WO2016203935A1 - Adhesive composition for polarizing plate, adhesive layer and adhesion sheet, and polarizing plate provided with adhesive layer - Google Patents

Abstract

[Problem] To provide an adhesive composition for a polarizing plate that is applicable to a configuration in which at least one of the polarizer protective films normally formed on both sides of a polarizer is omitted, it being possible to form an adhesive layer that has exceptional durability even in a high-humidity, high-heat environment and that is exceptional at minimizing polarizer shrinkage. [Solution] An adhesive composition for a polarizing plate, characterized by containing: (A) a (meth)acrylic copolymer obtained by copolymerizing a monomer component that contains 50 to 99% by mass of an alkyl methacrylate ester (a1) in which the alkyl groups have at least 8 carbons and the glass transition temperature (Tg) of a homopolymer is less than -10°C, and 0.5% to less than 10% by mass of a monomer (a2) containing a crosslinkable functional group; and (B) a crosslinking agent; the adhesive composition for a polarizing plate being used to form an adhesive layer in direct contact with a polarizer.

Description

Adhesive composition for polarizing plate, adhesive layer and adhesive sheet, and polarizing plate with adhesive layer

The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate, a pressure-sensitive adhesive layer and a pressure-sensitive adhesive sheet, and a polarizing plate with a pressure-sensitive adhesive layer.

The liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates (eg, a glass plate). A polarizing plate is attached to the surface of the substrate constituting the liquid crystal cell via an adhesive layer. Conventionally, in order to improve mechanical properties and optical durability, a polarizing plate generally has a structure in which a polarizer protective film such as a triacetyl cellulose film is laminated on both sides of a polarizer having a polarizing function. Has been.

In recent years, thinning of liquid crystal cells and thinning of polarizing plates have been demanded, and in order to meet the demand for thinning of polarizing plates, attempts have been made to omit the polarizer protective films formed on both sides of the polarizer. . However, a polarizing plate that does not have a polarizer protective film is easily affected by moisture, and in a high-humidity environment, problems such as cracking of the polarizer, significant shrinkage, and deterioration of optical performance may occur. Cheap.

Patent Document 1 is obtained by polymerizing a monomer component containing 19 to 99.5% by mass of an alkyl (meth) acrylate having a branched alkyl group having 10 to 24 carbon atoms at the terminal of the ester group (meth). A pressure-sensitive adhesive containing an acrylic polymer is described. However, no particular mention is made of problems such as cracks and shrinkage when the polarizer protective film is omitted and the pressure-sensitive adhesive layer is directly laminated on the polarizer.

Patent Document 2 is an adhesive polarizing plate having a polarizing plate and an adhesive layer provided on the polarizing plate, the polarizing plate having a transparent protective film only on one side of the polarizer, The structure provided in the polarizer of the side which does not have the said transparent protective film is described for the adhesive layer. However, no particular mention is made of problems such as cracks, shrinkage and optical performance associated with the omission of the transparent protective film.

JP 2012-246477 A JP 2012-247574 A

An object of the present invention is applicable to a configuration in which at least one of the polarizer protective films usually formed on both surfaces of the polarizer is omitted, and is excellent in durability even in a high-humidity environment and suppresses the contraction of the polarizer. It is in providing the adhesive composition for polarizing plates which can form the adhesive layer excellent in this.

The present inventors diligently studied to solve the above problems. As a result, it has been found that the above-mentioned problems can be solved by using a polarizing plate pressure-sensitive adhesive composition having the following specific configuration, and the present invention has been completed.
The present invention includes, for example, the following [1] to [5].

[1] (A) 50% by mass or more and 99.5% by mass or less of a methacrylic acid alkyl ester (a1) having a glass transition temperature (Tg) of the homopolymer of less than −10 ° C. and an alkyl group having 8 or more carbon atoms, A (meth) acrylic copolymer obtained by copolymerizing a monomer component containing the crosslinkable functional group-containing monomer (a2) in an amount of 0.5% by mass or more and less than 10% by mass; and (B) a crosslinking agent. And a pressure-sensitive adhesive composition for a polarizing plate, which is used for forming a pressure-sensitive adhesive layer in direct contact with a polarizer.
[2] A pressure-sensitive adhesive layer for a polarizing plate formed from the pressure-sensitive adhesive composition according to [1].
[3] The pressure-sensitive adhesive layer for a polarizing plate according to [2], wherein the water vapor transmission rate is 800 g / m ² · day or less.
[4] A pressure-sensitive adhesive sheet for polarizing plate having the pressure-sensitive adhesive layer according to [2] or [3].
[5] A polarizing plate with an adhesive layer having the adhesive layer according to [2] or [3], which is directly laminated on at least one surface of a polarizer.

According to the present invention, it is applicable to a configuration in which at least one of the polarizer protective films normally formed on both sides of the polarizer is omitted, and is excellent in durability even in a high-humidity environment and suppresses the contraction of the polarizer. It is possible to provide a pressure-sensitive adhesive composition for polarizing plates excellent in the above. Moreover, the adhesive layer for polarizing plates formed from the said composition, the adhesive sheet for polarizing plates which has the said adhesive layer, and the polarizing plate with an adhesive layer which has the said adhesive layer can be provided.

Hereinafter, the pressure-sensitive adhesive composition for polarizing plate, the pressure-sensitive adhesive layer for polarizing plate, the pressure-sensitive adhesive sheet for polarizing plate and the polarizing plate with the pressure-sensitive adhesive layer will be described. Hereinafter, the pressure-sensitive adhesive composition for polarizing plate, the pressure-sensitive adhesive layer for polarizing plate and the pressure-sensitive adhesive sheet for polarizing plate of the present invention are also referred to as “pressure-sensitive adhesive composition”, “pressure-sensitive adhesive layer” and “pressure-sensitive adhesive sheet”, respectively.

[Adhesive composition for polarizing plate]
The pressure-sensitive adhesive composition for polarizing plates of the present invention contains a (meth) acrylic copolymer (A) and a crosslinking agent (B) described below. The composition may contain at least one selected from a silane coupling agent (C) and an antistatic agent (D) as necessary, and may contain an organic solvent (E).

[(Meth) acrylic copolymer (A)]
The (meth) acrylic copolymer (A) contains 50% by mass or more of a methacrylic acid alkyl ester (a1) having a glass transition temperature (Tg) of a homopolymer of less than −10 ° C. and an alkyl group having 8 or more carbon atoms. 99.5% by mass or less, a copolymer of monomer components containing the crosslinkable functional group-containing monomer (a2) in an amount of 0.5% by mass or more and less than 10% by mass, that is, obtained by copolymerizing the monomer components. Copolymer.

In this specification, acrylic and methacryl are collectively referred to as “(meth) acryl”. Moreover, the structural unit derived from a certain monomer A contained in the polymer is also referred to as “monomer A unit”. The (a1) and (a2) are also referred to as “monomer (a1)” and “monomer (a2)”, respectively.

As the glass transition temperature (Tg) of the homopolymer of (meth) acrylic acid alkyl ester, a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003) is adopted.
In addition, about the monomer in which Tg is not described in the said literature, Tg of the homopolymer synthesize | combined on the following conditions is measured on the following conditions, for example. A reactor equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube is charged with 100 parts by mass of monomer and 100 parts by mass of ethyl acetate, and heated to 80 ° C. while introducing nitrogen gas. Next, 0.1 part by mass of 2,2′-azobisisobutyronitrile is added, and a polymerization reaction is performed at 80 ° C. for 6 hours in a nitrogen gas atmosphere. The homopolymer of the obtained monomer is enclosed in a simple sealed pan. Using a differential scanning calorimeter (DSC), measure the heat change by raising the temperature at 10 ° C / min in a nitrogen stream, and draw a graph of “endothermic heat generation” and “temperature”. The characteristic inflection is the glass transition. Tg uses a value obtained from the DSC curve by the midpoint method.

<< Methacrylic acid alkyl ester (a1) >>
The monomer (a1) is a methacrylic acid alkyl ester having a homopolymer Tg of less than −10 ° C. and an alkyl group having 8 or more carbon atoms. The above-mentioned monomer in which the Tg of the homopolymer is -80 ° C. or higher and lower than −10 ° C. and the alkyl group has 8 or more carbon atoms is preferred, the Tg is −70 to −30 ° C. and the alkyl group has 8 or more carbon atoms. The monomer having a Tg of −70 to −30 ° C. and an alkyl having 10 or more carbon atoms is more preferable. The upper limit of the carbon number of the alkyl group is 18, for example.

Hydrophobic that can prevent the entry of moisture into the polarizer by using the copolymer (A) obtained by copolymerizing the monomer (a1), and thus the copolymer (A) having the monomer (a1) unit. And a pressure-sensitive adhesive having an appropriate water vapor permeability can be obtained.

Examples of the monomer (a1) include octyl methacrylate (−20 ° C.), isooctyl methacrylate (−45 ° C.), isodecyl methacrylate (−41 ° C.), lauryl methacrylate (−65 ° C.), tetradecyl methacrylate (−72 ° C.). ) And isostearyl methacrylate (-18 ° C.). The numerical value in parenthesis shows Tg of the homopolymer of each monomer.

When a (meth) acrylic copolymer containing a structural unit derived from a methacrylic acid alkyl ester having a low homopolymer Tg is used, appropriate stress relaxation characteristics can be imparted to the pressure-sensitive adhesive layer. In addition, when a long chain alkyl group of methacrylic acid alkyl ester is used, hydrophobicity can be imparted in addition to stress relaxation characteristics. For example, by using the monomer (a1) having a long-chain alkyl group, there is a tendency to obtain a hydrophobic pressure-sensitive adhesive layer capable of preventing moisture from entering the polarizer.
A monomer (a1) may be used individually by 1 type, and may use 2 or more types.

In 100% by mass of the monomer component which is a raw material monomer of the copolymer (A), the amount of the monomer (a1) used is 50% by mass or more and 99.5% by mass or less, preferably 70 to 99% by mass, more preferably 80 to 98.5% by mass. When the usage-amount of a monomer (a1) exists in the said range, it is preferable at the point which the adhesive layer obtained can express sufficient hydrophobic function.

<< Crosslinkable functional group-containing monomer (a2) >>
The monomer component which is a raw material monomer of the copolymer (A) includes a monomer having a crosslinkable functional group capable of reacting with the crosslinker (B), that is, a crosslinkable functional group-containing monomer (a2). The polymer (A) has a monomer (a2) unit.
Examples of the monomer (a2) include a hydroxyl group-containing monomer and a carboxyl group-containing monomer.

Examples of the hydroxyl group-containing monomer include a hydroxyl group-containing (meth) acrylate, and specific examples include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. And hydroxyalkyl (meth) acrylates such as 6-hydroxyhexyl (meth) acrylate and 8-hydroxyoctyl (meth) acrylate. The number of carbon atoms of the hydroxyalkyl group in the hydroxyalkyl (meth) acrylate is usually 2 to 8, preferably 2 to 6.

Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth) acrylate, 5-carboxypentyl (meth) acrylate, mono (meth) acryloyloxyethyl ester succinate, and ω-carboxypolycaprolactone mono (meth) acrylate. Carboxyl group-containing (meth) acrylates such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid.

The monomer (a2) preferably has a methacrylic structure in order to improve the hydrophobicity of the pressure-sensitive adhesive layer, and the monomer (a2) may be used alone or in combination of two or more. Good.

In 100% by mass of the monomer component which is a raw material monomer of the copolymer (A), the amount of the monomer (a2) used is 0.5% by mass or more and less than 10% by mass, preferably 1 to 8% by mass, more preferably 2 to 6% by mass. When the amount of the monomer (a2) used is less than or less than the above upper limit, the crosslinking density formed by the copolymer (A) and the crosslinking agent (B) does not become too high, and the pressure-sensitive adhesive has excellent stress relaxation characteristics. A layer is obtained. When the usage-amount of a monomer (a2) is more than the said lower limit, a crosslinked structure is formed effectively and the adhesive layer which has appropriate intensity | strength at normal temperature is obtained.

Furthermore, the type and amount of the monomer (a2) are preferably set so that the acid value (mgKOH / g) of the copolymer (A) is 15 or less, more preferably 13 or less, still more preferably 12 or less. is there. When the acid value is less than or equal to the above upper limit, the polarity of the copolymer (A) is lowered, so that the hydrophobicity is further increased and a pressure-sensitive adhesive layer having a high effect of suppressing moisture intrusion into the polarizer is obtained.

In addition, the acid value of a copolymer (A) is computed by the following formula | equation based on the molecular weight of the carboxyl group-containing monomer used for copolymerization, and the compounding quantity (mass%) of a carboxyl group-containing monomer. 56.1 is the molecular weight of KOH.
Acid value of polymer (mgKOH / g) = 56.1 / X × (Y / 100) × 1000
= 561 / X × Y
X: Molecular weight of carboxyl group-containing monomer Y: Compounding amount of carboxyl group-containing monomer

《Other monomers》
As a monomer component which is a raw material monomer of the copolymer (A), as long as the physical properties of the copolymer (A) are not impaired, for example, (meth) acrylic acid alkyl esters other than the monomer (a1), alkoxyalkyl ( (Meth) acrylate, alkoxy polyalkylene glycol mono (meth) acrylate, alicyclic group or aromatic ring-containing (meth) acrylate, acid group-containing monomer other than carboxyl group-containing monomer, amino group-containing monomer, amide group-containing monomer, nitrogen-based Other monomers such as a heterocyclic ring-containing monomer and a cyano group-containing monomer can also be used.

The (meth) acrylic acid alkyl ester other than the monomer (a1) is represented, for example, by the formula: CH ₂ ═CR ¹ —COOR ² . In the formula, R ¹ is hydrogen or a methyl group, and R ² is an alkyl group having 1 to 18 carbon atoms. For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, Pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl acrylate, isooctyl acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl acrylate, undeca Examples include (meth) acrylate, lauryl acrylate, stearyl (meth) acrylate, and isostearyl acrylate.

Examples of the alkoxyalkyl (meth) acrylate include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl ( And (meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate.

Examples of the alkoxypolyalkylene glycol mono (meth) acrylate include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, ethoxytriethylene glycol mono (meth) acrylate, ethoxydiethylene glycol mono (meth) acrylate, And methoxytriethylene glycol mono (meth) acrylate.

Examples of the alicyclic group or aromatic ring-containing (meth) acrylate include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth) acrylate.

Examples of the acid group-containing monomer include maleic anhydride, itaconic anhydride, a (meth) acrylic monomer having a phosphate group in the side chain, and a (meth) acrylic monomer having a sulfate group in the side chain. Examples of the amino group-containing monomer include amino group-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate. Examples of the amide group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, and N-hexyl (meth) acrylamide. Examples of the nitrogen heterocycle-containing monomer include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

As other monomers, copolymerizable monomers such as styrene monomers and vinyl acetate can be used as long as the physical properties of the copolymer (A) are not impaired.

Examples of the styrenic monomer include styrene; methyl styrene, dimethyl styrene, trimethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene, octyl styrene, and other alkyl styrenes; fluorostyrene, chlorostyrene, bromostyrene, Halogenated styrene such as dibromostyrene and iodinated styrene; nitrostyrene, acetylstyrene, and methoxystyrene.
Other monomers may be used alone or in combination of two or more.

In 100% by mass of the monomer component which is a raw material monomer of the copolymer (A), the total amount of the above other monomers (for example, (meth) acrylic acid alkyl ester other than the monomer (a1), copolymerizable monomer) Is preferably 0 to 45% by mass, more preferably 0 to 25% by mass.

<< Production conditions for (meth) acrylic copolymer (A) >>
Although the manufacturing conditions of a (meth) acrylic-type copolymer (A) are not specifically limited, For example, it can manufacture by a solution polymerization method. Specifically, a polymerization solvent and a monomer component are charged into a reaction vessel, a polymerization initiator is added in an inert gas atmosphere such as nitrogen gas, and the reaction start temperature is usually 40 to 100 ° C., preferably 50 to 80 ° C. The reaction system is maintained at a temperature of usually 50 to 90 ° C., preferably 70 to 90 ° C., and allowed to react for 4 to 20 hours.

The copolymer (A) is obtained, for example, by copolymerizing the monomer components including the monomers (a1) and (a2) described above, but may be a random copolymer or a block copolymer. Among these, a random copolymer is preferable.

Examples of the polymerization solvent used for the solution polymerization include aromatic hydrocarbons such as benzene, toluene and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane and n-octane; cyclopentane, Cycloaliphatic hydrocarbons such as cyclohexane, cycloheptane, cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, diphenyl ether; chloroform, Halogenated hydrocarbons such as carbon tetrachloride, 1,2-dichloroethane, chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, methyl propionate; acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl Ketones such as T and cyclohexanone; amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethyl sulfoxide and sulfolane Etc. These polymerization solvents may be used alone or in combination of two or more.

Examples of the polymerization initiator used for solution polymerization include azo initiators and peroxide initiators. Specific examples include azo compounds such as 2,2'-azobisisobutyronitrile and peroxides such as benzoyl peroxide and lauroyl peroxide. Among these, an azo compound is preferable. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 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′-dimethyleneisobutylamidine), 2,2′-azobis (isobutylamide) dihydrate, 4,4′-azobis (4-cyanope) Tanic acid), 2,2′-azobis (2-cyanopropanol), dimethyl-2,2′-azobis (2-methylpropionate), 2,2′-azobis [2-methyl-N- (2- Hydroxyethyl) propionamide]. These polymerization initiators may be used alone or in combination of two or more.

The polymerization initiator is usually in the range of 0.01 to 5 parts by mass, preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the monomer component that is a raw material monomer of the (meth) acrylic copolymer (A). Used in quantity. Moreover, you may add suitably a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent during the said polymerization reaction.

<< Physical properties and content of (meth) acrylic copolymer (A) >>
The weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) method of the (meth) acrylic copolymer (A) is usually from 400,000 to 3 million in terms of polystyrene, preferably 60 It is 10,000 to 2.5 million, more preferably 800,000 to 2,000,000, still more preferably 800,000 to 1.3 million. By using the copolymer (A) having Mw in the above range and having the above monomer unit, it becomes possible to develop hydrophobicity capable of preventing moisture from entering the polarizer. Furthermore, it is easy to balance the adhesive force, and it is possible to obtain an adhesive composition having a viscosity suitable for coating.

The molecular weight distribution (Mw / Mn) of the (meth) acrylic copolymer (A) measured by the GPC method is usually 15 or less, preferably 2 to 15, more preferably 4 to 13.

The glass transition temperature (Tg) of the (meth) acrylic copolymer (A) can be calculated by, for example, the Fox formula from the monomer units constituting the copolymer and the content ratio thereof. The (meth) acrylic copolymer is used so that the glass transition temperature (Tg) determined by the Fox equation is usually −80 to −10 ° C., preferably −80 to −20 ° C., more preferably −70 to −30 ° C. A polymer (A) can be synthesized. By using the (meth) acrylic copolymer (A) having such a glass transition temperature (Tg), a pressure-sensitive adhesive composition excellent in stress relaxation characteristics and durability and having excellent adhesiveness at room temperature is obtained. be able to.
Fox formula: 1 / Tg = (W ₁ / Tg ₁ ) + (W ₂ / Tg ₂ ) +... + (W _m / Tg _m )
W ₁ + W ₂ + ... + W _m = 1

In the formula, Tg is a glass transition temperature of the (meth) acrylic copolymer (A), Tg ₁ , Tg ₂ ,..., Tg _m are glass transition temperatures of homopolymers composed of the respective monomers, W ₁ , W ₂ ,..., W _m are weight fractions of the structural units derived from the respective monomers in the copolymer (A). As the weight fraction of the structural unit derived from each monomer, the charging ratio of each monomer to the total monomers at the time of copolymer synthesis can be used.

As the glass transition temperature of the homopolymer composed of each monomer in the Fox formula, for example, a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003) can be used. In addition, about the monomer in which Tg is not described in the said literature, Tg of the homopolymer synthesize | combined on the conditions mentioned above is measured on the conditions mentioned above, for example.

In the pressure-sensitive adhesive composition of the present invention, the content of the (meth) acrylic copolymer (A) is usually 60 to 99.99% by mass, preferably 100 to 99.99% by mass, preferably 100% by mass of the solid content excluding the organic solvent in the composition. Is 70 to 99.95% by mass, particularly preferably 80 to 99.90% by mass. When the content of the (meth) acrylic copolymer (A) is in the above range, the performance as an adhesive is balanced and the adhesive properties are excellent.

[Crosslinking agent (B)]
The pressure-sensitive adhesive composition of the present invention further contains a crosslinking agent (B).
The crosslinking agent (B) is particularly limited as long as it is a component capable of causing a crosslinking reaction with the crosslinking functional group derived from the crosslinking functional group-containing monomer (a2) of the (meth) acrylic copolymer (A). Although not carried out, for example, an isocyanate compound (B1), a metal chelate compound (B2), and an epoxy compound (B3) can be mentioned.
A crosslinking agent (B) may be used individually by 1 type, and may use 2 or more types.

In the pressure-sensitive adhesive composition of the present invention, the content of the cross-linking agent (B) is usually 0.01 to 5 parts by mass, preferably 0.00 with respect to 100 parts by mass of the (meth) acrylic copolymer (A). 05 to 2.5 parts by mass, more preferably 0.1 to 1 part by mass. When the content is within the above range, it is preferable in terms of easy balance between durability and stress relaxation characteristics.

<< Isocyanate compound (B1) >>
As the isocyanate compound (B1), an isocyanate compound having 2 or more isocyanate groups in one molecule is usually used. A crosslinked body (network polymer) can be formed by crosslinking the (meth) acrylic copolymer (A) with the isocyanate compound (B1).

The number of isocyanate groups in the isocyanate compound (B1) is usually 2 or more, preferably 2 to 8, and more preferably 3 to 6. When the number of isocyanate groups is within the above range, it is preferable from the viewpoint of the crosslinking reaction efficiency between the (meth) acrylic copolymer (A) and the isocyanate compound (B1) and the flexibility of the pressure-sensitive adhesive layer.

Examples of the diisocyanate compound having 2 isocyanate groups in one molecule include aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl And aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate. Examples of alicyclic diisocyanates include alicyclic rings 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. Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

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

Examples of the isocyanate compound (B1) include multimers (for example, dimers or trimers, biurets, isocyanurates), derivatives (for example, many) of the above isocyanate compounds having 2 or 3 or more isocyanate groups. Addition reaction product of a dihydric alcohol and two or more molecules of a diisocyanate compound), and a polymer. Examples of the polyhydric alcohol in the derivative include trivalent or higher alcohols such as trimethylolpropane, glycerin and pentaerythritol as low molecular weight polyhydric alcohols; high molecular weight polyhydric alcohols such as polyether polyols, Examples include polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

Examples of such isocyanate compounds include diphenylmethane diisocyanate trimer, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or tolylene diisocyanate biuret or isocyanurate, trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate. Reaction product (for example, a trimolecular adduct of tolylene diisocyanate or xylylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a trimolecular adduct of hexamethylene diisocyanate), a polyether polyisocyanate, Polyester polyisocyanate is mentioned.

Among the isocyanate compounds (B1), reaction products of trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate (L-45 manufactured by Soken Chemical Co., Ltd., Soken Chemical Co., Ltd.) can improve the aging property. TD-75), isocyanurate of hexamethylene diisocyanate or tolylene diisocyanate (TSE-100 manufactured by Asahi Kasei Corporation, 2050 manufactured by Nippon Polyurethane Industry Co., Ltd.).
An isocyanate compound (B1) may be used individually by 1 type, and may use 2 or more types.

<< Metal chelate compound (B2) >>
Examples of the metal chelate compound (B2) include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium, alkoxide, acetylacetone, and ethyl acetoacetate. Examples include a coordinated compound.

Among these, an aluminum chelate compound (M-12AT manufactured by Soken Chemical Co., Ltd.) is particularly preferable. Specific examples include aluminum isopropylate, aluminum secondary butyrate, aluminum ethyl acetoacetate / diisopropylate, aluminum trisethyl acetoacetate, and aluminum trisacetylacetonate.
A metal chelate compound (B2) may be used individually by 1 type, and may use 2 or more types.

The metal chelate compound (B2) crosslinks the (meth) acrylic copolymer (A) by coordination bond (pseudocrosslinking). When the metal chelate compound (B2) is used as the cross-linking agent (B), the cross-linking is maintained at room temperature, and the polymer exhibits cohesiveness. Shows greater flexibility.

<< Epoxy compound (B3) >>
As the epoxy compound (B3), an epoxy compound having 2 or more epoxy groups in one molecule is usually used. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N ′ -Tetraglycidyl-m-xylylenediamine, N, N, N ', N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, mN, N-diglycidylaminophenyl glycidyl ether, N, N-diglycidyl Examples include toluidine and N, N-diglycidylaniline.

[Silane coupling agent (C)]
The pressure-sensitive adhesive composition of the present invention preferably further contains a silane coupling agent (C). A silane coupling agent (C) contributes to the point which adheres an adhesive layer firmly to adherends, such as a glass plate, and prevents peeling in a high-humidity heat environment.

Examples of the silane coupling agent (C) include polymerizable unsaturated group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane Epoxy groups such as 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Containing silane coupling agent; amino such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Group-containing silane coupling Grayed agent; 3-chloropropyl trimethoxysilane halogen-containing silane coupling agents such as 3-oxobutanoate 3- (trimethoxysilyl) propyl, and oligomeric silane coupling agent, and the like. Above all, a functional group that reacts with a functional group contained in the (meth) acrylic copolymer (A) to form a covalent bond, or a bond by interacting with the (meth) acrylic copolymer (A). A silane coupling agent having a functional group capable of forming a salt is preferable in that it is less likely to cause peeling in a wet and heat environment.

In the pressure-sensitive adhesive composition of the present invention, the content of the silane coupling agent (C) is usually 1 part by mass or less, preferably 0.01 with respect to 100 parts by mass of the (meth) acrylic copolymer (A). To 1 part by mass, more preferably 0.05 to 0.5 part by mass. When the content is in the above range, peeling of the polarizing plate in a high humidity environment and bleeding of the silane coupling agent (C) in a high temperature environment tend to be prevented.

[Antistatic agent (D)]
The antistatic agent (D) can be used, for example, to reduce the surface resistance value of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention. Examples of the antistatic agent (D) include a surfactant, an ionic compound, and a conductive polymer.

Examples of the surfactant include cationic surfactants having cationic groups such as quaternary ammonium salts, amide quaternary ammonium salts, pyridium salts, primary to tertiary amino groups; sulfonate groups, sulfate esters Anionic surfactants having an anionic group such as a base or a phosphate ester base; amphoteric surfactants such as alkylbetaines, alkylimidazolinium betaines, alkylamine oxides, amino acid sulfates, glycerin fatty acid esters Nonionic surfactants such as sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines and alkyldiethanolamides It is done.

Moreover, the reactive type emulsifier which has a polymeric group is also mentioned as surfactant, The polymeric surfactant which made high molecular weight the monomer component containing said surfactant or reactive emulsifier can also be used.
The ionic compound is composed of a cation part and an anion part, and may be either solid or liquid at room temperature (23 ° C./50% RH).

The cation portion constituting the ionic compound may be either an inorganic cation or an organic cation, or both. As the inorganic cation, alkali metal ions and alkaline earth metal ions are preferable, and Li ⁺ , Na ⁺ and K ⁺ having excellent antistatic properties are more preferable. Examples of organic cations include pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, pyrazolium cation, pyrazoli Examples thereof include a nium cation, a tetraalkylammonium cation, a trialkylsulfonium cation, a tetraalkylphosphonium cation, and derivatives thereof.

The anion moiety constituting the ionic compound is not particularly limited as long as it can form an ionic compound by ionic bonding with the cation moiety. Specifically, F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , SCN ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , CF ₃ COO ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (F ₂ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , TaF ₆ ⁻ , F (HF) _n ⁻ , (CN) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , C ₃ F ₇ COO ^-, and _{(CF 3 SO 2) (CF} 3 CO) N - are exemplified. Among these, an anion containing a fluorine atom is preferable because it gives an ionic compound having a low melting point, (F ₂ SO ₂ ) ₂ N ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ are particularly preferable, and deterioration of the polarizer (CF ₃ SO ₂ ) ₂ N ⁻ is particularly preferable in that it is difficult to cause oxidization.

Examples of the ionic compound include lithium bis (trifluoromethanesulfonyl) imide, lithium bis (difluorosulfonyl) imide, lithium tris (trifluoromethanesulfonyl) methane, potassium bis (trifluoromethanesulfonyl) imide, 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 (fluoro Sulfonyl) imide, 1-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide, tributylmethyla Monium bis (fluorosulfonyl) imide, tributylmethylammonium bis (trifluoromethanesulfonyl) imide, (N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate, N, N-diethyl-N- Methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide, 1-octylpyridinium fluorosulfonium imide, and 1-octyl-3-methylpyridinium trifluorosulfonium imide are preferred.
Examples of the conductive polymer include polythiophene, polyaniline, polypyrrole, and derivatives thereof.

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

[Organic solvent (E)]
The pressure-sensitive adhesive composition of the present invention preferably contains an organic solvent (E) in order to adjust its applicability. As an organic solvent, the polymerization solvent demonstrated in the column of the (meth) acrylic-type copolymer (A) is mentioned. For example, the pressure-sensitive adhesive composition can be prepared by mixing the polymer solution containing the (meth) acrylic copolymer (A) and the polymerization solvent obtained by the above copolymerization and the crosslinking agent (B). it can. In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent (E) is usually 50 to 90% by mass, preferably 60 to 85% by mass.

In the present specification, “solid content” refers to all components excluding the organic solvent (E) among the components contained in the pressure-sensitive adhesive composition, and “solid content concentration” refers to the pressure-sensitive adhesive composition 100. The ratio of the said solid content with respect to the mass% is said.

[Additive]
In addition to the above components, the pressure-sensitive adhesive composition of the present invention includes an antioxidant, a light stabilizer, a metal corrosion inhibitor, a tackifier, a plasticizer, a crosslinking accelerator, You may contain the 1 type (s) or 2 or more types selected from the (meth) acrylic-type polymer and rework agents other than A).

[Preparation of pressure-sensitive adhesive composition for polarizing plate]
The pressure-sensitive adhesive composition of the present invention is prepared by mixing the (meth) acrylic copolymer (A), the cross-linking agent (B), and other components as required by a conventionally known method. Can do. For example, the cross-linking agent (B) and, if necessary, other components may be added to the polymer solution containing the polymer obtained when the (meth) acrylic copolymer (A) is synthesized. It is done.

The pressure-sensitive adhesive composition of the present invention is suitable for use in bonding a substrate constituting a liquid crystal cell and a polarizer. In particular, even when the thickness of the glass plate constituting the thinned liquid crystal cell is as small as about 0.05 to 1.0 mm, it is suitable for use in bonding the substrate and the polarizer.

The gel fraction of the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition of the present invention is preferably 40% by mass or more, more preferably 40 to 95% by mass, and further preferably 45 to 90% by mass. The said gel fraction is a value measured about the adhesive extract | collected, for example by the conditions of an Example description.

[Adhesive layer for polarizing plate]
The pressure-sensitive adhesive layer for polarizing plates of the present invention is formed from the above-mentioned pressure-sensitive adhesive composition. By using the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive layer having the following water vapor transmission rate can be formed.

The pressure-sensitive adhesive layer of the present invention has a water vapor permeability of preferably 800 g / m ² · day or less, more preferably 600 g / m ² · day or less, and still more preferably 400 g / m ² · day or less.
The method for measuring the water vapor transmission rate will be described in detail in the Examples section below.

When the water vapor transmission rate is in the above range, the pressure-sensitive adhesive layer of the present invention can prevent the polarizer from contracting and the occurrence of cracks and the like even in a high humidity environment. Furthermore, since the deterioration of the iodine complex contained in the polarizer is also suppressed, the change in optical characteristics before and after the durability test is reduced.

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a gel fraction of preferably 40% by mass or more, more preferably from the viewpoints of distortion suppression, cohesive strength, adhesive strength, and removability of the polarizing plate. It is 40 to 95% by mass, more preferably 45 to 90% by mass. When the gel fraction is in the above range, the pressure-sensitive adhesive layer exhibits excellent durability.

The pressure-sensitive adhesive layer of the present invention specifically cross-links the (meth) acrylic copolymer (A) with the cross-linking agent (B) by, for example, advancing the crosslinking reaction in the above-mentioned pressure-sensitive adhesive composition. Is obtained.

The conditions for forming the pressure-sensitive adhesive layer are, for example, as follows. The pressure-sensitive adhesive composition of the present invention is applied on a support and varies depending on the type of solvent, but is usually 50 to 150 ° C., preferably 60 to 100 ° C., usually 1 to 10 minutes, preferably 2 to 7 minutes. Then, the solvent is removed and a coating film is formed. The film thickness of the dried coating film is usually 5 to 75 μm, preferably 10 to 50 μm.

The pressure-sensitive adhesive layer is preferably formed under the following conditions. After applying the pressure-sensitive adhesive composition of the present invention on a support and applying a cover film on the coating film formed under the above conditions, usually 3 days or more, preferably 7 to 10 days, usually 5 to 60 ° C., It is preferably cured in an environment of 15 to 40 ° C., usually 30 to 70% RH, preferably 40 to 70% RH. When crosslinking is performed under the aging conditions as described above, a crosslinked body (network polymer) can be efficiently formed.

As a method for applying the pressure-sensitive adhesive composition, a predetermined thickness is obtained by a known method such as spin coating, knife coating, roll coating, bar coating, blade coating, die coating, or gravure coating. Thus, a method of applying and drying can be used.

Examples of the support and cover film include polyester films such as polyethylene terephthalate (PET); plastic films such as polyolefin films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer.

[Plastic adhesive sheet]
The pressure-sensitive adhesive sheet for polarizing plates of the present invention has a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition. 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 layer formed on both surfaces 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 the surface, and a pressure-sensitive adhesive sheet having a peel-treated cover film attached to the surface of the pressure-sensitive adhesive sheet that is not in contact with the base material.

Examples of the base material and the cover film include polyester films such as polyethylene terephthalate (PET); plastic films such as polyolefin films such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer.
The conditions for forming the pressure-sensitive adhesive layer are the same as the conditions described in the column [Plastic pressure-sensitive adhesive layer].

The thickness of the pressure-sensitive adhesive layer is usually 5 to 75 μm, preferably 10 to 50 μm, from the viewpoint of maintaining the adhesive performance. The film thickness of the substrate and the cover film is not particularly limited, but is usually 10 to 125 μm, preferably 25 to 75 μm.

[Polarizing plate with adhesive layer]
The polarizing plate with the pressure-sensitive adhesive layer of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention, which is directly laminated on at least one surface of a polarizer. In this specification, “polarizing plate” is used to include “polarizing film”.

As the polarizing plate, a conventionally known polarizing film can be used. For example, the multilayer film which has polarizer itself, a polarizer, and the polarizer protective film arrange | positioned on a polarizer is mentioned. In the present invention, since the pressure-sensitive adhesive layer is disposed in direct contact with the polarizer, the polarizer protective film is disposed only on one side of the polarizer, and the polarizer protective film is disposed on both sides of the polarizer. There is no configuration.

Examples of the polarizer include a stretched film obtained by stretching a film made of a polyvinyl alcohol-based resin containing a polarizing component. 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 or a dichroic dye.

Examples of the polarizer protective film include a film made of a thermoplastic resin. Examples of the thermoplastic resin include cellulose resin such as triacetyl cellulose, polyester resin, polyethersulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, (meth) acrylic resin, cyclic polyolefin resin (norbornene) Resin), polyarylate resin, polystyrene resin, polyvinyl alcohol resin, and a mixture of two or more selected from these resins.

The thickness of the polarizing plate is usually 10 to 200 μm, preferably 30 to 100 μm. In this invention, since the polarizer protective film formed on a polarizer can be abbreviate | omitted, a polarizing plate can be reduced in thickness.

In the present invention, the pressure-sensitive adhesive layer is formed in direct contact with the polarizer. As a polarizing plate with an adhesive layer of the present invention, for example, a polarizer protective film, a polarizer, and the adhesive layer are laminated in this order, the adhesive layer, the polarizer protective film, the polarizer, and the above The structure by which the adhesive layer was laminated | stacked in this order, the structure by which the said adhesive layer, the polarizer, and the said adhesive layer were laminated | stacked in this order are mentioned. In these structures, the cover film mentioned above may be arrange | positioned as an outermost layer on the adhesive layer.

The method for forming the pressure-sensitive adhesive layer on the surface of the polarizer is not particularly limited. The method for applying the pressure-sensitive adhesive composition directly to the surface of the polarizer using a bar coater, drying and aging, the pressure-sensitive adhesive sheet for polarizing plate of the present invention There is a method in which the pressure-sensitive adhesive layer possessed by is transferred to the polarizer surface and aged. The conditions for drying and aging, the range of the gel fraction, and the like are the same as the conditions described in the section of [PSA layer for polarizing plate].

The thickness of the pressure-sensitive adhesive layer is usually 5 to 75 μm, preferably 10 to 50 μm in terms of dry film thickness. The pressure-sensitive adhesive layer only needs to be formed in contact with the polarizer on at least one surface of the polarizer, and the pressure-sensitive adhesive layer is formed only on one side of the polarizer, and the pressure-sensitive adhesive is formed on both sides of the polarizer. The aspect in which a layer is formed is mentioned.
Moreover, the layer which has other functions, such as a protective layer, a glare-proof layer, a phase difference layer, a viewing angle improvement layer, for example may be laminated | stacked on the said polarizing plate.

A liquid crystal element is produced by providing the polarizing plate with an adhesive layer of the present invention obtained as described above 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.

Examples of the substrate of the liquid crystal cell include a glass plate. The thickness of the substrate is usually 0.05 to 3 mm, preferably 0.2 to 1 mm. In this invention, by using the said adhesive composition, even when an adhesive layer is laminated | stacked directly on a polarizer, the curvature of a polarizing plate and a board | substrate can be suppressed. Therefore, even when the thickness of the substrate is small (eg, 1 mm or less, preferably 0.2 to 1 mm), the above-mentioned pressure-sensitive adhesive composition can be suitably used for bonding the polarizing plate and the substrate.

Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. In the following description of Examples and the like, “part” means “part by mass” unless otherwise specified.

[GPC]
About the (meth) acrylic-type copolymer, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were calculated | required on condition of the following by the gel permeation chromatography method (GPC method).
・ Measurement device: HLC-8320GPC (manufactured by Tosoh Corporation)
-GPC column configuration: The following four columns (all manufactured by Tosoh Corporation)
(1) TSKgel HxL-H (guard column)
(2) TSKgel GMHxL
(3) TSKgel GMHxL
(4) TSKgel G2500HxL
・ Flow rate: 1.0 mL / min
-Column temperature: 40 ° C
Sample concentration: 1.5% (w / v) (diluted with tetrahydrofuran)
・ Mobile phase solvent: Tetrahydrofuran ・ Standard polystyrene conversion

[Synthesis Example 1]
In a reaction apparatus equipped with a stirrer, reflux condenser, thermometer and nitrogen introduction tube, 98.3 parts of lauryl methacrylate, 1.5 parts of acrylic acid, 0.2 part of 2-hydroxyethyl acrylate and 100 parts of ethyl acetate solvent were added. The temperature was raised to 80 ° C. while introducing nitrogen gas. Next, 0.1 part of 2,2′-azobisisobutyronitrile was added, and a polymerization reaction was performed at 80 ° C. for 6 hours in a nitrogen gas atmosphere. After completion of the reaction, it was diluted with ethyl acetate to prepare a polymer solution having a solid content concentration of 30% by mass. The obtained (meth) acrylic copolymer A1 had a weight average molecular weight (Mw) of 800,000, a molecular weight distribution (Mw / Mn) of 8, and an acid value of 11.7 mgKOH / g.

[Synthesis Examples 2 to 8]
As in Synthesis Example 1, except that the amount of 2,2′-azobisisobutyronitrile used was 0.05 parts by mass and the monomer components used in the polymerization reaction were changed as shown in Table 1. And a polymer solution having a solid content concentration of 30% by mass was prepared. The results are shown in Table 1.

[Example 1]
(1) Preparation of pressure-sensitive adhesive composition For the polymer solution obtained in Synthesis Example 1 (solid content concentration 30% by mass) and 100 parts (solid content) of (meth) acrylic copolymer A1 contained in the solution As an isocyanate compound, 0.15 part (solid content) of “L-45” (solid content 45% by mass, ethyl acetate solution) manufactured by Soken Chemical Co., Ltd. and “A” manufactured by Soken Chemical Co., Ltd. as a silane coupling agent. -50 "(solid content 50% by weight, toluene solution) 0.2 part (solid content) and 0.8 part of tributylmethylammonium bis (trifluoromethanesulfonyl) imide as an antistatic agent I got a thing.

(2) Preparation of pressure-sensitive adhesive sheet On the polyethylene terephthalate film (PET film) subjected to release treatment, the pressure-sensitive adhesive composition obtained in the above (1) was applied using a doctor blade after removing bubbles, and at 90 ° C. The film was dried for 3 minutes to form a coating film having a dry film thickness of 20 μm. Two PET films were obtained by further laminating the peeled PET film on the surface of the coating film opposite to the surface on which the PET film was applied, and leaving it to stand for aging in a 23 ° C./50% RH environment for 7 days. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 20 μm sandwiched between the layers was obtained.

(3) Preparation of polarizing plate with pressure-sensitive adhesive layer On the peeled polyethylene terephthalate film (PET film), the pressure-sensitive adhesive composition obtained in (1) above was applied using a doctor blade after removing bubbles. And dried at 90 ° C. for 3 minutes to obtain a sheet having a coating film having a dry film thickness of 20 μm. The coating film surface of the sheet is in contact with the polyvinyl alcohol film surface of the polarizing plate having a two-layer structure (thickness 60 μm) composed of a polyvinyl alcohol film as a polarizer and a triacetyl cellulose film as a polarizer protective film. A polarizing plate with an adhesive layer having a PET film, an adhesive layer having a thickness of 20 μm, a polarizer, and a polarizer protective film, which is allowed to stand for aging at 23 ° C./50% RH for 7 days. Got.

[Examples 2 to 7, Comparative Examples 1 and 2]
In Example 1, the pressure-sensitive adhesive composition was changed in the same manner as in Example 1 except that the polymer solution was changed to the polymer solution obtained in Synthesis Examples 2 to 8 and the blending composition was changed as shown in Table 2. The polarizing plate with an adhesive sheet and an adhesive layer was obtained. TD-75 is an isocyanate compound (manufactured by Soken Chemical Co., Ltd.), and the other antistatic agent is 1-octyl-4-methylpyridinium bis (fluorosulfonyl) imide.

[Evaluation]
[Gel fraction]
About 0.1 g of the pressure-sensitive adhesive was collected in a sampling bottle from the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, and 30 mL of ethyl acetate was added and shaken for 4 hours. The contents of the sample bottle were made of 200 mesh stainless steel. The mixture was filtered through a wire mesh, the residue on the wire mesh was dried at 100 ° C. for 2 hours, and the dry weight was measured. The gel fraction of the pressure-sensitive adhesive was determined by the following formula.
Gel fraction (%) = (Dry weight / Adhesive sampling weight) × 100 (%)

[Measurement of adhesive strength]
The polarizing plate with the pressure-sensitive adhesive layer obtained in Examples and Comparative Examples (laminated body composed of PET film / pressure-sensitive adhesive layer / polarizer / polarizer protective film) was cut into a size of 70 mm × 25 mm, and the test piece was cut. Produced. The PET film was peeled from the test piece, and a laminate composed of the pressure-sensitive adhesive layer / polarizer / polarizer protective film was laminated on one side of a 2 mm thick glass plate using a 2 kg roller, and the pressure-sensitive adhesive layer, the glass plate, I stuck it to touch. The obtained laminate was allowed to stand in an environment of 23 ° C./50% RH for 2 hours, and then the end of the polarizing plate was pulled at a speed of 300 mm / min in the 90 ° direction with respect to the glass plate surface, and the adhesive strength (peel strength) ) Was measured.

(Water vapor transmission rate)
The water vapor transmission rate was measured as follows according to JIS Z0208. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 50 μm was prepared in the same manner as described in the column “(2) Preparation of pressure-sensitive adhesive sheet”. The PET film was peeled from this pressure-sensitive adhesive sheet, and a nonwoven fabric was bonded to both sides of the pressure-sensitive adhesive layer (the obtained laminate was referred to as “sheet A”), and cut according to the diameter of the moisture permeable cup. 10 g of calcium chloride was put in a moisture permeable cup (inner diameter 60 mm), and the cut sheet A, rubber packing, and cover ring were set and fixed with bolts. Under a constant temperature and humidity condition of 40 ° C./90% RH, a moisture permeable cup in which the sheet A or the like was set was put in. After 24 hours, the moisture permeable cup was taken out, and the weight of the moisture permeable cup was weighed (initial weight). The weighed moisture-permeable cup was returned to 40 ° C./90% RH condition, and the weight was weighed every 24 hours. When the increase in mass every 24 hours was within 5%, the water vapor transmission rate was calculated from the last mass change and measurement interval using the following formula.
Water vapor transmission rate [g / m ² · day] = 240 × M / T · S
M: Increased mass (mg) of the last two weighing intervals tested
T: Time of the last two weighing intervals during the test (hours)
S: Transmission area (cm ² )
In addition, g / m < ² > * day is the meaning of g / m < ² > / day.

[Durability Test (Heat and Moisture Resistance Test)]
The polarizing plate with a pressure-sensitive adhesive layer obtained in the examples and comparative examples (laminated body composed of PET film / pressure-sensitive adhesive layer / polarizer / polarizer protective film) was cut into a size of 150 mm × 250 mm, and the test piece was cut. Produced. The PET film is peeled from the test piece, and a laminate composed of an adhesive layer / polarizer / polarizer protective film is laminated on one side of a 0.5 mm thick glass plate using a laminator roll. I stuck it so that it touched. The obtained laminate was held in an autoclave adjusted to 50 ° C./5 atm for 20 minutes to prepare a test plate. Two similar test plates were produced. The test plate is allowed to stand for 500 hours under conditions of temperature 80 ° C./drying (heat resistance) or temperature 60 ° C./humidity 90% RH (moisture heat resistance), and foaming, floating and peeling occur according to the following criteria. Was observed and evaluated.
AA: Appearance defects such as foaming, floating, and peeling were not observed BB: Appearance defects such as foaming, floating, and peeling were slightly observed CC: Appearance defects such as foaming, floating, and peeling were clearly observed

[Optical test (heat-resistant optical characteristics / humid heat-resistant optical characteristics test)]
The polarizing plate with a pressure-sensitive adhesive layer obtained in the examples and comparative examples (laminated body composed of PET film / pressure-sensitive adhesive layer / polarizer / polarizer protective film) was cut into a size of 150 mm × 250 mm, and the test piece was cut. Produced. The PET film is peeled from the test piece, and using a laminator roll, the laminate composed of the pressure-sensitive adhesive layer / polarizer / polarizer protective film is perpendicular to the polarization axis on both sides of the 0.5 mm thick glass plate. The adhesive layer and the glass plate were attached so that they were in contact with each other. The obtained laminate was held in an autoclave adjusted to 50 ° C./5 atm for 20 minutes to prepare a test plate. Two similar test plates were prepared, and the test plate was allowed to stand for 500 hours at a temperature of 80 ° C./drying condition (heat resistance) or at a temperature of 60 ° C./humidity of 90% RH (humidity heat resistance), and haze. The total light transmittance was measured using a meter (HM-150 type: manufactured by Murakami Color Research Laboratory). The total light transmittance of the test plate before the durability test is 0%.

As an example of the monomer that forms the (meth) acrylic copolymer, (1) As shown in the examples, in the example in which the monomer (a1) and the monomer (a2) are used at the specific ratio, the water vapor permeability is low ( (High hydrophobicity), excellent durability, and excellent optical properties. (2) As shown in Comparative Example 1, an example of using an acrylic acid alkyl ester without using a methacrylic acid alkyl ester, and (3) Comparative Example 2 As shown in the above, in the example in which the monomer (a1) and the monomer (a2) are not used in the specific ratio, the water vapor transmission rate is high (low hydrophobicity), and the durability and optical properties of the pressure-sensitive adhesive sheet are inferior. became.

Claims (5)

1. (A) 50% by mass to 99.5% by mass of a methacrylic acid alkyl ester (a1) having a glass transition temperature (Tg) of the homopolymer of less than −10 ° C. and an alkyl group having 8 or more carbon atoms, a crosslinkable functional group A (meth) acrylic copolymer obtained by copolymerizing a monomer component containing the group-containing monomer (a2) in an amount of 0.5% by mass or more and less than 10% by mass;
   (B) contains a crosslinking agent,
   A pressure-sensitive adhesive composition for polarizing plates, which is used for forming a pressure-sensitive adhesive layer in direct contact with a polarizer.
2. A pressure-sensitive adhesive layer for a polarizing plate formed from the pressure-sensitive adhesive composition according to claim 1.
3. The pressure-sensitive adhesive layer for polarizing plates according to claim 2, wherein the water vapor permeability is 800 g / m ² · day or less.
4. A pressure-sensitive adhesive sheet for polarizing plates having the pressure-sensitive adhesive layer according to claim 2.
5. The polarizing plate with the adhesive layer which has an adhesive layer of Claim 2 or 3 directly laminated | stacked on the at least one surface of the polarizer.