WO2021075188A1 - Adhesive agent composition and adhesive sheet - Google Patents

Abstract

Provided is an adhesive agent composition which enables the formation of an adhesive agent layer that rarely undergoes the occurrence of defects, such as detachment from an object of interest, under high-temperature environments and also rarely undergoes the occurrence of whitening under high-humidity and high-temperature environments.　An adhesive agent composition comprising: a (meth)acrylic copolymer (A) which is a copolymer of monomer components comprising 51 to 99% by mass of a (meth)acrylate represented by formula (a1): CH₂=CR¹-COO-(R²-O)_n-R³ (wherein R¹ represents a hydrogen atom or a methyl group; R² represents an alkanediyl group; R³ represents an alkyl group; and n represents an integer of 1 or more), 0.4 to 5% by mass of a tertiary nitrogen-containing monomer and 0.5 to 10% by mass of a crosslinkable functional-group-containing monomer and which has a weight average molecular weight of 700,000 to 1,800,000; and a crosslinking agent (B).

Description

Adhesive composition and adhesive sheet

The present invention relates to an adhesive composition and an adhesive sheet.

A pressure-sensitive adhesive composition containing a (meth) acrylic copolymer has been conventionally known (see, for example, Patent Document 1). In recent years, the applications to which the pressure-sensitive adhesive composition is applied have expanded, and the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is exposed to a high-temperature environment or a high-humidity heat environment, for example, in an in-vehicle application. In some cases.

Japanese Unexamined Patent Publication No. 2018-021127

When the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition containing a (meth) acrylic copolymer and in contact with the adherend is exposed to a high temperature environment, the pressure-sensitive adhesive layer is peeled off from the adherend. Defects may occur. Further, when the pressure-sensitive adhesive layer is exposed to a high humidity and heat environment, a phenomenon called whitening may occur in the pressure-sensitive adhesive layer.

One aspect of the present invention is to form an adhesive layer in which the occurrence of defects such as peeling of the adhesive layer from the adherend is suppressed in a high temperature environment and the occurrence of whitening is suppressed in a high humidity environment. The purpose is to provide a possible pressure-sensitive adhesive composition.

The present inventors have made diligent studies to solve the above problems. As a result, they have found that a pressure-sensitive adhesive composition having the following constitution can solve the above-mentioned problems, and have completed the present invention.
The present invention relates to, for example, the following [1] to [6].

[1] formula (a1): in represented by ^{_{CH 2 = CR 1 -COO- (R}} 2 -O) n -R 3 ( meth) acrylate (Formula (a1), R ¹ is a hydrogen atom or a methyl group Yes, R ² is an alcandiyl group, R ³ is an alkyl group, n is an integer greater than or equal to 1) in 51-99% by weight, and tertiary nitrogen-containing monomers in 0.4-5% by weight, and A (meth) acrylic copolymer (A) having a weight average molecular weight of 700,000 to 1.8 million, which is a copolymer of a monomer component containing 0.5 to 10% by mass of a crosslinkable functional group-containing monomer, and a crosslinking agent. A pressure-sensitive adhesive composition containing (B).

[2] The pressure-sensitive adhesive composition according to the above [1], wherein n in the formula (a1) is 1.
[3] The pressure-sensitive adhesive composition according to the above [1] or [2], wherein the tertiary nitrogen-containing monomer is at least one selected from N-vinylpyrrolidone and acryloylmorpholine.

[4] The pressure-sensitive adhesive composition according to any one of the above [1] to [3], wherein the tertiary nitrogen-containing monomer is N-vinylpyrrolidone.
[5] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above [1] to [4].

[6] An optical member having an adhesive layer formed from the adhesive composition according to any one of the above [1] to [4].

According to one aspect of the present invention, the occurrence of defects such as peeling of the pressure-sensitive adhesive layer from the adherend is suppressed in a high-temperature environment, and the occurrence of whitening is suppressed in a high-humidity heat environment, that is, the pressure-sensitive adhesive layer. It is possible to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer having excellent high-temperature durability and whitening resistance.

Hereinafter, the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet according to the embodiment of the present invention will be described.
In the present specification, acrylic and methacrylic are collectively referred to as "(meth) acrylic", and acrete and methacrylate are also collectively referred to as "(meth) acrylate".

[Adhesive composition]
The pressure-sensitive adhesive composition according to one embodiment of the present invention (hereinafter, also referred to as “the pressure-sensitive adhesive composition of the present embodiment”) includes a specific (meth) acrylic copolymer (A) and a cross-linking agent (B). Contains. By using the pressure-sensitive adhesive composition of the present embodiment, even when it is placed in a high temperature environment (for example, 100 ° C. dry environment) or a moist heat environment (for example, 60 ° C./90% RH environment), it can be removed from the adherend. There are few defects such as peeling and cracks, and it has excellent durability at high temperature and humidity, and even when placed in a high humidity environment (for example, 85 ° C / 85% RH environment), there is little whitening and it has whitening resistance. An excellent pressure-sensitive adhesive layer can be formed.

<(Meta) acrylic copolymer (A)>
The (meth) acrylic copolymer (A) is a (meth) acrylate represented by the following formula (a1) (hereinafter, also referred to as “(meth) acrylate (a1)”) in an amount of 51 to 99% by mass of tertiary nitrogen. It is a copolymer of a monomer component containing 0.4 to 5% by mass of a containing monomer and 0.5 to 10% by mass of a crosslinkable functional group-containing monomer, and is obtained by copolymerizing the monomer component.
The monomer component is usually a polymerizable double bond-containing monomer.

<(Meta) acrylate represented by the formula (a1)>
Equation (a1) is shown below.
Equation (a1): CH ₂ = CR ¹ -COO- (R ^2- O) _n- R ³
In formula (a1), R ¹ is a hydrogen atom or a methyl group, R ² is an alkanediyl group, R ³ is an alkyl group, and n is an integer of 1 or more.

Examples of the alkanediyl group include a methanediyl group, an ethane-1,2-diyl group, a propane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diyl group, and a hexane-. Examples thereof include a 1,6-diyl group and an octane-1,8-diyl group. The alkanediyl group may be linear or branched. The number of carbon atoms of the alkanediyl group is preferably 1 to 10, more preferably 1 to 5, and even more preferably 2 to 4.

Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a tert-butyl group, a hexyl group and an octyl group. The alkyl group may be linear or branched. The alkyl group preferably has 1 to 10, more preferably 1 to 5, and even more preferably 1 to 4.

In the formula (a1), n is an integer of 1 or more, preferably 1 to 10, more preferably 1 to 5, still more preferably 1 to 3, and particularly preferably 1.
By using a copolymer containing a structural unit derived from (meth) acrylate (a1), the moisture absorbed in the pressure-sensitive adhesive layer in a high humidity and heat environment is dispersed in the pressure-sensitive adhesive layer to enhance whitening resistance. be able to.

Examples of the alkoxyalkyl (meth) acrylate in which n is 1 in the formula (a1) include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and 3-methoxypropyl. Examples thereof include (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate.

Examples of the (meth) acrylate in which n is 2 or more in the formula (a1) include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, ethoxytriethylene glycol mono (meth) acrylate, and ethoxydiethylene glycol. Examples thereof include mono (meth) acrylate and methoxytriethylene glycol mono (meth) acrylate.
One type or two or more types of (meth) acrylate (a1) can be used.

The amount of (meth) acrylate (a1) in all the monomer components used to form the (meth) acrylic copolymer (A) is 51 to 99% by mass, preferably 60% by mass or more, more preferably. Is 70% by mass or more, more preferably more than 80% by mass, still more preferably 85% by mass or more, particularly preferably 90% by mass or more, and the upper limit thereof is preferably 98% by mass. When the amount of the (meth) acrylate (a1) is at least the above lower limit value, the moisture that has penetrated into the pressure-sensitive adhesive layer can be efficiently dispersed, and the whitening resistance becomes high. Especially when it exceeds 80% by mass, the whitening resistance becomes high. When the property becomes higher and is not more than the upper limit value, it is advantageous to improve the cohesive force. Further, in the (meth) acrylic copolymer (A), the structural unit derived from the (meth) acrylate (a1) is preferably 51 to 99% by mass, more preferably 60 to 99% by mass, and further preferably 70. It has ~ 99% by mass, more preferably more than 80% by mass and 99% by mass or less, and particularly preferably 85 to 98% by mass. The amount of the structural unit can be grasped from, for example, the amount of the monomer component charged.

<Classic nitrogen-containing monomer>
By using a copolymer containing a structural unit derived from a tertiary nitrogen-containing monomer, the high-temperature durability of the pressure-sensitive adhesive layer can be improved, and the whitening resistance can be improved. The tertiary nitrogen means a nitrogen atom in which three bonds of the nitrogen atom are bonded to an atom other than a hydrogen atom, preferably a carbon atom.

Examples of the tertiary nitrogen-containing monomer include an amino group-containing monomer, an amide group-containing monomer, and a nitrogen-based heterocycle-containing monomer in which the nitrogen atom in the amino group, the amide group, and the nitrogen-based heterocycle is tertiary. Specific examples thereof include (meth) acrylates and vinyl compounds; specifically, N, N-dialkylaminoalkyl (meth) acrylates such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate. ) Acrylic; N, N-dialkyl (meth) acrylamide such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide; N-vinylpyrrolidone, N-vinylcaprolactam, (meth) acryloylmorpholine, etc. Nitrogen-based heterocycle-containing monomer can be mentioned. Among these, at least one selected from N-vinylpyrrolidone and acryloylmorpholine is preferable, and N-vinylpyrrolidone is more preferable.
One type or two or more types of tertiary nitrogen-containing monomers can be used.

The amount of the tertiary nitrogen-containing monomer in all the monomer components used for forming the (meth) acrylic copolymer (A) is 0.4 to 5% by mass, and the upper limit thereof is preferably 4. It is 8% by mass, more preferably 4% by mass, still more preferably 3% by mass, and its lower limit is preferably 1% by mass. When the amount of the tertiary nitrogen-containing monomer is not more than the above upper limit value, the pressure-sensitive adhesive layer is less likely to cause defects such as peeling and cracking even when placed in a moist heat environment, as compared with the case where it exceeds 5% by mass. It is excellent in that it can be formed. When the amount of the tertiary nitrogen-containing monomer is at least the above lower limit value, it is advantageous in improving high temperature durability, wet heat durability and whitening resistance, and particularly excellent in that an adhesive layer having excellent high temperature durability can be formed. There is. Further, the (meth) acrylic copolymer (A) contains a structural unit derived from a tertiary nitrogen-containing monomer, preferably 0.4 to 5% by mass, more preferably 0.4 to 4.8% by mass. It is more preferably 0.4 to 4% by mass, and particularly preferably 1 to 3% by mass. The amount of the structural unit can be grasped from, for example, the amount of the monomer component charged.

<Crosslinkable functional group-containing monomer>
Examples of the crosslinkable functional group-containing monomer include a hydroxyl group-containing monomer and an acid group-containing monomer, and among these, a hydroxyl group-containing monomer is preferable.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroshikibutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl ( Hydroxyl-containing (meth) acrylates such as hydroxyalkyl (meth) acrylates such as meta) acrylates; hydroxyethyl (meth) acrylamides can be mentioned.

Examples of the acid group include a carboxy group, an acid anhydride group, a phosphoric acid group, and a sulfate group. Examples of the carboxy group-containing monomer include β-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylate, mono (meth) acryloyloxyethyl ester of succinate, and ω-carboxypolycaprolactone mono (meth) acrylate. Such as carboxy group-containing (meth) acrylate; (meth) acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid and the like. Examples of the acid group-containing monomer other than the carboxy group include acid anhydride group-containing monomers such as phthalic anhydride and maleic anhydride; and phosphoric acid group-containing monomers such as (meth) acrylic monomers having a phosphate group in the side chain. A sulfate group-containing monomer such as a (meth) acrylic monomer having a sulfate group in the side chain can be mentioned.

When corrosion due to an acid group becomes a problem in the adherend in contact with the pressure-sensitive adhesive layer, for example, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present embodiment may be a wiring made of a metal or a metal oxide. In the case of direct contact with the member, it is preferable not to substantially use the acid group-containing monomer as the monomer component used for forming the (meth) acrylic copolymer (A) in order to suppress the corrosion of the member. That is, it is preferable that the (meth) acrylic copolymer (A) has substantially no acid group. The fact that the (meth) acrylic copolymer (A) has substantially no acid group means that the acid value of the (meth) acrylic copolymer (A) is 0.5 mgKOH / g or less.

The conventional pressure-sensitive adhesive layer using a (meth) acrylic copolymer having substantially no acid group has defects such as peeling and cracking from the adherend when placed in a high temperature environment. May occur and the high temperature durability may not be sufficient. In the present embodiment, the amount of the tertiary nitrogen-containing monomer in all the monomer components used for forming the (meth) acrylic copolymer (A) is set within a specific range to obtain the (meth) acrylic copolymer. Even when (A) has substantially no acid group, a pressure-sensitive adhesive layer having excellent high-temperature durability can be obtained.

Among the crosslinkable functional group-containing monomers, hydroxyl group-containing monomers are preferable. When the pressure-sensitive adhesive layer is applied to a place where it comes into direct contact with a member such as a wiring made of metal or metal oxide, a hydroxyl group-containing monomer is preferable from the viewpoint of corrosion prevention. At least a part of the hydroxyl group derived from the hydroxyl group-containing monomer becomes a cross-linking point in the (meth) acrylic copolymer (A), and is cross-linked by reacting with the isocyanate group of the isocyanate-based cross-linking agent (B1) described later, for example. Structures can be formed.
One or more crosslinkable functional group-containing monomers can be used.

The amount of the crosslinkable functional group-containing monomer in all the monomer components used for forming the (meth) acrylic copolymer (A) is 0.5 to 10% by mass, preferably 1 to 8% by mass. More preferably, it is 1 to 5% by mass. In such an embodiment, a crosslinked structure is appropriately formed from the (meth) acrylic copolymer (A), and a pressure-sensitive adhesive layer having appropriate flexibility tends to be obtained. Further, the (meth) acrylic copolymer (A) contains a structural unit derived from a crosslinkable functional group-containing monomer, preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, and even more preferably. It has 1 to 5% by mass. The amount of the structural unit can be grasped from, for example, the amount of the monomer component charged.

<Other monomers>
Examples of the monomer other than the (meth) acrylate (a1), the tertiary nitrogen-containing monomer and the crosslinkable functional group-containing monomer described above include alkyl (meth) acrylate, alicyclic hydrocarbon group or aromatic hydrocarbon group. Examples thereof include amide group-containing monomers other than contained (meth) acrylates, styrene-based monomers and tertiary nitrogen-containing monomers, cyano group-containing monomers, vinyl acetate, and polymerizable macromonomers.

The number of carbon atoms of the alkyl group in the alkyl (meth) acrylate is preferably 1 to 20. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, and iso-butyl (iso-butyl). Meta) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, n-nonyl (meth) Acrylate, iso-nonyl (meth) acrylate, n-decyl (meth) acrylate, iso-decyl (meth) acrylate, undeca (meth) acrylate, lauryl (meth) acrylate, oleyl (meth) acrylate, n-stearyl (meth) Examples thereof include acrylate and iso-stearyl (meth) acrylate.

Examples of the alicyclic hydrocarbon group or aromatic hydrocarbon group-containing (meth) acrylate include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, and phenoxyethyl (meth). ) Acrylate can be mentioned.

Examples of the styrene-based monomer include styrene; alkyl styrene such as methyl styrene, dimethyl styrene, trimethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, and octyl styrene; fluorostyrene, chloro styrene, bromo styrene, and dibromo styrene. Such as halogenated styrene; functionalized styrene such as nitrostyrene, acetylstyrene, and methoxystyrene.

Examples of the amide group-containing monomer other than the tertiary nitrogen-containing monomer include (meth) acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and N-hexyl (meth). ) N-alkyl (meth) acrylamide such as acrylamide; N-alkoxyalkyl (meth) acrylamide such as N-methoxymethyl (meth) acrylamide can be mentioned. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

Examples of the monomer of the polymer chain (main chain) portion constituting the polymerizable macromonomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate and Examples thereof include alkyl (meth) acrylates such as tert-butyl (meth) acrylates, and the alkyl group preferably has 1 to 20 carbon atoms, and (meth) acrylonitrile; styrene, α-methylstyrene and the like. A styrene-based monomer can also be mentioned.

The macromonomer is preferably, for example, a (meth) acrylic macromonomer, a (meth) acrylonitrile-based macromonomer, and a styrene-based macromonomer, and can be produced according to various known methods. It can be produced by the method described in paragraph [0039] of the publication.

As the macromonomer, a commercially available product may be used. For example, a macromonomer in which the main chain constituent monomer is methyl methacrylate (product names: 45% AA-6 (AA-6S), AA-6; manufactured by Toa Synthetic). , Macromonomer whose main chain is a styrene / acrylonitrile copolymer (product name: AN-6S; manufactured by Toa Synthetic), and macromonomer whose main chain constituent monomer is butyl acrylate (product name: AB-6; manufactured by Toa Synthetic) These are methacryloyl groups at the ends.
Other monomers may be used alone or in combination of two or more.

The amount of other monomers in the total monomer components used to form the (meth) acrylic copolymer (A) is preferably 48% by mass or less, more preferably 39% by mass or less, still more preferably 29% by mass. Hereinafter, particularly preferably, it is 19% by mass or less, 13% by mass or less, or 8% by mass or less. Further, in the (meth) acrylic copolymer (A), the amount of structural units derived from other monomers is preferably 48% by mass or less, more preferably 39% by mass or less, still more preferably 29% by mass or less, particularly. Preferably, it is 19% by mass or less, 13% by mass or less, or 8% by mass or less. The amount of the structural unit can be grasped from, for example, the amount of the monomer component charged.

<Construction and manufacturing method of (meth) acrylic copolymer (A)>
The weight average molecular weight (Mw) of the (meth) acrylic copolymer (A) is 700,000 to 1.8 million, preferably 750,000 to 1.8 million, and more preferably 1.1 million to 1.8 million. In such an embodiment, a pressure-sensitive adhesive having excellent high-temperature durability and wet-heat durability can be obtained.

The molecular weight distribution (Mw / Mn) of the (meth) acrylic copolymer (A) is preferably 2 to 15, more preferably 2.5 to 10, and even more preferably 3 to 8. In such an embodiment, a pressure-sensitive adhesive having excellent high-temperature durability and wet-heat durability can be obtained.
Mw and Mw / Mn are measured by a gel permeation chromatography (GPC) method, and specifically, can be measured by the method described in Examples.

The glass transition temperature (Tg) of the (meth) acrylic copolymer (A) determined by the so-called Fox formula is preferably −55 to 0 ° C., more preferably −50 to −30 ° C. In such an embodiment, a pressure-sensitive adhesive having excellent adhesive strength at room temperature can be obtained. In the calculation of the Fox formula, the glass transition temperature (Tg) of the homopolymer formed from each monomer can be, for example, the value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003). ..

The total content ratio of the (meth) acrylic copolymer (A) and the cross-linking agent (B) described later in the pressure-sensitive adhesive composition is preferably 60% by mass or more based on 100% by mass of the solid content of the pressure-sensitive adhesive composition. , More preferably 65% by mass or more, still more preferably 70% by mass or more. The solid content is a component excluding the solvent.

The (meth) acrylic copolymer (A) can be produced by a known method, but it is preferably produced by solution polymerization. Specifically, a monomer component and a polymerization solvent are charged in a reaction vessel, a polymerization initiator is added in an atmosphere of an inert gas such as nitrogen gas, the reaction temperature is heated to about 50 to 90 ° C., and the reaction is carried out for 2 to 20 hours. Let me. Further, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be additionally added as appropriate during the polymerization reaction.

Examples of the polymerization initiator include organic polymerization initiators, specifically, peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as 2,2'-azobisisobutyronitrile. Can be mentioned. Among these, the azo compound is preferable.

Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 2,2'-azobis (2-cyclopropyl). Propionitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile) , 2- (Carbamoylazo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis ( N, N'-Azobisisobutyamidine), 2,2'-Azobis [2-methyl-N- (2-Hydroxyethyl) -propionamide], 2,2'-Azobis (isobutylamide) dihydrate, 4,4 '-Azobis (4-cyanopentanoic acid), 2,2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis [2- Methyl-N- (2-hydroxyethyl) propionamide].

One kind or two or more kinds of polymerization initiators can be used.
The amount of the polymerization initiator used is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the monomer component. In such an embodiment, the Mw of the (meth) acrylic copolymer (A) can be adjusted within an appropriate range.

In solution polymerization, examples of the polymerization solvent include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane; cyclopentane and cyclohexane. , Cycloheptane, cyclooctane and other alicyclic hydrocarbons; diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, diphenyl ether and other ethers; chloroform, carbon tetrachloride , 1,2-Dichloroethane, chlorobenzene and other halogenated hydrocarbons; ethyl acetate, propyl acetate, butyl acetate, methyl propionate and other esters; acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketones; N, N -Amids such as dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethylsulfoxide and sulfolanes. One kind or two or more kinds of polymerization solvents can be used.

<Crosslinking agent (B)>
The cross-linking agent (B) is not particularly limited as long as it is a component capable of causing a cross-linking reaction with the (meth) acrylic copolymer (A). For example, an isocyanate-based cross-linking agent (B1), a metal chelate-based cross-linking agent (B2), and an epoxy-based cross-linking agent (B3) can be mentioned.
The cross-linking agent (B) may be used alone or in combination of two or more.

In the pressure-sensitive adhesive composition of the present embodiment, the content of the cross-linking agent (B) is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). Is 0.05 to 3 parts by mass, more preferably 0.1 to 3 parts by mass. In such an embodiment, it is possible to obtain a pressure-sensitive adhesive in which a crosslinked structure is sufficiently and appropriately formed, the cohesive force is high, the balance of adhesive physical characteristics is excellent, and the durability is excellent.

<Isocyanate-based cross-linking agent (B1)>
The isocyanate-based cross-linking agent (B1) is, for example, an isocyanate compound having two or more isocyanate groups in one molecule. The number of isocyanate groups in one molecule of the isocyanate-based cross-linking agent (B1) is preferably 2 to 8, more preferably 2 to 5. When the number of isocyanate groups is in the above range, it is preferable in terms of cross-linking reaction efficiency and availability.

Examples of the diisocyanate compound having 2 isocyanate groups in one molecule include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl. Examples thereof include aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate. As the alicyclic diisocyanate, an alicyclic having 7 to 30 carbon atoms such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylylene diisocyanate. Group diisocyanates can be mentioned. Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylenediocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenyl propane diisocyanate.

Examples of the isocyanate compound having 3 or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples thereof include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanatebenzene, and 4,4', 4 "-triphenylmethane triisocyanate.

Examples of the isocyanate compound include a multimer (for example, a dimer or a trimer, a biuret, and an isocyanurate) and a derivative (for example, a polyhydric alcohol) of the above-mentioned isocyanate compound having 2 or 3 or more isocyanate groups. Addition reaction products with two or more molecules of diisocyanate compounds) and polymers. Examples of the polyhydric alcohol in the derivative include trihydric or higher alcohols such as trimethylolpropane, glycerin, and pentaerythritol as low molecular weight polyhydric alcohols; and examples of high molecular weight polyhydric alcohols include polyether polyols. Examples thereof include polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols.

Examples of such isocyanate compounds include trimer of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or biuret or isocyanurate of tolylene diisocyanate, trimethyl propane and tolylene diisocyanate or xylylene diisocyanate. Reaction products with (for example, three-molecule adduct of tolylene diisocyanate or xylylene diisocyanate), reaction products of trimethylolpropane and hexamethylene diisocyanate (for example, three-molecule adduct of hexamethylene diisocyanate), polyether polyisocyanate, Examples include polyester polyisocyanate.
One type or two or more types of isocyanate-based cross-linking agent (B1) can be used.

<Metal chelate cross-linking agent (B2)>
Examples of the metal chelate cross-linking agent (B2) include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium, alkoxide, acetylacetone, ethyl acetoacetate and the like. Examples include compounds coordinated with. Among these, an aluminum chelate compound is particularly preferable. Specific examples thereof include aluminum isopropylate, aluminum secondary butyrate, aluminum ethyl acetoacetate / diisopropirate, aluminum tris ethyl acetoacetate, and aluminum tris acetyl acetonate.
One kind or two or more kinds of metal chelate cross-linking agents (B2) can be used.

<Epoxy cross-linking agent (B3)>
Examples of the epoxy-based cross-linking agent (B3) include epoxy compounds having two or more epoxy groups in one molecule, and specific examples thereof include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and glycerin diglycidyl ether. Glycerin triglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N', N'-tetraglycidyl-m-xylylene diamine, N, N, N', N' -Tetraglycidylaminophenylmethane, triglycidyl isocyanurate, mn, N-diglycidylaminophenylglycidyl ether, N, N-diglycidyl toluidine, N, N-diglycidylaniline can be mentioned.
One type or two or more types of epoxy-based cross-linking agent (B3) can be used.

<Additives>
In addition to the above components, the pressure-sensitive adhesive composition of the present embodiment contains a silane coupling agent, an antistatic agent, a peeling force adjusting agent (for example, an organopolysiloxane compound), and ultraviolet absorption as long as the effects of the present embodiment are not impaired. It may contain at least one selected from agents, antioxidants, tackifier resins, plasticizers, defoamers, fillers, stabilizers, softeners, and wettability modifiers.

Examples of the silane coupling agent include a polymerizable unsaturated group-containing silane coupling agent such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacrypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-. Epoxy group-containing silane cups such as glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Ring agent; Amino group-containing silanes such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Coupling agents: Halogen-containing silane coupling agents such as 3-chloropropyltrimethoxysilane, 3- (trimethoxysilyl) propyl 3-oxobutanoate, and the like.

In the pressure-sensitive adhesive composition of the present embodiment, the content of the silane coupling agent is preferably 1 part by mass or less, more preferably 0.01 with respect to 100 parts by mass of the (meth) acrylic copolymer (A). It is ~ 1 part by mass, more preferably 0.05 to 0.8 part by mass.

Examples of the antistatic agent include a surfactant and an ionic compound.
Examples of the surfactant include a cationic surfactant having a cationic group such as a quaternary ammonium salt, an amide quaternary ammonium salt, a pyridium salt, and a primary to tertiary amino group; a sulfonic acid base and a sulfate ester. Anionic surfactants having anionic groups such as bases and phosphate ester bases; amphoteric surfactants such as alkylbetaines, alkylimidazolinium betaines, alkylamine oxides, amino acid sulfate esters; glycerin fatty acid esters , Solbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines, alkyldiethanolamides and other nonionic surfactants. Be done.

Examples of the ionic compound include lithium bis (trifluoromethanesulfonyl) imide, lithium bis (difluorosulfonyl) imide, lithium tris (trifluoromethanesulfonyl) methane, potassium bis (trifluoromethanesulfonyl) imide, and potassium bis (difluorosulfonyl) imide. , 1-Ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium bis (Fluorosulfonyl) imide, 1-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide, (N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate, N, N- Examples thereof include diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide, 1-octylpyridinium fluoroshoniumimide, 1-octyl-3-methylpyridinium, and trifluorosulfoniumimide.

In the pressure-sensitive adhesive composition of the present embodiment, the content of the antistatic agent is preferably 3 parts by mass or less, more preferably 0.01 to 100 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A). It is 3 parts by mass, more preferably 0.05 to 2.5 parts by mass.

<Organic solvent>
The pressure-sensitive adhesive composition of the present embodiment may contain an organic solvent.
Examples of the organic solvent include the polymerization solvent described in the description of the method for producing the (meth) acrylic copolymer (A). For example, a pressure-sensitive adhesive composition can be prepared by mixing a polymer solution containing the (meth) acrylic copolymer (A) and a polymerization solvent, a cross-linking agent (B), and an additive if necessary. it can. In the pressure-sensitive adhesive composition of the present embodiment, the content ratio of the organic solvent is preferably 0 to 90% by mass, more preferably 10 to 80% by mass.

[Adhesive sheet]
The pressure-sensitive adhesive sheet according to an embodiment of the present invention (hereinafter, also referred to as “the pressure-sensitive adhesive sheet of the present embodiment”) has a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition of the present embodiment. The pressure-sensitive adhesive layer can be obtained by cross-linking the pressure-sensitive adhesive composition, specifically, by cross-linking the (meth) acrylic copolymer (A) with the cross-linking agent (B).

Examples of the pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet having only the pressure-sensitive adhesive layer, a base material, and a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layers formed on both sides of the base material, the base material, and one of the base materials. Examples thereof include a single-sided pressure-sensitive adhesive sheet having the above-mentioned pressure-sensitive adhesive layer formed on a surface, and a pressure-sensitive adhesive sheet in which a peel-treated separator is attached to a surface of these pressure-sensitive adhesive sheets that is not in contact with another layer.

The conditions for forming the pressure-sensitive adhesive layer are as follows, for example.
The pressure-sensitive adhesive composition is applied onto a separator or a substrate and dried at preferably 60 to 120 ° C., more preferably 70 to 110 ° C., preferably 1 to 5 minutes, more preferably 2 to 4 minutes to form a coating film. To form. Examples of the method for applying the pressure-sensitive adhesive composition include known methods such as spin coating method, knife coating method, roll coating method, bar coating method, blade coating method, die coating method, and gravure coating method.

Subsequently, when applied on a separator, the base material or separator is attached to the coating film on the side without the separator, and when applied on the base material, the separator is attached on the coating film. Subsequently, an environment of preferably 1 day or more, more preferably 3 to 10 days, preferably 5 to 60 ° C., more preferably 15 to 40 ° C., preferably 30 to 70% RH, more preferably 40 to 70% RH. Cure (ripen) underneath. When cross-linking is performed under the above-mentioned aging conditions, a cross-linked product (network polymer) can be efficiently formed. In the case of a coating film sandwiched between separators, one of the separators may be peeled off after aging and the base material may be attached to the exposed pressure-sensitive adhesive layer.

Examples of the base material and the separator include plastic films such as polyester (eg, polyethylene terephthalate), polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; non-woven fabric; and paper separators. The surfaces of the base material and the separator may be peeled off. Further, by using a functional member such as a polarizing plate or a polarizing film as a base material, an optical member described later can be manufactured.

The thickness of the pressure-sensitive adhesive layer is preferably 3 to 1000 μm, more preferably 5 to 500 μm. The thickness of the base material and the separator is preferably 10 to 1000 μm.
The gel fraction of the pressure-sensitive adhesive layer is preferably 40 to 90% by mass from the viewpoint of improving cohesive force, adhesive force and removability. The gel fraction of the pressure-sensitive adhesive layer can be determined as follows. Approximately 0.1 g of adhesive was collected from the adhesive layer in a sampling bottle, 30 mL of ethyl acetate was added, and the mixture was shaken for 4 hours. Then, the contents of this sample bottle were filtered through a 200 mesh stainless wire mesh and remained on the wire mesh. The product is dried at 100 ° C. for 2 hours and the dry mass is measured. The gel fraction of the pressure-sensitive adhesive layer is calculated by the following formula. Gel fraction (mass%) = (dry mass / adhesive sampling mass) x 100 (%)

The adhesive sheet of the present embodiment has an adhesive layer having excellent high temperature durability, wet heat durability and whitening resistance. The pressure-sensitive adhesive sheet of the present embodiment can be widely used as an industrial pressure-sensitive adhesive sheet or for bonding various resin films. For example, in automobile applications such as automobile applications, high temperature / wet heat durability higher than that of general applications is required for reasons such as high temperature in summer. However, the adhesive layer in the adhesive sheet of the present embodiment has high temperature / wet heat durability. The adhesive sheet is suitably used for in-vehicle applications because of its excellent properties.

The adherend to which the pressure-sensitive adhesive layer is applied includes, for example, a plastic film such as polyester (eg, polyethylene terephthalate), polyethylene, polypropylene, ethylene-vinyl acetate copolymer, polymethylmethacrylate; glass plate; metal or metal. Examples thereof include members having wirings and electrodes made of oxide, and functional members described below.

[Optical member]
The pressure-sensitive adhesive composition of this embodiment is suitable for use in optical members.
The optical member according to one embodiment of the present invention (hereinafter, also referred to as “optical member of the present embodiment”) has a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition of the present embodiment. The optical member preferably includes a functional member such as a polarizing plate, a polarizing film, a retardation film, an elliptically polarizing film, an antireflection film, a brightness improving film, a light diffusing film, and a hard coat film, and the functional member. It has the pressure-sensitive adhesive layer formed. Among these, an optical member having a polarizing plate or a polarizing film and the pressure-sensitive adhesive layer is preferable. As the method for forming the pressure-sensitive adhesive layer, the above-mentioned conditions for forming the pressure-sensitive adhesive layer can be referred to.

Further, the optical member of the present embodiment is required to have higher temperature / wet heat durability than general use due to reasons such as high temperature in summer in automobile applications such as automobile applications, and the adhesive layer is required to have high temperature / wet heat durability. Since the optical member has excellent durability, the optical member can be suitably used for in-vehicle applications.

In the following description, "polarizing plate" is used to include "polarizing film". Hereinafter, an optical member having a polarizing plate and the pressure-sensitive adhesive layer formed on the polarizing plate (hereinafter, also referred to as “polarizing plate with a pressure-sensitive adhesive layer”) will be described.

As the polarizing plate, a conventionally known polarizing plate can be used, and examples thereof include a polarizing plate having a polarizing element and a protective film arranged on one side or both sides of the polarizer.
Examples of the polarizer include a stretched film obtained by adding a polarizing component to a film made of a polyvinyl alcohol-based resin and stretching the film. Examples of the polyvinyl alcohol-based resin include saponified products of polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, and ethylene / vinyl acetate copolymer. Examples of the polarizing component include iodine and dichroic dyes.

Examples of the protective film include a film made of a thermoplastic resin. Examples of the thermoplastic resin include cellulose resins such as triacetyl cellulose, polyester resins, polyether sulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cycloolefin resins, and polys. Examples thereof include allylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures of two or more selected from these resins.

Among these, as the protective film, a cellulose-based film, a polyester-based film, a polyether sulfone-based film, a polycarbonate-based film, a cycloolefin polymer-based film, and a (meth) acrylic polymer-based film are preferable, and the protector film for the polarizer is cyclo. In the case of an olefin polymer-based film, the shrinkage of the protective film due to heating is small, which is more preferable.

Even if the polarizing plate uses a cycloolefin polymer film, a (meth) acrylic polymer film, or a polyester film as the protective film, whitening can be suppressed by the pressure-sensitive adhesive layer of the present embodiment. These protective films have low moisture permeability, and once the pressure-sensitive adhesive layer absorbs moisture in a high-humidity heat environment, the moisture tends to be difficult to be released from the pressure-sensitive adhesive layer due to the low moisture permeability of the protective film. However, since the pressure-sensitive adhesive layer of the present embodiment has good water dispersibility, it is considered that whitening due to the water content can be suppressed even if water is transferred from the protective film or the side surface of the pressure-sensitive adhesive layer.

The thickness of the polarizing plate is preferably 30 to 250 μm, more preferably 50 to 200 μm. The thickness of the pressure-sensitive adhesive layer is preferably 3 to 1000 μm, more preferably 5 to 500 μm. Further, the polarizing plate may be laminated with layers having other functions such as an antiglare layer, a retardation layer, and a viewing angle improving layer.

The polarizing plate with an adhesive layer is a polarizing plate in which the pressure-sensitive adhesive layer is formed on at least one surface of the polarizing plate surface. The method of forming the pressure-sensitive adhesive layer on the surface of the polarizing plate is not particularly limited, and a method of directly applying the pressure-sensitive adhesive composition to the surface of the polarizing plate using a bar coater or the like, drying and aging, and the above-mentioned pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet. Examples thereof include a method of transferring to the surface of a polarizing plate and aging as necessary. As the method for forming the pressure-sensitive adhesive layer, the above-mentioned conditions for forming the pressure-sensitive adhesive layer can be referred to.

A liquid crystal element can be manufactured by providing the polarizing plate with an adhesive layer on the substrate surface of the liquid crystal cell. Here, the liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates.

Hereinafter, the present embodiment will be described in more detail based on the examples, but the present embodiment is not limited to these examples. In the description of the following examples and the like, "parts" means "parts by mass" unless otherwise specified.
Each measured value in the example was obtained by the following method.

<Weight average molecular weight (Mw)>
For the (meth) acrylic copolymer, the weight average molecular weight (Mw) in terms of standard polystyrene was determined by the gel permeation chromatography (GPC) method under the following conditions.
-Measuring device: HLC-8120GPC (manufactured by Tosoh)
-GPC column configuration: The following 5-column column (all manufactured by Tosoh)
(1) TSK-GEL HXL-H (guard column)
(2) TSK-GEL G7000HXL
(3) TSK-GEL GMHXL
(4) TSK-GEL GMHXL
(5) TSK-GEL G2500HXL
・ Sample concentration: ^{Dilute with tetrahydrofuran so as to be 1.0 mg / cm 3}・ Mobile phase solvent: Tetrahydrofuran ・ Flow rate: 1.0 cm ³ / min
-Column temperature: 40 ° C

<Glass transition temperature (Tg)>
The glass transition temperature (Tg) of the (meth) acrylic copolymer was determined by the Fox formula.

[Example 1]
In a reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen introduction tube, 95 parts of 2-methoxyethyl acrylate (MEA), 2 parts of N-vinylpyrrolidone (NVP), 2-hydroxyethyl acrylate (HEA) 3 A portion and 100 portions of ethyl acetate were charged, and the temperature was raised to 70 ° C. while introducing nitrogen gas. Next, 0.1 part of 2,2'-azobisisobutyronitrile was added, and a polymerization reaction was carried out at 69 to 70 ° C. for 4 hours under a nitrogen atmosphere. After completion of the reaction, the reaction solution was diluted with ethyl acetate to prepare a polymer solution having a solid content concentration of 20% by mass. The Mw of the obtained (meth) acrylic copolymer was 800,000.

0.2 parts of isocyanate-based cross-linking agent "TD-75" (manufactured by Soken Kagaku) and silane coupling agent "KBM-403" (manufactured by Shin-Etsu Chemical) with respect to 100 parts of the solid content of the (meth) acrylic copolymer. ) 0.2 parts of each component was added to the polymer solution to obtain a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition was applied onto a stripped polyethylene terephthalate (PET) film so that the thickness after drying was 25 μm, and dried at 90 ° C. for 3 minutes to form a pressure-sensitive adhesive layer. A polarizing plate (polarizer protective film (cycloolefin polymer) / polarizer / polarizer protective film (cycloolefin polymer)) is bonded to the side where the peeled PET film of the pressure-sensitive adhesive layer is not bonded, and 23 A polarizing plate with an adhesive layer was produced by aging for 7 days in a ° C./50% RH environment.

[Examples 2 to 9, Comparative Examples 1 to 3]
A (meth) acrylic copolymer was synthesized using the monomer components shown in Table 1, and the same procedure as in Example 1 was carried out except that the copolymer was used to obtain a polarizing plate with an adhesive layer. In Examples 6 to 8 and Comparative Example 3, the molecular weight was adjusted by changing the amount of the solvent.

[Evaluation]
<Durability evaluation (high temperature durability test and wet heat durability test)>
The polarizing plate with the adhesive layer was cut into a size of 150 mm × 250 mm to prepare a test piece. The PET film peeled off from the test piece was peeled off, the exposed adhesive layer was attached to a glass plate (made by AGC Fabricec, float glass: 1.1 mm), and the obtained laminate was adjusted to 50 ° C./5 atm. A test plate was prepared by holding it in an autoclave for 20 minutes. Two similar test plates were prepared and left to stand in a 100 ° C. dry environment and a 60 ° C./90% RH environment for 500 hours, and the occurrence of appearance defects (defects) such as peeling was visually observed and evaluated according to the following criteria. did.
AA: No defects were found.
BB: Slight defects were found, but there is no problem in actual use.
CC: The defective area is large and there is a problem in actual use.

<Whitening resistance test>
In the above Examples and Comparative Examples, the obtained pressure-sensitive adhesive composition was applied onto a stripped polyethylene terephthalate (PET) film so as to have a thickness of 25 μm after drying, and the thickness after drying was 25 μm, and the pressure was 90 ° C. for 3 minutes. After drying to form the pressure-sensitive adhesive layer, a 40 μm-thick COP (cycloolefin polymer) film is bonded to the side where the peeled PET film of the pressure-sensitive adhesive layer is not bonded, and the environment is 23 ° C./50% RH. Aging was carried out underneath for 7 days to produce a laminate consisting of a COP film / adhesive layer / peeled PET film. The laminate was cut into a size of 60 mm × 50 mm to prepare a test piece. The PET film peeled off from the test piece was peeled off, the exposed adhesive layer was attached to a glass plate (made by AGC Fabricec, float glass: 1.1 mm), and the obtained laminate was adjusted to 50 ° C./5 atm. A test plate was prepared by holding it in an autoclave for 20 minutes. After leaving the test plate under 85 ° C / 85% RH conditions for 100 hours and then leaving it in a 23 ° C / 50% RH environment for 5 minutes, a haze meter (HM-150 type: manufactured by Murakami Color Technology Laboratory) was used. Whitening resistance was evaluated according to the following criteria.
AA: The haze was 1% or less.
BB: The haze was more than 1% and less than 3%.
CC: Haze exceeded 3%.

As shown in Table 1, the polarizing plates with an adhesive layer obtained in Examples 1 to 9 are excellent in high temperature / wet heat durability and whitening resistance. In Comparative Example 1 in which the tertiary nitrogen-containing monomer is not used in the (meth) acrylic copolymer, the high temperature durability is not sufficient. In Comparative Example 2 in which the amount of alkoxyalkyl (meth) acrylate is small in the (meth) acrylic copolymer, the whitening resistance is not sufficient. Comparative Example 3 in which the weight average molecular weight of the (meth) acrylic copolymer is low does not have sufficient high-temperature / wet-heat durability.

Claims (6)

1. Equation (a1): in ^{_{CH 2 = CR 1 -COO- (R}} 2 -O) represented by _n -R ³ (meth) acrylate (Formula (a1), R ¹ is a hydrogen atom or a methyl radical, R ² is an alkanediyl group, R ³ is an alkyl group, and n is an integer of 1 or more) in 51 to 99% by mass, tertiary nitrogen-containing monomer in 0.4 to 5% by mass, and crosslinkable functionality. A (meth) acrylic copolymer (A) which is a copolymer of a monomer component containing 0.5 to 10% by mass of a group-containing monomer and has a weight average molecular weight of 700,000 to 1.8 million.
   A pressure-sensitive adhesive composition containing a cross-linking agent (B).
2. The pressure-sensitive adhesive composition according to claim 1, wherein n in the formula (a1) is 1.
3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the tertiary nitrogen-containing monomer is at least one selected from N-vinylpyrrolidone and acryloylmorpholine.
4. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the tertiary nitrogen-containing monomer is N-vinylpyrrolidone.
5. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 4.
6. An optical member having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 4.