JP6950530B2 - Acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive using the same, a pressure-sensitive adhesive for polarizing plates, and an image display device. - Google Patents

Description

The present invention relates to an acrylic pressure-sensitive adhesive composition, a pressure-sensitive adhesive using the same, and a pressure-sensitive adhesive for a polarizing plate. It relates to an acrylic pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive.

Conventionally, a polarizing plate made of a polyvinyl alcohol-based film or the like to which polarization property is imparted and whose both sides are coated with a protective film is laminated on the surface of a liquid crystal cell in which an oriented liquid crystal component is sandwiched between two glass plates. However, an image display device is manufactured. The lamination of the polarizing plate on the surface of the liquid crystal cell is usually carried out by abutting and pressing the pressure-sensitive adhesive layer provided on the surface of the polarizing plate against the surface of the liquid crystal cell.

An adhesive containing a polyvinyl alcohol-based resin is preferably used as an adhesive for adhering these protective films and a polarizing element. Specifically, an aqueous solution obtained by blending a polyvinyl alcohol-based resin and a cross-linking agent is used as a polarizing element. A polarizing plate is manufactured by applying it on top, laminating a protective film, and then heating and drying it. In the manufacturing process of the polarizing plate, it is preferable that the moisture contained in the adhesive permeates the protective film, and as the protective film, a highly breathable triacetyl cellulose film (TAC film) has been preferably used so far. ..

However, in recent years, from the viewpoint of dimensional stability and durability, an olefin film, particularly a cycloolefin film (COP film), has come to be used as a protective film for a polarizing plate instead of a TAC film. When such a COP film is used, the wet and heat resistance of the polarizing plate is improved, but when the liquid crystal display device in which the polarizing plate is attached to the liquid crystal cell via the adhesive is exposed to a moist heat environment, the adhesive is used. There was a problem that the whitening phenomenon of the layer was likely to occur.
This is because when the adhesive layer is left under moist heat conditions for a long time, moisture gradually infiltrates into the adhesive layer, and when the temperature is returned to room temperature, the moisture condenses in the adhesive layer, but the COP film has low moisture permeability. This is because the release of water in the pressure-sensitive adhesive layer is suppressed.

Further, the adhesive for adhering the polarizing plate and the liquid crystal cell is required to have durability such as heat resistance and moist heat resistance. However, especially in a moist heat environment, moisture penetrates into the pressure-sensitive adhesive layer to form a glass substrate. There is a problem that the polarizing plate partially floats or peels off from the glass substrate because the adhesiveness of the glass substrate is lowered, and in order to improve the adhesiveness between the glass substrate and the pressure-sensitive adhesive layer, a silane coupling agent is generally used. Is known to contain. The silane coupling agent is hydrolyzed by water to become silanol, which reacts with and bonds with the hydroxyl group on the glass surface to improve the adhesiveness.

As a pressure-sensitive adhesive having excellent moisture-heat resistance, for example, Patent Document 1 describes that an acrylic pressure-sensitive adhesive using an acrylic resin copolymerized with a larger amount of hydroxyl group monomers than usual has excellent moisture-heat bleaching resistance. ing.

Japanese Unexamined Patent Publication No. 2013-213203

The pressure-sensitive adhesive described in Patent Document 1 has a high content of hydroxyl group monomers (polar group-containing monomers) in acrylic resins, and therefore has excellent moisture-heat bleaching resistance, but on the other hand, it has high hydrophilicity and is in a normal environment. Moisture easily penetrates into the adhesive layer even below.

Here, in the manufacture of an image display device, usually, an adhesive layer is provided on the release-treated film, and the adhesive layer surface on the opposite side of the release film is attached to the polarizing plate to obtain a polarizing plate with an adhesive layer. It is manufactured by peeling off the release film and attaching the adhesive layer and the glass substrate of the liquid crystal cell when the film is attached to the liquid crystal cell.

Therefore, when the pressure-sensitive adhesive described in Patent Document 1 is used as a pressure-sensitive adhesive for a polarizing plate, although the moisture-heat whitening resistance and the initial durability are good, after manufacturing the polarizing plate with the pressure-sensitive adhesive layer, the glass of the liquid crystal cell. The silane coupling agent is gradually hydrolyzed by the moisture contained in the pressure-sensitive adhesive layer while it is stored until it is bonded to the substrate, and the alkoxy group that contributes to the adhesiveness to the glass is reduced by the condensation reaction or the like. There is a problem that the adhesiveness between the polarizing plate and the glass substrate when bonded to the liquid crystal cell is lowered (the durability after aging is lowered), that is, the storage stability of the pressure-sensitive adhesive layer is lowered.

Therefore, in the present invention, even when used as an adhesive for a polarizing plate for bonding a polarizing plate and a glass substrate or the like under such a background, it is excellent in moisture-heat whitening resistance, initial durability, and storage stability ( It is an object of the present invention to provide an acrylic pressure-sensitive adhesive composition capable of obtaining a pressure-sensitive adhesive layer having excellent durability over time.

However, as a result of diligent research in view of such circumstances, the present inventors have relatively many structural units derived from polar group-containing monomers in an acrylic pressure-sensitive adhesive composition containing an acrylic resin and a silane coupling agent. By using the contained acrylic resin and further blending a silane coupling agent having a specific alkoxy group, whitening of the pressure-sensitive adhesive layer can be suppressed even under moist heat conditions, and a pressure-sensitive adhesive having excellent storage stability can be obtained. I found.

That is, the present invention is an acrylic pressure-sensitive adhesive composition containing an acrylic resin (A) and a silane coupling agent (B) containing at least one reactive functional group and one or more alkoxy groups in the structure. Te, the acrylic resin (a), a structural unit derived from polar group-containing monomer (a1) containing from 5 to 50 wt%, the polar group-containing monomer (a1) is a hydroxyl group-containing monomer, the weight average molecular weight The first gist is an acrylic pressure-sensitive adhesive composition in which 600,000 to 2.5 million acrylic resins and the alkoxy group contained in the silane coupling agent (B) contains an ethoxy group and a methoxy group.
Further, in the present invention, the pressure-sensitive adhesive obtained by cross-linking the acrylic pressure-sensitive adhesive composition of the first gist with the cross-linking agent (C) is the second gist, and the polarizing agent is obtained by using the pressure-sensitive adhesive of the second gist. The third gist is the adhesive for plates, and the fourth gist is an image display device in which a polarizing plate and a liquid crystal cell are bonded together with the adhesive of the second gist.

The present invention is an acrylic pressure-sensitive adhesive composition containing an acrylic resin (A) and a silane coupling agent (B) containing at least one reactive functional group and one or more alkoxy groups in the structure. the acrylic resin (a), a structural unit derived from polar group-containing monomer (a1) containing from 5 to 50 wt%, the polar group-containing monomer (a1) is a hydroxyl group-containing monomer, the weight average molecular weight of 60 It is an acrylic resin of 10,000 to 2.5 million , and the alkoxy group contained in the silane coupling agent (B) is an acrylic pressure-sensitive adhesive composition containing an ethoxy group and a methoxy group. Therefore, the pressure-sensitive adhesive obtained by using the acrylic pressure-sensitive adhesive composition of the present invention is excellent in durability and moisture-heat whitening resistance even when used as a pressure-sensitive adhesive for bonding a polarizing plate and a glass substrate or the like. Also excellent in storage stability of the adhesive layer. Therefore, by using this acrylic pressure-sensitive adhesive composition, it is possible to obtain an image display device that does not deteriorate in performance and exhibits excellent optical characteristics even when used in a harsher environment such as under moist heat conditions. can. In particular, even when either a TAC film or a COP film is used as the protective film for the polarizing plate, the pressure-sensitive adhesive layer has excellent moisture-heat whitening resistance and storage stability of the pressure-sensitive adhesive layer. Very useful as an adhesive.

Since the polar group-containing monomer (a1) is a hydroxyl group-containing monomer, and more excellent in wet heat whitening resistance, excellent in adhesive properties.

When the alkoxy group contained in the silane coupling agent (B) is an ethoxy group and a methoxy group, the durability and the storage stability of the pressure-sensitive adhesive layer are further excellent.

When the silane coupling agent (B) contains 5% by weight or more of an alkoxy group in its structure, the durability and the storage stability of the pressure-sensitive adhesive layer are further excellent, and the reworkability is also excellent.

When the reactive functional group equivalent of the silane coupling agent (B) is 50 to 1000 g / mol, the durability and reworkability are further excellent.

Hereinafter, the present invention will be described in detail.
In the present invention, (meth) acrylic means acrylic or methacrylic, (meth) acryloyl means acryloyl or methacrylic, 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-based monomer.

The acrylic pressure-sensitive adhesive composition of the present invention contains an acrylic resin (A) and a silane coupling agent (B) as essential components.

<Acrylic resin (A)>
The acrylic resin (A) used in the present invention is an acrylic resin containing 5 to 50% by weight of a structural unit derived from the polar group-containing monomer (a1). For example, 5 to 50% by weight of the polar group-containing monomer (a1) is contained. It is obtained by copolymerizing a copolymerization component containing 50% by weight. The copolymerization component of the acrylic resin (A) may contain a (meth) acrylic acid alkyl ester-based monomer (a2) or another copolymerizable ethylenically unsaturated monomer (a3), if necessary.

The polar group-containing monomer (a1) is at least one selected from a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a nitrogen-containing monomer.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl ( Acrylic acid hydroxyalkyl esters such as meta) acrylates, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylates, oxyalkylene-modified monomers such as diethylene glycol (meth) acrylates and polyethylene glycol (meth) acrylates, and others 2- Primary hydroxyl group-containing monomers such as acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol (meth) acrylamide, hydroxyethyl acrylamide; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3 -Secondary hydroxyl group-containing monomers such as chloro2-hydroxypropyl (meth) acrylate; tertiary hydroxyl group-containing monomers such as 2,2-dimethyl2-hydroxyethyl (meth) acrylate can be mentioned.

Among the above hydroxyl group-containing monomers, a primary hydroxyl group-containing monomer is preferable in terms of excellent reactivity with a cross-linking agent and improvement in moisture-heat whitening resistance, and further, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are used. It is preferable because it has few impurities such as di (meth) acrylate and is easy to manufacture.

As the hydroxyl group-containing monomer used in the present invention, it is preferable to use a monomer having a content ratio of the impurity di (meth) acrylate of 0.5% by weight or less, more preferably 0.2% by weight or less. Particularly preferably, it is 0.1% by weight or less. Specifically, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and 2-hydroxypropyl acrylate are preferable.

Examples of the carboxyl group-containing monomer include (meth) acrylic acid, dimer acid of acrylic acid such as β-carboxyethyl acrylate, and the like, among which, in terms of moisture-heat whitening resistance and stability during polymerization ( Meta) Acrylic acid is preferred.

Examples of the nitrogen-containing monomer include an amino group-containing monomer and an amide group-containing monomer.

Examples of the amino group-containing monomer include a primary amino group-containing monomer such as aminomethyl (meth) acrylate and aminoethyl (meth) acrylate, and a secondary amino group-containing monomer such as tert-butylaminoethyl (meth) acrylate. Examples thereof include tertiary amino group-containing monomers such as ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and diethylaminoethyl (meth) acrylate.
Among the above amino group-containing monomers, a tertiary amino group-containing monomer is preferable, and dimethylaminoethyl (meth) acrylate is particularly preferable, from the viewpoint of storage stability of the resin solution and the effect of promoting cross-linking.

Examples of the amide group-containing monomer include methoxymethyl (meth) acrylamide, ethoxymethyl (meth) acrylamide, propoxymethyl (meth) acrylamide, isopropoxymethyl (meth) acrylamide, n-butoxymethyl (meth) acrylamide, and isobutoxy. Alkoxyalkyl (meth) acrylamide-based monomers such as methyl (meth) acrylamide; dialkyl (meth) acrylamide-based monomers such as dimethyl (meth) acrylamide and diethyl (meth) acrylamide; (meth) acrylamide; N- (hydroxymethyl) acrylamide; (Meta) Acrylamide morpholine and the like can be mentioned.

Among the amide group-containing monomers, alkoxyalkyl (meth) acrylamide-based monomers and dialkyl (meth) acrylamide-based monomers are preferable in terms of stability of the resin solution and suppression of migration of the antistatic agent.

The above polar group-containing monomer (a1) is stickies resistance and wet heat whitening resistance, using a hydroxyl group-containing monomer in terms of excellent long-term reworkability.

The content of the polar group-containing monomer (a1) (when two or more kinds are used in combination, the total content thereof) is 5 to 50% by weight, particularly 6 to 30% by weight, based on the total copolymerization component. %, More preferably 7 to 25% by weight, more preferably 8 to 20% by weight. If the content is too small, the moisture-heat bleaching resistance is lowered, and if it is too high, the storage stability of the adhesive is lowered.

As the (meth) acrylic acid alkyl ester-based monomer (a2), for example, the alkyl group usually has 1 to 20 carbon atoms (preferably 1 to 18, particularly preferably 1 to 12, still more preferably 1 to 8). Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, and n-propyl (. Meta) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) Examples include acrylate. These may be used alone or in combination of two or more.

Among these, methyl acrylate, 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-based monomer (a2) is preferably 20 to 95% by weight, particularly preferably 40 to 94% by weight, still more preferably 45 to 45% by weight, based on the total copolymerization component. It is 93% by weight, especially 50 to 92% by weight.
If the content is too small, it tends to be difficult to balance the sticky physical properties, and if it is too large, the moist heat bleaching property tends to decrease.

Examples of the other copolymerizable ethylenically unsaturated monomer (a3) include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, and 2-hydroxy-3-phenoxypropyl (meth). ) Aromatic ring-containing monomers such as acrylate and orthophenylphenoxyethyl (meth) acrylate; cyclohexyl (meth) acrylate, cyclohexyloxyalkyl (meth) acrylate, tert-butylcyclohexyloxyethyl (meth) acrylate, isobornyl (meth) acrylate. , Dicyclopentanyl (meth) acrylate and other alicyclic-containing monomers; 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, lauroxypolyethylene glycol mono (meth) acrylate, stearoxypolyethylene glycol mono (meth) acrylate and other ether chain-containing monomers. These may be used alone or in combination of two or more.

Among these, aromatic ring-containing monomers are preferable (particularly preferably benzyl (meth) acrylate, phenoxy (meth) ethyl acrylate, and phenoxydiethylene glycol (meth) acrylate) in that the refractive index and the double refraction can be easily adjusted. An alicyclic-containing monomer is preferable because it is easy to adjust the refractive index and double refraction and it is excellent in adhesion to a low-polarity adherend (for example, cycloolefin).

When the acrylic pressure-sensitive adhesive composition of the present invention is used as a polarizing plate, the content of the aromatic ring-containing monomer or the alicyclic monomer is adjusted in terms of light leakage resistance, and the birefringence of the entire member after the durability test is performed. It is preferable to adjust the birefringence of the pressure-sensitive adhesive so that
The content of the other copolymerizable ethylenically unsaturated monomer (a3) is preferably 35% by weight or less, more preferably 25% by weight or less. If there are too many other copolymerizable ethylenically unsaturated monomers (a3), the light leakage resistance tends to decrease.

The acrylic resin (A) used in the present invention is a polar group-containing monomer (a1), preferably a (meth) acrylic acid alkyl ester-based monomer (a2) or other copolymerizable ethylenically unsaturated monomer (a2). It can be produced by appropriately selecting and polymerizing a copolymerization component containing a3). The above-mentioned polymerization can be carried out by conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization and emulsion polymerization.
For example, a polymerization component containing a polar group-containing monomer (a1) and a polymerization initiator are mixed or dropped in an organic solvent to polymerize under predetermined polymerization conditions. Of these polymerization methods, solution radical polymerization and bulk polymerization are preferable, and solution radical polymerization is more preferable.

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. Examples thereof include aliphatic alcohols such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and ketones such as cyclohexanone.
Among these organic solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are selected from the viewpoints of ease of polymerization reaction, effect of chain transfer, ease of drying when coating adhesive, and safety. Preferably, more preferably, ethyl acetate, acetone, methyl ethyl ketone.
These organic solvents may be used alone or in combination of two or more.

Examples of the polymerization initiator used for such radical polymerization include 2,2'-azobisisobutyronitrile and 2,2'-azobis-2-methylbutyronitrile, which are ordinary radical polymerization initiators. Azo-based initiators such as 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (methylpropionic acid), benzoyl peroxide, laurolyl peroxide, di-tert-butyl peroxide, cumene. Examples thereof include organic radicals such as hydroperoxide, which can be appropriately selected and used according to the monomer to be 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 5 to 50% by weight of a structural unit derived from the polar group-containing monomer (a1), preferably 6 to 30% by weight, and particularly 7 to 25% by weight. %, Especially preferably 8 to 20% by weight. If the number of structural units derived from the polar group-containing monomer (a1) is too small, the moisture-heat bleaching resistance is lowered, and if it is too large, the reworkability and durability are lowered.

The weight average molecular weight of the acrylic resin (A) is 600,000 to 2.5 million , particularly preferably 800,000 to 2 million, still more preferably 1 million to 1.8 million, and particularly preferably 1.1 million to 1.6 million.
If the weight average molecular weight is too small, the durability tends to be lowered, and if the weight average molecular weight is too large, a large amount of diluting solvent is required at the time of production, the drying property is lowered, and the residual solvent is increased in the pressure-sensitive adhesive layer. , Heat resistance tends to decrease.

The dispersity (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 10 or less, particularly preferably 7 or less, and further preferably 5 or less.
If the degree of dispersion is too high, the reworkability tends to decrease and the durability tends to decrease. The lower limit of the degree of dispersion is usually 1.

The above weight average molecular weight is a weight average molecular weight converted to a standard polystyrene molecular weight, and is used on a high-speed liquid chromatograph (“Waters 2695 (main body)” and “Waters 2414 (detector)” manufactured by Japan Waters Co., Ltd.). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ^7, separation range: one hundred to two × 10 ^7, theoretical plate number: 10,000 plates / the filler material: styrene - divinylbenzene copolymer, filler It is measured by using three series having a particle size (particle size: 10 μm), and the number average molecular weight can also be measured by the same method. The degree of dispersion is obtained 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 −60 to −10 ° C., and even more preferably −50 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：アクリル系樹脂（Ａ）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 by the following Fox formula.

Tg: Glass transition temperature (K) of acrylic resin (A)
Tga: Monomer A homopolymer glass transition temperature (K) Wa: Monomer A weight fraction Tgb: Monomer B homopolymer glass transition temperature (K) Wb: Monomer B weight fraction Tgn: Monomer N homo Polymer glass transition temperature (K) Wn: Weight fraction of monomer N (Wa + Wb + ... + Wn = 1)

That is, the glass transition temperature (Tg) of the acrylic resin (A) is the glass transition temperature and the weight fraction when each of the monomers constituting the acrylic resin (A) is homopolymerized in the above Fox formula. It is a value calculated by applying it.
The glass transition temperature when the monomer constituting the acrylic resin (A) is homopolymer is usually measured by a differential scanning calorimeter (DSC), and is usually measured by JIS K7121-1987 or JIS K 6240. It can be measured by a method conforming to.

The refractive index of the acrylic resin (A) is usually 1.440 to 1.600, preferably 1.460 to 1.550, and particularly preferably 1.470 to 1.500. As for the refractive index, it is preferable to reduce the difference in the refractive index of the members to be laminated because the light loss at the interface of the members is small.
The above-mentioned refractive index is a value obtained by measuring a thin-film acrylic resin (A) with a NaD line at 23 ° C. using a refractive index measuring device (“Abbe Refractometer 1T” manufactured by Atago Co., Ltd.).

The haze of the single layer 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 using this as an adhesive tends to deteriorate.
For haze, the diffusion transmittance and the total light transmittance were measured using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Kogyo Co., Ltd.), and the obtained diffusion transmittance and total light transmittance values were substituted into the following equations. , Calculated. This machine complies with JIS K7361-1.
Haze (%) = (diffusion transmittance / total light transmittance) x 100

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

<Silane coupling agent (B)>
Usually, the silane coupling agent is an organosilicon compound containing one or more reactive functional groups and one or more alkoxy groups in the structure.
In the present invention, a silane coupling agent (B) containing at least one reactive functional group and one or more alkoxy groups in the structure and the alkoxy group containing an ethoxy group and a methoxy group is used as an essential component.

The alkoxy group defined in the present invention refers to an alkoxy group derived from alkoxysilane, and does not include an alkoxy group contained in other molecules.
For example, the end of the polyether chain or the polyether structure of the polyether-modified silane is not included as an alkoxy group.

Examples of the reactive functional group include an epoxy group, a (meth) acryloyl group, a mercapto group, a hydroxyl group, a carboxyl group, an amino group, an amide group, an isocyanate group, and the like. From the viewpoint, an epoxy group and a mercapto group are preferable, and an epoxy group is particularly preferable from the viewpoint of durability and storage stability.

Silane-coupling agent (B), in terms of durability and storage stability, it is those which contain both ethoxy groups and a methoxy group as an alkoxy group in its structure.

The silane coupling agent (B) may have an organic substituent other than the reactive functional group and the alkoxy group, for example, an alkyl group, a phenyl group and the like.

The silane coupling agent (B) preferably contains an alkoxy group in an amount of 5% by weight or more, particularly preferably 5 to 80% by weight, and further preferably 5 to 80% by weight, from the viewpoint of storage stability, reworkability, and durability. It is preferably 15 to 70% by weight, particularly preferably 30 to 60% by weight. If the content of the alkoxy group is too small, the storage stability and durability under moist heat resistant conditions tend to decrease, and if it is too large, the reworkability tends to decrease.

The silane coupling agent (B) preferably has a reactive functional group equivalent of 50 to 1000 g / mol, more preferably 100 to 900 g / mol, and particularly preferably 300 to 850 g / mol. If the reactive functional group equivalent is too small, the reworkability tends to decrease, and if it is too large, the durability under moist heat resistant conditions tends to decrease.

The weight average molecular weight of the silane coupling agent (B) is preferably 500 to 20,000, more preferably 1,000 to 15,000, because it does not volatilize during drying and tends to improve reworkability. More preferably, it is 2,000 to 14,000.

The above weight average molecular weight is a weight average molecular weight converted to standard polystyrene molecular weight, and can be measured by the following method. Further, the number average molecular weight can be measured by the same method, and the degree of dispersion (weight average molecular weight / number average molecular weight) can be obtained from the weight average molecular weight and the number average molecular weight.
Equipment: Gel permeation chromatograph detector: Differential refractive index detector RI (RI-8020 type manufactured by Tosoh Corporation, sensitivity 32)
Column: TSKgel guardcolum H _HR- H (1) (Tosoh φ6 mm x 4 cm), TSKgel GMH _HR- N (2) (Tosoh φ7.8 mm x 30 cm)
Solvent: tetrahydrofuran (THF)
Column temperature: 23 ° C
Flow rate: 1.0 mL / min

As the silane coupling agent (B), even if it is a monomer-type organosilicon compound, an oligomer-type organosilicon compound such as a dimer or a trimer in which a part of the organosilicon compound is hydrolyzed and polycondensed. Although it may be (organosiloxane compound), it is preferable to use a dimer or more oligomer-type organosilicon compound from the viewpoint of reworkability and long-term storage stability.

As the silane coupling agent (B), for example, an organosilicon compound such as γ-glycidoxypropyltriethoxysilane or γ-glycidoxypropylmethyldiethoxysilane, or a part of the organosilicon compound is hydrolyzed. An epoxy group-containing silane coupling agent such as a polycondensed oligomer-type organosilicon compound (epoxy group-containing silicone alkoxy oligomer, etc.) or an organosilicon compound obtained by ether-modifying a part of these organosilicon compounds; γ-mercaptopropyltriethoxysilane Examples thereof include an organosilicon compound such as, and a mercapto group-containing silane coupling agent of an oligomer-type organosilicon compound (mercapto group-containing silicone alkoxy oligomer, etc.) in which a part of the organosilicon compound is hydrolyzed and polycondensed.

Specifically, the silane coupling agent (B) used in the present invention is "X-41-1059A" (containing reactive functional group; epoxy group, contained alkoxy), which is a commercially available product manufactured by Shin-Etsu Chemical Industry Co., Ltd. Group: methoxy group and ethoxy group), "X-41-1805" (containing reactive functional group: mercapto group, contained alkoxy group: methoxy group and ethoxy group), "X-41-1818" (containing reactive functional group) : Mercapto group, contained alkoxy group: ethoxy group) and the like may be used. Among these, "X-41-1059A" is particularly preferable in that it is excellent in reworkability and storage stability.

The content of the silane coupling agent (B) is preferably 0.005 to 1 part by weight, more preferably 0.01 to 0.5 part by weight, based on 100 parts by weight of the acrylic resin (A). Parts, particularly preferably 0.025 to 0.15 parts by weight. If the content of the silane coupling agent (B) is too large, it tends to bleed and the durability under heat-resistant conditions tends to decrease, and if it is too small, the moisture-heat resistance decreases or the storage stability decreases. Tend to do.

As the silane coupling agent (B), only one type may be used, or two or more types may be used in combination.

A silane coupling agent other than the above silane coupling agent (B) can be used as long as the effect of the present invention is not impaired, but if the content of the silane coupling agent is too large, the durability will be increased due to bleeding. Tends to decline. Therefore, the content of the silane coupling agent other than the silane coupling agent (B) is preferably 0.5 parts by weight or less with respect to 100 parts by weight of the acrylic resin (A). It is more preferably 0.3 parts by weight or less, and particularly preferably 0.2 parts by weight or less.

The acrylic pressure-sensitive adhesive composition of the present invention preferably contains a cross-linking agent (C) and an antistatic agent (D) in addition to the above-mentioned acrylic resin (A) and silane coupling agent (B).

<Crosslinking agent (C)>
The cross-linking agent (C) used in the present invention includes, for example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an aziridine-based cross-linking agent, a melamine-based cross-linking agent, an aldehyde-based cross-linking agent, an amine-based cross-linking agent, and a metal chelate-based cross-linking agent. Among these, it is preferable to use an isocyanate-based cross-linking agent because it improves the adhesiveness to the base material and is excellent in the reactivity with the acrylic resin (A).

Examples of the isocyanate-based cross-linking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and hexamethylene. Diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalenediocyanate, triphenylmethane triisocyanate, and polyisocyanate compounds thereof. Examples thereof include an adduct form of and a polyol compound such as trimethylolpropane, a bullet form of these polyisocyanate compounds, and an isocyanurate form.

Examples of the epoxy-based cross-linking agent include bisphenol A / epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol diglycidyl ether. , Trimethylol propantriglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether and the like.

Examples of the aziridine-based cross-linking agent include tetramethylolmethane-tri-β-aziridinyl propionate, trimethylolpropane-tri-β-aziridinyl propionate, and N, N'-diphenylmethane-4,4. ′ -Bis (1-aziridine carboxylamide), N, N'-hexamethylene-1,6-bis (1-aziridine carboxylamide) and the like can be mentioned.

Examples of the melamine-based cross-linking agent include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexabutoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyl oxymethyl melamine, and melamine resin.

Examples of the aldehyde-based cross-linking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardaldehyde, formaldehyde, acetaldehyde, and benzaldehyde.

Examples of the amine-based cross-linking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resin, and polyamide.

Examples of the metal chelate-based cross-linking agent include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, panadium, chromium and zirconium. Can be mentioned.

The above-mentioned cross-linking agent (C) may be used alone or in combination of two or more.
Among the cross-linking agents (C), the isocyanate-based cross-linking agent is preferably used in terms of improving the adhesion to the base material and the reactivity with the acrylic resin (A).
Among the isocyanate-based cross-linking agents, tolylene diisocyanate is preferable in terms of pot life and durability, xylylene diisocyanate or nurate skeleton-containing isocyanate is preferable in terms of shortening the aging time, and non-aromatic isocyanate is preferable in terms of yellowing resistance. preferable. Among these, specifically, tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate and trimethylolpropane adduct, and isocyanurate are preferable because they are excellent in balance of durability, pot life, and cross-linking rate.

The content of the cross-linking agent (C) is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 1 part by weight, and particularly preferably 0.05 to 1 part by weight, based on 100 parts by weight of the acrylic resin (A). Is 0.1 to 0.5 parts by weight.
If the content of the cross-linking agent (C) is too small, the durability tends to decrease, and if it is too large, the stress relaxation property decreases and the substrate tends to warp, or aging for a long time is required. Tend to do.

<Antistatic agent (D)>
The acrylic pressure-sensitive adhesive composition of the present invention preferably further contains an antistatic agent (D), and the ionic compound (D1) is particularly preferable as the antistatic agent (D).
As the ionic compound (D1), it is preferable to contain an ionic compound composed of at least one of a metal salt and an organic salt from the viewpoint of anti-electrostatic measures.

Examples of the metal salt include alkali metal salts such as lithium salt, sodium salt, calcium salt and potassium salt, phosphonium salt and the like.

Examples of the organic salt include onium salts such as ammonium salt, imidazolium salt, pyridinium salt, piperidinium salt, pyrrolidinium salt and sulfonium salt.

Among these, as the ionic compound (D1), an organic salt is preferable, and an ammonium salt, an imidazolium salt, a pyridinium salt, a piperidinium salt, and a pyrrolidinium are more preferable from the viewpoint of compatibility with a resin and corrosion prevention. It is an onium salt composed of a nitrogen-containing cation such as a salt, particularly preferably an alkylammonium salt, and more preferably an ammonium salt composed of an acyclic tetraalkylammonium cation and an N, N-bis (trifluoromethanesulfonyl) imide anion.

The melting point of the ionic compound (D1) is preferably 10 to 100 ° C, particularly preferably 20 to 80 ° C, and even more preferably 25 to 50 ° C. If the melting point is too high, it tends to precipitate at a low temperature, and if it is too low, the color loss of the polarizing plate tends to occur in a moist heat environment.

The content of the antistatic agent (D) is preferably 0.5 to 10 parts by weight, more preferably 2 to 8 parts by weight, still more preferably 2 to 5 parts by weight, based on 100 parts by weight of the acrylic resin (A). , Particularly preferably 2.5 to 4.5 parts by weight. If the content of the antistatic agent (D) is too small, the antistatic performance cannot be obtained and display unevenness due to static electricity tends to occur. It tends to be less sexual or bleed out to reduce durability.

Further, in the acrylic pressure-sensitive adhesive composition of the present invention, as other components, a resin component, an acrylic monomer, a polymerization inhibitor, an antioxidant, a corrosion inhibitor, and a cross-linking promotion can be used as long as the effects of the present invention are not impaired. Various additives such as agents, radical generators, peroxides and radical scavengers, metal and resin particles and the like can be blended. In addition to the above, a small amount of impurities and the like contained in the raw materials for producing the constituent components of the acrylic pressure-sensitive adhesive composition may be contained.

The content of the other components is preferably 5 parts by weight or less, particularly 1 part by weight or less, and further 0.5 parts by weight or less with respect to 100 parts by weight of the acrylic resin (A). preferable. If the content is too large, the compatibility with the acrylic resin (A) tends to decrease, and the moisture-heat bleaching resistance tends to decrease.

Thus, the acrylic pressure-sensitive adhesive composition of the present invention is obtained by mixing an acrylic resin (A), a silane coupling agent (B), a cross-linking agent (C), an antistatic agent (D) and other components as required. Can be obtained. The mixing method is not particularly limited, and various methods such as a method of mixing each component at once, a method of mixing arbitrary components, and then a method of mixing the remaining components collectively or sequentially are adopted. can do.

The acrylic pressure-sensitive adhesive composition of the present invention can be made into a pressure-sensitive adhesive by curing (crosslinking), and further, a pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive is laminated on an optical member (optical laminate). Therefore, 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 surface of the optical member of the pressure-sensitive adhesive layer.

As a method for manufacturing the optical member with an adhesive layer,
[1] A method in which an acrylic pressure-sensitive adhesive composition is applied onto an optical member, dried, and then a release sheet is attached, and the treatment is performed by aging at at least one of room temperature (23 ° C.) and a heated state.
[2] A method of applying an acrylic pressure-sensitive adhesive composition on a release sheet, drying it, attaching an optical member, and performing a treatment by aging at at least one of room temperature and a heated state.
And so on. Among these, the method of aging at room temperature by the method of [2] is preferable in that it does not damage the optical member and is excellent in adhesion to the optical member.
In the above, the optical member is particularly effective when it is a polarizing plate.

Such an aging treatment is carried out in order to balance the adhesive physical characteristics as the reaction time of the chemical cross-linking of the pressure-sensitive adhesive, and the aging conditions are such that the temperature is usually room temperature to 70 ° C. and the time is usually 1 to 30 days. Specifically, it may be carried out under the conditions of, for example, 23 ° C. for 1 to 20 days, 23 ° C. for 3 to 10 days, 40 ° C. for 1 to 7 days, and the like.

When applying the acrylic pressure-sensitive adhesive composition, it is preferable to dilute the acrylic pressure-sensitive adhesive composition with a solvent and apply it, and the dilution concentration is preferably 5 to 60% by weight, particularly as a solid content concentration. It is preferably 10 to 30% by weight.
The solvent is not particularly limited as long as it dissolves the acrylic pressure-sensitive adhesive composition, and is, for example, an ester solvent such as methyl acetate, ethyl acetate, methyl acetoacetate, ethyl acetoacetate, acetone, and the like. Ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents 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 acrylic pressure-sensitive adhesive composition can be 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 30 to 95% by weight, particularly preferably 40 to 85% by weight, more preferably 40 to 85% by weight, from the viewpoint of durability performance and suppression of decrease in polarization degree. Is 60 to 80% by weight. If the gel fraction is too low, the reworkability tends to decrease, and if it is too high, floating or peeling tends to occur.

The gel fraction is a measure of the degree of cross-linking (degree of curing), and is calculated by, for example, the following method. That is, the adhesive was collected by picking from an optical member, particularly an adhesive sheet in which an adhesive layer was formed on a base material such as a polarizing plate, and the adhesive was wrapped in a 200 mesh SUS wire mesh and adjusted to 23 ° C. ethyl acetate. The gel fraction is defined as the weight percentage of the insoluble adhesive component remaining in the wire mesh after being immersed in the gel for 24 hours.

The gel fraction of the pressure-sensitive adhesive is adjusted to the above range by adjusting the type and amount of the cross-linking agent.

It is preferable that the pressure-sensitive adhesive layer produced by the above method has a good tack feeling when touched with a finger because it has good wettability when actually applied to an adherend, and thus tends to improve workability. ..

As for the electrical characteristics of the pressure-sensitive adhesive layer obtained by using the acrylic pressure-sensitive adhesive composition of the present invention, a low surface resistance value is preferable as a countermeasure against static electricity, and particularly preferably 5 × 10 ¹² Ω / cm ² or less, more preferably. Is 1 × 10 ¹¹ Ω / cm ² or less, particularly preferably 5 × 10 ¹⁰ Ω / cm ² or less. If the surface resistance value is too high, the polarizing plate and the pressure-sensitive adhesive layer are likely to be charged, and display unevenness tends to occur.

The thickness of the pressure-sensitive adhesive layer after drying in the obtained optical member with a pressure-sensitive adhesive layer is preferably 5 to 200 μm, particularly preferably 10 to 100 μm, and further preferably 10 to 30 μm. If the thickness of the pressure-sensitive adhesive layer is too thin, the sticky physical properties tend to be difficult to stabilize, and if it is too thick, the amount of water infiltrated from the end portion tends to increase and the storage stability tends to decrease.

In the present invention, the optical member with an adhesive layer, particularly the polarizing plate with an adhesive layer, is directly or has a release sheet, the release sheet is peeled off, and then the adhesive layer surface is attached to a glass substrate, for example. It is used for image display devices.

The initial adhesive strength of the pressure-sensitive adhesive layer is appropriately determined depending on the material of the adherend and the like. For example, when bonded to a glass substrate, it preferably has an adhesive strength of 15 N / 25 mm or less, particularly preferably 0.1 to 12 N / 25 mm, and further preferably 0.5 to 8 N / 25 mm. ..

The initial adhesive strength is calculated as follows.
The polarizing plate with an adhesive layer is cut to a width of 25 mm, the release film is peeled off, and the adhesive layer side is pressed against a non-alkali glass plate (“Eagle XG” manufactured by Corning Inc.) to form a polarizing plate. Adhere to the glass plate. Then, after performing an autoclave treatment (50 ° C. × 0.5 MPa × 20 minutes), the mixture is left at 23 ° C. × 50% RH for 24 hours, and then a peeling test is performed at a peeling angle of 180 ° and a peeling speed of 300 mm / min.

The acrylic pressure-sensitive adhesive composition of the present invention can obtain a pressure-sensitive adhesive having excellent durability, moisture-heat whitening resistance, storage stability, and reworkability in a well-balanced manner, and is a pressure-sensitive adhesive for optical members. In particular, it is useful as an adhesive for a polarizing plate that adheres a polarizing plate to a glass substrate or the like.

Examples of the protective film constituting the polarizing plate include a triacetyl cellulose-based film, an acrylic film, a polyethylene-based film, a polypropylene-based film, and a cycloolefin-based film. However, a polarizing plate on which a cycloolefin film is laminated is particularly preferable because the effect of the present invention can be easily obtained.

Further, by using the above-mentioned adhesive, an image display device can be manufactured by laminating a polarizing plate and a liquid crystal cell, and the obtained image display device can be manufactured with high accuracy and has excellent durability.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. In the example, "part" and "%" mean the weight standard.

First, various acrylic resins were prepared as follows. The weight average molecular weight, dispersity, and glass transition temperature of the acrylic resin (A) were measured according to the above-mentioned method.
The viscosity was measured according to the 4.5.3 rotational viscometer method of JIS K5400 (1990).

<Preparation of acrylic resin (A)>
[Manufacturing of acrylic resin (A-1)]
6 parts of 2-hydroxyethyl acrylate (a1), 0.7 parts of acrylic acid (a1), n-butyl in a 4-neck round bottom flask equipped with a reflux cooler, a stirrer, a nitrogen gas inlet and a thermometer. Add 73.3 parts of acrylate (a2), 20 parts of benzyl acrylate (a3), 54.9 parts of ethyl acetate, 42 parts of acetone, and 0.013 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator to carry out the reaction. Starting, 30 parts of an ethyl acetate solution containing 0.04% AIBN was added dropwise and reacted at a reflux temperature for 3.25 hours, then diluted with ethyl acetate to form an acrylic resin (A-1) solution (solid content 20). 9.9%, viscosity 4,770 mPa · s / 25 ° C., acrylic resin (A-1): glass transition temperature −43 ° C., weight average molecular weight 1.29 million, degree of dispersion 4.3) were obtained.

The monomers used above were those of the following manufacturers.
-2-Hydroxyethyl acrylate (Tg-15 ° C, manufactured by Osaka Organic Chemical Co., Ltd.)
・ Acrylic acid (Tg 106 ℃ manufactured by Mitsubishi Chemical Corporation)
-Butyl acrylate (Tg-56 ° C manufactured by Mitsubishi Chemical Corporation)
・ Benzyl acrylate (Viscoat # 160 Tg 6 ℃ manufactured by Osaka Organic Chemical Co., Ltd.)
The Tg is a homopolymer Tg of each monomer.

[Manufacturing of Acrylic Resins (A-2) to (A-4) and (A'-1), (A'-2)]
Using the copolymerization components shown in Table 1 below, the process was carried out according to the method for producing the acrylic resin (A-1), and the acrylic resins (A-2) to (A-4) and (A'-1) were used. ), (A'-2) solution was obtained. The obtained solutions of the acrylic resins (A-2) to (A-4) and (A'-1) and (A'-2) are as shown in Table 1 below.

<Silane coupling agent (B)>
The following were prepared as the silane coupling agent (B). The weight average molecular weight and the degree of dispersion of the silane coupling agent (B) were measured according to the above-mentioned method. As for the content of the reactive functional group, the equivalent of the reactive functional group, the content of the alkoxy group, and the content of the alkoxy group, the catalog values were adopted unless otherwise specified.

(B-1): Alkoxy group and methoxy group-containing oligomer-type silane coupling agent (“X41-1059A” manufactured by Shin-Etsu Chemical Industry Co., Ltd., contained reactive functional group: epoxy group, reactive functional group equivalent: 350 g / mol, contained Alkoxy group: methoxy group and ethoxy group, alkoxy group content: 42%, weight average molecular weight: 2,270, dispersibility: 1.86)

(B-2): Alkoxy group and methoxy group-containing oligomer-type silane coupling agent (“X41-1805” manufactured by Shin-Etsu Chemical Industry Co., Ltd., contained reactive functional group: mercapto group, reactive functional group equivalent: 800 g / mol, contained Alkoxy group: methoxy group and ethoxy group, alkoxy group content: 50%, weight average molecular weight: 3,450, dispersibility: 1.85)

(B'-1): Methoxy group-containing silane coupling agent ("KBM-403" manufactured by Shin-Etsu Chemical Industry Co., Ltd., contained reactive functional group: epoxy group, reactive functional group equivalent: 236.3 g / mol (calculated value)) , Alkoxy group contained: methoxy group, alkoxy group content: 39% (calculated value), molecular weight: 236.3)
The reactive functional group equivalent of B'-1 was calculated as the molecular weight with respect to 1 mol of the epoxy group. As for the alkoxy group content, a value obtained by dividing the weight of the methoxy group by the molecular weight was adopted (number of methoxy groups: 3, weight of one methoxy group: 31, molecular weight: 236.6).

(B'-2); Methoxy group-containing silane coupling agent (“KBM-803” manufactured by Shin-Etsu Chemical Industry Co., Ltd., contained reactive functional group: alkoxyl group, reactive functional group equivalent: 196.4 g / mol (calculated value)) , Alkoxy group contained: methoxy group, alkoxy group content: 47% (calculated value), molecular weight: 196.4)
The reactive functional group equivalent of B'-2 was calculated as the molecular weight with respect to 1 mol of the mercapto group. As for the alkoxy group content, a value obtained by dividing the weight of the methoxy group by the molecular weight was adopted (number of methoxy groups: 3, weight of one methoxy group: 31, molecular weight: 196.4).

(B'-3): Methoxy group-containing oligomer-type silane coupling agent (“X-24-9590” manufactured by Shin-Etsu Chemical Industry Co., Ltd., contained reactive functional group: epoxy group, functional group equivalent: 592 g / mol, contained alkoxy group : Methoxy group, alkoxy group content: 9.5%, weight average molecular weight: 13,700, dispersibility: 3.44)

<Crosslinking agent (C)>
The following were prepared as the cross-linking agent (C).
(C-1): Adduct of tolylene diisocyanate and trimethylolpropane ("Coronate L55E" manufactured by Tosoh Corporation: 55% active ingredient)

<Antistatic agent (D)>
The following antistatic agents (D) were prepared.
(D1-1): Tri-n-butylmethylammonium N, N-bis (trifluoromethanesulfonyl) imide (manufactured by 3M Ltd., "FC-4400")

<Examples 1 to 5, Comparative Examples 1 to 5>
The above components (A) to (D) were blended as shown in Table 2 below, and the solid content concentration was adjusted to 12.5% with ethyl acetate to obtain an acrylic pressure-sensitive adhesive composition.

Using the acrylic pressure-sensitive adhesive composition obtained above, an evaluation sample was prepared as follows, and the following performance was evaluated. The evaluation results are shown in Table 3.

[Preparation of evaluation sample]
The acrylic pressure-sensitive adhesive composition obtained above is applied to a release sheet (“Lumilar SP-0138BU” manufactured by Mitsui Chemicals Tohcello Co., Ltd.) having a thickness of 38 μm so that the thickness after drying becomes 25 μm, and is applied at 100 ° C. for 3 minutes. After drying, a polarizing plate having the following two types of configurations is attached to the pressure-sensitive adhesive layer surface on the opposite side of the release sheet, and then aged in an environment of 23 ° C. × 50% RH for 7 days to polarize with the pressure-sensitive adhesive layer. I got a board.

Polarizing plate with adhesive layer [I]: TAC film 1 / PVA film (polarizer) / TAC film 2 / adhesive layer / release sheet The TAC film is a triacetyl cellulose film (TAC film 1: thickness 60 μm). , TAC film 2: thickness 40 μm).
Polarizing plate with adhesive layer [II]: TAC film / PVA film (polarizer) / COP film (corona treatment) / adhesive layer / release sheet The above TAC film is a triacetyl cellulose film (thickness 50 μm). , COP film is a cycloolefin film (thickness 60 μm).
The following evaluation was performed using a polarizing plate with a pressure-sensitive adhesive layer [I] and a polarizing plate with a pressure-sensitive adhesive layer [II].

[Reworkability]
The polarizing plate [I] with an adhesive layer obtained above is cut to a width of 25 mm, the release sheet is peeled off, and the adhesive layer surface is made of alkali-free glass (“Eagle XG” manufactured by Corning Inc .: thickness 1.1 mm). It is pressed and bonded with a 2 kg roller, autoclaved (0.5 MPa x 50 ° C x 20 minutes), left to stand for 24 hours in an environment of 23 ° C x 50% RH, and then peeled off at an angle of 180 °. The adhesive strength when peeled off at a peeling speed of 300 mm / min was measured and evaluated according to the following criteria.
(Evaluation criteria)
◎ ・ ・ ・ 10N / 25mm or more ○ ・ ・ ・ 10N / 25mm or more, 16N / 25mm or less Δ ・ ・ ・ 16N / 25mm or more, 20N / 25mm or less × ・ ・ ・ 20N / 25mm or more, or adhesive residue occurs

[Preparation of sample for moisture resistance heat bleaching test]
The polarizing plate [II] with an adhesive layer is cut into a size of 3.5 cm × 3.5 cm, the release sheet is peeled off, and the adhesive layer side is made of non-alkali glass (“Eagle XG” manufactured by Corning Inc .: thickness 1. It was pressed against 1 mm) and reciprocated twice with a 2 kg roller, and then autoclaved (0.5 MPa × 50 ° C. × 20 minutes) to prepare a sample for a moisture heat whitening test.
Using the obtained test sample, the moisture-heat whitening resistance of the pressure-sensitive adhesive layer was evaluated as follows.

[Moisture heat whitening resistance]
The sample for the moisture resistance heat bleaching test was exposed to an environment of 60 ° C. × 90% RH for 250 hours, and then taken out and left at room temperature (23 ° C.). The haze immediately after taking out and 3 hours after taking out was measured, and the moisture heat whitening resistance was evaluated according to the following criteria. The haze value is a value obtained by subtracting 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% △ ・ ・ ・ 2% or more and less than 4% × ・ ・ ・ 4% or more ・ Haze 3 hours after removal ◎ ・・ ・ Less than 1% ○ ・ ・ ・ 1% or more and less than 2% △ ・ ・ ・ 2% or more and less than 4% × ・ ・ ・ 4% or more

〔durability〕
<Moisture and heat resistance evaluation>
The obtained polarizing plate [I] with an adhesive layer is cut into a size of 20 cm × 15 cm, the release sheet is peeled off, and the adhesive layer surface is pressed against alkali-free glass (“Eagle XG” manufactured by Corning Inc .: thickness 1.1 mm). After two reciprocating movements with a 2 kg roller, autoclaving treatment (0.5 MPa × 50 ° C. × 20 minutes) was performed to prepare a sample for the initial durability test.
The obtained sample was exposed to an environment of 60 ° C. × 90% RH for 250 hours to perform a durability test, and after taking out, the durability was evaluated as follows.
(Evaluation criteria)
○ ・ ・ ・ No foaming or floating of edges was observed on the entire surface of the polarizing plate × ・ ・ ・ Foaming or floating of edges was observed on the front surface of the polarizing plate.

<Heat resistance evaluation>
The obtained polarizing plates [I] and [II] with an adhesive layer were cut into 20 cm × 15 cm, the release sheet was peeled off, and the adhesive layer surface was made of alkali-free glass (“Eagle XG” manufactured by Corning Inc .: thickness 1. It was pressed against 1 mm) and reciprocated twice with a 2 kg roller, and then autoclaved (0.5 MPa × 50 ° C. × 20 minutes) to prepare a sample for the initial durability test.
The obtained sample was exposed to an environment of 80 ° C. for 250 hours to perform a durability test, and after taking out, the durability was evaluated as follows.
(Evaluation criteria)
○ ・ ・ ・ No foaming or floating of edges was observed on the entire surface of the polarizing plate × ・ ・ ・ Foaming or floating of edges was observed on the front surface of the polarizing plate.

[Durability after deterioration acceleration test (test after exposure under high humidity conditions)]
<Moisture and heat resistance>
The obtained polarizing plate [I] with an adhesive layer was previously exposed to an environment of 45 ° C. × 90% RH for 3 days, and then deteriorated by controlling the temperature and humidity for 1 week in an environment of 23 ° C. × 50% RH. A polarizing plate with an adhesive layer after acceleration was obtained.
The obtained polarizing plate is cut into a size of 20 cm × 15 cm, the release sheet is peeled off, the adhesive layer surface is pressed against alkali-free glass (“Eagle XG” manufactured by Corning Inc .: thickness 1.1 mm), and two reciprocations are performed with a 2 kg roller. After bonding, an autoclave treatment (0.5 MPa × 50 ° C. × 20 minutes) was performed to prepare a sample for durability after a deterioration acceleration test.
The obtained sample was exposed to an environment of 60 ° C. × 90% RH for 250 hours to perform a durability test, and after taking out, the durability was evaluated as follows.
(Evaluation criteria)
○ ・ ・ ・ No foaming or floating of edges was observed on the entire surface of the polarizing plate × ・ ・ ・ Foaming or floating of edges was observed on the front surface of the polarizing plate.

<Heat resistance>
The obtained polarizing plate [I] with an adhesive layer was previously exposed to an environment of 45 ° C. × 90% RH for 3 days, and then deteriorated by controlling the temperature and humidity for 1 week in an environment of 23 ° C. × 50% RH. A polarizing plate with an adhesive layer after acceleration was obtained.
The obtained polarizing plate is cut into 20 cm × 15 cm, the release sheet is peeled off, the adhesive layer surface is pressed against alkali-free glass (“Eagle XG” manufactured by Corning Inc .: thickness 1.1 mm), and two reciprocations are performed with a 2 kg roller. After bonding, an autoclave treatment (0.5 MPa × 50 ° C. × 20 minutes) was performed to prepare a sample for durability after a deterioration acceleration test.
The obtained sample was exposed to an environment of 80 ° C. for 250 hours to perform a durability test, and after taking out, the durability was evaluated as follows.
(Evaluation criteria)
○ ・ ・ ・ No foaming or floating of edges was observed on the entire surface of the polarizing plate × ・ ・ ・ Foaming or floating of edges was observed on the front surface of the polarizing plate.

[Gel fraction]
The release sheet of the obtained polarizing plate [I] with an adhesive layer was peeled off, the adhesive was picked from the surface of the adhesive layer, wrapped in a 200 mesh wire mesh made of SUS, and then placed in ethyl acetate adjusted to 23 ° C. for 24 hours. The weight percentage of the insoluble adhesive component remaining in the wire mesh after immersion was defined as the gel fraction (%).

[Antistatic property]
<Surface resistance value>
After allowing the polarizing plate [I] with an adhesive layer to stand in an atmosphere of 23 ° C. × 50% RH for 24 hours, the release sheet of the adhesive layer is removed and a surface resistance measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) The surface resistance value of the pressure-sensitive adhesive layer was measured using the apparatus name "Hiresta-UP MCP-HT450").

Examples 1 to 5 using a pressure-sensitive adhesive containing an acrylic resin having a polar group of 5 to 50% by weight and a silane coupling agent containing an alkoxy group having 2 or more carbon atoms have moisture-heat whitening resistance and storage stability. It turns out that it is excellent.

On the other hand, Comparative Examples 1 and 2 having few polar groups of the acrylic resin are inferior in moisture and heat whitening resistance, and comparative examples 3 to 3 containing a silane coupling agent consisting of only methoxy groups although the polar groups of the acrylic resin are relatively large. No. 5 is excellent in moisture and heat whitening resistance, but inferior in storage stability due to infiltration of water, and inferior in durability after the deterioration acceleration test.

Further, when an image display device was produced by laminating a polarizing plate and a liquid crystal cell using a pressure-sensitive adhesive obtained by cross-linking the acrylic pressure-sensitive adhesive compositions of Examples 1 to 5, the obtained image display device was obtained. It could be manufactured with high accuracy and had excellent durability.

Although the specific embodiments of the present invention have been shown in the above examples, the above examples are merely examples and are not to be interpreted in a limited manner. Various variations apparent to those skilled in the art are intended to be within the scope of the present invention.

The acrylic pressure-sensitive adhesive composition of the present invention is excellent in durability, moisture-heat bleaching resistance, and storage stability (durability after aging) even when used as a pressure-sensitive adhesive for bonding a polarizing plate and a glass substrate or the like. ), A pressure-sensitive adhesive with a good balance of reworkability can be obtained, and a pressure-sensitive adhesive for an optical member for bonding a display and optical components constituting the display, particularly a polarizing plate and a glass substrate of a liquid crystal cell, etc. It is useful as a pressure-sensitive adhesive for polarizing plates for bonding.

Claims (9)

An acrylic pressure-sensitive adhesive composition containing an acrylic resin (A) and a silane coupling agent (B) containing at least one reactive functional group and one alkoxy group in the structure.
The acrylic resin (A), a structural unit derived from polar group-containing monomer (a1) containing from 5 to 50 wt%, the polar group-containing monomer (a1) is a hydroxyl group-containing monomer, the weight average molecular weight of 60 An acrylic pressure-sensitive adhesive composition comprising 10,000 to 2.5 million acrylic resins, wherein the alkoxy group contained in the silane coupling agent (B) contains an ethoxy group and a methoxy group. Alkoxy group containing the above silane coupling agent (B), acrylic pressure-sensitive adhesive composition of claim 1 Symbol mounting, characterized in that the ethoxy and methoxy group. The acrylic pressure-sensitive adhesive composition according to claim 1 or 2, wherein the silane coupling agent (B) contains 5% by weight or more of an alkoxy group in its structure. The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 3 , wherein the silane coupling agent (B) has a reactive functional group equivalent of 50 to 1000 g / mol. The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 4 , further containing a cross-linking agent (C). The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 5 , further containing an antistatic agent (D). A pressure-sensitive adhesive characterized in that the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 6 is crosslinked by a cross-linking agent (C). A pressure-sensitive adhesive for a polarizing plate, which comprises using the pressure-sensitive adhesive according to claim 7. An image display device according to claim 7 , wherein a polarizing plate and a liquid crystal cell are bonded together.