WO2024142832A1

WO2024142832A1 - Optical film and polarizing plate using same

Info

Publication number: WO2024142832A1
Application number: PCT/JP2023/043841
Authority: WO
Inventors: 谷澤克也; 畑中真吾
Original assignee: 大倉工業株式会社
Priority date: 2022-12-26
Filing date: 2023-12-07
Publication date: 2024-07-04

Abstract

[Problem] The purpose of the present invention is to provide an optical film having an easily adhesive layer that has excellent adhesiveness with respect to a cycloolefin-based film and blocking resistance when rolled into a roll, that has excellent solvent resistance, and that can suppress deterioration in optical characteristics caused by an organic solvent and can suppress occurrence of cracks at end portions in a solvent resistance test performed using a hydrocarbon solvent such as hexane. [Solution] This optical film has a cured coating of an active energy ray curable composition on the surface of a resin film containing, as a main component, a polymer having an alicyclic structure. The optical film is characterized in that: the active energy ray curable composition contains an active energy ray curable compound (A) and inorganic fine particles (B) having an average primary particle size of 5-100 nm; the active energy ray curable compound (A) contains an epoxy (meth)acrylate (a1); the inorganic fine particles (B) are contained in a range of 30-80 parts by weight with respect to 100 parts by weight of the active energy ray curable compound (A); and the thickness of the cured coating is more than 50 nm but less than 3500 nm.

Description

Optical film and polarizing plate using the same

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

In recent years, applications for organic electroluminescence displays, touch panels, etc. are expanding. In such devices, various resin films are used as protective films, retardation films, etc. Among them, cycloolefin-based films made from cycloolefin polymers are preferably used because they have high heat resistance, excellent dimensional stability, and a low photoelastic coefficient that keeps birefringence low, making them a material with excellent optical properties.

Cycloolefin-based films are non-polar films with no or very few polar groups, and therefore have poor adhesion. To address this problem, a coating layer such as an easy-adhesion layer is laminated on the coating layer, and other components such as a polarizer are attached to the coating layer via an adhesive or pressure-sensitive adhesive, or an optically functional layer such as a hard coat layer is formed via the coating layer.

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

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

In addition, optical films having a cycloolefin-based film and an easy-adhesion layer are wound into rolls during storage and transportation, but when wound into a roll, blocking occurs between the optical films, which can cause problems such as poor handling of the roll film. To address this problem, fine particles are added to the easy-adhesion layer to impart blocking resistance to the easy-adhesion layer.

For example, Patent Document 3 describes an optical film having an easy-adhesion layer that contains a polyurethane resin with a glass transition temperature of 50°C or higher, fine particles with an average particle size 1 to 5 times the thickness of the easy-adhesion layer, and a surfactant, with the aim of increasing the blocking resistance of the optical film having a substrate and an easy-adhesion layer made of a cyclic olefin resin.

Patent Publication 2019-116640 Patent Publication No. 2020-055185 WO16/047359

When a protective film or a retardation film is laminated to other components such as a polarizer, dirt on the surface of the protective film or the retardation film is removed with an organic solvent such as acetone or ethyl acetate before lamination. However, when the surface of a cycloolefin film is laminated with an organic solvent, the organic solvent swells and dissolves the cycloolefin film, causing the cycloolefin film to whiten and resulting in a decrease in optical properties. In addition, an organic solvent such as methyl isobutyl ketone (MIBK) or cyclohexanone (CHN) is used as an active energy ray curable composition for forming a functional layer such as a hard coat layer. When an active energy ray curable composition containing an organic solvent is applied onto an easy-adhesion layer of a cycloolefin film, the organic solvent swells and dissolves the cycloolefin film, making it impossible to form a functional layer with excellent optical properties on the cycloolefin film. For this reason, it is desirable for the easy-adhesion layer of a cycloolefin film to have excellent solvent resistance.

On the other hand, the cycloolefin-based film having an easy-adhesion layer disclosed in the above document has poor solvent resistance in the easy-adhesion layer, and organic solvents swell and dissolve the easy-adhesion layer and the cycloolefin-based film, causing the cycloolefin-based film to whiten and resulting in reduced optical properties.

Furthermore, retardation films made of cycloolefin-based films are generally used by laminating them with polarizers, and an image display panel is formed by laminating a polarizer and retardation film with an adhesive layer between them and an image display cell such as a liquid crystal cell or an organic electroluminescence cell to form a polarizing plate. However, when the polarizing plate is washed with a hydrocarbon solvent such as hexane during the assembly of an image display panel or an image display device using said panel, fine cracks may occur from the edge of the cycloolefin-based film, and it is therefore required that edge cracks are unlikely to occur even in a solvent resistance test using a hydrocarbon solvent such as hexane.

The present invention has been made in consideration of these problems, and aims to provide an optical film having a cured coating that has excellent adhesion to cycloolefin-based films, excellent blocking resistance when wound into a roll, and excellent solvent resistance, and can suppress the deterioration of optical properties due to organic solvents and the occurrence of edge cracks in solvent resistance tests using hydrocarbon solvents such as hexane.

The inventors of the present invention have conducted extensive research into an easy-to-adhere layer that has excellent adhesion and blocking resistance and can suppress deterioration of optical properties caused by organic solvents. As a result, they have discovered that the above problems can be solved by forming an easy-to-adhere layer from a cured coating film of an active energy ray-curable composition that contains an epoxy (meth)acrylate-based active energy ray-curable compound and inorganic fine particles, and that contains a specific amount of inorganic fine particles relative to the total amount of the active energy ray-curable compound, thereby completing the present invention.

According to the present invention,
(1) There is provided an optical film having a cured coating film of an active energy ray curable composition on a surface of a resin film containing a polymer having an alicyclic structure as a main component, the active energy ray curable composition containing an active energy ray curable compound (A) and inorganic fine particles (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 parts by weight or more and 80 parts by weight or less with respect to 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 3,500 nm,
(2) There is provided the optical film according to (1), wherein the epoxy (meth)acrylate (a1) contains a plurality of (meth)acryloyl groups and a hydroxyl group in the molecule;
(3) There is provided the optical film according to (1), wherein the epoxy (meth)acrylate (a1) is a hydroxyl group-containing (meth)acrylic copolymer which is a reaction product of a radical polymer of a monomer component containing an epoxy group-containing mono(meth)acrylate and an α,β-unsaturated carboxylic acid;
(4) There is provided the optical film according to (1), wherein the active energy ray-curable compound (A) contains a hydroxyl group-containing polyfunctional (meth)acrylate (a2) having at least three (meth)acryloyl groups;
(5) The optical film according to (1), wherein the inorganic fine particles (B) are silica fine particles,
(6) There is provided the optical film according to (1), wherein the resin film is a stretched film.

The optical film of the present invention contains an epoxy (meth)acrylate-based active energy ray curable compound and inorganic fine particles, and has an easy-adhesion layer made of a cured coating of an active energy ray curable composition containing a specific amount of inorganic fine particles relative to the total amount of the active energy ray curable compound, which provides excellent adhesion to the cycloolefin-based film and excellent blocking resistance by suppressing blocking between the optical films when wound into a roll. In addition, the optical film of the present invention has excellent solvent resistance to organic solvents, and can suppress deterioration of optical properties when beautifying with organic solvents or when an active energy ray curable coating agent using an organic solvent is applied to the easy-adhesion layer, and can suppress the occurrence of fine cracks from the end face of the cycloolefin-based film when a polarizing plate is washed with a hydrocarbon solvent such as hexane during the assembly of an image display panel or an image display device using the panel.

FIG. 1 is a schematic cross-sectional view illustrating an example of an optical film of the present invention. FIG. 1 is a schematic cross-sectional view illustrating an example of the polarizing plate of the present invention.

The present invention will be described in detail below. Note that the present invention is not limited to the following form, and various forms are possible as long as the effects of the present invention are achieved.

[Resin film]
The resin film is made of a thermoplastic resin containing a polymer having an alicyclic structure as a main component. Here, the term "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, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more.

A polymer having an alicyclic structure is a polymer having an alicyclic structure in the structural unit of the polymer. A polymer having an alicyclic structure may have an alicyclic structure in the main chain, or may have an alicyclic structure 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 preferable.

Examples of alicyclic structures include saturated alicyclic hydrocarbon (cycloalkane) structures and unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structures. Among these, from the standpoint of mechanical strength, heat resistance, etc., cycloalkane structures and cycloalkene structures are preferred, and cycloalkane structures are particularly preferred.

The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, and 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 moldability.

In a polymer having an alicyclic structure, the proportion of structural units having an alicyclic structure can be appropriately selected depending on the purpose of use. The proportion of structural units having an alicyclic structure in a polymer having an alicyclic structure is preferably 55% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the proportion of structural units having an alicyclic structure in a polymer having an alicyclic structure is within this range, the transparency and heat resistance of a resin film containing the polymer having an alicyclic structure will be good.

Among the polymers having an alicyclic structure, cycloolefin polymers are preferred. Cycloolefin polymers are polymers having a structure obtained by polymerizing cycloolefin monomers. Cycloolefin monomers are compounds having a ring structure formed of carbon atoms and having a polymerizable carbon-carbon double bond in the ring structure. Examples of the polymerizable carbon-carbon double bond include polymerizable carbon-carbon double bonds such as those of ring-opening polymerization. Examples of the ring structure of cycloolefin monomers include monocyclic, polycyclic, condensed polycyclic, bridged rings, and polycyclic combinations of these. Among these, polycyclic cycloolefin monomers are preferred from the viewpoint of achieving a high level of balance between the dielectric properties, heat resistance, and other properties of the polymer having an alicyclic structure.

Preferred cycloolefin polymers include norbornene-based polymers, monocyclic olefin-based polymers, cyclic conjugated diene-based polymers, and hydrogenated versions of these. Of these, norbornene-based polymers are particularly suitable due to their good moldability.

Examples of norbornene-based polymers include ring-opening polymers of monomers having a norbornene structure and hydrogenated products thereof; addition polymers of monomers having a norbornene structure and hydrogenated products thereof. Examples of ring-opening polymers of monomers having a norbornene structure include ring-opening homopolymers of one type of monomer having a norbornene structure, ring-opening copolymers of two or more types of monomers having a norbornene structure, and ring-opening copolymers of a monomer having a norbornene structure and other monomers copolymerized therewith. Examples of addition polymers of monomers having a norbornene structure include addition homopolymers of one type of monomer having a norbornene structure, addition copolymers of two or more types of 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 moisture absorption, dimensional stability, light weight, etc.

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 ]deca-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 (for example, those having a substituent on the ring). Here, examples of the substituent include an alkyl group, an alkylene group, a polar group, and the like. In addition, these substituents may be the same or different, and a plurality of them may be bonded to the ring. The monomer having a norbornene structure may be used alone or in combination of two or more kinds at any ratio.

Types of polar groups include, for example, heteroatoms and atomic groups having heteroatoms. Examples of heteroatoms include oxygen atoms, nitrogen atoms, sulfur atoms, silicon atoms, and halogen atoms. Specific examples of polar groups include carboxyl groups, carbonyloxycarbonyl groups, epoxy groups, hydroxyl groups, oxy groups, ester groups, silanol groups, silyl groups, amino groups, nitrile groups, and sulfonic acid groups.

Other monomers capable of ring-opening copolymerization with a monomer having a norbornene structure include, for example, monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene, and derivatives thereof; cyclic conjugated dienes such as cyclohexadiene and cycloheptadiene, and derivatives thereof; and the like. The other monomers capable of ring-opening copolymerization with a monomer having a norbornene structure may be used alone or in combination of two or more types in any ratio. A ring-opening polymer of a monomer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing the monomer in the presence of a ring-opening polymerization catalyst.

Examples of monomers capable of addition copolymerization with a 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; and 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. Furthermore, the monomers capable of addition copolymerization with a monomer having a norbornene structure may be used alone, or two or more types may be used in combination in any ratio. An addition polymer of a monomer having a norbornene structure can be produced, for example, by polymerizing or copolymerizing the monomer in the presence of an addition polymerization catalyst.

The hydrogenated products of the ring-opening polymer and addition polymer described above can be produced, for example, by hydrogenating the carbon-carbon unsaturated bonds, preferably to 90% or more, 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.

Among norbornene-based polymers, those having structural units of X: bicyclo[3.3.0]octane-2,4-diyl-ethylene structure and Y: tricyclo[ ^4.3.0.12,5 ]decane-7,9-diyl-ethylene structure, the amount of these structural units being 90% by weight or more based on the total structural units of the norbornene-based polymer, and the ratio of the proportion of X to the proportion of Y being 100:0 to 40:60 by weight ratio of X:Y are preferred. By using such a polymer, a resin film containing the norbornene-based polymer can be made to have no dimensional change over the long term and excellent stability of optical properties.

Examples of monocyclic olefin polymers include addition polymers of monocyclic olefin monomers such as cyclohexene, cycloheptene, and cyclooctene.

Examples of cyclic conjugated diene polymers include polymers obtained by cyclization reaction of 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 of these.

The weight average molecular weight (Mw) of the polymer having an alicyclic structure is usually 30,000 or more, preferably 35,000 or more, more preferably 40,000 or more, and preferably 80,000 or less, more preferably 60,000 or less, and particularly preferably 50,000 or less. By making the weight average molecular weight (Mw) of the polymer having an alicyclic structure equal to or greater than the lower limit of the above range, the adhesive layer can effectively prevent cohesive failure of the resin film, thereby improving the adhesion between the optical film and the polarizer. By making it equal to or less than the upper limit, the mechanical strength and moldability of the resin film can be improved. Therefore, by making the weight average molecular weight (Mw) of the polymer having an alicyclic structure fall within the above range, the optical film can be made excellent in cohesive force, mechanical strength, and moldability.

The glass transition temperature (Tg) of the polymer having an alicyclic structure is preferably 100°C or higher, more preferably 110°C or higher, particularly preferably 120°C or higher, and is preferably 190°C or lower, more preferably 180°C or lower, particularly preferably 170°C or lower. By making the glass transition temperature of the thermoplastic resin equal to or higher than the lower limit of the above range, the durability of the resin film in a high-temperature environment can be increased. Also, by making it equal to or lower than the upper limit, the stretching process can be easily performed.

The resin film may contain resin components other than the polymer having an alicyclic structure, as long as the effects of the present invention are not impaired. Examples of resin components other than the polymer having an alicyclic structure include cellulose-based resins, polyester-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyolefin-based resins, (meth)acrylic-based resins, polyarylate-based resins, polystyrene-based resins, and polyvinyl alcohol-based resins. These may be used alone or in combination of two or more. The content of other resin components in the resin film is not particularly limited, but is preferably 0 to 50% by weight, more preferably 0 to 30% by weight, and even more preferably 0 to 20% by weight.

The resin film may contain any additives, etc., as long as they do not impair the effects of the present invention. Examples of additives include colorants such as pigments and dyes; plasticizers; fluorescent whitening agents; dispersants; heat stabilizers; light stabilizers; UV absorbers; static electricity inhibitors; antioxidants; fine particles; surfactants, etc. These can be used alone or in combination of two or more kinds. The amount of additives in the resin film is not particularly limited, but is preferably 0 to 5% by weight, more preferably 0 to 3% by weight, and even more preferably 0 to 0.5% by weight.

The resin film may or may not have been stretched, but it is preferable that it has been stretched. The stretching may be uniaxial or biaxial, but the stretching ratio is preferably 1.2 times or more in terms of area ratio, and more preferably 1.4 times or more. In general, the solvent resistance of a resin film is considered to depend on its material, and there is no close relationship between the solvent resistance of a resin film and the stretching treatment. However, the present inventors have found that the solvent resistance of a resin film containing a polymer having an alicyclic structure such as a cycloolefin polymer changes due to the stretching treatment, and that when the resin film is washed with a hydrocarbon solvent such as hexane, fine cracks occur from the end approximately parallel to the stretching direction. Specifically, the solvent resistance of a resin film containing a polymer having an alicyclic structure such as a cycloolefin polymer that has been stretched decreases due to the stretching treatment. Therefore, the optical film of the present invention is preferably provided with a resin film that has been subjected to a stretching process (sometimes referred to as a stretched film) because this effectively solves problems that have been difficult to solve in the past and allows the effects of the present invention to be effectively utilized.

The total light transmittance of the resin film converted to a thickness of 1 mm is preferably 80% or more, and more preferably 90% or more. The total light transmittance can be measured in accordance with JIS K0115 using a spectrophotometer (V-570 ultraviolet-visible-near infrared spectrophotometer manufactured by JASCO Corporation). The haze of the resin film converted to a thickness of 1 mm is preferably 0.3% or less, and more preferably 0.2% or less. By keeping the haze within the above range, it is possible to prevent depolarization when the optical film is bonded to a polarizer. The haze can be measured in accordance with JIS K7361-1997 using a turbidity meter NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd.

The thickness of the resin film is preferably 5 μm or more, more preferably 8 μm or more, particularly preferably 10 μm or more, and is preferably 100 μm or less, more preferably 70 μm or less, particularly preferably 60 μm or less. By making the thickness of the resin film equal to or greater than the lower limit of the above range, the mechanical strength of the resin film can be increased. Also, by making the thickness equal to or less than the upper limit, the thickness of the resin film can be reduced.

[Active energy ray-curable composition]
The active energy ray curable composition contains the active energy ray curable compound (A) and the inorganic fine particles (B) described below. The cured coating film made of the active energy ray curable composition has excellent adhesion to a cycloolefin-based film, and suppresses blocking between optical films when wound into a roll, resulting in excellent blocking resistance. In addition, the cured coating film has excellent solvent resistance to organic solvents, and can suppress the deterioration of optical properties when beautifying with an organic solvent or when an active energy ray curable coating agent using an organic solvent is applied onto the easy-adhesion layer, and can suppress the occurrence of fine cracks from the end face when washed with a hydrocarbon solvent such as hexane.

The active energy ray curable compound (A) contains an epoxy (meth)acrylate (a1). Epoxy (meth)acrylate has high reactivity and excellent crosslinking structure formation, and therefore has excellent solvent resistance after curing. There are no particular limitations on the epoxy (meth)acrylate, but it is preferable that the epoxy (meth)acrylate contains 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, excellent adhesion to cycloolefin-based films, excellent crosslinking structure formation, and excellent solvent resistance. In this specification, "(meth)acrylic" means acrylic and/or methacrylic.

The hydroxyl group concentration of the epoxy (meth)acrylate (a1) is not particularly limited, but is preferably 0.8 mmol/g or more, more preferably 1.6 to 4.7 mmol/g, and even more preferably 2.0 to 4.7 mmol/g. The hydroxyl group concentration here is a value calculated from the number of hydroxyl groups in the (a1) component and the molecular weight. Specifically, when the (a1) component is other than a polymer, the value is calculated from {the number of moles of hydroxyl groups contained in 1 mole of the (a1) component/the molecular weight of the (a1) component}. When the (a1) component is a polymer, the value is calculated from {the number of moles of hydroxyl groups contained in 1 mole of the repeating structure of the (a1) component/the formula weight of the repeating structure of the (a1) component}. When the hydroxyl group concentration is within the above range, the adhesion to cycloolefin-based films and adhesion to other optical members are excellent.

The weight average molecular weight of the epoxy (meth)acrylate (a1) is not particularly limited, but from the viewpoint of solvent resistance, it is preferably in the range of about 1,000 to 100,000, and more preferably about 10,000 to 50,000. The weight average molecular weight here is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

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

Epoxy group-containing mono(meth)acrylates are compounds that have at least one epoxy group and one polymerizable unsaturated double bond in the molecule. Specific examples include glycidyl (meth)acrylate, β-methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, vinylcyclohexene monoxide (i.e., 1,2-epoxy-4-vinylcyclohexane), and the like. These may be used alone or in combination of two or more. Of these, glycidyl (meth)acrylate is preferred in terms of availability and procurement costs. In addition to the epoxy group-containing mono(meth)acrylate, copolymerizable monomers may also be included. Specific examples of the monomer include (meth)acrylic acid esters having a chain alkyl group such as methyl (meth)acrylate and ethyl (meth)acrylate, (meth)acrylic acid esters having an alicyclic structure such as isobornyl (meth)acrylate, (meth)acrylic acid esters having an aromatic ring such as ethoxylated o-phenylphenol acrylate, nitrogen-containing acrylic acid esters such as acryloylmorpholine, aromatic vinyl compounds such as (meth)acrylamide, acrylonitrile, styrene, α-methylstyrene, and vinyl toluene, vinyl acetate, and macromonomers having an unsaturated double bond at one end and not containing an epoxy group or a carboxyl group. These may be blended alone or in combination of two or more.

As the α,β-unsaturated carboxylic acid, various known α,β-unsaturated carboxylic acids can be used without any particular limitation, so long as they are capable of undergoing an addition reaction with an epoxy group. Specific examples include α,β-unsaturated monocarboxylic acids such as (meth)acrylic acid, and α,β-unsaturated dicarboxylic acids such as maleic acid and fumaric acid. These may be used alone or in combination of two or more. Of these, (meth)acrylic acid is preferred from the viewpoints of reactivity and storage stability.

It is preferable that the active energy ray curable compound (A) further contains a hydroxyl group-containing polyfunctional (meth)acrylate (a2) having at least three (meth)acryloyl groups. The hydroxyl group-containing polyfunctional (meth)acrylate (a2) is a (meth)acrylate containing at least three (meth)acryloyl groups and at least one hydroxyl group in one molecule, and various known ones can be used without particular restrictions. Specific examples include 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, and polytrimethylolpropane poly(meth)acrylates containing one or more hydroxyl groups and three or more (meth)acryloyl groups in the molecule, such as ditrimethylolpropane tri(meth)acrylate. These may be blended alone or in combination of two or more. When two or more types are used, the proportion of each polyfunctional (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 each of these can be used alone or in combination of two or more types.

The hydroxyl group concentration of the hydroxyl group-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 even more preferably 2.0 to 4.7 mmol/g.

In addition to the above, the active energy ray curable compound (A) may contain poly(meth)acrylates that do not contain hydroxyl groups. Specific examples of poly(meth)acrylates include polypentaerythritol poly(meth)acrylates that do not contain hydroxyl groups in the molecule, such as pentaerythritol tetra(meth)acrylate and dipentaerythritol hexa(meth)acrylate, and polytrimethylolpropane poly(meth)acrylates that do not contain hydroxyl groups in the molecule, such as ditrimethylolpropane tetra(meth)acrylate.

The epoxy (meth)acrylate (a1) and the hydroxyl group-containing polyfunctional (meth)acrylate (a2) can be used alone or in combination. When used in combination, their mass ratio is not particularly limited, but from the viewpoint of hard coat properties and curing properties, it is usually in the range of about 1/99 to 80/20, preferably about 5/95 to 50/50.

Examples of inorganic fine particles (B) include inorganic oxides such as silica, titania, alumina, and zirconia, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, and calcium phosphate. Among these, silica-based fine particles are preferred. Silica-based fine particles have excellent blocking suppression ability, excellent transparency, do not cause haze, and are not colored, so that the adhesion layer has a smaller effect on the optical properties.

Any of the known silica-based microparticles can be used without particular restrictions, but hydrophilic silica microparticles with a specific range of silanol group concentration on the surface are preferred. The silanol group concentration on the surface is preferably in the range of 60 to 200 μmol/g, more preferably 100 to 200 μmol/g, and even more preferably about 120 to 200 μmol/g. If the silanol group concentration on the surface is in the above range, the cured coating film has high hydrophilicity and therefore excellent adhesion to cycloolefin-based films and adhesion to other optical components. The silanol group concentration on the surface referred to here is a value determined by the methyl red adsorption method. The methyl red adsorption method is described, for example, in The Journal of the American Chemical Society, 72, 776-782 (1950) and Industrial Chemistry Journal, Vol. 68, No. 3, 429-432 (1965).

Examples of silica microparticles include colloidal silica produced by a wet method and fumed silica produced by a dry method. Specific examples of colloidal silica include aqueous colloids using water as a dispersion medium, and organosols (e.g., organosilica sols) in which colloidal silica is dispersed in a hydrophilic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, or propylene glycol monomethyl ether. Fumed silica is amorphous silica produced by a dry method, and can be obtained by reacting a volatile compound containing silicon in the gas phase. Specific examples include those produced by hydrolyzing a silicon compound such as silicon tetrachloride (SiCl4) in a flame of oxygen and hydrogen. Commercially available colloidal silica products include, for example, Snowtex, MA-ST-M, MA-ST-L, IPA-ST, IPA-ST-L, IPA-ST-ZL, IPA-ST-UP, PGM-ST (all manufactured by Nissan Chemical Industries, Ltd.), Quattron (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.).

The average primary particle diameter of the inorganic fine particles is 5 nm or more and 100 nm or less. The average primary particle diameter is preferably 10 nm or more and 75 nm or less, more preferably 10 nm or more and 50 nm or less, and even more preferably 10 nm or more and 25 nm or less. If it is in the above range, it has excellent blocking suppression ability when wound into a roll. The average primary particle diameter is measured by the BET method.

The amount of inorganic fine particles (B) in the active energy ray curable composition is 30 parts by weight or more and 80 parts by weight or less per 100 parts by weight (solid content equivalent) of the active energy ray curable compound (A). The lower limit of the amount is preferably 35 parts by weight or more, more preferably 40 parts by weight or more, and even more preferably 45 parts by weight or more. The upper limit of the amount is preferably 75 parts by weight or less, more preferably 70 parts by weight or less, and even more preferably 65 parts by weight or less. If the amount of inorganic fine particles is within the above range, it is possible to suppress the deterioration of optical properties during beautification using organic solvents or when an active energy ray curable coating agent using an organic solvent is applied onto the easy-adhesion layer, and to suppress the occurrence of fine cracks from the end face when cleaning with a hydrocarbon solvent such as hexane. The reason for this is unclear, but it is speculated that inorganic fine particles such as silica-based fine particles form aggregates (secondary particles) with a particle size larger than the primary particle size when multiple primary particles aggregate and weld together like beads, and multiple such aggregates aggregate to form large particles that form pores. Therefore, when the amount of inorganic fine particles is increased, the pore volume of the inorganic fine particles in the cured coating film increases relatively, making it easier for organic solvents to penetrate into the pores, and dissolving and swelling the cycloolefin-based film through these pores.

The active energy ray curable composition may contain a polymerization initiator (C) as necessary. As the polymerization initiator (C), any of various known initiators may be used without any particular limitation, so long as they are capable of being decomposed by active energy rays to generate radicals and initiate polymerization. Specific examples include 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-cyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-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 can be used alone or in combination of two or more.

Commercially available polymerization initiators (C) include Irgacure 651, Irgacure 184, Irgacure 1173, Irgacure 2959, Irgacure 127, Irgacure 907, Irgacure 369, Irgacure 819, Irgacure TPO (all manufactured by BASF), Omnirad 651, Omnirad 184, Om Examples include nirad 1173, Omnirad 2959, Omnirad 127, Omnirad 907, Omnirad 369, Omnirad 819, Omnirad TPO (all manufactured by IGM Resins), Speedcure TPO, Speedcure MBP (all manufactured by Lambson), etc. These can be used alone or in combination of two or more types.

The amount of the polymerization initiator (C) is not particularly limited, but is, for example, 0.1 parts by weight or more and 20 parts by weight or less per 100 parts by weight (solid content equivalent) of the total of the active energy ray-curable compound (A) and the inorganic fine particles (B).

The active energy ray curable composition may contain a polyfunctional (meth)acrylate (D) other than those mentioned above, if necessary. As the polyfunctional (meth)acrylate (D), any known polyfunctional (meth)acrylate having at least two (meth)acryloyl groups in one molecule may be used without any particular limitation. Specific examples include pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin propoxy tri(meth)acrylate, ε-caprolactone modified tris-(2-(meth)acryloxyethyl)isocyanurate, urethane (meth)acrylate, and polyester (meth)acrylate.

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

The active energy ray curable composition may contain additives as necessary. Additives include antioxidants, UV absorbers, light stabilizers, defoamers, surface conditioners, antifouling agents, pigments, antistatic agents, and metal oxide fine particle dispersions.

The thickness of the cured coating film is more than 50 nm and less than 3500 nm. The lower limit is preferably more than 65 nm, more preferably more than 75 nm, even more preferably more than 85 nm, and particularly preferably more than 100 nm. The upper limit is preferably less than 3000 nm, more preferably less than 2000 nm, even more preferably less than 1000 nm, and particularly preferably 500 nm or less. Within the above range, the optical film has excellent blocking suppression ability when wound into a roll, and has excellent solvent resistance to organic solvents, and can suppress the deterioration of optical properties when beautified with organic solvents or when an active energy ray curable coating agent using an organic solvent is applied to the easy-adhesion layer, and the occurrence of fine cracks from the end face when washed with a hydrocarbon solvent such as hexane.

[Optical film]
An example of the optical film of the present invention is shown in Figure 1. The optical film 1 shown in Figure 1 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. It is sufficient that the cured coating film 3 is formed on at least one surface of the resin film 2, and it may be formed on both surfaces of the resin film 2.

In order for the optical film to stably perform its functions as an optical component, it is preferable that the total light transmittance is 85% or more, and more preferably 90% or more. The light transmittance can be measured in accordance with JIS K0115 using a spectrophotometer (V-570 ultraviolet-visible-near infrared spectrophotometer manufactured by JASCO Corporation).

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

The in-plane retardation Re and thickness direction retardation Rth of the optical film can be set arbitrarily depending on the application of the optical film. A specific range of the in-plane retardation Re is preferably 1 nm or more and 200 nm or less. Also, a specific range of the thickness direction retardation Rth is preferably 50 nm or more and 300 nm or less.

The total thickness of the optical film is preferably 5 μm or more, more preferably 8 μm or more, even more preferably 10 μm or more, and is preferably 200 μm or less, more preferably 100 μm or less, and particularly preferably 70 μm or less. By making the total thickness of the optical film equal to or greater than the lower limit, the mechanical strength of the optical film can be increased. Also, by making it equal to or less than the upper limit, the overall thickness of the optical film can be reduced.

The optical film of the present invention is, for example, a polarizer protection film, a phase difference film, a viewing angle compensation film, a light diffusion film, a reflection film, an anti-reflection film, an anti-glare film, a brightness enhancement film, or a conductive film for a touch panel. The optical film of the present invention may be an optically isotropic film, or may be an optically anisotropic film (for example, a film that exhibits birefringence such as phase difference).

[Method of manufacturing optical film]
The method for producing an optical film of the present invention includes a step of forming a coating film by applying a coating liquid of an active energy ray-curable composition containing an active energy ray-curable compound (A), inorganic fine particles (B), and optionally a solvent, to at least one surface of a resin film containing a polymer having an alicyclic structure as a main component, and a step of irradiating the coating film with active energy rays to form a cured coating film.

(Coating process)
The coating step is a step of coating a coating solution of an active energy ray curable composition onto a resin film containing a polymer having an alicyclic structure as a main component. Any suitable method can be adopted as the coating method in the coating step, and examples thereof include a bar coating method, a dip method, a spray method, a spin coating method, a roll coating method, a gravure coating method, an air knife coating method, a curtain coating method, a slide coating method, and an extrusion coating method. 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.

The active energy ray curable composition may be diluted with a solvent as necessary. As the solvent, various known solvents can be used without particular limitation, for example, 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, di Examples of the solvent include acetone 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, and propylene glycol monomethyl ether. These can be used alone or in combination of two or more.

The surface of the resin film may be subjected to a surface modification treatment in order to improve the adhesion between the resin film and the cured coating film. Examples of surface modification treatments include energy ray irradiation treatment and chemical treatment. Examples of energy ray irradiation treatments include corona discharge treatment, plasma treatment, electron beam irradiation treatment, and ultraviolet ray irradiation treatment. From the viewpoint of treatment efficiency, corona discharge treatment and plasma treatment are preferred, and corona discharge treatment is particularly preferred. Examples of chemical treatments include saponification treatment, and a treatment in which the film is immersed in an aqueous solution of an oxidizing agent such as a potassium dichromate solution or concentrated sulfuric acid, followed by washing with water.

(Drying process)
After the coating step, a drying step of drying the coating film may be included as necessary. The drying step is not particularly limited, and a conventionally known method can 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.

(Curing process)
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. As the active energy rays, ultraviolet rays are preferred, and the ultraviolet irradiation is not particularly limited as long as it is light having a wavelength of 400 nm or less, but for example, an ultra-high pressure mercury lamp, a high pressure mercury lamp, a medium pressure mercury lamp, a low pressure mercury lamp, a xenon lamp, a halogen lamp, a metal halide lamp, etc. can be used. As the irradiation conditions, the ultraviolet irradiation amount is usually preferably 100 to 800 mJ/ ^cm2 .

[Polarizer]
Next, a polarizing plate will be described as an example of the optical member of the present invention. Fig. 2 shows a polarizing plate as an example of the optical member of the present invention. The polarizing plate 10 shown in Fig. 2 has a structure in which a polarizer 6 is laminated via an adhesive 5 on the surface of the cured coating film side of an optical film 4 having a cured coating film 3 made of an active energy ray curable composition on one surface of a resin film 2 containing a polymer having an alicyclic structure as a main component. Although not shown, the polarizing plate may have another polarizer protective film, a retardation film, etc. laminated via an adhesive layer on the opposite side of the polarizer to the optical film.

As the polarizer, any suitable polarizer can be adopted depending on the purpose. For example, a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene-vinyl acetate copolymer partially saponified film is uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye, or a polyene-based oriented film such as a dehydrated polyvinyl alcohol or a dehydrochlorinated polyvinyl chloride. Among these, a polarizer obtained by adsorbing a dichroic substance such as iodine to a polyvinyl alcohol film and uniaxially stretching the film is particularly preferred because it has a high polarization dichroic ratio. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm. As the adhesive for forming the adhesive layer, any suitable adhesive can be adopted, and examples thereof include an adhesive composition containing a polyvinyl alcohol resin, a pressure-sensitive adhesive composition containing an acrylic resin, and an ultraviolet-curable adhesive composition containing an acrylic resin.

The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited to the following examples.

Example 1
A coating solution of an active energy ray curable composition (1) ["BS CH271" manufactured by Arakawa Chemical Industries, Ltd.] containing epoxy (meth)acrylate as an active energy ray curable compound and containing 65 parts by weight of silica-based fine particles having an average primary particle diameter of 5 to 100 nm per 100 parts by weight of the active energy ray curable compound was applied to one surface of a cycloolefin film (Tg: 135°C, thickness: 37 μm, stretch ratio: vertical 1.45 times) using a bar coater, and then placed in a hot air dryer and dried at 80°C for 60 seconds. Next, the coating film after drying was irradiated with ultraviolet light from a high pressure mercury lamp so that the accumulated light amount was 500 mJ/ ^cm2 to cure the coating film, and an optical film having a cured coating film with a thickness of 100 nm was obtained.

(Examples 2 to 4, Comparative Examples 1 and 2)
Optical films were produced under the same conditions as in Example 1, except that the thickness of the cured coating film was changed as shown in Table 1.

(Examples 5 to 7, Comparative Example 3)
An optical film was obtained under the same conditions as in Example 1, except that an active energy ray-curable composition (2) containing an epoxy (meth)acrylate as an active energy ray-curable compound and containing 45 parts by weight of silica-based fine particles having an average primary particle diameter of 5 to 100 nm per 100 parts by weight of the active energy ray-curable compound was used, and the thickness of the cured coating film was changed as shown in Table 1.

(Comparative Examples 4 to 6)
An optical film was obtained under the same conditions as in Example 1, except that an active energy ray-curable composition (3) containing an epoxy (meth)acrylate as an active energy ray-curable compound and containing 85 parts by weight of silica-based fine particles having an average primary particle diameter of 5 to 100 nm per 100 parts by weight of the active energy ray-curable compound was used, and the thickness of the cured coating film was changed as shown in Table 1.

(Comparative Example 7)
An optical film was obtained under the same conditions as in Example 1, except that an active energy ray-curable composition (4) ["Z-773" manufactured by AICA Kogyo Co., Ltd.] containing urethane (meth)acrylate and silica-based fine particles was used as the active energy ray-curable compound, and the thickness of the cured coating film was changed as shown in Table 1.

(Comparative Example 8)
An optical film was obtained under the same conditions as in Example 1, except that an active energy ray curable composition (5) ["UT-1121" manufactured by Nippon Paint Automotive Co., Ltd.] containing erythritol (meth)acrylate as an active energy ray curable compound and containing 10 to 20 parts by weight of silica-based fine particles per 100 parts by weight of the active energy ray curable compound was used, and the thickness of the cured coating film was changed as shown in Table 1.

(Comparative Example 9)
An optical film was produced under the same conditions as in Example 1, except that an emulsion of a water-dispersible urethane resin (polyester-based polyurethane, "Superflex (registered trademark) 210" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was used, a coating liquid containing 30 parts by weight of silica-based fine particles per 100 parts by weight of the solid content of the polyester-based polyurethane was used, and the thickness of the coating film after drying was changed as shown in Table 1.

The optical films obtained in the examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 1.
[Adhesion]
According to the cross-cut method of JIS K5400, 100 cross-cut masses of ¹ mm2 were prepared using a checkerboard peel test jig, and adhesive tape (CT405AP-18) manufactured by Nichiban Co., Ltd. was attached onto the masses, which were then pressed evenly with a spatula or the like, and peeled off at a 90 degree angle to evaluate the remaining rate of the cured coating (number of remaining masses/100). The evaluation criteria were as follows:
○: Residual rate of cross-cut mass is 100%
×: Residual rate of cross-cut mass is less than 100% [blocking resistance]
The optical film after the formation of the cured coating film was held for 1 hour under conditions of 23°C and 50% relative humidity, and then cut into two pieces with a size of 5 cm x 5 cm. The two films were overlapped so that the cured coating film of one film was in contact with the cycloolefin-based film surface of the other film, and the overlapped state was left to stand, and one of the films was pressed by hand and slid laterally to evaluate the blocking resistance of the optical film. The evaluation criteria are as follows.
○: Easily slips when force is applied in the lateral direction. △: Slips when strong force is applied in the lateral direction. ×: Does not slip even when strong force is applied in the lateral direction. [Solvent resistance]
A few drops of an organic solvent (acetone, ethyl acetate, MIBK, CHN) were dropped onto the cured coating of the optical film using a dropper and held for 1 minute, after which the organic solvent was wiped off with a rag and the appearance of the film at the point where the organic solvent was dropped was evaluated. Films that showed no change in appearance were judged to have solvent resistance.

As reference examples, the blocking resistance and solvent resistance were also evaluated for an unstretched cycloolefin film with no cured coating formed, a stretched cycloolefin film with no cured coating formed and stretched by 1.45 times in the longitudinal direction, and a stretched cycloolefin film with no cured coating formed and stretched by 4.9 times in the transverse direction.

As shown in Table 1, the optical films of Examples 1 to 7, which contain epoxy (meth)acrylate as an active energy ray curable compound, have inorganic fine particles 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, and have a cured coating thickness in the range of more than 50 nm and less than 3500 nm, showed excellent adhesion between the cycloolefin film and the cured coating, excellent blocking resistance, and excellent solvent resistance to organic solvents.

On the other hand, as shown in Table 1, the optical films of Comparative Examples 1 and 3, which contain epoxy (meth)acrylate as the active energy ray curable compound, have inorganic fine particles in the range of 30 parts by weight to 80 parts by weight to 100 parts by weight of the active energy ray curable compound, and have a cured coating thickness of 50 nm, showed poor solvent resistance. The optical film of Comparative Example 2, which contains epoxy (meth)acrylate as the active energy ray curable compound, has inorganic fine particles in the range of 30 parts by weight to 80 parts by weight to 100 parts by weight of the active energy ray curable compound, and has a cured coating thickness of 3500 nm, showed poor blocking resistance. Furthermore, the optical films of Comparative Examples 4 to 6, which contain epoxy (meth)acrylate as the active energy ray curable compound, and have inorganic fine particles in the range of more than 80 parts by weight to 100 parts by weight of the active energy ray curable compound, showed poor solvent resistance regardless of the thickness of the cured coating.

In addition, the optical films of Comparative Examples 7 and 8, which contain urethane (meth)acrylate and erythritol (meth)acrylate as active energy ray curable compounds, both showed poor solvent resistance, and the optical film of Comparative Example 9, which contains polyester polyurethane instead of active energy ray curable compounds, also showed poor solvent resistance.

In addition, unstretched cycloolefin-based films on which no cured coating film is formed showed poor results in both blocking resistance and solvent resistance. Stretched cycloolefin-based films on which no cured coating film is formed and stretched by a factor of 1.45 in the longitudinal direction, and stretched cycloolefin-based films on which no cured coating film is formed and stretched by a factor of 4.9 in the transverse direction showed poorer solvent resistance than unstretched cycloolefin-based films. As can be seen from this, the inclusion of a resin film that has been subjected to a stretching process in the optical film of the present invention is an embodiment that can effectively solve problems that have been difficult to solve in the past, and is preferable because it allows the effects of the present invention to be effectively utilized.

Next, a solvent resistance test using hexane was conducted to evaluate the occurrence of edge cracks.

(Example 8)
A coating solution of an active energy ray curable composition (1) ["BS CH271" manufactured by Arakawa Chemical Industries, Ltd.] containing epoxy (meth)acrylate as an active energy ray curable compound and containing 65 parts by weight of silica-based fine particles having an average primary particle diameter of 5 to 100 nm per 100 parts by weight of the active energy ray curable compound was applied to one surface of a cycloolefin film (Tg: 135°C, thickness: 37 μm, stretch ratio: vertical 1.45 times) using a bar coater, and then placed in a hot air dryer and dried at 80°C for 60 seconds. Next, the coating film after drying was irradiated with ultraviolet light from a high pressure mercury lamp so that the accumulated light amount was 500 mJ/ ^cm2 to cure the coating film, and an optical film having a cured coating film with a thickness of 350 nm was obtained.

Example 9
An optical film was produced under the same conditions as in Example 8, except that a cured coating film was formed on both sides of the cycloolefin film.

Example 10
Optical films were produced under the same conditions as in Example 8, except that the thickness of the cured coating film was changed as shown in Table 2.

(Example 11)
Cured coating films were formed on both sides of a cycloolefin film, and optical films were produced under the same conditions as in Example 8, except that the thickness of the cured coating film was changed as shown in Table 2.

The following evaluations were carried out 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.
[Solvent resistance (edge cracks)]
A polyethylene terephthalate-based protective film with an adhesive layer (manufactured by Fujimori Kogyo Co., Ltd., NBO-0424, thickness 38 μm) was attached to both sides of the optical film, and then cut to a size of 50 mm x 50 mm to prepare a sample. Next, this sample was heated at 95°C for 10 minutes and immediately immersed in a hexane solvent for 3 minutes, and edge cracks generated in the sample were visually evaluated. The evaluation criteria are as follows.
◎: No edge cracks occurred. ◯: The number of edge cracks occurred was 1 to 10. △: The number of edge cracks occurred was 11 to 30. ×: The number of edge cracks occurred was 31 or more.

As shown in Table 2, the cycloolefin film of Reference Example 2 that does not have a cured coating on its surface had many fine cracks generated from the cut edge surface after immersion in hexane, approximately parallel to the stretching direction of the cycloolefin film. This phenomenon occurs because the shrinkage stress in the stretching direction of the cycloolefin film and the tensile stress of the protective film laminated to the cycloolefin film are perpendicular to each other, so it is presumed that solvent cracks are generated by the penetration of hexane from the edge surface, and edge cracks are generated by the tensile stress starting from the solvent cracks. On the other hand, as shown in Table 2, the cycloolefin films of Examples 8 to 11 that have a cured coating showed results that suppressed cracks from the cut edge surface after immersion in hexane. This is presumed to be because the cured coating has excellent solvent resistance to organic solvents, excellent adhesion to the cycloolefin film, and excellent restraining force, thereby suppressing solvent cracks caused by swelling and dissolution of the cycloolefin film, and restraining the shrinkage stress of the cycloolefin film, thereby suppressing the occurrence of cracks from the edge surface.

1: Optical film 2: Resin film 3: Cured coating film 4: Optical film 5: Adhesive layer 6: Polarizer 10: Polarizing plate

Claims

An optical film having a cured coating film of an active energy ray-curable composition on a 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 fine particles (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 parts by weight or more and 80 parts by weight or less based on 100 parts by weight of the active energy ray-curable compound (A);
The optical film has a thickness of more than 50 nm and less than 3,500 nm.
The optical film according to claim 1, characterized in that the epoxy (meth)acrylate (a1) contains multiple (meth)acryloyl groups and hydroxyl groups in the molecule.
The optical film described in claim 1, characterized in that the epoxy (meth)acrylate (a1) is a hydroxyl group-containing (meth)acrylic copolymer that is a reaction product of a radical polymer of a monomer component containing an epoxy group-containing mono(meth)acrylate and an α,β-unsaturated carboxylic acid.
The optical film according to claim 1, characterized in that the active energy ray curable compound (A) contains a hydroxyl group-containing polyfunctional (meth)acrylate (a2) having at least three (meth)acryloyl groups.
The optical film according to claim 1, characterized in that the inorganic fine particles (B) are silica fine particles.
The optical film according to claim 1 , wherein the resin film is a stretched film.