JP2023132197A - Adhesive composition and laminate - Google Patents

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

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

Generally, a liquid crystal display device includes a liquid crystal cell having a liquid crystal layer sandwiched between two glass substrates, and polarizing plates arranged on both sides of the liquid crystal cell. For bonding a liquid crystal cell and a polarizing plate, a (meth)acrylic adhesive composition is often used from the viewpoint of ensuring visibility of the liquid crystal display device.

For example, Patent Document 1 describes a (meth)acrylic adhesive composition suitable for optical members such as polarizing plates, which is an adduct of a (meth)acrylic acid ester copolymer and a polyisocyanate compound. Disclosed is an adhesive composition characterized by containing a crosslinking agent in which the content ratio of a bifunctional adduct and a trifunctional or higher adduct is 100:0 to 10:90 by weight. ing.

Japanese Patent Application Publication No. 2001-262103

Conventionally, triacetylcellulose (TAC) film has been used as the base material of polarizing plates, but from the viewpoint of suppressing deterioration of the polarizer due to the adsorption of moisture in the atmosphere, polymethyl methacrylate (PMMA) film, Films with low moisture permeability, such as cycloolefin resin (COP) films, are being used. When a TAC film is used as a base material for a polarizing plate, polar groups are present on the surface of the base material due to the saponification treatment on the surface of the base material, so that the adhesiveness between the base material and the adhesive layer is excellent. However, PMMA and COP have low polarity due to their molecular structures and do not have polar groups, so the adhesion between the base material and the adhesive layer is inferior to that of TAC. A polarizing plate is constructed by laminating members with different shrinkage rates, and tends to shrink due to temperature changes. In recent years, as displays have become larger and narrower, adhesive compositions used for polarizing plates are required to better suppress the shrinkage of polarizing plates that can occur when placed in harsh environments. There is a tendency to require the ability to form layers. However, if the adhesion between the base material and the adhesive layer is poor, the adhesive layer cannot follow the shrinkage of the polarizing plate, and stress due to the shrinkage of the polarizing plate is applied to the adhesive layer, causing the adhesive layer to leak from the liquid crystal cell. Peeling may occur. Furthermore, if the adhesion between the base material and the adhesive layer is poor, the adhesive layer may not be able to suppress outgas from the polarizing plate, and foaming may occur.

The present disclosure has been made in view of the above situation.
The problem to be solved by an embodiment of the present disclosure is to provide excellent adhesion to a base material with low moisture permeability, and to avoid shrinkage of the base material that may occur when placed in a high-temperature environment, as well as between low and high temperatures. An object of the present invention is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that can satisfactorily suppress foaming and peeling that may occur when placed in an environment where repeated exposures occur.
Problems to be solved by other embodiments of the present disclosure are the shrinkage of the base material that may occur when it is placed in a high temperature environment, as well as the shrinkage of the base material when it is placed in a high temperature environment. It is an object of the present invention to provide a laminate including an adhesive layer that can satisfactorily suppress foaming and peeling that may occur when placed in an environment where .

Specific means for solving the problem include the following aspects.
<1> A (meth)acrylic polymer having a hydroxyl group and a carboxyl group, a tolylene diisocyanate compound having an average number of isocyanate groups in one molecule in the range of 2.5 to 3.0, and an average number of isocyanate groups in one molecule. a diphenylmethane diisocyanate compound having an isocyanate group number in the range of 2.0 or more and less than 2.5, and a pressure-sensitive adhesive composition in which the content mass ratio of the diphenylmethane diisocyanate compound to the tolylene diisocyanate compound is 2 or less. .
<2> The (meth)acrylic polymer contains a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a carboxy group, and the above-mentioned in the (meth)acrylic polymer The content of the structural unit derived from a monomer having a hydroxyl group is in the range of 0.1% by mass or more and 5.0% by mass or less based on the total structural units, and the above-mentioned carboxylic acid in the (meth)acrylic polymer is The adhesive composition according to <1>, wherein the content of the structural unit derived from the monomer having a group is in the range of 0.1% by mass or more and 3.0% by mass or less based on the total structural 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 based on 100 parts by mass of the (meth)acrylic polymer, and the diphenylmethane diisocyanate compound The pressure-sensitive adhesive composition according to <1> or <2>, wherein the amount is from 0.01 parts by mass to 1.0 parts by mass based on 100 parts by mass of the (meth)acrylic polymer.
<4> The pressure-sensitive adhesive composition according to any one of <1> to <3>, wherein the (meth)acrylic polymer has a weight average molecular weight in the range of 400,000 to 2,500,000.
<5> A polarizing plate provided with a layer containing at least one resin selected from the group consisting of (meth)acrylic resin and cycloolefin resin on one or both sides, and provided on the layer, and < A laminate comprising an adhesive layer formed from the adhesive composition according to any one of items 1> to <4>.

According to an embodiment of the present disclosure, the substrate has excellent adhesion to a base material with low moisture permeability, and shrinkage of the base material that may occur when placed in a high temperature environment, and an environment where low and high temperatures are repeated. Provided is a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that can satisfactorily suppress foaming and peeling that may occur when the pressure-sensitive adhesive composition is placed underneath.
According to another embodiment of the present disclosure, the material has excellent adhesion to a base material with low moisture permeability, and shrinkage of the base material that may occur when placed in a high temperature environment, and repeated low and high temperatures. A laminate is provided that includes an adhesive layer that can satisfactorily suppress foaming and peeling that may occur when placed in an environment.

Hereinafter, the adhesive composition and laminate of the present disclosure will be described in detail. Although the description of the requirements set forth below may be based on representative implementations of this disclosure, this disclosure is not limited to such implementations and is within the scope of this disclosure. can be implemented with appropriate changes.

In the present disclosure, a numerical range indicated using "~" means a range that includes the numerical values written before and after "~" as the lower limit and upper limit, respectively.
In the numerical ranges described step by step in the present disclosure, the upper limit or lower limit described in a certain numerical range may be replaced with the upper limit or lower limit of another numerical range described step by step. Furthermore, in the numerical ranges described in this disclosure, the upper limit or lower limit described in a certain numerical range may be replaced with the value shown in the Examples.

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

In the present disclosure, if there are multiple substances corresponding to each component in the adhesive composition, unless otherwise specified, the amounts of each component in the adhesive composition are as follows: Refers to the total amount of multiple substances.

In the present disclosure, "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group.
In the present disclosure, "(meth)acrylic polymer" includes structural units derived from (meth)acrylic monomers, and the proportion of structural units derived from (meth)acrylic monomers is 50% by mass or more.

In this disclosure, "(meth)acrylic" is a term that includes both "acrylic" and "methacrylic", "(meth)acrylate" is a term that includes both "acrylate" and "methacrylate", "(Meth)acryloyl" is a term that includes both "acryloyl" and "methacryloyl," and "(meth)acrylamide" is a term that includes both "acrylamide" and "methacrylamide."

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

In this disclosure, "polymer" and "polymer" have the same meaning.

[Adhesive composition]
The adhesive composition of the present disclosure comprises a (meth)acrylic polymer having a hydroxyl group and a carboxy group, and 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 in the range of 2.0 or more and less than 2.5, wherein the content mass ratio of the diphenylmethane diisocyanate compound to the tolylene diisocyanate compound is 2 or less. It is.
The adhesive composition of the present disclosure has excellent adhesion to substrates with low moisture permeability, and can be used in environments where the substrate shrinks, which may occur when placed in high-temperature environments, and in environments where low and high temperatures are repeated. It is possible to form an adhesive layer that can satisfactorily suppress foaming and peeling that may occur when placed on a substrate.

Although the reason why the adhesive composition of the present disclosure can exhibit such effects is not clear, the present inventors speculate as follows. However, the following speculations are not intended to limit the pressure-sensitive adhesive composition of the present disclosure, but are explained as an example.

The adhesive composition of the present disclosure uses as a crosslinking agent for crosslinking a (meth)acrylic polymer having a hydroxyl group and a carboxyl group, the adhesive composition having an average number of isocyanate groups in one molecule in the range of 2.5 to 3.0. diisocyanate-based compounds (hereinafter also referred to as "trifunctional TDI-based compounds") and diphenylmethane diisocyanate-based compounds (hereinafter referred to as " (also referred to as "bifunctional MDI compound") in a specific proportion.
In the adhesive composition of the present disclosure, the trifunctional TDI compound forms a three-dimensional network structure through a crosslinking reaction with a (meth)acrylic polymer having a hydroxyl group and a carboxy group. Crosslinking using a trifunctional TDI compound strengthens the entanglement between the molecular chains of the (meth)acrylic polymer and causes the adhesive layer to develop high cohesive force. This high cohesive force is thought to contribute to suppressing shrinkage of the base material by the adhesive layer.
On the other hand, in crosslinking using only a trifunctional crosslinking agent, the crosslinked structure is fixed by a three-dimensional network structure, so the formed adhesive layer has poor flexibility and poor adhesion to the substrate. In this regard, in the adhesive composition of the present disclosure, since a bifunctional MDI compound is used in addition to a trifunctional TDI compound, a two-dimensional network structure is formed by the bifunctional MDI compound. This improves the flexibility of the adhesive layer. It is thought that this improvement in flexibility results in excellent adhesion of the pressure-sensitive adhesive layer to a base material with low moisture permeability.
In the adhesive composition of the present disclosure, a trifunctional TDI compound and a bifunctional MDI compound are used together in a specific ratio, so that the adhesive layer formed has appropriate flexibility. It is thought that a moderately high cohesive force is imparted in a well-balanced manner.
Furthermore, crosslinking using a bifunctional MDI compound results in appropriately rigid crosslinking because the MDI compound has two aromatic rings. Therefore, appropriate elasticity is imparted to the adhesive layer formed. Furthermore, in crosslinking using a bifunctional MDI compound, steric hindrance occurs due to the aromatic ring, so the network of the crosslinked structure expands at the crosslinking site. For this reason, the formed adhesive layer is provided with appropriate stress relaxation properties. The adhesive layer formed from the adhesive composition of the present disclosure has appropriate elasticity and stress relaxation properties, so it is resistant to shrinkage, foaming, and peeling of the base material that may occur when placed in a harsh environment. It is thought that this can be suppressed well.

By the way, as a method of imparting flexibility to the adhesive layer to be formed, for example, a hexamethylene diisocyanate (HMDI)-based compound, which is a bifunctional crosslinking agent and a structurally flexible aliphatic isocyanate compound, is used. It is also possible to do so. However, HMDI-based compounds have lower reactivity than TDI-based compounds and MDI-based compounds. Furthermore, xylylene diisocyanate (XDI)-based compounds in which an isocyanate group is bonded to an aromatic ring via a methylene group also have lower reactivity than TDI-based compounds and MDI-based compounds. The reason is considered to be that the electron donating property due to the inducing effect of the alkylene group weakens the polarization of the isocyanate group, thereby reducing the nucleophilic reactivity at the carbon of the isocyanate group. Therefore, when a bifunctional crosslinking agent such as HMDI-based compounds and Since a cross-linked structure consisting only of the structure is formed, the bifunctional cross-linking agents HMDI-based compounds and XDI-based compounds that react afterwards only serve to reinforce the cross-linked structure of the TDI-based compounds, and the pressure-sensitive adhesive layer It is thought that it will not contribute to providing flexibility to
On the other hand, in the adhesive composition of the present disclosure, since a trifunctional TDI compound and a bifunctional MDI compound having the same high reactivity are used together, the trifunctional TDI compound and the trifunctional TDI compound are used together. It is thought that the bifunctional MDI compound acts almost simultaneously on the (meth)acrylic polymer having a hydroxyl group and a carboxy group. As a result, it is possible to form a three-dimensional network crosslinked structure using the trifunctional TDI compound while appropriately proceeding with two-dimensional crosslinking using the bifunctional MDI compound, thereby achieving appropriate flexibility and It is believed that it is possible to form an adhesive layer that has both moderately high cohesive force.

From the above, the adhesive layer formed using the adhesive composition of the present disclosure has excellent adhesion to a low moisture permeable base material, and shrinkage of the base material that may occur when placed in a high temperature environment. It is also presumed that foaming and peeling that may occur when placed in an environment where low and high temperatures are repeated can be effectively suppressed.

In the present disclosure, "a (meth)acrylic polymer having a hydroxyl group and a carboxy group" is also referred to as a "specific (meth)acrylic polymer." In addition, in the present disclosure, "a tolylene diisocyanate compound having an average number of isocyanate groups in one molecule in a range of 2.5 or more and 3.0 or less" is also referred to as a "specific tolylene diisocyanate compound." In addition, in the present disclosure, "a diphenylmethane diisocyanate compound having an average number of isocyanate groups in one molecule in a range of 2.0 or more and less than 2.5" is also referred to as a "specific diphenylmethane diisocyanate compound."

[Specific (meth)acrylic polymer]
The adhesive composition of the present disclosure includes a (meth)acrylic polymer having a hydroxyl group and a carboxy group (ie, a specific (meth)acrylic polymer).
The hydroxyl group and carboxy group in the specific (meth)acrylic polymer can undergo a crosslinking reaction with the isocyanate group contained in the specific tolylene diisocyanate compound and the specific diphenylmethane diisocyanate compound described below.
The adhesive composition of the present disclosure may contain only one type of specific (meth)acrylic polymer, or may contain two or more types of specific (meth)acrylic polymer.

The specific (meth)acrylic polymer may be a homopolymer or a copolymer. When the specific (meth)acrylic polymer is a copolymer, the copolymer may be a copolymer of two or more (meth)acrylic monomers, and (meth)acrylic monomers may be copolymerized. The monomer may be copolymerized with a monomer other than the (meth)acrylic monomer.
The specific (meth)acrylic polymer may be, for example, one in which a hydroxyl group and a carboxyl group are introduced by substitution into a (meth)acrylic polymer that does not have either a hydroxyl group or a carboxy group, or a polymer having a hydroxyl group. , and a (meth)acrylic polymer that does not have a carboxy group and may have a carboxy group introduced by substitution, or a (meth)acrylic polymer that has a carboxy group and does not have a hydroxyl group. In addition, a hydroxyl group may be introduced by substitution. Further, the specific (meth)acrylic polymer may be, for example, a copolymer of a monomer having a hydroxyl group and a monomer having a carboxy group.

In a preferred embodiment of the specific (meth)acrylic polymer, the specific (meth)acrylic polymer contains a constitutional unit derived from a monomer having a hydroxyl group and a constitutional unit derived from a monomer having a carboxyl group, which will be described later. This embodiment has a hydroxyl group and a carboxy group.

<Structural unit derived from a monomer having a hydroxyl group>
It is preferable that the specific (meth)acrylic polymer contains a structural unit derived from a monomer having a hydroxyl group. In the present disclosure, "a structural unit derived from a monomer having a hydroxyl group" means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

The type of monomer having a hydroxyl group is not particularly limited.
Examples of the monomer having a hydroxyl group include a monomer having at least one hydroxyl group and an ethylenically unsaturated group in one molecule.
The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinyl phenyl group, a (meth)acrylamide group, and a (meth)acryloyl group.
As the ethylenically unsaturated group, a (meth)acryloyl group is preferable.

Specific examples of monomers having hydroxyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxypropyl (meth)acrylate. Hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate ) 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, since it has good copolymerizability with other monomers. As the hydroxyalkyl (meth)acrylate, hydroxyalkyl (meth)acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms is preferred, and 2-hydroxyethyl acrylate is more preferred.

When the specific (meth)acrylic polymer contains a structural unit derived from a monomer having a hydroxyl group, it may contain only one type of structural unit derived from a monomer having a hydroxyl group, or it may contain two or more types of structural units derived from a monomer having a hydroxyl group. It's okay to stay.

When the specified (meth)acrylic polymer contains a structural unit derived from a monomer having a hydroxyl group, the content of the structural unit derived from a monomer having a hydroxyl group in the specified (meth)acrylic polymer is particularly Although not limited, for example, the range is preferably 0.05% by mass or more and 10.0% by mass or less, and 0.1% by mass or more5. It is more preferably in the range of 0 mass% or less, even more preferably in the range of 0.1 mass% or more and 3.0 mass% or less, and even more preferably in the range of 0.2 mass% or more and 1.0 mass% or less. It is particularly preferable.
When the content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic polymer is 0.05% by mass or more based on the total structural units of the specific (meth)acrylic polymer, The formed adhesive layer tends to be able to better suppress foaming that may occur when placed in an environment where low and high temperatures are repeated.
The content of structural units derived from a monomer having a hydroxyl group in the specific (meth)acrylic polymer is 10.0% by mass or less based on the total structural units of the specific (meth)acrylic polymer, The adhesive layer that is formed tends to have improved adhesion to substrates with low moisture permeability. Further, the formed adhesive layer shows a tendency to better suppress peeling that may occur when placed in an environment where low and high temperatures are repeated.

<Monomer having a carboxy group>
It is preferable that the specific (meth)acrylic polymer contains a structural unit derived from a monomer having a carboxy group.
In the present disclosure, "a structural unit derived from a monomer having a carboxy group" means a structural unit formed by addition polymerization of a monomer having a carboxy group.

The type of monomer having a carboxy 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 examples thereof include a vinyl group, an allyl group, a vinyl phenyl group, a (meth)acrylamide group, and a (meth)acryloyl group.
As the ethylenically unsaturated group, a (meth)acryloyl group is preferable.

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 (eg, 2-acryloyloxyethyl-succinic acid).
The monomer having a carboxy group is preferably a (meth)acrylic monomer having a carboxy group. As the (meth)acrylic monomer having a carboxy group, acrylic acid is preferred.

When the specific (meth)acrylic polymer contains a structural unit derived from a monomer having a carboxy group, it may contain only one type of structural unit derived from a monomer having a carboxy group, or two types of structural units may be contained. It may contain more than that.

When the specified (meth)acrylic polymer contains a structural unit derived from a monomer having a carboxy group, the content of the structural unit derived from a monomer having a carboxy group in the specified (meth)acrylic polymer is Although not particularly limited, for example, it is preferably in the range of 0.05% by mass or more and 5.0% by mass or less, and 0.1% by mass or more, based on the total constitutional units of the specific (meth)acrylic polymer. The range is more preferably 3.0% by mass or less, even more preferably the range from 0.1% by mass to 2.0% by mass, and the range from 0.2% by mass to 1.0% by mass. It is particularly preferable that
The content of structural units derived from a monomer having a carboxy group in the specified (meth)acrylic polymer is 0.05% by mass or more based on the total structural units of the specified (meth)acrylic polymer. The adhesive layer formed tends to be able to better suppress foaming that may occur when placed in an environment where low and high temperatures are repeated.
The content of structural units derived from a monomer having a carboxy group in the specified (meth)acrylic polymer is 5.0% by mass or less based on the total structural units of the specified (meth)acrylic polymer. The adhesive layer thus formed tends to have improved adhesion to a substrate with low moisture permeability. Further, the formed adhesive layer shows a tendency to better suppress peeling that may occur when placed in an environment where low and high temperatures are repeated.

When the specified (meth)acrylic polymer contains a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a carboxy group, the content of a structural unit derived from a monomer having a hydroxyl group As a combination of the ratio and the content of structural units derived from monomers having a carboxy group, the content of structural units derived from a monomer having a hydroxyl group in a specific (meth)acrylic polymer is the total structural unit. The content of structural units derived from a monomer having a carboxy group in the specific (meth)acrylic polymer is within the range of 0.05% by mass or more and 10.0% by mass or less based on the total structural units. It is preferable that the content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic polymer is in the range of 0.05% by mass or more and 5.0% by mass or less based on the total structural units. The content of structural units derived from a monomer having a carboxy group in the specific (meth)acrylic polymer is 0.1% by mass or more and 5.0% by mass or less based on the total structural units. It is more preferable that the content of the structural unit derived from a monomer having a hydroxyl group in the specific (meth)acrylic polymer is in the range of .1% by mass or more and 3.0% by mass or less, based on the total structural units. The range is from 0.1% by mass to 3.0% by mass, and the content of structural units derived from a monomer having a carboxy group in the specific (meth)acrylic polymer is 0.1% by mass to all structural units. More preferably, the content is in the range of 1% by mass or more and 2.0% by mass or less, and the content of structural units derived from monomers having hydroxyl groups in the specific (meth)acrylic polymer is 0% relative to all structural units. .2% by mass or more and 1.0% by mass or less, and the content of structural units derived from a monomer having a carboxy group in the specific (meth)acrylic polymer is 0.2% relative to all structural units. Particularly preferred is an embodiment in which the content is in the range of 1.0% by mass or more and 1.0% by mass or less.

<Structural unit derived from (meth)acrylic acid alkyl ester monomer>
The specific (meth)acrylic polymer preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer.
In the present disclosure, "a structural unit derived from a (meth)acrylic acid alkyl ester monomer" means a structural unit formed by addition polymerization of a (meth)acrylic acid alkyl ester monomer. In addition, the "(meth)acrylic acid alkyl ester monomer" in this disclosure includes monomers that correspond to monomers that have a carboxy group and monomers that correspond to monomers that have a hydroxyl group. Not done.

The type of (meth)acrylic acid alkyl ester monomer is not particularly limited.
The (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer.
The alkyl group possessed by the (meth)acrylic acid alkyl ester monomer may be unsubstituted, or may have a substituent (excluding carboxy groups and hydroxyl groups), but is unsubstituted. It is preferable.
The alkyl group that the (meth)acrylic acid alkyl ester monomer has may be linear, branched, or cyclic.
The number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester monomer is preferably from 1 to 18, more preferably from 1 to 12, even more preferably from 1 to 8, Particularly preferably 1 to 4.

Specific examples of (meth)acrylic acid alkyl ester monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, and s-butyl (meth)acrylate. 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, Examples include n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate.
The (meth)acrylic acid alkyl ester monomer is preferably at least one selected from the group consisting of n-butyl acrylate, methyl acrylate, and methyl methacrylate.

When the specific (meth)acrylic polymer contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, it must contain only one type of structural unit derived from the (meth)acrylic acid alkyl ester monomer. or two or more types may be included.

When the specified (meth)acrylic polymer contains a structural unit derived from an alkyl (meth)acrylate monomer, the unit derived from the alkyl (meth)acrylate monomer in the specified (meth)acrylic polymer The content of the structural units is not particularly limited, but for example, it is preferably in the range of 50.0% by mass or more and 99.9% by mass or less based on all the structural units of the specific (meth)acrylic polymer. It is 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 even more preferably in the range of 65.0% by mass or more and 99.8% by mass or less. A range of 8% by mass or less is particularly preferred.
Here, the content of the structural units derived from the (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic polymer is 50.0% relative to the total structural units of the specific (meth)acrylic polymer. % by mass or more means that the structural unit derived from the (meth)acrylic acid alkyl ester monomer is contained as the main component of the structural units constituting the specific (meth)acrylic polymer. .

<Other constituent units>
Other structural units that the specific (meth)acrylic polymer may contain include structural units derived from (meth)acrylates having an aromatic ring such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; methoxy Structural units derived from alkoxyalkyl (meth)acrylates represented by ethyl (meth)acrylate and ethoxyethyl (meth)acrylate; styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyl Structural units derived from aromatic monovinyl represented by toluene; Structural units derived from vinyl cyanide represented by acrylonitrile and methacrylonitrile; Vinyl represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate. Structural units derived from esters; and the like.
When the specific (meth)acrylic polymer contains other structural units, structural units derived from (meth)acrylate having an aromatic ring are preferable from the viewpoint of suppressing white spots.

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

When the specific (meth)acrylic polymer contains other structural units, the content of the other structural units in the specific (meth)acrylic polymer is within the range that does not impair the effect of the adhesive composition of the present disclosure. Can be set as appropriate.

-Weight average molecular weight of specific (meth)acrylic polymer-
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, for example, 700,000 to 2,500,000. It is more preferably in the following ranges, 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 the specific (meth)acrylic polymer is 400,000 or more, the adhesive layer formed will suffer from shrinkage of the base material that may occur when placed in a high-temperature environment, and between low and high temperatures. It shows a tendency to be able to better suppress foaming that may occur when placed in an environment where .
The weight average molecular weight of the specific (meth)acrylic polymer is preferably 2.5 million or less from the viewpoint of productivity of the specific (meth)acrylic polymer.

The weight average molecular weight of the 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 the specific (meth)acrylic polymer is applied to a release paper and dried at 100° C. for 1 minute to obtain a film-like specific (meth)acrylic polymer.
[2] Using the film-shaped 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. Note that the "solid content concentration" herein means the mass proportion 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 value by gel permeation chromatography (GPC) under the following conditions.

～Conditions～
Measuring device: High-speed GPC [Model number: HLC-8220 GPC, manufactured by Tosoh Corporation]
Detector: Differential refractometer (RI) [built into HLC-8220, manufactured by Tosoh Corporation]
Column: 4 TSKgel GMH _XL [manufactured by Tosoh Corporation] Column temperature: 40°C
Eluent: Tetrahydrofuran Injection volume of sample solution: 100 μL
Flow rate: 0.8mL/min

The weight average molecular weight of a specific (meth)acrylic polymer can be determined by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomer. By doing so, the desired value can be obtained.

-Content of specific (meth)acrylic polymer-
The specific (meth)acrylic polymer in the adhesive composition of the present disclosure is not particularly limited; It is preferably from 85.0% by mass to 99.8% by mass, and even more preferably from 90.0% by mass to 99.8% by mass.

In the present disclosure, the "total solid content in the adhesive composition" means the total mass of the adhesive composition when the adhesive composition does not contain a solvent; In this case, it means the mass of the residue after removing the solvent from the adhesive composition.
In this disclosure, "solvent" means water and organic solvents.

[Method for producing specific (meth)acrylic polymer]
The method for producing the specific (meth)acrylic polymer is not particularly limited.
The specific (meth)acrylic polymer can be produced by polymerizing the monomers mentioned above using known polymerization methods such as solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Can be manufactured.
As the polymerization method, a solution polymerization method is preferable because the processing steps are relatively simple and can be carried out in a short time when preparing the adhesive composition after production.

In the solution polymerization method, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as necessary are generally placed in a polymerization tank, and the polymerization is carried out at, for example, the reflux temperature of the organic solvent while stirring. Heat and react for several hours. In this case, at least a portion of the organic solvent, monomer, polymerization initiator, and optionally used chain transfer agent may be added sequentially. Alternatively, the reaction may be carried out in a nitrogen stream.

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

When producing a specific (meth)acrylic polymer, it is preferable to use an organic solvent that does not easily cause chain transfer during the polymerization reaction of aromatic hydrocarbon compounds, ester compounds, ketone compounds, etc. From the viewpoint of polymer solubility, ease of polymerization reaction, etc., it is preferable to use ethyl acetate.

At the time of the polymerization reaction, only one type of organic solvent may be used, or two or more types may be used.

Examples of the polymerization initiator include organic peroxides and azo compounds used in common solution polymerization methods.
Specific examples of organic peroxides include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i- Propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butylperoxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)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-cumylperoxy) cyclohexyl)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], and 2,2'-azobis(4 -methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and dimethyl 2,2'-azobis(isobutyrate).

At the time of the polymerization reaction, only one kind of polymerization initiator may be used, or two or more kinds of polymerization initiators may be used.

The amount of the 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.

When producing the specific (meth)acrylic polymer, a chain transfer agent may be used if necessary.
Examples of chain transfer agents include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, α-methylstyrene, anthracene, phenanthrene, and fluorene. , and aromatic compounds represented by 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and aromatic nitro compounds represented by p-nitrotoluene, benzoquinone, and Benzoquinone derivatives represented by 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane , tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and halogenated hydrocarbon compounds represented by 3-chloro-1-propene, aldehyde compounds represented by chloral and furaldehyde, alkyl having 1 to 18 carbon atoms. Mercaptan compounds, 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 pinene and terpinolene. Typical examples include terpene compounds.

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 may vary depending on the molecular weight of the desired specific (meth)acrylic polymer. , can be set as appropriate.

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

[Specific tolylene diisocyanate compounds]
The adhesive composition of the present disclosure contains a tolylene diisocyanate compound (ie, a specific tolylene diisocyanate compound) having an average number of isocyanate groups in one molecule in a range of 2.5 or more and 3.0 or less.
The adhesive composition of the present disclosure may contain only one type of specific tolylene diisocyanate-based compound, or may contain two or more types of specific tolylene diisocyanate compounds.

The specific tolylene diisocyanate compound has an average number of isocyanate groups in one molecule in a range of 2.5 or more and 3.0 or less, preferably in a range of 2.7 or more and 3.0 or less.

In the present disclosure, the "average number of isocyanate groups in one molecule" of a specific tolylene diisocyanate-based compound is a value determined by the following calculation formula. Note that the "number average molecular weight of the specific tolylene diisocyanate compound" in the following calculation formula is determined by gel permeation chromatography (GPC). Moreover, in the following calculation formula, "concentration of isocyanate groups" means the mass proportion (unit: mass %) of isocyanate groups contained in the specific tolylene diisocyanate-based compound. Further, the "formula weight of the isocyanate group" in the following calculation formula is 42.
Average number of isocyanate groups in one molecule = (number average molecular weight of specific tolylene diisocyanate compound x concentration of isocyanate groups) / (formula weight of isocyanate groups x 100)

In the present disclosure, the "tolylene diisocyanate compound" includes, for example, tolylene diisocyanate (also referred to as "TDI"), a polymer of tolylene diisocyanate, and a tolylene diisocyanate and polyol compound [e.g., trimethylolpropane (TMP)]. ] and a biuret form of tolylene diisocyanate.
Specific examples of tolylene diisocyanate include 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate.
The type of tolylene diisocyanate compound is not particularly limited, but is preferably an adduct of TDI and TMP, for example.

As the specific tolylene diisocyanate compound, commercially available products can be used.
Examples of commercially available specific tolylene diisocyanate compounds include "Coronate (registered trademark) L-45E" and "Coronate (registered trademark) L" manufactured by Tosoh Corporation.

[Specified diphenylmethane diisocyanate compounds]
The adhesive composition of the present disclosure includes a diphenylmethane diisocyanate compound (ie, a specific diphenylmethane diisocyanate compound) having an average number of isocyanate groups in one molecule in a range of 2.0 or more and less than 2.5.
The adhesive composition of the present disclosure may contain only one type of specific diphenylmethane diisocyanate-based compound, or may contain two or more types of specific diphenylmethane diisocyanate compounds.

The specific diphenylmethane diisocyanate-based compound has an average number of isocyanate groups in one molecule in a range of 2.0 or more and less than 2.5, preferably in a range of 2.0 or more and 2.3 or less.
In the present disclosure, the "average number of isocyanate groups in one molecule" of the specific diphenylmethane diisocyanate-based compound is a value determined by the same calculation formula as the "average number of isocyanate groups in one molecule" of the specific tolylene diisocyanate-based compound described above. be.

In the present disclosure, "diphenylmethane diisocyanate compounds" include, for example, diphenylmethane diisocyanate (also referred to as "MDI"), diphenylmethane diisocyanate polymers, diphenylmethane diisocyanate and polyol compounds [e.g., polytetramethylene ether glycol (PTMG)], and the biuret form of diphenylmethane diisocyanate.
Specific examples of diphenylmethane diisocyanate 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 is preferably an adduct of MDI and PTMG, for example.

As the specific diphenylmethane diisocyanate compound, commercially available products can be used.
An example of a commercially available specific diphenylmethane diisocyanate compound is "Coronate (registered trademark) 4370" manufactured by Tosoh Corporation.

The mass ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound in the adhesive composition of the present disclosure (i.e., the content mass of the specific diphenylmethane diisocyanate compound/the content mass of the specific tolylene diisocyanate compound) is 2 or less. It is.
When the mass ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound in the adhesive composition of the present disclosure is 2 or less, shrinkage of the base material that may occur when placed in a high temperature environment is effectively suppressed. It is possible to form an adhesive layer that can be used. From this viewpoint, the mass ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound in the adhesive composition of the present disclosure is preferably in the range of 1/100 or more and 2/1 or less, and 1/100 or more and 2/1 or less, and It is more preferably in the range of 50 or more and 1/1 or less, even more preferably in the range of 1/10 or more and 1/1 or less, and particularly preferably in the range of 1/5 or more and 1/2 or less.

The content of the specific tolylene diisocyanate compound and the content of the specific diphenylmethane diisocyanate compound in the pressure-sensitive adhesive composition of the present disclosure are such that the pressure-sensitive adhesive composition of the present disclosure contains the specific tolylene diisocyanate compound and the specific diphenylmethane diisocyanate compound. , and the content ratio of the specific diphenylmethane diisocyanate compound to the specific tolylene diisocyanate compound is not particularly limited, as long as it is 2 or less.
The adhesive composition of the present disclosure has, for example, excellent adhesion to a substrate with low moisture permeability, and is resistant to shrinkage of the substrate that may occur when placed in a high-temperature environment, and repeated exposure to low and high temperatures. From the viewpoint of forming an adhesive layer that can better suppress foaming and peeling that may occur when placed in an environment, the content of the specific tolylene diisocyanate compound is set to 100 parts by mass of the specific (meth)acrylic polymer. The specified diphenylmethane diisocyanate-based compound is in the range of 0.01 parts by weight or more and 7.0 parts by weight or less based on 100 parts by weight of the specified (meth)acrylic polymer. It is preferable that the content of the specific tolylene diisocyanate compound is in the range of 0.1 parts by mass or more and 5.0 parts by mass or less based on 100 parts by mass of the specific (meth)acrylic polymer, It is more preferable that the specific diphenylmethane diisocyanate compound is in the range of 0.01 parts by mass or more and 1.0 parts by mass or less based on 100 parts by mass of the specific (meth)acrylic polymer, and 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 based on 100 parts by mass of the specific (meth)acrylic polymer, and the specific diphenylmethane diisocyanate compound is added to 100 parts by mass of the specific (meth)acrylic polymer. It is more preferable that the content of the specific tolylene diisocyanate compound is in the range of 0.05 parts by mass or more and 0.5 parts by mass or less based on 100 parts by mass of the specific (meth)acrylic polymer. The range is from 0.5 parts by mass to 0.5 parts by mass, and the specific diphenylmethane diisocyanate compound is from 0.1 parts by mass to 0.3 parts by mass based on 100 parts by mass of the specific (meth)acrylic polymer. It is particularly preferable.

〔Silane coupling agent〕
The adhesive composition of the present disclosure preferably contains a silane coupling agent.
When the adhesive composition of the present disclosure contains a silane coupling agent, the formed adhesive layer may, for example, foam when placed in an environment where low and high temperatures are repeated while bonded to glass. and exhibits a tendency to better suppress peeling. The reason is presumed to be that the interaction between the formed adhesive layer and the glass is increased more appropriately.

The type of silane coupling agent is not particularly limited.
Examples of the silane coupling agent include silane compounds containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane. - Thiol group-containing silane compounds such as mercaptopropyltriethoxysilane and 3-mercaptopropyldimethoxymethylsilane, 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane Representative epoxy group-containing silane compounds, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxy Examples include amino group-containing silane compounds such as silane, and tris-(3-trimethoxysilylpropyl)isocyanurate.

As the silane coupling agent, commercially available products can be used.
Examples of commercially available silane coupling agents include "KBM-803", "KBM-802", "X-41-1810", "X-41-1811", and "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).

When the adhesive composition of the present disclosure contains a silane coupling agent, it may contain only one type of silane coupling agent, or may contain two or more types of silane coupling agent.

When the adhesive composition of the present disclosure contains a silane coupling agent, the content of the silane coupling agent is not particularly limited, but for example, 0.1 parts by mass based on 100 parts by mass of the specific (meth)acrylic polymer. It is preferably in the range of 0.1 parts by mass or more and 0.5 parts by mass or less, and more preferably in the range of 0.1 parts by mass or more and 0.3 parts by mass or less. It is more preferable that
When the content of the silane coupling agent in the adhesive composition of the present disclosure is within the above range based on 100 parts by mass of the specific (meth)acrylic polymer, the adhesive layer formed has a low moisture permeability. The adhesiveness to the base material tends to be further improved. Further, when the content of the silane coupling agent in the adhesive composition of the present disclosure is within the above range with respect to 100 parts by mass of the specific (meth)acrylic polymer, the adhesive layer formed is, for example, When placed in an environment where low and high temperatures are repeated while bonded to glass, foaming and peeling tend to be better suppressed.

〔Organic solvent〕
The adhesive composition of the present disclosure may contain an organic solvent.
When the adhesive composition of the present disclosure contains an organic solvent, the coating properties may be improved.
Examples of the organic solvent include organic solvents similar to those used in the polymerization reaction of the specific (meth)acrylic polymer described above.

When the adhesive composition of the present disclosure contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types of organic solvent.

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

[Other ingredients]
The adhesive composition of the present disclosure may contain components other than those described above (so-called other components), as necessary, within a range that does not impair its effects.
Other components include polymers other than specific (meth)acrylic polymers, crosslinking catalysts, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., ultraviolet absorbers), and antistatic agents. Various additives such as

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

<Applications of adhesive composition>
The use of the adhesive composition of the present disclosure is not particularly limited.
The adhesive composition of the present disclosure can form an adhesive layer with excellent adhesion to a low moisture permeable substrate, and is therefore suitable as an adhesive composition for use on a substrate using a low moisture permeable material.
The material with low moisture permeability is not particularly limited, but it is preferable that the material has a moisture permeability of 200 g/(m ² ·24 hr) or less when a film with a thickness of 40 μm is formed.
The moisture permeability is measured by a method based on the moisture permeability test method (cup method) of JIS Z 0208:2021. Specifically, it is measured by the following method. A test piece obtained by cutting a 40 μm thick film into a disk shape with a diameter of 70 mm was sealed in a moisture permeable cup (aluminum cup) containing approximately 15 g of calcium chloride (hygroscopic agent), and the temperature was 40°C and the humidity was 90% RH. Store in a constant temperature and humidity chamber set to 24 hours. By measuring the change in mass of calcium chloride before and after this standing still, the moisture permeability [unit: g/(m ² ·24 hr)] is determined.

Examples of low moisture permeable materials include resins such as (meth)acrylic resins and cycloolefin resins.

In the present disclosure, "(meth)acrylic resin" includes structural units derived from (meth)acrylic monomers, and the proportion of structural units derived from (meth)acrylic monomers is It means a resin containing 50% by mass or more.
In the present disclosure, "cycloolefin resin" is an amorphous olefin resin in which a cyclic olefin structure is introduced into the polymer chain, and is obtained from cyclic olefins such as norbornene, tetracyclododecene, and derivatives thereof. means resin. 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, or one or more cyclic olefins. It may be a random copolymer of two or more cyclic olefins and an α-olefin (eg, ethylene, propylene, etc.), or it may be a hydrogenated product of these polymers.

The low moisture permeability material is preferably at least one selected from (meth)acrylic resins and cycloolefin resins, more preferably (meth)acrylic resins or cycloolefin resins, and (meth)acrylic resins or cycloolefin resins. ) More preferably, it is an acrylic resin.
As the (meth)acrylic resin, polymethyl methacrylate (PMMA) is preferable.
The cycloolefin resin is preferably a cycloolefin resin (COP). In the present disclosure, "cycloolefin resin" means a polymer consisting only of one or more cyclic olefins.

The adhesive layer formed by the adhesive composition of the present disclosure can be made of, for example, not only polymethyl methacrylate (PMMA) and cycloolefin resin (COP), which are low moisture permeable materials, but also triacetyl cellulose (TAC). It also has excellent adhesion. All of these resins are used as materials for members (for example, protective films and retardation films) that constitute polarizing plates. In addition, the adhesive layer formed from the adhesive composition of the present disclosure may suffer from shrinkage of the base material that may occur when placed in a high-temperature environment, and when placed in an environment where low and high temperatures are repeated. Foaming and peeling that may occur can be effectively suppressed. Therefore, the adhesive composition of the present disclosure is suitable as an adhesive composition for use in polarizing plates (so-called adhesive composition for polarizing plates).
Specific applications of the pressure-sensitive adhesive composition of the present disclosure include applications in which a polarizing plate is bonded to a glass substrate of a liquid crystal cell, applications in which a retardation film and a protective film that constitute a polarizing plate are bonded together, and the like.

[Laminated body]
The laminate of the present disclosure includes a polarizing plate provided on one or both sides with a layer containing at least one resin selected from the group consisting of (meth)acrylic resin and cycloolefin resin, and a polarizing plate provided on the layer. , and an adhesive layer formed from the adhesive composition of the present disclosure.
In the laminate of the present disclosure, the adhesive composition of the present disclosure is formed on a layer containing at least one resin selected from the group consisting of (meth)acrylic resin and cycloolefin resin, which is included in the polarizing plate. An adhesive layer is provided. Since the adhesive layer formed from the adhesive composition of the present disclosure has excellent adhesion to a base material with low moisture permeability, the laminate of the present disclosure is made of a (meth)acrylic resin and a cycloolefin resin. Excellent adhesion between the layer containing at least one resin selected from the group and the adhesive layer. Furthermore, since the laminate of the present disclosure includes an adhesive layer formed from the adhesive composition of the present disclosure, the layer included in the polarizing plate is unlikely to shrink even when placed in a high-temperature environment, and Even when placed in an environment where low and high temperatures are repeated, foaming and peeling are unlikely to occur.

The laminate of the present disclosure includes a polarizing plate.
The polarizing plate included in the laminate of the present disclosure includes a layer (hereinafter also referred to as "specific resin layer") containing at least one resin selected from the group consisting of (meth)acrylic resin and cycloolefin resin on one or both sides. ).
The polarizing plate may be provided with the specific resin layer only on one side, or may be provided on both sides.

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 among (meth)acrylic resin and cycloolefin resin, or may contain only (meth)acrylic resin. It may contain only a cycloolefin resin.
The proportion of the (meth)acrylic resin and cycloolefin resin in all the resins in the specific resin layer is not particularly limited, but for example, it is preferably 50% by mass or more, more preferably 70% by mass or more. Preferably, it is more preferably 80% by mass or more,
It is particularly preferably 90% by mass or more, and may be 100% by mass.

When 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).

The specific resin layer may contain components other than the specific resin, as necessary, within a range that does not impair the effects of the laminate of the present disclosure.
Components other than the specific resin include resins other than the specific resin, antioxidants, light stabilizers (for example, ultraviolet absorbers), and various additives such as antistatic agents.

The surface of the specific resin layer on which the adhesive layer is provided is subjected to surface treatments such as corona discharge treatment and plasma discharge treatment (so-called easy-adhesion treatment) in order to further improve the adhesion between the specific resin layer and the adhesive layer. processing) may be applied.

The thickness of the specific resin layer is not particularly limited, but is preferably, for example, 10 μm to 100 μm, more preferably 20 μm to 80 μm.
The thickness of the specific resin layer here refers to the thickness of one side.

The "thickness of a specific resin layer" in the present disclosure means the average thickness of the specific resin layer.
The average thickness of the specific resin layer is a value determined by the following method.
The thickness of the specific resin layer at 10 randomly selected locations in the thickness direction is measured using a film thickness meter. The arithmetic mean value of the measured values is determined, and the obtained value is taken as the average thickness of the specific resin layer.

The laminate of the present disclosure includes an adhesive layer formed from the adhesive composition of the present disclosure.
The adhesive layer included in 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 that is crosslinked and cured with a specific tolylene diisocyanate compound and a specific diphenylmethane diisocyanate compound.

The adhesive layer included in the laminate of the present disclosure is provided on the specific resin layer included in the polarizing plate.
When the polarizing plate included in the laminate of the present disclosure includes specific resin layers on both sides, the adhesive layer is provided only on one of the two specific resin layers. Alternatively, an adhesive layer may be provided on both specific resin layers.

The thickness of the adhesive layer included in the laminate of the present 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.

The "thickness of the adhesive layer" in the present disclosure means the average thickness of the adhesive layer. The average thickness of the adhesive layer is a value determined by the same method as the average thickness of the specific resin layer described above.

The polarizing plate included in the laminate of the present disclosure preferably includes a specific resin layer as a functional film such as a protective film or a retardation film.
When a polarizing plate includes a specific resin layer as a protective film or a retardation film, the layer structure of the laminate of the present disclosure includes, for example, 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 [retardation film (specific resin layer)/polarizer/retardation film (specific resin layer)], adhesive layer/polarizing plate [retardation film (specific resin layer)/polarizer], adhesive layer/polarizing plate [protective film (specific resin layer)/polarizer/protective film (specific resin layer) ] and the like.

In the laminate of the present 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.

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

[Method for producing laminate]
The method for producing the laminate of the present disclosure is not particularly limited.
The laminate of the present disclosure can be produced by a known method.
Examples of methods for producing the laminate of the present disclosure include the following method.
Note that the following method will be described using an example in which the layer configuration of the polarizing plate is "specific resin layer/polarizer/specific resin layer."

A coating film is formed on the release sheet by applying the adhesive composition of the present disclosure to the easily peelable surface of the release sheet. Next, by drying the formed coating film, an adhesive film is formed on the release sheet. Next, the exposed surface of the formed adhesive film is laminated on the surface of the specific resin layer of the polarizing plate, and then curing is performed to form the release sheet/adhesive layer/polarizing plate (specific resin layer/polarizing plate). A laminate of the present disclosure having a laminate structure of a specific resin layer and a specific resin layer can be produced.

Other methods include, for example, the following method.
A coating film is formed on the specific resin layer by applying the adhesive composition of the present disclosure to the surface of the specific resin layer included in the polarizing plate. Next, by drying the formed coating film, an adhesive film is formed on the specific resin layer. Next, the exposed surface of the formed adhesive film is laminated on the easily peelable surface of the release sheet, and then cured to form the release sheet/adhesive layer/polarizing plate (specific resin layer/polarizer/ A laminate of the present disclosure having a laminate structure of a specific resin layer) can be produced.

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

The method of drying the coating film is not particularly limited.
Examples of methods for drying the coating film include methods such as 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 appropriately set depending on the thickness of the coating film, the amount of organic solvent in the coating film, and the like.
An example of drying conditions includes drying at 70° C. to 120° C. for 30 seconds to 180 seconds using a hot air circulation dryer.

As a curing method, for example, a method of leaving it 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% can be mentioned.

Hereinafter, the adhesive composition of the present disclosure will be explained in more detail with reference to Examples. The present disclosure is not limited to the following examples unless it exceeds the spirit thereof.

[Production of (meth)acrylic polymer]
[Manufacture example A-1]
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 79.2 parts by mass of n-butyl acrylate [n-BA; acrylic acid alkyl ester monomer] and phenoxyethyl acrylate [PHEA] were placed. Other monomers] 20.0 parts by mass, 2-hydroxyethyl acrylate [2HEA; monomer having a hydroxyl group] 0.3 parts by mass, acrylic acid [AA; monomer having a carboxy group] 0.5 Parts by mass and 70.0 parts by mass of ethyl acetate [organic solvent] were added and mixed to obtain a mixture, and then the inside of the reactor was purged with nitrogen.
Next, the temperature of the mixture in the reactor was raised to 70° C. while stirring, and then 0.2% of 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; polymerization initiator] was added to the mixture in the reactor. 02 parts by mass of ethyl acetate and 120.0 parts by mass of ethyl acetate were successively added, and after the addition was completed, the mixture was maintained for 6 hours to complete the polymerization reaction. Next, the solution obtained by completing the polymerization reaction was 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. .

The "solid content concentration" herein means the mass proportion of (meth)acrylic polymer A-1 in the solution of (meth)acrylic polymer A-1. The same applies to each solution of (meth)acrylic polymers A-2 to A-14 produced below.

[Production Examples A-2, A-3, and A-6 to A-14]
Production Examples A-2, A-3, and A-6 to A-14 are the same as Production Examples except that the monomer composition of the (meth)acrylic polymer was changed to the monomer composition shown in Table 1. The same operation as A-1 was performed to obtain each solution of (meth)acrylic polymers A-2, A-3, and A-6 to A-14 with a solid content concentration of 18.5% by mass. .

[Production examples A-4 and A-5]
In Production Examples A-4 and A-5, when producing a (meth)acrylic polymer, by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used, the (meth)acrylic polymer The same operation as in Production Example A-1 was performed except that the weight average molecular weight of the polymer was adjusted to the weight average molecular weight shown in Table 1, and a (meth)acrylic polymer with a solid content concentration of 18.5% by mass was prepared. Solutions of combined A-4 and A-5 were obtained.

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

The weight average molecular weight (Mw) of the (meth)acrylic polymers A-1 to A-14 was measured by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic polymer described above.

Among the (meth)acrylic polymers A-1 to A-14, (meth)acrylic polymers A-1 to A-11 correspond to specific (meth)acrylic polymers in the present disclosure.

Details of each monomer listed in Table 1 are as shown below.
<Monomer with hydroxyl group>
"2HEA": 2-hydroxyethyl acrylate <monomer having a carboxy group>
"AA": Acrylic acid <(meth)acrylic acid alkyl ester monomer>
“n-BA”: n-butyl acrylate “MA”: Methyl acrylate “MMA”: Methyl methacrylate <Other monomers>
"PHEA": Phenoxyethyl acrylate

In Table 1, "-" in the monomer composition column means that the monomer corresponding to that column was not used.

[Preparation of adhesive composition]
[Example 1]
540.5 parts by mass of a solution of (meth)acrylic polymer A-1 (100 parts by mass as solid content) and Coronate (registered trademark) L-45E [trade name, tolylene diisocyanate (trade name) as a specific tolylene diisocyanate compound. TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, average number of isocyanate groups in one molecule: 2.7, manufactured by Tosoh Corporation] 0.67 parts by mass (solid content: 0 .3 parts by mass) and Coronate (registered trademark) 4370 as a specific diphenylmethane diisocyanate-based compound [trade name, adduct of diphenylmethane diisocyanate (MDI) and polytetramethylene ether glycol (PTMG), solid content concentration: 100% by mass, Average number of isocyanate groups in one molecule: 2.1, manufactured by Tosoh Corporation] 0.1 part by mass (0.1 part by mass as solid content), and a silane coupling agent X-41-1810 [trade name, thiol Group-containing silane compound, solid content concentration: 100% by mass, Shin-Etsu Chemical Co., Ltd.] 0.2 parts by mass (0.2 parts by mass as solid content) and an appropriate amount of ethyl acetate [organic solvent] were sufficiently added. The adhesive composition of Example 1 was obtained by mixing.

[Examples 2 to 22]
In Example 1, the same operation as in Example 1 was performed except that the composition of the adhesive composition was changed to the composition shown in Table 2, and each adhesive composition of Examples 2 to 22 was obtained.

[Comparative Examples 1 to 10]
In Example 1, the same operation as in Example 1 was performed except that the composition of the adhesive composition was changed to the composition shown in Table 3, and each adhesive composition of Comparative Examples 1 to 10 was obtained.

Details of the components listed in Table 2 and/or Table 3 are as shown below.
<TDI compound>
"Coronate L-45E" [Product name, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45% by mass, average number of isocyanate groups in one molecule: 2.7, Tosoh ( Co., Ltd.]
<MDI compound>
"Coronate 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, Tosoh Corporation ) made]

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

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

<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.]

In Tables 2 and 3, the values listed in the "Amount" column are all converted to solid content.
In Tables 2 and 3, "-" means that the component corresponding to that column is not blended.
In Tables 2 and 3, the "blended mass ratio of the diphenylmethane diisocyanate compound to the tolylene diisocyanate compound" is expressed as "mass ratio (M/T)."

[Preparation of polarizing plate (A) with adhesive layer]
The adhesive prepared above was applied to the easy-release surface of a release film [type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation] that had been surface-treated with a silicone-based release agent (so-called easy-release treatment). The composition was applied to form a coating film. The amount of the adhesive composition applied was such that the thickness of the adhesive film, which will be described later, would be 15 μm. Next, the formed coating film is dried by blowing 100°C air at a wind speed of 3 m/sec for 60 seconds using a hot air circulation dryer, and a 15 μm thick adhesive film is formed on the release film. was formed. Next, the exposed surface of the formed adhesive film and one side 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 laminating the surfaces of the PMMA layer and the PMMA layer, the release film/adhesive layer/polarizing plate ( A polarizing plate (A) with an adhesive layer having a layer structure of (PMMA layer/PVA layer/PMMA layer) was produced.

[Preparation of polarizing plate (B) with adhesive layer]
The same operation as in the production of the adhesive layer-attached polarizing plate (A) was performed to form an adhesive film with a thickness of 15 μm on the release film. Next, the exposed surface of the formed adhesive film and one COP 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 stacking and bonding the surfaces of the layers, the release film/adhesive layer/polarizing plate (COP A polarizing plate (B) with an adhesive layer having a layer structure of layer/PVA layer/COP layer was produced.

[Preparation of polarizing plate (C) with adhesive layer]
The same operation as in the production of the adhesive layer-attached polarizing plate (A) was performed to form an adhesive film with a thickness of 15 μm on the release film. Next, the exposed surface of the formed adhesive film and one TAC of a polarizing plate (thickness: 150 μm) having a layer structure of triacetyl cellulose (TAC) layer/polyvinyl alcohol (PVA) layer containing a polarizer/TAC layer After laminating the surfaces of the layers, the release film/adhesive layer/polarizing plate (TAC A polarizing plate (C) with an adhesive layer having a layer structure of layer/PVA layer/TAC layer was produced.

[Measurement and evaluation]
1. Adhesion The polarizing plate with the adhesive layer prepared above was cut so that the long side was 0° with respect to the absorption axis of the polarizing plate, and a test piece with a size of 25 mm x 60 mm (long side) was prepared. did. Next, the release film of the prepared test piece was peeled off to expose the adhesive layer surface, which was then subjected to corona treatment. Next, one side of a polyethylene terephthalate (PET) film [trade name: Toyobo Ester (registered trademark) film G2, thickness: 38 μm, manufactured by Toyobo Co., Ltd.] was subjected to corona treatment, and then the corona treated side of the PET film and An evaluation sample was prepared by stacking and bonding the corona-treated surface of the adhesive layer of the test piece and allowing it to stand for 24 hours in an environment with an ambient temperature of 23° C. and 50% RH. The prepared evaluation samples were 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 (COP layer/PVA layer/COP layer). It has a layer structure of film/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer).

Regarding the evaluation sample prepared above, the peeling rate was measured using a single column material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd. under an environment of an ambient temperature of 23°C and 50% RH. The PET film was peeled 180° in the long side (60 mm) direction from the polarizing plate under conditions of 300 mm/min. Visually observe the peeled surface of the PET film after peeling to confirm whether or not the adhesive layer has transferred to the PET film. If transfer of the adhesive layer is confirmed, transfer to the PET film. The area of the attached adhesive layer was measured, and the ratio to the bonding area (that is, the area of the portion where the PET film and the adhesive layer were bonded in the evaluation sample) was calculated. The area measurement function of a digital microscope (model number: 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 outline of the adhesive layer attached to the PET film, the area of the adhesive layer was measured using the function of the above device, and the ratio to the bonding area (25 mm x 60 mm) was calculated. Then, evaluation was performed according to the following evaluation criteria. The results are shown in Tables 4 and 5.
In the following evaluation criteria, "A", "B", "C", and "D" are at a practical level, and "A" is most preferable.

-Evaluation criteria-
A: No transfer of the adhesive layer to the PET film was observed.
B: The area of the adhesive layer transferred to the PET film was in the range of more than 0% and 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% or more and 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% or more and 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.

2. Shrinkage suppression The polarizing plate with the adhesive layer prepared above was cut so that the long side was 0° with respect to the absorption axis of the polarizing plate, and a test piece with a size of 62 mm x 110 mm (long side) was prepared. did. Next, the release film of the test piece was peeled off, and the test piece was stacked so that the surface of the adhesive layer exposed by peeling was in contact with one surface of a glass plate [type: soda glass, manufactured by Matsunami Glass Industries Co., Ltd.]. Thereafter, a test sample was prepared by bonding the test piece and a glass plate together using a laminator. The prepared test samples were 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 It has a layer structure of plate/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer).

The test sample prepared above was autoclaved for 20 minutes at a treatment temperature of 50° C. and a treatment pressure of 5 kg/cm ² , and then left for 24 hours in an environment with an ambient temperature of 23° C. and 50% RH. After being left still, the test sample was left to stand for 150 hours in an environment with an ambient temperature of 85° C. and 10% RH or less (so-called high temperature, low humidity environment). After standing still, the length of the long side of the test sample (i.e., the side at 0° with respect to the absorption axis) is measured using a digital microscope [Model: VHX-100F, manufactured by Keyence Corporation]. Then, the shrinkage rate was calculated using the following formula. Note that the calculated value was rounded to the third decimal place.
Shrinkage rate (unit: %)
= [[Length of the long side of the test sample before standing (unit: mm)] - [Length of the long side of the test sample after standing (unit: mm)] / Test before standing Length of long side of sample (unit: mm) x 100

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 following evaluation criteria, "A", "B", "C", and "D" are at a practical level, and "A" is most preferable.

-Evaluation criteria-
A: The shrinkage rate of the test sample was less than 0.20%.
B: The shrinkage rate of the test sample was in the range of 0.20% or more and less than 0.35%.
C: The shrinkage rate of the test sample was in the range of 0.35% or more and less than 0.50%.
D: The shrinkage rate of the test sample was in the range of 0.50% or more and less than 1.00%.
E: The shrinkage rate of the test sample was 1.00% or more.

3. Durability (heat shock environment)
The polarizing plate with an adhesive layer produced above was cut so that the long side was 0° with respect to the absorption axis of the polarizing plate to prepare a test piece with a size of 62 mm x 110 mm (long side). Next, the release film of the test piece was peeled off, and the test piece was stacked so that the surface of the adhesive layer exposed by peeling was in contact with one surface of a glass plate [type: soda glass, manufactured by Matsunami Glass Industries Co., Ltd.]. Thereafter, a test sample was prepared by bonding the test piece and a glass plate together using a laminator. The test sample has a layer structure of glass plate/adhesive layer/polarizing plate (PMMA layer/PVA layer/PMMA layer). The prepared test samples were 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 It has a layer structure of plate/adhesive layer/polarizing plate (TAC layer/PVA layer/TAC layer).

The test sample prepared above was autoclaved for 20 minutes at a treatment temperature of 50° C. and a treatment pressure of 5 kg/cm ² , and then left for 24 hours in an environment with an ambient temperature of 23° C. and 50% RH. After this test sample was left still for 0.5 hours at an ambient temperature of -40°C using a thermal shock device [Model: TSA-301L-W, manufactured by ESPEC Co., Ltd.] A test was conducted in which a cycle of standing for 0.5 hours in an environment with an ambient temperature of 85° C. was repeated 300 times. After the test was completed, the condition of the test sample was visually observed and evaluated according to the following evaluation criteria. The results are shown in Tables 4 and 5.
In the following evaluation criteria, "A", "B", and "C" are at a practical level, and "A" is most preferable.

- Evaluation criteria (foaming) -
A: No foaming was observed in the test sample.
B: Slight foaming was observed in the test sample, but it was at a level that caused no practical problems.
C: Foaming was observed in the test sample, but it was at a practically acceptable level.
D: Foaming was clearly observed in the test sample, and the level was unacceptable for practical use.

-Evaluation criteria (peeling)-
A: No peeling was observed in the test sample.
B: Although slight peeling was observed in the test sample, it was at a level that caused no practical problems.
C: Peeling was observed in the test sample, but it was at a practically acceptable level.
D: Significant peeling was observed in the test sample, which was at a practically unacceptable level.

As shown in Table 4, it was confirmed that the adhesive layers formed from the adhesive compositions of Examples 1 to 22 had excellent adhesion to low moisture permeability substrates. Furthermore, it was confirmed that the adhesive layers formed from the adhesive compositions of Examples 1 to 22 were able to satisfactorily suppress shrinkage of the base material that may occur when placed in a high temperature environment. Furthermore, it was confirmed that the adhesive layers formed from the adhesive compositions of Examples 1 to 22 were able to successfully suppress foaming and peeling that may occur when placed in an environment where low and high temperatures are repeated. .

On the other hand, as shown in Table 5, the adhesive layer formed from the adhesive composition of Comparative Example 1, which does not contain a specific tolylene diisocyanate-based compound, exhibits shrinkage of the base material that may occur when placed in a high-temperature environment. It was also confirmed that foaming, which may occur when placed in an environment where low and high temperatures are repeated, could not be suppressed well.
The adhesive layer formed from the adhesive composition of Comparative Example 2, which does not contain a specific diphenylmethane diisocyanate-based compound, may not be able to satisfactorily suppress foaming that may occur when placed in an environment where low and high temperatures are repeated. confirmed.
The adhesive layer formed of the adhesive composition of Comparative Example 3 in which the content mass ratio of the specific diphenylmethane diisocyanate-based compound to the specific tolylene diisocyanate-based compound exceeds 2 is a base material that may be formed when placed in a high-temperature environment. It was confirmed that the shrinkage of the product could not be suppressed well.
The adhesive layer formed by the adhesive composition of Comparative Example 4 containing a hexamethylene diisocyanate-based compound instead of the specific diphenylmethane diisocyanate-based compound is susceptible to foaming that may occur when placed in an environment where low and high temperatures are repeated. It was confirmed that this could not be suppressed well.
The adhesive layer formed by the adhesive composition of Comparative Example 5 containing a xylylene diisocyanate-based compound instead of the specific diphenylmethane diisocyanate-based compound had poor adhesion to a low-moisture-permeable base material, and had poor adhesion to low- and high-temperature substrates. It was confirmed that foaming, which can occur when placed in an environment where repeated
The adhesive layer formed by the adhesive composition of Comparative Example 6 containing a hexamethylene diisocyanate-based compound instead of the specific tolylene diisocyanate-based compound is free from shrinkage of the base material that may occur when placed in a high-temperature environment, and It was confirmed that foaming, which can occur when placed in an environment where low and high temperatures are repeated, cannot be effectively suppressed.
The adhesive layer formed by the adhesive composition of Comparative Example 7 containing a xylylene diisocyanate compound instead of the specific tolylene diisocyanate compound has good resistance to shrinkage of the base material that may occur when placed in a high temperature environment. It was confirmed that this could not be suppressed.
The adhesive layer formed from the adhesive composition of Comparative Example 8 in which the (meth)acrylic polymer does not have a carboxyl group has good resistance to foaming that may occur when placed in an environment where low and high temperatures are repeated. It was confirmed that this could not be suppressed.
The adhesive layer formed from the adhesive composition of Comparative Example 9 in which the (meth)acrylic polymer does not have a hydroxyl group has excellent resistance to foaming that may occur when placed in an environment where low and high temperatures are repeated. It was confirmed that it cannot be suppressed.
The adhesive layer formed by the adhesive composition of Comparative Example 10 in which the (meth)acrylic polymer does not have either a hydroxyl group or a carboxyl group has poor adhesion to a low moisture permeable base material and is difficult to use in high-temperature environments. It was confirmed that shrinkage of the substrate, which may occur when placed under the substrate, could not be well suppressed.

Claims (5)

A (meth)acrylic polymer having a hydroxyl group and a carboxy group,
a tolylene diisocyanate compound having an average number of isocyanate groups in one molecule in the range of 2.5 or more and 3.0 or less;
A diphenylmethane diisocyanate compound having an average number of isocyanate groups in one molecule in a range of 2.0 or more and less than 2.5;
including;
A pressure-sensitive adhesive composition in which the content ratio of the diphenylmethane diisocyanate-based compound to the tolylene diisocyanate-based compound is 2 or less. The (meth)acrylic polymer contains a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a monomer having a carboxy group,
The content of structural 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 based on the total structural units,
A claim in which the content of structural units derived from the monomer having a carboxy group in the (meth)acrylic polymer is in the range of 0.1% by mass or more and 3.0% by mass or less based on the total structural units. Item 1. The adhesive composition according to item 1. 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 based on 100 parts by mass of the (meth)acrylic polymer,
The adhesive composition according to claim 1 or 2, wherein the diphenylmethane diisocyanate compound is in a range of 0.01 parts by mass or more and 1.0 parts by mass or less based on 100 parts by mass of the (meth)acrylic polymer. thing. The pressure-sensitive 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. A polarizing plate equipped with a layer containing at least one resin selected from the group consisting of (meth)acrylic resin and cycloolefin resin on one or both sides;
an adhesive layer provided on the layer and formed from the adhesive composition according to any one of claims 1 to 4;
A laminate comprising: