Adhesive composition and laminate

Abstract

To provide: an adhesive composition capable of forming an adhesive layer which has excellent adhesion to a low moisture-permeable base material and can suppress shrinkage of the base material which may occur when placed in a high temperature environment, and foaming and peeling which may occur when placed in an environment where low and high temperatures are repeated; and a laminate.SOLUTION: There are provided: an adhesive composition which comprises a (meth)acrylic polymer having a hydroxyl group and a carboxy group, a tolylene diisocyanate-based compound having an average isocyanate group number in the range of 2.5 or more and 3.0 or less in one molecule and a diphenylmethane diisocyanate-based compound having an average isocyanate group number in the range of 2.0 or more and less than 2.5 in one molecule, wherein the content mass ratio of the diphenylmethane diisocyanate-based compound to the tolylene diisocyanate-based compound is 2 or less; and its application.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an adhesive composition and a laminate.

Background Art

[0002] Generally, a liquid crystal display device includes a liquid crystal cell in which a liquid crystal layer is sandwiched between two glass substrates, and polarizing plates disposed on both surfaces of the liquid crystal cell. For bonding the liquid crystal cell and the polarizing plates, a (meth)acrylic adhesive composition is frequently used from the viewpoint of ensuring the visibility of the liquid crystal display device.

[0003] For example, Patent Document 1 discloses a (meth)acrylic adhesive composition suitable for use as an optical member such as a polarizing plate, which comprises a (meth)acrylic acid ester copolymer and an adduct of a polyisocyanate compound, wherein the content ratio of a bifunctional adduct to an adduct having three or more functional groups is from 100:0 to 10:90 by weight, and a crosslinking agent is included.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Traditionally, triacetylcellulose (TAC) film has been used as the substrate for polarizing plates. However, from the viewpoint of suppressing the deterioration of polarizers due to the adsorption of moisture from the atmosphere, low-moisture-permeability films such as polymethyl methacrylate (PMMA) film and cycloolefin resin (COP) film are increasingly being used. When TAC film is used as the substrate for polarizing plates, the adhesion between the substrate and the adhesive layer is excellent because polar groups are present on the substrate surface due to saponification treatment of the substrate surface. However, PMMA and COP have low polarity due to their molecular structure and do not have polar groups, so the adhesion between the substrate and the adhesive layer is inferior compared to that of TAC. Polarizing plates are constructed by laminating materials with different shrinkage rates and are prone to shrinkage due to temperature changes. With the recent increase in the size and narrowing of bezels of displays, there is a growing demand for adhesive compositions used in polarizing plates that can form an adhesive layer that can better suppress the shrinkage of the polarizing plate that may occur when placed in harsh environments. However, if the adhesion between the substrate and the adhesive layer is poor, the adhesive layer cannot follow the shrinkage of the polarizing plate, causing stress on the adhesive layer due to the shrinkage of the polarizing plate, which can lead to the adhesive layer peeling off from the liquid crystal cell. In addition, if the adhesion between the substrate and the adhesive layer is poor, the adhesive layer cannot suppress outgassing from the polarizing plate, which can lead to foaming.

[0006] This disclosure is made in light of the circumstances described above. The problem that one embodiment of this disclosure aims to solve is to provide an adhesive composition that can form an adhesive layer that has excellent adhesion to a low-moisture-permeability substrate and can effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment where low and high temperatures are repeatedly alternated. The problems that other embodiments of this disclosure aim to solve are to provide a laminate comprising an adhesive layer that exhibits excellent adhesion to a low-moisture-permeability substrate and can effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment where low and high temperatures are repeatedly alternating. [Means for solving the problem]

[0007] The following are examples of specific means for solving the problem: <1> An adhesive composition comprising a (meth)acrylic polymer having hydroxyl groups and carboxyl groups, a tolylene diisocyanate compound having an average number of isocyanate groups per molecule in the range of 2.5 to 3.0, and a diphenylmethane diisocyanate compound having an average number of isocyanate groups per molecule in the range of 2.0 to less than 2.5, wherein the mass ratio of the diphenylmethane diisocyanate compound to the tolylene diisocyanate compound is 2 or less. <2> The above (meth)acrylic polymer contains 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 in the above (meth)acrylic polymer is in the range of 0.1% by mass or more and 5.0% by mass or less relative to the total constituent units, and the content of constituent units derived from monomers having carboxyl groups in the above (meth)acrylic polymer is in the range of 0.1% by mass or more and 3.0% by mass or less relative to the total constituent units. <1> The adhesive composition described above. <3> The content of the above-mentioned tolylene diisocyanate compound is in the range of 0.1 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the above-mentioned (meth)acrylic polymer, and the content of the above-mentioned diphenylmethane diisocyanate compound is in the range of 0.01 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of the above-mentioned (meth)acrylic polymer. <1> or <2> The adhesive composition described above. <4> The weight-average molecular weight of the above (meth)acrylic polymer is in the range of 400,000 to 2,500,000. <1> ~ <3> An adhesive composition as described in any one of the following. <5> A polarizing plate having a layer on one or both sides containing at least one resin selected from the group consisting of (meth)acrylic resins and cycloolefin resins, and provided on the above layer, <1> ~ <4> A laminate comprising an adhesive layer formed by an adhesive composition according to any one of the above. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, an adhesive composition is provided that can form an adhesive layer that exhibits excellent adhesion to a low-moisture-permeability substrate and effectively suppresses shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment where low and high temperatures are repeatedly alternating. According to other embodiments of the present disclosure, a laminate is provided which has excellent adhesion to a low-permeability substrate and which can effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment where low and high temperatures are repeatedly alternated. [Modes for carrying out the invention]

[0009] The adhesive compositions and laminates of this disclosure will be described in detail below. The descriptions of the requirements below may be based on typical embodiments of this disclosure, but this disclosure is not limited to such embodiments and may be modified as appropriate within the scope of the purposes of this disclosure.

[0010] In this disclosure, a numerical range indicated using "~" means a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0011] In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0012] In this disclosure, the amount of each component in the adhesive composition means the total amount of any multiple substances present in the adhesive composition, unless otherwise specified, if there are multiple substances corresponding to each component in the adhesive composition.

[0013] In this disclosure, "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group. In this disclosure, "(meth)acrylic polymer" means a polymer 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.

[0014] 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."

[0015] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0016] In this disclosure, "polymer" and "polymer" are synonymous.

[0017] [Adhesive composition] The adhesive composition of this disclosure comprises a (meth)acrylic polymer having hydroxyl groups and carboxyl groups, a tolylene diisocyanate compound having an average number of isocyanate groups per molecule in the range of 2.5 to 3.0, and a diphenylmethane diisocyanate compound having an average number of isocyanate groups per molecule in the range of 2.0 to less than 2.5, wherein the mass ratio of the diphenylmethane diisocyanate compound to the tolylene diisocyanate compound is 2 or less. The adhesive composition of this disclosure has excellent adhesion to low-moisture permeability substrates and can form an adhesive layer that effectively suppresses shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment where low and high temperatures are repeatedly alternated.

[0018] Although the reason why the adhesive composition of the present disclosure can exhibit such an effect is not clear, the inventors speculate as follows. However, the following speculation does not limit the interpretation of the adhesive composition of the present disclosure and is for illustrative purposes only.

[0019] The adhesive composition of the present disclosure contains, as a crosslinking agent for crosslinking a (meth)acrylic polymer having a hydroxyl group and a carboxyl group, a tolylene diisocyanate compound (hereinafter, also referred to as a "trifunctional TDI-based compound") having an average number of isocyanate groups per molecule in the range of 2.5 or more and 3.0 or less, and a diphenylmethane diisocyanate compound (hereinafter, also referred to as a "bifunctional MDI-based compound") having an average number of isocyanate groups per molecule in the range of 2.0 or more and less than 2.5, in a specific ratio. In the adhesive composition of the present disclosure, the trifunctional TDI-based compound forms a three-dimensional network structure by a crosslinking reaction with a (meth)acrylic polymer having a hydroxyl group and a carboxyl group. The crosslinking by the trifunctional TDI-based compound strengthens the entanglement of the molecular chains of the (meth)acrylic polymer and exhibits high cohesive force in the adhesive layer. This high cohesive force is considered to contribute to the suppression of the shrinkage of the substrate by the adhesive layer. On the other hand, in the crosslinking by only the trifunctional crosslinking agent, since the crosslinked structure is fixed by the three-dimensional network structure, the formed adhesive layer has poor flexibility and poor adhesion to the substrate. In this regard, in the adhesive composition of the present disclosure, in addition to the trifunctional TDI-based compound, a bifunctional MDI-based compound is used, so that a two-dimensional network structure by the bifunctional MDI-based compound is formed, and the flexibility of the adhesive layer is improved. Due to this improvement in flexibility, the adhesion of the adhesive layer to a low moisture permeability substrate is considered to be excellent. And in the adhesive composition of the present disclosure, since the trifunctional TDI-based compound and the bifunctional MDI-based compound are used in combination at a specific ratio, it is considered that appropriate flexibility and appropriately high cohesive force are imparted to the formed adhesive layer in a balanced manner. Furthermore, crosslinking with a bifunctional MDI compound results in a moderately rigid crosslink because the MDI compound has two aromatic rings. As a result, the formed adhesive layer is given appropriate elasticity. In addition, crosslinking with a bifunctional MDI compound causes steric hindrance due to the aromatic rings, which widens the crosslinking structure at the crosslinking site. As a result, the formed adhesive layer is given appropriate stress relaxation properties. The adhesive layer formed by the adhesive composition of this disclosure has appropriate elasticity and appropriate stress relaxation properties, and is therefore considered to be able to effectively suppress shrinkage, foaming, and peeling of the substrate that may occur when placed in a harsh environment.

[0020] Incidentally, as a method for imparting flexibility to the formed adhesive layer, one could consider using hexamethylene diisocyanate (HMDI) compounds, which are bifunctional crosslinking agents and structurally flexible aliphatic isocyanate compounds. However, HMDI compounds have lower reactivity compared to TDI and MDI compounds. Similarly, xylylene diisocyanate (XDI) compounds, in which the isocyanate group is bonded to the aromatic ring via a methylene group, also have lower reactivity compared to TDI and MDI compounds. This is thought to be because the electron-donating effect of the alkylene group weakens the polarization of the isocyanate group, thereby reducing the nucleophilic reactivity of the carbon atom of the isocyanate group. Therefore, when bifunctional crosslinking agents, such as HMDI and XDI compounds, are used in combination with trifunctional TDI compounds, the trifunctional TDI compounds react quickly first, forming a crosslinked structure consisting only of a three-dimensional network structure. Consequently, the bifunctional crosslinking agents, such as HMDI and XDI compounds, which react afterward, only reinforce the structure crosslinked by the TDI compounds and do not contribute to imparting flexibility to the adhesive layer. In contrast, the adhesive composition of this disclosure uses a bifunctional MDI compound that has a reactivity as high as that of a trifunctional TDI compound. Therefore, it is considered that the trifunctional TDI compound and the bifunctional MDI compound act almost simultaneously on the (meth)acrylic polymer having hydroxyl and carboxyl groups. As a result, it is possible to form a three-dimensional network crosslinked structure by the trifunctional TDI compound while moderately promoting two-dimensional crosslinking by the bifunctional MDI compound, thereby forming an adhesive layer that combines moderate flexibility with moderately high cohesive force.

[0021] From the above, it is presumed that the adhesive layer formed by the adhesive composition of this disclosure has excellent adhesion to low-moisture-permeability substrates and can effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment where low and high temperatures are repeatedly alternating.

[0022] In this disclosure, "(meth)acrylic polymers having hydroxyl groups and carboxyl groups" are also referred to as "specific (meth)acrylic polymers." In this disclosure, "tolylene diisocyanate compounds having an average number of isocyanate groups in one molecule in the range of 2.5 or more and 3.0 or less" are also referred to as "specific tolylene diisocyanate compounds." In this disclosure, "diphenylmethane diisocyanate compounds having an average number of isocyanate groups in one molecule in the range of 2.0 or more and less than 2.5" are also referred to as "specific diphenylmethane diisocyanate compounds."

[0023] [Specific (meth)acrylic polymers] The adhesive composition of this disclosure comprises a (meth)acrylic polymer having hydroxyl groups and carboxyl groups [i.e., a specific (meth)acrylic polymer]. The hydroxyl groups and carboxyl groups in the specific (meth)acrylic polymer can crosslink with the isocyanate groups of the specific tolylene diisocyanate compounds and specific diphenylmethane diisocyanate compounds described later. The adhesive composition of this disclosure may contain only one specific (meth)acrylic polymer, or it may contain two or more specific polymers.

[0024] The specific (meth)acrylic polymer may be a homopolymer or a copolymer. If the specific (meth)acrylic polymer is a copolymer, the copolymer may be a copolymer of two or more (meth)acrylic monomers, or a copolymer of a (meth)acrylic monomer and a monomer other than a (meth)acrylic monomer. The specific (meth)acrylic polymer may be, for example, a (meth)acrylic polymer that does not have either a hydroxyl group or a carboxyl group, into which both a hydroxyl group and a carboxyl group have been introduced by substitution; a (meth)acrylic polymer that has a hydroxyl group but does not have a carboxyl group, into which a carboxyl group has been introduced by substitution; or a (meth)acrylic polymer that has a carboxyl group but does not have a hydroxyl group, into which a hydroxyl group has been introduced by substitution. Furthermore, the specific (meth)acrylic polymer may be, for example, a copolymer of a monomer having a hydroxyl group and a monomer having a carboxyl group.

[0025] A preferred embodiment of the specific (meth)acrylic polymer is one in which the specific (meth)acrylic polymer contains constituent units derived from monomers having hydroxyl groups and monomers having carboxyl groups, as described below.

[0026] <Constituent units derived from monomers containing hydroxyl groups> The specific (meth)acrylic polymer preferably contains structural units derived from monomers having hydroxyl groups. In this disclosure, "structural units derived from monomers having hydroxyl groups" means structural units formed by addition polymerization of monomers having hydroxyl groups.

[0027] 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.

[0028] 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. The monomer having a hydroxyl group is preferably a hydroxyalkyl (meth)acrylate, for example, because it exhibits good copolymerization with other monomers. The hydroxyalkyl (meth)acrylate is preferably a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group with 2 to 4 carbon atoms, and more preferably 2-hydroxyethyl acrylate.

[0029] When a specific (meth)acrylic polymer contains constituent units derived from monomers having hydroxyl groups, it may contain only one type of constituent unit derived from monomers having hydroxyl groups, or it may contain two or more types.

[0030] When a specific (meth)acrylic polymer contains constituent units derived from monomers having hydroxyl groups, the content of constituent units derived from monomers having hydroxyl groups in the specific (meth)acrylic polymer is not particularly limited, but for example, it is preferably in the range of 0.05% by mass or more and 10.0% by mass or less, more preferably in the range of 0.1% by mass or more and 5.0% by mass or less, even more preferably in the range of 0.1% by mass or more and 3.0% by mass or less, and particularly preferably in the range of 0.2% by mass or more and 1.0% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer. When the content of constituent units derived from monomers having hydroxyl groups in a specific (meth)acrylic polymer is 0.05% by mass or more relative to the total constituent units of the specific (meth)acrylic polymer, the resulting adhesive layer tends to suppress foaming that may occur when placed in an environment with repeated low and high temperatures more effectively. When the content of constituent units derived from monomers having hydroxyl groups in a specific (meth)acrylic polymer is 10.0% by mass or less relative to the total constituent units of the specific (meth)acrylic polymer, the formed adhesive layer tends to exhibit improved adhesion to low-moisture-permeability substrates. Furthermore, the formed adhesive layer tends to better suppress peeling that may occur when subjected to repeated low and high temperature fluctuations.

[0031] <Monomers containing a carboxyl group> The specific (meth)acrylic polymer preferably contains constituent units derived from monomers having a carboxyl group. In this disclosure, "constituent unit derived from a monomer having a carboxyl group" means a constituent unit formed by the addition polymerization of monomers having a carboxyl group.

[0032] 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.

[0033] 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). The monomer having a carboxyl group is preferably a (meth)acrylic monomer having a carboxyl group. Acrylic acid is preferred as the (meth)acrylic monomer having a carboxyl group.

[0034] When a specific (meth)acrylic polymer contains constituent units derived from monomers having a carboxyl group, it may contain only one type of constituent unit derived from monomers having a carboxyl group, or it may contain two or more types.

[0035] When a specific (meth)acrylic polymer contains constituent units derived from monomers having carboxyl groups, the content of constituent units derived from monomers having carboxyl groups in the specific (meth)acrylic polymer is not particularly limited, but is preferably in the range of 0.05% by mass or more and 5.0% by mass or less, more preferably in the range of 0.1% by mass or more and 3.0% by mass or less, even more preferably in the range of 0.1% by mass or more and 2.0% by mass or less, and particularly preferably in the range of 0.2% by mass or more and 1.0% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic polymer is 0.05% by mass or more relative to the total constituent units of the specific (meth)acrylic polymer, the resulting adhesive layer tends to suppress foaming that may occur when placed in an environment with repeated low and high temperatures. When the content of constituent units derived from monomers having carboxyl groups in a specific (meth)acrylic polymer is 5.0% by mass or less relative to the total constituent units of the specific (meth)acrylic polymer, the formed adhesive layer tends to exhibit improved adhesion to low-moisture-permeability substrates. Furthermore, the formed adhesive layer tends to better suppress peeling that may occur when subjected to repeated low and high temperature fluctuations.

[0036] When a specific (meth)acrylic polymer contains constituent units derived from monomers having hydroxyl groups and constituent units derived from monomers having carboxyl groups, the preferred combination of the content of constituent units derived from monomers having hydroxyl groups and the content of constituent units derived from monomers having carboxyl groups is such that the content of constituent units derived from monomers having hydroxyl groups in the specific (meth)acrylic polymer is in the range of 0.05% by mass or more and 10.0% by mass or less of the total constituent units, and the content of constituent units derived from monomers having carboxyl groups in the specific (meth)acrylic polymer is in the range of 0.05% by mass or more and 5.0% by mass or less of the total constituent units, and the preferred combination of the content of constituent units derived from monomers having hydroxyl groups in the specific (meth)acrylic polymer is in the range of 0.1% by mass or more and 5.0% by mass or less of the total constituent units. A more preferable embodiment is one in which the content of constituent units derived from monomers having a hydroxyl group is in the range of 0.1% by mass or more and 3.0% by mass or less relative to the total constituent units; a more preferable embodiment is one in which the content of constituent units derived from monomers having a hydroxyl group in a specific (meth)acrylic polymer is in the range of 0.1% by mass or more and 3.0% by mass or less relative to the total constituent units, and the content of constituent units derived from monomers having a carboxyl group in a specific (meth)acrylic polymer is in the range of 0.1% by mass or more and 2.0% by mass or less relative to the total constituent units; a particularly preferable embodiment is one in which the content of constituent units derived from monomers having a hydroxyl group in a specific (meth)acrylic polymer is in the range of 0.2% by mass or more and 1.0% by mass or less relative to the total constituent units, and the content of constituent units derived from monomers having a carboxyl group in a specific (meth)acrylic polymer is in the range of 0.2% by mass or more and 1.0% by mass or less relative to the total constituent units.

[0037] <Constituent units derived from alkyl methacrylate monomers> The specific (meth)acrylic polymer preferably contains constituent units derived from alkyl (meth)acrylate monomers. In this disclosure, "constituent units derived from (meth)acrylate alkyl ester monomers" means constituent 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 carboxyl group or monomers having a hydroxyl group.

[0038] 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 carboxyl and hydroxyl 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.

[0039] 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 acrylate, and methyl methacrylate is preferred.

[0040] When a specific (meth)acrylic polymer 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.

[0041] When a specific (meth)acrylic polymer contains constituent units derived from alkyl (meth)acrylate monomers, the content of constituent units derived from alkyl (meth)acrylate monomers in the specific (meth)acrylic polymer is not particularly limited, but is preferably in the range of 50.0% by mass or more and 99.9% by mass or less, more preferably in the range of 55.0% by mass or more and 99.8% by mass or less, even more preferably in the range of 60.0% by mass or more and 99.8% by mass or less, and particularly preferably in the range of 65.0% by mass or more and 99.8% by mass or less, relative to the total constituent units of the specific (meth)acrylic polymer. Here, the fact that the content of constituent units derived from alkyl (meth)acrylate monomers in a specific (meth)acrylic polymer is 50.0% by mass or more relative to the total constituent units of the specific (meth)acrylic polymer 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 polymer.

[0042] <Other constituent units> Other constituent units that a specific (meth)acrylic polymer may contain include: constituent units derived from (meth)acrylates having aromatic rings, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; constituent units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; constituent units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; constituent units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; and constituent units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate. When a specific (meth)acrylic polymer contains other structural units, structural units derived from (meth)acrylate having an aromatic ring are preferred from the viewpoint of suppressing whitening.

[0043] If a specific (meth)acrylic polymer contains other constituent units, it may contain only one type of other constituent unit, or it may contain two or more types of other constituent units.

[0044] If the specific (meth)acrylic polymer contains other constituent units, the content of the other constituent units in the specific (meth)acrylic polymer can be appropriately set within a range that does not impair the effect of the adhesive composition of this disclosure.

[0045] -Weight-average molecular weight of specific (meth)acrylic polymers- The weight-average molecular weight (hereinafter also referred to as "Mw") of the specific (meth)acrylic polymer is not particularly limited, but is preferably in the range of 400,000 to 2,500,000, more preferably in the range of 700,000 to 2,500,000, even more preferably in the range of 1,000,000 to 2,500,000, and particularly preferably in the range of 1,200,000 to 2,500,000. When the weight-average molecular weight of a specific (meth)acrylic polymer is 400,000 or more, the resulting adhesive layer tends to better suppress shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming that may occur when placed in an environment with repeated fluctuations between low and high temperatures. The weight-average molecular weight of the specific (meth)acrylic polymer is preferably 2.5 million or less, from the viewpoint of the manufacturability of the specific (meth)acrylic polymer.

[0046] The weight-average molecular weight of a specific (meth)acrylic polymer is a value measured by the following method. Specifically, it is measured according to [1] to [3] below. [1] A solution of a specific (meth)acrylic polymer is applied to release paper and dried at 100°C for 1 minute to obtain a film-like specific (meth)acrylic polymer. [2] Using the film-like specific (meth)acrylic polymer obtained in (1) above and tetrahydrofuran, a sample solution having 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 polymer in the sample solution. [3] The weight-average molecular weight of the specific (meth)acrylic polymer is determined as a standard polystyrene equivalent by gel permeation chromatography (GPC) under the following conditions.

[0047] ~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 GMH XL Four units manufactured by Tosoh Corporation were used. Column temperature: 40℃ Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0048] The weight-average molecular weight of a specific (meth)acrylic polymer 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 monomer.

[0049] -Content of specific (meth)acrylic polymers- The specific (meth)acrylic polymer in the adhesive composition of this disclosure is not particularly limited, but is preferably 80.0% to 99.9% by mass, more preferably 85.0% to 99.8% by mass, and even more preferably 90.0% to 99.8% by mass, based on the total solid content in the adhesive composition.

[0050] 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.

[0051] [Meth)acrylic polymer manufacturing method] The method for producing the specific (meth)acrylic polymer is not particularly limited. Specific (meth)acrylic polymers 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 after manufacturing are relatively simple and can be carried out in a short time.

[0052] 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 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.

[0053] 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.

[0054] In the production of specific (meth)acrylic polymers, 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 solubility of the specific (meth)acrylic polymer and ease of polymerization reaction, the use of ethyl acetate is preferred.

[0055] During the polymerization reaction, one organic solvent may be used, or two or more may be used.

[0056] 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.

[0057] During the polymerization reaction, one polymerization initiator may be used, or two or more may be used.

[0058] 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 polymer.

[0059] In the production of specific (meth)acrylic polymers, 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.

[0060] When using a chain transfer agent in the production of a specific (meth)acrylic polymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set according to, for example, the molecular weight of the target specific (meth)acrylic polymer.

[0061] The polymerization temperature is not particularly limited and can be set appropriately depending on the molecular weight of the target (meth)acrylic polymer, for example.

[0062] [Specific tolylene diisocyanate compounds] The adhesive composition of this disclosure comprises a tolylene diisocyanate compound [i.e., a specific tolylene diisocyanate compound] having an average number of isocyanate groups in one molecule in the range of 2.5 to 3.0. The adhesive composition of this disclosure may contain only one specific tolylene diisocyanate compound, or it may contain two or more specific tolylene diisocyanate compounds.

[0063] The specific tolylene diisocyanate compound has an average number of isocyanate groups in one molecule that is in the range of 2.5 to 3.0, and preferably in the range of 2.7 to 3.0.

[0064] In this disclosure, the "average number of isocyanate groups per molecule" of a specific tolylene diisocyanate compound is a value obtained by the following formula. The "number-average molecular weight of the specific tolylene diisocyanate compound" in the following formula is determined by gel permeation chromatography (GPC). Furthermore, in the following formula, "concentration of isocyanate groups" refers to the mass percentage (unit: mass%) of isocyanate groups contained in the specific tolylene diisocyanate 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 a specific tolylene diisocyanate compound × concentration of isocyanate group) / (Formula weight of isocyanate group × 100)

[0065] In this disclosure, "tole diisocyanate compounds" include, for example, tole diisocyanate (also known as "TDI"), polymers of tole diisocyanate, adducts of tole diisocyanate and polyol compounds [e.g., trimethylolpropane (TMP)], and biuret compounds of tole diisocyanate. Specific examples of tolylene diisocyanates include 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. The type of tolylene diisocyanate compound is not particularly limited, but it is preferably an adduct of TDI and TMP, for example.

[0066] Commercially available tolerened isocyanate compounds can be used as the specific tolylene diisocyanate compounds. Examples of commercially available specific tolylene diisocyanate compounds include "Coronate® L-45E" and "Coronate® L" manufactured by Tosoh Corporation.

[0067] [Specific diphenylmethane diisocyanate compounds] The adhesive composition of this disclosure comprises a diphenylmethane diisocyanate compound [i.e., a specific diphenylmethane diisocyanate compound] having an average number of isocyanate groups in one molecule in the range of 2.0 or more and less than 2.5. The adhesive composition of this disclosure may contain only one specific diphenylmethane diisocyanate compound, or it may contain two or more specific diphenylmethane diisocyanate compounds.

[0068] The specific diphenylmethane diisocyanate compound has an average number of isocyanate groups in one molecule that is in the range of 2.0 or more and less than 2.5, and preferably in the range of 2.0 or more and 2.3 or less. In this disclosure, the "average number of isocyanate groups per molecule" of a specific diphenylmethane diisocyanate compound is a value obtained by the same calculation formula as the "average number of isocyanate groups per molecule" of the specific tolylene diisocyanate compound described above.

[0069] In this disclosure, "diphenylmethane diisocyanate compounds" include, for example, diphenylmethane diisocyanate (also known as "MDI"), polymers of diphenylmethane diisocyanate, adduct compounds of diphenylmethane diisocyanate and polyol compounds [e.g., polytetramethylene ether glycol (PTMG)], and biuret compounds of diphenylmethane diisocyanate. Specific examples of diphenylmethane diisocyanates include 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate. The type of diphenylmethane diisocyanate compound is not particularly limited, but it is preferably an adduct of MDI and PTMG, for example.

[0070] Commercially available products can be used as specific diphenylmethane diisocyanate compounds. An example of a commercially available specific diphenylmethane diisocyanate compound is "Coronate® 4370" manufactured by Tosoh Corporation.

[0071] The mass ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound in the adhesive composition of this disclosure (i.e., the mass content of the specific diphenylmethane diisocyanate compound / the mass content of the specific tolylene diisocyanate compound) is 2 or less. When the mass ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound in the adhesive composition of this disclosure is 2 or less, an adhesive layer can be formed that can effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment. From this viewpoint, the mass ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound in the adhesive composition of this disclosure is preferably in the range of 1 / 100 to 2 / 1, more preferably in the range of 1 / 50 to 1 / 1, even more preferably in the range of 1 / 10 to 1 / 1, and particularly preferably in the range of 1 / 5 to 1 / 2.

[0072] The content of specific tolylene diisocyanate compounds and specific diphenylmethane diisocyanate compounds in the adhesive composition of this disclosure is not particularly limited, as long as the adhesive composition of this disclosure contains specific tolylene diisocyanate compounds and specific diphenylmethane diisocyanate compounds, and the mass ratio of the specific diphenylmethane diisocyanate compounds to the specific tolylene diisocyanate compounds is 2 or less. The adhesive composition of this disclosure preferably has superior adhesion to low-permeability substrates and can form an adhesive layer that better suppresses shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment with repeated low and high temperatures. From the viewpoint of this, the content of the specific tolylene diisocyanate compound is preferably in the range of 0.1 parts by mass or more and 7.0 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer, and the content of the specific diphenylmethane diisocyanate compound is preferably in the range of 0.01 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of the specific (meth)acrylic polymer. It is more preferable that the compound is in the range of 0.01 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of the specific (meth)acrylic polymer, the content of the specific tolylene diisocyanate compound is in the range of 0.01 parts by mass or more and 0.8 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer, it is even more preferable that the compound is in the range of 0.05 parts by mass or more and 0.5 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer, the content of the specific tolylene diisocyanate compound is in the range of 0.1 parts by mass or more and 0.5 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer, and it is particularly preferable that the compound is in the range of 0.1 parts by mass or more and 0.3 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer.

[0073] [Silane coupling agent] The adhesive composition of this disclosure preferably contains a silane coupling agent. When the adhesive composition of this disclosure contains a silane coupling agent, the formed adhesive layer tends to suppress foaming and peeling more effectively, for example, when subjected to repeated low and high temperature fluctuations while bonded to glass. This is presumed to be because the interaction between the formed adhesive layer and the glass is more appropriately enhanced.

[0074] The type of silane coupling agent is not particularly limited. Examples of silane coupling agents include polymerizable unsaturated group-containing silane compounds represented by vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane; thiol group-containing silane compounds represented by 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane; epoxy group-containing silane compounds represented by 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane compounds represented by 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; and tris-(3-trimethoxysilylpropyl)isocyanurate.

[0075] 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.

[0076] If the adhesive composition of this disclosure contains a silane coupling agent, it may contain only one silane coupling agent or two or more silane coupling agents.

[0077] When the adhesive composition of this disclosure contains a silane coupling agent, the content of the silane coupling agent is not particularly limited, but is preferably in the range of 0.1 parts by mass or more and 1 part by mass or less, more preferably in the range of 0.1 parts by mass or more and 0.5 parts by mass or less, and even more preferably in the range of 0.1 parts by mass or more and 0.3 parts by mass or less, per 100 parts by mass of the specific (meth)acrylic polymer. When the silane coupling agent content in the adhesive composition of this disclosure is within the above range relative to 100 parts by mass of a specific (meth)acrylic polymer, the formed adhesive layer tends to exhibit improved adhesion to low-moisture-permeability substrates. Furthermore, when the silane coupling agent content in the adhesive composition of this disclosure is within the above range relative to 100 parts by mass of a specific (meth)acrylic polymer, the formed adhesive layer tends to exhibit better suppression of foaming and peeling when subjected to repeated low and high temperatures, for example, when bonded to glass.

[0078] [Organic solvents] The adhesive composition of this disclosure may contain an organic solvent. The adhesive composition of this disclosure may have improved applicability 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 polymers described above.

[0079] If the adhesive composition of this disclosure contains an organic solvent, it may contain only one organic solvent or two or more organic solvents.

[0080] 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.

[0081] [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 polymers other than specific (meth)acrylic polymers, crosslinking catalysts, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., UV absorbers), antistatic agents, and various other additives.

[0082] 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.

[0083] <Uses of adhesive compositions> The uses of the adhesive composition disclosed herein are not particularly limited. The adhesive composition of this disclosure is suitable as an adhesive composition for use with substrates made of low moisture permeability materials, because it can form an adhesive layer with excellent adhesion to low moisture permeability substrates. Low moisture permeability materials are not particularly limited, but when a 40 μm thick film is formed, the moisture permeability is 200 g / m². 2 It is preferable that the time is 24 hours or less. The moisture permeability is measured according to the moisture permeability test method (cup method) of JIS Z 0208:2021. Specifically, it is measured by the following method: A test piece cut from a 40 μm thick film into a 70 mm diameter disc is sealed in a moisture permeability cup (aluminum cup) containing approximately 15 g of calcium chloride (desiccant), and placed in a constant temperature and humidity chamber set to 40°C and 90% RH, and left to stand for 24 hours. The change in mass of calcium chloride before and after this standing period is measured to determine the moisture permeability [unit: g / (m³)]. 2 (24 hours)

[0084] Examples of materials with low moisture permeability include resins such as (meth)acrylic resins and cycloolefin resins.

[0085] In this disclosure, "(meth)acrylic resin" means a resin 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. In this disclosure, "cycloolefin resin" means an amorphous olefin resin in which a cyclic olefin structure is introduced into the polymer chain, and refers to a resin obtained from cyclic olefins such as norvonene, tetracyclododecene, and their derivatives. The cycloolefin resin may be, for example, a ring-opening polymer of one or more cyclic olefins, an addition polymer of one or more cyclic olefins, a random copolymer of one or more cyclic olefins and α-olefins (e.g., ethylene, propylene, etc.), or a hydride of these polymers.

[0086] The low-moisture-permeability material is preferably at least one selected from (meth)acrylic resins and cycloolefin resins, more preferably a (meth)acrylic resin or a cycloolefin resin, and even more preferably a (meth)acrylic resin. As the (meth)acrylic resin, polymethyl methacrylate (PMMA) is preferred. The cycloolefin resin is preferably a cycloolefin resin (COP). In this disclosure, "cycloolefin resin" means a polymer consisting only of one or more cyclic olefins.

[0087] The adhesive layer formed by the adhesive composition of this disclosure exhibits excellent adhesion not only to low-moisture permeability materials such as polymethyl methacrylate (PMMA) and cycloolefin resin (COP), but also to triacetylcellulose (TAC). These resins are all used as materials for components constituting polarizing plates (e.g., protective films and phase difference films). Furthermore, the adhesive layer formed by the adhesive composition of this disclosure effectively suppresses shrinkage of the substrate that may occur when placed in a high-temperature environment, as well as foaming and peeling that may occur when placed in an environment with repeated fluctuations between low and high temperatures. For this reason, the adhesive composition of this disclosure is suitable as an adhesive composition used in polarizing plates (a so-called polarizing plate adhesive composition). Specific applications of the adhesive composition of this disclosure include bonding polarizing plates to glass substrates of liquid crystal cells, and bonding phase difference films constituting polarizing plates to protective films.

[0088] [Laminated structure] The laminate of the present disclosure comprises a polarizing plate having a layer on one or both sides containing at least one resin selected from the group consisting of (meth)acrylic resins and cycloolefin resins, and an adhesive layer provided on the above layer and formed of the adhesive composition of the present disclosure. In the laminate of the present disclosure, an adhesive layer formed by the adhesive composition of the present disclosure is provided on a layer containing at least one resin selected from the group consisting of (meth)acrylic resins and cycloolefin resins that is present in the polarizing plate. Since the adhesive layer formed by the adhesive composition of the present disclosure has excellent adhesion to a low moisture permeability substrate, the laminate of the present disclosure has excellent adhesion between the layer containing at least one resin selected from the group consisting of (meth)acrylic resins and cycloolefin resins and the adhesive layer. Furthermore, because the laminate of the present disclosure has an adhesive layer formed by the adhesive composition of the present disclosure, shrinkage of the above layer of the polarizing plate is less likely to occur even when placed in a high-temperature environment, and foaming and peeling are less likely to occur even when placed in an environment where low and high temperatures are repeatedly fluctuated.

[0089] The laminate of this disclosure comprises a polarizing plate. The polarizing plate of the laminate of this disclosure has a layer on one or both sides containing at least one resin selected from the group consisting of (meth)acrylic resins and cycloolefin resins (hereinafter also referred to as the "specific resin layer"). The polarizing plate may have a specific resin layer on only one side, or it may have one on both sides.

[0090] The specific resin layer is a layer containing at least one resin selected from the group consisting of (meth)acrylic resins and cycloolefin resins. The specific resin layer may contain both (meth)acrylic resin and cycloolefin resin, only (meth)acrylic resin, or only cycloolefin resin. The proportion of (meth)acrylic resin and cycloolefin resin in the total resin within a specific resin layer is not particularly limited, but is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. It is particularly preferable that the amount be 90% by mass or more, and may be 100% by mass.

[0091] If the specific resin layer contains a (meth)acrylic resin, the (meth)acrylic resin is preferably polymethyl methacrylate (PMMA). When the specific resin layer contains a cycloolefin resin, the cycloolefin resin is preferably a cycloolefin resin (COP).

[0092] The specific resin layer may, if necessary, contain components other than the specific resin, as long as they do not impair the effects of the laminate of this disclosure. Components other than the specified resin include other resins, antioxidants, light stabilizers (e.g., UV absorbers), and various other additives.

[0093] The side of the specific resin layer on which the adhesive layer is provided may be subjected to surface treatments such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatments) from the viewpoint of further improving the adhesion between the specific resin layer and the adhesive layer.

[0094] The thickness of the specific resin layer is not particularly limited, but is preferably 10 μm to 100 μm, and more preferably 20 μm to 80 μm. The thickness of the specific resin layer referred to here refers to the thickness on one side.

[0095] In this disclosure, "thickness of the specific resin layer" refers to the average thickness of the specific resin layer. The average thickness of a specific resin layer is determined by the following method. The thickness of a specific resin 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 specific resin layer.

[0096] The laminate of the present disclosure comprises an adhesive layer formed by the adhesive composition of the present disclosure. The adhesive layer of the laminate of the present disclosure includes a cured product of the adhesive composition of the present disclosure. The cured product includes, for example, a crosslinked product of a specific (meth)acrylic polymer obtained by crosslinking and curing with a specific tolylene diisocyanate compound and a specific diphenylmethane diisocyanate compound.

[0097] The adhesive layer of the laminate of this disclosure is provided on a specific resin layer of the polarizing plate. If the polarizing plate of the laminate of this disclosure has specific resin layers on both sides, the adhesive layer may be provided on only one of the two specific resin layers, or on both specific resin layers.

[0098] The thickness of the adhesive layer in the laminate of this disclosure is not particularly limited. The thickness of the adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0099] 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 same method as the average thickness of the specific resin layer described above.

[0100] The polarizing plate in the laminate of this disclosure preferably comprises a specific resin layer as a functional film such as a protective film or a phase difference film. When a polarizing plate includes a specific resin layer as a protective film or phase difference film, examples of the layer configuration of the laminate of this disclosure include adhesive layer / polarizing plate [protective film (specific resin layer) / polarizer / protective film (specific resin layer)], adhesive layer / polarizing plate [protective film (specific resin layer) / polarizer], adhesive layer / polarizing plate [phase difference film (specific resin layer) / polarizer / phase difference film (specific resin layer)], adhesive layer / polarizing plate [phase difference film (specific resin layer) / polarizer], and adhesive layer / polarizing plate [protective film (specific resin layer) / polarizer / protective film (specific resin layer)].

[0101] In the laminate 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.

[0102] 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.

[0103] [Method for fabricating laminates] The method for producing the laminate according to this disclosure is not particularly limited. The laminates of this disclosure can be fabricated by known methods. Examples of methods for fabricating the laminates of this disclosure include the following: The following method will be explained using the example of a polarizing plate with a layer structure of "specific resin layer / polarizer / specific resin layer".

[0104] By applying the adhesive composition of this disclosure to the easily peelable 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 surface of a specific resin layer on a polarizing plate and bonded together, and then cured, thereby producing the laminate of this disclosure having a laminated structure of release sheet / adhesive layer / polarizing plate (specific resin layer / polarizer / specific resin layer).

[0105] Another possible method is the following: By applying the adhesive composition of this disclosure to the surface of a specific resin layer on a polarizing plate, a coating film is formed on the specific resin layer. Next, by drying the formed coating film, an adhesive film is formed on the specific resin layer. Then, by overlapping the exposed surface of the formed adhesive film with the easily peelable surface of a release sheet and bonding them together, and then curing, a laminate of this disclosure having a laminated structure of release sheet / adhesive layer / polarizing plate (specific resin layer / polarizer / specific resin layer) can be produced.

[0106] 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.

[0107] 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 dry at 70°C to 120°C for 30 to 180 seconds.

[0108] 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 55%. [Examples]

[0109] 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.

[0110] [Production of (meth)acrylic polymers] [Manufacturing example A-1] In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 79.2 parts by mass of n-butyl acrylate [n-BA; alkyl acrylate monomer], 20.0 parts by mass of phenoxyethyl acrylate [PHEA; other monomer], 0.3 parts by mass of 2-hydroxyethyl acrylate [2HEA; monomer having a hydroxyl group], 0.5 parts by mass of acrylic acid [AA; monomer having a carboxyl group], 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 being stirred. 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 added sequentially to the mixture in the reactor. After the addition was complete, the mixture was held for 6 hours to complete the polymerization reaction. The solution obtained from the completion of the polymerization reaction was then diluted with ethyl acetate to a solid content concentration of 18.5% by mass, and then cooled to obtain a solution of (meth)acrylic polymer A-1.

[0111] Here, "solids concentration" refers to the mass ratio of (meth)acrylic polymer A-1 to the solution of (meth)acrylic polymer A-1. The same applies to the solutions of (meth)acrylic polymers A-2 to A-14 prepared below.

[0112] [Manufacturing examples A-2, A-3, and A-6~A-14] In production examples A-2, A-3, and A-6 to A-14, the same procedure as in production example A-1 was followed, except that the monomer composition of the (meth)acrylic polymer was changed to the monomer composition shown in Table 1, to obtain solutions of (meth)acrylic polymers A-2, A-3, and A-6 to A-14, each with a solid content concentration of 18.5% by mass.

[0113] [Manufacturing Examples A-4 and A-5] In production examples A-4 and A-5, the same procedure as in production example A-1 was followed, except that the weight-average molecular weight of the (meth)acrylic polymer was adjusted to the weight-average molecular weight shown in Table 1 by adjusting at least one of the amounts of organic solvent and polymerization initiator used when producing the (meth)acrylic polymer. Solutions of (meth)acrylic polymers A-4 and A-5, each with a solid content concentration of 18.5% by mass, were obtained.

[0114] Table 1 shows the monomer composition [unit: mass%] and weight-average molecular weight (Mw) of (meth)acrylic polymers A-1 to A-14.

[0115] The weight-average molecular weight (Mw) of (meth)acrylic polymers A-1 to A-14 was measured using the same method as described above for measuring the weight-average molecular weight of the specified (meth)acrylic polymers.

[0116] Of the (meth)acrylic polymers A-1 to A-14, (meth)acrylic polymers A-1 to A-11 correspond to the specified (meth)acrylic polymers in this disclosure.

[0117] [Table 1]

[0118] Details of each monomer listed in Table 1 are as follows: <Monomers containing hydroxyl groups> "2HEA": 2-hydroxyethyl acrylate <Monomers containing a carboxyl group> "AA": Acrylic acid <(meth)acrylate alkyl monomer> "n-BA": n-butyl acrylate "MA": Methyl acrylate "MMA": Methyl methacrylate <Other monomers> "PHEA": Phenoxyethyl acrylate

[0119] In Table 1, a "-" in the monomer composition column indicates that the monomer corresponding to that column was not used.

[0120] [Preparation of adhesive composition] [Example 1] 540.5 parts by mass (100 parts by mass as solids) of a solution of (meth)acrylic polymer A-1, 0.67 parts by mass (0.3 parts by mass as solids) of Coronate® L-45E [trade name, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, average number of isocyanate groups per molecule: 2.7, manufactured by Tosoh Corporation] as a specific tolylene diisocyanate compound, and Coronate® as a specific diphenylmethane diisocyanate compound. 0.1 parts by mass (0.1 parts by mass as solids) of 4370 [product name, adduct of diphenylmethane diisocyanate (MDI) and polytetramethylene ether glycol (PTMG), solid content concentration: 100% by mass, average number of isocyanate groups per molecule: 2.1, manufactured by Tosoh Corporation], 0.2 parts by mass (0.2 parts by mass as solids) of X-41-1810 [product 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.

[0121] [Examples 2 to 22] In Example 1, the same operations as in Example 1 were carried out except that the composition of the adhesive composition was changed to the composition shown in Table 2, and the respective adhesive compositions of Examples 2 to 22 were obtained.

[0122] [Comparative Examples 1 to 10] In Example 1, the same operations as in Example 1 were carried out except that the composition of the adhesive composition was changed to the composition shown in Table 3, and the respective adhesive compositions of Comparative Examples 1 to 10 were obtained.

[0123] [Table 2]

[0124] [Table 3]

[0125] The details of the components described in Table 2 and / or Table 3 are as shown below. <TDI-based compound> "Coronate L-45E" [trade name, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, average number of isocyanate groups per molecule: 2.7, manufactured by Tosoh Corporation] <MDI-based compound> "Coronate 4370" [trade name, adduct of diphenylmethane diisocyanate (MDI) and polytetramethylene ether glycol (PTMG), solid content concentration: 100% by mass, average number of isocyanate groups per molecule: 2.1, manufactured by Tosoh Corporation]

[0126] The above "Coronate L-45E" corresponds to a specific tolylene diisocyanate-based compound, and the above "Coronate 4370" corresponds to a specific diphenylmethane diisocyanate-based compound. The above "Coronate" is a registered trademark.

[0127] <Other crosslinking agents> <<Hexamethylene diisocyanate compounds>> "Sumijule N-75" [Product name, biuret form of hexamethylene diisocyanate (HMDI), solid content concentration: 75% by mass, manufactured by Sumika Covestro Urethane Co., Ltd.] <<Xylylene diisocyanate compounds>> "Takenate D-110N" [Product name, adduct body of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content concentration: 75% by mass, manufactured by Mitsui Chemicals, Inc.] The above terms, "Sumijuru" and "Takenate," are both registered trademarks.

[0128] <Silane coupling agent> "X-41-1810" [Product name, thiol group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.] "KBM-403" [Product name, epoxy group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.]

[0129] In Tables 2 and 3, the values ​​listed in the "Amount" column are all based on solid content. In Tables 2 and 3, "-" indicates that the ingredient corresponding to that column is not included. In Tables 2 and 3, the "mass ratio of diphenylmethane diisocyanate compounds to tolylene diisocyanate compounds" is expressed as "mass ratio (M / T)".

[0130] [Fabrication of polarizing plate with adhesive layer (A)] 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 15 μm. Next, the formed coating film was dried by blowing 100°C air at a wind speed of 3 m / s for 60 seconds using a hot air circulation dryer, thereby forming an adhesive film with a thickness of 15 μm on the release film. Next, the exposed surface of the formed adhesive film was bonded to one side of the PMMA layer of a polarizing plate (thickness: 100 μm) having a layer structure of polymethyl methacrylate (PMMA) layer / polyvinyl alcohol (PVA) layer containing a polarizer / PMMA layer. After bonding, the plate was left to stand for 7 days in an environment of 23°C and 50% RH to cure the adhesive film, thereby producing an adhesive-coated polarizing plate (A) having a layer structure of release film / adhesive layer / polarizing plate (PMMA layer / PVA layer / PMMA layer).

[0131] [Fabrication of polarizing plate with adhesive layer (B)] An adhesive film with a thickness of 15 μm was formed on a release film by performing the same procedure as in the preparation of the adhesive-coated polarizing plate (A) described above. Next, the exposed surface of the formed adhesive film was bonded to one side of the COP layer of a polarizing plate (thickness: 160 μm) having a layer structure of cycloolefin resin (COP) layer / polyvinyl alcohol (PVA) layer containing a polarizer / COP layer. After bonding these together, the plate was left to stand for 7 days in an environment of 23°C and 50% RH to cure the adhesive film, thereby producing an adhesive-coated polarizing plate (B) having a layer structure of release film / adhesive layer / polarizing plate (COP layer / PVA layer / COP layer).

[0132] [Fabrication of polarizing plate with adhesive layer (C)] An adhesive film with a thickness of 15 μm was formed on a release film by performing the same procedure as in the preparation of the adhesive-coated polarizing plate (A) described above. Next, the exposed side of the formed adhesive film was bonded to one side of the TAC layer of a polarizing plate (thickness: 150 μm) having a layer structure of triacetylcellulose (TAC) layer / polyvinyl alcohol (PVA) layer containing a polarizer / TAC layer. After bonding these together, the plate was left to stand for 7 days in an environment of 23°C and 50% RH to cure the adhesive film, thereby producing an adhesive-coated polarizing plate (C) having a layer structure of release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0133] [Measurement and Evaluation] 1. Adhesion The polarizing plate with 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 specimen measuring 25 mm × 60 mm (long side) was prepared. Next, the release film was peeled off the prepared test specimen to expose the adhesive layer surface, and then it was corona treated. Then, one side of a polyethylene terephthalate (PET) film [product name: Toyobo Ester® Film G2, thickness: 38 μm, manufactured by Toyobo Co., Ltd.] was corona treated, and the corona-treated side of the PET film and the corona-treated side of the adhesive layer of the test specimen were overlapped and bonded together. An evaluation sample was prepared by leaving it to stand for 24 hours in an environment of 23°C and 50% RH. The prepared evaluation samples have a layer structure of PET film / adhesive layer / polarizing plate (PMMA layer / PVA layer / PMMA layer), PET film / adhesive layer / polarizing plate (COP layer / PVA layer / COP layer), or PET film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0134] For the evaluation samples prepared as described above, a single-column material testing machine (model: STA-1225) manufactured by A&D Co., Ltd. was used to peel the PET film from the polarizing plate at a length of 60 mm in a 180° direction under conditions of an ambient temperature of 23°C and 50% RH, and a peeling speed of 300 mm / min. The peeled surface of the PET film was visually observed to confirm whether or not the adhesive layer had transferred to the PET film. If transfer of the adhesive layer was confirmed, the area of ​​the adhesive layer transferred to the PET film was measured, and its ratio to the bonded area (i.e., the area of ​​the portion of the evaluation sample where the PET film and the adhesive layer were bonded) was calculated. The area measurement function of a digital microscope (model: VHX-7000) manufactured by Keyence Corporation was used to measure the area of ​​the adhesive layer transferred to the PET film. After manually tracing the contour of the adhesive layer attached to the PET film, the area of ​​the adhesive layer was measured using the functions of the above-mentioned device, and the ratio to the bonded area (25 mm × 60 mm) was calculated. Then, evaluation was performed according to the evaluation criteria below. The results are shown in Tables 4 and 5. In the evaluation criteria below, "A," "B," "C," and "D" represent usable levels, with "A" being the most preferable.

[0135] -Evaluation Criteria- A: No transfer of the adhesive layer to the PET film was observed at all. B: The area of ​​the adhesive layer transferred to the PET film was in the range of 0% to less than 5% of the bonding area. C: The area of ​​the adhesive layer transferred to the PET film was in the range of 5% to less than 10% of the bonding area. D: The area of ​​the adhesive layer transferred to the PET film was in the range of 10% to less than 30% of the bonding area. E: The area of ​​the adhesive layer transferred to the PET film was 30% or more of the bonding area.

[0136] 2. Contraction suppression The polarizing plate with 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 62 mm × 110 mm (long side) was prepared. Next, the release film was peeled off the test piece, and 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.]. Then, the test piece and the glass plate were pressed together using a laminator to create a test sample. The prepared test sample had a layer structure of glass plate / adhesive layer / polarizing plate (PMMA layer / PVA layer / PMMA layer), glass plate / adhesive layer / polarizing plate (COP layer / PVA layer / COP layer), or glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0137] The test sample prepared as described above 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 24 hours in an environment with an ambient temperature of 23°C and 50% RH. The test samples after this standing period were then left to stand for 150 hours in an environment with an ambient temperature of 85°C and 10% RH or less (a so-called high-temperature, low-humidity environment). The length of the long side of the test samples after this standing period (i.e., the side at 0° with respect to the absorption axis) was measured using a digital microscope [Model: VHX-100F, manufactured by Keyence Corporation], and the shrinkage rate was calculated using the following formula. The calculated value was rounded to three decimal places. Shrinkage rate (unit: %) =[Length of the longest side of the test sample before standing (unit: mm)] - [Length of the longest side of the test sample after standing (unit: mm)] / Length of the longest side of the test sample before standing (unit: mm) × 100

[0138] Based on the calculated shrinkage rate, evaluation was performed according to the following evaluation criteria. The results are shown in Tables 4 and 5. In the evaluation criteria below, "A," "B," "C," and "D" represent usable levels, with "A" being the most preferable.

[0139] -Evaluation Criteria- A: The shrinkage rate of the test sample was less than 0.20%. B: The shrinkage rate of the test samples was in the range of 0.20% to less than 0.35%. C: The shrinkage rate of the test samples was in the range of 0.35% to less than 0.50%. D: The shrinkage rate of the test samples was in the range of 0.50% to less than 1.00%. E: The shrinkage rate of the test sample was 1.00% or higher.

[0140] 3. Durability (thermal shock environment) The polarizing plate with 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 62 mm × 110 mm (long side) was prepared. Next, the release film was peeled off the test piece, and 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.]. Then, the test piece and the glass plate were pressed together using a laminator to create a test sample. The test sample has a layer structure of glass plate / adhesive layer / polarizing plate (PMMA layer / PVA layer / PMMA layer). The prepared test sample has a layer structure of glass plate / adhesive layer / polarizing plate (PMMA layer / PVA layer / PMMA layer), glass plate / adhesive layer / polarizing plate (COP layer / PVA layer / COP layer), or glass plate / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0141] The test sample prepared as described above 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 24 hours in an environment of 23°C and 50% RH. The test samples after this standing period were subjected to a thermal shock test using a thermal shock device (model: TSA-301L-W, manufactured by ESPEC Corporation). This test involved repeatedly placing the samples in an environment of -40°C for 0.5 hours, followed by 85°C for 0.5 hours, repeating this cycle 300 times. After the test, the condition of the test samples was visually observed and evaluated according to the evaluation criteria below. The results are shown in Tables 4 and 5. In the evaluation criteria below, "A," "B," and "C" represent usable levels, with "A" being the most preferable.

[0142] -Evaluation Criteria (Foaming)- A: No foaming was observed in the test sample. B: A slight foaming was observed in the test sample, but it was at a level that does not pose a practical problem. C: Foaming was observed in the test sample, but it was at a level that was practically acceptable. D: Significant foaming was observed in the test sample, at a level unacceptable for practical use.

[0143] -Evaluation Criteria (Peeling)- A: No peeling was observed at all in the test samples. B: Slight peeling was observed in the test sample, but it was at a level that did not pose a practical problem. C: Peeling was observed in the test sample, but it was at a level that was practically acceptable. D: Significant peeling was observed in the test sample, reaching a level unacceptable for practical use.

[0144] [Table 4]

[0145] [Table 5]

[0146] As shown in Table 4, the adhesive layers formed by the adhesive compositions of Examples 1 to 22 were confirmed to have excellent adhesion to low-moisture-permeability substrates. Furthermore, the adhesive layers formed by the adhesive compositions of Examples 1 to 22 were confirmed to effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment. In addition, the adhesive layers formed by the adhesive compositions of Examples 1 to 22 were confirmed to effectively suppress foaming and peeling that may occur when placed in an environment with repeated fluctuations between low and high temperatures.

[0147] On the other hand, as shown in Table 5, it was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 1, which does not contain a specific tolylene diisocyanate compound, could not effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment, nor foaming that may occur when placed in an environment where low and high temperatures are repeatedly alternating. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 2, which does not contain a specific diphenylmethane diisocyanate compound, could not effectively suppress foaming that may occur when placed in an environment with repeated low and high temperatures. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 3, in which the mass ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound exceeds 2, cannot effectively suppress the shrinkage of the substrate that may occur when placed in a high-temperature environment. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 4, which contains a hexamethylene diisocyanate compound instead of a specific diphenylmethane diisocyanate compound, could not effectively suppress foaming that may occur when placed in an environment with repeated low and high temperatures. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 5, which contains a xylylene diisocyanate compound instead of a specific diphenylmethane diisocyanate compound, exhibits poor adhesion to low-moisture-permeability substrates and fails to effectively suppress foaming that may occur when placed in an environment with repeated fluctuations between low and high temperatures. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 6, which contains a hexamethylene diisocyanate compound instead of a specific tolylene diisocyanate compound, could not effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment, nor foaming that may occur when placed in an environment where low and high temperatures are repeatedly alternating. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 7, which contains a xylylene diisocyanate compound instead of a specific tolylene diisocyanate compound, could not effectively suppress the shrinkage of the substrate that may occur when placed in a high-temperature environment. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 8, in which the (meth)acrylic polymer does not have a carboxyl group, cannot effectively suppress foaming that may occur when placed in an environment with repeated low and high temperatures. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 9, in which the (meth)acrylic polymer does not have hydroxyl groups, cannot effectively suppress foaming that may occur when placed in an environment with repeated low and high temperatures. It was confirmed that the adhesive layer formed by the adhesive composition of Comparative Example 10, in which the (meth)acrylic polymer does not have either hydroxyl or carboxyl groups, exhibits poor adhesion to low-moisture-permeability substrates and fails to effectively suppress shrinkage of the substrate that may occur when placed in a high-temperature environment.

Claims

1. A (meth)acrylic polymer having hydroxyl groups and carboxyl groups, A tolylene diisocyanate compound having an average number of isocyanate groups in one molecule in the range of 2.5 to 3.0, A diphenylmethane diisocyanate compound having an average number of isocyanate groups in one molecule that is in the range of 2.0 or more and less than 2.5, Includes, The (meth)acrylic polymer contains constituent units derived from monomers having carboxyl groups, and the content of the constituent units derived from monomers having carboxyl groups in the (meth)acrylic polymer is in the range of 0.5% by mass or more and 5.0% by mass or less relative to the total constituent units. An adhesive composition in which the mass ratio of the diphenylmethane diisocyanate compound to the tolylene diisocyanate compound is in the range of 1 / 100 to 2 / 1.

2. The (meth)acrylic polymer contains constituent units derived from monomers having hydroxyl groups, The adhesive composition according to claim 1, wherein the content of constituent units derived from the monomer having a hydroxyl group in the (meth)acrylic polymer is in the range of 0.1% by mass or more and 5.0% by mass or less with respect to the total number of constituent units.

3. The content of the tolylene diisocyanate compound is in the range of 0.1 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer. The adhesive composition according to claim 1 or claim 2, wherein the diphenylmethane diisocyanate compound is in the range of 0.01 parts by mass or more and 1.0 part by mass or less per 100 parts by mass of the (meth)acrylic polymer.

4. The adhesive composition according to any one of claims 1 to 3, wherein the weight-average molecular weight of the (meth)acrylic polymer is in the range of 400,000 to 2,500,000.

5. A polarizing plate having a layer on one or both sides containing at least one resin selected from the group consisting of (meth)acrylic resins and cycloolefin resins, An adhesive layer provided on the aforementioned layer and formed by the adhesive composition according to any one of claims 1 to 4, A laminate comprising the following features.

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