Optical film and polarizing plate using same

Abstract

The purpose of the present invention is to provide an optical film having a highly adhesive layer, which has excellent adhesion to a cycloolefin film, excellent blocking resistance when wound into a roll, excellent solvent resistance, and excellent adhesion properties when wound into a roll. And can suppress the occurrence of end cracks in a solvent resistance test due to a hydrocarbon solvent such as hexane and the reduction in optical properties due to an organic solvent. Provided is an optical film obtained by having a cured coating film of an active energy ray-curable composition on the surface of a resin film containing a polymer having an alicyclic structure as a main component, the active energy ray-curable composition contains an active energy ray-curable compound (A) and inorganic microparticles (B) having an average primary particle diameter of 5 nm or more and 100 nm or less, the active energy ray-curable compound (A) contains an epoxy (meth) acrylate (a1), the inorganic fine particles (B) are in the range of 30-80 parts by weight (inclusive) per 100 parts by weight of the active energy ray-curable compound (A), and the thickness of the cured coating film is more than 50 nm and less than 3500 nm.

Description

Technical Field

[0001] The present invention relates to an optical film having a cured coating film of an active energy ray-curable composition on the surface of a resin film containing a polymer having an alicyclic structure as a main component. Background Art

[0002] In recent years, the use of organic electroluminescent display devices, touch panels, etc. is expanding. In such devices, various resin films are used as protective films or phase difference films. Among them, cycloolefin-based films composed of cycloolefin polymers have high heat resistance, excellent dimensional stability, and low optical elastic coefficient, so they can suppress birefringence to a low value. They are also materials with excellent optical properties, so they are preferably used.

[0003] Since cycloolefin-based films are non-polar films with no polar groups or very few polar groups, they lack adhesion, and the following operations are performed: laminating a coating layer such as an easy-to-adhesive layer, bonding other components such as a polarizer to the coating layer via an adhesive or a pressure-sensitive adhesive, and forming an optical functional layer such as a hard coating layer via the coating layer.

[0004] For example, Patent Document 1 describes a multilayer film, the purpose of which is to improve the adhesion between a stretched film composed of a cycloolefin polymer and a polarizer, and an easy-adhesion layer composed of polyurethane with a single film elongation of 300% to 1000% in a dry state is provided on the stretched film.

[0005] For example, Patent Document 2 describes a hard coat film in which a primer layer composed of a modified polyolefin is provided for the purpose of imparting good adhesion to a cycloolefin polymer film and a hard coat layer containing an ionizing radiation curable resin, and is laminated via the primer layer.

[0006] In addition, an optical film having a cycloolefin film and an easy-adhesive layer is wound into a roll during storage or transportation. However, when the optical films are wound into a roll, adhesion occurs between the optical films, and the operability of the so-called roll film is deteriorated. Therefore, fine particles are mixed into the easy-adhesive layer to impart anti-blocking properties to the easy-adhesive layer.

[0007] For example, Patent Document 3 describes an optical film provided with an easy-adhesive layer, the purpose of which is to improve the anti-adhesive property of an optical film having a substrate composed of a cyclic olefin resin and an easy-adhesive layer, wherein the easy-adhesive layer comprises: a polyurethane resin with a glass transition temperature of 50°C or above; microparticles having an average particle size of 1 to 5 times the thickness of the easy-adhesive layer; and a surfactant.

[0008] [Prior art literature]

[0009] [Patent Document]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-116640

[0011] [Patent Document 2] Japanese Patent Application Laid-Open No. 2020-055185

[0012] [Patent document 3] WO16 / 047359. Summary of the invention

[0013] [Problems to be Solved by the Invention]

[0014] However, when a protective film or a phase difference film is bonded to other components such as a polarizer, before bonding, there is a case where dirt attached to the surface of the protective film or the phase difference film is beautified using an organic solvent such as acetone or ethyl acetate. However, when an organic solvent is used to beautify the surface of a cycloolefin film, the organic solvent will swell and dissolve the cycloolefin film, causing the cycloolefin film to whiten, and the optical properties will be reduced. In addition, the active energy ray-curable composition for forming a functional layer such as a hard coat layer uses an organic solvent such as methyl isobutyl ketone (MIBK) or cyclohexanone (CHN). When the active energy ray-curable composition containing an organic solvent is applied to the easy-adhesive layer of the cycloolefin film, the organic solvent will swell and dissolve the cycloolefin film, and a functional layer with excellent optical properties cannot be formed on the cycloolefin film. Therefore, it is desired that the easy-adhesive layer of the cycloolefin film has excellent solvent resistance.

[0015] On the other hand, the cycloolefin film having an easy-adhesion layer disclosed in the above document has poor solvent resistance of the easy-adhesion layer. Organic solvents cause the easy-adhesion layer and the cycloolefin film to swell and dissolve, causing the cycloolefin film to whiten and deteriorate its optical properties.

[0016] In addition, a phase difference film composed of a cycloolefin film is generally used for bonding with a polarizer. The polarizer formed by laminating the polarizer and the phase difference film via an adhesive layer is bonded to an image display unit such as a liquid crystal unit or an organic electroluminescent unit to form an image display panel. However, when a hydrocarbon solvent such as hexane is used to clean the polarizer in the assembly of the image display panel or the image display device using the panel, fine cracks may be generated from the end surface of the cycloolefin film. It is required that end cracks are not easily generated even in a solvent resistance test using a hydrocarbon solvent such as hexane.

[0017] The present invention has been made in view of such problems, and its object is to provide an optical film having a cured coating film, which has excellent adhesion to a cycloolefin film and anti-blocking property when wound into a roll, and also has excellent solvent resistance, and can suppress the reduction of optical properties due to organic solvents and the generation of edge cracks in a solvent resistance test due to hydrocarbon solvents such as hexane.

[0018] [Methods to solve the problem]

[0019] As a result of in-depth research on an easy-to-bond layer that has excellent adhesion and anti-blocking properties and can suppress the reduction in optical properties caused by organic solvents, the inventors found that the easy-to-bond layer can solve the above-mentioned problems by being set as a cured coating film of an active energy ray-curable composition comprising an epoxy (meth)acrylate-based active energy ray-curable compound and inorganic microparticles, and containing inorganic microparticles in a specific amount range relative to the total amount of the active energy ray-curable compound, thereby completing the present invention.

[0020] According to the present invention, the following (1) to (6) can be provided.

[0021] (1) An optical film obtained by having a cured coating of an active energy ray-curable composition on the surface of a resin film containing a polymer having an alicyclic structure as a main component, characterized in that the active energy ray-curable composition contains an active energy ray-curable compound (A) and inorganic microparticles (B) having an average primary particle size of 5 nm to 100 nm, the active energy ray-curable compound (A) contains epoxy (meth)acrylate (a1), the amount of the inorganic microparticles (B) is in the range of 30 parts by weight to 80 parts by weight per 100 parts by weight of the active energy ray-curable compound (A), and the thickness of the cured coating is greater than 50 nm and less than 3500 nm.

[0022] (2) The optical film according to (1), wherein the epoxy (meth)acrylate (a1) contains a plurality of (meth)acryloyl groups and hydroxyl groups in a molecule.

[0023] (3) The optical film according to (1), wherein the epoxy (meth)acrylate (a1) is a hydroxyl-containing (meth)acrylic copolymer comprising a radical polymer of a monomer component of an epoxy group-containing mono(meth)acrylate and a reaction product of an α,β-unsaturated carboxylic acid.

[0024] (4) The optical film according to (1), wherein the active energy ray-curable compound (A) comprises a hydroxyl-containing polyfunctional (meth)acrylate (a2) having at least three (meth)acryloyl groups.

[0025] (5) The optical film according to (1), wherein the inorganic fine particles (B) are silica fine particles.

[0026] (6) The optical film according to (1), wherein the resin film is a stretched film.

[0027] [Effects of the Invention]

[0028] The optical film of the present invention is an easy-adhesive layer composed of a cured coating of an active energy ray-curable composition comprising an active energy ray-curable compound of the epoxy (meth) acrylate system and inorganic microparticles, and containing inorganic microparticles in a specific amount range relative to the total amount of the active energy ray-curable compound. It has excellent adhesion to the cycloolefin film and can suppress the adhesion of the optical films when they are wound into a roll, and has excellent anti-adhesion properties. In addition, the optical film of the present invention has excellent solvent resistance to organic solvents. When beautified with an organic solvent, or when an active energy ray-curable coating agent using an organic solvent is applied to the easy-adhesive layer, it can suppress the reduction of optical properties. When a hydrocarbon solvent such as hexane is used to clean the polarizing plate in the assembly of an image display panel or an image display device using the panel, it can also suppress the fine cracks generated from the end surface of the cycloolefin film. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] [ Figure 1 ] is a schematic cross-sectional view showing an example of the optical film of the present invention.

[0030] [ Figure 2 ] is a schematic cross-sectional view showing an example of a polarizing plate of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below. The present invention is not limited to the following aspects, and can be implemented in various aspects within the scope in which the effects of the present invention can be exhibited.

[0032] [Resin film]

[0033] The resin film is composed of a thermoplastic resin containing a polymer having an alicyclic structure as a main component. Here, "main component" means that the composition ratio of the components constituting the resin film is 50% by weight or more, preferably 60% by weight or more, more preferably 80% by weight or more, further preferably 90% by weight or more, and particularly preferably 95% by weight or more.

[0034] The polymer having an alicyclic structure is a polymer having an alicyclic structure in the structural unit of the polymer. The polymer having an alicyclic structure may have an alicyclic structure in the main chain or in the side chain. Among them, from the viewpoint of mechanical strength and heat resistance, a polymer having an alicyclic structure in the main chain is preferred.

[0035] Examples of the alicyclic structure include saturated alicyclic hydrocarbon (cycloalkane) structures, unsaturated alicyclic hydrocarbon (cycloolefin, cycloalkyne) structures, etc. Among them, from the viewpoints of mechanical strength, heat resistance, etc., cycloalkane structures and cycloalkene structures are preferred, and cycloalkane structures are particularly preferred.

[0036] The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less per alicyclic structure. By setting the number of carbon atoms constituting the alicyclic structure within this range, the resin film containing the polymer having the alicyclic structure has excellent mechanical strength, heat resistance, and formability.

[0037] In the polymer with alicyclic structure, the ratio of the structural unit with alicyclic structure can be appropriately selected according to the purpose of use. The ratio of the structural unit with alicyclic structure in the polymer with alicyclic structure is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. If the ratio of the structural unit with alicyclic structure in the polymer with alicyclic structure is within this range, the transparency and heat resistance of the resin film containing the polymer with alicyclic structure will be good.

[0038] Among the polymers with alicyclic structures, cycloolefin polymers are preferred. Cycloolefin polymers are polymers having a structure obtained by polymerizing cycloolefin monomers. In addition, cycloolefin monomers are compounds having a ring structure formed by carbon atoms and having polymerizable carbon-carbon double bonds in the ring structure. As polymerizable carbon-carbon double bonds, polymerizable carbon-carbon double bonds such as ring-opening polymerization can be cited. In addition, as the ring structure of the cycloolefin monomer, for example, monocyclic, polycyclic, condensed polycyclic, bridged ring and polycyclic combinations of these can be cited. Among them, from the perspective of highly balancing the dielectric properties and heat resistance of the polymer with an alicyclic structure, polycyclic cycloolefin monomers are preferred.

[0039] Preferred among the cycloolefin polymers include norbornene polymers, monocyclic cyclic olefin polymers, cyclic conjugated diene polymers, and hydrogenated products thereof. Of these, norbornene polymers are particularly suitable because of their excellent moldability.

[0040] Examples of norbornene-based polymers include ring-opening polymers of monomers having a norbornene structure and their hydrogenates; addition polymers of monomers having a norbornene structure and their hydrogenates. In addition, examples of ring-opening polymers of monomers having a norbornene structure include: ring-opening homopolymers of one monomer having a norbornene structure; ring-opening copolymers of two or more monomers having a norbornene structure; and ring-opening copolymers of a monomer having a norbornene structure and other monomers copolymerized therewith. Furthermore, examples of addition polymers of monomers having a norbornene structure include: addition homopolymers of one monomer having a norbornene structure; addition copolymers of two or more monomers having a norbornene structure; and addition copolymers of a monomer having a norbornene structure and other monomers copolymerized therewith. Among these, hydrogenated products of ring-opening polymers of monomers having a norbornene structure are particularly suitable from the viewpoints of moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like.

[0041] Examples of monomers having a norbornene structure include bicyclo[2.2.1]hept-2-ene (common name: norbornene), tricyclo[4.3.0.1 2,5 ]Deca-3,7-diene (common name: dicyclopentadiene), 7,8-benzotricyclo[4.3.0.1 2,5 ]dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodeca-3-ene (common name: tetracyclododecene), and derivatives of these compounds (e.g., those having a substituent on the ring), etc. Here, as a substituent, for example, an alkyl group, an alkylene group, a polar group, etc. can be cited. In addition, these substituents can be the same or different, and a plurality of them can be bonded to the ring. The monomer having a norbornene structure can be used alone or in combination of two or more in any ratio.

[0042] As the type of polar group, for example, heteroatom or atomic group having heteroatom can be mentioned. As heteroatom, for example, oxygen atom, nitrogen atom, sulfur atom, silicon atom, halogen atom can be mentioned. As specific examples of polar group, carboxyl group, carbonyloxycarbonyl group, epoxy group, hydroxyl group, oxy group, ester group, silanol group, silane group, amino group, nitrile group, sulfonic acid group and the like can be mentioned.

[0043] As other monomers that can be ring-opening copolymerized with the monomer having a norbornene structure, for example, monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and their derivatives; cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene and their derivatives, etc. can be cited. The other monomers that can be ring-opening copolymerized with the monomer having a norbornene structure can be used alone or in combination of two or more in any ratio. For example, the ring-opening polymer of the monomer having a norbornene structure can be manufactured by polymerizing or copolymerizing the monomer in the presence of a ring-opening polymerization catalyst.

[0044] Examples of monomers that can be addition-copolymerized with the monomer having a norbornene structure include: α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cycloolefins such as cyclobutene, cyclopentene, and cyclohexene, and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene. Among these, α-olefins are preferred, and ethylene is more preferred. In addition, the monomers that can be addition-copolymerized with the monomer having a norbornene structure may be used alone or in combination of two or more in any ratio. For example, an addition polymer of a monomer having a norbornene structure may be produced by polymerizing or copolymerizing the monomers in the presence of an addition polymerization catalyst.

[0045] The hydrogenated products of the above-mentioned ring-opening polymer and addition polymer can be produced, for example, by hydrogenating preferably 90% or more of the carbon-carbon unsaturated bonds in a solution of the ring-opening polymer and addition polymer in the presence of a hydrogenation catalyst containing a transition metal such as nickel or palladium.

[0046] Among the norbornene-based polymers, the following are preferred: a polymer having X: a bicyclo[3.3.0]octane-2,4-diyl-ethylene structure and Y: a tricyclo[4.3.0.1 2,5 ] decane-7,9-diyl-ethylene structure as a structural unit, the amount of these structural units relative to the total structural units of the norbornene polymer is 90% by weight or more, and the ratio of X to Y is 100:0 to 40:60 in terms of the weight ratio of X:Y. By using such a polymer, the resin film containing the norbornene polymer will not undergo dimensional changes for a long time, and the stability of optical properties is excellent.

[0047] Examples of the monocyclic cyclic olefin polymer include addition polymers of a monocyclic cyclic olefin monomer such as cyclohexene, cycloheptene, and cyclooctene.

[0048] Examples of the cyclic conjugated diene polymer include polymers obtained by cyclizing addition polymers of conjugated diene monomers such as 1,3-butadiene, isoprene, and chloroprene; 1,2- or 1,4-addition polymers of cyclic conjugated diene monomers such as cyclopentadiene and cyclohexadiene; and hydrogenated products thereof.

[0049] The weight average molecular weight (Mw) of the polymer with an alicyclic structure is usually 30,000 or more, preferably 35,000 or more, more preferably 40,000 or more, preferably 80,000 or less, more preferably 60,000 or less, and particularly preferably 50,000 or less. By setting the weight average molecular weight (Mw) of the polymer with an alicyclic structure to above the lower limit of the above range, the cohesion damage of the resin film caused by the easy-adhesive layer can be effectively prevented, so the close contact between the optical film and the polarizer can be improved. In addition, by setting it below the upper limit, the mechanical strength and molding processability of the resin film can be improved. Therefore, by keeping the weight average molecular weight (Mw) of the polymer with an alicyclic structure in the above range, an optical film with excellent cohesion, mechanical strength and molding processability can be obtained.

[0050] The glass transition temperature (Tg) of the polymer having an alicyclic structure is preferably 100°C or more, more preferably 110°C or more, particularly preferably 120°C or more, preferably 190°C or less, more preferably 180°C or less, particularly preferably 170°C or less. By setting the glass transition temperature of the thermoplastic resin to be above the lower limit of the above range, the durability of the resin film in a high temperature environment can be improved. In addition, by setting it to be below the upper limit, the stretching process can be easily performed.

[0051] In the range that does not hinder the effect of the present invention, the resin film may also contain resin components other than the polymer having an alicyclic structure. As resin components other than the polymer having an alicyclic structure, for example, cellulose resins, polyester resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyolefin resins, (meth) acrylic resins, aromatic polyester (polyarylates) resins, polystyrene resins, polyvinyl alcohol resins, etc. can be cited. These can be used alone or in combination of two or more. The content ratio of other resin components in the resin film is not particularly limited, preferably 0 to 50% by weight, more preferably 0 to 30% by weight, and further preferably 0 to 20% by weight.

[0052] The resin film may also contain any additives, etc., within the scope that does not hinder the effect of the present invention. Examples of additives include colorants such as pigments and dyes; plasticizers; fluorescent whitening agents; dispersants; heat stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; antioxidants; microparticles; surfactants, etc. These can be used alone or in combination of two or more. The amount of additives in the resin film is not particularly limited, and is preferably 0 to 5% by weight, more preferably 0 to 3% by weight, and further preferably 0 to 0.5% by weight.

[0053] The resin film may be subjected to stretching treatment or not, and it is preferred to be subjected to stretching treatment. The stretching treatment may be uniaxial stretching or biaxial stretching, and the stretching ratio is preferably 1.2 times or more, and more preferably 1.4 times or more in terms of area ratio. Generally speaking, the solvent resistance of the resin film depends on its material, so there is no close relationship between the solvent resistance of the resin film and the stretching treatment, but the inventors have found that in the resin film containing a polymer having an alicyclic structure such as a cycloolefin polymer, the solvent resistance changes due to the stretching treatment, and when a hydrocarbon solvent such as hexane is used for cleaning, fine cracks will be generated from the end in a direction roughly parallel to the stretching direction. Specifically, the resin film containing a polymer having an alicyclic structure such as a cycloolefin polymer subjected to the stretching treatment will cause the solvent resistance to decrease due to the stretching treatment. Therefore, the optical film of the present invention has a resin film (sometimes referred to as a "stretched film") subjected to the stretching treatment, which is a way to effectively solve the problems that were difficult to solve in the past, and is preferred because the effects of the present invention can be effectively used.

[0054] The total light transmittance of the resin film is preferably 80% or more, more preferably 90% or more, based on a thickness of 1 mm. The total light transmittance is measured according to JIS K0115 using a spectrophotometer (V-570, UV-visible near-infrared spectrophotometer manufactured by Japan Spectrophotometer). In addition, the haze of the resin film is preferably 0.3% or less, more preferably 0.2% or less, based on a thickness of 1 mm. By keeping the haze within the range, polarization can be prevented from being eliminated when the optical film is bonded to the polarizer. The haze is measured according to JIS K7361-1997 using a "turbidimeter NDH-300A" manufactured by Nippon Denshoku Industries.

[0055] The thickness of the resin film is preferably 5 μm or more, more preferably 8 μm or more, particularly preferably 10 μm or more, preferably 100 μm or less, more preferably 70 μm or less, particularly preferably 60 μm or less. By setting the thickness of the resin film to be above the lower limit of the above range, the mechanical strength of the resin film can be improved. In addition, by setting it to be below the upper limit, the thickness of the resin film can be reduced.

[0056] [Active energy ray-curable composition]

[0057] The active energy ray curable composition contains the following active energy ray curable compound (A) and the following inorganic microparticles (B). The cured coating composed of the active energy ray curable composition has excellent adhesion to the cycloolefin film, and can also suppress the adhesion of the optical films when they are wound into a roll, and the anti-blocking property is also excellent. In addition, the cured coating has excellent solvent resistance to organic solvents, and can suppress the reduction of optical properties when beautifying with organic solvents or applying an active energy ray curable coating agent using organic solvents on the easy-adhesion layer. At the same time, it can suppress the fine cracks generated from the end surface when washing with hydrocarbon solvents such as hexane.

[0058] The active energy line curable compound (A) includes epoxy (meth) acrylate (a1). Since epoxy (meth) acrylate has high reactivity and excellent cross-linking structure formation, it has excellent solvent resistance after curing. There is no particular limitation on epoxy (meth) acrylate, but it is preferably one containing multiple (meth) acryloyl groups and hydroxyl groups in the molecule. Epoxy (meth) acrylate containing multiple (meth) acryloyl groups and hydroxyl groups in the molecule has high surface tension and excellent adhesion to cycloolefin-based films, and excellent cross-linking structure formation, so it has excellent solvent resistance. In addition, in this specification, "(meth) acrylic acid" means acrylic acid and / or methacrylic acid.

[0059] The hydroxyl concentration of epoxy (meth) acrylate (a1) is not particularly limited, and is preferably 0.8 mmol / g or more, more preferably 1.6 to 4.7 mmol / g, and further preferably 2.0 to 4.7 mmol / g. The so-called hydroxyl concentration here is a value calculated from the number of hydroxyl groups in the component (a1) and the molecular weight. Specifically, if the component (a1) is other than a polymer, it is a value calculated by {the number of mol of hydroxyl groups contained in 1 mol of the component (a1) / the molecular weight of the component (a1)}. If the component (a1) is a polymer, it is a value calculated by {the number of mol of hydroxyl groups contained in 1 mol of the repeating structure of the component (a1) / the formula weight of the repeating structure of the component (a1)}. When the hydroxyl concentration is within the above range, the adhesion to the cycloolefin film and the adhesion to other optical components are excellent.

[0060] The weight average molecular weight of epoxy (meth)acrylate (a1) is not particularly limited, but is about 1,000 to 100,000, preferably about 10,000 to 50,000, from the viewpoint of solvent resistance. The weight average molecular weight here is a polystyrene conversion value obtained by gel permeation chromatography (GPC).

[0061] The epoxy (meth)acrylate (a1) is preferably a "hydroxyl-containing (meth)acrylic copolymer" which is an addition reaction product of a "radical polymer containing a monomer component of epoxy-containing mono(meth)acrylate" and an α,β-unsaturated carboxylic acid.

[0062] Epoxy-containing mono(meth)acrylate is a compound having at least one epoxy group and one polymerizable unsaturated double bond in the molecule. Specifically, glycidyl(meth)acrylate, β-methylglycidyl(meth)acrylate, 3,4-epoxycyclohexylmethyl(meth)acrylate, vinylcyclohexene oxide (i.e., 1,2-epoxy-4-vinylcyclohexane), etc. can be cited. These can be prepared alone or in combination of two or more. Among these, glycidyl(meth)acrylate is preferred in terms of ease of acquisition and procurement cost. In addition, in addition to epoxy-containing mono(meth)acrylate, copolymerizable monomers may also be included. Specific examples of the monomer include (meth)acrylates having a chain alkyl group such as methyl (meth)acrylate and ethyl (meth)acrylate, (meth)acrylates having an alicyclic structure such as isobornyl (meth)acrylate, (meth)acrylates having an aromatic ring such as ethoxylated o-phenylphenol acrylate, nitrogen-containing acrylates such as acryloylmorpholine, (meth)acrylamide, acrylonitrile, styrene, α-methylstyrene, vinyltoluene and other aromatic vinyl compounds, vinyl acetate, and macromonomers having an unsaturated double bond at the end of any of them but not containing an epoxy group and a carboxyl group, etc. These can be prepared alone or in combination of two or more.

[0063] α,β-unsaturated carboxylic acid, as long as it is an α,β-unsaturated carboxylic acid that can undergo addition reaction with an epoxy group, various known types can be used without particular limitation. Specifically, α,β-unsaturated monocarboxylic acids such as (meth) acrylic acid, α,β-unsaturated dicarboxylic acids such as maleic acid or fumaric acid, etc. can be cited. These can be used alone, or two or more can be used in combination. Among these, (meth) acrylic acid is preferred from the viewpoint of reactivity or storage stability.

[0064] The active energy line curable compound (A) preferably further comprises a hydroxyl-containing multifunctional (meth)acrylate (a2) having at least 3 (meth)acryloyl groups. The hydroxyl-containing multifunctional (meth)acrylate (a2) is a (meth)acrylate containing at least 3 (meth)acryloyl groups and at least 1 hydroxyl group in one molecule, and various known types can be used without particular restrictions. Specifically, polypentaerythritol poly(meth)acrylates containing one or more hydroxyl groups and three or more (meth)acryloyl groups in the molecule such as pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate, polytrimethylolpropane poly(meth)acrylate containing one or more hydroxyl groups and three or more (meth)acryloyl groups in the molecule such as ditrimethylolpropane tri(meth)acrylate, etc. can be cited. These can be used separately, or two or more can be used in combination. If two or more types are used, the usage ratio of each multifunctional (meth)acrylate component is not particularly limited. Commercially available products include, for example, Aronix M-303, M-305, M-306, M-400, M-402, M-403, M-404, M-405, and M-406 (all manufactured by Toagosei Co., Ltd.), NK Ester A-9530, A-9550, A-9550W, A-9570W, A-TMM-3, A-TMM-3L, and A-TMM-3LM-N (all manufactured by Shin-Nakamura Chemical Co., Ltd.), and these may be used alone or in combination of two or more.

[0065] The hydroxyl concentration of the hydroxyl-containing polyfunctional (meth)acrylate (a2) is not particularly limited, but is preferably 0.8 mmol / g or more, more preferably 1.6 to 4.7 mmol / g, and further preferably 2.0 to 4.7 mmol / g.

[0066] In addition to the above, the active energy ray-curable compound (A) may also include "poly(meth)acrylates not containing hydroxyl groups". Specific examples of poly(meth)acrylates include polypentaerythritol poly(meth)acrylates not containing hydroxyl groups in the molecule such as pentaerythritol tetra(meth)acrylate and dipentaerythritol hexa(meth)acrylate, and polytrimethylolpropane poly(meth)acrylates not containing hydroxyl groups in the molecule such as ditrimethylolpropane tetra(meth)acrylate.

[0067] The epoxy (meth)acrylate (a1) and the hydroxyl-containing multifunctional (meth)acrylate (a2) may be used alone or in combination. When used in combination, the mass ratio is not particularly limited, but is generally about 1 / 99 to 80 / 20, preferably about 5 / 95 to 50 / 50, from the viewpoint of hard coating properties or curing properties.

[0068] Examples of the inorganic fine particles (B) include inorganic acids such as silicon dioxide, titanium dioxide, aluminum oxide, and zirconium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Among these, silicon dioxide-based fine particles are preferred. Silica-based fine particles have excellent adhesion inhibition, excellent transparency, no haze, and no coloring, so the adhesion layer has little effect on optical properties.

[0069] As silica-based microparticles, various known types can be used without particular limitation, and hydrophilic silica microparticles having a silanol group concentration on the surface in a specific range are preferred. The silanol group concentration on the surface is preferably 60 to 200 μmol / g, more preferably 100 to 200 μmol / g, and further preferably in the range of about 120 to 200 μmol / g. If the silanol group concentration on the surface is within the above range, the cured coating film has high hydrophilicity, so the adhesion to the cycloolefin film and other optical components is excellent. The so-called silanol group concentration on the surface is the value obtained by the methyl red adsorption method. The methyl red adsorption method is a method described in, for example, The Journal of the American Chemical Society, 72, 776 to 782 (1950), Industrial Chemistry Journal Vol. 68, No. 3, 429 to 432 (1965), etc.

[0070] As silica particles, colloidal silica produced by a wet method or fumed silica produced by a dry method can be cited. Specifically, colloidal silica can be exemplified by aqueous colloids using water as a dispersion medium, or organic sols (e.g., organic silica sols) dispersed in a hydrophilic solvent such as methanol, ethanol, isopropanol, ethylene glycol, or propylene glycol monomethyl ether in a colloid state. Fumed silica is amorphous silica produced by a dry method, which can be obtained by reacting a volatile compound containing silicon in a gas phase. Specifically, it can be generated by hydrolyzing silicon compounds such as silicon tetrachloride (SiCl4) in a flame of oxygen and hydrogen. Examples of commercially available colloidal silica include Snowtex, MA-ST-M, MA-ST-L, IPA-ST, IPA-ST-L, IPA-ST-ZL, IPA-ST-UP, and PGM-ST (all manufactured by Nissan Chemical Industries, Ltd.), Quartron (manufactured by Fuso Chemical Industries, Ltd.), Aerosil (manufactured by Nippon Aerosil Co., Ltd.), SILDEX (manufactured by Asahi Glass Co., Ltd.), and Silysia 470 (manufactured by Fuji Silysia Chemical Co., Ltd.).

[0071] The average primary particle size of the inorganic microparticles is between 5 nm and 100 nm. The average primary particle size is preferably between 10 nm and 75 nm, more preferably between 10 nm and 50 nm, and further preferably between 10 nm and 25 nm. If the above range is used, the adhesion inhibition of the particles when wound into a roll can be excellent. The average primary particle size is measured by the BET method.

[0072] The amount of inorganic microparticles (B) in the active energy ray curable composition is 30 parts by weight or more and 80 parts by weight or less relative to 100 parts by weight of the active energy ray curable compound (A) (converted into solid content). The lower limit of the amount of the compounding is preferably 35 parts by weight or more, more preferably 40 parts by weight or more, and further preferably 45 parts by weight or more. The upper limit of the amount of the compounding is preferably 75 parts by weight or less, more preferably 70 parts by weight or less, and further preferably 65 parts by weight or less. When the amount of the inorganic microparticles is within the above range, the solvent resistance to organic solvents is excellent, and the reduction of optical properties when beautifying with an organic solvent or applying an active energy ray curable coating agent using an organic solvent to the easy-adhesive layer can be suppressed, as well as the generation of fine cracks from the end surface when cleaning with a hydrocarbon solvent such as hexane. The reason for this has not been determined, but it is speculated as follows: Inorganic particles such as silica particles are multiple primary particles that aggregate and fuse into a beaded shape to form aggregates (secondary particles) with a larger particle size than the primary particles. Since multiple aggregates aggregate to form agglomerated particles, pores are formed. As the amount of inorganic particles added increases, the volume of pores caused by the inorganic particles in the cured coating increases relatively, making it easier for organic solvents to penetrate into the pores and dissolve and swell the cycloolefin film through the pores.

[0073] The active energy ray-curable composition may contain a polymerization initiator (C) as required. The polymerization initiator (C) may be any known type as long as it is decomposed by active energy rays to generate radicals and initiate polymerization, and is not particularly limited. Specific examples include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-cyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propane-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, and 4-methylbenzophenone. These may be used alone or in combination of two or more.

[0074] Commercially available products of the polymerization initiator (C) include Irgacure 651, Irgacure 184, Irgacure 1173, Irgacure 2959, Irgacure 127, Irgacure 907, Irgacure 369, Irgacure 819, and Irgacure TPO (all manufactured by BASF), Omnirad 651, Omnirad 184, Omnirad 1173, Omnirad 2959, Omnirad 127, Omnirad 907, Omnirad 369, Omnirad 819, and Omnirad TPO (all manufactured by IGM Resins), Speedcure TPO, and Speedcure MBP (all manufactured by Lambson), and these may be used alone or in combination of two or more.

[0075] The amount of the polymerization initiator (C) to be added is not particularly limited, and is, for example, 0.1 to 20 parts by weight based on 100 parts by weight (solid content) of the total of the active energy ray-curable compound (A) and the inorganic fine particles (B).

[0076] As required, the active energy ray-curable composition may also be formulated with multifunctional (meth)acrylates (D) other than those mentioned above. Multifunctional (meth)acrylates (D) may be (meth)acrylates having at least two (meth)acryloyl groups in one molecule, and various known types may be used without particular limitation. Specifically, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerol propoxy tri(meth)acrylate, ε-caprolactone-modified tri-(2-(meth)acryloyloxyethyl) isocyanurate, urethane (meth)acrylate, and polyester (meth)acrylate may be cited.

[0077] The amount of the polyfunctional (meth)acrylate (D) is not particularly limited, but is, for example, 5 parts by weight or more and 95 parts by weight or less based on 100 parts by weight (solid content) of the total of the active energy ray-curable compound (A) and the inorganic fine particles (B).

[0078] The active energy ray-curable composition may be formulated with additives as required, such as antioxidants, ultraviolet absorbers, light stabilizers, defoamers, surface conditioners, antifouling agents, pigments, antistatic agents, and metal oxide fine particle dispersions.

[0079] The thickness of the cured coating is more than 50nm and less than 3500nm. The lower limit is preferably more than 65nm, more preferably more than 75nm, more preferably more than 85nm, and particularly preferably more than 100nm. The upper limit is preferably less than 3000nm, more preferably less than 2000nm, more preferably less than 1000nm, and particularly preferably less than 500nm. If it is the above range, the adhesion inhibition ability of the optical film when it is wound into a roll is excellent, and the solvent resistance for organic solvents is excellent, and it is possible to suppress the reduction of optical properties when beautifying by organic solvents or applying the coating agent of the active energy line curing type using organic solvents on the easy bonding layer, and the generation of fine cracks from the end face when cleaning with hydrocarbon solvents such as hexane.

[0080] [Optical Film]

[0081] Figure 1 An example of the optical film of the present invention is shown. Figure 1 The optical film 1 shown has a cured coating film 3 of an active energy ray-curable composition containing an active energy ray-curable compound (A) and inorganic fine particles (B) on one surface of a resin film 2 containing a polymer having an alicyclic structure as a main component. The specific configurations of the resin film 2 and the cured coating film 3 are as described above. In addition, the cured coating film 3 may be formed on both surfaces of the resin film 2 as long as it is formed on at least one surface of the resin film 2.

[0082] The optical film preferably has a total light transmittance of 85% or more, more preferably 90% or more, from the viewpoint of stably performing the function as an optical member. The light transmittance can be measured using a spectrophotometer (UV-visible near-infrared spectrophotometer "V-570" manufactured by JASCO Corporation) according to JIS K0115.

[0083] The haze of the optical film is not particularly limited, but is preferably 1.0% or less, more preferably 0.8% or less, and further preferably 0.5% or less. The haze can be measured using a "turbidimeter NDH-300A" manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7361-1997.

[0084] The in-plane retardation Re and the retardation Rth in the thickness direction of the optical film can be arbitrarily set according to the use of the optical film. The specific range of the in-plane retardation Re is preferably 1 nm to 200 nm. In addition, the specific retardation Rth in the thickness direction is preferably 50 nm to 300 nm.

[0085] The total thickness of the optical film is preferably 5 μm or more, more preferably 8 μm or more, further preferably 10 μm or more, preferably 200 μm or less, more preferably 100 μm or less, and particularly preferably 70 μm or less. By setting the total thickness of the optical film to be above the lower limit, the mechanical strength of the optical film can be improved. In addition, by setting it to be below the upper limit, the overall thickness of the optical film can be reduced.

[0086] The optical film of the present invention is, for example, a polarizer protective film, a phase difference film, a viewing angle compensation film, a light diffusion film, a reflective film, an anti-reflective film, an anti-glare film, a brightness enhancement film, and a conductive film for a touch panel. The optical film of the present invention may be an optically isotropic film or an optically anisotropic film (for example, exhibiting birefringence such as phase difference).

[0087] [Method for producing optical film]

[0088] The method for producing an optical film of the present invention comprises the following steps: a step of applying a coating liquid of an active energy ray-curable composition comprising an active energy ray-curable compound (A), inorganic fine particles (B) and, if necessary, a solvent, onto at least one surface of a resin film containing a polymer having an alicyclic structure as a main component to form a coating film; and a step of irradiating the coating film with active energy rays to form a cured coating film.

[0089] (Coating step)

[0090] The coating step is a step of coating a coating liquid of an active energy ray-curable composition on a resin film containing a polymer having an alicyclic structure as a main component. Any appropriate method may be used as the coating method in the coating step, and examples thereof include rod coating, dipping, spraying, spin coating, roll coating, gravure coating, air knife coating, curtain coating, oblique plate coating, and extrusion coating. The thickness of the coating film formed in the coating step can be appropriately adjusted according to the thickness required when the coating film becomes a cured coating film.

[0091] The active energy ray-curable composition may be diluted with a solvent as needed. As the solvent, various known types may be used without particular limitation, and examples thereof include water, dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3-dioxolane, 1,3,5-trioxane, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), diethyl ketone, dipropyl ketone, diisobutyl ketone, cyclopentanone (CPN), cyclohexanone (CHN), methylcyclohexanone, ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, Methyl propionate, ethyl propionate, n-pentyl acetate, acetylacetone, diacetone alcohol, methyl acetoacetate, ethyl acetoacetate, toluene, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-methyl-2-butanol, cyclohexanol, isopropyl alcohol (IPA), isobutyl acetate, methyl isobutyl ketone (MIBK), 2-octanone, 2-pentanone, 2-hexanone, 2-heptanone, 3-heptanone, ethylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, etc. These may be used alone or in combination of two or more.

[0092] In order to improve the close adhesion between the resin film and the cured coating film, the surface of the resin film can be subjected to surface modification. As surface modification, for example, energy line irradiation treatment and chemical treatment can be cited. As energy line irradiation treatment, for example, corona discharge treatment, plasma treatment, electron beam irradiation treatment, ultraviolet irradiation treatment, etc. can be cited. In terms of treatment efficiency, corona discharge treatment and plasma treatment are preferably used, and corona discharge treatment is particularly preferred. In addition, as chemical treatment, for example, saponification treatment and film immersion in an aqueous oxidant solution of potassium dichromate solution and concentrated sulfuric acid, followed by washing with water, etc. can be cited.

[0093] (Drying step)

[0094] After the coating step, a drying step of drying the coating film may be performed as required. The drying step is not particularly limited, and a conventionally known method may be used. The drying temperature is typically 60° C. or higher, preferably 80° C. or higher, and more preferably 100° C. or higher. The upper limit of the drying temperature is preferably 200° C. or lower, and more preferably 180° C. or lower.

[0095] (Curing step)

[0096] The curing step is a step of curing the coating film of the active energy ray curable composition by irradiating the coating film with active energy rays such as ultraviolet rays and electron beams. The active energy rays are preferably ultraviolet rays. When irradiating with ultraviolet rays, there are no particular restrictions as long as the wavelength is less than 400nm. For example, ultrahigh pressure mercury lamps, high pressure mercury lamps, medium pressure mercury lamps, low pressure mercury lamps, xenon lamps, halogen lamps, metal halide lamps, etc. can be used. As irradiation conditions, the ultraviolet irradiation amount is usually preferably 100 to 800mJ / cm 2 .

[0097] [Polarizing plate]

[0098] Next, a polarizing plate as an example of the optical member of the present invention will be described. Figure 2 A polarizing plate is shown as an example of the optical member of the present invention. Figure 2 The polarizing plate 10 shown has the following structure: an optical film 4 having a cured coating 3 composed of an active energy line-curable composition on one surface of a resin film 2 having a polymer having an alicyclic structure as a main component, and a polarizer 6 is laminated to the surface of the cured coating side of the optical film 4 via an adhesive 5. In addition, although not shown, the polarizing plate may also have other polarizer protective films or retardation films, etc., which are laminated to the surface of the polarizer on the opposite side of the optical film via an adhesive layer.

[0099] As a polarizer, any appropriate polarizer can be used according to the purpose. For example, a film obtained by adsorbing a dichroic substance such as iodine or a dichroic dye on a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formaldehyded polyvinyl alcohol film, and a partially saponified film of an ethylene-vinyl acetate copolymer and uniaxially stretching, a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride, etc. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine on a polyvinyl alcohol film and uniaxially stretching is particularly preferred because of its high polarization dichroic ratio. The thickness of these polarizers is not particularly limited, and is generally about 1 to 80 μm. As an adhesive for forming an adhesive layer, any appropriate adhesive can be used, and for example, an adhesive composition containing a polyvinyl alcohol resin, an adhesive composition containing an acrylic resin, and an ultraviolet curing adhesive composition containing an acrylic resin can be mentioned.

[0100] [Example]

[0101] Hereinafter, the present invention will be described in more detail by way of examples. In addition, the present invention is not limited to the following examples.

[0102] (Example 1)

[0103] Using a bar coater, a coating liquid of an active energy ray-curable composition (1) [BSCH271 manufactured by Arakawa Chemical Industries, Ltd.] containing epoxy (meth)acrylate as an active energy ray-curable compound and 65 parts by weight of silica-based microparticles having an average primary particle size of 5 to 100 nm relative to 100 parts by weight of the active energy ray-curable compound was applied to one surface of a cycloolefin-based film (Tg: 135°C, thickness: 37 μm, elongation ratio: 1.45 times in the longitudinal direction), and then placed in a hot air dryer and dried at 80°C for 60 seconds. Next, a high-pressure mercury lamp was used to heat the film with a cumulative light intensity of 500 mJ / cm 2 The dried coating film was irradiated with ultraviolet rays to cure the coating film, thereby obtaining an optical thin film having a cured coating film with a thickness of 100 nm.

[0104] (Examples 2 to 4, Comparative Examples 1 and 2)

[0105] Except that the thickness of the cured coating film was changed as described in Table 1, the same conditions as in Example 1 were used to produce an optical film.

[0106] (Examples 5 to 7, Comparative Example 3)

[0107] An optical film was obtained under the same conditions as in Example 1 except that the active energy ray-curable composition (2) was used and the thickness of the cured coating film was changed as described in Table 1, wherein the active energy ray-curable composition (2) contained epoxy (meth)acrylate as an active energy ray-curable compound and contained 45 parts by weight of silica-based fine particles having an average primary particle size of 5 to 100 nm based on 100 parts by weight of the active energy ray-curable compound.

[0108] (Comparative Examples 4 to 6)

[0109] An optical film was obtained by using the same conditions as in Example 1 except that the active energy ray-curable composition (3) was used and the thickness of the cured coating film was changed as described in Table 1, wherein the active energy ray-curable composition (3) contained epoxy (meth)acrylate as an active energy ray-curable compound and contained 85 parts by weight of silica-based fine particles having an average primary particle size of 5 to 100 nm based on 100 parts by weight of the active energy ray-curable compound.

[0110] (Comparative Example 7)

[0111] An optical film was obtained under the same conditions as in Example 1, except that the active energy ray-curable composition (4) [“Z-773” manufactured by Aica Industries Co., Ltd.] was used and the thickness of the cured coating film was changed as described in Table 1, wherein the active energy ray-curable composition (4) contained urethane (meth)acrylate as an active energy ray-curable compound and contained silica-based fine particles.

[0112] (Comparative Example 8)

[0113] An optical film was obtained under the same conditions as in Example 1 except that the active energy ray-curable composition (5) [“UT-1121” manufactured by Nippon Paint-Automotive Co., Ltd.] was used and the thickness of the cured coating film was changed as described in Table 1, wherein the active energy ray-curable composition (5) contained butanetrol (meth)acrylate as an active energy ray-curable compound and contained 10 to 20 parts by weight of silica-based fine particles based on 100 parts by weight of the active energy ray-curable compound.

[0114] (Comparative Example 9)

[0115] An optical film was produced under the same conditions as in Example 1, except that an emulsion of a water-dispersible urethane resin (polyester polyurethane, "Superflex (registered trademark) 210" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as the coating liquid, and 30 parts by weight of silica-based fine particles were contained relative to 100 parts by weight of the solid content of the polyester polyurethane, and the thickness of the coating film after drying was changed to that described in Table 1.

[0116] The optical films obtained in Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 1.

[0117] [Adhesion]

[0118] According to the cross-cut method of JIS K5400, 100 1 mm thick strips were prepared using a checkerboard peel test jig. 2 A cross-cut grid was cut and Nichiban Co., Ltd. adhesive tape (CT405AP-18) was attached to it. After being pressed evenly with a spatula, the tape was peeled off in a 90-degree direction to evaluate the residual rate of the cured coating film (number of remaining pieces / 100). The evaluation criteria are as follows.

[0119] ○: The remaining rate of the cross-cut grid is 100%

[0120] ×: The cross-cut grid residual rate is less than 100%

[0121] [Anti-blocking properties]

[0122] After the optical film with the cured coating formed was kept at 23°C and 50% relative humidity for 1 hour, it was cut into two pieces of 5 cm × 5 cm. The two films were stacked so that the cured coating of one film was in contact with the surface of the cycloolefin film of the other film. The two films were left to stand while being stacked, and the anti-blocking property of the optical film was evaluated by sliding one film in the lateral direction while pressing it by hand. The evaluation criteria were as follows.

[0123] ○: Easy to slide due to force applied in the lateral direction

[0124] △: Sliding due to strong force applied in the lateral direction

[0125] ×: No slippage even when strong force is applied in the lateral direction

[0126] [Solvent resistance]

[0127] Use a burette to drop a few drops of organic solvent (acetone, ethyl acetate, MIBK, CHN) onto the cured coating of the optical film and leave it for 1 minute. Then wipe off the organic solvent with a rag and evaluate the film appearance at the site where the organic solvent was dropped. Films with no change in appearance are judged to be solvent resistant.

[0128] In addition, as reference examples, the anti-blocking properties and solvent resistance were also evaluated for an unstretched cycloolefin film without forming a cured coating film, a stretched cycloolefin film without forming a cured coating film and having a stretching ratio of 1.45 times in the longitudinal direction, and a stretched cycloolefin film without forming a cured coating film and having a stretching ratio of 4.9 times in the transverse direction.

[0129] Table 1

[0130]

[0131] As shown in Table 1, the "optical films of Examples 1 to 7" containing epoxy (meth) acrylate as an active energy ray-curable compound, with the inorganic fine particles in the range of 30 parts by weight to 80 parts by weight relative to 100 parts by weight of the active energy ray-curable compound, and the thickness of the cured coating film in the range of more than 50 nm and less than 3500 nm, show excellent adhesion and anti-blocking properties between the cycloolefin-based film and the cured coating film, and also excellent solvent resistance to organic solvents.

[0132] On the other hand, as shown in Table 1, the "optical films of Comparative Examples 1 and 3" containing epoxy (meth) acrylate as an active energy line curable compound, and the inorganic microparticles are in the range of 30 parts by weight or more and 80 parts by weight or less relative to 100 parts by weight of the active energy line curable compound, and the thickness of the cured coating is 50nm, and the results of poor solvent resistance are shown. The "optical film of Comparative Example 2" containing epoxy (meth) acrylate as an active energy line curable compound, and the inorganic microparticles are in the range of 30 parts by weight or more and 80 parts by weight or less relative to 100 parts by weight of the active energy line curable compound, and the thickness of the cured coating is 3500nm, and the results of poor anti-blocking are shown. Furthermore, the "optical films of Comparative Examples 4 to 6" containing epoxy (meth) acrylate as an active energy line curable compound, and the inorganic microparticles are in the range of more than 80 parts by weight relative to 100 parts by weight of the active energy line curable compound, regardless of the thickness of the cured coating, all show poor solvent resistance.

[0133] In addition, the "optical films of Comparative Examples 7 and 8" containing urethane (meth) acrylate and tetramethylene glycol (meth) acrylate as active energy ray-curable compounds all showed poor solvent resistance. Even the "optical film of Comparative Example 9" containing polyester polyurethane as a substitute for active energy ray-curable compounds also showed poor solvent resistance.

[0134] In addition, the unstretched cycloolefin film without forming a cured coating film shows poor results in terms of anti-blocking and solvent resistance. Compared with the unstretched cycloolefin film, the stretched cycloolefin film with an extension ratio of 1.45 times along the longitudinal direction without forming a cured coating film and the stretched cycloolefin film with an extension ratio of 4.9 times along the transverse direction without forming a cured coating film show poor results in terms of solvent resistance. It can also be known that the optical film of the present invention has a resin film that has been subjected to an extension treatment, which is a method that can effectively solve problems that were difficult to solve in the past, and is preferred because the effect of the present invention can be effectively used.

[0135] Next, the occurrence of end cracks was evaluated by a solvent resistance test using hexane.

[0136] (Example 8)

[0137] Using a bar coater, a coating liquid of an active energy ray-curable composition (1) [BSCH271 manufactured by Arakawa Chemical Industries, Ltd.] containing epoxy (meth)acrylate as an active energy ray-curable compound and 65 parts by weight of silica-based microparticles having an average primary particle size of 5 to 100 nm relative to 100 parts by weight of the active energy ray-curable compound was applied to one surface of a cycloolefin-based film (Tg: 135°C, thickness: 37 μm, elongation ratio: 1.45 times in the longitudinal direction), and then placed in a hot air dryer and dried at 80°C for 60 seconds. Next, a high-pressure mercury lamp was used to heat the film with a cumulative light intensity of 500 mJ / cm 2 The dried coating film was irradiated with ultraviolet rays to cure the coating film, thereby obtaining an optical thin film having a cured coating film with a thickness of 350 nm.

[0138] (Example 9)

[0139] An optical film was produced under the same conditions as in Example 8 except that a cured coating film was formed on both surfaces of the cycloolefin film.

[0140] (Example 10)

[0141] An optical film was produced under the same conditions as in Example 8 except that the thickness of the cured coating film was changed as described in Table 2.

[0142] (Example 11)

[0143] An optical film was produced under the same conditions as in Example 8 except that the cured coating films were formed on both surfaces of the cycloolefin-based film and the thickness of the cured coating films was changed as described in Table 2.

[0144] The following evaluations were performed on the optical films obtained in Examples 8 to 11 and the cycloolefin-based film of Reference Example 2. The evaluation results are shown in Table 2.

[0145] [Solvent resistance (end cracks)]

[0146] A polyethylene terephthalate protective film (manufactured by Fujimori Industries Co., Ltd., NBO-0424, thickness 38 μm) with an adhesive layer was bonded to both sides of the optical film and cut into a size of 50 mm × 50 mm to prepare a sample. Next, the sample was heated at 95°C for 10 minutes and then immersed in a hexane solvent for 3 minutes, and the edge cracks generated in the sample were evaluated by visual inspection. The evaluation criteria are as follows.

[0147] ◎: No end cracks

[0148] ○: The number of end cracks is 1 or more and 10 or less

[0149] △: The number of cracks at the end is 11 or more and 30 or less

[0150] ×: The number of cracks at the end is 31 or more

[0151] Table 2

[0152]

[0153] As shown in Table 2, the cycloolefin film of Reference Example 2, which does not have a cured coating on the surface, has many fine cracks from the cut end face along a direction roughly parallel to the extension direction of the cycloolefin film after being immersed in hexane. This phenomenon is speculated as follows: since the shrinkage stress in the extension direction of the cycloolefin film and the tensile stress of the protective film laminated to the cycloolefin film occur in an orthogonal direction, solvent cracks will be generated when hexane penetrates from the end face, because the tensile stress takes the solvent crack as the starting point and generates end cracks. On the other hand, as shown in Table 2, the cycloolefin film with a cured coating of Examples 8 to 11 shows that the cracks from the cut end face after hexane immersion are suppressed. This is presumed to be the following: by providing a cured coating film that has excellent solvent resistance to organic solvents, excellent adhesion to the cycloolefin film, and excellent restraining force, solvent cracks caused by swelling and dissolution of the cycloolefin film are suppressed, and by restraining the shrinkage stress of the cycloolefin film, cracks generated from the end surface are suppressed.

[0154] Description of Reference Numerals

[0155] 1. Optical film; 2. Resin film; 3. Cured coating film; 4. Optical film; 5. Adhesive layer; 6. Polarizer; 10. Polarizing plate.

Claims

1. An optical film, comprising a cured coating of an active energy ray-curable composition on the surface of a resin film having a polymer having an alicyclic structure as a main component, wherein the active energy ray-curable composition contains an active energy ray-curable compound (A) and inorganic microparticles (B) having an average primary particle size of 5 nm to 100 nm, the active energy ray-curable compound (A) contains epoxy (meth)acrylate (a1), the inorganic microparticles (B) are in an amount of 30 parts by weight to 80 parts by weight relative to 100 parts by weight of the active energy ray-curable compound (A), and the thickness of the cured coating is greater than 50 nm and less than 3500 nm.

2. The optical film according to claim 1, wherein: The epoxy (meth)acrylate (a1) contains a plurality of (meth)acryloyl groups and hydroxyl groups in the molecule.

3. The optical film according to claim 1, wherein: The epoxy (meth)acrylate (a1) is a hydroxyl group-containing (meth)acrylic copolymer comprising a radical polymer of a monomer component of an epoxy group-containing mono(meth)acrylate and a reaction product of an α,β-unsaturated carboxylic acid.

4. The optical film according to claim 1, wherein: The active energy ray-curable compound (A) includes a hydroxyl group-containing polyfunctional (meth)acrylate (a2) having at least three (meth)acryloyl groups.

5. The optical film according to claim 1, wherein: The inorganic fine particles (B) are silicon dioxide fine particles.

6. The optical film according to claim 1, wherein: The resin film is a stretched film.

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