Adhesive composition for optical film

Abstract

The present invention addresses the problem of providing an adhesive composition which is capable of forming an adhesive that has enhanced refractive index and transparency regardless of film thickness.　An adhesive composition for an optical film according to the present invention contains a copolymer (A), a monomer (a), and inorganic particles (B). The adhesive composition is characterized in that: the copolymer (A) contains a constituent unit (A1) derived from an aromatic hydrocarbon group-containing (meth)acrylic acid ester-based monomer (a1) and a constituent unit (A2) derived from a hydroxyl group-containing (meth)acrylic acid ester-based monomer (a2); the monomer (a) includes an aromatic hydrocarbon group-containing (meth)acrylic acid ester-based monomer (a1) and a hydroxyl group-containing (meth)acrylic acid ester-based monomer (a2); the content of the constituent unit (A2) is 1-40 mass% in 100 mass% of the copolymer (A); and the proportion of the monomer (a) is 45-95 mass% in a total of 100 mass% of the copolymer (A) and the monomer (a).

Description

Pressure-sensitive adhesive composition for optical films

[0001] The present invention relates to a pressure-sensitive adhesive composition for an optical film and a pressure-sensitive adhesive layer.

[0002] Image display devices such as liquid crystal display devices, organic EL display devices, and plasma display panels, as well as optical discs, include optical films such as polarizing plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion films, etc. When bonding optical films together or an optical film to another member, a method of using a pressure-sensitive adhesive with a high refractive index is known in order to prevent the functions of the optical film from being impaired.

[0003] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition containing, as a main component, a (meth)acrylic acid ester polymer containing, as monomer units constituting the polymer, a monomer having a plurality of aromatic rings and a monomer having a hydroxyl group.

[0004] Japanese Patent Application Laid-Open No. 2017-128732

[0005] The pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition of Patent Document 1 is required to have a further improved refractive index. To further improve the refractive index, a method of incorporating inorganic particles into the pressure-sensitive adhesive is known. However, the present inventors have found that the compatibility between inorganic particles and a (meth)acrylic acid ester polymer is poor, and even if the resulting pressure-sensitive adhesive layer has excellent transparency when it is formed into a thick film of 50 μm or more, which is required for pressure-sensitive adhesives for optical films, the resulting layer does not exhibit sufficient transparency.

[0006] Therefore, an object of the present invention is to provide a pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive having an increased refractive index and transparency not only in the case of a thin pressure-sensitive adhesive layer but also in the case of a thick pressure-sensitive adhesive layer.

[0007] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that, when a pressure-sensitive adhesive composition containing a (meth)acrylic acid ester polymer and inorganic particles contains a predetermined amount of a monomer similar to a monomer constituting the polymer as a monomer without being polymerized, when the composition is formed into a coating film, a pressure-sensitive adhesive having an increased refractive index and transparency can be obtained, both in the case of a thin film and in the case of a thick film of 50 μm or more, and have completed the present invention.

[0008] That is, the present invention is as follows: [1] A pressure-sensitive adhesive composition for an optical film, comprising a (meth)acrylic acid ester copolymer (A), a (meth)acrylic acid ester monomer (a), and inorganic particles (B), wherein the copolymer (A) comprises a structural unit (A1) derived from an aromatic hydrocarbon group-containing (meth)acrylic acid ester monomer (a1) and a structural unit (A2) derived from a hydroxyl group-containing (meth)acrylic acid ester monomer (a2), the monomer (a) comprises the aromatic hydrocarbon group-containing (meth)acrylic acid ester monomer (a1) and the hydroxyl group-containing (meth)acrylic acid ester monomer (a2), the content of the structural unit (A2) is 1 to 40 mass% based on 100 mass% of the copolymer (A), and the content of the monomer (a) is 45 to 95 mass% based on 100 mass% of the total of the copolymer (A) and the monomer (a). [2] The pressure-sensitive adhesive composition according to [1], further comprising a photopolymerization initiator (E). [3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the monomer (a1) is at least one selected from the group consisting of an aryl ester of (meth)acrylic acid, an aralkyl ester of (meth)acrylic acid, and an aryloxyalkyl ester of (meth)acrylic acid, wherein the aryl ester of (meth)acrylic acid, the aralkyl ester of (meth)acrylic acid, and the aryloxyalkyl ester of (meth)acrylic acid may have an aryl group, an arylalkyl group, an aryloxy group, or an aryloxyalkyl group bonded thereto, and wherein the aryl ester of (meth)acrylic acid, the aralkyl ester of (meth)acrylic acid, and the aryloxyalkyl ester of (meth)acrylic acid may be an alkylene oxide-modified product.[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the copolymer (A) contains a structural unit (A3) derived from another monomer (a3) ​​other than the aromatic hydrocarbon group-containing (meth)acrylic ester monomer (a1) and the hydroxyl group-containing (meth)acrylic ester monomer (a2), the (meth)acrylic ester monomer (a) contains another monomer (a3) ​​other than the aromatic hydrocarbon group-containing (meth)acrylic ester monomer (a1) and the hydroxyl group-containing (meth)acrylic ester monomer (a2), and the content of the structural unit (A3) is 50 mass% or less in 100 mass% of the copolymer (A). [5] The pressure-sensitive adhesive composition according to [4], wherein the other monomer (a3) ​​comprises at least one selected from the group consisting of an alicyclic hydrocarbon group-containing (meth)acrylic acid ester monomer, a nitrogen atom-containing (meth)acrylic acid ester monomer, an alkoxyalkyl group-containing (meth)acrylic acid ester monomer, a low Tg (meth)acrylic acid alkyl ester monomer having a homopolymer glass transition temperature of −20° C. or lower, and an acid group-containing monomer. [6] The pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the weight average molecular weight of the copolymer (A) is 500,000 to 6,000,000. [7] The pressure-sensitive adhesive composition according to any one of [1] to [6], wherein the inorganic particles (B) are particles composed of at least one selected from the group consisting of aluminum oxide, titanium oxide, zirconium oxide, indium oxide, zinc oxide, tin oxide, lanthanum oxide, yttrium oxide, cerium oxide, magnesium oxide, niobium oxide, tantalum oxide, indium tin oxide, antimony tin oxide, barium titanate, strontium titanate, perovskite, and spinel. [8] The pressure-sensitive adhesive composition according to any one of [1] to [7], wherein the inorganic particles (B) have a volume-average particle diameter of 1 to 100 nm. [9] The pressure-sensitive adhesive composition according to any one of [1] to [8], wherein the inorganic particles (B) have a ratio (D90 / D50) of the volume-based cumulative 90% particle diameter D90 to the volume-based cumulative 50% particle diameter D50, as measured by dynamic light scattering, of 3.0 or less.

[10] The pressure-sensitive adhesive composition according to any one of [1] to [9], further comprising a chain transfer agent (F).

[11] The pressure-sensitive adhesive composition according to any one of [1] to

[10] , wherein a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition has a refractive index of 1.58 to 1.80.

[12] The pressure-sensitive adhesive composition according to any one of [1] to

[11] , wherein a 100 μm-thick pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition has a haze of 3.0% or less.

[13] A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to

[12] .

[14] Use of the composition according to any one of [1] to

[12] in a pressure-sensitive adhesive to be laminated on an optical film.

[15] A laminate comprising an optical film and the pressure-sensitive adhesive layer according to

[13] laminated on the optical film.

[16] A method for producing a pressure-sensitive adhesive-laminated optical film, comprising the steps of: applying the composition according to any one of [1] to

[12] to a substrate; and curing the coating layer obtained in the coating step to form a pressure-sensitive adhesive layer, wherein the substrate used in the coating step is an optical film, or the method further comprises a transfer step of transferring the pressure-sensitive adhesive layer to the optical film after the pressure-sensitive adhesive layer-forming step.

[17] A pressure-sensitive adhesive layer for an optical film, comprising a (meth)acrylic acid ester copolymer (A) and inorganic particles (B), wherein the pressure-sensitive adhesive layer has a thickness of 50 μm or more, a haze of 3.0% or less, the copolymer (A) comprises a structural unit (A1) derived from an aromatic hydrocarbon group-containing (meth)acrylic acid ester monomer (a1) and a structural unit (A2) derived from a hydroxyl group-containing (meth)acrylic acid ester monomer (a2), and the content of the structural unit (A2) is 1 to 40 mass% relative to 100 mass% of the total of the structural units (A1) and (A2).

[18] The pressure-sensitive adhesive layer according to

[17] , further comprising a photopolymerization initiator residue.

[0009] According to the present invention, a pressure-sensitive adhesive composition can be provided that can form a pressure-sensitive adhesive having an increased refractive index and transparency even in a thick film. The pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition has an increased refractive index and transparency even in a thick film, and is therefore suitable for use as a pressure-sensitive adhesive for optical films.

[0010] 1. Pressure-sensitive adhesive composition The pressure-sensitive adhesive composition of the present invention is preferably used for optical films and contains a (meth)acrylic acid ester copolymer (A) (hereinafter sometimes simply referred to as copolymer (A)), a (meth)acrylic acid ester monomer (a) (hereinafter sometimes simply referred to as monomer (a)), and inorganic particles (B). By including copolymer (A), the pressure-sensitive adhesive composition exhibits adhesive properties, and by including inorganic particles (B), the pressure-sensitive adhesive layer can have a high refractive index, making it suitable for adhering (bonding) optical films. Although the inclusion of inorganic particles (B) generally tends to reduce transparency, the pressure-sensitive adhesive composition contains monomer (a), thereby increasing the dispersibility of inorganic particles (B) in the pressure-sensitive adhesive composition. Furthermore, even after the pressure-sensitive adhesive composition is applied and the proportion of monomer (a) is reduced to solidify the pressure-sensitive adhesive composition, high dispersibility can be maintained, thereby increasing the transparency of the pressure-sensitive adhesive layer.

[0011] 1.1 (Meth)acrylic acid ester copolymer (A) The (meth)acrylic acid ester copolymer (A) comprises a structural unit (A1) (hereinafter, sometimes simply referred to as aromatic structural unit (A1) or structural unit (A1)) derived from an aromatic hydrocarbon group-containing (meth)acrylic acid ester monomer (a1) (hereinafter, sometimes simply referred to as aromatic monomer (a1) or monomer (a1)), and a structural unit (A2) (hereinafter, sometimes simply referred to as hydroxyl group-containing structural unit (A2) or structural unit (A2)) derived from a hydroxyl group-containing (meth)acrylic acid ester monomer (a2) (hereinafter, sometimes simply referred to as hydroxyl group-containing monomer (a2) or monomer (a2)). The inclusion of the aromatic structural unit (A1) can increase the refractive index of the pressure-sensitive adhesive layer, making it suitable for use in optical films. Furthermore, the difference in refractive index with the inorganic particles (B) can be reduced, contributing to increased transparency of the pressure-sensitive adhesive layer. The inclusion of the hydroxyl group-containing structural unit (A2) can enhance affinity with the inorganic particles (B), and can also reduce the size of water droplets formed in the pressure-sensitive adhesive layer by moisture that has penetrated under humid conditions, thereby improving transparency under humid conditions.

[0012] 1.1.1 Aromatic Structural Unit (A1) The aromatic monomer (a1) that constitutes the aromatic structural unit (A1) is preferably a monomer having an aromatic hydrocarbon ring (sometimes referred to as an aryl unit) and a (meth)acryloyl group in the molecule. Examples of the aromatic monomer (a1) include aryl esters of (meth)acrylic acid, aralkyl esters of (meth)acrylic acid (i.e., arylalkyl esters of (meth)acrylic acid), and aryloxyalkyl esters of (meth)acrylic acid. These may be used alone or in combination of two or more. The aryl esters of (meth)acrylic acid, aralkyl esters of (meth)acrylic acid, and aryloxyalkyl esters of (meth)acrylic acid may have an aromatic substituent having an aromatic hydrocarbon ring bonded thereto, such as an aryl group, an arylalkyl group, an aryloxy group, or an aryloxyalkyl group bonded thereto. The aryl ester of (meth)acrylic acid, the aralkyl ester of (meth)acrylic acid, and the aryloxyalkyl ester of (meth)acrylic acid may be alkylene oxide-modified products.

[0013] The aryl unit contained in the (meth)acrylic acid aryl ester, (meth)acrylic acid aryl alkyl ester (i.e., aralkyl ester), (meth)acrylic acid aryloxyalkyl ester, aryl group, arylalkyl group, aryloxy group, and aryloxyalkyl group includes a benzene ring unit, a naphthalene ring unit, an azulene ring unit, an anthracene ring unit, a phenanthrene ring unit, a pyrene ring unit, a chrysene ring unit, a naphthacene ring unit, a triphenylene ring unit, a fluorene ring unit, a dinaphthothiophene ring unit, and the like, with a benzene ring unit, a naphthalene ring unit, a fluorene ring unit, and the like being preferred. Furthermore, by bonding an aromatic substituent such as an aryl group, an arylalkyl group, an aryloxy group, or an aryloxyalkyl group to an aryl (meth)acrylate ester, an arylalkyl (meth)acrylate ester (i.e., an aralkyl ester), or an aryloxyalkyl (meth)acrylate ester, a group containing a plurality of aryl groups can be formed. Examples of such groups containing a plurality of aryl groups include a biphenyl ring group, a phenoxybenzyl group, an o-terphenyl ring group, an m-terphenyl ring group, and a p-terphenyl ring group.

[0014] The alkyl units contained in the (meth)acrylic acid arylalkyl esters (i.e., aralkyl esters), (meth)acrylic acid aryloxyalkyl esters, arylalkyl groups, aryloxyalkyl groups, and the like, include alkyl units having 1 to 10 carbon atoms, preferably alkyl units having 1 to 4 carbon atoms, and more preferably alkyl units having 1 or 2 carbon atoms.

[0015] The alkylene oxide includes ethylene oxide, propylene oxide, etc., with ethylene oxide being preferred.

[0016] Specific examples of the aromatic monomer (a1) include benzyl (meth)acrylate, phenyl (meth)acrylate, benzylphenyl (meth)acrylate, p-phenylbenzyl (meth)acrylate, o-phenylphenol (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, p-t-butylphenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate. acrylate, phenoxy polyethylene glycol (meth)acrylate having 3 or more (preferably 3 to 20) repeating units of ethylene glycol, ethylene oxide-modified nonylphenol (meth)acrylate, nonylphenoxy polypropylene glycol (meth)acrylate, nonylphenoxy polyethylene glycol-polypropylene glycol (meth)acrylate, ethylene oxide-modified cresol (meth)acrylate, phenol ethylene oxide-modified (meth)acrylate, 2-hydroxy-3-phenoxypropyl Monomers having a benzene ring unit such as (meth)acrylate, methoxybenzyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, polystyryl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalate, and monohydroxyethyl phthalate (meth)acrylate; hydroxyethylated β-naphthol (meth)acrylate, 2-naphthoethyl (meth)acrylate, and 2-naphthoxyethyl (meth)acrylate; Monomers having a naphthalene ring unit, such as 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate, 1-naphthylmethyl (meth)acrylate, 2-naphthylmethyl (meth)acrylate, and hydroxynaphthyl (meth)acrylate; monomers having a biphenyl ring group, such as biphenyl (meth)acrylate; monomers having a fluorene ring unit, such as fluorenyl (meth)acrylate, 9-fluorenylmethyl (meth)acrylate (9-(meth)acryloyloxymethylfluorene), and hydroxyfluorenyl (meth)acrylate;Monomers having a dinaphthothiophene ring unit, such as 5-dinaphthothiophenylethyl (meth)acrylate, 6-dinaphthothiophenylethyl (meth)acrylate, and 6-dinaphthothiophenylmethyl (meth)acrylate, are preferred. The monomer (a1) preferably does not have a carboxy group, a phosphoric acid group, a phosphoric acid ester group, a sulfonic acid group, or a sulfonic acid ester group.

[0017] Furthermore, as the monomer (a1), commercially available products such as M-101A, M-102, M-111, M-113, M-5400, and M-5700 manufactured by Toagosei Co., Ltd.; Plenmer ANP-300 and 75ANEP-600 manufactured by NOF Corporation; and NK Ester AMP-20GY manufactured by Shin-Nakamura Chemical Co., Ltd. may be used.

[0018] Preferred aromatic monomers (a1) include aralkyl esters of (meth)acrylic acid (e.g., benzyl (meth)acrylate, naphthylmethyl (meth)acrylate, etc.), or aralkyl esters of (meth)acrylic acid to which an aromatic substituent (preferably an aryl group or an aryloxy group) is bonded (e.g., p-phenylbenzyl acrylate, phenoxybenzyl acrylate, etc.), aryloxyalkyl esters of (meth)acrylic acid (e.g., phenoxyethyl (meth)acrylate, etc.), and aryloxyalkyl esters of (meth)acrylic acid to which an aromatic substituent (preferably an aryl group) is bonded (e.g., ethoxylated o-phenylphenol (meth)acrylate, etc.).

[0019] In particular, the aromatic monomer (a1) preferably includes an aralkyl ester of (meth)acrylic acid having an aromatic substituent (preferably an aryl group or an aryloxy group) bonded thereto, and / or an aryloxyalkyl ester of (meth)acrylic acid; more preferably includes at least an aralkyl ester of (meth)acrylic acid having an aromatic substituent (preferably an aryl group or an aryloxy group) bonded thereto; and even more preferably includes an aralkyl ester of (meth)acrylic acid having an aromatic substituent (preferably an aryl group or an aryloxy group) bonded thereto, and an aryloxyalkyl ester of (meth)acrylic acid.

[0020] The aralkyl ester of (meth)acrylic acid includes (meth)acrylic acid C 6-10 Aryl C 1-4 Alkyl esters are preferred, and phenyl (meth)acrylate C 1-4 Alkyl ester, naphthyl (meth)acrylate C 1-4 As the aralkyl ester of (meth)acrylic acid having an aromatic substituent bonded thereto, the preferred embodiment of the aralkyl ester of (meth)acrylic acid (i.e., (meth)acrylic acid C 6-10 Aryl C 1-4 Alkyl ester, (meth)acrylic acid phenyl C 1-4 Alkyl ester, or naphthyl (meth)acrylate C 1-4 In the preferred embodiment of the aralkyl ester of (meth)acrylic acid, an aryl group or an aryloxy group (particularly an aryloxy group) is bonded, and in the preferred embodiment of the aralkyl ester of (meth)acrylic acid, an aryl group or a phenoxy group (particularly a phenoxy group) is bonded more preferably. 6-10 Aryloxy C 1-4 Alkyl esters are preferred, and phenoxy C of (meth)acrylic acid 1-4The aryloxyalkyl ester of (meth)acrylic acid having an aromatic substituent bonded thereto is preferably the above-mentioned preferred embodiment of the aryloxyalkyl ester of (meth)acrylic acid (i.e., C 6-10 Aryloxy C 1-4 Alkyl ester or (meth)acrylic acid phenoxy C 1-4 In a preferred embodiment of the aryloxyalkyl ester of (meth)acrylic acid, an aryl group is bonded thereto, or an alkylene oxide-modified product thereof is preferred, and in a preferred embodiment of the aryloxyalkyl ester of (meth)acrylic acid described above, an aryl group is bonded thereto, or an ethylene or propylene oxide-modified product thereof is more preferred, and in a preferred embodiment of the aryloxyalkyl ester of (meth)acrylic acid described above, a phenyl group is bonded thereto, or an ethylene or propylene oxide-modified product thereof is even more preferred.

[0021] The content of the aromatic structural unit (A1) is, for example, 40 to 99% by mass, preferably 50 to 95% by mass, and more preferably 70 to 90% by mass, based on 100% by mass of the copolymer (A). The greater the content of the aromatic structural unit (A1), the higher the refractive index of the pressure-sensitive adhesive layer can be. The greater the transparency of the pressure-sensitive adhesive layer also tends to be.

[0022] The proportions of the structural units ((A1), and (A2), (A3), etc. described below) in copolymer (A) can be determined by separating the monomer (a) in the PSA composition from copolymer (A) by solid-liquid separation or extraction, and analyzing copolymer (A) by NMR or the like. Furthermore, if it is known that the proportions of the monomers (a1), (a2), and (a3) ​​(specifically, (a31) to (a42)) at the time of polymerization charging are equal to the proportions of the structural units (A1), (A2), and (A3) (specifically, (A31) to (A42)) in copolymer (A), the proportions of the structural units (A1), (A2), and (A3) (specifically, (A31) to (A42)) in copolymer (A) may be determined based on the charging ratio instead of analysis.

[0023] 1.1.2 Hydroxyl Group-Containing Structural Unit (A2) The hydroxyl group-containing monomer (a2) that becomes the hydroxyl group-containing structural unit (A2) is preferably a monomer that has a hydroxyl group and a (meth)acryloyl group in the molecule (but does not have an aromatic hydrocarbon ring). Examples of the hydroxyl group-containing monomer (a2) include hydroxy C such as 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, hydroxymethyl(meth)acrylate, and 2-hydroxypropyl(meth)acrylate. 1-10 Alkyl (meth)acrylates; polyC such as polyethylene glycol mono(meth)acrylate having 2 or more (preferably 2 or more and 20 or less) repeating units of ethylene glycol, and polypropylene glycol mono(meth)acrylate having 2 or more (preferably 2 or more and 20 or less) repeating units of propylene glycol; 2-4 Alkylene glycol mono(meth)acrylate; Hydroxy C 1-10 Examples thereof include caprolactone-modified alkyl(meth)acrylates; (meth)acrylic acid esters having a hydroxyl group and an aliphatic hydrocarbon ring, such as 1,4-cyclohexanedimethanol mono(meth)acrylate; and (meth)acrylamides, such as N-(2-hydroxyethyl)(meth)acrylamide, N-(2-hydroxypropyl)(meth)acrylamide, and N-(2,2-dimethyl-β-hydroxyethyl)(meth)acrylamide. Furthermore, as the monomer (a2), commercially available products such as Plaxel FA1, FA1DDM, FA2, FA2D, FA3, FA4, FA5, FA10L, FM1, FM1D, FM2, FM2D, FM3, FM4, and FM5 manufactured by Daicel Corporation, and Plenmer AE-90U, AE-200, AE-400, AP-200, AP-400, AP-400D, AP-550, AP-800, and AP-1000D manufactured by NOF Corporation may be used. These hydroxyl group-containing monomers (a2) may be used alone or in combination of two or more.

[0024] Among these, hydroxy C is preferred from the viewpoints of good transparency, a small amount of gel components in the copolymer (A), and a good appearance. 2-4 Alkyl (meth)acrylate, N-(hydroxy C 2-4Preferred are 4-hydroxybutyl (meth)acrylate, N-(2-hydroxyethyl) (meth)acrylamide, and PLACCEL (particularly F series) manufactured by Daicel Corporation, and more preferred are 4-hydroxybutyl (meth)acrylate, N-(2-hydroxyethyl) (meth)acrylamide, and PLACCEL FA1DDM, FA2D, FM1D, FM2D, and FM5. 1-10 Alkyl (meth)acrylate is preferred, and hydroxy C 2-4 Alkyl (meth)acrylates are more preferred.

[0025] The content of the hydroxyl group-containing structural unit (A2) is, for example, 1 to 40 mass%, preferably 3 to 30 mass%, more preferably 7 to 25 mass%, and may be 12 to 25 mass%, based on 100 mass% of the copolymer (A) (preferably, based on 100 mass% of the total of the structural units (A1) and (A2)). The greater the content of the hydroxyl group-containing structural unit (A2), the higher the affinity with the inorganic particles (B) can be, and the higher the transparency under humidified conditions can be. Furthermore, the lower the content of the hydroxyl group-containing structural unit (A2), the higher the humidity and heat durability of the pressure-sensitive adhesive composition, and the better the adhesiveness and coatability.

[0026] The total content of the aromatic structural unit (A1) and the hydroxyl group-containing structural unit (A2) is, for example, 50 to 100% by mass, preferably 60 to 99% by mass, more preferably 75 to 95% by mass, and may be 85 to 100% by mass or 95 to 100% by mass, based on 100% by mass of the copolymer (A). The mass ratio (A1 / A2) of the aromatic structural unit (A1) to the hydroxyl group-containing structural unit (A2) is, for example, 50 / 50 to 99 / 1, preferably 70 / 30 to 98 / 2, more preferably 75 / 25 to 95 / 5, even more preferably 80 / 20 to 90 / 10, and particularly preferably 83 / 17 to 88 / 12.

[0027] 1.1.3 Other Structural Unit (A3) The copolymer (A) may contain a structural unit (A3) derived from a monomer (a3) ​​other than the aromatic monomer (a1) and the hydroxyl group-containing monomer (a2) (hereinafter, this may be referred to as the other structural unit (A3) or the structural unit (A3)). By containing the other structural unit (A3), the copolymer (A) can be endowed with various properties.

[0028] The content of the other structural unit (A3) is, for example, 0 to 50 mass%, preferably 1 to 50 mass%, more preferably 1 to 40 mass%, and even more preferably 5 to 25 mass%, based on 100 mass% of the copolymer (A).

[0029] Examples of the other monomer (a3) ​​that becomes the other structural unit (A3) include an alicyclic hydrocarbon group-containing (meth)acrylic acid ester monomer (a31), a nitrogen atom-containing (meth)acrylic acid ester monomer (a32), an alkoxyalkyl group-containing (meth)acrylic acid ester monomer (a33), a low Tg (meth)acrylic acid alkyl ester monomer (a34) in which the glass transition temperature of the homopolymer is −20° C. or lower, a (meth)acrylic acid alkyl ester monomer (a35) in which the glass transition temperature of the homopolymer is higher than −20° C., an acid group-containing monomer (a36), and a (meth)acrylic acid ester monomer (a37) having an acyl group or a cyclic ether group (particularly an epoxy group). Examples of suitable monomers include (a38) having a phosphate group, (a39) a sulfonic acid group-containing monomer, (a40) a vinyl monomer having a silane group, (a41) a styrene-based monomer, and (a42) a macromonomer. Monomers (a31) to (a40) are preferred, with (a31) an alicyclic hydrocarbon group-containing (meth)acrylic acid ester-based monomer, (a32) a nitrogen atom-containing (meth)acrylic acid ester-based monomer, (a33) an alkoxyalkyl group-containing (meth)acrylic acid ester-based monomer, (a34) a low Tg (meth)acrylic acid alkyl ester-based monomer having a homopolymer glass transition temperature of −20° C. or lower, and (a36) an acid group-containing monomer. These other monomers (a3) ​​may be used alone or in combination of two or more. The use of (a31) an alicyclic hydrocarbon group-containing (meth)acrylic acid ester-based monomer can reduce the dielectric constant of the pressure-sensitive adhesive layer. The use of a nitrogen atom-containing (meth)acrylic acid ester monomer (a32) can increase the hydrophilicity of the pressure-sensitive adhesive layer, thereby suppressing clouding of the layer in a humidified environment, and can also increase the cohesive strength, thereby improving the adhesive strength of the pressure-sensitive adhesive layer. The use of an alkoxyalkyl group-containing (meth)acrylic acid ester monomer (a33) can increase the hydrophilicity of the pressure-sensitive adhesive layer, while also increasing the cohesive strength, thereby improving the adhesive strength of the pressure-sensitive adhesive layer. The use of a low Tg (meth)acrylic acid alkyl ester monomer (a34), the glass transition temperature of which of the homopolymer is −20° C. or lower, can increase the adhesiveness, thereby improving the adhesive strength of the pressure-sensitive adhesive layer. The use of an acid group-containing monomer (a36) can increase the cohesive strength, thereby improving the adhesive strength of the pressure-sensitive adhesive layer.The structural unit derived from monomer (a31) will be referred to as structural unit (A31), and similarly, the structural units derived from monomers (a32) to (a42) will be referred to as structural units (A32) to (A42), respectively.

[0030] The alicyclic hydrocarbon group-containing (meth)acrylic acid ester monomer (a31) (sometimes simply referred to as monomer (a31)) is preferably a monomer having an alicyclic hydrocarbon ring and a (meth)acryloyl group in the molecule (but not having an aromatic hydrocarbon ring or a hydroxyl group). Examples of the monomer (a31) include monocyclic monomers typified by cycloalkyl (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and 3,3,5-trimethylcyclohexyl (meth)acrylate; and bridged ring monomers such as isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, adamantyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate; with bridged ring monomers such as isobornyl (meth)acrylate being preferred. Furthermore, the monomer (a31) may be a commercially available product such as Fancryl FA-511AS, FA-512AS, or FA-513AS manufactured by Resonac Co., Ltd. The content of the structural unit (A31) derived from the monomer (a31) is, for example, 0 to 50% by mass, preferably 5 to 40% by mass, and more preferably 10 to 30% by mass, relative to 100% by mass of the copolymer (A).

[0031] The nitrogen atom-containing (meth)acrylic acid ester monomer (a32) (sometimes simply referred to as monomer (a32)) is preferably a monomer having a nitrogen atom and a (meth)acryloyl group in the molecule (but having no aromatic hydrocarbon ring or hydroxyl group). Examples of the monomer (a32) include amino group-containing monomers such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, N-t-butylaminoethyl (meth)acrylate, and (meth)acryloyloxyethyl trimethylammonium chloride; amide group-containing monomers such as N-(meth)acryloylmorpholine, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, (meth)acrylamide, N-isopropyl(meth)acrylamide, N-t-butyl(meth)acrylamide, and diacetone (meth)acrylamide; urethane group-containing monomers such as urethane (meth)acrylate; and imide group-containing monomers such as N-(meth)acryloyloxyethyl hexahydrophthalimide; with preference given to amide group-containing monomers such as N-acryloylmorpholine. Furthermore, commercially available products such as M-140 manufactured by Toagosei Co., Ltd. may also be used as the monomer (a32). In this specification, a monomer having a nitrogen atom, a (meth)acryloyloxy group, and an alicyclic hydrocarbon ring in the molecule (but not having an aromatic hydrocarbon ring or a hydroxyl group) is classified as monomer (a32). The content of the structural unit (A32) derived from the monomer (a32) is, for example, 0 to 50% by mass, preferably 1 to 30% by mass, and more preferably 5 to 20% by mass, relative to 100% by mass of the copolymer (A).

[0032] The alkoxyalkyl group-containing (meth)acrylic acid ester monomer (a33) (sometimes simply referred to as monomer (a33)) is preferably a monomer having an alkoxyalkyl group and a (meth)acryloyl group in the molecule (but having no aromatic hydrocarbon ring or hydroxyl group). Examples of the monomer (a33) include alkoxyalkyl (meth)acrylates (preferably C) such as methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, and 2-ethylhexyloxyethyl (meth)acrylate. 1-4 Alkoxy C 1-4 alkyl(meth)acrylate); ethoxy-diethylene glycol (meth)acrylate, ethoxy-triethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, methoxy-diethylene glycol (meth)acrylate, propoxy-diethylene glycol (meth)acrylate, propoxy-triethylene glycol (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate (2-ethylhexyloxy-diethylene glycol (meth)acrylate), 2-ethylhexyloxy-triethylene glycol (meth)acrylate, 2-ethylhexyloxy-polyethylene glycol (meth)acrylate having 4 or more (preferably 4 or more and 10 or less) repeating units of ethylene glycol, methoxy-polyethylene glycol (meth)acrylate having 4 or more (preferably 4 or more and 25 or less, more preferably 4 or more and 10 or less) repeating units of ethylene glycol, methoxydipropylene glycol (meth)acrylate, and the like. 1-8 Alkoxy(poly)C 2-4 alkylene glycol (meth)acrylate; and C 1-4 Alkoxy C 1-4Alkyl (meth)acrylate is preferred. Furthermore, commercially available products such as M-120 manufactured by Toagosei Co., Ltd., Plenmer AME-400 manufactured by NOF Corporation, and NK Ester AM-90G, AM-130G, and AM-230G manufactured by Shin-Nakamura Chemical Co., Ltd. may also be used as the monomer (a33). The content of the structural unit (A33) derived from the monomer (a33) is, for example, 0 to 50% by mass, preferably 5 to 40% by mass, and more preferably 10 to 30% by mass, relative to 100% by mass of the copolymer (A).

[0033] The low Tg (meth)acrylic acid alkyl ester monomer (a34) (sometimes simply referred to as monomer (a34)) having a homopolymer glass transition temperature of −20° C. or lower and the (meth)acrylic acid alkyl ester monomer (a35) (sometimes simply referred to as monomer (a35)) having a glass transition temperature of more than −20° C. include the following examples having the corresponding glass transition temperatures: methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, ... t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth)acrylate, t-butyl (meth Acrylate, isopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate (n-lauryl (meth)acrylate), stearyl (meth)acrylate, isostearyl (meth)acrylate, cetyl (meth)acrylate, behenyl (meth)acrylate. Furthermore, commercially available products such as Plemmer CA and VA manufactured by NOF Corporation and Fancryl FA-111A manufactured by Resonac Co., Ltd. may also be used as the monomer (a34) and the monomer (a35). Preferred examples of the monomer (a34) include ethyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, 2-octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, and isononyl acrylate, with n-butyl acrylate and 2-ethylhexyl acrylate being more preferred. The content of the structural unit (A34) derived from the monomer (a34) is, for example, 0 to 50% by mass, preferably 0 to 30% by mass, and more preferably 1 to 20% by mass, based on 100% by mass of the copolymer (A).The content of the structural unit (A35) derived from the monomer (a35) in 100% by mass of the copolymer (A) is, for example, 0 to 50% by mass, preferably 0 to 10% by mass, and more preferably 0 to 5% by mass.

[0034] The acid group-containing monomer (a36) (sometimes simply referred to as monomer (a36)) is preferably a monomer having a carboxy group and a polymerizable unsaturated group in the molecule (but not having an aromatic hydrocarbon ring or a hydroxyl group). Examples of the monomer (a36) include unsaturated monocarboxylic acids such as (meth)acrylic acid, cinnamic acid, crotonic acid, myristoleic acid, palmitoleic acid, and oleic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid; monoesters of unsaturated dicarboxylic acids such as maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid monomethyl ester, and itaconic acid monobutyl ester; anhydrides of unsaturated dicarboxylic acids such as maleic anhydride, fumaric anhydride, and itaconic anhydride; saturated dicarboxylic acid monoesters having a polymerizable unsaturated group in the ester moiety such as 2-(meth)acryloyloxyethyl succinic acid and 2-(meth)acryloyloxyethylhexahydrophthalic acid; and ω-carboxy-polycaprolactone mono(meth)acrylate. Among these, unsaturated monocarboxylic acids are preferred, and (meth)acrylic acid is more preferred. Furthermore, commercially available products such as M-5300 manufactured by Toagosei Co., Ltd. and NK Ester A-SA manufactured by Shin-Nakamura Chemical Co., Ltd. may also be used as the monomer (a36). In this specification, a monomer having a carboxy group, a polymerizable unsaturated group, and an alicyclic hydrocarbon ring in the molecule (but not having an aromatic hydrocarbon ring or a hydroxyl group) is classified as monomer (a36). The content of the structural unit (A36) derived from the monomer (a36) is, for example, 0 to 50% by mass, preferably 0 to 30% by mass, more preferably 0 to 10% by mass, and may even be 0% by mass (i.e., acid-free type) relative to 100% by mass of the copolymer (A).

[0035] The (meth)acrylic acid ester monomer (a37) having an acyl group or a cyclic ether group (sometimes simply referred to as monomer (a37)) is preferably a monomer having an acyl group and / or a cyclic ether group and a (meth)acryloyl group in the molecule (but not having an aromatic hydrocarbon ring or a hydroxyl group). Examples of the cyclic ether group include cyclic ether groups having one ether bond, such as an epoxy group, an oxetanyl group, or a tetrahydrofuryl group; and cyclic ether groups having two ether bonds, such as a 1,3-dioxolanyl group or a 1,3-dioxanyl group; and among these, an epoxy group is preferred. That is, the monomer (a37) is preferably a (meth)acrylic acid ester monomer having an acyl group or an epoxy group. Examples of the monomer (a37) include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, tetrahydrofurfuryl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, 2-acetoacetoxyethyl (meth)acrylate, etc. The content of the structural unit (A37) derived from the monomer (a37) is, for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass, relative to 100% by mass of the copolymer (A).

[0036] The (meth)acrylic monomer (a38) having a phosphate group (sometimes simply referred to as monomer (a38)) is preferably a monomer having a phosphate group and / or a phosphate ester group and a polymerizable unsaturated group in the molecule (but not having an aromatic hydrocarbon ring or a hydroxyl group). Examples of monomer (a38) include 2-methacryloyloxyethyl diphenyl phosphate (meth)acrylate, trimethacryloyloxyethyl phosphate (meth)acrylate, and triacryloyloxyethyl phosphate (meth)acrylate. The content of the structural unit (A38) derived from the monomer (a38) is, for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass, based on 100% by mass of copolymer (A).

[0037] The sulfonic acid group-containing monomer (a39) (sometimes simply referred to as monomer (a39)) is preferably a monomer having a sulfonic acid group and / or a sulfonate ester group and a polymerizable unsaturated group in the molecule (but not having an aromatic hydrocarbon ring or a hydroxyl group). Examples of the monomer (a39) include sodium sulfopropyl (meth)acrylate, sodium 2-sulfoethyl (meth)acrylate, and sodium 2-acrylamido-2-methylpropanesulfonate. The content of the structural unit (A39) derived from the monomer (a39) is, for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass, relative to 100% by mass of the copolymer (A).

[0038] The vinyl monomer (a40) having a silane group (sometimes simply referred to as monomer (a40)) is preferably a monomer having a silane group and a vinyl group in the molecule (but having no aromatic hydrocarbon ring or hydroxyl group). Examples of monomer (a40) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethyl)silane, vinyltriacetylsilane, and methacryloyloxypropyltrimethoxysilane. In this specification, a monomer having a silane group, a vinyl group, and an acyl group in the molecule (but having no aromatic hydrocarbon ring or hydroxyl group) is classified as monomer (a40). The content of the structural unit (A40) derived from the monomer (a40) is, for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass, based on 100% by mass of copolymer (A).

[0039] The styrene-based monomer (a41) (sometimes simply referred to as monomer (a41)) is preferably a monomer having a styrene skeleton (but not having a hydroxyl group). Examples of the monomer (a41) include styrene, 4-tert-butylstyrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, p-chlorostyrene, and p-chloromethylstyrene. The content of the structural unit (A41) derived from the monomer (a41) is, for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass, relative to 100% by mass of the copolymer (A).

[0040] The macromonomer (a42) (sometimes simply referred to as the monomer (a42)) refers to a high-molecular-weight monomer having a polymerizable unsaturated group. The number-average molecular weight of the monomer (a42) is not particularly limited, but is, for example, 3,000 to 30,000. The monomer (a42) is preferably a macromonomer having as its main component at least one selected from the group consisting of (meth)acrylic acid alkyl esters, styrene-based monomers, and (meth)acrylonitrile, and is preferably a macromonomer having as its main component at least one selected from the group consisting of (meth)acrylic acid C 1-4 Macromonomers containing at least one selected from alkyl esters, styrene, and (meth)acrylonitrile as a main component are more preferred. The term "main component" refers to a component that constitutes, for example, 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more of the macromonomer. As the monomer (a42), commercially available products such as AA-6, AS-6, AN-6S, AB-6, AW-6S, AK-5, and AK-32 manufactured by Toagosei Co., Ltd. may also be used. The content of the structural unit (A42) derived from the monomer (a42) is, for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass, based on 100% by mass of the copolymer (A).

[0041] The weight average molecular weight of the copolymer (A) is, for example, 500,000 to 6,000,000, preferably 1,000,000 to 4,000,000, more preferably 1,200,000 to 3,500,000, and may be 1,800,000 to 3,500,000, 2,000,000 to 3,500,000, or 2,500,000 to 3,500,000. The refractive index of the copolymer (A) is, for example, 1.50 to 1.65, preferably 1.52 to 1.63, more preferably 1.55 to 1.60.

[0042] The copolymer (A) can be produced by copolymerizing a (meth)acrylic acid ester monomer (a). The polymerization method is not particularly limited, but a bulk polymerization method using a thermal polymerization initiator or a photopolymerization initiator is preferably used.

[0043] Examples of the thermal polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile), azobiscyanovaleric acid, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), tolyl), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis[N-(2-propenyl)-2-methylpropionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2'-azobis[2-methyl-N-(2-hydrogen Examples of the thermal polymerization initiator include azo compounds such as t-butyl peroxypivalate, t-butyl peroxybenzoate, t-butylperoxy-2-ethylhexanoate, di-t-butyl peroxide, cumene hydroperoxide, benzoyl peroxide, and t-butyl hydroperoxide; and inorganic peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate, and sodium persulfate. These thermal polymerization initiators can be used singly or in combination of two or more.

[0044] Examples of the photopolymerization initiator include alkylphenones such as acetophenone, 3-methylacetophenone, benzyl dimethyl ketal, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 1-hydroxycyclohexyl phenyl ketone; benzophenones such as benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone; benzoin ethers such as benzoin propyl ether and benzoin ethyl ether; thioxanthones such as 4-isopropylthioxanthone; xanthone; fluorenone; camphorquinone; benzaldehyde; anthraquinone; and the like. These photopolymerization initiators may be used alone or in combination of two or more.

[0045] In the copolymerization reaction, a chain transfer agent may be used. Examples of the chain transfer agent include mercaptans such as methyl mercaptan, t-butyl mercaptan, decyl mercaptan, benzyl mercaptan, stearyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid and its esters (e.g., 2-ethylhexyl-3-mercaptopropionate), 2-ethylhexyl thioglycol, and octyl thioglycolate; methanol, ethanol, propanol, n-butanol, isopropyl alcohol, and the like. Examples of the chain transfer agent include alcohols such as propanol, t-butanol, hexanol, benzyl alcohol, and allyl alcohol; halogenated hydrocarbons such as chloroethane, fluoroethane, and trichloroethylene; carbonyls such as acetone, methyl ethyl ketone, cyclohexanone, acetophenone, acetaldehyde, propionaldehyde, n-butylaldehyde, furfural, and benzaldehyde; methyl-4-cyclohexene-1,2-dicarboxylic anhydride; and α-methylstyrene. These chain transfer agents can be used singly or in combination of two or more.

[0046] Examples of bulk polymerization methods using a photopolymerization initiator (hereinafter referred to as photo-based bulk polymerization methods) include a method in which raw material monomers and a photopolymerization initiator are added, and the mixture is irradiated with active energy rays in a nitrogen atmosphere at a reaction initiation temperature of 20° C. to 35° C. When the temperature in the reaction system has increased by 5° C. to 20° C. from the reaction initiation temperature, the reaction is terminated by introducing air into the reaction system, for example, to obtain copolymer (A).

[0047] Examples of active energy rays used in photo-based bulk polymerization methods include ultraviolet rays, laser rays, α rays, β rays, γ rays, X-rays, and electron beams. Ultraviolet rays are preferably used from the viewpoints of controllability, ease of handling, cost, and the like. More preferably, ultraviolet rays with a wavelength of 200 nm or more and 400 nm or less are used. Ultraviolet rays can be irradiated using light sources such as high-pressure mercury lamps, microwave-excited lamps, chemical lamps, black lights, LEDs, and metal halide lamps.

[0048] In a bulk polymerization method using a thermal polymerization initiator (hereinafter referred to as thermal bulk polymerization method), the temperature and time of the copolymerization reaction can be appropriately combined within the ranges of, for example, a reaction temperature of 40°C to 90°C and a reaction time of 0.1 to 10 hours or 1 to 10 hours. Preferred reaction conditions are those that allow production of copolymer (A) while leaving a necessary amount of residual monomer (a), and for example, a combination of a reaction temperature of 70°C or less and a reaction time of 2 hours or less may be selected from the above ranges.

[0049] Depending on the polymerization conditions, the copolymerization reaction may proceed until the amount of the remaining monomer (a) after polymerization becomes insufficient. In such cases, the pressure-sensitive adhesive composition of the present invention can be prepared by adding the monomer (a) after the reaction is completed.

[0050] 1.2 (Meth)acrylic acid ester monomer (a) As described above, the pressure-sensitive adhesive composition contains a (meth)acrylic acid ester monomer (a). By containing the (meth)acrylic acid ester monomer (a), the dispersibility of the inorganic particles (B) can be improved, and the transparency of the pressure-sensitive adhesive layer can be increased. The (meth)acrylic acid ester monomer (a) may be the unreacted remainder of the monomer (a) used during polymerization of the (meth)acrylic acid ester copolymer (A) (so-called residual monomer), or may be the monomer (a) added after the reaction, or a mixture thereof.

[0051] When the monomer (a) in the PSA composition consists solely of residual monomers, the monomer (a1) that forms the structural unit (A1) is equal to the monomer (a1) in the PSA composition. Similarly, the monomer (a2) that forms the structural unit (A2) is equal to the monomer (a2) in the PSA composition, and the monomer (a3) ​​that forms the structural unit (A3) is equal to the monomer (a3) ​​in the PSA composition.

[0052] The content of the monomer (a) is, for example, 45 to 95% by mass, preferably 55 to 93% by mass, more preferably 63 to 90% by mass, even more preferably 70 to 90% by mass, and particularly preferably 75 to 90% by mass, based on 100% by mass of the total of the copolymer (A) and the monomer (a). By appropriately adjusting the amount of the monomer (a), the pressure-sensitive adhesive layer can exhibit excellent transparency even when the pressure-sensitive adhesive layer is thick.

[0053] The monomer (a) includes an aromatic monomer (a1), a hydroxyl group-containing monomer (a2), etc., and optionally includes another monomer (a3). Specific examples and preferred examples of these are the same as those described above for the copolymer (A). The content of each monomer in the PSA composition relative to 100% by mass of the total monomers (a) is, for example, as follows: Aromatic monomer (a1) content: For example, 40 to 99% by mass, preferably 50 to 95% by mass, and more preferably 70 to 90% by mass. Hydroxyl group-containing monomer (a2) content: For example, 1 to 40% by mass, preferably 3 to 30% by mass, and more preferably 7 to 25% by mass. It may also be 12 to 25% by mass. Other monomer (a3) ​​content: For example, 0 to 50% by mass, preferably 1 to 50% by mass, more preferably 1 to 40% by mass, even more preferably 5 to 25% by mass, and particularly preferably 5 to 20% by mass. The content of the alicyclic hydrocarbon group-containing (meth)acrylic acid ester monomer (a31): for example, 0 to 50% by mass, preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and even more preferably 10 to 20% by mass. The content of the nitrogen atom-containing (meth)acrylic acid ester monomer (a32): for example, 0 to 50% by mass, preferably 1 to 30% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 10% by mass. The content of the alkoxyalkyl group-containing (meth)acrylic acid ester monomer (a33): for example, 0 to 50% by mass, preferably 5 to 40% by mass, and more preferably 10 to 30% by mass. The content of the low Tg (meth)acrylic acid alkyl ester monomer (a34) having a homopolymer glass transition temperature of −20° C. or lower: for example, 0 to 50% by mass, preferably 0 to 30% by mass, and more preferably 1 to 20% by mass. The content of the (meth)acrylic acid alkyl ester-based monomer (a35) having a glass transition temperature exceeding −20° C.: for example, 0 to 50% by mass, preferably 0 to 10% by mass, and more preferably 0 to 5% by mass. The content of the acid group-containing monomer (a36): for example, 0 to 50% by mass, preferably 0 to 30% by mass, more preferably 0 to 10% by mass, or 0% by mass. The content of the (meth)acrylic acid ester-based monomer (a37) having an acyl group or an epoxy group: for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass.The content of the (meth)acrylic monomer (a38) having a phosphate group: for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. The content of the sulfonic acid group-containing monomer (a39): for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. The content of the vinyl monomer (a40) having a silane group: for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. The content of the styrene monomer (a41): for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. The content of the macromonomer (a42): for example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass.

[0054] The total content of the aromatic monomer (a1) and the hydroxyl group-containing monomer (a2) is, for example, 50 to 100 mass%, preferably 60 to 99 mass%, more preferably 75 to 95 mass%, or may be 85 to 100 mass% or 95 to 100 mass%, based on 100 mass% of the monomer (a) in the PSA composition. The mass ratio (a1 / a2) of the aromatic monomer (a1) to the hydroxyl group-containing monomer (a2) is, for example, 50 / 50 to 99 / 1, preferably 70 / 30 to 98 / 2, more preferably 75 / 25 to 95 / 5, even more preferably 80 / 20 to 90 / 10, and particularly preferably 83 / 17 to 89 / 11.

[0055] The proportions of the monomers (a1), (a2), and (a3) ​​(specifically, (a31) to (a42)) in the monomer (a) in the PSA composition can be determined by separating the monomer (a) in the PSA composition from the copolymer (A) by solid-liquid separation, extraction, or the like, and analyzing the separated product by gas chromatography, NMR, etc. Furthermore, when the monomer (a) is a residual monomer and it is known that the proportions of the monomers (a1), (a2), and (a3) ​​(specifically, (a31) to (a42)) at the time of polymerization charging are equal to the proportions of the residual monomers, the proportions of the monomers (a1), (a2), and (a3) ​​(specifically, (a31) to (a42)) in the PSA composition may be determined based on the charging ratio instead of analysis.

[0056] 1.3 Inorganic particles (B) The pressure-sensitive adhesive composition contains inorganic particles (B). By containing the inorganic particles (B), the refractive index of the pressure-sensitive adhesive layer can be increased, making the pressure-sensitive adhesive composition suitable for use as a pressure-sensitive adhesive for optical films.

[0057] Examples of the inorganic particles (B) include aluminum oxide, titanium oxide, zirconium oxide (zirconia), indium oxide, zinc oxide, tin oxide, lanthanum oxide, yttrium oxide, cerium oxide, magnesium oxide, niobium oxide, tantalum oxide, indium tin oxide, antimony tin oxide, barium titanate, strontium titanate, perovskite, and spinel, among which aluminum oxide, titanium oxide, zirconium oxide, and zinc oxide are preferred, and zirconium oxide is more preferred. These may be used alone or in combination of two or more.

[0058] The inorganic particles (B) are preferably coated with a coating agent such as a carboxylic acid compound. Examples of the carboxylic acid compound include: linear saturated aliphatic carboxylic acids such as oxalic acid, malonic acid, butyric acid, succinic acid, valeric acid, glutaric acid, hexanoic acid, adipic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, palmitic acid, and stearic acid; branched saturated aliphatic carboxylic acids such as pivalic acid, 2,2-dimethylbutyric acid, 3,3-dimethylbutyric acid, 2,2-dimethylvaleric acid, 2,2-diethylbutyric acid, 3,3-diethylbutyric acid, 2-ethylhexanoic acid, 2-methylheptanoic acid, 4-methyloctanoic acid, and neodecanoic acid; alicyclic hydrocarbon group-containing carboxylic acids such as naphthenic acid and cyclohexanedicarboxylic acid; linear unsaturated aliphatic carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, oleic acid, linoleic acid, and linolenic acid; ether bond-containing carboxylic acids such as methoxyacetic acid, ethoxyacetic acid, 3-ethoxypropionic acid, 2-methoxyethoxyacetic acid, and 2-methoxyethoxyethoxyacetic acid; hydroxy group-containing carboxylic acids such as lactic acid, malic acid, citric acid, and hydroxystearic acid; carbonyl group-containing carboxylic acids such as pyruvic acid; aromatic carboxylic acids such as benzoic acid, phthalic acid, and isophthalic acid; (meth)acryloyl group-containing carboxylic acids such as 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, 2-acryloyloxyethyl hexahydrophthalic acid, 2-methacryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxyethyl phthalic acid, and 2-methacryloyloxyethyl phthalic acid; and the like.

[0059] The inorganic particles (B) are preferably coated with a carboxylic acid compound (particularly a monocarboxylic acid compound) having a total carbon number of 6 or more (preferably 7 or more), and more preferably coated with a branched-chain saturated aliphatic carboxylic acid (particularly a monocarboxylic acid compound) having a total carbon number of 6 or more (preferably 7 or more). The inorganic particles (B) are preferably coated with two or more carboxylic acid compounds, and are preferably coated with at least a branched-chain saturated aliphatic carboxylic acid having a total carbon number of 6 or more (preferably 7 or more) and an ether bond-containing carboxylic acid.

[0060] The branched saturated aliphatic carboxylic acid is preferably a branched saturated aliphatic carboxylic acid having a total carbon number of 9 or less, more preferably a branched saturated aliphatic carboxylic acid having a total carbon number of 8 or less, and particularly preferably 2-ethylhexanoic acid. The ether bond-containing carboxylic acid is preferably methoxyacetic acid, ethoxyacetic acid, 3-ethoxypropionic acid, 2-methoxyethoxyacetic acid, or 2-methoxyethoxyethoxyacetic acid, more preferably methoxyacetic acid or ethoxyacetic acid, and even more preferably methoxyacetic acid.

[0061] The refractive index of the inorganic particles (B) is, for example, 1.60 to 2.72 (titania alkyl type), preferably 1.65 to 2.50, and more preferably 1.70 to 2.20. The volume average particle diameter of the inorganic particles (B) is, for example, 1 to 100 nm, preferably 3 to 30 nm, and even more preferably 5 to 20 nm. The smaller the volume average particle diameter, the greater the difficulty of dispersing the inorganic particles (B), but the higher the transparency when dispersion is successful. The volume average particle diameter of the inorganic particles (B) can be determined based on a dynamic light scattering method. The number average particle diameter of the inorganic particles (B) is, for example, 1 to 100 nm, preferably 3 to 30 nm, and even more preferably 5 to 20 nm. The number average particle diameter of the inorganic particles (B) can be determined by measuring the length of each of any 100 inorganic particles (B) in the major axis direction using an electron microscope and calculating the average value. The ratio (D90 / D50) of the volume-based cumulative 90% particle diameter D90 to the volume-based cumulative 50% particle diameter D50 in particle diameter measurement of the inorganic particles (B) by dynamic light scattering is, for example, 3.0 or less, preferably 2.5 or less, and more preferably 2.0 or less. The smaller D90 / D50, the easier it is to uniformly disperse the inorganic particles (B).

[0062] When the inorganic particles (B) are zirconium oxide, the half-width of the (101) plane measured by XRD using CuKα radiation as a light source is preferably 1.20° or less. By setting the half-width to 1.20° or less, the crystallite diameter increases, and the refractive index can be increased. The half-width is preferably 0.6° to 1.1°, more preferably 0.65° to 1.0°, and even more preferably 0.7° to 1.0°. By setting the half-width to 0.6° or more, the transparency of the pressure-sensitive adhesive layer can be further increased.

[0063] When the inorganic particles (B) are coated zirconium oxide particles, the refractive index of the zirconium oxide particles is preferably 1.7 or more, more preferably 1.8 to 2.2, and even more preferably 1.8 to 1.9.

[0064] The amount of inorganic particles (B) in the pressure-sensitive adhesive composition is, for example, 20 to 2000 parts by mass, preferably 50 to 1500 parts by mass, more preferably 80 to 1000 parts by mass, and may be 80 to 600 parts by mass or 80 to 350 parts by mass, relative to 100 parts by mass of the total of copolymer (A) and monomer (a). By adjusting the proportion of inorganic particles (B) within the above range, it becomes easier to achieve both refractive index and transparency.

[0065] The total content of the copolymer (A), the monomer (a), and the inorganic particles (B) in the pressure-sensitive adhesive composition is preferably 80 to 100 mass%, more preferably 90 to 99.9 mass%, and even more preferably 95 to 99.9 mass%, based on 100 mass% of the solid content of the pressure-sensitive adhesive composition. In this specification, the solid content refers to the components excluding the solvent.

[0066] 1.4 Silane Coupling Agent (C) The PSA composition preferably further contains a silane coupling agent (C), which improves the durability of the PSA layer and also improves the adhesion between the PSA layer and the adherend (particularly glass).

[0067] Examples of the silane coupling agent (C) include silane coupling agents (particularly di- or trialkoxysilanes) having a reactive group such as an epoxy group (glycidoxy group), a polymerizable group (vinyl group, (meth)acryloyl group, etc.), an amino group, a mercapto group, a halogen atom, or an isocyanate group, and silane coupling agents (particularly di- or trialkoxysilanes) having a hydrocarbon group, among which silane coupling agents having a reactive group are preferred, and silane coupling agents having an epoxy group (glycidoxy group) are more preferred.

[0068] Examples of the silane coupling agent (C1) having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, and γ-glycidoxypropyltriethoxysilane.

[0069] Examples of the silane coupling agent (C2) having a polymerizable group include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, and γ-acryloxypropyltrimethoxysilane.

[0070] Examples of the silane coupling agent (C3) having an amino group include N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane.

[0071] Examples of the silane coupling agent (C4) having a mercapto group include γ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, and bis-(3-[triethoxysilyl]propyl)tetrasulfide.

[0072] Examples of the silane coupling agent (C5) having a halogen atom (particularly a halogenated hydrocarbon group) include γ-chloropropyltrimethoxysilane.

[0073] Examples of the silane coupling agent (C6) having a hydrocarbon group include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, n-propyltrimethoxysilane, ethyltrimethoxysilane, diethyldiethoxysilane, n-butyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, and cyclohexylmethyldimethoxysilane.

[0074] The silane coupling agent (C) may be a combination of two kinds of silane coupling agents whose reactive groups react with each other, or a reaction product thereof.Also usable is a compound having a hydrolyzable silyl group obtained by reacting the reactive group of a silane coupling agent having a reactive group with another coupling agent, polyisocyanate, etc.

[0075] The silane coupling agent (C) can be obtained from Shin-Etsu Chemical Co., Ltd. as, for example, KBM-303, KBM-403, KBE-402, KBE-403, KBE-502, KBE-503, KBM-5103, KBM-573, KBM-802, KBM-803, KBE-846, KBE-9007, etc.

[0076] The silane coupling agent (C) may be used alone or in combination of two or more.

[0077] The amount of silane coupling agent (C) in the pressure-sensitive adhesive composition is, for example, 0.001 to 5 parts by mass, preferably 0.001 to 4 parts by mass, and more preferably 0.01 to 3 parts by mass, per 100 parts by mass of the total of copolymer (A) and monomer (a). The more silane coupling agent (C) is contained, the more improved the durability of the pressure-sensitive adhesive layer. Furthermore, by not using an excess of silane coupling agent (C), heat foaming due to low-molecular-weight compounds can be suppressed.

[0078] 1.5 Crosslinking Agent (D) The pressure-sensitive adhesive composition preferably further contains a crosslinking agent (D). The crosslinking agent (D) can react with the copolymer (A) to form a crosslinked structure, thereby increasing the adhesiveness (tackiness) of the pressure-sensitive adhesive layer and enhancing its durability.

[0079] Examples of the crosslinking agent (D) include an isocyanate compound (D1), a carbodiimide compound (D2), an oxazoline compound (D3), an epoxy compound (D4), a polyfunctional (meth)acrylic acid ester monomer (D5), a polyfunctional allyl monomer (D6), and a peroxide (D7). These may be used alone or in combination of two or more. When two or more types are combined, two or more types of crosslinking agents of the same type (for example, two or more types of polyfunctional (meth)acrylic acid ester monomer (D5)) may be combined, or one or more types of crosslinking agents of different types (for example, one type of isocyanate compound (D1) and one type of peroxide (D7)) may be combined.

[0080] Examples of the isocyanate compound (D1) include aromatic diisocyanates such as dimer acid diisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), 1,4-phenylene diisocyanate, xylylene diisocyanate (XDI), tetramethylxylidene diisocyanate (TMXDI), tolidine diisocyanate (TODI), and 1,5-naphthalene diisocyanate (NDI). aliphatic diisocyanates such as allyl isocyanate, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and norbornane diisocyanatomethyl (NBDI); alicyclic diisocyanates such as transcyclohexane-1,4-diisocyanate, isophorone diisocyanate (IPDI), H6-XDI (hydrogenated XDI), and H12-MDI (hydrogenated MDI); carbodiimide-modified diisocyanates of the above diisocyanates; or isocyanurate-modified diisocyanates thereof. Adducts of the above-mentioned isocyanate compound (D1) with polyol compounds such as trimethylolpropane, polytetramethylene ether glycol (PTMG), and polypropylene glycol (PPG), as well as biuret and isocyanurate forms of these isocyanate compounds (D1) can also be suitably used.

[0081] The isocyanate compound (D1) can be obtained, for example, from Tosoh Corporation under the trade names of Coronate (registered trademark, the same hereinafter) L, Coronate HL, Coronate HX, Coronate 2030, and Coronate 2031; from Mitsui Chemicals, Inc. under the trade names of Takenate (registered trademark, the same hereinafter) D-102, Takenate D-110N, Takenate D-200, and Takenate D-202; and from Duranate (registered trademark, the same hereinafter) 24A-100, Duranate TPA-100, Duranate TKA-100, Duranate P301-75E, Duranate E402-90T, Duranate E405-80T, Duranate TSE-100, Duranate D-101, and Duranate These polyurethanes are available from Asahi Kasei Corporation under the names of Sumidur (registered trademark) N-75, N-3200, N-3300, etc., from Sumika Covestro Urethane Co., Ltd., and are available from Sanprene (registered trademark, the same applies hereinafter) P-6090 (PTMG / MDI based), Sanprene P-663L (PTMG / TDI based), Sanprene P-664 (PTMG / TDI based), Sanprene P-665 (PTMG / TDI based), Sanprene P-667 (PTMG / TDI based), Sanprene P-868 (PTMG / HMDI based), Sanprene P-870 (PTMG / HMDI based), Sanprene C-810 (PPG / TDI based), etc.

[0082] The isocyanate compound (D1) is preferably used in an unblocked form, but may also be a blocked isocyanate compound obtained by reacting it with a blocking agent that protects the isocyanate group. Examples of the blocked isocyanate compound include Duranate MF-B60X (blocked 1,6-hexamethylene diisocyanate) and Duranate MF-K60X (blocked 1,6-hexamethylene diisocyanate) manufactured by Asahi Kasei Corporation; Coronate AP-M, 2503, 2507, 2513, 2515, Millionate (registered trademark) MS-50, and the like manufactured by Tosoh Corporation; Takenate B-830 (blocked tolylene diisocyanate), B-815N (blocked 4,4'-methylenebis(cyclohexyl isocyanate)), B-842N (blocked 1,3-bis(isocyanatomethyl)cyclohexane), and B-842N (blocked 1,3-bis(isocyanatomethyl)cyclohexane) manufactured by Mitsui Chemicals, Inc. Examples of suitable urethane-modified polyisocyanates include B-846N (blocked 1,3-bis(isocyanatomethyl)cyclohexane), B-874N (blocked isophorone diisocyanate), and B-882N (blocked 1,6-hexamethylene diisocyanate); BURNOCK (registered trademark) D-500 (blocked tolylene diisocyanate) and D-550 (blocked 1,6-hexamethylene diisocyanate) manufactured by DIC Corporation; and ELASTRON (registered trademark) BN-P17 (blocked 4,4'-diphenylmethane diisocyanate), BN-04, BN-08, BN-44, and BN-45 (all of which are blocked urethane-modified polyisocyanates) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. Of these, Duranate MF-K60X is preferred.

[0083] As the carbodiimide compound (D2), for example, a high molecular weight polycarbodiimide produced by subjecting a diisocyanate (D22) to a decarboxylation condensation reaction in the presence of a carbodiimidization catalyst (D21) can be used. Examples of the diisocyanate (D22) to be subjected to the decarboxylation condensation reaction include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 3,3'-dimethyl-4,4'-diphenylether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and tetramethylxylylene diisocyanate.

[0084] Examples of the carbodiimidization catalyst (D21) used in the decarboxylation condensation reaction include phospholene oxides such as 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, and 3-phospholene isomers thereof.

[0085] The oxazoline compound (D3) is preferably an oxazoline group-containing polymer, and examples thereof include an oxazoline group-containing acrylic / styrene polymer having an acrylic skeleton and a styrene skeleton in the main chain and having oxazoline groups in side chains of the main chain; and an oxazoline group-containing acrylic polymer having an acrylic skeleton in the main chain and having oxazoline groups in side chains of the main chain.

[0086] Examples of the oxazoline group include a 2-oxazoline group, a 3-oxazoline group, and a 4-oxazoline group, with a 2-oxazoline group being preferred. The oxazoline group-containing polymer may also have a polyoxyalkylene group in addition to the oxazoline group.

[0087] Examples of the oxazoline compound (D3) include oxazoline group-containing acrylic polymers such as EPOCROS (registered trademark) WS-300, EPOCROS (registered trademark) WS-500, and EPOCROS (registered trademark) WS-700, all of which are manufactured by Nippon Shokubai Co., Ltd.; and oxazoline group-containing acrylic / styrene polymers such as EPOCROS (registered trademark) K-1000 series and EPOCROS (registered trademark) K-2000 series, all of which are manufactured by Nippon Shokubai Co., Ltd.

[0088] As the epoxy compound (D4), known epoxy-based crosslinking agents can be used, including, for example, liquid epoxy resins such as "TETRAD (registered trademark)-C" and "TETRAD (registered trademark)-X" manufactured by Mitsubishi Gas Chemical Company, Inc., "ADEKA RESIN (registered trademark) EPU series" and "ADEKA RESIN (registered trademark) EPR series" manufactured by ADEKA Corporation, and "CELLOXIDE (registered trademark)" manufactured by Daicel Corporation. These liquid epoxy resins are preferred in that they facilitate mixing operations when producing the pressure-sensitive adhesive composition.

[0089] The polyfunctional (meth)acrylic acid ester monomer (D5) is a (meth)acrylic acid ester monomer having multiple (two or more) (meth)acryloyl groups. Hereinafter, a (meth)acrylic acid ester monomer having N (meth)acryloyl groups per molecule may be referred to as an N-functional monomer. Examples of such (meth)acrylic acid ester monomers include hydrocarbon-based polyfunctional monomers (D51) and hydrocarbon ether-based polyfunctional monomers (D52). The hydrocarbon-based or hydrocarbon ether-based polyfunctional monomers (D51) and (D52) are preferably compounds in which the hydroxy group of a polyhydric alcohol having a hydrocarbon group or hydrocarbon ether group as the main skeleton having from 10 to 100 carbon atoms is (meth)acrylated. Such compounds are preferred from the viewpoint of improving adhesiveness (tackiness) through crosslinking. Examples of the hydrocarbon group of the polyhydric alcohol include linear or branched aliphatic hydrocarbon groups, aromatic hydrocarbon groups, alicyclic hydrocarbon groups, and hydrocarbon groups formed by combining these hydrocarbon groups. Examples of the hydrocarbon ether group include those obtained by etherifying the hydrocarbon group. Examples of polyhydric alcohols having a hydrocarbon ether group as the main skeleton include compounds obtained by adding alkylene oxides having 2 to 4 carbon atoms to the polyhydric alcohols (addition number: 1 to 30). Further examples include polyalkylene glycols (addition number: 1 to 30) obtained from alkylene oxides having 2 to 4 carbon atoms.

[0090] Examples of the bifunctional monomer (D511) among the hydrocarbon-based polyfunctional monomers (D51) include di(meth)acrylates of alkylene glycols such as ethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; di(meth)acrylates of diol compounds having an alicyclic hydrocarbon group such as cyclohexane dimethanol di(meth)acrylate and tricyclodecane dimethanol di(meth)acrylate (dimethylol-tricyclodecane diacrylate); and di(meth)acrylates of diol compounds having an aromatic hydrocarbon group such as bisphenol A di(meth)acrylate.

[0091] Among the hydrocarbon ether-based polyfunctional monomers (D52), examples of the bifunctional monomers (D521) include di(meth)acrylates of compounds in which alkylene oxide is added to the alkylene glycols or diol compounds described in the above hydrocarbon-based bifunctional monomers (D511), such as alkoxylated hexanediol di(meth)acrylate, alkoxylated cyclohexanedimethanol di(meth)acrylate, alkoxylated di(meth)acrylate, alkoxylated neopentyl glycol di(meth)acrylate, and alkoxylated bisphenol A di(meth)acrylate. Further, more specific examples of the hydrocarbon ether-based bifunctional monomer (D521) include di(meth)acrylates of polyalkylene glycols such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and dipropylene glycol di(meth)acrylate, as well as dioxane glycol di(meth)acrylate.

[0092] Examples of trifunctional to hexafunctional monomers among the hydrocarbon or hydrocarbon ether polyfunctional monomers (D51) and (D52) include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, glyceryl tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and dipentaerythritol penta(meth)acrylate. Examples of the alkylene oxide include tri(meth)acrylates, tetra(meth)acrylates, penta(meth)acrylates, and hexa(meth)acrylates of tri-, tetra-, penta-, or hexaol compounds such as dipentaerythritol hexa(meth)acrylate, and also include tri(meth)acrylates, tetra(meth)acrylates, penta(meth)acrylates, and hexa(meth)acrylates of compounds obtained by adding alkylene oxide to the tri-, tetra-, penta-, or hexaol compounds.

[0093] The polyfunctional (meth)acrylic acid ester monomer (D5) may be any monomer other than the hydrocarbon-based or hydrocarbon ether-based polyfunctional monomers (D51) and (D52) as long as it is a (meth)acrylic acid ester monomer having a plurality (two or more) of (meth)acryloyl groups. Examples of such monomers include polyester poly(meth)acrylates and epoxy (meth)acrylates each having two or more (meth)acryloyl groups at its terminal.

[0094] Among these polyfunctional (meth)acrylic acid ester monomers (D5), polyfunctional monomers (D51) and / or polyfunctional monomers (D52) are preferred, and polyfunctional monomers (D51) and / or polyfunctional monomers (D52) which are trifunctional to hexafunctional monomers are more preferred.

[0095] The polyfunctional allyl monomer (D6) is a monomer having at least one allyl group and a plurality (two or more) of radically polymerizable functional groups including the allyl group, such as allyl (meth)acrylate, diallyl phthalate (DAP), trimethylolpropane diallyl ether, pentaerythritol triallyl ether, and triallyl isocyanurate.

[0096] From the viewpoints of productivity and stability, the peroxide (D7) preferably has a 1-minute half-life temperature of 80 to 160° C., more preferably 80 to 140° C., even more preferably 80 to 125° C., and particularly preferably 90 to 125° C. The "half-life of the peroxide" means the time until the remaining amount of the peroxide is reduced to half, and values ​​in manufacturer catalogs, for example, values ​​listed in the Organic Peroxide Catalog, 9th Edition (May 2003) published by NOF Corporation, can be referenced.

[0097] Examples of peroxides (D7) include diisopropyl peroxydicarbonate (one-minute half-life temperature: 88.3°C; hereinafter, the temperature in parentheses indicates the one-minute half-life temperature), di(2-ethylhexyl)peroxydicarbonate (90.6°C), bis(4-t-butylcyclohexyl)peroxydicarbonate (92.1°C), di-sec-butyl peroxydicarbonate (92.4°C), t-butyl peroxyneodecanoate (103.5°C), t-hexyl peroxypivalate (109.1°C), and t-butyl peroxypivalate (110.3°C). °C), dilauroyl peroxide (116.4 °C), bis-n-octanoyl peroxide (117.4 °C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (124.3 °C), di(4-methylbenzoyl) peroxide (128.2 °C), dibenzoyl peroxide (benzoyl peroxide) (130.0 °C), a mixture of dibenzoyl peroxide, benzoyl m-methylbenzoyl peroxide, and m-toluoyl peroxide (131.1 °C), and t-butyl peroxybutyrate (136.1 °C). Among these, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, and t-butyl peroxyneodecanoate are preferred. These may be used alone or in combination of two or more. As a combination of two or more, a combination of di(4-t-butylcyclohexyl) peroxydicarbonate and dilauroyl peroxide is preferred.

[0098] Peroxide (D7) is available from NOF Corporation under the trade names: "Perloyl (registered trademark, the same hereinafter) IB" (85.1°C), "Percumyl (registered trademark, the same hereinafter) ND" (94.0°C), "Perloyl NPP" (94.0°C), "Perloyl IPP" (88.3°C), "Perloyl SBP" (92.4°C), "Perocta (registered trademark, the same hereinafter) ND" (92.4°C), "Perloyl TCP" (92.1°C), and "Perloyl OPP" (9 0.6°C), "Perhexyl (registered trademark, the same below) ND" (100.9°C), "Perbutyl (registered trademark, the same below) ND" (103.5°C), "Perbutyl NHP" (104.6°C), "Perhexyl PV" (109.1°C), "Perbutyl PV" (110.3°C), "Peroyl 355" (112.6°C), "Peroyl L" (116.4°C), "Perocta O" (124.3°C), "Peroyl SA" (131.8°C), "Per Hexa (registered trademark, the same below) 25O (118.8°C), Perhexyl O (132.6°C), Niper (registered trademark, the same below) PMB (128.2°C), Perbutyl O (134.0°C), Niper BMT (131.1°C), Niper BW (130.0°C), Niper BMT-K40 (131.1°C), Niper BMT-M (131.1°C), Perhexa MC (142.1°C), Perhexa TM H" (147.1°C), "Perhexa HC" (149.2°C), "Perhexa C" (153.8°C), "Pertetra (registered trademark, the same applies hereinafter) A" (153.8°C), "Perhexyl I" (155.0°C), "Perbutyl L" (159.4°C), "Perbutyl I" (158.8°C), "Perhexa 25Z" (158.2°C), "Perbutyl A" (159.9°C), "Perhexa 22" (159.9°C), etc.

[0099] The amount of crosslinking agent (D) in the pressure-sensitive adhesive composition is, for example, preferably 0.001 to 5 parts by mass, more preferably 0.005 to 3 parts by mass, even more preferably 0.01 to 1 part by mass, and particularly preferably 0.02 to 0.2 parts by mass, relative to 100 parts by mass of the total of copolymer (A) and monomer (a). When the content of crosslinking agent (D) is within the above range, durability can be further improved.

[0100] 1.6 Photopolymerization Initiator (E) The pressure-sensitive adhesive composition of the present invention is preferably a photocurable pressure-sensitive adhesive composition. Specifically, the pressure-sensitive adhesive composition preferably contains a photopolymerization initiator (E). By including the photopolymerization initiator (E), the monomer (a) can be cured after coating. As the photopolymerization initiator, any of the photopolymerization initiators listed as usable for the polymerization of the copolymer (A) can be used. The amount of the photopolymerization initiator (E) in the pressure-sensitive adhesive composition is, for example, 0.001 to 10 parts by mass, preferably 0.01 to 5 parts by mass, and more preferably 0.05 to 1 part by mass, per 100 parts by mass of the total of the copolymer (A) and the monomer (a).

[0101] 1.7 Chain Transfer Agent (F) The PSA composition may contain a chain transfer agent (F). By including the chain transfer agent (F), it is possible to control the molecular weight when curing the monomer (a) after coating. As the chain transfer agent (F), the chain transfer agents listed as usable in the polymerization of the copolymer (A) can be used. The amount of the chain transfer agent (F) in the PSA composition is, for example, 0.001 to 10 parts by mass, preferably 0.01 to 5 parts by mass, and more preferably 0.05 to 1 part by mass, per 100 parts by mass of the total of the copolymer (A) and the monomer (a).

[0102] 1.8 Solvent (G) The PSA composition may contain a solvent (G). By including the solvent (G), the viscosity of the PSA composition can be adjusted. Examples of the solvent (G) include organic solvents such as esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl ethyl ketone, methyl isobutyl ketone and acetone; and glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether and ethylene glycol dimethyl ether. These solvents may be used alone or in combination of two or more.

[0103] The amount of the solvent (G) in the PSA composition is, for example, 200 parts by mass or less, preferably 100 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 10 parts by mass or less, per 100 parts by mass of the total of the copolymer (A) and the monomer (a). The PSA composition may be substantially free of the solvent (G), and for example, the amount of the solvent (G) may be 1 part by mass or less or 0 part by mass, per 100 parts by mass of the total of the copolymer (A) and the monomer (a).

[0104] 1.9 Other Additive Components (H) The PSA composition may contain, as necessary, other known additive components such as a crosslinking accelerator, an antioxidant, a filler, a colorant (pigment, dye, etc.), an ultraviolet absorber, an antioxidant, a plasticizer, a softener, a surfactant, an antistatic agent, and a dispersant, within the range that does not impair the effects of the present invention.

[0105] As the dispersant, a conventionally known dispersant can be used. The acid value of the dispersant is, for example, preferably 150 mgKOH / g or less, and the lower limit is not particularly limited, but may be 5 mgKOH / g or more, 6 mgKOH / g or more, or 7 mgKOH / g or more. The dispersant preferably has a polyoxyalkylene glycol group. Examples of dispersants include Disperbyk-102, Disperbyk-111, Disperbyk-190, Disperbyk-191, Disperbyk-194N, Disperbyk-2010, Disperbyk-2012, and Disperbyk-2015 manufactured by BYK Japan Co., Ltd., TEGO Dispers-715W, TEGO Dispers-750W, and TEGO Dispers-755W manufactured by Evonik Japan Co., Ltd., and Efka 6230 manufactured by BASF. The content of the dispersant is not particularly limited, but is, for example, 0 to 30 parts by mass, preferably 1 to 15 parts by mass, and more preferably 3 to 10 parts by mass relative to 100 parts by mass of the inorganic particles (B).

[0106] 2. Pressure-sensitive adhesive layer / laminate The pressure-sensitive adhesive layer can be formed by a step of applying the pressure-sensitive adhesive composition to a suitable substrate and a step of curing (preferably photocuring) the coating layer obtained in the application step to form a pressure-sensitive adhesive layer.

[0107] The substrate is not particularly limited and may be a release film or a member to which adhesiveness is to be imparted (for example, an optical member such as an optical film). By using an optical member (for example, an optical film) as the substrate, an optical member (for example, an optical film) on which a pressure-sensitive adhesive (pressure-sensitive adhesive layer) is laminated can be produced. Furthermore, by using a release film as the substrate, the pressure-sensitive adhesive (pressure-sensitive adhesive layer) can be transferred to various members. As a result, a member (for example, an optical member such as an optical film) on which a pressure-sensitive adhesive (pressure-sensitive adhesive layer) is laminated can be produced. As the release film, a conventionally known release film can be used, and a plastic film is preferred from the viewpoints of cost and excellent surface smoothness.

[0108] In the curing step of the pressure-sensitive adhesive layer formation step, it is preferable to irradiate the coating layer obtained in the coating step with active energy rays. Examples of the active energy rays include ultraviolet rays, laser rays, α rays, β rays, γ rays, X-rays, and electron beams. From the viewpoints of controllability, ease of handling, cost, etc., ultraviolet rays are preferably used. More preferably, ultraviolet rays with a wavelength of 200 nm or more and 400 nm or less are used. The ultraviolet rays can be irradiated using a light source such as a high-pressure mercury lamp, a microwave excitation lamp, a chemical lamp, a black light, an LED, or a metal halide lamp. The curing step is preferably carried out in a nitrogen atmosphere and / or with the coating layer laminated with a release film.

[0109] By such a method, a laminate including a substrate and a pressure-sensitive adhesive layer laminated on the substrate can be produced. Such a laminate is also encompassed by the present invention. A laminate including a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention may be one in which the pressure-sensitive adhesive layer is laminated on any substrate (for example, the above-mentioned release film or optical member), but is preferably a laminate in which the pressure-sensitive adhesive layer is laminated on an optical member such as an optical film. Note that, in a laminate including a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, other members may be laminated on the surface of the substrate on which the pressure-sensitive adhesive layer is not laminated or on the surface of the pressure-sensitive adhesive layer on which the substrate is not laminated, as long as the substrate and the pressure-sensitive adhesive layer are directly laminated.

[0110] The pressure-sensitive adhesive layer thus formed contains a copolymer (A) and inorganic particles (B). The copolymer (A) in the pressure-sensitive adhesive layer is a copolymer (A) containing an aromatic structural unit (A1) and a hydroxyl group-containing structural unit (A2), and the content of the structural unit (A2) is preferably 1 to 40 mass% based on 100 mass% of the copolymer (A) (preferably, based on 100 mass% of the total of the structural units (A1) and (A2)). This copolymer (A) is preferably the same as the copolymer (A) in the pressure-sensitive adhesive composition in that the content of the structural unit (A2) is 1 to 40 mass% based on 100 mass% of the copolymer (A) (preferably, based on 100 mass% of the total of the structural units (A1) and (A2)). Hereinafter, a pressure-sensitive adhesive layer containing a copolymer (A) and inorganic particles (B), wherein the copolymer (A) contains the structural unit (A1) and the structural unit (A2), and the content of the structural unit (A2) is 1 to 40 mass% based on 100 mass% of the copolymer (A) (preferably, based on 100 mass% of the total of the structural units (A1) and (A2)), will be referred to as the pressure-sensitive adhesive layer of the present invention.

[0111] The copolymer (A) contained in the pressure-sensitive adhesive layer of the present invention contains structural units (A1), structural units (A2), and the like, and optionally contains structural unit (A3) (specifically, structural units (A31) to (A42)). Specific examples and preferred examples of these structural units are the same as those described above for copolymer (A). The content of each structural unit in 100% by mass of copolymer (A) in the pressure-sensitive adhesive layer of the present invention is, for example, as follows: Content of structural unit (A1): For example, 40 to 99% by mass, preferably 50 to 95% by mass, and more preferably 70 to 90% by mass. Content of structural unit (A2): For example, 1 to 40% by mass, preferably 3 to 30% by mass, and more preferably 7 to 25% by mass. It may also be 12 to 25% by mass. Content of structural unit (A3): For example, 0 to 50% by mass, preferably 1 to 50% by mass, more preferably 1 to 40% by mass, even more preferably 5 to 25% by mass, and particularly preferably 5 to 20% by mass. The content of the structural unit (A31): for example, 0 to 50% by mass, preferably 5 to 40% by mass, more preferably 10 to 30% by mass, and even more preferably 10 to 20% by mass. The content of the structural unit (A32): for example, 0 to 50% by mass, preferably 1 to 30% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 10% by mass. The content of the structural unit (A33): for example, 0 to 50% by mass, preferably 5 to 40% by mass, and more preferably 10 to 30% by mass. The content of the structural unit (A34): for example, 0 to 50% by mass, preferably 0 to 30% by mass, and more preferably 1 to 20% by mass. The content of the structural unit (A35): for example, 0 to 50% by mass, preferably 0 to 10% by mass, and more preferably 0 to 5% by mass. The content of the structural unit (A36): for example, 0 to 50% by mass, preferably 0 to 30% by mass, more preferably 0 to 10% by mass, or even 0% by mass. Content of structural unit (A37): For example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. Content of structural unit (A38): For example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. Content of structural unit (A39): For example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass.Content of structural unit (A40): For example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. Content of structural unit (A41): For example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass. Content of structural unit (A42): For example, 0 to 50% by mass, preferably 0 to 20% by mass, and more preferably 0 to 10% by mass.

[0112] The total content of the structural unit (A1) and the structural unit (A2) is, for example, 50 to 100% by mass, preferably 60 to 99% by mass, more preferably 75 to 95% by mass, and may be 85 to 100% by mass or 95 to 100% by mass, based on 100% by mass of the copolymer (A) in the pressure-sensitive adhesive layer. The mass ratio (A1 / A2) of the structural unit (A1) to the structural unit (A2) is, for example, 50 / 50 to 99 / 1, preferably 70 / 30 to 98 / 2, more preferably 75 / 25 to 95 / 5, even more preferably 80 / 20 to 90 / 10, and particularly preferably 83 / 17 to 89 / 11.

[0113] The weight average molecular weight of the copolymer (A) in the pressure-sensitive adhesive layer of the present invention is, for example, 500,000 to 3,000,000, preferably 700,000 to 2,500,000, more preferably 1,000,000 to 2,000,000, and particularly preferably 1,200,000 to 1,500,000.

[0114] When a pressure-sensitive adhesive layer is formed by curing a pressure-sensitive adhesive composition using a photopolymerization initiator, the pressure-sensitive adhesive layer usually contains photopolymerization initiator residues.

[0115] The amount of the residual monomer (a) in the pressure-sensitive adhesive layer of the present invention is, for example, 1 part by mass or less, preferably 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, relative to 100 parts by mass of the copolymer (A). When the pressure-sensitive adhesive composition contains a sufficient amount of the monomer (a) before curing, the inorganic particles (B) are appropriately dispersed, and this property is maintained even if the amount of the monomer (a) in the pressure-sensitive adhesive layer after curing decreases, and high transparency can be maintained even if the thickness of the pressure-sensitive adhesive layer increases.

[0116] The preferred embodiments of the inorganic particles (B) contained in the pressure-sensitive adhesive layer after curing are the same as those explained above for the inorganic particles (B) before curing.

[0117] The amount of inorganic particles (B) in the pressure-sensitive adhesive layer of the present invention is, for example, 20 to 2000 parts by mass, preferably 50 to 1500 parts by mass, more preferably 80 to 1000 parts by mass, and may be 80 to 500 parts by mass or 80 to 250 parts by mass, relative to 100 parts by mass of copolymer (A). By adjusting the proportion of inorganic particles (B) within the above range, it becomes easier to achieve both refractive index and transparency.

[0118] The total content of the copolymer (A) and the inorganic particles (B) in the pressure-sensitive adhesive layer of the present invention is preferably 80 to 100 mass%, more preferably 90 to 99.9 mass%, and even more preferably 95 to 99.9 mass%, based on 100 mass% of the pressure-sensitive adhesive layer.

[0119] When the thickness of the pressure-sensitive adhesive layer of the present invention is 100 μm, the haze is, for example, 3.0% or less, preferably 2.0% or less, and more preferably 1.0% or less.

[0120] The thickness of the pressure-sensitive adhesive layer of the present invention is not particularly limited, and may be, for example, 1 to 2000 μm, 30 to 1000 μm, 50 to 700 μm, or approximately 100 to 500 μm. In particular, since the pressure-sensitive adhesive layer of the present invention is formed from a specific pressure-sensitive adhesive composition, it is possible to achieve both transparency and refractive index even when the pressure-sensitive adhesive layer is made thick (for example, 50 μm or more, preferably 100 μm or more), making it suitable for use in adhering optical films. Furthermore, the thickness of the pressure-sensitive adhesive layer of the present invention may be 2 to 300 μm, 3 to 200 μm, or 5 to 100 μm.

[0121] The haze of the pressure-sensitive adhesive layer of the present invention is, for example, 3.0% or less, preferably 2.0% or less, more preferably 1.0% or less, regardless of the thickness, and the lower limit may be about 0.1%.

[0122] Furthermore, since the copolymer (A) constituting the pressure-sensitive adhesive layer of the present invention contains a hydroxyl group-containing structural unit (A2), the increase in haze is small even when left under humid conditions. The haze after a humidification test (temperature 60°C, relative humidity 95% RH, 500 hours) described below is, for example, 13% or less, preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less, and the lower limit may be about 1%.

[0123] The refractive index of the pressure-sensitive adhesive layer of the present invention is, for example, 1.58 to 1.80, preferably 1.60 to 1.75, and more preferably 1.61 to 1.72. When the refractive index of the pressure-sensitive adhesive layer is within this range, it can be suitably used for adhesion of optical films.

[0124] The pressure-sensitive adhesive composition and pressure-sensitive adhesive layer can be used for various applications, and are preferably used for bonding optical components such as optical films, i.e., as a pressure-sensitive adhesive layer laminated on optical components such as optical films. Specifically, they are preferably used for bonding optical components such as optical films in image display devices such as liquid crystal displays, organic electroluminescent displays, plasma displays (PDPs), micro LED displays, curved displays, and flexible displays. In particular, the pressure-sensitive adhesive composition and pressure-sensitive adhesive layer are preferably used for thin pressure-sensitive adhesive optical films used in large liquid crystal panels. Examples of optical films include polarizing plates, retardation plates for preventing coloration, optical compensation films such as viewing angle expansion films for improving the viewing angle of liquid crystal displays, brightness enhancement films for increasing the contrast of displays, light extraction films for increasing the light extraction efficiency of surface light emitters, and laminates of these.

[0125] This application claims the benefit of priority based on Japanese Patent Application No. 2024-064673 filed on April 12, 2024, Japanese Patent Application No. 2024-082136 filed on May 20, 2024, and Japanese Patent Application No. 2024-179870 filed on October 15, 2024. The entire contents of the specifications of Japanese Patent Application No. 2024-064673 filed on April 12, 2024, Japanese Patent Application No. 2024-082136 filed on May 20, 2024, and Japanese Patent Application No. 2024-179870 filed on October 15, 2024 are incorporated herein by reference.

[0126] 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, and can be practiced with appropriate modifications within the scope of the above and below-described aims, all of which are within the technical scope of the present invention. In the following description, all "parts" mean "parts by mass." Unless otherwise specified, operations and measurements of physical properties were carried out at room temperature of 23°C and a relative humidity of 55% RH.

[0127] 1. Measurement Method 1.1 Weight-average molecular weight (Mw) The weight-average molecular weight (Mw) of the (meth)acrylic acid ester-based copolymer (A) was measured by GPC (gel permeation chromatography) under the following conditions: Analytical apparatus: HLC-8120GPC, manufactured by Tosoh Corporation Column: G7000HXL+GMHXL+GMHXL, manufactured by Tosoh Corporation Column size: each 7.8 mmφ×30 cm, total 90 cm Column temperature: 40°C Flow rate: 0.8 ml / min Injection volume: 100 μl Eluent: tetrahydrofuran Detector: differential refractometer (RI) Standard sample: polystyrene

[0128] 1.2 Amount of (meth)acrylic acid ester monomer (a) The remaining amount and composition of the (meth)acrylic acid ester monomer (a) were determined using GC / MS (GC—GC7980A manufactured by Agilent, MS—Q-1050GC manufactured by JEOL Ltd.).

[0129] 1.3 Composition of Copolymer (A) The composition of the copolymer was determined by NMR. In the NMR method, peaks of copolymer components were assigned with reference to the "Aldrich Library of NMR Spectra" and the "13C-NMR Spectra" of Sadtler Research Lab. The copolymer composition was 1 H and 13 The measurement was performed using the integral value of C. The measurement device used was a JNM-GX400 (manufactured by JEOL Ltd.), deuterated chloroform was used as the solvent, and the measurement temperature was 27°C.

[0130] 1.4 Refractive Index The refractive index of the pressure-sensitive adhesive layer (thickness: 20 μm) obtained in each of the Examples and Comparative Examples was measured at 25° C. using an Abbe refractometer as a value relative to the sodium D line.

[0131] 1.5 Haze The PET film on one side of the adhesive layer (thickness: 100 μm) sandwiched between PET films obtained in the Examples or Comparative Examples was peeled off, and the exposed adhesive surface was roll-pressed onto alkali-free glass (82 mm × 53 mm × thickness 0.5 mm). Next, the other PET film was peeled off, and alkali-free glass (82 mm × 53 mm × thickness 0.5 mm) was laminated using a roll. Thereafter, autoclave treatment (50 ° C, gauge pressure 0.4 MPa, 20 minutes) was performed to perform finish lamination, and an evaluation sample was prepared. The haze of the obtained evaluation sample was measured in accordance with JIS K7136 (2000) using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in an environment of 25 ° C and 55% RH.

[0132] 1.6 Durability (heating test, humidification test, HS test) An organic EL display device was produced as described below by bonding a polarizing plate with an optical compensation layer having a pressure-sensitive adhesive layer (thickness: 20 μm) produced in Examples or Comparative Examples, and used as a sample for durability evaluation. The obtained sample was subjected to the following tests, and its appearance was visually inspected and evaluated according to the following criteria. (1) Treated at a temperature of 85°C for 500 hours (heat test) (2) Treated in an atmosphere of a temperature of 60°C and a relative humidity of 95% RH for 500 hours (humidification test) (3) Treated for 300 cycles (300 hours) with one cycle consisting of leaving it in an environment of a temperature of 85°C for 30 minutes and then leaving it in an environment of -40°C for 30 minutes (heat shock (HS) test) - Evaluation criteria - ◎: No bubbles at all on the edge ○: There are a few bubbles on the edge, but there is no practical problem △: There are bubbles on the edge, but there is no practical problem unless it is for a special purpose ×: There are a considerable number of bubbles on the edge, and there is a practical problem

[0133] 1.7 Haze (%) after humidification test The sample subjected to the above-mentioned durability humidification test was taken out into a room temperature (23°C, 55% RH) environment and allowed to stand for 3 hours. After that, the haze was measured in an environment of a temperature of 25°C and a relative humidity of 55% RH using a haze meter (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136 (2000).

[0134] 1.8 Coatability The surface condition of the pressure-sensitive adhesive layer (thickness: 20 μm) of each Example or Comparative Example immediately after its formation was visually observed and evaluated according to the following criteria. 5-point scale: 5 is the best, and 3 or above is practically usable. 5: No coating streaks or coating unevenness 4: Weak coating streaks or weak coating unevenness partially present 3: Weak coating streaks or weak coating unevenness over the entire surface 2: Strong coating streaks or strong coating unevenness partially present or over the entire surface 1: Unable to form a uniformly coated surface

[0135] 2. Production of (Meth)acrylic Acid Ester-Based Copolymer (A) [Production Examples 1 to 13, 19 to 21, 26 to 31] Four UV black light lamps (FL20SBL, manufactured by Sankyo Electric Co., Ltd.) were installed on each of the four sides of a reaction box that blocked external ultraviolet light. A 2-L four-neck flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, and condenser was placed in the reaction box. The aromatic monomer (a1), hydroxyl group-containing monomer (a2), and other monomer (a3) ​​were charged into the flask in the amounts shown in Tables 1 to 3, and the mixture was heated to 30°C while replacing the air in the flask with nitrogen. Next, the photopolymerization initiator was charged in the amount shown in Tables 1 to 3 with stirring, and the mixture was mixed uniformly. To initiate polymerization, ultraviolet light was irradiated using a black light (cumulative light dose 200 mJ / cm 2 After the reaction started, when the reaction temperature rose by 10°C, air was introduced into the flask with an air pump to terminate the reaction, thereby obtaining acrylic syrups containing (meth)acrylic acid ester copolymers (A-1) to (A-13), (A-19) to (A-21), and (A-26) to (A-31). The properties of the copolymers (A) and residual monomers (a) in the acrylic syrups are shown in Tables 1 to 3.

[0136] [Production Examples 14 to 18] A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with the aromatic monomer (a1), the hydroxyl group-containing monomer (a2), the other monomer (a3), and a thermal polymerization initiator in the amounts shown in Table 2, and nitrogen gas was introduced while gently stirring. After nitrogen gas replacement, the liquid temperature in the flask was controlled to around 60°C, and a polymerization reaction was carried out for 0.5 hours to prepare acrylic syrups containing (meth)acrylic acid ester-based copolymers (A-14) to (A-18), respectively. The properties of the copolymer (A) and the residual monomer (a) in the acrylic syrup are shown in Table 2.

[0137] [Production Examples 22 to 25] A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with the aromatic monomer (a1), the hydroxyl group-containing monomer (a2), the other monomer (a3), and a thermal polymerization initiator in the amounts shown in Table 3, and 100 parts by mass of ethyl acetate was also charged. Nitrogen gas was then introduced into the flask with gentle stirring. After nitrogen gas replacement, the liquid temperature in the flask was controlled to around 80°C, and a polymerization reaction was carried out for 2 hours to prepare solutions of (meth)acrylic acid ester-based copolymers (A-22) to (A-25). The properties of the copolymer (A) and the residual monomer (a) in the solution are shown in Table 3.

[0138]

[0139]

[0140]

[0141] The symbols in Tables 1 to 3 have the following meanings: A-BPML: p-phenylbenzyl acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) NMT-A: 1-naphthylmethyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.) A-LEN-10: ethoxylated o-phenylphenol acrylate (A-LEN-10, manufactured by Shin-Nakamura Chemical Co., Ltd.) POB-A: phenoxybenzyl acrylate (light acrylate POB-A, manufactured by Kyoeisha Chemical Co., Ltd.) PhEA: phenoxyethyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.) BzA: benzyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) 4HBA: 4-hydroxybutyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) HEAA: N-hydroxyethyl acrylamide (manufactured by KJ Chemicals Co., Ltd.) IBXA: isobornyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) ACMO (registered trademark): N-acryloylmorpholine (manufactured by KJ Chemicals Co., Ltd.) BA: n-butyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) 2EHA: 2-ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) MEA: methoxyethyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) AA: acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) Omnirad (registered trademark) 651: 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by IGM Resins B.V.) AIBN: 2,2'-azobisisobutyronitrile (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0142] 3. Preparation of Pressure-Sensitive Adhesive Compositions [Examples 1 to 24, Comparative Examples 1 to 13] Each syrup of the (meth)acrylic acid ester copolymer (A) obtained in Production Examples 1 to 31 (provided that the total amount of the solids in the syrup, i.e., the (meth)acrylic acid ester copolymer (A) and the residual monomer (a) in the syrup, was 100 parts by mass) or each solution of the (meth)acrylic acid ester copolymer (A) (provided that the total amount of the solids in the solution, i.e., the (meth)acrylic acid ester copolymer (A) and the residual monomer (a) in the solution, was 100 parts by mass) was mixed with inorganic particles (B) (in terms of zirconia fine particles), silane coupling agent (C), crosslinking agent (D) (in terms of active ingredient), additional monomer (a), photopolymerization initiator (E), and chain transfer agent (F) shown in Tables 4 to 6, and the mixture was degassed to prepare a pressure-sensitive adhesive composition.

[0143] 4. Preparation of Pressure-Sensitive Adhesive Layer [Examples 1 to 24, Comparative Examples 8 to 13] The obtained pressure-sensitive adhesive composition was applied to a release-treated surface of a 75 μm-thick polyethylene terephthalate (PET) film, one side of which had been treated with a release agent (silicone treatment), to a predetermined coating thickness (target thickness of the pressure-sensitive adhesive layer). The release-treated surface of a 75 μm-thick release-treated PET film was attached to this coated surface, and the PET films were placed above and below the pressure-sensitive adhesive composition, forming a sealed sandwich. A black light was used from above and below at 2.0 mW / cm 2 (Integrated light intensity: 400 mJ / cm each 2 ) to obtain a pressure-sensitive adhesive layer.

[0144] [Comparative Examples 1 to 7] The obtained pressure-sensitive adhesive compositions were applied to the release-treated surface of a 75 μm-thick polyethylene terephthalate (PET) film that had been subjected to a release treatment (silicone treatment) so that the thickness of the coating film after heat treatment would be the desired thickness of the pressure-sensitive adhesive layer. The film was then heated at 120°C for 2 minutes to form a coating film. The heat treatment was carried out using a float drying method in which hot air was blown directly from above and below the film. The release-treated surface of a 75 μm-thick PET film that had been release-treated was then attached to the dried coating film surface, and the PET films were placed above and below the coating film to form a sealed sandwich. The coating film was then heated using a black light at 2.0 mW / cm from above and below. 2 (Integrated light intensity: 400 mJ / cm each 2 ) to obtain a pressure-sensitive adhesive layer.

[0145] The properties of the resulting pressure-sensitive adhesive layer were evaluated, and the results are shown in Tables 4 to 6.

[0146]

[0147]

[0148]

[0149] The symbols in Tables 4 to 6 have the following meanings: [HR-LP-3-1]: Zirconia microparticle dispersion (manufactured by Nippon Shokubai Co., Ltd. (a specific production method is shown below in "Production of Zirconia Microparticles (HR-LP-3-1)"), volume average particle size 18 nm, particle refractive index 1.86, dispersion of monomer POBA (phenoxybenzyl acrylate), solid content concentration 85% by mass) [KBM-403]: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) [A-DPH]: Dipentaerythritol polyacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate) [POBA (1)]: Phenoxybenzyl acrylate derived from HR-LP-3-1 [POBA (2)]: Phenoxybenzyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., Light Acrylate POB-A) [POBA total]: total of phenoxybenzyl acrylate (total of POBA (1) and POBA (2)) [Omnirad (registered trademark) 184]: 1-hydroxycyclohexyl-phenyl ketone (manufactured by IGM Resins B.V.) [EHMP]: 2-ethylhexyl-3-mercaptopropionate (manufactured by SC Organic Chemical Co., Ltd.)

[0150] [Production of Zirconia Fine Particles (HR-LP-3-1)] A solution of zirconium 2-ethylhexanoate in mineral spirits (782 parts, zirconium 2-ethylhexanoate content: 44% by mass) was mixed with pure water (268 parts). The resulting mixture was placed in an autoclave equipped with a stirrer, and the atmosphere inside the autoclave was replaced with nitrogen gas. The mixture was then heated to 210°C and maintained at that temperature for 16 hours to react, producing zirconium oxide (zirconia) particles. The reacted mixture was then removed, and the precipitate that had accumulated at the bottom was filtered out, washed with acetone, and then dried. The dried precipitate (100 parts) was dispersed in toluene (700 parts), resulting in a cloudy white solution. Next, as a purification step, the mixture was again filtered using quantitative filter paper (Advantec Toyo Co., Ltd., No. 5C) to remove coarse particles and other particles from the precipitate. The filtrate was then concentrated under reduced pressure to remove the toluene, and white zirconia fine particles were recovered. The number-average particle diameter of the recovered zirconia microparticles was measured by observation with an ultra-high resolution field emission scanning electron microscope (S-4800, manufactured by Hitachi High-Technologies Corporation). The zirconia microparticles were observed at a magnification of 150,000 times, and the length of each of 100 randomly selected particles in the major axis direction was measured, and the average value was taken as the number-average particle diameter. The number-average particle diameter of the zirconia microparticles measured with an electron microscope was 18 nm. A zirconia microparticle dispersion (HR-LP-3-1) was prepared by mixing and stirring the zirconia microparticles obtained above, phenoxybenzyl acrylate (Light Acrylate POB-A, manufactured by Kyoeisha Chemical Co., Ltd.), and DISPER BYK-111 (manufactured by BYK Japan KK) in a mass ratio of zirconia microparticles / phenoxybenzyl acrylate / BYK-111 = 80.0 / 15.0 / 5.0. The volume average particle size of the zirconia fine particles in the resulting dispersion was 18 nm, and the particle refractive index was 1.86.

[0151] In the evaluation of durability and the evaluation of haze after the humidification test, an organic EL display device manufactured as follows was used.

[0152] 5. Organic EL display device 5.1 Preparation of polarizing plate A-PET (amorphous polyethylene terephthalate) film (manufactured by Mitsubishi Chemical Corporation, product name: Novaclear (registered trademark) SH046, thickness 200 μm) was prepared as a substrate, and the surface was corona-treated (corona discharge amount 58 W min / m 2 ) was applied. Separately, polyvinyl alcohol (PVA, polymerization degree 4200, saponification degree 99.2%) to which 1% by mass of acetoacetyl-modified polyvinyl alcohol (manufactured by Mitsubishi Chemical Corporation, trade name: Gohsefimer (trade name) Z200, polymerization degree 1200, saponification degree 99.0% or more, acetoacetyl-modification degree 4.6%) was added was prepared. This polyvinyl alcohol was applied to the corona-treated surface of the A-PET film so that the film thickness after drying would be 12 μm, and the film was dried by hot air drying in an atmosphere of 60°C for 10 minutes. In this way, a laminate having a polyvinyl alcohol (PVA)-based resin layer provided on the substrate was produced.

[0153] Next, this laminate was first stretched 2.0 times in air at 130°C to obtain a stretched laminate. Next, the stretched laminate was immersed in a boric acid insolubilizing aqueous solution at a liquid temperature of 30°C for 30 seconds to insolubilize the PVA-based resin layer in which polyvinyl alcohol molecules contained in the stretched laminate were oriented. This boric acid insolubilizing aqueous solution had a boric acid content of 3% by mass relative to 100% by mass of water. A colored laminate was produced by dyeing this stretched laminate. The colored laminate was produced by immersing the stretched laminate in a dyeing solution containing iodine and potassium iodide at a liquid temperature of 30°C, thereby adsorbing iodine to the PVA-based resin layer contained in the stretched laminate. The iodine concentration and immersion time were adjusted so that the single transmittance of the resulting polarizer was 44.5%. Specifically, the dye solution contained water as a solvent, had an iodine concentration in the range of 0.08% by mass to 0.25% by mass, and a potassium iodide concentration in the range of 0.56% by mass to 1.75% by mass, with the ratio of the iodine and potassium iodide concentrations being 1:7.

[0154] Next, the colored laminate was immersed in a boric acid crosslinking aqueous solution at 30°C for 60 seconds to crosslink the PVA molecules of the iodine-adsorbed PVA-based resin layer. The boric acid crosslinking aqueous solution used in this step had a boric acid content of 3% by mass relative to 100% by mass of water and a potassium iodide content of 3% by mass relative to 100% by mass of water. The resulting colored laminate was then stretched 2.7 times in the boric acid aqueous solution at a stretching temperature of 70°C in the same direction as the stretching in air described above, resulting in a final stretch ratio of 5.4 times, thereby obtaining a substrate / polarizer laminate. The polarizer had a thickness of 5 μm. The boric acid crosslinking aqueous solution used in this step had a boric acid content of 6.5% by mass relative to 100% by mass of water and a potassium iodide content of 5% by mass relative to 100% by mass of water. The resulting laminate was removed from the boric acid aqueous solution, and the boric acid adhering to the polarizer surface was washed with an aqueous solution containing 2% by mass of potassium iodide relative to 100% by mass of water. The washed laminate was dried with hot air at 60°C.

[0155] An acrylic film having a thickness of 40 μm was attached to the polarizer surface of the substrate / polarizer laminate obtained above via a PVA adhesive, to obtain a polarizing plate having a protective layer / polarizer / resin substrate structure.

[0156] 5.2 Preparation of Liquid Crystal Alignment Solidified Layer Constituting the First Optical Compensation Layer A liquid crystal alignment solidified layer (first optical compensation layer) was formed on a substrate (TAC film) according to the procedure described in paragraphs

[0151] to

[0156] of JP 2006-133652 A. Note that the direction of the rubbing treatment was such that, when attached to the polarizer, it was at a 15° counterclockwise angle relative to the direction of the absorption axis of the polarizer as viewed from the viewing side. The thickness of the first optical compensation layer was 1.7 μm, and the in-plane retardation Re(550) was 270 nm. Furthermore, the first optical compensation layer was a negative A plate exhibiting refractive index characteristics of nx = nz > ny. Furthermore, no protrusions with a height of 0.4 μm or more were observed on the surface of the first optical compensation layer (negative A plate).

[0157] 5.3 Preparation of Liquid Crystal Alignment Solidified Layer Constituting Second Optical Compensation Layer 10 g of a polymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (manufactured by BASF, trade name "Paliocolor (registered trademark) LC242") and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (Omnirad (registered trademark) 907; manufactured by IGM Resins B.V.) were dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).

[0158] A photo-alignment film was coated on the surface of a polyethylene terephthalate (PET) film (thickness: 38 μm), and then photo-alignment treatment was performed. The direction of the photo-alignment treatment was set to a 75° counterclockwise angle, as viewed from the viewing side, with respect to the direction of the absorption axis of the polarizer when it was attached to the polarizer. The liquid crystal composition was coated on this photo-alignment-treated surface using a bar coater, and the liquid crystal compound was aligned by heating and drying at 90° C. for 2 minutes. The liquid crystal layer thus formed was irradiated with 1 mJ / cm using a metal halide lamp. 2 The liquid crystal layer was cured by irradiating the liquid crystal layer with light of 1000 nm to form a liquid crystal alignment solidified layer (second optical compensation layer) on the substrate (PET film). The second optical compensation layer had a thickness of 1.2 μm and an in-plane retardation Re(550) of 140 nm. Furthermore, the second optical compensation layer was a positive A plate exhibiting refractive index characteristics of nx > ny = nz.

[0159] 5.4 Preparation of Polarizing Plate with Optical Compensation Layer The A-PET film substrate was peeled from the polarizing plate obtained above, and the first optical compensation layer was transferred from the substrate / first optical compensation layer laminate to the peeled surface via a UV-curable adhesive. Furthermore, the second optical compensation layer was transferred from the substrate / second optical compensation layer laminate to the surface of the first optical compensation layer via a UV-curable adhesive. In this way, a polarizing plate with optical compensation layers was obtained having a configuration of protective layer / polarizer / first optical compensation layer (negative A plate: λ / 2 plate) / second optical compensation layer (positive A plate: λ / 4 plate).

[0160] 5.5 Preparation of Pressure-Sensitive Adhesive Layer and Polarizing Plate with Optical Compensation Layer A corona discharge of 80 W·min / m was applied to the polarizing plate side (opposite to the protective film side) on which the pressure-sensitive adhesive layer of the polarizing plate with optical compensation layer obtained above was to be formed. 2Next, the PET film on which the pressure-sensitive adhesive layer was formed was attached so that the formed easy-adhesion treatment layer and the pressure-sensitive adhesive layer (thickness: 20 μm) obtained in the Examples or Comparative Examples were in contact with each other, thereby producing a polarizing plate with a pressure-sensitive adhesive layer and an optical compensation layer.

[0161] 5.6 Fabrication of Organic EL Display Device The obtained pressure-sensitive adhesive layer and polarizing plate with optical compensation layer were cut into a size of 100 mm x 50 mm. A smartphone (Galaxy-S23) manufactured by Samsung Electronics Co., Ltd. was disassembled to remove the organic EL display device. The polarizing film attached to this organic EL display device was peeled off, and the polarizing plate with optical compensation layer cut out above was attached instead to obtain an organic EL display device.

[0162] The pressure-sensitive adhesive composition and pressure-sensitive adhesive layer of the present invention can be used for adhesion or bonding of various members, preferably optical films.

Claims

1. A pressure-sensitive adhesive composition for optical films, comprising a composition comprising a (meth)acrylic acid ester copolymer (A), a (meth)acrylic acid ester monomer (a), and inorganic particles (B), wherein the copolymer (A) comprises a structural unit (A1) derived from an aromatic hydrocarbon group-containing (meth)acrylic acid ester monomer (a1) and a structural unit (A2) derived from a hydroxyl group-containing (meth)acrylic acid ester monomer (a2), the monomer (a) comprises the aromatic hydrocarbon group-containing (meth)acrylic acid ester monomer (a1) and the hydroxyl group-containing (meth)acrylic acid ester monomer (a2), the content of the structural unit (A2) is 1 to 40 mass% based on 100 mass% of the copolymer (A), and the content of the monomer (a) is 45 to 95 mass% based on 100 mass% of the total of the copolymer (A) and the monomer (a).

2. The pressure-sensitive adhesive composition according to claim 1, further comprising a photopolymerization initiator (E).

3. The pressure-sensitive adhesive composition according to claim 1, wherein the monomer (a1) is at least one selected from the group consisting of aryl esters of (meth)acrylic acid, aralkyl esters of (meth)acrylic acid, and aryloxyalkyl esters of (meth)acrylic acid, and the aryl esters of (meth)acrylic acid, aralkyl esters of (meth)acrylic acid, and aryloxyalkyl esters of (meth)acrylic acid may have an aryl group, arylalkyl group, aryloxy group, or aryloxyalkyl group bonded thereto, and the aryl esters of (meth)acrylic acid, aralkyl esters of (meth)acrylic acid, and aryloxyalkyl esters of (meth)acrylic acid may be alkylene oxide-modified products.

4. The pressure-sensitive adhesive composition according to claim 1, wherein the copolymer (A) contains a structural unit (A3) derived from another monomer (a3) ​​other than the aromatic hydrocarbon group-containing (meth)acrylic ester monomer (a1) and the hydroxyl group-containing (meth)acrylic ester monomer (a2), the (meth)acrylic ester monomer (a) contains another monomer (a3) ​​other than the aromatic hydrocarbon group-containing (meth)acrylic ester monomer (a1) and the hydroxyl group-containing (meth)acrylic ester monomer (a2), and the content of the structural unit (A3) is 50 mass% or less in 100 mass% of the copolymer (A).

5. The pressure-sensitive adhesive composition according to claim 4, wherein the other monomer (a3) ​​comprises at least one member selected from the group consisting of alicyclic hydrocarbon group-containing (meth)acrylic acid ester monomers, nitrogen atom-containing (meth)acrylic acid ester monomers, alkoxyalkyl group-containing (meth)acrylic acid ester monomers, low Tg (meth)acrylic acid alkyl ester monomers whose homopolymers have a glass transition temperature of −20°C or lower, and acid group-containing monomers.

6. The pressure-sensitive adhesive composition according to claim 1, wherein the weight-average molecular weight of the copolymer (A) is 500,000 to 6,000,000.

7. The pressure-sensitive adhesive composition according to claim 1, wherein the inorganic particles (B) are particles composed of at least one selected from the group consisting of aluminum oxide, titanium oxide, zirconium oxide, indium oxide, zinc oxide, tin oxide, lanthanum oxide, yttrium oxide, cerium oxide, magnesium oxide, niobium oxide, tantalum oxide, indium tin oxide, antimony tin oxide, barium titanate, strontium titanate, perovskite, and spinel.

8. The pressure-sensitive adhesive composition according to claim 1, wherein the inorganic particles (B) have a volume average particle size of 1 to 100 nm.

9. The pressure-sensitive adhesive composition according to claim 1, wherein the ratio (D90 / D50) of the volume-based cumulative 90% particle diameter D90 to the volume-based cumulative 50% particle diameter D50, as measured by dynamic light scattering, of the inorganic particles (B) is 3.0 or less.

10. The pressure-sensitive adhesive composition according to claim 1, further comprising a chain transfer agent (F).

11. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition has a refractive index of 1.58 to 1.

80.

12. The pressure-sensitive adhesive composition according to claim 1, wherein a 100 μm thick pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition has a haze of 3.0% or less.

13. A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 12.

14. Use of the composition according to any one of claims 1 to 12 as an adhesive to be laminated to an optical film.

15. A laminate comprising an optical film and the pressure-sensitive adhesive layer according to claim 13 laminated on the optical film.

16. A method for producing an optical film laminated with an adhesive, comprising: a step of applying the composition according to any one of claims 1 to 12 to a substrate; and a step of curing the coating layer obtained in the application step to form an adhesive layer, wherein the substrate used in the application step is an optical film, or the method further comprises a transfer step of transferring the adhesive layer to an optical film after the adhesive layer formation step.

17. A pressure-sensitive adhesive layer for an optical film comprising a (meth)acrylic acid ester copolymer (A) and inorganic particles (B), wherein the pressure-sensitive adhesive layer has a thickness of 50 μm or more, a haze of 3.0% or less, the copolymer (A) comprises a structural unit (A1) derived from an aromatic hydrocarbon group-containing (meth)acrylic acid ester monomer (a1) and a structural unit (A2) derived from a hydroxyl group-containing (meth)acrylic acid ester monomer (a2), and the content of the structural unit (A2) is 1 to 40% by mass, based on 100% by mass of the total of the structural units (A1) and (A2).

18. The pressure-sensitive adhesive layer according to claim 17, which contains a photopolymerization initiator residue.

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