JP2018002771A - Adhesive composition and adhesive using the same, and adhesive for polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition capable of obtaining an adhesive in which a polarizing plate can exhibit excellent optical characteristics (degree of polarization) even under moist heat condition when used as an adhesive that bonds the polarizing plate and a glass substrate, and that is also excellent in moist heat whitening resistance, antistatic property and reworkability in a balanced manner.SOLUTION: An adhesive composition contains an acrylic resin (A), an ionic compound (B) and an isocyanate-based crosslinking agent (C), where the acrylic resin (A) is an acrylic resin (A) containing 6.5-20 wt.% of a hydroxyl group-containing monomer (a1)-derived structural unit, the ionic compound (B) is an ionic compound made of ammonium cation and trifluoromethane sulfonyl imide anion, and the isocyanate-based crosslinking agent (C) is a reaction product of a polyhydric alcohol compound (c1) and a polyhydric isocyanate compound (c2).SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive using the pressure-sensitive adhesive composition, and a pressure-sensitive adhesive for polarizing plates, and more specifically, polarized light even under wet heat conditions when used as a pressure-sensitive adhesive for bonding a polarizing plate and a glass substrate. The present invention relates to a pressure-sensitive adhesive composition that can provide a pressure-sensitive adhesive that can exhibit excellent optical properties (polarization degree) and is excellent in moisture and heat whitening resistance, antistatic properties, and reworkability.

Conventionally, a polarizing plate in which both sides of a polarizer made of a polyvinyl alcohol film to which polarizing properties are imparted is coated with a protective film is attached to the surface of a liquid crystal cell in which a liquid crystal component oriented between two glass plates is sandwiched. A liquid crystal display panel is manufactured by laminating.
The lamination of the polarizing plate on the surface of the liquid crystal cell is usually performed by bringing the pressure-sensitive adhesive layer provided on the surface of the polarizing plate into contact with the liquid crystal cell surface and pressing it.

  An adhesive containing a polyvinyl alcohol resin is preferably used as an adhesive for laminating the protective film and the polarizer. Specifically, an aqueous solution obtained by blending a polyvinyl alcohol resin and a crosslinking agent is used as the polarizer. After applying and laminating a protective film on top, a polarizing plate is produced by heating and drying. In the manufacturing process of the polarizing plate, it is preferable that moisture contained in the adhesive permeate the protective film, and a triacetyl cellulose film (TAC film) having high moisture permeability has been suitably used as the protective film. .

  However, in recent years, from the viewpoint of dimensional stability and durability, olefin films, particularly cycloolefin films, have been used as protective films for polarizing plates instead of TAC films. When is used, the wet heat resistance of the polarizing plate is improved. However, when a liquid crystal display device in which a polarizing plate is bonded to a liquid crystal cell via an adhesive is exposed to a wet heat environment, there is a problem that the whitening phenomenon of the adhesive layer is likely to occur. This is because when the liquid crystal display device is subjected to wet heat for a long time, moisture gradually enters the pressure-sensitive adhesive layer, and when the liquid crystal display device is returned to room temperature, the moisture is condensed in the pressure-sensitive adhesive layer, but the moisture permeability is low. This is because moisture release is suppressed by the protective film.

  Further, since the liquid crystal cell causes a display defect due to the disorder of the liquid crystal alignment due to static electricity, the polarizing plate is provided with a countermeasure against static electricity. Specifically, a technique for producing a polarizing plate with an adhesive having excellent antistatic performance by imparting antistatic performance to the protective film or adding an antistatic agent to the adhesive layer is known. .

  As a pressure-sensitive adhesive developed for such a purpose, for example, in Patent Document 1, an acrylic pressure-sensitive adhesive using an acrylic resin copolymerized with a larger amount of hydroxyl monomers than usual has excellent moisture and heat whitening resistance. Is described. Patent Document 2 describes a pressure-sensitive adhesive composition comprising an ionic compound composed of an acrylic resin and an ammonium cation as a pressure-sensitive adhesive composition having excellent antistatic performance and durability.

JP2013-213203A Special table 2012-524143

However, in recent years, with the widespread use of liquid crystal displays, it has come to be used in various environments, and is used in a harsher environment, especially in a humid heat environment, compared to an environment that is used indoors such as in-vehicle or outdoor applications. There is a demand for pressure-sensitive adhesives having excellent optical properties and visibility.
The pressure-sensitive adhesive described in Patent Document 1 is excellent in moisture and heat whitening resistance, but has a high moisture permeability because the hydroxyl group content is too large, and moisture easily enters the pressure-sensitive adhesive layer. Therefore, when used as a pressure-sensitive adhesive for polarizing plates, the ionic compound (antistatic agent) in the pressure-sensitive adhesive layer passes through the protective film together with moisture and moves to the polarizer, and the polarization degree of the polarizer. There was a problem of causing a drop in The pressure-sensitive adhesive described in Patent Document 2 is excellent in antistatic performance and durability, but inferior in moisture and heat whitening resistance.

  Therefore, in the present invention, under such a background, when used as an adhesive for laminating a polarizing plate and a glass substrate, the polarizing plate can exhibit excellent optical properties (degree of polarization) even under wet heat conditions, An object of the present invention is to provide a pressure-sensitive adhesive composition capable of obtaining a pressure-sensitive adhesive that is excellent in moisture heat whitening resistance, antistatic property and reworkability.

  However, as a result of intensive studies in view of such circumstances, the present inventor used an acrylic resin containing a specific amount of a structural unit derived from a hydroxyl group-containing monomer, and further identified an ionic compound comprising an ammonium cation and a specific anion, When the pressure-sensitive adhesive is obtained by blending the above isocyanate-based crosslinking agent, whitening of the pressure-sensitive adhesive layer and a decrease in the degree of polarization of the polarizing plate can be suppressed even under wet heat conditions, and the antistatic property and reworkability are well balanced. As a result, the present invention was completed.

That is, the gist of the present invention is a pressure-sensitive adhesive composition containing an acrylic resin (A), an ionic compound (B), and an isocyanate crosslinking agent (C), wherein the acrylic resin (A) is a hydroxyl group-containing monomer. It is an acrylic resin containing 6.5 to 20% by weight of the structural unit derived from (a1), the ionic compound (B) is an ionic compound comprising an ammonium cation and a trifluoromethanesulfonylimide anion, and an isocyanate crosslinking agent The present invention relates to a pressure-sensitive adhesive composition in which (C) is an isocyanate compound that is a reaction product of a polyhydric alcohol compound (c1) and a polyvalent isocyanate compound (c2).
Furthermore, it is related with the adhesive which uses the said adhesive composition, and the adhesive for polarizing plates.

  The pressure-sensitive adhesive obtained by using the pressure-sensitive adhesive composition of the present invention can suppress a decrease in the degree of polarization of the polarizing plate even under wet heat conditions when used as a pressure-sensitive adhesive for bonding a polarizing plate and a glass substrate, etc. Excellent anti-static property and reworkability. Therefore, by using this pressure-sensitive adhesive composition, a liquid crystal display device exhibiting excellent optical characteristics can be obtained without deterioration in performance even when used under a severer environment than usual, such as under wet heat conditions.

The present invention is described in detail below.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate. The acrylic resin is a resin obtained by polymerizing a polymerization component containing at least one (meth) acrylate monomer.

  The pressure-sensitive adhesive composition of the present invention contains an acrylic resin (A), an ionic compound (B), and an isocyanate crosslinking agent (C) as essential components.

<Acrylic resin (A)>
The acrylic resin (A) used in the present invention is an acrylic resin containing 6.5 to 20% by weight of a structural unit derived from the hydroxyl group-containing monomer (a1). It is obtained by copolymerizing a copolymer component containing 5 to 20% by weight. The acrylic resin (A) may contain a (meth) acrylic acid alkyl ester monomer (a2) or other copolymerizable ethylenically unsaturated monomer (a3) as a copolymerization component, if necessary.

Examples of the hydroxyl group-containing monomer (a1) include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8- Hydroxyalkyl esters of acrylic acid such as hydroxyoctyl (meth) acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylate, oxyalkylene-modified monomers such as diethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, etc. Primary hydroxyl group-containing compounds such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol (meth) acrylamide, hydroxyethylacrylamide, etc. Ma;
Secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-chloro 2-hydroxypropyl (meth) acrylate;
There may be mentioned tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth) acrylate.

  Among the hydroxyl group-containing monomers (a1), a primary hydroxyl group-containing monomer is preferable in terms of excellent reactivity with the crosslinking agent (C). The use of 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate is particularly preferable from the viewpoint of few impurities such as di (meth) acrylate and easy production.

  As the hydroxyl group-containing monomer (a1) used in the present invention, it is also preferable to use a monomer having a content of di (meth) acrylate as an impurity of 0.5% or less, more preferably 0.2% or less. It is preferable to use 0.1% or less.

  The content of the hydroxyl group-containing monomer (a1) is preferably 6.5 to 20% by weight, particularly 7 to 15% by weight, more preferably 8 to 10% by weight, based on the entire copolymerization component. It is preferable. When the content is too small, the heat-and-moisture whitening resistance is lowered, and when it is too much, durability and reworkability are lowered.

  As said (meth) acrylic-acid alkylester type monomer (a2), carbon number of an alkyl group is 1-20 normally (preferably 1-18, Especially preferably, 1-12, More preferably, it is 1-8.) Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (Meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) ) Acrylate and the like. These may be used alone or in combination of two or more.

  Among these, n-methyl acrylate, n-ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate are preferable in terms of versatility and adhesive properties.

  The content of the (meth) acrylic acid alkyl ester monomer (a2) is preferably 50 to 93.5% by weight, particularly 50 to 85% by weight, and more preferably 50%, based on the entire copolymerization component. It is preferably ˜80% by weight. If the content is too small, it tends to be difficult to balance the physical properties of the adhesive, and if it is too large, the wet heat whitening property tends to be lowered.

Examples of the other copolymerizable ethylenically unsaturated monomer (a3) include carboxyl group-containing monomers such as dimer acid of acrylic acid such as (meth) acrylic acid and β-carboxyethyl acrylate;
Aromatic ring-containing monomers such as benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and orthophenylphenoxyethyl (meth) acrylate;
Cyclohexyl (meth) acrylate, cyclohexyloxyalkyl (meth) acrylate, t-butylcyclohexyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentanyl (meth) acrylate Alicyclic-containing monomers such as
Alkoxyalkyl such as methoxymethyl (meth) acrylamide, ethoxymethyl (meth) acrylamide, propoxymethyl (meth) acrylamide, isopropoxymethyl (meth) acrylamide, n-butoxymethyl (meth) acrylamide, isobutoxymethyl (meth) acrylamide ( (Meth) acrylamide monomers such as (meth) acrylamide monomers, (meth) acryloylmorpholine, dimethyl (meth) acrylamide, diethyl (meth) acrylamide, (meth) acrylamide N-methylol (meth) acrylamide;
2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2-butoxydiethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) Acrylate, methoxytriethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol-polypropylene glycol-mono (meth) acrylate, Lauro Xylethylene glycol mono (meth) acrylate, stearoxypolyethylene glycol mono (meth) acrylate Ether chains containing over preparative like (meth) acrylic acid ester monomer;
Acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, itaconic acid dialkyl ester, fumaric acid dialkyl ester, allyl alcohol, acrylic chloride , Methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinylketone and the like.
These may be used alone or in combination of two or more.

Among these, an aromatic ring-containing monomer is preferable in terms of easy adjustment of refractive index and birefringence, and benzyl (meth) acrylate, phenoxy (meth) ethyl acrylate, and phenoxydiethylene glycol (meth) acrylate are particularly preferable. .
In addition, an alicyclic-containing monomer is preferable, and cyclohexyl (meth) acrylate is particularly preferable in terms of easy adjustment of refractive index and birefringence and excellent adhesion to a low-polar adherend (such as cycloolefin). , Isobornyl (meth) acrylate.
In terms of easy adjustment of adhesion to the substrate / adherent, cohesion, and resin compatibility, amide monomers are preferred, and acrylamide, methacrylamide, alkoxyacrylamide, dialkylacrylamide, and hydroxyalkylacrylamide are particularly preferred. .

  As content of the said other copolymerizable ethylenically unsaturated monomer (a3), when (a3) is an aromatic ring containing monomer and an alicyclic ring containing monomer, it is 5-30 weight with respect to the whole copolymerization component. %, Particularly preferably 10 to 30% by weight, more preferably 15 to 25% by weight. When the content of the aromatic ring-containing monomer and the alicyclic ring-containing monomer is too large, the positive birefringence increases. When the content is too small, the negative birefringence increases, both of which tend to deteriorate light leakage after durability.

When the other copolymerizable ethylenically unsaturated monomer (a3) is a carboxyl group-containing monomer, it is preferably 0.01 to 3% by weight, more preferably 0.1%, based on the entire copolymerization component. -1% by weight, more preferably 0.6-1% by weight. If the content of the carboxyl group monomer is too large, the TAC film may be decomposed, or if the adherend is a metal, it tends to corrode. If the content is too small, the reactivity with the cross-linking agent decreases, and aging takes time. There is such a tendency.
When the other copolymerizable ethylenically unsaturated monomer (a3) is an amino group-containing monomer, it is preferably 0.005 to 1.0% by weight, more preferably 0, based on the entire copolymerization component. 0.01 to 0.50% by weight, more preferably 0.05 to 0.2% by weight. In the present invention, since the content of the hydroxyl group-containing monomer is large, if the content of the amino group-containing monomer is too large, the pot life tends to be shortened or the degree of polarization tends to be lowered. There is a tendency to take or not complete.
As the other copolymerization component (a3), it is preferable to use any one of a carboxyl group-containing monomer and an amino group-containing monomer in terms of improving the reactivity with the crosslinking agent.

The acrylic resin (A) used in the present invention comprises a hydroxyl group-containing monomer (a1), a (meth) acrylic acid alkyl ester monomer (a2) and other copolymerizable ethylenically unsaturated monomers ( It can be produced by appropriately selecting and polymerizing a copolymer component containing a3).
The polymerization can be performed by a conventionally known method such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, and the like. For example, a copolymer component containing a hydroxyl group-containing monomer (a1) in an organic solvent, A polymerization initiator is mixed or dropped and polymerized under predetermined polymerization conditions. Among these polymerization methods, solution radical polymerization and bulk polymerization are preferable, and solution radical polymerization is more preferable from the viewpoint that a high molecular weight acrylic resin can be stably obtained.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, n-propyl alcohol, and isopropyl alcohol. Aliphatic alcohols such as acetone, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.
Among these solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are preferred from the viewpoint of ease of polymerization reaction, chain transfer effect, ease of drying during adhesive coating, and safety. More preferably, ethyl acetate, acetone, and methyl ethyl ketone are preferable.

  Examples of the polymerization initiator used for such radical polymerization include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, which are ordinary radical polymerization initiators, Azo initiators such as 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (methylpropionic acid), benzoyl peroxide, laurolyl peroxide, di-t-butyl peroxide, cumene Examples thereof include organic peroxides such as hydroperoxide, which can be appropriately selected according to the monomer used. These polymerization initiators may be used alone or in combination of two or more.

  The acrylic resin (A) used in the present invention contains 6.5 to 20% by weight of a structural unit derived from the hydroxyl group-containing monomer (a1), preferably 7 to 15% by weight, particularly 8 to 10%. It is preferable that it is contained by weight. If the number of structural units derived from a hydroxyl group-containing monomer is too small, the wet heat whitening resistance is lowered, and if too much, the reworkability and durability are lowered.

The weight average molecular weight of the acrylic resin (A) is preferably 800,000 to 2,500,000, particularly preferably 1,000,000 to 2,000,000, and more preferably 1,200,000 to 1,500,000.
If the weight average molecular weight is too small, the durability tends to decrease, and if the weight average molecular weight is too large, a large amount of a diluent solvent is required during production, and the drying property tends to decrease.

The degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 15 or less, particularly preferably 10 or less, more preferably 5 or less, and particularly preferably 4.5 or less. is there. The lower limit of the dispersity is usually 1.1 from the viewpoint of production limit.
If the degree of dispersion is too high, the cohesive force tends to decrease, and if the degree of dispersion is too low, tack tends to be low and sticking tends to be difficult. Note that the lower limit of the degree of dispersion is usually 1.

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and it is a column in a high performance liquid chromatography (The Japan Waters company, "Waters 2695 (main body)" and "Waters 2414 (detector)"). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinylbenzene copolymer, filler The number average molecular weight can also be measured by the same method. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight.

The glass transition temperature (Tg) of the acrylic resin (A) is preferably −80 to 0 ° C., particularly preferably −55 to −15 ° C., and further preferably −45 to −20 ° C.
If the glass transition temperature is too high, the tack tends to decrease, and if it is too low, the heat resistance tends to decrease.

Ｔｇ：共重合体のガラス転移温度（Ｋ）
Ｔga：モノマーＡのホモポリマーのガラス転移温度（Ｋ） Ｗａ：モノマーＡの重量分率
Ｔgb：モノマーＢのホモポリマーのガラス転移温度（Ｋ） Ｗｂ：モノマーＢの重量分率
Ｔgn：モノマーＮのホモポリマーのガラス転移温度（Ｋ） Ｗｎ：モノマーＮの重量分率
（Ｗａ＋Ｗｂ＋・・・＋Ｗｎ＝１） The glass transition temperature is calculated from the following Fox equation.

Tg: Glass transition temperature of copolymer (K)
Tga: Glass transition temperature (K) of monomer A homopolymer Wa: Weight fraction of monomer A Tgb: Glass transition temperature of homopolymer of monomer B (K) Wb: Weight fraction of monomer B Tgn: Homogeneity of monomer N Glass transition temperature (K) of polymer Wn: weight fraction of monomer N (Wa + Wb +... + Wn = 1)

The refractive index of the acrylic resin (A) may usually be 1.440 to 1.600, preferably 1.460 to 1.550, and particularly preferably 1.470 to 1.500. For such a refractive index, it is preferable to reduce the difference in refractive index between the members to be laminated, since light loss at the member interface is small.
The said refractive index is the value which measured the acrylic resin made into the thin film with the NaD line | wire using the refractive index measuring apparatus ("Abbe refractometer" by Atago Co., Ltd.).

The haze of the acrylic resin (A) is preferably 1.0 or less, more preferably 0.8 or less, and particularly preferably 0.5 or less. If the haze is too high, the image quality of the display tends to deteriorate.
For haze, diffuse transmittance and total light transmittance are measured using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and the obtained diffuse transmittance and total light transmittance value are substituted into the following formula. , Calculated. This machine complies with JIS K7361-1.
Haze (%) = (diffuse transmittance / total light transmittance) × 100

  Thus, the acrylic resin (A) used in the present invention is obtained.

<Ionic compound (B)>
The ionic compound (B) used in the present invention is an ionic compound comprising an ammonium cation and a trifluoromethanesulfonylimide anion.

The ammonium cation has a structure in which a nitrogen atom has four substituents and is positively charged. Each of the four substituents is independently hydrogen, an alkyl group having 1 to 24 carbon atoms, or a hydroxyl group. Either is preferable.
Among these, it is preferable that at least one substituent is an alkylammonium cation which is an alkyl group having 1 to 24 carbon atoms, and in particular, four substituents from the viewpoint of suppressing a decrease in the degree of polarization in a wet heat environment. Particularly preferred are tetraalkylammonium cations, all of which are alkyl groups having 1 to 24 carbon atoms.
Examples of the ammonium cation include tetramethyl ammonium cation, tetraethyl ammonium cation, tetrabutyl ammonium cation, tetrahexyl ammonium cation, trimethyl decyl ammonium cation, triethyl methyl ammonium cation, tributyl methyl ammonium cation, tributyl ethyl ammonium cation, dodecyl trimethyl ammonium. Examples include cations, cyclohexyltrimethylammonium cations, benzyldimethyltetradecylammonium cations, trimethylacetohydrazide ammonium cations, and bis (2-hydroxyethyl) dimethylammonium.

  Moreover, it is preferable that the sum total of carbon number of the alkyl group of four substituents is 10-30, and it is more preferable that it is 11-15. When the total number of carbon atoms of the alkyl group is too large, the compatibility with the acrylic resin (A) tends to be lowered, and when too small, the degree of polarization tends to be lowered in a moist heat environment.

Specific examples of the ionic compound (B) of the present invention include tri-n-butylmethylammonium bistrifluoromethanesulfonylimide (27.5 ° C), tetrabutylammonium bistrifluoromethanesulfonylimide (94-96 ° C), and the like. Among these, tri-n-butylmethylammonium bistrifluoromethanesulfonylimide is preferable in terms of compatibility with the resin and difficulty in decreasing the degree of polarization.
In addition, the inside of () shows melting | fusing point of an ionic compound (B).

  It is preferable that melting | fusing point of the ionic compound (B) of this invention is 0-1500 degreeC, Especially preferably, it is 25-80 degreeC, More preferably, it is 25-50 degreeC. If the melting point of the ionic compound (B) is too low, the degree of polarization tends to decrease in a wet and heat environment, and if the melting point is too high, the compatibility with the acrylic resin (A) may decrease, Or tend to precipitate.

  The content of the ionic compound (B) is preferably 1 to 10 parts by weight, particularly 2 to 5 parts by weight, and more preferably 3 to 4.5 parts by weight with respect to 100 parts by weight of the acrylic resin (A). It is preferable that it is a weight part. When the content of the ionic compound (B) is too small, sufficient antistatic performance tends to be not obtained, and when it is too large, the degree of polarization tends to decrease under wet heat conditions.

  In addition, in the range which does not inhibit the effect of this invention, you may use together ionic compounds other than an ionic compound (B), but when there is too much, it exists in the tendency for a polarization degree to fall and acrylic resin (A) 100. The amount is preferably 2 parts by weight or less, more preferably 1 part by weight or less, particularly preferably 0.5 part or less, relative to parts by weight.

The isocyanate-based crosslinking agent (C) used in the present invention is an isocyanate compound obtained by reacting a polyhydric alcohol compound (c1) and a polyvalent isocyanate compound (c2).
By using an isocyanate compound which is a reaction product of a polyvalent isocyanate compound (c1) and a polyhydric alcohol compound (c2) as the isocyanate-based crosslinking agent (C), an acrylic resin (A ) And an ionic compound (B) composed of an ammonium cation and a trifluoromethanesulfonylimide anion, and the movement of the ionic compound (B) in a moist heat environment is suppressed to suppress the decrease in the degree of polarization. It is thought that it can be done.

Examples of the polyhydric alcohol (c1) include compounds having two hydroxyl groups such as 1,4-butanediol, 1,6-hexanediol and 1,9-nonanediol, and three hydroxyl groups such as glycerin and trimethylolpropane. Compounds having four hydroxyl groups such as pentaerythritol, mannitol having five or more hydroxyl groups, and derivatives thereof.
Among them, a compound having three or more hydroxyl groups is preferable, and a compound having three hydroxyl groups is particularly preferable in terms of excellent balance between the compatibility of the acrylic resin (A) and the ionic compound (B). Trimethylolpropane is preferred.

Examples of the polyvalent isocyanate compound (c2) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, and 1,4-xylylene diisocyanate. Aromatic polyisocyanates such as triphenylmethane triisocyanate and tetramethylxylylene diisocyanate; diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,5-naphthalene diisocyanate, etc. Alicyclic polyisocyanates: pentamethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate Over aliphatic polyvalent isocyanate such bets; and the like.
Especially, it is preferable to use an alicyclic polyvalent isocyanate and / or an aliphatic polyvalent isocyanate from the point which can suppress the fall of a polarization degree.

  The isocyanate-based crosslinking agent (C) is preferably a reaction product using trimethylolpropane as (c1) in terms of excellent compatibility between the acrylic resin (A) and the ionic compound (B). Furthermore, it is preferably a reaction product of trimethylolpropane and an alicyclic polyvalent isocyanate and / or an aliphatic polyvalent isocyanate in that the decrease in polarization degree can be suppressed.

The content of the isocyanate crosslinking agent (C) is preferably 0.05 to 3 parts by weight, particularly preferably 0.1 to 1 part by weight, based on 100 parts by weight of the acrylic resin (A). More preferably, it is 0.1-0.6 weight part, Most preferably, it is 0.15-0.4 weight part.
When the content of such a crosslinking agent is too small, the durability tends to decrease, and when it is too large, the stress relaxation property tends to decrease or long-term aging tends to be required.

  In the present invention, an isocyanate-based crosslinking agent other than the isocyanate compound obtained by reacting the polyvalent isocyanate compound (c2) and the polyhydric alcohol compound (c1) and other crosslinking agents within a range that does not impair the effects of the present invention. Specifically, the polyvalent isocyanate compound (c2), epoxy crosslinking agent, aziridine crosslinking agent, melamine crosslinking agent, aldehyde crosslinking agent, amine crosslinking agent, metal chelate crosslinking agent can be used. Agents and the like.

  In the pressure-sensitive adhesive composition of the present invention, it is preferable that a silane coupling agent (D) is further added from the viewpoint of improving the adhesion to the optical member.

  The silane coupling agent (D) is a silane compound having a substituent having a functional group and an alkoxy group as a substituent.

  Examples of the functional group include an epoxy group, a mercapto group, a hydroxyl group, a carboxyl group, an amino group, an amide group, an isocyanate group, and a (meth) acryloyl group.

  Moreover, as an alkoxy group, it is preferable to have a C1-C8 alkoxy group from the point of durability and storage stability, Furthermore, it is preferable to have a C2 or more alkoxy group, and especially an ethoxy group is included. It is preferable to have.

  In addition, the silane coupling agent (D) has an alkoxy group content (alkoxy group content per weight) of 30% by weight or more from the viewpoint of maintaining heat and moisture resistance over a long period of time and storage stability. It is preferable.

  Further, the silane coupling agent (D) may be a monomer type silane compound or an oligomer type silane compound which is partially hydrolyzed and polycondensed. However, it is excellent in durability and reworkability, and is coated with an adhesive. It is preferable to use an oligomer type silane compound in that it is less likely to volatilize during drying after work.

Examples of the silane coupling agent (D) include an epoxy group-containing silane coupling agent, a (meth) acryloyl group-containing silane coupling agent, a mercapto group-containing silane coupling agent, a hydroxyl group-containing silane coupling agent, and a carboxyl group-containing silane. Examples include coupling agents, amino group-containing silane coupling agents, amide group-containing silane coupling agents, and isocyanate group-containing silane coupling agents. These may be used alone or in combination of two or more.
Among these, an epoxy group-containing silane coupling agent and a mercapto group-containing silane coupling agent are preferably used, and it is also possible to use an epoxy group-containing silane coupling agent and a mercapto group-containing silane coupling agent in combination with moisture and heat resistance. It is preferable in that the improvement and the adhesive strength are not excessively increased.

Specific examples of the epoxy group-containing silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and γ-glycol. Silane compounds such as Sidoxypropylmethyldimethoxysilane, Methyltri (glycidyl) silane, β- (3,4Epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4Epoxycyclohexyl) ethyltrimethoxysilane, and some silane compounds Hydrolyzed and polycondensed oligomer type silane compounds (such as epoxy group-containing silicone alkoxy oligomers), or silane compounds obtained by ether-modifying a part of these silane compounds.
Among these, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, and silane are preferable. Examples thereof include oligomeric silane compounds such as compounds, or silane compounds obtained by ether-modifying a part of these silane compounds.

  Specific examples of the mercapto group-containing silane coupling agent include, for example, silane compounds such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropyldimethoxymethylsilane, and some silane compounds. Hydrolyzed and polycondensed oligomer type silane compounds (such as mercapto group-containing silicone alkoxy oligomers).

In the present invention, as the silane coupling agent (D), among the above silane compounds, it is preferable to use an oligomer type silane compound, and further from the viewpoint of storage stability, an oligomer type silane compound having an ethoxy group as an alkoxy group. Most preferably, is used.
Specifically, commercially available products such as “X41-1805” and “X41-1059” manufactured by Shin-Etsu Chemical Co., Ltd. may be used.

As content of the said silane coupling agent (D), it is 0.001-2 weight part normally with respect to 100 weight part of acrylic resin (A), Preferably 0.01-0.4 weight part, Particularly preferred is 0.015 to 0.1 part by weight.
If the content of the silane coupling agent (D) is too small, the effect tends not to be obtained. If the content is too large, bleeding tends to occur and durability tends to decrease.

In the pressure-sensitive adhesive composition of the present invention, other acrylic pressure-sensitive adhesives, other pressure-sensitive adhesives, urethane resins, rosins, rosin esters, hydrogenated rosin esters, phenol resins, aliphatics, as long as the effects of the present invention are not impaired. Various additives such as tackifiers such as petroleum-based petroleum resins, alicyclic petroleum resins, and styrene-based resins, colorants, fillers, antioxidants, ultraviolet absorbers, functional dyes, and UV or radiation irradiation Compounds that cause color or discoloration can be blended. In addition to the above additives, a small amount of impurities and the like contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition may be contained.
The content of the other components may be appropriately set so as to obtain desired physical properties, but is preferably 5 parts by weight or less, particularly 1 part by weight or less, based on the acrylic resin (A). Furthermore, it is preferable that it is 0.5 weight or less. When there is too much this content, compatibility with acrylic resin (A) will fall, and there exists a tendency for transparency to be impaired.

Thus, the pressure-sensitive adhesive composition of the present invention can be obtained.
When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive for laminating a polarizing plate and a glass substrate, the polarizing plate can exhibit excellent optical properties (degree of polarization) even under wet heat conditions, and is resistant to heat and heat whitening. , Antistatic and reworkable pressure-sensitive adhesives can be obtained in a balanced manner. Adhesives for optical members for bonding displays and optical components constituting them, particularly polarizing plates and liquid crystal cells It is useful as an adhesive for polarizing plates for bonding glass substrates and the like.

The pressure-sensitive adhesive composition of the present invention can be made into a pressure-sensitive adhesive by crosslinking with an isocyanate-based crosslinking agent (C), and further, a pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive is laminated on an optical member (optical laminate). By forming, an optical member with an adhesive layer can be obtained.
It is preferable that the optical member with the pressure-sensitive adhesive layer is further provided with a release sheet on the surface opposite to the optical member surface of the pressure-sensitive adhesive layer.

As a manufacturing method of the optical member with the pressure-sensitive adhesive layer,
[1] A method of applying a pressure-sensitive adhesive composition on an optical member, drying, pasting a release sheet, and performing a treatment by at least one of aging at room temperature or in a heated state,
[2] There is a method of applying an adhesive composition on a release sheet, drying, then bonding an optical member, and performing treatment by at least one of aging at room temperature or in a heated state.
Among these, the method of aging at room temperature by the method [2] is preferable in that it does not damage the substrate and is excellent in substrate adhesion.

  The aging treatment is performed to balance the physical properties of the adhesive as the reaction time of the chemical crosslinking of the adhesive. As the aging conditions, the temperature is usually from room temperature to 70 ° C., and the time is usually from 1 day to 30 days. Specifically, for example, the treatment may be performed under conditions such as 23 ° C. for 1 day to 20 days, 23 ° C. for 3 to 10 days, 40 ° C. for 1 day to 7 days, and the like.

  In applying the pressure-sensitive adhesive composition, it is preferable to dilute the pressure-sensitive adhesive composition in a solvent, and the diluted concentration is preferably 5 to 60% by weight, particularly preferably 10%, as a heating residue concentration. ~ 30% by weight. The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition. For example, ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, acetone, methyl ethyl ketone, A ketone solvent such as methyl isobutyl ketone, an aromatic solvent such as toluene and xylene, and an alcohol solvent such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate and methyl ethyl ketone are preferably used from the viewpoints of solubility, drying property, price, and the like.

  The pressure-sensitive adhesive composition is applied by a conventional method such as roll coating, die coating, gravure coating, comma coating, or screen printing.

  The gel fraction of the pressure-sensitive adhesive layer produced by the above method is preferably 40 to 99%, particularly preferably 50 to 97%, more preferably 70, from the viewpoint of durability performance and suppression of decrease in polarization degree. ~ 95%. If the gel fraction is too low, the movement of the ionic compound cannot be suppressed and the degree of polarization tends to decrease, and if it is too high, the antistatic performance tends to decrease.

The gel fraction is a measure of the degree of crosslinking (curing degree), and is calculated, for example, by the following method. That is, the adhesive layer is scraped from an adhesive sheet (not provided with a separator) in which an adhesive layer is formed on a substrate such as a polarizing plate, and the adhesive layer is wrapped in a 200-mesh SUS metal mesh and placed in ethyl acetate. The weight percentage of the insoluble adhesive component remaining in the wire mesh after being immersed at 23 ° C. for 24 hours is defined as the gel fraction. Moreover, in the case of a double-sided separator, after removing the single-sided separator, it may be measured by scraping from the separator on the side where the adhesive is formed.
In addition, in adjusting a gel fraction to the said range, it is achieved by adjusting the kind and quantity of a crosslinking agent, etc.

  The pressure-sensitive adhesive layer produced by the above method preferably has a good tack feeling when touched with a finger, because it has good wettability when actually attached to an adherend, and therefore tends to improve workability. .

  Moreover, it is preferable that the thickness of the adhesive layer in the optical member with an adhesive layer obtained is 5-300 micrometers, It is especially 10-50 micrometers, Furthermore, it is preferable that it is 10-30 micrometers. If the thickness of the pressure-sensitive adhesive layer is too thin, the physical properties of the pressure-sensitive adhesive tend to be unstable. If the thickness is too large, the content of the ionic compound increases, and thus the degree of polarization decreases or the wet heat whitening property tends to deteriorate. .

  The optical member with the pressure-sensitive adhesive layer of the present invention has a release sheet directly or after peeling off the release sheet, and then the surface of the pressure-sensitive adhesive layer is bonded to a glass substrate and used for, for example, a liquid crystal display board.

  The initial adhesive strength of the pressure-sensitive adhesive layer of the present invention is appropriately determined according to the material of the adherend. For example, when adhering to a glass substrate, it preferably has an adhesive strength of 0.2 N / 25 mm to less than 15 N / 25 mm, particularly preferably less than 0.5 N / 25 mm to 10 N / 25 mm, more preferably 2 N / 25 mm to less than 5 N / 25 mm.

  The initial adhesive strength is calculated as follows. About the polarizing plate with an adhesive layer, it cuts to width 25mm width, peels off a release film, presses the adhesive layer side to a non-alkali glass board (Corning company make, "Eagle XG"), A glass plate is bonded. Then, after performing an autoclave process (50 degreeC, 0.5 MPa, 20 minutes), 23 degreeC and 50% R. H. Then, after leaving for 24 hours, perform a 180 ° C. peel test.

  The polarizing plate used in the present invention is usually one obtained by laminating a triacetyl cellulose (TAC) film as a protective film on both sides of a polarizing film, and the polarizing film has an average degree of polymerization of 1,500 to 10, A uniaxially stretched film dyed with an aqueous solution of iodine-potassium iodide or a dichroic dye using a film made of a polyvinyl alcohol resin having a saponification degree of 85 to 100 mol% as a raw film (usually 2 to 10 Times, preferably a draw ratio of about 3 to 7 times).

  The polyvinyl alcohol resin is usually produced by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate, but a small amount of unsaturated carboxylic acid (including salt, ester, amide, nitrile, etc.), olefins, vinyl ether And a component copolymerizable with vinyl acetate, such as an unsaturated sulfonate. Moreover, what is called polyvinyl acetal resin and polyvinyl alcohol derivatives, such as polybutyral resin and polyvinyl formal resin, which are obtained by reacting polyvinyl alcohol with an aldehyde in the presence of an acid can be mentioned.

Examples of the protective film for the polarizing plate include acrylic films, polyethylene films, polypropylene films, cycloolefin films and the like in addition to conventional TAC films.
Moreover, the single-sided protective film polarizing plate which eliminated the protective film on the side bonded to an optical member for film thickness reduction is also mentioned.
The pressure-sensitive adhesive composition of the present invention is suitably used for any protective film selected from a TAC film, an acrylic film, a cycloolefin film, a PET film, and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight basis.

First, various acrylic resins were prepared as follows. In addition, regarding the measurement of the weight average molecular weight, dispersion degree, and glass transition temperature of acrylic resin (A), it measured according to the above-mentioned method.
In addition, regarding the measurement of a viscosity, it measured according to the 4.5.3 rotational viscometer method of JISK5400 (1990).

<Preparation of acrylic resin (A)>
[Production of acrylic resin (A-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 7.0 parts by weight of 2-hydroxyethyl acrylate (a1) and 73.3 parts by weight of butyl acrylate (a2) Parts, benzyl acrylate (a3) 19 parts, acrylic acid (a1) 0.7 parts, ethyl acetate 54.9 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator The reaction was started and the AIBN ethyl acetate solution was added dropwise appropriately, followed by reaction at reflux temperature for 3.25 hours, and then diluted with ethyl acetate to obtain an acrylic resin (A-1) solution (solid content 22.8%, Viscosity 7,900 mPa · s / 25 ° C., glass transition temperature −43 ° C.) was obtained.

[Production of acrylic resin (A-2)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet, and a thermometer, 8.0 parts by weight of 2-hydroxyethyl acrylate (a1) and 72.3 parts by weight of butyl acrylate (a2) Parts, benzyl acrylate (a3) 19 parts, acrylic acid (a1) 0.7 parts, ethyl acetate 56.3 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator The reaction was started, and AIBN ethyl acetate solution was added dropwise appropriately, followed by reaction at reflux temperature for 3.25 hours, then diluted with ethyl acetate to obtain an acrylic resin (A-2) solution (solid content 22.9%, Viscosity 8,600 mPa · s / 25 ° C., glass transition temperature −43 ° C.).

[Production of acrylic resin (A-3)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 9.0 parts by weight of 2-hydroxyethyl acrylate (a1) and 71.3 parts by weight of butyl acrylate (a2) Parts, benzyl acrylate (a3) 19 parts, acrylic acid (a1) 0.7 parts, ethyl acetate 54.9 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator The reaction was started, and AIBN ethyl acetate solution was added dropwise appropriately. After reacting at reflux temperature for 3.25 hours, the reaction mixture was diluted with ethyl acetate to obtain an acrylic resin (A-3) solution (solid content 21.2%, A viscosity of 6,900 mPa · s / 25 ° C. and a glass transition temperature of −42 ° C. was obtained.

[Production of acrylic resin (A-4)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 10.0 parts by weight of 2-hydroxyethyl acrylate (a1) and 70.3 parts by weight of butyl acrylate (a2) Parts, benzyl acrylate (a3) 19 parts, acrylic acid (a1) 0.7 parts, ethyl acetate 54.9 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator The reaction was started, and AIBN ethyl acetate solution was added dropwise appropriately, followed by reaction at reflux temperature for 3.25 hours, then diluted with ethyl acetate to obtain an acrylic resin (A-4) solution (solid content: 18.0%, Viscosity 3,500 mPa · s / 25 ° C., glass transition temperature −42 ° C.) was obtained.

[Production of acrylic resin (A-5)]
In a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet, and a thermometer, 15.0 parts by weight of 2-hydroxyethyl acrylate (a1) and 62.6 parts by weight of butyl acrylate (a2) Parts, benzyl acrylate (a3) 19 parts, acrylic acid (a1) 0.7 parts, ethyl acetate 47.2 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator The reaction was started, and AIBN ethyl acetate solution was added dropwise appropriately. After reacting at reflux temperature for 3.25 hours, the mixture was diluted with ethyl acetate to obtain an acrylic resin (A-5) solution (solid content 17.6%, Viscosity 3,100 mPa · s / 25 ° C., glass transition temperature −42 ° C.).

[Manufacture of acrylic resin (A′-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 3.5 parts by weight of 2-hydroxyethyl acrylate (a1) and 77.8% by weight of butyl acrylate (a2) Parts, benzyl acrylate (a3) 18 parts, acrylic acid (a1) 0.7 parts, ethyl acetate 52.5 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator The reaction was started, and AIBN ethyl acetate solution was added dropwise appropriately. After reacting at reflux temperature for 3.25 hours, the reaction mixture was diluted with ethyl acetate to obtain an acrylic resin (A′-1) solution (solid content: 23.3%). And a viscosity of 8,300 mPa · s / 25 ° C., a glass transition temperature of −45 ° C.).

[Production of acrylic resin (A'-2)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 6.0 parts by weight of 2-hydroxyethyl acrylate (a1) and 74.3 parts by weight of butyl acrylate (a2) Parts, benzyl acrylate (a3) 19 parts, acrylic acid (a1) 0.7 parts, ethyl acetate 54.9 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator The reaction was started and the AIBN ethyl acetate solution was added dropwise appropriately. After reacting at reflux temperature for 3.25 hours, the reaction mixture was diluted with ethyl acetate to obtain an acrylic resin (A′-2) solution (solid content 22.9%). , Viscosity 8,400 mPa · s / 25 ° C., glass transition temperature −43 ° C.).

<Ionic compound (B)>
The following were prepared as ionic compounds comprising an ammonium cation and a trifluoromethanesulfonylimide anion.
B-1: Tributylmethylammonium trifluoromethanesulfonylimide

<Crosslinking agent (C)>
The following were prepared as a crosslinking agent (C).
C-1: Adduct body of tolylene diisocyanate and trimethylolpropane ("Coronate L" manufactured by Tosoh Corporation)
C-2: Adduct body of xylylene diisocyanate and trimethylolpropane (“Takenate D-110N” manufactured by Mitsui Chemicals, Inc.)
C-3: Adduct body of hexamethylene diisocyanate and trimethylolpropane (“Takenate D-160N” manufactured by Mitsui Chemicals, Inc.)
C-4: Adduct body of isophorone diisocyanate and trimethylolpropane (“Takenate D-140N” manufactured by Mitsui Chemicals, Inc.)
C-5: Adduct body of hydrogenated xylylene diisocyanate and trimethylolpropane (“Takenate D-120N” manufactured by Mitsui Chemicals, Inc.)
C′-1: Biuret of hexamethylene diisocyanate (“Duranate 24A-100” manufactured by Asahi Kasei Corporation)
C′-2: Nuredate of hexamethylene diisocyanate (“Coronate HX” manufactured by Tosoh Corporation)

<Silane coupling agent (D)>
The following were prepared as a silane coupling agent (D).
D-1: Oligomer type silane compound (“X41-1059A” manufactured by Shin-Etsu Chemical Co., Ltd., containing functional group: epoxy group, containing alkoxy group: methoxy group and ethoxy group, alkoxy group content: 42%)

<Examples 1-5, Comparative Examples 1-2>
Said component (A)-(D) was mix | blended as the following Table 1, solid content concentration was adjusted to 12.5% with ethyl acetate, and the adhesive composition was obtained.

[Preparation of polarizing plate with adhesive layer (1)]
The obtained pressure-sensitive adhesive composition was applied to a 38 μm separator (“Lumirror SP-0138BU” manufactured by Toray Industries, Inc.), dried at 100 ° C. for 3 minutes, and then subjected to a corona-treated cycloolefin film and a TAC film on each side. The pressure-sensitive adhesive layer side opposite to the separator is bonded to the cycloolefin surface of the polarizing plate laminated on the plate, and cured for 7 days in a 23 ° C. × 50% RH environment to obtain a polarizing plate with a pressure-sensitive adhesive layer. (Layer constitution; separator / adhesive layer / cycloolefin film / polarizer / TAC film). Using the obtained polarizing plate with the pressure-sensitive adhesive layer, reworkability (adhesive strength / glue residue) was evaluated.

<Reworkability>
The polarizing plate with the pressure-sensitive adhesive layer obtained above was cut to a width of 25 mm, the separator was removed, and it was bonded to an alkali-free glass (Corning “Eagle XG”: 1.1 mm thickness) with a 2 kg roller and autoclaved (0 5Mpa × 50 ° C × 20 minutes), left at 23 ° C × 50% RH for 24 hours, and then peeled off 180 ° to remove the adhesive strength and adhesive residue on the glass. evaluated.

〔Adhesive force〕
(Evaluation criteria)
◎ ・ ・ ・ 5N / 25mm or less ○ ・ ・ ・ Higher than 5N / 25mm and less than 10N / 25mm Δ ・ ・ ・ 10N / 25mm or more to less than 15N / 25mm × ・ ・ ・ 15N / 25mm or more [adhesive residue]
(Evaluation criteria)
○ ・ ・ ・ No glue residue × ・ ・ ・ There is glue residue

[Preparation of moisture and heat whitening test sample]
The pressure-sensitive adhesive composition obtained above was applied to a 38 μm separator (“Lumirror SP-0138BU” manufactured by Toray Industries, Inc.), dried at 100 ° C. for 3 minutes, and then subjected to corona treatment on the surface of the pressure-sensitive adhesive layer opposite to the separator. The applied cycloolefin film was bonded and cured in an environment of 23 ° C. × 50% RH for 7 days to obtain a cycloolefin film with an adhesive layer (layer constitution; separator / adhesive layer / cycloolefin film).
The obtained cycloolefin film with a pressure-sensitive adhesive layer was cut to 3.5 cm × 3.5 cm, the separator was peeled off, and the pressure-sensitive adhesive layer side was alkali-free glass (Corning “Eagle XG”: thickness 1.1 mm) Then, the sample was subjected to autoclave treatment (0.5 MPa × 50 ° C. × 20 minutes) to prepare a sample for a heat and humidity resistance whitening test.
Using the obtained test sample, the wet heat whitening resistance was evaluated as follows. The results are shown in Table 1.

<Heat and heat whitening resistance>
The sample for moisture and heat whitening test was exposed to an environment of 60 ° C. and 90% RH for 200 hours, and the haze was measured immediately after removal and 1 hour after removal to evaluate moisture and heat whitening resistance. In addition, a haze value is the value which deducted the value of 1.1 mm non-alkali glass as a blank.
(Evaluation criteria)
[Haze immediately after removal]
◎ ・ ・ ・ less than 1 ○ ・ ・ ・ 1 or more and less than 2 Δ ・ ・ ・ 2 or more and less than 3 × ・ ・ ・ 3 or more [haze after taking out 1 hour]
○ ・ ・ ・ less than 1 △ ・ ・ ・ 1 or more and less than 2 × ・ ・ ・ 2 or more

From the results shown in Table 1, in Examples using the pressure-sensitive adhesive composition of the present invention containing the acrylic resin (A) obtained by copolymerizing a hydroxyl group-containing monomer at a specific ratio, the pressure-sensitive adhesive even immediately after taking out in the moisture and heat resistance test. It can be seen that the haze of the layer is low and the heat and heat resistance is excellent.
On the other hand, Comparative Examples 1 and 2 using the pressure-sensitive adhesive composition containing an acrylic resin whose hydroxyl group-containing monomer content does not satisfy the scope of the present invention are the haze of the pressure-sensitive adhesive layer immediately after taking out and after 1 hour. It is high and it turns out that it is inferior to moisture-and-heat whitening resistance.

<Examples 6-9 and Comparative Examples 3-4>
Next, the said component (A)-(D) was mix | blended as shown in following Table 2, solid content concentration was adjusted to 12.5% with ethyl acetate, and the adhesive composition was obtained.

[Preparation of polarizing plate with adhesive layer (2)]
The obtained pressure-sensitive adhesive composition was applied to a 38 μm separator (“Lumirror SP-0138BU” manufactured by Toray Industries, Inc.), dried at 100 ° C. for 3 minutes, and then one TAC surface of a polarizing plate in which TAC films were laminated on both sides. The surface of the pressure-sensitive adhesive layer opposite to the separator was bonded to each other and cured for 7 days in an environment of 23 ° C. × 50% RH to obtain a polarizing plate with a pressure-sensitive adhesive layer (layer structure; separator / pressure-sensitive adhesive layer / TAC film / polarized light). Child / TAC film). Antistatic performance (surface resistivity) and wet heat resistance (polarization degree) were evaluated using the obtained polarizing plate with an adhesive layer. The results are shown in Table 2.

<Antistatic performance>
The polarizing plate with the pressure-sensitive adhesive layer obtained above was allowed to stand in an atmosphere of 23 ° C. × 50% RH for 24 hours, and then the separator was peeled off, and a surface resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd., device name “ Hiresta-UP MCP-HT450 ") was used to measure the surface resistivity of the adhesive layer. The evaluation criteria are as follows.
(Evaluation criteria)
○ ・ ・ ・ less than 1.0E + 11 × ・ ・ ・ 1.0E + 11 or more

The polarizing plate with the pressure-sensitive adhesive layer obtained above was cut to 3.5 cm × 3.5, the separator was peeled off, and the pressure-sensitive adhesive layer side was made an alkali-free glass plate (“Eagle XG” manufactured by Corning): thickness 1.1 mm ) And pasting the polarizing plate and the glass plate, followed by autoclaving (50 ° C., 0.5 MPa, 20 minutes) to produce a sample for a moisture heat resistance test.

<Heat and heat resistance>
[Degree of polarization]
The polarization degree (initial polarization degree) of the sample for moisture and heat resistance test obtained above was measured. Thereafter, the degree of polarization (polarization degree after wet heat) after being exposed and taken out in an environment of 80 ° C. × 90% RH for 5 days was measured, and the maintenance ratio of the degree of polarization before and after the durability test was determined from the following formula (1). Evaluation was performed as follows.
The degree of polarization was measured using “UV-visible near-infrared spectrophotometer: V7000 and automatic polarization measuring device VAP7070” manufactured by JASCO Corporation. Polarization degree maintenance rate (%) = degree of polarization after wet heat / initial degree of polarization (1)
(Evaluation criteria)
◎ ... 99.70 or more ○ ... 99.60 to less than 99.70 Δ ... 99.50 to less than 99.60 × ... less than 99.50

From the results in Table 2, an acrylic resin (A) obtained by copolymerizing a hydroxyl group-containing monomer in a specific content range, a specific ionic compound (B), and a polyhydric alcohol compound and a polyhydric acid as an isocyanate cross-linking agent (C). In Examples 6 to 9 using the pressure-sensitive adhesive composition containing an isocyanate compound obtained by reacting an isocyanate compound, it can be seen that there is little decrease in the degree of polarization before and after the wet heat resistance test.
On the other hand, in Comparative Examples 3 and 4 using a pressure-sensitive adhesive composition containing a crosslinking agent other than an isocyanate compound obtained by reacting a polyhydric alcohol compound and a polyvalent isocyanate compound as a crosslinking agent, It can be seen that the degree of polarization has decreased after the test, and the optical properties in a heat and humidity resistant environment are poor.

  When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive for laminating a polarizing plate and a glass substrate, the polarizing plate can exhibit excellent optical properties (degree of polarization) even under wet heat conditions, and is resistant to heat and heat whitening. , Antistatic and reworkable pressure-sensitive adhesives can be obtained in a balanced manner. Adhesives for optical members for bonding displays and optical components constituting them, particularly polarizing plates and liquid crystal cells It is useful as an adhesive for polarizing plates for bonding glass substrates and the like.

Claims (7)

A pressure-sensitive adhesive composition containing an acrylic resin (A), an ionic compound (B) and an isocyanate-based crosslinking agent (C),
The acrylic resin (A) is an acrylic resin containing 6.5 to 20% by weight of a structural unit derived from the hydroxyl group-containing monomer (a1),
The ionic compound (B) is an ionic compound comprising an ammonium cation and a trifluoromethanesulfonylimide anion,
A pressure-sensitive adhesive composition, wherein the isocyanate-based crosslinking agent (C) is an isocyanate compound that is a reaction product of a polyhydric alcohol compound (c1) and a polyvalent isocyanate compound (c2).   The pressure-sensitive adhesive composition according to claim 2, wherein the acrylic resin (A) has a weight average molecular weight of 80 to 3,000,000.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the polyhydric alcohol compound (c1) is trimethylolpropane.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the polyvalent isocyanate compound (c2) is an alicyclic polyvalent isocyanate and / or an aliphatic polyvalent isocyanate.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the isocyanate-based crosslinking agent (C) is a reaction product of trimethylolpropane and an alicyclic polyvalent isocyanate and / or an aliphatic polyvalent isocyanate. .   The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive composition is crosslinked with an isocyanate-based crosslinking agent (C).   A pressure-sensitive adhesive for polarizing plates, comprising the pressure-sensitive adhesive according to claim 6.