS K5400. This is because if the surface hardness is 2H or more, it is difficult for the surface to be scratched.

  The method for forming the low refractive index film 15 on the hard coat film 12 is not particularly limited, and the low refractive index film 15 can be formed by applying a paint containing the above material on the hard coat film 12. The coating method is not particularly limited, for example, a coating method such as roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, or printing methods such as gravure printing, screen printing, offset printing, and ink jet printing. Etc. can be used.

<Hard coat film>
The binder component constituting the material of the hard coat film 12 has a light-transmitting property, can form a film having a hardness higher than that of the light-transmitting substrate 10, and has a higher refractive index than the material of the low-refractive index film. If it has, it will not specifically limit. Examples of the binder component contained in the coating material for forming the hard coat film 12 include ionizing radiation curable resins and thermosetting resins. As the ionizing radiation curable resin, the same ionizing radiation curable resin as that used for forming the low refractive index film can be used. Examples of the thermosetting resin include urethane, melamine, epoxy, and acrylic thermosetting resins. Among these, it is more preferable to use an ionizing radiation curable resin capable of forming a film having a high surface hardness.

  The hard coat film 12 preferably contains a conductive metal oxide and / or a conductive resin and has an antistatic function. This is because if the hard coat film 12 has an antistatic function, it is possible to prevent adhesion of dust, dirt, and the like due to static electricity on the screen surface of the display.

  The content of the conductive metal oxide in the hard coat film 12 is preferably 5% by mass to 15% by mass and more preferably 9% by mass to 12% by mass with respect to the total mass of the hard coat film. . This is because if the content of the conductive metal oxide is less than 5% by mass, the antistatic function is insufficient, and if it exceeds 15% by mass, the total light transmittance of the optical film decreases.

Examples of the conductive metal oxide contained in the hard coat film 12 include antimony-tin composite oxide (ATO), indium-tin composite oxide (ITO), zinc oxide (ZnO), tin oxide (SnO), and antimony. Examples thereof include zinc acid (ZnSb ₂ O ₆ ). The conductive metal oxide is preferably in the form of fine particles having good dispersibility in a binder component such as an ionizing radiation curable resin, and the primary particle diameter is preferably 100 nm or less, more preferably 50 nm or less, and 20 nm or less. Is particularly preferred. In addition, since the said primary particle diameter is so small that content of the electroconductive metal oxide in the hard-coat film 12 can be increased and transparency of the hard-coat film 12 becomes high, it is preferable.

  Conductive metal oxide fine particles can be easily obtained as an organosol dispersed in an organic solvent. It is preferable to use an organic solvent having a solubility parameter of 9.5 or more as the dispersion medium constituting the organosol because the conductivity of the hard coat film 12 is improved. Furthermore, in order to improve the conductivity of the hard coat film 12, 0.05 wt% to 80 wt% of an organic solvent having a solubility parameter of 9.5 or more is blended in the paint for forming the hard coat film 12. It is preferable.

  When the conductive metal oxide fine particles are dispersed in the hard coat film 12 with good uniformity, the conductivity of the hard coat film 12 is improved. Therefore, it is preferable that a dispersant is added to the paint for forming the hard coat film 12. As the dispersant, a cationic, weakly cationic, nonionic or amphoteric surfactant can be used. In particular, alkylamine surfactants modified with lower (C2 to C3) alkylene oxides such as propylene oxide or ethylene oxide are preferred. The content of the dispersant in the hard coat film or the blending amount in the hard coat film forming coating is preferably 0.05 to 15 parts by mass with respect to 100 parts by mass of the conductive metal oxide, and 0.5 to 10 parts. More preferably, it is part by mass. It is because the effect of a dispersing agent will be acquired reliably if it is in these ranges, the translucency of the hard-coat film | membrane 12 can be maintained, and intensity | strength can be ensured.

  Examples of the conductive resin contained in the hard coat film 12 include polyaniline, polyethylenedioxythiophene (PEDOT), and polypyrrole. The conductive resin is preferably soluble in an organic solvent contained in the coating material for forming the hard coat film 12 or in the form of fine particles having good dispersibility in the organic solvent. When the conductive resin is in the form of fine particles, it is more preferable that the primary particle size is 100 nm or less because the dispersibility in the curable vine is good.

  There is no particular limitation on the method of forming the hard coat film 12 on the one main surface side of the translucent substrate 10, and the paint for forming the hard coat film 12 is formed as in the case of forming the low refractive index film 15. It can form by apply | coating to an adjacent layer, drying a coating film, and hardening | curing the binder component contained in a coating film.

  The surface hardness of the hard coat film 12 is preferably H or higher, more preferably 2H or higher, as evaluated by a pencil hardness test defined in JIS K5400. Moreover, 2-7 micrometers is preferable and, as for the thickness of the hard-coat film | membrane 12, 3-5 micrometers is more preferable. If the thickness is less than 2 μm, it will be difficult to maintain the hardness, and if it exceeds 7 μm, cracks are likely to occur, and curling (warping of the film) is likely to occur, and thus the total light transmittance of the optical film 1 is reduced. It is because it becomes easy to do.

  The hard coat film 12 forming paint preferably contains a polymerization initiator. When the binder component contained in the coating material for forming the hard coat film 12 is an ionizing radiation curable resin and ultraviolet rays are used for curing the resin, a photopolymerization initiator may be used as the polymerization initiator. As this photopolymerization initiator, for example, the same photopolymerization initiator used for the low refractive index film may be used.

The surface resistance value on the antireflection layer side of the optical film 1 is preferably 5 × 10 ¹² Ω / □ or less, and more preferably 1 × 10 ¹¹ Ω / □ or less. This is because if the surface resistance value exceeds 5 × 10 ¹² Ω / □, dust tends to adhere, which is not preferable. The surface resistance value is preferably as low as possible. However, if the amount of the conductive metal oxide is increased in an attempt to reduce the surface resistance value, the color of the hard coat film increases and the total light transmittance of the optical film increases. descend. Further, the hardness of the antireflection layer is reduced and the scratch resistance is lowered. Therefore, the lower limit of the surface resistance value is suitably about 10 ⁸ Ω / □.

<Easily adhesive layer>
As shown in FIG. 2, in another example of the optical film 2 of the present embodiment, an easy-adhesion layer 11 is disposed between the translucent substrate 10 and the hard coat film 12. The adhesive strength between the easily adhesive layer 11 and the translucent substrate 10 and the adhesive strength between the easily adhesive layer 11 and the hard coat layer 12 are the adhesion between the translucent substrate 10 and the hard coat layer 12 in contact therewith. Higher than strength. Therefore, providing the easy-adhesion layer 11 between the translucent substrate 10 and the hard coat film 12 is preferable in terms of improving the bonding strength between the translucent substrate 10 and the hard coat film 12. In addition, when the adhesive strength of the translucent base material 10 and the hard-coat layer 12 which contact | connects this is enough, it is better not to have the easily bonding layer 11 from a viewpoint of reducing interference spots.

  Examples of the material used for the easy adhesion layer 11 include a polyester resin, a polyurethane resin, and an acrylic resin. These resins may be used alone or in combination of two or more as a polymer blend. When a copolymer obtained by copolymerizing a monomer having a hydrophilic group such as a carboxyl group or a hydroxyl group with a monomer constituting these resins is used as a material for the easy adhesion layer 11, the easy adhesion layer and the light transmissive layer are used. This is more preferable because the adhesion to the conductive substrate is further improved.

  The easy-adhesion layer 11 improves the handling properties of the translucent substrate 10 such as slipping property, winding property, and blocking resistance, and wear properties such as wear resistance and scratch resistance, and adjusts the refractive index. In addition, at least one kind of particles selected from inorganic particles and heat-resistant polymer particles may be included. Inorganic particles include calcium carbonate particles, calcium phosphate particles, silica particles, kaolin particles, talc particles, titanium dioxide particles, alumina particles, barium sulfate particles, calcium fluoride particles, lithium fluoride particles, zeolite particles, molybdenum sulfide particles, Shu Examples of the heat-resistant polymer particles include crosslinked polymer particles. Among these particles, silica particles are preferable. This is because the refractive index of silica particles having the following average particle diameter is relatively close to the refractive index of the polyester resin, and high transparency is easily obtained.

  The average particle diameter of the particles is usually 0.005 μm to 1.0 μm, preferably 0.005 μm to 0.5 μm, and more preferably 0.005 μm to 0.1 μm. This is because if the average particle diameter exceeds 1.0 μm, the surface of the easy-adhesion layer tends to become rough and the transparency of the easy-adhesion layer 11 tends to decrease.

  Content of the said particle | grains contained in the easily bonding layer 11 is 60 mass% or less normally, Preferably it is 50 mass% or less, More preferably, it is 40 mass% or less. This is because if the content of the particles is too large, the easy adhesion of the easy adhesion layer 11 may be impaired.

  The easy-adhesion layer 11 can be formed by applying a paint containing the resin component, the particles, a solvent, and the like to the translucent substrate 10, for example. The coating method is not particularly limited. For example, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation coating method, curtain coating method. Etc. These methods may be used alone or in combination of two or more.

  The easy-adhesion layer 11 forming coating may be applied to the translucent substrate that has been biaxially stretched and heat-fixed, but is applied to the translucent substrate before stretching. Later, stretching and heat setting may be performed. In order to apply the paint with good uniformity, it is preferable to apply the paint to the translucent substrate before stretching.

The solid content concentration (total concentration of the remaining components excluding the solvent) in the paint for forming the easy adhesion layer 11 is usually 30% by mass or less, preferably 10% by mass or less. The coating amount of the easy-adhesion layer 11 forming coating is preferably 0.01 to 5 g and more preferably 0.2 to 4 g with respect to 1 m ^{2 of the} running film. The degree of cleanliness of the translucent substrate 10 when applying the paint for forming the easy adhesion layer 11 is preferably class 1000 or less from the viewpoint of reducing the adhesion of dust.

The thickness of the easy adhesion layer 11 is preferably less than 1 μm, and more preferably less than 0.7 μm. If the thickness of the easy-adhesion layer 11 is 1 μm or more, not only does the effect of improving the adhesion reach saturation, but it is economically disadvantageous, and the thickness of the optical film 1 becomes undesirably thick. When it is necessary to reduce the reflected light at the interface between the hard coat film 12 and the translucent substrate 10 and reduce the occurrence of interference fringes by the hard coat film 12, the following relational expression is satisfied. If the thickness (d _P ) of the easy-adhesion layer is set, the reflected light at the interface is effectively reduced, and the generation of interference fringes can be prevented.

(Equation 1)
d _P = (2N−1) × λ / (4n _P )

Here, N is a natural number, λ is the wavelength of light with high visibility to human eyes (often set to 550 nm), and n _P is the refractive index of the easy adhesion layer.

<Near infrared absorbing layer>
As shown in FIG. 3, in still another example of the optical film 3 of the present embodiment, a near-infrared absorbing layer 14 may be disposed on the side opposite to the antireflection layer side of the translucent substrate 10. Thereby, if the optical film 1 is affixed on the surface of PDP, the near-infrared absorption layer 14 can absorb the near infrared rays radiated | emitted with plasma discharge. For this reason, the problem that peripheral electronic devices malfunction due to near infrared rays radiated from the PDP, in particular, malfunction of remote controls such as televisions and air conditioners is solved.

  In this case, as shown in FIG. 3, an easy adhesion layer 13 may be disposed between the translucent substrate 10 and the near infrared absorption layer 14. The material, the formation method, and the like of the easy adhesion layer 13 are the same as those of the easy adhesion layer 11 disposed between the translucent substrate 10 and the hard coat film 12. In the optical film 1 shown in FIG. 3, since the antireflection layer 9 is provided, the total light transmittance of the optical film 1 is high, so that the degree of freedom in designing the near-infrared absorbing layer 14 is increased.

  The near-infrared absorbing compound contained in the near-infrared absorbing layer 14 is preferably a compound having a maximum absorption wavelength in the wavelength region of 850 nm to 1100 nm. When the near-infrared absorbing layer contains the above-mentioned near-infrared absorbing compound, it is possible to reduce the near-infrared transmittance in the wavelength region of 850 nm to 1100 nm without greatly reducing the visible light transmittance in the wavelength range of 400 nm to 850 nm. It becomes. Therefore, the optical film of the present embodiment can be suitably used as a near infrared absorption filter such as PDP.

  Examples of the near-infrared absorbing compound having the maximum absorption wavelength in the wavelength region of 850 nm to 1100 nm include, for example, aminium-based, azo-based, azine-based, anthraquinone-based, indigoid-based, oxazine-based, quinophthalonine-based, squalium-based, stilbene-based, Organic pigments such as phenylmethane, naphthoquinone, diimonium, phthalocyanine, cyanine, and polymethine are listed.

  Examples of the binder component for dispersing the near-infrared absorbing compound include polyester resin, acrylic resin, polyurethane resin, polyvinyl chloride resin, epoxy resin, polyvinyl acetate resin, polystyrene resin, cellulose resin, and polybutyral resin. These resins may be used alone or in combination of two or more as a polymer blend.

  As the solvent contained in the paint for forming the near-infrared absorbing layer 14, a conventionally known solvent used in the paint for forming the near-infrared absorbing layer 14 may be used. Moreover, what is necessary is just to select suitably the mixing | blending ratio of the solvent contained in the coating material for near-infrared absorption layer 14 formation according to the coating method etc. of a coating material.

  There is no particular limitation on the method for forming the near infrared absorption layer 14 on the side opposite to the hard coat film 12 side of the translucent substrate 10. For example, a paint for forming the near infrared absorption layer 14 is applied to the translucent substrate. Then, it can be formed by removing the solvent in the coating film. Application methods include, for example, coating methods such as roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, and gravure coating, or printing methods such as gravure printing, screen printing, offset printing, and inkjet printing. it can.

  The thickness of the near infrared absorption layer 14 is preferably 1 μm to 10 μm, and more preferably 2 μm to 7 μm. If the thickness is less than 1 μm, near-infrared absorption is insufficient, and if it exceeds 10 μm, cracks are likely to occur, and curling (film warpage) is likely to occur.

  A compound that cuts the neon emission line spectrum (orange) of PDP may be appropriately added to the near infrared absorption layer 14. Thereby, red color can be more vividly developed in the PDP. As the compound that cuts off the neon emission line spectrum, an organic dye having a maximum absorption wavelength in the wavelength region of 580 to 620 nm can be used. For example, cyanine-based, azulenium-based, squalium-based, diphenylmethane-based, triphenylmethane-based, oxazine-based, Organic dyes such as azine, thiopylium, viologen, azo, azo metal complex, azaporphyrin, bisazo, anthraquinone, and phthalocyanine can be used.

  The thickness of the near-infrared absorbing layer 14, the type of material, the content of the near-infrared absorbing compound, and the like are appropriately determined so that the spectral transmittance of the optical film is 20% or less in the entire wavelength region of wavelengths from 850 nm to 1100 nm. That's fine.

(Embodiment 2)
Embodiment 2 demonstrates an example of the manufacturing method of the optical film of Embodiment 1 shown in FIG.

  As shown in FIG. 4, the strip-shaped laminate A in which the light-transmitting substrate 10 and the easy-adhesion layer 11 and the hard coat film 12 are formed in this order on one main surface thereof are wound in a roll shape. It is in the state. The laminated body A is fed out from the wound body 101 around which the laminated body A is wound, and is conveyed to the coating material application unit 4.

  In the paint application unit 4, the low refractive index film-forming paint is applied to the hard coat film constituting the laminate A. Subsequently, the laminate A ′ having a coating film formed on the hard coat film is conveyed into the dryer 29. In the dryer 29, the solvent in the coating film is removed. The atmospheric temperature in the dryer 29 and the conveying speed of the laminate A ′ may be set so that most of the solvent in the coating film can be removed in the dryer 29. Moreover, what is necessary is just to set so that the damage by the heat | fever of a translucent base material or a hard-coat film may become as small as possible.

  Next, radiation (for example, ultraviolet rays) is irradiated to the laminated body A ″ from which the solvent in the coating film has been removed by passing through the dryer 29 by, for example, a radiation irradiation apparatus. By being irradiated with radiation, the curable binder in the coating film is cured, and the coating film becomes the low refractive index film 15 (see FIG. 1). The oxygen concentration in the atmosphere in which the radiation is performed may be equal to the oxygen concentration in the air.

  Next, the laminate A ′ ″ is once wound up in a roll shape. Next, the laminate A ′ ″ is unwound from the wound body 102, and the laminate A ′ ″ is inspected for optical defects (inspection process).

  Next, a protective laminate film is applied to the laminate A ′ ″ that has undergone the inspection process. The protective laminate film is attached to the low refractive index film constituting the laminate A ′ ″.

  Next, the easy-adhesion layer and the near-infrared absorbing layer 14 are formed in this order on the surface opposite to the surface of the translucent substrate 10 on the hard coat film side. The easy-adhesion layer and the near-infrared absorbing layer may be formed after the laminate A ′ ″ with the protective laminate film is once wound into a roll shape, but immediately after the protective laminate film is pasted without winding. You may go to There is no restriction | limiting in particular about the formation method of an easily bonding layer and a near-infrared absorption layer, What is necessary is just to form by a conventionally well-known method.

  In the method for producing an optical film of the present embodiment, as shown in the results described in the examples below, a coating material for forming a low refractive index film containing hollow silica fine particles, a curable binder, and a polymerization initiator is used. A low refractive index film is formed, and the void ratio of the hollow silica fine particles is more than 30% and 50% or less, and the blending ratio of the polymerization initiator in this coating is 3% by weight with respect to 100 parts by weight of the curable binder. An optical film comprising an antireflection layer having a low reflectivity and high scratch resistance even when the curable binder is not cured in an atmosphere having an oxygen concentration lower than that in air because it is 10 parts by weight or more and 10 parts by weight or less. Can provide.

  Hereinafter, an example of the present invention will be described based on examples, but the present invention is not limited to the following examples. In addition, in any of the following Examples 1 to 10 and Comparative Examples 1 to 6, irradiation with ultraviolet rays was performed in air with no composition adjustment.

<Preparation of translucent substrate with easy adhesion layer>
A first easy-adhesion layer made of a silica fine particle-containing polyester resin (refractive index: 1.58) is formed on one main surface of an ultraviolet-cut polyethylene terephthalate (PET) film, and a silica-containing acrylic resin is formed on the other main surface. A light transmissive substrate with an easy adhesion layer (total light transmittance: 92.4%) having a thickness of 100 μm and having a second easy adhesion layer formed of was prepared.

<Preparation of hard coat film forming paint>
The following materials were sufficiently mixed and stirred to prepare a coating material for forming a hard coat film.
(1) Zinc antimonate fine particles (manufactured by Nissan Chemical Co., Ltd., “Selnax CX-Z210IP-F2”, isopropyl alcohol sol having a solid content of 20% by mass, primary particle size: 20 nm): 15 parts by weight (2) pentaerythritol triacrylate : 8 parts by weight (3) Dipentaerythritol hexaacrylate: 8 parts by weight (4) Photopolymerization initiator (Ciba Specialty Chemicals, "IRGACURE (registered trademark) 907"): 1 part by weight (5) Isopropyl alcohol (Solubility parameter: 11.5): 68 parts by weight

Next, the hard coat film forming paint was applied onto the first easy-adhesion layer using a micro gravure coater (manufactured by Yasui Seiki Co., Ltd.) in an environment with a relative humidity of 60%. Then, the coating film was dried, and then the coating film was irradiated with ultraviolet rays at a dose of 100 mJ / cm ² to cure the coating film to obtain a hard coat film having a thickness of 3 μm.

<Preparation of coating material for low refractive index film>
The following materials were mixed and stirred to prepare a coating material for forming a low refractive index film.
(1) Hollow silica fine particles (porosity: 35%, manufactured by Catalyst Kasei Co., Ltd.): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiation Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 1.6 parts by weight (5) Polymer surface modifier (Nippon Yushi Co., Ltd., “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

Next, the coating material for forming a low refractive index film was applied onto the hard coat film by using the micro gravure coater to form a coating film on the hard coat film. Thereafter, the coating film was dried, and then the coating film was irradiated with ultraviolet rays at a dose of 300 mJ / cm ² to cure the coating film, thereby forming a low refractive index film having a refractive index of 1.37% and a thickness of 106 nm. . The optical film for evaluation of Example 1 was produced as described above.

An optical film for evaluation was produced in the same manner as in Example 1 except that a coating material for forming a low refractive index film having the following composition was used.
(1) Hollow silica fine particles (porosity: 35%, manufactured by Catalyst Kasei Co., Ltd.): 55 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 25 parts by weight (4) Photopolymerization initiation Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 1.8 parts by weight (5) Polymer surface modifier (Nippon Yushi Co., Ltd., “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

An optical film for evaluation was produced in the same manner as in Example 1 except that a coating material for forming a low refractive index film having the following composition was used.
(1) Hollow silica fine particles (porosity: 35%, manufactured by Catalyst Kasei Co., Ltd.): 50 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 30 parts by weight (4) Photopolymerization started Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 2.0 parts by weight (5) Polymer surface modifier “Modiper F600” (manufactured by NOF Corporation): 1 part by weight (6 ) Isopropyl alcohol: 2000 parts by weight

An optical film for evaluation was produced in the same manner as in Example 1 except that a coating material for forming a low refractive index film having the following composition was used.
(1) Hollow silica fine particles (porosity: 35%, manufactured by Catalyst Kasei Co., Ltd.): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiation Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 2.4 parts by weight (5) Polymer surface modifier (manufactured by NOF Corporation, “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

An optical film for evaluation was produced in the same manner as in Example 1 except that the coating material for forming a low refractive index film having the following composition was used.
(1) Hollow silica fine particles (porosity: 35%, manufactured by Catalyst Kasei Co., Ltd.): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiation Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 1.2 parts by weight (5) Polymer surface modifier (Nippon Yushi Co., Ltd., “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

  An optical film for evaluation was produced in the same manner as in Example 1 except that a near-infrared absorbing layer was formed on the second easy-adhesion layer using a paint for forming a near-infrared absorbing layer having the following composition.

<Preparation of paint for forming near-infrared absorbing layer>
The following materials were mixed and stirred to produce a near-infrared absorbing layer forming coating.
(1) Acrylic resin (Mitsubishi Rayon Co., Ltd., “Dianar”): 100 parts by weight (2) Aromatic dimonium dye (Nippon Carlit Co., Ltd., “CIR-1085”): 6 parts by weight (3) Cyanine moiety / dithiol Metal complex site-containing near infrared absorbing compound (Sumitomo Seika Co., Ltd., “SD50-E04N”, maximum absorption wavelength: 877 nm): 1 part by weight (4) Cyanine site / dithiol metal complex site containing near infrared absorbing compound (Sumitomo Seika) “SD50-E05N”, maximum absorption wavelength: 833 nm): 1 part by weight (5) methyl ethyl ketone: 125 parts by weight (6) toluene: 460 parts by weight

  Next, the near-infrared absorbing layer forming coating was applied to the second easy-adhesion layer using the microgravure coater to form a coating film. Thereafter, the coating film was dried to form a near-infrared absorbing layer having a thickness of 4 μm.

  An antireflection layer was formed in the same manner as in Example 2, and a near infrared absorption layer was formed in the same manner as in Example 6 to produce an optical film for evaluation.

An optical film for evaluation was produced in the same manner as in Example 1 except that a coating material for forming a low refractive index film having the following composition was used.
(1) Hollow silica fine particles (porosity: 40%): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiator (Ciba “IRGACURE (registered trademark) 907” manufactured by Specialty Chemicals Co., Ltd.): 2.4 parts by weight (5) Polymer surface modifier (“MODIPER F600” manufactured by NOF Corporation): 1 part by weight (6) Isopropyl alcohol : 2000 parts by weight

An optical film for evaluation was produced in the same manner as in Example 1 except that a coating material for forming a low refractive index film having the following composition was used.
(1) Hollow silica fine particles (porosity: 45%): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiator “(Ciba -Specialty Chemicals, IRGACURE (registered trademark) 907 "): 2.4 parts by weight (5) Polymer surface modifier (" MODIPER F600 ", manufactured by NOF Corporation): 1 part by weight (6) Isopropyl alcohol : 2000 parts by weight

An optical film for evaluation was produced in the same manner as in Example 1 except that a coating material for forming a low refractive index film having the following composition was used.
(1) Hollow silica fine particles (porosity: 50%): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiator (Ciba “IRGACURE (registered trademark) 907” manufactured by Specialty Chemicals Co., Ltd.): 2.4 parts by weight (5) Polymer surface modifier (“MODIPER F600” manufactured by NOF Corporation): 1 part by weight (6) Isopropyl alcohol : 2000 parts by weight

(Comparative Example 1)
An optical film for evaluation was produced in the same manner as in Example 1 except that a low refractive index forming paint was produced using the following materials.
(1) Hollow silica fine particles (porosity: 30%, produced by Catalyst Kasei Co., Ltd.): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiation Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 0.8 part by weight (5) Polymer surface modifier (Nippon Yushi Co., Ltd., “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

(Comparative Example 2)
An optical film for evaluation was produced in the same manner as in Example 1 except that a low refractive index forming paint was produced using the following materials.
(1) Hollow silica fine particles (porosity: 55%): 55 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 25 parts by weight (4) Photopolymerization initiator (Ciba "IRGACURE (registered trademark) 907" manufactured by Specialty Chemicals Co., Ltd.): 4.5 parts by weight (5) Polymer surface modifier (manufactured by NOF Corporation, "Modiper F600"): 1 part by weight (6) Isopropyl alcohol : 2000 parts by weight

(Comparative Example 3)
An optical film for evaluation was produced in the same manner as in Example 1 except that a low refractive index forming paint was produced using the following materials.
(1) Hollow silica fine particles (porosity: 35%, manufactured by Catalyst Kasei Co., Ltd.): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiation Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 0.8 part by weight (5) Polymer surface modifier (Nippon Yushi Co., Ltd., “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

(Comparative Example 4)
An optical film for evaluation was produced in the same manner as in Example 1 except that a low refractive index paint was produced using the following materials.
(1) Hollow silica fine particles (porosity: 35%, manufactured by Catalyst Kasei Co., Ltd.): 60 parts by weight (2) Pentaerythritol triacrylate: 20 parts by weight (3) Dipentaerythritol hexaacrylate: 20 parts by weight (4) Photopolymerization initiation Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 4.8 parts by weight (5) Polymer surface modifier (Nippon Yushi Co., Ltd., “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

(Comparative Example 5)
An optical film for evaluation was produced in the same manner as in Example 1 except that a coating material for forming a low refractive index film was produced using the following materials.
(1) Hollow silica fine particles (porosity: 30%, manufactured by Catalyst Kasei Co., Ltd.): 70 parts by weight (2) Pentaerythritol triacrylate: 15 parts by weight (3) Dipentaerythritol hexaacrylate: 15 parts by weight (4) Photopolymerization started Agent (Ciba Specialty Chemicals, “IRGACURE (registered trademark) 907”): 3.0 parts by weight (5) Polymer surface modifier (Nippon Yushi Co., Ltd., “Modiper F600”): 1 part by weight ( 6) Isopropyl alcohol: 2000 parts by weight

  The characteristics of the optical films of Examples 1 to 10 and Comparative Examples 1 to 5 were evaluated by the following method and are shown in Table 1. In Table 1, “polymerization initiator (parts by weight)” is a value relative to 100 parts by weight of the curable binder contained in the coating material for forming a low refractive index film, and “hollow silica content (% by mass)” is The value is when the total weight of the curable binder and the hollow silica fine particles in the coating material for forming a low refractive index film is 100% by mass.

<Refractive index>
The refractive indexes of the hard coat film and the low refractive index film of the optical film for each evaluation were measured using a refractive index measuring device “FilmTek 3000” (manufactured by SCI).

<Reflectance>
Using a spectrophotometer “Ubest V-570 type” (manufactured by JASCO Corporation), the visibility reflectance Y was measured in the wavelength region of 300 to 800 nm.

<Pencil hardness>
The pencil hardness of the antireflection layer of each optical film for evaluation was measured based on JIS K5400.

<Steel wool resistance>
Using a steel wool of # 0000, with a load of 1.96 N / cm ² applied to the low refractive index film of each optical film for evaluation, the steel wool was reciprocated 10 times, and then the surface state of the low refractive index film was changed. Observed and evaluated in the following four stages.

A: No scratch was found.
○: Scratches hardly visible.
Δ: Scratches could be clearly confirmed.
X: Peeling of the film occurred.

<Total light transmittance>
Using a spectrophotometer “Ubest V-570 type” (manufactured by JASCO Corp.), the total light transmittance of each optical film for evaluation was measured. Light was incident from the opposite surface of the light-transmitting substrate on the hard coat film side. In addition, about the optical film for evaluation provided with the near-infrared absorption layer, after forming an antireflection layer, before providing a near-infrared absorption layer, the total light transmittance was measured.

<Measurement method of porosity>
The porosity of the hollow silica fine particles is the refractive index of the low refractive index film, the curable binder in the cured state and the refractive index of the silica (curable binder: 1.50, silica: 1.44), hollow in the low refractive index film. It was calculated from the volume content of silica fine particles and the composition of the low refractive index film.

<Measurement method of average particle diameter>
The average particle diameter of the particles is a dispersion average particle diameter (nm) measured using a laser Doppler type particle size distribution analyzer N4 PLUS manufactured by Coulter.

  As is clear from Table 1, the optical films of Examples 1 to 10 have a low refractive index, a low reflectance, and an excellent antireflection ability as compared with the optical film of Comparative Example 1. Recognize. Moreover, it turns out that the optical films of Examples 1-10 can make the pencil hardness of an antireflection layer 2H compared with Comparative Examples 2-5, have good steel wool resistance, and have high scratch resistance.

  As described above, according to the present invention, an optical film including an antireflection layer having a low reflectance and a high scratch resistance can be provided, and an optical filter suitable for various displays, particularly, a PDP can be provided.

Sectional drawing of an example of the optical film of this invention Sectional drawing of the other example of the optical film of this invention Sectional drawing of another example of the optical film of this invention Process sectional drawing of an example of the manufacturing method of the optical film of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical film 9 Antireflection layer 10 Translucent base material 11 Easy-adhesion layer 12 Hard coat film 13 Easy-adhesion layer 14 Near-infrared absorption layer 15 Low refractive index film

Claims (13)

A translucent substrate, a hard coat film disposed on one main surface side of the translucent substrate, and a low refractive index film disposed on the hard coat film and having a smaller refractive index than the hard coat film A method for producing an optical film comprising:
A paint for forming a low refractive index film containing hollow silica fine particles, a curable binder, and a polymerization initiator is applied onto the hard coat film disposed on the one main surface side of the translucent substrate. And after forming a coating film on the hard coat film, including a low refractive index film forming step of curing the curable binder in the coating film to form the low refractive index film,
The porosity of the hollow silica fine particles is more than 30% and 50% or less,
In the paint, the polymerization initiator is contained in an amount of 3 to 10 parts by weight with respect to 100 parts by weight of the curable binder.   The manufacturing method of the optical film of Claim 1 which further includes the near-infrared absorption layer formation process of forming a near-infrared absorption layer in the other main surface side of the said translucent base material.   The method for producing an optical film according to claim 1, further comprising an easy-adhesion layer forming step of forming an easy-adhesion layer on the other main surface of the translucent substrate before the near-infrared absorbing layer formation step.   The method for producing an optical film according to claim 1, wherein the curable binder is an ionizing radiation curable resin.   The method for producing an optical film according to claim 1, wherein the ionizing radiation curable resin includes an acrylic compound having two or more polymerizable unsaturated bonds.   2. The method for producing an optical film according to claim 1, wherein a blending ratio of the hollow silica fine particles in the paint is 65% by weight or less of a total weight of the curable binder and the hollow silica fine particles.   An optical film manufactured by the method for manufacturing an optical film according to claim 1.   The optical film of Claim 7 which further contains the near-infrared absorption layer arrange | positioned at the other main surface side of the said translucent base material.   The optical film according to claim 8, wherein an easy-adhesion layer is disposed between the near-infrared absorbing layer and the light-transmitting substrate.   The optical film according to claim 7, wherein the curable binder contains an ionizing radiation curable resin.   The optical film according to claim 10, wherein the curable binder includes a polymer of an acrylic compound having two or more polymerizable unsaturated bonds.   The optical film according to claim 7, wherein the content of the hollow silica fine particles in the low refractive index film is 65% by weight or less of the total weight of the curable binder and the hollow silica fine particles.   The optical film according to claim 7, wherein the optical film has a total light transmittance of 91% or more, which is higher than a total light transmittance of the translucent substrate alone.

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