TW201706388A - Adhesive composition for polarizing plate, adhesive sheet and polarizing plate with adhesive layer - Google Patents

Abstract

An objective of this invention is to provide an adhesive composition for polarizing plate, capable of suppressing the bending of liquid crystal cell and forming an adhesive layer with superior durability. The approach of addressing this objective is an adhesive composition for polarizing plate containing: (A) a (meth)acrylic acid copolymer obtained by copolymerizing monomers including an alkyl (meth)acrylate with a carbon number of 4 to 18 and a carboxyl group-containing monomer, wherein the copolymer has a degree of branch of 0.55 or less measured by gel permission chromatography /multi-angle laser light scattering detector (GPC-MALS); (B1) an isocyanate compound and (B2) a metal chelating compound.

Description

Adhesive composition for polarizing plate, 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 in a high-temperature/high-humidity heat environment, and since it is easily heat-shrinked, there is a lack of dimensional stability and a phenomenon in which the liquid crystal cell is bent. 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 bending of the liquid crystal cell in a high-temperature/high-humidity heat environment becomes a problem. The reason why the liquid crystal cell is bent is, for example, that the adhesive layer cannot follow the heat shrinkage (dimension change) of the polarizing plate, and the stress relaxation property of the adhesive layer is low.

Further, in a high-temperature/high-humidity heat environment, defects such as foaming at the interface between the polarizing plate and the substrate, breakage of the adhesive layer, and peeling of the polarizing plate are likely to occur. Therefore, an adhesive for a polarizing plate requires high durability.

In general, as a bending hand that suppresses the liquid crystal cell Examples of the segment include a method of using an adhesive layer which is highly flexible in accordance with the dimensional change of the polarizing plate. However, such an adhesive layer causes problems such as insufficient cohesive force, deterioration in durability, and deterioration in workability.

For example, in Patent Document 1, it is disclosed that a specific (meth)acrylic polymer and an isocyanate crosslink are contained in terms of durability, stress relaxation characteristics (bending of glass) and removability due to dimensional change of an optical member. In the adhesive material composition for an optical member of the agent, in Patent Document 2, an adhesive composition containing a specific copolymer, a metal tongs-based curing agent, and an isocyanate-based curing agent is disclosed for the purpose of rework and durability. Things.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-219526

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-132752

An object of the present invention is to provide an adhesive composition for a polarizing plate which can suppress the bending of a liquid crystal cell and which can form an adhesive layer having excellent durability, and a polarizing plate for an adhesive layer formed of the above-mentioned composition. A sheet and a polarizing plate with an adhesive layer of the aforementioned adhesive layer.

The inventors of the present invention have focused on the above problems in order to solve the above problems. discuss. As a result, it has been found that when a (meth)acrylic copolymer having a specific degree of branching is used and an isocyanate compound and a metal nip compound are used in combination as a crosslinking agent, the bending of the liquid crystal cell can be suppressed and durability can be formed. Good adhesive layer. In the above Patent Documents 1 to 2, there is no mention about such a degree of branching. 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 [9].

[1] An adhesive composition for a polarizing plate, comprising: (A) a monomer component of a (meth)acrylic acid alkyl ester having a carbon number of 4 to 18 and a carboxyl group-containing monomer; Polymerization of the obtained (meth)acrylic copolymer, and the branching degree of the copolymer measured by gel permeation chromatography/multi-angle laser light scattering detector (GPC-MALS) is 0.55 or less; (B1) Isocyanate compound; and (B2) metal clamp compound.

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

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

The adhesive composition for polarizing plates of the above-mentioned (meth)acrylic-type copolymer (A) as measured by GPC-MALS. The branching is from 0.10 to 0.54.

The adhesive composition for polarizing plates of any one of the above-mentioned (meth)acrylic- The copolymer obtained by copolymerization of a polar group-containing monomer.

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

[7] The adhesive composition for a polarizing plate according to any one of the above [1], wherein the adhesive composition of the adhesive composition for a polarizing plate has a gel fraction of 20 to 70% by mass.

[8] An adhesive sheet for a polarizing plate according to any one of the above [1] to [7], wherein the adhesive layer is formed of the pressure-sensitive adhesive composition for a polarizing plate.

[9] A polarizing plate with an adhesive layer, comprising: a polarizing plate and an adhesive layer, wherein the adhesive layer is an adhesive composition for a polarizing plate according to any one of the above [1] to [7] And formed on at least one side of the polarizing plate.

According to the present invention, it is possible to provide an adhesive composition for a polarizing plate which can suppress bending of a liquid crystal cell and which can form an adhesive layer having excellent durability, and a polarizing plate for an adhesive layer formed of the above-mentioned composition. A sheet and a polarizing plate with an adhesive layer of the aforementioned adhesive layer.

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

[Adhesive Composition for Polarizing Plate]

The adhesive composition for a polarizing plate of the present invention contains a (meth)acrylic copolymer (A); an isocyanate compound (B1); and a metal compound (B2). The adhesive composition 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.

Hereinafter, the isocyanate compound (B1) and the metal compounding compound (B2) are also collectively referred to as "crosslinking agent (B)". In the present invention, the (meth)acrylic copolymer (A) is used in combination with the crosslinking agents to form an adhesive layer.

[(Meth)acrylic copolymer (A)]

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

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

Determination of (meth)acrylic copolymer (A) by gel permeation chromatography / multi-angle laser light scattering detector (GPC-MALS) The degree of branching is 0.55 or less, more desirably 0.10 to 0.54, more desirably 0.20 to 0.53, and particularly desirably 0.30 to 0.53. The details of the measurement conditions of the branching degree are described in the examples.

The branching degree indicates that the branched polymer is 0.55 or less, and the index of the linear polymer when it exceeds 0.55. Further, in the case of the branched polymer, when the value of the degree of branching is small, the branch of the polymer molecule is large, and the branch has a high branching chain. When the value of the degree of branching is large, the branch of the polymer molecule is small, and the display is low. Branch chain.

The (meth)acrylic copolymer (A) having a degree of branching in the above range, (1) at the room temperature, many entanglements of the branched chains of the polymer molecules occur, and as a result, even the molecular weight of the polymer And in the design in which the gel fraction of the adhesive layer is low, the cohesiveness of the polymer is maintained, and the storage property such as the adhesive property, the processing property such as the hole of the adhesive layer, the deformation of the adhesive layer, and the small amount of bleeding are good. (2) at a high temperature (for example, 60 ° C), the aforementioned entanglement of the polymer molecules is partially relaxed, so that the adhesive layer exhibits good flexibility, and the bending of the polarizing plate is suppressed. Preferably, the adhesive layer exhibits good durability due to a portion of the remaining entanglement remaining.

In the above (1) and (2), in the present invention, a part of the crosslinking agent is a metal-clamping compound (B2), and the (meth)acrylic copolymer (A)/metal compound (B2) is used. Crosslinking (pseudo-crosslinking) is formed by a coordination bond. Therefore, the above-mentioned crosslinking is maintained at the above room temperature, and the cohesiveness of the polymer is exhibited. On the other hand, at the high temperature, the crosslinking is partially released, and the adhesive layer exhibits better flexibility.

The reason for suppressing the bending of the polarizing plate is presumed to be the following reason. For example, in the configuration of the polarizing plate/adhesive layer/attached body, a case where a glass plate is used as an adherend will be described as an example. The heat shrinkage rate of each of the polarizing plate and the glass plate is different, and the heat shrinkage ratio (size change) of the polarizing plate is generally larger than that of the glass plate. When the adhesive layer lacks flexibility in a high-temperature/high-humidity heat environment, the adhesive layer cannot follow the dimensional change of the polarizing plate, the stress cannot be alleviated in the adhesive layer, and the stress concentrates on the glass plate, so that the glass plate is bent. On the other hand, the adhesive layer formed using the adhesive composition of the present invention contains a high-branched chain polymer, and a part of the crosslinking agent uses a metal-clamping compound, so that the above-mentioned entangled part in a high-temperature/high-humidity heat environment The part is loose or a part of the cross-linking is loosened, so that the adhesive layer can follow the dimensional change of the polarizing plate, no stress is generated, and the stress is not concentrated on the glass plate. Moreover, the polarizing plate can also be heat-shrinked uniformly without anisotropy, and does not cause birefringence of the polarizing plate. As described above, in the present invention, it is presumed that the adhesive layer can absorb/slow the stress accompanying the dimensional change of the polarizing plate, so that excessive stress (load) is not applied to the glass plate, and thus it is associated with the suppression of the bending of the glass plate.

Since the adhesive composition of the present invention has the above characteristics, it is suitable for use in bonding a substrate constituting a liquid crystal cell and a polarizing plate. In particular, in the case where the thickness of the glass plate constituting the liquid crystal cell which is thinned is as small as about 0.1 to 1.0 mm, it is still suitable for the bonding of the substrate and the polarizing plate.

"Alkyl (meth)acrylate"

As the (meth)acrylic acid alkyl ester, 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, and R ² is used) The alkyl group having 4 to 18 carbon atoms is more preferably 4 to 12 carbon atoms.

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

When 100% by mass of the monomer component of the (meth)acrylic copolymer (A) is formed, the total amount of the alkyl (meth)acrylate having 4 to 18 carbon atoms in the alkyl group exhibits good adhesion and durability. From the viewpoint of properties, it is preferably from 99.8 to 20% by mass, more desirably from 99.5 to 30% by mass, still more desirably 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 ) can also be used. It is a hydrogen atom or a methyl group, and R ⁴ is 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, and n-propyl (meth)acrylate. Base) 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 50% by mass based on 100% by mass of the monomer component. The mass% or less is more preferably 40% by mass or less.

"Carboxyl group-containing monomer"

Examples of the monomer having a carboxyl group include β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(methyl)propenyloxyethyl succinate, and ω-carboxyl groups. a carboxyl group-containing (meth) acrylate such as polycaprolactone mono(meth)acrylate; acrylic acid, methacrylic acid, methylene succinic acid, 2-butenoic acid, fumaric acid, butene Diacid.

In the present specification, the monomer having a carboxyl group also includes a monomer having an acid anhydride group formed by dehydration condensation of two carboxyl groups, and examples thereof include a carboxylic acid anhydride such as maleic anhydride or methylene succinic anhydride.

The monomer having a carboxyl group may be used alone or in combination of two or more.

The carboxyl group contained in the carboxyl group-containing monomer functions as a crosslinkable functional group with the isocyanate compound (B1) and the metal-clamping compound (B2). The amount of the carboxyl group-containing monomer to be used is preferably 0.01 to 15% by mass, more preferably 0.05 to 10% by mass, still more preferably 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 0.1 to 117 mgKOH/g, more preferably from 0.4 to 78 mgKOH/g.

When the amount of the carboxyl group-containing monomer used is at most the above upper limit, the (meth)acrylic copolymer (A) and the crosslinking agent (B) are formed. The joint density does not become too high, and an adhesive layer having excellent stress relaxation properties can be obtained. When the amount of the carboxyl group-containing monomer used is at least the above lower limit value, the crosslinked structure can be effectively formed, and an adhesive layer having an appropriate strength at normal temperature can be obtained.

"Polymers Containing Polar Groups"

Examples of the polar group-containing monomer include a hydroxyl group-containing monomer, an acid group-containing monomer other than the carboxyl group-containing monomer, an amine group-containing monomer, a guanamine group-containing monomer, and a nitrogen-containing system. A heterocyclic monomer, a cyano group-containing monomer. As the monomer having a polar group, a monomer having a polar group (crosslinkable functional group) reactive with a crosslinkable functional group of the crosslinking agent (B) is preferably used.

The (meth)acrylic copolymer (A) is preferably a copolymer obtained by copolymerizing a carboxyl group-containing monomer together with a polar group-containing monomer other than the monomer. Among these, from the viewpoint of improving the adhesion of the substrate to an optical film such as a polarizing plate, it is preferred to use a monomer having a carboxyl group together with a monomer having a hydroxyl group.

Examples of the monomer having a hydroxyl group include a (meth) acrylate having a hydroxyl group, and specific examples thereof include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (methyl). A hydroxyalkyl (meth)acrylate such as 4-hydroxybutyl acrylate, 6-hydroxyhexyl (meth)acrylate or 8-hydroxyoctyl (meth)acrylate. The hydroxyalkyl group of the (hydroxy) hydroxyalkyl acrylate has a carbon number of usually 2 to 8, more preferably 2 to 6.

The hydroxyl group contained in the hydroxyl group-containing monomer exhibits crosslinkability as an isocyanate group contained in the isocyanate compound (B1). The function of the functional group. 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, even more preferably from 0.1 to 7% by mass, based on 100% by mass of the monomer component. When the amount of the hydroxyl group-containing monomer used is at most the above upper limit value, the crosslinking density formed by the (meth)acrylic copolymer (A) and the isocyanate compound (B1) does not become too high, and stress can be obtained. A layer of adhesive with good properties. When the amount of the hydroxyl group-containing monomer used is at least the above lower limit value, the crosslinked structure can be effectively formed, and an adhesive layer having an appropriate strength at normal temperature can be obtained.

In the present specification, examples of the acid group include a phosphate group and a sulfate group. Examples of the monomer having a phosphate group include a (meth)acrylic monomer having a phosphate group in a side chain, and examples of a monomer having a sulfate group include a (meth)acrylic acid having a sulfate group in a side chain. body.

Examples of the monomer having an amine group include an amine group-containing (meth) acrylate such as dimethylaminoethyl (meth)acrylate or diethylaminoethyl (meth)acrylate. Examples of the monomer containing a guanamine group include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, and N-propyl ( Methyl) acrylamide, N-hexyl (meth) acrylamide. Examples of the monomer containing a nitrogen-based heterocyclic ring include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactam. Examples of the cyano group-containing monomer include cyano (meth) acrylate and (meth) acrylonitrile.

The monomer having a polar group may be used alone or in combination of two or more.

Other Monomers

The monomer component forming the (meth)acrylic copolymer (A) may contain, for example, an alkoxyalkyl (meth)acrylate, within the range of physical properties of the (meth)acrylic copolymer (A). Other (meth) acrylates such as alkoxy polyalkylene glycol mono(meth)acrylates, (meth)acrylates containing an alicyclic group or an aromatic ring.

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

Examples of the alkoxy polyalkylene glycol mono(meth)acrylate include methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, and B. Oxyethylene triethylene glycol mono (meth) acrylate, ethoxy diethylene glycol mono (meth) acrylate, methoxy triethylene glycol mono (meth) acrylate.

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

The total amount of the other (meth) acrylate used in the above-mentioned copolymerization 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, in the range of the physical properties of the non-destructive (meth)acrylic copolymer (A), for example, styrene, methylstyrene, dimethylstyrene, trimethylstyrene, propylstyrene, and butyl can be used. Styrene, hexyl Alkyl styrenes such as styrene, heptyl styrene and octyl styrene, fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, styrene iodide, nitrostyrene, ethyl styrene styrene And a styrene monomer such as methoxystyrene; and a copolymerizable monomer such as vinyl acetate.

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

The other monomer 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 polymerization initiator. In other words, by using a peroxide-based polymerization initiator as a polymerization initiator, a copolymer having a degree of branching in the above range tends to be obtained.

The (meth)acrylic copolymer (A) can be produced by a conventional polymerization method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, or a suspension polymerization method, among which solution polymerization is used. More ideal. Specifically, a polymerization solvent and a monomer component are placed in a reaction container, and a polymerization initiator is added in an inert gas atmosphere such as nitrogen gas. The temperature at which the reaction starts is usually 40 to 100 ° C, preferably 50 to 80 ° C, usually The reaction system is maintained at a temperature of 50 to 90 ° C, preferably 70 to 90 ° C, for 4 to 20 hours.

Examples of the peroxide-based polymerization initiator include di(2-tert-butylperoxyisopropyl)benzene, dicumyl peroxide, and 2,5-dimethyl-2,5-di. Dialkyl peroxides such as (t-butylperoxy)hexane, tert-butylperoxy cumene, di-thylhexyl peroxide, and di-tert-butyl peroxide (for example: ROOR A compound of the formula wherein R in the formula is independently an alkyl group or an alkyl group substituted with an aryl group; a compound represented by ROOAOOR, wherein R in the formula is independently an alkyl group or an alkyl group substituted with an aryl group, and A represents Divalent sulfhydryl peroxide; diisobutyl hydrazino peroxide, bis(3,5,5-trimethylhexyl) peroxide, dilauroyl peroxide, benzoyl peroxide, benzo Dimethyl group such as mercapto (3-methylbenzhydryl) peroxide, bis(3-methylbenzhydryl) peroxide, bis(4-methylbenzylidene) peroxide Oxide (for example, a compound represented by R-COO-OCO-R, wherein R in the formula is independently an alkyl group or an aromatic group); di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate Di(4-tert-butylcyclohexyl peroxydicarbonate) a peroxydicarbonate such as di(2-ethylhexyl) peroxydicarbonate or dibutyl butyl dicarbonate (for example, a compound represented by R-OCO-OO-COO-R, wherein R is independently alkyl or cycloalkyl); cumene peroxy neodecanoate, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, third peroxy neodecanoate Hexyl ester, tert-butyl peroxy neodecanoate, tert-butyl peroxy neoheptanoate, third hexyl peroxypivalate, tert-butyl peroxypivalate, 2-ethylhexyl peroxide 1,1,3,3-tetramethylbutyl acid, 2,5-dimethyl-2,5-di(2-ethylhexylperoxy)hexane, 2-ethylhexanoic acid peroxide Third hexyl ester, tert-butyl peroxy 2-ethylhexanoate, third butyl peroxy 3,5,5-trimethylhexanoate, third butyl laurate, benzoic acid Trihexyl ester, 2,5-dimethyl-2,5-bis(benzhydrylperoxy)hexane, tert-butyl peroxyacetate, tert-butyl 3-methylbenzoate, tertiary butyl peroxide and other peroxy benzoate esters (for example: a compound represented by R1-OO-CO-R2, wherein R1 is an alkyl group or an aromatic group substituted by an alkyl group, R ² is a group, an aromatic group or an alkyl group substituted with an aryl group; a compound represented by R-CO-OOAOO-CO-R, wherein R is independently an alkyl group or an aromatic group, and A is a divalent hydrocarbon group; Peroxymonocarbonates such as hexyl peroxyethylene monooxylate, butyl tributyl peroxymonocarbonate, and 2-ethylhexyl peroxybutyl monocarbonate (for example: ROO-COO-R) The compound shown, wherein R in the formula is independently alkyl).

In the case of the (meth)acrylic copolymer which can obtain a highly branched chain, a peroxy ester is preferable, and a peroxide represented by the following formula (1) is more preferable. It is a polymerization initiator.

In the formula (1), R ^A to R ^F are each independently a hydrogen atom, an alkyl group or an aromatic group, and from the viewpoint of a copolymer which can obtain a highly branched chain, an alkyl group having 1 to 10 carbon atoms or a phenyl group is preferable. More preferably, it is an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably an alkyl group having 1 to 2 carbon atoms.

Among the peroxide-based polymerization initiators represented by the formula (1), Ideally, third butyl peroxypivalate, third hexyl peroxypivalate, tert-butyl peroxy neodecanoate, tert-butyl peroxy neoheptate, 2-ethylhexanoic acid peroxide The third butyl ester and cumene peroxy neodecanoate are particularly preferably a third butyl peroxypivalate or a third hexyl peroxypivalate, in view of a copolymer which can obtain a high branched chain. Tert-butyl peroxy neodecanoate, tert-butyl peroxy neoheptanoate, and tert-butyl peroxy 2-ethylhexanoate.

The peroxide polymerization initiator may be used alone or in combination of two or more. Further, in the polymerization, it is not limited to the addition of a plurality of peroxide-based polymerization initiators.

As a polymerization initiator, as long as the degree of branching is in the above range, a peroxide-based polymerization initiator can be used together with an azo-based initiator. Examples of the azo initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 2 , 2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methyl Butyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2-(aminomercaptoazo)isobutyronitrile, 2-phenylazo-4-methoxy- 2,4-Dimethylvaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethylene isobutylene Base, 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 An azo compound such as -methylpropionate) or 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propanamide. These polymerization initiators may be used alone or in combination of two or more.

Peroxide polymerization initiator, relative to formation (methyl) The amount of the monomer component of the acrylic copolymer (A) is usually 0.001 to 5 parts by mass, and more preferably 0.005 to 3 parts by mass. In addition, it is preferable that the amount of the azo-based initiator is not more than 0.5 parts by mass, more preferably 0.2 parts by mass or less, more preferably 100 parts by mass of the peroxide-based polymerization initiator. It is 0 parts by mass. However, there is no limitation on the use for the purpose of reducing the amount of monomers remaining in the latter half of the reaction. Further, in the above polymerization reaction, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be appropriately added.

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

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

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

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

For the above-mentioned peroxide-based polymerization initiator, in order to obtain the frequency factor (A) and the activation energy (ΔE), for example, a value described in the Organic Peroxide Catalogue (10th Edition) of Nippon Oil Co., Ltd. can be used. For example, the third butyl peroxypivalate is ΔE=119.1kJ/mol, A=6.93×10 ¹⁷ hr ^-1 , and the third hexyl peroxypivalate is ΔE=118.5kJ/mol, A=6.45. ×10 ¹⁷ hr ^-1 , cumene peroxy neodecanoate was ΔE = 105.3 kJ/mol, A = 3.94 × 10 ¹⁶ hr ^-1 .

Therefore, since kd at the predetermined temperature can be calculated, the residual ratio (%) of the peroxide-based polymerization initiator after the reaction time t at the predetermined temperature can be calculated from the above formula. Then, the residual amount of the peroxide-based polymerization initiator contained in the adhesive composition can be calculated from the amount of the peroxide-based polymerization initiator used in the copolymerization × the residual ratio (%).

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

The weight average molecular weight (Mw) of the (meth)acrylic copolymer (A) measured by the GPC method is usually 200,000 to 1,500,000, preferably 400,000 to 1,300,000 in terms of polystyrene. More preferably, it is between 500,000 and 1.1 million. The copolymer (A) has a high branching chain even if Mw is in the above range, so that the chains of the copolymer (A) are entangled with each other moderately, and the adhesive layer is resistant to each other. Long-term and processability will not deteriorate. In particular, when the Mw is 400,000 or more, an 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, for example, from the monomeric unit constituting the polymer and the content ratio thereof by the Fox formula. For example, the (meth)acrylic copolymer (A) can be synthesized such that the glass transition temperature (Tg) obtained by the Fox method is usually -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 good adhesion at normal temperature can be obtained.

Fox type: 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), and Tg ₁ , Tg ₂ , ..., Tg _m are glass transition temperatures of the homopolymer composed of each monomer, W ₁ And W ₂ , ..., W _m is a weight fraction in the said copolymer (A) from the structural unit of each monomer.

The glass transition temperature of the homopolymer composed of the respective monomers of the above-mentioned Fox type 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, except for the organic solvent (E) in the composition The solid content of 100% by mass is usually 50 to 99.99% by mass, more desirably 60 to 99.95% by mass, and particularly desirably 80 to 99.90% by mass. When the content of the (meth)acrylic copolymer (A) is in the above range, a balance of properties as an adhesive is obtained, and the adhesive property is good.

[Isocyanate Compound (B1)]

As the isocyanate compound (B1), an isocyanate compound having a number of isocyanate groups of 1 or more in one molecule is usually used. The (meth)acrylic copolymer (A) is crosslinked by the isocyanate compound (B1) to form a crosslinked body (mesh polymer).

The number of isocyanate groups of the isocyanate compound (B1) is usually 2 or more, 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.

Examples of the diisocyanate compound having a number of isocyanate groups in one molecule of 2 include an aliphatic diisocyanate, an alicyclic diisocyanate, and an aromatic diisocyanate. Examples of the aliphatic diisocyanate include ethyl diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, and 2-methyl-1,5-pentane diisocyanate. An aliphatic diisocyanate having 4 to 30 carbon atoms such as 3-methyl-1,5-pentane diisocyanate or 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated methyl phenyl diisocyanate, and hydrogen. An alicyclic diisocyanate having 7 to 30 carbon atoms such as diphenylmethane diisocyanate or hydrogenated tetramethylxylylene diisocyanate. Examples of the aromatic diisocyanate include phenyldiphenyl diisocyanate, methylphenyl diisocyanate, benzoyl diisocyanate, stilbene diisocyanate, diphenyl ether diisocyanate, and diphenylmethane diisocyanate. An aromatic diisocyanate having 8 to 30 carbon atoms such as diphenylpropane diisocyanate.

Examples of the isocyanate compound having 3 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.

Further, examples of the isocyanate compound (B1) include a polymer of the above isocyanate compound having a number of isocyanate groups of 2 or more (for example, a 2-mer or a 3-mer, a biuret, an isocyanurate). And a derivative (for example, an addition reaction product of a polyhydric alcohol and two or more molecules of a diisocyanate compound) or a polymer. Examples of the polyol in the above-mentioned derivative include, as a low molecular weight polyol, a trihydric or higher alcohol such as trimethylolpropane, glycerin or neopentyl alcohol; and a high molecular weight polyol, For example, a polyether polyol, a polyester polyol, an acryl polyol, a polybutadiene polyol, and a polyisoprene polyol can be mentioned.

Examples of such an isocyanate compound include a dimer of diphenylmethane diisocyanate, a polymethylene polyphenyl polyisocyanate, a hexamethylene diisocyanate or a methylenediphenyl diisocyanate biuret or Isocyanurate, trimethylolpropane and methylphenyl diisocyanate Reaction product of an acid ester or benzodimethyl diisocyanate (for example, a 3-molecular adduct of methylphenylene diisocyanate or benzodimethyl diisocyanate), trimethylolpropane and hexamethylene diisocyanate The reaction product (for example, a 3-molecular adduct of hexamethylene diisocyanate), a polyether polyisocyanate, or a polyester polyisocyanate.

The isocyanate compound (B1) is preferably a reaction product of trimethylolpropane with methylphenyl diisocyanate or benzoyl diisocyanate from the viewpoint of improving aging property and light leakage performance (Zhejiang chemistry) Company-made L-45, TD-75, etc. from Synthetic Chemical Co., Ltd.), isocyanurate of hexamethylene diisocyanate or methyl phenyl diisocyanate (TSE-100 manufactured by Asahi Kasei Kogyo Co., Ltd., 2050 manufactured by Polyurethane Co., Ltd., Japan) Wait).

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

[Metal clamp compound (B2)]

In the present invention, a part of the crosslinking agent (B) is compounded with a metal compound (B2). The metal compound (B2) is a compound (B) which crosslinks the (meth)acrylic copolymer (A) by a coordinate bond. Therefore, at a high temperature, the aforementioned cross-linking is partially loosened, and the adhesive layer exhibits better flexibility.

Examples of the metal nip compound (B2) include alkoxides and acethanides coordinated to polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, ruthenium, magnesium, vanadium, chromium, and zirconium. A compound such as acetone or ethyl acetate. Among these, it is preferable to use an aluminum clamp compound (M-12AT manufactured by Soken Chemical Co., Ltd.). Specific examples thereof include aluminum isopropoxide, aluminum second butoxide, ethyl acetate, aluminum diisopropylate, ethyl aluminum acetate, and aluminum. Acetylacetone aluminum.

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

In the adhesive composition of the present invention, the total content of the isocyanate compound (B1) and the metal compound (B2) is usually 0.01 to 100 parts by mass of the (meth)acrylic copolymer (A). 5 parts by mass, more preferably 0.05 to 2.5 parts by mass, still more desirably 0.1 to 1 part by mass. When the content is in the above range, it is preferable from the viewpoint of easily obtaining a balance between durability and stress relaxation characteristics.

In the adhesive composition of the present invention, the content of the metal nip compound (B2) is usually 10 to 1000 parts by mass, more preferably 50 to 600 parts by mass, per 100 parts by mass of the isocyanate compound (B1). More preferably, it is 100 to 400 parts by mass. When the content is in the above range, it is preferable from the viewpoint of suppressing the amount of warpage and improving the adhesion of the substrate to an optical film such as a polarizing plate.

[decane coupling agent (C)]

The adhesive composition for a polarizing plate of the present invention preferably 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 to prevent peeling in a high-humidity heat environment.

Examples of the decane coupling agent (C) include a decane coupling agent containing a polymerizable unsaturated group such as vinyl trimethoxy decane, vinyl triethoxy decane or methacryloxypropyl trimethoxy decane. 3-glycidoxypropyltrimethoxydecane, 3-glycidoxypropyltriethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, 3-ring Oxypropyl Epoxy-containing decane coupling agent such as oxypropylmethyldiethoxydecane or 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane; 3-aminopropyltrimethoxy矽, N-(2-aminoethyl)-3-aminopropyltrimethoxydecane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxydecane, etc. A halogen-containing decane coupling agent such as an amine-based decane coupling agent; 3-chloropropyltrimethoxydecane.

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 based on 100 parts by mass of the (meth)acrylic copolymer (A), and is preferably 1 part by mass or less. 0.01 to 1 part by mass, more preferably 0.05 to 0.5 part 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 bleed out of the decane coupling agent (C) in a high-temperature environment.

[Antistatic agent (D)]

The antistatic agent (D) can be used, for example, in order to lower the surface resistance value of the 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, for example, a 4-stage ammonium salt, a guanamine 4-grade ammonium salt, a pyridinium salt, a cationic surfactant having a cationic group such as a first- to third-order amine group; and a sulfonic acid group; An anionic surfactant such as a salt group, a sulfate group or a phosphate group; an alkylbetaine, an alkylimidazolium betaine, an alkylamine oxide, an amino acid sulfate, etc. Amphoteric surfactant; glycerol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkane Amines, alkyls A nonionic surfactant such as ethanolamine.

Further, examples of the surfactant include a reactive emulsifier having a polymerizable group, and 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 may be either solid or liquid at room temperature (23 ° C / 50% RH).

The cation part 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 pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, and pyrazolium. 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 ion-bonded to the cation portion to form an ionic compound. Specifically, F ^- , Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , SCN ^- , ClO ₄ ^- , NO ₃ ^- , CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (F ₂ SO ₂ ) ₂ N ^- , (CF ₃ SO ₂ ) ₃ C ^- , AsF ₆ ^- , SbF ₆ ^- , NbF ₆ ^- , TaF ₆ ^- , F(HF) _n ^- , (CN) ₂ N ^- , C ₄ 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 containing a fluorine atom is preferred because it imparts a low melting point ionic compound, and particularly preferably (F ₂ SO ₂ ) ₂ N ^- and (CF ₃ SO ₂ ) ₂ N ^- .

As the ionic compound, it is preferably lithium bis(trifluoromethanesulfonyl) quinone imine, lithium bis(difluorosulfonyl) quinone imine, lithium tris(trifluoromethanesulfonyl)methane, potassium double (Trifluoromethanesulfonyl) quinone imine, potassium bis(difluorosulfonyl) quinone imine, 1-ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl -4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium bis(fluorosulfonyl) quinone imine, 1-octyl-4-methylpyridinium bis(trifluoromethanesulfonyl) quinone imine, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium Fluoroborate, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl) quinone imine, 1-octylpyridinium fluorene 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 based on 100 parts by mass of the (meth)acrylic copolymer (A), and is preferably 3 parts by mass or less. 0.01 to 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 thereof. The organic solvent may, for example, be a polymerization solvent described in the column of the (meth)acrylic copolymer (A). For example, polymerization of the (meth)acrylic copolymer (A) and the polymerization solvent obtained by the above copolymerization can be carried out. The solution is mixed with the isocyanate compound (B1) and the metal compound (B2) 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 the present specification, the term "solid content" means all components other than the organic solvent (E) among the components contained in the adhesive composition, and the "solid content concentration" means the adhesive relative to the adhesive. The ratio of the above-mentioned solid content of 100% by mass of the composition.

[peroxide]

The adhesive composition of the present invention is preferably a peroxide (peroxide crosslinking agent) which is not a crosslinking agent. The residual amount of the peroxide-based polymerization initiator used in the synthesis of the (meth)acrylic copolymer (A), and the content of the peroxide are 100 parts by mass based on the (meth)acrylic copolymer (A). The amount is preferably 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. By using the isocyanate compound (B1) and the metal-clamping compound (B2) as a crosslinking agent, it is possible to suppress the deterioration of the adhesive layer due to residual peroxide over time without using a peroxide-based crosslinking agent.

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

[Modulation of Adhesive Composition for Polarizing Plate]

The adhesive composition for a polarizing plate of the present invention can be obtained from the (meth)acrylic copolymer (A), the isocyanate compound (B1), the metal compound (B2), and other components as needed. The method is mixed and modulated. For example, in the polymer solution containing the polymer obtained by synthesizing the (meth)acrylic copolymer (A), the isocyanate compound (B1) and the metal compound (B2) and other components as needed are blended. .

The gel fraction of the adhesive formed of the adhesive composition of the present invention is desirably 20 to 70% by mass, more desirably 24 to 60% by mass, still more desirably 30 to 55% by mass. The gel fraction is, for example, a value measured for the adhesive taken according to the conditions described in the examples.

[Adhesive layer]

The adhesive layer of the present invention is, for example, subjected to a crosslinking reaction in the above-mentioned adhesive composition, specifically by using an isocyanate compound (B1) and a metal chelating compound for the (meth)acrylic copolymer (A). (B2) is obtained by cross-linking.

The formation conditions of the adhesive layer are as follows, for example. The application of the adhesive composition of the present invention to the support varies depending on the type of the solvent, but is usually 50 to 150 ° C, preferably 60 to 100 ° C, and usually 1 to 10 minutes, preferably 2 dry. The solvent was removed to form a coating film until 7 minutes. 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. Coating the adhesive composition of the present invention on a support, in the form of the above conditions After the cover film is attached to the formed film, it is usually 3 days or longer, preferably 7 to 10 days, usually 5 to 60 ° C, more preferably 15 to 40 ° C, usually 30 to 70%. RH is preferably aged in an environment of 40 to 70% RH. When cross-linking is carried out under the above-described ripening conditions, the cross-linking (network polymer) can be efficiently formed.

As a coating method of the adhesive composition, a conventional method such as a spin coating method, a knife coating method, a roll coating method, a bar coating method, a blade coating method, or a die coating method can be used. A method of coating/drying to a predetermined thickness, such as a method or a gravure coating method.

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

The adhesive layer formed of the adhesive composition of the present invention preferably has a gel fraction of 20 to 70% by mass, more preferably 20 to 70% by mass, from the viewpoints of bending suppression, cohesive force, adhesion, and removability of the polarizing plate. 24 to 60% by mass, more desirably 30 to 55% by mass. Even if the gel fraction is in the above range, since the (meth)acrylic copolymer (A) has a high branched chain, the branched chains of the copolymer (A) can be appropriately entangled with each other, and the durability of the adhesive layer, Processability will not deteriorate. In particular, when the gel fraction is 30% by mass or more, an adhesive layer having high cohesiveness can be obtained. When the gel fraction exceeds the above range, the adhesive layer may not sufficiently absorb/alleviate the stress due to the dimensional change of the polarizing plate in a high-temperature/high-humidity heat environment.

[Adhesive sheet for polarizing plate]

The pressure-sensitive adhesive sheet for a polarizing plate of the present invention has the above-mentioned pressure-sensitive adhesive layer formed of an 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 side formed on the base material. The one-sided adhesive sheet of the above-mentioned adhesive layer and the adhesive sheet of the peeling-treated coating film are attached to the surface of the adhesive layer of the adhesive sheet which is not in contact with the substrate.

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

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

The film thickness of the adhesive layer is usually from 5 to 75 μm, preferably from 10 to 50 μm, from the viewpoint of maintaining adhesive properties. The film thickness of the substrate and the coating film is not particularly limited and 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 by comprising a polarizing plate and an adhesive layer formed of the adhesive composition for a polarizing plate of the present invention on at least one surface of the polarizing plate. 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, there is a stretched film obtained by stretching a film made of a polyvinyl alcohol-based resin and containing a polarizing component, and a stretched film disposed on the stretched film. A multilayer film of a protective film. Examples of the polyvinyl alcohol-based resin include a saponified product of polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, and ethylene vinyl acetate copolymer. Examples of the polarizing component include iodine or a dichroic dye. Examples of the protective film include a cellulose film such as triethylenesulfonyl cellulose, a polycarbonate film, and 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 adhesive layer on the surface of the polarizing plate is not particularly limited, and a method of applying the above-mentioned adhesive composition to the surface of the polarizing plate and drying it by using a bar coater or the like, and a method of using the adhesive sheet for a polarizing plate of the present invention A method in which an adhesive layer is transferred to a surface of a polarizing plate and matured. The conditions for drying and aging, the range of the gel fraction, and the like are the same as those described in the [Adhesive Layer] column.

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 an adhesive layer may be formed on both surfaces of the polarizing plate only in the case where the adhesive layer is formed on one surface of the polarizing plate.

Further, a layer having other functions such as a protective layer, an anti-glare layer, a phase difference layer, and a layer for improving the viewing angle may be laminated on the polarizing plate.

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

As a substrate which the liquid crystal cell has, a glass plate is mentioned, for example. The thickness of the substrate is usually 0.1 to 1 mm, more preferably 0.15 to 0.8 mm. In particular, in the present invention, by using the above-described adhesive composition, the bending 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, or preferably 0.15 to 0.7 mm), the above-mentioned adhesive composition can be suitably used for bonding the polarizing plate to the substrate.

[Examples]

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

[GPC and GPC-MALS]

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

‧Measurement device: HLC-8320GPC (made by Tosoh)

‧GPC column structure: The following four connecting columns (all made by Tosoh)

(1) TSKgel HxL-H (guard column)

(2) TSKgel GMHxL

(3) TSKgel GMHxL

(4)TSKgel G2500HxL

‧Flow rate: 1.0mL/min

‧column temperature: 40 ° C

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

‧Mobile phase solvent: tetrahydrofuran

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

‧Standard polystyrene conversion (when measuring Mw and Mn)

[Synthesis Example 1]

In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas introduction tube, 98.8 parts of n-butyl acrylate, 1 part of 4-hydroxybutyl acrylate, 0.2 part of acrylic acid, and 100 parts of an ethyl acetate solvent were placed, and nitrogen gas was introduced thereto. While raising the temperature to 80 °C. Then, 0.1 part of perbutyl pivalate 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, a branching degree of 0.51, and an acid value of 1.6 mgKOH/g.

[Synthesis Examples 2 to 12]

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 concentration: 30% by mass) obtained in Synthesis Example 1 and 100 parts (solid content) of the (meth)acrylic polymer contained in the solution "T-75" (solid content: 75 mass%, ethyl acetate solution), 0.05 parts (solid content), which is a compound of the isocyanate compound, and "M. -12AT" (solid content: 10% by mass, toluene, acetonitrile and acetone solution), 0.14 parts (solid content), "KBM-403" (solid content: 100%), 0.2 parts by Shin-Etsu Chemical Co., Ltd. as a decane coupling agent And 1 part of "AS-804" (100% solid content) manufactured by the First Industrial Pharmaceutical Co., Ltd. as an antistatic agent was mixed to obtain an adhesive composition.

(2) Production of adhesive sheets

After removing the air bubbles, the adhesive composition obtained in the above (1) was applied onto the peeled polyethylene terephthalate film (PET film) using a doctor blade, and dried at 90 ° C for 3 minutes. A coating film having a dry film thickness of 20 μm was formed. The peeling-treated PET film was bonded to the surface of the coating film opposite to the surface of the PET film, and left to stand in a 23° C./50% RH atmosphere for 7 days to be aged, and the obtained film was sandwiched between two pieces. An adhesive sheet of an adhesive layer having a thickness of 20 μm between the PET films.

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

After removing the air bubbles, the adhesive composition obtained in the above (1) was applied onto the peeled polyethylene terephthalate film (PET film) using a doctor blade, and dried at 90 ° C for 3 minutes to obtain a dryness. Coating film with a film thickness of 20 μm Thin sheet. The sheet and the polarizing plate (thickness: 110 μm, layer composition: triethylenesulfonated cellulose film/polyvinyl alcohol film/triethylenesulfonated cellulose film) are attached so that the coating film is in contact with the polarizing plate. After standing at 23 ° C / 50% RH for 7 days, aging was carried out to obtain a polarizing plate having a PET film, an adhesive layer having a thickness of 20 μm, and an adhesive layer of a polarizing plate.

[Examples 2 to 11 and Comparative Examples 1 to 2]

In the same manner as in Example 1, except that the (meth)acrylic polymer solution was changed to the polymer solution obtained in Synthesis Examples 2 to 12, and the blending composition was changed to the one shown in Table 2, the same procedure as in Example 1 was carried out. , an adhesive composition, an adhesive sheet, and a polarizing plate with an adhesive layer are obtained.

[Evaluation]

[Gel fraction]

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

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

[potential change (Creep) value]

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

The adhesive sheet for evaluation evaluation was subjected to autoclave treatment (50 ° C, 5 atm (atm)), and allowed to stand in an environment of 23 ° C / 50% RH for 24 hours. Then, the aforementioned test piece was placed in a chamber BOX of a micro-latency measuring machine with a length of 15 mm of a clamp portion for fixing. The tensile strength was 800 g and the stretching time was 1000 seconds, and the evaluation of the test piece was performed by adhering the polarizing plate to the bonding surface of the polarizing plate and the glass plate in the longitudinal direction of the polarizing plate. The offset distance (μm) of the aforementioned glass plate of the test piece and the bonded portion of the polarizing plate was taken as a latent value.

[Measurement of adhesion]

The polarizing plate (the laminated body composed of the PET film/adhesive layer/polarizing plate) with the adhesive layer obtained in the example/comparative example 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 a laminate composed of an adhesive layer/polarizing plate was attached to one side of a glass plate having a thickness of 2 mm so as to be in contact with the glass plate by using a laminator roll. The obtained laminate was held in an autoclave adjusted to 50 ° C / 5 atm for 20 minutes. Thereafter, after standing for 1 hour in an environment of 23 ° C / 50% RH, 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 surface of the glass plate, and the adhesive force (peeling strength) was measured.

[bending]

The polarizing plate (the laminated body composed of the PET film/adhesive layer/polarizing plate) with the adhesive layer obtained in the example/comparative example was cut into a size of 35 mm × 400 mm (the direction of the extending axis) to prepare a test piece. Stripped from the test piece In the PET film, a laminated body composed of an adhesive layer/polarizing plate was attached to one side of a glass plate of 40 mm × 410 mm having a thickness of 0.7 mm by bringing the adhesive layer into contact with the glass plate using a laminated roller. 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 end of one side was fixed to a wall surface perpendicular to the ground, and the amount of floating of the end on the opposite side was measured with a ruler. The measurement was carried out just after taking it out of the oven and after 24 hours.

[Durability Test]

The polarizing plate (the laminated body composed of the PET film/adhesive layer/polarizing plate) with the adhesive layer obtained in the example/comparative example 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 side of the glass plate having a thickness of 2 mm so that the adhesive layer was in contact with the glass plate by using a laminated roller. The obtained laminate was held in an autoclave adjusted to 50 ° C / 5 atm for 20 minutes to prepare a test plate. Make two identical test boards. 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 occurrence of foaming and fracture was observed by the following criteria. Evaluation. The foaming system is generated when the cohesive force is insufficient, and the fracture system is generated 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 more than 1% of the total and less than 5%

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

(fracture)

‧AA: No breaks at all

‧BB: The area of the break is less than 1% of the whole

‧CC: The area of the fracture is less than 5% of the total area of less than 5%

‧DD: The area of the fracture is more than 5% of the whole

In Table 2, the amount of the peroxide-based polymerization initiator was calculated in the following manner. From the above formula of the residual ratio: exp(-k _d t) × 100 (%), for example, in the first embodiment, k _d = A × exp (-ΔE / RT), A = 6.93 × 10 ¹⁷ hr ^-1 , ΔE=119.1 kJ/mol, R=8.314 J/mol‧K, T=353K, reaction time t=6h, the amount of the peroxide-based polymerization initiator used by the above copolymerization × residual ratio (%) It was calculated to be 5 × 10 ^-3 parts by mass.

In Comparative Examples 1 and 2, a (meth)acrylic copolymer having a degree of branching of 0.59 was used. Therefore, in the system having a high gel fraction (Comparative Example 1), the bending evaluation after 24 hours was poor (5.0 mm or more), and although the foaming was not observed in the durability evaluation, many fractures occurred. Further, in the system having a low gel fraction (Comparative Example 2), a lot of foaming occurred.

Since the copolymer of Comparative Example 1 is a linear copolymer, the appearance of cohesive force is only related to the bonding of the crosslinking agent to the functional group in the copolymer. Therefore, setting the gel fraction is high, and it is necessary to maintain the cohesive force. However, when the gel fraction was high, in the system of Comparative Example 1, since the stress relaxation property was lowered, deterioration of bending and durability (breaking resistance) was observed.

On the other hand, in the examples, since the (meth)acrylic copolymer having a branching degree of 0.55 or less and the isocyanate compound and the metal-clamping compound were used as the crosslinking agent, the bending evaluation after 24 hours was high (3.0 mm). In the following), and in the durability evaluation, the generation of foaming/fracture is within an allowable range.

Since a large number of branched chains are generated in the polymer, since the crosslinking agent and the functional groups in the copolymer are bonded, and entanglement occurs in the branched portion, cohesive force can be exhibited even in a low gel fraction. and so, In the high temperature, since the entanglement is loose, the bending is good, and the durability tends to be improved.

Claims (9)

An adhesive composition for a polarizing plate comprising: (A) a copolymerization of a monomer component of a (meth)acrylic acid alkyl ester having 4 to 18 carbon atoms and a carboxyl group-containing monomer; Acrylic copolymer, and the degree of branching of the (meth)acrylic copolymer measured by gel permeation chromatography/multi-angle laser light scattering detector (GPC-MALS) is 0.55 or less; (B1 An isocyanate compound; and (B2) a metal chelating compound. The adhesive composition for a polarizing plate according to the first aspect of the invention, wherein the (meth)acrylic copolymer (A) is obtained by the copolymerization in the presence of a peroxide polymerization initiator. Copolymer. The adhesive composition for a polarizing plate according to claim 1 or 2, wherein the (meth)acrylic copolymer (A) is determined by gel permeation chromatography (GPC method). The weight average molecular weight (Mw) is from 200,000 to 1.5 million. The adhesive composition for a polarizing plate according to claim 1 or 2, wherein the (meth)acrylic copolymer (A) has a degree of branching of 0.10 to 0.54 as measured by GPC-MALS. The adhesive composition for a polarizing plate according to the first aspect of the invention, wherein the (meth)acrylic copolymer (A) is a monomer having a polar group other than a carboxyl group-containing monomer. The resulting copolymer was copolymerized. The adhesive composition for a polarizing plate according to the first aspect of the invention, 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 adhesive composition for a polarizing plate according to the first aspect of the invention, wherein the adhesive composition of the adhesive composition for a polarizing plate has a gel fraction of 20 to 70% by mass. An adhesive sheet for a polarizing plate, comprising: an adhesive layer formed of the adhesive composition for a polarizing plate according to any one of claims 1 to 7. A polarizing plate with an adhesive layer, comprising: a polarizing plate and an adhesive layer, wherein the adhesive layer is an adhesive composition for a polarizing plate according to any one of claims 1 to 7 A face formed on at least one side of the polarizing plate.