JPWO2017029959A1 - Adhesive layer and adhesive composition for polarizing plate - Google Patents

Abstract

[PROBLEMS] To provide a pressure-sensitive adhesive layer that can be applied to a configuration in which at least one of the polarizer protective films conventionally formed on both surfaces of a polarizer is omitted, and is excellent in light leakage prevention and durability. [Solution] A structural unit derived from an alkyl ester of (meth) acrylic acid having a photoelastic coefficient of a homopolymer of −1000 × 10 −12 to −100 × 10 −12 (m 2 / N), and a photoelastic coefficient of the homopolymer The photoelastic coefficient is −200 × 10 −12 to + 200 × 10 −12 having structural units derived from + 500 × 10 −12 to + 2000 × 10 −12 (m 2 / N) aromatic ring-containing (meth) acrylate. m2 / N) and a pressure-sensitive adhesive composition containing an isocyanate-based crosslinking agent having no aromatic ring, and has a photoelastic coefficient of −200 × 10 −12 to + 200 ×. A pressure-sensitive adhesive layer for a polarizing plate, wherein the pressure-sensitive adhesive layer is 10 −12 (m 2 / N) and is disposed in direct contact with a polarizer.

Description

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

  The liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates (for example, a glass plate). A polarizing plate is attached to the surface of the substrate constituting the liquid crystal cell via an adhesive layer. In general, a polarizing plate has a structure in which a polarizer protective film such as a triacetyl cellulose film is laminated on both surfaces of a polarizer having a polarizing function in order to improve its mechanical properties and optical durability. I came.

  In recent years, attempts have been made to omit one or both of the polarizer protective films formed on both sides of the polarizer in response to the demand for lightening and thinning the polarizing plate (see, for example, Patent Document 1). However, in the polarizing plate in which one or both of the polarizer protective films are omitted, the pressure-sensitive adhesive layer is in direct contact with the polarizer. Large stress is applied, and problems such as peeling of the adhesive layer are likely to occur. In addition, the stress applied to the pressure-sensitive adhesive layer due to thermal contraction of the polarizer increases, and there is a problem that birefringence is likely to occur.

  Accordingly, the pressure-sensitive adhesive for polarizing plates is required to have excellent light leakage prevention and durability. Regarding the problem of light leakage, Patent Document 2 discloses 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 discloses positive photoelasticity. It describes about the pressure sensitive adhesive composition for polarizing plates containing the component which has a coefficient. However, these documents do not describe providing an adhesive layer directly on a polarizer.

JP 2012-128099 A JP 2010-090354 A JP-T-2004-516359

  A polarizing plate in which at least one of the polarizer protective films conventionally formed on both surfaces of the polarizer is omitted is required to be further excellent in light leakage prevention and durability. An object of the present invention 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 provides an adhesive layer excellent in light leakage prevention and durability. There is.

  The present inventors diligently studied to solve the above problems. As a result, it has been found that when a (meth) acrylic copolymer and a cross-linking agent described below are used, an adhesive layer excellent in the above light leakage prevention property and durability can be formed. That is, the present inventors have found that the above problems can be solved by using a polarizing plate pressure-sensitive adhesive layer having the following specific configuration, and have completed the present invention.

The present invention includes, for example, the following [1] to [10].
[1] (meth) acrylic acid alkyl ester (a11) derived constituent units of the homopolymer of photoelastic coefficient of ^{-1000 × 10 -12 ~-100 ×} 10 -12 (m 2 / N), and homopolymers light The photoelastic coefficient is −200 × 10 ⁻¹² having a structural unit derived from an aromatic ring-containing (meth) acrylic acid ester (a12) having an elastic modulus of + 500 × 10 ⁻¹² to + 2000 × 10 ⁻¹² (m ² / N). ~ + 200 × 10 ⁻¹² (m ² / N) (meth) acrylic copolymer (A1) and an adhesive composition containing an isocyanate-based crosslinking agent (B1) having no aromatic ring. The pressure-sensitive adhesive layer for a polarizing plate has a photoelastic coefficient of −200 × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N) and is disposed in direct contact with the polarizer.

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

  [3] The adhesive composition 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) with respect to 100 parts by mass of the copolymer (A1). Pressure-sensitive adhesive layer for polarizing plate.

[4] 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 are contained. It is formed from an adhesive composition, has a photoelastic coefficient of −200 × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N), and is disposed in direct contact with a polarizer. Adhesive layer.

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

  [6] The 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) with respect to 100 parts by mass of the copolymer (A2). Adhesive layer.

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

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

[9] (meth) acrylic acid alkyl ester (a11) derived constituent units of the homopolymer of photoelastic coefficient of ^{-1000 × 10 -12 ~-100 ×} 10 -12 (m 2 / N), and homopolymers light The photoelastic coefficient is −200 × 10 ⁻¹² having a structural unit derived from an aromatic ring-containing (meth) acrylic acid ester (a12) having an elastic modulus of + 500 × 10 ⁻¹² to + 2000 × 10 ⁻¹² (m ² / N). It contains a (meth) acrylic copolymer (A1) of ~ + 200 × 10 ⁻¹² (m ² / N) and an isocyanate crosslinking agent (B1) having no aromatic ring, and is described in the above [1]. The adhesive composition for polarizing plates used in order to form the adhesive layer of this.

[10] 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 adhesive composition for polarizing plates used in order to form the adhesive layer as described in said [4].

  ADVANTAGE OF THE INVENTION According to this invention, it is applicable to the structure by which at least one of the polarizer protective films conventionally formed on both surfaces of the polarizer was abbreviate | omitted, and provides the adhesive layer excellent in light leakage prevention property and durability. be able to.

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

[Adhesive composition for polarizing plate]
The first pressure-sensitive adhesive composition for polarizing plate of the present invention comprises a (meth) acrylic copolymer (A1) having a photoelastic coefficient of −200 × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N) and And an isocyanate-based cross-linking agent (B1) having no aromatic ring, and used to form an adhesive layer in direct contact with the polarizer.

The photoelastic coefficient is obtained by crosslinking a (meth) acrylic copolymer having a photoelastic coefficient in the above range with an isocyanate-based crosslinking agent that does not have an aromatic ring and has a small contribution to the photoelastic coefficient of the pressure-sensitive adhesive layer. Can be formed as a pressure-sensitive adhesive layer in the range of −200 × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N).

The second pressure-sensitive adhesive composition for polarizing plate of the present invention comprises a (meth) acrylic copolymer (A2) having a photoelastic coefficient of less than −200 × 10 ⁻¹² (m ² / N), an aromatic ring. It is used for forming a pressure-sensitive adhesive layer in direct contact with the polarizer.

By cross-linking 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 plus side, the photoelastic coefficient is -200. A pressure-sensitive adhesive layer in the range of × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N) can be formed.

  In the present specification, the copolymers (A1) and (A2) are collectively referred to as “copolymer (A)”, and the first and second pressure-sensitive adhesive compositions for polarizing plates of the present invention are respectively referred to as “copolymer (A)”. These are also referred to as “first pressure-sensitive adhesive composition” and “second pressure-sensitive adhesive composition”, and are collectively referred to as “pressure-sensitive adhesive composition of the present invention”.

  In this specification, acrylic and methacryl are collectively referred to as “(meth) acryl”. Moreover, the structural unit derived from a certain monomer A contained in the polymer is also referred to as “monomer A unit”. Moreover, a certain ester (a) may be described as "monomer (a)" for convenience.

In this specification, unless otherwise specified, the unit of the photoelastic coefficient of the homopolymer, (meth) acrylic copolymer and pressure-sensitive adhesive layer formed from each monomer is “× 10 ⁻¹² m ² / N”. is there. Further, for example, −200 × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N) is −200 × 10 ⁻¹² (m ² / N) or more and + 200 × 10 ⁻¹² (m ² / N) or less. means. 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 produced by the following procedure. A reactor equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube is charged with 100 parts by mass of a monomer and 100 parts by mass of an ethyl acetate solvent, and heated to 80 ° C. while introducing nitrogen gas. Next, 0.1 part by mass of 2,2′-azobisisobutyronitrile is added, and a polymerization reaction is performed at 80 ° C. for 6 hours in a nitrogen gas atmosphere. After completion of the reaction, the mixture is diluted with ethyl acetate to prepare a homopolymer solution of the monomer having a solid concentration of 30% by mass.

  The homopolymer solution is applied to the release-treated surface of the release-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. The homopolymer layers having a dry film thickness of 20 μm are bonded together several times in an environment of 23 ° C./50% RH, and processed for 20 minutes in an autoclave adjusted to 50 ° C./5 atm to form a homopolymer layer having a thickness of 1.0 mm. Make it.

  A homopolymer layer having a thickness of 1.0 mm is cut into a size of 15 mm × 50 mm and attached to an automatic wavelength scanning ellipsometer (model “M-220”, manufactured by JASCO Corporation) using a jig. The retardation is measured at a measurement wavelength of 633 nm while changing the stress. A plot when the stress is plotted on the horizontal axis and the retardation is plotted on the vertical axis is linearly approximated, and the slope is taken as the photoelastic coefficient of the homopolymer formed from the monomer.

As the glass transition temperature (Tg) of the homopolymer formed from each monomer, for example, a value described in Polymer Handbook Fourth Edition (Wiley-Interscience 2003) can be adopted.
In addition, about the monomer in which Tg is not described in the said literature, Tg of the homopolymer synthesize | combined on the following conditions is measured on the following conditions, for example. A reactor equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube is charged with 100 parts by mass of a monomer and 100 parts by mass of an ethyl acetate solvent, and heated to 80 ° C. while introducing nitrogen gas. Next, 0.1 part by mass of 2,2′-azobisisobutyronitrile is added, and a polymerization reaction is performed 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), measure the heat change by raising the temperature at 10 ° C / min in a nitrogen stream, and draw a graph of “endothermic heat generation” and “temperature”. The characteristic inflection is the glass transition. Tg uses a value obtained from the DSC curve by the midpoint method.

[(Meth) acrylic copolymer (A1)]
The (meth) acrylic copolymer (A1) has a structural unit derived from (meth) acrylic acid alkyl ester (a11) having a homopolymer photoelastic coefficient of −1000 to −100, and a homopolymer photoelastic coefficient of +500. And a structural unit derived from +2000 aromatic ring-containing (meth) acrylic acid ester (a12). A copolymer (A1) is a copolymer obtained by copolymerizing the monomer component containing a monomer (a11) and a monomer (a12), for example.

The monomer component (that is, the raw material monomer component of (A1)) is preferably 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 the monomer (a11) having a negative photoelastic coefficient of the homopolymer and the monomer (a12) having a positive photoelastic coefficient of the homopolymer, a copolymer (A1) having a photoelastic coefficient in the above range is obtained. be able to. By using the copolymer (A1) and the isocyanate-based crosslinking agent (B1) having no aromatic ring, the photoelastic coefficient of the pressure-sensitive adhesive layer can be brought close to the range described below, in particular, 0. Light leakage in the polarizing plate can be suppressed.

<< (Meth) acrylic acid alkyl ester (a11) (monomer (a11)) >>
The monomer (a11) is a (meth) acrylic acid alkyl ester having a homopolymer photoelastic coefficient of −1000 to −100. The monomer having a photoelastic coefficient of homopolymer in the range of −750 to −150 is preferable, and the monomer in the range of −500 to −200 is more preferable.

  By using the copolymer (A1) obtained by copolymerizing a monomer (a11) having a photoelastic coefficient of the above-mentioned range, the pressure-sensitive adhesive layer is given softness and exhibits light leakage prevention properties. be able to.

  The monomer (a11) is preferably a (meth) acrylic acid alkyl ester having a homopolymer Tg of −30 ° C. or less, and the Tg is more preferably −100 to −30 ° C., further preferably −70 to −30. ° C.

Examples of the monomer (a11) include compounds in which the photoelastic coefficient of the homopolymer is in the above range among the compounds represented by CH ₂ ═CR ¹ —COOR ² . 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. 2-16 are preferable and, as for carbon number of the said alkyl group, 4-12 are more preferable.

Examples of the monomer (a11) include n-butyl acrylate (-400; -50), 2-ethylhexyl acrylate (-700; -70), isodecyl methacrylate (-190; -41), and lauryl methacrylate (-460; -65). The numerical values in parentheses indicate the photoelastic coefficient (× 10 ⁻¹² m ² / N) on the left side and the Tg (° C.) on the right side of the homopolymer formed from each monomer.

  A monomer (a11) may be used individually by 1 type, and may use 2 or more types. When using 2 or more types of monomers (a11), it is preferable that each monomer satisfy | fills the requirements of a 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, and further preferably 60 to 80% by mass. %. It is preferable that the amount of the monomer (a11) used is in the above range in that the photoelastic coefficient of the copolymer (A1) obtained can be adjusted in the above range.

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

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.

Examples of the monomer (a12) include compounds in which the photoelastic coefficient of the homopolymer is in the above range among the compounds represented by CH ₂ ═CR ³ —COOR ⁴ . 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 a phenyl group, arylalkyl groups such as a benzyl group, and aryloxyalkyl groups such as a phenoxyethyl group. The carbon number 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 (× 10 ⁻¹² m ² / N) on the left side and the Tg (° C.) on the right side of the homopolymer formed from each monomer. In addition, examples of the monomer (a12) include phenyl acrylate, phenyl methacrylate, and phenoxyethyl methacrylate.

  A monomer (a12) may be used individually by 1 type, and may use 2 or more types. When using 2 or more types of monomers (a12), it is preferable that each monomer satisfy | fills the requirements of a 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 further preferably 15 to 30% by mass. %. It is preferable that the amount of the monomer (a12) used is in the above range in that the photoelastic coefficient of the copolymer (A1) obtained can be adjusted in the above range.

<< Crosslinkable 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 crosslinker (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).

The monomer (a13) preferably 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 a hydroxyl group-containing (meth) acrylate, specifically, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate. , Hydroxyalkyl (meth) acrylates such as 6-hydroxyhexyl (meth) acrylate and 8-hydroxyoctyl (meth) acrylate. Carbon number of the hydroxyalkyl group in hydroxyalkyl (meth) acrylate is 2-8 normally, Preferably it is 2-6.

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

A 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 10% by mass or less, more preferably 0.5-7% by mass, More preferably, it is 1-5 mass%. When the usage-amount of a monomer (a13) is below the said upper limit, the crosslinking density formed with a copolymer (A1) and a crosslinking agent (B1) will not become high too much. When the usage-amount of a monomer (a13) is more than the said lower limit, a crosslinked structure is formed effectively and the adhesive layer which has suitable intensity | strength is obtained.

《Other monomers》
The raw material monomer component of the copolymer (A1) is, for example, an alkyl (meth) acrylate other than the monomer (a11), an alkoxyalkyl (meth) acrylate, an alkoxy, as long as the physical properties of the copolymer (A1) are not impaired. Other monomers such as polyalkylene glycol mono (meth) acrylate, alicyclic group-containing (meth) acrylate, amino group-containing monomer and amide group-containing monomer can also be used. That is, the copolymer (A1) may further have structural units derived from other monomers.

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

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

  Examples of the alkoxypolyalkylene glycol mono (meth) acrylate include methoxydiethylene glycol mono (meth) acrylate, methoxydipropylene glycol mono (meth) acrylate, ethoxytriethylene glycol mono (meth) acrylate, ethoxydiethylene glycol mono (meth) acrylate, And methoxytriethylene glycol mono (meth) acrylate.

Examples of the alicyclic group-containing (meth) acrylate include cyclohexyl (meth) acrylate.
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.

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 use amount of the other monomers is not particularly limited as long as the photoelastic coefficient of the (A1) is in the above range, but is 0 to 10% by mass. It is preferable that it is 0 to 5% by mass.

[(Meth) acrylic copolymer (A2)]
The (meth) acrylic copolymer (A2) is a copolymer having a photoelastic coefficient of less than −200, preferably from −500 to less than −200, more preferably from −300 to less than −200. Such a copolymer has, for example, a structural unit derived from a (meth) acrylic acid alkyl ester (a21) having a photoelastic coefficient of less than −200 of a homopolymer, for example, a monomer component containing the monomer (a21) Is obtained by copolymerization.

The monomer component (that is, the raw material monomer component of (A2)) is preferably a polymerizable unsaturated double bond-containing monomer.
By using the copolymer (A2) and the isocyanate-based cross-linking agent (B2) having an aromatic ring, the photoelastic coefficient of the pressure-sensitive adhesive layer can be brought close to the range described below, in particular, 0. The light leak in can be suppressed.

<< (Meth) acrylic acid alkyl ester (a21) (monomer (a21)) >>
As the monomer (a21), an ester having a photopolymer coefficient of less than −200 of the homopolymer among the above-mentioned (meth) acrylic acid alkyl ester (a11) can be exemplified. The monomer having a photoelastic coefficient of the homopolymer of −750 or more and less than −200 is preferable, and the monomer having a −500 or more and less than −200 is more preferable.

  A monomer (a21) may be used individually by 1 type, and may use 2 or more types. When using 2 or more types of monomers (a21), it is preferable that each monomer satisfy | fills the requirement of a 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 further preferably 69 to 97% by mass. %. It is preferable that the amount of the monomer (a21) used is in the above range in that the photoelastic coefficient of the obtained copolymer (A2) can be adjusted in the above range.

<< Crosslinkable 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 crosslinker (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 a monomer (a22), the crosslinkable functional group containing monomer (a13) mentioned above can be illustrated, and its preferable example is also the same. A 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) used is preferably more than 0% by mass and 10% by mass or less, more preferably 0.5-7% by mass, More preferably, it is 1-5 mass%. When the usage-amount of a monomer (a22) is below the said upper limit, the crosslinking density formed with a copolymer (A2) and a crosslinking agent (B2) will not become high too much. When the usage-amount of a monomer (a22) is more than the said lower limit, a crosslinked structure is formed effectively and the adhesive layer which has appropriate intensity | strength is obtained.

《Other monomers》
The raw material monomer component of the copolymer (A2) is, for example, an alkyl (meth) acrylate, alkoxyalkyl (meth) acrylate, alkoxy other than the monomer (a21) as long as the physical properties of the copolymer (A2) are not impaired. Other monomers such as polyalkylene glycol mono (meth) acrylate, alicyclic group-containing (meth) acrylate, aromatic ring-containing (meth) acrylate, amino group-containing monomer and amide group-containing monomer can also be used. That is, the copolymer (A2) may further have structural units derived from other monomers.

  Examples of these monomers include the respective compounds described in << other monomers >> in the column of the copolymer (A1). Examples of the aromatic ring-containing (meth) acrylate include phenyl (meth) acrylate, benzyl (meth) acrylate, and phenoxyethyl (meth) acrylate.

  However, the (meth) acrylic acid alkyl ester having a homopolymer photoelastic coefficient of +100 to +1000, and the aromatic ring-containing (meth) acrylic acid ester having a photoelastic coefficient of +500 to +2000 (the monomer (a12) described above) From the viewpoint of adjusting the photoelastic coefficient of the copolymer (A2) to the above range, it is preferable to adjust the amount of use as appropriate.

Examples of the (meth) acrylic acid alkyl ester having a homopolymer photoelastic coefficient of +100 to +1000 include, for example, methyl acrylate (600), t-butyl methacrylate (130), n-butyl methacrylate (320), 2-ethylhexyl methacrylate ( 420). The numerical value in the parenthesis indicates 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 use amount of the other monomers is not particularly limited as long as the photoelastic coefficient of the (A2) is in the above range, but is 0 to 35% by mass. The content is preferably 0, more preferably 0 to 30% by mass, and still more preferably 0 to 26% by mass.

[Production conditions for (meth) acrylic copolymer (A)]
Although the manufacturing conditions of a (meth) acrylic-type copolymer (A) are not specifically limited, For example, it can manufacture by a solution polymerization method. Specifically, a polymerization solvent and a monomer component are charged into a 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 used. The reaction is carried out for 2 to 20 hours while maintaining the temperature at 50 to 90 ° C, preferably 70 to 90 ° C. The polymerization reaction can be performed, for example, in an inert gas atmosphere such as nitrogen gas.

  The copolymer (A) is obtained, for example, by copolymerizing the monomer components described above, 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; cyclopentane, cyclohexane, and cycloheptane. Cycloaliphatic hydrocarbons such as cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, diphenyl ether; chloroform, carbon tetrachloride, Halogenated hydrocarbons such as 1,2-dichloroethane and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate and methyl propionate; acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexane Ketones such as non; amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; sulfoxides such as dimethyl sulfoxide and sulfolane It is done. These polymerization solvents may be used alone or in combination of two or more.

  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 the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), and 2,2′-azobis (2-cyclopropyl). Propionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile) 2- (carbamoylazo) isobutyronitrile, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis ( N, N′-dimethyleneisobutylamidine), 2,2′-azobis (isobutyramide) dihydrate, 4,4′-azobis (4-cyanopentanoic acid), 2 2'-azobis (2-cyanopropanol), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propionamide] Is mentioned. These polymerization initiators may be used alone or in combination of two or more.

  A polymerization initiator is 0.01-5 mass parts normally with respect to 100 mass parts of raw material monomer components of a (meth) acrylic-type copolymer (A), Preferably it exists in the range of 0.1-3 mass parts. Used in quantity. Moreover, you may add suitably a polymerization initiator, a chain transfer agent, a monomer component, and a polymerization solvent during the said polymerization reaction.

[Physical properties and content of (meth) 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 a polystyrene conversion value, and is usually 300,000 to 2,000,000, preferably Is 400,000 to 1.8 million, more preferably 500,000 to 1,500,000. By using the copolymer (A) having Mw in the above range and having the above monomer unit, it is easy to balance the adhesive force, and a pressure-sensitive adhesive composition suitable for coating can be obtained. Moreover, an adhesive layer with higher durability can be obtained by using the copolymer (A) having an Mw of 500,000 or more.

The molecular weight distribution (Mw / Mn) measured by the GPC method of the (meth) acrylic copolymer (A) is usually 20 or less, preferably 2-15, more preferably 2-9.
The glass transition temperature (Tg) of the (meth) acrylic copolymer (A) can be calculated by, for example, the Fox formula from the monomer units constituting the copolymer and the content ratio thereof. For example, the (meth) acrylic copolymer (A) is synthesized so that the glass transition temperature (Tg) determined by the Fox equation is usually −70 to −10 ° C., preferably −60 to −20 ° C. It is preferable to do. By using the (meth) acrylic copolymer (A) having such a glass transition temperature (Tg), a pressure-sensitive adhesive composition excellent in stress relaxation characteristics and durability and having excellent adhesiveness at room temperature is obtained. be able to.
Fox 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 are the glass transition temperatures (K) of homopolymers composed of the respective monomers. W ₁ , W ₂ ,..., W _m are the weight fractions of the structural units derived from the respective monomers in the copolymer (A). As the weight fraction of the structural unit derived from each monomer, the charging ratio of each monomer to the total monomers at the time of copolymer synthesis can be used.

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

  In the first pressure-sensitive adhesive composition, the content of the (meth) acrylic copolymer (A1) is 100% by mass of the solid content excluding the organic solvent in the composition, usually 60 to 99.95% by mass, Preferably it is 70-99.5 mass%, Most preferably, it is 80-99.0 mass%. When the content of the (meth) acrylic copolymer (A1) is in the above range, the performance as an adhesive is balanced and the adhesive properties are excellent.

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

[Crosslinking agent (B)]
The 1st adhesive composition further contains the isocyanate type crosslinking agent (B1) which does not have an aromatic ring. The second pressure-sensitive adhesive composition further contains an isocyanate-based crosslinking agent (B2) having an aromatic ring.

<< Isocyanate-based crosslinking agent (B1) >>
As the isocyanate-based crosslinking agent (B1), an isocyanate compound having 2 or more isocyanate groups in one molecule and having no aromatic ring is usually used. By crosslinking the (meth) acrylic copolymer (A1) with the crosslinking agent (B1), a crosslinked body (network polymer) having excellent durability can be formed. Moreover, the adhesive which has a photoelastic coefficient in the range of -200- + 200 by using the crosslinking agent (B1) which does not have an aromatic ring with the copolymer (A1) which has a photoelastic coefficient in the range of -200- + 200. An agent layer can be formed.

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

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

Examples of the isocyanate compound having 3 or more isocyanate groups in one molecule include aliphatic polyisocyanates and alicyclic polyisocyanates.
Examples of the crosslinking agent (B1) include multimers (for example, dimers or trimers, biurets, isocyanurates) and derivatives (for example, many) of the above isocyanate compounds having 2 or more isocyanate groups. Addition reaction product of a dihydric alcohol and two or more molecules of the diisocyanate compound), and a polymer. Examples of the polyhydric alcohol in the derivative include trivalent or higher alcohols such as trimethylolpropane, glycerin and pentaerythritol as low molecular weight polyhydric alcohols; high molecular weight polyhydric alcohols such as polyether polyols, Examples include polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

  Examples of such an isocyanate compound include a biuret or isocyanurate of hexamethylene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate (for example, a trimolecular adduct of hexamethylene diisocyanate), polyether polyisocyanate, Polyester polyisocyanate is mentioned.

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

A crosslinking agent (B1) may be used individually by 1 type, and may use 2 or more types.
In the first pressure-sensitive adhesive composition, the content of the crosslinking agent (B1) is usually 0.05 to 10 parts by mass, preferably 0 with respect to 100 parts by mass of the (meth) acrylic copolymer (A1). .5-8 parts by mass, more preferably 1-5 parts by mass. When the content of the cross-linking agent (B1) is in the above range, it is preferable in terms of easy balance between durability and light leakage prevention.

<< Isocyanate-based crosslinking agent (B2) >>
As the isocyanate-based crosslinking agent (B2), an isocyanate compound having an aromatic ring having 2 or more isocyanate groups in one molecule is usually used. By crosslinking the (meth) acrylic copolymer (A2) with the crosslinking agent (B2), it is possible to form a crosslinked body (network polymer) excellent in durability. Further, by using the crosslinking agent (B2) having an aromatic ring together with the copolymer (A2) having a photoelastic coefficient in the range of less than −200, an adhesive layer having a photoelastic coefficient in the range of −200 to +200 is obtained. Can be formed.

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

  Examples of the diisocyanate compound having 2 isocyanate groups in one molecule include aromatic diisocyanates. Examples of the aromatic diisocyanate include aromatic diisocyanates having 8 to 30 carbon atoms such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

  Examples of the isocyanate compound having 3 or more isocyanate groups in one molecule include aromatic polyisocyanates. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4 ′, 4 ″ -triphenylmethane triisocyanate.

  Examples of the crosslinking agent (B2) include multimers (for example, dimers or trimers, biurets, isocyanurates), derivatives (for example, many) of the above isocyanate compounds having 2 or more isocyanate groups. Addition reaction product of a dihydric alcohol and two or more molecules of the diisocyanate compound), and a polymer. Examples of the polyhydric alcohol in the derivative include trivalent or higher alcohols such as trimethylolpropane, glycerin and pentaerythritol as low molecular weight polyhydric alcohols; high molecular weight polyhydric alcohols such as polyether polyols, Examples include polyester polyol, acrylic polyol, polybutadiene polyol, and polyisoprene polyol.

  Examples of such an isocyanate compound include diphenylmethane diisocyanate trimer, polymethylene polyphenyl polyisocyanate, tolylene diisocyanate biuret or isocyanurate, and reaction reaction of trimethylolpropane with 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 a tolylene diisocyanate cross-linking agent and a xylylene diisocyanate cross-linking agent is preferable in that aging property and light leakage prevention property can be improved. A cross-linking agent is more preferable. Examples of tolylene diisocyanate crosslinking agents include tolylene diisocyanate and derivatives thereof, biuret bodies or isocyanurate bodies. Examples of the xylylene diisocyanate-based crosslinking agent include xylylene diisocyanate and derivatives thereof, biuret or isocyanurate. Moreover, as a commercial item, "L-45" by Soken Chemical Co., Ltd. is mentioned, for example.

A crosslinking agent (B2) may be used individually by 1 type, and may use 2 or more types.
In the second pressure-sensitive adhesive composition, the content of the crosslinking agent (B2) is usually 2 parts by mass or more, preferably 4 to 30 parts by mass with respect to 100 parts by mass of the (meth) acrylic copolymer (A2). Part, more preferably 8 to 15 parts by mass. When the content of the crosslinking agent (B2) is in the above range, even a composition containing the copolymer (A2) having a negative photoelastic coefficient can form a layer having a photoelastic coefficient of around 0. This is preferable in terms of easy balance between durability and light leakage prevention.

《Other cross-linking agents》
As long as the photoelastic coefficient of the obtained pressure-sensitive adhesive layer is within the above-mentioned range, the first and second pressure-sensitive adhesive compositions respectively contain other crosslinking agents other than the crosslinking agent (B1) or the crosslinking agent (B2). Furthermore, you may contain. For example, by using a crosslinking agent that does not greatly shift the photoelastic coefficient of the pressure-sensitive adhesive layer to the plus side together with the above-mentioned crosslinking agent, the durability is further improved while maintaining the photoelastic coefficient in the range described later. You can also.

  The other cross-linking agent is not particularly limited as long as it is a component capable of causing a cross-linking reaction with a cross-linkable functional group derived from a cross-linkable functional group-containing monomer. For example, a metal chelate compound (B3), an epoxy compound (B4) Is mentioned.

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

<Metal chelate compound (B3)>
Examples of the metal chelate compound (B3) include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium, alkoxide, acetylacetone, and ethyl acetoacetate. Examples include a coordinated compound.

  Among these, an aluminum chelate compound is particularly preferable. Specific examples include aluminum isopropylate, aluminum secondary butyrate, aluminum ethyl acetoacetate / diisopropylate, aluminum trisethyl acetoacetate, and aluminum trisacetylacetonate. Moreover, as a commercial item, "M-12AT" by Soken Chemical Co., Ltd. is mentioned, for example.

A 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 bond (pseudocrosslinking). When the metal chelate compound (B3) is further used as a cross-linking agent, the cross-linking is maintained at room temperature and the polymer exhibits cohesiveness, whereas the cross-linking is partially released at a high temperature and the pressure-sensitive adhesive layer is more excellent. Show flexibility.

<< Epoxy compound (B4) >>
As the epoxy compound (B4), an epoxy compound having 2 or more epoxy groups in one molecule is usually used. For example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N, N, N ′, N ′ -Tetraglycidyl-m-xylylenediamine, N, N, N ', N'-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, m-N, N-diglycidylaminophenyl glycidyl ether, N, N-diglycidyl Examples include toluidine and N, N-diglycidylaniline. Moreover, as a commercial item, "E-5C" by Soken Chemical Co., Ltd. is mentioned, for example.

[Silane coupling agent (C)]
The pressure-sensitive adhesive composition of the present invention preferably further contains a silane coupling agent (C). A silane coupling agent (C) contributes to the point which adheres an adhesive layer firmly to adherends, such as a glass plate, and prevents peeling of a polarizing plate in a high-humidity heat environment.

  Examples of the silane coupling agent (C) include polymerizable unsaturated group-containing silane coupling agents such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane Epoxy groups such as 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Containing silane coupling agent; amino such as 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane Group-containing silane coupling Agent; 3- halogen-containing silane coupling agents such as chloropropyltrimethoxysilane, 3-oxobutanoate 3- (trimethoxysilyl) propyl and the like. Moreover, as a commercial item, "A-50" 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 0.8 parts per 100 parts by mass of the (meth) acrylic copolymer (A). It is 01-1 mass part, More preferably, it is 0.05-0.5 mass part. When the content is in the above range, peeling of the polarizing plate in a high humidity environment and bleeding of the silane coupling agent (C) in a high temperature environment tend to be prevented.

[Antistatic agent (D)]
The antistatic agent (D) can be used, for example, 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 a surfactant, an ionic compound, and a conductive polymer.

  Examples of the surfactant include quaternary ammonium salts, amide quaternary ammonium salts, pyridium salts, cationic surfactants having a cationic group such as primary to tertiary amino groups; sulfonate groups, sulfate esters Anionic surfactants having an anionic group such as a base or a phosphate ester base; amphoteric surfactants such as alkylbetaines, alkylimidazolinium betaines, alkylamine oxides, amino acid sulfates, glycerin fatty acid esters Nonionic surfactants such as sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines, and alkyldiethanolamides It is done.

  Moreover, the reactive type emulsifier which has a polymeric group is also mentioned as surfactant, The polymeric surfactant which made high molecular weight the monomer component containing said surfactant or reactive emulsifier can also be used.

The ionic compound is composed of a cation part and an anion part, and may be either solid or liquid at room temperature (23 ° C./50% RH).
The cation portion constituting the ionic compound may be either an inorganic cation or an organic cation, or both. As the inorganic cation, alkali metal ions and alkaline earth metal ions are preferable, and Li ⁺ , Na ⁺ and K ⁺ having excellent antistatic properties are more preferable. Examples of the organic cation include pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, pyrazolium cation, pyrazoli Examples thereof include a nium cation, a tetraalkylammonium cation, a trialkylsulfonium cation, a tetraalkylphosphonium cation, and derivatives thereof.

The anion moiety constituting the ionic compound is not particularly limited as long as it can form an ionic compound by ionic bonding with the cation moiety. 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, an anion containing a fluorine atom is preferable because it gives an ionic compound having a low melting point, and (F ₂ SO ₂ ) ₂ N ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ are particularly preferable.

  Examples of the ionic compound include lithium bis (trifluoromethanesulfonyl) imide, lithium bis (difluorosulfonyl) imide, lithium tris (trifluoromethanesulfonyl) methane, potassium bis (trifluoromethanesulfonyl) imide, potassium bis (difluorosulfonyl) imide, 1 -Ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium bis (fluoro Sulfonyl) imide, 1-octyl-4-methylpyridinium bis (trifluoromethanesulfonyl) imide, tributylmethyla Monium bis (fluorosulfonyl) imide, tributylmethylammonium bis (trifluoromethanesulfonyl) imide, (N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate, N, N-diethyl-N- Methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide, 1-octylpyridinium fluorosulfonium imide, and 1-octyl-3-methylpyridinium trifluorosulfonium imide 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 parts per 100 parts by mass of the (meth) acrylic copolymer (A). -3 parts by mass, more preferably 0.05-2.5 parts by mass.

[Organic solvent (E)]
The pressure-sensitive adhesive composition of the present invention preferably contains an organic solvent (E) in order to adjust its applicability. As an organic solvent, the solvent illustrated as a polymerization solvent in the column of the manufacturing conditions of a (meth) acrylic-type copolymer (A) is mentioned. For example, the pressure-sensitive adhesive composition can be prepared by mixing the polymer solution containing the (meth) acrylic copolymer (A) and the polymerization solvent obtained by the above copolymerization and the crosslinking agent (B). it can. 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 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 pressure-sensitive adhesive composition 100. The ratio of the said solid content with respect to the mass% is said.

[Additive]
In addition to the above components, the pressure-sensitive adhesive composition of the present invention includes an antioxidant, a light stabilizer, a metal corrosion inhibitor, a tackifier, a plasticizer, a crosslinking accelerator, You may contain the 1 type (s) or 2 or more types selected from the (meth) acrylic-type polymer and rework agents other than A).

[Preparation of pressure-sensitive adhesive composition for polarizing plate]
The pressure-sensitive adhesive composition of the present invention is prepared by mixing the (meth) acrylic copolymer (A), the cross-linking agent (B), and other components as required by a conventionally known method. Can do. For example, the cross-linking agent (B) and, if necessary, other components may be added to the polymer solution containing the polymer obtained when the (meth) acrylic copolymer (A) is synthesized. It is done.

Using the pressure-sensitive adhesive composition of the present invention, a pressure-sensitive adhesive layer is formed on a polarizing plate having a polarizer protective film on only one side of the polarizer and on a polarizing plate having no polarizer protective film on both sides of the polarizer. In this case, the light leakage phenomenon can be suppressed. In the present invention, even when the pressure-sensitive adhesive layer is in direct contact with the polarizer, tearing of the pressure-sensitive adhesive layer, peeling of the polarizing plate, and the like can be suppressed under a high temperature and high humidity environment.
The said composition is suitable for the bonding application of the board | substrate and polarizer which comprise a liquid crystal cell.

[Adhesive layer for polarizing plate]
The 1st adhesive layer for polarizing plates of this invention is formed from the above-mentioned 1st adhesive composition. The 2nd adhesive layer for polarizing plates of this invention is formed from the above-mentioned 2nd adhesive composition. 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, and further preferably −70 to +70. The unit of the photoelastic coefficient is “× 10 ⁻¹² m ² / N”.

  The photoelastic coefficient is measured at a measurement wavelength of 633 nm, for example, by laminating the adhesive layers a plurality of times to produce a laminate having a thickness of about 1.0 mm. Details of the measurement conditions are as described in the examples.

  Since the pressure-sensitive adhesive layer of the present invention has the above characteristics, it is excellent in light leakage prevention property under a high temperature and high humidity heat environment. Moreover, since the adhesive layer of this invention is excellent in durability, it is hard to generate | occur | produce tearing of an adhesive layer and peeling of the adhesive layer from a polarizing plate.

  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, and further preferably from the viewpoints of distortion suppression of the polarizing plate, cohesive force, adhesive strength, and removability. Is 60-95 mass%. When the gel fraction is in the above range, the pressure-sensitive adhesive layer exhibits excellent durability. Details of the measurement conditions are as described in the examples.

  The pressure-sensitive adhesive layer of the present invention specifically cross-links the (meth) acrylic copolymer (A) with the cross-linking agent (B) by, for example, advancing the crosslinking reaction in the above-mentioned pressure-sensitive adhesive composition. Is obtained.

  The conditions for forming the pressure-sensitive adhesive layer are, for example, as follows. Although the adhesive composition of this invention is apply | coated on a support body and it changes also with kinds of solvent, it is 50-150 degreeC normally, Preferably it is 60-100 degreeC, Usually, 1-10 minutes, Preferably it is 2-7. Dry for minutes to remove the solvent and form a coating. The film thickness of the coated film after drying 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 in the above range. The film thickness can be measured by, for example, a dial thickness gauge.

  The pressure-sensitive adhesive layer is preferably formed 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-mentioned conditions, and applying a cover film on the coating film as necessary, it is usually 3 days or more, preferably 7 to It is cured for 10 days under an environment of usually 5 to 60 ° C., preferably 15 to 40 ° C., usually 30 to 70% RH, preferably 40 to 70% RH. When crosslinking is performed under the aging conditions as described above, a crosslinked body (network polymer) can be efficiently formed.

  As a method for applying the pressure-sensitive adhesive composition, a predetermined thickness is obtained by a known method such as spin coating, knife coating, roll coating, bar coating, blade coating, die coating, or gravure coating. The method of apply | coating 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.

[Plastic adhesive sheet]
The pressure-sensitive adhesive sheet for polarizing plates 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 base material, and a double-sided pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed on both surfaces of the base material, the base material, and one of the base materials. Examples thereof include a single-sided pressure-sensitive adhesive sheet having the above-mentioned pressure-sensitive adhesive layer formed on the surface, and a pressure-sensitive adhesive sheet having a peel-treated cover film attached to the surface of the pressure-sensitive adhesive sheet that is not in contact with the base material.

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

The conditions for forming the pressure-sensitive adhesive layer are the same as the conditions described in the column [Plastic pressure-sensitive adhesive layer].
The 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. Although the film thickness of a base material and a cover film is not specifically limited, Usually, it is 10-125 micrometers, Preferably it is 25-75 micrometers.

[Polarizing plate with adhesive layer]
The polarizing plate with an adhesive layer of this invention has a polarizer and the adhesive layer formed from the adhesive composition of this invention directly laminated | stacked on the at least one surface of the said polarizer. In this specification, “polarizing plate” is used to include “polarizing film”.

  A conventionally well-known polarizing film can be used as a polarizing plate. For example, the multilayer film which has polarizer itself, a polarizer, and the polarizer protective film arrange | positioned on a polarizer is mentioned. In the present invention, since the pressure-sensitive adhesive layer is disposed in direct contact with the polarizer, for example, the polarizer protective film is disposed only on one surface of the polarizer, and the polarizer protective film is not disposed on the other surface. The structure and the structure by which the polarizer protective film is not arrange | positioned on both surfaces of a polarizer are mentioned.

  As a polarizer, the stretched film obtained by making a film which consists of polyvinyl alcohol-type resins contain a polarizing component, and extending | stretching is mentioned, for example. Examples of the polyvinyl alcohol-based resin include polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, and a saponified product of an ethylene-vinyl acetate copolymer. Examples of the polarization component include iodine or a dichroic dye.

  Examples of the polarizer protective film include a film made of a thermoplastic resin. Examples of the thermoplastic resin include cellulose resin such as triacetyl cellulose, polyester resin, polyethersulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, (meth) acrylic resin, cyclic polyolefin resin (norbornene) Resin), polyarylate resin, polystyrene resin, polyvinyl alcohol resin, and a mixture 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 this invention, since the polarizer protective film formed on a polarizer can be abbreviate | omitted, a polarizing plate can be reduced in thickness.

  In the present invention, the pressure-sensitive adhesive layer is formed in direct contact with the polarizer. As a polarizing plate with an adhesive layer of the present invention, for example, a polarizer protective film, a polarizer, and the adhesive layer are laminated in this order, the adhesive layer, the polarizer protective film, the polarizer, and the above The structure by which the adhesive layer was laminated | stacked in this order, the structure by which the said adhesive layer, the polarizer, and the said adhesive layer were laminated | stacked in this order are mentioned. In these structures, the cover film mentioned above may be arrange | positioned as an outermost layer on the adhesive layer.

  There is no restriction | limiting in particular in the method of forming an adhesive layer in the polarizer surface, The method of apply | coating the said adhesive composition on a polarizer surface, drying and aging, Polarizing the adhesive layer which the adhesive sheet for polarizing plates of this invention has is polarized. Examples include a method of pasting or transferring to a child surface and aging. The conditions for drying and aging, the range of the gel fraction, and the like are the same as the conditions described in the section of [PSA layer for polarizing plate].

  The thickness of the pressure-sensitive adhesive layer is usually 5 to 75 μm, preferably 10 to 50 μm. The pressure-sensitive adhesive layer only needs to be formed in contact with the polarizer on at least one surface of the polarizer, and the pressure-sensitive adhesive layer is formed only on one side of the polarizer, and the pressure-sensitive adhesive is formed on both sides of the polarizer. The aspect in which a layer is formed is mentioned.

Moreover, the layer which has other functions, such as a protective layer, a glare-proof layer, a phase difference layer, a viewing angle improvement layer, for example may be laminated | stacked on the said polarizing plate.
A liquid crystal element is produced by providing the polarizing plate with the pressure-sensitive adhesive layer of the present invention obtained as described above on the substrate surface of the liquid crystal cell. Here, the liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates. An example of the substrate that the liquid crystal cell has is a glass plate. The thickness of the substrate is usually 0.05 to 3 mm, preferably 0.2 to 1 mm.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples. In the following description of Examples and the like, “part” means “part by mass” unless otherwise specified.

[GPC]
About the (meth) acrylic-type copolymer, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were calculated | required on condition of the following by the gel permeation chromatography method (GPC method).
-Measuring 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: 1.0 mL / min
-Column temperature: 40 ° C
Sample concentration: 1.5% (w / v) (diluted with tetrahydrofuran)
・ Mobile phase solvent: Tetrahydrofuran ・ Standard polystyrene conversion

[Photoelastic coefficient]
For the (meth) acrylic copolymer, the photoelastic coefficient was measured as follows.
The polymer solution containing the (meth) acrylic copolymer obtained in the synthesis example was applied to the release-treated surface of the release-treated polyethylene terephthalate film, dried at 90 ° C. for 3 minutes, and a dry film thickness of 20 μm. A coating film (polymer layer) was formed. Polymer layers with a dry film thickness of 20 μm were bonded together in an environment of 23 ° C./50% RH multiple times and treated with an autoclave adjusted to 50 ° C./5 atm for 20 minutes to produce a polymer layer with a thickness of 1.0 mm. . A polymer layer having a thickness of 1.0 mm is cut into a size of 15 mm × 50 mm, and this is attached to an automatic wavelength scanning ellipsometer (model “M-220”, manufactured by JASCO Corporation) using a jig, Retardation was measured at a measurement wavelength of 633 nm while changing the stress. The slope of the straight line when the stress is taken on the horizontal axis and the retardation is taken on the vertical axis was taken as the photoelastic coefficient of the (meth) acrylic copolymer.

[Synthesis Example 1]
In a reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, 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 ethyl acetate solvent was charged, and the temperature was raised to 80 ° C. while introducing nitrogen gas. Next, 0.1 part of 2,2′-azobisisobutyronitrile was added, and a polymerization reaction was performed at 80 ° C. for 6 hours in a nitrogen gas atmosphere. 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 obtained (meth) acrylic copolymer 1 has a weight average molecular weight (Mw) of 800,000, a molecular weight distribution (Mw / Mn) of 7.5, and a photoelastic coefficient of −58 × 10 ⁻¹² ( m ² / N).

[Synthesis Examples 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 components used in the polymerization reaction were changed as described in Table 1. The results are shown in Table 1.

[Example A1]
(1) Preparation of pressure-sensitive adhesive composition Based on the polymer solution obtained in Synthesis Example 1 (solid content concentration of 30% by mass) and 100 parts (solid content) of (meth) acrylic copolymer 1 contained in the solution As the isocyanate compound, 2.0 parts (solid content) of “D-94” manufactured by Soken Chemical Co., Ltd. and 0.2 part (solid content) of “M-12AT” manufactured by Soken Chemical Co., Ltd. as the metal chelate compound, As a silane coupling agent, 0.2 part of “A-50” (solid content: 100% by mass) manufactured by Soken Chemical Co., Ltd. was mixed to obtain an adhesive composition.

(2) Preparation of pressure-sensitive adhesive sheet On the polyethylene terephthalate film (PET film) subjected to release treatment, the pressure-sensitive adhesive composition obtained in the above (1) was applied using a doctor blade after removing bubbles, and at 90 ° C. The film was dried for 3 minutes to form a coating film having a dry film thickness of 20 μm. Two PET films were obtained by further laminating the peeled PET film on the surface of the coating film opposite to the surface on which the PET film was applied, and leaving it to stand for aging in a 23 ° C./50% RH environment for 7 days. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 20 μm sandwiched between the layers was obtained.

(3) Preparation of polarizing plate with pressure-sensitive adhesive layer On the peeled polyethylene terephthalate film (PET film), the pressure-sensitive adhesive composition obtained in (1) above was applied using a doctor blade after removing bubbles. And dried at 90 ° C. for 3 minutes to obtain a sheet having a coating film having a dry film thickness of 20 μm. The coating film surface of the sheet is in contact with the polyvinyl alcohol film surface of the polarizing plate having a two-layer structure (thickness 60 μm) composed of a polyvinyl alcohol film as a polarizer and a triacetyl cellulose film as a polarizer protective film. A polarizing plate with an adhesive layer having a PET film, an adhesive layer having a thickness of 20 μm, a polarizer, and a polarizer protective film, which is allowed to stand for aging at 23 ° C./50% RH for 7 days. Got.

[Examples B1 and B2, Comparative Examples A1 and A2, B1 and B3]
In Example A1, the adhesive composition was changed 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 blending composition was changed as shown in Table 2. Thing, the adhesive sheet, and the polarizing plate with an adhesive layer were obtained.

[Evaluation]
[Gel fraction]
From the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, about 0.1 g of pressure-sensitive adhesive was collected in a sampling bottle, 30 mL of ethyl acetate was added, and the mixture was shaken for 4 hours. The mixture was filtered through a mesh stainless steel wire mesh, the residue on the wire mesh was dried at 100 ° C. for 2 hours, and the dry weight was measured. The gel fraction of the pressure-sensitive adhesive was determined by the following formula.
Gel fraction (%) = (Dry weight / Adhesive sampling weight) × 100 (%)

[Photoelastic coefficient]
In the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, the PET film was peeled off, and the pressure-sensitive adhesive layers having a thickness of 20 μm were bonded together in a 23 ° C./50% RH environment several times, and adjusted to 50 ° C./5 atm. It processed for 20 minutes by the autoclave and produced the 1.0-mm-thick adhesive layer. A 1.0 mm thick adhesive layer is cut to a size of 15 mm × 50 mm and attached to an automatic wavelength scanning ellipsometer (model “M-220”, manufactured by JASCO Corporation) using a jig. The retardation was measured at a measurement wavelength of 633 nm while changing the stress. The slope of the straight line when the stress is taken on the horizontal axis and the retardation is taken on the vertical axis was taken as the photoelastic coefficient of the pressure-sensitive adhesive layer.

[Light leakage test]
Two polarizing plates with adhesive (PET film / adhesive layer / polarizer / polarizer protective film laminate) obtained in Examples and Comparative Examples were cut into a size of 310 mm × 385 mm and tested. Created a piece. The PET film is peeled from the test piece, and a laminate composed of an adhesive layer / polarizer / polarizer protective film is laminated on both sides of a 0.5 mm thick glass plate using a laminator roll so that the polarization axes are orthogonal to each other. And it stuck so that an adhesive layer and a glass plate might contact | connect. The obtained laminate was held in an autoclave adjusted to 50 ° C./5 atm for 20 minutes to prepare a test plate. This test plate was allowed to stand for 500 hours under the condition 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 was slightly observed CC: Light leakage was clearly observed

[Durability Test (Heat and Moisture Resistance Test)]
The polarizing plate with a pressure-sensitive adhesive layer obtained in the examples and comparative examples (laminated body composed of PET film / pressure-sensitive adhesive layer / polarizer / polarizer protective film) was cut into a size of 150 mm × 250 mm, and the test piece was cut. Created. The PET film is peeled from the test piece, and a laminate composed of an adhesive layer / polarizer / polarizer protective film is laminated on one side of a 0.5 mm thick glass plate using a laminator roll. I stuck it so that it touched. The obtained laminate was held in an autoclave adjusted to 50 ° C./5 atm for 20 minutes to prepare a test plate. Two similar test plates were prepared. The test plate is allowed to stand for 500 hours under conditions of a temperature of 80 ° C./dry (heat resistance) or a temperature of 60 ° C./humidity of 90% RH (moisture heat resistance), and defects (foaming, floating, peeling off) according to the following criteria: ) Was evaluated.
AA: No defect BB: Defect area is 5% or less, no problem in practical use CC: Defect area exceeds 5%, there is a problem in practical use

D-94: hexamethylene diisocyanate crosslinking agent
(Soken Chemical Co., Ltd., solid content 90% by mass)
L-45: Tolylene diisocyanate crosslinking agent (manufactured by Soken Chemical Co., Ltd., solid content 45% by mass, ethyl acetate / toluene solution)
・ E-5C: Epoxy crosslinking agent
(Soken Chemical Co., Ltd., solid content 5 mass%)
M-12AT: Aluminum chelate crosslinker (manufactured by Soken Chemical Co., Ltd., solid content: 10% by mass, toluene / acetylacetone solution)
A-50: Silane coupling agent
(Soken Chemical Co., Ltd., solid content 50 mass%, toluene solution)

Claims (10)

(Meth) acrylic acid alkyl ester (a11) derived constituent units of the homopolymer of photoelastic coefficient of ^{-1000 × 10 -12 ~-100 ×} 10 -12 (m 2 / N), and the photoelastic coefficient of the homopolymer The photoelastic coefficient is −200 × 10 ⁻¹² to + 200 × having a structural unit derived from an aromatic ring-containing (meth) acrylic acid ester (a12) of + 500 × 10 ⁻¹² to + 2000 × 10 ⁻¹² (m ² / N). 10 ⁻¹² (m ² / N) (meth) acrylic copolymer (A1);
Formed from an adhesive composition containing an isocyanate-based crosslinking agent (B1) having no aromatic ring,
The photoelastic coefficient is −200 × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N),
A pressure-sensitive adhesive layer for polarizing plates, which is disposed in direct contact with a polarizer.   The pressure-sensitive adhesive layer for a polarizing plate according to claim 1, wherein the isocyanate-based crosslinking agent (B1) is a hexamethylene diisocyanate-based crosslinking agent.   The pressure-sensitive adhesive for polarizing plates according to claim 1 or 2, 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). layer. 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. Formed from things,
The photoelastic coefficient is −200 × 10 ⁻¹² to + 200 × 10 ⁻¹² (m ² / N),
A pressure-sensitive adhesive layer for polarizing plates, which is disposed in direct contact with a polarizer.   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 a tolylene diisocyanate-based crosslinking agent and a xylylene diisocyanate-based crosslinking agent.   The pressure-sensitive adhesive layer for a polarizing plate according to claim 4 or 5, 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 an adhesive layer of any one of Claims 1-6.   The polarizing plate with an adhesive layer which has a polarizer and the adhesive layer of any one of Claims 1-6 directly laminated | stacked on the at least one surface of the said polarizer. (Meth) acrylic acid alkyl ester (a11) derived constituent units of the homopolymer of photoelastic coefficient of ^{-1000 × 10 -12 ~-100 ×} 10 -12 (m 2 / N), and the photoelastic coefficient of the homopolymer The photoelastic coefficient is −200 × 10 ⁻¹² to + 200 × having a structural unit derived from an aromatic ring-containing (meth) acrylic acid ester (a12) of + 500 × 10 ⁻¹² to + 2000 × 10 ⁻¹² (m ² / N). 10 ⁻¹² (m ² / N) (meth) acrylic copolymer (A1);
Containing an isocyanate-based crosslinking agent (B1) having no aromatic ring,
The adhesive composition for polarizing plates used in order to form the adhesive layer of 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 adhesive composition for polarizing plates used in order to form the adhesive layer of Claim 4.