KR102243893B1 - Adhesive layer and adhesive composition for polarizing plate - Google Patents

Abstract

[assignment]
It is applicable to a configuration in which at least one of the polarizer protective films conventionally formed on both sides of the polarizer is omitted, and provides a pressure-sensitive adhesive layer having excellent light leakage prevention properties and durability.
[Remedy]
Constituent units derived from alkyl (meth)acrylates having a homopolymer having a photoelastic coefficient of -1000×10 ^-12 ~-100×10 ^-12 (m ² /N) and a homopolymer having a photoelastic coefficient of +500×10 ^-12 ~ ^{+ 2000 × 10 -12 (m 2} / N) of the aromatic ring-containing (meth) acrylate ester-derived structural unit of the photoelastic coefficient of ^{-200 × 10 -12 ~ + 200 ×} 10 -12 with (m ² / N) of It is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer and an isocyanate-based crosslinking agent that does not have an aromatic ring, and has a photoelastic coefficient of -200×10 ^-12 to +200×10 ^-12 (m ² /N) And, the pressure-sensitive adhesive layer for a polarizing plate, characterized in that disposed in direct contact with the polarizer.

Description

Adhesive layer and adhesive composition for polarizing plate

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

The liquid crystal cell has a structure sandwiched between two liquid crystal layers (eg, a glass plate). A polarizing plate is affixed to the surface of the substrate constituting the liquid crystal cell through the pressure-sensitive adhesive layer. In general, as a polarizing plate, in order to improve its mechanical properties and optical durability, a structure in which a polarizer protective film such as a triacetylcellulose film is laminated on both surfaces of a polarizer having a polarizing function has been adopted.

In recent years, in response to the demand for reduction in weight and thickness of the polarizing plate, attempts have been made to omit one or both of the polarizer protective films formed on both sides of the polarizer (see, for example, Patent Document 1). However, in a polarizing plate in which one or both of the polarizer protective films are omitted, since the adhesive layer directly contacts the polarizer, a large stress is applied to the adhesive layer due to heat contraction of the polarizer in a high temperature/high humidity heat environment, causing problems such as peeling of the adhesive layer easy. In addition, there is a problem in that the stress applied to the pressure-sensitive adhesive layer is increased due to thermal contraction of the polarizer, and birefringence is liable to occur.

Therefore, the pressure-sensitive adhesive for a polarizing plate is required to have excellent light leakage prevention properties and durability. Regarding the problem of light leakage, Patent Document 2 relates to a polarizing film having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition for a polarizing plate containing a large amount of an isocyanate compound, and Patent Document 3 describes a polarizing plate containing a component having a positive photoelastic coefficient. It is described for the pressure-sensitive adhesive composition. However, these documents do not describe directly providing the pressure-sensitive adhesive layer on the polarizer.

Japanese Unexamined Patent Publication No. 2012-128099 Japanese Unexamined Patent Publication No. 2010-090354 Japanese Patent Publication No. 2004-516359

In a polarizing plate in which at least one of the polarizer protective films conventionally formed on both sides of the polarizer is omitted, it is required to have more excellent light leakage prevention properties and durability. An object of the present invention is to provide a pressure-sensitive adhesive layer that is applicable to a configuration in which at least one of the polarizer protective films conventionally formed on both sides of a polarizer is omitted, and has excellent light leakage prevention properties and durability.

The inventors of the present invention carefully studied in order to solve the above problems. As a result, it was found that when the (meth)acrylic copolymer described below and a crosslinking agent were used, a pressure-sensitive adhesive layer having excellent light leakage prevention properties and durability described above could be formed. That is, the inventors of the present invention have found that the above problem can be solved by using the pressure-sensitive adhesive layer for polarizing plates having the following specific configurations, and the present invention has been completed.

The present invention is, for example, the following [1] to [10].

[1] A structural unit derived from an alkyl (meth)acrylate (a11) having a homopolymer having a photoelastic coefficient of -1000×10 ^-12 ~-100×10 ^-12 (m ^{2 /N) and a homopolymer having a photoelastic coefficient of +} 500×10 ^-12 ~+2000×10 ^-12 (m ² /N) Aromatic ring-containing (meth)acrylic acid ester (a12) with a structural unit derived from the photoelastic coefficient -200×10 ^-12 ~+200×10 ^It is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer (A1) of -12 (m ² /N) and an isocyanate crosslinking agent (B1) having no aromatic ring, and has a photoelastic coefficient of -200 × 10 ^-12 ~ +200 × 10 ^-12 (m ² /N), characterized in that the polarizing plate adhesive layer disposed in direct contact with the polarizer.

[2] The pressure-sensitive adhesive layer for polarizing plates according to the above [1], wherein the isocyanate-based crosslinking agent (B1) is a hexamethylenediisocyanate-based crosslinking agent.

[3] The pressure-sensitive adhesive layer for a polarizing plate according to [1] or [2], wherein the pressure-sensitive adhesive composition contains 0.05 to 10 parts by mass of an isocyanate-based crosslinking agent (B1) per 100 parts by mass of the copolymer (A1).

[4] Formed from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer (A2) having a ^{photoelastic coefficient of less than -200×10 -12} (m ^{2 /N) and an isocyanate crosslinking agent (B2) having an aromatic ring} And a photoelastic coefficient of -200×10 ^-12 to +200×10 ^-12 (m ² /N), and a pressure-sensitive adhesive layer for a polarizing plate, which is disposed in direct contact with a polarizer.

[5] The pressure-sensitive adhesive layer for a polarizing plate according to [4], wherein the isocyanate-based crosslinking agent (B2) is at least one selected from tolylenediisocyanate-based crosslinking agents and xylylenediisocyanate-based crosslinking agents.

[6] The pressure-sensitive adhesive layer for a polarizing plate according to [4] or [5], wherein the pressure-sensitive adhesive composition contains 2 parts by mass or more of an isocyanate-based crosslinking agent (B2) based on 100 parts by mass of the copolymer (A2).

[7] A pressure-sensitive adhesive sheet for polarizing plates having the pressure-sensitive adhesive layer according to any one of [1] to [6].

[8] A polarizing plate with a pressure-sensitive adhesive layer, comprising a polarizer and the pressure-sensitive adhesive layer according to any one of [1] to [6], which is directly laminated on at least one surface of the polarizer.

[9] A structural unit derived from an alkyl (meth)acrylate (a11) having a homopolymer having a photoelastic coefficient of -1000×10 ^-12 to -100×10 ^-12 (m ^{2 /N) and a homopolymer having a photoelastic coefficient of +} 500×10 ^-12 ~+2000×10 ^-12 (m ² /N) Aromatic ring-containing (meth)acrylic acid ester (a12) with a structural unit derived from the photoelastic coefficient -200×10 ^-12 ~+200×10 ^In order to form the pressure-sensitive adhesive layer according to [1], containing -12 (m ² /N) of the (meth)acrylic copolymer (A1) and an isocyanate-based crosslinking agent (B1) having no aromatic ring A pressure-sensitive adhesive composition for a polarizing plate to be used.

[10] A ^{(meth)acrylic copolymer (A2) having a photoelastic coefficient of less than -200×10 -12} (m ² /N) and an isocyanate-based crosslinking agent (B2) having an aromatic ring, wherein [4] ] A pressure-sensitive adhesive composition for a polarizing plate used to form the pressure-sensitive adhesive layer described in

According to the present invention, it is applicable to a configuration in which at least one of the polarizer protective films conventionally formed on both surfaces of a polarizer is omitted, and a pressure-sensitive adhesive layer having excellent light leakage prevention properties and durability can be provided.

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

[Adhesive composition for polarizing plate]

The pressure-sensitive adhesive composition for a first polarizing plate of the present invention ^{includes a (meth)acrylic copolymer (A1) having a photoelastic coefficient of -200×10 -12} to +200×10 ^-12 (m ² /N), and an isotropic ring having no aromatic ring. It contains a cyanate-type crosslinking agent (B1), and is used in order to form a pressure-sensitive adhesive layer in direct contact with a polarizer.

By crosslinking the (meth)acrylic copolymer having a photoelastic coefficient in the above range with an isocyanate-based crosslinking agent having no aromatic ring, which has a small contribution to the photoelastic coefficient of the pressure-sensitive adhesive layer, the photoelastic coefficient is -200×10 ^-12 A pressure-sensitive adhesive layer of ~+200×10 ^-12 (m ^{2 /N) can be formed.}

The second pressure-sensitive adhesive composition for a polarizing plate of the present invention includes a ^{(meth)acrylic copolymer (A2) having a photoelastic coefficient of less than -200 × 10 -12} (m ² /N) and an isocyanate-based crosslinking agent (B2) having an aromatic ring. It contains and is used in order to form a pressure-sensitive adhesive layer in direct contact with a polarizer.

By crosslinking the (meth)acrylic copolymer having a negative photoelastic coefficient with an isocyanate-based crosslinking agent having an aromatic ring that shifts the photoelastic coefficient of the pressure-sensitive adhesive layer to the positive side, the photoelastic coefficient is -200×10 ^-12 to +200 A pressure-sensitive adhesive layer in x10 ^-12 (m ^{2 /N) can be formed.}

In the present specification, copolymers (A1) and (A2) are collectively referred to as ``copolymer (A)'', and the first and second adhesive compositions for polarizing plates of the present invention are referred to as ``first adhesive composition'' and `` It is also called "2nd adhesive composition", and these are also collectively called "the adhesive composition of this invention."

In this specification, acrylic and methacrylic are collectively referred to as "(meth)acrylic". Moreover, the structural unit derived from any monomer A contained in a polymer is also described as "monomer A unit." Moreover, some ester (a) is sometimes described as "monomer (a)" for convenience.

In the present specification, unless otherwise specified, the unit of the photoelastic coefficient of the homopolymer, (meth)acrylic copolymer and the pressure-sensitive adhesive layer formed from each monomer is "x10 ^-12 m ² /N". Also, for example, -200×10 ^-12 to +200×10 ^-12 (m ² /N) is -200×10 ^-12 (m ² /N) or more, +200×10 ^-12 (m ² /N) It means the following. The same applies to other numerical ranges.

The photoelastic coefficient of the homopolymer formed from each monomer is determined as follows.

The homopolymer used for the measurement of the photoelastic coefficient is prepared in the following procedure. 100 parts by mass of a monomer and 100 parts by mass of an ethyl acetate solvent are introduced into a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, and the temperature is raised to 80° C. while introducing nitrogen gas. Next, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and a polymerization reaction was carried out at 80°C for 6 hours in a nitrogen gas atmosphere. After completion of the reaction, it is diluted with ethyl acetate to prepare a homopolymer solution of the monomer having a solid content concentration of 30% by mass.

The homopolymer solution was applied to the peeling-treated surface of the peel-treated polyethylene terephthalate film, and dried at 90° C. for 3 minutes to form a coating film (homopolymer layer) having a dry film thickness of 20 μm. Homopolymer layers having a dry film thickness of 20 μm are bonded multiple times in an environment of 23° C./50% RH, and treated for 20 minutes in an autoclave controlled at 50° C./5 atm to prepare a homopolymer layer having a thickness of 1.0 mm.

A 1.0mm-thick homopolymer layer is cut into a size of 15mm x 50mm, and it is attached to an automatic wavelength scanning ellipsometer (model ``M-220'', manufactured by Nippon Bunko Co., Ltd.) using a jig and retardation. Is measured at a measurement wavelength of 633 nm while changing the stress. The plot when stress is taken as the horizontal axis and retardation is taken as the vertical axis is approximated by a straight line, and the slope is taken as the photoelastic coefficient of the homopolymer formed from the monomer.

The glass transition temperature (Tg) of the homopolymer formed from each monomer may be, for example, a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003).

In addition, for a monomer for which Tg is not described in the above document, for example, Tg of a homopolymer synthesized under the following conditions is measured under the following conditions. 100 parts by mass of a monomer and 100 parts by mass of an ethyl acetate solvent are introduced into a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, and the temperature is raised to 80° C. while introducing nitrogen gas. Next, 0.1 parts by mass of 2,2'-azobisisobutyronitrile was added, and a polymerization reaction was carried out at 80°C for 6 hours in a nitrogen gas atmosphere. The obtained homopolymer is sealed in a simple airtight pan. Using a differential scanning calorimeter (DSC), the temperature was raised at 10°C/min under a nitrogen stream to measure the heat change, and graphs of "heat absorption" and "temperature" were drawn, and the characteristic inflection observed at this time was converted into a glass transition. do. In addition, Tg uses the value obtained by the midpoint method from the DSC curve.

[( Meta )Acrylic copolymer (A1)]

The (meth)acrylic copolymer (A1) is a constituent unit derived from an alkyl (meth)acrylate (a11) having a homopolymer having a photoelastic coefficient of -1000 to -100, and a homopolymer having a photoelastic coefficient of +500 to +2000. It has a structural unit derived from a ring-containing (meth)acrylic acid ester (a12). The copolymer (A1) is, for example, a copolymer obtained by copolymerizing a monomer component containing a monomer (a11) and a monomer (a12).

It is preferable that the said monomer component (that is, the raw material monomer component of (A1)) is a polymerizable unsaturated double bond containing monomer.

The photoelastic coefficient of the (meth)acrylic copolymer (A1) is -200 to +200, preferably -100 to +100, more preferably -70 to +70.

By copolymerizing a monomer (a11) having a negative photoelastic coefficient of the homopolymer and a monomer (a12) having a positive photoelastic coefficient of the homopolymer, a copolymer (A1) having a photoelastic coefficient within the above range can be obtained. By using the copolymer (A1) and using the isocyanate-based crosslinking agent (B1) having no aromatic ring, the photoelastic coefficient of the pressure-sensitive adhesive layer can be brought to a range described later, particularly close to 0, and thereby the polarizing plate Light leakage can be suppressed.

《 (Meth)acrylate alkyl ester (a11) (monomer (a11))》

The monomer (a11) is an alkyl (meth)acrylate having a photoelastic coefficient of -1000 to -100 of the homopolymer. The monomer having a photoelastic coefficient of -750 to -150 of the homopolymer is preferable, and the monomer having a photoelastic coefficient of -500 to -200 is more preferable.

By using the copolymer (A1) obtained by copolymerizing the monomer (a11) having a photoelastic coefficient of the homopolymer in the above range, flexibility can be provided to the pressure-sensitive adhesive layer, and light leakage prevention properties can be expressed.

The monomer (a11) is preferably an alkyl (meth)acrylate having a homopolymer Tg of -30°C or less, and the Tg is more preferably -100 to -30°C, still more preferably -70 to -30°C. .

As the monomer (a11) _{, among the compounds represented by CH 2} =CR ¹ -COOR ² , compounds in which the photoelastic coefficient of the homopolymer is in the above range can be exemplified. In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 20 carbon atoms. The number of carbon atoms in the alkyl group is preferably 2 to 16, more preferably 4 to 12.

As the monomer (a11), for example, n-butyl acrylate (-400;-50), 2-ethylhexyl acrylate (-700;-70), isodecyl methacrylate (-190;-41), lauryl And methacrylate (-460;-65). The numerical values in parentheses indicate the photoelastic coefficient (x10 ^-12 m ² /N) on the left and Tg (°C) on the right side of the homopolymer formed from each monomer.

Monomer (a11) may be used individually by 1 type, and may use 2 or more types. When two or more types of monomers (a11) are used, it is preferable that each monomer satisfies the requirements of the photoelastic coefficient and Tg.

In 100% by mass of the raw material monomer component of the copolymer (A1), the amount of the monomer (a11) used is preferably 50 to 90% by mass, more preferably 55 to 85% by mass, still more preferably 60 to 80% by mass to be. When the amount of the monomer (a11) used is within the above range, it is preferable that the photoelastic coefficient of the obtained copolymer (A1) can be adjusted within the above range.

《 Aromatic ring contain (Meth)acrylic acid ester (a12) (monomer (a12)) 》

The monomer (a12) is an aromatic ring-containing (meth)acrylic acid ester having a photoelastic coefficient of +500 to +2000 of the homopolymer. The monomer having a photoelastic coefficient of +700 to +1950 of the homopolymer is preferable, and the monomer having a photoelastic coefficient of +800 to +1900 is more preferable.

By using the copolymer (A1) obtained by copolymerizing the monomer (a12) having a photoelastic coefficient of the homopolymer in the above range, appropriate durability can be imparted to the pressure-sensitive adhesive layer.

The monomer (a12) is preferably an aromatic ring-containing (meth)acrylic acid ester having a homopolymer Tg of -50°C or higher, and the Tg is more preferably -40 to 130°C, further preferably -30 to 120°C. .

As the monomer (a12) _{, among the compounds represented by CH 2} =CR ³ -COOR ⁴ , compounds in which the photoelastic coefficient of the homopolymer is in the above range can be exemplified. In the formula, R ³ is a hydrogen atom or a methyl group, and R ⁴ is an aromatic ring-containing group. Examples of the aromatic ring-containing group include aryl groups such as phenyl groups, arylalkyl groups such as benzyl groups, and aryloxyalkyl groups such as phenoxyethyl groups. The number of carbon atoms of R ⁴ is preferably 6 to 12, more preferably 6 to 10, and still more preferably 7 to 9.

Examples of the monomer (a12) include benzyl acrylate (1840;6), benzyl methacrylate (1530;54), and phenoxyethyl acrylate (1830;-22). The numerical values in parentheses indicate the photoelastic coefficient (x10 ^-12 m ² /N) on the left and Tg (°C) on the right side of the homopolymer formed from each monomer. Other examples of the monomer (a12) include phenyl acrylate, phenyl methacrylate, and phenoxyethyl methacrylate.

Monomer (a12) may be used individually by 1 type, and may use 2 or more types. When two or more types of monomers (a12) are used, it is preferable that each monomer satisfies the requirements of the photoelastic coefficient and Tg.

In 100% by mass of the raw material monomer component of the copolymer (A1), the amount of the monomer (a12) used is preferably 9 to 40% by mass, more preferably 12 to 35% by mass, and still more preferably 15 to 30% by mass. to be. When the amount of the monomer (a12) used is within the above range, it is preferable because the photoelastic coefficient of the obtained copolymer (A1) can be adjusted within the above range.

《 Crosslinking Functional group Containing Monomer (a13) >>

The raw material monomer component of the copolymer (A1) preferably further contains a monomer having a crosslinkable functional group capable of reacting with the isocyanate-based crosslinking agent (B1), that is, a crosslinkable functional group-containing monomer (a13). That is, it is preferable that the copolymer (A1) further has a structural unit derived from the monomer (a13).

It is preferable that the monomer (a13) has a polymerizable unsaturated double bond.

Examples of the crosslinkable functional group include a hydroxyl group and a carboxyl group. Examples of the monomer (a13) include a hydroxyl group-containing monomer and a carboxyl group-containing monomer.

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

Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloyloxyethyl succinate, and ω-carboxypolycaprolactone mono(meth)acrylic. Carboxyl group-containing (meth)acrylates such as rate; Acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid.

Monomer (a13) may be used individually by 1 type, and may use 2 or more types.

In 100% by mass of the raw material monomer component of the copolymer (A1), the amount of the monomer (a13) used is preferably more than 0% by mass and not more than 10% by mass, more preferably 0.5 to 7% by mass, even more preferably 1 It is -5 mass%. When the amount of the monomer (a13) used is equal to or less than the above upper limit, the crosslinking density formed by the copolymer (A1) and the crosslinking agent (B1) does not become too high. When the amount of the monomer (a13) used is equal to or greater than the lower limit, a crosslinked structure is effectively formed, and a pressure-sensitive adhesive layer having an appropriate strength is obtained.

《Other monomers》

As the raw material monomer component of the copolymer (A1), for example, alkyl (meth) acrylates other than the above monomer (a11), alkoxyalkyl (meth) acrylate, alkoxypolyalkyl within the range that does not impair the physical properties of the copolymer (A1). Other monomers such as renglycol mono(meth)acrylate, alicyclic group-containing (meth)acrylate, amino group-containing monomer, and amide group-containing monomer may also be used. That is, the copolymer (A1) may further have structural units derived from other monomers.

Examples of alkyl (meth)acrylates other than the monomer (a11) include methyl acrylate (600;8), t-butyl methacrylate (130;118), and n-butyl methacrylate (320;20), 2-ethylhexyl methacrylate (420;-10) is mentioned. The numerical values in parentheses indicate the photoelastic coefficient (x10 ^-12 m ² /N) on the left and Tg (°C) on the right side of the homopolymer formed from each monomer.

As alkoxyalkyl (meth)acrylate, for example, methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth) Acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate are mentioned.

As alkoxypolyalkylene glycol mono(meth)acrylate, for example, methoxydiethylene glycol mono(meth)acrylate, methoxydipropylene glycol mono(meth)acrylate, ethoxytriethylene glycol Colmono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, and methoxytriethylene glycol mono(meth)acrylate are mentioned.

As an alicyclic group-containing (meth)acrylate, cyclohexyl (meth)acrylate is mentioned, for example.

Examples of the amino group-containing monomer include amino group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate.

Examples of the amide group-containing monomer include (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, and N-hexyl (meth)acrylamide. Can be lifted.

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

In 100% by mass of the raw material monomer component of the copolymer (A1), the total amount of the other monomers is not particularly limited as long as the photoelastic coefficient of (A1) is in the above range, but is preferably 0 to 10% by mass, More preferably, it is 0-5 mass %.

[( Meta )Acrylic copolymer (A2)]

The (meth)acrylic copolymer (A2) is a copolymer having a photoelastic coefficient of less than -200, preferably -500 or more and less than -200, and more preferably -300 or more and less than -200. Such a copolymer has, for example, a structural unit derived from an alkyl (meth)acrylate ester (a21) having a photoelastic coefficient of less than -200 of a homopolymer, and is obtained by copolymerizing a monomer component including the monomer (a21), for example. Lose.

It is preferable that the said monomer component (that is, the raw material monomer component of (A2)) is a polymerizable unsaturated double bond containing monomer.

By using the copolymer (A2) and using the isocyanate-based crosslinking agent (B2) having an aromatic ring, the photoelastic coefficient of the pressure-sensitive adhesive layer can be brought to a range described later, particularly close to 0, whereby in the polarizing plate Light leakage can be suppressed.

《 (Meth)acrylate alkyl ester (a21) (monomer (a21))》

Examples of the monomer (a21) include esters in which the homopolymer has a photoelastic coefficient of less than -200 among the above-described alkyl (meth)acrylate esters (a11). The monomer having a photoelastic coefficient of -750 or more and less than -200 is preferable, and the monomer having a photoelastic coefficient of -500 or more and less than -200 is more preferable.

Monomer (a21) may be used individually by 1 type, and may use 2 or more types. When two or more types of monomers (a21) are used, it is preferable that each monomer satisfies the requirement of the photoelastic coefficient.

In 100% by mass of the raw material monomer component of the copolymer (A2), the amount of the monomer (a21) used is preferably 59 to 99% by mass, more preferably 64 to 98% by mass, and still more preferably 69 to 97% by mass. to be. When the amount of the monomer (a21) used is within the above range, it is preferable that the photoelastic coefficient of the obtained copolymer (A2) can be adjusted within the above range.

《 Crosslinking Functional group Containing Monomer (a22) >>

The raw material monomer component of the copolymer (A2) preferably further contains a monomer having a crosslinkable functional group capable of reacting with the isocyanate-based crosslinking agent (B2), that is, a crosslinkable functional group-containing monomer (a22). That is, it is preferable that the copolymer (A2) further has a structural unit derived from the monomer (a22).

As the monomer (a22), the above-described crosslinkable functional group-containing monomer (a13) can be exemplified, and a preferred example is also the same. Monomer (a22) may be used individually by 1 type, and may use 2 or more types.

In 100% by mass of the raw material monomer component of the copolymer (A2), the amount of the monomer (a22) to be used is preferably more than 0% by mass and not more than 10% by mass, more preferably 0.5 to 7% by mass, further preferably 1 It is -5 mass%. When the amount of the monomer (a22) used is equal to or less than the above upper limit, the crosslinking density formed by the copolymer (A2) and the crosslinking agent (B2) does not become too high. When the amount of the monomer (a22) used is equal to or greater than the lower limit, a crosslinked structure is effectively formed, and an adhesive layer having an appropriate strength is obtained.

《Other monomers》

As a raw material monomer component of the copolymer (A2), for example, alkyl (meth) acrylates other than the above monomer (a21), alkoxyalkyl (meth) acrylate, alkoxypolyalkyl within the range that does not impair the physical properties of the copolymer (A2). Other monomers such as renglycol mono(meth)acrylate, alicyclic group-containing (meth)acrylate, aromatic ring-containing (meth)acrylate, amino group-containing monomer, and amide group-containing monomer may also be used. That is, the copolymer (A2) may further have structural units derived from other monomers.

As these monomers, the respective compounds described in "Other monomers" in the column of the copolymer (A1) can be exemplified. Examples of the aromatic ring-containing (meth)acrylate include phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

However, (meth)acrylic acid alkyl ester having a photoelastic coefficient of +100 to +1000 of a homopolymer and an aromatic ring containing (meth)acrylic acid ester having a photoelastic coefficient of +500 to +2000 of a homopolymer (the above-described monomer (a12)) It is preferable that the amount of used is appropriately adjusted from the viewpoint of adjusting the photoelastic coefficient of the copolymer (A2) within the above range.

Examples of (meth)acrylate alkyl esters having a homopolymer photoelastic coefficient of +100 to +1000 include methyl acrylate (600), t-butyl methacrylate (130), n-butyl methacrylate (320), 2 -Ethylhexyl methacrylate (420) is mentioned. The numerical values in parentheses indicate the photoelastic coefficient (×10 ^-12 m ² /N) of the homopolymer formed from each monomer.

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

In 100% by mass of the raw material monomer component of the copolymer (A2), the total amount of the other monomers is not particularly limited as long as the photoelastic coefficient of (A2) is within the above range, but is preferably 0 to 35% by mass, More preferably, it is 0-30 mass%, More preferably, it is 0-26 mass%.

[( Meta ) Production conditions of the acrylic copolymer (A)]

Although the production conditions of the (meth)acrylic copolymer (A) are not particularly limited, it can be produced by, for example, a solution polymerization method. Specifically, a polymerization solvent and a monomer component are introduced into the reaction vessel, a polymerization initiator is added, the reaction initiation temperature is usually set to 40 to 100°C, preferably 50 to 90°C, and the reaction system is usually 50 to 90°C. Maintained at a temperature of °C, preferably 70 to 90 °C, and reacted for 2 to 20 hours. The polymerization reaction can be carried out under an inert gas atmosphere such as nitrogen gas.

The copolymer (A) is obtained by copolymerizing the above-described monomer components, for example, but may be a random copolymer or a block copolymer. Among these, a random copolymer is preferable.

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

Examples of the polymerization initiator include an azo initiator and a peroxide initiator. Specific examples include azo compounds such as 2,2'-azobisisobutyronitrile, and peroxides such as benzoyl peroxide and lauroyl peroxide. Among these, an azo compound is preferable. Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azo Bis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1, 1'-azobis(cyclohexane-1-carbonitrile), 2-(carbamoylazo)isobutyronitryl, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis(isobutyl Amide) dihydrate, 4,4'-azobis (4-cyanopentane), 2,2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methyl Propionate) and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]. These polymerization initiators may be used alone or in combination of two or more.

The polymerization initiator is usually used in an amount within the range of 0.01 to 5 parts by mass, preferably 0.1 to 3 parts by mass per 100 parts by mass of the raw material monomer component of the (meth)acrylic copolymer (A). Further, during the polymerization reaction, a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent may be appropriately added.

[( Meta ) Physical properties and content of acrylic copolymer (A)]

The photoelastic coefficient of the (meth)acrylic copolymer (A) is as described above.

The weight average molecular weight (Mw) measured by the gel permeation chromatography method (GPC method) of the (meth)acrylic copolymer (A) is usually 300,000 to 2 million, preferably 400,000 to 2 million in terms of polystyrene. 1.8 million, more preferably 500,000 to 1.5 million. By using the copolymer (A) having Mw in the above range and having the above monomer units, it is easy to balance the adhesive force, and a pressure-sensitive adhesive composition having a viscosity suitable for coating can be obtained. Further, by using the copolymer (A) having an Mw of 500,000 or more, a pressure-sensitive adhesive layer having higher durability can be obtained.

The molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer (A) measured by the GPC method is usually 20 or less, preferably 2 to 15, and more preferably 2 to 9.

The glass transition temperature (Tg) of the (meth)acrylic copolymer (A) can be calculated, for example, from the monomer units constituting the copolymer and the content ratio thereof by the formula of Fox. For example, to synthesize the (meth)acrylic copolymer (A) so that the glass transition temperature (Tg) obtained by Fox's formula is usually -70 to -10°C, preferably -60 to -20°C. desirable. By using the (meth)acrylic copolymer (A) having such a glass transition temperature (Tg), it is possible to obtain a pressure-sensitive adhesive composition having excellent stress relaxation properties and durability, and excellent adhesiveness at room temperature.

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

W ₁ +W ₂ +… +W _m =1

In the formula, Tg is the glass transition temperature (K) of the (meth)acrylic copolymer (A), and Tg ₁ , Tg ₂ , ... , Tg _m is the glass transition temperature (K) of the homopolymer composed of each monomer, W ₁ , W ₂ , ... , W _m is the weight fraction in the copolymer (A) of the structural unit derived from each monomer. As the weight fraction of the constituent units derived from each monomer, the ratio of the introduction of each monomer to the total monomers at the time of synthesizing the copolymer can be used.

The glass transition temperature of the homopolymer composed of each monomer in the Fox formula is, for example, a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003). In addition, for a monomer in which Tg is not described in the above document, for example, a value obtained by the above-described method is used.

In the first pressure-sensitive adhesive composition, the content of the (meth)acrylic copolymer (A1) is usually 60 to 99.95% by mass, preferably 70 to 99.5% by mass, particularly preferably, in 100% by mass of the solid content excluding the organic solvent in the composition. It is 80-99.0 mass %. When the content of the (meth)acrylic copolymer (A1) is in the above range, a balance of performance as a pressure-sensitive adhesive can be obtained, and adhesion properties are excellent.

In the second pressure-sensitive adhesive composition, the content of the (meth)acrylic copolymer (A2) is usually 60 to 98.0% by mass, preferably 70 to 96.2% by mass, particularly preferably, in 100% by mass of the solid content excluding the organic solvent in the composition. It is 80 to 92.6% by mass. When the content of the (meth)acrylic copolymer (A2) is in the above range, a balance of performance as an adhesive can be obtained, and adhesive properties are excellent.

[ Crosslinking agent (B)]

The first pressure-sensitive adhesive composition further contains an isocyanate-based crosslinking agent (B1) having no aromatic ring. The second pressure-sensitive adhesive composition further contains an isocyanate-based crosslinking agent (B2) having an aromatic ring.

《 Isocyanate type Crosslinking agent (B1)》

As the isocyanate crosslinking agent (B1), an isocyanate compound having no aromatic ring having two or more isocyanate groups in one molecule is usually used. By crosslinking the (meth)acrylic copolymer (A1) with a crosslinking agent (B1), a crosslinked product (network polymer) excellent in durability can be formed. In addition, by using a crosslinking agent without an aromatic ring (B1) with a copolymer (A1) having a photoelastic coefficient in the range of -200 to +200, a pressure-sensitive adhesive layer having a photoelastic coefficient in the range of -200 to +200 can be formed. I can.

The number of isocyanate groups of the crosslinking agent (B1) is usually 2 or more, preferably 2 to 8, and more preferably 3 to 6. When the number of isocyanate groups is in the above range, it is preferable in terms of the crosslinking reaction efficiency of the (meth)acrylic copolymer (A1) and the crosslinking agent (B1) and maintaining the flexibility of the pressure-sensitive adhesive layer.

Examples of the diisocyanate compound having two isocyanate groups in one molecule include aliphatic diisocyanate and alicyclic diisocyanate. As aliphatic diisocyanate, for example, ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-phene Tedi isocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, etc. Aliphatic diisocyanates are mentioned. As alicyclic diisocyanate, for example, isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene dia. And alicyclic diisocyanates having 7 to 30 carbon atoms such as isocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

Examples of the isocyanate compound having 3 or more isocyanate groups in one molecule include aliphatic polyisocyanates and alicyclic polyisocyanates.

In addition, as the crosslinking agent (B1), for example, a multimer (e.g., a dimer or trimer, a biuret or an isocyanurate) or derivative of the isocyanate compound having 2 or 3 or more isocyanate groups. (For example, the addition reaction product of a polyhydric alcohol and the said diisocyanate compound of 2 or more molecules), and a polymer are mentioned. Examples of the polyhydric alcohol in the above derivative include trihydric or higher alcohols such as trimethylolpropane, glycerin, and pentaerythritol as low molecular weight polyhydric alcohols; Examples of the high molecular weight polyhydric alcohol include polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

As such an isocyanate compound, for example, a biuret body or an isocyanurate body of hexamethylenediisocyanate, a reaction product of trimethylolpropane and hexamethylenediisocyanate (for example, hexamethylenediisocyanate 3-molecular adducts of methylene diisocyanate), polyether polyisocyanate, and polyester polyisocyanate.

Among the crosslinking agents (B1), hexamethylene diisocyanate-based crosslinking agents are preferable because aging properties and light leakage prevention properties can be improved. Examples of the hexamethylene diisocyanate-based crosslinking agent include hexamethylene diisocyanate and its derivatives, biuret or isocyanurate. Moreover, as a commercial item, "D-94" made by Soken Chemical Co., Ltd. is mentioned, for example.

Crosslinking agent (B1) may be used individually by 1 type, and may use 2 or more types.

In the first adhesive composition, the content of the crosslinking agent (B1) is usually 0.05 to 10 parts by mass, preferably 0.5 to 8 parts by mass, and more preferably 1 based on 100 parts by mass of the (meth)acrylic copolymer (A1). It is ~5 parts by mass. When the content of the crosslinking agent (B1) is in the above range, it is preferable from the viewpoint of easy balance of durability and light leakage prevention.

《 Isocyanate type Crosslinking agent (B2)》

As the isocyanate-based crosslinking agent (B2), an isocyanate compound having an aromatic ring having two or more isocyanate groups in one molecule is usually used. By crosslinking the (meth)acrylic copolymer (A2) with the crosslinking agent (B2), a crosslinked product (network polymer) excellent in durability can be formed. In addition, by using the crosslinking agent (B2) having an aromatic ring together with the copolymer (A2) having a photoelastic coefficient of less than -200, a pressure-sensitive adhesive layer having a photoelastic coefficient of -200 to +200 can be formed.

The number of isocyanate groups of the crosslinking agent (B2) is usually 2 or more, preferably 2 to 8, and more preferably 3 to 6. When the number of isocyanate groups is in the above range, it is preferable in terms of the crosslinking reaction efficiency of the (meth)acrylic copolymer (A2) and the crosslinking agent (B2) and maintaining the flexibility of the pressure-sensitive adhesive layer.

As a diisocyanate compound having 2 isocyanate groups in one molecule, aromatic diisocyanate is mentioned, for example. Examples of aromatic diisocyanates include phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, and diphenyl ether diisocyanate. And aromatic diisocyanates having 8 to 30 carbon atoms such as diphenyl methane diisocyanate and diphenyl propane diisocyanate.

As an isocyanate compound having 3 or more isocyanate groups in one molecule, an aromatic polyisocyanate is mentioned, for example. Specifically, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanatebenzene, and 4,4',4''-triphenylmethane triisocyanate are mentioned. have.

In addition, as the crosslinking agent (B2), for example, a multimer (e.g., a dimer or trimer, a biuret or an isocyanurate) or derivative of the isocyanate compound having 2 or 3 or more isocyanate groups. (For example, an addition reaction product of a polyhydric alcohol and the said diisocyanate compound of 2 or more molecules), and a polymer can be mentioned. Examples of the polyhydric alcohol in the above derivative include trihydric or higher alcohols such as trimethylolpropane, glycerin, and pentaerythritol as low molecular weight polyhydric alcohols; Examples of the high molecular weight polyhydric alcohol include polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

As such an isocyanate compound, for example, a trimer of diphenylmethane diisocyanate, a polymethylene polyphenyl polyisocyanate, a biuret body or an isocyanate body of tolylene diisocyanate. , The reaction product of trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate (for example, a trimolecular adduct of tolylene diisocyanate or xylylene diisocyanate ), polyether polyisocyanate, and polyester polyisocyanate.

Among the cross-linking agents (B2), at least one selected from tolylene diisocyanate-based cross-linking agents and xylylene diisocyanate-based cross-linking agents is preferable from the viewpoint of improving aging properties and light leakage prevention properties, and tolylene A diisocyanate-based crosslinking agent is more preferable. Examples of the tolylene diisocyanate-based crosslinking agent include tolylene diisocyanate and its derivatives, biuret or isocyanurate. Examples of the xylylene diisocyanate-based crosslinking agent include xylylene diisocyanate and derivatives thereof, biuret or isocyanurate. Moreover, as a commercial item, "L-45" made by Soken Chemical Co., Ltd. is mentioned, for example.

Crosslinking agent (B2) may be used individually by 1 type, and may use 2 or more types.

In the second adhesive composition, the content of the crosslinking agent (B2) is usually 2 parts by mass or more, preferably 4 to 30 parts by mass, and more preferably 8 to 100 parts by mass of the (meth)acrylic copolymer (A2). It is 15 parts by mass. When the content of the crosslinking agent (B2) is within the above range, a layer having a photoelastic coefficient of around 0 can be formed even with a composition containing a copolymer (A2) having a negative photoelastic coefficient, so that a balance between durability and light leakage prevention is achieved. It is preferable in terms of ease.

《Other Crosslinking agent 》

The first and second pressure-sensitive adhesive compositions may further contain other crosslinking agents other than the crosslinking agent (B1) or the crosslinking agent (B2), respectively, as long as the photoelastic coefficient of the pressure-sensitive adhesive layer obtained is within the above range. For example, by using a crosslinking agent that does not significantly shift the photoelastic coefficient of the pressure-sensitive adhesive layer to the positive side together with the crosslinking agent, durability can be further improved while maintaining the photoelastic coefficient within the range described later.

The other crosslinking agent is not particularly limited as long as it is a component capable of causing a crosslinking reaction with a crosslinkable functional group derived from a crosslinkable functional group-containing monomer, and examples thereof include a metal chelate compound (B3) and an epoxy compound (B4).

In the first and second pressure-sensitive adhesive compositions, when other crosslinking agents are used, their content is preferably 2 parts by mass or less, more preferably 0.01 to 1.5 parts by mass per 100 parts by mass of the (meth)acrylic copolymer (A). It is a mass part, More preferably, it is 0.03-1 mass part.

<Metal chelate compound (B3)>

As the metal chelate compound (B3), alkoxide, acetylacetone, ethyl acetoacetate, etc. are doubled with polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium. And compounds for.

Among these, an alumina chelate compound is particularly preferred. Specifically, aluminum isopropylate, aluminum secondary reviewylate, aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate are exemplified. Moreover, as a commercial item, "M-12AT" made by Soken Chemical Co., Ltd. is mentioned, for example.

The metal chelate compound (B3) may be used individually by 1 type, and may use 2 or more types.

The metal chelate compound (B3) crosslinks the (meth)acrylic copolymer (A) by coordination bonds (pseudo crosslinking). When a metal chelate compound (B3) is additionally used as a crosslinking agent, the crosslinking is maintained at room temperature, and the polymer exhibits cohesiveness, whereas at high temperatures, the crosslinking partially dissolves, and the pressure-sensitive adhesive layer exhibits more excellent flexibility. .

<< epoxy compound (B4) >>

As the epoxy compound (B4), an epoxy compound having two or more epoxy groups per molecule is usually used. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin iglycidyl ether, glycerin triglycidyl ether, 1,3-bis(N,N -Diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N,N',N'-tetraglycidylaminophenyl Methane, triglycidyl isocyanurate, mN,N-diglycidylaminophenylglycidyl ether, N,N-diglycidyltoluidine, and N,N-diglycidylaniline. have. Moreover, as a commercial item, "E-5C" made by Soken Chemical Co., Ltd. is mentioned, for example.

[ Silane coupling agent (C)]

It is preferable that the pressure-sensitive adhesive composition of the present invention further contains a silane coupling agent (C). The silane coupling agent (C) strongly adheres the pressure-sensitive adhesive layer to an adherend such as a glass plate, thereby contributing to preventing peeling of the polarizing plate under a high humidity and heat environment.

Examples of the silane coupling agent (C) include polymerizable unsaturated group-containing silane coupling agents such as vinyl trimethoxysilane, vinyl triethoxysilane, and methacryloxypropyl trimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, Epoxy group-containing silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, etc. Silane coupling agents containing amino groups; Halogen-containing silane coupling agents, such as 3-chloropropyl trimethoxysilane, and 3-oxobutaneic acid-3-(trimethoxysilyl)propyl are mentioned. Moreover, as a commercial item, "A-50" made by Soken Chemical Co., Ltd. is mentioned, for example.

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

[Antistatic agent (D)]

The antistatic agent (D) can be used, for example, in order to reduce the surface resistance value of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention. Examples of the antistatic agent (D) include surfactants, ionic compounds, and conductive polymers.

Examples of the surfactant include cationic surfactants having cationic groups such as quaternary ammonium salts, amide quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups; Anionic surfactants having anionic groups such as a sulfonate group, a sulfuric ester base, and a phosphate ester base; Amphoteric surfactants such as alkyl betaines, alkyl imidazolinium betaines, alkylamine oxides, amino acid sulfuric acid esters, etc., glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acids Nonionic surfactants, such as esters, N-hydroxyethyl-N-2-hydroxyalkylamines, and alkyl diethanolamides, are mentioned.

Further, as the surfactant, a reactive emulsifier having a polymerizable group is also exemplified, and a polymeric surfactant obtained by high molecular weight of the monomer component including the surfactant or the reactive emulsifier described above can also be used.

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

The cation moiety constituting the ionic compound may be either an inorganic cation or an organic cation, or both. As the inorganic cation, alkali metal ions and alkaline earth metal ions are preferable, and Li+, Na+, and K+ having excellent antistatic properties are more preferable. Examples of organic cation include pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, and dihydropyri Midinium cation, pyrazolium cation, pyrazolinium cation, tetraalkylammonium cation, trialkylsulfonium cation, tetraalkylphosphonium cation, and derivatives thereof.

The anionic moiety constituting the ionic compound is not particularly limited as long as it can be ionically bonded to the cation moiety 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 -, (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, the anion containing a fluorine atom is preferable because it imparts an ionic compound with a low melting point, and (F ₂ SO ₂ ) ₂ N- and (CF ₃ SO ₂ ) ₂ N- are particularly preferable.

As an ionic compound, lithium bis (trifluoromethanesulfonyl) imide, lithium bis (difluorosulfonyl) imide, lithium tris (trifluoromethanesulfonyl) methane, potassium bis (trifluoromethanesulfonyl) imide Phonyl)imide, potassiumbis(difluorosulfonyl)imide, 1-ethylpyridiniumhexafluorophosphate, 1-butylpyridiniumhexafluorophosphate, 1-hexyl-4-methylpyridiniumhexafluorophosphate , 1-octyl-4-methylpyridiniumhexafluorophosphate, 1-octyl-4-methylpyridiniumbis(fluorosulfonyl)imide, 1-octyl-4-methylpyridiniumbis(trifluoromethanesulfur) Phonyl)imide, tributylmethylammoniumbis(fluorosulfonyl)imide, tributylmethylammoniumbis(trifluoromethanesulfonyl)imide, (N,N-diethyl-N-methyl-N-( 2-methoxyethyl)ammonium tetrafluoroborate, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammoniumbis(trifluoromethanesulfonyl)imide, 1-octylpyridinium Fluorosulfoniumimide and 1-octyl-3-methylpyridiniumtrifluorosulfoniumimide are preferred.

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

In the pressure-sensitive adhesive composition of the present invention, the content of the antistatic agent (D) is usually 3 parts by mass or less, preferably 0.01 to 3 parts by mass, more preferably, based on 100 parts by mass of the (meth)acrylic copolymer (A). It is 0.05 to 2.5 parts by mass.

[Organic solvent (E)]

It is preferable that the pressure-sensitive adhesive composition of the present invention contains an organic solvent (E) in order to adjust its coatability. Examples of the organic solvent include a solvent exemplified as a polymerization solvent in the column of the production conditions for the (meth)acrylic copolymer (A). For example, a polymer 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 a pressure-sensitive adhesive composition. In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent (E) is usually 50 to 90% by mass, preferably 60 to 85% by mass.

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

[additive]

In addition to the above components, the pressure-sensitive adhesive composition of the present invention includes antioxidants, light stabilizers, metal corrosion inhibitors, tackifiers, plasticizers, crosslinking accelerators, (meth)acrylic polymers and polymers other than the above (A) within the range that does not impair the effects of the present invention. You may contain 1 type or 2 or more types selected from work agents.

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

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

Even when the pressure-sensitive adhesive layer is formed on a polarizing plate having a polarizer protective film only on one side of the polarizer and a polarizing plate having no polarizer protective film on both sides of the polarizer by using the pressure-sensitive adhesive composition of the present invention, the light leakage phenomenon can be suppressed. Further, in the present invention, even if the pressure-sensitive adhesive layer is in direct contact with the polarizer, heat insulation of the pressure-sensitive adhesive layer, peeling of the polarizing plate, and the like can be suppressed under a high-temperature, high-humidity heat environment.

The composition is suitable for bonding of a polarizer and a substrate constituting a liquid crystal cell.

〔For polarizing plate Adhesive layer 〕

The pressure-sensitive adhesive layer for a first polarizing plate of the present invention is formed from the first pressure-sensitive adhesive composition described above. The pressure-sensitive adhesive layer for a second polarizing plate of the present invention is formed from the second pressure-sensitive adhesive composition described above. The first and second pressure-sensitive adhesive layers are collectively referred to as "the pressure-sensitive adhesive layer of the present invention".

By using the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive layer having the following photoelastic properties can be formed. The photoelastic coefficient of the pressure-sensitive adhesive layer of the present invention is -200 to +200, preferably -150 to +150, more preferably -100 to +100, still more preferably -70 to +70. The unit of the photoelastic coefficient is "x10 ^-12 m ² /N".

The photoelastic coefficient is, for example, a plurality of times of bonding the pressure-sensitive adhesive layers to prepare a laminate having a thickness of about 1.0 mm, and the laminate is measured at a measurement wavelength of 633 nm. The details of the measurement conditions are as described in Examples.

Since the pressure-sensitive adhesive layer of the present invention has the above characteristics, it is excellent in preventing light leakage in a high-temperature, high-humidity heat environment. Further, since the pressure-sensitive adhesive layer of the present invention is excellent in durability, heat insulation of the pressure-sensitive adhesive layer and peeling of the pressure-sensitive adhesive layer to the polarizing plate are difficult to occur.

The pressure-sensitive adhesive layer of the present invention has a gel fraction of preferably 40% by mass or more, more preferably 50 to 97% by mass, further preferably 60 to 95% by mass, from the viewpoint of warpage suppression, cohesive force, adhesive force, and re-peelability of the polarizing plate. %to be. When the gel fraction is in the above range, the pressure-sensitive adhesive layer exhibits excellent durability. The details of the measurement conditions are as described in Examples.

The pressure-sensitive adhesive layer of the present invention is specifically obtained by cross-linking the (meth)acrylic copolymer (A) with a cross-linking agent (B) by, for example, performing a cross-linking reaction in the pressure-sensitive adhesive composition described above.

The conditions for forming the pressure-sensitive adhesive layer are as follows, for example. The pressure-sensitive adhesive composition of the present invention is applied on a support and varies depending on the type of solvent, but usually at 50 to 150°C, preferably at 60 to 100°C, usually 1 to 10 minutes, preferably 2 to 7 After drying for a minute, the solvent is removed, and a coating film is formed. The film thickness of the dried coating film is usually 5 to 75 µm, preferably 10 to 50 µm, and the film thickness of the finally obtained pressure-sensitive adhesive layer is also preferably within the above range. The film thickness can be measured, for example, with a dial thickening gauge.

It is preferable to form the pressure-sensitive adhesive layer under the following conditions. After applying the pressure-sensitive adhesive composition of the present invention on a support to form a coating film under the above conditions, and attaching a cover film on the coating film as necessary, usually 3 days or more, preferably 7 to 10 days, usually 5 Curing is carried out in an environment of ~60°C, preferably 15 to 40°C, usually 30 to 70% RH, preferably 40 to 70% RH. When crosslinking is performed under the above aging conditions, it is possible to efficiently form a crosslinked product (network polymer).

As a method of applying the pressure-sensitive adhesive composition, a known method, for example, a spin coating method, a knife coating method, a roll coating method, a bar coating method, a blade coating method, a die coating method, a gravure coating method, etc., is applied to a predetermined thickness. Method can be used.

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

[Adhesive sheet for polarizing plate]

The pressure-sensitive adhesive sheet for a polarizing plate of the present invention has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention. Examples of the pressure-sensitive adhesive sheet include a double-sided pressure-sensitive adhesive sheet having only the pressure-sensitive adhesive layer, a double-sided pressure-sensitive adhesive sheet having a substrate and the pressure-sensitive adhesive layer formed on both sides of the substrate, and a single-sided pressure-sensitive adhesive sheet having a substrate and the pressure-sensitive adhesive layer formed on one side of the substrate. , And a pressure-sensitive adhesive sheet in which a peeling-treated cover film is affixed on a surface of the pressure-sensitive adhesive layer of these pressure-sensitive adhesive sheets that is not in contact with the substrate.

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

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

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

〔 Adhesive layer Attached polarizing plate]

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

As a polarizing plate, a conventionally known polarizing film can be used. For example, a polarizer itself, a polarizer, and a multilayer film having a polarizer protective film disposed on the polarizer may be mentioned. In the present invention, since the pressure-sensitive adhesive layer is disposed in direct contact with the polarizer, for example, a polarizer protective film is disposed only on one side of the polarizer, and a polarizer protective film is not disposed on the other side, and a polarizer protective film is disposed on both sides of the polarizer. There are configurations that have not been made.

Examples of the polarizer include a stretched film obtained by adding a polarizing component to a film made of a polyvinyl alcohol-based resin and stretching it. Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol, polyvinyl foam, polyvinyl acetal, and saponified products of an ethylene-vinyl acetate copolymer. As a polarizing component, iodine or a dichroic dye is mentioned, for example.

As a polarizer protective film, a film made of a thermoplastic resin is mentioned, for example. Examples of thermoplastic resins include cellulose resins such as triacetylcellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic Polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures of two or more selected from these resins.

The thickness of the polarizing plate is usually 10 to 200 μm, preferably 30 to 100 μm. In the present invention, since the polarizer protective film formed on the polarizer can be omitted, the polarizing plate can be made thinner.

In the present invention, the pressure-sensitive adhesive layer is formed in direct contact with the polarizer. As the polarizing plate with the pressure-sensitive adhesive layer of the present invention, for example, a polarizer protective film, a polarizer, and the pressure-sensitive adhesive layer are stacked in this order, the pressure-sensitive adhesive layer, a polarizer protective film, a polarizer, and the pressure-sensitive adhesive layer are stacked in this order, the pressure-sensitive adhesive layer And a configuration in which the polarizer and the pressure-sensitive adhesive layer are laminated in this order. In these configurations, the above-described cover film may be disposed as the outermost layer on the pressure-sensitive adhesive layer.

There is no particular limitation on the method of forming the pressure-sensitive adhesive layer on the surface of the polarizer, a method of applying the pressure-sensitive adhesive composition to the surface of the polarizer, drying and aging, and aging by attaching or transferring the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet for a polarizing plate of the present invention to the surface of the polarizer A method to let you do is mentioned. The conditions for drying and aging, the range of the gel fraction, and the like are the same as those described in the column of [Polling Plate Adhesive Layer].

The thickness of the pressure-sensitive adhesive layer is usually 5 to 75 μm, preferably 10 to 50 μm. In addition, the pressure-sensitive adhesive layer may be formed on at least one side of the polarizer in contact with the polarizer, and examples include a mode in which the pressure-sensitive adhesive layer is formed only on one side of the polarizer, and a mode in which the pressure-sensitive adhesive layer is formed on both sides of the polarizer.

Further, layers having other functions such as a protective layer, an anti-glare layer, a retardation layer, and a viewing angle enhancement layer may be stacked on the polarizing plate.

A liquid crystal element is manufactured by installing the polarizing plate with the pressure-sensitive adhesive layer of the present invention obtained as described above on the substrate surface of a liquid crystal cell. Here, the liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates. As a substrate that a liquid crystal cell has, a glass plate is mentioned, for example. The thickness of the substrate is usually 0.05 to 3 mm, preferably 0.2 to 1 mm.

Example

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

〔 GPC 〕

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

Measurement device: HLC-8320GPC (manufactured by Tosoh Corporation)

GPC column configuration: the following four columns (all manufactured by Tosoh Corporation)

(1) TSKgel HxL-H (guard column)

(2) TSKgel GMHxL

(3) TSKgel GMHxL

(4) TSKgel G2500HxL

Flow rate: 1.0mL/min

·Column temperature: 40℃

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

·Mobile phase solvent: Tetrahydrofuran

·Standard polystyrene conversion

〔 Photoelasticity Coefficient〕

About the (meth)acrylic copolymer, the photoelastic coefficient was measured as follows.

The polymer solution containing the (meth)acrylic copolymer obtained in Synthesis Example was applied to the peeling-treated surface of the peel-treated polyethylene terephthalate film, and dried at 90° C. for 3 minutes to obtain a coating film (polymer layer) having a dry film thickness of 20 μm. Formed. Polymer layers having a dry film thickness of 20 μm were bonded multiple times in an environment of 23° C./50% RH, and treated in an autoclave controlled at 50° C./5 atm for 20 minutes to prepare a polymer layer having a thickness of 1.0 mm. A 1.0mm-thick polymer layer is cut into a size of 15mm x 50mm, and it is attached to an automatic wavelength scanning ellipsometer (model ``M-220'', manufactured by Nippon Bunko Co., Ltd.) using a jig, and retardation is applied. It measured at a measurement wavelength of 633 nm while changing the stress. The slope of the straight line when the stress was taken on the horizontal axis and the retardation was taken on the vertical axis was taken as the photoelastic coefficient of the (meth)acrylic copolymer.

[ Synthesis example One]

76.5 parts of n-butyl acrylate, 19.0 parts of phenoxyethyl acrylate, 1.5 parts of acrylic acid, 3.0 parts of acrylamide, and 100 parts of an ethyl acetate solvent were introduced into a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen introduction tube, and nitrogen The temperature was raised to 80°C while introducing gas. Next, 0.1 part of 2,2'-azobisisobutyronitrile was added, and polymerization reaction was performed at 80 degreeC under nitrogen gas atmosphere for 6 hours. After completion of the reaction, it was diluted with ethyl acetate to prepare a polymer solution having a solid content concentration of 30% by mass. The weight average molecular weight (Mw) of the obtained (meth)acrylic copolymer 1 was 800,000, the molecular weight distribution (Mw/Mn) was 7.5, and the photoelastic coefficient was -58×10 ^-12 (m ² /N).

[ Synthesis example 2~3]

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 used in the polymerization reaction was changed as described in Table 1. Table 1 shows the results.

[ Example A1]

(1) Preparation of pressure-sensitive adhesive composition

With respect to the polymer solution (solid content concentration 30% by mass) obtained in Synthesis Example 1 and 100 parts (solid content) of the (meth)acrylic copolymer 1 contained in the solution, as an isocyanate compound, manufactured by Soken Chemical Co., Ltd. D-94" 2.0 parts (solid content) and Soken Chemical Co., Ltd.'s "M-12AT" 0.2 parts (solid content) as a metal chelate compound, and Soken Chemical Co., Ltd.'s "A-" as a silane coupling agent. 50" (solid content 100 mass%) 0.2 part was mixed, and the adhesive composition was obtained.

(2) Preparation of adhesive sheet

The pressure-sensitive adhesive composition obtained in (1) above is applied on the peel-treated polyethylene terephthalate film (PET film) using a doctor blade after the foam is released, and dried at 90° C. for 3 minutes to form a dry film thickness of 20 μm. did. A peel-treated PET film is further affixed to the side opposite to the affixed surface of the PET film of the coating film, and allowed to stand for 7 days in an environment of 23°C/50% RH and aged, and a 20 μm-thick adhesive layer sandwiched between two PET films A pressure-sensitive adhesive sheet was obtained.

(3) Adhesive layer Fabrication of the attached polarizing plate

The pressure-sensitive adhesive composition obtained in the above (1) is applied on the peel-treated polyethylene terephthalate film (PET film) using a doctor blade after the foam has been removed, and dried at 90° C. for 3 minutes, having a dry film thickness of 20 μm. I got a sheet. The coating surface of the sheet and the polyvinyl alcohol film surface of a polarizing plate having a two-layer structure (60 μm in thickness) consisting of a polyvinyl alcohol film as a polarizer and a triacetyl cellulose film as a polarizer protective film are bonded to come into contact with each other, and 23° C./50% RH It was allowed to stand still for 7 days under the conditions of and aged to obtain a polarizing plate with a pressure-sensitive adhesive layer having a PET film, an adhesive layer having a thickness of 20 μm, and a polarizer and a polarizer protective film.

[ Example B1~B2, Comparative example A1~A2, B1~B3]

In Example A1, in the same manner as in Example A1, except that the polymer solution was changed to the polymer solution obtained in each synthesis example, and/or the compounding composition was changed as described in Table 2, the pressure-sensitive adhesive composition, the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive A polarizing plate with a layer was obtained.

[evaluation]

[Gel fraction]

About 0.1 g of pressure-sensitive adhesive from the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples was collected in a sampling bottle, 30 mL of ethyl acetate was added, and after shaking for 4 hours, the contents of the sample bottle were filtered through a 200 mesh stainless steel wire mesh. The residue on the wire mesh was dried at 100° C. for 2 hours to measure the dry weight. The gel fraction of the pressure-sensitive adhesive was determined by the following equation.

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

〔 Photoelasticity Coefficient〕

In the pressure-sensitive adhesive sheet obtained in Examples and Comparative Examples, the PET film was peeled, and the pressure-sensitive adhesive layers having a thickness of 20 μm were bonded multiple times in an environment of 23° C./50% RH, and in an autoclave adjusted to 50° C./5 atm for 20 minutes. By processing, a pressure-sensitive adhesive layer having a thickness of 1.0 mm was produced. A 1.0mm-thick adhesive layer is cut into a size of 15mm x 50mm, and it is attached to an automatic wavelength scanning ellipsometer (model ``M-220'', manufactured by Nippon Bunko Co., Ltd.) using a jig, and retardation is applied. It measured at a measurement wavelength of 633 nm while changing the stress. The slope of the straight line when stress was taken as the horizontal axis and retardation as the vertical axis was taken as the photoelastic coefficient of the pressure-sensitive adhesive layer.

〔 Light leakage exam〕

Two polarizing plates with an adhesive obtained in Examples and Comparative Examples (a laminate consisting of a PET film/adhesive layer/polarizer/polarizer protective film) were cut to a size of 310 mm x 385 mm to prepare a test piece. The PET film was peeled from the test piece, and a laminate made of a pressure-sensitive adhesive layer/polarizer/polarizer protective film was adhered on both sides of a glass plate having a thickness of 0.5 mm so that the polarization axes were orthogonal to each other, and the pressure-sensitive adhesive layer and the glass plate were in contact with each other using a laminator roll. The obtained laminate was held for 20 minutes in an autoclave adjusted to 50° C./5 atm to prepare a test plate. This test plate was allowed to stand for 500 hours under conditions of a temperature of 80°C/dry, and light leakage was observed according to the following criteria.

AA: No light leakage was observed

BB: Light leakage is slightly observed

CC: Light leakage is clearly observed

[Durability test (heat resistance· Moisture and heat resistance exam)〕

The polarizing plate with a pressure-sensitive adhesive layer obtained in Examples and Comparative Examples (a laminate consisting of a PET film/adhesive layer/polarizer/polarizer protective film) was cut to a size of 150 mm×250 mm to prepare a test piece. The PET film was peeled from the test piece, and a laminate made of a pressure-sensitive adhesive layer/polarizer/polarizer protective film was adhered to one side of a 0.5 mm-thick glass plate so that the pressure-sensitive adhesive layer and the glass plate were in contact with each other using a laminator roll. The obtained laminate was held for 20 minutes in an autoclave adjusted to 50° C./5 atm to prepare a test plate. Two similar trial versions were prepared. The test plate was allowed to stand for 500 hours under the conditions of a temperature of 80°C/dry (heat resistance) or a temperature of 60°C/humidity 90% RH (moisture and heat resistance), and defects (foaming, lifting, peeling) were observed according to the following criteria. And evaluated.

AA: No defect

BB: The defect area is 5% or less, and there is no problem in practical use.

CC: Defect area exceeds 5%, there is a problem in practical use

D-94: hexamethylene diisocyanate-based crosslinking agent

(Soken Chemical Co., Ltd. product, solid content 90% by mass)

L-45: Tolylene diisocyanate-based crosslinking agent

(Soken Chemical Co., Ltd. product, solid content 45 mass%, ethyl acetate/toluene solution)

E-5C: Epoxy crosslinking agent

(Soken Chemical Co., Ltd., solid content 5% by mass)

M-12AT: Aluminic chelate crosslinking agent

(Soken Chemical Co., Ltd. product, solid content 10 mass%, toluene/acetylacetone solution)

·A-50: Silane coupling agent

(Soken Chemical Co., Ltd. product, 50 mass% of solid content, toluene solution)

Claims (10)

The structural unit derived from the (meth)acrylate alkyl ester (a11) whose photoelastic coefficient of the homopolymer is -1000×10 ^-12 to -100×10 ^-12 (m ^{2 /N) and the photoelastic coefficient of the homopolymer are +500×10 The} photoelastic coefficient having a structural unit derived from an aromatic ring-containing (meth)acrylic acid ester (a12) of -12 to +2000 × 10 ^-12 (m ^{2 /N) is -200 × 10 -12} to +200 × 10 ^-12 ( m ² /N) (meth)acrylic copolymer (A1),
Isocyanate crosslinking agent without aromatic ring (B1)
It is formed from a pressure-sensitive adhesive composition containing,
The photoelastic coefficient is -200×10 ^-12 ~+70×10 ^-12 (m ² /N),
Placed in direct contact with the polarizer
A pressure-sensitive adhesive layer for a polarizing plate, characterized in that. The pressure-sensitive adhesive layer for a polarizing plate according to claim 1, wherein the isocyanate-based crosslinking agent (B1) is a hexamethylenediisocyanate-based crosslinking agent. The pressure-sensitive adhesive layer for a polarizing plate according to claim 1, wherein the pressure-sensitive adhesive composition contains 0.05 to 10 parts by mass of an isocyanate-based crosslinking agent (B1) with respect to 100 parts by mass of the copolymer (A1). It is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer (A2) having a photoelastic coefficient of ^{less than -200×10 -12} (m ^{2 /N) and an isocyanate-based crosslinking agent (B2) having an aromatic ring,}
The photoelastic coefficient is -200×10 ^-12 ~+70×10 ^-12 (m ² /N),
Placed in direct contact with the polarizer
A pressure-sensitive adhesive layer for a polarizing plate, characterized in that. The pressure-sensitive adhesive layer for a polarizing plate according to claim 4, wherein the isocyanate-based crosslinking agent (B2) is at least one selected from tolylenediisocyanate-based crosslinking agents and xylylenediisocyanate-based crosslinking agents. The pressure-sensitive adhesive layer for a polarizing plate according to claim 4, wherein the pressure-sensitive adhesive composition contains 2 parts by mass or more of an isocyanate-based crosslinking agent (B2) with respect to 100 parts by mass of the copolymer (A2). The adhesive sheet for polarizing plates which has the adhesive layer in any one of Claims 1-6. A polarizing plate with a pressure-sensitive adhesive layer having a polarizer and the pressure-sensitive adhesive layer according to any one of claims 1 to 6 directly laminated on at least one surface of the polarizer. The structural unit derived from the (meth)acrylate alkyl ester (a11) whose photoelastic coefficient of the homopolymer is -1000×10 ^-12 to -100×10 ^-12 (m ^{2 /N) and the photoelastic coefficient of the homopolymer are +500×10 The} photoelastic coefficient having a structural unit derived from an aromatic ring-containing (meth)acrylic acid ester (a12) of -12 to +2000 × 10 ^-12 (m ^{2 /N) is -200 × 10 -12} to +200 × 10 ^-12 ( m ² /N) (meth)acrylic copolymer (A1),
Isocyanate crosslinking agent without aromatic ring (B1)
Contains,
The pressure-sensitive adhesive composition for polarizing plates used to form the pressure-sensitive adhesive layer according to claim 1. A (meth)acrylic copolymer (A2) having a photoelastic coefficient of ^{less than -200×10 -12} (m ² /N) and an isocyanate crosslinking agent (B2) having an aromatic ring,
The pressure-sensitive adhesive composition for polarizing plates used to form the pressure-sensitive adhesive layer according to claim 4.