TW201623518A - Adhesive composition for polarizing plate and polarizing plate with adhesive layer - Google Patents

Abstract

An objective of the present invention is to provide an adhesive composition for polarizing plate capable of forming an adhesive layer. The adhesive layer is capable of being used in a construction that at least one of polarizer protective films which usually formed on two surfaces of the polarizer is omitted, and excellent in durability. The adhesive composition for polarizing plate is characterized by comprising (A) a (meth)acrylic copolymer and (B) an isocyanate-based crosslinker of 10 to 40 mass parts by mass with respect to the copolymer (A) 100 parts by mass, and being used for forming an adhesive layer direct contacted with the polarizer. Wherein the (A) (meth)acrylic copolymer is obtained by copolymerizing monomer components of 10 to 30 mass % of an alkyl (meth)acrylate (a1) that the glass transition temperature is 0 DEG C or more, and 0.1 to 5 mass % of a (a2) crosslinkalble functional group containing monomer which comprises a hydroxyl group containing monomer and a carboxyl group containing monomer, and the (A) (meth)acrylic polymer has a weight-average molecular weight of 600,000 or less as determined by gel permeation chromatography and a glass transition temperature of -80 DEG C to 0 DEG C.

Description

Adhesive composition for polarizing plate and polarizing plate with adhesive layer

The present invention relates to an adhesive composition for a polarizing plate, a polarizing plate with an adhesive layer, and the like.

A liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates (for example, a glass plate). A polarizing plate is attached to the surface of the substrate constituting the liquid crystal cell via the adhesive layer. In the past, in order to improve mechanical properties and optical durability, a polarizing plate has a structure in which a polarizer protective film such as a cellulose triacetate film is laminated on both sides of a polarizer having a polarizing function.

In recent years, it has been desired to reduce the thickness of the liquid crystal cell and to reduce the thickness of the polarizing plate. In order to reduce the thickness of the polarizing plate, it has been attempted to omit the polarizing film protective film formed on both sides of the polarizing plate. However, when the adhesive layer is in direct contact with the polarizer, in a high-temperature, high-humidity heat environment, with the thermal contraction of the polarizer, a large stress is applied to the adhesive layer, and there is a problem such as peeling of the polarizing plate. problem.

Patent Document 1 describes a polarizing plate with an adhesive layer which is provided on at least one side of a polarizer and also has polarizer protection. The adhesive layer of the function of the film, wherein the adhesive layer is formed by a reaction product of an acrylic copolymer having a reactive functional group and a crosslinking agent having a functional group reactive with the reactive functional group. However, in the configuration of Patent Document 1, the heat resistance and the moist heat resistance of the pressure-sensitive adhesive layer are insufficient, and further improvement is expected.

[Previous Technical Literature] [Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-128099

An object of the present invention is to provide an adhesive composition for a polarizing plate which can form an adhesive layer which is applicable to at least one of a polarizer protective film which is usually formed on both sides of a polarizer. The structure is excellent in durability.

The inventors of the present invention have carefully studied in order to solve the above problems. As a result, it has been found that the above problems can be solved by using an adhesive composition for a polarizing plate having the following specific constitution, and thus the present invention has been completed.

The present invention is, for example, the following [1] to [6].

[1] An adhesive composition for a polarizing plate, which is used for forming an adhesive layer in direct contact with a polarizer, characterized by comprising (A) (meth)acrylic copolymer and (B) isocyanate crosslinking. a crosslinking agent (B) containing 10 to 40 parts by mass based on 100 parts by mass of the copolymer (A); The copolymer (A) contains 10 to 30% by mass of an alkyl (meth)acrylate (a1) having a glass transition temperature of 0 ° C or higher, and a carboxyl group-containing monomer and a carboxyl group-containing monomer. The monomer component of the crosslinkable functional group-containing monomer (a2) is copolymerized in an amount of 0.1 to 5% by mass, and the weight average molecular weight of the copolymer (A) by gel permeation chromatography is 600,000 or less. And the glass transition temperature is -80 to 0 °C.

[2] An adhesive layer for a polarizing plate, which is formed of the adhesive composition according to the above [1].

[3] The adhesive layer for a polarizing plate according to the above [2], wherein the storage elastic modulus at 23 ° C is 0.50 MPa or more, and the storage elastic modulus at 85 ° C is 0.10. Above MPa.

[4] The adhesive layer for a polarizing plate according to the above [2] or [3], wherein the gel fraction is 80% by mass or more.

[5] An adhesive sheet for a polarizing plate, which has the adhesive layer according to any one of the above [2] to [4].

[6] A polarizing plate with an adhesive layer, which has an adhesive layer as described in any one of the above [2] to [4], which is laminated on at least one side of the polarizer.

According to the present invention, it is possible to provide an adhesive composition for a polarizing plate capable of forming an adhesive layer which is applicable to at least one of a polarizer protective film which is usually formed on both sides of a polarizer. The structure is excellent in durability. Further, an adhesive layer for a polarizing plate formed of the above composition, an adhesive sheet for a polarizing plate having the above-mentioned adhesive layer, and a polarizing plate having an adhesive layer of the above-mentioned adhesive layer can be provided.

Hereinafter, the adhesive composition for a polarizing plate, the adhesive layer for a polarizing plate, the adhesive sheet for a polarizing plate, and a polarizing plate with an adhesive layer will be described. In the following, the adhesive composition for a polarizing plate, the adhesive layer for a polarizing plate, and the adhesive sheet for a polarizing plate of the present invention are also referred to as "adhesive composition", "adhesive layer", and "adhesive sheet", respectively.

[Adhesive Composition for Polarizing Plate]

The adhesive composition for a polarizing plate of the present invention contains the (meth)acrylic copolymer (A) and the isocyanate crosslinking agent (B) described below. The composition may contain at least one selected from the group consisting of a decane coupling agent (C) and an antistatic agent (D), and may also contain an organic solvent (E).

[(Meth)acrylic copolymer (A)]

The (meth)acrylic copolymer (A) contains a copolymer of the following monomer components (a1) and (a2): an alkyl (meth)acrylate (a1), and a glass transition temperature (Tg) of the homopolymer. a monomer (a2) having a crosslinkable functional group containing a hydroxyl group-containing monomer and a carboxyl group-containing monomer; and the copolymer (A) is a monomer component (a1) and (a2) Copolymerization. The aforementioned copolymer (A) usually has come The constituent unit of the alkyl (meth)acrylate (a1) and the constituent unit derived from the monomer (a2) containing a crosslinkable functional group.

In the present specification, acrylic acid and methacrylic acid are also collectively referred to as "(meth)acrylic acid". Further, the constituent unit derived from a certain monomer a contained in the polymer is also referred to as "monomer a unit". Further, the alkyl (meth)acrylate (a1) and the monomer (a2) having a crosslinkable functional group are also referred to as "monomer (a1)" and "monomer (a2)".

The glass transition temperature (Tg) of the homopolymer of (meth)acrylic acid alkyl ester is a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003).

"alkyl (meth) acrylate (a1)"

The monomer (a1) is an alkyl (meth)acrylate having a Tg of a homopolymer of 0 ° C or higher. It is preferred that the homopolymer has a Tg of from 0 to 200 ° C, and particularly preferably a monomer having a Tg of from 0 to 50 ° C.

When the copolymer (A) obtained by copolymerizing the monomer (a1) having a high Tg of the homopolymer is used, and the isocyanate crosslinking agent (B) is used in a large amount, it can be formed at normal temperature (23 ° C) and high temperature. The storage elastic modulus in (85 ° C) is a high adhesive layer. Therefore, even when the adhesive layer is directly laminated on the polarizer, the adhesive layer caused by the thermal contraction of the polarizer in a high-temperature, high-humidity heat environment caused by the high storage elastic modulus of the adhesive layer can be suppressed. The phenomenon of floating or peeling.

In the monomer (a1), for example, a compound represented by CH ₂ =CR ¹ -COOR ² may, for example, be a compound having a Tg of 0 ° C or higher. In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 16 carbon atoms. The alkyl group preferably has 1 to 4 carbon atoms.

Examples of the monomer (a1) include methyl acrylate (8 ° C), propyl acrylate (3 ° C), butyl acrylate (43 ° C), amyl acrylate (22 ° C), and acrylic acid. Alkyl acrylate such as tetraalkyl ester (24 ° C), cetyl acrylate (35 ° C); methyl methacrylate (105 ° C), ethyl methacrylate (65 ° C), propyl methacrylate (35 ° C ), isopropyl methacrylate (81 ° C), butyl methacrylate (118 ° C), n-butyl methacrylate (20 ° C), isobutyl methacrylate (48 ° C), methacrylic acid An alkyl methacrylate such as cetyl ester (15 ° C). The values in parentheses show the Tg of the homopolymer of each monomer.

The monomer (a1) may be used alone or in combination of two or more.

The monomer (a1) is used in an amount of 10 to 30% by mass, preferably 15 to 25% by mass, particularly preferably 18 to 22% by mass, based on 100% by mass of the monomer component of the copolymer (A). The copolymer (A) obtained by copolymerizing the monomer (a1) in the above range is cured by a large amount of the isocyanate crosslinking agent (B), whereby an adhesive layer having a high elastic modulus can be formed.

"Crosslinking functional group-containing monomer (a2)"

Forming the monomer component of the copolymer (A), further comprising: a monomer having a crosslinkable functional group reactive with the isocyanate crosslinking agent (B), that is, a monomer having a crosslinkable functional group (a2) .

The monomer (a2) having a crosslinkable functional group may, for example, be a hydroxyl group-containing monomer, an acid group-containing monomer, an amine group-containing monomer, or a guanamine-containing group. Monomer, nitrogen-containing heterocyclic monomer, cyano group-containing monomer. In the present specification, examples of the acid group include a carboxyl group, an acid anhydride group, a phosphoric acid group, and a sulfuric acid group.

In the present invention, the monomer (a2) is a combination of a hydroxyl group-containing monomer and a carboxyl group-containing monomer. The monomer (a2) is preferably a hydroxyl group-containing monomer and a carboxyl group-containing monomer.

The adhesive layer having a high modulus of elasticity is stored, and the adhesion to the polarizer (the wettability of the adhesive composition to the polarizer) sometimes decreases. In the present invention, since the copolymer (A) is obtained by using a hydroxyl group-containing monomer and a carboxyl group-containing monomer in combination and copolymerization, it is possible to suppress a decrease in the adhesion (wettability) of the obtained pressure-sensitive adhesive layer.

The hydroxyl group-containing monomer (excluding the monomer having a carboxyl group from the hydroxyl group-containing monomer) may, for example, be a hydroxyl group-containing (meth) acrylate, and specific examples thereof include 2-hydroxyethyl (meth)acrylate. Ester, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, etc. (methyl) Hydroxyalkyl acrylate. The hydroxyalkyl group in the hydroxyalkyl (meth) acrylate has a carbon number of 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(methyl)propenyloxyethyl succinate, and ω-carboxyl groups. A carboxyl group-containing (meth) acrylate such as polycaprolactone mono(meth)acrylate; acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid.

Examples of the acid anhydride group-containing single system include maleic anhydride and itaconic anhydride. The mono-system containing a phosphate group may, for example, be a (meth)acrylic monomer having a phosphate group in a side chain, and a single system containing a sulfate group may, for example, A (meth)acrylic monomer having a sulfate group in its side chain is exemplified.

The amine group-containing monomer may, for example, be an amino group-containing (meth) acrylate such as dimethylaminoethyl (meth)acrylate or diethylamine ethyl (meth)acrylate. Examples of the mercapto group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, and N-propyl (A). Base) acrylamide, N-hexyl (meth) acrylamide. Examples of the monomer containing a nitrogen-containing hetero ring include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

Two or more types of monomers (a2) may be used, and three or more types may be used.

The monomer (a2) containing a crosslinkable functional group is used in an amount of from 0.1 to 5% by mass, preferably from 1 to 5% by mass, particularly preferably from 2 to 100% by mass of the monomer component of the copolymer (A). 4% by mass. When the amount of the monomer (a2) is at most the above upper limit value, the crosslinking density formed by the copolymer (A) and the crosslinking agent (B) is not excessively high, and an adhesive layer excellent in stress relaxation properties can be obtained. When the amount of the monomer (a2) is at least the above lower limit value, the bonded structure can be effectively formed, and an adhesive layer having an appropriate strength at normal temperature can be obtained.

The amount of the carboxyl group-containing monomer is preferably from 300 to 2400 parts by mass, particularly preferably from 500 to 2200 parts by mass, more preferably from 800 to 2000 parts by mass, per 100 parts by mass of the hydroxyl group-containing monomer.

Other Monomers

The monomer component forming the copolymer (A) preferably contains a homopolymer having a Tg of less than 0 ° C from the viewpoint of maintaining wettability as an adhesive. Alkyl acrylate (a3). That is, the copolymer (A) preferably has a constituent unit derived from an alkyl (meth)acrylate (a3). The alkyl (meth)acrylate (a3) is also referred to as "monomer (a3)".

In the case of the monomer (a3), for example, a compound represented by CH ₂ =CR ³ -COOR ⁴ may be a compound in which the homopolymer has a Tg of less than 0 °C. In the formula, R ³ is a hydrogen atom or a methyl group, and R ⁴ is an alkyl group having 2 to 16 carbon atoms. The alkyl group preferably has 2 to 8 carbon atoms.

Examples of the monomer (a3) include ethyl acrylate (-24 ° C), isopropyl acrylate (-3 ° C), n-butyl acrylate (-50 ° C), and isobutyl acrylate (-40). °C), hexyl acrylate (-57 ° C), octyl acrylate (-65 ° C), isooctyl acrylate (-58 ° C), 2-ethylhexyl acrylate (-70 ° C), decyl acrylate (-58 °C), alkyl acrylate such as lauryl acrylate (-3 ° C); amyl methacrylate (-5 ° C), hexyl methacrylate (-5 ° C), octyl methacrylate (-20 ° C), A Isooctyl acrylate (-45 ° C), 2-ethylhexyl methacrylate (-10 ° C), isodecyl methacrylate (-41 ° C), lauryl methacrylate (-65 ° C), A An alkyl methacrylate such as tetradecyl acrylate (-72 ° C). The values in parentheses show the Tg of the homopolymer of each monomer.

In the case where 100% by mass of the monomer component of the copolymer (A) is formed, the amount of the monomer (a3) is preferably from 65 to 89.9% by mass, particularly preferably 70, from the viewpoint of maintaining wettability as an adhesive. It is up to 84% by mass, more preferably from 75 to 80% by mass.

Further, the monomer component forming the copolymer (A) may contain, for example, an alkoxyalkyl (meth)acrylate or a mono(meth)acrylate, within a range not impairing the physical properties of the copolymer (A). Oxyalkyl alkane ester, alicyclic Other (meth) acrylates such as (meth) acrylates of aromatic or aromatic rings. That is, the copolymer (A) may further have a constituent unit derived from the other (meth) acrylate described above.

Examples of the alkoxyalkyl (meth)acrylate include methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate. Ester, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxy (meth)acrylate Butyl ester.

Examples of the mono(meth)acrylic alkoxypolyalkylene glycol esters include methoxybisethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, and mono(A). Ethylene ethoxylated triethylene glycol acrylate, ethoxylated diethylene glycol mono(meth)acrylate, methoxytriethylene glycol mono(meth)acrylate.

Examples of the (meth) acrylate containing an alicyclic group or an aromatic ring include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate. The light leakage resistance of the adhesive layer can be improved by using an aromatic ring-containing (meth) acrylate.

In the case where 100% by mass of the monomer component of the copolymer (A) is formed, the total amount of the other (meth) acrylate is preferably 40% by mass or less, and particularly preferably 20% by mass or less.

Further, the monomer component forming the copolymer (A) may contain, for example, a copolymerizable monomer such as a styrene monomer or vinyl acetate, within a range not impairing the physical properties of the copolymer (A). That is, the copolymer (A) may further have a constituent unit derived from the above-mentioned copolymerizable monomer.

Examples of the styrene monomer include styrene; methyl styrene, dimethyl styrene, trimethyl styrene, propyl styrene, butyl styrene, hexyl styrene, and heptyl styrene. Alkyl styrene such as octyl styrene; halogenated styrene such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodine styrene; nitrostyrene, ethyl styrene styrene, methoxy benzene Ethylene and the like.

In 100% by mass of the monomer component of the copolymer (A), the total amount of the above-mentioned copolymerizable monomer is preferably 40% by mass or less, and particularly preferably 20% by mass or less.

The other single system may be used alone or in combination of two or more.

<<Production Conditions of (Meth)Acrylic Copolymer (A)>>

The production conditions of the (meth)acrylic copolymer (A) are not particularly limited, and can be produced, for example, by a solution polymerization method. Specifically, a polymerization solvent, a monomer component, and a chain transfer agent as necessary are charged into a reaction vessel, and a polymerization initiator is added in an inert gas atmosphere such as nitrogen to set the reaction initiation temperature to usually 40 to 100. °C, preferably 50 to 80 ° C, and the reaction system is maintained at a temperature of usually 50 to 90 ° C, preferably 70 to 90 ° C, for 4 to 20 hours. Further, in the above polymerization reaction, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be appropriately added.

The copolymer (A) is obtained, for example, by copolymerizing the above monomer components, and may be a random copolymer or a block copolymer. Among these, A random copolymer is preferred.

Examples of the polymerization solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; and cyclopentane, cyclohexane, and cycloheptane. An alicyclic hydrocarbon such as an alkane or a cyclooctane; diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, benzene Ethers such as diethyl ether and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, chlorobenzene; ethyl acetate, propyl acetate, butyl acetate, methyl propionate, etc. Esters; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone; N,N-dimethylformamide, N,N-dimethylacetamidine Amidoxines such as amines and N,N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and anthraquinones such as dimethyl hydrazine and cyclobutyl hydrazine. These polymerization solvents may be used alone or in combination of two or more.

Examples of the chain transfer agent include n-dodecyl mercaptan and α-methylstyrene dimer. The molecular weight of the produced copolymer (A) can be controlled by using a chain transfer agent. These chain transfer agents may be used alone or in combination of two or more.

The chain transfer agent can be used in an amount of usually 0.1 part by mass or less, preferably 0.01 to 0.09 part by mass, per 100 parts by mass of the monomer component of the (meth)acryl-based copolymer (A).

Examples of the polymerization initiator include an azo initiator and a peroxide initiator. Specific examples thereof include an azo compound such as 2,2'-azobisisobutyronitrile; a peroxide such as benzamidine peroxide or lauric acid peroxide. Among these, an azo compound is preferred. Examples of the azo compound are exemplified 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2- Cyclopropylpropionitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-even Nitrogen bis(cyclohexane-1-carbonitrile), 2-(aminomercaptoazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2-formamidinylpropane) dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylcarbenyl), 2,2'- Azobis[2-methyl-N-(2-hydroxyethyl)-propanamide], dihydrated 2,2'-azobis(isobutylamine), 4,4'-azobis Azo such as (4-cyanovaleric acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methylpropionate) Compound. These polymerization initiators may be used alone or in combination of two or more.

The polymerization initiator is usually used in an amount ranging from 0.01 to 5 parts by mass, preferably from 0.01 to 3 parts by mass, per 100 parts by mass of the monomer component forming the (meth)acryl-based copolymer (A). use.

"Physical properties and content of (meth)acrylic copolymer (A)"

The weight average molecular weight (Mw) of the (meth)acrylic copolymer (A) measured by a gel permeation chromatography (GPC) method is preferably 600,000 or less in terms of polystyrene, preferably 300,000 to 580,000, especially 400,000 to 550,000.

The adhesive layer having a high modulus of elasticity is stored, and the adhesion to the polarizer (the wettability of the adhesive composition to the polarizer) sometimes decreases. In the present invention, since the copolymer (A) has the Mw in the above range, the adhesion (wetability) of the obtained adhesive layer can be suppressed from being lowered.

(meth)acrylic copolymer (A) as measured by GPC method The molecular weight distribution (Mw/Mn) obtained is usually 10 or less, preferably 1 to 5, and particularly preferably 1 to 3.

The glass transition temperature (Tg) of the (meth)acrylic copolymer (A) can be calculated, for example, from the monomer unit constituting the copolymer and the content ratio thereof according to the formula of Fox. For example, the (meth)acrylic copolymer can be synthesized in such a manner that the glass transition temperature (Tg) obtained by the calculation formula according to Fox is usually -80 to 0 ° C, preferably -60 to -30 ° C. (A). By using the (meth)acrylic copolymer (A) having such a glass transition temperature (Tg), an adhesive composition excellent in adhesion at normal temperature can be obtained.

Fox's 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 (unit: K) of the (meth)acrylic copolymer (A), and Tg ₁ , Tg ₂ , ‧ ‧ and Tg _m are homopolymers composed of each monomer The glass transition temperature (unit: K), W ₁ , W ₂ , ‧ ‧ , W _m is the weight fraction of the constituent unit derived from each monomer in the copolymer (A). The weight fraction of the constituent units derived from the respective monomers can be used for the ratio of the loading of each monomer to the total monomers when the copolymer is synthesized.

In the above formula of Fox, the glass transition temperature of the homopolymer composed of each monomer can be, for example, a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003).

In the adhesive composition of the present invention, (meth)acrylic acid The content of the copolymer (A) is usually from 60 to 90% by mass, particularly preferably from 70 to 89.9% by mass, particularly preferably from 80 to 100% by mass based on 100% by mass of the solid content of the organic solvent (E). 89.5 mass%. When the content of the (meth)acrylic copolymer (A) is in the above range, a balance of properties as an adhesive can be obtained, and the adhesive property is excellent.

[Isocyanate crosslinking agent (B)]

The adhesive composition of the present invention further contains an isocyanate crosslinking agent (B).

The isocyanate crosslinking agent (B) is usually an isocyanate compound having 2 or more isocyanate groups in one molecule. By crosslinking the (meth)acrylic copolymer (A) with the isocyanate crosslinking agent (B), a crosslinked body (network polymer) can be formed.

The isocyanate crosslinking agent (B) has an isocyanate group number of usually 2 or more, preferably 2 to 8, and more preferably 3 to 6. When the number of isocyanate groups is in the above range, from the viewpoint of the crosslinking reaction efficiency of the (meth)acrylic copolymer (A) and the isocyanate crosslinking agent (B), and the viewpoint of maintaining the flexibility of the adhesive layer, good.

The isocyanate compound having an isocyanate group number of 2 in one molecule may, for example, be an aliphatic diisocyanate, an alicyclic diisocyanate or an aromatic diisocyanate. Examples of the aliphatic diisocyanate include ethyl diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, and 3 -Methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene An aliphatic diisocyanate having 4 to 30 carbon atoms such as isocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogen tetramethylate. An alicyclic diisocyanate having 7 to 30 carbon atoms such as xylene diisocyanate. Examples of the aromatic diisocyanate include carbon number such as phenylene diisocyanate, toluene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate. 8 to 30 aromatic diisocyanates.

The isocyanate compound having 3 or more isocyanate groups in one molecule may, for example, be an aromatic polyisocyanate, an aliphatic polyisocyanate or an alicyclic polyisocyanate. Specific examples thereof include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4',4"-triphenylmethane triisocyanate.

Further, the isocyanate crosslinking agent (B) may, for example, be a polymer of the above isocyanate compound having an isocyanate group number of 2 or more (for example, a dimer or a trimer, a biuret or a isocyanuric acid). A compound, a derivative (for example, an addition reaction product of a polyhydric alcohol and two or more molecules of a diisocyanate compound), a polymer, or the like. Examples of the polyhydric alcohol in the above-mentioned derivative include a trihydric or higher alcohol such as trimethylolpropane, glycerin or neopentyl alcohol. Examples of the high molecular weight polyhydric alcohol include polyether polyol and polycondensation. Ester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol.

Examples of such an isocyanate compound include diphenyl a trimer of methane diisocyanate, a polymethylene polyphenyl polyisocyanate, a bishexamethylene diisocyanate or a toluene diisocyanate of a toluene diisocyanate, a trimethylolpropane and a toluene diisocyanate or a reaction product of xylene diisocyanate (for example, a three-molecular adduct of toluene diisocyanate or xylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, hexamethylene diisocyanate) The three-molecular adduct), polyether polyisocyanate, polyester polyisocyanate.

From the viewpoint of improving the light leakage resistance of the adhesive layer, the isocyanate crosslinking agent (B) is preferably a compound having a benzene nucleus. For example, an aromatic diisocyanate, a polymer or derivative of an aromatic diisocyanate, a polymer, and an aromatic polyisocyanate are mentioned.

In the isocyanate crosslinking agent (B), from the viewpoint of improving the ripening property and light leakage resistance, a reaction product of trimethylolpropane with toluene diisocyanate or xylene diisocyanate is preferred. Tri-isocyanate of toluene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., 2050, etc.).

The isocyanate-based crosslinking agent (B) may be used alone or in combination of two or more.

In the adhesive composition of the present invention, the isocyanate crosslinking agent (B) is contained in an amount of 10 to 40 parts by mass, preferably 10 to 15 parts by mass based on 100 parts by mass of the (meth)acrylic copolymer (A). Share. When the content is in the above range, a highly hard adhesive layer can be formed, and the phenomenon that the adhesive layer floats or peels off during thermal contraction of the polarizer can be suppressed.

[decane coupling agent (C)]

The adhesive composition of the present invention preferably further contains a decane coupling agent (C). The decane coupling agent (C) is used to firmly adhere the adhesive layer to a adherend such as a glass plate to help prevent peeling in a high-humidity environment.

Examples of the decane coupling agent (C) include a polymerizable unsaturated group-containing decane coupling agent such as vinyltrimethoxydecane, vinyltriethoxysilane or methacryloxypropyltrimethoxydecane. 3-glycidoxypropyltrimethoxydecane, 3-glycidoxypropyltriethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, 3-ring An epoxy group-containing decane coupling agent such as oxypropoxypropylmethyldiethoxy decane or 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane; 3-aminopropyltrimethoxy Baseline, N-(2-aminoethyl)-3-aminopropyltrimethoxydecane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane, etc. A halogen-containing decane coupling agent such as an amine group-containing decane coupling agent; 3-chloropropyltrimethoxy decane.

In the adhesive composition of the present invention, the content of the decane coupling agent (C) is usually 1 part by mass or less, preferably 0.01 to 1 part by mass, based on 100 parts by mass of the (meth)acryl-based copolymer (A). It is particularly preferably from 0.05 to 0.5 parts by mass. When the content is in the above range, it tends to prevent peeling of the polarizing plate in a high-humidity heat environment or bleed out of the decane coupling agent (C) in a high-temperature environment.

[Antistatic agent (D)]

The antistatic agent (D) can be used, for example, to reduce the adhesive group of the present invention. The surface resistance value of the adhesive layer formed by the product. Examples of the antistatic agent (D) include a surfactant, an ionic compound, and a conductive polymer.

Examples of the surfactant include a 4-stage ammonium salt, a guanamine 4-grade ammonium salt, a pyridinium salt, and a cationic surfactant having a cationic group such as a 1st to a third amine group; Anionic surfactants such as an anionic group such as a sulfonate group or a phosphate group; an alkylbetaine, an alkylimidazolium betaine, an alkylamine oxide, an amino acid sulfate, etc. Sexual surfactants, glycerol fatty acid esters, sorbitan fatty acid esters, polyoxyethylidene amines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkane A nonionic surfactant such as a base amine or an alkyl diethanolamine.

Further, as the surfactant, a reactive emulsifier having a polymerizable group may be used, and a polymerization of a monomer component containing the above surfactant or reactive emulsifier may be used. System surfactant.

The ionic compound is composed of a cationic portion and an anionic portion, and may be either solid or liquid at room temperature (23 ° C / 50% RH).

The cation portion constituting the ionic compound may be either or both of an inorganic cation or an organic cation. The inorganic cation is preferably an alkali metal ion or an alkaline earth metal ion, and particularly preferably Li ⁺ , Na ⁺ and K ⁺ having excellent antistatic properties. Examples of the organic cation system include a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a dihydropyrrole cation, a pyrrole cation, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, and a pyrazolium cation. And pyrazolinium cations, tetraalkylammonium cations, trialkylsulfonium cations, tetraalkylphosphonium cations and derivatives thereof.

The anion portion constituting the ionic compound is not particularly limited as long as it can be ionically bonded to the cation portion to form an ionic compound. Specific examples thereof include 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 H 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 ^- . Among these, an anion containing a fluorine atom is preferred because it can impart an ionic compound having a low melting point, and particularly preferably (F ₂ SO ₂ ) ₂ N ^- and (CF ₃ SO ₂ ) ₂ N ^- .

The ionic compound is preferably lithium bis(trifluoromethanesulfonyl) phthalimide, lithium bis(difluorosulfonyl) ruthenium, lithium tris(trifluoromethanesulfonyl)methane, bis(trifluoromethane) Sulfonyl) sulfinium imide, potassium bis(difluorosulfonyl) sulfinium imide, 1-ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl hexafluorophosphate -4-methylpyridinium salt, 1-octyl-4-methylpyridinium hexafluorophosphate, bis(fluorosulfonyl) quinone imine 1-octyl-4-methylpyridinium salt, double Trifluoromethanesulfonyl) quinone imine 1-octyl-4-methylpyridinium salt, tetrafluoroboric acid (N,N-diethyl-N-methyl-N-(2-methoxyethyl) Ammonium, bis(trifluoromethanesulfonyl) quinone imine N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium, quinone imine 1-octylpyridinium Fluoranthene, 1-octyl-3-methylpyridinium, quinoneimine trifluorofluorene.

Examples of the conductive polymer include polythiophene and polyphenylene. Amines, polypyrroles and derivatives thereof.

In the 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 3 parts by mass, per 100 parts by mass of the (meth)acrylic copolymer (A). More preferably, it is 0.05 to 2.5 parts by mass.

[Organic solvent (E)]

In order to adjust the coatability, the adhesive composition of the present invention preferably contains an organic solvent (E). The organic solvent is a polymerization solvent described in the column of the (meth)acrylic copolymer (A). For example, the polymer solution containing the (meth)acrylic copolymer (A) and the polymerization solvent obtained by the above copolymerization may be mixed with the crosslinking agent (B) to prepare an adhesive composition. In the adhesive composition of the present invention, the content of the organic solvent (E) is usually from 50 to 90% by mass, preferably from 60 to 85% by mass.

In the present specification, the term "solid content" means all components after the organic solvent (E) is deducted from the components of the adhesive composition, and the "solid content concentration" means the composition of the solid component relative to the adhesive. The ratio of 100% by mass of the substance.

[additive]

The adhesive composition of the present invention may contain, in addition to the above components, an antioxidant, a light stabilizer, a metal corrosion inhibitor, an adhesion promoter, a plasticizer, and the like, within a range not impairing the effects of the present invention. One combination of a co-promoter, a (meth)acrylic polymer other than the above (A), and a rework agent or 2 or more types.

[Modulation of Adhesive Composition for Polarizing Plate]

The adhesive composition of the present invention can be prepared by mixing a (meth)acrylic copolymer (A) with an isocyanate crosslinking agent (B) and other components as necessary by a general method known in the art. For example, the isocyanate crosslinking agent (B) and other components necessary for the preparation of the (meth)acrylic copolymer (A) can be blended in a polymerization solution containing the polymer.

The adhesive composition of the present invention is used to form an adhesive layer in direct contact with a polarizer. For example, the above composition is suitable for use in bonding a substrate (for example, a glass plate) constituting a liquid crystal cell to a polarizer.

[Adhesive layer for polarizing plate]

The adhesive layer for a polarizing plate of the present invention is formed of the above-described adhesive composition. By using the adhesive composition of the present invention, an adhesive layer having the following storage elastic modulus characteristics can be formed.

The storage elastic layer of the present invention preferably has a storage elastic modulus (G'1) at 23 ° C of 0.5 MPa or more, particularly preferably 0.60 to 1.50 MPa, particularly preferably 0.70 to 1.20 MPa; and storage at 85 ° C. The modulus of elasticity (G'2) is preferably 0.10 MPa or more, particularly preferably 0.20 to 0.80 MPa, and particularly preferably 0.30 to 0.50 MPa.

The storage elastic modulus is, for example, that the adhesive layers are bonded to each other a plurality of times to form a laminate having a thickness of about 1.0 mm, and The value calculated in the dynamic viscoelastic spectrum measured by the laminate.

When the storage elastic modulus (G'1) at 23 ° C is in the above range, the adhesive layer of the present invention is excellent in hardness at normal temperature and improves workability. For example, when the adhesive layer is cut, it is possible to prevent the adhesive from adhering to the cutting edge or the drawing of the adhesive layer.

When the adhesive layer is directly laminated on the polarizer, a large stress is applied in the high-temperature, high-humidity heat environment due to thermal contraction of the polarizer, and thus problems such as floating or peeling from the polarizing plate are likely to occur. By setting the storage elastic modulus (G'2) at 85 ° C to the above range, this problem can be prevented even when the polarizer is thermally contracted.

The adhesive layer formed of the adhesive composition of the present invention preferably has a gel fraction of 80% by mass or more, and particularly preferably 80, from the viewpoints of strain suppression, cohesive force, adhesion, and removability of the polarizing plate. It is 98% by mass, more preferably 85 to 95% by mass. When the gel fraction is in the above range, the adhesive layer can exhibit excellent durability.

The adhesive layer of the present invention is, for example, a crosslinking reaction in the above-mentioned adhesive composition, specifically, a (meth)acrylic copolymer (A) by an isocyanate crosslinking agent (B). Get it by cross-linking.

The conditions for forming the adhesive layer are, for example, those described below. The adhesive composition of the present invention is applied to a support, although it varies depending on the kind of the solvent, but is usually 50 to 150 ° C, preferably 60 to 100 ° C, usually dried for 1 to 10 minutes, preferably 2 to dry. The solvent was removed in 7 minutes to form a coating film. The film thickness of the dried coating film is usually from 5 to 75 μm, preferably from 10 to 50 μm.

The adhesive layer is preferably formed by the following conditions. Applying the adhesive composition of the present invention to a support, and attaching a cover film to the coating film formed under the above conditions, usually for 3 days or longer, preferably 7 to 10 days, and The aging is usually carried out at 5 to 60 ° C, preferably 15 to 40 ° C, usually in an environment of 30 to 70% RH, preferably 40 to 70% RH. When cross-linking is carried out under the above-mentioned ripening conditions, the cross-linking (network polymer) can be efficiently formed.

The coating method of the adhesive composition can be a generally known method, for example, by a spin coating method, a knife coating method, a roll coating method, a bar coating method, a blade coating method, or a die coating method. A method of applying and drying the film to a predetermined thickness, such as a gravure coating method.

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

[Adhesive sheet for polarizing plate]

The adhesive sheet for a polarizing plate of the present invention has an adhesive layer formed of the above-mentioned adhesive composition. The adhesive sheet may, for example, be a double-sided adhesive sheet having only the above adhesive layer; a double-sided adhesive sheet having a substrate and the above-mentioned adhesive layer formed on both sides of the substrate; and a substrate and a substrate; One side of the adhesive layer on one side of the adhesive sheet; and an adhesive sheet on which the cover film after the release treatment is applied is adhered to the surface of the adhesive layer of the adhesive sheet which is not in contact with the substrate.

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

The conditions for forming the adhesive layer are the same as those described in the column of [Adhesive Layer for Polarizing Plate].

The film thickness of the adhesive layer is usually 5 to 75 μm, preferably 10 to 50 μm from the viewpoint of maintaining adhesive properties. 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.

[Polarizer with Adhesive Layer]

The adhesive layer-attached polarizing plate of the present invention has an adhesive layer which is directly laminated on at least one side of the polarizer and which is formed of the adhesive composition of the present invention. In the present specification, the "polarizing plate" is used in the sense of including a "polarizing film".

As the polarizing plate, a conventionally known polarizing film can be used. For example, the polarizer itself and a multilayer film having a polarizer and a polarizer protective film disposed on the polarizer can be exemplified. In the present invention, since the adhesive layer is disposed in direct contact with the polarizer, a configuration in which the polarizer protective film is disposed only on one surface of the polarizer, and a polarizer protective film is not disposed on both surfaces of the polarizer The composition.

The polarizing film is, for example, a stretched film obtained by including a polarizing component in a film made of a polyvinyl alcohol-based resin and extending it. Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol and polyvinyl alcohol. A saponified product of a polyvinyl formal, a polyvinyl acetal, or an ethylene-vinyl acetate copolymer. Examples of the polarizing component include iodine or a dichroic dye.

The polarizer protective film may, for example, be a film made of a thermoplastic resin. Examples of the thermoplastic resin include cellulose resins such as cellulose triacetate, polyester resins, polyether oxime resins, polyfluorene resins, polycarbonate resins, polyamide resins, polyimide resins, and polyolefin resins. (meth)acrylic resin, cyclic polyolefin resin (northene-based resin), polyarylate resin, polystyrene resin, polyvinyl alcohol resin, and a mixture of two or more kinds selected from these resins.

The thickness of the polarizing plate is usually from 10 to 200 μm, preferably from 50 to 100 μm. In the present invention, since the polarizer protective film formed on the polarizer can be omitted, the thickness of the polarizing plate can be reduced.

In the present invention, the adhesive layer is formed by directly contacting the polarizer. The polarizing plate with an adhesive layer of the present invention includes, for example, a structure in which a polarizer protective film and a polarizer and the adhesive layer are sequentially laminated; the adhesive layer and the polarizer protective film are sequentially laminated; The polarizer and the adhesive layer are formed; the adhesive layer and the polarizer and the adhesive layer are laminated in this order. In such a configuration, the cover film may be disposed as the outermost layer on the adhesive layer.

The method of forming the adhesive layer on the surface of the polarizer is not particularly limited, and a method of directly applying the above-described adhesive composition to the surface of the polarizer using a bar coater or the like, followed by drying and aging; The adhesive for the polarizing plate of the polarizing plate of the present invention A method in which a layer is transferred to a surface of a polarizer and aged. The conditions for drying and aging, the range of the gel fraction, and the like are the same as those described in the column of [Adhesive Layer for Polarizing Plate].

The thickness of the adhesive layer is usually from 5 to 75 μm, preferably from 10 to 50 μm, in terms of dry film thickness. Further, the adhesive layer may be formed by contacting the polarizer on at least one surface of the polarizer, and examples thereof include an adhesive layer formed only on one surface of the polarizer and both sides of the polarizer. Formed with an adhesive layer.

Further, on the above polarizing plate, for example, a protective layer, an antiglare layer, a phase difference layer, a viewing angle lifting layer, or the like having other functions may be laminated.

A liquid crystal element was produced by disposing a polarizing plate of the adhesive layer of the present invention obtained as described above on the surface of a substrate of a liquid crystal cell. Here, the liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates.

The substrate of the liquid crystal cell is, for example, a glass plate. The thickness of the substrate is usually from 0.05 to 3 mm, preferably from 0.2 to 1 mm. The adhesive layer formed using the above adhesive composition is excellent in adhesion to the substrate (wet property of the adhesive composition to the substrate).

Example

The present invention will be more specifically described below based on examples, but the present invention is not limited to the examples. In the following description of the examples and the like, "parts" means "parts by mass" unless otherwise specified.

[GPC]

The (meth)acrylic copolymer was obtained by gel permeation chromatography (GPC method), and the weight average molecular weight (Mw) and the number average molecular weight (Mn) were determined under the following conditions.

‧Measurement device: HLC-8320GPC (manufactured by Tosoh Co., Ltd.)

‧GPC column structure: The following 4 series column (both made by Tosoh Co., Ltd.)

(1) TSKgel HxL-H (guard column, guard column)

(2) TSKgel GMHxL

(3) TSKgel GMHxL

(4)TSKgel G2500HxL

‧Flow rate: 1.0ml/min

‧column temperature: 40 ° C

‧ Sample concentration: 1.5% (w / v) (diluted with tetrahydrofuran)

‧Mobile phase solvent: tetrahydrofuran

‧Standard polystyrene conversion

[Synthesis Example 1]

20 parts of methyl acrylate, 0.2 parts of 2-hydroxyethyl acrylate, 3 parts of acrylic acid, 76.8 parts of n-butyl acrylate, 0.045 parts of n-dodecyl mercaptan and 100 parts of ethyl acetate solvent, and equipped with a stirrer and reflux cooling The temperature of the reactor, the thermometer, and the nitrogen gas introduction tube was raised to 65 ° C while introducing nitrogen gas. Next, 0.1 part of 2,2'-azobisisobutyronitrile was added, and polymerization was carried out at 65 ° C for 4 hours under a nitrogen atmosphere. After completion of the reaction, the mixture was diluted with ethyl acetate to prepare a polymer solution having a solid concentration of 30% by mass. Weight average molecular weight (Mw) of the obtained (meth)acrylic copolymer A1 It was 520,000 and the molecular weight distribution (Mw/Mn) was 2.4.

[Synthesis Examples 2 to 8]

The polymer solution having a solid 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) Modulation of adhesive composition

The polymer solution obtained in Synthesis Example 1 (solid content concentration: 30% by mass) and the (meth)acrylic copolymer A1 contained in the solution (100 parts by mass) were used as an isocyanate crosslinking agent. 12 parts (solid content) of "L-45" (solid content: 45 mass%) and "KBM-403" (solid content 100) manufactured by Shin-Etsu Chemical Co., Ltd. as a decane coupling agent The mass%) was mixed in an amount of 0.2 parts, and then the ethyl acetate solvent was added so that the solid content concentration became 25% by mass to obtain an adhesive composition.

(2) Production of adhesive sheets

The adhesive composition obtained in the above (1) was subjected to defoaming, and then applied to a polyethylene terephthalate film (PET film) subjected to release treatment using a blade coater, and dried at 90 ° C for 3 minutes. On the other hand, a coating film having a dry film thickness of 20 μm was formed. The PET film after the release treatment was further bonded to the surface of the coating film opposite to the bonding surface of the PET film, and allowed to stand in an environment of 23° C./50% RH for 7 days to be aged. An adhesive sheet having an adhesive layer having a thickness of 20 μm held in two PET films.

(3) Fabrication of a polarizing plate with an adhesive layer

The adhesive composition obtained in the above (1) was subjected to defoaming, and then applied to a polyethylene terephthalate film (PET film) which had been subjected to release treatment using a blade coater, and dried at 90 ° C for 3 minutes. And get a dry film thickness of 20μ A thin film of m coating film. A polyvinyl alcohol film surface of a polarizing plate (thickness: 60 μm) composed of a double layer composed of a polyvinyl alcohol film as a polarizer and a cellulose triacetate film as a polarizer protective film The contact was applied, and it was allowed to stand in an environment of 23 ° C / 50% RH for 7 days to be aged, thereby obtaining an adhesive layer having a PET film and an adhesive layer having a thickness of 20 μm and a polarizer and a polarizer protective film. Polarized plate.

[Examples 2 to 3, Comparative Examples 1 to 7]

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/or the composition of the formulation was changed as shown in Table 2 in the first embodiment. The adhesive composition, the adhesive sheet, and the polarizing plate with the adhesive layer are obtained.

[assessment] [Gel fraction]

From the adhesive sheets obtained in the examples and the comparative examples, about 0.1 g of the adhesive was collected into the sample bottle, and 30 mL of ethyl acetate was added and shaken for 4 hours, and then the contents of the sample bottle were filtered with a stainless steel gold mesh of 200 mesh, and The residue on the gold mesh was dried at 100 ° C for 2 hours, and the dry weight was measured. The gel fraction of the adhesive was determined by the following formula.

‧gel fraction (%) = (dry weight) / (adhesive collection weight) × 100 (%)

[Storage Elastic Modulus]

In the adhesive sheets obtained in the examples and the comparative examples, the adhesive layers having a thickness of 20 μm were bonded to each other in an environment of 23° C./50% RH, and The autoclave at 50 ° C / 5 atm was treated for 20 minutes to prepare an adhesive layer having a thickness of 1.0 mm. "Physica MCR300" manufactured by Anton Paar Co., Ltd., according to the dynamic viscoelasticity measurement method based on JIS K7244 (temperature range -40 to 160 ° C, temperature rising rate 3.67 ° C / min, frequency 1 Hz), the thickness is 1.0 mm The adhesive layer was measured for the viscoelastic spectrum to determine the storage elastic modulus at temperatures of 23 ° C and 85 ° C.

[Measurement of adhesion]

The polarizing plate with the adhesive layer obtained in the examples and the comparative examples (the laminated body composed of the PET film/adhesive layer/polarizing sheet/polarizing sheet protective film) was cut into a size of 70 mm×25 mm to prepare a test. sheet. The PET film was peeled off from the test piece, and a laminate of the adhesive layer/polarizer/polarizer protective film was applied to the glass plate having a thickness of 2 mm by using a pressure roller so that the adhesive layer was in contact with the glass plate. One side. The obtained laminate was kept in an autoclave adjusted to 50 ° C / 5 atm for 20 minutes. Then, after standing for 1 hour in an environment of 23 ° C / 50% RH, the end portion of the polarizing plate was pulled at a rate of 90° with respect to the glass plate at a speed of 300 mm/min, and the adhesion (peel strength) was measured. .

[Measurement of adhesion]

The polarizing plate with the adhesive layer obtained in the examples and the comparative examples (the laminated body composed of the PET film/adhesive layer/polarizing sheet/polarizing sheet protective film) was cut into a size of 70 mm×25 mm to prepare a test. sheet. The polarizer protective film of the test piece was rubbed with a finger, and the adhesion was performed by the following reference Observed.

AA: The adhesion of the adhesive layer from the polarizer was not confirmed.

BB: Confirm that the adhesive layer is peeled off from the polarizer

CC: Confirmed that the adhesive layer was peeled off from the polarizer

[Durability test (heat resistance, heat and humidity resistance test)]

The polarizing plate with the adhesive layer obtained in the examples and the comparative examples (the laminated body composed of the PET film/adhesive layer/polarizing sheet/polarizing sheet protective film) was cut into a size of 150 mm×250 mm to prepare a test. sheet. The PET film was peeled off from the test piece, and a laminate body composed of an adhesive layer/polarizer/polarizer protective film was attached to the glass having a thickness of 0.5 mm by using a pressure roller so that the adhesive layer was in contact with the glass plate. One side of the board. The obtained laminate was held in an autoclave adjusted to 50 ° C / 5 atm for 20 minutes to prepare a test plate. Make two identical test panels. The test plate was placed under conditions of a temperature of 80 ° C (heat resistance) or a temperature of 60 ° C / humidity of 90% RH (moisture resistance) for 500 hours, and foaming, floating, and the like were observed by the following criteria. The production of peeling is performed for evaluation.

AA: No appearance defects such as foaming, floating, peeling, etc. were observed.

BB: Only a few appearances such as foaming, floating, peeling, etc. were observed.

CC: Obvious failure in appearance such as foaming, floating, peeling, etc.

[Light leakage test]

Two polarizing plates with an adhesive layer obtained in the examples and the comparative examples (a laminate composed of a PET film/adhesive layer/polarizer/polarizer protective film) A test piece was produced by cutting to a size of 310 mm × 385 mm. The PET film was peeled off from the test piece, and a laminating body composed of an adhesive layer/polarizer/polarizer protective film was attached to the test piece so that the polarizing axes were orthogonal to each other and the adhesive layer was in contact with the glass plate. On both sides of a glass plate with a thickness of 0.5 mm. 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 at a temperature of 80 ° C for 500 hours, and observation of light leakage was performed by the following reference.

AA: No light leakage was observed

BB: I noticed some light leakage.

CC: Observed significant light leakage

Claims (6)

An adhesive composition for a polarizing plate, which is used for forming an adhesive layer in direct contact with a polarizer, characterized by comprising (A) a (meth)acrylic copolymer and (B) an isocyanate crosslinking agent; And the crosslinking agent (B) is contained in an amount of 10 to 40 parts by mass based on 100 parts by mass of the copolymer (A); the copolymer (A) is such that the glass transition temperature of the homopolymer is 0 ° C or more (A) 10 to 30% by mass of the alkyl acrylate (a1), and a monomer component having 0.1 to 5 mass% of the monomer (a2) containing the carboxyl group-containing monomer and the carboxyl group-containing monomer Further, the copolymer (A) has a weight average molecular weight of 600,000 or less by gel permeation chromatography, and a glass transition temperature of -80 to 0 °C. An adhesive layer for a polarizing plate is formed by the adhesive composition described in claim 1 of the patent application. The adhesive layer for a polarizing plate according to the second aspect of the invention is characterized in that the storage elastic modulus at 23 ° C is 0.50 MPa or more, and the storage elastic modulus at 85 ° C is 0.10 MPa or more. The adhesive layer for a polarizing plate according to the second or third aspect of the invention is a gel fraction of 80% by mass or more. An adhesive sheet for a polarizing plate, which is the adhesive layer according to any one of claims 2 to 4. A polarizing plate with an adhesive layer, which has a direct lamination on a polarizer The adhesive layer of any one of claims 2 to 4 of at least one of the claims.