TW201623523A - Adhesive composition for polarizing plate and polarizing plate with adhesive layer - Google Patents

Abstract

An objective of this invention is to provide an adhesive composition for polarizing plate capable of forming an adhesive layer capable being applied in a structure in which at least one of polarizer protection films usually formed on two surfaces of the polarizer is omitted, capable of suppressing the curving(bending)of liquid crystal cell, and excellent in durability. The present invention provides an adhesive composition for polarizing plates which is characterized by containing (A) methacrylate copolymer, and (B) crosslinker, and being used as an adhesive layer for directly in contact with the polarizer, wherein, the (meth)acrylate copolymer is obtained by copolymerizing monomer components containing 30 mass% or more and less than 90 mass% of an alkyl acrylate (a1) in which the carbon number of the alkyl group is 8 or more, 10 mass% or more and less than 70 mass% of an alkyl methacrylate (a2) in which the carbon number of the alkyl group is 8 or more, and more than 0 mass% and 10 mass% or less of a monomer (a3) having a crosslinkable functional group.

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). On the surface of the substrate constituting the liquid crystal cell, a polarizing plate is attached through the adhesive layer. In order to improve the mechanical properties and optical durability, the polarizing plate is usually used on both sides of a polarizing plate having a polarizing function, and has a structure in which a polarizer protective film such as a cellulose triacetate film is laminated.

In recent years, with the reduction in thickness of the liquid crystal cell and the reduction in thickness of the polarizing plate, the warpage of the liquid crystal cell in a high-temperature/high-humidity heat environment has become a major problem. The reason why the liquid crystal cell is warped is, for example, that the stress relaxation property of the previous adhesive layer is low, and the stress caused by the thermal contraction (size change) of the polarizer cannot be sufficiently alleviated.

On the other hand, in order to reduce the thickness of the polarizing plate, it is attempted to omit the polarizer protective film formed on both surfaces of the polarizer. However, a polarizing plate that does not have a polarizer protective film is directly attached to the adhesive layer. In the high-temperature, high-humidity heat environment, the light sheet is subjected to a large stress to the adhesive layer in the high-temperature and high-humidity heat environment, which is not only the warpage of the liquid crystal cell, but also defects such as breakage of the adhesive layer and peeling of the polarizing plate.

Patent Document 1 describes an adhesive composition containing a methacrylic polymer, wherein the methacrylic polymer contains 40 to 99.5% by mass of an alkyl group having a C10 to C18 in a side chain. The monomer component of the alkyl methacrylate is obtained by polymerization, and the glass transition temperature (Tg) is 0 ° C or lower. However, the above-mentioned warpage problem when the polarizer protective film is omitted and the adhesive layer is directly laminated on the polarizer is not particularly mentioned.

Patent Document 2 discloses an adhesive polarizing plate comprising a polarizing plate and an adhesive layer provided on the polarizing plate, wherein the polarizing plate has a transparent protective film only on one side of the polarizing plate, and the adhesive layer is It is disposed on the side of the polarizer that does not have the aforementioned transparent protective film. However, the above-mentioned warpage problem accompanying the omission of the aforementioned transparent protective film is not particularly mentioned.

Prior technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2013-001761

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2012-247574

The object of the present invention is to provide an adhesive bond An adhesive composition for a polarizing plate of a coating layer, which is applicable to a configuration in which at least one of the polarizer protective films which are usually formed on both surfaces of the polarizer is omitted, and the liquid crystal cell can be prevented from being warped (bent) and durable. Excellent sex.

The present inventors have carefully studied to solve the above problems. As a result, it has been found that when a specific (meth)acrylic copolymer is used and a crosslinking agent is used, an adhesive layer capable of suppressing warpage (bending) of the liquid crystal cell described above and having excellent durability can be formed.

In other words, the present inventors have found that the above problems can be solved by using an adhesive composition for a polarizing plate having the following specific configuration, 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, comprising: (A) a methacrylic copolymer, which comprises an alkyl acrylate having an alkyl group number of 8 or more and 30% by mass or more and less than 90% by mass. (a1); 10% by mass or more and less than 70% by mass of alkyl methacrylate (a2) having an alkyl group number of 8 or more; and a crosslinkable functional group in an amount of more than 0% by mass and 10% by mass or less The monomer component of the monomer (a3) is obtained by copolymerization; and (B) the crosslinking agent, and the adhesive composition for the polarizing plate is used to form an adhesive layer directly in contact with the polarizer.

[2] The adhesive composition for a polarizing plate according to the above [1], wherein the adhesive formed by the adhesive composition for a polarizing plate has a gel fraction of 40% by mass or more.

[3] An adhesive layer for a polarizing plate is as described above [1] Or the adhesive composition described in [2].

[4] The adhesive layer for a polarizing plate according to the above [3], wherein the storage elastic modulus at 23 ° C is 0.10 MPa or more, the storage elastic modulus at 85 ° C is 0.05 MPa or less, and a certain temperature T is set. The storage elastic modulus of °C is set to G' _T , and the storage elastic modulus of T+1 °C is set to G' _T+1 . In the range of temperature T of 23 to 50 ° C, G' _T / is constantly satisfied _. G' _T+1 <1.07.

[5] An adhesive sheet for a polarizing plate, comprising the adhesive layer according to the above [3] or [4].

[6] A polarizing plate with an adhesive layer, which has an adhesive layer as described in the above [3] or [4], 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 which forms an adhesive layer, and the adhesive layer can be applied to a configuration in which at least one of the polarizer protective films which are usually formed on both surfaces of the polarizer is omitted, and It is possible to suppress warpage (bending) of the liquid crystal cell and to have excellent durability. Further, it is possible to provide an adhesive layer for a polarizing plate formed using 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.

Hereinafter, the adhesive composition for a polarizing plate, the adhesive layer for a polarizing plate, the adhesive sheet for a polarizing plate, and an adhesive layer will be described. Polarizer. 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 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) as necessary, and may also contain an organic solvent (E).

[(Meth)acrylic copolymer (A)]

(meth)acrylic copolymer (A) is a copolymer containing the following monomer component: 30% by mass or more and less than 90% by mass of alkyl acrylate (a1), 10% by mass or less More than 70% by mass of the alkyl methacrylate (a2) having an alkyl carbon number of 8 or more, and a crosslinkable functional group-containing monomer (a3) in an amount of more than 0% by mass and 10% by mass or less; It is obtained by copolymerizing the above monomer components. The copolymer (A) usually has a constituent unit derived from an alkyl acrylate (a1), a constituent unit derived from an alkyl methacrylate (a2), and a composition derived from a crosslinkable functional group-containing monomer (a3). unit.

In the present specification, acrylic acid and methacrylic acid are also collectively referred to as "(meth)acrylic acid". Further, the constituent unit derived from the monomer A contained in the polymer is also referred to as "monomer A unit". In addition, the above (a1), (a2), and (a3) are also referred to as "single (a1)" and "single (a2), respectively. And "monomer (a3)".

"Alkyl acrylate (a1)"

The monomer (a1) is an alkyl acrylate having an alkyl group number of 8 or more, and is represented, for example, by the formula: CH ₂ =CH-COOR ¹ . R ¹ is an alkyl group having 8 or more carbon atoms. The alkyl group has a carbon number of preferably from 8 to 18, more preferably from 8 to 12.

When a (meth)acrylic copolymer containing an alkyl acrylate unit having such a long-chain alkyl group is used, appropriate stress relaxation properties and hydrophobicity can be imparted to the adhesive layer. For example, by using the monomer (a1), the storage elastic modulus at 85 ° C is 0.05 MPa or less, and it is flexible, and there is a tendency to obtain a hydrophobic adhesive layer which can prevent moisture from entering the polarizer.

Examples of the monomer (a1) include 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, decyl acrylate, isodecyl acrylate, decyl acrylate, isodecyl acrylate, and acrylic acid. Ester, lauryl acrylate, stearyl acrylate, isostearyl acrylate.

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

In the case where 100% by mass of the monomer component of the copolymer (A) is formed, the amount of the monomer (a1) used is 30% by mass or more and less than 90% by mass, preferably 30 to 70% by mass, more preferably 30 to 50% by mass. %. When the amount of use of the monomer (a1) is in the above range, it is preferable that the storage elastic modulus of the obtained pressure-sensitive adhesive layer can be adjusted to a range described later (balance of flexibility and hardness).

"Alkyl methacrylate (a2)"

The monomer (a2) is an alkyl methacrylate having a carbon number of 8 or more, and is represented, for example, by the formula: CH ₂ =C(CH ₃ )-COOR ² . R ² is an alkyl group having 8 or more carbon atoms. The alkyl group has a carbon number of preferably from 8 to 18, more preferably from 8 to 12.

When a (meth)acrylic copolymer containing an alkyl methacrylate unit having such a long-chain alkyl group is used, appropriate workability and hydrophobicity can be imparted to the adhesive layer. For example, by using the monomer (a2), the storage elastic modulus at 23 ° C is 0.10 MPa or more, which is hard, and there is a tendency to obtain a hydrophobic adhesive layer which can prevent moisture from entering the polarizer.

Examples of the monomer (a2) include 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, decyl methacrylate, isodecyl methacrylate, and methyl group. Ethyl acrylate, isodecyl methacrylate, eleven methacrylate, lauryl methacrylate, stearyl methacrylate, stearyl isomethacrylate.

The monomer (a2) may be used alone or in combination of two or more.

In the case where 100% by mass of the monomer component of the copolymer (A) is formed, the amount of the monomer (a2) used is 10% by mass or more and less than 70% by mass, preferably 30 to 65% by mass, more preferably 40 to 60% by mass. %. When the amount of use of the monomer (a2) is in the above range, it is preferable to adjust the storage elastic modulus of the obtained adhesive layer to a range to be described later (balance of flexibility and hardness) and hydrophobization. .

When the use ratio of the monomer (a2) is increased, the storage of the adhesive layer The storage elastic modulus tends to increase, and when the use ratio of the monomer (a2) is decreased, the storage elastic modulus of the adhesive layer tends to decrease.

Since the present invention uses an alkyl acrylate (a1) having an alkyl carbon number of 8 or more and an alkyl methacrylate (a2) in combination, an alkyl methacrylate having an alkyl carbon number of 8 or more is not used. When two or more kinds of alkyl acrylates having an alkyl group number of 8 or more are used in combination, the present invention is excellent in that it has hydrophobicity and can exhibit adhesive properties.

"Crosslinking functional group-containing monomer (a3)"

The monomer component forming the copolymer (A) may further contain a monomer having a crosslinkable functional group capable of reacting with the crosslinking agent (B), that is, a monomer (a3) having a crosslinkable functional group.

Examples of the monomer (a3) include a hydroxyl group-containing monomer, an acid group-containing monomer, an amine group-containing monomer, a guanamine group-containing monomer, a nitrogen-containing heterocyclic monomer, and a cyanide-containing monomer. Base monomer. Examples of the acid group in the present specification include a carboxyl group, an acid anhydride group, a phosphoric acid group, and a sulfuric acid group.

Examples of the hydroxyl group-containing monomer include a hydroxyl group-containing (meth) acrylate, and specific examples thereof include 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate. A hydroxyalkyl (meth) acrylate such as 4-hydroxybutyl methacrylate, 6-hydroxyhexyl (meth) acrylate or 8-hydroxyoctyl (meth) acrylate. The carbon number of the hydroxyalkyl group of 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, and succinic acid (A). a carboxyl group-containing (meth) acrylate such as propylene methoxyethyl ester or ω-carboxy polycaprolactone mono (meth) acrylate; acrylic acid, methacrylic acid, itaconic acid, crotonic acid, and anti-butyl Aenedioic acid, maleic acid. Examples of the acid anhydride group-containing monomer include maleic anhydride and itaconic anhydride. Examples of the phosphoric acid group-containing monomer include a (meth)acrylic monomer having a phosphate group in a side chain, and the sulfuric acid group-containing monomer may be a (meth)acrylic acid having a sulfate group in a side chain. Is a monomer.

Examples of the amino group-containing monomer include an amino group-containing (meth) acrylate such as dimethylaminoethyl (meth)acrylate or diethylamine ethyl (meth)acrylate. Examples of the guanamine group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, and N-propyl ( Methyl) acrylamide, N-hexyl (meth) acrylamide. Examples of the nitrogen-containing heterocyclic monomer include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactam. Examples of the cyano group-containing monomer include (meth)acrylic acid cyanoacrylate and (meth)acrylonitrile.

From the viewpoint of crosslinkability with the crosslinking agent (B), the monomer (a3) is preferably at least one selected from the group consisting of hydroxyl group-containing monomers (however, the carboxyl group-containing monomer is removed from the hydroxyl group-containing monomer. The monomer) and the carboxyl group-containing monomer are more preferably a hydroxyl group-containing monomer.

The monomer (a3) 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 (a3) used is more than 0% by mass and 10% by mass or less, preferably 2 to 8% by mass, more preferably 4 to 6% by mass. %. The amount of monomer (a3) used is When the amount is less than or equal to the above upper limit, the crosslinking density of 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 use of the monomer (a3) is at least the above lower limit value, the adhesive structure can be effectively formed, and an adhesive layer having an appropriate strength at normal temperature can be obtained.

Other Monomers

The monomer component forming the copolymer (A) is in the range of not impairing the physical properties of the copolymer (A), and for example, an alkyl (meth)acrylate having an alkyl group number of 1 to 7 or a methyl group can also be used. Other (meth) acrylates such as alkoxyalkyl acrylates, alkoxy polyalkylene mono(meth)acrylates, (meth)acrylates containing an alicyclic group or an aromatic ring. That is, the copolymer (A) may further have a constituent unit derived from the other (meth) acrylate source.

The alkyl (meth)acrylate having an alkyl group having 1 to 7 carbon atoms is represented, for example, by the formula: CH ₂ =CR ³ -COOR ⁴ . In the formula, R ³ is a hydrogen atom or a methyl group, and R ⁴ is an alkyl group having 1 to 7 carbon atoms. For example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, (methyl) Isobutyl acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate.

Examples of the alkoxyalkyl (meth)acrylate include methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethoxy(meth)acrylate. Ethyl ester, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, (A) Base) 4-ethoxybutyl acrylate.

Examples of the mono(meth)acrylic alkoxy polyalkylene glycol esters include methoxybisethylene glycol mono(meth)acrylate and methoxydipropylene glycol mono(meth)acrylate. Ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene 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.

In addition, as a monomer component which forms the copolymer (A), a copolymerizable monomer such as a styrene monomer or a vinyl acetate can be used as long as the physical properties of the copolymer (A) are not impaired. That is, the copolymer (A) may further have a constituent unit derived from the above-mentioned copolymerizable monomer.

Examples of the styrene-based 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 or styrene iodide; nitrostyrene, ethyl styrene styrene, methoxy group Styrene.

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

In the case where 100% by mass of the monomer component of the copolymer (A) is formed, the total amount of the other monomer (for example, another (meth) acrylate or copolymerizable monomer) is preferably from 0 to 10% by mass. , preferably 0 to 5 mass %.

<<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 and a monomer component are added to the reaction vessel, and a polymerization initiator is added in an inert gas atmosphere such as nitrogen, and the reaction initiation temperature is usually 40 to 100 ° C, preferably 50 to 80 ° C. And the reaction system is usually maintained at a temperature of 50 to 90 ° C, preferably 70 to 90 ° C and reacted for 4 to 20 hours.

The copolymer (A) is obtained by, for example, copolymerizing a monomer component containing the above monomers (a1) to (a3), and may be a random copolymer or a block copolymer. Among these, a random copolymer is preferred.

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

Examples of the polymerization initiator used in the solution polymerization include an azo initiator and a peroxide initiator. Specific examples thereof include azo compounds such as 2,2'-azobisisobutyronitrile; peroxides such as benzamidine peroxide and lauric acid peroxide. Among these, an azo compound is preferred. Examples of the azo compound include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 2,2. '-Azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile ), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(aminomercaptoazo)isobutyronitrile, 2-phenylazo-4-methoxy-2, 4-dimethylvaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethylene isobutyl hydrazine , 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylguanamine) dihydrate, 4 , 4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis(2-methyl Propionate). These polymerization initiators may be used alone or in combination of two or more.

The polymerization initiator is usually 0.01 to 5 parts by mass, preferably in an amount ranging from 0.1 to 3 parts by mass, based on 100 parts by mass of the monomer component forming the (meth)acryl-based copolymer (A). Further, in the above polymerization reaction, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be added as appropriate.

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

(meth)acrylic copolymer (A) The weight average molecular weight (Mw) measured by a gel permeation chromatography (GPC) method, usually in terms of polystyrene It is 400,000 to 1.8 million, preferably 600,000 to 1.4 million, and more preferably 800,000 to 1 million. By using the copolymer (A) having the above-mentioned range of Mw and having the above monomer unit, the balance of the adhesive force (the balance of the storage elastic modulus (G'1) and (G'2)) and the viscosity are easily obtained. It is a suitable adhesive composition for coating.

The molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer (A) measured by the GPC method is usually 15 or less, preferably 2 to 10, and more preferably 4 to 8.

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 in accordance with the formula of Fox. For example, the monomers (a1) and (a2) having a glass transition temperature (Tg) of the homopolymer in the above range can be used in combination, and the glass transition temperature (Tg) obtained according to the formula of Fox is usually -70 to -20. The (meth)acrylic copolymer (A) is synthesized in a manner of °C, preferably from -60 to -30 °C. By using the (meth)acrylic copolymer (A) having the glass transition temperature (Tg), it is possible to obtain an adhesive composition which is excellent in stress relaxation properties and durability and excellent in adhesion at room temperature.

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, the glass transition temperature (unit: K), Tg ₁ , Tg ₂ , ..., Tg _m of the Tg-based (meth)acrylic copolymer (A) is a glass transition of a homopolymer composed of each monomer. Temperature (unit: K), W ₁ , W ₂ , ..., W _m is a weight fraction of the constituent unit derived from each monomer in the copolymer (A). As a weight fraction of the structural unit derived from each monomer, the ratio of addition of each monomer to all monomers at the time of copolymer synthesis can be used.

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, the content of the (meth)acrylic copolymer (A) in the solid content of 100% by mass of the composition other than the organic solvent is usually 60 to 99.99% by mass, preferably 70 to 99.95% by mass, particularly preferably 80 to 99.90% by mass. When the content of the (meth)acrylic copolymer (A) is in the above range, it is excellent in balance adhesive properties as an adhesive property.

[Crosslinking agent (B)]

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

The crosslinking agent (B) is a component which can cause a crosslinking reaction with a crosslinkable functional group derived from the crosslinking functional group-containing monomer (a3) which the (meth)acrylic copolymer (A) has. There is no particular limitation, and examples thereof include an isocyanate compound (B1), a metal chelate compound (B2), and an epoxy compound (B3).

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

In the adhesive composition of the present invention, relative to (methyl) The content of the crosslinking agent (B) is usually 0.01 to 5 parts by mass, preferably 0.05 to 2.5 parts by mass, more preferably 0.1 to 1 part by mass, based on 100 parts by mass of the acrylic copolymer (A). When the content is in the above range, it is preferable from the viewpoint of easily obtaining a balance between durability and stress relaxation characteristics.

Isocyanate Compound (B1)

As the isocyanate compound (B1), an isocyanate compound having two or more isocyanate groups in one molecule is usually used. By crosslinking the (meth)acryl-based copolymer (A) with the isocyanate compound (B1), a crosslinked body (network polymer) can be formed.

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

Examples of the diisocyanate compound having 2 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, and 2-methyl-1,5-pentyl. An aliphatic diisocyanate having 4 to 30 carbon atoms such as an alkyl diisocyanate, 3-methyl-1,5-pentane diisocyanate or 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, and cyclohexyl diisocyanate. An alicyclic diisocyanate having 7 to 30 carbon atoms such as hydrogenated benzodimethyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogen tetramethyl dimethyl diisocyanate. Examples of the aromatic diisocyanate include benzodiisocyanate, toluene diisocyanate, benzodimethyl diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate. An aromatic diisocyanate having a carbon number of 8 to 30.

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.

In addition, examples of the isocyanate compound (B1) include 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 an isocyanurate). And a derivative (for example, an addition reaction product of a polyhydric alcohol and two or more molecules of a diisocyanate compound) or a polymer. Examples of the low molecular weight polyol as the polyol in the above-mentioned derivative include a trivalent or higher alcohol such as trimethylolpropane, glycerin or neopentyl alcohol; and in the case of a high molecular weight polyol, For example, a polyether polyol, a polyester polyol, an acryl polyol, a polybutadiene polyol, and a polyisoprene polyol are mentioned.

Examples of the isocyanate compound include a trimer of diphenylmethane diisocyanate, a polymethylene polyphenyl polyisocyanate, a hexamethylene diisocyanate or a toluene diisocyanate biuret or Reaction product of isomeric cyanurate, trimethylolpropane with toluene diisocyanate or benzodimethyl diisocyanate (for example, a three-molecular adduct of toluene diisocyanate or dimethyl diisocyanate), trishydroxyl A reaction product of methyl propane and hexamethylene diisocyanate (for example, a 3-molecular adduct of hexamethylene diisocyanate), a polyether polyisocyanate, or a polyester polyisocyanate.

In the isocyanate compound (B1), a reaction product of trimethylolpropane with toluene diisocyanate or benzodimethyl diisocyanate is preferred from the viewpoint of the improvement of the ripening property (L-45, manufactured by Soken Chemical Co., Ltd.) , TD-75, etc. from Synthetic Chemical Co., Ltd.), isoamethylene cyanate of hexamethylene diisocyanate or toluene diisocyanate (TSE-100 manufactured by Asahi Kasei Co., Ltd., 2050 manufactured by Japan POLYURETHANE INDUSTRIAL CO., LTD., etc.) ).

The isocyanate compound (B1) may be used alone or in combination of two or more.

Metal Chelate Compound (B2)

Examples of the metal chelate compound (B2) include alkoxide, acetamidineacetone, ethyl acetate and the like, and are coordinated to aluminum, iron, copper, zinc, tin, titanium, nickel, ruthenium, magnesium, vanadium, A compound of a polyvalent metal such as chromium or zirconium.

Among these, an aluminum chelate compound (M-12AT manufactured by Soken Chemical Co., Ltd.) is particularly preferred. Specific examples include aluminum isopropylate, aluminum second butyrate, ethyl acetate, ethyl diisopropylate, aluminum triethyl acetate, and aluminum triethyl acetonate.

The metal chelate compound (B2) can be used alone or in combination. Two or more types can be used.

The metal chelate compound (B2) crosslinks (virtual crosslinks) the (meth)acrylic copolymer (A) by a coordinate bond. When the metal chelate compound (B2) is used as the crosslinking agent (B), the crosslinking is maintained and the polymer is cohesive at room temperature, and at a high temperature, a part of the crosslinking is released to cause the adhesive. The layer shows superior softness.

Epoxy Compound (B3)

As the epoxy compound (B3), an epoxy compound having 2 or more epoxy groups in one molecule is usually used. For example, ethylene glycol diepoxypropyl ether, polyethylene glycol diepoxypropyl ether, glycerol diepoxypropyl ether, glycerol triepoxypropyl ether, 1,3-double (N, N) -diepoxypropylamine methyl)cyclohexane, N,N,N',N'-tetraepoxypropyl-m-xylylenediamine, N,N,N',N'-tetraepoxypropyl Phenylaminomethane, triglycidyl isocyanate, N,N-diepoxypropylamine phenylepoxypropyl ether, N,N-diepoxypropyltoluamide, N, N-diepoxypropyl aniline.

[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 glass plate or the like to help prevent peeling in a high moist heat environment.

Examples of the decane coupling agent (C) include a polymerizable unsaturated group-containing decane coupling agent such as vinyl trimethoxy decane, vinyl triethoxy decane or methacryloxypropyl trimethoxy decane; 3-glycidoxypropyltrimethoxydecane, 3-glycidoxypropyltriethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, 3-epoxy Propoxypropylmethyldiethoxydecane, 2-(3,4-epoxy Epoxy-containing decane coupling agent such as hexyl)ethyltrimethoxydecane; 3-aminopropyltrimethoxydecane, N-(2-aminoethyl)-3-aminopropyltrimethoxydecane, N- An amine group-containing decane coupling agent such as (2-aminoethyl)-3-aminopropylmethyldimethoxydecane; or a halogen-containing decane coupling agent such as 3-chloropropyltrimethoxydecane.

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, per 100 parts by mass of the (meth)acrylic copolymer (A). More preferably, it is 0.05 to 0.5 part by mass. When the content is in the above range, there is a tendency to prevent the polarizing plate from peeling off in a high-humidity heat environment and the decane coupling agent (C) to ooze out in a high-temperature environment.

[Antistatic agent (D)]

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

Examples of the surfactant include a cationic surfactant of a 4-stage ammonium salt, a guanamine 4-grade ammonium salt, a pyridium salt, and a cationic group having a first- to third-order amine group; An anionic surfactant having an anionic group such as a sulfonate group, a sulfate group or a phosphate group; an alkylbetaine, an alkylimidazole betaine, an alkylamine oxide, an amino acid Amphoteric surfactants such as sulfates, glycerin fat Acid esters, sorbitan fatty acid esters, polyoxyethylidene amines, polyoxyalkylene amine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines, alkanes A nonionic surfactant such as bisestole amide.

Further, a reactive emulsifier having a polymerizable group may be used as the surfactant, and a polymer interface activity obtained by polymerizing a monomer component containing the above surfactant or reactive emulsifier may be used. Agent.

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 cationic 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 more preferably Li ⁺ , Na ⁺ and K ⁺ having excellent antistatic properties. Examples of the organic cation include a pyridinium cation, a piperidine cation, a pyrrolidine cation, a pyrroline cation, a pyrrole cation, an imidazolium cation, a tetrahydropyrimidine cation, a dihydropyrimidinium cation, a pyrazole cation, and a pyrazoline. a cation, a tetraalkylammonium cation, a trialkylsulfonium cation, a tetraalkylphosphonium cation, and the like.

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 ^- , Al2Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , SCN ^- , ClO ₄ ^- , NO ₃ ^- , CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (F ₂ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₃ C ^- , AsF ₆ ^- , SbF ₆ ^- , NbF ₆ ^- , TaF ₆ ^- , F(HF) _n ^- , (CN) ₂ N ^- , C ₄ F ₉ SO ₃ ^- , (C ₂ F ₅ SO ₂ ) ₂ N ^- , C ₃ F ₇ COO ^- and (CF ₃ SO ₂ )(CF ₃ CO)N ^- . Among these, since an anion of a fluorine atom can provide an ionic compound having a lower melting point, it is preferably (F ₂ SO ₂ ) ₂ N ^- and (CF ₃ SO ₂ ) ₂ N ^- .

As the ionic compound, lithium bis(trifluoromethanesulfonyl) phthalimide, lithium bis(difluorosulfonyl) ruthenium, lithium sulfonate (trifluoromethanesulfonyl) methane, and bis (three) are preferable. Fluoromethanesulfonyl) sulfonium imide, potassium bis(difluorosulfonyl) phthalimide, 1-ethylpyridine hexafluorophosphate, 1-butylpyridine hexafluorophosphate, 1-hexyl-4- Methylpyridine hexafluorophosphate, 1-octyl-4-methylpyridine hexafluorophosphate, 1-octyl-4-methylpyridine bis(fluorosulfonyl) quinone imide salt, 1-octyl- 4-methylpyridine bis(trifluoromethanesulfonyl) sulfinium salt, (N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate, N,N-Diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl) quinone imide salt, 1-octylpyridine fluoroquinone imide salt , 1-octyl-3-methylpyridine, trifluoroimide.

Examples of the conductive polymer include polythiophene, polyaniline, polypyrrole, and the like.

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 Organic solvent (E). The organic solvent may, for example, be 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 and the crosslinking agent (B) can be mixed 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 the total component obtained by removing the organic solvent (E) from the components contained in the adhesive composition, and the "solid content concentration" means the adhesive relative to the adhesive. 100% by mass of the composition, the ratio of the aforementioned solid content.

[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 a crosslinking promotion, insofar as the effects of the present invention are not impaired. One or two or more kinds of the (meth)acrylic polymer and the rework agent other than the above (A).

[Modulation of Adhesive Composition for Polarizing Plate]

The adhesive composition of the present invention can be prepared by mixing a (meth)acrylic copolymer (A), a crosslinking agent (B), and other components as necessary, by a conventionally known method. For example, in the polymer solution containing the polymer obtained by synthesizing the (meth)acrylic copolymer (A), the crosslinking agent (B) and other components as necessary may be blended.

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

The gel fraction of the adhesive formed of the adhesive composition of the present invention is preferably 40% by mass or more, more preferably 50 to 80% by mass, still more preferably 55 to 70% by mass. The gel fraction is a value measured for the adhesive to be taken, for example, under the conditions described in the examples.

[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 adhesive layer of the present invention has a storage elastic modulus (G'1) at 23 ° C of preferably 0.10 MPa or more, more preferably 0.10 to 0.20 MPa, particularly preferably 0.10 to 0.15 MPa; storage elasticity at 85 ° C The modulus (G'2) is preferably 0.05 MPa or less, more preferably 0.01 to 0.04 MPa, and particularly preferably 0.01 to 0.03 MPa.

In the adhesive layer of the present invention, the storage elastic modulus of a certain temperature T°C is set to G′ _T , the storage elastic modulus of T+1° C. is set to G′ _T+1 , and the temperature T is 23 to 50° C. The range is preferably constant to satisfy G' _T /G' _T+1 <1.07, and more preferably satisfies 1≦G' _T /G' _T+1 ≦1.05.

The above storage elastic modulus is, for example, the above adhesive A layered body having a thickness of about 1.0 mm was bonded to the layers to form a value calculated from the dynamic viscoelastic spectrum measured by the layered body.

By setting the storage elastic modulus (G'1) at 23 ° C to the above range, the adhesive layer of the present invention is excellent in room temperature hardness and improved in workability. For example, when the adhesive layer is cut, it is possible to prevent the adhesive from adhering to the cutting blade, the drawing of the adhesive layer, and the like.

By setting the storage elastic modulus (G'2) at 85 ° C to the above range, since the adhesive layer of the present invention has sufficient flexibility in a high temperature environment, heat shrinkage (size) due to the polarizer can be obtained. The stress of change) is fully mitigated. Therefore, even if exposed to a high temperature environment, the warpage of the adherend can be reduced, and the adhesive layer is not easily broken, and the adhesive layer is peeled off from the polarizer.

The fact that G' _T /G' _T+1 <1.07 is constantly satisfied in the range of 23 to 50 ° C means that the change in the elastic modulus in this temperature range is small, and deformation and extrusion of the adhesive layer can be suppressed.

The adhesive layer formed of the adhesive composition of the present invention preferably has a gel fraction of 40% by mass or more, more preferably from the viewpoints of strain suppression, cohesive force, adhesion, and removability of the polarizing plate. 50 to 80% by mass, and more preferably 55 to 70% by mass. When the gel fraction is in the above range, the adhesive layer exhibits excellent durability.

The adhesive layer of the present invention is subjected to a crosslinking reaction by, for example, the above-mentioned adhesive composition, specifically, crosslinking by a crosslinking agent (B) starting (meth)acrylic copolymer (A). get.

The conditions for forming the adhesive layer are as follows, for example. will The adhesive composition of the present invention is applied to a support, and depending on the kind 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 The solvent was removed to form a coating film up to 7 minutes. 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 under the following conditions. The adhesive composition of the present invention is applied onto a support, and after the cover film is attached to the coating film formed under the above conditions, it is usually 3 days or longer, preferably 7 to 10 days, usually 5 to The aging is carried out in an environment of 60 ° C, preferably 15 to 40 ° C, usually 30 to 70% RH, preferably 40 to 70% RH. When cross-linking is carried out under the above-mentioned ripening conditions, the crosslinked body (mesh polymer) can be efficiently formed.

As a coating method of the adhesive composition, a well-known method can be used, for example, a spin coating method, a knife coating method, a roll coating method, a bar coating method, a blade coating method, a die coating method, and a gravure coating method. A method of coating/drying, such as a cloth method, to have a predetermined thickness.

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-described adhesive composition. Examples of the adhesive sheet include a double-sided adhesive sheet having only the above-mentioned adhesive layer; a substrate; and two sides of the substrate; a double-sided adhesive sheet of the above adhesive layer; a single-sided adhesive sheet having a substrate and the above-mentioned adhesive layer formed on one side of the substrate; and a surface of the adhesive layer of the adhesive sheet not in contact with the substrate Adhesive sheets made of a release-coated cover film are attached.

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 from 5 to 75 μm, preferably from 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 polarizing plate with an adhesive layer of the present invention has an adhesive layer formed of the adhesive composition of the present invention directly laminated on at least one side of the polarizing plate. In addition, in the present specification, the "polarizing plate" is used in the sense of including a "polarizing film".

As the polarizing plate, a previously known polarizing film can be used. For example, a polarizer itself, and a multilayer film having a polarizer and a polarizer protective film disposed on the polarizer may be mentioned. In the present invention, since the pressure-sensitive adhesive layer is directly placed in contact with the polarizer, a configuration in which the polarizer protective film is disposed only on one surface of the polarizer, and the polarizer is disposed on the polarizer The polarizer protective film is not disposed on both sides.

The polarizing film is, for example, a stretched film obtained by stretching a film made of a polyvinyl alcohol-based resin and containing a polarizing component. Examples of the polyvinyl alcohol-based resin include saponified products of polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, and ethylene-vinyl acetate copolymer. Examples of the polarizing component include iodine or a dichroic dye.

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

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

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 is, for example, a laminated polarizer protective film, a polarizer, and the above-mentioned adhesive layer; the adhesive layer, the polarizer protective film, the polarizer, and the above adhesive are sequentially laminated. The composition of the layers; and the formation of the above-mentioned adhesive layer, polarizer and the above-mentioned adhesive layer. In such a configuration, the cover film may be disposed on the adhesive layer as the outermost layer.

The method of forming an adhesive layer on the surface of the polarizer is not In particular, a method of applying the above-described adhesive composition to the surface of a polarizer and drying and aging it by using a bar coater or the like; and an adhesive layer having the adhesive sheet for a polarizing plate of the present invention A method of transferring to a surface of a polarizer and aging it. The conditions for drying and aging, the gel fraction range, 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. Further, the adhesive layer may be formed by contacting the polarizer with at least one surface of the polarizer, and may be an aspect in which an adhesive layer is formed only on one surface of the polarizer; and an adhesive layer is formed on both surfaces of the polarizer. Aspect.

Further, in the polarizing plate, a layer having other functions such as a protective layer, an antiglare layer, a retardation layer, and a viewing angle lifting layer may be laminated.

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

As a substrate which a liquid crystal cell has, a glass plate is mentioned, for example. The thickness of the substrate is usually from 0.05 to 3 mm, preferably from 0.2 to 1 mm. In the present invention, by using the above-described adhesive composition, warpage of the polarizing plate and the substrate can be suppressed even when the adhesive layer is directly laminated on the polarizer. Therefore, even when the thickness of the substrate is small (for example, 1 mm or less, preferably 0.2 to 1 mm), the above-mentioned adhesive composition can be suitably used for bonding a polarizing plate and a substrate.

[Examples]

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the examples. In the following 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) under the following conditions to obtain a weight average molecular weight (Mw) and a number average molecular weight (Mn).

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

. GPC column structure: The following four connecting columns (all manufactured by TOSOH Co., Ltd.)

(1)TSKgel HxL-H (protective 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]

In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen introduction tube, 39 parts of 2-ethylhexyl acrylate, 56 parts of 2-ethylhexyl methacrylate, and 5 parts of 2-hydroxyethyl methacrylate were added. And ethyl acetate 100 parts of the solvent was heated to 80 ° C while introducing nitrogen gas. Next, 0.1 part of 2,2'-azobisisobutyronitrile was added, and the polymerization reaction was carried out for 6 hours under a nitrogen atmosphere at 80 °C. 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. The weight average molecular weight (Mw) of the obtained (meth)acrylic copolymer A1 was 910,000, and the molecular weight distribution (Mw/Mn) was 6.2.

[Synthesis Examples 2 to 5]

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 to those shown 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 (solid content), "TD-75" (solid content: 75 mass%, ethyl acetate solution) 0.2 parts (solid content), which is an isocyanate compound, and Shin-Etsu Chemical Industry Co., Ltd. as a decane coupling agent 0.2 parts of "KBM-403" (100% by mass of solid content) manufactured by the company was mixed to obtain an adhesive composition.

(2) Manufacture of adhesive sheets

The adhesive composition obtained in the above (1) was defoamed, coated on a release-treated polyethylene terephthalate film (PET film) using a knife coater, and dried at 90 ° C for 3 minutes to form a dry film. A coating film having a film thickness of 20 μm. The PET film which was peeled off was further bonded to the surface of the coating film opposite to the surface of the PET film, and it was aged at 7 ° C / 50% RH for 7 days, and it was obtained in two pieces. The PET film was sandwiched by an adhesive sheet having an adhesive layer having a thickness of 20 μm.

(3) Manufacture of polarizing plate with adhesive layer

The adhesive composition obtained in the above (1) was defoamed, and then applied onto a release-treated polyethylene terephthalate film (PET film) using a knife coater, followed by drying at 90 ° C for 3 minutes. A sheet having a coating film having a dried film thickness of 20 μm. The coating film surface of the sheet was in contact with the polyvinyl alcohol film of a polarizing plate composed of two layers (thickness: 60 μm) composed of a polyvinyl alcohol film of a polarizing plate and a cellulose triacetate film of a polarizer. The film was laminated, and it was aged at 7 ° C / 50% RH for 7 days to obtain an adhesive layer having a PET film, a thickness of 20 μm, a polarizer, and a polarizer protective film. A polarizing plate of the adhesive layer.

[Example 2, Comparative Examples 1 to 3]

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 5, and the composition was changed to the same as in Example 1, the adhesive composition was obtained. Adhesive sheet and polarizing plate with adhesive layer.

[Evaluation] [Gel fraction]

From the adhesive sheets obtained in the examples and the comparative examples, about 0.1 g of an adhesive was applied to a sampling bottle, and 30 mL of ethyl acetate was added thereto, and after shaking for 4 hours, the contents of the sample bottle were filtered using a 200 mesh stainless steel wire mesh. Further, the residue on the wire mesh was dried at 100 ° C for 2 hours and the dry weight was measured. The gel fraction of the adhesive was determined according to the following formula.

. Gel fraction (%) = (dry weight / adhesive 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 a 23° C./50% RH atmosphere, and were subjected to an autoclave treatment at 50° C./5 atm for 20 minutes to have a thickness of 1.0. Mm adhesive layer. For the adhesive layer having a thickness of 1.0 mm, "Physica MCR300" manufactured by Anton Paar was used and the dynamic viscoelasticity measurement method according to JIS K7244 (temperature range -40 to 160 ° C, temperature increase rate 3.67 ° C / minute, frequency 1 Hz) was used. The viscoelastic spectrum was determined to determine the storage elastic modulus at temperatures of 23 ° C and 85 ° C, and the maximum value of G' _T /G' _T+1 in the range of 23 to 50 ° C.

[Measurement of adhesion]

Will be the embodiment. The polarizing plate with an adhesive layer obtained in the comparative example (a laminate composed of a PET film/adhesive layer/polarizer/polarizer protective film) was cut into a size of 70 mm × 25 mm to prepare a test piece. The PET film was peeled off from the test piece, and the laminate composed of the adhesive layer/polarizer/polarizer protective film was attached to one side of the glass plate having a thickness of 2 mm by using the adhesive layer in contact with the glass plate. . The obtained laminate was kept in an autoclave adjusted to 50 ° C / 5 atmosphere for 20 minutes. Next, after allowing to stand in an environment of 23 ° C / 50% RH for 1 hour, the end portion of the polarizing plate was stretched at a speed of 300 mm/min in a direction of 90° with respect to the glass plate surface, and the adhesion (peeling strength) was measured.

[Water vapor transmission rate]

The water vapor transmission rate was measured in accordance with JIS Z0208 as follows. An adhesive sheet having an adhesive layer having a thickness of 50 μm was produced in the same manner as in the method described in "(2) Manufacturing of Adhesive Sheet". The PET film was peeled off from the test piece, and the nonwoven fabric was bonded to both surfaces of the pressure-sensitive adhesive layer (the obtained laminate was referred to as "sheet A"), and the diameter of the moisture-permeable cup was adjusted to cut. 10 g of calcium chloride was added to the moisture permeable cup (inner diameter 60 mm), and the cut sheet A, the rubber spacer, and the cover ring were attached and fixed by bolts. Sheet A will be installed under constant temperature and humidity conditions of 40 ° C / 90% RH After the moisture-permeable cup is put in, the moisture-permeable cup is taken out after 24 hours and the weight (initial weight) of the moisture-permeable cup is weighed. The weighed cup after weighing was placed back to 40 ° C / 90% RH and weighed for 24 hours. When the mass increase per 24 hours is within the range of 5%, the water vapor transmission rate is calculated from the last mass change amount and the measurement interval by the following formula.

Water vapor transmission rate [g/m ² /day]=240×M/T×S

M: the mass of the last two weighing intervals of the test (mg)

T: time (hours) between the last two weighing intervals of the test

S: transmission area (cm ² )

[Durability Test (Heat Resistance, Moisture and Heat Resistance Test)]

The polarizing plate with an 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 make a test. sheet. The PET film was peeled off from the test piece, and the laminate composed of the adhesive layer/polarizer/polarizer protective film was attached to the glass having a thickness of 0.5 mm by contact with the glass plate using a bonding machine roll. One side of the board. The obtained laminate was held in an autoclave adjusted to 50 ° C / 5 atmosphere 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 peeling were observed based on the following criteria. The evaluation was made.

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

BB: Only some appearance defects such as micro-foaming, floating, peeling, etc. were observed.

CC: Observed obvious appearance defects such as foaming, floating, peeling, etc.

[warping (bending) test]

The polarizing plate with an adhesive layer obtained in the examples and the comparative examples (the laminated body composed of the PET film/adhesive layer/polarizer/polarizer protective film) was cut into 35 mm×400 mm (extension axis direction). Make a test piece of size. The PET film was peeled off from the test piece, and the laminate composed of the adhesive layer/polarizer/polarizer protective film was attached to the thickness of 0.7 mm and 40 mm by contact of the adhesive layer with the glass plate using a bonding machine roll. One side of a ×410mm glass plate. The obtained laminate was allowed to stand in an environment of 23 ° C / 50% RH for 24 hours, and then kept in an oven at 60 ° C for 72 hours. One end was fixed to a wall surface perpendicular to the ground, and the amount of floating at the opposite end was measured using a ruler. The observation of warpage (bending) was performed based on the following criteria.

AA: The floating of the end is 3mm or less

BB: The floating of the end is more than 3mm and less than 5mm

CC: The floating at the end is 5mm or more

[Processability (cutting)]

The adhesive sheets obtained in the examples and the comparative examples were cut into 30 pieces using a THOMSON punching machine and a THOMSON blade of 50 mm × 50 mm. The shape of the end portion immediately after the cutting was observed, and the extrusion of the paste, the collapse of the end portion, and the defect of the adhesive layer were not observed in one of the 30 sheets, and it was judged as AA, and the observer was judged to be CC.

[Adhesive deformability]

The polarizing plate with the adhesive layer obtained in the examples and the comparative examples was cut into 100 mm × 100 mm and 10 sheets were laminated, and a load of 1 kg was applied from above and left for 24 hours, and the adhesive layer was visually observed based on the following criteria. Extrusion.

AA: No adhesive layer extrusion observed

BB: Only some micro-adhesive layer extrusion was observed.

CC: Obvious adhesion of the adhesive layer was observed

As a monomer for forming a (meth)acrylic copolymer, as shown in the embodiment (1), the monomer (a1) and the monomer (a2) are used in the above specific ratio, and have durability and warpage. The inhibition, workability, and adhesion non-deformability are excellent; as shown in (2) Comparative Example 1, the monomer (a1) is not used, The heat resistance and the suppression of warpage are poor; as shown in (3) Comparative Example 2, the monomer (a1) and the monomer (a2) are not used in the above specific ratio, and the heat resistance and the warpage are poor. As shown in (4) Comparative Example 3, the example in which the monomer (a2) was not used was a result of poor workability and adhesion non-deformability.

Claims (6)

An adhesive composition for a polarizing plate comprising: (A) a methacrylic copolymer containing an alkyl acrylate (a1) having an alkyl carbon number of 8 or more and 30% by mass or more and less than 90% by mass 10% by mass or more and less than 70% by mass of an alkyl methacrylate (a2) having an alkyl group number of 8 or more, and a crosslinkable functional group-containing monomer in an amount of more than 0% by mass and 10% by mass or less (a3) a monomer component obtained by copolymerization; and (B) a crosslinking agent, and the above-mentioned adhesive composition for a polarizing plate is used to form an adhesive layer directly in contact with the polarizer. The adhesive composition for a polarizing plate according to the first aspect of the invention, wherein the adhesive composition of the adhesive composition for a polarizing plate has a gel fraction of 40% by mass or more. An adhesive layer for a polarizing plate is formed of the adhesive composition as described in claim 1 or 2. The adhesive layer for a polarizing plate according to claim 3, wherein the storage elastic modulus at 23 ° C is 0.10 MPa or more, the storage elastic modulus at 85 ° C is 0.05 MPa or less, and a certain temperature T ° C When the storage elastic modulus is set to G' _T and the storage elastic modulus of T+1 ° C is set to G' _T+1 , the temperature T is in the range of 23 to 50 ° C, and the G' _T /G is constantly satisfied. ' _T+1 <1.07. An adhesive sheet for a polarizing plate having an adhesive layer as described in claim 3 or 4. A polarizing plate with an adhesive layer having an adhesive layer directly laminated on at least one side of the polarizer as described in claim 3 or 4.