TW201706386A - Adhesive composition for polarizer, adhesive layer, adhesive sheet and polarizer attached with adhesive layer - Google Patents

Abstract

The present invention provides an adhesive composition for polarizer which is possible to form an adhesive layer capable of suppressing bending of liquid crystal cell and excellent in durability. The adhesive composition for the polarizer comprises (A) an acrylic polymer prepared by copolymerizing an alkyl (meth)acrylate ester having an alkyl group of 4-18 carbon atoms and a monomer component containing a polar group-containing monomer, and (B) a crosslinking agent; wherein the adhesive layer formed from the adhesive composition has a loss tangent (tan [delta]1) at 23 DEG C of 0.33 to 0.55, and a loss tangent (tan [delta]2) at 80 DEG C of 0.40 to 0.65.

Description

Adhesive composition for polarizing plate, adhesive layer, adhesive sheet and polarizing plate with adhesive layer

The present invention relates to an 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 polarizing plate is attached to the surface of the substrate via an adhesive layer. The polarizing plate is easily heat-shrinked in a high-temperature, high-humidity heat environment, so that the dimensional stability is lacking, and the liquid crystal cell is warped. In recent years, as the thickness of the liquid crystal cell is reduced (for example, the thickness of the substrate constituting the liquid crystal cell) and the thickness of the polarizing plate are reduced, the warpage of the liquid crystal cell in a high-temperature, high-humidity heat environment becomes a problem. The reason why the liquid crystal cell is warped is, for example, that the adhesive layer cannot follow the heat shrinkage (size change) of the polarizing plate, or the stress relaxation property of the adhesive layer is low.

Further, in a high-temperature, high-humidity heat environment, there are problems such as foaming at the interface between the polarizing plate and the substrate, cracking of the adhesive layer, and peeling of the polarizing plate. Therefore, for the adhesive for polarizing plates, high durability is required.

In general, as means for suppressing warpage of a liquid crystal cell, For example, a method of using an adhesive layer having high flexibility depending on the size of the polarizing plate can be used. However, such an adhesive layer has insufficient cohesive force, which causes problems such as deterioration in durability and deterioration in workability.

For example, in Patent Documents 1 and 2, when a triacetyl cellulose (TAC) substrate and a glass substrate are laminated on an adhesive layer, the adhesive film of the TAC substrate is prevented from the glass base under high temperature and humidity. The problem of material floating is to reveal an adhesive layer having a specific range of loss tangent (tan δ), which is an adhesive layer containing an acrylic adhesive, an isocyanate curing agent, and an acrylic copolymer.

Patent Document 1: Japanese Laid-Open Patent Publication No. 2013-141801

Patent Document 2: Japanese Laid-Open Patent Publication No. 2013-063631

An object of the present invention is to provide an adhesive composition for a polarizing plate capable of forming an adhesive layer capable of suppressing warpage of a liquid crystal cell and having excellent durability, and an adhesive layer for a polarizing plate formed of the above composition An adhesive sheet for a polarizing plate having the above-mentioned adhesive layer, and a polarizing plate having an adhesive layer of the above-mentioned adhesive layer.

The inventors of the present invention have been striving to solve the above problems. As a result, it was found that the adhesive composition containing the specific (meth)acrylic copolymer and the crosslinking agent, and the loss tangent at 23 ° C and 80 ° C of the adhesive layer formed of the above composition was a specific range. Adhesive composition, An adhesive layer capable of suppressing warpage of the liquid crystal cell and having excellent durability is 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 [12].

[1] An adhesive composition for a polarizing plate comprising (A) a (meth)acrylic acid alkyl ester having an alkyl group having 4 to 18 carbon atoms and a monomer component containing a polar group-containing monomer. a (meth)acrylic copolymer obtained by polymerization and (B) a crosslinking agent, wherein a loss tangent (tan δ ₁ ) at 23 ° C of the adhesive layer formed by the composition is 0.33 to 0.55, and 80 The loss tangent (tan δ ₂ ) in °C is 0.40 to 0.65.

[2] The adhesive composition for a polarizing plate according to the above [1], wherein the crosslinking agent (B) contains an isocyanate compound (B1) and a metal compound (B2).

[3] The adhesive composition for a polarizing plate according to the above [2], wherein the content of the metal-clamping compound (B2) is 10 to 1000 parts by mass based on 100 parts by mass of the isocyanate compound (B1).

[4] The adhesive composition for a polarizing plate according to any one of the above [1], wherein the polar group of the polar group-containing monomer is a carboxyl group and/or a hydroxyl group.

The adhesive composition for polarizing plates of any one of the above-mentioned (meth)acrylic copolymer (A) is based on the polymerization of a peroxide system. The resulting copolymer is copolymerized in the presence of a starter.

[6] The adhesive composition for a polarizing plate according to any one of the above [1], wherein the (meth)acrylic copolymer (A) is subjected to gel permeation chromatography. The weight average molecular weight (Mw) measured by the (GPC method) is 200,000 to 1,500,000.

[7] The adhesive composition for a polarizing plate according to any one of the above [1], wherein the content of the peroxide is 100% by weight based on the (meth)acrylic copolymer (A). The serving is 0.1 parts by mass or less.

[8] The adhesive composition for a polarizing plate according to any one of the above [1], wherein the gel fraction of the adhesive formed by the adhesive composition for a polarizing plate is 10 to 70% by mass.

[9] An adhesive layer for a polarizing plate, which is characterized in that the adhesive composition for a polarizing plate according to any one of the above [1] to [8] is formed, and the loss tangent at 23 ° C (tan δ) ₁ ) is from 0.33 to 0.55, and the loss tangent (tan δ ₂ ) at 80 ° C is from 0.40 to 0.65.

[10] The adhesive layer for a polarizing plate according to the above [9], wherein the gel fraction is 10 to 70% by mass.

[11] An adhesive sheet for a polarizing plate, which is characterized in that the adhesive layer for a polarizing plate according to the above [9] or [10] is used.

[12] A polarizing plate with an adhesive layer, comprising: a polarizing plate; and an adhesive layer for a polarizing plate according to the above [9] or [10] formed on at least one surface of the polarizing plate.

According to the present invention, it is possible to provide a polarizing plate capable of forming an adhesive layer capable of suppressing warpage of a liquid crystal cell and having excellent durability. An adhesive composition, an adhesive layer for a polarizing plate formed of the above composition, an adhesive sheet for a polarizing plate having the above-mentioned adhesive layer, and a polarizing plate having an adhesive layer of the above-mentioned adhesive layer.

Hereinafter, the adhesive composition for a polarizing plate, the adhesive layer for a polarizing plate, the adhesive sheet for a polarizing plate, and a polarizing plate with an adhesive layer will be described. In the following, the adhesive composition for a polarizing plate of the present invention may be simply referred to as an "adhesive composition". The adhesive layer for a polarizing plate of the present invention may be simply referred to as an "adhesive layer", and the adhesive sheet for a polarizing plate of the present invention may be simply referred to as It is a "sticky piece".

Adhesive composition for polarizing plate

The adhesive composition for a polarizing plate of the present invention contains a composition of a (meth)acrylic copolymer (A) and a crosslinking agent (B), wherein the adhesive layer formed by the adhesive composition 23 The loss tangent (tan δ ₁ ) in °C is 0.33 to 0.55, and the loss tangent (tan δ ₂ ) at 80 ° C is 0.40 to 0.65.

The adhesive composition of the present invention may contain at least one selected from the group consisting of a decane coupling agent (C), an antistatic agent (D), and an organic solvent (E), as needed.

Here, the characteristics of the adhesive composition of the present invention are as follows: "The Physica MCR300" manufactured by Anton Paar is used for the adhesive layer having a thickness of 1.0 mm formed under the following conditions, and the dynamic viscoelasticity measurement method according to JIS K 7244 (temperature range) The viscosity is obtained by performing a viscoelastic pattern at -40 to 180 ° C, a temperature rise condition of 3.67 ° C / min, and a frequency of 1 Hz.

The adhesive layer of the dynamic viscoelasticity measurement is as follows form. The adhesive composition was applied to a polyethylene terephthalate film (PET film) after peeling treatment so that the thickness after drying was 20 μm, and dried at 90 ° C for 3 minutes to remove the solvent to form a coating film. On the opposite side of the PET film attachment surface of the coating film, the PET film after the release treatment was attached, and aged for 7 days in an environment of 23 ° C / 50% RH to form an adhesive layer having a thickness of 20 μm. After the aging was completed, the PET film on one side of the obtained adhesive sheet was peeled off, and the adhesive layers having a thickness of 20 μm were bonded to each other to form an adhesive layer having a final thickness of 1.0 mm, and the adhesive layer was measured. Viscoelastic map.

Further, the above-described formation conditions of the adhesive layer are described in the loss tangent for measuring the characteristics of the adhesive composition of the present invention, and the adhesive layer formed by the adhesive composition of the present invention is of course not limited to The adhesive layer formed by the above conditions.

Loss tangent (tan δ) is the ratio of the storage elastic modulus G' showing the elastic property to the loss elastic modulus G" showing the viscous property: expressed as G'/G", the larger the value is the viscosity The greater the contribution, the smaller the value means the greater the contribution to elasticity.

In the above adhesive layer, the loss tangent (tan δ ₁ ) at 23 ° C is 0.33 to 0.55, preferably 0.35 to 0.52, particularly preferably 0.40 to 0.49; and the loss tangent (tan δ ₂ ) at 80 ° C is 0.40. It is 0.65, preferably 0.42 to 0.62, and particularly preferably 0.47 to 0.56.

Since the loss tangent (tan δ ₁ ) at 23 ° C is in the above range, moderate elasticity can be exhibited, which is advantageous in terms of adhesion to the adherend and workability. When tan δ _{1 is} higher than the above range, the viscosity of the adhesive layer is excessively increased, and the product yield tends to decrease during work steps such as handling and punching. When the tan δ _{1 is} less than the above range, the elasticity of the adhesive layer is excessively large, and the wettability of the adherend is lowered, and the adhesion tends to be lowered.

Since the loss tangent (tan δ ₁ ) at 80 ° C is in the above range, the flexibility is excellent, and the adhesive layer can follow the heat shrinkage (size change) of the polarizing plate at a high temperature. When tan δ _{2 is} more than the above range, the agglomeration property of the adhesive layer is lowered, and there is a tendency that durability is not obtained. When the tan δ _{2 is} less than the above range, the adhesive layer cannot follow the heat shrinkage (size change) of the polarizing plate at a high temperature, and tends to cause warpage of the polarizing plate or cracking of the adhesive layer.

The above-described adhesive agent layer, under the 23 ℃ loss tangent (tan δ ₁₎ and the loss tangent at the 80 deg.] C (tan δ ₂₎ ratio _{(tan δ 2 / tan δ 1} ), is preferably 1.10 or more, more preferably 1.10 Up to 5.0, more preferably from 1.10 to 2.0. By the loss tangent ratio being in the above range, the above-mentioned adhesive layer is softened at a high temperature and can follow the heat shrinkage (size change) of the polarizing plate.

In order to form the adhesive layer having the loss tangent (tan δ ₁ , tan δ ₂ ) in the above range, for example, as the component of the adhesive composition, the (meth)acrylic copolymer (A) described below is used. A crosslinking agent (B) such as an isocyanate compound (B1) or a metal compounding compound (B2). For example, when the total amount of (B1) and (B2) is fixed, if the amount of the metal-clamping compound (B2) relative to the isocyanate compound (B1) is decreased, the crosslinking ratio by chemical bond is increased, and the adhesive layer is increased. The loss tends to decrease tangentially.

The gel fraction of the adhesive formed by the adhesive composition of the present invention is preferably from 10 to 70% by mass, more preferably from 15 to 65% by mass, More preferably, it is 20 to 60% by mass. The gel fraction is, for example, a value measured by the adhesive used in the conditions described in the examples.

Since the adhesive composition of the present invention has the above characteristics, it is suitable for the bonding of the substrate constituting the liquid crystal cell and the polarizing plate. In particular, 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 can be applied to the bonding application of the substrate and the polarizing plate.

[(Meth)acrylic copolymer (A)]

(meth)acrylic copolymer (A) is a copolymer obtained by copolymerizing an alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms and a monomer component containing a polar group-containing monomer. . The monomer component of the copolymer (A) may, for example, be a monomer other than these.

In the present specification, an acryl group and a methacryl group are collectively referred to as "(meth)acrylic acid". Further, the constituent unit derived from the monomer a contained in the polymer is referred to as "monomer a unit".

"Alkyl (meth)acrylate"

The alkyl (meth)acrylate is an alkyl (meth)acrylate having an alkyl group having 4 to 18 carbon atoms (CH ₂ =CR ¹ -COOR ² ; R ¹ is a hydrogen atom or a methyl group, R ² It is an alkyl group having 4 to 18 carbon atoms, and the carbon number of the above alkyl group is more preferably 4 to 12.

The alkyl (meth) acrylate having 4 to 18 carbon atoms in the alkyl group may, for example, be n-butyl (meth)acrylate or isobutyl (meth)acrylate. Tertiary butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (methyl) Octyl acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, (methyl) Octadecyl acrylate, isostearyl (meth)acrylate. These may be used alone or in combination of two or more.

The total amount of the (meth)acrylic copolymer (A) is 100% by mass, and the alkyl group has a carbon number of 4 to 18 (meth)acrylic acid alkyl ester, which is good in adhesion and durability. The viewpoint of properties is preferably from 99.8 to 20% by mass, more preferably from 99.5 to 30% by mass, still more preferably from 99 to 50% by mass.

As the monomer component of the (meth)acrylic copolymer (A), an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms (CH ₂ =CR ³ -COOR ⁴ ; R ³ is also used; A hydrogen atom or a methyl group, and R ⁴ is an alkyl group having 1 to 3 carbon atoms).

The alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms may, for example, be methyl (meth)acrylate, ethyl (meth)acrylate or n-propyl (meth)acrylate, or (methyl). ) Isopropyl acrylate. 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 100% by mass or less, based on the stress relaxation property. 50% by mass or less, and more preferably 40% by mass or less.

"Polymer-containing monomers"

The polar group-containing monomer may, for example, be 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, or a cyano group. Monomer. The acid group in the present specification may, for example, be a carboxyl group, an acid anhydride group, a phosphoric acid group or a sulfuric acid group. As the polar group-containing monomer, a monomer having a polar group (crosslinkable functional group) reactive with the crosslinkable functional group of the crosslinking agent (B) is preferably used.

Among these, from the viewpoint of efficiently obtaining a crosslinked structure, easily obtaining good durability, and improving the adhesion of the substrate to an optical film such as a polarizing plate, the polar group is a carboxyl group and/or a hydroxyl group. The monomer is preferably used, that is, at least one selected from the group consisting of a carboxyl group-containing monomer and a hydroxyl group-containing monomer.

The hydroxyl group-containing monomer may, for example, be 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 acrylate, 6-hydroxyhexyl (meth) acrylate or 8-hydroxyoctyl (meth) acrylate. The hydroxyalkyl group of the hydroxyalkyl (meth) acrylate has a carbon number of usually 2 to 8, preferably 2 to 6.

The hydroxyl group-containing monomer may be used alone or in combination of two or more.

The hydroxyl group contained in the hydroxyl group-containing monomer is, for example, a function as a crosslinkable functional group with an isocyanate group contained in the isocyanate compound (B1). The amount of the hydroxyl group-containing monomer to be used is preferably from 0 to 15% by mass, more preferably from 0.05 to 10% by mass, still more preferably from 0.1 to 7% by mass, based on 100% by mass of the monomer component. The amount of the hydroxyl group-containing monomer used is the aforementioned upper limit value. When the crosslinking density of the (meth)acrylic copolymer (A) and the isocyanate compound (B1) is not excessively high, an adhesive layer having excellent stress relaxation properties can be obtained. When the amount of the hydroxyl group-containing monomer used is at least the above lower limit value, an adhesive layer having sufficient strength at room temperature to effectively form a crosslinked structure can be obtained.

The hydroxyl group-containing monomer may, for example, be β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloxyethyl succinate, or ω-carboxypoly a carboxyl group-containing (meth) acrylate such as a lactone mono(meth)acrylate; acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid. The acid anhydride group-containing monomer may, for example, be maleic anhydride or itaconic anhydride. The phosphate group-containing monomer may, for example, be a (meth)acrylic monomer having a phosphate group in a side chain, or a sulfate group-containing monomer, and for example, a (meth)acrylic acid having a sulfate group in a side chain body.

The acid group contained in the acid group-containing monomer functions, for example, as a crosslinkable functional group with the isocyanate compound (B1) or the metal-clamping compound (B2). The amount of the acid group-containing monomer to be used is preferably from 0 to 15% by mass, more preferably from 0.05 to 10% by mass, still more preferably from 0.1 to 5% by mass, based on 100% by mass of the monomer component. For example, the acid value of the (meth)acrylic copolymer (A) is preferably from 0 to 117 mgKOH/g, more preferably from 0.4 to 78 mgKOH/g.

When the amount of the acid group-containing monomer used is at most the above upper limit value, the crosslinking density of the (meth)acrylic copolymer (A) and the crosslinking agent (B) does not become excessively high. An adhesive layer having excellent stress relaxation properties is obtained. When the amount of the acid group-containing monomer used is at least the above lower limit value, an adhesive layer having sufficient strength at room temperature to effectively form a crosslinked structure can be obtained.

The amine group-containing monomer may, for example, be an amino group-containing (meth) acrylate such as dimethylaminoethyl (meth)acrylate or diethylaminoethyl (meth)acrylate. The mercapto group-containing monomer may, for example, be (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (methyl) Acrylamide, N-pentyl (meth) acrylamide. Examples of the nitrogen-containing heterocyclic monomer include vinyl pyrrolidone, propylene morpholine, and ethylene caprolactone. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

The polar group-containing monomer may be used alone or in combination of two or more.

Other Monomers

The monomer component of the (meth)acrylic copolymer (A) may contain, for example, a (meth)acrylic alkoxyalkyl group within a range that does not impair the physical properties of the (meth)acrylic copolymer (A). Other (meth) acrylates such as a base ester, an alkoxy polyalkylene glycol mono(meth) acrylate, an alicyclic group-containing or an aromatic ring (meth) acrylate.

The alkoxyalkyl (meth)acrylate may, for example, be methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate or 2-ethoxyethyl (meth)acrylate. Ester, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxy (meth)acrylate Butyl ester.

The alkoxy polyalkylene glycol mono(meth)acrylate may, for example, be methoxydiethylene glycol mono(meth)acrylate or methoxydipropylene glycol. Mono (meth) acrylate, ethoxy triethylene glycol mono (meth) acrylate, ethoxy diethylene glycol mono (meth) acrylate, methoxy triethylene glycol mono (methyl) Acrylate.

The (meth) acrylate containing an alicyclic group or an aromatic ring may, for example, be cyclohexyl (meth)acrylate, benzyl (meth)acrylate or phenyl (meth)acrylate.

In the above copolymerization, the total amount of the other (meth) acrylate used is preferably 60% by mass or less, and more preferably 40% by mass or less based on 100% by mass of the monomer component.

Further, styrene, methyl styrene, dimethyl styrene, trimethylstyrene, propylbenzene can be used, for example, insofar as the physical properties of the (meth)acrylic copolymer (A) are not impaired. Alkyl styrene such as ethylene, butyl styrene, hexyl styrene, heptyl styrene and octyl styrene; fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, styrene iodide, nifediene a styrene monomer such as ethylene, acetamidine or methoxystyrene; or a copolymerizable monomer such as vinyl acetate.

In the above-mentioned copolymerization, the total amount of the above-mentioned copolymerizable monomer is preferably 40% by mass or less, more preferably 20% by mass or less, based on 100% by mass of the monomer component.

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

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

The (meth)acrylic copolymer (A) is preferably a copolymer obtained by the above copolymerization in the presence of a peroxide-based polymerization initiator. By making When a peroxide-based polymerization initiator is used as a polymerization initiator, there is a tendency that a copolymer having a large amount of branching can be obtained. Therefore, (1) at room temperature, the polymer molecules are often entangled with each other, and as a result, even if the molecular weight of the polymer and the gel fraction of the adhesive layer are designed to be low, it is possible to maintain the polymerization. Adhesive layer having excellent aggregability, adhesive properties, punching of the adhesive layer, deformation of the adhesive layer, and poor adhesion, etc.; (2) at high temperature (for example, 60 ° C) due to the polymer The intertwining of the molecules with each other is partially slowed down, so that the viscosity of the adhesive layer is highly dependent on the temperature, and the adhesive layer exhibits excellent softness. Therefore, the bending of the polarizing plate is excellent, and the adhesive layer exhibits excellent durability due to the aforementioned mutual entanglement.

With regard to the above (1) and (2), when the metal compound (B2) is used as a part of the crosslinking agent (B), the (meth)acrylic copolymer (A) / metal compound (B2) Crosslinking (false crosslinks) is formed due to the coordination bond. Therefore, the polymer can exhibit agglomerability with respect to the above-mentioned cross-linking at the room temperature, and the cross-linking is partially decomposed at the high temperature, and the adhesive layer tends to exhibit more excellent flexibility.

The reason why the polymer molecules having a large number of branches contribute to suppressing the warpage of the polarizing plate is presumed to be the following reason. For example, in the case of a polarizing plate/adhesive layer/adhered body, a case where a glass plate is used as an adherend will be described as an example. The heat shrinkage rate of the polarizing plate and the glass plate is different, and usually the heat shrinkage rate (size change) of the polarizing plate is larger than that of the glass plate. When the adhesive layer is lacking in the softness under high temperature and high humidity, the adhesive layer cannot follow the dimensional change of the polarizing plate, and the adhesive layer cannot be adhered to. The stress is relieved, and the stress is concentrated on the glass plate, so the glass plate is warped. On the other hand, when a metal-clamping compound is used in a part of the multi-branched polymer and the crosslinking agent, the above-mentioned intertwining tends to be locally slow in a high-temperature, high-humidity heat environment, and the cross-linking partially decomposes, so that adhesion is caused. The layer of the agent can follow the change in the size of the polarizing plate. Therefore, no stress is generated and the stress is not concentrated on the glass plate. Moreover, the polarizing plate can also be uniformly heat-shrinked without anisotropy, and does not cause birefringence of the polarizing plate. As described above, since the adhesive layer can absorb and relax the stress accompanying the dimensional change of the polarizing plate, excessive stress (load) is not applied to the glass plate, and it is presumed to be related to the warpage suppression of the glass plate.

The (meth)acrylic copolymer (A) can be produced, for example, by a conventional polymerization method such as a solution polymerization method, a monolith polymerization method, an emulsion polymerization method or a suspension polymerization method, and among these, a solution polymerization method is preferred. Specifically, the polymerization solvent and the monomer component are charged into a reaction vessel, and a polymerization initiator is added under an inert gas atmosphere such as nitrogen, and the reaction initiation temperature is generally set to 40 to 100 ° C, preferably 50 to 80 ° C. The reaction system is generally maintained at a temperature of from 50 to 90 ° C, preferably from 70 to 90 ° C, for a period of from 4 to 20 hours.

The peroxide-based polymerization initiator may, for example, be bis(2-tert-butylperoxyisopropyl)benzene, bisisophenylpropyl peroxide or 2,5-dimethyl-2,5-di. Dialkyl peroxides such as (tertiary butyl peroxy) hexane, tertiary butyl isophenyl propyl peroxide, di- or tertiary hexyl peroxide, and di-tertiary butyl peroxide ( Example: a compound represented by ROOR, wherein R is independently an alkyl or aryl-substituted alkyl group; a compound represented by ROOAOOR, wherein R is independently an alkyl or aryl-substituted alkane. Base, A is a divalent hydrocarbon group; diisobutyl decyl peroxide, bis(3,5,5-trimethylhexyl) peroxide, dilauroyl peroxide, benzoyl peroxide Oxide, benzhydryl (3-methylbenzhydryl) peroxide, bis(3-methylbenzhydryl) peroxide, bis(4-methylbenzylidene) peroxide a quinone-based peroxide (for example, a compound represented by R-COO-OCO-R, wherein R is independently an alkyl group or an aryl group); di-n-propyl dicarbonate peroxide, Diisopropyl dicarbonate peroxide, bis(4-tert-butylcyclohexyl) peroxide Peroxydicarbonate such as carbonate, di(2-ethylhexyl) dicarbonate or di-secondary butyl dicarbonate (example: compound represented by R-OCO-OO-COO-R) Wherein R is independently alkyl or cycloalkyl); isopropyl neodecanoate, 1,1,3,3-tetramethylbutyl neodecanoate, peroxide III Grade hexyl neodecanoate, tertiary butyl neodecanoate peroxide, tertiary butyl neoheptanoate peroxide, tertiary hexyl pivalate peroxide, tertiary butyl pivalate peroxide, 1,1,3,3-tetramethylbutyl-2-ethylhexanoate, 2,5-dimethyl-2,5-di(2-ethylhexyl)peroxide , tertiary hexyl-2-ethylhexanoate peroxide, tertiary butyl-2-ethylhexanoate peroxide, tertiary butyl-3,5,5-trimethylhexanoate, Tert-butyl butyl laurate peroxide, tertiary hexyl benzoate peroxide, 2,5-dimethyl-2,5-di(benzylidene peroxide) hexane, tertiary butyl peroxide acetate, 3-methyl-tert.butyl peroxy benzoate, tert.butyl peroxy benzoate, peroxy esters and the like ^{(Example: R 1 -OO-CO-R} 2 represented Compound of the formula R ¹ is a substituted alkyl or aryl group, R ² is an alkyl group, an aryl group or a substituted aryl group; compound R-CO-OOAOO-CO- R represented by the formula of R Individually independently alkyl or aryl, A is a divalent hydrocarbon group; tertiary hexyl isopropyl monocarbonate, tertiary butyl isopropyl peroxide monoester, tertiary butyl peroxide - A peroxymonocarbonate such as 2-ethylhexylmonocarbonate (for example, a compound represented by ROO-COO-R, wherein R is each independently an alkyl group).

Among the peroxide-based polymerization initiators, a peroxy ester is preferred because it is a more branched (meth)acrylic copolymer, and more preferably a peroxidation represented by the following formula (1) The system polymerization initiator.

In the formula (1), R ^A to R ^F are each independently a hydrogen atom, an alkyl group or an aryl group, and a copolymer having a more branched chain, preferably an alkyl group having 1 to 10 carbon atoms, a phenyl group, or more It is preferably an alkyl group having 1 to 8 carbon atoms, still 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 tertiary butyl pivalate peroxide, tertiary hexyl pivalate peroxide, and tertiary butyl neodymium peroxide. Acid ester, tributyl butyl neoheptanoate, tributyl butyl 2-ethylhexanoate, isopropyl neodecanoate, due to copolymers which are more branched Good oxidized tertiary butyl pivalic acid Ester, tertiary hexyl pivalate peroxylate, tertiary butyl neodecanoate peroxide, tertiary butyl neoheptanoate peroxide, and tertiary butyl-2-ethylhexanoate peroxide.

The peroxide-based polymerization initiator may be used singly or in combination of two or more. Further, in the polymerization, a peroxide-based polymerization initiator may be repeatedly added.

As the polymerization initiator, an azo polymerization initiator may be used together with the peroxide-based polymerization initiator as long as it is a copolymer which is more branched. The azo polymerization initiator may, for example, be 2,2'-azobisisobutyronitrile or 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2 , 2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methyl Butyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(aminomethylmercaptoazo)isobutyronitrile, 2-phenylazo-4-methoxy-2 , 4-dimethylvaleronitrile, 2,2-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethylene isobutylphosphonium , 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-A An azo compound such as propylpropionate or 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propanamide. These polymerization initiators may be used alone or in combination of two or more.

The peroxide-based polymerization initiator is usually 0.001 to 5 parts by mass, preferably 0.005 to 3 parts by mass, per 100 parts by mass of the monomer component forming the (meth)acryl-based copolymer (A). The amount within the range is used. Further, it is preferred that the azo-based initiator is not used, and the amount thereof is used. The peroxide-based polymerization initiator is 100 parts by mass, preferably 0.5 parts by mass or less, more preferably 0.2 parts by mass or less, still more preferably 0 parts by mass. However, the user is not limited in the latter half of the reaction in order to reduce residual monomers. Further, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be appropriately added to the above polymer reaction.

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; cyclopentane and cyclohexane. An alicyclic hydrocarbon such as an alkane, cycloheptane or cyclooctane; diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, benzene Ethers such as ethyl ether and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, chlorobenzene; ethyl acetate, propyl acetate, butyl acetate, propionic acid Esters such as methyl ester; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone; N, N-dimethylformamide, N,N-dimethylacetamide, Amidoxime such as N-methylpyrrolidone; a nitrile such as acetonitrile or benzonitrile; an anthracene such as dimethyl hydrazine or cyclobutyl hydrazine. These polymerization solvents may be used alone or in combination of two or more.

In the adhesive composition of the present invention, after the (meth)acrylic copolymer (A) is produced, the peroxide-based polymerization initiator which is preferably used as a polymerization initiator is reacted for t hours. The residual rate (%) can be obtained by the following formula.

Residual rate (%) = exp(-K _d t) × 100 (%)

Where K _d is the thermal decomposition rate constant, expressed as Arrhenius formula: K _d =A × exp(-ΔE/RT), where A is the frequency factor and △E is the polymerization initiation The activation energy in the thermal decomposition reaction of the agent, R is the gas constant (8.314 J/mol.K), T is the absolute temperature (K); t is the reaction time.

The frequency factor (A) and the activation energy (ΔE) can be determined for the peroxide-based polymerization initiator, and for example, the value described in the organic peroxide catalog (10th edition) can be used. For example, in the third-grade butyl pivalate peroxide, △E = 119.1k J / mol, A = 6.93 × 10 ¹⁷ hr ^-1 , in the third-grade hexyl pivalate peroxide, △ E = 118.5k J /mol, A = 6.45 × 10 ¹⁷ hr ^-1 , in isopropyl neodecanoate, ΔE = 105.3 k J / mol, A = 3.94 × 10 ¹⁶ hr ^-1 .

Therefore, since the K _d of the predetermined temperature can be calculated, the residual ratio (%) of the peroxide-based polymerization initiator after the reaction at a predetermined temperature for t hours can be calculated according to the above formula. Thereby, the residual amount of the peroxide-based polymerization initiator contained in the adhesive composition can be calculated by the amount of the peroxide-based polymerization initiator used in the above copolymerization × the residual ratio (%). Out.

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

The (meth)acrylic copolymer (A) has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC method), and is usually 200,000 to 1,500,000 in terms of polystyrene. The best is 400,000 to 1.3 million, and more preferably 500,000 to 1.1 million. For example, when the copolymer (A) having a small Mw is used, the molecular weight of the polymer after crosslinking can be suppressed to be small, so that the fluidity of the adhesive at a high temperature is increased, and the loss tangent tends to become large. On the other hand, when the copolymer (A) having a large Mw is used, the molecular weight of the polymer after crosslinking increases, and the fluidity of the adhesive at a high temperature decreases, and the loss tangent tends to decrease.

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

The (meth)acrylic copolymer (A) has a degree of branching as measured by the GPC-MALS method, preferably 0.55 or less, more preferably 0.10 to 0.54, still more preferably 0.20 to 0.53, and particularly preferably 0.30 to 0.53. . The measurement conditions of the detailed branching degree are described in the examples. In order to adjust the loss tangent of the adhesive layer to the above range, it is preferred to use the copolymer (A) having a branching degree within the above range.

The degree of branching is a branched polymer when it is 0.55 or less, and is a linear polymer when it exceeds 0.55, and is an index indicating whether or not the branch is branched. Further, in the branched polymer, when the value of the degree of branching is small, it means that the branch of the polymer molecule is large, and it shows that it has a multi-branched chain. When the value of the degree of branching is large, it means that the branch of the polymer molecule is small, and it shows that it has few branches.

The glass transition temperature (Tg) of the (meth)acrylic copolymer (A) can be calculated, for example, from the formula of Fox by the monomer unit constituting the polymer and the ratio thereof. For example, the (meth)acrylic copolymer (A) can be synthesized in such a manner that the glass transition temperature (Tg) obtained by the formula of Fox is generally -70 to 0 ° C, preferably -60 to -30 ° C. . By using the (meth)acrylic copolymer (A) having such a glass transition temperature (Tg), an adhesive composition having excellent adhesion at normal temperature can be obtained.

Fox's formula: 1/Tg=(W ₁ /Tg ₁ )+(W ₂ /Tg ₂ )+...+(W _m /Tg _m )

W ₁ +W ₂ +...+W _m =1

In the formula, Tg is a glass transition temperature of the (meth)acrylic copolymer (A); Tg ₁ , Tg ₂ , and Tg _m are glass transition temperatures of a homopolymer composed of each monomer; W ₁ , W ₂ , ..., W _m is the weight fraction in the aforementioned copolymer (A) derived from the constituent unit of each monomer.

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

The content of the (meth)acrylic copolymer (A) in the adhesive composition of the present invention is usually 50 to 99.99% by mass in 100% by mass of the solid matter of the organic solvent (E) in the composition. More preferably, it is 60 to 99.95 mass%, and particularly preferably 80 to 99.90 mass%. When the content of the (meth)acrylic copolymer (A) is in the above range, the balance of the properties of the adhesive can be obtained, and the adhesive property is excellent.

[Crosslinking agent (B)]

The crosslinking agent (B) is not particularly limited as long as it can form a crosslinking reaction with the (meth)acryl-based copolymer (A), and examples thereof include an isocyanate compound (B1) and a metal compound ( B2), epoxy compound (B3).

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

Among the crosslinking agents (B), the isocyanate compound (B1) and the metal compound (B2) are preferably used in combination. From the viewpoint of adjusting the loss tangent of the adhesive layer to the above range, it is preferred to form a crosslink of the (meth)acrylic copolymer (A) by a covalent bond of the isocyanate compound (B1). A pseudo-crosslinker formed by a coordinate bond of a metal compound (B2).

In the adhesive composition of the present invention, the total content of the crosslinking agent (B) is preferably 100 parts by mass based on the (meth)acrylic copolymer (A). It is 0.01 to 5 parts by mass, more preferably 0.05 to 2.5 parts by mass, still more preferably 0.1 to 1 part by mass. By containing such a fixed amount of the crosslinking agent (B), a sufficient degree of crosslinking can be achieved, and excellent adhesion, dimensional stability, and durability in a high moist heat environment can be achieved.

Isocyanate Compound (B1)

The isocyanate compound (B1) is usually an isocyanate compound having 2 or more isocyanate groups in one molecule. By crosslinking the (meth)acrylic copolymer (A) with the cyanate compound (B1), a crosslinked body (mesh polymer) can be formed.

The isocyanate group (B1) has an isocyanate group number of usually 2 or more, preferably 2 to 8, more preferably 3 to 6. When the number of the 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 pressure-sensitive adhesive layer.

The isocyanate compound having an isocyanate group number of 2 or more in one molecule may, for example, be an aliphatic diisocyanate, an alicyclic diisocyanate or an aromatic diisocyanate. Examples of the aliphatic diisocyanate include ethyl diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, and 3 An aliphatic diisocyanate having 4 to 30 carbon atoms such as methyl-1,5-pentane diisocyanate or 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated deuterated diisocyanate, and hydrogenated methyl group. An alicyclic diisocyanate having 7 to 30 carbon atoms such as phenyl diisocyanate, hydrogenated diphenylmethane diisocyanate or hydrogenated tetramethyl decyl diisocyanate. The aromatic diisocyanate may, for example, be a phenyl diisocyanate, a methylphenyl diisocyanate, a decyl diisocyanate, a naphthyl diisocyanate, a diphenyl ether diisocyanate, a diphenylmethane diisocyanate or a diphenyl group. An aromatic diisocyanate having 8 to 30 carbon atoms such as propane diisocyanate.

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

Further, the isocyanate compound (B1) may, for example, be a polymer of the above isocyanate compound having an isocyanate group number of 2 or more (for example, a 2-mer or a trimer, a biuret or a trimer isocyanate), or a derivative. (for example, an addition reaction product of a polyhydric alcohol with two or more molecules of a diisocyanate compound) or a polymer. The polyhydric alcohol in the above-mentioned derivative may, for example, be a trivalent or higher alcohol such as trimethylolpropane, glycerin or neopentyl alcohol as the low molecular weight polyol; and as the high molecular weight polyol, for example, a polyether polyol , polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol.

Examples of such an isocyanate compound include a trimer of diphenylmethane diisocyanate, a polymethylene polyphenyl polyisocyanate, a hexamethylene diisocyanate or a methylenediphenyl diisocyanate biuret or three. Polyisocyanate, trimethylolpropane and methylphenyl diisocyanate or a reaction product of a mercapto diisocyanate (for example, a 3-molecular adduct of methylphenyl diisocyanate or decyl diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example) , a 3-molecular adduct of hexamethylene diisocyanate), a polyether polyisocyanate, a polyester polyisocyanate.

Among the isocyanate compounds (B1), from the viewpoint of improving aging property and light leakage performance, a reaction product of trimethylolpropane with methylphenylene diisocyanate or decyl diisocyanate is preferred (manufactured by Soochaya Chemical Co., Ltd.) -45, TD-75, etc., manufactured by Ivy Research Chemical Co., Ltd.), hexamethylene diisocyanate or methyl phenyl diisocyanate, a trimeric isocyanate (TSE-100 manufactured by Asahi Kasei Kogyo Co., Ltd., 2050 manufactured by Japan Polyurethane Co., Ltd., etc.) ).

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

Metal Clamp Compound (B2)

The metal nip compound (B2) may, for example, be a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, ruthenium, magnesium, vanadium, chromium, zirconium or the like, coordinated with an alkoxide, B. A compound such as acetone, ethyl acetate or the like. Among these, an aluminum clamp compound (M-12AT manufactured by Soken Chemical Co., Ltd.) is particularly preferable. Specifically, for example, aluminum isopropyl ester, aluminum secondary butyrate, aluminum ethyl acetonitrile acetate can be mentioned. Diisopropyl acrylate, aluminum triethyl acetonitrile acetate, aluminum triethyl acetonate.

The metal conjugated compound (B2) may be used alone or in combination of two or more.

In the adhesive composition of the present invention, when the isocyanate compound (B1) and the metal compound (B2) are used, the total content of the above (B1) and (B2) is relative to the (meth)acrylic copolymer (A). 100 parts by mass, preferably 0.01 to 5 parts by mass, more preferably 0.05 to 2.5 parts by mass, still more preferably 0.1 to 1 part by mass. When the content is in the above range, the tangent of the adhesive layer can be adjusted to the above range, which is preferable. When the content is more than the above range, the loss tangent of the adhesive layer tends to be too small, and if it is less than the above range, the loss tangent of the adhesive layer tends to be too large.

In the adhesive composition of the present invention, the content of the metal nip compound (B2) is preferably from 10 to 1,000 parts by mass, more preferably from 50 to 600 parts by mass, even more preferably 100 parts by mass based on the isocyanate compound (B1). It is preferably 100 to 400 parts by mass. When the content is in the above range, the loss of the adhesive layer can be adjusted to the above range, which is preferable. When the total amount of (B1) and (B2) is fixed, if the content of (B2) exceeds the above range, the loss tangent of the adhesive layer tends to be too large, and if it is less than the above range, the adhesive layer The loss tangent tends to become too small.

Epoxy Compound (B3)

The epoxy compound (B3) is usually an epoxy compound having 2 or more epoxy groups in one molecule. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triepoxypropyl ether, 1,3-bis(N,N-diepoxypropane) Aminomethyl)cyclohexane, N,N,N',N'-tetraepoxypropyl-m-decyldiamine, N,N,N',N'-tetraepoxypropylamino Phenylmethane, triepoxypropyl trimer isocyanate, m-N,N-diepoxypropylaminobenzene Glycidyl ether, N,N-diepoxypropyl toluidine, N,N-diepoxypropyl aniline.

In the adhesive composition of the present invention, when the epoxy compound (B3) is used as the crosslinking agent (B), the content of the above (B) is 100 parts by mass based on the (meth)acrylic copolymer (A). It is preferably 0 to 2 parts by mass, more preferably 0 to 1 part by mass, still more preferably 0 to 0.5 part by mass.

[Chane coupling agent (C)]

The adhesive composition for a polarizing plate of the present invention preferably further contains a decane coupling agent (C). The decane coupling agent (C) helps to firmly adhere the adhesive layer to an adherend such as a glass plate and to prevent peeling in a high moist heat environment.

The decane coupling agent (C) may, for example, be a decane coupling agent containing a polymerizable unsaturated group such as vinyltrimethoxysilane, vinyl ethoxysilane or methacryloxypropyltrimethoxysilane; Oxypropyltrimethoxydecane, 3-glycidoxypropyltriethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, 3-glycidoxypropylmethyldi An epoxy group-containing decane coupling agent such as ethoxysilane or 2-(3,4-ethoxycyclohexyl)ethyltrimethoxyoxane; 3-aminopropyltrimethoxy decane, N-(2-aminoethyl) Amino group-containing decane coupling agent such as 3-aminopropyltrimethoxyoxane or N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane; 3-chloropropyl group A halogen-containing decane coupling agent such as trimethoxy decane.

The content of the decane coupling agent (C) in the adhesive composition for a polarizing plate of the present invention is usually 1 part by mass or less, preferably 0.01 to 100 parts by mass based on the (meth)acrylic copolymer (A). 1 part by mass, better It is 0.05 to 0.5 parts by mass. When the content is in the above range, there is a tendency to prevent peeling of the polarizing plate in a high-humidity heat environment and leakage of the decane coupling agent (C) in a high-temperature environment.

[Antistatic agent (D)]

The antistatic agent (D) can be used, for example, for lowering the surface resistance value of the adhesive composition for a polarizing plate of the present invention. The antistatic agent (D) may, for example, be a surfactant, an ionic compound or a conductive polymer.

The surfactant may, for example, be a 4-stage ammonium salt, a guanamine 4-grade ammonium salt, a pyridinium salt, a cationic surfactant having a cationic group such as a 1st to a third amine group; and a sulfonate group; Anionic surfactants such as an anionic group such as a sulfate group or a phosphate group; and amphoteric bases, alkylimidazolium betaines, alkyl amine oxides, and amine sulfates Surfactants, glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines, A nonionic surfactant such as an alkyl diethanol amide.

Further, the surfactant may be, for example, a reactive emulsifier having a polymerizable group, or a polymer-based surfactant obtained by polymerizing a monomer component containing the above surfactant or reactive emulsifier.

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

The cation portion constituting the ionic compound may be either an inorganic cation or an organic cation or both. 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 piperidinium cation, a pyrrolidinium cation, a dihydropyrrole cation, a pyrrole cation, an imidazolium cation, a tetrahydropyrimidinium cation, a dihydropyrimidinium cation, and a pyrazolinium quinone. a cation, a pyrazolinium 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 ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF6 ^- , 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, an anion of a fluorine-containing atom is preferred because it provides an ionic compound having a low melting point, and particularly preferably (F ₂ SO ₂ ) ₂ N ^- and (CF ₃ SO ₂ ) ₂ N ^- .

An ionic compound, preferably lithium bis(trifluoromethanesulfonyl)imide, lithium bis(difluorosulfonyl)imide, lithium tris(trifluoromethanesulfonyl)methane, bis(trifluoromethanesulfonate) Mercapto) potassium imide, potassium bis(difluorosulfonyl)imide, 1-ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl-4-methylpyridine Hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium bis(fluorosulfonyl)imide, 1-octyl-4- Methylpyridinium bis(trifluoromethanesulfonyl)imide, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate, N,N-di Ethyl-N-methyl-N-(2-methoxyethyl)bis(trifluoromethanesulfonyl)imide ammonium, 1-octylpyridinium fluorene Yttrium imine, 1-octyl-3-methylpyridinium trifluoroimide.

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

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

[Organic solvent (E)]

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

In addition, the term "solid matter" as used herein means a total component in which the organic solvent (E) is removed from the component contained in the adhesive composition, and the "solid content" means the composition 100 with respect to the adhesive. % by mass of the aforementioned solids ratio.

[peroxide]

In the adhesive composition of the present invention, it is preferred that the peroxide (peroxide crosslinking agent) as a crosslinking agent is not blended. Also contains (meth)acrylic acid The residual amount of the peroxide-based polymerization initiator used in the synthesis of the copolymer (A) and the content of the peroxide are preferably 100 parts by mass based on 100 parts by mass of the (meth)acryl-based copolymer (A). It is 0.1 part by mass or less, more preferably 0.05 part by mass or less, still more preferably 0.01 part by mass or less. The crosslinking agent (B) can be inhibited from being caused by the use of the isocyanate compound (B1), the metal-clamping compound (B2), the epoxy crosslinking agent (B3), or the like without using a peroxide-based crosslinking agent. The peroxide layer of the peroxide deteriorates with time.

[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 agent, within a range not impairing the effects of the present invention. One or two or more kinds of the accelerator, the (meth)acrylic polymer other than the above (A), and the release agent.

[Modulation of Adhesive Composition for Polarizing Plate]

The adhesive composition for a polarizing plate 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 conventional method. For example, in the polymer solution of the polymer obtained by synthesizing the (meth)acrylic copolymer (A), the crosslinking agent (B) and other components as necessary may be blended.

[Adhesive layer for polarizing plate]

The adhesive layer of the present invention can be promoted, for example, by promoting the above adhesive The crosslinking reaction in the composition can be specifically obtained by crosslinking the (meth)acrylic copolymer (A) with a crosslinking agent (B).

The adhesive layer of the present invention has a loss tangent (tan δ ₁ ) at 23 ° C of 0.33 to 0.55, preferably 0.35 to 0.52, particularly preferably 0.40 to 0.49, and a loss tangent at 80 ° C (tan δ ₂ ). It is 0.40 to 0.65, preferably 0.42 to 0.62, and particularly preferably 0.47 to 0.56.

The above-mentioned adhesive layer, the loss tangent at 23 ℃ (tan δ ₁₎ and the loss tangent at the 80 deg.] C (tan δ ₂₎ ratio _{(tan δ 2 / tan δ 1} ), is preferably 1.10 or more, more preferably 1.10 to 5.0, more preferably 1.10 to 2.0.

In the above-described loss tangent, for example, the adhesive layers are bonded to each other a plurality of times to form a laminate having a thickness of about 1.0 mm, and the dynamic viscoelastic spectrum of the laminate is measured, and the value calculated from the map is used.

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

The adhesive layer is preferably formed under the following conditions. Applying the adhesive composition of the present invention to a support, and attaching a cover film to the coating film formed under the above conditions, generally for 3 days or longer, preferably 7 to 10 days, and generally 5 to 60 ° C, It is preferably cured in an environment of 15 to 40 ° C, typically 30 to 70% RH, preferably 40 to 70% RH. By cross-linking under the above-mentioned ripening conditions, it is possible to efficiently cross-link the crosslinked body (mesh polymer).

The coating method of the adhesive composition may be, for example, a week of use. A method of coating and drying a predetermined thickness by a spin coating method, a knife coating method, a roll coating method, a bar coating method, a sheet coating method, a die coating method, a gravure coating method, or the like, for example. .

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

The adhesive layer formed by the adhesive composition of the present invention preferably has a gel fraction of from 10 to 70% by mass, more preferably from the viewpoints of strain suppression, cohesive force, adhesion, and removability of the polarizing plate. It is 15 to 65 mass%, more preferably 20 to 60 mass%. Even if the gel fraction is in the above range, since the (meth)acrylic copolymer (A) has a multi-branched chain, the branches of the copolymer (A) are entangled with each other moderately, and the durability of the adhesive layer and Processability will not deteriorate. In particular, when the gel fraction is 20% by mass or more, an adhesive layer having high aggregability can be obtained. When the gel fraction is outside the above range, the stress due to the change in the size of the polarizing plate in a high-temperature, high-humidity heat environment cannot be sufficiently absorbed and alleviated by the adhesive layer.

[Adhesive sheet for polarizing plate]

The adhesive sheet for a polarizing plate of the present invention is an adhesive layer formed of the above-described adhesive composition for a polarizing plate. Examples of the adhesive sheet include a double-sided adhesive sheet having only the above-mentioned adhesive layer, a double-sided adhesive sheet having a base material and the above-mentioned adhesive layer formed on both surfaces of the base material, and a base material and a surface formed on the base material. The single-sided adhesive sheet of the adhesive layer and the surface which is not in contact with the substrate of the adhesive layer of the adhesive sheet are covered with a peeling treatment Adhesive film of the film.

The base material and the cover film may, for example, be a polyester film such as polyethylene terephthalate film (PET); or a plastic film such as a polyolefin film such as polyethylene, polypropylene or ethylene-vinyl acetate copolymer. .

The conditions for forming the adhesive layer, the loss tangent, and the gel fraction are the same as those described in the column of [Adhesive Layer for Polarizing Plate].

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

[Polarizer with Adhesive Layer]

The polarizing plate with an adhesive layer of the present invention is characterized in that it has a polarizing plate and an adhesive layer formed of the adhesive composition for a polarizing plate of the present invention on either side of the polarizing plate. Further, in the present specification, the "polarizing plate" is used in the sense of including a "polarizing film".

As the polarizing plate, a conventional polarizing film can be used. For example, a multilayer film having a stretched film obtained by stretching a film composed of a polyvinyl alcohol-based resin and stretching the film, and a protective film disposed on the stretched film may be used. Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol, polyethylene formaldehyde, polyethylene acetal, and ethylene. a saponified product of a vinyl acetate copolymer. The polarizing component may, for example, be iodine or a dichroic dye. The protective film may, for example, be a cellulose film such as triacetyl cellulose, a polycarbonate film or a polyether ruthenium film.

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

The method of forming the pressure-sensitive adhesive layer on the surface of the polarizing plate is not particularly limited, and for example, a method of applying and drying the above-mentioned adhesive composition directly on the surface of the polarizing plate using a bar coater or the like, and a polarizing plate having the present invention A method in which an adhesive layer of an adhesive sheet is transferred to a surface of a polarizing plate to be cooked. The conditions for drying and ripening, the range of loss tangent, and the gel fraction are the same as those described in the column of [Adhesive Layer for Polarizing Plate].

The thickness of the adhesive layer formed on the polarizing plate is usually 5 to 75 μm, preferably 10 to 50 μm in terms of dry film thickness. In addition, the adhesive layer may be formed on at least one side of the polarizing plate, and for example, an adhesive layer may be formed on only one surface of the polarizing plate, and an adhesive layer may be formed on both surfaces of the polarizing plate.

Further, 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 on the polarizing plate.

The liquid crystal element can be manufactured by disposing the polarizing plate of the adhesive layer of the present invention 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.

The substrate of the liquid crystal cell may be, for example, a glass plate. The thickness of the substrate is usually from 0.1 to 1 mm, preferably from 0.15 to 0.8 mm. Particularly in the present invention, warpage of the polarizing plate and the substrate can be suppressed by using the above-described adhesive composition. Therefore, even if the thickness of the substrate is small (for example, 0.8 mm or less, preferably 0.15 to 0.7 mm), the above-described adhesive composition can be used for bonding the polarizing plate to the 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 description of the examples and the like, "parts" means "parts by mass" unless otherwise specified.

[GPC and GPC-MALS]

The (meth)acrylic copolymer is subjected to gel permeation chromatography (GPC method) under the following conditions, and the weight average molecular weight (Mw) and the number average molecular weight (Mn) are determined by gel permeation chromatography/ A multi-angle laser light scattering detector (GPC-MALS) was used to determine the degree of branching under the following conditions.

. Measuring device: HLC-8320GPC (made by Tosoh Corporation)

. GPC pipe column structure: the following 4 connected pipe columns (all are made by Tosoh Corporation)

(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

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

. Standard polystyrene conversion (when Mw and Mn are measured)

[Synthesis Example 1]

In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, 98.8 parts of n-butyl acrylate, 1 part of 4-hydroxybutyl acrylate, 0.2 parts of acrylic acid, and 100 parts of an ethyl acetate solvent were introduced for introduction of nitrogen gas. The temperature was raised to 80 ° C. Next, 0.1 part of tributyl butyl pivalate was added, and polymerization was carried out at 80 ° C for 6 hours under a nitrogen atmosphere. After completion of the reaction, the mixture was diluted with ethyl acetate to prepare a polymer solution having a solid concentration of 30% by mass. The obtained (meth)acrylic copolymer A had a weight average molecular weight (Mw) of 700,000, a molecular weight distribution (Mw/Mn) of 7.1, and an acid value of 1.6 mgKOH/g.

[Synthesis Examples 2 to 13]

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 component and the polymerization initiator used in the polymerization reaction were changed to those described in Table 1. The results are shown in Table 1.

[Example 1]

(1) Modulation of adhesive composition

The (meth)acrylic polymer solution (solid content: 30% by mass) obtained in Synthesis Example 1 and 100 parts (solid content) of the (meth)acrylic polymer contained in the solution, mixed with an isocyanate compound "M-TAT" (solid content: 10% by mass) of "TD-75" (solid content: 75 mass%, ethyl acetate solution), 0.05 parts (solid content), metal compounding compound, "M-12AT" , toluene, acetonitrile, acetone, 0.14 parts (solid content), ketone coupling agent, "SKM-403" (solid content 100% by mass) 0.2 parts, and the first industrial pharmaceutical with antistatic agent One part of "AS-804" (solid content: 100% by mass) was prepared to prepare an adhesive composition.

(2) Making of adhesive sheets

The adhesive composition obtained in the above (1) was applied onto a polyethylene terephthalate film (PET film) after defoaming and after peeling treatment, and dried at 90 ° C for 3 minutes to form a dry film thickness. 20 μm coating film. On the opposite side of the attached surface of the PET film of the coating film, the peeled PET film was attached, and it was allowed to stand at 23 ° C / 50% RH for 7 angels to obtain a PET film holder. An adhesive sheet of an adhesive layer having a thickness of 20 μm.

(3) Production of polarizing plate with adhesive layer

Applying the adhesive composition obtained in the above (1) to a polyethylene terephthalate film (PET film) after defoaming and peeling treatment, using a doctor blade, It was dried at 90 ° C for 3 minutes to obtain a sheet having a coating film having a dry film thickness of 20 μm. The sheet and the polarizing plate (thickness: 110 μm, layer composition: triacetyl cellulose film/polyvinyl alcohol film/triethylene cellulose film) were bonded together so that the coating film was in contact with the polarizing plate. The glaze was allowed to stand at 23 ° C / 50% RH for 7 days, and a polarizing plate having a PET film, an adhesive layer having a thickness of 20 μm, and an adhesive layer of a polarizing plate was obtained.

[Examples 2 to 14 and Comparative Example 1]

In Example 1, the (meth)acrylic polymer solution was changed to the polymer solution obtained in Synthesis Examples 2 to 13, and/or the formulation was changed to those shown in Table 2, and In the same manner as in Example 1, a pressure-sensitive adhesive composition, an adhesive sheet, and a polarizing plate with an adhesive layer were prepared.

[Evaluation]

[loss tangent]

In the adhesive sheets obtained in the examples and the comparative examples, the adhesive layers having a thickness of 20 μm were bonded to each other in an environment of 23° C./50% RH, and treated in an autoclave at 50° C./5 atm for 20 minutes to prepare 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 in accordance with the dynamic viscoelasticity measurement method of JIS K7244 (temperature range -40 to 180 ° C, temperature increase rate 3.67 ° C / minute, frequency 1 Hz) The viscoelastic spectrum was measured to determine the loss tangent (tan δ) at a temperature of 23 ° C and 80 ° C.

[Gel fraction]

From the adhesive sheets obtained in the examples and the comparative examples, about 0.1 g of an adhesive was applied to the sample vial, and after adding ethyl acetate 30 mL for 4 hours, the contents of the vial were filtered through a mesh of 200 mesh stainless steel. The residue on the net was dried at 100 ° C for 2 hours to determine its dry weight. The gel fraction of the adhesive was determined by the following formula.

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

[potential change (Creep) value]

The polarizing plate (the laminated film composed of the PET film/adhesive layer/polarizing plate) with the adhesive layer obtained in the examples and the comparative examples was cut into a width of 10 mm × a length of 100 mm, and the peeled PET film was peeled off. In the alkali-treated glass plate, the adhesive layer was bonded to the glass plate to form a bonding area of 10 mm × 10 mm, and a test piece for evaluation of the adhesive polarizing plate was obtained.

The test piece for evaluation of the adhesive processing polarizing plate was subjected to autoclave treatment (50 ° C, 5 atm), and left to stand in an environment of 23 ° C / 50% RH for 24 hours. Next, the test piece was placed in a chamber of a micro-latency measuring machine so that the length of the fixing jig portion was 15 mm. The tensile test load of 800 g and the stretching time of 1000 seconds were used to test the adhesive test polarizing plate test piece in the test piece, and to be parallel to the back surface of the polarizing plate and the glass plate and the length direction of the polarizing plate. The distance (μm) from which the bonding portion of the glass plate and the polarizing plate was offset in the test piece was measured as a latent value.

[Measurement of adhesion]

The polarizing plate (the laminated film composed of the PET film/adhesive layer/polarizing plate) with the adhesive layer obtained in the examples and the comparative examples 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 laminated body composed of the adhesive layer/polarizing plate was attached to one surface of a glass plate having a thickness of 2 mm so that the adhesive layer was in contact with the glass plate by using a build-up roll. 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.

[Bending]

The polarizing plate (the laminated film composed of the PET film/adhesive layer/polarizing plate) with the adhesive layer obtained in the examples and the comparative examples was cut into a size of 35 mm × 400 mm (direction of the stretching axis) to prepare a test piece. . The PET film was peeled off from the test piece, and the laminated body composed of the adhesive layer/polarizing plate was attached to a glass plate having a thickness of 0.7 mm and 40 mm×410 mm by using a build-up roll so that the adhesive layer was in contact with the glass plate. On one side. 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. The one end of the one side was fixed to a wall perpendicular to the ground, and the amount of lift of the other end was measured with a ruler. The measurement was carried out after taking out in an oven and 24 hours later.

[Endurance test]

The polarizing plate (the laminated film composed of the PET film/adhesive layer/polarizing plate) with the adhesive layer obtained in the examples and the comparative examples was cut into a size of 150 mm × 250 mm to prepare a test piece. The PET film was peeled off from the test piece, and the laminated body composed of the adhesive layer/polarizing plate was attached to one surface of a glass plate having a thickness of 2 mm so that the adhesive layer was in contact with the glass plate by using a build-up roll. The obtained laminate was held in an autoclave adjusted to 50 ° C / 5 atmosphere for 20 minutes to prepare a test plate. Two pieces of the same test plate were produced. The test plate was allowed to stand under the 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 the generation of foaming and cracking was observed from the following basis. Evaluation. The foaming occurs when the cohesive force is insufficient, and the cracking occurs when the stress relaxation is insufficient.

(foaming)

. 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 of the whole and less than 5%.

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

(rupture)

. AA: No cracks at all

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

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

. DD: The area of the rupture is more than 5% of the whole

As shown in Table 2, when the tan δ ₁ (23 ° C) of the adhesive layer is 0.33 or more and the tan δ ₂ (80 ° C) is 0.40 or more, the warpage and durability (foam resistance and crack resistance) are satisfied. )By. On the other hand, if the tan δ ₁ (23 ° C) of the adhesive layer is less than 0.33 and tan δ ₂ (80 ° C) is less than 0.40, warpage and durability (breaking resistance) are low.

In Table 2, the peroxide polymerization starting dose was calculated as follows. From the above residual rate formula: exp(-K _d t) × 100 (%), for example, in Example 1, by K _d = A × exp (-ΔE / RT), A = 6.93 × 10 ¹⁷ hr ^{- 1} , △ E = 119.1k J / mol, R = 8.314J / mol. K, T = 353 K, and reaction time t = 6 h, and 5 × 10 ^-3 parts by mass was calculated from the residual ratio (%) of the amount of the peroxide-based polymerization initiator used in the above copolymerization.

Claims (12)

An adhesive composition for a polarizing plate obtained by copolymerizing (A) an alkyl (meth) acrylate having a carbon number of 4 to 18 and a monomer component containing a polar group-containing monomer ( a (meth)acrylic copolymer and (B) a crosslinking agent, wherein a loss tangent (tan δ ₁ ) at 23 ° C of the adhesive layer formed of the above composition is 0.33 to 0.55, and 80 ° C The loss tangent (tan δ ₂ ) is 0.40 to 0.65. The adhesive composition for a polarizing plate according to claim 1, wherein the crosslinking agent (B) contains an isocyanate compound (B1) and a metal compound (B2). The adhesive composition for a polarizing plate according to the second aspect of the invention, wherein the metal compound (B2) is contained in an amount of 10 to 1000 parts by mass based on 100 parts by mass of the isocyanate compound (B1). The adhesive composition for a polarizing plate according to any one of claims 1 to 3, wherein the polar group of the polar group-containing monomer is a carboxyl group and/or a hydroxyl group. The adhesive composition for a polarizing plate according to any one of claims 1 to 3, wherein the (meth)acrylic copolymer (A) is a peroxide polymerization initiator. The copolymer obtained by the aforementioned copolymerization in the presence of the copolymer. The adhesive composition for a polarizing plate according to any one of claims 1 to 3, wherein the (meth)acrylic copolymer (A) The weight average molecular weight (Mw) measured by gel permeation chromatography (GPC method) is 200,000 to 1,500,000. The adhesive composition for a polarizing plate according to any one of claims 1 to 3, wherein the content of the peroxide is 100 parts by weight based on 100 parts by weight of the (meth)acrylic copolymer (A). 0.1 part by mass or less. The adhesive composition for a polarizing plate according to any one of claims 1 to 3, wherein the adhesive composition of the adhesive composition for a polarizing plate has a gel fraction of 10 to 70. quality%. A polarizing plate with the adhesive layer, characterized in line: a polarizing plate formed of a patented scope of any one of claims 1 to 8 with the adhesive composition, in the 23 ℃ loss tangent (tan δ ₁₎ is 0.33 to 0.55, and the loss tangent (tan δ ₂ ) at 80 ° C is 0.40 to 0.65. The adhesive layer for a polarizing plate according to claim 9, wherein the gel fraction is 10 to 70% by mass. An adhesive sheet for a polarizing plate, characterized by comprising the adhesive layer for a polarizing plate according to claim 9 or 10. A polarizing plate with an adhesive layer, comprising: a polarizing plate; and an adhesive layer for a polarizing plate according to claim 9 or 10, which is formed on at least one side of the polarizing plate.