Adhesive composition, adhesive film, polarizing plate with adhesive layer, and liquid crystal panel

Abstract

To provide an adhesive composition, an adhesive film, a polarizing plate with an adhesive layer, and a liquid crystal panel, which enable excellent antistatic performance with the surface resistivity of the adhesive layer being 9.0×10+10 Ω / sq. or less, without compromising its durability.SOLUTION: An adhesive composition comprising: an acrylic polymer obtained by copolymerizing (A) n-butyl acrylate, (B) at least one selected from t-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, and methyl acrylate, (C) a copolymerizable vinyl monomer containing a hydroxy group and / or a carboxyl group, and (D) a copolymerizable vinyl monomer containing an aromatic group; (E) an ionic compound composed of an ammonium cation and a fluoro group-containing anion as an antistatic agent; (F) a crosslinker selected from isocyanate compounds or epoxy compounds; and (G) a silane coupling agent containing a functional group selected from epoxy groups, mercapto groups, and acid anhydride groups.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive film that can be used, for example, when the adherend is a liquid crystal panel and can be attached to an in-cell panel incorporating a touch panel function. In particular, the surface resistivity of the adhesive layer is 9.0 × 10 +10 The present invention relates to a pressure-sensitive adhesive composition having extremely excellent antistatic properties of Ω / □ or less, 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] Incidentally, in the case of an adhesive layer used to bond a polarizing plate to a liquid crystal panel, when the liquid crystal panel becomes an in-cell panel incorporating a touch panel function, the surface resistivity of the adhesive layer is required to be lower than the conventional surface resistivity. Therefore, the adhesive layer used to attach the polarizing plate to the liquid crystal panel should have a surface resistivity of 9.0 × 10 +10 Although it is desired to reduce the antistatic property to Ω / □ or less, it has been extremely difficult to achieve such high antistatic properties with conventional techniques. Even if such high antistatic performance can be achieved, it has been difficult to simultaneously maintain the durability of the pressure-sensitive adhesive layer.

[0005] In the present invention, the surface resistivity of the pressure-sensitive adhesive layer is 9.0×10 +10 The present invention addresses the problem of providing a pressure-sensitive adhesive composition that has extremely excellent antistatic performance of Ω / □ or less and does not impair durability, and a pressure-sensitive adhesive film using the same. [Means for solving the problem]

[0006] The inventors of the present invention have worked diligently to solve the difficult problem of simultaneously achieving both high antistatic performance and durability. As a result, they have succeeded in solving this problem by limiting the number of carbon atoms in the alkyl groups of the alkyl (meth)acrylates constituting the acrylic polymer of the pressure-sensitive adhesive composition to a specific range, thereby obtaining an acrylic polymer consisting of a copolymer obtained by copolymerizing two or more alkyl (meth)acrylates in a specific combination, and further by preparing a pressure-sensitive adhesive composition containing a specific antistatic agent.

[0007] The present inventors have found that by incorporating the acrylic polymer and an ammonium-based antistatic agent having a fluoro group-containing anion in a ratio of 2.5 to 15 parts by weight per 100 parts by weight of the acrylic polymer, a pressure-sensitive adhesive composition can be obtained that has extremely superior antistatic performance compared to conventional pressure-sensitive adhesive compositions, does not precipitate the antistatic agent, does not deteriorate over time, and has excellent durability, and has completed the present invention.

[0008] The pressure-sensitive adhesive composition of the present invention has a surface resistivity of the pressure-sensitive adhesive layer of 9.0×10 +10 In order to achieve extremely excellent antistatic performance of Ω / □ or less, an ammonium-based antistatic agent having a fluoro group-containing anion is contained in an amount of 2.5 to 15 parts by weight per 100 parts by weight of the acrylic polymer. Thus, in the present invention, the content of the antistatic agent is increased in order to obtain extremely excellent antistatic performance. For this reason, the technical concept is that the acrylic polymer contained in the adhesive composition is mainly made of n-butyl acrylate (BA) and is copolymerized with selected monomers that are copolymerizable with BA, so that the ammonium-based antistatic agent with a fluoro group-containing anion contained in large quantities in the adhesive layer will not precipitate on the surface of the adhesive layer after durability testing of the adhesive layer in a high-temperature, high-humidity environment, and the adhesive layer will be able to maintain durability.

[0009] In order to solve the above-mentioned problems, the present invention provides a pressure-sensitive adhesive composition comprising an acrylic polymer, an antistatic agent, and a crosslinking agent, wherein the acrylic polymer is an acrylic polymer obtained by copolymerizing (A) n-butyl acrylate, (B) at least one selected from the group consisting of t-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, and methyl acrylate, (C) at least one copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group, and (D) at least one copolymerizable vinyl monomer containing an aromatic group, and the weight-average molecular weight of the copolymer is 1,000,000 to 3,000,000; and The pressure-sensitive adhesive composition contains, as an antistatic agent, an ammonium-based antistatic agent having a fluoro group-containing anion in a ratio of 2.5 to 15 parts by weight relative to 100 parts by weight of the acrylic polymer, and as the (F) crosslinking agent, at least one crosslinking agent selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds, and the pressure-sensitive adhesive composition further contains (G) a monomeric or oligomeric silane coupling agent containing at least one functional group selected from an epoxy group, a mercapto group, and an acid anhydride group, and the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 9.0 × 10 +10 The present invention provides a pressure-sensitive adhesive composition characterized in that the antistatic agent does not precipitate on the surface of the pressure-sensitive adhesive layer after the pressure-sensitive adhesive layer is subjected to a durability test under a test environment of 85°C x 750 hours or a durability test under a test environment of 60°C x 90% RH x 750 hours.

[0010] Furthermore, it is preferable that the antistatic agent is an ionic compound composed of a fluoro group-containing anion and an ammonium cation, and has a melting point of 25°C or higher, and that the fluoro group-containing anion is one selected from the group consisting of pentafluorobenzenesulfonate, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, and triflate.

[0011] It is preferable that the acrylic polymer contains 40 to 89 parts by weight of (A) n-butyl acrylate and 5 to 40 parts by weight of (B) a total of at least one selected from the group consisting of t-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, and methyl acrylate, relative to 100 parts by weight of the acrylic polymer, and that the ratio (A) / (B) of (A) to (B) is 1.0 to 17.8.

[0012] When a polarizing plate having a total thickness of 80 μm is bonded to alkali-free glass via a 20 μm-thick adhesive layer obtained by crosslinking the adhesive composition, the adhesive strength of the adhesive layer to the alkali-free glass is 1.0 to 6.0 N / 25 mm, and it is preferable that a test piece obtained by bonding a 10 cm square polarizing plate having a total thickness of 80 μm to alkali-free glass via a 20 μm-thick adhesive layer obtained by crosslinking the adhesive composition is free from bubbling and peeling after being subjected to a durability test in a test environment of 85°C x 750 hours or a durability test in a test environment of 60°C x 90% RH x 750 hours.

[0013] The (C) 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, and is contained in a proportion of 0.1 to 5 parts by weight per 100 parts by weight of the total of the (A), the (B), and the (D), and the copolymerizable monomer containing a hydroxyl group is 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 ... and the copolymerizable monomer containing a carboxyl group is preferably at least one selected from the group of compounds consisting of (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl maleic acid, carboxypolycaprolactone mono(meth)acrylate, and 2-(meth)acryloyloxyethyl tetrahydrophthalic acid.

[0014] The pressure-sensitive adhesive layer had an initial surface resistivity of 9.0×10 and a surface resistivity of 9.0×10 after being subjected to a durability test under a test environment of 85°C for 750 hours. +10 It is preferably Ω / □ or less.

[0015] The present invention also provides a pressure-sensitive adhesive film, characterized in that it comprises a resin film and a pressure-sensitive adhesive layer formed by crosslinking the above-mentioned pressure-sensitive adhesive composition laminated on one side thereof.

[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 the above-mentioned pressure-sensitive adhesive film for polarizing plates, which is used to bond a polarizing plate to an in-cell panel.

[0018] The present invention also provides an adhesive film characterized by having a release film / adhesive layer / release film structure, in which an adhesive layer formed by crosslinking the above-mentioned adhesive composition is formed on one side of the release film to a thickness of 1 μm to 25 μm.

[0019] The present invention also provides an optical film with a pressure-sensitive adhesive layer, characterized in that the pressure-sensitive adhesive layer is formed by crosslinking the pressure-sensitive adhesive composition described above and laminated on at least one surface of the optical film, and has a release film / pressure-sensitive adhesive layer / optical film structure.

[0020] The present invention also provides a polarizing plate with a pressure-sensitive adhesive layer, characterized in that the polarizing plate has a structure of release film / pressure-sensitive adhesive layer / polarizing plate, and the pressure-sensitive adhesive layer is formed by crosslinking the pressure-sensitive adhesive composition described above and laminated on one side of the polarizing plate.

[0021] The present invention also provides a liquid crystal panel, characterized in that the above-mentioned polarizing plate with a pressure-sensitive adhesive layer is used.

[0022] The present invention also provides an in-cell type liquid crystal panel, characterized in that the above-mentioned polarizing plate with a pressure-sensitive adhesive layer is used. [Effects of the Invention]

[0023] According to the present invention, the surface resistivity of the pressure-sensitive adhesive layer is 9.0 × 10 +10 It is possible to provide a pressure-sensitive adhesive composition that has extremely excellent antistatic performance of Ω / □ or less and does not impair durability, and a pressure-sensitive adhesive film using the same. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described below based on preferred embodiments.

[0025] 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 is an acrylic polymer obtained by copolymerizing (A) n-butyl acrylate, (B) at least one selected from the group consisting of t-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, and methyl acrylate, (C) at least one copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group, and (D) at least one copolymerizable vinyl monomer containing an aromatic group, and the weight-average molecular weight of the copolymer is 1,000,000 to 3,000,000; and and (F) the crosslinking agent is at least one crosslinking agent selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds. The pressure-sensitive adhesive composition further contains (G) 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 pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition has a surface resistivity of 9.0×10 +10 The adhesive layer is characterized in that the resistance is Ω / □ or less, and the antistatic agent does not precipitate on the surface of the adhesive layer after the adhesive layer is subjected to a durability test under a test environment of 85°C x 750 hours or a durability test under a test environment of 60°C x 90% RH x 750 hours.

[0026] (A) n-butyl acrylate and (B) at least one selected from the group consisting of t-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, and methyl acrylate each correspond to an alkyl(meth)acrylate monomer. In the pressure-sensitive adhesive composition of the present embodiment, the alkyl(meth)acrylate monomer constituting the acrylic polymer is preferably a combination of two or more specific types of (A) and (B).

[0027] The acrylic polymer of this embodiment preferably contains (A) n-butyl acrylate as a main component, for example, in an amount of 40 to 89 parts by weight of (A) n-butyl acrylate per 100 parts by weight of the acrylic polymer. Furthermore, the acrylic polymer preferably contains (B) at least one alkyl (meth)acrylate monomer other than (A) n-butyl acrylate, selected from the group consisting of t-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, and methyl acrylate, in an amount of 5 to 40 parts by weight. Furthermore, the ratio (A) / (B) of (A) to (B) is preferably 1.0 to 17.8 by weight.

[0028] The (C) copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group may 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 proportion of the (C) copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group is preferably 0.1 to 5 parts by weight per 100 parts by weight of the total of (A), (B), and (D). Note that (A), (B), and (D) are all vinyl monomers containing no hydroxyl or carboxyl groups.

[0029] Examples of the hydroxyl group-containing monomer include at least one of hydroxyalkyl (meth)acrylates such as 8-hydroxyoctyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxyethyl (meth)acrylate, and hydroxyl group-containing (meth)acrylamides such as N-hydroxy(meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxyethyl (meth)acrylamide. The hydroxyl group-containing monomer contained in the pressure-sensitive adhesive composition of this embodiment can be used as a copolymerizable monomer to reduce the content of carboxyl group-containing monomers, which are believed to affect the corrosiveness of the resulting pressure-sensitive adhesive layer against easily corroded substrates such as the ITO surface of a transparent conductive film. Therefore, the hydroxyl group-containing monomer can be used to improve the adhesive strength of the pressure-sensitive adhesive layer and reduce corrosiveness. The proportion of the hydroxyl group-containing monomer contained in the pressure-sensitive adhesive composition of this embodiment is preferably 0.1 to 5.0 parts by weight, more preferably 0.1 to 4.4 parts by weight, and particularly preferably 0.1 to 3.8 parts by weight, per 100 parts by weight of the total of (A), (B), and (D).

[0030] Examples of carboxyl group-containing monomers include at least one 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 carboxyl group-containing monomer contained in the pressure-sensitive adhesive composition of this embodiment can impart the necessary cohesive strength to the resulting pressure-sensitive adhesive layer. The proportion of the carboxyl group-containing monomer in the pressure-sensitive adhesive composition of this embodiment is preferably 0 to 5.0 parts by weight per 100 parts by weight of the total of (A), (B), and (D). When a hydroxyl group-containing monomer is copolymerized with an acrylic polymer, it is acceptable not to copolymerize the carboxyl group-containing monomer. When a carboxyl group-containing monomer is copolymerized, the proportion is more preferably 0.01 to 5.0 parts by weight, particularly preferably 0.01 to 3.3 parts by weight, and most preferably 0.01 to 2.8 parts by weight.

[0031] Examples of (D) 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. (D) Aromatic group-containing copolymerizable vinyl monomers preferably contain an aromatic group-containing (meth)acrylate monomer, since this exhibits excellent copolymerizability with the alkyl (meth)acrylate monomers formed from the combination of (A) and (B).

[0032] To obtain a pressure-sensitive adhesive layer with a high refractive index, it is preferable to blend at least one type of (meth)acrylate monomer containing an aromatic group into the pressure-sensitive adhesive composition of this embodiment. By copolymerizing these (meth)acrylate monomers containing an aromatic group with an acrylic polymer, the refractive index of the resulting pressure-sensitive adhesive layer can be increased and adjusted, thereby reducing the refractive index difference between optical components and reducing total reflection, thereby improving total light transmittance. In the pressure-sensitive adhesive composition of this embodiment, the (meth)acrylate monomer containing an aromatic group is preferably contained in an amount of 5 to 30 parts by weight, more preferably 6 to 28 parts by weight, and particularly preferably 6 to 24 parts by weight, per 100 parts by weight of the acrylic polymer.

[0033] 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 such as solution polymerization, emulsion polymerization, etc. The weight-average molecular weight of the copolymer of the acrylic polymer is preferably 1,000,000 to 3,000,000.

[0034] The pressure-sensitive adhesive composition according to this embodiment contains an antistatic agent (E) to achieve antistatic properties. The antistatic agent (E) is an ammonium-based antistatic agent having a fluoro group-containing anion, preferably in an amount of 2.5 to 15 parts by weight, more preferably 3 to 15 parts by weight, and particularly preferably 4 to 15 parts by weight, per 100 parts by weight of the acrylic polymer. This antistatic agent is an ionic compound comprising a fluoro group-containing anion and an ammonium cation. This ionic compound preferably has a melting point of 25°C or higher and is solid at room temperature (e.g., 25°C). Furthermore, this ionic compound is more preferably an ionic compound that is solid at 25°C and has a melting point of 25°C to 80°C.

[0035] The fluoro group-containing anion contained in the (E) antistatic agent may be an inorganic or organic fluoro group-containing anion. Here, the fluoro group means a fluorine atom bonded to another atom constituting the anion. Examples of inorganic fluoro group-containing anions include PF6 - , AsF6 - , SbF6 - , BF4 - , AlF4 - , (FSO2)2N - , FSO3 - Examples of organic fluoro group-containing anions include fluoro group-containing sulfonate anions (RSO3 - ), fluoro-group-containing carboxylate anion (RCOO - ), alkoxide or phenoxide anion containing a fluoro group (RO - ), fluoro-group-containing organic imide anions (RN - ), fluoro-containing methides (R3C - ) anion, fluoro-group-containing organic borate (R4B -) anions, etc., in which at least one of R has a fluoro group-containing organic group. Examples of the organic group include one or more of an alkyl group, an alkoxy group, an aromatic group (aryl group, aralkyl group, etc.), an alkylcarbonyl group, an aromatic carbonyl group, an alkylsulfonyl group, an aromatic sulfonyl group, etc. When the anion has two or more R, a bond may be formed between the two or more R to form a ring. Among these, one selected from the group consisting of pentafluorobenzenesulfonate, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, and triflate is preferred.

[0036] The ammonium cation contained in the (E) antistatic agent may be an organic ammonium cation having 1 to 4 organic groups, and particularly a quaternary ammonium cation (R4N + ) is preferred. Examples of R include hydrocarbon groups such as acyclic or cyclic alkyl groups and aromatic groups (aryl groups, aralkyl groups, etc.). When the cation has two or more R, the two or more R may have a bond between them to form a ring.

[0037] The pressure-sensitive adhesive composition according to the present embodiment further contains (F) a crosslinking agent, which is at least one selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds. The proportion of (F) crosslinking agent is, for example, 0.01 to 5 parts by weight per 100 parts by weight of the acrylic polymer.

[0038] Examples of tri- or higher functional isocyanate compounds 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 tri- or higher functional 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.

[0039] The pressure-sensitive adhesive composition according to this embodiment further contains a (G) silane coupling agent. Examples of the (G) silane coupling agent include compounds having at least one organic functional group and at least one hydrolyzable group in one molecule, where the hydrolyzable group is an alkoxy group bonded to a silicon atom. The (G) silane coupling agent contains at least one functional group selected from an epoxy group, a mercapto group, and an acid anhydride group. The (G) silane coupling agent may be at least one of a monomer type or an oligomer type, or both. The proportion of the silane coupling agent is, for example, 0.01 to 0.5 parts by weight per 100 parts by weight of the acrylic polymer.

[0040] 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, and 3-mercaptopropyltriethoxysilane. Examples of silane coupling agents having an acid anhydride group include 3-trimethoxysilylpropylsuccinic anhydride and 3-triethoxysilylpropylsuccinic anhydride. In addition, oligomerized alkoxy oligomers (silicone alkoxy oligomers) can also be used as silane coupling agents.

[0041] The pressure-sensitive adhesive composition of the present embodiment may contain, as optional components, known additives such as antioxidants, surfactants, curing accelerators, plasticizers, fillers, crosslinking catalysts, crosslinking retarders, curing retarders, processing aids, and antioxidants. These may be used alone or in combination of two or more.

[0042] The surface resistivity of the pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of this embodiment is 9.0 × 10 +10 It is preferable that the resistance is Ω / □ or less, and 5.0×10 +10 Ω / □ or less is more preferable, and 2.0×10 +10It is particularly preferable that the initial surface resistivity and the surface resistivity after the durability test of this pressure-sensitive adhesive layer are both 9.0×10 +10 It is preferable that the resistance is Ω / □ or less, and 5.0×10 +10 Ω / □ or less is more preferable, and 2.0×10 +10 It is particularly preferably Ω / □ or less. Here, the initial surface resistivity refers to the surface resistivity before the pressure-sensitive adhesive layer is subjected to a durability test. Furthermore, the surface resistivity after the durability test refers to the surface resistivity after the pressure-sensitive adhesive layer is subjected to a durability test under a test environment of 85°C x 750 hours. Here, the test environment of 85°C x 750 hours may be a dry condition.

[0043] The pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition of the present embodiment is free from deposition of the antistatic agent (E) on the surface of the pressure-sensitive adhesive layer after being subjected to a durability test under a test environment of 85°C x 750 hours and a durability test under a test environment of 60°C x 90% RH x 750 hours. Here, the test environment of 85°C x 750 hours may be a dry condition. The anti-precipitation performance of the (E) antistatic agent in the pressure-sensitive adhesive composition of this embodiment may be such that two or more samples of a pressure-sensitive adhesive layer crosslinked from the same pressure-sensitive adhesive composition are prepared, one sample is subjected to a durability test under a test environment of 85°C x 750 hours, after which the (E) antistatic agent does not precipitate, and another sample is subjected to a durability test under a test environment of 60°C x 90% RH x 750 hours, after which the (E) antistatic agent does not precipitate.

[0044] When a polarizing plate having a total thickness of 80 μm is attached to alkali-free glass via a 20 μm-thick adhesive layer obtained by crosslinking the adhesive composition of the present embodiment, the adhesive layer preferably has an adhesive strength to the alkali-free glass of 1.0 to 6.0 N / 25 mm. Furthermore, it is preferable that a test piece obtained by bonding a polarizing plate having a 10 cm square and a total thickness of 80 μm to alkali-free glass via a 20 μm thick adhesive layer is subjected to a durability test in a test environment of 85°C x 750 hours and a durability test in a test environment of 60°C x 90% RH x 750 hours, and thereafter there is no foaming or peeling. The performance of the pressure-sensitive adhesive composition of the present embodiment without foaming or peeling may be such that two or more test pieces are prepared using the same pressure-sensitive adhesive composition, one test piece is subjected to a durability test under a test environment of 85°C x 750 hours, and thereafter there is no foaming or peeling, and another test piece is subjected to a durability test under a test environment of 60°C x 90% RH x 750 hours, and thereafter there is no foaming or peeling.

[0045] 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.

[0046] When the pressure-sensitive adhesive layer according to the present embodiment is used for bonding between layers of optical components, it is desirable that the difference in refractive index between the pressure-sensitive adhesive layer and the optical component be as small as possible to reduce reflection of light at the interface between the pressure-sensitive adhesive layer and the optical component. Therefore, the refractive index of the pressure-sensitive adhesive layer is preferably 1.47 to 1.50.

[0047] 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. Resin films such as polyester films can be used as the resin film substrate 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 substrate 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 may be, for example, 1 μm to 25 μm.

[0048] A "release film / adhesive layer / release film" configuration can also be achieved by attaching the release-treated surfaces of release films to both sides of a single adhesive layer. In this case, the release films on both sides can be peeled off sequentially or simultaneously to expose the adhesive surface, making it possible to bond it to an optical component such as an optical film. Examples of optical films include polarizing films, retardation films, anti-reflection films, anti-glare films, UV-absorbing films, infrared-absorbing films, optical compensation films, and brightness-enhancing films. Examples of devices to which optical components can be applied include liquid crystal panels, organic electroluminescence (EL) panels, touch panels, and in-cell liquid crystal panels.

[0049] The pressure-sensitive adhesive film of this embodiment is suitable as a pressure-sensitive adhesive film for polarizing plates. In particular, it may be used to bond a polarizing plate to an in-cell panel. Furthermore, the pressure-sensitive adhesive layer may be laminated on at least one surface of the optical film described above to form a pressure-sensitive adhesive layer-attached optical film. By using the pressure-sensitive adhesive film on one surface of a polarizing plate, a pressure-sensitive adhesive layer-attached polarizing plate can be provided. The pressure-sensitive adhesive layer-attached polarizing plate described above can be used to provide a liquid crystal panel such as an in-cell type liquid crystal panel. Specific examples of the laminate structure of 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 laminate structures may be included as a partial structure of a liquid crystal panel or the like. [Example]

[0050] The present invention will be specifically described below with reference to examples.

[0051] <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. Then, 70 parts by weight of n-butyl acrylate, 15 parts by weight of n-butyl methacrylate, 2.0 parts by weight of 8-hydroxyoctyl acrylate, 15 parts by weight of benzyl acrylate, and a solvent (ethyl acetate) were added to the reactor. Then, 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 6 hours, yielding a solution of the acrylic polymer used in Example 1. [Examples 2 to 7 and Comparative Examples 1 to 3] Acrylic polymer solutions used in Examples 2 to 7 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 above, except that the monomer compositions were as shown in Table 1 (A) to (D), respectively. Although no specific measurement results are shown, the weight average molecular weight of the copolymer contained in the acrylic polymer solutions of Examples 1 to 7 and Comparative Examples 1 to 3 is in the range of 1,000,000 to 3,000,000.

[0052] <Manufacturing of adhesive film> [Example 1] To the acrylic polymer solution of Example 1 prepared as described above, 10 parts by weight of cyclohexyltrimethylammonium bis(trifluoromethanesulfonyl)imide, 0.1 parts by weight of a crosslinking agent (D-110N), and 0.05 parts by weight of a silane coupling agent (X-12-967C) were added and mixed by stirring to obtain a pressure-sensitive adhesive composition of Example 1. This pressure-sensitive adhesive composition was applied to a release film made of a silicone resin-coated polyethylene terephthalate (PET) film so that the thickness of the pressure-sensitive adhesive layer after drying would be 20 μm, and the solvent was then removed by drying at 90° C. Thereafter, the film was aged for 7 days in an atmosphere of 23° C. and 50% RH to obtain a pressure-sensitive adhesive film of Example 1 having a pressure-sensitive adhesive layer formed by crosslinking the pressure-sensitive adhesive composition on one side of the release film, and having a structure of release film / pressure-sensitive adhesive layer / release film. [Examples 2 to 7 and Comparative Examples 1 to 3] PSA films of Examples 2 to 7 and Comparative Examples 1 to 3 were obtained in the same manner as the PSA film of Example 1 above, except that the compositions of the additives were changed as shown in Table 1 (E) to (G), respectively.

[0053] [Table 1]

[0054] In Table 1, the numerical value following the abbreviation for each component indicates parts by weight. This weight part is calculated assuming the total of (A), (B), and (D) is 100 parts by weight. Table 2 also shows the compound names for the abbreviations of each component used in Table 1. For convenience, IOA is included in (B). For (C), monomers containing a hydroxyl group are classified as "(C)OH" and monomers containing a carboxyl group are classified as "(C)COOH."

[0055] [Table 2]

[0056] In Table 2, Coronate (registered trademark) L is a product name of Tosoh Corporation, D-110N is a product name of Mitsui Chemicals, Inc., and TETRAD (registered trademark)-X is a product name of Mitsubishi Gas Chemical Company, Inc. Also, TDI means tolylene diisocyanate, TMP means trimethylolpropane, and XDI means xylylene diisocyanate. Also, KBM-403, X-12-967C, X-41-1805, and KBM-503 are all product names of Shin-Etsu Chemical Co., Ltd.

[0057] <Test method and evaluation> The release film (a silicone resin-coated PET film) was peeled off from the pressure-sensitive adhesive film in Examples 1 to 7 and Comparative Examples 1 to 3 to expose one side of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film. Thereafter, the pressure-sensitive adhesive film was attached to one side of a polarizing plate (resin film) having a thickness of 80 μm via the pressure-sensitive adhesive layer to obtain a polarizing plate with a pressure-sensitive adhesive layer having a release film / pressure-sensitive adhesive layer / polarizing plate configuration.

[0058] <Method for measuring adhesive strength> The release film was removed from the resulting polarizing plate with a pressure-sensitive adhesive layer, and the polarizing plate with a pressure-sensitive adhesive layer was attached to the acetone-cleaned surface of alkali-free glass (Corning Eagle XG®) using a pressure roller, via the pressure-sensitive adhesive layer, to prepare a test specimen. The test specimen was then autoclaved at 50°C and 0.5 MPa for 20 minutes. The specimen was then returned to an atmosphere of 23°C and 50% RH. After 1 hour, the peel strength of the polarizing plate with a pressure-sensitive adhesive layer was measured using a tensile tester in accordance with JIS Z0237 "Test Method for Adhesive Tapes and Sheets." The peel strength measured when peeled at a speed of 0.3 m / min in a 180° direction was taken as the adhesive strength of the pressure-sensitive adhesive layer to the alkali-free glass.

[0059] <Method for measuring surface resistivity> The surface resistivity (Ω / □) of the pressure-sensitive adhesive layer of the obtained polarizing plate with a pressure-sensitive adhesive layer was measured using a resistivity meter HIRESTA (registered trademark) UP-HT450 (manufactured by Mitsubishi Chemical Analytech) under an atmosphere of 23°C x 50% RH to determine the initial surface resistivity. The same polarizing plate with a pressure-sensitive adhesive layer was subjected to a durability test under a test environment of 85°C x 750 hours, and then the surface resistivity was measured in the same way to determine the surface resistivity after the durability test.

[0060] <Durability test method> Using the same method as in measuring adhesive strength, the release film was peeled off from a 10cm square polarizing plate with an adhesive layer, and the plate was 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 under a test environment of 85°C x 750 hours and a test environment of 60°C x 90% RH x 750 hours, after which it was removed from the test piece and placed in a 23°C x 50% RH atmosphere. After 1 hour, the state of the adhesive layer was visually observed to determine its durability. ○: There is absolutely no foaming or peeling of the adhesive layer. △: Foaming and peeling occurred in part of the adhesive layer. ×: Foaming and peeling have occurred throughout the adhesive layer.

[0061] <Method for evaluating the precipitation state of antistatic agents> Using the same method as in the measurement of adhesive strength, the release film was peeled off from a 10 cm square polarizing plate with an adhesive layer, and the plate was attached to the acetone-cleaned surface of alkali-free glass to prepare a test piece. The test piece was then subjected to a durability test under a test environment of 85°C x 750 hours and a durability test under a test environment of 60°C x 90% RH x 750 hours, after which it was removed from the test piece and placed in a 23°C x 50% RH atmosphere. After 1 hour, the state of the adhesive layer was visually observed to determine the state of precipitation of the antistatic agent on the surface of the adhesive layer. ○: There is absolutely no deposition of antistatic agent on the surface of the adhesive layer. △: Precipitation of the antistatic agent occurred on part of the surface of the adhesive layer. ×: Precipitation of the antistatic agent occurs over the entire surface of the adhesive layer.

[0062] Table 3 shows the evaluation results.

[0063] [Table 3]

[0064] The adhesive films of Examples 1 to 7 had an adhesive strength to non-alkali glass of 1.0 to 6.0 N / 25 mm, and the initial surface resistivity of the adhesive layer and the surface resistivity after a durability test under a test environment of 85°C x 750 hours were both 9.0 x 10 +10 The adhesive films of Examples 1 to 7 had a resistivity of Ω / □ or less, and after a durability test under a test environment of 85°C x 750 hours and a durability test under a test environment of 60°C x 90% RH x 750 hours, there was no foaming or peeling, and they were durable, and there was no deposition of the antistatic agent on the surface of the adhesive layer. In other words, the evaluation results for the adhesive films of Examples 1 to 7 demonstrate that the problems of the present invention were solved.

[0065] In the adhesive film of Comparative Example 1, the alkyl (meth)acrylate monomer copolymerized with the acrylic polymer was not TBA, IBA, BMA, or MA, and no copolymerizable vinyl monomer containing an aromatic group (D) was copolymerized. Therefore, the adhesive layer of the adhesive film of Comparative Example 1 had excessively high adhesive strength before the durability test, but poor durability. Furthermore, the adhesive film of Comparative Example 1 contained a high proportion of (E) antistatic agent, which reduced the surface resistivity of the adhesive layer, but the antistatic agent precipitated over the entire surface of the adhesive layer after the durability test.

[0066] The pressure-sensitive adhesive film of Comparative Example 2 contains a silane coupling agent (G), but does not contain at least one functional group selected from an epoxy group, a mercapto group, and an acid anhydride group. As a result, the pressure-sensitive adhesive film of Comparative Example 2 had poor durability of the pressure-sensitive adhesive layer, and the antistatic agent partially precipitated on the surface of the pressure-sensitive adhesive layer after the durability test.

[0067] In the PSA film of Comparative Example 3, the alkyl (meth)acrylate monomer copolymerized with the acrylic polymer was not TBA, IBA, BMA, or MA, and no copolymerizable vinyl monomer containing an aromatic group (D) was copolymerized. Therefore, even though the PSA film of Comparative Example 3 did not contain a silane coupling agent (G), the PSA layer had excessively high adhesive strength before the durability test, but had poor durability. Furthermore, because the PSA film of Comparative Example 3 contained a low proportion of the antistatic agent (E), there was no precipitation of the antistatic agent on the surface of the PSA layer after the durability test, but the surface resistivity of the PSA layer was high.

[0068] As described above, the pressure-sensitive adhesive films of Comparative Examples 1 to 3 could not solve the problems of the present invention.

[0069] According to the present invention, the surface resistivity of the pressure-sensitive adhesive layer is 9.0 × 10 +10It is possible to provide a pressure-sensitive adhesive composition having extremely excellent antistatic performance of Ω / □ or less without impairing durability, and a pressure-sensitive adhesive film using the same. Therefore, the pressure-sensitive adhesive composition according to the present invention and the pressure-sensitive adhesive film using the same have extremely excellent antistatic performance and durability as a pressure-sensitive adhesive composition for use in bonding a polarizing plate and a liquid crystal panel, and a pressure-sensitive adhesive film using the same, and are therefore of great industrial utility.

Claims

1. A pressure-sensitive adhesive composition comprising an acrylic polymer, (E) an antistatic agent, and (F) a crosslinking agent, The acrylic polymer (A) n-butyl acrylate, (B) at least one selected from the group consisting of t-butyl acrylate, isobutyl acrylate, n-butyl methacrylate, and methyl acrylate; (C) at least one copolymerizable vinyl monomer containing a hydroxyl group and / or a carboxyl group; (D) at least one copolymerizable vinyl monomer containing an aromatic group; and the copolymer is an acrylic polymer having a weight average molecular weight of 1,000,000 to 3,000,000. the (C) 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 (E) antistatic agent contains an ionic compound having a melting point of 25°C or higher, which is composed of a fluoro group-containing anion and an ammonium cation, in an amount of 2.5 to 15 parts by weight per 100 parts by weight of the acrylic polymer; the fluoro group-containing anion is one selected from the group consisting of pentafluorobenzenesulfonate, hexafluorophosphate, bis(trifluoromethanesulfonyl)imide, bis(fluorosulfonyl)imide, and triflate; The (F) crosslinking agent contains at least one crosslinking agent selected from the group consisting of trifunctional or higher isocyanate compounds and difunctional or higher epoxy compounds, The pressure-sensitive adhesive composition further comprises (G) a monomeric or oligomeric silane coupling agent containing at least one functional group selected from an epoxy group, a mercapto group, and an acid anhydride group.

2. 10. 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 laminated thereon.

3. A pressure-sensitive adhesive film having a release film / pressure-sensitive adhesive layer / release film structure, in which a pressure-sensitive adhesive layer obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1 is formed on one side of the release film to a thickness of 1 μm to 25 μm.

4. A polarizing plate with a pressure-sensitive adhesive layer, which is obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1, laminated on one side of the polarizing plate, and which has a structure of release film / pressure-sensitive adhesive layer / polarizing plate.

5. A liquid crystal panel comprising a polarizing plate with a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer being obtained by crosslinking the pressure-sensitive adhesive composition according to claim 1 and laminated on one side of the polarizing plate.

Images