KR20160135198A - Adhesive composition for polarizing plate, adhesive sheet and polarizing plate with adhesive layer - Google Patents

Abstract

[assignment]
A pressure-sensitive adhesive composition for a polarizing plate capable of suppressing warping (bending) of a liquid crystal cell and capable of forming a pressure-sensitive adhesive layer having excellent durability.
[Solution]
(A) a monomer component comprising a (meth) acrylic acid alkyl ester having 4 to 18 carbon atoms in the alkyl group and a hydroxyl group-containing monomer, and is obtained by copolymerization with a gel permeation chromatography / polygonal laser light scattering detector (GPC-MALS) (B) an isocyanate compound, wherein the (meth) acrylic copolymer has a degree of branching of not more than 0.55 as measured by a differential scanning calorimeter.

Description

TECHNICAL FIELD [0001] The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate, a pressure-sensitive adhesive sheet, and a polarizer having a pressure-

The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate.

The liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates (for example, a glass plate), and a polarizer is attached to the surface of the substrate through a pressure-sensitive adhesive layer. The polarizing plate is liable to have insufficient dimensional stability due to easy heat shrinkage under a high temperature and high humidity and heat environment, and the liquid crystal cell may be warped in some cases. In recent years, according to the thinning of the liquid crystal cell (for example, the thinning of the substrate constituting the liquid crystal cell) and the thinning of the polarizing plate, warping of the liquid crystal cell under a high temperature and high humidity heat environment becomes more serious. Examples of the cause of the warping of the liquid crystal cell include the fact that the pressure-sensitive adhesive layer can not follow the heat shrinkage (dimensional change) of the polarizing plate and the stress relieving property of the pressure-sensitive adhesive layer is low.

Further, under a high temperature / high humidity / heat environment, problems such as foaming at the interface between the polarizing plate and the substrate, heat insulation of the pressure-sensitive adhesive layer, and peeling of the polarizing plate are likely to occur. Therefore, a high durability is required for the pressure sensitive adhesive for a polarizing plate.

Generally, as a means for suppressing warping of a liquid crystal cell, a method of using a pressure-sensitive adhesive layer having high flexibility capable of coping with the dimensional change of the polarizing plate can be mentioned. However, in such a pressure-sensitive adhesive layer, cohesive force is insufficient and problems such as deterioration of durability and deterioration of workability are caused.

For example, Patent Document 1 discloses a method of forming a pressure-sensitive adhesive layer by cross-linking a specific (meth) acrylic polymer with a pressure-sensitive adhesive for an optical film containing a peroxide and an isocyanate compound. Patent Document 1 discloses that by using both a crosslinking method using a thermal decomposition crosslinking reaction by peroxide and a crosslinking method using an isocyanate compound forming a urethane bond, sufficient stress is applied to the stress due to the dimensional change of the optical film It is described that high durability can be maintained while maintaining the relaxation characteristics.

Japanese Patent Application Laid-Open No. 2006-183022

A pressure sensitive adhesive composition for a polarizing plate capable of suppressing warping (bending) of a liquid crystal cell and capable of forming a pressure sensitive adhesive layer having excellent durability, a pressure sensitive adhesive sheet for a polarizing plate having a pressure sensitive adhesive layer formed from the composition, Sensitive adhesive layer with a pressure-sensitive adhesive layer.

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above problems. As a result, it is possible to suppress warpage (bending) of the liquid crystal cell when a (meth) acrylic copolymer having a branching degree in a specific range is used and an isocyanate compound is used as a crosslinking agent, A pressure-sensitive adhesive layer can be formed. The above-mentioned Patent Document 1 does not mention such a branching diagram at all. That is, the present inventors have found that the above problems can be solved by using the pressure-sensitive adhesive composition for a polarizing plate having the following specific composition, and have completed the present invention.

The present invention is, for example, the following [1] to [8].

[1] A method for producing an acrylic resin composition, which comprises the steps of (A) copolymerizing a monomer component comprising (A) a (meth) acrylic acid alkyl ester having 4 to 18 carbon atoms in the alkyl group and a monomer containing a hydroxyl group, (Meth) acrylic copolymer having a degree of branching of not more than 0.55 as measured by MALS and (B) an isocyanate compound.

[2] The pressure-sensitive adhesive composition for a polarizing plate according to the above [1], wherein the (meth) acrylic copolymer (A) is a copolymer obtained by copolymerization in the presence of a peroxide-based polymerization initiator.

[3] The toner according to the above [1] or [2], wherein the weight average molecular weight (Mw) of the (meth) acrylic copolymer (A) measured by gel permeation chromatography (GPC) Sensitive adhesive composition for a polarizing plate.

[4] The pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [3], wherein the branching degree measured by GPC-MALS of the (meth) acrylic copolymer (A) is 0.10 to 0.54.

[5] The pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [4], wherein the content of peroxide is 0.1 part by mass or less based on 100 parts by mass of the (meth) acrylic copolymer (A).

[6] The pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [5], wherein the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition for a polarizing plate has a gel fraction of 20 to 70 mass%.

[7] A pressure-sensitive adhesive sheet for a polarizing plate, comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [6].

[8] A polarizing plate with a pressure-sensitive adhesive layer, comprising a polarizing plate and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [6], on at least one surface of the polarizing plate.

According to the present invention, it is possible to provide a pressure-sensitive adhesive composition for a polarizing plate capable of suppressing bending (bending) of a liquid crystal cell and capable of forming a pressure-sensitive adhesive layer having excellent durability, a pressure-sensitive adhesive sheet for a polarizing plate having a pressure- Sensitive adhesive layer-containing polarizer can be provided.

Hereinafter, the pressure-sensitive adhesive composition for a polarizing plate, the pressure-sensitive adhesive sheet for a polarizing plate and the polarizing plate with a pressure-sensitive adhesive layer of the present invention will be described. Hereinafter, the pressure-sensitive adhesive composition for a polarizing plate of the present invention is also simply referred to as a "pressure-sensitive adhesive composition", and the pressure-sensitive adhesive sheet for a polarizing plate of the present invention is also simply referred to as "pressure-sensitive adhesive sheet".

[Pressure sensitive adhesive composition for polarizing plate]

The pressure-sensitive adhesive composition for a polarizing plate of the present invention contains a (meth) acrylic copolymer (A) and an isocyanate compound (B). The pressure-sensitive adhesive composition may contain at least one member selected from a silane coupling agent (C), an antistatic agent (D) and an organic solvent (E), if necessary.

[( Meta ) Acrylic copolymer (A)]

(Meth) acrylic copolymer (A) is a copolymer obtained by copolymerizing a monomer component containing an alkyl (meth) acrylic acid alkyl ester having 4 to 18 carbon atoms in the alkyl group and a hydroxyl group-containing monomer. Examples of the monomer component of the copolymer (A) include a monomer having a polar group other than the monomer having a hydroxyl group, and other monomers.

In the present specification, acrylic and methacrylic are collectively referred to as " (meth) acrylic ". The structural unit derived from any monomer a contained in the polymer is also referred to as " monomer a unit ".

The (meth) acrylic copolymer (A) has a degree of branching of 0.55 or less, preferably 0.10 to 0.54, more preferably 0.20 to 0.50, as measured by a gel permeation chromatography / multi-angle laser light scattering detector (GPC-MALS) 0.53, particularly preferably 0.30 to 0.53. The details of the measurement conditions of the branching degree are described in Examples.

The degree of branching is an indicator indicating that the polymer is a linear polymer when it is 0.55 or less and is a linear polymer when it is more than 0.55. When the value of the branching degree in the branched polymer is small, the branches of the polymer molecules are highly branched so as to have a high branching chain. When the branching degree is large, the branches of the polymer molecules are divided little, .

The (meth) acrylic copolymer (A) having the branching degree within the above range is likely to be entangled with each other due to branching of the polymer molecules at room temperature (1), and as a result, the molecular weight of the polymer and the gel fraction Also in this low design, the cohesiveness of the polymer is maintained, so that a pressure-sensitive adhesive layer having excellent adhesive properties, processability such as punching of the pressure-sensitive adhesive layer, and less deformation or puckering of the pressure-sensitive adhesive layer or excellent storage property can be obtained; (2) At the high temperature (for example, 60 DEG C), the entanglement between the polymer molecules is partially loosened, so that the pressure-sensitive adhesive layer exhibits excellent flexibility and is excellent in suppressing bending of the polarizing plate, The pressure-sensitive adhesive layer exhibits excellent durability.

It is presumed that the reason why the warpage of the polarizing plate is suppressed is as follows. For example, in the case of a polarizer / pressure-sensitive adhesive layer / adherend, a glass plate is used as an adherend. The polarizing plate and the glass plate each have different heat shrinkage ratios, and the polarizing plate usually has a larger heat shrinkage ratio (dimensional change) than a glass plate. The pressure-sensitive adhesive layer can not follow the dimensional change of the polarizing plate and the stress can not be relaxed in the pressure-sensitive adhesive layer, so that the stress is concentrated on the glass plate, Warpage occurs. On the other hand, the pressure-sensitive adhesive layer formed by using the pressure-sensitive adhesive composition of the present invention contains a high branching-chain polymer, and the entanglement is partially loosened under a high-temperature and high-humidity heat environment. Therefore, Therefore, stress does not occur and stress is not concentrated on the glass plate. Also, the polarizing plate can be uniformly heat-shrunk without anisotropy and does not cause birefringence of the polarizing plate. As described above, in the present invention, it is assumed that the pressure sensitive adhesive layer can absorb and mitigate the stress due to the dimensional change of the polarizing plate, and therefore, the excessive stress (load) is not applied to the glass plate.

The pressure-sensitive adhesive composition of the present invention is suitable for the application of the substrate constituting the liquid crystal cell and the polarizing plate in the point of having the above-described characteristics. Particularly, even when the thickness of the glass plate constituting the thinned liquid crystal cell is as small as about 0.1 to 1.0 mm, it is suitable for the application of the substrate to the polarizing plate.

"( Meta ) Acrylic acid Alkyl ester "

As the (meth) acrylic acid alkyl ester, a (meth) acrylic acid alkyl ester (CH ₂ = CR ¹ -COOR ² wherein the alkyl group has 4 to 18 carbon atoms, R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 4 to 18 carbon atoms ) Is used, wherein the number of carbon atoms of the alkyl group is more preferably 4 to 12 carbon atoms.

Examples of the (meth) acrylic acid alkyl ester having 4 to 18 carbon atoms in the alkyl group include n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert- (Meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (Meth) acrylate, undecane (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate and isostearyl (meth) acrylate. These may be used alone or in combination of two or more.

From the viewpoint of good adhesion and durability, the total amount of the alkyl (meth) acrylic copolymer (A) and the (meth) acrylic acid alkyl ester having 4 to 18 carbon atoms in the alkyl group in 100 mass% of the monomer component is preferably 99.8 to 20 mass %, More preferably 99.5 to 30 mass%, still more preferably 99 to 50 mass%.

(Meth) acrylic acid alkyl ester (CH ₂ = CR ³ -COOR ^{4 wherein} R ³ is a hydrogen atom or a methyl group and R ⁴ is a carbon number Or an alkyl group having 1 to 3 carbon atoms).

Examples of the (meth) acrylic acid alkyl ester having 1 to 3 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate and isopropyl (meth) . These may be used alone or in combination of two or more.

The amount of the (meth) acrylic acid alkyl ester having 1 to 3 carbon atoms in the alkyl group is preferably 60% by mass or less, more preferably 50% by mass or less, and still more preferably 60% by mass or less based on 100% by mass of the monomer component from the standpoint of stress relaxation property Is not more than 40% by mass.

&Quot; Hydroxyl group-containing monomers "

Examples of the hydroxyl group-containing monomer include hydroxyl group-containing (meth) acrylates. Specific examples thereof include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (Meth) acrylate such as hydroxyethyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and 8-hydroxyoctyl (meth) acrylate. The number of carbon atoms of the hydroxyalkyl group in the hydroxyalkyl (meth) acrylate is usually 2 to 8, preferably 2 to 6.

The hydroxyl group contained in the hydroxyl group-containing monomer functions as a crosslinkable functional group with the isocyanate group contained in the isocyanate compound (B). The amount of the hydroxyl group-containing monomer to be used is preferably 0.01 to 15% by mass, more preferably 0.05 to 10% by mass, and still more preferably 0.1 to 5% by mass in 100% by mass of the monomer component. When the amount of the hydroxyl group-containing monomer is not more than the upper limit, the crosslink density formed by the (meth) acrylic copolymer (A) and the isocyanate compound (B) is not excessively high and an adhesive layer excellent in stress relaxation properties is obtained . When the amount of the hydroxyl group-containing monomer is not less than the lower limit value, a crosslinking structure is effectively formed, and a pressure-sensitive adhesive layer having appropriate strength at room temperature can be obtained.

&Quot; Polar group containing monomer "

The monomer component forming the (meth) acrylic copolymer (A) may further contain a polar group-containing monomer in addition to the monomer. As the polar group-containing monomer, it is preferable to use a monomer having a polar group (crosslinkable functional group) capable of reacting with an isocyanate group of the isocyanate compound (B).

Examples of the polar group-containing monomer include an acid group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, a nitrogen-containing heterocyclic group-containing monomer, and a cyano group-containing monomer. In the present specification, examples of the acid group include a carboxyl group, an acid anhydride group, a phosphoric acid group and a sulfuric acid group.

Examples of the carboxyl group-containing monomers include (meth) acrylic acid? -Carboxyethyl, (meth) acrylic acid 5-carboxypentyl, succinic acid mono (meth) acryloyloxyethyl ester,? -Carboxypolycaprolactone mono Carboxyl group-containing (meth) acrylates such as a carboxylate group; Acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid and 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 (meth) acrylic monomers having a phosphate group in the side chain and the (meth) acrylic monomers having a sulfate group in the side chain.

Examples of the amino group-containing monomer include amino group-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate. Examples of the amide group-containing monomer include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide and N-hexyl . Examples of the nitrogen-containing heterocyclic ring-containing monomer include vinyl pyrrolidone, acryloyl pyridine and vinyl caprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

The polar group-containing monomers may be used singly or in combination of two or more.

The total amount of the polar group-containing monomer in the copolymerization is preferably 20 mass% or less, more preferably 10 mass% or less, in 100 mass% of the monomer component. The acid value of the (meth) acrylic copolymer (A) is preferably 10.0 mgKOH / g or less, and more preferably 5.0 mgKOH / g or less.

"Other monomers"

The monomer component forming the (meth) acrylic copolymer (A) may be, for example, an alkoxyalkyl (meth) acrylate, an alkoxypolyalkyleneglycolmono (meth) acrylate or the like in the range not impairing the physical properties of the (Meth) acrylate, an alicyclic group, or an aromatic ring-containing (meth) acrylate.

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

Examples of the alkoxypolyalkylene glycol mono (meth) acrylate include methoxy diethylene glycol mono (meth) acrylate, methoxy dipropylene glycol mono (meth) acrylate, ethoxy triethylene glycol (Meth) acrylate, methoxy (meth) acrylate, ethoxy diethylene glycol mono (meth) acrylate, and methoxy triethylene glycol mono (meth) acrylate.

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

The total amount of the other (meth) acrylic acid esters in the copolymerization is preferably 60 mass% or less, more preferably 40 mass% or less, in 100 mass% of the monomer component.

In the range of not impairing the physical properties of the (meth) acrylic copolymer (A), for example, styrene, methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, butylstyrene, hexylstyrene, There may be mentioned styrene such as styrene, styrene and alkyl styrene such as octylstyrene, fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, styrene iodide, nitrostyrene, acetylstyrene and methoxystyrene Styrene-based monomers; A copolymerized monomer such as vinyl acetate may be used.

The total amount of the copolymerizable monomers used in the copolymerization is preferably 40 mass% or less, more preferably 20 mass% or less, in 100 mass% of the monomer component.

The other monomers may be used singly or in combination of two or more kinds.

"( Meta ) Production Conditions of Acrylic Copolymer (A) "

The (meth) acrylic copolymer (A) is preferably a copolymer obtained by copolymerization in the presence of a peroxide-based polymerization initiator. That is, by using a peroxide-based polymerization initiator as a polymerization initiator, a copolymer having a branching degree within the above range tends to be obtained.

The (meth) acrylic copolymer (A) can be produced by a conventionally known polymerization method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method and a suspension polymerization method, and among these, a solution polymerization method is preferable . Specifically, a polymerization initiator is added in an inert gas atmosphere such as a nitrogen gas by adding a polymerization solvent and a monomer component in a reaction vessel, and the reaction initiation temperature is usually set at 40 to 100 캜, preferably 50 to 80 캜, The reaction system is maintained at a temperature of 50 to 90 ° C, preferably 70 to 90 ° C, and the reaction is carried out for 4 to 20 hours.

As the peroxide-based polymerization initiator, for example,

Di (2-tert-butylperoxyisopropyl) benzene, dicumylperoxide, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, tert- butylcumylperoxide, dialkyl peroxides such as tert-butyl peroxide, tert-hexyl peroxide and di-tert-butylperoxide (for example, compounds represented by ROOR, each R in the formula is independently an alkyl group or an aryl group substituted alkyl group; R is independently an alkyl group or an aryl group substituted alkyl group, and A is a divalent hydrocarbon group);

Di (3-methylbenzoyl) peroxide, di (3-methylbenzoyl) peroxide, diisobutyryl peroxide, di (3,5,5-trimethylhexanoyl) peroxide, diarooyl peroxide, dibenzoyl peroxide, Diacyl peroxides such as peroxide and di (4-methylbenzoyl) peroxide (e.g., a compound represented by R-COO-OCO-R, each R in the formula is independently an alkyl group or an aryl group);

(4-tert-butylcyclohexyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, di-tert-butyl peroxydicarbonate, di- Peroxydicarbonates such as tylperoxydicarbonate (e.g., compounds represented by R-OCO-OO-COO-R, each R in the formula is independently an alkyl group or a cycloalkyl group);

Butylperoxy neodecanoate, tert-butylperoxy neodecanoate, tert-butylperoxy neodecanoate, 1,1,3,3-tetramethylbutylperoxy neodecanoate, tert-hexylperoxy neodecanoate, Hexylperoxy pivalate, tert-butylperoxy pivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl- Hexylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxy-3 , 5,5-trimethylhexanoate, tert-butylperoxy laurate, tert-hexylperoxy benzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) butylperoxy acetate, tert- butylperoxy-3-methylbenzoate, tert- butylperoxy benzoate, etc. of peroxy acid esters (for example: a compound represented by R ¹ -OO-CO-R ^2, in the formula R ¹ Is an alkyl group or aryl group substituted alkyl And, R ² is an alkyl group, an aryl group or an aryl group-substituted alkyl group is a; and the compound represented by R-CO-OOAOO-CO-R, expression R in is an alkyl group or an aryl group with independently of each other group, A is a divalent hydrocarbon group to be);

peroxymonocarbonates such as tert-hexylperoxy isopropyl monocarbonate, tert-butylperoxy isopropyl monocarbonate and tert-butylperoxy-2-ethylhexyl monocarbonate (for example, those represented by ROO-COO-R Compound, each R in the formula is independently an alkyl group);

.

Among the peroxide-based polymerization initiators, peroxyesters are preferred, and peroxide-based polymerization initiators represented by the following formula (1) are more preferable since a (branched) polymer having a high branching number can be obtained.

In the formula (1), R ^A to R ^F each independently represent a hydrogen atom, an alkyl group or an aryl group, and from the viewpoint of obtaining a copolymer having a high branching chain, preferably an alkyl group having 1 to 10 carbon atoms or a phenyl group, Is an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, particularly preferably an alkyl group having 1 to 2 carbon atoms.

Among the peroxide-based polymerization initiators represented by the formula (1), preferred are tert-butylperoxy pivalate, tert-hexyl peroxy pivalate, tert-butylperoxy neodecanoate, tert-butylperoxy neoheptanoate, tert- Tert-butylperoxy pivalate, tert-hexyl peroxy pivalate, tert-butyl peroxypivalate, tert-butyl peroxypivalate, tert-butyl peroxypivalate and tert -Butylperoxy neodecanoate, tert-butylperoxy neoheptanoate and tert-butylperoxy-2-ethylhexanoate are particularly preferred.

The peroxide-based polymerization initiator may be used alone or in combination of two or more. Also, the addition of the peroxide-based polymerization initiator plural times during the polymerization is not limited.

As the polymerization initiator, an azo initiator may be used together with a peroxide initiator as long as the degree of branching is in the above range. Examples of the azo initiator 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'-azobis (cyclohexane-1-carbonitrile), 2- (carbamoylazo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile , 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis (N, N'-dimethyleneisobutylamidine) (2-hydroxyethyl) -propionamide], 2,2'-azobis (isobutylamide) dihydrate, 4,4'-azobis Azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis [ - (2-hydroxyethyl) propionamide]. These polymerization initiators may be used alone or in combination of two or more.

The peroxide-based polymerization initiator is used in an amount within a range of usually 0.001 to 5 parts by mass, preferably 0.005 to 3 parts by mass based on 100 parts by mass of the monomer component forming the (meth) acrylic copolymer (A). The azo-based initiator is preferably not used, and its amount to be used is preferably 0.5 part by mass or less, more preferably 0.2 parts by mass or less, and even more preferably 0 part by mass with respect to 100 parts by mass of the peroxide-based polymerization initiator. However, it is not limited to use for the purpose of reducing the residual monomer in the second half of the reaction. In addition, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be appropriately added during the polymerization reaction.

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

The residual ratio (%) of the peroxide-based polymerization initiator, which is preferably used as a polymerization initiator in the production of the (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention, after the reaction for a time period t can be obtained by the following formula have.

Remaining rate (%) = exp (-k _d t) x 100 (%)

Wherein, _d k is the thermal decomposition rate constant of Arrhenius equation ah: is represented by _{k d = A × exp (-ΔE} / RT), where A is a frequency factor, ΔE is in the thermal decomposition reaction of the polymerization initiator Activation energy, R is the gas constant (8.314 J / mol.K), T is the absolute temperature (K); t is the reaction time.

For the peroxide-based polymerization initiator, the frequency factor (A) and the activation energy (? E) are obtained. For example, the values listed in the catalog of Organic Peroxides (10th Edition) of Nippon Oil & For example, in tert-butylperoxy pivalate, ΔE = 119.1 kJ / mol, A = 6.93 × 10 ¹⁷ hr ^-1 , ΔE = 118.5 kJ / mol in tert-hexylperoxy pivalate and 6.45 × 10 ¹⁷ hr < ^-1 >, and DELTA E = 105.3 kJ / mol and A = 3.94x10 < ¹⁶ > hr < ^-1 > in the case of cumylperoxyneodecanoate.

Therefore, the residual rate (%) of the peroxide-based polymerization initiator after the reaction at the predetermined temperature for the time t can be calculated according to the above formula, in that k _d at the predetermined temperature can be calculated. Therefore, the residual amount of the peroxide-based polymerization initiator contained in the pressure-sensitive adhesive composition can be calculated from the amount of the peroxide-based polymerization initiator used in the copolymerization and the residual ratio (%).

"( Meta ) Physical Properties and Content of Acrylic Copolymer (A) "

The weight average molecular weight (Mw) of the (meth) acrylic copolymer (A) measured by the GPC method is generally in the range of 200,000 to 1,500,000, preferably 400,000 to 1,300,000, more preferably 500,000 ~ 110 million. Since the copolymer (A) has a high branching chain even when the Mw is in the above range, the copolymer (A) chains can be intertwined with each other moderately so that the durability and workability of the pressure-sensitive adhesive layer do not deteriorate. In particular, when Mw is 400,000 or more, a pressure-sensitive adhesive layer having high cohesiveness can be obtained.

The molecular weight distribution (Mw / Mn) of the (meth) acrylic copolymer (A) measured by the GPC method is usually 50 or less, preferably 30 or less, more preferably 20 or less.

The glass transition temperature (Tg) of the (meth) acrylic copolymer (A) can be calculated from Fox's equation based on, for example, the monomer units constituting the polymer and the content thereof. (Meth) acrylic copolymer (A) can be synthesized such that the glass transition temperature (Tg) determined by Fox equation is usually -70 to 0 占 폚, preferably -60 to -30 占 폚. By using the (meth) acrylic copolymer (A) having such a glass transition temperature (Tg), a pressure-sensitive adhesive composition having excellent adhesiveness at room temperature can be obtained.

Fox equation: 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 of the (meth) acrylic copolymer (A), and Tg ₁ , Tg ₂ , ... , Tg _m is the glass transition temperature of the homopolymer composed of each monomer, and W ₁ , W ₂ , ... , And W _m is a weight fraction of the respective monomer-derived constituent units in the copolymer (A).

The glass transition temperature of the homopolymer composed of each monomer in the Fox equation may be, for example, a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 1999).

The content of the (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition of the present invention is usually 50 to 99.99% by mass, more preferably 60 to 99.95% by mass, in the composition 100% , And particularly preferably 80 to 99.90 mass%. When the content of the (meth) acrylic copolymer (A) is in the above range, the performance as a pressure sensitive adhesive is balanced and the adhesive property is excellent.

[ Isocyanate  Compound (B)]

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

The number of isocyanate groups of the isocyanate compound (B) is usually 2 or more, preferably 2 to 8, and more preferably 3 to 6. When the number of isocyanate groups is in the above range, the crosslinking reaction efficiency of the (meth) acrylic copolymer (A) and the isocyanate compound (B) is preferred and flexibility of the pressure-sensitive adhesive layer is maintained.

Examples of the diisocyanate compound having an isocyanate group number of 2 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 Aliphatic diisocyanates having 4 to 30 carbon atoms such as cyanate, 3-methyl-1,5-pentane diisocyanate and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. Cyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, Alicyclic diisocyanates having 7 to 30 carbon atoms such as hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethyl xylylene diisocyanate, and the like. Examples of the aromatic diisocyanate include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether isocyanate , Diphenylmethane diisocyanate, diphenyl propane diisocyanate, and other aromatic diisocyanates having 8 to 30 carbon atoms.

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

Examples of the isocyanate compound (B) include, for example, oligomers of the above isocyanate compounds having an isocyanate group of 2 or 3 or more (for example, a dimer or a trimer, a buret or an isocyanurate ), A derivative (for example, an addition reaction product of a polyhydric alcohol and at least two diisocyanate compounds), and a polymer. Examples of the polyhydric alcohol in the derivative include low molecular weight polyhydric alcohols such as trimethylolpropane, glycerin and pentaerythritol; Examples of the high molecular weight polyhydric alcohol include polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol and polyisoprene polyol.

Examples of such isocyanate compounds include dimers of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or tolylene diisocyanate The reaction product of burette or isocyanurate, trimethylol propane and tolylene diisocyanate or xylylene diisocyanate (for example, tolylene diisocyanate or xylylene diisocyanate Cyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a three-molecule adduct of hexamethylene diisocyanate), a polyether polyisocyanate Cyanate, and polyester polyisocyanate.

Among the isocyanate compounds (B), the reaction product of trimethylolpropane with tolylene diisocyanate or xylylene diisocyanate (available from Soken Chemical Co., Ltd., (Trade name: L-45 manufactured by Nippon Polyurethane Industry Co., Ltd., TD-75 made by Soken Chemical Industry Co., Ltd.), hexamethylene diisocyanate or toluylene diisocyanate isocyanurate (TSE-100 manufactured by Asahi Chemical Co., 2050, etc.) is preferable.

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

In the pressure-sensitive adhesive composition of the present invention, the content of the isocyanate compound (B) is usually 0.01 to 5 parts by mass, more preferably 0.05 to 2.5 parts by mass, relative to 100 parts by mass of the (meth) acrylic copolymer (A) More preferably 0.1 to 1 part by mass. When the content is within the above range, it is preferable that the durability and the stress relaxation property are easily balanced.

[ Silane coupling agent (C)]

The pressure-sensitive adhesive composition for a polarizing plate of the present invention preferably also contains a silane coupling agent (C). The silane coupling agent (C) contributes to adhesion of the pressure-sensitive adhesive layer to an adherend such as a glass plate, thereby preventing peeling in a high-humidity environment.

Examples of the silane coupling agent (C) include silane coupling agents containing polymerizable unsaturated groups such as vinyltrimethoxysilane, vinyltriethoxysilane and methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxysilane, A silane coupling agent containing an epoxy group such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; Aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane. An amino group-containing silane coupling agent; And halogen-containing silane coupling agents such as 3-chloropropyltrimethoxysilane.

The content of the silane coupling agent (C) in the pressure-sensitive adhesive composition for a polarizing plate of the present invention is usually 1 part by mass or less, preferably 0.01 to 1 part by mass, more preferably 0.01 to 1 part by mass based on 100 parts by mass of the (meth) acrylic copolymer (A) Preferably 0.05 to 0.5 parts by mass. When the content is in the above range, peeling of the polarizing plate under a high humidified environment or bleeding of the silane coupling agent (C) under a high temperature environment tends to be prevented.

[Antistatic agent (D)]

The antistatic agent (D) can be used, for example, to lower the surface resistance value of the pressure-sensitive adhesive composition for a polarizing plate of the present invention. Examples of the antistatic agent (D) include a surfactant, an ionic compound, and a conductive polymer.

Examples of the surfactant include cationic surfactants having cationic groups such as quaternary ammonium salts, amide quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups; Anionic surfactants having anionic groups such as sulfonic acid bases, sulfuric acid ester bases and phosphoric acid ester bases; Amphoteric surfactants such as alkyl betaines, alkyl imidazolium betaines, alkylamine oxides and amino acid sulfuric acid esters, glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters Non-ionic surfactants such as N-hydroxyethyl-N-2-hydroxyalkylamines, alkyldiethanolamides, and the like.

A reactive emulsifier having a polymerizable group as a surfactant can also be used, and a polymer surfactant obtained by polymerizing a monomer component containing the above-mentioned surfactant or reactive emulsifier may be used.

The ionic compound is composed of a cation portion and an anion portion, and may be any of solid phase liquid phase at room temperature (23 ° C / 50% RH).

The cationic moiety constituting the ionic compound may be either of an inorganic cation or an organic cation. As the inorganic cation, alkali metal ions and alkaline earth metal ions are preferable, and Li ⁺ , Na ^+, and K ⁺ having excellent antistatic properties are more preferable. Examples of the organic cation are, for example, pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, dihydro Pyrimidinium cation, pyrazolium cation, pyrazolinium cation, tetraalkyl ammonium cation, trialkylsulfonium cation, tetraalkylphosphonium cation, and derivatives thereof.

The anion moiety constituting the ionic compound is not particularly limited as long as it can form an ionic compound by ionic bonding with the cation moiety. Specific examples thereof include F ^- , Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , SCN ^- , ClO ₄ ^- , NO ₃ ^- , CH ₃ COO ^{- _{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 ^- . Of these, anions containing fluorine atoms are preferred because they give ionic compounds having a low melting point, and (F ₂ SO ₂ ) ₂ N ^- and (CF ₃ SO ₂ ) ₂ N ^- are particularly preferred.

Examples of the ionic compound include lithium bis (trifluoromethanesulfonyl) imide, lithium bis (difluorosulfonyl) imide, lithium tris (trifluoromethanesulfonyl) methane, potassium bis (trifluoromethanesulfonyl) (Phenylsulfonyl) imide, potassium bis (difluorosulfonyl) imide, 1-ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl-4-methylpyridinium hexafluorophosphate Octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide, 1-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide, (N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate, Ethyl) ammonium bis (trifluoromethanesulfonyl) imide, 1-octylpyridinium fluorosulfonium imide, 1-octyl- Preferred are ridinium and trifluorosulfoniumimide.

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

The content of the antistatic agent (D) in the pressure-sensitive adhesive composition for a polarizing plate of the present invention is generally 3 parts by mass or less, preferably 0.01 to 3 parts by mass, more preferably 0.01 to 3 parts by mass based on 100 parts by mass of the (meth) acrylic copolymer (A) Is 0.05 to 2.5 parts by mass.

[Organic solvent (E)]

The pressure-sensitive adhesive composition of the present invention preferably contains an organic solvent (E) in order to prepare the coating property. Examples of the organic solvent include the polymerization solvents described in the column of the (meth) acrylic copolymer (A). For example, a pressure sensitive adhesive composition can be prepared by mixing a polymer solution containing a (meth) acrylic copolymer (A) obtained by the copolymerization and a polymerization solvent and an isocyanate compound (B). In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent is usually 50 to 90% by mass, preferably 60 to 85% by mass.

In the present specification, the term "solid content" refers to all components except for the organic solvent (E) contained in the pressure-sensitive adhesive composition, and "solid content concentration" refers to the ratio of the solid content to 100% by mass of the pressure-sensitive adhesive composition.

[peroxide]

It is preferable that the pressure-sensitive adhesive composition of the present invention does not contain a peroxide (peroxide-based crosslinking agent) as a crosslinking agent. The content of the peroxide is preferably 0.1 parts by mass or less based on 100 parts by mass of the (meth) acrylic copolymer (A), including the residual amount of the peroxide-based polymerization initiator used in the synthesis of the (meth) More preferably 0.05 parts by mass or less, and even more preferably 0.01 parts by mass or less. By using the isocyanate compound (B) as the crosslinking agent and not using the peroxide-based crosslinking agent, deterioration with time of the pressure-sensitive adhesive layer based on the residual peroxide can be suppressed.

[additive]

The pressure-sensitive adhesive composition of the present invention may contain, in addition to the above components, antioxidants, light stabilizers, metal corrosion inhibitors, tackifiers, plasticizers, crosslinking accelerators, (meth) acrylic polymers other than the above (A) And one or two or more kinds selected from a worker.

[Preparation of pressure-sensitive adhesive composition for polarizing plate]

The pressure-sensitive adhesive composition for a polarizing plate of the present invention can be prepared by mixing the (meth) acrylic copolymer (A), the isocyanate compound (B) and other components as required by a conventionally known method. For example, an isocyanate compound (B) and, if necessary, other components are blended in a polymer solution containing the polymer obtained when the (meth) acrylic copolymer (A) is synthesized.

The gel fraction of the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition of the present invention is preferably 20 to 70 mass%, more preferably 24 to 60 mass%, still more preferably 30 to 55 mass%. The gel fraction is a value measured for, for example, a pressure-sensitive adhesive collected under the conditions described in the examples.

[ The pressure- ]

The pressure-sensitive adhesive layer of the invention is obtained, for example, by carrying out a crosslinking reaction in the above-mentioned pressure-sensitive adhesive composition, specifically by crosslinking the (meth) acrylic copolymer (A) with the isocyanate compound (B).

The conditions for forming the pressure-sensitive adhesive layer are as follows, for example. The pressure-sensitive adhesive composition of the present invention is coated on a support and dried usually at 50 to 150 ° C, preferably 60 to 100 ° C, for 1 to 10 minutes, preferably 2 to 7 minutes, though it may vary depending on the type of solvent The solvent is removed and a coating film is formed. The film thickness of the dried coating film is usually 5 to 75 占 퐉, preferably 10 to 50 占 퐉.

The pressure-sensitive adhesive layer is preferably formed under the following conditions. The pressure-sensitive adhesive composition of the present invention is applied onto a support, and the cover film is applied on the coating film formed under the above conditions, and then applied for usually 3 days or more, preferably 7 to 10 days, usually 5 to 60 ° C, Deg.] C, usually 30 to 70% RH, preferably 40 to 70% RH. When the crosslinking is carried out under the above-described maturation conditions, a crosslinked product (network polymer) can be efficiently formed.

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

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

The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention preferably has a gel fraction of preferably from 20 to 70% by mass, more preferably from 24 to 60% by mass, still more preferably from 20 to 70% by mass, from the viewpoints of suppression of distortion, cohesion, Is 30 to 55% by mass. Even when the gel fraction is within the above range, the branched chains of the copolymer (A) can be entangled with each other properly because the (meth) acrylic copolymer (A) has a high branch chain, and the durability and workability of the pressure sensitive adhesive layer do not deteriorate . Particularly, when the gel fraction is 30 mass% or more, a highly adhesive pressure-sensitive adhesive layer can be obtained. When the gel fraction exceeds the above range, the pressure-sensitive adhesive layer can not sufficiently absorb and relax the stress due to the dimensional change of the polarizing plate under a high-temperature and high-humidity heat environment.

[Pressure sensitive adhesive sheet for polarizing plate]

The pressure-sensitive adhesive sheet for a polarizing plate of the present invention has a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition for a polarizing plate. As the pressure sensitive adhesive sheet, for example, a pressure sensitive adhesive double coated sheet having a pressure sensitive adhesive layer having only the above pressure sensitive adhesive layer, a substrate, a double - sided pressure sensitive adhesive sheet having the pressure sensitive adhesive layer formed on both surfaces of the substrate, And a pressure-sensitive adhesive sheet in which a peeled-off cover film is adhered to a surface of the pressure-sensitive adhesive sheet of the pressure-sensitive 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 polyolefin films such as polyethylene, polypropylene and ethylene-vinyl acetate copolymer.

The forming conditions of the pressure-sensitive adhesive layer are the same as those described in the section of [pressure-sensitive adhesive layer].

The thickness of the pressure-sensitive adhesive layer is usually 5 to 75 占 퐉, preferably 10 to 50 占 퐉, from the viewpoint of maintaining the adhesive property. The thickness of the base material and the cover film is not particularly limited, but is usually 10 to 125 占 퐉, preferably 25 to 75 占 퐉.

[ The pressure-  Attached polarizer plate]

The polarizing plate with a pressure-sensitive adhesive layer of the present invention has a polarizing plate and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate of the present invention on at least one surface of the polarizing plate. In the present specification, the term " polarizing plate " is used to mean " polarizing film ".

As the polarizing plate, conventionally known polarizing films can be used. For example, a stretched film obtained by stretching a film made of a polyvinyl alcohol-based resin with a polarizing component, and a multilayer film having a protective film disposed on the stretched film. Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, and saponified ethylene-vinyl acetate copolymer. Examples of the polarizing component include iodine and dichroic dyes. Examples of the protective film include a cellulose film such as triacetyl cellulose, a polycarbonate film, and a polyethersulfone film.

The thickness of the polarizing plate is usually 30 to 250 占 퐉, preferably 50 to 200 占 퐉.

There is no particular limitation on the method of forming the pressure-sensitive adhesive layer on the surface of the polarizing plate, and a method of applying and drying the pressure-sensitive adhesive composition using a bar coater or the like directly on the surface of the polarizing plate, a method of drying the pressure-sensitive adhesive layer of the pressure- Transferring and aging. The conditions of drying and aging, the range of the gel fraction, and the like are the same as those described in the column of [pressure-sensitive adhesive layer].

The thickness of the pressure-sensitive adhesive layer formed on the polarizing plate is usually 5 to 75 占 퐉, preferably 10 to 50 占 퐉, as a dried film thickness. The pressure-sensitive adhesive layer may be formed on at least one surface of the polarizing plate. The pressure-sensitive adhesive layer may be formed on only one side of the polarizing plate. The pressure-sensitive adhesive layer may be formed on both surfaces of the polarizing plate.

Further, the polarizing plate may be laminated with layers having different functions such as a protective layer, an antiglare layer, a retardation layer, and a viewing angle improving layer.

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

As the substrate having the liquid crystal cell, for example, a glass plate can be given. The thickness of the substrate is usually 0.1 to 1 mm, preferably 0.15 to 0.8 mm. In particular, in the present invention, by using the pressure-sensitive adhesive composition, warping of the polarizing plate and the substrate can be suppressed. Therefore, even when the thickness of the substrate is small (for example, 0.8 mm or less, preferably 0.15 to 0.7 mm), the pressure-sensitive adhesive composition can be suitably used for bonding the polarizing plate and the substrate.

Example

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

[ GPC  And GPC - MALS ]

(Mw) and number-average molecular weight (Mn) of the (meth) acrylic copolymer were determined by gel permeation chromatography (GPC) under the following conditions by Gel Permeation Chromatography / (GPC-MALS) under the following conditions.

Measurement apparatus: HLC-8320GPC (manufactured by TOSOH CORPORATION)

GPC Column Composition: The following four columns (all manufactured by TOSOH CORPORATION)

(1) TSKgel HxL-H (guard column)

(2) TSKgel GMHxL

(3) TSKgel GMHxL

(4) TSKgel G2500HxL

Flow rate: 1.0 mL / min

Column temperature: 40 ° C

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

Mobile phase solvent: tetrahydrofuran

· Detector: DAWN HELEOS (MALS detector) + Optilab rEX (RI detector)

Standard polystyrene conversion (when measuring Mw and Mn)

[ Synthetic example  One]

A reactor equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube was charged with 99 parts of n-butyl acrylate, 1 part of 4-hydroxybutyl acrylate and 100 parts of an ethyl acetate solvent. While introducing nitrogen gas, did. Then, 0.1 part of tert-butylperoxy pivalate was added, and polymerization was carried out at 80 ° C for 6 hours in a nitrogen gas atmosphere. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to prepare a polymer solution having a solid content concentration of 30% by mass. The resulting (meth) acrylic copolymer A had a weight average molecular weight (Mw) of 400,000, a molecular weight distribution (Mw / Mn) of 7.2, a degree of branching of 0.52 and an acid value of 0 mgKOH / g.

[ Synthetic example  2 to 10]

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 and the polymerization initiator used in the polymerization reaction were changed as shown in Table 1. The results are shown in Table 1.

[ Example  One]

(1) Preparation of pressure-sensitive adhesive composition

(Solid content concentration: 30% by mass) obtained in Synthesis Example 1 and 100 parts (solid content) of the (meth) acryl-based polymer contained in the solution were mixed with 100 parts by mass of an isocyanate compound ) 0.19 part (solids content) of "TD-75" (solid content 75% by mass, ethyl acetate solution) and 0.2 part of KBM-403 (solid content 100%) made by Shinetsu Kagakukyo Co., Ltd. as a silane coupling agent And 1 part of "AS-804" (100% solids) manufactured by Daiichi Kikio Seiyaku Co., Ltd. as an antistatic agent were mixed to obtain a pressure-sensitive adhesive composition.

(2) Production of adhesive sheet

The pressure-sensitive adhesive composition obtained in the above (1) was coated on a peeled polyethylene terephthalate film (PET film) after the foam was removed using a doctor blade and dried at 90 캜 for 3 minutes to form a coat film having a dry film thickness of 20 탆 . The peeled PET film was further adhered to the surface of the coating film opposite to the PET film adhering surface and allowed to stand for 7 days under an environment of 23 deg. C / 50% RH for aging to obtain a pressure-sensitive adhesive layer Sensitive adhesive sheet.

(3) The pressure-  Manufacture of Polarizer

The pressure-sensitive adhesive composition obtained in the above (1) was coated on a peeled polyethylene terephthalate film (PET film) after the foam was removed using a doctor blade and dried at 90 ° C for 3 minutes to obtain a sheet having a dried film thickness of 20 μm . The sheet and a polarizing plate (thickness: 110 탆; layer composition: triacetyl cellulose film / polyvinyl alcohol film / triacetyl cellulose film) were laminated so that the coating film and polarizing plate were in contact with each other. To give a polarizing plate with a pressure-sensitive adhesive layer having a PET film, a pressure-sensitive adhesive layer having a thickness of 20 mu m, and a polarizing plate.

[ Example  2 to 9, Comparative Example  One]

Except that the (meth) acrylic polymer solution in Example 1 was changed to the polymer solution obtained in Synthesis Examples 2 to 10, and the blend composition was changed as shown in Table 2, the pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet And a polarizer with a pressure-sensitive adhesive layer were obtained.

[evaluation]

[Gel fraction]

About 0.1 g of the pressure sensitive adhesive was collected from the pressure sensitive adhesive sheet obtained in the examples and comparative examples into a sampling bottle, and 30 ml of ethyl acetate was added and shaken for 4 hours. The content of the sample bottle was filtered with a 200 mesh thick stainless steel net, The residue was dried at 100 DEG C for 2 hours to measure the dry weight. The gel fraction of the pressure-sensitive adhesive was determined by the following formula.

Gel fraction (%) = (dry weight / adhesive weight) 100 (%)

[ Creep value ]

EXAMPLES The polarizing plate with a pressure-sensitive adhesive layer (a laminate composed of a PET film / pressure-sensitive adhesive layer / polarizing plate) obtained in the Examples and Comparative Examples was cut into a width of 10 mm and a length of 100 mm, the PET film thus peeled off was peeled off, Layer was brought into contact with the glass plate so as to have a bonding area of 10 mm x 10 mm to obtain a test piece for pressure-sensitive adhesive polarizing plate for evaluation.

The pressure-sensitive adhesive polarizing plate test piece for evaluation was subjected to an autoclave treatment (50 DEG C, 5 atm), and left under an atmosphere of 23 DEG C / 50% RH for 24 hours. Then, the test piece was set in the chamber box of the microcryp measuring instrument at a length of 15 mm for the fixing chuck portion. Tensile load: 800 g, tensile time: 1000 sec. The pressure-sensitive adhesive polarizing plate for evaluation in the test piece was stretched in parallel with the bonding surface between the polarizing plate and the glass and in the longitudinal direction of the polarizing plate, And the distance (μm) of the displacement of the joining portion with the polarizing plate was measured as a creep value.

[Measurement of adhesive force]

EXAMPLES A polarizing plate with a pressure-sensitive adhesive layer (a laminate composed of a PET film, a pressure-sensitive adhesive layer, and a polarizing plate) obtained in Examples and Comparative Examples was cut into a size of 70 mm x 25 mm to prepare test pieces. The PET film was peeled from the test piece and laminated with a pressure-sensitive adhesive layer / polarizing plate was adhered to one side of a glass plate having a thickness of 2 mm so that the pressure-sensitive adhesive layer and the glass plate were in contact with each other using a laminator roll. The obtained laminate was held in an autoclave adjusted at 50 캜 / 5 atm for 20 minutes. Subsequently, the sample was allowed to stand in an environment of 23 ° C / 50% RH for 1 hour, and then the end of the polarizing plate was stretched at a rate of 300 mm / min in the direction of 90 ° with respect to the glass plate surface to measure the adhesive strength (peel strength).

[ Bending (warp)〕

EXAMPLES A test piece was prepared by cutting the polarizing plate with a pressure-sensitive adhesive layer (laminate composed of PET film / pressure-sensitive adhesive layer / polarizing plate) obtained in Examples and Comparative Examples to a size of 35 mm x 400 mm (stretching axis direction). The PET film was peeled from the test piece and laminated with a pressure-sensitive adhesive layer / polarizing plate was adhered to one side of a glass plate having a thickness of 0.7 mm and a size of 40 mm x 410 mm using a laminator roll so that the pressure sensitive adhesive layer and the glass plate were in contact with each other. The obtained laminate was allowed to stand in an environment of 23 ° C / 50% RH for 24 hours, and then held in an oven at 60 ° C for 72 hours. One end was fixed to a wall surface perpendicular to the bottom surface, and the floating amount of the opposite end was measured as a ruler. Measurements were taken immediately after extraction from the oven and after 24 hours.

[Durability test]

EXAMPLES A polarizing plate with a pressure-sensitive adhesive layer (a laminate composed of a PET film, a pressure-sensitive adhesive layer, and a polarizing plate) obtained in Examples and Comparative Examples was cut into a size of 150 mm x 250 mm to prepare test pieces. The PET film was peeled from the test piece and laminated with a pressure-sensitive adhesive layer / polarizing plate was adhered to one side of a glass plate having a thickness of 2 mm so that the pressure-sensitive adhesive layer and the glass plate were in contact with each other using a laminator roll. The obtained laminate was held in an autoclave adjusted to 50 캜 / 5 atm for 20 minutes to prepare a test plate. I wrote two similar trials. The test plate was allowed to stand for 500 hours under the conditions of a temperature of 80 占 폚 (heat resistance) or a temperature of 60 占 폚 / humidity of 90% RH (humid heat resistance), and the occurrence of foaming and thermal insulation was observed and evaluated. Foaming occurs in the case of lack of cohesion and insulation occurs in the case of lack of stress relief.

(firing)

AA: No foaming at all.

BB: The area of foaming is less than 1% of the whole.

CC: The area of foaming is 1% or more and less than 5% of the whole.

DD: The area of foaming is 5% or more of the whole.

(Insulation)

AA: No insulation is seen at all.

BB: The area of insulation is less than 1% of the total.

CC: The area of the insulation is 1% or more and less than 5% of the total area.

DD: The area of the insulation is 5% or more of the total.

The amount of the peroxide-based polymerization initiator in Table 2 was calculated in the following manner. For example, k _d = A x exp (-ΔE / RT) and A = 6.93 × 10 ¹⁷ hr ^-1 (%) are calculated from the above-described residual ratio expression: exp (-k _d t) , ΔE = 119.1kJ / mol, R = 8.314J / mol · K, T = 353K, and the reaction time from t = 6h to the amount by × remaining ratio (%) of the peroxide-based polymerization initiator used in the copolymerization 5 × 10 ^{- 3} Mass part.

In Comparative Example 1, since the (meth) acrylic copolymer having a branching degree of 0.59 was used, the bending evaluation after 24 hours was poor (5.0 mm or more) and foaming was not observed in the durability evaluation, . Since the copolymer in Comparative Example 1 is a linear polymer, the cohesive force expression depends only on the bonding between the crosslinking agent and the functional group in the copolymer. Therefore, it is necessary to set the gel fraction to be high for maintaining the cohesive force. However, when the gel fraction is high, the stress relaxation property is lowered in the system of Comparative Example 1, so that bending and durability (heat resistance) are deteriorated.

On the other hand, in the embodiment, since the (meth) acrylic copolymer having a branching degree of 0.55 or less is used, the bending evaluation after 24 hours is high (3.0 mm or less) and the occurrence of foaming and thermal insulation in the durability evaluation is allowed Range. In Examples 1 to 8, since the (meth) acrylic copolymer having a branching degree of 0.54 or less was used, the bending evaluation after 24 hours was superior (1.0 mm or less).

Claims (8)

(A) a monomer component comprising a (meth) acrylic acid alkyl ester having 4 to 18 carbon atoms in the alkyl group and a hydroxyl group-containing monomer, and is obtained by copolymerization with a gel permeation chromatography / polygonal laser light scattering detector (GPC-MALS) (Meth) acrylic copolymer having a branching degree of not more than 0.55,
(B) an isocyanate compound
Wherein the pressure-sensitive adhesive composition is a pressure-sensitive adhesive composition for a polarizing plate. The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the (meth) acrylic copolymer (A) is a copolymer obtained by copolymerization in the presence of a peroxide-based polymerization initiator. The positive resist composition according to any one of claims 1 to 3, wherein the weight average molecular weight (Mw) of the (meth) acrylic copolymer (A) as measured by gel permeation chromatography (GPC) is from 200,000 to 1,500,000 By weight of the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 3, wherein the branching degree measured by GPC-MALS of the (meth) acrylic copolymer (A) is 0.10 to 0.54. The pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 4, wherein the content of the peroxide is 0.1 part by mass or less based on 100 parts by mass of the (meth) acrylic copolymer (A). The pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition for a polarizing plate has a gel fraction of 20 to 70 mass%. A pressure-sensitive adhesive sheet for a polarizing plate, comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 6. A polarizing plate with a pressure-sensitive adhesive layer, comprising a polarizing plate and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to any one of claims 1 to 6 on at least one surface of the polarizing plate.