Adhesive composition, adhesive sheet, optical component, and display device

Abstract

To provide an adhesive composition capable of forming an adhesive layer excellent in high-temperature durability, processability, and warpage suppressing properties, and to provide an adhesive sheet, an optical member, and a display device.SOLUTION: The adhesive composition contains: a (meth)acrylic copolymer which contains a constituent unit derived from a hydroxyl group-containing monomer and a constituent unit derived from a carboxy group-containing monomer, with the content of the constituent unit derived from the hydroxyl group-containing monomer being more than 0 mass% and less than 0.5 mass% based on all the constituent units, and which does not contain a constituent unit derived from an aromatic ring-containing monomer; a polyfunctional isocyanate compound having a number average molecular weight of 1,000 or more and 50,000 or less and a melting point of 10°C or higher and 90°C or lower; and a silane coupling agent. The adhesive sheet, the optical member, and the display device are also provided.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 Art

[0002] A liquid crystal display device generally includes a liquid crystal cell in which a liquid crystal layer is sandwiched between two support substrates, and optical films such as a polarizing plate, a retardation film, and a brightness enhancement film. When manufacturing a liquid crystal display device by laminating a liquid crystal cell and an optical film, and laminating optical films to each other, these members are bonded via a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition. In liquid crystal display devices, (meth)acrylic pressure-sensitive adhesive compositions are widely used from the viewpoint of ensuring visibility.

[0003] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition for an optical film containing a (meth)acrylate copolymer (A) and an isocyanate compound (B), wherein the (meth)acrylate copolymer (A) comprises a structural unit derived from an alkyl (meth)acrylate monomer (a1) and a structural unit derived from a (meth)acrylate monomer having a hydroxyl group (a2), the content of the structural unit derived from the (meth)acrylate monomer (a2) having a hydroxyl group is more than 0.5% by mass and 10% by mass or less based on 100% by mass of the total structural units constituting the (meth)acrylate copolymer (A), the isocyanate compound (B) has a number average molecular weight of 900 or more and 10,000 or less, and contains a compound obtained by reacting an isocyanate monomer and a compound having two functional groups capable of reacting with isocyanate groups, and the content of the isocyanate compound (B) is 0.01 part by mass or more and 20 parts by mass or less relative to 100 parts by mass of the (meth)acrylate copolymer (A). Furthermore, Patent Document 2 discloses an adhesive composition for optical films comprising a (meth)acrylate copolymer (A) and an isocyanate compound (B), wherein the (meth)acrylate copolymer (A) comprises (a1) a structural unit derived from an alkyl (meth)acrylate monomer, (a2) a structural unit derived from a (meth)acrylate monomer having a hydroxyl group, and (a3) ​​a structural unit derived from a (meth)acrylate monomer having an aromatic ring, and the isocyanate compound (B) has a number average molecular weight of 900 or more and 10,000 or less. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-95843 [Patent Document 2] Japanese Patent Publication No. 2018-95844 [Overview of the project] [Problems that the invention aims to solve]

[0005] Optical films such as polarizers are typically constructed by laminating multiple components with different shrinkage rates, making them susceptible to dimensional changes due to temperature fluctuations. For example, if a liquid crystal panel with an optical film bonded to it via an adhesive layer is placed in a high-temperature environment, the optical film may shrink, causing wrinkles in the adhesive layer and / or the optical film, or delamination at the interface between the optical film and / or the liquid crystal cell and the adhesive layer.

[0006] Furthermore, in thin LCD panels, shrinkage of the optical film can cause the LCD panel to warp. Warping of the LCD panel degrades the display quality. In recent years, with the increasing size of displays, the area of ​​the optical film required has also increased, making LCD panels more susceptible to the effects of optical film shrinkage than ever before.

[0007] The wrinkles and peeling caused by the shrinkage of the optical film, as well as the warping of the liquid crystal panel, can be resolved, for example, by easing the internal stress of the optical film caused by shrinkage with an adhesive layer. To easing the internal stress of the optical film, one could consider weakening the cohesive force of the adhesive layer and giving the adhesive layer flexibility. However, if the cohesive force of the adhesive layer is weakened, the adhesive layer is more likely to protrude when the optical film with the adhesive layer is cut.

[0008] Furthermore, in liquid crystal panels where an optical film is bonded via an adhesive layer, moisture in the adhesive layer may evaporate when exposed to high-temperature environments, potentially causing foaming at the interface between the adhesive layer and the liquid crystal cell.

[0009] This disclosure is made in light of the circumstances described above. One embodiment of this disclosure aims to solve the problem of providing an adhesive composition that can form an adhesive layer with excellent high-temperature durability, processability, and warp suppression. Other embodiments of this disclosure aim to solve the problems described above by providing an adhesive sheet, an optical component, and a display device comprising the adhesive layer. [Means for solving the problem]

[0010] The following are examples of specific means for solving the problem: <1> A (meth)acrylic copolymer comprising constituent units derived from monomers having hydroxyl groups and constituent units derived from monomers having carboxyl groups, wherein the content of constituent units derived from monomers having hydroxyl groups is greater than 0% by mass and less than 0.5% by mass relative to the total constituent units, and which does not contain constituent units derived from monomers having aromatic rings, A polyfunctional isocyanate compound having a number-average molecular weight of 1,000 or more and 50,000 or less, and a melting point of 10°C or more and 90°C or less, Silane coupling agent and An adhesive composition containing the following: <2> The weight-average molecular weight of the above (meth)acrylic copolymer is between 400,000 and 2,500,000. <1> The adhesive composition described above. <3> The content of constituent units derived from the monomer having the carboxyl group in the above (meth)acrylic copolymer is greater than 0.5% by mass and less than or equal to 15.0% by mass relative to the total constituent units. <1> or <2> The adhesive composition described above. <4> The content of the above polyfunctional isocyanate compound is 0.6 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of the above (meth)acrylic copolymer. <1> ~ <3> An adhesive composition as described in any one of the following. <5> The above polyfunctional isocyanate compound is an aromatic polyfunctional isocyanate compound. <1> ~ <4> An adhesive composition as described in any one of the following. <6> The above polyfunctional isocyanate compound is at least one selected from the group consisting of diphenylmethane diisocyanate compounds and tolylene diisocyanate compounds. <1> ~ <5> An adhesive composition as described in any one of the following. <7> Substrate and The above-mentioned substrate is provided on at least one side, and <1> ~ <6> An adhesive layer formed by the adhesive composition described in any one of the following, An adhesive sheet equipped with [a specific feature]. <8> The above substrate is an optical film. <7> The adhesive sheet described above. <9> The optical film described above is a polarizing plate. <8> The adhesive sheet described above. <10> Glass substrate and <1> ~ <6> An adhesive layer formed by the adhesive composition described in any one of the following, Optical film and An optical component comprising the elements in this order. <11> <10> A display device comprising the optical components described above. [Effects of the Invention]

[0011] According to one embodiment of the present disclosure, an adhesive composition is provided that can form an adhesive layer with excellent high-temperature durability, processability, and warp suppression. According to another embodiment of the present disclosure, there are provided a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer described above, an optical member, and a display device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [Figure 1] It is a figure for demonstrating the evaluation method of workability in an Example. MODE FOR CARRYING OUT THE INVENTION

[0013] Hereinafter, the pressure-sensitive adhesive composition, the pressure-sensitive adhesive sheet, the optical member, and the display device of the present disclosure will be described in detail. Description of the requirements described below may be made based on typical embodiments of the present disclosure, but the present disclosure is not limited to such embodiments, and modifications can be appropriately made and implemented within the scope of the object of the present disclosure.

[0014] In the present disclosure, a numerical range indicated using "~" means a range including the numerical values described before and after "~" as the lower limit and the upper limit, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of another stepwise described numerical range. In addition, in the numerical ranges described in the present disclosure, the upper limit or lower limit described in a certain numerical range may be replaced with the values shown in the examples.

[0015] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0016] In the present disclosure, when a plurality of substances corresponding to each component are present in the pressure-sensitive adhesive composition, the amount of each component means the total amount of the plurality of substances present in the pressure-sensitive adhesive composition, unless otherwise specified.

[0017] In the present disclosure, "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. In this disclosure, "(meth)acrylic copolymer" means a copolymer that contains constituent units derived from (meth)acrylic monomers, and in which the proportion of constituent units derived from (meth)acrylic monomers is 50% by mass or more.

[0018] In this disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic," "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate," "(meth)acryloyl" is a term that encompasses both "acryloyl" and "methacryloyl," and "(meth)acrylamide" is a term that encompasses both "acrylamide" and "methacrylamide."

[0019] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0020] In this disclosure, "mass%" and "weight%" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0021] In this disclosure, "polymer" and "polymer" are synonymous.

[0022] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved.

[0023] In this disclosure, "high temperature durability" means the property of being able to effectively suppress wrinkles, peeling, and foaming that may occur in high-temperature environments. In this disclosure, "warpage suppression" means the property of being able to effectively suppress warpage of the adherend that may occur due to the shrinkage of the substrate in a high-temperature environment.

[0024] [Adhesive composition] The adhesive composition of this disclosure comprises a (meth)acrylic copolymer containing constituent units derived from monomers having hydroxyl groups and constituent units derived from monomers having carboxyl groups, wherein the content of constituent units derived from monomers having hydroxyl groups is greater than 0% by mass and less than 0.5% by mass relative to the total constituent units, and does not contain constituent units derived from monomers having aromatic rings. The present invention comprises a polyfunctional isocyanate compound having a number-average molecular weight of 1,000 to 50,000 and a melting point of 10°C to 90°C, and a silane coupling agent. According to the adhesive composition of this disclosure, an adhesive layer can be formed that is excellent in high-temperature durability, processability, and warping suppression. The reason why the adhesive composition of this disclosure may produce such effects is not clear, but the inventors speculate as follows. However, the following speculation is not intended to be restrictive to the adhesive composition of this disclosure, but is provided as an example.

[0025] The adhesive composition of this disclosure contains a crystalline polyfunctional isocyanate compound in addition to an amorphous (meth)acrylic copolymer. Therefore, it is considered that crystallization sites of the polyfunctional isocyanate compound will occur in a portion of the formed adhesive layer. The polyfunctional isocyanate compound contained in the adhesive composition of this disclosure has a melting point in a specific temperature range. Therefore, at the processing temperature range [around room temperature (20°C)], the adhesive layer has crystallization sites and high cohesive force, while at temperatures above the melting point, crystallization is eliminated and cohesive force decreases. Furthermore, the polyfunctional isocyanate compound contained in the adhesive composition of this disclosure has a moderately large number-average molecular weight, resulting in a moderately long crosslinking distance and a moderately low crosslinking density of the adhesive layer. In addition, the (meth)acrylic copolymer contained in the adhesive composition of this disclosure contains constituent units derived from monomers having hydroxyl groups and constituent units derived from monomers having carboxyl groups, and thus possesses both hydroxyl and carboxyl groups. Both the hydroxyl and carboxyl groups of (meth)acrylic copolymers react with polyfunctional isocyanate compounds. The bonds formed by the reaction of hydroxyl and carboxyl groups with isocyanate groups are different. The reaction between hydroxyl and isocyanate groups forms urethane bonds, while the reaction between carboxyl and isocyanate groups forms amide bonds. Because the active hydrogen at the amide bond site is highly reactive, if the (meth)acrylic copolymer has only carboxyl groups, the crosslinking density of the adhesive layer will be high. However, the presence of hydroxyl groups in the (meth)acrylic copolymer prevents the crosslinking density of the adhesive layer from becoming excessively high. On the other hand, if many hydroxyl groups remain in the adhesive layer, the adhesive layer will absorb a large amount of moisture from the air due to the hydroxyl groups. When the adhesive layer is placed in a high-temperature environment, moisture will volatilize from the adhesive layer, causing foaming at the interface between the adhesive layer and the adherend. However, since the (meth)acrylic copolymer contained in the adhesive composition of this disclosure has relatively few hydroxyl groups, it is considered that hydroxyl groups are unlikely to remain in the adhesive layer. Furthermore, since the (meth)acrylic copolymer contained in the adhesive composition of this disclosure does not contain constituent units derived from monomers having aromatic rings, the entanglement of (meth)acrylic copolymers with each other is not inhibited by the bulkiness of the aromatic rings, and the cohesive force of the adhesive layer does not decrease.Furthermore, since the adhesive composition of this disclosure contains a silane coupling agent, the adhesion of the adhesive layer to the adherend is enhanced. The adhesive composition of this disclosure, having the above-described structure, controls the cohesive force and crosslinking density of the adhesive layer in a specific temperature range, enhances the adhesion of the adhesive layer to the adherend, suppresses the absorption of moisture into the adhesive layer, and achieves the formation of an adhesive layer that combines high-temperature durability, processability, and warp suppression.

[0026] In this disclosure, a (meth)acrylic copolymer containing constituent units derived from monomers having hydroxyl groups and constituent units derived from monomers having carboxyl groups, wherein the content of constituent units derived from monomers having hydroxyl groups is greater than 0% by mass and less than 0.5% by mass relative to the total constituent units, and does not contain constituent units derived from monomers having aromatic rings, is also referred to as a "specific (meth)acrylic copolymer." Furthermore, in this disclosure, "a polyfunctional isocyanate compound having a number-average molecular weight of 1,000 or more and 50,000 or less, and a melting point of 10°C or more and 90°C or less" is also referred to as "a specific polyfunctional isocyanate compound."

[0027] [Specific (meth)acrylic copolymer] The adhesive composition of this disclosure includes a (meth)acrylic copolymer [i.e., a specific (meth)acrylic copolymer] comprising constituent units derived from monomers having hydroxyl groups and constituent units derived from monomers having carboxyl groups, wherein the content of constituent units derived from monomers having hydroxyl groups is greater than 0% by mass and less than 0.5% by mass relative to the total constituent units, and does not contain constituent units derived from monomers having aromatic rings. The adhesive composition of this disclosure may contain only one specific (meth)acrylic copolymer, or it may contain two or more specific (meth)acrylic copolymers.

[0028] <Constituent units derived from monomers containing hydroxyl groups> The specified (meth)acrylic copolymer contains constituent units derived from monomers having hydroxyl groups in a proportion of more than 0% by mass and less than 0.5% by mass relative to the total constituent units. In this disclosure, "constituent units derived from monomers having hydroxyl groups" means constituent units formed by addition polymerization of monomers having hydroxyl groups.

[0029] The type of monomer having a hydroxyl group is not particularly limited. Examples of monomers having a hydroxyl group include monomers having at least one hydroxyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited and includes, for example, a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. A (meth)acryloyl group is preferred as the ethylenically unsaturated group.

[0030] Specific examples of monomers having hydroxyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (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. As monomers having hydroxyl groups, hydroxyalkyl (meth)acrylates are preferred, for example, because they exhibit good copolymerization with other monomers. As hydroxyalkyl (meth)acrylates, hydroxyalkyl (meth)acrylates having a hydroxyalkyl group with 2 to 4 carbon atoms are preferred, at least one selected from 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is more preferred, and 2-hydroxyethyl acrylate is even more preferred.

[0031] The specific (meth)acrylic copolymer may contain only one type of constituent unit derived from a monomer having a hydroxyl group, or it may contain two or more types.

[0032] The content of constituent units derived from monomers having hydroxyl groups in the specified (meth)acrylic copolymer is greater than 0% by mass and less than 0.5% by mass relative to the total constituent units of the specified (meth)acrylic copolymer. When the content of constituent units derived from monomers having hydroxyl groups in a specific (meth)acrylic copolymer exceeds 0% by mass relative to the total constituent units of the specific (meth)acrylic copolymer, the high-temperature durability and warping suppression of the formed adhesive layer tend to be excellent. From this viewpoint, the content of constituent units derived from monomers having hydroxyl groups in a specific (meth)acrylic copolymer is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more, relative to the total constituent units of the specific (meth)acrylic copolymer. If a large number of hydroxyl groups remain after a reaction with a specific polyfunctional isocyanate compound, these remaining hydroxyl groups can absorb moisture from the air, and when the adhesive layer is bonded to the substrate and then placed in a high-temperature environment (for example, at 105°C), foaming may occur at the interface between the adhesive layer and the substrate. When the content of constituent units derived from monomers having hydroxyl groups in a specific (meth)acrylic copolymer is less than 0.5% by mass relative to the total constituent units of the specific (meth)acrylic copolymer, foaming tends to be less likely to occur at the interface between the adhesive layer and the adherend in a high-temperature environment. This is thought to be because hydroxyl groups are less likely to remain after reaction with isocyanate groups. From this viewpoint, the content of constituent units derived from monomers having hydroxyl groups in a specific (meth)acrylic copolymer is preferably 0.4% by mass or less, and more preferably 0.3% by mass or less, relative to the total constituent units of the specific (meth)acrylic copolymer. In a particular (meth)acrylic copolymer, the content of constituent units derived from monomers having hydroxyl groups may, in a certain embodiment, be 0.05% by mass or more and less than 0.5% by mass, 0.1% by mass or more and less than 0.5% by mass, 0.1% by mass or more and 0.4% by mass or less, or 0.1% by mass or more and 0.3% by mass or less.

[0033] <Constituent units derived from monomers containing a carboxyl group> A specific (meth)acrylic copolymer contains constituent units derived from monomers having carboxyl groups. In this disclosure, "constituent units derived from monomers having carboxyl groups" means constituent units formed by addition polymerization of monomers having carboxyl groups.

[0034] The type of monomer having a carboxyl group is not particularly limited. Examples of monomers having a carboxyl group include monomers having at least one carboxyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited and includes, for example, a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. A (meth)acryloyl group is preferred as the ethylenically unsaturated group.

[0035] Specific examples of monomers having a carboxyl 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). As the monomer having a carboxyl group, a (meth)acrylic monomer having a carboxyl group is preferred. As the (meth)acrylic monomer having a carboxyl group, at least one selected from acrylic acid and methacrylic acid is preferred, and acrylic acid is more preferred.

[0036] The specific (meth)acrylic copolymer may contain only one or more constituent units derived from monomers having a carboxyl group.

[0037] The content of constituent units derived from monomers having carboxyl groups in the specific (meth)acrylic copolymer is not particularly limited, but for example, it is preferably more than 0.5% by mass and 15.0% by mass or less, more preferably 1.0% by mass or more and 15.0% by mass or less, and even more preferably 3.0% by mass or less and 10.0% by mass or less, relative to the total constituent units of the specific (meth)acrylic copolymer. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic copolymer exceeds 0.5% by mass relative to the total constituent units of the specific (meth)acrylic copolymer, the high-temperature durability of the formed adhesive layer tends to be superior. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic copolymer is 15.0% by mass or less relative to the total constituent units of the specific (meth)acrylic copolymer, haze is less likely to occur in the formed adhesive layer, and the transparency of the adhesive layer is less likely to be impaired. In a particular (meth)acrylic copolymer, the content of constituent units derived from monomers having carboxyl groups may, in a certain embodiment, be 0.1% by mass or more and 15.0% by mass or less.

[0038] <Constituent units derived from alkyl methacrylate monomers> The specific (meth)acrylic copolymer preferably contains structural units derived from (meth)acrylate alkyl ester monomers. In this disclosure, "structural units derived from (meth)acrylate alkyl ester monomers" means structural units formed by the addition polymerization of (meth)acrylate alkyl ester monomers. In this disclosure, "(meth)acrylate alkyl ester monomers" do not include monomers having a hydroxyl group, monomers having a carboxyl group, or monomers having an aromatic ring.

[0039] The type of alkyl (meth)acrylate monomer is not particularly limited. The alkyl (meth)acrylate monomer may be an alkyl acrylate monomer or an alkyl methacrylate monomer. The alkyl group in the alkyl (meth)acrylate monomer may be unsubstituted or may have substituents (excluding hydroxyl groups, carboxyl groups, and aromatic ring groups), but it is preferable that it be unsubstituted. The alkyl group in the alkyl (meth)acrylate monomer may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group of the (meth)acrylate monomer is preferably 1 to 18, more preferably 1 to 12, even more preferably 1 to 8, and particularly preferably 1 to 4.

[0040] Specific examples of alkyl (meth)acrylate monomers 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. As the alkyl (meth)acrylate monomer, at least one selected from the group consisting of n-butyl acrylate, methyl methacrylate, and 2-ethylhexyl acrylate is preferred.

[0041] When a specific (meth)acrylic copolymer contains constituent units derived from alkyl (meth)acrylate monomers, it may contain only one type of constituent unit derived from alkyl (meth)acrylate monomers, or it may contain two or more types.

[0042] When a specific (meth)acrylic copolymer contains structural units derived from alkyl (meth)acrylate monomers, the content of structural units derived from alkyl (meth)acrylate monomers is not particularly limited, but is preferably 50% by mass or more, more preferably 50% to 99.5% by mass, even more preferably 70% to 99.5% by mass, and particularly preferably 80% to 99.5% by mass, relative to the total structural units of the specific (meth)acrylic copolymer. Here, the content of constituent units derived from alkyl (meth)acrylate monomers in a specific (meth)acrylic copolymer being 50% by mass or more of the total constituent units of the specific (meth)acrylic copolymer means that constituent units derived from alkyl (meth)acrylate monomers are included as the main component of the constituent units of the specific (meth)acrylic copolymer.

[0043] <Constituent units derived from monomers containing aromatic rings> The specified (meth)acrylic copolymer does not contain structural units derived from monomers having aromatic rings. In this disclosure, "structural units derived from monomers having aromatic rings" means structural units formed by addition polymerization of monomers having aromatic rings. When a (meth)acrylic copolymer contains constituent units derived from monomers having aromatic rings, the bulkiness of the aromatic rings inhibits the entanglement of the (meth)acrylic copolymers, which tends to reduce the cohesive force of the adhesive layer. In contrast, the adhesive composition of this disclosure does not contain constituent units derived from monomers having aromatic rings in the (meth)acrylic copolymer, so the reduction in cohesive force of the adhesive layer due to the aromatic rings does not occur, and the processability of the formed adhesive layer tends not to be impaired.

[0044] The type of monomer having an aromatic ring is not particularly limited. Examples of monomers having aromatic rings include monomers having at least one aromatic ring and an ethylenically unsaturated group in one molecule. Examples of aromatic rings include aromatic hydrocarbon rings and aromatic heterocycles. Specific examples of aromatic hydrocarbon rings include benzene rings, naphthalene rings, and anthracene rings. Specific examples of aromatic heterocycles include imidazole rings, oxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrrole rings, furan rings, thiophene rings, pyrazole rings, isoxazole rings, isothiazole rings, pyridazine rings, and pyrimidine rings. The ethylenically unsaturated group is not particularly limited and includes, for example, a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. A (meth)acryloyl group is preferred as the ethylenically unsaturated group.

[0045] Specific examples of monomers having aromatic rings include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene.

[0046] <Constituent units derived from other monomers> A specific (meth)acrylic copolymer may contain constituent units derived from monomers that do not fall under any of the constituent units derived from monomers having a hydroxyl group, monomers having a carboxyl group, alkyl (meth)acrylate monomers, or monomers having an aromatic ring (so-called other monomers). In this disclosure, "constituent units derived from other monomers" means constituent units formed by addition polymerization of other monomers.

[0047] Other constituent units derived from monomers include those derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; those derived from vinyl cyanide, such as acrylonitrile and methacrylonitrile; and those derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate.

[0048] If a specific (meth)acrylic copolymer contains other constituent units, it may contain only one type of other constituent unit or two or more types.

[0049] If the specific (meth)acrylic copolymer contains other constituent units, the content of the other constituent units can be set appropriately within a range that does not impair the effect of the adhesive composition of this disclosure.

[0050] <<Physical Properties of Specific (Meth)acrylic Copolymers>> The weight-average molecular weight (also called "Mw") of the specific (meth)acrylic copolymer is not particularly limited, but is preferably 400,000 to 2,500,000, more preferably 600,000 to 2,500,000, even more preferably 800,000 to 2,500,000, and particularly preferably 1,000,000 to 2,500,000. When the weight-average molecular weight of a specific (meth)acrylic copolymer is 400,000 or more, the processability of the resulting adhesive layer tends to improve. Specific (meth)acrylic copolymers tend to be easier to manufacture if their weight-average molecular weight is 2.5 million or less.

[0051] The weight-average molecular weight of a specific (meth)acrylic copolymer is a value measured by the following method. Specifically, it is measured according to (1) to (3) below. (1) A solution of the specific (meth)acrylic copolymer is applied to release paper and dried at 100°C for 1 minute to obtain a film-like specific (meth)acrylic copolymer. (2) Using the film-like specific (meth)acrylic copolymer obtained in (1) above and tetrahydrofuran, a sample solution with a solid content concentration of 0.2% by mass is obtained. Here, "solid content concentration" refers to the mass ratio of the specific (meth)acrylic copolymer in the sample solution. (3) The weight-average molecular weight of the specific (meth)acrylic copolymer is determined as a standard polystyrene equivalent by gel permeation chromatography (GPC) under the following conditions.

[0052] ~Conditions~ Measurement device: High-speed GPC [Model number: HLC-8420 GPC, manufactured by Tosoh Corporation] Detector: Differential Refractometer (RI) [Integrated into HLC-8420, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Two units manufactured by Tosoh Corporation were used. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0053] The weight-average molecular weight of a specific (meth)acrylic copolymer can be adjusted to a desired value by controlling the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, and amount of polymerization initiator used during the polymerization of the monomers.

[0054] <<Content of specific (meth)acrylic copolymer>> The content of the specific (meth)acrylic copolymer in the adhesive composition of this disclosure is not particularly limited, but is preferably 50.0% to 99.9% by mass, more preferably 70.0% to 99.5% by mass, and even more preferably 80.0% to 99.1% by mass, based on the total solid content in the adhesive composition.

[0055] In this disclosure, "total solid content in the adhesive composition" means the total mass of the adhesive composition if the adhesive composition does not contain a solvent, and the mass of the residue remaining after removing the solvent from the adhesive composition if the adhesive composition contains a solvent. In this disclosure, "solvent" means water and organic solvents.

[0056] [Meth)acrylic copolymer manufacturing method] The method for producing the specific (meth)acrylic copolymer is not particularly limited. Specific (meth)acrylic copolymers can be produced by polymerizing the monomers described above using known polymerization methods, such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. As for the polymerization method, solution polymerization is preferred because the processing steps for preparing the adhesive composition of this disclosure after manufacturing are relatively simple and can be carried out in a short time.

[0057] In solution polymerization, a predetermined organic solvent, monomer, polymerization initiator, and a chain transfer agent (if necessary) are generally placed in a polymerization tank, and the reaction is carried out by heating for several hours at, for example, the reflux temperature of the organic solvent while stirring. In this case, at least a portion of the organic solvent, monomer, polymerization initiator, and chain transfer agent (if necessary) may be added sequentially. Alternatively, the reaction may be carried out under a nitrogen atmosphere.

[0058] Examples of organic solvents used in polymerization reactions include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, organic solvents used in polymerization reactions 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 spirits, petroleum naphtha, and turpentine oil; 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; and methyl Examples include ketone compounds represented by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds represented 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 represented by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0059] In the production of specific (meth)acrylic copolymers, it is preferable to use organic solvents that do not easily cause chain transfer during polymerization reactions, such as aromatic hydrocarbon compounds, ester compounds, and ketone compounds. In particular, from the viewpoint of the solubility of the specific (meth)acrylic copolymer and the ease of polymerization, the use of ethyl acetate is preferred.

[0060] During the polymerization reaction, one organic solvent may be used, or two or more may be used.

[0061] Examples of polymerization initiators include organic peroxides and azo compounds commonly used in conventional solution polymerization methods. Specific examples of organic peroxides include t-butylperoxy-2-ethylhexanoate, t-butylhydroperoxide, cumenehydroperoxide, dicumylperoxide, benzoylperoxide, lauroylperoxide, caproylperoxide, di-i-propylperoxydicarbonate, di-2-ethylhexylperoxydicarbonate, t-butylperoxypivalate, and 2,2-bis(4,4-di-t-butylperoxy). Examples include chlorohexyl)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-carbonitride), and 2,2'-azobis(isobutyric acid)dimethyl.

[0062] During the polymerization reaction, one polymerization initiator may be used, or two or more may be used.

[0063] The amount of polymerization initiator used is not particularly limited and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0064] In the production of specific (meth)acrylic copolymers, chain transfer agents may be used as needed. Examples of chain transfer agents include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid with 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid with 1 to 8 carbon atoms, aromatic compounds represented by α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, and tetra- Examples include halogenated hydrocarbon compounds represented by carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene; aldehyde compounds represented by chloral and furaldihydes; alkyl mercaptan compounds having 1 to 18 carbon atoms; aromatic mercaptan compounds represented by 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 represented by pinene and terpinolene.

[0065] When using a chain transfer agent in the production of a specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set, for example, depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0066] The polymerization temperature is not particularly limited and can be set appropriately depending on the molecular weight of the target specific (meth)acrylic copolymer.

[0067] [Specific polyfunctional isocyanate compounds] The adhesive composition of this disclosure comprises a polyfunctional isocyanate compound [i.e., a specific polyfunctional isocyanate compound] having a number average molecular weight of 1,000 or more and 50,000 or less, and a melting point of 10°C or more and 90°C or less. In the adhesive composition of this disclosure, the specific polyfunctional isocyanate compound functions as a crosslinking agent.

[0068] In this disclosure, "polyfunctional isocyanate compound" refers to a compound in which the average number of isocyanate groups in one molecule exceeds 1.0. The specific polyfunctional isocyanate compound preferably has an average number of isocyanate groups per molecule that is greater than 1.0 and less than or equal to 10.0, and more preferably between 2.0 and 5.0.

[0069] In this disclosure, the "average number of isocyanate groups per molecule" of a specific polyfunctional isocyanate compound is a value obtained by the following formula. The "number-average molecular weight of the specific polyfunctional isocyanate compound" in the following formula is determined by gel permeation chromatography (GPC) as described later. Furthermore, in the following formula, "concentration of isocyanate groups" refers to the mass percentage (unit: mass%) of isocyanate groups contained in the specific polyfunctional isocyanate compound. Also, the "formula weight of isocyanate groups" in the following formula is 42. Average number of isocyanate groups in one molecule = (Number average molecular weight of the specific polyfunctional isocyanate compound × concentration of isocyanate group) / (Formula weight of isocyanate group × 100)

[0070] The number-average molecular weight (Mn) of specific polyfunctional isocyanate compounds is between 1,000 and 50,000. When the number-average molecular weight of a specific polyfunctional isocyanate compound is 1,000 or more, the resulting adhesive layer tends to exhibit excellent high-temperature durability and warp suppression. This is thought to be because an appropriate distance between crosslinking points is obtained, resulting in an appropriate crosslinking density in the adhesive layer, allowing the adhesive layer to fully exhibit stress relaxation properties against shrinkage of the substrate. From this viewpoint, the number-average molecular weight of the specific polyfunctional isocyanate compound is preferably 1,100 or more, more preferably 1,200 or more, and even more preferably 1,500 or more. When the number-average molecular weight of the specific polyfunctional isocyanate compound is 50,000 or less, the resulting adhesive layer tends to have excellent processability. This is thought to be because the distance between crosslinking points does not become excessively long, resulting in a moderately high crosslinking density in the adhesive layer and thus a high cohesive force in the adhesive layer. From this viewpoint, the number-average molecular weight of the specific polyfunctional isocyanate compound is preferably 10,000 or less, more preferably 5,000 or less, and even more preferably 3,000 or less.

[0071] The number-average molecular weight of specific polyfunctional isocyanate compounds is determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) under the following conditions.

[0072] ~Conditions~ Measurement device: High-speed GPC [Model number: HLC-8220 GPC, manufactured by Tosoh Corporation] Detector: Differential Refractometer (RI) [Integrated into HLC-8220, manufactured by Tosoh Corporation] Column: TSKgel G1000H XL [Manufactured by Tosoh Corporation] Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.2mL / min

[0073] The specific polyfunctional isocyanate compound has a melting point between 10°C and 90°C. When the specific polyfunctional isocyanate compound has a melting point of 10°C or higher, the resulting adhesive layer tends to have excellent processability. This is thought to be because, in the temperature range in which processing takes place, crystallization sites are formed in a part of the adhesive layer due to the specific polyfunctional isocyanate compound, increasing the cohesive force of the adhesive layer. From this viewpoint, the specific polyfunctional isocyanate compound is preferably one with a melting point of 15°C or higher, and more preferably one with a melting point of 20°C or higher. When the specific polyfunctional isocyanate compound has a melting point of 90°C or lower, the resulting adhesive layer tends to exhibit excellent high-temperature durability and warp suppression. From this viewpoint, the specific polyfunctional isocyanate compound is preferably one with a melting point of 80°C or lower, more preferably one with a melting point of 50°C or lower, and even more preferably one with a melting point of 30°C or lower. In some embodiments, the specific polyfunctional isocyanate compound may have a melting point of 10°C to 80°C, 10°C to 50°C, 10°C to 30°C, 10°C to 20°C, 15°C to 50°C, 15°C to 30°C, or 20°C to 50°C.

[0074] The melting point of a specific polyfunctional isocyanate compound is a value measured by the following method. Using a differential scanning calorimetry (DSC), 10 mg of the sample (i.e., a specific polyfunctional isocyanate compound) is heated to 50°C at a heating rate of 10°C / min in a nitrogen stream, and then the temperature is maintained for 1 hour. Next, the sample is cooled to -70°C at a cooling rate of 10°C / min, and then the temperature is maintained for 20 minutes. Next, the sample is heated to 120°C at a heating rate of 10°C / min (hereinafter also referred to as the "heating process"). The maximum value of the endothermic peak during the heating process in the heat-temperature plot obtained in the above manner is defined as the melting point. In the case of a mixture of two or more specific polyfunctional isocyanate compounds, if multiple endothermic peaks are observed, the maximum value of the endothermic peak at the lowest temperature is defined as the melting point. As a differential scanning calorimetry device, for example, a differential scanning calorimeter (product name: Discovery DSC 2500) manufactured by T.A. Instrument Japan Co., Ltd. can be suitably used. However, the differential scanning calorimetry device is not limited to this.

[0075] The type of specific polyfunctional isocyanate compound is not particularly limited. Examples of specific polyfunctional isocyanate compounds include aliphatic polyfunctional isocyanate compounds, alicyclic polyfunctional isocyanate compounds, and aromatic polyfunctional isocyanate compounds.

[0076] "Aliphatic polyfunctional isocyanate compounds" include, for example, aliphatic polyfunctional isocyanate compounds, polymers of aliphatic polyfunctional isocyanate compounds, reaction products of aliphatic polyfunctional isocyanate compounds and polyol compounds, and biuret derivatives of aliphatic polyfunctional isocyanate compounds. Specific examples of aliphatic polyfunctional isocyanate compounds include hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0077] "Alicyclic polyfunctional isocyanate compounds" include, for example, alicyclic polyfunctional isocyanate compounds, polymers of alicyclic polyfunctional isocyanate compounds, reaction products of alicyclic polyfunctional isocyanate compounds and polyol compounds, and biuret forms of alicyclic polyfunctional isocyanate compounds. Specific examples of alicyclic polyfunctional isocyanate compounds include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0078] "Aromatic polyfunctional isocyanate compounds" include, for example, aromatic polyfunctional isocyanate compounds, polymers of aromatic polyfunctional isocyanate compounds, reaction products of aromatic polyfunctional isocyanate compounds and polyol compounds, and biuret compounds of aromatic polyfunctional isocyanate compounds. Specific examples of aromatic polyfunctional isocyanate compounds include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4'-diphenylmethane diisocyanate (MDI).

[0079] Examples of polyol compounds include trimethylolpropane (TMP), polytetramethylene ether glycol (PTMG), diethylene glycol (DG), and polyethylene glycol (PEG).

[0080] The specific polyfunctional isocyanate compound is preferably an aromatic polyfunctional isocyanate compound from the viewpoint of reactivity with hydroxyl groups, and more preferably at least one selected from the group consisting of diphenylmethane diisocyanate compounds and tolylene diisocyanate compounds.

[0081] "Diphenylmethane diisocyanate compounds" include, for example, MDI, MDI polymers, reaction products of MDI and polyol compounds, and biuret compounds of MDI. A reaction product of MDI and PTMG is preferred as the diphenylmethane diisocyanate compound. "Tolylene diisocyanate compounds" include, for example, TDI, TDI polymers, reaction products of TDI and polyol compounds, and biuret compounds of TDI. A reaction product of TDI and PTMG is preferred as the tolylene diisocyanate compound.

[0082] The specific polyfunctional isocyanate compound may be a synthetic product or a commercially available product. The method for synthesizing specific polyfunctional isocyanate compounds is not particularly limited and can be synthesized by known methods. Specific polyfunctional isocyanate compounds can be suitably synthesized, for example, by the method described in the examples below.

[0083] Examples of commercially available specific polyfunctional isocyanate compounds include "Coronate® 4370" manufactured by Tosoh Corporation, and "Sunprene® P-665" and "Sunprene® P-870" manufactured by Sanyo Chemical Industries, Ltd.

[0084] The adhesive composition of this disclosure may contain only one specific polyfunctional isocyanate compound, or it may contain two or more specific polyfunctional isocyanate compounds.

[0085] The content of the specific polyfunctional isocyanate compound in the adhesive composition of this disclosure is not particularly limited, but is preferably 0.6 parts by mass or more and 20.0 parts by mass or less, more preferably 0.8 parts by mass or more and 15.0 parts by mass or less, and even more preferably 1.0 part by mass or more and 10.0 parts by mass or less, per 100 parts by mass of the specific (meth)acrylic copolymer. When the content of the specific polyfunctional isocyanate compound in the adhesive composition of this disclosure is 0.6 parts by mass or more per 100 parts by mass of the specific (meth)acrylic copolymer, the processability of the formed adhesive layer tends to be superior. When the content of the specific polyfunctional isocyanate compound in the adhesive composition of this disclosure is 20.0 parts by mass or less per 100 parts by mass of the specific (meth)acrylic copolymer, the high-temperature durability and warping suppression of the formed adhesive layer tend to be superior.

[0086] [Silane coupling agent] The adhesive composition of this disclosure comprises a silane coupling agent. When the adhesive composition of this disclosure contains a silane coupling agent, the resulting adhesive layer tends to exhibit superior high-temperature durability. This is because the alkoxy group of the silane coupling agent undergoes hydrolysis to become a silanol group, which reacts with the hydroxyl groups on the surface of the adherend (e.g., glass). Therefore, when the adhesive composition of this disclosure contains a silane coupling agent, the resulting adhesive layer exhibits improved adhesion to the adherend (e.g., glass), thus demonstrating superior high-temperature durability.

[0087] The type of silane coupling agent is not particularly limited. Examples of silane coupling agents include polymerizable unsaturated group-containing silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane; thiol group-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; epoxy group-containing silane compounds such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane compounds such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; and tris-(3-trimethoxysilylpropyl)isocyanurate. Examples of silane coupling agents include silane compounds having multiple reactive functional groups such as polymerizable unsaturated groups, thiol groups, epoxy groups, and amino groups (so-called polyfunctional silane compounds).

[0088] Commercially available silane coupling agents can be used. Examples of commercially available silane coupling agents include "KBM-803", "KBM-802", "X-41-1810", "X-41-1811", "X-41-1805", "X-41-1818", "KBM-403", "KBM-303", "KBM-402", "KBE-402", "KBE-403", "X-41-1053", "X-41-1056", "KBM-9659", "KBE-9007N", and "KBM-573" (all product names) manufactured by Shin-Etsu Chemical Co., Ltd.

[0089] The adhesive composition of this disclosure may contain only one silane coupling agent or may contain two or more silane coupling agents.

[0090] The content of the silane coupling agent in the adhesive composition of this disclosure is not particularly limited, but is preferably 0.1 to 1 part by mass, more preferably 0.1 to 0.8 parts by mass, and even more preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of the specific (meth)acrylic copolymer.

[0091] [Organic solvents] The adhesive composition of this disclosure may contain an organic solvent. The adhesive composition of this disclosure may have improved applicability and pot life when it contains an organic solvent. Examples of organic solvents include those similar to those used in the polymerization reaction of the specific (meth)acrylic copolymers described above.

[0092] If the adhesive composition of this disclosure contains an organic solvent, it may contain only one organic solvent or two or more organic solvents.

[0093] If the adhesive composition of this disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be set as appropriate depending on the purpose.

[0094] [Other ingredients] The adhesive composition of this disclosure may, if necessary, contain components other than those described above (so-called other components), as long as they do not impair its effect. Other components include, for example, polymers other than specific (meth)acrylic copolymers, crosslinking catalysts, antioxidants, light stabilizers (e.g., UV absorbers), and various other additives.

[0095] If the adhesive composition of this disclosure contains other components, the content of these other components can be set as appropriate, as long as it does not impair the effects of the adhesive composition of this disclosure.

[0096] <<Applications of Adhesive Compositions>> The uses of the adhesive composition disclosed herein are not particularly limited. The adhesive composition of this disclosure is suitable for use in optical films (preferably polarizing plates) because it exhibits excellent high-temperature durability, processability, and warping suppression. Specific applications of the adhesive composition disclosed herein include bonding polarizing plates to glass substrates of liquid crystal cells, and bonding optical films to each other.

[0097] [Adhesive sheet] The adhesive sheet of this disclosure comprises a substrate and an adhesive layer provided on at least one side of the substrate and formed of the adhesive composition of this disclosure as described above. That is, the adhesive sheet of this disclosure has a structure in which the substrate and the adhesive layer formed of the adhesive composition of this disclosure are laminated together. The adhesive sheet of this disclosure comprises an adhesive layer formed by the adhesive composition of this disclosure, and is therefore less prone to wrinkling, peeling, and foaming even when placed in a high-temperature environment, and has excellent high-temperature durability. Furthermore, because the adhesive sheet of this disclosure comprises an adhesive layer formed by the adhesive composition of this disclosure, the adhesive layer is less likely to protrude even when the adhesive sheet is cut, and has excellent processability. In addition, because the adhesive sheet of this disclosure comprises an adhesive layer formed by the adhesive composition of this disclosure, it is less likely to cause warping of the adherend in a high-temperature environment.

[0098] The substrate is not particularly limited, as long as it can form an adhesive layer on it. Examples of substrates 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., triacetylcellulose), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluororesins.

[0099] The side of the substrate on which the adhesive layer is provided may be subjected to surface treatment such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatment) from the viewpoint of improving the adhesion between the substrate and the adhesive layer.

[0100] The base material may contain various additives such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, and fillers. The base material may have a pattern applied to part or all of it.

[0101] The substrate is preferably an optical film. The type of optical film is not particularly limited. Specific examples of optical films include polarizers, anti-glare (AG) polarizers, waveplates (e.g., half-wave plates and quarter-wave plates), phase difference films including the above waveplates, angle-of-view compensation films, optical compensation films, brightness-enhancing films, light guide plates, reflective films, anti-reflective films, prism sheets, lens sheets, diffusers, and transparent conductive films.

[0102] A polarizing plate is preferred as the optical film. A polarizing plate is composed of at least a polarizer, and may consist of a polarizer alone or a polarizer and a protective film laminated together. That is, a polarizing plate may have a single-layer structure with a polarizer alone, a two-layer structure with a protective film on one side of the polarizer, or a three-layer structure with protective films on both sides of the polarizer.

[0103] When the substrate is a polarizing plate, possible layer configurations include, for example, adhesive layer / polarizing plate [protective film / polarizer / protective film], adhesive layer / polarizing plate [phase difference film / polarizer / protective film], and adhesive layer / polarizing plate [phase difference film / protective film / polarizer / protective film].

[0104] The protective film may include films containing resins such as triacetylcellulose (TAC), polycycloolefin (COP), polyethylene terephthalate (PET), or polymethyl methacrylate (PMMA). For polarizers, for example, stretched polyvinyl alcohol (PVA) films impregnated with iodine are used. For example, a film containing a resin such as polycycloolefin (COP) can be used as a phase difference film.

[0105] The thickness of the substrate is not particularly limited, but is preferably 10 μm to 300 μm, more preferably 10 μm to 200 μm, and even more preferably 10 μm to 100 μm.

[0106] In this disclosure, "thickness of the substrate" refers to the average thickness of the substrate. The average thickness of the substrate is 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 gauge. The arithmetic mean of the measured values ​​is calculated, and this value is taken as the average thickness of the substrate.

[0107] The adhesive layer of the adhesive sheet of this disclosure includes a cured product of the adhesive composition of this disclosure. The cured product includes, for example, a crosslinked product of a specific (meth)acrylic copolymer that has been crosslinked and cured with the specific polyfunctional isocyanate compound described above.

[0108] The thickness of the adhesive layer is not particularly limited, but is generally 1 μm to 100 μm, preferably 3 μm to 50 μm, and more preferably 5 μm to 30 μm.

[0109] In this disclosure, "thickness of the adhesive layer" refers to the average thickness of the adhesive layer. The average thickness of the adhesive layer is 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 gauge. The arithmetic mean of the measured values ​​is calculated, and this value is taken as the average thickness of the adhesive layer.

[0110] In the adhesive sheet of this disclosure, the exposed surface of the adhesive layer may be protected by a release sheet. Generally, the release sheet protects the surface of the adhesive layer until the adhesive sheet is put into practical use and is peeled off at the time of use.

[0111] The release sheet is not particularly limited as long as it can be easily peeled off from the adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, and composite sheets made by laminating two or more of these materials, all of which have been surface-treated with a release agent on one or both sides (so-called easy-peel treatment). In this disclosure, a release sheet in which one or both sides of a resin film are subjected to a surface treatment with a release agent (so-called easy-release treatment) is also referred to as a "release film." Examples of release agents include silicone-based release agents (e.g., silicone), wax-based release agents (e.g., paraffin wax), and fluorine-based release agents (e.g., fluorine-based resins). Examples of resin films include polyester films, such as polyethylene terephthalate (PET) film. Examples of paper include high-quality paper and coated paper. The film thickness of the release sheet is not particularly limited, but is generally between 20 μm and 180 μm.

[0112] Examples of substrates to which the adhesive sheet of this disclosure is applied include glass substrates of liquid crystal cells and optical films.

[0113] [Method for making adhesive sheets] The method for producing the adhesive sheet described herein is not particularly limited. The adhesive sheet of this disclosure can be manufactured by known methods.

[0114] Examples of methods for producing the adhesive sheet of this disclosure include the following: By applying the adhesive composition of this disclosure to the easily adhesive treated surface of a substrate, a coating film is formed on the substrate. Next, by drying the formed coating film, an adhesive film is formed on the substrate. Then, the exposed surface of the formed adhesive film is placed on top of the easily peeled surface of a release sheet and bonded together, and then cured, thereby producing the adhesive sheet of this disclosure having a laminated structure of substrate / adhesive layer / release sheet.

[0115] Another possible method is the following: By applying the adhesive composition of this disclosure to the easily removable surface of a release sheet, a coating film is formed on the release sheet. Next, by drying the formed coating film, an adhesive film is formed on the release sheet. Then, the exposed surface of the formed adhesive film is placed on top of the easily removable surface of a substrate and bonded together, and then cured, thereby producing the adhesive sheet of this disclosure having a laminated structure of substrate / adhesive layer / release sheet.

[0116] The method of applying the adhesive composition is not particularly limited. Examples of known methods for applying adhesive compositions include gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, knife coaters, spray coaters, bar coaters, applicators, and the like. The amount of adhesive composition applied is not particularly limited and can be appropriately set, for example, depending on the thickness of the adhesive layer to be formed.

[0117] The method for drying the coating film is not particularly limited. Methods for drying the coated film include, for example, 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 according to the thickness of the coating film, the amount of organic solvent in the coating film, etc. One example of drying conditions is to use a hot air circulation dryer and blow air at 70°C to 120°C at a wind speed of 2 m / s to 10 m / s for 30 to 180 seconds.

[0118] One method of curing is to leave the product undisturbed 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%.

[0119] [Optical components] The optical component of this disclosure comprises, in this order, a glass substrate, an adhesive layer formed with the adhesive composition of this disclosure described above, and an optical film. Since the optical component of this disclosure comprises an adhesive layer formed with the adhesive composition of this disclosure described above, peeling and foaming are less likely to occur at the interface between the adhesive layer and the optical film and / or glass substrate even when placed in a high-temperature environment, and wrinkles tend to form in the adhesive layer and / or optical film. Furthermore, since the optical component of this disclosure comprises an adhesive layer formed with the adhesive composition of this disclosure described above, warping of the optical film tends to be less likely to occur even when placed in a high-temperature environment.

[0120] 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.

[0121] Examples of glass substrates include soda-lime glass, alkali-free glass, and glass coated with an ITO (Indium Tin Oxide) film.

[0122] The adhesive layer and optical film in the optical member of this disclosure are synonymous with the adhesive layer and optical film in the adhesive sheet of this disclosure, and the preferred embodiments are also the same; therefore, a detailed explanation is omitted here.

[0123] The optical components of this disclosure can be suitably used, for example, as components of a display device. Examples of display devices include liquid crystal displays and organic EL (Electro-Luminescence) displays.

[0124] The method for manufacturing the optical component described herein is not particularly limited. The optical component of this disclosure can be manufactured, for example, by using an optical film as a substrate, preparing an adhesive sheet of this disclosure by the method described above, and then bonding the adhesive layer of the adhesive sheet to a glass substrate.

[0125] [Display device] The display device of this disclosure comprises the optical component of this disclosure described above. Because the display device of this disclosure includes the optical components of this disclosure, peeling and foaming are less likely to occur at the interface between the adhesive layer and the optical film and / or glass substrate, even when placed in a high-temperature environment, and wrinkles tend to form in the adhesive layer and / or optical film. Furthermore, because the display device of this disclosure includes the optical components of this disclosure, warping of the optical film tends to be less likely to occur even when placed in a high-temperature environment.

[0126] Specific examples of display devices are as previously described. [Examples]

[0127] The adhesive compositions of this disclosure will be described in more detail below with reference to examples. This disclosure is not limited to the following examples unless it exceeds the spirit of the disclosure.

[0128] [Production of (meth)acrylic copolymers] [Manufacturing example A-1] In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 96.9 parts by mass of n-butyl acrylate [n-BA; alkyl acrylate monomer], 0.1 parts by mass of 2-hydroxyethyl acrylate [2HEA; monomer with hydroxyl groups], 3.0 parts by mass of acrylic acid [AA; monomer with carboxyl groups], and 70.0 parts by mass of ethyl acetate [organic solvent] were added and mixed to obtain a mixture, after which the reactor was purged with nitrogen. Next, the mixture in the reactor was heated to 70°C while stirring, and then 0.02 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] and 120.0 parts by mass of ethyl acetate were sequentially added to the mixture in the reactor and held for 6 hours to complete the polymerization reaction. Next, the solution obtained from the completion of the polymerization reaction was diluted with ethyl acetate to a solid content concentration of 18.5% by mass, cooled, and a solution of (meth)acrylic copolymer A-1 was obtained.

[0129] Here, "solid content concentration" refers to the mass ratio of (meth)acrylic copolymer A-1 to the solution of (meth)acrylic copolymer A-1. The same applies to each of the solutions of (meth)acrylic copolymers A-2 to A-19 prepared below.

[0130] [Manufacturing examples A-2 to A-9 and A-12 to A-19] In production examples A-2 to A-9 and A-12 to A-19, the monomer composition of the (meth)acrylic copolymer was changed to the monomer composition shown in Table 1, and the weight-average molecular weight of the (meth)acrylic copolymer was adjusted to the weight-average molecular weight shown in Table 1 by adjusting the amount of organic solvent and polymerization initiator used. The same procedure as in production example A-1 was followed to obtain solutions of (meth)acrylic copolymers A-2 to A-9 and A-12 to A-19, each with a solid content concentration of 18.5% by mass.

[0131] [Manufacturing Examples A-10 and A-11] In production examples A-10 and A-11, the same procedure as in production example A-1 was followed, except that the weight-average molecular weight of the (meth)acrylic copolymer was adjusted to the weight-average molecular weight shown in Table 1 by adjusting the amount of organic solvent and polymerization initiator used, to obtain solutions of (meth)acrylic copolymers A-10 and A-11, respectively, with a solid content concentration of 18.5% by mass.

[0132] Table 1 shows the monomer composition [unit: mass%] and weight-average molecular weight (Mw) of (meth)acrylic copolymers A-1 to A-19.

[0133] The weight-average molecular weights of (meth)acrylic copolymers A-1 to A-19 were measured using the same method as described above for measuring the weight-average molecular weight of specific (meth)acrylic copolymers.

[0134] Of the (meth)acrylic copolymers A-1 to A-19, (meth)acrylic copolymers A-1 to A-3, A-5 to A-7, A-10 to A-15, and A-18 correspond to the specified (meth)acrylic copolymers in this disclosure.

[0135] [Table 1]

[0136] Details of each monomer listed in Table 1 are as follows: <(meth)acrylate alkyl monomer> "n-BA": n-butyl acrylate "2EHA": 2-ethylhexyl acrylate "MA": Methyl acrylate "MMA": Methyl methacrylate <Monomers containing aromatic rings> "BzA": Benzyl acrylate "PhEA": Phenoxyethyl acrylate <Monomers containing hydroxyl groups> "2HEA": 2-hydroxyethyl acrylate "4HBA": 4-hydroxybutyl acrylate <Monomers containing a carboxyl group> "AA": Acrylic acid "MAA": Methacrylic acid

[0137] [Synthesis of polyfunctional isocyanate compounds] [Compound (A)] 100 parts by mass of polyethylene glycol (PEG) [product name: Polyethylene Glycol 2,000, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] and 25 parts by mass of diphenylmethane diisocyanate (MDI) [product name: Cosmonate® PH, manufactured by Mitsui Chemicals, Inc.] were mixed and stirred. After cooling the resulting mixture, short-step distillation (temperature: 100°C to 150°C, pressure: 0.01 MPa to 0.1 MPa) was performed until the MDI content in the mixture was less than 2.0% by mass to obtain compound (A) [reaction product of MDI and PEG]. The number-average molecular weight (Mn) of the obtained compound (A) was measured to be 2,500. The melting point of the obtained compound (A) was measured to be 50°C. The NCO content of the obtained compound (A) was measured to be 3.40% by mass.

[0138] [Compound (B)] 100 parts by mass of tetrahydrofuran (THF), 5.6 parts by mass of acetic anhydride, and 0.2 parts by mass of acetic acid were mixed with 3.5 parts by mass of zirconia silica catalyst [product name: Zirconia Silica Beads 0.2 mm, manufactured by Biomedical Science Co., Ltd.] and reacted at 40°C for 5 hours. The resulting mixture was filtered to remove the catalyst, and then batch distillation was performed under atmospheric pressure to remove most of the unreacted material. Next, batch distillation was performed under reduced pressure of 1.3 MPa to remove residual acetic anhydride and acetic acid, and then a small amount of nitrogen was introduced under further reduced pressure to remove volatile components. Through these operations, 37 parts by mass of polytetramethylene ether glycol (PTMG) with a molecular weight of 2,000 was obtained. The residual acetic anhydride and acetic acid were 0.1% by mass and 0.005% by mass, respectively. A methanol solution containing 35% by mass of PTMG and 0.2% by mass of calcium hydroxide was charged at 50 kg / hr into an atmospheric distillation column (upper diameter: 0.20 m, lower diameter: 0.5 m) equipped with an 8-stage theoretical rectification section packed with a ball ring at the top and 10-stage bubble trays at the bottom of the charging section, and operated at a reflux ratio of 15. The column was operated so that the methyl acetate concentration at the bottom was 0.003% by mass. Methyl acetate is a decomposition product of acetic anhydride produced during distillation. Next, the distillate [methyl acetate / methanol = 20 / 80 (mass ratio)] was withdrawn from the top of the column at 87 kg / hr, and the bottom liquid [PTMG / methanol = 60 / 40 (mass ratio)] was withdrawn from the bottom of the column. After cooling, the calcium hydroxide was removed by filtration, and the bottom liquid was introduced into a column packed with sulfonic acid type strong acid ion exchange resin [product name: SK1BH, manufactured by Mitsubishi Chemical Corporation] to remove dissolved Ca ions. The resulting solution was used as the raw material solution.

[0139] Next, a 1 L (liter; hereafter the same) round-bottom four-necked flask, to which an electromagnetic induction stirrer and a distillation unit were connected, was subjected to continuous distillation. The raw material solution was discharged at a rate of 1 kg / hr using a pump, while the liquid was continuously withdrawn from the bottom of the flask at a rate of 620 g / hr using a pump. The distillation was carried out under atmospheric pressure, with an oil bath temperature of 100°C and a stirring speed of 500 rpm. The liquid in the flask (first stage bottom output) recovered by the continuous distillation described above was passed through a heat exchanger heated to 130°C, and then loaded into a packed column with six theoretical stages, consisting of a 50mm inner diameter column packed with 600mm of 5mm-sized Raschig rings. After loading, nitrogen heated to 130°C was passed through the bottom of the packed column. The nitrogen flow rate was set to 5.6 L / hr using a mass flow control before preheating. Analysis of the bottom liquid (second stage bottom liquid) extracted from the packed column revealed that it was polytetramethylene ether glycol (PTMG) with a molecular weight of 1940, as measured by gel permeation chromatography (GPC). The methanol content was below the detection limit (0.002%) of gas chromatography (GC).

[0140] 454.55 parts by mass of the obtained polytetramethylene ether glycol (PTMG), 1.60 parts by mass of methanol, and 57.44 parts by mass of diphenylmethane diisocyanate (MDI) [trade name: Cosmonate® PH, manufactured by Mitsui Chemicals, Inc.] were mixed and stirred. After cooling the resulting mixture, short-step distillation (temperature: 100°C to 150°C, pressure: 0.01 MPa to 0.1 MPa) was performed until the MDI content in the mixture was less than 2.0% by mass to obtain compound (B) [reaction product of MDI and PTMG]. The number-average molecular weight (Mn) of the obtained compound (B) was measured to be 10,000. The melting point of the obtained compound (B) was measured to be 10°C. The NCO content of the obtained compound (B) was measured to be 0.84% ​​by mass.

[0141] [Compound (C)] 888.89 parts by mass of polytetramethylene ether glycol (PTMG) obtained in the production of "Compound (B)" above, 0.64 parts by mass of methanol, and 111.33 parts by mass of diphenylmethane diisocyanate (MDI) [trade name: Cosmonate® PH, manufactured by Mitsui Chemicals, Inc.] were mixed and stirred. After cooling the resulting mixture, short-step distillation (temperature: 100°C to 150°C, pressure: 0.01 MPa to 0.1 MPa) was performed until the MDI content in the mixture was less than 2.0% by mass to obtain compound (C) [reaction product of MDI and PTMG]. The number-average molecular weight (Mn) of the obtained compound (C) was measured to be 50,000. The melting point of the obtained compound (C) was measured to be 10°C. The NCO content of the obtained compound (C) was measured to be 0.17% by mass.

[0142] [Compound (D)] 100 parts by mass of polytetramethylene ether glycol (PTMG) obtained in the production of "Compound (B)" above and 22 parts by mass of isophorone diisocyanate (IPDI) [product name: Desmodule® I, manufactured by Sumika Covestro Urethane Co., Ltd.] were mixed and stirred. After cooling the resulting mixture, short-step distillation (temperature: 100°C to 150°C, pressure: 0.01 MPa to 0.1 MPa) was performed until the IPDI content in the mixture was less than 2.0% by mass to obtain compound (D) [reaction product of IPDI and PTMG]. The number-average molecular weight (Mn) of the obtained compound (D) was measured to be 2,500. The melting point of the obtained compound (D) was measured to be 10°C. The NCO content of the obtained compound (D) was measured to be 3.30% by mass.

[0143] [Compound (E)] 100 parts by mass of polytetramethylene ether glycol (PTMG) obtained in the production of "Compound (B)" above and 20 parts by mass of xylylene diisocyanate (XDI) [trade name: m-Xylyene Diisocyanate, manufactured by Tokyo Chemical Industry Co., Ltd.] were mixed and stirred. After cooling the resulting mixture, short-step distillation (temperature: 100°C to 150°C, pressure: 0.01 MPa to 0.1 MPa) was performed until the XDI content in the mixture was less than 2.0% by mass to obtain compound (E) [reaction product of XDI and PTMG]. The number-average molecular weight (Mn) of the obtained compound (E) was measured to be 2,500. The melting point of the obtained compound (E) was measured to be 20°C. The NCO content of the obtained compound (E) was measured to be 3.75% by mass.

[0144] [Compound (F)] 100 parts by mass of tetramethylene glycol [trade name: 1,4-Butanediol, manufactured by Tokyo Chemical Industry Co., Ltd.] and 500 parts by mass of diphenylmethane diisocyanate (MDI) [trade name: Cosmonate® PH, manufactured by Mitsui Chemicals, Inc.] were mixed and stirred. After cooling the resulting mixture, short-step distillation (temperature: 100°C to 150°C, pressure: 0.01 MPa to 0.1 MPa) was performed until the MDI content in the mixture was less than 2.0% by mass to obtain compound (F) [reaction product of MDI and tetramethylene glycol]. The number-average molecular weight (Mn) of the obtained compound (F) was measured to be 600. The melting point of the obtained compound (F) was measured to be 30°C. The NCO content of the obtained compound (F) was measured to be 14.0% by mass.

[0145] [Compound (G)] 1081.08 parts by mass of polytetramethylene ether glycol (PTMG) obtained in the production of "Compound (B)" above, 0.64 parts by mass of methanol, and 135.41 parts by mass of diphenylmethane diisocyanate (MDI) [trade name: Cosmonate® PH, manufactured by Mitsui Chemicals, Inc.] were mixed and stirred. After cooling the resulting mixture, short-step distillation (temperature: 100°C to 150°C, pressure: 0.01 MPa to 0.1 MPa) was performed until the MDI content in the mixture was less than 2.0% by mass to obtain compound (G) [reaction product of MDI and PTMG]. The number-average molecular weight (Mn) of the obtained compound (G) was measured to be 60,000. The melting point of the obtained compound (H) was measured to be 10°C. The NCO content of the obtained compound (G) was measured to be 0.14% by mass.

[0146] The number-average molecular weight (Mn) of compounds (A) to (G) was measured using the same method as the method for measuring the number-average molecular weight (Mn) of the specific polyfunctional isocyanate compounds described above. The melting points of compounds (A) to (G) were measured using the same method as described above for measuring the melting points of specific polyfunctional isocyanate compounds. The NCO content of compounds (A) to (G) was measured using the same method as the method for measuring the NCO content of specific polyfunctional isocyanate compounds described above.

[0147] [Preparation of adhesive composition] [Example 1] 540.5 parts by mass (100 parts by mass as solids) of a solution of (meth)acrylic copolymer A-1, 1.0 part by mass (1.0 part by mass as solids) of Coronate (registered trademark) 4370 [trade name, reaction product of diphenylmethane diisocyanate (MDI) and polytetramethylene ether glycol (PTMG), solid content concentration: 100% by mass, manufactured by Tosoh Corporation] as a polyfunctional isocyanate compound, 0.3 parts by mass (0.3 parts by mass as solids) of X-41-1810 [trade name, thiol group-containing silane compound, solid content concentration: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.] as a silane coupling agent, and an appropriate amount of ethyl acetate [organic solvent] were thoroughly mixed to obtain the adhesive composition of Example 1.

[0148] [Examples 2-26] Except for changing the composition of the adhesive composition to the composition shown in Table 2 in Example 1, the same procedure as in Example 1 was followed to obtain the adhesive compositions of Examples 2 to 26.

[0149] [Comparative Examples 1-15] The same procedure as in Example 1 was followed, except that the composition of the adhesive composition was changed to the composition shown in Table 3, to obtain the adhesive compositions of Comparative Examples 1 to 15.

[0150] [Fabrication of polarizing plates with adhesive layer] 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 easy-release treatment) was coated with the adhesive composition prepared above to form a coating film. The amount of adhesive composition applied was such that the thickness of the adhesive film described later was 10 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 an adhesive film with a thickness of 10 μm on the release film. Next, the exposed surface of the formed adhesive film was laminated to one side of the TAC layer of a polarizing plate (thickness: 75 μm) having a triacetylcellulose (TAC) layer / polyvinyl alcohol (PVA) layer containing a polarizer / TAC layer. Next, the laminate obtained by lamination was left to stand for 6 days in an environment with an ambient temperature of 23°C and 65% RH to cure the adhesive film. As described above, an adhesive-coated polarizing plate (thickness: 123 μm) having the structure of release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer) was fabricated.

[0151] [evaluation] 1.High temperature durability (1) Preparation of samples for durability evaluation The polarizing plate with the adhesive layer prepared as described above was cut so that its long side was at 0° with respect to the absorption axis of the polarizing plate, and a test piece measuring 67.6 mm × 106.9 mm (long side) was prepared. Next, the release film was peeled off the test piece. The surface of the adhesive layer exposed by peeling was placed in contact with one side of a glass plate [Type: Soda glass, manufactured by Matsunami Glass Industry Co., Ltd.], and then the test piece and the glass plate were bonded together by pressing them with a laminator. As described above, a sample for durability evaluation was prepared, having the following configuration: glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0152] (2) Durability evaluation test The durability evaluation sample prepared as described above was subjected to a processing temperature of 50°C and a processing pressure of 5 kg / cm². 2After autoclaving for 20 minutes under the specified conditions, the samples were left to stand for 24 hours in an environment with an ambient temperature of 23°C and 50% RH. The durability evaluation samples, after this 24-hour standing period, were then left to stand for 500 hours in an environment with an ambient temperature of 105°C and 10% RH or less. The condition of the durability evaluation samples after this 500-hour standing period was visually observed, and evaluated according to the evaluation criteria described below. The results are shown in Tables 2 and 3. In the evaluation criteria below, "A," "B," and "C" represent usable levels, with "A" being the most preferable.

[0153] -Evaluation Criteria- A: No wrinkles, peeling, or foaming were observed in the durability evaluation samples. B: Slight wrinkles, peeling, and foaming were observed at the edges of the durability evaluation samples, but these were at levels that did not pose any practical problems. C: At least one of the following was observed at the edges of the durability evaluation sample: wrinkles, peeling, and foaming, but these were at a level acceptable for practical use. D: At least one of the following was clearly observed at the edge of the durability evaluation sample: wrinkles, peeling, or foaming, or foaming was observed at a location other than the edge of the durability evaluation sample.

[0154] 2. Processability The polarizing plate with adhesive layer prepared as described above was cut to obtain a test specimen measuring 100 mm x 100 mm. Next, the test specimen was left to stand in a room temperature (20°C) environment for 24 hours. After standing for 24 hours, the test specimen was subjected to edge-face processing using an edge-face processing machine [model: MCPB-600A-SP, manufactured by Megalo Technica Co., Ltd.] with a blade rotation speed of 3000 rpm and a cutting pitch of 200 μm. The processed edge of the test sample after edge-face processing was observed using a digital microscope [model: VHX7000, magnification: 500x, manufactured by Keyence Corporation], and the length of the excess adhesive layer was measured. The specific measurement method will be explained with reference to Figure 1. Figure 1 shows an example of the state of the processed end surface of test piece 100 after end surface processing. At the processed end surface of test sample 100, which has a layer structure of release film 10 / adhesive layer 20 / polarizing plate 30, the interface between the adhesive layer 20 and the polarizing plate 30 was defined as point 0, and the maximum length of the adhesive layer overhang was calculated. The evaluation was then performed according to the evaluation criteria below. The results are shown in Tables 2 and 3. In the evaluation criteria below, "A," "B," and "C" represent usable levels, with "A" being the most preferable.

[0155] -Evaluation Criteria- A: The maximum length of the adhesive layer overhang was less than 1 μm. B: The maximum length of the adhesive layer overhang was in the range of 1 μm or more and less than 5 μm. C: The maximum length of the adhesive layer overhang was in the range of 5 μm or more and less than 10 μm. D: The maximum length of the adhesive layer overhang was 10 μm or more.

[0156] 3. Suppression of warping (1) Preparation of samples for warping evaluation The polarizing plate with adhesive layer prepared as described above was cut so that its long side was at 0° to the absorption axis of the polarizing plate, and a test specimen measuring 120 mm × 340 mm (long side) was prepared. Next, the release film was peeled off the test specimen. The surface of the adhesive layer exposed by peeling was placed in contact with the entire surface of one side of a glass plate [Type: soda glass, Thickness: 1.0 mm, Size: 100 mm × 320 mm, Manufactured by Matsunami Glass Industry Co., Ltd.], and then pressed together using a laminator. After pressing, the excess portion of the polarizing plate with adhesive layer that protruded was cut and removed to create a laminate. The prepared laminate was subjected to a processing temperature of 50°C and a processing pressure of 5 kg / cm². 2 After autoclaving under these conditions for 20 minutes, the samples were left to stand for 1 hour in an environment with an ambient temperature of 23°C and 50% RH. Samples for warpage evaluation were prepared in this manner.

[0157] (2) Warping evaluation test The sample prepared above for warpage evaluation was left at an ambient temperature of 85°C for 100 hours. After this period, the sample was placed on a smooth surface at an ambient temperature of 23°C and 50% RH, and the amount of warpage at both ends of the sample was measured using a laser displacement meter (model number: LK-H027K, manufactured by Keyence Corporation). The average of the measured values ​​at both ends was calculated and defined as the amount of warpage. Based on the amount of warpage, evaluation was performed according to the evaluation criteria below. The results are shown in Tables 2 and 3. If evaluation was not possible, "-" is indicated. In the evaluation criteria below, "A," "B," and "C" represent usable levels, with "A" being the most preferable.

[0158] -Evaluation Criteria- A: The amount of curvature was less than 0.1 cm. B: The amount of curvature was in the range of 0.1 cm or more and less than 0.5 cm. C: The amount of warping was in the range of 0.5 cm or more and less than 1.0 cm. D: The amount of curvature was 1.0 cm or more.

[0159] [Table 2]

[0160] [Table 3]

[0161] Details of the commercially available products listed in Tables 2 and 3 are as follows: <Polyfunctional isocyanate compounds> "Coronate 4370" [Product name, reaction product of diphenylmethane diisocyanate (MDI) and polytetramethylene ether glycol (PTMG), solid content concentration: 100% by mass, NCO content (catalog value): 15.0% by mass, manufactured by Tosoh Corporation] "Samplen P-665" [Product name, reaction product of tolylene diisocyanate (TDI) and polytetramethylene ether glycol (PTMG), NCO content on a solids basis (catalog value): 6.15% by mass, manufactured by Sanyo Chemical Industries, Ltd.] "Samplen P-870" [Product name, reaction product of hexamethylene diisocyanate (HMDI) and polytetramethylene ether glycol (PTMG), NCO content on a solids basis (catalog value): 12.0% by mass, manufactured by Sanyo Chemical Industries, Ltd.] "Takenate D-140N" [Product name, reaction product of isophorone diisocyanate (IPDI) and trimethylolpropane (TMP), solid content: 75% by mass, NCO content (catalog value): 10.5% by mass, manufactured by Mitsui Chemicals, Inc.] "Coronate L-45E" [Product name, reaction product of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, NCO content (catalog value): 7.9% by mass, manufactured by Tosoh Corporation] "Samplen C-810" [Product name, reaction product of hexamethylene diisocyanate (HMDI) and polytetramethylene ether glycol (PTMG), NCO content on a solids basis (catalog value): 9.78% by mass, manufactured by Sanyo Chemical Industries, Ltd.] "Cosmonate PH" [Product name, diphenylmethane diisocyanate (MDI), solid content concentration: 100% by mass, NCO content (theoretical value): 33.58% by mass, manufactured by Mitsui Chemicals, Inc.] The above-mentioned "Coronate," "Samplen," "Takenate," and "Cosmonate" are all registered trademarks.

[0162] <Silane coupling agent> "X-41-1810" [Product name, thiol group-containing silane compound, manufactured by Shin-Etsu Chemical Co., Ltd.] "X-41-1053" [Product name, epoxy group-containing silane compound, manufactured by Shin-Etsu Chemical Co., Ltd.]

[0163] In Tables 2 and 3, the values ​​listed in the "Amount" column are all based on solid content. In Tables 2 and 3, "-" means that there is no corresponding entry in that column. For example, "-" in the melting point column means that there is no melting point. The number-average molecular weight (indicated as "Mn" in the tables) of the polyfunctional isocyanate compounds listed in Tables 2 and 3 was measured using the same method as the method for measuring the number-average molecular weight of the specific polyfunctional isocyanate compounds described above. The melting points of the polyfunctional isocyanate compounds listed in Tables 2 and 3 were measured using the same method as described above for measuring the melting points of specific polyfunctional isocyanate compounds.

[0164] The results shown in Table 2 clearly demonstrate that the adhesive layers formed by the adhesive compositions of Examples 1 to 26 exhibit excellent high-temperature durability, processability, and warp suppression. On the other hand, as shown in Table 3, the adhesive layers formed by the adhesive compositions of Comparative Examples 1 to 15 were found to be inferior to the adhesive layers formed by the adhesive compositions of the Examples in at least one evaluation item of high-temperature durability, processability, and warping suppression. [Explanation of symbols]

[0165] 10: Release film, 20: Adhesive layer, 30: Polarizing plate, 100: Test sample (polarizing plate with adhesive layer), X: Maximum overhang of the adhesive layer

Claims

1. A (meth)acrylic copolymer comprising constituent units derived from monomers having hydroxyl groups and constituent units derived from monomers having carboxyl groups, wherein the content of constituent units derived from monomers having hydroxyl groups is greater than 0% by mass and less than 0.5% by mass relative to the total constituent units, and which does not contain constituent units derived from monomers having aromatic rings, A polyfunctional isocyanate compound having a number-average molecular weight of 1,000 or more and 50,000 or less, and a melting point of 10°C or more and 90°C or less, Silane coupling agent and An adhesive composition containing the following:

2. The adhesive composition according to claim 1, wherein the weight-average molecular weight of the (meth)acrylic copolymer is 400,000 or more and 2,500,000 or less.

3. The adhesive composition according to claim 1, wherein the content of constituent units derived from the monomer having the carboxyl group in the (meth)acrylic copolymer is greater than 0.5% by mass and less than or equal to 15.0% by mass with respect to the total number of constituent units.

4. The adhesive composition according to claim 1, wherein the content of the polyfunctional isocyanate compound is 0.6 parts by mass or more and 20.0 parts by mass or less per 100 parts by mass of the (meth)acrylic copolymer.

5. The adhesive composition according to claim 1, wherein the polyfunctional isocyanate compound is an aromatic polyfunctional isocyanate compound.

6. The adhesive composition according to claim 1, wherein the polyfunctional isocyanate compound is at least one selected from the group consisting of diphenylmethane diisocyanate compounds and tolylene diisocyanate compounds.

7. Substrate and An adhesive layer provided on at least one side of the substrate and formed with the adhesive composition according to any one of claims 1 to 6, An adhesive sheet equipped with [a specific feature].

8. The adhesive sheet according to claim 7, wherein the substrate is an optical film.

9. The adhesive sheet according to claim 8, wherein the optical film is a polarizing plate.

10. Glass substrate and An adhesive layer formed by the adhesive composition according to any one of claims 1 to 6, Optical film and An optical component comprising the elements in this order.

11. A display device comprising the optical member described in claim 10.

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