TWI675083B - Adhesive composition for polarizing plate and polarizing plate with adhesive layer - Google Patents

Abstract

An object of the present invention is to provide an adhesive composition for a polarizing plate capable of forming an adhesive layer, which is applicable to at least one of the polarizer protective films that omit the double-sided polarizer usually formed on a polarizer. Structure and excellent durability.

The solution of the present invention is an adhesive composition for polarizing plates, which is used to form an adhesive layer in direct contact with a polarizer, and is characterized by containing (A) (meth) acrylic copolymer and (B) isocyanate. Based on 100 parts by mass of the copolymer (A), it contains 10 to 40 parts by mass of the cross-linking agent (B); the copolymer (A) is such that the glass transition temperature of the copolymer (A) is: 10 to 30% by mass of the alkyl (meth) acrylate (a1) above 0 ° C, and 0.1 to 5% by mass of the monomer (a2) containing a carboxyl group-containing monomer and a carboxyl group-containing crosslinkable functional group The monomer components are copolymerized, and the copolymer (A) has a weight average molecular weight of 600,000 or less obtained by gel permeation chromatography, and a glass transition temperature of -80 to 0 ° 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 an adhesive layer. In the past, in order to improve the mechanical properties and optical durability of polarizers, a polarizer having a polarizing function is generally used on both sides, and a structure of a polarizer protective film such as a cellulose triacetate film is laminated.

In recent years, it is expected to reduce the thickness of a liquid crystal cell and the thickness of a polarizing plate. To reduce the thickness of a polarizing plate, attempts have been made to omit a double-sided polarizer protective film formed on a polarizer. However, when the adhesive layer is in direct contact with the polarizer, in a high temperature and high humidity environment, accompanied by the thermal contraction of the polarizer, a large stress is applied to the adhesive layer, which may cause problems such as peeling of the polarizer. 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 a polarizer protection A functional adhesive layer of a film, the adhesive layer is formed by a reaction product of an acrylic copolymer having a reactive functional group and a cross-linking agent having a functional group capable of reacting with the reactive functional group. However, in the structure of Patent Document 1, the heat resistance and moisture and heat resistance of the adhesive layer are insufficient, and further improvements are expected.

[Prior technical literature] [Patent Literature]

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

An object of the present invention is to provide an adhesive composition for a polarizing plate capable of forming an adhesive layer, which is applicable to at least one of the polarizer protective films that omit the double-sided polarizer usually formed on a polarizer. Structure and excellent durability.

The present inventors have carefully studied in order to solve the above problems. As a result, it was found that the above-mentioned problems can be solved by using an adhesive composition for a polarizing plate having the following specific structure, and 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 to form an adhesive layer in direct contact with a polarizer, and is characterized by containing (A) (meth) acrylic copolymer and (B) isocyanate-based crosslink An agent; wherein 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); This copolymer (A) contains 10 to 30% by mass of an alkyl (meth) acrylate (a1) containing a homopolymer having a glass transition temperature of 0 ° C or higher, and a carboxyl group-containing monomer and a carboxyl group-containing monomer. Crosslinked functional group-containing monomer (a2) is obtained by copolymerizing 0.1 to 5% by mass of monomer components, and the copolymer (A) has a weight average molecular weight obtained by gel permeation chromatography of 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 as described in [1] above.

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

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

[6] A polarizing plate with an adhesive layer, which has the adhesive layer as described in any one of [2] to [4] above, which is directly 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 in which a double-sided polarizer usually formed on a polarizer is omitted. Structure and excellent durability. Further, an adhesive layer for a polarizing plate formed from the aforementioned composition, an adhesive sheet for a polarizing plate having the aforementioned adhesive layer, and a polarizing plate with an adhesive layer with the aforementioned adhesive layer can be provided.

The following describes the adhesive composition for polarizing plates, the adhesive layer for polarizing plates, the adhesive sheet for polarizing plates, and the polarizing plate with an adhesive layer of the present invention. Hereinafter, the adhesive composition for polarizing plates, the adhesive layer for polarizing plates, and the adhesive sheet for polarizing plates 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 polarizing plates of this invention contains the (meth) acrylic-type copolymer (A) and isocyanate-type crosslinking agent (B) demonstrated below. The said composition may contain at least 1 sort (s) chosen from a silane coupling agent (C) and an antistatic agent (D) as needed, and may also contain an organic solvent (E).

[(Meth) acrylic copolymer (A)]

The (meth) acrylic copolymer (A) is a copolymer containing the following monomer components (a1) and (a2): an alkyl (meth) acrylate (a1), and a glass transition temperature (Tg) of a homopolymer thereof ) Is 0 ° C or higher; and a crosslinkable functional group-containing monomer (a2) containing a hydroxyl-containing monomer and a carboxyl-containing monomer; and the copolymer (A) is a mixture of the aforementioned monomer components (a1) and (a2) Copolymerized. The aforementioned copolymer (A) usually has From the structural unit of the said (meth) acrylic acid alkyl ester (a1) and the structural unit derived from the crosslinkable functional group containing monomer (a2).

In this specification, acrylic acid and methacrylic acid are collectively referred to as "(meth) acrylic acid". Moreover, the structural unit derived from a certain monomer a contained in a polymer is also described as a "monomer a unit". In addition, the alkyl (meth) acrylate (a1) and the crosslinkable functional group-containing monomer (a2) are also referred to as "monomer (a1)" and "monomer (a2)".

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

`` (Meth) acrylate (a1) ''

The monomer (a1) is an alkyl (meth) acrylate whose Tg is 0 ° C or higher. The aforementioned monomers having a Tg of 0 to 200 ° C are preferred, and the aforementioned monomers having a Tg of 0 to 50 ° C are particularly preferred.

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

The monomer (a1) includes, for example, a compound represented by CH ₂ = CR ¹ -COOR ² , and a compound having a Tg of a homopolymer 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 carbon number of the aforementioned alkyl group is preferably 1 to 4.

The monomer (a1) includes, for example, methyl acrylate (8 ° C), propyl acrylate (3 ° C), tertiary butyl acrylate (43 ° C), amyl acrylate (22 ° C), and acrylic acid ten. Alkyl acrylates such as tetraalkyl esters (24 ° C), cetyl acrylate (35 ° C); methyl methacrylate (105 ° C), ethyl methacrylate (65 ° C), propyl methacrylate (35 ° C ), Isopropyl methacrylate (81 ° C), tertiary butyl methacrylate (118 ° C), n-butyl methacrylate (20 ° C), isobutyl methacrylate (48 ° C), methacrylic acid Alkyl methacrylate such as cetyl ester (15 ° C). The numerical 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.

In 100% by mass of the monomer component forming the copolymer (A), the amount of the monomer (a1) is 10 to 30% by mass, preferably 15 to 25% by mass, and particularly preferably 18 to 22% by mass. The copolymer (A) obtained by copolymerizing the monomer (a1) within the aforementioned range is hardened with a large amount of an isocyanate-based crosslinking agent (B), thereby forming an adhesive layer having a high storage elastic modulus.

"Crosslinking functional group-containing monomer (a2)"

The monomer component forming the copolymer (A) further includes a monomer having a crosslinkable functional group capable of reacting with the isocyanate crosslinking agent (B), that is, a monomer (a2) containing a crosslinkable functional group .

Examples of the crosslinkable functional group-containing monomer (a2) include a hydroxyl group-containing monomer, an acid group-containing monomer, an amine group-containing monomer, and a fluorene-amine group. Monomers, nitrogen-containing heterocyclic monomers, cyano-containing monomers. Examples of the acid group in this specification include a carboxyl group, an acid anhydride group, a phosphate group, and a sulfate group.

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

The adhesive layer with a high storage elastic modulus may have reduced adhesion to the polarizer (wetting property of the adhesive composition to the polarizer). In the present invention, the copolymer (A) is obtained by copolymerizing a hydroxy-containing monomer and a carboxyl-containing monomer in combination, so that the decrease in the adhesiveness (wetability) of the obtained adhesive layer can be suppressed.

Hydroxyl-containing monomers (but excluding carboxyl-containing monomers from the hydroxyl-containing monomers) include, for example, hydroxyl-containing (meth) acrylates, and specifically, 2-hydroxyethyl (meth) acrylate Ester, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, etc. Hydroxyalkyl acrylate. The carbon number 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) acrylic acid ethoxyethyl succinate, and ω-carboxyl. Carboxyl-containing (meth) acrylates 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. Examples of the single system containing a phosphate group include (meth) acrylic monomers having a phosphate group in a side chain, and the single system containing a sulfuric acid group, for example. Examples of the (meth) acrylic monomer having a sulfate group in the side chain.

Examples of the amine group-containing monomer include amine group-containing (meth) acrylates such as dimethylamine ethyl (meth) acrylate and diethylamine ethyl (meth) acrylate. Examples of the amine group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, and N-propyl (methyl Group) acrylamide, N-hexyl (meth) acrylamide. Examples of the nitrogen-containing heterocyclic monomer include vinylpyrrolidone, acrylamidomorpholine, and vinylcaprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

The monomer (a2) may be used in two or more kinds, and may be used in three or more kinds.

In 100% by mass of the monomer component forming the copolymer (A), the amount of the crosslinkable functional group-containing monomer (a2) is 0.1 to 5% by mass, preferably 1 to 5% by mass, and even more preferably 2 to 4% by mass. When the amount of the monomer (a2) is equal to or less than the aforementioned upper limit value, the crosslinking density formed by the copolymer (A) and the crosslinking agent (B) is not excessively high, and an adhesive layer having excellent stress relaxation properties can be obtained. When the amount of the monomer (a2) is greater than or equal to the aforementioned lower limit value, the crosslinked structure can be effectively formed, and an adhesive layer having appropriate strength at normal temperature can be obtained.

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

"Other monomers"

From the viewpoint of maintaining the wettability as an adhesive, the monomer component forming the copolymer (A) preferably contains a (meth) group whose Tg of the homopolymer is less than 0 ° C. Alkyl acrylate (a3). That is, it is preferable that the said copolymer (A) has a structural unit derived from the alkyl (meth) acrylate (a3) more. The alkyl (meth) acrylate (a3) is also called "monomer (a3)".

As the monomer (a3), for example, among the compounds represented by CH ₂ = CR ³ -COOR ⁴ , compounds having a Tg of a homopolymer of less than 0 ° C can be mentioned. 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 carbon number of the aforementioned alkyl group is preferably 2 to 8.

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

The amount of the monomer (a3) in 100% by mass of the monomer component forming the copolymer (A) is preferably 65 to 89.9% by mass, and more preferably 70 from the viewpoint of maintaining the wettability as an adhesive. To 84% by mass, more preferably 75 to 80% by mass.

The monomer component forming the copolymer (A) may include, for example, an alkoxyalkyl (meth) acrylate and an alkyl (meth) acrylate, as long as the physical properties of the copolymer (A) are not impaired. Polyoxyalkylene glycol, alicyclic type And other (meth) acrylates such as (meth) acrylates of aromatic groups or aromatic rings. That is, the said copolymer (A) may further have the structural unit derived from the said other (meth) acrylate.

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 alkoxy polyalkylene glycol mono (meth) acrylate include methoxy diethylene glycol mono (meth) acrylate, methoxy dipropylene glycol mono (meth) acrylate, and mono (meth) acrylate. Ethoxy triethylene glycol acrylate, ethoxy diethylene glycol mono (meth) acrylate, and methoxy triethylene 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. By using an aromatic ring-containing (meth) acrylate, the light leakage resistance of the adhesive layer can be improved.

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

The monomer component forming the copolymer (A) may include a copolymerizable monomer such as a styrene-based monomer or vinyl acetate, as long as the physical properties of the copolymer (A) are not impaired. That is, the said copolymer (A) may further have the structural unit derived from the said copolymerizable monomer.

Examples of the styrene-based monomer include styrene; methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, Alkyl styrenes such as octyl styrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodostyrene; nitrostyrene, ethylfluorenylstyrene, methoxybenzene Ethylene, etc.

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

Other single systems can be used alone or in combination of two or more.

<< Production conditions of (meth) acrylic copolymer (A) >>

The manufacturing conditions of a (meth) acrylic-type copolymer (A) are not specifically limited, For example, it can manufacture by a solution polymerization method. Specifically, a polymerization solvent, a monomer component, and a necessary chain transfer agent are charged into a reaction container, and a polymerization initiator is added under an inert gas environment such as nitrogen, and the reaction start temperature is usually set to 40 to 100. C, preferably 50 to 80C, and the reaction system is maintained at a temperature of usually 50 to 90C, preferably 70 to 90C, and the reaction is performed for 4 to 20 hours. In addition, in the above-mentioned 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 by copolymerizing the above-mentioned 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; cyclopentane, cyclohexane, and cycloheptane Alicyclic hydrocarbons such as alkane, cyclooctane; diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, benzene Ethers such as diethyl ether, diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and 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 Amines such as amines, N, N-methylpyrrolidone; nitriles such as acetonitrile, benzonitrile; and other fluorenes such as dimethyl fluorene and cyclobutane. These polymerization solvents may be used alone or in combination of two or more.

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

The chain transfer agent may be used in an amount of usually 0.1 to 0.09 parts by mass based on 100 parts by mass of the monomer component forming the (meth) acrylic copolymer (A), preferably 0.01 to 0.09 parts by mass.

Examples of the polymerization initiator system include an azo-based initiator and a peroxide-based initiator. Specific examples include: azo compounds such as 2,2'-azobisisobutyronitrile; peroxides such as benzamidine peroxide and lauryl peroxide. Among these, an azo compound is preferred. Examples of the azo compound system include 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'-couple Azobis (cyclohexane-1-carbonitrile), 2- (aminomethylamidoazo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis (2-methylfluorenylpropane) dihydrochloride, 2,2'-azobis (N, N'-dimethylene isobutylmethylfluorenyl), 2,2'- Azobis [2-methyl-N- (2-hydroxyethyl) -propylamidamine], 2,2'-azobis (isobutylamidamine) dihydrate, 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methylpropionate), etc. Compound. These polymerization initiators may be used individually by 1 type, and may use 2 or more types.

The polymerization initiator is usually 0.01 to 5 parts by mass, and preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the monomer component forming the (meth) acrylic 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 the gel permeation chromatography (GPC) method is 600,000 or less in terms of polystyrene conversion, preferably 300,000 to 580,000, particularly preferably 400,000 to 550,000.

The adhesive layer having a high storage elastic modulus may have reduced adhesion to the polarizer (wetting of the adhesive composition to the polarizer). In the present invention, since the copolymer (A) has the Mw within the above range, it is possible to suppress a decrease in the adhesiveness (wettability) of the obtained adhesive layer.

(Meth) acrylic copolymer (A) measured by GPC method The obtained molecular weight distribution (Mw / Mn) 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 from, for example, the monomer units constituting the copolymer and the content ratio thereof based on Fox's formula. For example, the (meth) acrylic copolymer can be synthesized such that the glass transition temperature (Tg) obtained according to the formula of 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 having excellent adhesiveness at room 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 the glass transition temperature (unit: K) of the (meth) acrylic copolymer (A), and Tg ₁ , Tg ₂ , ‧‧‧, and Tg _m are the homopolymers made of each monomer. The glass transition temperature (unit: K), W ₁ , W ₂ , ‧‧‧, and W _m are the weight fractions of the constituent units derived from each monomer in the aforementioned copolymer (A). The weight fraction of the constituent units derived from each monomer enables the loading ratio of each monomer to all monomers used in the copolymer synthesis.

In the above-mentioned formula of Fox, the glass transition temperature of a 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 The content of the copolymer (A) in the composition minus 100% by mass of the solid content of the organic solvent (E) is usually 60 to 90% by mass, particularly preferably 70 to 89.9% by mass, and particularly preferably 80 to 89.5% by mass. When the content of the (meth) acrylic copolymer (A) is in the aforementioned range, a balance of performance as an adhesive can be obtained, and excellent adhesive properties can be obtained.

[Isocyanate-based crosslinking agent (B)]

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

As the isocyanate-based crosslinking agent (B), an isocyanate compound having two or more isocyanate groups in one molecule is usually used. The (meth) acrylic copolymer (A) is crosslinked with an isocyanate-based crosslinking agent (B) to form a crosslinked body (network polymer).

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

Examples of the isocyanate compound having two isocyanate groups in one molecule include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of the aliphatic diisocyanate include ethylene 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 di Aliphatic diisocyanates such as isocyanates having 4 to 30 carbon atoms. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethyl. A cycloaliphatic diisocyanate having 7 to 30 carbon atoms such as xylene diisocyanate. Examples of the aromatic diisocyanate include carbon numbers such as benzene diisocyanate, toluene diisocyanate, xylene diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate. 8 to 30 aromatic diisocyanates.

Examples of the isocyanate compound having three 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, 4,4 ', 4 "-triphenylmethane triisocyanate.

Examples of the isocyanate-based cross-linking agent (B) include, for example, a polymer (for example, a dimer or trimer, a biuret, or a trimer isocyanate) of the isocyanate compound having an isocyanate group of 2 or 3 or more. Polymers), derivatives (for example, the addition reaction product of a polyol and two or more diisocyanate compounds), polymers, and the like. Regarding the polyol in the derivative, examples of the low-molecular-weight polyol include trihydric or higher alcohols such as trimethylolpropane, glycerol, and neopentyl tetraol, and examples of the high-molecular-weight polyol include polyether polyols and polyether polyols. Ester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol.

Examples of such isocyanate compounds include diphenyl Trimer of methylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or biuret body of toluene diisocyanate or triisocyanate body, trimethylolpropane and toluene diisocyanate or Reaction product of xylene diisocyanate (e.g. toluene diisocyanate or trimolecular adduct of xylene diisocyanate), reaction product of trimethylolpropane and hexamethylene diisocyanate (e.g. hexamethylene diisocyanate Three molecular adducts), polyether polyisocyanate, polyester polyisocyanate.

From the viewpoint of improving the light leakage resistance of the adhesive layer, the isocyanate-based crosslinking agent (B) is preferably a compound having a benzene nucleus. Examples include aromatic diisocyanates, polymers or derivatives of aromatic diisocyanates, polymers, and aromatic polyisocyanates.

Among the isocyanate-based cross-linking agents (B), from the viewpoint of improving the curing properties and light leakage resistance, a reaction product of trimethylolpropane and toluene diisocyanate or xylene diisocyanate is preferred (Kkenken Chemical Co., Ltd. L-45 manufactured by the company, TD-75 manufactured by Soken Chemical Co., Ltd., etc.), and trimeric isocyanate bodies of toluene diisocyanate (2050 manufactured by Nippon Polyurethane Industry Co., Ltd.).

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 content of the isocyanate-based crosslinking agent (B) is 10 to 40 parts by mass, and preferably 10 to 15 parts by mass based on 100 parts by mass of the (meth) acrylic copolymer (A). Serving. When the content is in the foregoing range, a hard adhesive layer can be formed, and the phenomenon of floating or peeling of the adhesive layer when the polarizer is thermally contracted can be suppressed.

[Silane coupling agent (C)]

The adhesive composition of the present invention preferably further contains a silane coupling agent (C). The silane coupling agent (C) firmly adheres the adhesive layer to an adherend such as a glass plate, and helps prevent peeling under a high humidity and heat environment.

Examples of the silane coupling agent (C) include polymerizable unsaturated group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane, and the like. ; 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-ring Epoxy-containing silane coupling agents such as oxypropoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-aminopropyltrimethoxy Silyl, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, etc. Silane coupling agents containing amine groups; halogen-containing silane coupling agents such as 3-chloropropyltrimethoxysilane.

In the adhesive composition of the present invention, the content of the silane coupling agent (C) is usually 1 part by mass or less, preferably 0.01 to 1 part by mass, with respect to 100 parts by mass of the (meth) acrylic copolymer (A). It is particularly preferably from 0.05 to 0.5 parts by mass. When the content is in the aforementioned range, it tends to prevent peeling of the polarizing plate in a high-humidity environment or exudation of the silane coupling agent (C) in a high-temperature environment.

[Antistatic agent (D)]

The antistatic agent (D) is used, for example, to reduce the adhesive composition of the present invention. 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 system include: quaternary ammonium salts, ammonium quaternary ammonium salts, pyridinium salts, cationic surfactants having cationic groups such as amine groups of grades 1 to 3, and sulfonates Anionic surfactants such as anionic groups such as amino groups, sulfate ester groups, phosphate ester groups; alkyl betaines, alkyl imidazolium betaines, alkyl oxide amines, amino acid sulfates, and the like Surfactants, glycerin fatty acid esters, sorbitol fatty acid esters, polyoxyethylaminoamines, polyoxyethylaminoamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkane Non-ionic surfactants such as amines and alkyl diethanolamines.

In addition, as the surfactant, a reactive emulsifier having a polymerizable group may also be mentioned, and a polymer obtained by polymerizing a monomer component containing the surfactant or the reactive emulsifier may be used. System surfactants.

The ionic compound is composed of a cation part and an anion part, and can be either solid or liquid at room temperature (23 ° C / 50% RH).

The cationic portion constituting the ionic compound may be any one or both of an inorganic cation and an organic cation. The inorganic cations are preferably alkali metal ions and alkaline earth metal ions, 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 pyrrolidium cation, a dihydropyrrole cation, a pyrrole cation, an imidazolium cation, a tetrahydropyrimidium cation, a dihydropyrimidinium cation, and a pyrazolium cation. , Pyrazolinium cation, tetraalkylammonium cation, trialkylphosphonium cation, tetraalkylphosphonium cation, and derivatives thereof.

The anion part constituting the ionic compound is not particularly limited as long as it can form an ionic compound by ionic bonding with a cationic part. Specific 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, a fluorine atom-containing anionic compound of the ion due to impart a low melting point, it is preferred, particularly preferably _{(F 2 SO 2) 2 N} - and _{(CF 3 SO 2) 2 N} -.

The ionic compounds are preferably lithium bis (trifluoromethanesulfonyl) fluorenimide, lithium bis (difluorosulfonyl) fluorenimide, lithium tris (trifluoromethanesulfonyl) methane, and bis (trifluoromethane) Sulfosulfonyl) sulfonium potassium imine, bis (difluorosulfonyl) sulfonium potassium imine, 1-ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl hexafluorophosphate 4-methylpyridinium salt, 1-octyl-4-methylpyridinium hexafluorophosphate, bis (fluorosulfonyl) fluorenimine 1-octyl-4-methylpyridinium salt, bis ( Trifluoromethanesulfonyl) fluorenimine 1-octyl-4-methylpyridinium salt, tetrafluoroborate (N, N-diethyl-N-methyl-N- (2-methoxyethyl ) Ammonium, bis (trifluoromethanesulfonyl) fluorenimide N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium, fluorenimine 1-octylpyridinium Fluorofluorene, 1-octyl-3-methylpyridinium, fluorenimine trifluorofluorene.

Examples of the conductive polymer system include polythiophene and polybenzene. Amine, polypyrrole 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, relative to 100 parts by mass of the (meth) acrylic copolymer (A). It is particularly preferably from 0.05 to 2.5 parts by mass.

[Organic solvent (E)]

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

In the present specification, the "solid content" means all components after deducting the organic solvent (E) from the contained components of the adhesive composition, and the "solid content concentration" means the solid component relative to the adhesive composition. 100% by mass.

[additive]

The adhesive composition of the present invention may contain, in addition to the above-mentioned components, a compound selected from the group consisting of antioxidants, light stabilizers, anti-corrosive agents, adhesion-imparting agents, plasticizers, and solvents, as long as the effects of the invention are not impaired. One of a crosslinking accelerator, a (meth) acrylic polymer other than the aforementioned (A), and a reworking agent, or 2 or more.

[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-based crosslinking agent (B) and other necessary components by a conventionally known general method. For example, an isocyanate-based cross-linking agent (B) and other components as necessary are formulated in a polymerization solution containing the polymer obtained when the (meth) acrylic copolymer (A) is synthesized.

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

[Adhesive layer for polarizing plate]

The adhesive layer for polarizing plates of the present invention is formed from the above-mentioned 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 modulus (G'1) of the adhesive layer of the present invention at 23 ° C is preferably 0.5 MPa or more, particularly preferably 0.60 to 1.50 MPa, particularly preferably 0.70 to 1.20 MPa; storage at 85 ° C The elastic modulus (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, bonding the above-mentioned adhesive layers to each other multiple times to produce a laminated body having a thickness of about 1.0 mm, and The value calculated from the dynamic viscoelasticity spectrum measured by the laminate.

By setting the storage elastic modulus (G'1) at 23 ° C to be in the above range, the adhesive layer of the present invention is excellent in rigidity at normal temperature and improves processability. For example, when cutting the adhesive layer, it can prevent the adhesive from attaching to the cutting edge or the drawing of the adhesive layer.

Laminated directly on the adhesive layer of the polarizer, under high temperature, high humidity and heat environment, large stress is applied along with the thermal contraction of the polarizer, so it is easy to cause problems such as floating or peeling from the polarizer. By setting the storage elastic modulus (G'2) at 85 ° C to the above range, even if the polarizer undergoes heat shrinkage, this problem can be prevented.

The adhesive layer formed from the adhesive composition of the present invention preferably has a gel fraction of 80% by mass or more, and more preferably 80%, from the viewpoints of strain suppression, cohesion, adhesion, and re-peelability of the polarizing plate. To 98% by mass, more preferably 85 to 95% by mass. When the gel fraction is in the aforementioned range, the adhesive layer can show excellent durability.

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

The formation conditions of the adhesive layer are, for example, the following. Although the adhesive composition of the present invention is coated on a support, although it varies depending on the type of the solvent, it is usually 50 to 150 ° C, preferably 60 to 100 ° C, and usually dried for 1 to 10 minutes, preferably 2 to 10 minutes. The solvent was removed for 7 minutes to form a coating film. The film thickness of the dry coating film is usually 5 to 75 μm, and preferably 10 to 50 μm.

The adhesive layer is preferably formed under the following conditions. After the adhesive composition of the present invention is coated on a support, and a cover film is attached to a coating film formed under the above conditions, it is usually more than 3 days, preferably 7 to 10 days, and The aging is usually performed at an environment of 5 to 60 ° C, preferably 15 to 40 ° C, usually 30 to 70% RH, preferably 40 to 70% RH. When the crosslinking is performed under the above-mentioned curing conditions, the crosslinked body (network polymer) can be efficiently formed.

As the method for applying the adhesive composition, generally known methods can be used, such as a spin coating method, a knife coating method, a roll coating method, a bar coating method, a blade coating method, and a mold coating method. , Gravure coating method, etc., a method of coating and drying so as to have a predetermined thickness.

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

[Adhesive sheet for polarizing plate]

The adhesive sheet for polarizing plates of the present invention has an adhesive layer formed of the above-mentioned adhesive composition. Examples of the adhesive sheet include: a double-sided adhesive sheet having only the above-mentioned adhesive layer; a double-sided adhesive sheet having a substrate and the above-mentioned adhesive layer formed on both sides of the substrate; a substrate and a substrate formed on the substrate The single-sided adhesive sheet of the above-mentioned adhesive layer on one side; and the adhesive sheet of the cover film after the peeling treatment is pasted on the surface of the adhesive layer of the adhesive sheet that is not in contact with the substrate.

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

The formation conditions of the adhesive layer are the same as those described in the column of [Adhesive layer for polarizing plates].

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

[Polarizer with adhesive layer]

The polarizing plate with an adhesive layer of the present invention has an adhesive layer directly laminated on at least one side of the polarizer and formed of the adhesive composition of the present invention. In this specification, "polarizing plate" is used with the meaning including "polarizing film".

As the polarizing plate, a conventionally known polarizing film can be used. Examples thereof include a polarizer itself, and a multilayer film having a polarizer and a polarizer protective film disposed on the polarizer. In the present invention, since the above-mentioned adhesive layer is disposed in direct contact with the polarizer, a configuration in which a polarizer protective film is disposed only on one side of the polarizer, and a polarizer protective film is not disposed on both sides of the polarizer are listed. Of the composition.

The polarizer is, for example, an stretched film obtained by stretching a polarizing component in a film made of a polyvinyl alcohol resin. Examples of the polyvinyl alcohol resin include polyvinyl alcohol and polyvinyl group. Saponified formaldehyde (polyvinyl formal), polyvinyl acetal, ethylene-vinyl acetate copolymer. Examples of the polarizing component include iodine and a dichroic dye.

Examples of the polarizer protective film include a film made of a thermoplastic resin. Examples of the thermoplastic resin include cellulose resins such as cellulose triacetate, polyester resins, polyether resins, poly resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, The (meth) acrylic resin, cyclic polyolefin resin (norbornene 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 10 to 200 μm, and preferably 50 to 100 μm. In the present invention, since the polarizer protective film formed on the polarizer can be omitted, the thickness of the polarizer 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 may include, for example, the following constitutions: a structure in which a polarizer protective film and a polarizer and the adhesive layer are sequentially laminated; a layer in which the adhesive layer and the polarizer protective film are sequentially laminated; and The structure of the polarizer and the above-mentioned adhesive layer; the structure of the above-mentioned adhesive layer and the polarizer and the above-mentioned adhesive layer are sequentially laminated. In these configurations, the above-mentioned cover film may be disposed on the adhesive layer as the outermost layer.

The method of forming the adhesive layer on the surface of the polarizer is not particularly limited, and examples thereof include a method of directly applying the above adhesive composition to the surface of the polarizer using a bar coater, etc., and then drying and curing it; Adhesive possessed by adhesive sheet for 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 curing, 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 5 to 75 μm, preferably 10 to 50 μm, based on the dry film thickness. In addition, the adhesive layer may be formed by contacting the polarizer on at least one side of the polarizer. Examples of the adhesive layer include an adhesive layer formed on only one side of the polarizer, and on both sides of the polarizer. Formed with an adhesive layer.

In addition, a layer having other functions, such as a protective layer, an anti-glare layer, a retardation layer, and a viewing angle enhancement layer, can be laminated on the polarizing plate.

The polarizing plate with the adhesive layer of the present invention obtained as described above is provided on the substrate surface of a liquid crystal cell to manufacture a liquid crystal element. Here, the liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates.

Examples of the substrate included in the liquid crystal cell include a glass plate. The thickness of the substrate is usually 0.05 to 3 mm, preferably 0.2 to 1 mm. The adhesive layer formed using the above-mentioned adhesive composition has excellent adhesion to a substrate (wetting property of the adhesive composition to a substrate).

Examples

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 examples and the like, "part" means "mass part" unless otherwise specified.

[GPC]

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

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

‧GPC string structure: The following 4 series strings (all made by Tosoh Co., Ltd.)

(1) TSKgel HxL-H (guard column)

(2) TSKgel GMHxL

(3) TSKgel GMHxL

(4) TSKgel G2500HxL

‧Flow rate: 1.0ml / min

‧Column temperature: 40 ℃

‧Concentration of sample: 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-dodecanethiol, and 100 parts of ethyl acetate solvent were charged into a stirrer and reflux-cooled In the reaction device of a heater, a thermometer, and a nitrogen introduction tube, the temperature was raised to 65 ° C. while introducing nitrogen gas. Next, 0.1 part of 2,2'-azobisisobutyronitrile was added, and a polymerization reaction was performed at 65 ° C for 4 hours under a nitrogen atmosphere. After completion of the reaction, a polymer solution having a solid content concentration of 30% by mass was prepared by diluting with ethyl acetate. Weight average molecular weight (Mw) of the obtained (meth) acrylic copolymer A1 It was 520,000, and molecular weight distribution (Mw / Mn) was 2.4.

[Synthesis Examples 2 to 8]

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 adhesive composition

The polymer solution (solid content concentration: 30% by mass) obtained in Synthesis Example 1 was used as an isocyanate-based crosslinking agent with respect to 1100 parts (solid content) of the (meth) acrylic copolymer A contained in the solution. 12 parts (solid content) of "L-45" (45% by mass of solid content) manufactured by Soken Chemical Co., Ltd., and "KBM-403" (solid content of 100) manufactured by Shin-Etsu Chemical Industry Co., Ltd. as a silane coupling agent Mass part) 0.2 parts were mixed, and ethyl acetate solvent was added so that solid content concentration might be 25 mass%, and the adhesive composition was obtained.

(2) Production of adhesive sheet

The adhesive composition obtained in the above (1) was defoamed, and then coated on a polyethylene terephthalate film (PET film) after peeling treatment using a blade coater, and dried at 90 ° C for 3 minutes. To form a coating film with a dry film thickness of 20 μm. On the opposite side of the coating film to the above-mentioned PET film, the PET film after the peeling treatment was further bonded, and was left to stand for 7 days in an environment of 23 ° C./50% RH for curing to obtain An adhesive sheet having an adhesive layer with a thickness of 20 μm sandwiched between two PET films.

(3) Fabrication of polarizing plate with adhesive layer

After defoaming, the adhesive composition obtained in the above (1) was applied to a peeled polyethylene terephthalate film (PET film) using a blade coater and dried at 90 ° C for 3 minutes. And got a dry film thickness of 20μ m of coating film. The film coating surface of the sheet and the polyvinyl alcohol film surface of the polarizing plate (thickness: 60 μm) composed of a double layer (polyvinyl alcohol film as a polarizer and a cellulose triacetate film as a polarizer protective film) Lamination was carried out by contact method, and it was left to stand for 7 days in an environment of 23 ° C / 50% RH for curing. Thus, an adhesive layer with a PET film and a thickness of 20 μm, and an adhesive layer with a polarizer and a polarizer protective film were obtained. Of polarizing plate.

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

In Example 1, except that the polymer solution was changed to the polymer solution obtained in Synthesis Examples 2 to 8, and / or the blending composition was changed as described in Table 2, the rest were the same as in Example 1. Then, an adhesive composition, an adhesive sheet, and a polarizing plate with an adhesive layer are obtained.

[Evaluation] [Gel fraction]

From the adhesive sheets obtained in the examples and comparative examples, collect about 0.1 g of the adhesive into a sample bottle, add 30 mL of ethyl acetate and shake for 4 hours, and then filter the contents of the sample bottle with a 200-mesh stainless steel gold 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 comparative examples, an adhesive layer having a thickness of 20 μm was bonded to each other several times under an environment of 23 ° C./50% RH, and then It was processed in an autoclave at 50 ° C./5 atm for 20 minutes to produce an adhesive layer having a thickness of 1.0 mm. The "Physica MCR300" manufactured by Anton Paar was used in accordance with the dynamic viscoelasticity measurement method based on JIS K7244 (temperature range: -40 to 160 ° C, temperature increase rate of 3.67 ° C / min, and frequency of 1Hz), and the thickness was 1.0 mm. The viscoelastic spectrum of the adhesive layer was measured to determine the storage elastic modulus at temperatures of 23 ° C and 85 ° C.

[Determination of adhesion]

The polarizing plate (layered body consisting of a PET film, an adhesive layer, a polarizer, and a polarizer protective film) with an adhesive layer obtained in the examples and comparative examples was cut to a size of 70 mm × 25 mm to produce a test. sheet. The PET film was peeled from the test piece, and the laminated body composed of the adhesive layer / polarizer / polarizer protective film was attached to a glass plate having a thickness of 2 mm so that the adhesive layer was in contact with the glass plate using a pressure roller One-sided. The obtained laminate was kept in an autoclave adjusted to 50 ° C / 5 atm for 20 minutes. Then, it was left to stand in an environment of 23 ° C./50% RH for 1 hour, and then the end of the polarizing plate was pulled away at a speed of 90 ° with respect to the glass plate at a speed of 300 mm / minute, and the adhesive force (peel strength) was measured. .

[Measurement of Adhesive Force]

The polarizing plate (layered body consisting of a PET film, an adhesive layer, a polarizer, and a polarizer protective film) with an adhesive layer obtained in the examples and comparative examples was cut to a size of 70 mm × 25 mm to produce a test. sheet. The polarizer protective film of the test piece was rubbed with a finger, and the adhesiveness was measured by the following criteria. Observed.

AA: No peeling of the adhesive layer from the polarizer was confirmed

BB: slight peeling of the adhesive layer from the polarizer was confirmed

CC: Clear peeling of the adhesive layer from the polarizer was confirmed

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

The polarizing plate (layered body composed of PET film / adhesive layer / polarizer / polarizer protective film) with an adhesive layer obtained in the examples and comparative examples was cut to a size of 150 mm × 250 mm to produce a test sheet. The PET film was peeled from the test piece, and the laminated body composed of the adhesive layer / polarizer / polarizer protective film was attached to a glass having a thickness of 0.5 mm so that the adhesive layer was in contact with the glass plate using a pressure roller. One side of the board. The obtained laminated body was kept in an autoclave adjusted to 50 ° C / 5 atm for 20 minutes, and a test plate was produced. Two identical test plates were made. The aforementioned test plate was left for 500 hours under the conditions of a temperature of 80 ° C (heat resistance) or a temperature of 60 ° C / humidity 90% RH (humidity and heat resistance), and the following criteria were used to observe foaming, floating, Generation of peeling for evaluation.

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

BB: Only slight appearance defects such as foaming, floating, and peeling were observed

CC: Obvious appearance defects such as foaming, floating, peeling are observed

[Light leakage test]

The two polarizing plates with an adhesive layer obtained in the examples and comparative examples (a laminated body composed of a PET film, an adhesive layer, a polarizer, and a polarizer protective film) The test piece was cut into a size of 310 mm x 385 mm. The PET film was peeled from the test piece, and a laminated body composed of an adhesive layer, a polarizer, and a polarizer protective film was adhered to each other so that polarizing axes were orthogonal to each other and the adhesive layer was in contact with the glass plate using a pressure roller On both sides of a glass plate with a thickness of 0.5mm. The obtained laminated body was kept in an autoclave adjusted to 50 ° C / 5 atm for 20 minutes, and a test plate was produced. This test plate was left at a temperature of 80 ° C. for 500 hours, and light leakage was observed by the following criteria.

AA: No light leakage was observed

BB: Some light leakage was observed

CC: Obvious light leakage is observed

Claims (6)

An adhesive composition for a polarizing plate is used to form an adhesive layer in direct contact with a polarizer. The adhesive composition for a polarizing plate contains (A) (meth) acrylic copolymer and (B) isocyanate system. A crosslinking agent; wherein 10 to 40 parts by mass of the crosslinking agent (B) is contained with respect to 100 parts by mass of the copolymer (A); the copolymer (A) contains 10 to 30% by mass of (a1) and (A2) is obtained by copolymerizing a monomer component of (a2) in an amount of 0.1 to 5% by mass, wherein (a1) is a (meth) acrylic acid alkyl ester having a glass transition temperature of 0 ° C or higher of a homopolymer, and (a2) contains A hydroxyl group-containing monomer and a carboxyl group-containing monomer having a crosslinkable functional group, and the weight average molecular weight of the copolymer (A) obtained by gel permeation chromatography is 600,000 or less, and the glass transition temperature is -80 to 0 ° C. An adhesive layer for polarizing plates is formed by the adhesive composition described in item 1 of the scope of patent application. For example, the adhesive layer for polarizing plates described in item 2 of the scope of patent application has a storage elastic modulus at 23 ° C of 0.50 MPa or more, and a storage elastic modulus at 85 ° C of 0.10 MPa or more. The adhesive layer for polarizing plates according to item 2 or 3 of the scope of patent application, the gel fraction is 80% by mass or more. An adhesive sheet for a polarizing plate is provided with the adhesive layer according to any one of claims 2 to 4 of the scope of patent application. A polarizing plate with an adhesive layer is a polarizing plate which is directly laminated on a polarizer. At least one side applies for the adhesive layer described in any one of items 2 to 4 of the patent scope.