Curable composition, polarizer protective film and polarizing plate

Abstract

To provide: a curable composition capable of improving adhesiveness with a substrate while almost maintaining scratch resistance of a hard coat layer in a laminate such as a polarizer protective film having a hard coat layer on the surface of various substrates; a polarizer protective film composed of a laminate having a hard coat layer composed of a cured product of the curable composition on the surface of a substrate film; and a polarizing plate obtained by laminating the polarizer protective film on a polarizer.SOLUTION: There is provided a curable composition comprising a (meth)acrylate (M) having three or more radically polymerizable double bonds, an acrylic polymer (P) and an acrylic polymer (R) having a radically polymerizable double bond on the side chain. There is provided a polarizer protective film composed of a laminate obtained by laminating a hard coat layer composed of a cured product of the curable composition on one surface of a plastic film. There is provided a polarizing plate obtained by laminating a surface having no hard coat layer of the polarizer protective film on a polarizer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a curable composition for forming a hard coat layer for imparting scratch resistance to the surface of a plastic substrate, a polarizer protective film consisting of a laminate having a hard coat layer made of a cured product of the curable composition on the surface of a substrate film, and a polarizing plate obtained by laminating the polarizer protective film to a polarizer. [Background technology]

[0002] Polarizing plates used in liquid crystal displays and the like have a polarizer with a polarizer protective film laminated thereon. Conventionally, triacetyl cellulose (hereinafter referred to as TAC) films have been used as polarizer protective films. Since TAC films generally have low surface hardness, a hard coat layer is laminated on the surface to prevent scratches.

[0003] In recent years, as liquid crystal displays have become larger and thinner, the use of various plastic films such as acrylic polymers, which have higher moisture resistance than TAC, polyethylene terephthalate (hereinafter referred to as PET), and cyclic olefin polymers (hereinafter referred to as COP) as polarizer protective films has been considered.

[0004] In addition, in electronic devices having liquid crystal display devices such as mobile phones and smartphones, with the progress of diversifying designs, thinning, and enlarging the area, there is an increasing demand for the liquid crystal display device covers themselves to be thin, lightweight, inexpensive, etc. A glass substrate is generally used as the display cover, but with the demand for the display cover itself to be thin, lightweight, inexpensive, etc., the use of various plastic sheets similar to the above-mentioned polarizer protective film is currently being considered.

[0005] Such polarizer protective films and display covers are also required to have a hard coat layer on the surface to prevent scratches. For example, Patent Document 1 describes a laminate film in which a cured product of a curable composition containing (meth)acrylate and an acrylic polymer having a radically polymerizable double bond in a side chain is laminated on the surface of a cyclic olefin resin film, and a polarizing plate in which the laminate film is laminated on a polarizer. Patent Documents 2 and 3 describe a laminate film in which a cured product of a curable composition containing (meth)acrylate and an acrylic polymer having a radically polymerizable double bond in a side chain is laminated on the surface of a resin film. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2016 / 010115 [Patent Document 2] JP 2007-106955 A [Patent Document 3] JP 2007-230208 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the layer made of the cured product of the curable composition described in Patent Documents 1 to 3 has a problem of low adhesion to a substrate depending on the material of the substrate. On the other hand, when the cured product is softened, the adhesion generally tends to be improved, but there is a problem of sacrificing scratch resistance. The present invention aims to provide a curable composition that can improve adhesion to a substrate while generally maintaining the scratch resistance of the hard coat layer in a laminate such as a polarizer protective film having a hard coat layer on the surface of various substrates; a polarizer protective film consisting of a laminate having a hard coat layer made of a cured product of this curable composition on the surface of a substrate film; and a polarizing plate obtained by bonding this polarizer protective film to a polarizer. [Means for solving the problem]

[0008] The above problems can be solved by the present invention. The gist of the present invention is as follows [1] to

[13] . [1] A curable composition comprising: a (meth)acrylate (M) having three or more radically polymerizable double bonds; an acrylic polymer (P); and an acrylic polymer (R) having a radically polymerizable double bond in a side chain. [2] The curable composition according to the above [1], further comprising a photopolymerization initiator (I). [3] The curable composition according to [2], wherein the photopolymerization initiator (I) contains an intramolecular cleavage type photopolymerization initiator (I1). [4] The curable composition according to [3], wherein the intramolecular cleavage type photopolymerization initiator (I1) is a compound having a maximum absorption wavelength in the region of 280 nm or more and 380 nm or less in the light absorption spectrum. [5] The curable composition according to any one of the above [2] to [4], wherein the photopolymerization initiator (I) contains a hydrogen abstraction type photopolymerization initiator (I2). [6] The curable composition according to [5], wherein the hydrogen abstraction type photopolymerization initiator (I2) is a compound having a maximum absorption wavelength in the region of 200 nm or more and 280 nm or less in the light absorption spectrum. [7] The curable composition according to [6], wherein the hydrogen abstraction type photopolymerization initiator (I2) is benzophenone. [8] The curable composition according to any one of [1] to [7], wherein the (meth)acrylate (M) has 4 or more and 15 or less radically polymerizable double bonds. [9] The curable composition according to any one of the above [1] to [8], wherein the acrylic polymer (P) has a weight average molecular weight of 1,000 or more and 70,000 or less.

[10] The curable composition according to any one of [1] to [9], wherein the acrylic polymer (P) is a polymer having 80% or more by weight of structural units derived from methyl methacrylate.

[11] The curable composition according to any one of the above [1] to

[10] , wherein the amount of double bonds in the acrylic polymer (R) is 0.1 mmol / g or more and 10 mmol / g or less.

[12] A polarizer protective film comprising a laminate in which a hard coat layer made of a cured product of the curable composition according to any one of the above [1] to

[11] is laminated on only one side of a plastic film.

[13] A polarizing plate obtained by attaching the surface of the polarizer protective film according to

[12] above, which surface does not have a hard coat layer, to a polarizer. Effect of the Invention

[0009] According to the present invention, it is possible to provide a curable composition that can improve adhesion to a substrate while generally maintaining the scratch resistance of the hard coat layer in a laminate such as a polarizer protective film having a hard coat layer on the surface of various substrates; a polarizer protective film consisting of a laminate having a hard coat layer made of a cured product of this curable composition on the surface of a substrate film; and a polarizing plate obtained by bonding this polarizer protective film to a polarizer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] In the present invention, when the expression "(meth)acrylate" is used, it means one or both of "acrylate" and "methacrylate". When the expression "(meth)acryloyl" is used, it means one or both of "acryloyl" and "methacryloyl". When the expression "(meth)acrylic" is used, it means one or both of "acrylic" and "methacrylic".

[0011] The present invention relates to a curable composition (hereinafter also referred to as the composition of the present invention) containing a (meth)acrylate (M) having three or more radically polymerizable double bonds, an acrylic polymer (P), and an acrylic polymer (R) having a radically polymerizable double bond in a side chain.

[0012] By using the composition of the present invention, it is possible to form a cured layer having good adhesion to various substrates. This cured layer also has good scratch resistance, making it suitable as a hard coat layer.

[0013] [(Meth)acrylate (M)] The (meth)acrylate (M) having three or more radically polymerizable double bonds that constitutes the composition of the present invention contributes to improving the surface hardness of the cured layer.

[0014] Examples of the (meth)acrylate (M) include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris-2-hydroxyethyl isocyanurate tri(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane hexa(meth)acrylate, and the like. Examples of the polyfunctional (meth)acrylate include polyfunctional (meth)acrylates having three or more functional groups, such as (meth)acrylates; modified polyfunctional (meth)acrylate compounds in which a portion of these polyfunctional (meth)acrylates having three or more functional groups is substituted with an alkyl group or ε-caprolactone; polyfunctional (meth)acrylates having a nitrogen atom-containing heterocyclic structure, such as an isocyanurate structure; polyfunctional (meth)acrylates having a multi-branched resinous structure, such as polyfunctional (meth)acrylates having a dendrimer structure and polyfunctional (meth)acrylates having a hyperbranched structure; and urethane (meth)acrylates in which (meth)acrylates having a hydroxyl group, such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, are added to isocyanates, triisocyanates, and isocyanurates. Among these, from the viewpoint of compatibility with the acrylic polymer (P), pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate are preferred, and dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate are more preferred.

[0015] The number of radically polymerizable double bonds in the (meth)acrylate (M) is preferably from 4 to 15, and more preferably 10 or less, from the viewpoint of the scratch resistance of the cured product layer.

[0016] The composition of the present invention may contain monofunctional or difunctional (meth)acrylates other than the (meth)acrylate (M) in order to adjust the appearance of the cured layer and the viscosity of the composition liquid.

[0017] Examples of monofunctional (meth)acrylates include alkyl (meth)acrylates such as methyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate; methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, and ethoxypropyl (meth)acrylate; Examples of suitable (meth)acrylates include alkoxyalkyl (meth)acrylates such as acrylate; aromatic (meth)acrylates such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; amino group-containing (meth)acrylates such as diaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; ethylene oxide-modified (meth)acrylates such as methoxyethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate and phenylphenol ethylene oxide-modified (meth)acrylate; and heterocycle-containing (meth)acrylates such as glycidyl (meth)acrylate and tetrahydrofurfuryl (meth)acrylate.

[0018] Examples of bifunctional (meth)acrylates include alkanediol di(meth)acrylates such as 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and tricyclodecanedimethylol di(meth)acrylate; bisphenol-modified di(meth)acrylates such as bisphenol A ethylene oxide-modified di(meth)acrylate and bisphenol F ethylene oxide-modified di(meth)acrylate; polyalkylene glycol di(meth)acrylates such as polyethylene glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate; urethane di(meth)acrylate; and epoxy di(meth)acrylate.

[0019] [Acrylic polymer (P)] The acrylic polymer (P) constituting the composition of the present invention contributes to improving the adhesion between the cured layer and various substrates.

[0020] The acrylic polymer (P) is a polymer having a (meth)acrylic acid alkyl ester as a main structural unit, and is a polymer other than the acrylic polymer (R) having a radically polymerizable double bond in a side chain, which will be described in detail later. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, and n-hexyl (meth)acrylate. These may be used alone or in combination of two or more. Among these, methyl (meth)acrylate is preferred from the viewpoints of the compatibility of the acrylic polymer (P) with the (meth)acrylate (M) and the heat resistance of the hard coat layer.

[0021] The proportion of the constituent units derived from (meth)acrylic acid alkyl ester, particularly methyl methacrylate, constituting the acrylic polymer (P) is preferably 60% or more by weight, more preferably 70% or more, and even more preferably 80% or more and 99.9% or less. In order to improve the adhesion and surface hardness of the cured layer, the acrylic polymer (P) is also preferably one having a radically polymerizable double bond at its terminal.

[0022] The weight average molecular weight of the acrylic polymer (P) is preferably from 1000 to 70000, more preferably from 3000 to 60000, and even more preferably from 5000 to 50000. By using it within the above range, the scratch resistance and smoothness of the cured layer can be ensured.

[0023] The glass transition temperature (Tg) of the acrylic polymer (P) is preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher, from the viewpoint of improving the mechanical properties of the cured layer. The glass transition temperature (Tg) is preferably 140° C. or lower, more preferably 130° C. or lower, and even more preferably 120° C. or lower, from the viewpoint of improving the processability of the laminate obtained by laminating the cured layer.

[0024] The glass transition temperature (Tg) can be calculated from the type and mass fraction of the monomer units constituting the acrylic polymer (P) by the following Fox's formula. 1 / Tg=Σ(Wi / Tgi) In this formula, Tg is the glass transition temperature (unit: K) of the acrylic polymer (P), Wi is the mass fraction of the monomer unit derived from the monomer i constituting the acrylic polymer (P), and Tgi is the glass transition temperature (unit: K) of the homopolymer of the monomer i. The value of Tgi can be the value described in POLYMER HANDBOOK Volume 1 (WILEY-INTERSCIENCE).

[0025] Examples of the method for producing the acrylic polymer (P) include a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. The weight average molecular weight of the acrylic polymer (P) can be adjusted by a polymerization initiator, a chain transfer agent, a solid content concentration, reaction conditions, etc.

[0026] The composition of the present invention may contain an organic solvent. In this case, it is preferable to use a particulate acrylic polymer (P) because it can be easily dissolved in the organic solvent. The method for producing the particulate acrylic polymer (P) is preferably a suspension polymerization method.

[0027] Examples of the method for producing the acrylic polymer (P) by the suspension polymerization method include a method in which a polymerization initiator is added to an aqueous suspension containing water, a dispersant and a monomer, the suspension is heated to carry out polymerization, and then the aqueous suspension containing the particulate acrylic polymer (P) is filtered, washed, dehydrated and dried.

[0028] Examples of dispersants used in the suspension polymerization method include poly(alkali metal (meth)acrylate), copolymers of alkali metal (meth)acrylate and methyl (meth)acrylate, polyvinyl alcohol having a saponification degree of 70% to 100%, and methyl cellulose, etc. These may be used alone or in combination of two or more.

[0029] The amount of the dispersant added in the suspension polymerization method is preferably 0.005 parts by mass or more and 5 parts by mass or less, and more preferably 0.01 parts by mass or more and 1 part by mass or less, relative to 100 parts by mass of the total monomers to be polymerized, from the viewpoint of improving the dispersion stability in the suspension polymerization and the washability, dewaterability, drying property and flowability of the obtained particulate polymer.

[0030] In the suspension polymerization method, an electrolyte such as sodium carbonate, sodium sulfate, manganese sulfate, etc. may be added to the aqueous suspension for the purpose of improving the dispersion stability.

[0031] Examples of polymerization initiators used in the suspension polymerization method include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile); organic peroxides such as benzoyl peroxide, lauroyl peroxide, t-butylperoxy 2-ethylhexanoate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, and t-hexyl hydroperoxide; and inorganic peroxides such as hydrogen peroxide, sodium persulfate, and ammonium persulfate. These may be used alone or in combination of two or more.

[0032] When producing the acrylic polymer (P), a chain transfer agent can be used. Examples of the chain transfer agent include mercaptans such as n-dodecyl mercaptan, thioglycolic acid esters such as octyl thioglycolate, cobalt metal complexes such as bis(boron difluorodiphenyl glyoximate) cobalt (II), α-methylstyrene dimer, and terpinolene. These may be used alone or in combination of two or more. Among these, cobalt metal complexes such as bis(boron difluorodiphenyl glyoximate) cobalt (II) are preferred from the viewpoints of odor of the composition of the present invention and weather resistance of the cured product of the composition of the present invention.

[0033] The polymerization temperature in producing the acrylic polymer (P) is preferably from 50° C. to 130° C., more preferably from 60° C. to 100° C., from the viewpoints of short-time polymerization and polymerization stability.

[0034] [Acrylic polymer (R)] The acrylic polymer (R) having a radically polymerizable double bond in the side chain, which constitutes the composition of the present invention, contributes to the scratch resistance of the cured layer and adhesion to various substrates.

[0035] The acrylic polymer (R) having a radically polymerizable double bond in the side chain is a compound having a radically polymerizable double bond such as a carbon-carbon double bond in the side chain of the acrylic polymer. Examples of the method for introducing the double bond include a method of reacting an acrylic polymer having an epoxy group with a compound having a double bond and a carboxyl group (Method 1), a method of reacting an acrylic polymer having a carboxyl group with a compound having a double bond and an epoxy group (Method 2), a method of reacting an acrylic polymer having a hydroxyl group with a compound having a double bond and a carboxyl group (Method 3), a method of reacting an acrylic polymer having a carboxyl group with a compound having a double bond and a hydroxyl group (Method 4), a method of reacting an acrylic polymer having an isocyanate group with a compound having a double bond and a hydroxyl group (Method 5), and a method of reacting an acrylic polymer having a hydroxyl group with a compound having a double bond and an isocyanate group (Method 6). The above methods may be used in combination. In the following, a radically polymerizable monomer having a carbon-carbon double bond may be referred to as a vinyl monomer.

[0036] In the above-mentioned method 1, examples of vinyl monomers having an epoxy group used to obtain an acrylic polymer having an epoxy group include glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, and 3,4-epoxycyclohexylmethyl (meth)acrylate. Among these, glycidyl (meth)acrylate is preferred, and glycidyl methacrylate is particularly preferred, in consideration of good reactivity and ease of use of the material. These may be used alone or in combination of two or more.

[0037] In addition, the compound having a double bond and a carboxyl group in the method 1 may be, for example, (meth)acrylic acid, carboxyethyl (meth)acrylate, an adduct of glycerin di(meth)acrylate and succinic anhydride, an adduct of pentaerythritol tri(meth)acrylate and succinic anhydride, or an adduct of pentaerythritol tri(meth)acrylate and phthalic anhydride. Among these, (meth)acrylic acid and an adduct of pentaerythritol tri(meth)acrylate and succinic anhydride are preferred, and (meth)acrylic acid is particularly preferred. The compound having a double bond and a carboxyl group may be used alone or in combination of two or more.

[0038] In the method 2, examples of the vinyl monomer having a carboxyl group used to obtain an acrylic polymer having a carboxyl group include (meth)acrylic acid, carboxyethyl (meth)acrylate, and polybasic acid-modified (meth)acrylate. Among these, (meth)acrylic acid is preferred. These may be used alone or in combination of two or more.

[0039] In the method 2, examples of the compound having a double bond and an epoxy group include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, etc. Among these, glycidyl (meth)acrylate is preferred. These may be used alone or in combination of two or more.

[0040] In the method 3, examples of the vinyl monomer having a hydroxyl group used to obtain an acrylic polymer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxypropyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0041] In the method 3, the compound having a double bond and a carboxyl group may be the same as the compound in the method 1.

[0042] In the method 4, the acrylic polymer having a carboxyl group may be the same as that in the method 2.

[0043] In the method 4, examples of the compound having a double bond and a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxypropyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0044] In the method 5, examples of the vinyl monomer having an isocyanate group used to obtain an acrylic polymer having an isocyanate group include isocyanate ethyl (meth)acrylate.

[0045] In the method 5, the compound having a double bond and a hydroxyl group may be, for example, the same compound as that exemplified in the method 4.

[0046] In the method 6, the acrylic polymer having a hydroxyl group may be the same as the compound in the method 3.

[0047] In the method 6, examples of the compound having a double bond and an isocyanate group include isocyanate ethyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0048] Among the above methods, method 1 is preferred because the reaction is easy to control. In method 1, the double bond is introduced by a ring-opening addition reaction between the epoxy group of the acrylic polymer having an epoxy group and the carboxyl group of the compound having a double bond and a carboxyl group.

[0049] In the above-mentioned method 1, the monomer having an epoxy group in the acrylic polymer having an epoxy group is preferably 5% by weight or more, more preferably 10% by weight or more, even more preferably 20% by weight or more, and particularly preferably 50% by weight or more of the total amount of monomers constituting the acrylic polymer having an epoxy group. There is no particular upper limit, but it is preferably 99.9% by weight or less. By using it in this range, it is possible to achieve improvement in adhesion to the substrate and improvement in hardness.

[0050] In the method 1, the compound having a double bond and a carboxyl group is preferably 10 to 150 mol%, more preferably 30 to 130 mol%, and even more preferably 50 to 110 mol% relative to the epoxy groups in the acrylic polymer having an epoxy group. By using the compound in the above range, the reaction proceeds without excess or deficiency, and it is preferable from the viewpoint of reducing the residue of the raw material.

[0051] Furthermore, the acrylic polymer, such as the above-mentioned acrylic polymer having an epoxy group, may be a copolymer of (meth)acrylates other than those mentioned above or other vinyl monomers. The polymerization reaction of these raw materials is usually radical polymerization, and can be carried out under conventionally known conditions.

[0052] Monomers that can be used in combination as raw materials include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, methoxy(poly)ethylene glycol (meth)acrylate, methoxy(poly)propylene glycol (meth)acrylate, methoxy(poly)ethylene glycol (poly)propylene glycol (meth)acrylate, octoxy(poly)ethylene glycol (meth)acrylate, octoxy(poly)propylene glycol (meth)acrylate, )acrylate, octoxytetramethylene glycol (meth)acrylate, lauroxy(poly)ethylene glycol (meth)acrylate, stearoxy(poly)ethylene glycol (meth)acrylate, etc. (meth)acrylates; ethyl(meth)acrylamide, n-butyl(meth)acrylamide, i-butyl(meth)acrylamide, t-butyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, N-hydroxypropyl(meth)acrylamide, N,N-dihydroxyethyl(meth)acrylamide, etc. acrylamides; styrene, p-chlorostyrene, p-bromostyrene, etc. styrene monomers, etc. These may be used alone or in combination of two or more.

[0053] The acrylic polymer can be produced by a radical polymerization reaction using the above-mentioned raw material vinyl monomers. The radical polymerization reaction is preferably carried out in an organic solvent in the presence of a radical polymerization initiator.

[0054] Examples of organic solvents used in radical polymerization include ketone solvents such as acetone and methyl ethyl ketone (MEK), alcohol solvents such as ethanol, methanol, isopropyl alcohol (IPA), and isobutanol, ether solvents such as ethylene glycol dimethyl ether and propylene glycol monomethyl ether, ester solvents such as ethyl acetate, propylene glycol monomethyl ether acetate, and 2-ethoxyethyl acetate, and aromatic hydrocarbon solvents such as toluene. These organic solvents may be used alone or in combination of two or more.

[0055] Examples of radical polymerization initiators used in radical polymerization include organic peroxides such as benzoyl peroxide and di-t-butyl peroxide; and azo compounds such as 2,2'-azobisbutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile). These radical polymerization initiators may be used alone or in combination of two or more. The radical polymerization initiator is preferably used in the range of 0.01 to 5 parts by weight per 100 parts by weight of the total of the vinyl monomers as the raw material.

[0056] In addition, during radical polymerization, a chain transfer agent can be used for the purpose of controlling the weight average molecular weight of the acrylic polymer. Examples of the chain transfer agent include butanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, cyclohexyl mercaptan, thiophenol, octyl thioglycolate, octyl 2-mercaptopropionate, octyl 3-mercaptopropionate, 2-ethylhexyl mercaptopropionate, 2-ethylhexyl thioglycolate, butyl-3-mercaptopropionate, mercaptopropyltrimethoxysilane, methyl-3-mercaptopropionate, 2,2-(ethylenediaminetetraacetate), ... Examples of the thiol-based compounds include thiol compounds such as oxy)diethanethiol, ethanethiol, 4-methylbenzenethiol, octanoic acid 2-mercaptoethyl ester, 1,8-dimercapto-3,6-dioxaoctane, decane trithiol, dodecyl mercaptan, diphenyl sulfoxide, dibenzyl sulfide, 2,3-dimethylcapto-1-propanol, mercaptoethanol, thiosalicylic acid, thioglycerol, thioglycolic acid, 3-mercaptopropionic acid, thiomalic acid, mercaptoacetic acid, mercaptosuccinic acid, and 2-mercaptoethanesulfonic acid. These may be used alone or in combination of two or more.

[0057] The amount of the chain transfer agent used is preferably 0.1 to 25 parts by weight, more preferably 0.5 to 20 parts by weight, and even more preferably 1.0 to 15 parts by weight, based on 100 parts by weight in total of the vinyl monomers as the raw material.

[0058] The reaction time of the radical polymerization is preferably 1 to 20 hours, more preferably 3 to 12 hours, and the reaction temperature is preferably 40 to 120°C, more preferably 50 to 100°C.

[0059] In order to react a compound having a double bond and a carboxyl group with an acrylic polymer, the compound having a double bond and a carboxyl group is added to the acrylic polymer obtained as described above, and reacted in the presence of one or more catalysts such as triphenylphosphine, tetrabutylammonium bromide, tetramethylammonium chloride, and triethylamine at a temperature of usually 90 to 140 ° C., preferably 100 to 120 ° C., for usually about 3 to 9 hours. Here, it is preferable to use the catalyst in a ratio of about 0.5 to 3 parts by weight per 100 parts by weight of the total of the raw material (meth)acrylic acid ester polymer and the compound having a double bond and a carboxyl group. This reaction may be carried out continuously after the acrylic polymer is produced by polymerization reaction, or may be carried out by adding the compound having a double bond and a carboxyl group after once separating the acrylic polymer from the reaction system.

[0060] The amount of double bonds in the acrylic polymer (R) is preferably 0.1 to 10 mmol / g, more preferably 0.5 to 7.0 mmol / g, further preferably 1.0 to 6.0 mmol / g, and particularly preferably 2.5 to 5.0 mmol / g. By using within this range, the scratch resistance of the cured layer and the adhesion to various substrates are improved. The amount of double bonds means the concentration of (meth)acryloyl groups in the acrylic polymer, that is, the amount of (meth)acryloyl groups introduced.

[0061] [Composition ratio of curable composition] The proportion of the (meth)acrylate (M) in the composition of the present invention is preferably 5 to 90% by weight, more preferably 10 to 80% by weight, further preferably 15 to 70% by weight, and particularly preferably 20 to 60% by weight, based on all components excluding the solvent. By using it within this range, good scratch resistance can be obtained.

[0062] The proportion of the acrylic polymer (P) in the composition of the present invention is preferably 5 to 80% by weight, more preferably 8 to 70% by weight, further preferably 10 to 60% by weight, and particularly preferably 15 to 50% by weight, based on all components excluding the solvent. By using it within this range, good adhesion between the cured product layer and the substrate can be obtained.

[0063] The proportion of the acrylic polymer (R) in the composition of the present invention is preferably 5 to 80% by weight, more preferably 8 to 60% by weight, further preferably 10 to 50% by weight, and particularly preferably 12 to 40% by weight, based on all components excluding the solvent. By using it within this range, it becomes easier to achieve both scratch resistance and adhesion between the cured product and the substrate.

[0064] [Photopolymerization initiator (I)] In addition, the composition of the present invention preferably further contains a photopolymerization initiator (I). The photopolymerization initiator (I) has a catalytic action of inducing a polymerization reaction by light irradiation, and therefore, it is expected to improve the curability of the composition of the present invention. Examples of the photopolymerization initiator (I) include an intramolecular cleavage type photopolymerization initiator (I1) and a hydrogen abstraction type photopolymerization initiator (I2). The intramolecular cleavage type photopolymerization initiator (I1) is a type that absorbs given light to become excited, and then photocleaves itself to generate two radicals, while the hydrogen abstraction type photopolymerization initiator (I2) is a type that abstracts hydrogen from other molecules to generate radicals.

[0065] The use of an intramolecular cleavage type photopolymerization initiator (I1) improves scratch resistance, while the use of a hydrogen abstraction type photopolymerization initiator (I2) tends to improve adhesion of the cured layer to the substrate. In addition, by using these in combination, both scratch resistance and adhesion can be achieved.

[0066] Examples of the intramolecular cleavage type photopolymerization initiator (I1) include 1-hydroxycyclohexyl phenyl ketone [e.g., trade name "Omnirad (registered trademark) 184", manufactured by IGM], 2,2-dimethoxy-1,2-diphenylethan-1-one [e.g., trade name "Omnirad (registered trademark) 651", manufactured by IGM], bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide [e.g., trade name "Omnirad (registered trademark) 819", manufactured by IGM], 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one [e.g., trade name "Omnirad (registered trademark) 907", manufactured by IGM], and 2-hydroxy-2-methyl-1-phenylpropan-1-one [e.g., trade name "Darocure (registered trademark) 1173", manufactured by IGM]. These may be used alone or in combination of two or more kinds. Among these, compounds such as 2,2-dimethoxy-1,2-diphenylethan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, which have a maximum absorption wavelength in the wavelength range of 280 nm or more and less than 380 nm in the light absorption spectrum, are preferred because they are easily cleaved even by light rays with relatively low energy and have high curability.

[0067] Examples of the hydrogen abstraction type photopolymerization initiator (I2) include benzophenones such as 2-ethylanthraquinone, 2,4-diethylthioxanthone, benzophenone and derivatives thereof. These may be used alone or in combination of two or more. Among these, compounds having a maximum absorption wavelength in the wavelength range of 200 nm or more and less than 280 nm in the light absorption spectrum are preferred because when a curable composition applied to a substrate is irradiated with active energy rays to form a cured layer, the curing of the deep part of the coating film is delayed compared to the surface, thereby increasing the adhesion between the cured layer and the substrate. Examples of such compounds include benzophenone.

[0068] The content of the photopolymerization initiator (I) in the composition of the present invention is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, based on 100 parts by mass of the total of the compounds having a (meth)acryloyl group, from the viewpoint of improving the curability of the composition of the present invention. Also, from the viewpoint of good stability of the composition of the present invention, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less.

[0069] [Light absorber (H)] The composition of the present invention is also preferably further comprised of a light absorber (H). By blending the light absorber (H), deterioration of the cured layer can be prevented, and the adhesion of the cured layer can be improved. Examples of the light absorber (H) include an ultraviolet absorber and a hindered amine-based light stabilizer.

[0070] Examples of ultraviolet absorbers include 2-(2-hydroxy-5-tert-butylphenyl)-2H-benzotriazole [e.g., trade name "Tinuvin (registered trademark) PS", manufactured by BASF] and 2,4-bis(2-hydroxy-4-butyloxyphenyl)-6-(2,4-bis-butyloxyphenyl)-1,3,5-triazine [e.g., trade name "Tinuvin (registered trademark) 460", manufactured by BASF].

[0071] Examples of the hindered amine light stabilizer include bis[2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidine sebacate [e.g., trade name "Tinuvin (registered trademark) 123", manufactured by BASF] and bis[1,2,2,6,6-pentamethyl-4-piperidine sebacate [e.g., trade name "Tinuvin (registered trademark) 292", manufactured by BASF].

[0072] These light absorbents (H) may be used alone or in combination of two or more. Among these, bis[2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidine] sebacate is preferred because it has good compatibility with the (meth)acrylate (M) and the acrylic polymer (P).

[0073] The content of the light absorber (H) in the composition of the present invention is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, based on 100 parts by mass of the compounds having (meth)acryloyl groups in total, from the viewpoint of improving the adhesion of the cured layer. Also, from the viewpoint of improving the curability, the content is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less.

[0074] [Other ingredients] The composition of the present invention may contain "other components" other than the (meth)acrylate (M), acrylic polymer (P), acrylic polymer (R), photopolymerization initiator (I), light absorber (H), and (meth)acrylate (M) described above, as long as the effects of the present invention are not impaired. Examples of other components include organic solvents, fillers, silane coupling agents, antistatic agents, organic pigments, organic particles, inorganic particles, leveling agents, dispersants, thixotropy-imparting agents (thickeners), antifoaming agents, antioxidants, and photoacid generators.

[0075] The organic solvent is not particularly limited, and can be appropriately selected in consideration of the type of components contained in the curable composition. Specific examples of the organic solvent include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone (MEK), acetone, methyl isobutyl ketone (MIBK), and cyclohexanone; ether solvents such as diethyl ether, isopropyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether (PGM), anisole, and phenetole; ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, and ethylene glycol diacetate; amide solvents such as dimethylformamide, diethylformamide, and N-methylpyrrolidone; cellosolve solvents such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; alcohol solvents such as methanol, ethanol, propanol, isopropanol, and butanol; and halogen solvents such as dichloromethane and chloroform.

[0076] The organic solvent may be used alone or in combination of two or more. Among these, ester-based solvents, ether-based solvents, alcohol-based solvents and ketone-based solvents are preferred because they provide good compatibility between the (meth)acrylate (M) and the acrylic polymer (P).

[0077] [Method of producing curable composition] The method for producing the composition of the present invention is not particularly limited, and examples thereof include a method of mixing the (meth)acrylate (M), the acrylic polymer (P), the acrylic polymer (R), and, if necessary, the polymerization initiator (I), the light absorber (H), a (meth)acrylate other than the (meth)acrylate (M), and other components, etc. When mixing, it is preferable to mix uniformly using a disperser, a stirrer, etc.

[0078] [Base material] The substrate on which the cured layer of the composition of the present invention is laminated may be made of various materials, but a plastic substrate is particularly suitable in terms of adhesion to the cured layer. The substrate may be in the form of a sheet, a film, or the like.

[0079] Examples of materials for the plastic substrate include polyester resin, polycarbonate resin, polyurethane resin, polyamide resin, polyimide resin, polyvinyl alcohol resin, polyethylene resin, polypropylene resin, polycycloolefin resin, triacetyl cellulose resin, acrylic resin, etc. Among these, triacetyl cellulose resin, acrylic resin, polyester resin, and polycycloolefin resin are preferred because of their good transparency and optical properties, and acrylic resin is preferred because of their good mechanical properties and heat resistance.

[0080] In addition, the portion of the substrate other than the surface on which the cured layer is directly laminated, for example, the inside of the substrate or the opposite surface, may be made of a material different from that of the surface. Examples of such different materials include polyester resin, polycarbonate resin, polyurethane resin, polyamide resin, polyimide resin, polyvinyl alcohol resin, polyethylene resin, polypropylene resin, polycycloolefin resin, triacetyl cellulose resin, (meth)acrylic resin, etc. Among these, polycarbonate resin is preferred because of its good transparency and heat resistance, and polyvinyl alcohol resin is preferred because of its good chemical resistance. Therefore, the substrate is preferably one in which a layer of the plastic substrate is laminated on a layer of these resins.

[0081] The substrate can be produced by any method, such as a melt extrusion method such as an inflation method or a T-die method, a solution casting method, a calendar method, etc. Furthermore, uniaxial or biaxial stretching treatment may be performed as necessary.

[0082] In addition to the resin, the base material may contain additives such as a functional polymer, an ultraviolet absorber, an antioxidant, a plasticizer, a release agent, a coloring inhibitor, a colorant, an antistatic agent, a flame retardant, a retardation reducing agent, inorganic particles, and organic particles.

[0083] [Laminate] The method of manufacturing a laminate by laminating a cured product layer of the composition of the present invention on a substrate is not particularly limited, but for example, a method of applying the composition of the present invention to the surface of the substrate and curing it can be mentioned. Note that the laminate may have a cured product layer formed on only a part of the surface of the substrate, for example, only one side when the substrate is in the form of a sheet or film, or may have a cured product layer formed on the other side, for example, the back side when the substrate is in the form of a sheet or film. The cured product layer functions as a hard coat layer of the substrate.

[0084] Examples of methods for applying the composition of the present invention to a substrate include reverse coating, gravure coating, rod coating, bar coating, Mayer bar coating, die coating, and spray coating.

[0085] A method for curing the composition applied to the substrate includes a method in which the composition is dried at a temperature of preferably 40° C. to 100° C., more preferably 50° C. to 80° C., and then irradiated with active energy rays at a temperature of 40° C. to 100° C. Examples of active energy rays include ultraviolet rays, electron beams, X-rays, infrared rays, and visible light. Among these, ultraviolet rays and electron beams are preferred from the viewpoints of curability and prevention of deterioration of the substrate.

[0086] When ultraviolet rays are used as the active energy rays, various ultraviolet ray irradiation devices can be used. As the light source of the ultraviolet ray irradiation device, a xenon lamp, a high-pressure mercury lamp, a metal halide lamp, an LED-UV lamp, etc. can be used.

[0087] The amount of ultraviolet light irradiation is determined appropriately depending on the reaction rate of the (meth)acryloyl group required in the curing process, but is usually 10 mJ / cm 2 More than 10000mJ / cm 2 From the viewpoints of the curability of the curable composition, the flexibility of the cured product, etc., it is preferable that the curing rate is 20 mJ / cm or less. 2 More than 5000mJ / cm 2 Less than 30 mJ / cm is preferable. 2More than 3000mJ / cm 2 Less than 50 mJ / cm is more preferable. 2 More than 1000mJ / cm 2 In order to improve productivity, it is more preferable that the irradiation amount is even lower, and it is preferably 500 mJ / cm2 or less. 2 Below 400mJ / cm 2 Below, especially 200mJ / cm 2 The following are preferred: The composition of the present invention is characterized in that it easily exhibits its performance even with a small amount of irradiation.

[0088] The UV light intensity is 50mW / cm 2 More than 600mW / cm 2 Less than 75mW / cm is preferable. 2 More than 450mW / cm 2 Less than 100 mW / cm is more preferable. 2 More than 300mW / cm 2 The following is even more preferred:

[0089] When using electron beams as active energy rays, various electron beam irradiation devices can be used. The irradiation dose of electron beams is appropriately determined according to the reaction rate of (meth)acryloyl group required in the curing process, but is usually 0.5 Mrad or more and 20 Mrad or less. From the viewpoints of the curability of the composition, the flexibility of the cured product, and the prevention of damage to the substrate, it is preferably 1 Mrad or more and 15 Mrad or less.

[0090] In forming the cured layer, the coating and curing of the composition of the present invention may be carried out once or multiple times. By repeating the coating and curing multiple times, warping of the substrate can be prevented.

[0091] The thickness of the cured layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 4 μm or more from the viewpoint of the pencil hardness and scratch resistance of the resulting laminate, and is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, and particularly preferably 8 μm or less from the viewpoint of crack resistance.

[0092] The thickness of the substrate is not limited. When the substrate is in the form of a film, the thickness is preferably from 5 μm to 3 mm, more preferably from 10 μm to 2 mm, further preferably from 15 μm to 1 mm, and particularly preferably from 20 μm to 250 μm.

[0093] The thickness of the laminate is also arbitrary. In the case of a film-like laminate, the thickness of the laminate is preferably 6 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, because each layer needs to fully exert its respective function. In addition, from the viewpoint of the demand for thinning and weight reduction of the product to which the laminate is applied, the thickness of the laminate is preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and particularly preferably 300 μm or less.

[0094] The laminate obtained by laminating the cured product layer of the composition of the present invention on a substrate as a hard coat layer has excellent adhesion between the substrate and the hard coat layer and excellent scratch resistance. Therefore, the laminate can be suitably used for surface covers of a wide range of products, such as optical display parts such as liquid crystal televisions, organic EL televisions, electronic paper, touch panels, and smartphones; automobile-related parts such as lamp-related products and window-related products (rear windows, side windows, skylights, etc.); and housings for various electrical devices, decorative panels, and lifestyle-related products such as furniture. Among these, the laminate is suitable for optical display parts, and can be particularly suitable for polarizer protective films and display protective films that are attached to polarizers in the manufacture of polarizing plates for displays.

[0095] [Polarizer protection film, polarizing plate] The polarizer protective film of the present invention is a laminate in which a hard coat layer made of a cured product of the composition of the present invention is laminated on only one side of a plastic film. The polarizing plate of the present invention is obtained by laminating the side of the polarizer protective film of the present invention that does not have a hard coat layer to a polarizer. The polarizer protective film can be laminated to one or both sides of the polarizer. An adhesive, a pressure sensitive adhesive, or the like can be used for lamination. EXAMPLES

[0096] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples as long as it does not depart from the gist of the present invention.

[0097] [Weight average molecular weight (Mw) of acrylic polymer (P)] The weight average molecular weight (Mw) of the acrylic polymer (P) was measured using a gel permeation chromatography (GPC) "HLC-8120" (manufactured by Tosoh Corporation). The column used was TSKgel G5000HXL*GMHXL-L (manufactured by Tosoh Corporation). In addition, a calibration curve was created using F288 / F80 / F40 / F10 / F4 / F1 / A5000 / A1000 / A500 (manufactured by Tosoh Corporation) and styrene as standard polystyrenes. The measurement was carried out using 100 μl of a solution in which the polymer was dissolved in tetrahydrofuran to a concentration of 0.4%, at a column oven temperature of 40° C. The weight average molecular weight (Mw) was calculated in terms of standard polystyrene.

[0098] The examples and comparative examples were evaluated by the following methods. [Adhesion evaluation] The surface of the laminate on the cured layer side was evaluated according to the JIS K-5400 checkerboard peel test (number of checkers: 100), and the squares remaining after the peel test were evaluated. The more checkers remaining, the better the adhesion. In particular, for initial adhesion (adhesion without weather resistance testing), it is important that there is no peeling, preferably 96 or more, more preferably 98 or more, and even more preferably 100 (no peeling), and 100 is important for use in various applications.

[0099] [Evaluation of scratch resistance] The surface of the laminate on the side of the cured layer was fixed on a flat surface friction tester (manufactured by Coating Tester Co., Ltd.) and subjected to a friction load of 100 g / cm 2The steel wool #0000 was fixed to a jig so that the sliding surface of the steel wool with a load of 100 mm was approximately 2 cm x 2 cm, and a scratch resistance test was performed by moving the steel wool back and forth 10 times over a distance of 5 cm. The scratch resistance was evaluated by visually checking the number of scratches on the surface according to the following criteria. 5: Less than 5 scratches 4: 6-10 scratches 3: 11-20 scratches 2: 21-25 scratches 1: Many scratches, over 26 The higher the evaluation result, the better the result. 4 or more is preferable, and 5 is more preferable.

[0100] [(Meth)acrylate (M)] As the (meth)acrylate (M) having three or more radically polymerizable double bonds, the following commercially available products were used. (B-1I) Viscoat (registered trademark) #300 (manufactured by Osaka Organic Chemical Industry Ltd.) Mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (B-1II) NK Ester (registered trademark) A-TMPT (manufactured by Shin-Nakamura Chemical Co., Ltd.) Trimethylolpropane Triacrylate (B-1III) Kayarad (registered trademark) DPHA (manufactured by Nippon Kayaku Co., Ltd.) Mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate

[0101] [Acrylic polymer (P)] As the acrylic polymer (P), a polymer (B-2I) produced by the method described in the following Production Examples 1-1 to 1-3, or a polymer (B-2II) produced by the method described in Production Example 1-4 was used.

[0102] [Production Example 1-1] Production of Dispersant (X) In a flask equipped with a stirrer, a cooling tube and a thermometer, 900 parts of deionized water, 60 parts of 2-sulfoethyl sodium methacrylate, 10 parts of potassium methacrylate and 12 parts of methyl methacrylate were put and stirred, and the temperature was raised to 50°C while replacing the atmosphere in the flask with nitrogen. Next, 0.08 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride was added as a polymerization initiator to the flask, and the temperature was further raised to 60°C. After the temperature was raised, 18 parts of methyl methacrylate were continuously dropped at a rate of 0.24 parts / min using a dropping pump. The obtained reaction solution was kept at 60°C for 6 hours, and then cooled to room temperature to obtain a dispersant (X) with a solid content of 10% as a transparent aqueous solution.

[0103] [Production Example 1-2] Production of chain transfer agent (Y) In a flask equipped with a stirrer, 1.00 g of cobalt (II) acetate tetrahydrate, 1.93 g of diphenylglyoxime, and 80 ml of diethyl ether previously deoxygenated by nitrogen bubbling were placed under a nitrogen atmosphere and stirred at room temperature for 30 minutes. Then, 10 ml of boron trifluoride diethyl ether complex was added and stirred for another 6 hours. The resulting reaction product was filtered, the solid was washed with diethyl ether, and vacuum dried for 15 hours to obtain 2.12 g of a reddish brown solid chain transfer agent (Y).

[0104] [Production Example 1-3] Production of polymer (B-2I) In a flask equipped with a stirrer, a cooling tube, and a thermometer, 145 parts of deionized water, 0.1 parts of sodium sulfate, and 0.25 parts of dispersant (X) were added and stirred to obtain a uniform aqueous solution. Next, a monomer mixture of 100 parts of methyl methacrylate, 0.005 parts of chain transfer agent (Y), and 0.4 parts of 2,2'-azobis(2-methylbutyronitrile) was added to the flask to obtain an aqueous suspension. Next, the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 80°C, and the reaction was carried out for about 1 hour, and in order to further increase the polymerization rate, the temperature was raised to 93°C and maintained for 1 hour. Next, the reaction liquid was cooled to 40°C to obtain an aqueous polymer suspension. The polymer contained in this aqueous polymer suspension was filtered using a nylon filter cloth with a mesh size of 45 μm, washed with deionized water, and then dried at 40°C for 16 hours to obtain a polymer (B-2I). The polymer (B-2I) had a glass transition temperature (Tg) of 82° C. and a weight average molecular weight (Mw) of 7,800.

[0105] [Production Example 1-4] Production of polymer (B-2II) In a flask equipped with a stirrer, a cooling tube, and a thermometer, 145 parts of deionized water, 0.1 parts of sodium sulfate, and 0.25 parts of dispersant (X) were added and stirred to obtain a uniform aqueous solution. Next, a monomer mixture of 100 parts of methyl methacrylate, 0.9 parts of n-dodecyl mercaptan, and 0.2 parts of 2,2'-azobis(2-methylbutyronitrile) was added to the flask to obtain an aqueous suspension. Next, the atmosphere in the flask was replaced with nitrogen, the temperature was raised to 68°C, and the reaction was carried out for about 3 hours, and in order to further increase the polymerization rate, the temperature was raised to 93°C and maintained for 1 hour. Next, the reaction solution was cooled to 40°C to obtain an aqueous polymer suspension. The polymer contained in this aqueous polymer suspension was filtered using a nylon filter cloth with a mesh size of 45 μm, washed with deionized water, and then dried at 40°C for 16 hours to obtain a polymer (B-2II). The polymer (B-2II) had a glass transition temperature (Tg) of 105° C. and a weight average molecular weight (Mw) of 40,000.

[0106] [Acrylic polymer (R)] As the acrylic polymer (R) having a radically polymerizable double bond in the side chain, polymers (B-3I) and (B-3II) produced by the methods described in the following Production Examples 2-1 and 2-2 were used.

[0107] [Production Example 2-1] Production of (B-3I) Propylene glycol monomethyl ether (178 parts by mass), glycidyl methacrylate (66 parts by mass), methyl methacrylate (33 parts by mass), ethyl acrylate (1.0 part by mass), and 2,2'-azobis(2,4-dimethylvaleronitrile) (1.0 part by mass) were added to a flask equipped with a thermometer, a stirrer, and a reflux condenser, and the mixture was reacted at 65°C for 3 hours. Then, 2,2'-azobis(2,4-dimethylvaleronitrile) (0.5 parts by mass) was further added and reacted for 3 hours, after which propylene glycol monomethyl ether (48 parts by mass) and p-methoxyphenol (0.5 parts by mass) were added and heated to 100°C. Next, acrylic acid (34 parts by mass) and triphenylphosphine (1.6 parts by mass) were added and reacted at 110°C for 6 hours to obtain an acrylic polymer (B-3I) having a double bond capable of radical polymerization in the side chain with a double bond amount (acryloyl group concentration (amount of acryloyl group introduced)) of 3.4 mmol / g.

[0108] [Production Example 2-2] Production of (B-3II) Propylene glycol monomethyl ether (178 parts by mass), glycidyl methacrylate (20 parts by mass), methyl methacrylate (79 parts by mass), ethyl acrylate (1.0 part by mass), and 2,2'-azobis(2,4-dimethylvaleronitrile) (0.6 parts by mass) were added to a flask equipped with a thermometer, a stirrer, and a reflux condenser, and the mixture was reacted at 65°C for 3 hours. Then, 2,2'-azobis(2,4-dimethylvaleronitrile) (0.3 parts by mass) was further added and reacted for 3 hours, after which propylene glycol monomethyl ether (48 parts by mass) and p-methoxyphenol (0.5 parts by mass) were added and heated to 100°C. Next, acrylic acid (10 parts by mass) and triphenylphosphine (1.6 parts by mass) were added and reacted at 110°C for 6 hours to obtain an acrylic polymer (B-3I) having a double bond capable of radical polymerization in the side chain with a double bond amount (acryloyl group concentration (amount of acryloyl group introduced)) of 1.2 mmol / g.

[0109] As the inorganic particles, the following commercially available products were used. MEK-AC-2140Z (Nissan Chemical Co., Ltd.) Silica sol dispersed in methyl ethyl ketone (SiO2 40%)

[0110] As the photopolymerization initiator (I), the following commercially available product was used. (C-1) Benzophenone (manufactured by Daido Chemical Industry Co., Ltd.) (C-2) Omnirad-651 (manufactured by IGM) 2,2-Dimethoxy-1,2-diphenylethan-1-one

[0111] The following films were used as substrates: (F-1) A film (acrylic resin film) in which a polymethyl methacrylate layer and a polyethylene terephthalate layer are laminated, with the polymethyl methacrylate layer side of 40 μm thickness used (F-2) Triacetyl cellulose film, thickness 40 μm

[0112] [Example 1] A curable composition was obtained by mixing 30 parts by mass of "B-1I" as the (meth)acrylate (M), 70 parts by mass of "B-1III", 70 parts by mass of "B-2I" as the acrylic polymer (P), 30 parts by mass of "B-3I" as the acrylic polymer (R), and 6.2 parts by mass of "C-1", and diluting the mixture with a solvent, methyl isobutyl ketone (MIBK), to a solids concentration of 40% by mass.

[0113] The obtained curable composition was applied to the polymethyl methacrylate layer side of the acrylic resin film "F-1" as the substrate using a bar coater #10 so that the coating thickness after drying would be 5 μm, and then heated and dried at 70° C. for 1 minute. The coating of the curable composition was exposed to UV illumination of 120 mW / cm using Iwasaki Electric Co., Ltd.'s "US5-X0401" with a high-pressure mercury lamp as the light source. 2 The cumulative light intensity is 200 mJ / cm 2 The curable composition was cured by irradiating with ultraviolet light once so that the curable composition became cured, and a cured product layer was laminated on the surface of the substrate on the side of the polymethyl methacrylate layer to obtain a laminate.

[0114] The obtained laminate was evaluated for scratch resistance and adhesion. The evaluation results were both good, with the adhesion being 100 and the scratch resistance being 5. The composition of the curable composition (unit: parts by mass) and the evaluation results are shown in Table 1.

[0115] [Examples 2 to 10] A laminate was obtained by laminating a cured product layer in the same manner as in Example 1, except that the composition of the curable composition and the substrate film were changed as shown in Table 1. The evaluation results of the obtained laminate are shown in Table 1.

[0116] [Comparative Examples 1 to 3] A laminate was obtained by laminating a cured product layer in the same manner as in Example 1, except that the composition of the curable composition and the substrate film were changed as shown in Table 2. As shown in Table 2, the evaluation results of the obtained laminate were poor in either one or both of adhesion and scratch resistance.

[0117] [Table 1]

[0118] [Table 2] [Industrial Applicability]

[0119] A laminate obtained by laminating a cured product layer of the composition of the present invention as a hard coat layer on a substrate can be widely used in optical display components such as liquid crystal televisions, organic EL televisions, electronic paper, touch panels, smartphones, etc. In particular, it can be suitably used as a polarizer protective film to be attached to a polarizer in the production of a polarizing plate for a display, or as a display protective film.

Claims

1. A curable composition comprising: A (meth)acrylate (M) having three or more radically polymerizable double bonds; An acrylic polymer (P) (excluding the acrylic polymer (R)), an acrylic polymer (R) having a radically polymerizable double bond in a side chain; Contains The weight average molecular weight of the acrylic polymer (P) is 1,000 or more and 70,000 or less, the amount of double bonds in the acrylic polymer (R) is 0.1 mmol / g or more and 10 mmol / g or less, the proportion of the (meth)acrylate (M) in the curable composition is 5 to 90% by weight based on all components excluding the solvent; The proportion of the acrylic polymer (P) in the curable composition is 5 to 80% by weight based on all components excluding the solvent, A curable composition for use in a polarizing plate protective film, wherein the proportion of the acrylic polymer (R) in the curable composition is 5 to 80% by weight based on all components excluding the solvent.

2. The curable composition according to claim 1 , further comprising a photopolymerization initiator (I).

3. The curable composition according to claim 2 , wherein the photopolymerization initiator (I) comprises an intramolecular cleavage type photopolymerization initiator (I1).

4. The curable composition according to claim 3 , wherein the intramolecular cleavage type photopolymerization initiator (I1) is a compound having a maximum absorption wavelength in the region of 280 nm or more and 380 nm or less in the light absorption spectrum.

5. The curable composition according to any one of claims 2 to 4, wherein the photopolymerization initiator (I) comprises a hydrogen abstraction type photopolymerization initiator (I2).

6. The curable composition according to claim 5 , wherein the hydrogen abstraction type photopolymerization initiator (I2) is a compound having a maximum absorption wavelength in the region of 200 nm or more and 280 nm or less in the light absorption spectrum.

7. The curable composition according to claim 6, wherein the hydrogen abstraction type photopolymerization initiator (I2) is benzophenone.

8. The curable composition according to any one of claims 1 to 7, wherein the (meth)acrylate (M) has 4 or more and 15 or less radically polymerizable double bonds.

9. The curable composition according to any one of claims 1 to 8, wherein the acrylic polymer (P) is a polymer having 80% or more by weight of structural units derived from methyl methacrylate.

10. 10. A polarizer protective film comprising a laminate in which a hard coat layer made of a cured product of the curable composition according to any one of claims 1 to 9 is laminated on only one side of a plastic film.

11. A polarizing plate obtained by attaching the surface of the polarizer protective film according to claim 10 that does not have a hard coat layer to a polarizer.

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