JP7334604B2 - Adhesive composition for polarizing plate, polarizing plate with adhesive layer, and in-vehicle display device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition for polarizing plates, an adhesive layer-attached polarizing plate, and an in-vehicle display device.

2. Description of the Related Art Many mobile electronic devices such as mobile phones and mobile terminals incorporate a liquid crystal display device. Generally, a liquid crystal display device includes a liquid crystal cell in which a liquid crystal layer is sandwiched between two glass substrates, and polarizing plates arranged on both sides of the liquid crystal cell. From the viewpoint of ensuring the visibility of the liquid crystal display device, the liquid crystal cell and the polarizing plate are generally bonded via an adhesive layer formed of an acrylic adhesive.

Since the polarizing plate is usually composed of laminated members with different shrinkage rates, the polarizing plate may warp due to changes in temperature, humidity, etc. At the interface, bubbling, lifting and delamination may occur. Therefore, the adhesive used for bonding the liquid crystal cell and the polarizing plate has properties (so-called durability) that can suppress the occurrence of air bubbles, floating, and peeling even when exposed to harsh environments. is required.

For example, in Patent Document 1, a pressure-sensitive adhesive composition for polarizing plates that is excellent in durability and light leakage prevention effect contains 0.1 to 5% by mass of a carboxy group-containing monomer and 4 to 12% of tolylene diisocyanate-based cross-linking agent. A pressure-sensitive adhesive for polarizing plates having a gel fraction of 91% or more, including parts by weight, is disclosed.
Further, for example, Patent Document 2 describes a pressure-sensitive adhesive composition containing 5 parts by mass or more and 30 parts by mass or less of an isocyanate compound as a pressure-sensitive adhesive composition that has excellent durability under high temperature and high humidity and suppresses the occurrence of white spots. is disclosed.

WO2010/79653 JP 2010-090354 A

For example, when various optical display devices equipped with polarizing plates are installed in an environment of 100° C. or higher, the water contained in the adhesive layer of the polarizing plate is easily foamed due to evaporation, and the adhesive layer (i.e., The shrinkage of the polarizing plate (hereinafter sometimes referred to as "warping of the adhesive layer") causes white spots and the like, and changes in optical properties and poor appearance are likely to occur.
In recent years, various optical display devices equipped with polarizing plates are required to have durability at temperatures higher than conventional ones, for example, 115° C. or higher.
For example, Patent Document 1 described above describes a pressure-sensitive adhesive composition for polarizing plates that is excellent in durability evaluation test evaluation at 80°C for 500 hours. May be less durable when exposed to high temperatures.
Further, the pressure-sensitive adhesive composition described in Patent Document 2 is required to further improve durability and warpage under high-temperature conditions such as 115°C.

An object to be solved by one embodiment of the present invention is to provide a pressure-sensitive adhesive composition for a polarizing plate that is excellent in suppressing foaming from the resulting pressure-sensitive adhesive layer and warping of the resulting pressure-sensitive adhesive layer under high-temperature conditions. That is.
Another object of the present invention is to provide a pressure-sensitive adhesive layer-attached polarizing plate using the pressure-sensitive adhesive composition for a polarizing plate, and an in-vehicle display device including the pressure-sensitive adhesive layer-attached polarizing plate. It is to be.

Means for solving the above problems include the following aspects.
<1> At least selected from the group consisting of a structural unit formed by a (meth)acrylic acid alkyl ester, a structural unit formed by a monomer having a hydroxyl group, and a structural unit formed by a monomer having a carboxy group A (meth)acrylic copolymer containing one type of structural unit and a tolylene diisocyanate-based cross-linking agent, and the monomer having a hydroxyl group in the (meth)acrylic copolymer The total content of the structural units to be formed and the structural units formed by the monomer having a carboxy group is more than 0% by mass and 0.45% by mass or less with respect to all structural units,
A pressure-sensitive adhesive composition for a polarizing plate, wherein the ratio of the number of moles of isocyanate groups in the tolylene diisocyanate-based cross-linking agent to the total number of moles of the hydroxyl groups and the carboxy groups is 3.0 to 22.0.
<2> The (meth)acrylic copolymer is composed of a structural unit formed from the (meth)acrylic acid alkyl ester, a structural unit formed from the hydroxyl group-containing monomer, and a carboxyl group-containing monomer. The pressure-sensitive adhesive composition for a polarizing plate according to <1>, including the formed structural unit.
<3> The ratio of the number of moles of isocyanate groups in the tolylene diisocyanate cross-linking agent to the total number of moles of hydroxyl groups and carboxy groups in the (meth)acrylic copolymer is 6.0 to 13.0. The pressure-sensitive adhesive composition for a polarizing plate according to <1> or <2>.
<4> In the (meth)acrylic copolymer, the content of the structural units formed by the monomer having the carboxy group is higher than the content of the structural units formed by the monomer having the hydroxyl group. 1> to <3>, the pressure-sensitive adhesive composition for a polarizing plate.
<5> In the (meth)acrylic copolymer, the content of the structural unit formed by the monomer having the carboxy group and the content of the structural unit formed by the monomer having the hydroxyl group are the same. The pressure-sensitive adhesive composition for a polarizing plate according to any one of <1> to <3>.
<6> The pressure-sensitive adhesive composition for a polarizing plate according to any one of <1> to <5>, wherein the (meth)acrylic copolymer has a weight average molecular weight of 1,000,000 or more.
<7> The adhesive composition for a polarizing plate according to any one of <1> to <6>, further comprising an organometallic compound as a crosslinking catalyst.
<8> The pressure-sensitive adhesive composition for polarizing plate according to <7>, wherein the organometallic compound is at least one compound selected from the group consisting of a tin compound, a zinc compound, a zirconium compound, and an iron compound. .
<9> A polarizing plate with an adhesive layer, comprising an adhesive layer that is a crosslinked product of the adhesive composition for a polarizing plate according to any one of <1> to <8>.
<10> An in-vehicle display device comprising the pressure-sensitive adhesive layer-attached polarizing plate according to <9>.

According to one embodiment of the present invention, it is possible to provide a pressure-sensitive adhesive composition for a polarizing plate that is excellent in suppressing foaming from the resulting pressure-sensitive adhesive layer and warping of the resulting pressure-sensitive adhesive layer under high-temperature conditions.
Further, according to another embodiment of the present invention, it is possible to provide a polarizing plate with an adhesive layer using the adhesive composition for a polarizing plate, and an in-vehicle display device having the polarizing plate with an adhesive layer. .

The contents of the present invention will be described in detail below. The description of the constituent elements described below may be made based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
In this specification, the numerical range indicated using "to" indicates the range including the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described stepwise in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical range described in other steps. good. Moreover, in the numerical ranges described in this specification, the upper and lower limits of the numerical ranges may be replaced with the values shown in the examples.
In addition, in the present specification, the amount of each component in the composition refers to the amount of the multiple substances corresponding to that component, unless otherwise specified, when multiple types of substances corresponding to each component are used in combination in the composition. means total volume.

In addition, the term "step" in this specification is not only an independent step, but even if it cannot be clearly distinguished from other steps, if the intended purpose of the step is achieved included. Moreover, in the present invention, "% by mass" and "% by weight" have the same meaning, and "parts by mass" and "parts by weight" have the same meaning.
Furthermore, in the present invention, a combination of two or more preferred aspects is a more preferred aspect.

(Meth)acrylic means at least one of acrylic and methacrylic, and (meth)acrylate means at least one of acrylate and methacrylate.
In the present specification, the (meth)acrylic copolymer means a polymer formed by polymerizing a monomer having a (meth)acryloyl group at least as a main component among the monomers constituting the copolymer.
The main component in the (meth)acrylic copolymer means that the content (% by mass) is the highest among the monomer components forming the polymer. For example, in the case of the (meth)acrylic copolymer , means a monomer in which the content of structural units formed by a monomer having a (meth)acryloyl group is 50% by mass or more of all structural units.
The pressure-sensitive adhesive layer is a layer after the (meth)acrylic copolymer and the cross-linking agent are substantially cross-linked, and means, for example, a solid or gel layer.

(Adhesive composition for polarizing plate)
The pressure-sensitive adhesive composition for a polarizing plate according to the present invention (hereinafter also simply referred to as the "pressure-sensitive adhesive composition") has a structure formed of a structural unit formed of a (meth)acrylic acid alkyl ester and a monomer having a hydroxyl group. and at least one structural unit selected from the group consisting of structural units formed by monomers having a carboxy group, a (meth)acrylic copolymer (hereinafter referred to as "specific (meth)acrylic Also referred to as "system copolymer".) and a tolylene diisocyanate-based cross-linking agent (hereinafter also referred to as "specific cross-linking agent"), and the hydroxyl groups in the (meth)acrylic copolymer are The total content of the structural units formed by the monomer having the above The ratio of the number of moles of isocyanate groups in the tolylene diisocyanate-based cross-linking agent to the total number of moles of hydroxyl groups and carboxy groups (hereinafter also referred to as "specific functional groups") is 3.0 to 22.0.

In general, in the adhesive layer, compatibility between durability such as suppression of foaming and optical properties such as white spots caused by "warping" of the liquid crystal panel caused by shrinkage of the adhesive layer (that is, polarizing plate) is difficult. As a result of intensive studies by the present inventors, it was found that the pressure-sensitive adhesive composition according to the present invention, which has the above configuration, suppresses foaming from the pressure-sensitive adhesive layer obtained and warping of the pressure-sensitive adhesive layer obtained in a high-temperature environment. I found it to be excellent. Although the detailed mechanism by which the above effects are obtained is unknown, it is presumed as follows.

When the pressure-sensitive adhesive composition is left under temperature conditions exceeding the boiling point of water, for example, in a high temperature environment of 100° C. or higher, suppression of foaming from the pressure-sensitive adhesive composition is required.
The pressure-sensitive adhesive composition according to the present invention comprises a specific cross-linking agent, a structural unit formed from a (meth)acrylic acid alkyl ester, a structural unit formed from a monomer having a hydroxyl group, and a monomer having a carboxy group. and at least one structural unit selected from the group consisting of structural units, and a structural unit formed by a monomer having a hydroxyl group and a monomer having a carboxy group in the (meth)acrylic copolymer By making the total content of the constituent units to be formed more than 0% by mass and 0.45% by mass or less, the content of the specific functional group that can become water in the pressure-sensitive adhesive composition is reduced. Evaporation of moisture in the pressure-sensitive adhesive composition can be suppressed under the high-temperature environment described above.
In addition, since the total content is less than or equal to the specific amount, over-crosslinking of the specific functional group and the specific cross-linking agent can be suppressed, and the network structure of the formed cross-linked structure is widened. Since the pressure-sensitive adhesive layer has excellent stress relaxation properties, it is presumed that the warpage of the pressure-sensitive adhesive layer is suppressed in a high-temperature environment.
The tolylene diisocyanate-based cross-linking agent contained in the pressure-sensitive adhesive composition according to the present invention has a lower degree of structural freedom and a more rigid structure than cross-linking agents such as hexamethylene diisocyanate-based cross-linking agents. is. The pressure-sensitive adhesive composition according to the present invention comprises the above specific cross-linking agent, a structural unit formed from a (meth)acrylic acid alkyl ester, a structural unit formed from a monomer having a hydroxyl group, and a monomer having a carboxy group. At least one structural unit selected from the group consisting of structural units formed by the (meth)acrylic copolymer, wherein the number of moles of isocyanate groups in the tolylene diisocyanate-based cross-linking agent is ) By setting the molar equivalent ratio to 3.0 to 22.0 with respect to the total number of moles of hydroxyl groups and carboxy groups (specific functional groups) in the acrylic copolymer, the above specific crosslinked in the adhesive composition When the agent is sufficiently present, the cross-linking reaction efficiency between the specific cross-linking agent and the specific functional group is high and the cross-linking is sufficiently performed, so that the cohesive force of the pressure-sensitive adhesive composition is increased, and foaming can be suppressed even in a high-temperature environment. Excellent.
In addition, the isocyanate-based cross-linking agent that does not contribute to the cross-linking reaction forms a condensate, and the condensate is incorporated into the network structure, so that the pressure-sensitive adhesive layer maintains stress relaxation properties and can be used in a high-temperature environment. It is estimated that it is excellent in suppressing foaming from and warping of the adhesive layer.
Hereinafter, details of each constituent element contained in the pressure-sensitive adhesive composition according to the present invention will be described.

In this specification, a high-temperature environment means at least a temperature environment of 115° C. or higher under atmospheric pressure.

<<Specific (meth)acrylic copolymer>>
The pressure-sensitive adhesive composition according to the present invention comprises a structural unit formed from a (meth)acrylic acid alkyl ester, a structural unit formed from a monomer having a hydroxyl group, and a structural unit formed from a monomer having a carboxy group. and at least one structural unit selected from the group consisting of (meth)acrylic copolymers (specific (meth)acrylic copolymers).
From the viewpoint of suppressing foaming from the obtained pressure-sensitive adhesive layer and warping of the obtained pressure-sensitive adhesive layer in a high-temperature environment, the pressure-sensitive adhesive composition according to the present invention includes a structural unit formed of a (meth)acrylic acid alkyl ester, It preferably contains a structural unit formed of a (meth)acrylate monomer having a hydroxyl group and a (meth)acrylic copolymer containing a structural unit formed of a (meth)acrylate monomer having a carboxy group.

<(Meth)acrylic acid alkyl ester>
The specific (meth)acrylic copolymer contains a structural unit formed by a (meth)acrylic acid alkyl ester.
When the specific (meth)acrylic copolymer contains a structural unit formed by a (meth)acrylic acid alkyl ester, the resulting pressure-sensitive adhesive layer can be imparted with excellent adhesive strength.
The specific (meth)acrylic copolymer may contain one type of structural unit formed by a (meth)acrylic acid alkyl ester, or may contain two or more types.

The (meth)acrylic acid alkyl ester is not particularly limited, and may be, for example, a substituted or unsubstituted (meth)acrylic acid alkyl ester. Substituted or unsubstituted acrylic acid alkyl esters are preferable from the viewpoint that they are easy to use.
The alkyl group in the (meth)acrylic acid alkyl ester is not particularly limited, and may be linear, branched or cyclic.
The number of carbon atoms in the alkyl group is preferably from 1 to 18, more preferably from 1 to 12, from the viewpoint of the adhesive strength of the pressure-sensitive adhesive layer to the adherend and the adhesion to the substrate.

Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl ( meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, isonyl (meth) acrylate, n-decyl (meth) acrylate, n- dodecyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate and the like.

Among these, from the viewpoint of adhesive strength, the (meth)acrylic acid alkyl ester is preferably an acrylic acid alkyl ester, methyl acrylate (MA), t-butyl acrylate (t-BA), and n- More preferably, it is at least one monomer selected from the group consisting of butyl acrylate (n-BA), more preferably n-butyl acrylate (n-BA).

From the viewpoint of adhesive strength, the content of structural units formed by (meth)acrylic acid alkyl esters in the specific (meth)acrylic copolymer is On the other hand, it is preferably 50% by mass or more and 99.95% by mass or less, more preferably 60% by mass or more and 99.95% by mass or less, and 70% by mass or more and 99.95% by mass or less. More preferably, it is particularly preferably 80% by mass or more and 99.95% by mass or less.

<Structural Unit Formed from a Monomer Having a Hydroxyl Group>
The specific (meth)acrylic copolymer contains at least one structural unit selected from the group consisting of a structural unit formed by a monomer having a hydroxyl group and a structural unit formed by a monomer having a carboxy group. .
From the viewpoint of suppressing foaming from the obtained pressure-sensitive adhesive layer and warping of the obtained pressure-sensitive adhesive layer in a high-temperature environment, the specific (meth)acrylic copolymer should contain a structural unit formed by a monomer having a hydroxyl group. is preferred.
A structural unit formed by a monomer having a hydroxyl group may be contained singly or may be contained in two or more types.

The hydroxyl-containing monomer includes, for example, a monomer containing at least one hydroxyl group and at least one ethylenically unsaturated bond-containing group in one molecule.
The group having an ethylenically unsaturated bond includes a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, or a (meth)acryloyloxy group. A meth)acryloyloxy group is preferred.

Examples of monomers having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl ( meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl ( meth) acrylamide and the like.

From the viewpoint of suppressing foaming from the pressure-sensitive adhesive layer in a high-temperature environment and reactivity with a specific cross-linking agent described later, the monomer having a hydroxyl group contains one (meth)acryloyloxy group and one hydroxyl group in one molecule. It is preferably a hydroxyalkyl (meth)acrylate having a group (hydroxyl group), more preferably a hydroxyalkyl (meth)acrylate having 1 to 5 carbon atoms, and a hydroxyalkyl (meth)acrylate having a hydroxyalkyl group having 2 to 4 carbon atoms ( More preferred are meth)acrylates.

-Content rate-
When the specific (meth)acrylic copolymer contains a structural unit formed by a monomer having a hydroxyl group, the content of the structural unit formed by a monomer having a hydroxyl group in the specific (meth)acrylic copolymer is From the viewpoint of suppressing foaming from the pressure-sensitive adhesive layer obtained in a high-temperature environment and suppressing warping of the pressure-sensitive adhesive layer, the content of structural units formed by a monomer having a carboxy group described below is the same. is preferred.
In the present specification, the term "same amount" means not only when the content is equal, but also when the content of the structural unit formed by the monomer having a hydroxyl group and the structural unit formed by the monomer having a carboxy group. It also includes cases where the difference is within ±5%.
When the specific (meth)acrylic copolymer contains a structural unit formed by a monomer having a hydroxyl group, the specific (meth)acrylic copolymer can be It is preferable that the content of structural units formed by a monomer having a hydroxyl group in the polymer is less than that of a structural unit formed by a monomer having a carboxy group. Further, when the specific (meth)acrylic copolymer contains a structural unit formed by a monomer having a hydroxyl group, from the same point of view, it is formed by the monomer having a hydroxyl group in the specific (meth)acrylic copolymer The content of the structural unit is 0.45% by mass or less, preferably 0.3% by mass or less, and 0.01% by mass, based on the total structural units of the specific (meth)acrylic copolymer. It is more preferably 0.25% by mass or more, and even more preferably 0.05% by mass or more and 0.15% by mass or less.

<Structural Unit Formed by Monomer Having Carboxy Group>
The specific (meth)acrylic copolymer contains at least one structural unit selected from the group consisting of a structural unit formed by a monomer having a hydroxyl group and a structural unit formed by a monomer having a carboxy group. .
From the viewpoint of suppressing foaming and warping from the pressure-sensitive adhesive layer in a high-temperature environment, the specific (meth)acrylic copolymer preferably contains a structural unit formed by a monomer having a carboxy group.

The monomer having a carboxy group is not particularly limited, and examples thereof include monomers containing a group having at least one carboxy group and an ethylenically unsaturated bond in one molecule.
The group having an ethylenically unsaturated bond is synonymous with the group having an ethylenically unsaturated bond in the above-mentioned monomer having a hydroxyl group, and the preferred groups are also the same.

Examples of monomers having a carboxy group include acrylic acid (AA), methacrylic acid, crotonic acid , maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate ( Examples include ω-carboxy-polycaprolactone (n≈2) monoacrylate), succinic acid esters (eg, 2-acryloyloxyethyl-succinic acid), vinyl formate, vinyl acetate, vinyl propionate, vinyl neodecanoate, and the like. .
Among these, from the viewpoint of reactivity with a specific cross-linking agent described later, the monomer having a carboxy group is at least one selected from the group consisting of acrylic acid and ω-carboxy-polycaprolactone mono(meth)acrylate. It is preferably a monomer, more preferably acrylic acid.

When the specific (meth)acrylic copolymer contains a structural unit formed by a monomer having a carboxy group, the content of the structural unit formed by the monomer having a carboxy group in the specific (meth)acrylic copolymer may be the same amount as the structural unit formed by the monomer having a hydroxyl group, but the elastic modulus is unlikely to be excessive, and in a high-temperature environment, from the viewpoint of excellent suppression of warping of the resulting pressure-sensitive adhesive layer, It is preferable that the amount is greater than the constituent units formed by monomers having hydroxyl groups.
In addition, when the specific (meth)acrylic copolymer contains a structural unit formed by a monomer having a carboxy group, the content of the structural unit formed by a monomer having a hydroxyl group is It is 0.45% by mass or less, preferably 0.05% by mass or more and 0.30% by mass or less, and 0.05% by mass or more and 0.25% by mass or less, based on the total structural units of the coalescence. is more preferable.

<Total Content of Structural Units Formed by Monomers Having a Hydroxyl Group and Structural Units Formed by a Monomer Having a Carboxy Group>
In the pressure-sensitive adhesive composition according to the present invention, the total content of structural units formed from monomers having hydroxyl groups and monomers having carboxy groups in the specific (meth)acrylic copolymer is 0. It exceeds mass % and is 0.45 mass % or less.
When the total content is 0.45% by mass or less, vaporization of water contained in the pressure-sensitive adhesive composition is reduced in a high-temperature environment, so foaming from the pressure-sensitive adhesive layer obtained is excellently suppressed. Moreover, when the above total content exceeds 0% by mass, it is possible to undergo a cross-linking reaction with a specific cross-linking agent, which will be described later, so that foaming from the pressure-sensitive adhesive layer obtained in a high-temperature environment is excellently suppressed.
From the above point of view, the total content of the structural units formed by the monomers having a hydroxyl group and the structural units formed by the monomers having a carboxyl group in the specific (meth)acrylic copolymer is 0.05% by mass or more. It is preferably 0.3% by mass or less, more preferably 0.1% by mass or more and 0.4% by mass or less, even more preferably 0.15% by mass or more and 0.35% by mass or less, It is particularly preferable to be 0.15% by mass or more and 0.25% by mass or less.

The specific (meth)acrylic copolymer, within the scope in which the effect of the present invention is exhibited, is a structural unit formed by the above-mentioned (meth)acrylic acid alkyl ester, a structural unit formed by a monomer having a hydroxyl group, and , may contain structural units other than structural units formed by monomers having a carboxy group (hereinafter also referred to as "other structural units").
Monomers constituting other structural units are not particularly limited as long as they can be copolymerized with the above (meth)acrylic acid alkyl esters, hydroxyl group-containing monomers and carboxyl group-containing monomers, and can be appropriately selected according to the purpose. can be done.

Monomers constituting other structural units include monomers having functional groups such as alkylene oxide groups, glycidyl groups, amide groups, N-substituted amide groups, and tertiary amino groups, polyfunctional (meth)acrylic monomers, aromatic group monovinyl monomers, vinyl cyanide monomers, and (meth)acrylic monomers having an aromatic ring.

Examples of monomers having an alkylene oxide group include methoxyethyl (meth)acrylate, 2-(ethoxyethoxy)ethyl acrylate, polyethylene glycol (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, methoxypolypropyleneglycol (meth)acrylate, Polypropylene glycol (meth)acrylates and methoxypolyethylene glycol (meth)acrylates can be mentioned.

Monomers having a glycidyl group include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl vinyl ether, 3,4-epoxycyclohexyl vinyl ether, glycidyl (meth)allyl ether, and 3,4-epoxycyclohexyl. (Meth)allyl ether and the like can be mentioned.

Monomers having an amide group or N-substituted amide group include acrylamide, methacrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, ) acrylamide, N-propoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-tert-butylacrylamide, N-octylacrylamide, diacetoneacrylamide and the like.

Examples of monomers having a tertiary amino group include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, and the like.

Polyfunctional (meth)acrylic monomers include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth) Acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified di(meth)acrylate, di(meth)acryloxyethyl isocyanurate, tricyclodecanedimethanol (meth)acrylate, dimethyloldicyclopentane di(meth) Acrylates, ethylene oxide-modified hexahydrophthalic acid di(meth)acrylate, tricyclodecanedimethanol (meth)acrylate, neopentyl glycol-modified trimethylpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol tri( meth)acrylate, diglycerin tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate and the like.

Examples of aromatic monovinyl monomers include styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, vinyltoluene and vinylpyridine.
Vinyl cyanide monomers include, for example, acrylonitrile and methacrylonitrile.

Examples of (meth)acrylic monomers having an aromatic ring include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide (EO)-modified cresol (meth)acrylate, ethylene oxide (EO)-modified nonylphenol (meth)acrylate, hydroxyethylated β-naphthol acrylate, and biphenyl (meth)acrylate.

When the specific (meth)acrylic copolymer contains other structural units, the content of the other structural units in the specific (meth)acrylic copolymer is preferably 5% by mass to 25% by mass. % to 20% by mass is more preferable, and 11% to 18% by mass is even more preferable.

In the pressure-sensitive adhesive composition according to the present invention, the content of the specific (meth)acrylic copolymer can be appropriately adjusted according to the purpose. 80% by mass to 99% by mass is preferable, 85% by mass to 99% by mass is more preferable, and 90% by mass to 98% by mass is even more preferable.
In addition, the solid content total mass means the total mass of the residue after removing volatile components such as a solvent from the pressure-sensitive adhesive composition.

<<Weight average molecular weight (Mw) of specific (meth)acrylic copolymer>>
The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is not particularly limited, and is preferably 100,000 to 2,000,000, more preferably 600,000 to 2,000,000 in terms of improving adhesive strength. is more preferable, and 1,000,000 to 2,000,000 is even more preferable. The weight average molecular weight can be adjusted by the polymerization reaction temperature, time, amount of organic solvent, and the like.

-Method for measuring weight average molecular weight (Mw)-
The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is determined by the following measuring method.
More specifically, the weight average molecular weight (Mw) can be obtained by measuring according to the following (1) to (3).
(1) A solution of the specific (meth)acrylic copolymer is applied to release paper and dried at 100° C. for 1 minute to obtain a film-like specific (meth)acrylic copolymer.
(2) The film-shaped specific (meth)acrylic copolymer obtained in (1) above is dissolved in tetrahydrofuran so that the solid content is 0.2% by mass.
(3) Under the following conditions, gel permeation chromatography (GPC) is used to measure the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer as a standard polystyrene equivalent value.

(conditions)
GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
Column: TSK-GEL GMHXL [manufactured by Tosoh Corporation] 4 pieces used Mobile phase solvent: Tetrahydrofuran Flow rate: 0.8 mL/min Column temperature: 40°C

The glass transition temperature (Tg) of the specific (meth)acrylic copolymer is -60° C. to -5° C. from the viewpoint of increasing the adhesive strength of the resulting adhesive layer and keeping the tackiness after heating and cooling low. It is preferably -50°C to -30°C, more preferably -50°C to -30°C.

The glass transition temperature (Tg) of the specific (meth)acrylic copolymer is the molar average glass transition temperature calculated by the following formula.

In the formula, Tg ₁ , Tg _{2 ,} . temperature. m ₁ , m ₂ , . . . and _mn are the mole fractions of the respective monomer components.

The "glass transition temperature represented by the absolute temperature (K) of the homopolymer" refers to the glass transition temperature represented by the absolute temperature (K) of the homopolymer produced by polymerizing the monomer alone. . The glass transition temperature of the homopolymer was measured by measuring 10 mg of a measurement sample in a nitrogen stream using a differential scanning calorimeter (DSC) (manufactured by TA Instruments Japan Co., Ltd., DSC2500). , and the inflection point of the obtained DSC curve was taken as the glass transition temperature of the homopolymer.

The "glass transition temperature expressed in Celsius temperature (° C.) of a homopolymer" of typical monomers is 5° C. for methyl acrylate, −27° C. for ethyl acrylate, and −57° C. for n-butyl acrylate. , 2-ethylhexyl acrylate is −76° C., 2-hydroxyethyl acrylate is −15° C., 4-hydroxybutyl acrylate is −39° C., 2-hydroxyethyl methacrylate is 55° C., tert -butyl acrylate is 41°C, tert-butyl methacrylate is 107°C, benzyl acrylate is 6°C, phenoxyethyl acrylate is -22°C, acrylic acid is 163°C, ω-carboxy-poly Caprolactone (n≈2) monoacrylate is -41°C. For example, by using these representative monomers, it is possible to appropriately adjust the glass transition temperature described above.
By subtracting 273 from the absolute temperature (K), the absolute temperature (K) can be converted to the Celsius temperature (°C). K).

[Method for producing specific (meth)acrylic copolymer]
The method for producing the specific (meth)acrylic copolymer is not particularly limited, and it can be produced by polymerizing monomers by a method such as solution polymerization, emulsion polymerization, or suspension polymerization.
In preparing the pressure-sensitive adhesive composition according to the present invention after production, the specific (meth)acrylic copolymer is produced using solution polymerization because the treatment process can be performed relatively easily and in a short time. is preferred.

Solution polymerization is generally carried out by charging a given organic solvent, a monomer, a polymerization initiator, and, if necessary, a chain transfer agent into a polymerization vessel, and carrying out a number of A method of reacting with heating for time can be used. The weight average molecular weight of the specific (meth)acrylic copolymer can be adjusted to a desired value by adjusting the reaction temperature, time, amount of solvent, type and amount of catalyst.

The organic solvent used in the polymerization reaction of the specific (meth)acrylic copolymer is not particularly limited, but aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycols Ether compounds, alcohol compounds and the like can be mentioned.
These organic solvents may be used singly or in combination of two or more.

Examples of organic solvents used during the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, tert-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha. Representative aromatic hydrocarbon organic solvents, n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and aliphatic hydrocarbons typified by turpentine or alicyclic hydrocarbon-based organic solvents, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate. Ester-based organic solvents, acetone, methyl ethyl ketone, methyl-isobutyl ketone, isophorone, cyclohexanone, and ketone-based organic solvents represented by methyl cyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether , diethylene glycol monoethyl ether, and glycol ether organic solvents represented by diethylene glycol monobutyl ether, and methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, s-butyl alcohol, and alcohol-based organic solvents typified by tert-butyl alcohol.

Examples of the polymerization initiator include organic peroxides and azo compounds that can be used in ordinary polymerization methods.

<Specific cross-linking agent>
The pressure-sensitive adhesive composition according to the present invention contains a tolylene diisocyanate-based cross-linking agent (specific cross-linking agent). Tolylene diisocyanate-based cross-linking agent (specific cross-linking agent) has a more rigid structure than, for example, hexamethylene diisocyanate-based cross-linking agent. By containing the meth)acrylic copolymer, it is excellent in suppressing foaming from the pressure-sensitive adhesive layer obtained in a high-temperature environment.
The specific cross-linking agent may be used alone or in combination of two or more.

The specific cross-linking agent is not particularly limited, and includes, for example, a dimer or trimer of tolylene diisocyanate, or an adduct of tolylene diisocyanate and a polyol such as trimethylolpropane.

A commercial product on the market may be used as the specific cross-linking agent. Commercially available specific cross-linking agents include, for example, "Desmodur IL1451CN", "Desmodur ILBA", "Desmodur ILBA", "Desmodur HL", "Sumidur FL-2" and "Sumidur" manufactured by Sumitomo Bayer Urethane Co., Ltd. FL-3” and “SBU Isocyanate 0817”, trade names “Coronate L”, “Coronate 2030”, “Coronate 2031”, “Coronate 2037” manufactured by Tosoh Corporation, and trade names “Polurene” manufactured by SAPIC KC" and "Polurene HR" can be mentioned. Among these, "Coronate L", which is a trimethylolpropane adduct of tolylene diisocyanate, is preferable as the specific cross-linking agent from the viewpoint of cross-linking reactivity.

-Content rate-
The content of the specific cross-linking agent is preferably 1 part by mass to 20 parts by mass, and 1.5 parts by mass to 15 parts by mass with respect to 100 parts by mass of the specific (meth)acrylic copolymer. is more preferable, 3.5 parts by mass to 10 parts by mass is even more preferable, and 5.0 parts by mass to 10 parts by mass is particularly preferable.

<<ratio of the number of moles of isocyanate groups in the specific cross-linking agent to the total number of moles of hydroxyl groups and carboxy groups>>
In the adhesive composition according to the present invention, the ratio (molar equivalent ratio) of the number of moles of isocyanate groups in the specific cross-linking agent to the total number of moles of the hydroxyl groups and the carboxy groups (specific functional groups) is 3.0 to 22. There is .0.
When the molar equivalent ratio is 3.0 to 22.0, the isocyanate group in the specific cross-linking agent is in the adhesive composition more than the specific functional group contained in the specific (meth)acrylic copolymer. Since there are many of them, the specific functional group and the specific cross-linking agent can react efficiently, and the pressure-sensitive adhesive layer has sufficient cohesion, so it is excellent in suppressing foaming from the pressure-sensitive adhesive layer obtained in a high-temperature environment. . In addition, since the specific functional group in the adhesive composition is not too many and the specific functional group and the specific cross-linking agent are not excessively crosslinked, the stress relaxation property is excellent, and the pressure-sensitive adhesive layer obtained in a high-temperature environment Excellent in suppressing warpage.
From the above viewpoint, the molar equivalent ratio is preferably 3.5 to 22.0, more preferably 5.0 to 15.0, and further preferably 7.0 to 10.0. preferable.

The molar equivalent ratio is represented by the number of moles of the isocyanate group possessed by the specific cross-linking agent (formula (1) below) and the total number of moles of the specific functional groups possessed by the (meth)acrylic copolymer (formula (2) below). It is obtained by the following formula (3).

The number of moles of isocyanate groups possessed by the specific cross-linking agent used to calculate the molar equivalent ratio is the following formula using the cross-linking agent isocyanate group content, the solid content of the specific cross-linking agent, and the blending amount (parts by mass to be added). (1) can be obtained.

Number of moles of isocyanate groups in the specific cross-linking agent (unit: mmol/solid content of specific (meth)acrylic copolymer 100 g)
= [(Isocyanate group content in the specific cross-linking agent (unit: mass%) × amount of specific cross-linking agent (unit: g)) / solid content of specific cross-linking agent (unit: mass%)] / isocyanate group Molecular weight (unit: g/mol) × 1000 Formula (1)

Total number of moles of specific functional groups (unit: mmol/solid content of specific (meth)acrylic copolymer 100 g)
= [content rate of structural units formed by monomers having carboxy groups in specific (meth)acrylic copolymer (unit: % by mass) x structural units formed by monomers having carboxy groups Number of carboxy groups (valence) × 1000/molecular weight of structural units formed by monomers having carboxy groups (unit: g/mol)] + [specific (meth)acrylic copolymer hydroxyl groups in Content of structural units formed by a monomer having (unit: mass%) × Number of hydroxyl groups in a structural unit formed by a monomer having a hydroxyl group (valence) × 1000/monomer having a hydroxyl group Molecular weight of the structural unit formed by (unit: g / mol)] ... formula (2)

Ratio of the number of moles of isocyanate groups in the specific cross-linking agent to the total number of moles of hydroxyl groups and carboxy groups = above formula (1) / above formula (2)... formula (3)

The pressure-sensitive adhesive composition according to the present invention may contain a cross-linking agent other than the specific cross-linking agent (hereinafter also referred to as "other cross-linking agent"), but suppresses foaming from the pressure-sensitive adhesive layer in a high-temperature environment. From the viewpoint of superiority, it is preferred that no other cross-linking agent is included.
When the pressure-sensitive adhesive composition according to the present invention contains other cross-linking agents, from the viewpoint of suppressing warpage of the pressure-sensitive adhesive layer in a high-temperature environment, the content of the other cross-linking agents is It is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, even more preferably 0.3 parts by mass or less, with respect to 100 parts by mass of coalescence, and substantially free of is particularly preferred.
Note that "substantially free" means that the content is less than 0.05% by mass, preferably less than 0.01% by mass.

Other cross-linking agents include known cross-linking agents capable of cross-linking specific (meth)acrylic copolymers, for example, epoxy compounds, isocyanate compounds other than the specific cross-linking agents, aziridine compounds, and metal chelate compounds. be done. When the pressure-sensitive adhesive composition according to the present invention contains other cross-linking agents, epoxy compounds and metal chelate compounds are preferred.

Examples of epoxy compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromo Neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipate diglycidyl ester, phthalate diglycidyl ester, tris(glycidyl) isocyanurate, tris(glycidoxyethyl) ) isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine), phenylglycidyl ether.
These epoxy compounds may be used individually by 1 type, and may use 2 or more types together.

Examples of commercially available epoxy compounds include “TETRAD-X” and “TETRAD-C” manufactured by Mitsubishi Gas Chemical Co., Ltd., “Denacol EX-201” and “Denacol EX-203” manufactured by Nagase ChemteX Corporation. ”, “Denacol EX-141”, “Denacol EX-313”, “Denacol EX-946L”, “Denacol EX-991”, “Denacol EX-991L” and “Denacol EX-992L”. There are some.
From the viewpoint of excellent reworkability on adherends, it is more preferable to use an epoxy compound having two or less epoxy groups in the same molecule.

Examples of isocyanate compounds include aromatic polyisocyanate compounds represented by xylylene diisocyanate, diphenylmethane diisocyanate, and triphenylmethane triisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated products of the above aromatic polyisocyanate compounds. Chain or cyclic aliphatic polyisocyanate compounds, burettes, dimers, trimers or pentamers of these polyisocyanate compounds, adducts of these polyisocyanate compounds and polyol compounds such as trimethylolpropane is mentioned.
These isocyanate compounds may be used individually by 1 type, and may use 2 or more types together.

Examples of commercially available isocyanate compounds include "Coronate HX", "Coronate HL-S", "Coronate 2234", "Coronate 2785", "Aquanate 200" and "Aquanate 210" manufactured by Tosoh Corporation. , "Sumidur N3300", "Desmodur N3400", and "Sumidur N-75" manufactured by Sumika Covestro Urethane Co., Ltd., "Duranate E-405-80T" manufactured by Asahi Kasei Chemicals Co., Ltd., "Duranate 24A-100” and “Duranate TSE-100”, and “Takenate D-110N”, “Takenate D-120N”, “Takenate M-631N” and “MT-Olestar NP1200” manufactured by Mitsui Chemicals, Inc. can be preferably used.

-Silane coupling agent-
The pressure-sensitive adhesive composition according to the present invention may contain a silane coupling agent. When the pressure-sensitive adhesive composition contains a silane coupling agent, it is possible to improve the durability of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition against foaming in a high-temperature environment.

When the pressure-sensitive adhesive composition according to the present invention contains a silane coupling agent, a known silane coupling agent used for pressure-sensitive adhesive compositions can be suitably used as the silane coupling agent.
The silane coupling agent is not particularly limited, but examples include vinyltrimethoxysilane, vinyltriethoxysilane, and silane compounds containing polymerizable unsaturated groups such as 3-methacryloxypropyltrimethoxysilane, Thiol group-containing silane compounds such as methoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropyldimethoxymethylsilane, and 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl ) epoxy group-containing silane compounds such as ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3 -amino group-containing silane compounds such as aminopropylmethyldimethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate.
A silane coupling agent may be used individually by 1 type, and may be used in combination of 2 or more type.

As the silane coupling agent, a commercially available product may be used. Examples of commercially available products include Shin-Etsu Chemical Co., Ltd. trade names "KBM-803", "KBM-802", "X- 41-1810”, “X-41-1805”, “X-41-1818” and other silane coupling agents having thiol groups, trade names “KBM-403” and “KBM- 303”, “KBM-402”, “KBE-402”, “KBE-403” and other silane coupling agents having an epoxy group can be preferably used.

When the pressure-sensitive adhesive composition according to the present invention contains a silane coupling agent, the content of the silane coupling agent in the pressure-sensitive adhesive composition improves durability such as foaming from the pressure-sensitive adhesive layer in a high-temperature environment. From the viewpoint, it is preferably 0.01 parts by mass to 2.0 parts by mass, more preferably 0.05 parts by mass to 1.0 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic copolymer. , and more preferably 0.1 to 0.5 parts by mass.

-Crosslinking catalyst-
The pressure-sensitive adhesive composition according to the present invention may contain a cross-linking catalyst.
When the pressure-sensitive adhesive composition according to the present invention contains a cross-linking catalyst, the cross-linking reaction proceeds easily even when it contains a monomer having a bulky molecular structure, and a pressure-sensitive adhesive layer having a high cross-linking density can be formed. Durability and reworkability in a high-temperature environment are likely to be better.
When the pressure-sensitive adhesive composition according to the present invention contains a cross-linking catalyst, the cross-linking catalyst may be contained singly or in combination of two or more.

As the cross-linking catalyst, a known cross-linking catalyst that can be used in pressure-sensitive adhesive compositions can be suitably used.
The crosslinking catalyst is not particularly limited. 2-a] imidazole compounds typified by benzimidazole, organometallic compounds typified by dioctyltin dilaurate and 1,3-diacetoxytetrabutylstannoxane, and triethylenediamine and N-methylmorpholine typified by and tertiary amine compounds.

As the cross-linking catalyst which is an imidazole compound, a commercially available product may be used. Examples of commercially available imidazole compounds include “Curesol (registered trademark) 1B2MZ” and “Curesol (registered trademark) 1B2PZ” available from Shikoku Kasei Kogyo Co., Ltd. ”, “Curesol (registered trademark) TBZ”, and “Curesol (registered trademark) 1,2DMZ” (all trade names).

The pressure-sensitive adhesive composition according to the present invention preferably further contains an organometallic compound as a cross-linking catalyst.
When the pressure-sensitive adhesive composition according to the present invention contains an organometallic compound as a cross-linking catalyst, the organometallic compound acts as a catalyst to efficiently form a specific functional group and a coordinate bond of the specific (meth)acrylic copolymer. This cross-linking reaction increases the cohesive strength of the pressure-sensitive adhesive composition, which tends to be more excellent in suppressing foaming from the pressure-sensitive adhesive layer in a high-temperature environment.
In addition, when the pressure-sensitive adhesive composition according to the present invention contains an organometallic compound, due to the change in the crosslinked structure, the stress relaxation property is excellent even if the cohesive force is high, and the pressure-sensitive adhesive layer is more excellent in suppressing warping in a high-temperature environment. Tend.
Examples of organometallic compounds include tin compounds, zinc compounds, zirconium compounds, iron compounds, aluminum compounds, and titanium compounds in addition to the organometallic compounds described above.
As the organometallic compound, from the above viewpoint, it is particularly preferable to use at least one selected from the group consisting of tin compounds, zinc compounds, zirconium compounds and iron compounds, and it is more preferable to use tin compounds.
A zinc compound is preferably used as the organometallic compound from a comprehensive point of view such as durability, coloration of the adhesive layer, and ability to suppress an increase in adhesive strength to release paper over time.
An organic metal compound may be used individually by 1 type, and may use 2 or more types together.

A commercially available product may be used as the organometallic compound. Examples of commercially available organometallic compounds include "DOTDL (OT-1)" manufactured by ADEKA Corporation as dioctyltin dilaurate, which is a tin compound, "Nasem Zinc" manufactured by Nippon Kagaku Co., Ltd. as a zinc compound, and zirconium. "Nasem Zirconium" manufactured by Nippon Kagaku Co., Ltd. as a compound, "Nasem Iron" manufactured by Nippon Kagaku Co., Ltd. as an iron compound, "Aluminum Chelate A" manufactured by Kawaken Fine Chemicals Co., Ltd. as an aluminum compound, And as the titanium compound, those commercially available under the trade name of "Orgatics TC-100 or TC-401" manufactured by Matsumoto Fine Chemical Co., Ltd. can be mentioned.

When the pressure-sensitive adhesive composition according to the present invention contains a cross-linking catalyst, the content of the cross-linking catalyst is 0.00 per 100 parts by mass of the specific (meth)acrylic copolymer from the viewpoint of shortening the curing time. 01 parts by mass to 1.5 parts by mass, more preferably 0.05 parts by mass to 1.0 parts by mass, even more preferably 0.05 parts by mass to 0.5 parts by mass .

[Other ingredients]
The pressure-sensitive adhesive composition according to the present invention contains, in addition to the specific (meth)acrylic copolymer and the specific cross-linking agent, if necessary, an organic solvent, a weather stabilizer, a plasticizer, a softening agent, and a release agent. Auxiliaries, dyes, pigments, inorganic fillers, surfactants, antioxidants, metal corrosion inhibitors, tackifying resins, antistatic agents, UV absorbers, light stabilizers represented by hindered amine compounds, etc. Agents and the like may be contained as appropriate.

Antistatic agents include, for example, salts of nitrogen onium cations such as pyridinium cations and ammonium cations and fluorine-containing imide anions such as fluorosulfonylimide anions and trifluoromethanesulfonylimide anions.
Commercially available products of such antistatic agents include the trade name "FC-4400" manufactured by 3M Japan Co., Ltd., the trade names "MP-402A", "MP-430" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "AS-804" and "AS-110" can be preferably used.

-Gel fraction-
In the pressure-sensitive adhesive composition according to the present invention, the gel fraction (% by mass) after the completion of the cross-linking reaction, that is, after the cross-linked structure is formed between the (meth)acrylic copolymer and the specific cross-linking agent is preferably less than 75% by mass. When the gel fraction after the completion of the cross-linking reaction is less than 75% by mass, the cross-linking reaction between the (meth)acrylic copolymer and the specific cross-linking agent proceeds moderately, and the pressure-sensitive adhesive layer obtained has a moderate cohesive force. It has excellent stress relaxation properties and is more excellent in suppressing warping of the adhesive layer in a high temperature environment.
From the above point of view, the gel fraction after completion of the cross-linking reaction is more preferably 30% to 65% by mass, and even more preferably 35% to 60% by mass.

The gel fraction after completion of the cross-linking reaction is determined according to the procedures (1) to (17) below.
(1) The adhesive composition is applied on a PET (polyethylene terephthalate) film separator (release paper) with a thickness of 100 μm, air-dried at room temperature for 30 minutes, and then dried at 100 ° C. for 5 minutes to remove the adhesive layer. to obtain a pressure-sensitive adhesive layer with a separator.
(2) The obtained pressure-sensitive adhesive layer with a separator is aged for 10 days under the conditions of 23° C. and 65% relative humidity. After that, the separator-attached pressure-sensitive adhesive layer is cut into a size of 75 mm×75 mm. The weight of the pressure-sensitive adhesive layer of the cut sample is approximately 0.2 g.

(3) A metal wire mesh of 250 mesh (wire diameter 0.03 mm, opening 72 μm, made of stainless steel) is prepared, and the metal wire mesh is cut into a size of 100 mm×100 mm.
(4) The metal wire mesh is degreased with ethyl acetate and then dried. After degreasing and drying, the metal wire mesh is stored in a desiccator. In addition, fraying at the ends of the metal wire mesh causes measurement errors, so they should be removed in advance.
(5) Accurately measure the mass of the metal wire mesh. Let A be this mass.

(6) After attaching the pressure-sensitive adhesive layer with a separator of (2) cut into a size of 75 mm×75 mm to the center of the metal wire mesh, the PET film separator is peeled off from the pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is attached to the metal wire mesh so that the pressure-sensitive adhesive layer is positioned in the plane after the metal wire mesh is folded in the steps (7) to (9) described below.
(7) The metal wire mesh is folded in half from the back side toward the front side with the surface to which the film-like adhesive layer is attached facing inward.
(8) Fold the front third of the metal wire mesh (two ends on the front side) folded in half to the back, and then fold the back one third to the front (100 mm in the vertical direction) folded to one-sixth of the original, and not folded in the horizontal direction).
(9) Fold the above-mentioned wire mesh to the right side at the 1/3 portion from the left, and similarly fold it to the left side at the 1/3 portion from the right. This is referred to as Sample 1. In Sample 1, the size of the original metal wire mesh is folded to 1/6 in the vertical direction and 1/3 in the horizontal direction.
(10) Accurately measure the mass of the sample 1 above. Let this mass be B.

(11) Stapling the sample 1 so that the crease does not open. This is referred to as Sample 2. The mass of sample 2 is measured. Let C be this mass.
(12) Two samples 2 for gel fraction measurement are prepared for each pressure-sensitive adhesive composition.

(13) Sample 2 is placed in a glass bottle containing 80 g of ethyl acetate, and the bottle is capped.
(14) The glass bottle containing sample 2 is left for 3 days under conditions of 23° C. and 65% relative humidity.
(15) Remove sample 2 from the vial and wash briefly with ethyl acetate.
(16) After drying sample 2 at 120° C. for 24 hours, accurately measure the mass. Let this be D.

(17) Calculate the gel fraction by the following formula.
Gel fraction [mass%] = (D - (A + (C - B))) / (B - A) x 100

[Use of adhesive composition]
The use of the pressure-sensitive adhesive composition according to the present invention is not particularly limited, but it is preferably used for attaching a polarizing plate to an adherend via a pressure-sensitive adhesive layer. Uses for attaching to a liquid crystal cell, uses for attaching a polarizing plate to an optical film such as a retardation film, and the like can be mentioned.
Among these, the pressure-sensitive adhesive composition according to the present invention is excellent in suppressing foaming and warping from the pressure-sensitive adhesive layer obtained in a high-temperature environment, workability, and warp-suppressing properties when adhered to glass. It is preferably used for the purpose of attaching a polarizing plate to a liquid crystal cell.

[Polarizing plate with adhesive layer]
A pressure-sensitive adhesive layer-attached polarizing plate according to the present invention includes a polarizing plate and a pressure-sensitive adhesive layer provided on the polarizing plate and being a crosslinked product of the pressure-sensitive adhesive composition.
Since the pressure-sensitive adhesive layer-attached polarizing plate according to the present invention includes the pressure-sensitive adhesive layer which is a crosslinked product of the pressure-sensitive adhesive composition according to the present invention, foaming from the pressure-sensitive adhesive layer and warping of the pressure-sensitive adhesive layer obtained in a high-temperature environment occur. excellent in suppressing
Further, even when the pressure-sensitive adhesive layer-attached polarizing plate according to the present invention is adhered to, for example, a glass substrate of a liquid crystal cell, the pressure-sensitive adhesive layer-attached polarizing plate is less likely to warp in a high-temperature environment.

The polarizing plate used in the pressure-sensitive adhesive layer-attached polarizing plate according to the present invention may be a polarizer alone as long as it has at least a polarizer, or may be a laminate of a polarizer and a protective film. good.
The polarizing plate may have a one-layer structure with a polarizer alone, a two-layer structure with a protective film on one side of the polarizer, or a three-layer structure with protective films on both sides of the polarizer. good too.
A material for the polarizer is not particularly limited, and examples thereof include polyvinyl alcohol (PVA) film.
The protective film is not particularly limited, and examples thereof include triacetyl cellulose (TAC) film, polycycloolefin (COP) film, polyethylene terephthalate (PET) film, and acrylic film.

Examples of the layer structure of the pressure-sensitive adhesive layer-attached polarizing plate according to the present invention include pressure-sensitive adhesive layer/polarizer, pressure-sensitive adhesive layer/polarizer/protective film, pressure-sensitive adhesive layer/protective film/polarizer/protective film, and pressure-sensitive adhesive layer/polarizer. agent layer/protective film/polarizer.
Incidentally, between the polarizer and the protective film, between the protective film and the pressure-sensitive adhesive layer, and between the polarizer and the pressure-sensitive adhesive layer, a retardation film (e.g., EWV (excellent wide view) layer typified by It may have layers such as an optical functional layer, an adhesive layer, and an easy-adhesion layer.
Further, the outermost surface of the pressure-sensitive adhesive layer-attached polarizing plate may be protected with a release film.

For the release film that protects the surface of the adhesive layer, in order to make it easier to release the release film from the adhesive layer, the surface is treated with a release agent such as fluororesin, paraffin wax, silicone, or the like. Synthetic resin films such as polyester films are preferred.
When the surface opposite to the pressure-sensitive adhesive layer side is protected with a release film, examples of the release film include a surface protective film such as a hard-coated polyethylene terephthalate (PET) film.

The thickness of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive layer-attached polarizing plate according to the present invention can be appropriately set according to the types of substrate and adherend, the surface roughness of the substrate and adherend, and the like. Generally, the thickness of the adhesive layer is 1 μm to 100 μm, preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm.

The pressure-sensitive adhesive layer-attached polarizing plate according to the present invention is produced by a known method.
The method for producing the pressure-sensitive adhesive layer-attached polarizing plate is not particularly limited. is formed, the coating layer is transferred onto a polarizing plate and cured to prepare a polarizing plate with an adhesive layer.
Further, as another example of the method for producing a polarizing plate with an adhesive layer, the adhesive composition according to the present invention is applied onto a release film and dried to form a coating layer of the adhesive composition on the release film. After that, a release film is provided in close contact with the exposed surface of the coating layer to prepare a double-sided pressure-sensitive adhesive tape without a support. Next, the coating layer is cured to form an adhesive layer. Subsequently, there is a method of producing a polarizing plate with an adhesive layer by peeling off one release film and transferring the exposed adhesive layer onto a polarizing plate.
Another example of the method for producing a polarizing plate with an adhesive layer is a method of producing a polarizing plate with an adhesive layer by applying the adhesive composition according to the present invention onto a polarizing plate, drying and curing the composition. is mentioned.
The drying conditions include, for example, a hot air dryer at 70° C. to 120° C. for 1 minute to 3 minutes.

[In-vehicle display device]
An in-vehicle display device according to the present invention includes the pressure-sensitive adhesive layer-attached polarizing plate.
The in-vehicle display device according to the present invention includes an adhesive layer-attached polarizing plate having an adhesive layer that is a crosslinked product of the adhesive composition according to the present invention. Since it is excellent in suppressing foaming from the adhesive layer and warping of the adhesive layer, it is suitable as an in-vehicle display device suitable for the in-vehicle environment.
Examples of in-vehicle display devices include a monitor that displays various information such as position information and speed information, and a head-up display.

EXAMPLES The present invention will be specifically described below by way of examples, but the present invention is not limited to these examples.
The glass transition temperature (Tg), weight average molecular weight (Mw), and gel fraction (% by mass) of the examples were measured and calculated by the methods described above.

<Production of (meth)acrylic copolymer>
(Production Example 1; (meth)acrylic copolymer 1)
In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 45.000 parts by mass of n-butyl acrylate (n-BA), 37.775 parts by mass of methyl acrylate (MA), benzyl 17.000 parts by weight of acrylate (BZA), 0.075 parts by weight of 2-hydroxyethyl acrylate (2HEA), 0.15 parts by weight of acrylic acid (AA), and 110 parts by weight of ethyl acetate were mixed and then reacted. The inside of the vessel was replaced with nitrogen. Then, the mixture in the reactor was heated to 70° C. while stirring, and then 0.02 parts by mass of 2,2′-azobis(2,4-dimethylvaleronitrile) (ABVN) as a polymerization initiator and ethyl acetate. 40 parts by mass were successively added and kept for 6 hours for polymerization reaction. After completion of the polymerization reaction, the solution was diluted with ethyl acetate to obtain a solution of (meth)acrylic copolymer 1 having a solid content of 17.3% by mass and a weight average molecular weight (Mw) of 1,600,000.
The total number of moles of the specific functional group was determined from the above formula (2) and was 2.73 millimoles ([0.15 (unit: mass%) x 1/72 (unit: g/mol) + 0.075 ( unit: mass %)×1/116 (unit: g/mol)]×1000). AA has a molecular weight of 72 and a valence of 1, and 2HEA has a molecular weight of 116 and a valence of 1.
In addition, "solid content" means the residue amount which removed volatile components, such as a solvent, from the solution of a (meth)acrylic copolymer.

(Production Examples 2 to 20; (meth)acrylic copolymers 2 to 20)
A (meth)acrylic copolymer was prepared in the same manner as the (meth)acrylic copolymer 1 except that the monomer composition shown in Table 1 was used and the weight average molecular weight was adjusted by changing the amount of the organic solvent and the polymerization initiator. 2-20 were synthesized.
Table 1 shows the monomer compositions and weight average molecular weights (Mw) of the (meth)acrylic copolymers 2 to 20.

"-" in Table 1 indicates that the corresponding component is not included. In Table 1, the (A)+(B) content (% by mass) indicates the total content of structural units formed from monomers having hydroxyl groups and structural units formed from monomers having carboxy groups.
Abbreviations in Table 1 are as follows.
・BA: n-butyl acrylate ・MA: methyl acrylate ・t-BA: t-butyl acrylate ・PHEA: phenoxyethyl acrylate ・BZA: benzyl acrylate ・2HEA: 2-hydroxyethyl acrylate ・4HBA: 4-hydroxybutyl acrylate ・2HEMA : 2-hydroxyethyl methacrylate AA: acrylic acid M-5300: ω-carboxy-polycaprolactone (n≈2) monoacrylate (trade name: Aronix M-5300, manufactured by Toagosei Co., Ltd.)

(Example 1)
<<Preparation of adhesive composition>>
100 parts by mass of the solution of (meth)acrylic copolymer 1 prepared above (solid content conversion value), Coronate (registered trademark) L45E (tolylene diisocyanate (TDI), solid content: 45 mass%, isocyanate group Content rate: 7.9% by mass, manufactured by Tosoh Corporation) 6.0 parts by mass (solid content conversion value) and a silane coupling agent (trade name: KBM-403, solid content: 100% by mass, Shin-Etsu Chemical Co., Ltd. (manufactured by Co., Ltd.) were sufficiently stirred and mixed to obtain a pressure-sensitive adhesive composition.
The number of moles of isocyanate groups in the specific cross-linking agent was determined by the above formula (1) and was 25.08 millimoles ((7.9 (unit: mass%) x 6 (unit: g) / 45 (unit :% by mass))/42 (unit: g/mol)×1000).
The molecular weight of the isocyanate group was calculated as 42.
Ratio of the number of moles of isocyanate groups possessed by Coronate (registered trademark) L45E to the total number of moles of specific functional groups possessed by the (meth)acrylic copolymer 1 in the resulting pressure-sensitive adhesive composition (the tolylene diisocyanate compound possesses The number of moles of isocyanate groups/total number of moles of specific functional groups possessed by the (meth)acrylic copolymer) was found to be 25.08/2.73≈9.2 when calculated by the above-mentioned formula (3). Ta.
Moreover, the gel fraction of the obtained adhesive composition was 52%.

<<Preparation of polarizing plate with adhesive layer>>
Using the pressure-sensitive adhesive composition prepared above, a polarizing plate with a pressure-sensitive adhesive layer was produced as follows.
A release film (trade name: Film Bina (registered trademark) 100E-0010N023, manufactured by Fujimori Kogyo Co., Ltd.) that has been surface-treated with a silicone release agent is coated on the surface-treated side so that the thickness after drying becomes 25 μm. The pressure-sensitive adhesive composition was applied to form a coating film. Then, the formed coating film was dried at a drying temperature of 100° C. for 90 seconds using a hot air circulating dryer to form an adhesive layer on the release film. Next, one surface of a polarizing plate having a laminated structure of triacetyl cellulose (TAC) layer/polyvinyl alcohol (PVA) layer/TAC layer and the surface of the pressure-sensitive adhesive layer formed on the release film are laminated together. After that, it was pressed through pressure nip rolls. After crimping, autoclave treatment (temperature: 50°C, pressure: 5 kg/cm ² , treatment time: 20 minutes) was performed, and then cured for 96 hours in an environment of an ambient temperature of 23°C and 50% RH to form a release film/adhesive. A pressure-sensitive adhesive layer-attached polarizing plate having an adhesive layer/polarizing plate laminate structure was produced.

<Evaluation>
<<Preparation of foam evaluation sample>>
The pressure-sensitive adhesive layer-attached polarizing plate was cut so that the long side was 0° with respect to the absorption axis, and one test piece having a size of 50 mm×89 mm (long side) was prepared.
The release film of the test piece is peeled off, and the surface of the adhesive layer exposed by peeling is attached to one side of glass having a size of 250 mm x 350 (long side) and a thickness of 1.8 mm, and crimped using a laminator. Then, a laminate of the pressure-sensitive adhesive layer-attached polarizing plate and the glass was produced. After autoclave treatment (temperature: 50° C., pressure: 5 kg/cm ² , treatment time: 20 minutes) was applied to the produced laminate, it was left for 1 hour under conditions of 23° C. and 50% RH to evaluate foaming. A sample for

[Foaming suppression]
The foam evaluation sample prepared above was left at 115° C. for 168 hours. The appearance of the sample for foaming evaluation after standing was visually observed, and the foaming suppressing property in a high temperature environment (115°C) was evaluated according to the following evaluation criteria.
In addition, if the evaluation result is "A", "B", or "C", it can be said that the foaming suppressing property is excellent.
-Evaluation criteria-
A: No foaming is observed.
B: Slight foaming is observed in a portion within 0.3 mm from the edge of the foaming test sample.
C: Foaming is observed in a portion exceeding 0.3 mm and within 0.5 mm from the edge of the sample for foaming test.
D: Foaming is observed on the entire surface of the foaming test sample.

<<Preparation of sample for warpage evaluation>>
The pressure-sensitive adhesive layer-attached polarizing plate prepared above was cut into a size of 50 mm×160 mm (long side).
The release film of the adhesive layer-attached polarizing plate is peeled off, and the surface of the adhesive layer exposed by peeling is attached to one side of glass having a size of 50 mm × 160 mm (long side) and a thickness of 0.5 mm, and a laminator is used. was crimped using to produce a laminate. After autoclave treatment (temperature: 50° C., pressure: 5 kg/cm ² , treatment time: 20 minutes) was applied to the produced laminate, it was left for 1 hour under conditions of 23° C. and 50% RH to evaluate warpage. A sample for

[Warpage control]
The warpage evaluation sample prepared above was left at 115° C. for 168 hours. The sample for warp evaluation after standing is placed on a smooth table under conditions of 23 ° C. and 50% RH, and a laser displacement meter (LK-H027K model number manufactured by Keyence Corporation) is used to measure both ends of the sample. was measured. The average value of the measured values at both ends was evaluated according to the following evaluation criteria for suppressing warpage.
If the evaluation result is "A", "B", or "C", it can be said that the warpage suppressing property is excellent.
-Evaluation criteria-
A: The warp is less than 3.0 mm.
B: The warp is 3.0 mm or more and less than 3.3 mm.
C: The warp is 3.3 mm or more and less than 3.6 mm.
D: The warp is 3.6 mm or more.

(Examples 2 to 34 and Comparative Examples 1 to 7)
A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the (meth)acrylic copolymers 2 to 20 shown in Tables 2 to 4 were used. Each layered polarizing plate was produced. Each test sample was prepared in the same manner as in Example 1 using the prepared pressure-sensitive adhesive layer-attached polarizing plate, and each test sample was evaluated in the same manner as in Example 1. The results are shown in Tables 2-4.

Abbreviations in Tables 2 to 4 are as follows. The parts by mass in Tables 2 to 4 are converted values of solid content or active ingredients. In addition, the "ratio of the number of moles" in Tables 2 to 4 means the number of moles of isocyanate groups in the tolylene diisocyanate-based cross-linking agent with respect to the total number of moles of hydroxyl groups and carboxy groups in the (meth)acrylic copolymer. , and the ratio of the number of moles was obtained from the above formula (3). "-" in Tables 2 to 4 indicates that the corresponding component is not included.
In Tables 2 to 4, the columns of production examples of (meth)acrylic copolymers represent the numbers of production examples described in Table 1. For example, in Example 26 in Table 3, the (meth)acrylic copolymer 16 synthesized in Production Example 16 and the (meth)acrylic copolymer 17 synthesized in Production Example 17 are used. represent.
In Tables 2 to 4, Examples 26 to 34 show that the (meth)acrylic copolymer 16 and the (meth)acrylic copolymer 17 were blended to prepare pressure-sensitive adhesive compositions. For example, the blending amount of Example 26 in Table 3 indicates that the (meth)acrylic copolymer 16 is 80 parts by mass and the (meth)acrylic copolymer 17 is 20 parts by mass.
In Tables 2 to 4, the numerical values in parentheses of the evaluation results of the warp suppression property in the column of evaluation represent the measured values of the magnitude of warpage.

- TDI: tolylene diisocyanate-based cross-linking agent (product name: Coronate L45E, manufactured by Tosoh Corporation, an adduct of tolylene diisocyanate and trimethylolpropane)
・ HMDI: hexamethylene diisocyanate (trade name; “Sumidur N-75”, manufactured by Sumika Covestro Urethane Co., Ltd.)
・XDI: xylylene diisocyanate (trade name; “Takenate D-110”, manufactured by Mitsui Chemicals, Inc.)
・TETRAD-X: Epoxy compound (manufactured by Mitsubishi Gas Chemical Co., Ltd., N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine)) [the number of epoxy groups in the same molecule is 4]
・EX-141: epoxy compound (manufactured by Nagase ChemteX Co., Ltd., phenyl glycidyl ether), [the number of epoxy groups in the same molecule is 1]
・EX-201: epoxy compound (manufactured by Nagase ChemteX Co., Ltd., resorcinol diglycidyl ether) [the number of epoxy groups in the same molecule is 2]
· KBM-403: silane coupling agent (solid content: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.)
· X-41-1053: silane coupling agent (solid content: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.)
Curazole: an imidazole compound that is a cross-linking catalyst (1B2PZ 1-benzyl-2-phenylimidazole, solid content conversion value, manufactured by Shikoku Kasei Co., Ltd.)
-Sn compound: an organometallic compound (tin compound) that is a cross-linking catalyst (manufactured by ADEKA Corporation, trade name: DOTDL (OT-1))
Zn compound: an organometallic compound (zinc compound) that is a cross-linking catalyst (manufactured by Nippon Kagaku Co., Ltd., trade name: Nasem Zinc)
- Zr compound: an organometallic compound (zirconium compound) that is a cross-linking catalyst (manufactured by Nippon Kagaku Co., Ltd., trade name: Nasem zirconium)
- Fe compound: an organometallic compound (iron compound) that is a cross-linking catalyst (manufactured by Nippon Kagaku Co., Ltd., trade name: Nasem Iron)

As shown in the results of Tables 2 to 4, the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions for polarizing plates of Examples 1 to 34 are the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Comparative Examples 1 to 7. It can be seen that both suppression of foaming from the pressure-sensitive adhesive layer and suppression of warpage of the pressure-sensitive adhesive layer in a high-temperature environment are superior to those of the adhesive layer.

Claims (10)

A (meth)acrylic copolymer comprising a structural unit formed by a (meth)acrylic acid alkyl ester, a structural unit formed by a monomer having a hydroxyl group, and a structural unit formed by a monomer having a carboxyl group coalescence and
a tolylene diisocyanate-based cross-linking agent;
contains
In the (meth)acrylic copolymer, the total content of the structural units formed by the monomers having the hydroxyl group and the structural units formed by the monomers having the carboxyl group is more than 0% by mass and 0.40 % by mass or less,
The ratio of the number of moles of isocyanate groups in the tolylene diisocyanate-based cross-linking agent to the total number of moles of the hydroxyl groups and the carboxy groups is 3.0 to 10.0 .
A pressure-sensitive adhesive composition for a polarizing plate for an in-vehicle display device . The pressure-sensitive adhesive composition for a polarizing plate for a vehicle-mounted display device according to claim 1, wherein the (meth)acrylic copolymer contains a structural unit formed by a (meth)acrylic monomer having an aromatic ring. The ratio of the number of moles of isocyanate groups in the tolylene diisocyanate-based cross-linking agent to the total number of moles of hydroxyl groups and carboxy groups in the (meth)acrylic copolymer is 6.0 to 10.0 . The pressure-sensitive adhesive composition for a polarizing plate for an in-vehicle display device according to claim 1 or 2. In the (meth)acrylic copolymer, the content of structural units formed by the monomer having the carboxy group is higher than the content of the structural unit formed by the monomer having the hydroxyl group, claims 1 to 1 The pressure-sensitive adhesive composition for a polarizing plate for an in-vehicle display device according to claim 3 . In the (meth)acrylic copolymer, the content of the structural units formed by the monomer having the carboxy group and the content of the structural units formed by the monomer having the hydroxyl group are the same. The pressure-sensitive adhesive composition for a polarizing plate for an in-vehicle display device according to any one of claims 1 to 3. The pressure-sensitive adhesive composition for a polarizing plate for a vehicle-mounted display device according to any one of claims 1 to 5, wherein the (meth)acrylic copolymer has a weight average molecular weight of 1,000,000 or more. The pressure-sensitive adhesive composition for a polarizing plate for a vehicle-mounted display device according to any one of claims 1 to 6, further comprising an organometallic compound as a crosslinking catalyst. The pressure-sensitive adhesive composition for a polarizing plate for an in-vehicle display device according to claim 7, wherein the organometallic compound is at least one compound selected from the group consisting of a tin compound, a zinc compound, a zirconium compound, and an iron compound. thing. A polarizing plate with an adhesive layer for an in-vehicle display device, comprising an adhesive layer that is a crosslinked product of the adhesive composition for an in-vehicle display device polarizing plate according to any one of claims 1 to 8. An in-vehicle display device comprising the polarizing plate with an adhesive layer for an in-vehicle display device according to claim 9 .