JP6950531B2 - 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 capable of forming a pressure-sensitive adhesive which does not cause deterioration of properties.

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 above-mentioned 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, acrylic films, polyester films, olefin films and the like have come to be used instead of TAC films from the viewpoint of dimensional stability and durability. As the olefin-based film, a cycloolefin-based film (COP film) has come to be used as a protector film for a polarizer.

The adhesive used for bonding such a polarizing plate and a liquid crystal cell (glass substrate) is required to have durability such as heat resistance and moisture heat resistance. Especially in a high temperature and high humidity environment, there is a problem that moisture penetrates into the adhesive layer, the adhesiveness with the glass substrate is lowered, and the polarizing plate is partially lifted or peeled off from the glass substrate. rice field. In order to solve such a problem, the moisture resistance has been improved by adding a silane coupling agent to the pressure-sensitive adhesive, but when the silane coupling agent is added, the polarizing agent with a pressure-sensitive adhesive layer is used. When the plate is stored for a long period of time, the silane coupling agent is inactivated by the moisture in the environment and the moisture in the polarizing plate, which causes a new problem that the durability is lowered.

In addition, the adhesive used for bonding the polarizing plate and the liquid crystal cell (glass substrate) is a polarizing plate when foreign matter is caught or the position is displaced when the polarizing plate is bonded to the liquid crystal cell. Reworkability for peeling and reusing the liquid crystal cell has been required.
Furthermore, in recent years, the yield has been improved by improving the accuracy of the manufacturing process, so that defective products do not occur as much as before, and the rework process is performed after a certain number of defective products have accumulated. However, adhesives are required to be able to maintain reworkability for a long period of time.

Further, when a film having low moisture permeability other than the TAC film, particularly a cycloolefin-based film, is used, there arises a problem that a whitening phenomenon occurs in the pressure-sensitive adhesive layer when exposed to a moist heat environment. This is because the moisture that has gradually penetrated into the adhesive layer in a moist heat environment condenses when exposed to room temperature, and because it is covered with a film with low moisture permeability, the moisture does not escape and the moisture aggregates, resulting in white. It is thought that it has become.

To solve this problem, a pressure-sensitive adhesive having improved moisture-heat whitening resistance has been proposed by using an acrylic resin in which a large amount of polar group-containing monomers are copolymerized.
However, in the case of a pressure-sensitive adhesive using an acrylic resin in which a large amount of polar group-containing monomers are copolymerized in this way, the adhesiveness with the glass interface is enhanced due to the influence of the polar group, and the pressure-sensitive adhesive layer easily absorbs moisture. Since the hydrolysis becomes faster, there is a problem that the reworkability and the storage stability are further inferior.

Examples of the pressure-sensitive adhesive having excellent reworkability and initial moisture-heat resistance are described in Patent Document 1, for example, in Patent Document 1, 100 parts by weight of the pressure-sensitive adhesive resin (A), an epoxy equivalent of 100 to 2000 g / mol, and an alkoxyl group content. Acrylic adhesive obtained by polymerizing a monomer containing 0.1 to 20 parts by weight of a silicone alkoxy oligomer (B) containing 5 to 60% by weight and the pressure-sensitive adhesive resin (A) containing no carboxyl group. Described is a pressure-sensitive adhesive composition that is one or more selected from the group consisting of an agent resin (A1), a urethane-based pressure-sensitive adhesive resin (A2), and a polyester-based pressure-sensitive adhesive resin (A3).
Further, as a pressure-sensitive adhesive having excellent moisture-heat whitening resistance, for example, Patent Document 2 proposes a pressure-sensitive adhesive using an acrylic resin having a large amount of hydroxyl groups.

Japanese Unexamined Patent Publication No. 2016-44291 Japanese Unexamined Patent Publication No. 2013-213203

However, in the pressure-sensitive adhesive described in Patent Document 1, the functional group equivalent and the alkoxy group content of the silane coupling agent (silicone alkoxy oligomer) to be used are widely defined, and various types of silane coupling agents are specified. However, the adhesive using a silane coupling agent having a high alkoxy group content has a problem that the adhesive strength at the initial stage and after heating is low, but the long-term reworkability is inferior. rice field.
Further, as described in Patent Document 1, a pressure-sensitive adhesive using a silane coupling agent having a low alkoxy group content for the purpose of improving reworkability has a problem that it is excellent in reworkability but inferior in storage stability. There was a point.

Further, although the above-mentioned Patent Document 2 proposes an adhesive having excellent moisture-heat whitening resistance, long-term reworkability and storage stability are not considered at all, and further improvement is required. rice field.

Therefore, in the present invention, under such a background, when used as an adhesive used for bonding a polarizing plate (protective film) and a liquid crystal cell (glass) at the time of manufacturing an image display device, it is excellent for a long period of time. It is possible to obtain an adhesive that exhibits reworkability and is not easily affected by moisture and does not reduce durability. Furthermore, even when the number of polar groups is increased in consideration of moisture and heat whitening resistance, reworkability is achieved. To provide an acrylic pressure-sensitive adhesive composition having excellent storage stability.

However, as a result of diligent research in view of such circumstances, the present inventors and others have found that in an acrylic pressure-sensitive adhesive composition containing an acrylic resin and a silane coupling agent, a silane coupling agent having a low alkoxy group content and a large amount of silane It has been found that by using two kinds of coupling agents in combination, an acrylic pressure-sensitive adhesive composition that exhibits excellent reworkability for a long period of time, is not easily affected by moisture, and does not cause a decrease in durability can be obtained. ..

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 alkoxy group in the structure. As the silane coupling agent (B), a silane coupling agent (B1) having an alkoxy group content of 15% by weight or less and a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more are used. It contains, in which the weight-average molecular weight of the silane coupling agent (B2) is a der Ru acrylic adhesive composition 500 or the first aspect.
Further, in the present invention, the second gist is a pressure-sensitive adhesive obtained by cross-linking the acrylic pressure-sensitive adhesive composition of the first gist with a cross-linking agent (C) , and the second gist of the pressure-sensitive adhesive is a polarizing plate. The third gist is an image display device formed by laminating liquid crystal cells.
Further, 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. As the silane coupling agent (B), a silane coupling agent (B1) having an alkoxy group content of 15% by weight or less and a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more. The fourth gist is a pressure-sensitive adhesive for a polarizing plate, which is obtained by using a pressure-sensitive adhesive obtained by cross-linking an acrylic pressure-sensitive adhesive composition containing the above with a cross-linking agent (C).

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 alkoxy group in the structure. As the silane coupling agent (B), a silane coupling agent (B1) having an alkoxy group content of 15% by weight or less and a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more are contained. and a der Ru acrylic adhesive composition weight average molecular weight of 500 or more of the silane coupling agent (B2). Therefore, the pressure-sensitive adhesive obtained by using the acrylic pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive used for bonding a polarizing plate (protective film) and a liquid crystal cell (glass) at the time of manufacturing an image display device. It is a pressure-sensitive adhesive that exhibits excellent reworkability over a long period of time, is not easily affected by moisture, and does not cause a decrease in durability, and is very useful as a pressure-sensitive adhesive for polarizing plates.

The acrylic resin (A) is an acrylic resin containing 5 to 50% by weight of a structural unit derived from at least one polar group-containing monomer (a1) selected from a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a nitrogen-containing monomer. If there is, it is excellent in moisture-heat whitening resistance and adhesive property.

When the reactive functional group equivalent of the silane coupling agent (B1) is 1,600 g / mol or less, the durability is more excellent.

When the weight average molecular weight of the silane coupling agent (B1) is 3,000 or more, the reworkability and durability are more excellent.

When the reactive functional group equivalent of the silane coupling agent (B2) is 1,000 g / mol or less, the durability is more excellent.

Further, 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. As the silane coupling agent (B), a silane coupling agent (B1) having an alkoxy group content of 15% by weight or less and a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more. The acrylic pressure-sensitive adhesive composition containing the above is a pressure-sensitive adhesive for a polarizing plate, which comprises a pressure-sensitive adhesive obtained by cross-linking with a cross-linking agent (C). Therefore, the pressure-sensitive adhesive for polarizing plates of the present invention is a pressure-sensitive adhesive that exhibits excellent reworkability over a long period of time, is not easily affected by moisture, and does not deteriorate in durability.

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 preferably contains a structural unit derived from the polar group-containing monomer (a1), and the content thereof is preferably 5 to 50% by weight. For example, an acrylic resin obtained by copolymerizing a copolymerization component containing 5 to 50% by weight of the polar group-containing monomer (a1) is preferable.
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, those having a content ratio of di (meth) acrylate as an impurity of 0.5% by weight or less are preferably used, particularly preferably 0.2% by weight or less, and further preferably 0. .1% by weight or less. Specifically, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and 2-hydroxypropyl acrylate are particularly 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 (meth) acrylamide; methoxymethyl (meth) acrylamide, ethoxymethyl (meth) acrylamide, propoxymethyl (meth) acrylamide, isopropoxymethyl (meth) acrylamide, and n-butoxymethyl (meth). Alkoxyalkyl (meth) acrylamide-based monomers such as acrylamide and isobutoxymethyl (meth) acrylamide; dialkyl (meth) acrylamide-based monomers such as dimethyl (meth) acrylamide and diethyl (meth) acrylamide; N- (hydroxymethyl) acrylamide and the like Examples thereof include a hydroxyl group-containing amide monomer; (meth) acrylamide, and the like.
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.

Among the above-mentioned polar group-containing monomers (a1), hydroxyl group-containing monomers and carboxyl group-containing monomers are preferable in terms of moisture-heat whitening resistance and adhesive properties, and hydroxyl groups are also excellent in moisture-heat whitening resistance and long-term reworkability. The containing monomer is preferable. Further, the above-mentioned polar group-containing monomer (a1) can be used alone or in combination of two or more.

The content of the polar group-containing monomer (a1) (when two or more kinds are used in combination, the total content thereof) is preferably 5 to 50% by weight, particularly preferably 5 to 50% by weight based on the total copolymerization component. 6 to 30% by weight, more preferably 7 to 25% by weight, particularly preferably 8 to 20% by weight, and if the content is too small, the moisture and heat whitening resistance when used as an adhesive tends to decrease. If it is too large, it tends to gel during polymerization.

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 because of their excellent 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, phenoxyethyl (meth) acrylate, and phenoxydiethylene glycol (meth) in terms of easy adjustment of the refractive index and double refraction and excellent light leakage resistance. ) Acrylate), the refractive index and the double refraction can be easily adjusted, and the alicyclic-containing monomer is preferable in that it has excellent 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 (a3). ) Appropriately selected, and these polymerization components can be used, for example, by mixing or dropping the polymerization component and the polymerization initiator in an organic solvent and polymerizing the mixture.
The above-mentioned polymerization reaction can be carried out by conventionally known polymerization methods such as solution radical polymerization, suspension polymerization, bulk polymerization and emulsion polymerization. Among these, solution radical polymerization and bulk polymerization are preferable, and solution radicals are particularly preferable. It is a polymerization.

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, methyl Isobutyl ketone is preferably used, and more preferably ethyl acetate, acetone, or 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 solution radical polymerization include 2,2'-azobisisobutyronitrile and 2,2'-azobis-2-methylbutyronitrile, which are ordinary radical polymerization initiators. , 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (methylpropionic acid) and other azo-based initiators, benzoyl peroxide, laurolyl peroxide, di-tert-butyl peroxide, Examples thereof include organic radicals such as cumene 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 preferably contains 5 to 50% by weight of a structural unit derived from the polar group-containing monomer (a1), particularly preferably 6 to 30% by weight, still more preferably. Is 7 to 25% by weight, particularly preferably 8 to 20% by weight, and most preferably 8 to 15% by weight. If the number of structural units derived from the polar group-containing monomer is too small, the moisture-heat whitening resistance tends to decrease, and if it is too large, the reworkability and durability tend to decrease.

The weight average molecular weight of the acrylic resin (A) is preferably 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 160. It is ten thousand.
If the weight average molecular weight is too small, the durability tends to decrease, and if it is too large, a large amount of diluting solvent is required during production, the drying property decreases, the residual solvent increases in the pressure-sensitive adhesive layer, and the heat resistance becomes high. Tends to decline.

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）
即ち、アクリル系樹脂（Ａ）のガラス転移温度（Ｔｇ）とは、アクリル系樹脂（Ａ）を構成するそれぞれのモノマーをホモポリマーとした際のガラス転移温度及び重量分率を上記Ｆｏｘの式に当てはめて算出した値である。
なお、アクリル系樹脂（Ａ）を構成するモノマーをホモポリマーとした際のガラス転移温度は、通常、示差走査熱量計（ＤＳＣ）により測定されるものであり、ＪＩＳ Ｋ７１２１−１９８７や、ＪＩＳ Ｋ ６２４０に準拠した方法で測定することができる。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, particularly preferably 0.8 or less, and further 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, as the silane coupling agent (B) containing at least one reactive functional group and one or more alkoxy groups in the structure, the silane coupling agent (B1) having an alkoxy group content of 15% by weight or less, and It contains a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more.

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 terminal of the polyether portion of the polyether-modified silane and the polyether structure are 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. Among these, an epoxy group and a mercapto group are preferable because they are excellent in durability and reworkability.

Examples of the alkoxy group include a methoxy group, an ethoxy group, a propidoxy group and the like. Among these, an alkyl group having 1 to 8 carbon atoms is preferable, and an alkyl group having 1 to 2 carbon atoms is particularly preferable, and specifically, a methoxy group and an ethoxy group.

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 greatest feature of the present invention is to use a silane coupling agent (B1) having a low alkoxy group content and a silane coupling agent (B2) having a high alkoxy group content in combination. By doing so, it is possible to achieve the object of the present invention, which is excellent in durability and storage stability while maintaining long-term reworkability.

The alkoxy group content of the silane coupling agent (B1) needs to be 15% by weight or less, preferably 1 to 15% by weight, particularly preferably 3 to 15% by weight, still more preferably 5 to 14. 5% by weight.
If the alkoxy group content is too large, the long-term reworkability will decrease.

The weight average molecular weight of the silane coupling agent (B1) is preferably 3,000 or more, particularly preferably 4,000 to 30,000, still more preferably 4,500 to 20,000, and particularly preferably. It is 7,000 to 18,000.
If the weight average molecular weight is too small, the long-term reworkability tends to decrease, and if it is too large, bleed-out tends to occur and the durability tends to decrease.

The reactive functional group equivalent of the silane coupling agent (B1) is preferably 1,600 g / mol or less, particularly preferably 100 to 1,000 g / mol, still more preferably 200 to 900 g / mol, and particularly preferably 200 to 900 g / mol. It is preferably 300 to 650 g / mol.
When the reactive functional group equivalent is in the above range, the durability tends to be more excellent.

The alkoxy group content of the silane coupling agent (B2) needs to be 20% by weight or more, preferably 20 to 80% by weight, particularly preferably 25 to 70% by weight, and further preferably 30 to 60% by weight. %.
If the alkoxy group content is too small, the storage stability will be lowered.

The weight average molecular weight of the silane coupling agent (B2) is Ri der 500 or higher, preferably 500 to 5,000, particularly preferably 500～4,500, more preferably from 600～4,000.
If the weight average molecular weight is too small, the long-term reworkability tends to decrease.

The reactive functional group equivalent of the silane coupling agent (B2) is preferably 1,000 g / mol or less, particularly preferably 100 to 900 g / mol, and even more preferably 300 to 800 g / mol.
If the reactive functional group equivalent is in the above range, the durability tends to be improved.

The weight average molecular weights of the silane coupling agents (B1) and (B2) are weight average molecular weights in terms of 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

Here, regarding the weight average molecular weights of the silane coupling agents (B1) and (B2), the weight average molecular weight of the silane coupling agent (B1) is larger than the weight average molecular weight of the silane coupling agent (B2). It tends to have an excellent balance between long-term reworkability and storage stability, which is preferable.

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), an oligomer-type organosilicon compound is preferable because it has a plurality of reactive functional groups and alkoxy groups and is excellent in durability and reworkability.

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.
From these, the silane coupling agents (B1) and (B2) may be appropriately selected and used so as to satisfy the respective conditions. Further, the silane coupling agents (B1) and (B2) may be used alone or in combination of two or more.

As the silane coupling agent (B1), specifically, "X-24-9590" (weight average molecular weight: 13,700, containing alkoxy group: methoxy group, alkoxy group), which is a commercially available product manufactured by Shin-Etsu Chemical Industry Co., Ltd. Content: 9.5% by weight, reactive functional group: epoxy group, epoxy equivalent: 592 g / mol) and the like.

As the silane coupling agent (B2), specifically, "X-41-1059A" (weight average molecular weight: 2,300, containing alkoxy group: methoxy group, ethoxy group), which is a commercially available product manufactured by Shin-Etsu Chemical Industry Co., Ltd. , Alkoxy group content: 42% by weight, Reactive functional group: Epoxy group, Epoxy equivalent: 350 g / mol), "X-41-1810" (Weight average molecular weight: 640, Alkoxy group contained: methoxy group, Alkoxy group contained Amount: 30% by weight, reactive functional group: mercapto group, mercapto equivalent: 450 g / mol), "X-41-1805" (weight average molecular weight: 3,450, containing alkoxy group: methoxy group, ethoxy group, alkoxy group Content: 50% by weight, reactive functional group: alkoxy group, alkoxy equivalent: 800 g / mol) and the like.
Among these, "X-41-1059A" is particularly preferable in terms of storage stability and durability.

The content of the silane coupling agent (B1) is preferably 0.001 to 1 part by weight, particularly preferably 0.015 to 0.5 part by weight, based on 100 parts by weight of the acrylic resin (A). , More preferably 0.020 to 0.2 parts by weight, still more preferably 0.025 to 0.15.
If the content is too large, the durability tends to decrease, and if it is too small, the long-term reworkability tends to decrease.

The content of the silane coupling agent (B2) is preferably 0.001 to 1 part by weight, particularly preferably 0.015 to 0.5 part by weight, based on 100 parts by weight of the acrylic resin (A). It is more preferably 0.02 to 0.2 parts by weight, and particularly preferably 0.025 to 0.15.
If the content is too large, the durability tends to decrease, and if it is too small, the reworkability tends to decrease.

The content ratio (weight ratio) of the silane coupling agents (B1) and (B2) is preferably (B1) :( B2) = 50: 1 to 1: 5, and is particularly preferably (B1) :. (B2) = 30: 1 to 1: 2, more preferably (B1) :( B2) = 10: 1 to 1: 1.
If the content ratio is within the above range, the balance between durability and reworkability tends to be excellent.

In the acrylic pressure-sensitive adhesive composition of the present invention, silane coupling agents other than the above-mentioned silane coupling agents (B1) and (B2) can be used as long as the effects of the present invention are not impaired. If the content of the coupling agent is too high, the durability tends to decrease due to bleeding. Therefore, the content of the silane coupling agents other than the above silane coupling agents (B1) and (B2) is, specifically, 0.5 parts by weight or less with respect to 100 parts by weight of the acrylic resin (A). It is preferably 0.3 parts by weight or less, and particularly preferably 0.1 part 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)>
Examples of the cross-linking agent (C) include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, aldehyde-based cross-linking agents, amine-based cross-linking agents, and metal chelate-based cross-linking agents. 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 base polymer.

Examples of the isocyanate-based cross-linking agent include a tolylene diisocyanate-based cross-linking agent such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, and a xylylene diisocyanate-based cross-linking agent such as 1,3-xylylene diisocyanate. Diphenylmethane-based cross-linking agents such as diphenylmethane-4,4-diisocyanate, aromatic isocyanate-based cross-linking agents such as naphthalene diisocyanate such as 1,5-naphthalenediocyanate; isophorone diisocyanate, 1,4-cyclohexanediisocyanate, 4,4 Alicyclic isocyanate-based cross-linking agents such as'-dicyclohexylmethane diisocyanate, methylcyclohexanediisocyanate, isopropyridendicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane, norbornandiisocyanate; hexamethylenediisocyanate, trimethylhexa Examples thereof include aliphatic isocyanate-based cross-linking agents such as methylene diisocyanate; and adducts, bullets, and isocyanurates of the above isocyanate compounds.

Among these isocyanate-based cross-linking agents, the tolylene diisocyanate-based cross-linking agent is preferable in terms of pot life and durability, and the xylylene diisocyanate-based cross-linking agent or the isocyanurate skeleton-containing isocyanate-based cross-linking agent is not preferable in terms of shortening the aging time. An aromatic-free isocyanate-based cross-linking agent is preferable in terms of yellowing resistance. Specifically, among these, tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate and trimethylolpropane adduct, and isocyanurate are excellent in the balance of durability, pot life, and cross-linking rate. preferable.

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.

The content of the cross-linking agent (C) is preferably 0.01 to 5 parts by weight, particularly preferably 0.05 to 1.5 parts by weight, based on 100 parts by weight of the acrylic resin (A). More preferably, it is 0.1 to 0.5 parts by weight.
If the content is too small, the durability tends to decrease, and if it is too large, the stress relaxation property tends to decrease, the substrate tends to warp, and aging for a long time tends to be required.

<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 measures against charging.

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, organic salts are preferable, and ammonium cations, imidazolium cations, pyridinium cations, piperidinium cations, and pyrrolidis are preferable in terms of excellent corrosion prevention, long-term reworkability, and storage stability. Onium salts composed of nitrogen-containing cations such as nium cations are preferable, particularly preferably ammonium salts, more preferably acyclic ammonium cations and N, N-bis (trifluoromethanesulfonyl) imide anions, and acyclic ammonium cations and N, N-. It is an ammonium salt composed of a bis (fluorosulfonyl) imide cation.

The melting point of the ionic compound (D1) is preferably 10 to 100 ° C, particularly preferably 20 to 80 ° C, and particularly preferably 25 ° C 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 with respect to 100 parts by weight of the acrylic resin (A). It is ~ 5 parts by weight, particularly preferably 2.5 ~ 4.5 parts by weight. If the content is too small, antistatic performance is not obtained and display unevenness due to static electricity tends to occur, and if it is too large, the degree of polarization of the polarizing plate tends to decrease or bleed-out tends to decrease the durability. There is.

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 preferably 1 part by weight or less, and further preferably 0.5 parts by weight or less with respect to 100 parts by weight of the acrylic resin (A). .. 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 adhesiveness 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 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 90% by weight, more preferably 40 to 90% by weight, from the viewpoint of durability performance and suppression of decrease in polarization degree. Is 60-85% 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 pressure-sensitive adhesive is collected by picking from the pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is formed on an optical member, particularly a base material such as a polarizing plate, and the pressure-sensitive adhesive is wrapped in a 200-mesh SUS wire mesh and adjusted to 23 ° C. The gel fraction is defined as the weight percentage of the insoluble adhesive component remaining in the wire mesh after being immersed in ethyl 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. ..

The electrical characteristics of the pressure-sensitive adhesive layer obtained by using the acrylic resin composition of the present invention preferably have a surface resistance value of 1 × 10 ¹² Ω or less, particularly preferably 1 × 10 ¹¹ Ω or less, still more preferably. Is 5 × 10 ¹⁰ Ω 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 of the present invention is appropriately determined depending on the material of the adherend and the like. For example, when bonded to a glass substrate such as a liquid crystal cell, 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. Is.

The long-term adhesive strength (reworkability) of the pressure-sensitive adhesive of the present invention is appropriately determined depending on the material of the adherend and the like.
For example, when bonding to a glass substrate such as a liquid crystal cell, the adhesive strength 40 days after bonding is preferably 0.1 to 20 N / 25 mm, particularly preferably 1 to 15 N / 25 mm, and even more preferably 1. It is 10 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. Regarding long-term reworkability, after autoclaving, the product is left at 23 ° C. × 50% RH for a predetermined period of time, 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).

<Acrylic resin (A)>
[Manufacturing of acrylic resin (A-1)]
8 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 condenser, a stirrer, a nitrogen gas inlet and a thermometer. 71.3 parts of acrylate (a2), 20 parts of benzyl acrylate (a3), 53 parts of ethyl acetate, 42 parts of acetone, and 0.013 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator are charged, and the internal temperature is boiled. The reaction was started by raising the temperature to. Next, 30 parts of an ethyl acetate solution containing 0.04% of AIBN was added dropwise, and after reacting at a reflux temperature for 3.25 hours, the solution was diluted with ethyl acetate to form an acrylic resin (A-1) solution (solid content 21.3). %, Viscosity 5440 mPa · s / 25 ° C., Acrylic resin (A-1): Glass transition temperature −42 ° C., Weight average molecular weight 1.27 million, Dispersity 4.3).

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) and (A-3)]
Using the copolymerization components shown in Table 1, the above-mentioned production method for the acrylic resin (A-1) was carried out to obtain solutions of the acrylic resin (A-2) and (A-3). The obtained acrylic resin (A-2) and (A-3) solutions are as shown in Table 1.

<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. In addition, the catalog values were adopted for the alkoxy group content, the reactive functional group, the epoxy equivalent or the mercapto equivalent, and the contained alkoxy group.

・ (B1-1):
(Manufactured by Shinetsu Chemical Industry Co., Ltd., "X-24-9590", weight average molecular weight: 13,700, dispersity: 3.44, alkoxy group content: 9.5%, reactive functional group: epoxy group, epoxy equivalent : 592 g / mol, containing alkoxy group: methoxy group)

・ (B2-1):
(Manufactured by Shinetsu Chemical Industry Co., Ltd., "X-41-1059A", weight average molecular weight: 2,270, dispersity: 1.86, alkoxy group content: 42%, reactive functional group: epoxy group, epoxy equivalent: 350 g / Mol, Containing alkoxy group: methoxy group, ethoxy group)

・ (B2-2)
(Manufactured by Shinetsu Chemical Industry Co., Ltd., "X-41-1805", weight average molecular weight: 3,450, dispersity: 1.85, alkoxy group content: 50%, reactive functional group: mercapto group, mercapto equivalent: 800 g / Mol, Alkoxy group contained: methoxy group, ethoxy group),

<Crosslinking agent (C)>
The following were prepared as the cross-linking agent (C).
(C-1): Adduct of tolylene diisocyanate and trimethylolpropane (manufactured by Tosoh Corporation, "Coronate L55E": 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 4, 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 polarizing plates [I] and [II] with adhesive layer]
The obtained acrylic pressure-sensitive adhesive composition was applied to a release sheet having a thickness of 38 μm (“Lumilar SP-0138BU” manufactured by Mitsui Kagaku Tohcello Co., Ltd.) so that the thickness after drying was 25 μm, and dried at 100 ° C. for 3 minutes. After that, the adhesive layer surface on the opposite side of the release sheet was attached to the surface of one TAC film of the polarizing plate in which the triacetyl cellulose (TAC) film was laminated on both sides, and the environment of 23 ° C. × 50% RH was used for 7 days. Aging was performed to obtain a polarizing plate [I] with an adhesive layer (layer structure: release sheet / adhesive layer / TAC film 1 / polarizer / TAC film 2, TAC film 1: thickness 40 μm, TAC film 2: 60 μm. ).
Further, a polarizing plate with an adhesive layer [II] was obtained in the same manner except that the COP surface and the adhesive layer surface of the corona-treated cycloolefin-based film / polarizer / TAC-based film were bonded together.
The TAC film is a triacetyl cellulose film (thickness 60 μm), and the COP film is a cycloolefin film (thickness 50 μm).
The following evaluation was performed using the polarizing plate with a pressure-sensitive adhesive layer [I] and the 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). After pressing and bonding with a 2 kg roller and performing autoclave treatment (0.5 MPa × 50 ° C. × 20 minutes), it is allowed to stand in an environment of 23 ° C. × 50% RH for 1 day, 40 days, 50 days, and then. The adhesive strength at the time of peeling was measured at a peeling angle of 180 ° and a peeling speed of 300 mm / min, and evaluated according to the following criteria.
(Evaluation criteria)
・ 1 day after bonding ◎ ・ ・ ・ 5N / 25mm or less ○ ・ ・ ・ Higher than 5N / 25mm and less than 10N / 25mm × ・ ・ ・ 10N / 25mm or more ・ 40 days later ◎ ・ ・ ・ 10N / 25mm or less ○ ・ ・ ・Higher than 10N / 25mm and less than 15N / 25mm Δ ・ ・ ・ 15N / 25mm or more, less than 20N / 25mm × ・ ・ ・ 20N / 25mm or more, or adhesive residue occurs ・ ・ ・ 50 days later ◎ ・ ・ ・ 10N / 25mm or less ○ ・ ・・ Higher than 10N / 25mm and less than 18N / 25mm Δ ・ ・ ・ 18N / 25mm or more, less than 20N / 25mm × ・ ・ ・ 20N / 25mm or more, or adhesive residue occurs

〔durability〕
<Evaluation of initial durability>
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, they were bonded together and then autoclaved (0.5 MPa × 50 ° C. × 20 minutes) to prepare a sample for the initial durability test.
The obtained sample was evaluated as follows for the polarizing plate after being exposed to the conditions of (1) heat resistance (80 ° C. × 250 hours) and (2) moisture heat resistance (60 ° C. × 90% RH × 250 hours). rice field.
(Evaluation criteria)
○ ・ ・ ・ No firing or floating at the end of the polarizing plate × ・ ・ ・ Foaming or floating at the end of the polarizing plate

<Evaluation after deterioration acceleration test>
The obtained polarizing plate [I] with an adhesive layer was exposed to an environment of 45 ° C. and 90% RH for 3 days, and then the temperature and humidity were adjusted for 7 days in an environment of 23 ° C. and 50% RH. After that, it is cut to 20 cm x 15 cm, the release sheet is peeled off, the adhesive layer surface is pressed against non-alkali glass ("Eagle XG" manufactured by Corning Inc .: thickness 1.1 mm), and two reciprocations are made with a 2 kg roller to bond them together. , Autoclave treatment (0.5 MPa × 50 ° C. × 20 minutes) was carried out to prepare a sample for deterioration acceleration test.
The obtained sample was evaluated as follows for the polarizing plate after being exposed to the conditions of (1) heat resistance (80 ° C. × 250 hours) and (2) moisture heat resistance (60 ° C. × 90% RH × 250 hours). rice field.
(Evaluation criteria)
○ ・ ・ ・ No firing or floating at the end of the polarizing plate × ・ ・ ・ Foaming or floating at the end of the polarizing plate

[Moisture heat whitening resistance]
The obtained polarizing plate with an adhesive layer [II] was cut into a size of 3.5 cm × 3.5 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 a moisture-heat whitening resistance test.
The obtained sample was exposed to an environment of 60 ° C. × 90% RH for 250 hours, and then taken out and left at room temperature. Then, the haze 3 hours after taking out was measured, and the moisture heat bleaching 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 3 hours after removal ◎ ・ ・ ・ Less than 1% ○ ・ ・ ・ 1% or more and less than 2% △ ・ ・ ・ 2% or more and less than 4% × ・ ・ ・ 4% or more

[Gel fraction]
The release sheet of the obtained pressure-sensitive adhesive layered polarizing plate [I] was peeled off, the pressure-sensitive adhesive was picked from the pressure-sensitive adhesive layer surface, 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 for 24 hours in an atmosphere of 23 ° C. × 50% RH, the release sheet of the adhesive layer is removed and a surface resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) , The device name "Hiresta-UP MCP-HT450") was used to measure the surface resistivity of the pressure-sensitive adhesive layer.

From the above results, from an acrylic pressure-sensitive adhesive composition in which a silane coupling agent (B1) having an alkoxy group content of 15% by weight or less and a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more are used in combination. It can be seen that Examples 1 to 4 using the obtained pressure-sensitive adhesive are excellent in long-term reworkability, storage stability, and durability in a well-balanced manner.

On the other hand, Comparative Example 1 and Comparative Example 1 in which the silane coupling agent (B2) having an alkoxy group content of 20% by weight or more was not used and only the silane coupling agent (B1) having an alkoxy group content of 15% by weight or less was used. It can be seen that in No. 2, although the long-term reworkability is excellent, the storage stability is inferior.
Further, Comparative Examples 3 to 5 in which the silane coupling agent (B1) having an alkoxy group content of 15% by weight or less was not used and only the silane coupling agent (B2) having an alkoxy group content of 20% by weight or more was used. Then, it can be seen that it is inferior in long-term reworkability.

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 4, 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 rework for a long period of time when used as a pressure-sensitive adhesive used for bonding a polarizing plate (protective film) and a liquid crystal cell (glass) in the manufacture of a liquid crystal display device. It is possible to obtain an adhesive that exhibits properties, is not easily affected by moisture, and does not cause a decrease in durability, and is an adhesive for an optical member for bonding a display and its constituent optical components, particularly. , It is useful as an adhesive for a polarizing plate for bonding a polarizing plate and a glass substrate of a liquid crystal cell or the like.

Claims (10)

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.
As the silane coupling agent (B), a silane coupling agent (B1) having an alkoxy group content of 15% by weight or less and a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more are contained. and acrylic pressure-sensitive adhesive composition having a weight average molecular weight of the silane coupling agent (B2) is characterized in der Rukoto 500 or more. The acrylic resin (A) is an acrylic resin containing 5 to 50% by weight of a structural unit derived from at least one polar group-containing monomer (a1) selected from a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a nitrogen-containing monomer. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the composition is characterized by being present. The acrylic pressure-sensitive adhesive composition according to claim 1 or 2, wherein the reactive functional group equivalent of the silane coupling agent (B1) is 1,600 g / mol or less. The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the silane coupling agent (B1) has a weight average molecular weight of 3,000 or more. The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the reactive functional group equivalent of the silane coupling agent (B2) is 1,000 g / mol or less. The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 5 , further containing a cross-linking agent (C). The acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 6 , further containing an antistatic agent (D). A pressure-sensitive adhesive obtained by cross-linking the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 7 with a cross-linking agent (C). An image display device according to claim 8 , wherein a polarizing plate and a liquid crystal cell are bonded together. 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.
As the silane coupling agent (B), a silane coupling agent (B1) having an alkoxy group content of 15% by weight or less and a silane coupling agent (B2) having an alkoxy group content of 20% by weight or more are contained. A pressure-sensitive adhesive for a polarizing plate, wherein the acrylic pressure-sensitive adhesive composition is formed by using a pressure-sensitive adhesive obtained by cross-linking with a cross-linking agent (C).