Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, optical member, and display device

Abstract

To provide a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, an optical member, and a display device that can form a pressure-sensitive adhesive layer having superior durability at high temperature and high humidity, and long-term reworkability, even when applied to a thin optical film.SOLUTION: A pressure-sensitive adhesive composition comprises a (meth)acrylic polymer (A) having a carboxyl group, a crosslinking agent (B), a silane coupling agent (C) having an isocyanate group, and an alicyclic epoxy compound (D) represented by formula (I), wherein R in formula (I) represents a divalent organic linking group having an ester bond.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, an optical member, and a display device. [Background technology]

[0002] A liquid crystal display device generally includes a liquid crystal cell in which a liquid crystal component aligned in a predetermined direction is sandwiched between two support substrates, and optical films such as a polarizing plate, a retardation film, and a brightness enhancement film. When a liquid crystal display device is manufactured by laminating a liquid crystal cell and an optical film, or by laminating optical films together, these components are bonded together via a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition. In liquid crystal display devices, (meth)acrylic pressure-sensitive adhesive compositions are often used to ensure visibility.

[0003] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition comprising a (meth)acrylic polymer having a carboxy group, a polyisocyanate compound, an alicyclic epoxy compound having a specific structure, and a silane coupling agent, in which the content of the polyisocyanate compound is 0.1 to 11.0 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer, and the content of the alicyclic epoxy compound is 0.1 to 4.0 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer. Patent Document 2 also describes a one-sided protected polarizing film having a protective film only on one side of a polarizer, and a one-sided protected polarizing film with an adhesive layer, which has an adhesive layer on the polarizer side of the one-sided protected polarizing film directly or via a coating layer, wherein the adhesive layer contains, as a base polymer, a (meth)acrylic polymer having a weight-average molecular weight of 1,500,000 or less, and a silane coupling agent having at least one functional group selected from the group consisting of an epoxy group, an isocyanate group, a mercapto group, an acid anhydride group, and an amino group, and the (meth)acrylic polymer contains, as a monomer unit, an alkyl(meth)acrylate having a glass transition temperature of less than 0°C as a homopolymer. and 0.1 to 20 mass % of at least one high Tg monomer (B) selected from the group consisting of alkyl (meth)acrylates (b1) whose homopolymers have a glass transition temperature of 0°C or higher and (meth)acryloyl group-containing monomers (b2) whose homopolymers have a glass transition temperature of 0°C or higher and have a heterocycle, wherein the pressure-sensitive adhesive layer has a weight change rate of 1.1% or higher as calculated by a specific formula, and the pressure-sensitive adhesive layer has an adhesive strength P0 of 10 N / 25 mm or lower under specific conditions and an adhesive strength P1 of 1.6 N / 25 mm or higher under specific conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-115560 [Patent Document 2] Patent No. 7142497 Summary of the Invention [Problem to be solved by the invention]

[0005] Optical films such as polarizing plates are usually constructed by laminating multiple components with different shrinkage rates, and therefore are prone to dimensional changes due to temperature and / or humidity changes. For this reason, for example, when an optical film bonded to a liquid crystal cell via a pressure-sensitive adhesive layer is placed in a harsh environment, such as a high-temperature environment or a high-humidity environment, the optical film shrinks, which can cause problems such as peeling at the interface between the pressure-sensitive adhesive layer and the optical film and / or the liquid crystal cell. Therefore, there is a need for a pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer with excellent durability and that can effectively suppress peeling that can occur when placed in a high-temperature environment and / or a high-humidity environment. Furthermore, optical films such as polarizing plates are sometimes stored for a period of time in a state where they are bonded to a glass member, such as a glass substrate of a liquid crystal cell, and then peeled from the glass member for reuse. Therefore, there is a need for a pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer with excellent long-term reworkability, which can cleanly peel the optical film from the glass member without damaging them, even when the optical film is bonded to the glass member for a long period of time.

[0006] In recent years, as liquid crystal displays have become thinner, optical films have also been required to be thinner. The thickness of optical films, which was previously several hundred microns, has been significantly reduced to 100 μm or less, and even 50 μm or less. Furthermore, attempts have been made to reduce the number of layers in optical films having a multi-layer structure in order to achieve thinner films. For example, polarizing plates have begun to be distributed, in which a protective layer, which was previously provided on both sides of the polarizer, is provided only on one side. However, thin optical films are highly susceptible to shrinkage. Furthermore, optical films with asymmetrically stacked layers of different materials, such as single-sided protected polarizing plates, tend to curl excessively to one side of the stacking direction upon shrinkage, making them prone to peeling. For these reasons, the durability standards required for pressure-sensitive adhesive layers have become higher, and pressure-sensitive adhesive layers are required to be more resistant to peeling than ever before. Furthermore, optical films have become more brittle as they have become thinner. Therefore, if the adhesive strength of the pressure-sensitive adhesive layer is high when peeling them from a glass member, the optical film is likely to break. For this reason, the pressure-sensitive adhesive layer is required to have an adhesive strength that is unlikely to increase more than ever after the optical film and the glass member are attached to each other for a long period of time. Generally, to prevent peeling of the pressure-sensitive adhesive layer, a method is taken to improve the adhesive strength of the pressure-sensitive adhesive layer, but this method comes at the cost of worsening reworkability. Therefore, as optical films become thinner, it has become more difficult to achieve both durability and long-term reworkability of the pressure-sensitive adhesive layer.

[0007] The present disclosure has been made in light of the above-mentioned circumstances. An object of one embodiment of the present disclosure is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that exhibits excellent high-temperature durability, high-humidity durability, and long-term reworkability even when used in a thin optical film. Another problem to be solved by another embodiment of the present disclosure is to provide a pressure-sensitive adhesive sheet, an optical member, and a display device, each of which includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. [Means for solving the problem]

[0008] Specific means for solving the problems include the following aspects. <1> A pressure-sensitive adhesive composition comprising a (meth)acrylic polymer (A) having a carboxy group, a crosslinking agent (B), a silane coupling agent (C) having an isocyanate group, and an alicyclic epoxy compound (D) represented by the following formula (I):

[0009] [ka]

[0010] In formula (I), R represents a divalent organic linking group having an ester bond.

[0011] <2> The (meth)acrylic polymer (A) contains a structural unit (a1) derived from a monomer having a carboxy group, and the content of the structural unit (a1) is 0.5% by mass to 1.5% by mass based on all structural units. <1> The pressure-sensitive adhesive composition according to claim 1. <3> The (meth)acrylic polymer (A) contains a structural unit (a2) derived from a monomer having a hydroxyl group, and the content of the structural unit (a2) is 0.1% by mass to 1.0% by mass based on all structural units. <1> or <2> The pressure-sensitive adhesive composition according to claim 1. <4> The crosslinking agent (B) is an isocyanate-based crosslinking agent. <1> ~ <3> The pressure-sensitive adhesive composition according to any one of the above. <5> The isocyanate-based crosslinking agent is an aromatic polyisocyanate-based compound. <4> The pressure-sensitive adhesive composition according to claim 1. <6> The aromatic polyisocyanate compound is a tolylene diisocyanate compound. <5> The pressure-sensitive adhesive composition according to claim 1. <7> The content of the crosslinking agent (B) is 0.1 to 5.0 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A). <1> ~ <6> The pressure-sensitive adhesive composition according to any one of the above. <8> The silane coupling agent (C) is a compound that does not have a siloxane structure. <1> ~ <7> The pressure-sensitive adhesive composition according to any one of the above. <9> The silane coupling agent (C) is a compound represented by the following formula (X): <1> ~ <8> The pressure-sensitive adhesive composition according to any one of the above.

[0012] [ka]

[0013] In formula (X), R 1 , R 2 and R 3 each independently represents an alkyl group or an alkoxy group, and R 4 represents an alkylene group. 1 , R 2 and R 3 At least one of these represents an alkoxy group.

[0014] <10> The content of the silane coupling agent (C) is 0.1 to 3.0 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A). <1> ~ <9> The pressure-sensitive adhesive composition according to any one of the above. <11> The content of the alicyclic epoxy compound (D) is 0.1 to 6.0 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A). <1> ~ <10> The pressure-sensitive adhesive composition according to any one of the above. <12> <1> ~ <11> 1. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above items. <13> an optical film; and a protective film provided on at least one surface of the optical film, <1> ~ <11> and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above items. <14> The optical film is a polarizing plate. <13> The adhesive sheet according to claim 1. <15> The optical film has a thickness of 1 μm to 200 μm. <13> or <14> The adhesive sheet according to claim 1. <16> A glass substrate; <1> ~ <11> 1. An optical member comprising, in this order, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of 1 to 8, and an optical film. <17> <16> A display device comprising the optical member according to claim 1. [Effects of the Invention]

[0015] According to one embodiment of the present disclosure, there is provided a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that exhibits excellent high-temperature durability, high-humidity durability, and long-term reworkability even when used in a thin optical film. According to another embodiment of the present disclosure, there are provided a pressure-sensitive adhesive sheet, an optical member, and a display device, each comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. DETAILED DESCRIPTION OF THE INVENTION

[0016] The pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, optical member, and display device of the present disclosure are described in detail below. The following description of the requirements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0017] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0018] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0019] In the present disclosure, when the PSA composition contains a plurality of substances corresponding to each component, the amount of each component in the PSA composition means the total amount of the plurality of substances present in the PSA composition, unless otherwise specified.

[0020] In the present disclosure, unless otherwise specified, "solid content" means components other than the solvent contained in the composition, and "solvent" means water and organic solvents. For example, when the solvent contained in the composition is only an organic solvent, the solid content refers to the components contained in the composition other than the organic solvent, and when the solvent contained in the composition is water and an organic solvent, the solid content refers to the components contained in the composition other than water and the organic solvent.

[0021] In the present disclosure, the term "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. In the present disclosure, "(meth)acrylic polymer" means a polymer that contains structural units derived from (meth)acrylic monomers and in which the proportion of structural units derived from (meth)acrylic monomers is 50 mass % or more.

[0022] In the present disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic," "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate," and "(meth)acryloyl" is a term that encompasses both "acryloyl" and "methacryloyl."

[0023] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0024] In the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0025] In the present disclosure, the terms "monomer" and "monomer" are synonymous, and the terms "polymer" and "polymeric polymer" and "copolymer" are synonymous.

[0026] In the present disclosure, the term "structural unit derived from a monomer" refers to a structural unit formed by addition polymerization of a monomer.

[0027] [Adhesive composition] The pressure-sensitive adhesive composition of the present disclosure comprises a (meth)acrylic polymer (A) having a carboxy group, a crosslinking agent (B), a silane coupling agent (C) having an isocyanate group, and an alicyclic epoxy compound (D) represented by formula (I).

[0028] [ka]

[0029] In formula (I), R represents a divalent organic linking group having an ester bond.

[0030] According to the pressure-sensitive adhesive composition of the present disclosure, a pressure-sensitive adhesive layer can be formed that exhibits excellent high-temperature durability, high-humidity durability, and long-term reworkability even when used in a thin optical film. The reason why the PSA composition of the present disclosure can exhibit such effects is unclear, but the present inventors speculate as follows: However, the following speculation is not intended to limit the PSA composition of the present disclosure, but is provided as an example.

[0031] The (meth)acrylic polymer (A) having carboxy groups forms a dense three-dimensional network structure through a reaction between the carboxy groups and the crosslinking agent (B). The pressure-sensitive adhesive layer formed by the dense three-dimensional network structure has high cohesive strength and exhibits high adhesive strength to the adherend. It is also believed that the carboxy groups of the (meth)acrylic polymer (A) also react with the epoxy groups of the alicyclic epoxy compound (D), improving the cohesive strength of the pressure-sensitive adhesive layer. Therefore, it is presumed that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure will have excellent high-temperature durability. On the other hand, increasing the cohesive strength of the pressure-sensitive adhesive layer hardens it, which, in turn, reduces the wettability of the pressure-sensitive adhesive layer to the adherend. As a result, moisture easily penetrates the interface between the pressure-sensitive adhesive layer and the adherend, reducing the high-humidity durability of the pressure-sensitive adhesive layer. In contrast, the pressure-sensitive adhesive composition of the present disclosure contains a silane coupling agent (C) having an isocyanate group. The isocyanate group of the silane coupling agent (C) reacts with the carboxy group of the (meth)acrylic polymer (A), and the alkoxy group of the silane coupling agent (C) hydrolyzes to form a silanol group, which reacts with a hydroxyl group on the surface of the adherend (e.g., glass). These reactions strengthen the interaction at the interface between the pressure-sensitive adhesive layer and the adherend, improving adhesion between the pressure-sensitive adhesive layer and the adherend, which is thought to suppress moisture penetration at the interface between the pressure-sensitive adhesive layer and the adherend. Although the silane coupling agent (C) tends to volatilize, its use in combination with an alicyclic epoxy compound (D) suppresses volatilization. Therefore, the effects of the silane coupling agent (C) are unlikely to be impaired by volatilization of the silane coupling agent (C). Therefore, it is presumed that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure will have excellent high-humidity durability in addition to high-temperature durability. Furthermore, when the cohesive strength of the pressure-sensitive adhesive layer increases, the adhesive strength of the pressure-sensitive adhesive layer increases, resulting in a decrease in long-term reworkability. In contrast, in the pressure-sensitive adhesive composition of the present disclosure, the reaction between the carboxy group of the (meth)acrylic polymer (A) and the epoxy group of the alicyclic epoxy compound (D) is moderately controlled by the steric hindrance of the alicyclic structure of the alicyclic epoxy compound (D), so the cohesive strength of the pressure-sensitive adhesive layer does not increase excessively. Therefore, it is presumed that the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure will have excellent long-term reworkability in addition to high-temperature durability. The pressure-sensitive adhesive composition of the present disclosure utilizes a reaction between a (meth)acrylic polymer (A), a crosslinking agent (B), a silane coupling agent (C), and an alicyclic epoxy compound (D) to control the cohesive strength of the pressure-sensitive adhesive layer and impart adhesion to the adherend to the pressure-sensitive adhesive layer, thereby realizing the formation of a pressure-sensitive adhesive layer that exhibits excellent high-temperature durability, high-humidity durability, and long-term reworkability even when used in a thin optical film.

[0032] In contrast to the pressure-sensitive adhesive composition of the present disclosure, the pressure-sensitive adhesive composition described in Patent Document 1 contains a (meth)acrylic polymer having a carboxy group, a polyisocyanate compound, an alicyclic epoxy compound having a specific structure, and a silane coupling agent, but does not address the relationship between the type of functional group in the silane coupling agent and the high-temperature durability, high-humidity durability, and long-term reworkability of the pressure-sensitive adhesive layer formed, nor does it address the volatility of the silane coupling agent. The pressure-sensitive adhesive composition described in Patent Document 1 does not incorporate the idea of ​​suppressing the volatility of the silane coupling agent by combining a silane coupling agent having an isocyanate group with an alicyclic epoxy compound. Furthermore, the pressure-sensitive adhesive composition described in Patent Document 2 contains a silane coupling agent having an isocyanate group, but does not include an alicyclic epoxy compound having a specific structure. The pressure-sensitive adhesive composition described in Patent Document 2 does not incorporate the idea of ​​suppressing the volatility of the silane coupling agent, nor does it incorporate the idea of ​​suppressing the volatility of the silane coupling agent by combining a silane coupling agent having an isocyanate group with an alicyclic epoxy compound. Furthermore, neither the pressure-sensitive adhesive composition described in Patent Document 1 nor the pressure-sensitive adhesive composition described in Patent Document 2 is intended for application to thin optical films.

[0033] In the present disclosure, the "(meth)acrylic polymer (A) having a carboxy group" is also referred to as the "specific (meth)acrylic polymer (A)," the "silane coupling agent (C) having an isocyanate group" is also referred to as the "specific silane coupling agent (C)," and the "alicyclic epoxy compound (D) represented by formula (I)" is also referred to as the "specific alicyclic epoxy compound (D)."

[0034] [Specific (meth)acrylic polymer (A)] The pressure-sensitive adhesive composition of the present disclosure contains a (meth)acrylic polymer (A) having a carboxy group (ie, a specific (meth)acrylic polymer (A)). The carboxy group of the specific (meth)acrylic polymer (A) can react with both the crosslinking agent (B) and the specific alicyclic epoxy compound (D). The pressure-sensitive adhesive composition of the present disclosure may contain only one type of specific (meth)acrylic polymer (A), or may contain two or more types.

[0035] The specific (meth)acrylic polymer (A) may be a homopolymer or a copolymer. The specific (meth)acrylic polymer (A) may be, for example, a homopolymer or copolymer of a (meth)acrylic monomer having no carboxy group, into which a carboxy group has been introduced by substitution; or a copolymer of a (meth)acrylic monomer having no carboxy group and a monomer having no carboxy group but other than the (meth)acrylic monomer, into which a carboxy group has been introduced by substitution. The specific (meth)acrylic polymer (A) may also be, for example, a copolymer of a (meth)acrylic monomer having a carboxy group and a (meth)acrylic monomer having no carboxy group, a copolymer of a (meth)acrylic monomer having a carboxy group and a monomer having no carboxy group but other than the (meth)acrylic monomer, or a copolymer of a (meth)acrylic monomer having no carboxy group and a monomer having a carboxy group but other than the (meth)acrylic monomer.

[0036] The specific (meth)acrylic polymer (A) preferably contains a carboxy group by including a structural unit derived from a monomer having a carboxy group, which will be described later.

[0037] The specific (meth)acrylic polymer (A) may have, in addition to the carboxy group, a functional group other than the carboxy group that can react with the crosslinking agent (B) (so-called other reactive functional group). The other reactive functional groups are not particularly limited and include, for example, a hydroxyl group and an amino group. The other reactive functional groups preferably include a hydroxyl group.

[0038] When the specific (meth)acrylic polymer (A) has other reactive functional groups, it is preferable that the specific (meth)acrylic polymer (A) has other reactive functional groups by including a structural unit derived from a monomer having the other reactive functional group.

[0039] <Structural Unit (a1) Derived from a Monomer Having a Carboxy Group> The specific (meth)acrylic polymer (A) preferably contains a structural unit (a1) derived from a monomer having a carboxy group. The type of the monomer having a carboxy group is not particularly limited. Examples of the monomer having a carboxy group include a monomer having at least one carboxy group and an ethylenically unsaturated group in one molecule. Examples of the ethylenically unsaturated group include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. Specific examples of the monomer having a carboxy group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid derivatives (e.g., 2-acryloyloxyethyl-succinic acid). The monomer having a carboxy group preferably contains at least one selected from acrylic acid and ω-carboxy-polycaprolactone monoacrylate, more preferably contains acrylic acid, and even more preferably is acrylic acid.

[0040] When the specific (meth)acrylic polymer (A) contains the structural unit (a1), it may contain only one type of structural unit (a1), or may contain two or more types of structural unit (a1).

[0041] When the specific (meth)acrylic polymer (A) contains the structural unit (a1), the content of the structural unit (a1) in the specific (meth)acrylic polymer (A) is not particularly limited, but is, for example, preferably 0.5% by mass to 1.5% by mass, more preferably 0.5% by mass to 1.2% by mass, and even more preferably 0.8% by mass to 1.2% by mass, relative to all structural units of the specific (meth)acrylic polymer (A). When the content of the structural unit (a1) in the specific (meth)acrylic polymer (A) is 0.5 mass% or more relative to all structural units of the specific (meth)acrylic polymer (A), the high-temperature durability and high-humidity durability of the pressure-sensitive adhesive layer formed tend to be further improved. When the content of the structural unit (a1) in the specific (meth)acrylic polymer (A) is 1.5 mass% or less relative to all structural units of the specific (meth)acrylic polymer (A), the long-term reworkability of the pressure-sensitive adhesive layer formed tends to be further improved.

[0042] <Structural Unit (a2) Derived from a Monomer Having a Hydroxyl Group> The specific (meth)acrylic polymer (A) preferably contains a structural unit (a2) derived from a monomer having a hydroxyl group. The type of the hydroxyl group-containing monomer is not particularly limited. Examples of the monomer having a hydroxyl group include a monomer having at least one hydroxyl group and an ethylenically unsaturated group in one molecule. Examples of the ethylenically unsaturated group include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. Specific examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, butyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate. The monomer having a hydroxyl group preferably includes a hydroxyalkyl (meth)acrylate, more preferably includes at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, even more preferably includes at least one selected from 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate, and particularly preferably includes 2-hydroxyethyl acrylate.

[0043] When the specific (meth)acrylic polymer (A) contains the structural unit (a2), it may contain only one type of structural unit (a2), or may contain two or more types of structural unit (a2).

[0044] When the specific (meth)acrylic polymer (A) contains the structural unit (a2), the content of the structural unit (a2) in the specific (meth)acrylic polymer (A) is not particularly limited, but from the viewpoint of improving high-humidity durability, for example, it is preferably 0.1 to 1.0 mass%, more preferably 0.1 to 0.8 mass%, and even more preferably 0.2 to 0.8 mass%, of all structural units of the specific (meth)acrylic polymer (A).

[0045] <Structural Unit (a3) ​​Derived from a (Meth)acrylic Acid Alkyl Ester Monomer> The specific (meth)acrylic polymer (A) preferably contains a structural unit (a3) ​​derived from a (meth)acrylic acid alkyl ester monomer. The type of (meth)acrylic acid alkyl ester monomer is not particularly limited. The (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be unsubstituted or may have a substituent (excluding a carboxy group and a hydroxyl group), but is preferably unsubstituted. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. The alkyl moiety of the (meth)acrylic acid alkyl ester monomer preferably has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, further preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

[0046] Specific examples of the (meth)acrylic acid alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. The (meth)acrylic acid alkyl ester monomer preferably contains n-butyl acrylate, and more preferably is n-butyl acrylate.

[0047] When the specific (meth)acrylic polymer (A) contains the structural unit (a3), it may contain only one type of structural unit (a3), or may contain two or more types of structural unit (a3).

[0048] When the specific (meth)acrylic polymer (A) contains the structural unit (a3), the content of the structural unit (a3) ​​in the specific (meth)acrylic polymer (A) is not particularly limited, but, for example, it is preferably 50.0 mass% or more, more preferably 50.0 mass% to 99.5 mass%, even more preferably 60.0 mass% to 99.4 mass%, and particularly preferably 70.0 mass% to 99.0 mass%, relative to all structural units of the specific (meth)acrylic polymer (A). Here, the content of the structural unit (a3) ​​in the specific (meth)acrylic polymer (A) being 50.0 mass% or more relative to all structural units of the specific (meth)acrylic polymer (A) means that the structural unit (a3) ​​is contained as a main component of the structural units of the specific (meth)acrylic polymer (A).

[0049] <Constituent units derived from other monomers> The specific (meth)acrylic polymer (A) may contain a structural unit derived from a monomer (so-called other monomer) that does not fall into any of the categories of a monomer having a carboxy group, a monomer having a hydroxyl group, and a (meth)acrylic acid alkyl ester monomer.

[0050] Examples of structural units derived from other monomers include structural units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; structural units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; structural units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; and structural units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate.

[0051] From the viewpoint of suppressing white spots, the specific (meth)acrylic polymer (A) preferably contains, as a constituent unit derived from another monomer, a constituent unit derived from a (meth)acrylate having an aromatic ring, more preferably at least one selected from the group consisting of benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, even more preferably a constituent unit derived from phenoxyethyl (meth)acrylate, and particularly preferably a constituent unit derived from phenoxyethyl acrylate. Here, "white spots" refers to, for example, a phenomenon in which light leakage occurs in a liquid crystal display device, resulting in a white appearance.

[0052] When the specific (meth)acrylic polymer (A) contains other structural units, it may contain only one type of other structural unit, or may contain two or more types of other structural units.

[0053] When the specific (meth)acrylic polymer (A) contains other structural units, the content of the other structural units in the specific (meth)acrylic polymer (A) can be set appropriately within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0054] <<Weight-average molecular weight of specific (meth)acrylic polymer (A)>> The weight average molecular weight (also referred to as "Mw") of the specific (meth)acrylic polymer (A) is not particularly limited, but is preferably, for example, 500,000 to 2.5 million, more preferably 1,000,000 to 2.5 million, and even more preferably 1.5 million to 2.5 million. When the weight average molecular weight of the specific (meth)acrylic polymer (A) is 500,000 or more, high temperature durability tends to be further improved. The specific (meth)acrylic polymer (A) tends to be easier to produce when the weight average molecular weight is 2,500,000 or less.

[0055] The weight average molecular weight of the specific (meth)acrylic polymer (A) is a value measured by the following method, specifically, according to the following (1) to (3). (1) A solution of the specific (meth)acrylic polymer (A) is applied to a release paper and dried at 100° C. for 1 minute to obtain a film of the specific (meth)acrylic polymer (A). (2) Using the film-like specific (meth)acrylic polymer (A) obtained in (1) above and tetrahydrofuran, a sample solution having a solids concentration of 0.2% by mass is obtained. Here, the "solids concentration" refers to the mass proportion of the specific (meth)acrylic polymer (A) in the sample solution. (3) The weight average molecular weight of the specific (meth)acrylic polymer (A) is determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) under the following conditions.

[0056] ~Conditions~ Measurement equipment: High-speed GPC [Model: HLC-8420 GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) [built into HLC-8420, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Two Tosoh Corporation products are used. Column temperature: 40℃ Eluent: tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0057] The weight average molecular weight of the specific (meth)acrylic polymer (A) can be adjusted to a desired value by, for example, adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomers.

[0058] <<Content of specific (meth)acrylic polymer (A)>> The content of the specific (meth)acrylic polymer (A) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 80.0 mass % to 99.9 mass %, more preferably 85.0 mass % to 99.5 mass %, and even more preferably 89.0 mass % to 99.3 mass %, relative to the total solid content in the pressure-sensitive adhesive composition.

[0059] In the present disclosure, the "total solid content in the PSA composition" means the total mass of the PSA composition when the PSA composition does not contain a solvent, and means the mass of the residue remaining after removing the solvent from the PSA composition when the PSA composition contains a solvent.

[0060] [Method for producing specific (meth)acrylic polymer (A)] The method for producing the specific (meth)acrylic polymer (A) is not particularly limited. The specific (meth)acrylic polymer (A) can be produced by polymerizing the above-mentioned monomers using a known polymerization method, typically a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, or a bulk polymerization method. As the polymerization method, a solution polymerization method is preferred in that the processing steps for preparing the pressure-sensitive adhesive composition after production are relatively simple and can be carried out in a short time.

[0061] In the solution polymerization method, a predetermined organic solvent, monomers, a polymerization initiator, and an optional chain transfer agent are generally charged into a polymerization vessel and reacted by heating for several hours with stirring, for example, at the reflux temperature of the organic solvent. In this case, at least a portion of the organic solvent, monomers, polymerization initiator, and optional chain transfer agent may be added sequentially. Alternatively, the reaction may be carried out in a nitrogen gas stream.

[0062] Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine; ester compounds such as methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone; Examples of the alcohol compounds include ketone compounds typified by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds typified by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds typified by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0063] In producing the specific (meth)acrylic polymer (A), it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction, such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound. In particular, it is preferable to use ethyl acetate from the viewpoints of the solubility of the specific (meth)acrylic polymer (A), ease of the polymerization reaction, etc.

[0064] During the polymerization reaction, only one type of organic solvent may be used, or two or more types may be used.

[0065] Examples of the polymerization initiator include organic peroxides and azo compounds that are used in ordinary solution polymerization methods. Specific examples of organic peroxides include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxysilane), peroxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyrate) dimethyl.

[0066] In the polymerization reaction, only one type of polymerization initiator may be used, or two or more types may be used.

[0067] The amount of the polymerization initiator used is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic polymer (A).

[0068] In producing the specific (meth)acrylic polymer (A), a chain transfer agent may be used, if necessary. Examples of the chain transfer agent include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, α-methylstyrene, aromatic compounds such as anthracene, phenanthrene, fluorene, and 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, aromatic nitro compounds such as p-nitrophenol and p-nitrotoluene, benzoquinone derivatives such as benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives such as tributylborane, carbon tetrabromide, ... Examples of suitable mercaptan compounds include halogenated hydrocarbon compounds such as carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene, aldehyde compounds such as chloral and furaldehyde, alkyl mercaptan compounds having 1 to 18 carbon atoms, aromatic mercaptan compounds such as thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and terpene compounds such as pinene and terpinolene.

[0069] When a chain transfer agent is used in producing the specific (meth)acrylic polymer (A), the amount of the chain transfer agent used is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic polymer (A).

[0070] The polymerization temperature is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic polymer (A).

[0071] [Crosslinking agent (B)] The pressure-sensitive adhesive composition of the present disclosure contains a crosslinking agent (B). The type of crosslinking agent (B) is not particularly limited. Examples of the crosslinking agent (B) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, and aziridine-based crosslinking agents. The crosslinking agent (B) preferably contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, more preferably contains an isocyanate-based crosslinking agent, and even more preferably is an isocyanate-based crosslinking agent. The crosslinking agent (B) preferably does not have an alkoxysilyl group.

[0072] In this disclosure, "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate-based compound). Also, "epoxy-based crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (so-called bifunctional or higher epoxy-based compound). Also, "metal chelate-based crosslinking agent" refers to a metal chelate-based compound that functions as a crosslinking agent. Also, "aziridine-based crosslinking agent" refers to a compound having two or more aziridine groups in one molecule (so-called polyaziridine-based compound).

[0073] Examples of the isocyanate crosslinking agent include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds. "Aliphatic polyisocyanate compounds" include, for example, aliphatic polyisocyanate compounds, polymers of aliphatic polyisocyanate compounds, adducts of aliphatic polyisocyanate compounds and polyol compounds (e.g., trimethylolpropane (TMP); the same applies hereinafter), and biuret compounds of aliphatic polyisocyanate compounds. Specific examples of aliphatic polyisocyanate compounds include hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. The "alicyclic polyisocyanate compound" includes, for example, an alicyclic polyisocyanate compound, a polymer of an alicyclic polyisocyanate compound, an adduct of an alicyclic polyisocyanate compound and a polyol compound, and a biuret of an alicyclic polyisocyanate compound. Specific examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate. The "aromatic polyisocyanate compound" includes, for example, an aromatic polyisocyanate compound, a polymer of an aromatic polyisocyanate compound, an adduct of an aromatic polyisocyanate compound and a polyol compound, and a biuret of an aromatic polyisocyanate compound. Specific examples of the aromatic polyisocyanate compound include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4'-diphenylmethane diisocyanate.

[0074] The isocyanate-based crosslinking agent is preferably an aromatic polyisocyanate-based compound, more preferably a tolylene diisocyanate-based compound. The "tolylene diisocyanate compound" includes, for example, TDI, TDI polymers, adducts of TDI and polyol compounds, and biuret compounds of TDI. As the tolylene diisocyanate compound, an adduct of TDI and TMP is preferred.

[0075] As the isocyanate-based crosslinking agent, commercially available products can be used. Commercially available examples of isocyanate crosslinking agents include "Coronate HX," "Coronate HL-S," "Coronate L," "Coronate L-45E," "Coronate 2031," "Coronate 2037," "Coronate 2234," "Coronate 2785," "Aquanate 200," and "Aquanate 210" (all manufactured by Tosoh Corporation), "Sumidur N3300," "Desmodur N3400," and "Sumidur N75" (all manufactured by Sumika Covestro Urethane Co., Ltd.), "Duranate D201," "Duranate E405-70B," "Duranate E405-80T," "Duranate AE700-100," "Duranate 24A-100," and "Duranate TSE-100" (all manufactured by Asahi Kasei Corporation), and "Takenate Examples of such compounds include "Takenate D-110N," "Takenate D-101E," "Takenate D-120N," "Takenate D-140N," "Takenate M-631N," "MT-Olestar NP1200," and "Stabio XD-340N" (all manufactured by Mitsui Chemicals, Inc.). The above-mentioned "Coronate," "Aquanate," "Sumidur," "Desmodur," "Duranate," "Takenate," "Olestar," and "Stabio" are all registered trademarks.

[0076] Examples of bifunctional or higher functional epoxy compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, Examples include polyglycerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris(glycidyl)isocyanurate, tris(glycidoxyethyl)isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine).

[0077] As the epoxy-based crosslinking agent, commercially available products can be used. Examples of commercially available epoxy crosslinking agents include "TETRAD-X" and "TETRAD-C" (both manufactured by Mitsubishi Gas Chemical Company, Inc.), and "Denacol EX-201" and "Denacol EX-931" (both manufactured by Nagase ChemteX Corporation). "TETRAD" and "Denacol" are both registered trademarks.

[0078] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of crosslinking agent (B), or may contain two or more types.

[0079] The content of the crosslinking agent (B) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 0.1 to 5.0 parts by mass, more preferably 0.1 to 4.0 parts by mass, and even more preferably 0.1 to 3.0 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic polymer (A).

[0080] [Specific silane coupling agent (C)] The pressure-sensitive adhesive composition of the present disclosure contains a silane coupling agent (C) having an isocyanate group (i.e., specific silane coupling agent (C)). In the pressure-sensitive adhesive composition of the present disclosure, the specific silane coupling agent (C) contributes to improving the high-humidity durability of the pressure-sensitive adhesive layer that is formed.

[0081] The specific silane coupling agent (C) is not particularly limited in type as long as it is a silane coupling agent having an isocyanate group. The number of isocyanate groups contained in the specific silane coupling agent (C) is preferably one. The specific silane coupling agent (C) is preferably a compound that does not have a siloxane structure, for example, from the viewpoint of durability (particularly, high-temperature durability). The specific silane coupling agent (C) is preferably, for example, a compound represented by the following formula (X).

[0082] [ka]

[0083] In formula (X), R 1 , R 2 and R 3 R each independently represents an alkyl group or an alkoxy group. 1 , R 2 and R 3 may be the same or different, provided that R 1 , R 2 and R 3At least one of these represents an alkoxy group.

[0084] R 1 , R 2 and R 3 The alkyl group represented by the formula (I) may or may not have a substituent. R 1 , R 2 and R 3 The alkyl group represented by the formula (I) may be a straight-chain alkyl group, a branched alkyl group, or an alkyl group having a cyclic structure. R 1 , R 2 and R 3 The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably an alkyl group having 1 to 2 carbon atoms.

[0085] R 1 , R 2 and R 3 The alkoxy group represented by the formula (I) may be a straight-chain alkoxy group, a branched alkoxy group, or an alkoxy group having a cyclic structure. R 1 , R 2 and R 3 The alkoxy group represented by the following formula is preferably an alkoxy group having 1 to 4 carbon atoms, and more preferably an alkoxy group having 1 to 2 carbon atoms.

[0086] In formula (X), R 4 represents an alkylene group. R 4 The alkylene group represented by the formula (I) may be a straight-chain alkylene group, a branched alkylene group, or an alkylene group having a cyclic structure. R 4 The alkylene group represented by the following formula is preferably an alkylene group having 1 to 6 carbon atoms, and more preferably an alkylene group having 3 or 4 carbon atoms.

[0087] As an embodiment of the compound represented by formula (X), R 1 , R2 and R 3 are each independently an alkoxy group having 1 to 2 carbon atoms, and R 4 is preferably an alkylene group, and R 1 , R 2 and R 3 is an ethoxy group, and R 4 is more preferably a 1,3-propylene group.

[0088] As the specific silane coupling agent (C), commercially available products can be used. An example of a commercially available product of the specific silane coupling agent (C) is "KBE-9007N" manufactured by Shin-Etsu Chemical Co., Ltd.

[0089] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of specific silane coupling agent (C), or may contain two or more types.

[0090] The content of the specific silane coupling agent (C) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 0.1 to 3.0 parts by mass, more preferably 0.1 to 2.0 parts by mass, even more preferably 0.1 to 1.0 part by mass, and particularly preferably 0.2 to 0.5 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic polymer (A). When the content of the specific silane coupling agent (C) in the pressure-sensitive adhesive composition of the present disclosure is 0.1 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic polymer (A), the effect of the specific silane coupling agent (C) in improving the high-humidity durability of the pressure-sensitive adhesive layer tends to be well exhibited. When the content of the specific silane coupling agent (C) in the pressure-sensitive adhesive composition of the present disclosure is 3.0 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer (A), a decrease in the cohesive strength of the pressure-sensitive adhesive layer due to unreacted specific silane coupling agent (C) is unlikely to occur, and therefore the excellent high-temperature durability of the pressure-sensitive adhesive layer tends not to be impaired.

[0091] [Specific alicyclic epoxy compound (D)] The pressure-sensitive adhesive composition of the present disclosure contains an alicyclic epoxy compound (D) represented by the following formula (I) [i.e., specific alicyclic epoxy compound (D)]. In the pressure-sensitive adhesive composition of the present disclosure, the specific alicyclic epoxy compound (D) contributes to improving the high-temperature durability of the pressure-sensitive adhesive layer formed. In addition, in the pressure-sensitive adhesive composition of the present disclosure, the specific alicyclic epoxy compound (D) can also have the effect of suppressing the volatilization of the specific silane coupling agent (C).

[0092] [ka]

[0093] In formula (I), R represents a divalent organic linking group having an ester bond. The divalent organic linking group having an ester bond is not particularly limited, and examples thereof include an ester bond, as well as a group in which one or more ester bonds are linked to one or more divalent hydrocarbon groups. Examples of the divalent hydrocarbon group linked to an ester bond include a linear or branched alkylene group having 1 to 18 carbon atoms and a divalent alicyclic hydrocarbon group.

[0094] The divalent organic linking group represented by R has an ester bond. The specific alicyclic epoxy compound (D) has an ester bond, and therefore has good compatibility with the specific (meth)acrylic polymer (A) which also has an ester bond.

[0095] The number of atoms in the divalent organic linking group represented by R in formula (I) is not particularly limited, but is preferably 2 to 17, more preferably 3 to 10, and even more preferably 3 to 8, for example. When the divalent organic linking group represented by R in formula (I) has 2 or more atoms, the cohesive strength of the pressure-sensitive adhesive layer does not become excessively high, and high-temperature durability and long-term reworkability tend to be further improved. When the number of atoms of the divalent organic linking group represented by R in formula (I) is 17 or less, an appropriate cohesive force is exhibited, and high-temperature durability tends to be further improved. In the present disclosure, the "number of atoms in the organic linking group" refers to the number of atoms in the main chain of the organic linking group. The "number of atoms in the main chain" refers to the number of atoms in the atomic chain connecting the two alicyclic epoxy groups in formula (I), and does not include the number of atoms in the substituents. For example, if the main chain of the organic linking group contains a "cyclohexane ring," the number of atoms in the cyclohexane ring portion is counted as "6."

[0096] As the specific alicyclic epoxy compound (D), commercially available products can be used. Examples of commercially available specific alicyclic epoxy compounds (D) include "Celloxide 2021P" and "Celloxide 2081" (both manufactured by Daicel Corporation). The above "Celloxide" is a registered trademark.

[0097] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of specific alicyclic epoxy compound (D), or may contain two or more types.

[0098] The content of the specific alicyclic epoxy compound (D) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 0.1 to 6.0 parts by mass, more preferably 0.1 to 4.0 parts by mass, even more preferably 0.1 to 2.0 parts by mass, and particularly preferably 0.2 to 1.0 part by mass, relative to 100 parts by mass of the specific (meth)acrylic polymer (A). When the content of the specific alicyclic epoxy compound (D) in the pressure-sensitive adhesive composition of the present disclosure is 0.1 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic polymer (A), the effect of the specific alicyclic epoxy compound (D) in improving the high-temperature durability of the pressure-sensitive adhesive layer tends to be well exhibited. When the content of the specific alicyclic epoxy compound (D) in the pressure-sensitive adhesive composition of the present disclosure is 6.0 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer (A), the epoxy groups of the specific alicyclic epoxy compound (D) do not react excessively with the carboxy groups of the specific (meth)acrylic polymer (A), and a decrease in the wettability of the pressure-sensitive adhesive layer to the adherend, which would otherwise be caused by an excessively high cohesive strength of the pressure-sensitive adhesive layer, is suppressed, and the excellent high-temperature durability and high-humidity durability of the pressure-sensitive adhesive layer tend not to be impaired.

[0099] [Organic solvent] The pressure-sensitive adhesive composition of the present disclosure may contain an organic solvent. When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the coating properties can be improved. Examples of the organic solvent include the same organic solvents as those used in the polymerization reaction of the specific (meth)acrylic polymer (A) described above.

[0100] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types of organic solvents.

[0101] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be set appropriately depending on the purpose.

[0102] [Other ingredients] The pressure-sensitive adhesive composition of the present disclosure may contain components other than the components described above (so-called other components) as needed, provided that the effects of the composition are not impaired. Examples of other components include various additives such as polymers other than the specific (meth)acrylic polymer (A), crosslinking catalysts, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., ultraviolet absorbers), and antistatic agents.

[0103] When the pressure-sensitive adhesive composition of the present disclosure contains other components, the content of the other components can be set appropriately within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0104] <<Applications of adhesive compositions>> The use of the pressure-sensitive adhesive composition of the present disclosure is not particularly limited. The pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer that is excellent in high-temperature durability, high-humidity durability, and long-term reworkability, and is therefore suitable, for example, as a pressure-sensitive adhesive composition to be used in optical films (i.e., a pressure-sensitive adhesive composition for optical films), and is particularly suitable as a pressure-sensitive adhesive composition to be used in polarizing plates among optical films (i.e., a pressure-sensitive adhesive composition for polarizing plates). The pressure-sensitive adhesive composition of the present disclosure is also suitable as a pressure-sensitive adhesive composition for use in thin optical films (i.e., a pressure-sensitive adhesive composition for thin optical films) because the pressure-sensitive adhesive layer exhibits excellent high-temperature durability, high-humidity durability, and long-term reworkability even when applied to optical films (particularly polarizing plates), which have been required to be even thinner in recent years. Specific applications of the pressure-sensitive adhesive composition of the present disclosure include applications for bonding a polarizing plate to a glass substrate of a liquid crystal cell, and applications for bonding optical films together.

[0105] [Adhesive sheet] The pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure. The pressure-sensitive adhesive sheet of the present disclosure also includes a sheet-like pressure-sensitive adhesive layer itself formed from the pressure-sensitive adhesive composition of the present disclosure. The pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet of the present disclosure contains a cured product of the pressure-sensitive adhesive composition of the present disclosure. The cured product includes, for example, a crosslinked product of the specific (meth)acrylic polymer (A) obtained by crosslinking and curing with a crosslinking agent. The pressure-sensitive adhesive sheet of the present disclosure has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure as described above, and therefore exhibits excellent high-temperature durability, high-humidity durability, and long-term reworkability even when used in a thin optical film.

[0106] The thickness of the pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited. The thickness of the pressure-sensitive adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0107] In the present disclosure, the "thickness of the pressure-sensitive adhesive layer" refers to the average thickness of the pressure-sensitive adhesive layer. The average thickness of the pressure-sensitive adhesive layer is a value determined by the following method. The thickness of the adhesive layer is measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​is calculated and this value is taken as the average thickness of the adhesive layer.

[0108] The pressure-sensitive adhesive sheet of the present disclosure may be a substrate-less pressure-sensitive adhesive sheet that does not have a substrate, or may be a substrate-containing pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer on one or both sides of a substrate. When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-free type pressure-sensitive adhesive sheet that does not have a substrate, or when it is a substrate-containing type pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer on one side of a substrate, the exposed surface of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present disclosure may be protected by a release sheet. Generally, the release sheet protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put to practical use, and is peeled off at the time of use.

[0109] The release sheet is not particularly limited as long as it can be easily peeled off from the pressure-sensitive adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, and composite sheets made by laminating two or more of these, each of which has been surface-treated with a release agent on one or both sides (so-called easy-release treatment). In the present disclosure, a release sheet in an embodiment in which one or both sides of a resin film have been surface-treated with a release treatment agent (so-called easy-release treatment) is also referred to as a "release film." Examples of release agents include silicone-based release agents (such as silicone), wax-based release agents (such as paraffin wax), and fluorine-based release agents (such as fluorine-based resins). Examples of resin films include polyester films such as polyethylene terephthalate (PET) films. Examples of paper include fine paper and coated paper. The thickness of the release sheet is not particularly limited, and is generally 20 μm to 180 μm.

[0110] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate, the substrate is not particularly limited as long as a pressure-sensitive adhesive layer can be formed thereon. Examples of the substrate include films containing resins such as polyolefin resins (e.g., polyethylene (PE) and polypropylene (PP)), polyester resins (e.g., polyethylene terephthalate (PET)), acetate resins (e.g., triacetyl cellulose), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, (meth)acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine-based resins.

[0111] The surface of the substrate on which the adhesive layer is provided may be subjected to a surface treatment such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatment) in order to improve the adhesion between the substrate and the adhesive layer.

[0112] The substrate may contain various additives such as plasticizers, colorants (eg, dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, fillers, and the like. The substrate may be partially or entirely patterned.

[0113] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate, the substrate is preferably an optical film. In this case, a preferred embodiment of the pressure-sensitive adhesive sheet of the present disclosure includes an optical film and a pressure-sensitive adhesive layer provided on at least one surface of the optical film and formed from the pressure-sensitive adhesive composition of the present disclosure.

[0114] The type of optical film is not particularly limited. Specific examples of optical films include polarizing plates, AG (Anti-Glare) polarizing plates, wave plates (e.g., half-wave plates and quarter-wave plates), retardation films including the wave plates, viewing angle compensation films, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflection films, prism sheets, lens sheets, diffusion plates, and transparent conductive films.

[0115] The optical film is preferably a polarizing plate (so-called polarizing film). The polarizing plate is configured to include at least a polarizer, and may be a polarizer alone or a laminate of a polarizer and a protective film. That is, the polarizing plate may have a single-layer structure with a polarizer alone, a two-layer structure with a protective film provided on one side of the polarizer, or a three-layer structure with protective films provided on both sides of the polarizer.

[0116] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate and the substrate is a polarizing plate, examples of the layer configuration include pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer], pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [retardation film / polarizer], pressure-sensitive adhesive layer / polarizing plate [retardation film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [retardation film / protective film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [polarizer / brightness-enhancing film], pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer / brightness-enhancing film], pressure-sensitive adhesive layer / polarizing plate [polarizer / protective film / brightness-enhancing film], and pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer / protective film / brightness-enhancing film].

[0117] The protective film may be a film containing a resin such as triacetyl cellulose (TAC), polycycloolefin (COP), polyethylene terephthalate (PET), or polymethyl methacrylate (PMMA). The polarizer may be, for example, a stretched film of polyvinyl alcohol (PVA) impregnated with iodine. The retardation film may be a film containing a resin such as polycycloolefin (COP).

[0118] The thickness of the substrate (preferably, the optical film) is not particularly limited, but is, for example, preferably from 1 μm to 200 μm, more preferably from 10 μm to 100 μm, and even more preferably from 10 μm to 30 μm.

[0119] In this disclosure, "thickness of the substrate" means the average thickness of the substrate. The average thickness of the substrate is a value determined by the following method. The thickness of the substrate is measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​is calculated and this value is taken as the average thickness of the substrate.

[0120] [How to make adhesive sheets] The method for producing the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited. The pressure-sensitive adhesive sheet of the present disclosure can be produced by a known method. The pressure-sensitive adhesive sheet of the present disclosure can be produced, for example, by the following method.

[0121] When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-free type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present disclosure is applied to the easily peelable surface of the release sheet to form a coating film on the release sheet. The formed coating film is then dried to form an adhesive film on the release sheet. Next, the exposed surface of the formed adhesive film is laminated onto the easily peelable surface of a separately prepared release sheet, and then cured as necessary, thereby producing a pressure-sensitive adhesive sheet of the present disclosure having a laminated structure of release sheet / pressure-sensitive adhesive layer / release sheet.

[0122] When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present disclosure is applied to one surface of the substrate (preferably the surface treated for easy adhesion) to form a coating film on the substrate. The formed coating film is then dried to form a pressure-sensitive adhesive film on the substrate. Next, the exposed surface of the formed pressure-sensitive adhesive film is laminated onto the surface of a release sheet treated for easy release, and then cured as necessary to produce a pressure-sensitive adhesive sheet of the present disclosure having a laminate structure of substrate / pressure-sensitive adhesive layer / release sheet.

[0123] When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-containing pressure-sensitive adhesive sheet, another method may be mentioned, for example, as follows. The pressure-sensitive adhesive composition of the present disclosure is applied to the easy-release treated surface of a release sheet to form a coating film on the release sheet. The formed coating film is then dried to form a pressure-sensitive adhesive film on the release sheet. Next, the exposed surface of the formed pressure-sensitive adhesive film is laminated to one surface of the substrate (preferably the easy-adhesion treated surface), and then cured as necessary, thereby producing a pressure-sensitive adhesive sheet of the present disclosure having a laminated structure of substrate / pressure-sensitive adhesive layer / release sheet.

[0124] The method for applying the pressure-sensitive adhesive composition is not particularly limited. Examples of methods for applying the pressure-sensitive adhesive composition include known methods using a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, knife coater, spray coater, bar coater, applicator, etc. The amount of the pressure-sensitive adhesive composition to be applied is not particularly limited, and is set appropriately depending on, for example, the thickness of the pressure-sensitive adhesive layer to be formed.

[0125] The method for drying the coating film is not particularly limited. Examples of methods for drying the coating film include natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited, and are set appropriately depending on the thickness of the coating film, the amount of solvent contained in the coating film, and the like. Drying conditions include, for example, using a hot air circulation dryer to blow air at 60°C to 130°C at a speed of 3 m / sec to 5 m / sec for 30 seconds to 300 seconds.

[0126] The curing method may involve leaving the product to stand for 2 to 7 days in an environment with an ambient temperature of 20°C to 35°C and a relative humidity of 45% to 65%, for example.

[0127] [Optical components] The optical member of the present disclosure includes, in this order, a glass substrate, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and an optical film. The optical member of the present disclosure includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and therefore peeling is unlikely to occur at the interface between the pressure-sensitive adhesive layer and the optical film and / or liquid crystal cell even when placed in a high-temperature environment and / or a high-humidity environment. Furthermore, the optical member of the present disclosure includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and therefore the optical film can be cleanly peeled from the glass member without being damaged, even when stored for a long period of time. The optical member of the present disclosure can achieve the above-described effects even when it includes a thin optical film as the optical film.

[0128] The thickness of the glass substrate is not particularly limited, but is generally 0.3 mm to 0.7 mm, and preferably 0.3 mm to 0.5 mm.

[0129] Examples of the glass substrate include a soda glass plate, an alkali-free glass plate, and an ITO (Indium Tin Oxide) film-coated glass plate.

[0130] The pressure-sensitive adhesive layer and optical film in the optical member of the present disclosure have the same meaning as the pressure-sensitive adhesive layer and optical film in the pressure-sensitive adhesive sheet of the present disclosure, and preferred embodiments are also the same, so description thereof will be omitted here.

[0131] The optical member of the present disclosure can be suitably used, for example, as a member of a display device. Examples of display devices include liquid crystal displays and organic EL (Electro-Luminescence) displays.

[0132] The method for producing the optical member of the present disclosure is not particularly limited. The optical member of the present disclosure can be produced, for example, by using an optical film as a substrate, preparing a pressure-sensitive adhesive sheet of the present disclosure by the method described above, and then bonding the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet to a glass substrate.

[0133] [Display device] The display device of the present disclosure includes the optical member of the present disclosure. The display device of the present disclosure includes the optical member of the present disclosure described above, and therefore peeling is unlikely to occur at the interface between the pressure-sensitive adhesive layer and the optical film and / or the liquid crystal cell even when placed in a high-temperature environment and / or a high-humidity environment. Furthermore, the display device of the present disclosure includes the optical member of the present disclosure described above, and therefore the optical film and the glass member can be cleanly peeled off without breaking, even when stored for a long period of time. The display device of the present disclosure can achieve the above-described effects even when the optical member of the present disclosure includes a thin optical film as the optical film.

[0134] Specific examples of the display device are as described above. [Example]

[0135] The pressure-sensitive adhesive composition of the present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0136] [Production of (meth)acrylic polymer] [Manufacturing example A-1] A reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser was charged with 250.2 parts by weight of n-butyl acrylate (n-BA), 45.0 parts by weight of phenoxyethyl acrylate (PHEA), 3.0 parts by weight of acrylic acid (AA), 1.8 parts by weight of 2-hydroxyethyl acrylate (2HEA), and 200.0 parts by weight of methyl acetate (organic solvent). The atmosphere in the reactor was then purged with nitrogen. The mixture in the reactor was then heated to 70°C with stirring, and 0.003 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN; polymerization initiator) and 15.0 parts by weight of ethyl acetate (organic solvent) were added sequentially to the mixture in the reactor. After holding for 1 hour, 0.08 parts by weight of ABVN and 340.0 parts by weight of ethyl acetate were added sequentially. The mixture was then held for another 5 hours to allow polymerization to occur, resulting in a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to a solid content concentration of 15.0% by mass, and then cooled to obtain a solution of (meth)acrylic polymer A-1.

[0137] The term "solid content concentration" used herein refers to the mass proportion of the (meth)acrylic polymer A-1 in the solution of the (meth)acrylic polymer A-1. The same applies to the solutions of the (meth)acrylic polymers A-2 to A-8 produced below.

[0138] [Manufacturing examples A-2 to A-8] In Production Examples A-2 to A-8, the same operations as in Production Example A-1 were carried out except that the monomer composition of the (meth)acrylic polymer was changed to the monomer composition shown in Table 1, and solutions of (meth)acrylic polymers A-2 to A-8 each having a solids concentration of 15.0 mass% were obtained.

[0139] Table 1 shows the monomer compositions (unit: mass %) and weight average molecular weights (denoted as "Mw") of the (meth)acrylic polymers A-1 to A-8. The weight average molecular weights of the (meth)acrylic polymers A-1 to A-8 were measured by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0140] Among the (meth)acrylic polymers A-1 to A-8, the (meth)acrylic polymers A-1 to A-7 correspond to the specific (meth)acrylic polymer (A) in the present disclosure.

[0141] [Table 1]

[0142] Details of each monomer listed in Table 1 are as follows: <Monomers having a carboxy group> "AA": acrylic acid "M-5300": ω-carboxy-polycaprolactone (n≒2) monoacrylate <Monomers having a hydroxyl group> "2HEA": 2-hydroxyethyl acrylate "4HBA": 4-hydroxybutyl acrylate <(Meth)acrylic acid alkyl ester monomer> "n-BA": n-butyl acrylate <Other monomers> "PHEA": Phenoxyethyl acrylate

[0143] In Table 1, "-" in the column of monomer composition means that the monomer in that column was not used.

[0144] [Preparation of Pressure-Sensitive Adhesive Composition] Example 1 100 parts by mass (solid content equivalent) of the solution of (meth)acrylic polymer A-1, 0.15 parts by mass (solid content equivalent) of Takenate D-101E (trade name, isocyanate-based crosslinking agent, solid content concentration: 45% by mass, manufactured by Mitsui Chemicals, Inc.) as a crosslinking agent, 0.30 parts by mass (solid content equivalent) of KBE-9007N (trade name, isocyanate group-containing silane coupling agent, solid content concentration: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent, 0.40 parts by mass (solid content equivalent) of Celloxide (registered trademark) 2021P (trade name, solid content concentration: 100% by mass, manufactured by Daicel Corporation) as an alicyclic epoxy compound, and an appropriate amount of ethyl acetate (organic solvent) were thoroughly mixed to obtain a pressure-sensitive adhesive composition of Example 1.

[0145] Examples 2 to 14 The same procedure as in Example 1 was carried out except that the formulation of the adhesive composition in Example 1 was changed to the formulation shown in Table 2, to obtain adhesive compositions of Examples 2 to 14.

[0146] Comparative Examples 1 to 5 The same procedure as in Example 1 was carried out except that the formulation of the adhesive composition in Example 1 was changed to the formulation shown in Table 2, to obtain adhesive compositions of Comparative Examples 1 to 5.

[0147] [Preparation of polarizing plate samples with adhesive layer] The pressure-sensitive adhesive composition prepared above was applied to the easily peelable surface of a release film (type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation) that had been surface-treated with a silicone-based release agent (so-called easily peelable treatment) to form a coating film. The amount of pressure-sensitive adhesive composition applied was such that the thickness of the adhesive film described below would be 15 μm. Next, the formed coating film was dried by blowing 100°C air at a wind speed of 3 m / s for 180 seconds using a hot air circulation dryer, thereby forming a 15 μm-thick adhesive film on the release film. Next, a brightness-enhancing film was bonded to the surface of the PVA layer of a polarizing film (thickness: 15 μm) having a triacetyl cellulose (TAC) layer / polyvinyl alcohol (PVA) layer containing a polarizer (thickness: 15 μm) using the pressure-sensitive adhesive composition for brightness-enhancing films, to prepare a 50 μm-thick polarizing plate with a brightness-enhancing film (referred to as a "polarizing plate sample"). Next, the TAC layer surface of the prepared polarizing plate sample was laminated to the exposed surface of the adhesive film formed on the release film. The laminate obtained by lamination was then left to stand for 4 days (so-called curing period) in an environment of an atmospheric temperature of 35°C and 60% RH to cure the adhesive film, thereby obtaining a polarizing plate sample with an adhesive layer having a configuration of release film / adhesive layer / polarizing film (TAC layer / PVA layer) / adhesive layer for brightness enhancement film / brightness enhancement film.

[0148] [Preparation of evaluation samples] The polarizing plate sample with the adhesive layer prepared above was cut into a size of 25 mm (short side) x 100 mm (long side) so that the long side was at 0° with respect to the absorption axis of the polarizing plate. Next, the release film was peeled off from the cut polarizing plate sample with the adhesive layer to prepare a test piece. The surface of the adhesive layer of the test piece exposed by peeling off the release film was laminated on one side of a glass plate (type: soda glass, manufactured by Matsunami Glass Industry Co., Ltd.) and pressed using a laminator. The laminate obtained by pressing was treated at a temperature of 50°C and a pressure of 5 kg / cm. 2 By autoclaving for 20 minutes under the above conditions, an evaluation sample having a structure of glass plate / adhesive layer / polarizing film (TAC layer / PVA layer) / adhesive layer for brightness enhancement film / brightness enhancement film was obtained.

[0149] [Measurement and Evaluation] 1.High temperature durability The evaluation sample prepared as described above was allowed to stand for 30 minutes in an environment with an ambient temperature of 85°C (a so-called high-temperature environment). After standing for 30 minutes, the evaluation sample was peeled from the glass plate at an angle of 180° along the long side (100 mm) of the test piece (configuration: pressure-sensitive adhesive layer / polarizing film (TAC layer / PVA layer) / pressure-sensitive adhesive layer for brightness-enhancing film / brightness-enhancing film). The adhesive strength (unit: N / 25 mm) was measured at an ambient temperature of 85°C and a peeling rate of 0.3 m / min. The standing and adhesive strength measurements of the evaluation sample in the high-temperature environment were performed using a bench-top precision universal testing machine (model number: AGS-X, manufactured by Shimadzu Corporation) installed in a thermostatic chamber (model number: TCR-2A, manufactured by Shimadzu Corporation). Based on the measured adhesive strength, the high temperature durability was evaluated according to the following evaluation criteria. The measured adhesive strength values ​​and evaluation results are shown in Table 2. In the following evaluation criteria, "A," "B," and "C" are levels that are practically acceptable, with "A" being the most preferable.

[0150] -Evaluation criteria- A: The adhesive strength was 19N / 25mm or more. B: The adhesive strength was in the range of 14 N / 25 mm or more and less than 19 N / 25 mm. C: The adhesive strength was in the range of 10 N / 25 mm or more and less than 14 N / 25 mm. D: The adhesive strength was less than 10 N / 25 mm.

[0151] 2. High humidity durability The evaluation sample prepared above was left for 24 hours in an environment of 60°C and 90% RH (so-called high humidity environment) using a thermo-hygrostat (model: PR-2J) manufactured by Espec Corp. Immediately after leaving for 24 hours, the evaluation sample was peeled at an angle of 180° in the long side (100 mm) direction from the glass plate (composition: adhesive layer / polarizing film (TAC layer / PVA layer) / adhesive layer for brightness-enhancing film / brightness-enhancing film) to measure the adhesive strength (unit: N / 25 mm) using a desktop precision universal testing machine (model: AGS-X) manufactured by Shimadzu Corp. at an ambient temperature of 23°C and 50% RH at a peel speed of 0.3 m / min. Based on the measured adhesive strength, the high humidity durability was evaluated according to the following evaluation criteria. The measured adhesive strength values ​​and evaluation results are shown in Table 2. In the following evaluation criteria, "A," "B," and "C" are levels that are practically acceptable, with "A" being the most preferable.

[0152] -Evaluation criteria- A: The adhesive strength was 10N / 25mm or more. B: The adhesive strength was in the range of 7 N / 25 mm or more and less than 10 N / 25 mm. C: The adhesive strength was in the range of 5 N / 25 mm or more and less than 7 N / 25 mm. D: The adhesive strength was less than 5 N / 25 mm.

[0153] 3. Long-term reworkability The evaluation sample prepared above was left to stand for 15 days in an environment with an ambient temperature of 25°C and 50% RH. After leaving the evaluation sample for 15 days, the test piece [structure: pressure-sensitive adhesive layer / polarizing film (TAC layer / PVA layer) / pressure-sensitive adhesive layer for brightness-enhancing film / brightness-enhancing film] was peeled off from the glass plate at an angle of 180° along the long side (100 mm) to measure the adhesive strength (unit: N / 25 mm) using a desktop precision universal testing machine (model number: AGS-X) manufactured by Shimadzu Corporation at an ambient temperature of 23°C and 50% RH at a peeling speed of 0.3 m / min. Based on the measured adhesive strength, the long-term reworkability was evaluated according to the following evaluation criteria. The measured adhesive strength values ​​and evaluation results are shown in Table 2. In the following evaluation criteria, "A," "B," and "C" are levels that are practically acceptable, with "A" being the most preferable.

[0154] -Evaluation criteria- A: The adhesive strength was less than 6N / 25mm. B: The adhesive strength was in the range of 6 N / 25 mm or more and less than 8 N / 25 mm. C: The adhesive strength was in the range of 8 N / 25 mm or more and less than 10 N / 25 mm. D: The adhesive strength was 10 N / 25 mm or more.

[0155] [Table 2]

[0156] Details of the ingredients listed in Table 2 are as follows: <Crosslinking agent> -Isocyanate-based crosslinking agent- "Takenate D-101E" (product name, adduct of TDI and TMP, solid content: 45% by mass, manufactured by Mitsui Chemicals, Inc.) -Epoxy-based crosslinking agent- "TETRAD-X" (trade name, chemical name: N,N,N',N'-tetraglycidyl-m-xylylenediamine, solid content: 100% by mass, manufactured by Mitsubishi Gas Chemical Company, Inc.) "Takenate" and "TETRAD" are both registered trademarks.

[0157] <Silane coupling agent> -Specific silane coupling agent (C)- "KBE-9007N" [trade name, isocyanate group: present, siloxane structure: absent, compound represented by formula (X) (R 1 : ethoxy group, R 2 : ethoxy group, R 3 : ethoxy group, R 4: 1,3-propylene group), solid content concentration: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd. -Other silane coupling agents- "KBE-402" (product name, epoxy group-containing silane compound, isocyanate group: none, siloxane structure: none, solid content: 100% by mass, Shin-Etsu Chemical Co., Ltd.) "X-41-1810" (product name, thiol group-containing silane compound, isocyanate group: absent, siloxane structure: present, solid content: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0158] <Alicyclic epoxy compounds> -Specific alicyclic epoxy compound (D)- "Celloxide 2021P" (product name, chemical name: 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, solid content: 100% by mass, manufactured by Daicel Corporation) "Celloxide 2081" (trade name, chemical name: ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, solid content: 100% by mass, manufactured by Daicel Corporation) The above "Celloxide" is a registered trademark.

[0159] "Celloxide 2021P" has a structure represented by the following formula (A): The divalent organic linking group corresponding to R in formula (I) has three atoms.

[0160] [ka]

[0161] "Celloxide 2081" has a structure represented by the following formula (B): The divalent organic linking group corresponding to R in formula (I) has 10 atoms.

[0162] [ka]

[0163] In Table 2, the values ​​shown in the "blending amount" column are all solid content equivalents. In Table 2, "-" means that the ingredient in that column is not included.

[0164] As shown in Table 2, it was confirmed that the pressure-sensitive adhesive layers formed using the pressure-sensitive adhesive compositions of Examples 1 to 14 exhibit excellent high-temperature durability, high-humidity durability, and long-term reworkability even when used in thin optical films. On the other hand, it was confirmed that the adhesive layers formed using the adhesive compositions of Comparative Examples 1 to 5 were inferior to the adhesive layers formed using the adhesive compositions of the Examples in at least one of high temperature durability, high humidity durability, and long-term reworkability.

[0165] [Volatility of silane coupling agents] <Test Example 1: When specific silane coupling agent (C) exists alone> One gram of silane coupling agent (trade name: KBE-9007N, molecular weight: 247.4, manufactured by Shin-Etsu Chemical Co., Ltd.) was weighed into a pre-weighed aluminum container (a so-called aluminum cup; the same applies hereinafter), and the total weight including the aluminum cup was measured. The silane coupling agent in the aluminum cup was then dried at 100°C for 180 seconds using a dryer manufactured by Espec Corporation. After drying, the total weight including the aluminum cup was measured, and the weight of the silane coupling agent after drying was determined by subtracting the weight of the aluminum cup from the measured total weight. The residual rate of the silane coupling agent after drying was calculated from the weights of the silane coupling agent before and after drying according to the following formula: Residual rate of silane coupling agent after drying (unit: %) = [Weight of silane coupling agent after drying (unit: g) / Weight of silane coupling agent before drying (unit: g)] x 100

[0166] <Test Example 2: When specific alicyclic epoxy compound (D) exists alone> One gram of an alicyclic epoxy compound (trade name: Celloxide 2021P, molecular weight: 252, manufactured by Daicel Corporation) was weighed into a pre-weighed aluminum cup, and the total weight, including the aluminum cup, was measured. The alicyclic epoxy compound in the aluminum cup was then dried at 100°C for 180 seconds using a dryer manufactured by Espec Corporation. After drying, the total weight, including the aluminum cup, was measured, and the weight of the alicyclic epoxy compound after drying was calculated by subtracting the weight of the aluminum cup from the total weight. The residual percentage of the alicyclic epoxy compound after drying was then calculated from the weights of the alicyclic epoxy compound before and after drying according to the following formula: Residual rate of alicyclic epoxy compounds after drying (unit: %) = [Weight of alicyclic epoxy compound after drying (unit: g) / Weight of alicyclic epoxy compound before drying (unit: g)] x 100

[0167] <Test Example 3: When specific silane coupling agent (C) and specific alicyclic epoxy compound (D) coexist> 10 g of a silane coupling agent (trade name: KBE-9007N, manufactured by Shin-Etsu Chemical Co., Ltd.) and 10 g of an alicyclic epoxy compound (trade name: CELLOXIDE 2021P, manufactured by Daicel Corporation) were weighed into a container and thoroughly mixed and stirred to obtain a mixture of the silane coupling agent and the alicyclic epoxy compound. 1 g of the resulting mixture was weighed into a pre-weighed aluminum cup, and the total weight including the aluminum cup was measured. The mixture in the aluminum cup was then dried at 100°C for 180 seconds using an ESPEC Corporation dryer. After drying, the total weight including the aluminum cup was measured, and the weight of the dried mixture was calculated by subtracting the weight of the aluminum cup from the total weight. The residual ratio of the mixture after drying was calculated from the weights of the mixture before and after drying according to the following formula: Residual rate of the mixture after drying (unit: %) = [Weight of the mixture after drying (unit: g) / Weight of the mixture before drying (unit: g)] x 100

[0168] Table 3 shows the residual rates after drying of the silane coupling agent, the alicyclic epoxy compound, and the mixture of the silane coupling agent and the alicyclic epoxy compound. The higher the residual rate after drying, the lower the volatility.

[0169] [Table 3]

[0170] As shown in Table 3, the silane coupling agent "KBE-9007N" tends to be highly volatile when used alone. In contrast, when the silane coupling agent "KBE-9007N" was combined with the alicyclic epoxy compound "Celloxide 2021P," the volatilization of the silane coupling agent "KBE-9007N" was suppressed. These results suggest that the combined use of specific silane coupling agent (C) and specific alicyclic epoxy compound (D) makes the specific silane coupling agent (C) less likely to volatilize, even when the adhesive layer is placed in a high-temperature environment. This allows a sufficient amount of specific silane coupling agent (C) to remain stably in the adhesive layer, making it easier to achieve the desired effects.

Claims

1. A pressure-sensitive adhesive composition comprising: a (meth)acrylic polymer (A) having a carboxy group; a crosslinking agent (B); a silane coupling agent (C) having an isocyanate group; and an alicyclic epoxy compound (D) represented by the following formula (I): 【Chemical 1】 In formula (I), R represents a divalent organic linking group having an ester bond.

2. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic polymer (A) comprises a structural unit (a1) derived from a monomer having a carboxy group, and the content of the structural unit (a1) is 0.5% by mass to 1.5% by mass with respect to all structural units.

3. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic polymer (A) comprises a structural unit (a2) derived from a monomer having a hydroxyl group, and the content of the structural unit (a2) is 0.1% by mass to 1.0% by mass with respect to all structural units.

4. The pressure-sensitive adhesive composition according to claim 1 , wherein the crosslinking agent (B) is an isocyanate-based crosslinking agent.

5. The pressure-sensitive adhesive composition according to claim 4 , wherein the isocyanate-based crosslinking agent is an aromatic polyisocyanate-based compound.

6. The pressure-sensitive adhesive composition according to claim 5 , wherein the aromatic polyisocyanate compound is a tolylene diisocyanate compound.

7. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the crosslinking agent (B) is 0.1 to 5.0 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A).

8. The pressure-sensitive adhesive composition according to claim 1 , wherein the silane coupling agent (C) is a compound having no siloxane structure.

9. The pressure-sensitive adhesive composition according to claim 1 , wherein the silane coupling agent (C) is a compound represented by the following formula (X): 【Chemistry 2】 In formula (X), R １ , R ２ and R ３ each independently represents an alkyl group or an alkoxy group, R ４ represents an alkylene group. １ , R ２ and R ３ At least one of these represents an alkoxy group.

10. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the silane coupling agent (C) is 0.1 to 3.0 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A).

11. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the alicyclic epoxy compound (D) is 0.1 to 6.0 parts by mass per 100 parts by mass of the (meth)acrylic polymer (A).

12. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 11.

13. A pressure-sensitive adhesive sheet comprising: an optical film; and a pressure-sensitive adhesive layer provided on at least one surface of the optical film and formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 11.

14. The pressure-sensitive adhesive sheet according to claim 13 , wherein the optical film is a polarizing plate.

15. The pressure-sensitive adhesive sheet according to claim 13, wherein the optical film has a thickness of 1 μm to 200 μm.

16. An optical member comprising, in this order: a glass substrate; a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 11; and an optical film.

17. A display device comprising the optical member according to claim 16.

Images