WO2016199602A1 - Adhesive composition for polarizing plate, adhesive layer, adhesive sheet, and polarizing plate provided with adhesive layer - Google Patents

Abstract

[Problem] To provide an adhesive composition for a polarizing plate, whereby an adhesive layer having excellent durability in a high-temperature high-humidity environment can be formed, and the adhesive composition for a polarizing plate can be applied in a configuration in which at least one of the polarizer protective films conventionally formed on both surfaces of a polarizer is omitted. [Solution] An adhesive composition for a polarizing plate, used to form an adhesive layer in direct contact with a polarizer, and which contains an active-energy-ray-curable polyfunctional monomer (B) in a range of less than 20 parts by mass with respect to 100 parts by mass of a (meth)acrylic polymer (A).

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. In general, a polarizing plate has a structure in which a polarizer protective film such as a triacetyl cellulose film is laminated on both surfaces of a polarizer having a polarizing function in order to improve its mechanical properties and optical durability. I came.

In recent years, in order to meet the demand for reducing the weight and thickness of polarizing plates, attempts have been made to omit one or both of the polarizer protective films formed on both sides of the polarizer (see, for example, Patent Document 1). However, as compared with the case where the polarizer protective film is formed on both sides of the polarizer, when at least one of the polarizer protective films is omitted, the polarizer is more easily thermally contracted. For this reason, under a high temperature and high humidity environment, various problems such as cracks in the polarizer and deterioration of the optical performance of the polarizing plate occur. In addition, in the polarizing plate in which at least one of the polarizer protective films is omitted, since the pressure-sensitive adhesive layer is in direct contact with the polarizer, the pressure-sensitive adhesive layer is large due to thermal contraction of the polarizer in a high temperature / high humidity heat environment. Stress is applied, and problems such as peeling of the adhesive layer are likely to occur.

JP 2009-251177 A

A polarizing plate in which at least one of the polarizer protective films conventionally formed on both surfaces of the polarizer is omitted is required to have high durability. The subject of the present invention is applicable to a configuration in which at least one of the polarizer protective films conventionally formed on both sides of the polarizer is omitted, and is a pressure-sensitive adhesive layer excellent in durability under a high temperature and high humidity environment It is providing the adhesive composition for polarizing plates which can form.

The present inventors diligently studied to solve the above problems. As a result, the present inventors have found that the above problems can be solved by using a polarizing plate pressure-sensitive adhesive composition having the following specific configuration, and have completed the present invention.

The present invention includes, for example, the following [1] to [9].
[1] An adhesive layer containing the active energy ray-reactive polyfunctional monomer (B) in an amount of less than 20 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer (A) and in direct contact with the polarizer. A pressure-sensitive adhesive composition for a polarizing plate used for forming a film.
[2] The pressure-sensitive adhesive composition for a polarizing plate according to [1], wherein the polyfunctional monomer (B) is a polyfunctional (meth) acrylate having a molecular weight of less than 2000.
[3] The (meth) acrylic polymer (A) comprises 70 to 99.8 mass% of (meth) acrylic acid alkyl ester having 1 to 8 carbon atoms in the alkyl group, and a hydroxyl group and / or carboxyl group-containing monomer. The pressure-sensitive adhesive composition for polarizing plates according to the above [1] or [2], which is a copolymer obtained by copolymerizing a monomer component containing 0.1 to 10% by mass.
[4] The pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [3], further containing a polymerization initiator (C).
[5] The pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [4], further containing an isocyanate-based crosslinking agent (D).
[6] A pressure-sensitive adhesive layer for a polarizing plate formed from the pressure-sensitive adhesive composition according to any one of [1] to [5].
[7] The pressure-sensitive adhesive layer for a polarizing plate according to [6], wherein a storage elastic modulus at 23 ° C. is 2.0 MPa or more and a storage elastic modulus at 80 ° C. is 0.4 MPa or more.
[8] A pressure-sensitive adhesive sheet for polarizing plate having the pressure-sensitive adhesive layer according to [6] or [7].
[9] A polarizing plate with an adhesive layer having a polarizer and the adhesive layer according to [6] or [7], which is directly laminated on at least one surface of the polarizer.

According to the present invention, the pressure-sensitive adhesive layer can be applied to a configuration in which at least one of the polarizer protective films conventionally formed on both sides of the polarizer is omitted, and is excellent in durability under a high temperature and high humidity environment. Can be provided. 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 plate of the present invention contains a (meth) acrylic polymer (A) and an active energy ray-reactive polyfunctional monomer (B) described below, and is a pressure-sensitive adhesive that is in direct contact with the polarizer. Used to form a layer.

By curing the coating film comprising the pressure-sensitive adhesive composition of the present invention with active energy rays, the strength is improved, and it is possible to form a pressure-sensitive adhesive layer having good durability in a high temperature and high humidity environment. it can. For this reason, in the polarizing plate in which at least one of the polarizer protective films is omitted, the pressure-sensitive adhesive layer has improved defects such as generation of cracks in the polarizer, deterioration of the optical performance of the polarizing plate, and peeling of the pressure-sensitive adhesive layer. An attached polarizing plate can be provided.

[(Meth) acrylic polymer (A)]
The (meth) acrylic polymer (A) is preferably a polymer having a structural unit derived from (meth) acrylic acid ester, and (meth) acrylic acid alkyl ester having 1 to 8 carbon atoms in the alkyl group ( More preferred is a copolymer of monomer components containing a1) and a hydroxyl group and / or carboxyl group-containing monomer (a2), that is, a copolymer obtained by copolymerizing the monomer components.

The monomer component is preferably a polymerizable unsaturated double bond-containing monomer.
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. Therefore, specifically, the polymer (A) is preferably a copolymer having a monomer (a1) unit and a monomer (a2) unit.

<< (Meth) acrylic acid alkyl ester (a1) >>
The monomer (a1) is a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 8 carbon atoms, and is represented, for example, by the formula: CH ₂ ═CR ¹ —COOR ² . In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 8 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, Examples include pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.

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 polymer (A), the amount of the monomer (a1) used is usually 70 to 99.8% by mass, preferably 70 to 99% by mass, more preferably 72 to 97% by mass. When the usage-amount of a monomer (a1) exists in the said range, it is preferable at the point from which the adhesive layer which expresses favorable durability is obtained.

<< Hydroxyl group and / or carboxyl group-containing monomer (a2) >>
It is preferable that the monomer component which is a raw material monomer of the polymer (A) further includes a hydroxyl group and / or carboxyl group-containing monomer (a2) capable of reacting with a crosslinking agent.
The monomer (a2) preferably has a polymerizable unsaturated double bond.

Examples of the hydroxyl group-containing monomer include a hydroxyl group-containing (meth) acrylate, and specific examples include 2-hydroxyethyl (meth) acrylate, 3-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.

A monomer (a2) 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 polymer (A), the amount of the monomer (a2) used is usually 0.1 to 10% by mass, preferably 0.6 to 5% by mass, more preferably 1 to 3.5% by mass. When the usage-amount of a monomer (a2) is below the said upper limit, the crosslinking density formed with a polymer (A) and a crosslinking agent (D) will not become high too much. 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 suitable intensity | strength is obtained.

<Other monomer components>
As a monomer component which forms a polymer (A), other monomer components other than a monomer (a1) and (a2) can be used in the range which does not impair the physical property of a polymer (A).

Other monomer components include, for example, other (meth) acrylic acid esters other than the monomers (a1) and (a2), specifically, (meth) acrylic acid alkyl esters having an alkyl group with 9 or more carbon atoms, Examples include alkoxyalkyl (meth) acrylates, alkoxypolyalkylene glycol mono (meth) acrylates, alicyclic group-containing (meth) acrylates, aromatic ring-containing (meth) acrylates, and amino group-containing (meth) acrylates.

The (m) acrylic acid alkyl ester having 9 or more carbon atoms in the alkyl group is represented, for example, by the formula: CH ₂ ═CR ³ —COOR ⁴ . In the formula, R ³ is a hydrogen atom or a methyl group, and R ⁴ is an alkyl group having 9 or more carbon atoms. The alkyl group preferably has 9 to 18 carbon atoms, more preferably 9 to 12 carbon atoms. For example, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undeca (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate Is mentioned.

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-containing (meth) acrylate include cyclohexyl (meth) acrylate, and examples of the aromatic ring-containing (meth) acrylate include phenyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl ( And (meth) acrylate.
Examples of the amino group-containing (meth) acrylate include dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate.

Also, as other monomer components, amide group-containing monomers and acid anhydride group-containing monomers can be used. 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 acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride.

Other monomer components 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 polymer (A), the total amount of the other monomer components used is preferably 0 to 30% by mass, more preferably 0 to 25% by mass. .

<< Production conditions for (meth) acrylic polymer (A) >>
Although the manufacturing conditions of a (meth) acrylic-type polymer (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 90. The reaction system is maintained at a temperature of usually 50 to 90 ° C., preferably 70 to 90 ° C. for 2 to 20 hours.

The polymer (A) is obtained, for example, by polymerizing the above-described monomer components. In the case of a copolymer, it 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 (isobutylamido) 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] Is mentioned. 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 in the range of 0.1 to 3 parts by mass with respect to 100 parts by mass of the monomer component that is the raw material monomer of the (meth) acrylic polymer (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 polymer (A) >>
The weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) method of the (meth) acrylic polymer (A) is a polystyrene conversion value, and is usually 400,000 to 2 million, preferably 45 It is 10,000 to 1,800,000, more preferably 500,000 to 1,500,000. By using the polymer (A) having Mw in the above range, a pressure-sensitive adhesive composition suitable for coating can be obtained.

The molecular weight distribution (Mw / Mn) measured by the GPC method of the (meth) acrylic polymer (A) is usually 10 or less, preferably 2 to 9, more preferably 2 to 8.5.
The glass transition temperature (Tg) of the (meth) acrylic polymer (A) can be calculated by, for example, the Fox equation from the monomer units constituting the copolymer and the content ratio thereof. For example, the (meth) acrylic polymer (A) is synthesized so that the glass transition temperature (Tg) determined by the Fox equation is usually −70 to −20 ° C., preferably −60 to −30 ° C. be able to. By using the (meth) acrylic polymer (A) having such a glass transition temperature (Tg), a pressure-sensitive adhesive composition having excellent pressure-sensitive adhesive properties at room temperature can be obtained.

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 the glass transition temperature (K) of the (meth) acrylic polymer (A), and Tg ₁ , Tg ₂ ,..., Tg _m are the glass transition temperatures (K) of the homopolymer composed of each monomer. W ₁ , W ₂ ,..., W _m are weight fractions of the structural units derived from the respective monomers in the polymer (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 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.

In the pressure-sensitive adhesive composition of the present invention, the content of the (meth) acrylic polymer (A) is 100% by mass of the solid content excluding the organic solvent in the composition excluding the polyfunctional monomer (B). Usually, it is 60% by mass or more, preferably 60 to 99.99% by mass, more preferably 70 to 99.95% by mass, and particularly preferably 75 to 99.90% by mass. When the content of the (meth) acrylic polymer (A) is in the above range, the performance as an adhesive is balanced and the adhesive properties are excellent.

[Active energy ray reactive polyfunctional monomer (B)]
As the polyfunctional monomer (B), for example, a compound having two or more active energy ray reactive groups is preferable, a compound having two or more polymerizable unsaturated double bonds is more preferable, and two or more (meth) acryloyl groups are included. Polyfunctional (meth) acrylate is more preferable. In the polyfunctional (meth) acrylate, the number of (meth) acryloyl groups is 2 or more, preferably 2 to 8, more preferably 3 to 6.

Examples of active energy rays include ultraviolet rays, visible rays, and electron beams.
As polyfunctional (meth) acrylate, for example,
Di-, tri- or polyalkylene glycol-di (meth) acrylates such as diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polytetraethylene glycol di (meth) acrylate;
1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1 , 9-nonanediol di (meth) acrylate, alkanediol di (meth) acrylate such as tricyclodecane dimethylol di (meth) acrylate;
Bisphenol-based di (meth) acrylates such as bisphenol A alkylene oxide modified di (meth) acrylate, bisphenol F alkylene oxide modified di (meth) acrylate, tetrabromobisphenol A alkylene oxide modified di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, etc. (Meth) acrylate;
Glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, glycerol alkylene oxide modified tri (meth) acrylate, trimethylolpropane alkylene oxide modified tri (meth) acrylate, pentaerythritol alkylene oxide modified tri (meth) acrylate, pentaerythritol alkylene oxide modified tetra (meth) ) Acrylate, dipentaerythritol alkylene oxide modified hexa (meth) a Relate, dipentaerythritol caprolactone-modified hexa (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri (meth) tri- or more functional polyol poly (meth) acrylates such as acrylate;
Polyurethane di (meth) acrylate, polyurethane poly (meth) acrylate;
Is mentioned.

Examples of the alkylene oxide modification include ethylene oxide modification and propylene oxide modification. The number of repeating alkylene oxides is usually 1 to 18, preferably 2 to 9.

The molecular weight of the polyfunctional monomer (B) is preferably less than 2000, more preferably 200 to 1500, and still more preferably 250 to 1200. When a pressure-sensitive adhesive composition containing an active energy ray-reactive polyfunctional monomer (B) that is a low molecular weight substance is applied onto a polarizer, or when a coating film comprising the composition is transferred onto a polarizer, the composition Since the wettability of the object is excellent, excellent adhesion between the polarizer and the pressure-sensitive adhesive layer can be realized.

Among the polyfunctional monomers (B), a tri- or higher functional polyol poly (meth) acrylate is preferable. From the viewpoint of storage elastic modulus and durability of the pressure-sensitive adhesive layer, glycerin tri (meth) acrylate, trimethylolpropane tri (meth). Acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate are more preferable, and pentaerythritol Tetra (meth) acrylate and dipentaerythritol hexa (meth) acrylate are particularly preferred.

A polyfunctional monomer (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 polyfunctional monomer (B) is less than 20 parts by mass, preferably 8 to 19% with respect to 100 parts by mass of the (meth) acrylic polymer (A). 9 parts by mass, more preferably 10 to 19.8 parts by mass. When the content of the polyfunctional monomer (B) is in the above range, a pressure-sensitive adhesive layer excellent in polarizer adhesion and durability can be formed. When the content of the polyfunctional monomer (B) exceeds the above range, the pressure-sensitive adhesive layer after irradiation with active energy rays becomes too hard, and thus there is a tendency that problems such as peeling occur during the durability test.

[Polymerization initiator (C)]
When the pressure-sensitive adhesive composition of the present invention is cured by irradiating ultraviolet rays and visible light as active energy rays to form a pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition of the present invention further comprises a polymerization initiator (C). It is preferable to contain.

As the polymerization initiator (C), a photopolymerization initiator is preferable, and a photoradical polymerization initiator is more preferable, and examples thereof include acylphosphine oxide compounds, benzoin compounds, alkylphenone compounds, benzophenone compounds, and oxime ester compounds.

Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide.

Examples of the benzoin compound include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

Examples of the alkylphenone compound include 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl]- 2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl- Α-hydroxyalkylphenones such as propan-1-one; 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholino Phenyl) butan-1-one, 2- (2-methylbenzyl) -2-dimethylamino-1- (4-morpholinophenyl) bu Non, 2- (3-methylbenzyl) -2-dimethylamino-1- (4-morpholinophenyl) butanone, 2- (4-methylbenzyl) -2-dimethylamino-1- (4-morpholinophenyl) butanone, 2- (2-ethylbenzyl) -2-dimethylamino-1- (4-morpholinophenyl) butanone, 2- (2-propylbenzyl) -2-dimethylamino-1- (4-morpholinophenyl) butanone, and 2 Α-aminoalkylphenones such as-(2-butylbenzyl) -2-dimethylamino-1- (4-morpholinophenyl) butanone; 2,2-dimethoxy-1,2-diphenylethane-1-one, and 2, And dialkoxyacetophenone such as 2-diethoxyacetophenone.

Examples of the benzophenone compound include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, 3,3 ′, 4,4′-bis (diethylamino) benzophenone, 4, 4'-tetra (tert-butylperoxycarbonyl) benzophenone, and 2,4,6-trimethylbenzophenone.

Examples of oxime ester compounds include N-benzoyloxy-1- (4-phenylsulfanylphenyl) butan-1-one-2-imine, N-ethoxycarbonyloxy-1-phenylpropan-1-one-2-imine N-benzoyloxy-1- (4-phenylsulfanylphenyl) octane-1-one-2-imine, N-acetoxy-1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole-3 -Yl] ethane-1-imine and N-acetoxy-1- [9-ethyl-6- {2-methyl-4- (3,3-dimethyl-2,4-dioxacyclopentanylmethyloxy) benzoyl } -9H-carbazol-3-yl] ethane-1-imine.

A polymerization initiator (C) 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 polymerization initiator (C) is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the polyfunctional monomer (B). More preferably, it is 3 to 10 parts by mass.

[Isocyanate-based crosslinking agent (D)]
The pressure-sensitive adhesive composition of the present invention preferably further contains an isocyanate-based crosslinking agent (D). When the (meth) acrylic polymer (A) has a crosslinkable functional group (hydroxyl group and / or carboxyl group) derived from the monomer (a2), the crosslinkable functional group and the isocyanate crosslinker (D) are crosslinked. By making it, the adhesive layer excellent in durability can be formed.

As the isocyanate crosslinking agent (D), an isocyanate compound having two or more isocyanate groups in one molecule is usually used. A crosslinked body (network polymer) can be formed by crosslinking the (meth) acrylic polymer (A) with the crosslinking agent (D).

The number of isocyanate groups in the crosslinking agent (D) is usually 2 or more, preferably 2 to 8, 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 polymer (A) and the crosslinking agent (D) 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 crosslinking agent (D) include multimers (for example, dimers or trimers, biurets, isocyanurates), derivatives (for example, many) of the above isocyanate compounds having 2 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, the reaction product of trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate (L-45 manufactured by Soken Chemical Co., Ltd., TD manufactured by Soken Chemical Co., Ltd.) can improve the aging property. -75 etc.), isocyanurate of hexamethylene diisocyanate or tolylene diisocyanate (TSE-100 manufactured by Asahi Kasei Corporation, 2050 manufactured by Nippon Polyurethane Industry Co., Ltd.).

A crosslinking agent (D) 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 isocyanate-based crosslinking agent (D) is usually 0 to 15 parts by mass, more preferably 1 with respect to 100 parts by mass of the (meth) acrylic polymer (A). -15 parts by mass, more preferably 5-13 parts by mass. When the content is in the above range, it is preferable in that a pressure-sensitive adhesive layer having excellent durability can be obtained.

[Silane coupling agent (E)]
The pressure-sensitive adhesive composition of the present invention preferably further contains a silane coupling agent (E). A silane coupling agent (E) 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 (E) 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 agent and the like.

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

[Antistatic agent (F)]
The antistatic agent (F) 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 (F) 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.

In addition, a reactive emulsifier having a polymerizable group is also exemplified as the surfactant, and a polymer surfactant obtained by increasing the molecular weight of the monomer component containing the above 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, and (F ₂ SO ₂ ) ₂ N ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ are particularly preferable.

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, tributylmethyl Ammonium 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 (F) 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 polymer (A). 3 parts by mass, more preferably 0.05 to 2.5 parts by mass.

[Organic solvent (G)]
The pressure-sensitive adhesive composition of the present invention preferably contains an organic solvent (G) in order to adjust its applicability. As an organic solvent, the solvent illustrated as a polymerization solvent in the column of the (meth) acrylic-type polymer (A) is mentioned. In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent (G) is usually 50 to 90% by mass, preferably 60 to 85% by mass.

For example, the pressure-sensitive adhesive composition is obtained by mixing the polymer solution containing the (meth) acrylic polymer (A) and the polymerization solvent obtained by the above polymerization and the active energy ray-reactive polyfunctional monomer (B). Can be prepared.

In the present specification, “solid content” refers to all components excluding the organic solvent (G) 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 is an epoxy crosslinking agent, metal chelate compound, antioxidant, light stabilizer, metal corrosion inhibitor, tackifier, as long as the effects of the present invention are not impaired. You may contain 1 type, or 2 or more types selected from a plasticizer, a crosslinking accelerator, (meth) acrylic-type polymers other than said (A), and a rework agent.

[Preparation of pressure-sensitive adhesive composition for polarizing plate]
In the pressure-sensitive adhesive composition of the present invention, the (meth) acrylic polymer (A), the active energy ray-reactive polyfunctional monomer (B), and other components as necessary are mixed by a conventionally known method. Can be prepared. For example, the active energy ray-reactive polyfunctional monomer (B) and other components as necessary are added to a polymer solution containing the polymer obtained when the (meth) acrylic polymer (A) is synthesized. Mixing is mentioned.
The said composition is suitable for the bonding application of the board | substrate and polarizer which comprise a liquid crystal cell.

[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 storage elastic modulus characteristics can be formed.

The pressure-sensitive adhesive layer of the present invention has a storage elastic modulus at 23 ° C. of preferably 2.0 MPa or more, more preferably 2 to 10 MPa, particularly preferably 4 to 8 MPa; a storage elastic modulus at 80 ° C., preferably 0 4 MPa or more, more preferably 0.4 to 10 MPa, and particularly preferably 1 to 8 MPa.

The storage elastic modulus is, for example, a value calculated from a dynamic viscoelastic spectrum measured for the laminate by laminating the adhesive layers a plurality of times to produce a laminate having a thickness of about 1.0 mm. . Details of the measurement conditions are described in the examples.

When the storage elastic modulus at 23 ° C. and the storage elastic modulus at 80 ° C. are in the above ranges, the pressure-sensitive adhesive layer of the present invention can suppress thermal contraction of the polarizer. For this reason, even if the pressure-sensitive adhesive layer of the present invention is exposed to a high-temperature and high-humidity heat environment, peeling of the pressure-sensitive adhesive layer from the polarizer is suppressed, and the durability is excellent.

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a gel fraction of preferably 80% by mass or more, more preferably, from the viewpoints of distortion suppression of the polarizing plate, cohesion, adhesion, and removability. It is 90% by mass or more, more preferably 95 to 99% by mass. When the gel fraction is in the above range, the pressure-sensitive adhesive layer exhibits excellent durability. Details of the measurement conditions are described in the examples.

The pressure-sensitive adhesive layer of the present invention can be obtained, for example, by advancing a curing reaction in the above-described pressure-sensitive adhesive composition. Specifically, the curing reaction includes a polymerization / crosslinking reaction of the active energy ray-reactive polyfunctional monomer (B) and, if necessary, a crosslinking reaction between the acrylic polymer (A) and the isocyanate crosslinking agent (D). It is.

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 onto 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 The solvent is removed by drying for a minute to form a coating film. The film thickness of the dried coating film is usually 5 to 75 μm, preferably 10 to 50 μm. If necessary, a cover film is applied on the coating film.

As a method for applying the pressure-sensitive adhesive composition, a known method such as spin coating, knife coating, roll coating, bar coating, doctor blade coating, die coating, gravure coating, etc. 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.

Subsequently, the coating film is irradiated with active energy rays. Examples of active energy rays include ultraviolet rays, visible rays, and electron beams, and ultraviolet rays are preferred. Examples of the light source of the active energy ray include a high pressure mercury lamp, a low pressure mercury lamp, a halogen lamp, a light emitting diode, a laser, and an electron beam irradiation device. Among these, a high pressure mercury lamp, a low pressure mercury lamp, a halogen lamp, and a light emitting diode are preferable.

The irradiation amount of the active energy ray may be a sufficient amount for proceeding the curing reaction of the polyfunctional monomer (B). The composition of the pressure-sensitive adhesive composition, the amount used, and the thickness of the pressure-sensitive adhesive layer to be formed It can be selected according to the shape and the like. For example, when irradiating with ultraviolet rays, the irradiation amount is preferably 150 to 1500 mJ / cm ² , more preferably 250 to 1000 mJ / cm ² .

Since the pressure-sensitive adhesive layer of the present invention exhibits a high storage modulus immediately after irradiation with active energy rays, it exhibits high durability even when exposed to a high temperature / high humidity environment immediately after irradiation with active energy rays.
In the case of the pressure-sensitive adhesive composition containing the isocyanate-based crosslinking agent (D), the pressure-sensitive adhesive layer is preferably formed under the following conditions. After forming a coating film comprising the pressure-sensitive adhesive composition of the present invention on the support under the above conditions and removing the solvent, after pasting a cover film on this coating film, irradiation with active energy rays under the above conditions, Further aging is performed. The irradiation with active energy rays may be performed after aging.

The aging conditions are usually 5 to 60 ° C., preferably 15 to 40 ° C., usually 30 to 70% RH, preferably 40 to 70% RH, usually 3 days or more, preferably 7 to 10 days. It is. When crosslinking is performed under the aging conditions as described above, a crosslinked body (network polymer) can be efficiently formed.

[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 substrate 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.

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 adhesive performance. The 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 an adhesive layer of this invention has a polarizer and the adhesive layer formed from the adhesive composition of this invention directly laminated | stacked on the at least one surface of the said 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 the present invention, since one or both of the polarizer protective films formed on the polarizer can be omitted, the polarizing plate can be thinned.

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. For example, (1) a coating film of the pressure-sensitive adhesive composition is formed on the surface of the polarizer, and the coating film is irradiated with active energy rays and cured. (2) A coating film of the pressure-sensitive adhesive composition is formed on the surface of the polarizer, the coating film is aged, and the coating film after aging is irradiated with active energy rays. Examples of the curing method include (3) a method of transferring the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for polarizing plates of the present invention to the surface of the polarizer. In particular, the method (1) is preferred. The conditions for forming the coating film, the conditions for curing and aging, the range of the storage elastic modulus and the gel fraction of the pressure-sensitive adhesive layer, and the like are the same as the conditions and ranges described in the section [Pressure-sensitive adhesive 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 the pressure-sensitive 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. An example of the substrate that the liquid crystal cell has is a glass plate. The thickness of the substrate is usually 0.05 to 3 mm, preferably 0.2 to 1 mm.

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 polymer, 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 reactor equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube, 96.8 parts of n-butyl acrylate, 0.2 part of acrylic acid, 3.0 parts of 2-hydroxyethyl acrylate, and ethyl acetate solvent 100 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 1,200,000 and a molecular weight distribution (Mw / Mn) of 8.0.

[Synthesis Examples 2 to 4]
A polymer solution having a solid content concentration of 30% by mass was prepared in the same manner as in Synthesis Example 1 except that the monomer components used in the polymerization reaction were changed as described in Table 1. 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 19.8 parts of dipentaerythritol hexaacrylate as a polyfunctional monomer, 0.6 parts of “Irgacure 127” manufactured by BASF as a polymerization initiator, and “L-45” (manufactured by Soken Chemical Co., Ltd.) as an isocyanate crosslinking agent Tolylene diisocyanate cross-linking agent, solid content 45% by mass, ethyl acetate / toluene solution) 12 parts (solid content) and 0.2 parts (solid content) "KBM-403" manufactured by Shin-Etsu Silicone Co., Ltd. as a silane coupling agent ) To obtain a pressure-sensitive adhesive composition.

(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. The peeled PET film was further bonded to the surface of the coating film opposite to the surface on which the PET film was applied to obtain a laminate. The laminate was irradiated with ultraviolet rays under the conditions of an irradiation intensity of 100 mW / cm ² and an integrated light amount of 800 mJ / cm ² . Furthermore, the laminate was aged by leaving still for 7 days in a 23 ° C./50% RH environment. Thus, an adhesive sheet having an adhesive layer having a thickness of 20 μm sandwiched between two PET films 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. Subsequently, the coating film surface of the sheet, the polyvinyl alcohol film surface of the polarizing plate having a two-layer structure (thickness 60 μm) consisting of a polyvinyl alcohol film as a polarizer and a triacetyl cellulose film as a polarizer protective film; The laminate was obtained by bonding so as to contact each other. The laminate was irradiated with ultraviolet rays under the conditions of an irradiation intensity of 100 mW / cm ² and an integrated light amount of 800 mJ / cm ² . Further, the laminate was aged by leaving still for 7 days under the condition of 23 ° C./50% RH. Thus, the polarizing plate with an adhesive layer which has a PET film, a 20-micrometer-thick adhesive layer, a polarizer, and a polarizer protective film was obtained.

[Examples 2 to 9, Comparative Examples 1 to 3]
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 4 and the blending composition was changed as shown in Table 2. The polarizing plate with an adhesive sheet and an adhesive layer was obtained.

[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 (%)

[Storage modulus]
In the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, the pressure-sensitive adhesive layers having a thickness of 20 μm were bonded together in an environment of 23 ° C./50% RH several times and treated with an autoclave at 50 ° C./5 atm for 20 minutes. A pressure-sensitive adhesive layer having a thickness of 1.0 mm was produced. This pressure-sensitive adhesive layer having a thickness of 1.0 mm was subjected to a dynamic viscoelasticity measurement method (temperature range of −40 to 160 ° C., temperature increase rate of 3.67 ° C.) according to JIS K7244 using “Physica MCR300” manufactured by Anton Paar. / Min, conditions of frequency 1 Hz), the viscoelastic spectrum was measured, and the storage elastic modulus at temperatures 23 ° C. and 80 ° C. was determined.

[Transfer area test (polarizer adhesion)]
The polarizing plate with an adhesive layer obtained in Examples and Comparative Examples was cut into a size of 70 mm × 25 mm to prepare a test piece. Peel the PET film from the test piece, and use a laminator roll so that the adhesive layer / polarizing plate laminate is in contact with the adhesive layer and the alkali glass plate on one side of the 2 mm thick alkali glass plate. Sticked. The obtained laminate was allowed to stand for 1 hour in an 80 ° C./dry environment. Thereafter, the substrate was further left for 1 hour in an environment of 23 ° C./50% RH, and the end of the polarizing plate was pulled with respect to the alkali glass plate surface of the adherend at a peeling angle of 180 ° in a peeling speed of 300 mm / min. The pressure-sensitive adhesive layer transferred onto the glass plate surface was visually confirmed and evaluated according to the following criteria.
AA: There is no pressure-sensitive adhesive layer on the glass plate surface (adhesiveness between the pressure-sensitive adhesive layer and the polarizer is good)
BB: The pressure-sensitive adhesive layer is slightly transferred onto the glass plate surface CC: The pressure-sensitive adhesive layer is transferred onto the glass plate surface (adhesion between the pressure-sensitive adhesive layer and the polarizer is poor)

〔optical properties〕
Two polarizing plates with a pressure-sensitive adhesive layer (PET film / pressure-sensitive adhesive layer / polarizer / polarizer protective film) obtained in Examples and Comparative Examples were cut into a size of 310 mm × 385 mm to prepare a test piece. did. The PET film is peeled off from the test piece, and a laminator roll is used so that the laminated body 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. And it stuck so that an adhesive layer and a glass plate might contact | connect. The obtained laminate was held in an autoclave adjusted to 50 ° C./5 atm for 20 minutes to prepare a test plate. The test plate was allowed to stand for 500 hours at a temperature of 80 ° C./dry, photographed with a camera, and the optical characteristics were evaluated according to the following criteria.
AA: No light leakage BB: Light leakage was slightly observed CC: Light leakage was clearly observed

[Durability test]
The laminate (PET film / adhesive layer / polarizer / polarizer protective film laminate) obtained by Examples / Comparative Examples immediately after active energy ray irradiation and before aging is cut into a size of 150 mm × 250 mm. Thus, a test piece 1 was produced.

A polarizing plate with a 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 150 mm × 250 mm. Test piece 2 was produced.

The PET film is peeled from the test pieces 1 and 2, 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. The glass plate was attached 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 was allowed to stand for 500 hours under conditions of a temperature of 60 ° C./humidity of 90% RH, and evaluated by observing defects (foaming, floating, peeling) according to the following criteria. The test piece 1 was put into a durability test 6 hours after the application of the pressure-sensitive adhesive composition.
AA: No defect BB: Defect area is 3% or less, no problem in practical use CC: Defect area exceeds 3% and 5% or less, no problem in practical use DD: Defect area exceeds 5%, practical use There is a problem

Claims (9)

1. For 100 parts by mass of (meth) acrylic polymer (A),
   Containing the active energy ray-reactive polyfunctional monomer (B) in a range of less than 20 parts by mass;
   A pressure-sensitive adhesive composition for a polarizing plate used for forming a pressure-sensitive adhesive layer in direct contact with a polarizer.
2. The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the polyfunctional monomer (B) is a polyfunctional (meth) acrylate having a molecular weight of less than 2,000.
3. The (meth) acrylic polymer (A) comprises 70 to 99.8 mass% of (meth) acrylic acid alkyl ester having 1 to 8 carbon atoms in the alkyl group, and a hydroxyl group and / or carboxyl group-containing monomer 0.1. The pressure-sensitive adhesive composition for polarizing plates according to claim 1 or 2, which is a copolymer obtained by copolymerizing a monomer component containing ˜10% by mass.
4. Polymerization initiator (C)
   The pressure-sensitive adhesive composition for polarizing plates according to any one of claims 1 to 3, further comprising:
5. Isocyanate-based crosslinking agent (D)
   The pressure-sensitive adhesive composition for polarizing plates according to any one of claims 1 to 4, further comprising:
6. A pressure-sensitive adhesive layer for a polarizing plate formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5.
7. The storage elastic modulus at 23 ° C. is 2.0 MPa or more,
   The pressure-sensitive adhesive layer for a polarizing plate according to claim 6, wherein the storage elastic modulus at 80 ° C is 0.4 MPa or more.
8. A pressure-sensitive adhesive sheet for a polarizing plate having the pressure-sensitive adhesive layer according to claim 6 or 7.
9. The polarizing plate with an adhesive layer which has a polarizer and the adhesive layer of Claim 6 or 7 directly laminated | stacked on the at least one surface of the said polarizer.