Pressure-sensitive adhesive composition, pressure-sensitive adhesive film, pressure-sensitive adhesive layer-attached optical film, liquid crystal panel

Abstract

To provide: a pressure-sensitive adhesive composition which can make excellent antistatic performance and durability including pressure-sensitive adhesive performance compatible with each other; a pressure-sensitive adhesive film; an optical film with a pressure-sensitive adhesive layer; and a liquid crystal panel.SOLUTION: A pressure-sensitive adhesive composition is provided which comprises an acrylic polymer, an antistatic agent, and a cross-linking agent. The acrylic polymer has a glass transition temperature of 0°C or less. The cross-linking agent is one or more selected from the group consisting of tri- or more functional isocyanate compounds and di- or more functional epoxy compounds. The pressure-sensitive adhesive composition does not contain a plasticizer and includes a silane coupling agent of a monomer type having at least one functional group selected from an epoxy group, a mercapto group, and an acid anhydride group or of an oligomer type. The antistatic agent is an ionic compound having a melting point of 25°C or more, wherein the anion is one selected from a trifluoromethanesulfonate anion, a pentafluoroethanesulfonate anion, a heptafluoropropanesulfonate anion, and a nonafluorobutanesulfonate anion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition containing an antistatic agent and a pressure-sensitive adhesive film. More specifically, the present invention relates to a pressure-sensitive adhesive composition containing an ionic compound having a specific sulfonate anion, such as nonafluorobutanesulfonate, as an antistatic agent, thereby exhibiting excellent durability including excellent adhesive performance and antistatic performance, and a pressure-sensitive adhesive film using the same. [Background technology]

[0002] BACKGROUND ART Various pressure-sensitive adhesive films have been proposed for bonding optical members such as polarizing plates and retardation plates to adherends such as liquid crystal cells via a pressure-sensitive adhesive layer (see, for example, Patent Documents 1 and 2). Patent Document 1 describes an optical pressure-sensitive adhesive composition containing an acrylic polymer obtained by copolymerizing acrylamide compounds and the like with butyl acrylate or the like as a main component monomer. Patent Document 2 describes an optical pressure-sensitive adhesive composition containing an acrylic polymer obtained by copolymerizing a (meth)acrylate having an alkyl group with 4 to 8 carbon atoms as the main monomer, a carboxyl group-containing monomer, and a nitrogen-containing vinyl monomer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-177022 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-201734 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the surface of an optical film is subjected to an antifouling treatment or a low-reflection surface treatment using a composition containing a silicone compound or the like, the peeling electrification voltage increases when the adhesive film used in such an optical film is peeled off from the adherend.

[0005] Furthermore, for pressure-sensitive adhesive compositions with antistatic properties and pressure-sensitive adhesive films using such compositions, the relationship between the antistatic properties and durability, including adhesive properties to adherends, is a trade-off, and it has been difficult to improve durability, including adhesive properties, while maintaining antistatic properties. For this reason, there is a demand for a pressure-sensitive adhesive composition that can reduce the peeling electrification voltage when peeling an adhesive film from an optical film, even when the surface of the optical film has been surface-treated with a composition containing a silicone compound or the like, and that has durability including adhesive performance.

[0006] The present invention has been made in view of the above circumstances, and aims to solve a novel problem of providing a pressure-sensitive adhesive composition that can achieve both excellent antistatic performance and durability including adhesive performance, and a pressure-sensitive adhesive film using the same. [Means for solving the problem]

[0007] The present inventors have created a new pressure-sensitive adhesive composition containing a copolymer in which the number of carbon atoms in the alkyl group of the alkyl (meth)acrylate constituting the acrylic polymer of the pressure-sensitive adhesive composition is limited to a specific range and a specific combination of two or more alkyl (meth)acrylates is copolymerized, and an antistatic agent consisting of an ionic compound having a specific sulfonate anion and a melting point of 25°C or higher, such as nonafluorobutanesulfonate.The inventors have found that this makes it possible to obtain a pressure-sensitive adhesive composition that has superior durability, including adhesive performance, compared to conventional pressure-sensitive adhesive compositions for adhesive films, and that has excellent antistatic performance on peeling without deterioration over time, and have thus completed the present invention. In particular, the adhesive film of the present invention has superior durability, including adhesive performance, compared to conventional technology, and has excellent antistatic peel performance without deterioration over time, and has been found to be effective in achieving both antistatic performance and durability, including adhesive performance.

[0008] In order to solve the above problems, the present invention provides a pressure-sensitive adhesive composition containing an acrylic polymer, an antistatic agent, and a crosslinking agent, the acrylic polymer has a glass transition temperature of 0°C or less, the (D) crosslinking agent is one or more crosslinking agents selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds, the pressure-sensitive adhesive composition further comprises (H) a monomeric or oligomeric silane coupling agent containing at least one functional group selected from the group consisting of an epoxy group, a mercapto group, and an acid anhydride group; the antistatic agent is an ionic compound having a melting point of 25°C or higher and composed of a cation and an anion, the anion being one selected from the group consisting of a trifluoromethanesulfonate anion, a pentafluoroethanesulfonate anion, a heptafluoropropanesulfonate anion, and a nonafluorobutanesulfonate anion; The present invention provides a pressure-sensitive adhesive composition comprising, as an essential component, 0.01 to 10 parts by weight of the antistatic agent relative to 100 parts by weight of the acrylic polymer.

[0009] The acrylic polymer (A) at least one alkyl (meth)acrylate monomer having an alkyl group with a carbon number of C1 to C14; (B) at least one copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group; (C) an acrylic polymer of a copolymer obtained by copolymerizing at least one copolymerizable vinyl monomer containing an aromatic group, the acrylic polymer contains 0.1 to 5 parts by weight of at least one copolymerizable vinyl monomer (B) containing a hydroxyl group and / or a carboxyl group, relative to 100 parts by weight of the total of (A) and (C); In a test piece prepared by bonding a 20 μm thick adhesive layer obtained by crosslinking the adhesive composition to a polarizing plate having a total thickness of 80 μm, it is preferable that the adhesive strength of the 20 μm thick adhesive layer to alkali-free glass is 6 N / 25 mm or less, and that there is no foaming or peeling even after a durability test at 105°C for 500 hours.

[0010] The cation is preferably one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, lithium, and morpholinium.

[0011] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 1.0×10+ 12 It is preferably Ω / □ or less.

[0012] the (B) copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group is at least one selected from the group consisting of copolymerizable monomers containing a hydroxyl group and copolymerizable monomers containing a carboxyl group, the hydroxyl group-containing copolymerizable monomer is at least one selected from the group consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide; The copolymerizable monomer containing a carboxyl group is preferably at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalate.

[0013] The present invention also provides a pressure-sensitive adhesive film, characterized in that a pressure-sensitive adhesive layer obtained by crosslinking the above-mentioned pressure-sensitive adhesive composition is laminated on one surface of a resin film.

[0014] The present invention also provides an optical film with a pressure-sensitive adhesive layer, comprising an optical film and a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition, laminated on at least one surface of the optical film.

[0015] The present invention also provides a pressure-sensitive adhesive film, wherein one surface of the resin film opposite to the surface on which the pressure-sensitive adhesive layer is laminated is subjected to an antistatic treatment and an antifouling treatment.

[0016] The present invention also provides a pressure-sensitive adhesive film for polarizing plates, which uses the pressure-sensitive adhesive film.

[0017] The present invention also provides a pressure-sensitive adhesive film characterized by having a release film / pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition and laminated to a thickness of 1 μm to 25 μm on one side of the release film, and having a structure of release film / pressure-sensitive adhesive layer / release film.

[0018] The present invention also provides a liquid crystal panel, characterized in that the above-mentioned pressure-sensitive adhesive layer-attached optical film is used. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film that can achieve both excellent antistatic performance and durability including adhesive performance. The pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive film using the same have excellent durability, including excellent adhesive performance, compared to conventional technology, and have excellent antistatic performance against peeling without deterioration over time, even when the surface of the optical film to be adhered has been surface-treated with a composition containing a silicone compound or the like. In other words, the pressure-sensitive adhesive composition of the present invention and the pressure-sensitive adhesive film using the same have excellent antistatic properties and durability including excellent adhesive properties, and therefore have extremely high industrial utility value. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described below based on preferred embodiments. The pressure-sensitive adhesive composition of the present embodiment is a pressure-sensitive adhesive composition containing an acrylic polymer, an antistatic agent, and a crosslinking agent, wherein the acrylic polymer has a glass transition temperature of 0°C or lower, the (D) crosslinking agent is one or more crosslinking agents selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds, the pressure-sensitive adhesive composition further contains (H) a monomeric or oligomeric silane coupling agent containing at least one functional group selected from the group consisting of epoxy groups, mercapto groups, and acid anhydride groups, the antistatic agent is an ionic compound composed of a cation and an anion and having a melting point of 25°C or higher, the anion being one selected from the group consisting of trifluoromethanesulfonate anion, pentafluoroethanesulfonate anion, heptafluoropropanesulfonate anion, and nonafluorobutanesulfonate anion, and the pressure-sensitive adhesive composition contains the antistatic agent as an essential component in a ratio of 0.01 to 10 parts by weight per 100 parts by weight of the acrylic polymer. The antistatic agent is preferably an ionic compound having a solid melting point of 25°C or higher at a temperature of 25°C, and the melting point of the antistatic agent is preferably 450°C or lower.

[0021] The acrylic polymer used in the pressure-sensitive adhesive composition of the present embodiment has a glass transition temperature of 0° C. or lower. The acrylic polymer is preferably a copolymer containing, as a main component, at least one alkyl (meth)acrylate monomer (A) having an alkyl group with a carbon number of C1 to C14.

[0022] Furthermore, examples of (A) alkyl (meth)acrylate monomers having an alkyl group of C1 to C14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate. The alkyl group of the alkyl (meth)acrylate monomer may be linear, branched, or cyclic.

[0023] The acrylic polymer used in the pressure-sensitive adhesive composition of this embodiment can be copolymerized with at least one copolymerizable vinyl monomer (B) containing a hydroxyl group and / or a carboxyl group as an optional component. The copolymerizable vinyl monomer (B) containing a hydroxyl group and / or a carboxyl group can be at least one selected from the group consisting of copolymerizable monomers containing a hydroxyl group (hydroxyl group-containing monomers) and copolymerizable monomers containing a carboxyl group (carboxyl group-containing monomers). That is, either a hydroxyl group-containing monomer or a carboxyl group-containing monomer may be selected and copolymerized, or both a hydroxyl group-containing monomer and a carboxyl group-containing monomer may be copolymerized. The acrylic polymer preferably contains at least one copolymerizable vinyl monomer (B) containing a hydroxyl group and / or a carboxyl group in a proportion of 0.1 to 5 parts by weight, more preferably 0.1 to 4.2 parts by weight, and particularly preferably 0.1 to 2.8 parts by weight, per 100 parts by weight of the total of (A) and (C).

[0024] The hydroxyl group-containing monomer may be at least one selected from the group consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, etc. The proportion of the hydroxyl group-containing monomer contained in the pressure-sensitive adhesive composition of the present embodiment is preferably 0.1 to 5 parts by weight, more preferably 0.1 to 4.2 parts by weight, and particularly preferably 0.1 to 2.8 parts by weight, relative to 100 parts by weight of the total of (A) and (C) in the acrylic polymer.

[0025] Furthermore, examples of the carboxyl group-containing monomer include at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalate. The proportion of the carboxyl group-containing monomer in the pressure-sensitive adhesive composition according to the present embodiment is preferably 0 to 5.0 parts by weight relative to 100 parts by weight of the total of (A) and (C) of the acrylic polymer (it is also permissible if the carboxyl group-containing monomer is not copolymerized), and when the carboxyl group-containing monomer is copolymerized, the proportion is more preferably 0.1 to 5 parts by weight, particularly preferably 0.1 to 2.4 parts by weight, and most preferably 0.1 to 1.2 parts by weight.

[0026] The acrylic polymer used in the pressure-sensitive adhesive composition of this embodiment may be copolymerized with (C) an aromatic group-containing copolymerizable vinyl monomer as an optional component. Examples of (C) aromatic group-containing copolymerizable vinyl monomers include at least one of benzyl (meth)acrylate, naphthyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxybutyl (meth)acrylate, 2-(1-naphthyloxy)ethyl (meth)acrylate, 2-(2-naphthyloxy)ethyl (meth)acrylate, 6-(1-naphthyloxy)hexyl (meth)acrylate, 6-(2-naphthyloxy)hexyl (meth)acrylate, 8-(1-naphthyloxy)octyl (meth)acrylate, and 8-(2-naphthyloxy)octyl (meth)acrylate. When the copolymerizable vinyl monomer containing an aromatic group contains a (meth)acrylate monomer containing an aromatic group, it is preferable because it has excellent copolymerizability with alkyl(meth)acrylate monomers.

[0027] The method for producing the acrylic polymer contained in the pressure-sensitive adhesive composition according to the present embodiment is not particularly limited, and any known polymerization method can be used as appropriate, such as solution polymerization, emulsion polymerization, etc. In the pressure-sensitive adhesive composition according to the present embodiment, the weight-average molecular weight of the acrylic polymer copolymer used is preferably 1,000,000 to 3,000,000.

[0028] The pressure-sensitive adhesive composition according to this embodiment contains (G) an antistatic agent to obtain antistatic properties. (G) The antistatic agent is an ionic compound having a melting point of 25°C or higher and consisting of a cation and an anion, and the anion is a trifluoromethanesulfonate anion (CF3SO3 - ), pentafluoroethanesulfonate anion (CF3CF2SO3 - ), heptafluoropropanesulfonate anion (CF3CF2CF2SO3 - ), nonafluorobutanesulfonate anion (CF3CF2CF2CF2SO3 - The pressure-sensitive adhesive composition according to the present embodiment preferably contains an antistatic agent (G) in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the acrylic polymer as an essential component, and furthermore, the antistatic performance of the pressure-sensitive adhesive layer is enhanced so that the lower limit of the surface resistivity is 1.0 × 10 +10 When it is necessary to reduce the resistivity to Ω / □ or less, it is more preferable to contain the (G) antistatic agent in a proportion of 0.01 to 15 parts by weight.

[0029] The cation contained in the ionic compound may be one selected from the group consisting of pyridinium, imidazolium, phosphonium, sulfonium, pyrrolidinium, guanidinium, ammonium, isouronium, thiouronium, piperidinium, pyrazolium, methylium, lithium, and morpholinium. Specific examples of the (G) antistatic agent include lithium trifluoromethanesulfonate, lithium nonafluorobutanesulfonate, 1-methyl-3-octylpyridinium trifluoromethanesulfonate salt, 3-methyl-1-octylpyridinium trifluoromethanesulfonate salt, 1-methyl-4-octylpyridinium nonafluorobutanesulfonate salt, 4-methyl-1-octylpyridinium nonafluorobutanesulfonate salt, dimethyldioctylammonium pentafluoroethanesulfonate salt, 1-methyl-3-octylpyridinium heptafluoropropanesulfonate salt, 3-methyl-1-octylpyridinium heptafluoropropanesulfonate salt, 1-methyl-3-octylpyridinium nonafluorobutanesulfonate salt, 3-methyl-1-octylpyridinium nonafluorobutanesulfonate salt, and 1-octyl-3-methylimidazolium nonafluorobutanesulfonate salts.

[0030] The pressure-sensitive adhesive composition according to this embodiment further contains, as a (D) crosslinking agent, at least one crosslinking agent selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds. As the (D) crosslinking agent, a trifunctional or higher isocyanate compound and a difunctional or higher epoxy compound may be used in combination. The total content of the at least one (D) crosslinking agent is, for example, preferably 0.01 to 5 parts by weight, more preferably 0.01 to 2 parts by weight, and particularly preferably 0.03 to 0.8 parts by weight, per 100 parts by weight of the acrylic polymer.

[0031] Examples of the tri- or higher functional isocyanate compound include biuret-modified and isocyanurate-modified diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate, as well as adducts with trivalent or higher polyols such as trimethylolpropane and glycerin. Examples of difunctional or higher functional epoxy compounds include diglycidyl ethers of glycols, diglycidyl ethers of bisphenols, triglycidyl ethers of triols, diglycidyl esters of dicarboxylic acids, diglycidyl-substituted amines, and tetraglycidyl-substituted diamines.

[0032] The pressure-sensitive adhesive composition according to this embodiment further contains a (H) silane coupling agent. Examples of the (H) silane coupling agent include compounds having at least one organic functional group and at least one hydrolyzable group per molecule, where the hydrolyzable group is, for example, an alkoxy group bonded to a silicon atom. The (H) silane coupling agent contains at least one functional group selected from the group consisting of an epoxy group, a mercapto group, and an acid anhydride group. The (H) silane coupling agent may be at least one of a monomer type or an oligomer type, or both. The content of the silane coupling agent is, for example, preferably 0.01 to 2.0 parts by weight, more preferably 0.01 to 1.0 parts by weight, and particularly preferably 0.01 to 0.5 parts by weight, per 100 parts by weight of the acrylic polymer.

[0033] Furthermore, examples of silane coupling agents having an epoxy group include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 5,6-epoxyhexyltrimethoxysilane, 5,6-epoxyhexylmethyldimethoxysilane, 5,6-epoxyhexylmethyldiethoxysilane, and 5,6-epoxyhexyltriethoxysilane. Examples of silane coupling agents having a mercapto group include 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane. Furthermore, examples of silane coupling agents having an acid anhydride group include 3-trimethoxysilylpropyl succinic anhydride, 3-triethoxysilylpropyl succinic anhydride, 3-dimethylmethoxysilylpropyl succinic anhydride, 3-dimethylethoxysilylpropyl succinic anhydride, 3-trimethoxysilylpropyl cyclohexyl dicarboxylic anhydride, 3-triethoxysilylpropyl cyclohexyl dicarboxylic anhydride, 3-dimethylmethoxysilylpropyl cyclohexyl dicarboxylic anhydride, 3-dimethylethoxysilylpropyl cyclohexyl dicarboxylic anhydride, 3-trimethoxysilylpropyl phthalic anhydride, and 3-triethoxysilylpropyl phthalic anhydride. Furthermore, oligomerized alkoxy oligomers (silicone alkoxy oligomers containing alkoxyl groups) can also be used as silane coupling agents. Furthermore, it is preferable to use a silicone alkoxy oligomer having a relatively small molecular weight of 600 or more but less than 3,000, such as a tetraalkoxysiloxane, trialkoxysiloxane, or dialkoxysiloxane, whose molecular ends are blocked with alkoxysilyl groups represented by Si—OR.

[0034] The PSA composition of the present embodiment may contain, as appropriate, known additives such as, but not limited to, the additives described above, antioxidants, surfactants, curing accelerators, plasticizers, fillers, curing retarders, processing aids, and antioxidants, which may be used alone or in combination of two or more.

[0035] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment has a surface resistivity of 1.0×10 +12 It is preferable that the surface resistivity is 5.0×10 +11 It is more preferable that the surface resistivity is 2.0×10 +11 It is particularly preferable that the surface resistivity is Ω / □ or less. If the surface resistivity is high, the performance of dissipating static electricity generated by charging when the pressure-sensitive adhesive layer is peeled off from the adherend is poor. Therefore, by sufficiently reducing the surface resistivity of the pressure-sensitive adhesive layer, the peeling electrification voltage generated by static electricity generated when the pressure-sensitive adhesive layer is peeled off from the adherend can be reduced, and the influence on the adherend can be suppressed.

[0036] In a test piece prepared by bonding a 20 μm-thick adhesive layer obtained by crosslinking the adhesive composition of the present embodiment to a polarizing plate having a total thickness of 80 μm, the adhesive strength of the 20 μm-thick adhesive layer to alkali-free glass is 6 N / 25 mm or less, and the adhesive strength of the 20 μm-thick adhesive layer to alkali-free glass is free from bubbling and peeling even after a durability test at 105° C. for 500 hours. The adhesive strength of the 20 μm-thick adhesive layer to alkali-free glass is preferably 1 N / 25 mm or more and 6 N / 25 mm or less, and more preferably 1.5 N / 25 mm or more and 6 N / 25 mm or less.

[0037] The pressure-sensitive adhesive layer according to this embodiment can be obtained by applying the pressure-sensitive adhesive composition according to this embodiment to a substrate such as a resin film or a release film, and then crosslinking the pressure-sensitive adhesive composition.

[0038] When the pressure-sensitive adhesive layer according to this embodiment is used to attach an optical member, it is necessary to reduce the reflection of light at the interface between the pressure-sensitive adhesive layer and the optical member. In other words, it is desirable that the difference in refractive index between the optical member and the pressure-sensitive adhesive layer is as small as possible. For this reason, the refractive index of the pressure-sensitive adhesive layer is preferably 1.47 to 1.50.

[0039] The pressure-sensitive adhesive film according to this embodiment can be produced by forming the pressure-sensitive adhesive layer according to this embodiment on one side of a substrate such as a resin film or a release film. A polyester film or the like can be used as the substrate for the resin film or release film (separator). The release film may be subjected to a release treatment using a silicone-based or fluorine-based release agent on the side that faces the adhesive surface of the pressure-sensitive adhesive layer. The resin film that serves as the substrate for the pressure-sensitive adhesive film according to this embodiment may be subjected to an antifouling treatment using a silicone-based or fluorine-based release agent or coating agent, silica microparticles, or the like, or an antistatic treatment by coating or kneading an antistatic agent on the side opposite the side on which the pressure-sensitive adhesive layer is formed. The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film according to this embodiment is preferably, for example, 1 μm to 25 μm, more preferably 3 μm to 20 μm, and particularly preferably 5 μm to 20 μm.

[0040] The adhesive film according to this embodiment can also be configured as a "release film / adhesive layer / release film" by attaching release-treated surfaces of release films to both sides of a single adhesive layer. In this case, the release films on both sides are peeled off sequentially or simultaneously to expose the adhesive surface, making it possible to bond the film to an optical component such as an optical film. Examples of optical films include polarizing films, retardation films, anti-reflection films, anti-glare films, ultraviolet absorbing films, infrared absorbing films, optical compensation films, and brightness enhancing films. Examples of devices to which optical components are applied include liquid crystal panels, organic EL panels, and touch panels.

[0041] The pressure-sensitive adhesive film according to this embodiment is suitable as a pressure-sensitive adhesive film for a polarizing plate. The pressure-sensitive adhesive layer can be laminated on at least one side of the optical film to form a pressure-sensitive adhesive layer-attached optical film. Furthermore, by using the pressure-sensitive adhesive film on one side of a polarizing plate, a pressure-sensitive adhesive layer-attached polarizing plate can be provided. The pressure-sensitive adhesive layer-attached optical film can be used to provide a liquid crystal panel. Specific examples of the laminate structure of such an optical film with a pressure-sensitive adhesive layer include "release film / pressure-sensitive adhesive layer / optical film," "release film / pressure-sensitive adhesive layer / optical film / pressure-sensitive adhesive layer / release film," "optical film / pressure-sensitive adhesive layer / optical film," "optical film / pressure-sensitive adhesive layer," and "pressure-sensitive adhesive layer / optical film / pressure-sensitive adhesive layer." Specific examples of the laminate structure of a polarizing plate with a pressure-sensitive adhesive layer include "release film / pressure-sensitive adhesive layer / polarizing plate," "release film / pressure-sensitive adhesive layer / polarizing plate / pressure-sensitive adhesive layer / release film," "polarizing plate / pressure-sensitive adhesive layer," and "pressure-sensitive adhesive layer / polarizing plate / pressure-sensitive adhesive layer." These optical films with a pressure-sensitive adhesive layer or polarizing plates with a pressure-sensitive adhesive layer may be incorporated as a partial structure of a liquid crystal panel or the like. In addition, when a release film is included in the laminated structure, such as "release film / adhesive layer / optical film" or "release film / adhesive layer / polarizing plate," the release film is peeled off, and then the optical film or polarizing plate is attached to the adherend via the adhesive layer. [Example]

[0042] The present invention will be specifically described below with reference to examples.

[0043] <Production of acrylic polymers> [Example 1] Nitrogen gas was introduced into a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, and the air in the reactor was replaced with nitrogen gas. Subsequently, 50 parts by weight of butyl acrylate, 10 parts by weight of methyl acrylate, 20 parts by weight of 2-ethylhexyl acrylate, 1.0 part by weight of 6-hydroxyhexyl acrylate, 0.5 parts by weight of 4-hydroxybutyl acrylate, 20 parts by weight of benzyl acrylate, and 100 parts by weight of a solvent (ethyl acetate) were added to the reactor. Subsequently, 0.1 parts by weight of azobisisobutyronitrile as a polymerization initiator was added dropwise over 2 hours, and the mixture was allowed to react at 65°C for 8 hours, yielding an acrylic polymer solution of Example 1. [Examples 2 to 6 and Comparative Examples 1 to 3] Acrylic polymer solutions used in Examples 2 to 6 and Comparative Examples 1 to 3 were obtained in the same manner as the acrylic polymer solution used in Example 1 above, except that the monomer compositions were as shown in Table 1.

[0044] <Production of Pressure-Sensitive Adhesive Composition and Pressure-Sensitive Adhesive Film> [Example 1] To the acrylic polymer solution of Example 1 prepared as described above, 0.1 parts by weight of D-110N and 0.01 parts by weight of TX were added as crosslinking agents, 1.5 parts by weight of 1-methyl-3-octylpyridinium nonafluorobutanesulfonate salt as an antistatic agent, and 0.1 parts by weight of KBM-403 and 0.1 parts by weight of X-41-1805 as silane coupling agents, and the mixture was stirred to obtain the adhesive composition of Example 1. This adhesive composition was applied to a release film made of a silicone resin-coated polyethylene terephthalate (PET) film and then dried at 90°C to remove the solvent, resulting in an adhesive layer with a thickness of 20 μm. The adhesive layer was then aged for 7 days in an atmosphere of 23°C and 50% RH, resulting in the adhesive film of Example 1 having an adhesive layer crosslinked from the adhesive composition on one side of the release film, with a release film / adhesive layer / release film configuration. [Examples 2 to 6 and Comparative Examples 1 to 3] Pressure-sensitive adhesive films of Examples 2 to 6 and Comparative Examples 1 to 3 were obtained in the same manner as the pressure-sensitive adhesive film of Example 1 above, except that the compositions of the additives were changed as shown in Table 1.

[0045] [Table 1]

[0046] In Table 1, the parts by weight of each component were calculated based on 100 parts by weight of the total of (A) at least one alkyl (meth)acrylate monomer having an alkyl group with carbon atoms of C1 to C14 and (C) at least one copolymerizable vinyl monomer containing an aromatic group. In Table 1, in each of the columns (D), (H), and (G), the content (parts by weight) of each component is shown as a numerical value in parentheses ( ), with the acrylic polymer being 100 parts by weight. The compound names of the abbreviations of the components used in Table 1 are shown in Table 2. G-1 to G-7 all have melting points of 25°C or higher and are solid ionic compounds at 25°C.

[0047] [Table 2]

[0048] Coronate (registered trademark) HX, Coronate (registered trademark) HL, and Coronate (registered trademark) L are trade names of Tosoh Corporation, D-110N, D-127N, and Takenate (registered trademark) D-140N are trade names of Mitsui Chemicals, Inc., and TETRAD (registered trademark)-X is a trade name of Mitsubishi Gas Chemical Company, Inc. HDI means hexamethylene diisocyanate, IPDI means isophorone diisocyanate, XDI means xylylene diisocyanate, TDI means tolylene diisocyanate, and TMP means trimethylolpropane. KBM-403, X-12-967C, and X-41-1805 are all trade names of Shin-Etsu Chemical Co., Ltd.

[0049] <Test method and evaluation> The pressure-sensitive adhesive films of Examples 1 to 6 and Comparative Examples 1 to 3 were each aged for 7 days in an atmosphere of 23° C. and 50% RH, and then evaluated by the following test methods.

[0050] <Adhesive strength test method> One release film was peeled off from the pressure-sensitive adhesive film in Examples 1 to 6 and Comparative Examples 1 to 3 to expose one side of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film. The pressure-sensitive adhesive film was then attached to one side of an 80 μm-thick polarizing plate (a resin film; a polarizing plate with a TAC protective layer for the polarizer was used) via the pressure-sensitive adhesive layer to obtain a polarizing plate with a pressure-sensitive adhesive layer, which had a release film / pressure-sensitive adhesive layer / polarizing plate configuration. Furthermore, the release film was peeled off from the polarizing plate with the pressure-sensitive adhesive layer, and the polarizing plate with the pressure-sensitive adhesive layer was attached to an acetone-cleaned surface of alkali-free glass (Corning Eagle XG) via the pressure-sensitive adhesive layer using a pressure-sensitive adhesive roll to prepare a test piece. The test piece was then autoclaved at 50°C and 0.5 MPa for 20 minutes. The plate was then returned to an atmosphere of 23°C x 50% RH, and after 1 hour the peel strength of the polarizing plate with adhesive layer was measured using a tensile tester in accordance with JIS Z0237 "Test method for adhesive tapes and adhesive sheets." The peel strength when peeled in a 180° direction at a speed of 0.3 m / min was taken as the adhesive strength of the adhesive layer to the alkali-free glass.

[0051] <Surface resistivity test method> After aging the adhesive film and before bonding it to the adherend, the release film was peeled off to expose the adhesive layer, and the surface resistivity of the adhesive layer was measured using a resistivity meter, Hiresta UP-HT450 (manufactured by Mitsubishi Chemical Analytech).

[0052] <Durability test method> Using the same method as for measuring adhesive strength, a 10 cm square polarizing plate with an adhesive layer was peeled off the release film and attached to an acetone-cleaned surface of alkali-free glass to prepare a test piece. The test piece was then subjected to a durability test at 105°C for 500 hours, after which it was removed from the test piece and placed in a 23°C x 50% RH atmosphere. After 1 hour, the condition of the adhesive layer was visually observed to determine the durability of the adhesive layer. The durability evaluation criteria were as follows: no foaming or peeling of the adhesive layer was evaluated as "○", foaming or peeling occurred only in part of the adhesive layer was evaluated as "△", and foaming or peeling occurred throughout the adhesive layer was evaluated as "×".

[0053] Table 3 shows the evaluation results for the PSA films in Examples 1 to 6 and Comparative Examples 1 to 3. "Surface resistivity" is expressed as "m×10 +n " is expressed as "mE+n" (where m is any real number and n is a positive integer).

[0054] [Table 3]

[0055] The pressure-sensitive adhesive films of Examples 1 to 6 had a surface resistivity of the pressure-sensitive adhesive layer of 1.0 × 10 +12 The adhesive strength of the 20μm adhesive layer to alkali-free glass was 6N / 25mm or less, and there was no foaming or peeling even after a durability test at 105℃ for 500 hours, so in addition to having excellent adhesive and antistatic properties, the adhesive also had excellent durability. That is, the evaluation results shown in Table 3 for the pressure-sensitive adhesive films of Examples 1 to 6 demonstrate that the problems of the present invention were solved.

[0056] The PSA film of Comparative Example 1 contained PF6 as the antistatic agent (G) contained in the PSA composition. - Since an ionic compound having an anion is used, the surface resistivity of the pressure-sensitive adhesive layer is high and the durability is poor. In the adhesive film of Comparative Example 2, the glass transition temperature of the acrylic polymer contained in the adhesive composition exceeded 0°C (calculated value: +4.8°C). As a result, the adhesive performance was poor, the adhesive strength was excessive, the surface resistivity of the adhesive layer was high, and the durability was poor. Note that the acrylic polymer used in Comparative Example 2 contained a high proportion of methyl acrylate and acrylic acid, which have homopolymer glass transition temperatures of high values ​​(exceeding 0°C). The adhesive film of Comparative Example 3 did not contain either (H) the silane coupling agent or (G) the antistatic agent in the adhesive composition, and therefore had excessive adhesive strength, a high surface resistivity of the adhesive layer, and poor durability. As described above, the pressure-sensitive adhesive films of Comparative Examples 1 to 3 could not solve the problems of the present invention.

Claims

1. A pressure-sensitive adhesive composition comprising an acrylic polymer, an antistatic agent, and (D) a crosslinking agent, The acrylic polymer (A) at least one alkyl (meth)acrylate monomer having an alkyl group having 1 to 14 carbon atoms; (B) at least one copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group; (C) at least one copolymerizable vinyl monomer containing an aromatic group; and (meth)acrylic polymers (excluding (meth)acrylic polymers containing an N-vinyl group-containing lactam monomer) which are copolymers of the acrylic polymer has a glass transition temperature of 0°C or less, The (A) alkyl (meth)acrylate monomer having an alkyl group having a carbon number of C1 to C14 is at least one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, cyclopentyl (meth)acrylate, and cyclohexyl (meth)acrylate; the composition contains 0.1 to 1.5 parts by weight of the total of (B) at least one copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group, relative to 100 parts by weight of the total of (A) at least one alkyl(meth)acrylate monomer having an alkyl group with a carbon number of C1 to C14 and (C) at least one copolymerizable vinyl monomer containing an aromatic group, the (B) copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group is at least one selected from the group consisting of copolymerizable monomers containing a hydroxyl group and copolymerizable monomers containing a carboxyl group, the (D) crosslinking agent is one or more crosslinking agents selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds, the pressure-sensitive adhesive composition does not contain a plasticizer and contains (H) a monomer-type or oligomer-type silane coupling agent containing at least one functional group selected from the group consisting of an epoxy group, a mercapto group, and an acid anhydride group; the antistatic agent is an ionic compound having a melting point of 25°C or higher and composed of a cation and an anion, the anion being one selected from the group consisting of a trifluoromethanesulfonate anion, a pentafluoroethanesulfonate anion, a heptafluoropropanesulfonate anion, and a nonafluorobutanesulfonate anion; A pressure-sensitive adhesive composition comprising, as an essential component, 0.01 to 10 parts by weight of the antistatic agent relative to 100 parts by weight of the acrylic polymer.

2. the hydroxyl group-containing copolymerizable monomer is at least one selected from the group consisting of 8-hydroxyoctyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, N-hydroxy(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, and N-hydroxyethyl(meth)acrylamide; 2. The pressure-sensitive adhesive composition according to claim 1, wherein the copolymerizable monomer containing a carboxyl group is at least one selected from the group consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalate.

3. 3. A pressure-sensitive adhesive film comprising a resin film and a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition according to claim 1 or 2 laminated on one side of the resin film.

4. An optical film with a pressure-sensitive adhesive layer, comprising an optical film and a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition according to claim 1 or 2 laminated on at least one surface of the optical film.

5. An adhesive film for polarizing plates, comprising the adhesive film according to claim 3 .

6. A pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1 or 2 is laminated on one side of a release film to a thickness of 1 μm to 25 μm, and the pressure-sensitive adhesive film has a structure of release film / pressure-sensitive adhesive layer / release film.

7. A liquid crystal panel, comprising the pressure-sensitive adhesive layer-attached optical film according to claim 4.

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