JP2015205974A - Adhesive composition for polarizing plate, adhesive sheet, polarizing plate with adhesive layer, and laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition for a polarizing plate, from which such an adhesive layer can be formed that can suppress warpage (bending) of a liquid crystal cell even when a glass sheet as an adherend has a thickness of 0.5 mm or less, and that has excellent durability and prevents leakage of light with time.SOLUTION: The adhesive composition for a polarizing plate comprises: (A) a (meth)acrylic copolymer obtained by copolymerizing a monomer component including a monomer (a1) having an active hydrogen-containing functional group and a (meth)acrylate (a2) having no active hydrogen-containing functional group; (B) a (meth)acrylic copolymer obtained by copolymerizing a monomer component including a monomer (b1) having an isocyanate group and a (meth)acrylate (b2) having neither isocyanate group nor active hydrogen-containing functional group; and (C) a silane coupling agent. The composition is used for bonding a polarizing plate and a glass sheet having a thickness of 0.5 mm or less.

Description

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

  The liquid crystal cell has a structure in which a liquid crystal layer is sandwiched between two substrates (for example, a glass plate), and a polarizing plate is attached to the surface of the substrate via an adhesive layer. A polarizing plate is likely to be thermally contracted in a high temperature and high humidity environment, so that it lacks dimensional stability and may cause warpage in a liquid crystal cell. In recent years, with the thinning of liquid crystal cells (eg, thinning of the substrate constituting the liquid crystal cell) and the thinning of the polarizing plate, the warpage of the liquid crystal cell under a high temperature and high humidity environment has become a larger problem. As a cause of the warp of the liquid crystal cell, for example, the pressure-sensitive adhesive layer cannot follow the thermal contraction (dimensional change) of the polarizing plate, and the stress relaxation property of the pressure-sensitive adhesive layer is low.

  In general, as a means for suppressing the warpage of the liquid crystal cell, there is a method of using a highly flexible pressure-sensitive adhesive layer that can cope with a dimensional change of the polarizing plate. However, such a pressure-sensitive adhesive layer has insufficient cohesive force and causes problems such as deterioration of durability and deterioration of workability.

  For example, Patent Document 1 provides a pressure-sensitive adhesive layer for an optical member that is excellent in durability under a severe condition for a long period of time, a stress relaxation property due to a dimensional change of the optical member (warping of the optical member), and workability. It is disclosed that the storage elastic modulus at 23 ° C. and 80 ° C. is set to a specific range by crosslinking a layer composed of a pressure-sensitive adhesive layer containing a (meth) acrylic polymer and a peroxide. Yes.

  However, in the above publication, the peroxide remaining in the pressure-sensitive adhesive layer causes a crosslinking reaction to progress over time, and the physical properties of the pressure-sensitive adhesive change. This causes a problem that the pressure-sensitive adhesive deteriorates with time because it decomposes and generates radicals. For this reason, the method of suppressing the curvature of a liquid crystal cell without containing a peroxide is desired.

  With respect to the problem of the peroxide, Patent Document 2 discloses a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive and a specific amount of a curing agent. In the above publication, it is described that the shrinkage stress of the triacetyl cellulose base material can be relaxed and the warpage of the glass base material can be reduced without using a peroxide.

  However, in recent years, thinning of liquid crystal cells and polarizing plates has been desired, and it is considered that the stress relaxation characteristics at high temperatures are still insufficient with the method described in Patent Document 2 for such problems. In particular, even when the thickness of the substrate, which is an adherend, is 0.5 mm or less, it is possible to form a pressure-sensitive adhesive layer that can suppress warping (bending) of the liquid crystal cell and is excellent in light leakage prevention. A polarizing plate pressure-sensitive adhesive composition is desired.

  Moreover, in a high temperature and high humidity environment, problems such as foaming at the interface between the polarizing plate and the substrate, tearing of the pressure-sensitive adhesive layer, and peeling of the polarizing plate are likely to occur. Therefore, high durability is requested | required of the adhesive for polarizing plates.

Japanese Patent No. 4993245 JP 2012-057130 A

  The object of the present invention is to suppress the bending (bending) of the liquid crystal cell even when the thickness of the glass plate as the adherend is 0.5 mm or less, and is excellent in durability and preventing light leakage over time. A pressure-sensitive adhesive composition for a polarizing plate capable of forming an excellent pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet for a polarizing plate having a pressure-sensitive adhesive layer formed from the composition, and a polarized light with a pressure-sensitive adhesive layer having the pressure-sensitive adhesive layer It is in providing a board and a laminated body.

  The present inventors diligently studied to solve the above problems. As a result, when a specific (meth) acrylic copolymer is used as a crosslinking agent and a silane coupling agent is used in combination with a (meth) acrylic copolymer, the warping (bending) of the liquid crystal cell is reduced. It was found that a pressure-sensitive adhesive layer that can be suppressed, has excellent durability, and has excellent light leakage prevention properties over time 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 composition having the following specific configuration, and have completed the present invention.

The present invention includes, for example, the following [1] to [6].
[1] (A) obtained by copolymerizing a monomer component containing a monomer (a1) having an active hydrogen-containing functional group and a (meth) acrylic acid ester (a2) having no active hydrogen-containing functional group (meta ) Copolymerizing an acrylic copolymer and a monomer component containing (B) a monomer (b1) having an isocyanate group and a (meth) acrylic acid ester (b2) having no isocyanate group and no active hydrogen-containing functional group. A polarizing plate characterized in that it comprises (meth) acrylic copolymer and (C) a silane coupling agent, and is used for pasting a polarizing plate and a glass plate having a thickness of 0.5 mm or less. Adhesive composition for board.

  [2] The pressure-sensitive adhesive for polarizing plates according to [1], wherein the copolymer (B) has a molecular weight distribution (Mw / Mn) measured by a gel permeation chromatography method (GPC method) of 3 to 50. Agent composition.

[3] The pressure-sensitive adhesive composition for polarizing plates according to the above [1] or [2], wherein the gel fraction of the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition for polarizing plates is 20 to 80% by mass.
[4] A pressure-sensitive adhesive sheet for polarizing plates, comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for polarizing plates according to any one of [1] to [3].

  [5] Having a polarizing plate and an adhesive layer formed from the adhesive composition for polarizing plates according to any one of [1] to [3] on at least one surface of the polarizing plate. A polarizing plate with an adhesive layer.

  [6] A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to any one of [1] to [3] between a polarizing plate and a glass plate having a thickness of 0.5 mm or less. A laminate characterized by comprising:

  According to the present invention, even when the thickness of the glass plate as the adherend is 0.5 mm or less, the warping (bending) of the liquid crystal cell can be suppressed, the durability is excellent, and the light leakage prevention property with time With a pressure-sensitive adhesive composition for a polarizing plate capable of forming an excellent pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet for a polarizing plate having a pressure-sensitive adhesive layer formed from the composition, and a pressure-sensitive adhesive layer having the pressure-sensitive adhesive layer A polarizing plate and a laminate can be provided.

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

  In the present specification, active hydrogen means hydrogen bonded to an atom other than carbon atom (eg, oxygen atom, nitrogen atom) contained in a hydroxyl group, amino group, amide group, carboxyl group, etc. capable of reacting with an isocyanate group. An atom. The functional group having active hydrogen is also referred to as “active hydrogen-containing functional group”.

  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”.

[Adhesive composition for polarizing plate]
The pressure-sensitive adhesive composition for polarizing plates of the present invention comprises a (meth) acrylic copolymer (A) and a (meth) acrylic copolymer (B) described below, and a silane coupling agent (C). Containing. The pressure-sensitive adhesive composition may contain at least one selected from an antistatic agent (D) and an organic solvent (E) as necessary.

  In the present invention, the copolymer (A) is crosslinked with the copolymer (B) as a crosslinking agent and further used in combination with a silane coupling agent (C), so that (1) room temperature (example: 23 ° C.) Has a high storage elastic modulus, and (2) because of the use of a high molecular weight cross-linking agent, the cross-linking chain is long. It is possible to form a pressure-sensitive adhesive layer that is excellent in preventing light leakage over time and excellent in durability. Further, problems such as bleeding of the low molecular weight crosslinking agent can be avoided, and the light leakage prevention property can be improved.

[(Meth) acrylic copolymer (A)]
The (meth) acrylic copolymer (A) comprises a monomer component containing a monomer (a1) having an active hydrogen-containing functional group and a (meth) acrylic acid ester (a2) having no active hydrogen-containing functional group. It is a copolymer obtained by copolymerization. Hereinafter, (meth) acrylic acid ester (a2) is also referred to as “monomer (a2)”.

  By using the monomer (a1) having an active hydrogen-containing functional group as the monomer component constituting the copolymer (A), the active hydrogen that becomes a crosslinking point that can be crosslinked by the copolymer (B) used as a crosslinking agent. Can be introduced into the copolymer (A).

<< Monomer (a1) >>
Examples of the active hydrogen-containing functional group in the monomer (a1) include a hydroxyl group, an amino group, an amide group, and a carboxyl group. It is presumed that a crosslinked structure is formed by the reaction between the active hydrogen-containing functional group introduced into the copolymer (A) and the isocyanate group introduced into the copolymer (B).

  As the monomer (a1), for example, a radical polymerizable monomer having an active hydrogen-containing functional group is used. Specific examples include hydroxyl group-containing monomers, amino group-containing monomers, (meth) acrylamides, and carboxyl group-containing monomers.

  Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl ( Examples include hydroxyl-containing (meth) acrylates such as hydroxyalkyl (meth) acrylates such as (meth) acrylate. Carbon number of the hydroxyalkyl group in hydroxyalkyl (meth) acrylate is 2-8 normally, Preferably it is 2-6.

  Examples of the amino group-containing monomer include monoalkylaminoalkyl (meth) acrylate such as monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, and monoethylaminopropyl (meth) acrylate. ) Amino group-containing (meth) acrylates such as acrylate. Carbon number of the monoalkylaminoalkyl group in monoalkylaminoalkyl (meth) acrylate is 2-10 normally, Preferably it is 2-6.

  Examples of (meth) acrylamides include N-methyl (meth) acrylamide; N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-hexyl (meth) acrylamide and the like. Monoalkyl substituted acrylamides may be mentioned. Carbon number of the said alkyl group in N-monoalkyl substituted acrylamide is 1-10 normally, Preferably it is 1-4.

  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. And (meth) acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and other ethylenically unsaturated carboxylic acids.

A monomer (a1) may be used individually by 1 type, and may use 2 or more types.
As the monomer (a1), it is preferable to use at least a hydroxyl group-containing monomer from the viewpoint of realizing the adhesive strength suitable for the reactivity with the isocyanate group contained in the copolymer (B) and the reworkability. The amount of the hydroxyl group-containing monomer used in 100% by mass of the monomer (a1) is preferably 20 to 100% by mass, more preferably 30 to 100% by mass, and further preferably 40 to 100% by mass.

  In 100% by mass of the monomer component forming the copolymer (A), the amount of the monomer (a1) used is preferably 0.1 to 15% by mass from the viewpoint of durability due to appropriate crosslinking and expression of stress relaxation characteristics. More preferably, it is 0.1-10 mass%, More preferably, it is 0.1-5 mass%. When the amount of the monomer (a1) used is not more than the above upper limit value, the crosslink density formed by the copolymer (A) and the copolymer (B) does not become too high, and the pressure-sensitive adhesive layer has excellent stress relaxation properties. Is obtained. When the usage-amount of a monomer (a1) is more than the said lower limit, a crosslinked structure is formed effectively and the adhesive layer which has appropriate intensity | strength at normal temperature is obtained.

<< (Meth) acrylic acid ester (a2) >>
The no active hydrogen-containing functional group (meth) acrylic acid ester (a2), for ^{_{example, CH 2 = C (R 1}} ) a compound represented by -COO-R ² can be mentioned. In the above formula, R ¹ is a hydrogen atom or a methyl group, and R ² is a substituent having no active hydrogen-containing functional group.

Here, the number of carbon atoms of the substituents R ² to form an ester moiety, typically from 1 to 20, preferably from 1 to 18. Examples of the substituent R ² include an alkyl group, an alkoxyalkyl group, a cycloalkyl group, an aryl group, an aralkyl group, and an alkoxy polyalkylene glycol group.

  Specifically, (meth) acrylic acid alkyl ester, (meth) acrylic acid alkoxyalkyl ester, (meth) acrylic acid cycloalkyl ester, (meth) acrylic acid aryl ester, (meth) acrylic acid aralkyl ester, alkoxy polyalkylene Examples include glycol mono (meth) acrylate.

  Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). Acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl ( Examples include meth) acrylate, decyl (meth) acrylate, undeca (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and isostearyl (meth) acrylate.Carbon number of an alkyl group becomes like this. Preferably it is 1-18, More preferably, it is 1-12.

  Examples of (meth) acrylic acid alkoxyalkyl esters include methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, and 3-ethoxy. Examples include propyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, and 4-ethoxybutyl (meth) acrylate.

  Examples of (meth) acrylic acid cycloalkyl ester, (meth) acrylic acid aryl ester, and (meth) acrylic acid aralkyl ester include cyclohexyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (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.

A monomer (a2) may be used individually by 1 type, and may use 2 or more types.
As the monomer (a2), it is preferable to use at least a (meth) acrylic acid alkyl ester from the viewpoint of developing basic physical properties as an adhesive. In 100% by mass of the monomer (a2), the amount of the (meth) acrylic acid alkyl ester is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, and further preferably 70 to 100% by mass.

  In 100% by mass of the monomer component forming the copolymer (A), the amount of the monomer (a2) used is preferably 85 to 99.9% by mass, more preferably from the viewpoint of good adhesive strength and durability expression. It is 90-99.9 mass%, More preferably, it is 95-99.9 mass%.

<< Other monomer (a3) >>
As the monomer component for forming the copolymer (A), other monomers may be used as desired in addition to the monomers (a1) and (a2). Examples of other monomers used as desired include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene Styrene monomers such as α-methylstyrene; diene monomers such as butadiene, isoprene and chloroprene; nitrile monomers such as (meth) acrylonitrile; N, N-dimethylacrylamide, N, N-dimethylmethacrylamide and the like N, N-dialkyl-substituted acrylamide may be mentioned.

A monomer (a3) may be used individually by 1 type, and may use 2 or more types.
In 100% by mass of the monomer component forming the copolymer (A), the amount of the monomer (a3) used is preferably 14.9% by mass or less, more preferably 9.9% by mass or less, and further preferably 4.9. It is below mass%.

<< Physical properties and content of copolymer (A) >>
The weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) method of the copolymer (A) is a polystyrene conversion value, and is usually 800,000 to 2,500,000, preferably 800,000 to 2,000,000. More preferably, it is 800,000 to 1,800,000. When Mw is equal to or greater than the lower limit, sufficient adhesion durability tends to be obtained. When Mw is equal to or less than the upper limit value, the followability to the thermal contraction of the polarizing plate tends to be ensured.

  The molecular weight distribution (Mw / Mn) of the copolymer (A) measured by the GPC method is usually 4 to 20, preferably 4 to 13, and more preferably 4 to 7. When the molecular weight distribution is less than or equal to the above upper limit value, when it is cross-linked with the (meth) acrylic copolymer (B), it tends to be excellent in light leakage prevention property over time by expressing appropriate elasticity.

The glass transition temperature (Tg) of the copolymer (A) can be calculated by, for example, the Fox formula from the monomer units constituting the polymer and the content ratio thereof. For example, the copolymer (A) can be synthesized so that the glass transition temperature (Tg) determined by the Fox equation is usually −80 to −0 ° C., preferably −60 to −10 ° C. By using the copolymer (A) having such a glass transition temperature (Tg), it is possible to obtain a pressure-sensitive adhesive composition having excellent adhesiveness at room temperature.
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 of the copolymer (A), Tg ₁ , Tg ₂ ,..., Tg _m are the glass transition temperatures of homopolymers composed of the respective monomers, and W ₁ , W ₂ ,. W _m is the weight fraction of the structural unit derived from each monomer in the copolymer (A).

  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 1999) can be used.

  The content of the copolymer (A) in the pressure-sensitive adhesive composition of the present invention is usually 87 to 99.9% by mass, and more preferably 100% by mass in solid content excluding the organic solvent (E) in the composition. Is 90-99.9 mass%. When content of a copolymer (A) exists in the said range, the performance as an adhesive is balanced and it is excellent in an adhesive characteristic.

[(Meth) acrylic copolymer (B)]
The (meth) acrylic copolymer (B) comprises a monomer component containing a monomer (b1) having an isocyanate group and a (meth) acrylic acid ester (b2) having no isocyanate group and no active hydrogen-containing functional group. It is a copolymer obtained by copolymerization. Hereinafter, the (meth) acrylic acid ester (b2) is also referred to as “monomer (b2)”.
The copolymer (B) acts as a cross-linking agent that cross-links the copolymer (A).

<< Monomer (b1) >>
The monomer (b1) having an isocyanate group is not particularly limited as long as a radical polymerizable monomer having an isocyanate group is used and the monomer imparts a function as a crosslinking agent to the copolymer (B).

As a monomer (b1), the (meth) acrylic acid ester which has an isocyanate group is mentioned, for example. As the (meth) acrylic acid esters, for ^{_{example, CH 2 = C (R 3}} ) a compound represented by -COO-R ⁴ -NCO can be mentioned. In the above formula, R ³ is a hydrogen atom or a methyl group, and R ⁴ is an alkylene group having 1 to 6 carbon atoms. Specific examples include 2-isocyanatoethyl (meth) acrylate.

  Moreover, as a monomer (b1), the radically polymerizable monomer obtained from the radically polymerizable monomer which has a carboxyl group or a hydroxyl group, and a polyfunctional isocyanate compound can also be mentioned, for example.

  Examples of the radical polymerizable monomer having a carboxyl group or a hydroxyl group include (meth) acrylic acid; hydroxyl groups such as hydroxyalkyl (meth) acrylate such as 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. (Meth) acrylate is mentioned. Carbon number of the hydroxyalkyl group in hydroxyalkyl (meth) acrylate is 2-8 normally, Preferably it is 2-6.

  Examples of the polyfunctional isocyanate compound include aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, 2,2,4-trimethyl. Examples include aliphatic diisocyanates having 4 to 30 carbon atoms such as -1,6-hexamethylene diisocyanate. As the alicyclic diisocyanate, an alicyclic group having 7 to 30 carbon atoms such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, etc. Diisocyanate is mentioned. 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.

A monomer (b1) may be used individually by 1 type, and may use 2 or more types.
In 100% by mass of the monomer component forming the copolymer (B), the amount of the monomer (b1) used is preferably 0.1 to 0.1 from the viewpoint of expressing stress relaxation characteristics while maintaining a practical crosslinking reaction rate. 15 mass%, More preferably, it is 0.1-10 mass%, More preferably, it is 0.1-5 mass%. When the amount of the monomer (b1) used is less than or equal to the above upper limit, the crosslink density formed by the copolymer (A) and the copolymer (B) does not become too high, and the pressure-sensitive adhesive layer has excellent stress relaxation characteristics. Is obtained. When the usage-amount of a monomer (b1) is more than the said lower limit, a crosslinked structure is formed effectively and the adhesive layer which has appropriate intensity | strength at normal temperature is obtained.

<< (Meth) acrylic acid ester (b2) >>
The (meth) acrylic acid ester (b2) has neither an isocyanate group nor an active hydrogen-containing functional group. For example, the compound represented by the column of << (meth) acrylic acid ester (a2) >> represented by CH ₂ ═C (R ¹ ) —COO—R ² may be mentioned.

  Specifically, (meth) acrylic acid alkyl ester, (meth) acrylic acid alkoxyalkyl ester, (meth) acrylic acid cycloalkyl ester, (meth) acrylic acid aryl ester, (meth) acrylic acid aralkyl ester, alkoxy polyalkylene Examples include glycol mono (meth) acrylate. Specific examples thereof include the compounds exemplified in the column of << (meth) acrylic acid ester (a2) >>.

A monomer (b2) may be used individually by 1 type, and may use 2 or more types.
As the monomer (b2), it is preferable to use at least a (meth) acrylic acid alkyl ester from the viewpoint of enhancing the compatibility between the copolymer (A) and the copolymer (B). In 100% by mass of the monomer (b2), the amount of the (meth) acrylic acid alkyl ester is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, and further preferably 70 to 100% by mass.

  In 100% by mass of the monomer component forming the copolymer (B), the amount of the monomer (b2) used is preferably 85 to 99.9% by mass, more preferably from the viewpoint of good adhesion and durability. It is 90-99.9 mass%, More preferably, it is 95-99.9 mass%.

<< Other monomer (b3) >>
As the monomer component forming the copolymer (B), other monomers may be used as desired in addition to the monomers (b1) and (b2). As such other monomers used as desired, the compounds exemplified in the column of “other monomers (a3)” can be similarly exemplified.

A monomer (b3) may be used individually by 1 type, and may use 2 or more types.
In 100% by mass of the monomer component forming the copolymer (B), the amount of the monomer (b3) used is preferably 14.9% by mass or less, more preferably 9.9% by mass or less, and still more preferably 4.9. It is below mass%.

<< Physical properties and content of copolymer (B) >>
The weight average molecular weight (Mw) measured by the gel permeation chromatography (GPC) method of the copolymer (B) is a polystyrene equivalent value, usually 10,000 to 2,000,000, preferably 10,000 to 800,000, More preferably, it is 10,000 to 600,000. When Mw is equal to or greater than the lower limit, sufficient cohesiveness tends to be obtained. When Mw is less than or equal to the upper limit, sufficient applicability can be secured, and bending suppression and light leakage prevention properties with time tend to be excellent.

  The molecular weight distribution (Mw / Mn) measured by the GPC method of the copolymer (B) is usually from 3 to 50, preferably from 4 to 20, and more preferably from 4 to 15. When the molecular weight distribution is not more than the above upper limit value, the foam resistance tends to be excellent under a high temperature and high humidity environment and the light leakage prevention property with time.

  Content of the copolymer (B) in the adhesive composition of this invention is 0.1-15 mass parts normally with respect to 100 mass parts of copolymers (A), Preferably it is 0.1-10 mass. Part, more preferably 1 to 10 parts by mass. When the content is not less than the lower limit, a sufficient degree of crosslinking is obtained and the durability tends to be excellent. When the content is not more than the above upper limit value, the stress relaxation characteristics tend to be excellent.

[Production conditions for copolymers (A) and (B)]
Copolymers (A) and (B) can be produced, for example, by a conventionally known polymerization method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method, and among these, the solution polymerization method Is preferred. The copolymers (A) and (B) are not particularly limited as to their copolymerization form, and may be any of random, block, and graft copolymerization, but random copolymerization is preferred.

  Specifically, a polymerization solvent and a monomer component are charged into a reaction vessel, a polymerization initiator is added under an inert gas atmosphere such as nitrogen gas, and the reaction start temperature is usually 40 to 100 ° C., preferably 50 to 80 ° C. The reaction system is maintained at a temperature of usually 50 to 90 ° C., preferably 70 to 90 ° C., and allowed to react for 4 to 20 hours.

  The copolymers (A) and (B) are preferably copolymers obtained by the copolymerization in the presence of a polymerization initiator. Examples of the polymerization initiator include azo initiators and peroxide polymerization initiators.

  Examples of the azo initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2- Cyclopropylpropionitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbohydrate) Nitrile), 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 [2-methyl-N- (2-hydroxyethyl) -propionamide], , 2′-azobis (isobutyramide) dihydrate, 4,4′-azobis (4-cyanopentanoic acid), 2,2′-azobis (2-cyanopropanol), dimethyl-2,2′-azobis (2-methyl) Azo compounds such as propionate) and 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide].

  Examples of peroxide polymerization initiators include t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, and di-i-propyl peroxydicarbonate. , Di-2-ethylhexyl peroxydicarbonate, t-butyl peroxybivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4- Di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) ) Propane, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) Butane, 2,2-bis (4,4-di -t- octylperoxycarbonyl cyclohexyl), and butane.

These polymerization initiators may be used alone or in combination of two or more.
The polymerization initiator is usually in the range of 0.001 to 5 parts by mass, preferably 0.005 to 3 parts by mass with respect to 100 parts by mass of the monomer components forming each of the copolymers (A) and (B). 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.

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

[Silane coupling agent (C)]
The pressure-sensitive adhesive composition for polarizing plates of the present invention contains a silane coupling agent (C) together with the copolymers (A) and (B). By using the silane coupling agent (C) together with the copolymers (A) and (B), the pressure-sensitive adhesive has excellent durability (eg, foam resistance and tear resistance under high temperature and high humidity environment). The layer can also be formed on an adherend such as a glass plate having a thickness of 0.5 mm or less. Further, (C) is a method in which the pressure-sensitive adhesive layer is firmly adhered to an adherend such as a glass plate having a thickness of 0.5 mm or less, the polarizing plate is peeled off in a high-humidity heat environment, and the glass plate This contributes to preventing bending.

  Examples of the silane coupling agent (C) include vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, Polymerizable unsaturated group-containing silane coupling agents such as 3-methacryloxypropyltriethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane Epoxy group-containing silane coupling agents such as 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, 3-aminopropyl Pyrtriethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1, Examples include amino group-containing silane coupling agents such as 3-dimethyl-butylidene) propylamine and N-phenyl-3-aminopropyltrimethoxysilane; halogen-containing silane coupling agents such as 3-chloropropyltrimethoxysilane.

  The content of the silane coupling agent (C) in the pressure-sensitive adhesive composition for polarizing plates of the present invention is usually more than 0 parts by mass and preferably 1 part by mass or less, preferably 100 parts by mass of the copolymer (A). It is 0.01-1 mass part, More preferably, it is 0.05-0.5 mass part. If the content is in the above range, the detailed reason is not fully understood, but since the adhesive force of the adhesive to the glass plate is significantly improved, the stress relaxation to the adhesive sufficiently works, It is considered that bending in a glass plate having a thickness of 0.5 mm or less could be suppressed. Further, the pressure-sensitive adhesive layer is excellent in durability under a high-temperature and high-humidity heat environment, and there is a tendency that peeling of the polarizing plate under a high-humidity and heat environment and bleeding of the silane coupling agent (C) under a high-temperature environment are prevented.

[Antistatic agent (D)]
An antistatic agent (D) can be used in order to reduce the surface resistance value of the adhesive layer formed from the adhesive composition for polarizing plates of this invention, for example. 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, and pyrazolinium. Examples include cations, tetraalkylammonium cations, trialkylsulfonium cations, tetraalkylphosphonium cations, 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 ⁻ , F (HF) _n ⁻ , (CN) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , C ₃ F ₇ COO ^-, and _{(CF 3 SO 2) (CF} 3 CO) N - are exemplified. 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, (N, N-diethyl) N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide, 1-octylpyridinium fluorophospho Nium imide, 1-octyl-3-methylpyridinium, and trifluorosulfonium imide are preferable.

Examples of the conductive polymer include polythiophene, polyaniline, polypyrrole, and derivatives thereof.
The content of the antistatic agent (D) in the pressure-sensitive adhesive composition for polarizing plates of the present invention is usually 3 parts by mass or less, preferably 0.8 parts per 100 parts by mass of the (meth) acrylic copolymer (A). It is 01-3 mass parts, More preferably, it is 0.05-2.5 mass parts.

[Organic solvent (E)]
The pressure-sensitive adhesive composition of the present invention preferably contains an organic solvent (E) in order to adjust its coatability. As an organic solvent, the polymerization solvent demonstrated in the column of [Production conditions of copolymer (A) and (B)] is mentioned. For example, the polymer solution containing the copolymer (A) and the polymerization solvent obtained by the above copolymerization, the polymer solution containing the copolymer (B) and the polymerization solvent, and the silane coupling agent (C) are mixed. Thus, a pressure-sensitive adhesive composition can be prepared. In the pressure-sensitive adhesive composition of the present invention, the content of the organic solvent is usually 50 to 90% by mass, preferably 60 to 85% by mass.

  In the present specification, “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 1 type, or 2 or more types selected from (meth) acrylic-type polymers and rework agents other than A) and (B).

  In addition, from the viewpoint of preventing the change in the physical properties of the adhesive over time, the content of the peroxide as the crosslinking agent in the solid content of 100% by mass of the pressure-sensitive adhesive composition for polarizing plates of the present invention is 0.00. It is preferable that it is 1 mass% or less, More preferably, it is 0.02 mass% or less.

[Preparation of pressure-sensitive adhesive composition for polarizing plate]
The polarizing plate pressure-sensitive adhesive composition of the present invention comprises a copolymer (A), a copolymer (B), a silane coupling agent (C), and other components as required, which are conventionally known. It can prepare by mixing by the method. For example, the silane coupling agent (C) and, if necessary, other components are added to the polymer solution containing these polymers obtained when the copolymers (A) and (B) are synthesized. Is mentioned.

  The gel fraction of the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition of the present invention is preferably 20 to 80% by mass, more preferably 25 to 75% by mass, and further preferably 40 to 75% by mass. The said gel fraction is a value measured about the adhesive extract | collected, for example by the conditions of an Example description.

  In the present invention, since both copolymers (A) and (B) have a high molecular weight, they exhibit a certain level of cohesion even at room temperature (eg, 23 ° C.). Thus, a pressure-sensitive adhesive layer having excellent storage properties such as pressure-sensitive adhesive properties, processability such as punching out the pressure-sensitive adhesive layer, and less deformation and protrusion of the pressure-sensitive adhesive layer can be obtained. Further, since the copolymer (B) has a high molecular weight, the distance between cross-linking points in the cross-linked structure formed from the copolymers (A) and (B) is remarkably wide, so at a high temperature (eg, 80 ° C.). The pressure-sensitive adhesive layer exhibits excellent flexibility, is excellent in suppressing warping (bending) of the polarizing plate, can suppress light leakage over time, and has a strong chemical bond derived from the active hydrogen-containing functional group and the isocyanate group. Due to crosslinking, the pressure-sensitive adhesive layer exhibits excellent durability.

About the point by which the curvature of a polarizing plate is suppressed, it is estimated that it is based on the following reasons.
For example, in the configuration of polarizing plate / adhesive layer / adhered body, a case where a glass plate having a thickness of 0.5 mm or less is used as the adherend will be described as an example. The polarizing plate and the glass plate have different heat shrinkage rates, and the polarizing plate usually has a larger heat shrinkage rate (dimensional change) than the glass plate. If the pressure-sensitive adhesive layer lacks flexibility under a high-temperature, high-humidity heat environment, the pressure-sensitive adhesive layer cannot follow the dimensional change of the polarizing plate, and the pressure-sensitive adhesive layer cannot relieve stress. Stress concentrates on the glass plate, which causes warpage of the glass plate.

  On the other hand, in the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of the present invention, the copolymer (A) is cross-linked by the copolymer (B), so that a normal low molecular weight cross-linking agent is used. Compared to the above, the cross-linking chain is long, and the silane coupling agent (C) is chemically bonded to the glass plate surface. For this reason, the cohesive force is high at room temperature, the stress relaxation property is high, and the adhesive force between the pressure-sensitive adhesive layer and the glass plate is high. Therefore, since the pressure-sensitive adhesive layer can follow the dimensional change of the polarizing plate, no stress is generated and the stress is not concentrated on the glass plate. Further, the polarizing plate can also be thermally contracted uniformly without anisotropy, and does not induce birefringence of the polarizing plate. As described above, in the present invention, the pressure-sensitive adhesive layer can absorb and relieve the stress accompanying the dimensional change of the polarizing plate, and therefore, no excessive stress (load) is applied to the glass plate. It is presumed that this will lead to suppression of warpage of the plate.

  Since the pressure-sensitive adhesive composition of the present invention has the above properties, it is suitable for use in bonding a substrate constituting a liquid crystal cell and a polarizing plate. In particular, even when the thickness of the glass plate constituting the thinned liquid crystal cell is as small as 0.5 mm or less, it is suitable for bonding the substrate and the polarizing plate.

(Adhesive layer)
The pressure-sensitive adhesive layer of the present invention is obtained, for example, by proceeding with a crosslinking reaction in the above-mentioned pressure-sensitive adhesive composition, specifically, by crosslinking the copolymer (A) with the copolymer (B).

  The conditions for forming the pressure-sensitive adhesive layer are, for example, as follows. The pressure-sensitive adhesive composition of the present invention is applied onto a support and varies depending on the type of solvent, but is usually 50 to 150 ° C., preferably 60 to 100 ° C., usually 1 to 10 minutes, preferably 2 to 7 minutes. Then, 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.

  The pressure-sensitive adhesive layer is preferably formed under the following conditions. After apply | coating the adhesive composition of this invention on a support body and sticking a cover film on the coating film formed on the said conditions, normally 3 days or more, Preferably it is 7-10 days, Usually 5-60 degreeC, It is preferably cured under an environment of 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. Thus, a method of applying and drying 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.

  The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention has a gel fraction of preferably 20 to 80% by mass, more preferably from the viewpoints of distortion suppression, cohesive force, adhesive strength, and removability of the polarizing plate. Is 25 to 75 mass%, more preferably 40 to 75 mass%. Even if the gel fraction is in the above range, the cross-linked chain in the cross-linked structure is long, so the followability to deformation is high, and bending due to the warp of the glass hardly occurs, resulting in deterioration of the durability and workability of the pressure-sensitive adhesive layer. There is nothing to do. In particular, when the gel fraction is 40% by mass or more, a highly cohesive pressure-sensitive adhesive layer can be obtained. When the gel fraction exceeds the above range, the pressure-sensitive adhesive layer may not be able to sufficiently absorb or relax the stress caused by the dimensional change of the polarizing plate under a high temperature / high humidity heat environment.

In the pressure-sensitive adhesive layer, the storage elastic modulus (G′1) at 23 ° C. is preferably 2 × 10 ⁴ to 50 × 10 ⁴ Pa, more preferably 5 × 10 ^{4 to} 20 × 10 ⁴ Pa; The ratio (G′2 / G′1) of the storage elastic modulus (G′2) at 23 ° C. and the storage elastic modulus (G′1) at 23 ° C. is preferably 0.2 to 0.8, more preferably 0. 3 to 0.7.

  When the storage elastic modulus (G′1) at 23 ° C. is in the above range, the pressure-sensitive adhesive layer is excellent in hardness at room temperature, and processability is improved. For example, when the pressure-sensitive adhesive layer is cut, adhesion of the pressure-sensitive adhesive to the cutting blade, stringing of the pressure-sensitive adhesive layer, dents in the pressure-sensitive adhesive layer during coating, processing, and transportation are prevented.

  When the ratio (G'2 / G'1) is in the above range, the pressure-sensitive adhesive layer has excellent flexibility at high temperatures, and the pressure-sensitive adhesive layer follows the thermal contraction (dimensional change) of the polarizing plate at high temperatures. be able to. When the ratio (G′2 / G′1) is less than the above range, the cohesiveness of the pressure-sensitive adhesive layer is lowered, and foaming of the pressure-sensitive adhesive layer may occur. When the ratio (G'2 / G'1) exceeds the above range, the pressure-sensitive adhesive layer cannot follow the thermal contraction (dimensional change) of the polarizing plate at high temperature, and the warping of the polarizing plate and the pressure-sensitive adhesive layer Rupture may occur.

  Here, using “Physica MCR300” manufactured by Anton Paar, according to a dynamic viscoelasticity measurement method (temperature range of −40 to 160 ° C., temperature increase rate of 3.67 ° C./min, frequency of 1 Hz) in accordance with JIS K7244. By measuring the viscoelastic spectrum, the storage elastic modulus (G′1) and (G′2) can be obtained.

  The storage elastic modulus is, for example, a value calculated from a dynamic viscoelastic spectrum measured for the laminate by laminating the adhesive layers a plurality of times to produce a laminate having a thickness of about 1.0 mm. .

[Plastic adhesive sheet]
The pressure-sensitive adhesive sheet for polarizing plates of the present invention has a pressure-sensitive adhesive layer formed from the above-mentioned pressure-sensitive adhesive composition for polarizing plates. 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, the gel fraction, and the storage elastic modulus are the same as the conditions described in the [Pressure-sensitive adhesive layer] column.
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, 10-125 micrometers, Preferably it is 25-75 micrometers.

[Polarizing plate with adhesive layer and laminate]
The polarizing plate with a pressure-sensitive adhesive layer of the present invention comprises a polarizing plate and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate of the present invention on at least one surface of the polarizing plate. . In 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, a multilayer film having a stretched film obtained by adding a polarizing component to a film made of a polyvinyl alcohol-based resin and stretching, and a protective film disposed on the stretched film can be mentioned. 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 protective film include cellulose films such as triacetyl cellulose, polycarbonate films, and polyethersulfone films.

The thickness of the polarizing plate is usually 30 to 250 μm, preferably 50 to 200 μm.
There is no restriction | limiting in particular in the method of forming an adhesive layer in the polarizing plate surface, The method of apply | coating and drying the said adhesive composition directly using a bar coater etc. on the polarizing plate surface, The adhesive sheet for polarizing plates of this invention has A method of transferring the pressure-sensitive adhesive layer to the surface of the polarizing plate and aging is mentioned. Drying and aging conditions, gel fraction, storage elastic modulus ranges, and the like are the same as the conditions described in the [Adhesive layer] column.

  The thickness of the pressure-sensitive adhesive layer formed on the polarizing plate is usually 5 to 75 μm, preferably 10 to 50 μm in terms of dry film thickness. In addition, the adhesive layer should just be formed in at least one surface of a polarizing plate, the aspect in which an adhesive layer is formed only in the single side | surface of a polarizing plate, the aspect in which an adhesive layer is formed in both surfaces of a polarizing plate 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.

  For example, the laminated body which has the adhesive layer formed from the adhesive composition for polarizing plates of this invention between the said polarizing plate and the glass plate of thickness 0.5mm or less can be manufactured. In the laminated body, in the present invention, the bending (warpage) of the glass plate can be suppressed to 0 mm to 10 mm, preferably 0 mm to 5 mm. If bending (warping) is suppressed within the above range, light leakage in the liquid crystal cell can be reduced.

  The measuring method of bending is, for example, as follows. The laminate is allowed to stand in a 23 ° C./50% RH environment for 24 hours and then held in an oven at 60 ° C. for 72 hours, and then one end of the laminate is fixed to a wall surface perpendicular to the floor surface. Then, the amount of lifting from the wall surface at the opposite end is measured with a ruler. Here, measurement is carried out immediately after taking out the laminate from the oven. This lifting amount is defined as bending.

  As a board | substrate which a liquid crystal cell has, glass plates, such as an alkali free glass plate, are mentioned, for example. The thickness of the substrate is usually 0.5 mm or less, preferably 0.15 to 0.5 mm. Especially in this invention, the curvature of a polarizing plate and a board | substrate can be suppressed by using the said adhesive composition. For this reason, even when the thickness of a board | substrate is small, the said adhesive composition can be used suitably for bonding of a polarizing plate and a board | substrate.

  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

[Synthesis Example A1]
A reactor equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet tube was charged with 99 parts of n-butyl acrylate, 1 part of 4-hydroxybutyl acrylate, and 100 parts of ethyl acetate solvent, while introducing nitrogen gas. The temperature was raised to 80 ° C. 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 about 30% by mass. The obtained (meth) acrylic copolymer A1 had a weight average molecular weight (Mw) of 1,200,000 and a molecular weight distribution (Mw / Mn) of 5.1.

[Synthesis Examples A2 to A4]
Except having changed the monomer component used for polymerization reaction as described in Table 1, it carries out similarly to the synthesis example A1, and (solid) concentration of about 30 mass% containing (meth) acrylic-type copolymer A2-A4 is included. A polymer solution was prepared. The results are shown in Table 1.

[Synthesis Example B1]
In a reactor equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, 99 parts of n-butyl acrylate, 1 part of “Karenz AOI” (trade name; 2-isocyanatoethyl acrylate) manufactured by Showa Denko KK , And 100 parts of ethyl acetate, 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 about 30% by mass. The obtained (meth) acrylic copolymer B1 had a weight average molecular weight (Mw) of 1,000,000 and a molecular weight distribution (Mw / Mn) of 7.1.

[Synthesis Example B2]
A polymer solution of (meth) acrylic copolymer B2 (solid content concentration of about 30% by mass) was prepared in the same manner as in Synthesis Example B1 except that the amount of ethyl acetate charged was changed to 130 parts.

[Synthesis Example B3]
The monomer component used in the polymerization reaction was changed as described in Table 2, and the same procedure as in Synthesis Example B1 was carried out except that the amount of ethyl acetate charged was changed to 150 parts. (Meth) acrylic copolymer B3 (solid content A polymer solution having a concentration of about 30% by mass was prepared.

[Synthesis Example B4]
Synthesis was performed except that the monomer components used in the polymerization reaction were changed as described in Table 2, and the ethyl acetate charge was changed to 150 parts and the 2,2′-azobisisobutyronitrile addition was changed to 0.3 parts. In the same manner as in Example B1, a polymer solution of (meth) acrylic copolymer B4 (solid content concentration of about 30% by mass) was prepared.

[Synthesis Example B5]
A polymer solution of (meth) acrylic copolymer B5 (solid content concentration of about 30% by mass) was prepared in the same manner as in Synthesis Example B1 except that the amount of ethyl acetate charged was changed to 150 parts and the reaction time was changed to 10 hours. .
The results are shown in Table 2.

ＡＯＩ：昭和電工（株）製「カレンズＡＯＩ」（商品名）
ＭＯＩ：昭和電工（株）製「カレンズＭＯＩ」（商品名）

AOI: Showa Denko Co., Ltd. “Karenzu AOI” (trade name)
MOI: “Karenz MOI” (trade name) manufactured by Showa Denko KK

[Example 1]
(1) Preparation of pressure-sensitive adhesive composition (meth) acrylic polymer solution obtained in Synthesis Example A1 (solid content concentration 30.1% by mass) and (meth) acrylic polymer solution obtained in Synthesis Example B1 ( Solid content concentration 30.0% by mass), Shin-Etsu Chemical Co., Ltd. “KBM-403” (solid content 100%) as a silane coupling agent, and Daiichi Kogyo Seiyaku Co., Ltd. “AS” as an antistatic agent. -804 "(100% solid content) was mixed to obtain an adhesive composition. The ratio of each component was 7.0 parts of copolymer B1 obtained in Synthesis Example B1 with respect to 100 parts of copolymer A1 contained in the (meth) acrylic polymer solution obtained in Synthesis Example A1. , “KBM-403” 0.2 parts, “AS-804” 1 part (both solid content values).

(2) Preparation of pressure-sensitive adhesive sheet After removing bubbles, the pressure-sensitive adhesive composition obtained in (1) above was applied on a polyethylene terephthalate film (PET film) that had been peeled off at a liquid temperature of 25 ° C. using a doctor blade. The film was dried at 90 ° C. 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 After removing bubbles, the pressure-sensitive adhesive composition obtained in (1) above was peeled off onto a polyethylene terephthalate film (PET film) that had been subjected to release treatment using a doctor blade. It apply | coated at 0 degreeC and it dried for 3 minutes at 90 degreeC, and obtained the sheet | seat which has a coating film with a dry film thickness of 20 micrometers. The sheet and the polarizing plate (thickness: 110 μm, layer structure: triacetyl cellulose film / polyvinyl alcohol film / triacetyl cellulose film) were bonded together so that the coating film and the polarizing plate were in contact with each other, and 23 ° C./50%. The plate was allowed to stand and matured for 7 days under the conditions of RH to obtain a polarizing plate with a pressure-sensitive adhesive layer having a PET film, a pressure-sensitive adhesive layer having a thickness of 20 μm, and a polarizing plate.

[Examples 2-8, Comparative Examples 1-2]
In Example 1, the adhesive composition, the adhesive sheet, and the polarizing plate with an adhesive layer were obtained like Example 1 except having changed the compounding composition as described in Table 2. “TD-75” in Table 3 is “TD-75” (solid content: 75% by mass, ethyl acetate solution) manufactured by Soken Chemical Co., Ltd., which is a tolylene diisocyanate crosslinking agent.

[Evaluation]
[Gel fraction]
About 0.1 g of the pressure-sensitive adhesive was collected from the pressure-sensitive adhesive sheets obtained in the examples and comparative examples, added with 30 mL of ethyl acetate and shaken for 4 hours, and then the contents of the sample bottle were transferred to a 200 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 (%)

[Measurement of adhesive strength]
A polarizing plate with a pressure-sensitive adhesive layer obtained in Examples and Comparative Examples (a laminate comprising PET film / pressure-sensitive adhesive layer / polarizing plate) was cut into a size of 70 mm × 25 mm to prepare a test piece. The PET film was peeled from the test piece, and a laminate composed of the pressure-sensitive adhesive layer / polarizing plate was attached to one side of a 2 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 in an autoclave adjusted to 50 ° C./5 atm for 20 minutes. Next, after being left in a 23 ° C./50% RH environment for 1 hour, the end of the polarizing plate was pulled at a rate of 300 mm / min in the 90 ° direction with respect to the glass plate surface, and the adhesive strength (peel strength) was measured.

[Bending]
A test piece was prepared by cutting the polarizing plate with the pressure-sensitive adhesive layer (PET film / pressure-sensitive adhesive layer / laminate comprising the polarizing plate) obtained in Examples and Comparative Examples into a size of 35 mm × 400 mm (stretching axis direction). did. A PET film is peeled from a test piece, and a laminate composed of an adhesive layer / polarizing plate is laminated on one side of a non-alkali glass plate having a thickness of 0.3 mm and 40 mm × 410 mm using a laminator roll. I stuck it so that it touched. The obtained laminate was allowed to stand in a 23 ° C./50% RH environment for 24 hours, and then held in an oven at 60 ° C. for 72 hours. One end was fixed to a wall surface perpendicular to the floor surface, and the amount of lifting from the wall surface at the opposite end was measured with a ruler. Measurements were taken immediately after removal from the oven.

[Storage modulus]
In the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples, the pressure-sensitive adhesive layers having a thickness of 20 μm were bonded together in an environment of 23 ° C./50% RH several times and treated with an autoclave at 50 ° C./5 atm for 20 minutes. A pressure-sensitive adhesive layer having a thickness of 1.0 mm was produced. For the pressure-sensitive adhesive layer having a thickness of 1.0 mm, a dynamic viscoelasticity measurement method (temperature range: −40 to 160 ° C., temperature rising rate: 3.67 ° C.) based on JIS K7244 using “Physica MCR300” manufactured by Anton Paar. / Min, conditions of frequency 1 Hz), the viscoelastic spectrum was measured, and the storage elastic modulus at temperatures 23 ° C. and 80 ° C. was determined.

[Durability test]
A polarizing plate with a pressure-sensitive adhesive layer obtained in Examples and Comparative Examples (a laminate comprising PET film / pressure-sensitive adhesive layer / polarizing plate) was cut into a size of 150 mm × 250 mm to prepare a test piece. The PET film is peeled off from the test piece, and the laminate composed of the pressure-sensitive adhesive layer / polarizing plate is pasted on one side of a 2 mm-thick alkali-free glass plate so that the pressure-sensitive adhesive layer and the glass plate are in contact with each other using a laminator roll. I wore it. 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. (heat resistance) or a temperature of 60 ° C./humidity of 90% RH (humid heat resistance), and the occurrence of foaming and tearing is observed according to the following criteria. evaluated. Foaming occurs when cohesion is insufficient, and tearing occurs when stress relaxation is insufficient.

(Foam)
-AA: Foaming is not seen at all.
-BB: The area of foaming is less than 1% of the whole.
-CC: The area of foaming is 1% or more and less than 5% of the whole.
-DD: The area of foaming is 5% or more of the whole.

(Rupture)
-AA: No tear is seen at all.
-BB: The area of a tear is less than 1% of the whole.
-CC: The area of a fracture is 1% or more and less than 5% of the whole.
DD: The area of the tear is 5% or more of the whole.

[Light leakage characteristics (light leakage size R)]
A 19-inch liquid crystal cell is peeled off the peeled PET film from the polarizing plate with the pressure-sensitive adhesive layer obtained in Examples and Comparative Examples, and this polarizing plate is removed from the glass plate (thickness of the liquid crystal cell). And the polarizing plate and the liquid crystal cell are bonded together so as to be in a crossed Nicol state, and left in an 80 ° C. atmosphere for 240 hours, and then in a 23 ° C./50% RH atmosphere. And left for 2 hours.

  Thereafter, the liquid crystal cell with the polarizing plate attached thereto was connected to a personal computer in a dark room to display a full screen black. The luminance of the black display lighting state was measured from the front under an environment of 25 ° C. and 60% RH. Further, after aging for 100 hours in a 60 ° C. environment, measurement was performed in the same manner as before aging in a 25 ° C. and 60% RH environment. For the evaluation, the difference between the in-plane maximum luminance before aging and the in-plane maximum luminance after aging was used.

AA when the maximum luminance difference (cd / m ² ) is less than 0.15, BB when it is 0.15 or more and less than 0.4, CC if it is 0.4 or more and less than 0.6, 0.6 or more The case was evaluated as DD. Moreover, when it was not able to measure by generation | occurrence | production of foaming or tearing, it described as being unmeasurable.

Claims (6)

(A) A monomer (a1) having an active hydrogen-containing functional group and a (meth) acrylic copolymer obtained by copolymerizing a monomer component containing a (meth) acrylic acid ester (a2) having no active hydrogen-containing functional group A copolymer;
(B) A (meth) acrylic monomer obtained by copolymerizing a monomer component (b1) having an isocyanate group and a monomer component containing an isocyanate group and a (meth) acrylic acid ester (b2) having no active hydrogen-containing functional group A copolymer;
(C) containing a silane coupling agent,
A pressure-sensitive adhesive composition for a polarizing plate, which is used for pasting a polarizing plate and a glass plate having a thickness of 0.5 mm or less.   The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the copolymer (B) has a molecular weight distribution (Mw / Mn) measured by a gel permeation chromatography method (GPC method) of 3 to 50.   The adhesive composition for polarizing plates of Claim 1 or 2 whose gel fraction of the adhesive formed from the said adhesive composition for polarizing plates is 20-80 mass%.   It has an adhesive layer formed from the adhesive composition for polarizing plates of any one of Claims 1-3, The adhesive sheet for polarizing plates characterized by the above-mentioned.   A pressure-sensitive adhesive comprising: a polarizing plate; and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition for a polarizing plate according to claim 1 on at least one surface of the polarizing plate. A polarizing plate with layers.   It has the adhesive layer formed from the adhesive composition for polarizing plates of any one of Claims 1-3 between a polarizing plate and the glass plate of thickness 0.5mm or less, It is characterized by the above-mentioned. Laminated body.