JP2021107564A - Acrylic adhesive composition, adhesive obtained using the same, polarizing plate adhesive, and image display device - Google Patents

Abstract

To provide an acrylic adhesive composition with which it is possible to obtain an adhesive that exhibits excellent reworkability over a long period, and that does not undergo whitening due to heat and humidity even when exposed to a high-temperature, high-humidity environment when used as an adhesive for pasting together a polarizing plate (protective film) and a liquid crystal cell (glass) during the manufacturing of a liquid crystal display.SOLUTION: The acrylic adhesive composition contains an acrylic resin (A) and a silane coupling agent (B), which contains at least one each of a reactive functional group and an alkoxy group in a structure, wherein the acrylic resin (A) contains 5-50 wt.% of structural moieties derived from a hydroxyl group-containing monomer, and the silane coupling agent (B) contains an oligomer-type silane coupling agent (B1) in which the alkoxy group content is 15 wt.% or less.SELECTED DRAWING: None

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 polarizing plates. More specifically, the present invention exhibits excellent reworkability over a long period of time and is not easily affected by moisture. 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, an olefin-based film, particularly a cycloolefin-based film (COP film), has come to be used as a protector protective film for a polarizer instead of a TAC film from the viewpoint of dimensional stability and durability.

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 silane coupling agent is used. There is a problem that the adhesive force increases and the long-term reworkability decreases due to the gradual reaction.

Further, when a cycloolefin-based film is used as a protective film for a polarizing plate, when it is exposed to a moist heat environment, the pressure-sensitive adhesive layer is whitened due to a dew condensation phenomenon when the temperature is returned to room temperature (wet heat whitening phenomenon). was there.
Further, the pressure-sensitive adhesives conventionally used for polarizing plates are used properly depending on the type of polarizing plate, but in terms of cost and workability, a pressure-sensitive adhesive that can be used even when the types of polarizing plates are different is required. Was there.

Examples of the pressure-sensitive adhesive having excellent reworkability and moisture-heat whitening resistance include, for example, Patent Document 1 contains 100 parts by weight of the pressure-sensitive adhesive resin (A), an epoxy equivalent of 100 to 2000 g / mol, and an alkoxyl group. An acrylic-based adhesive resin (A) obtained by polymerizing a carboxyl group-free monomer containing 0.1 to 20 parts by weight of a silicone alkoxy oligomer (B) having an amount of 5 to 60% by weight. Described is a pressure-sensitive adhesive composition that is one or more selected from the group consisting of a pressure-sensitive adhesive resin (A1), a urethane-based pressure-sensitive adhesive resin (A2), and a polyester-based pressure-sensitive adhesive resin (A3).
Further, Patent Document 2 describes a pressure-sensitive adhesive using an acrylic resin in which a large amount of polar group-containing monomers is introduced in consideration of moisture-heat whitening resistance.

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, there is room for improvement in the moisture-heat whitening resistance when a protective film having low moisture permeability such as a cycloolefin-based film is used.

On the other hand, although Patent Document 2 considering moisture and heat whitening resistance describes that it can be used for various optical members, it is hydrophilic because a large amount of polar group-containing monomers is introduced into the acrylic resin. When a TAC or an acrylic film having high moisture permeability is used as the protective film, there is a problem that the hydrolysis of the silane coupling agent is promoted and the long-term reworkability is lowered.

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 a liquid crystal display device, it is excellent for a long period of time. It is an object of the present invention to provide an acrylic pressure-sensitive adhesive composition which exhibits reworkability and can obtain a pressure-sensitive adhesive which does not cause a whitening phenomenon even when exposed to a high temperature and high humidity environment.

However, as a result of intensive studies in view of such circumstances, the present inventors have conducted an acrylic-based composition containing a relatively large amount of structural units derived from a hydroxyl group-containing monomer in a pressure-sensitive adhesive composition containing an acrylic resin and a silane coupling agent. A pressure-sensitive adhesive that exhibits excellent reworkability over a long period of time and does not cause whitening under high-temperature and high-humidity conditions by using a resin and an oligomer-type silane coupling agent with a low alkoxy group content in combination. Was found to 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. The acrylic resin (A) is an acrylic resin containing 5 to 50% by weight of a structural unit derived from a hydroxyl group-containing monomer, and the silane coupling agent (B) is an oligomer having an alkoxy group content of 15% by weight or less. The first gist is an acrylic pressure-sensitive adhesive composition containing a type silane coupling agent (B1).
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 a polarizing plate made of the pressure-sensitive adhesive of the second gist. The third gist is the adhesive for use, and the fourth gist is an image display device formed by bonding a polarizing plate and a liquid crystal cell 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 alkoxy group in the structure. The system resin (A) is an acrylic resin containing 5 to 50% by weight of a structural unit derived from a hydroxyl group-containing monomer, and the silane coupling agent (B) is an oligomer type having an alkoxy group content of 15% by weight or less. It is an acrylic pressure-sensitive adhesive composition containing a silane coupling agent (B1). 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, and has excellent moisture-heat bleaching resistance and durability, and is very useful as a pressure-sensitive adhesive for polarizing plates.

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

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

^{The 1} HNMR spectrum of the silane coupling agent "X-24-9589" is shown.

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 needs to be an acrylic resin containing 5 to 50% by weight of a structural unit derived from a hydroxyl group-containing monomer. For example, it contains a carboxyl group together with a hydroxyl group-containing monomer. It is preferable that the acrylic resin is obtained by copolymerizing a copolymerization component containing 5 to 50% by weight of at least one polar group-containing monomer selected from a monomer and a nitrogen-containing monomer. Hereinafter, the hydroxyl group-containing monomer, the carboxyl group-containing monomer, and the nitrogen-containing monomer are collectively referred to as a polar group-containing monomer (a1).

The copolymerization component of the acrylic resin (A) may contain a (meth) acrylic acid alkyl ester-based monomer (a2) and other copolymerizable ethylenically unsaturated monomer (a3), if necessary.

First, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a nitrogen-containing monomer, which are polar group-containing monomers (a1), will be described.

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; hydroxyl group 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 2-hydroxyethyl (meth) acrylate is preferable in terms of stability during polymerization. 4-Hydroxybutyl (meth) acrylate is preferably used because it has a high reactivity with a cross-linking agent and shortens aging. Further, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferable because they have few impurities such as di (meth) acrylate and are easy to produce.

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 atom-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 in terms of high cross-linking promoting effect and high storage stability of the resin.
Heterocyclic amine monomers such as (meth) acryloyl morpholine are preferable because they have excellent durability and adhesion to metals and metal oxides. Of these, dimethylaminoethyl (meth) acrylate and (meth) acryloyl morpholine are particularly preferable.

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). Acrylamide (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 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 such polar group-containing monomers (a1), a hydroxyl group-containing monomer is used as an essential monomer because it is excellent in moisture-heat whitening resistance.
Further, the polar group-containing monomer (a1) may be used alone or in combination of two or more. It is also preferable to use a hydroxyl group-containing monomer and a carboxyl group-containing monomer, and a hydroxyl group-containing monomer and a tertiary amine-based monomer in combination because aging tends to be short.

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

The content of the hydroxyl group-containing monomer is 5 to 50% by weight, particularly preferably 6 to 35% by weight, still more preferably 7 to 25% by weight, and particularly preferably 8 to 50% by weight, based on the total copolymerization component. 20% by weight.
If the content of the hydroxyl group-containing monomer is too small, the moisture-heat whitening resistance is lowered, and if it is too high, the storage stability as an acrylic resin solution is lowered.

Further, in applications where corrosion is a problem, the content of the polar group-containing monomer (a1) when the carboxyl group-containing monomer is contained is preferably 1% by weight or less based on the total copolymerization component.

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) Acrylate, etc. can be mentioned. 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.

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 acrylates and orthophenylphenoxyethyl (meth) acrylates; cyclohexyl (meth) acrylates, cyclohexyloxyalkyl (meth) acrylates, tert-butylcyclohexyloxyethyl (meth) acrylates, isobornyl (meth) acrylates. , 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) Examples thereof include ether chain-containing monomers such as acrylate, octoxypolyethylene glycol-polypropylene glycol-mono (meth) acrylate, lauroxypolyethylene glycol mono (meth) acrylate, and stearoxypolyethylene glycol mono (meth) acrylate. 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) in terms of easy adjustment of the refractive index and birefringence and excellent light leakage resistance. ) Acrylate), the refractive index and birefringence 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) in which a hydroxyl group-containing monomer is an essential monomer, preferably a (meth) acrylic acid alkyl ester-based monomer (a2), and other copolymerization. It is produced by appropriately selecting a possible ethylenically unsaturated monomer (a3) and using these polymerization components to polymerize, for example, by mixing or dropping such a polymerization component and a polymerization initiator in an organic solvent. be able to.
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 initiators, benzoyl peroxide, laurolyl peroxide, di-tert-butyl peroxide, Examples thereof include organic peroxides 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 needs to contain 5 to 50% by weight of a structural unit derived from a hydroxyl group-containing monomer, preferably 6 to 35% by weight, and particularly preferably 7 to 50% by weight. It is 25% by weight, more preferably 8 to 20% by weight. If the number of structural units derived from the hydroxyl group-containing monomer is too small, the moisture-heat whitening resistance tends to decrease, and if it is too large, the storage stability of an acrylic resin solution tends 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 displayed on a high performance liquid chromatograph (“Waters 2695 (main body)” and “Waters 2414 (detector)” manufactured by Japan Waters Corp.). : Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ^7, separation range: from 100 to 2 × 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 −60 to 0 ° C., particularly preferably −50 to −20 ° C., and even more preferably 45 to −25 ° 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の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 by applying it to the Fox formula. It is a value calculated by.
The glass transition temperature when a homopolymer of the monomer constituting the acrylic resin (A) is used 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 is 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 oligomer-type silane coupling agent (B1) having an alkoxy group content of 15% by weight or less. Is contained.

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 alkoxy group content of the oligomer-type silane coupling agent (B1) needs to be 15% by weight or less, preferably 1 to 15% by weight, particularly preferably 3 to 14.5% by weight, and even more preferably. It is 5 to 14.5% by weight.
If the alkoxy group content is too large, the long-term reworkability tends to decrease. If the amount is too small, the durability tends to decrease.

The weight average molecular weight of the oligomer-type silane coupling agent (B1) is preferably 3,000 or more, particularly preferably 4,000 to 30,000, and even more preferably 4,500 to 20,000.
When the weight average molecular weight is in the above range, the balance between long-term reworkability and durability tends to be excellent.

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.
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 velocity: 1.0 mL / min

The reactive functional group equivalent of the oligomer-type silane coupling agent (B1) is preferably 1,600 g / mol or less, particularly preferably 100 to 900 g / mol, and even more preferably 300 to 700 g / mol.
When the reactive functional group equivalent is in the above range, the durability tends to be better.

The oligomer-type silane coupling agent (B1) is an oligomer-type silane coupling agent, in other words, an oligomer-type oligomer-type dimer or trimeric in which a part of an organosilicon compound is hydrolyzed and polycondensed. It is an organosilicon compound (organosiloxane compound).

The oligomer-type silane coupling agent (B1) is an oligomer obtained by hydrolyzing and polycondensing a part of an organosilicon compound such as γ-glycidoxypropyltriethoxysilane or γ-glycidoxypropylmethyldiethoxysilane. Oligomer-type epoxy group-containing silane coupling agent such as a type organosilicon compound (epoxy group-containing silicone alkoxy oligomer, etc.) or an oligomer-type organosilicon compound obtained by ether-modifying a part of these oligomer-type organosilicon compounds; γ-mercaptopropyl Oligomer-type mercapto group-containing silane coupling agents such as oligomer-type organosilicon compounds (mercapto group-containing silicone alkoxy oligomers and the like) in which a part of an organosilicon compound such as triethoxysilane is hydrolyzed and polycondensed; and the like.
From these, the oligomer-type silane coupling agent (B1) may be appropriately selected and used so as to satisfy each condition. Further, as the oligomer type silane coupling agent (B1), only one type may be used, or two or more types may be used in combination.

Specifically, as the oligomer-type silane coupling agent (B1), a commercially available product manufactured by Shin-Etsu Chemical Industry Co., Ltd., "X-24-9590" (weight average molecular weight: 13,700, containing alkoxy group: methoxy group, Alkoxy group content: 9.5% by weight, reactive functional group: epoxy group, epoxy equivalent: 592 g / mol), "X-24-9589" (weight average molecular weight: 4,700, contained alkoxy group: ethoxy group, Alkoxy group content: 13.2%, reactive functional group: epoxy group, epoxy equivalent: 1509 g / mol) and the like.
Among these, "X-24-9590" is particularly preferable.

The content of the oligomer-type silane coupling agent (B1) is preferably 0.001 to 1 part by weight, particularly preferably 0.015 to 0.5, based on 100 parts by weight of the acrylic resin (A). By weight, more preferably 0.020 to 0.3 parts by weight, even 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.

In the acrylic pressure-sensitive adhesive composition of the present invention, a silane coupling agent other than the above-mentioned oligomer-type silane coupling agent (B1) can be used as long as the effects of the present invention are not impaired. If the content of the agent is too high, the durability tends to decrease due to bleeding. Therefore, the content of the silane coupling agent other than the oligomer-type silane coupling agent (B1) is, specifically, 0.5 part by weight or less with respect to 100 parts by weight of the acrylic resin (A). Is more preferable, and more 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 acrylic resin (A).

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 isocyanate-based 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 propan triglycidyl 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 carboxamide), N, N'-hexamethylene-1,6-bis (1-aziridine carboxamide) and the like can be mentioned.

Examples of the melamine-based cross-linking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, 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 and the substrate tends to warp, or 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 anti-electrostatic measures.

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

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. An onium salt composed of a nitrogen-containing cation such as a nium cation, particularly preferably an alkylammonium salt, more preferably an acyclic tetraalkylammonium cation and an N, N-bis (trifluoromethanesulfonyl) imide anion, and an ammonium cation and N, N. -Ammonium salt composed of bis (fluorosulfonyl) imide anion and the like can be mentioned.

The melting point of the ionic compound (D1) is preferably 10 ° C to 100 ° C, particularly preferably 20 ° C 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 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 is lowered, the moisture resistance and heat whitening resistance is lowered, and bleeding It tends to be out and its durability is reduced.

Further, the acrylic pressure-sensitive adhesive composition of the present invention contains, as other components, a resin component, an acrylic monomer, a polymerization inhibitor, an antioxidant, an antioxidant, an antioxidant, and cross-linking promotion, 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 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 the acrylic resin (A), the silane coupling agent (B), the cross-linking agent (C), the 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 of applying an acrylic pressure-sensitive adhesive composition on an optical member, drying it, attaching a release sheet, and performing a treatment 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 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 preferably 5 to 60% by weight as the solid content concentration. It is 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, dryness, price and the like.

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

The gel fraction of the pressure-sensitive adhesive layer produced by the above method is preferably 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 an optical member, particularly a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on a substrate 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 even more preferably 10 to 30 μm. If the thickness is too thin, the adhesive 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 long-term reworkability 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 bonded to a glass substrate, for example. It is used for an image display device.

The 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, in the case of bonding to a glass substrate such as a liquid crystal cell, the adhesive strength one day after bonding is preferably 0.1 to 10 N / 25 mm, more preferably 0.1 to 5 N / 25 mm. The adhesive strength after 20 days is preferably 0.1 to 20 N / 25 mm, more preferably 0.1 to 15 N / 25 mm, and particularly preferably 0.1 to 10 N / 25 mm. Further, the adhesive strength after 50 days is preferably 0.1 to 20 N / 25 mm, more preferably 0.1 to 15 N / 25 mm, and particularly preferably 0.1 to 10 N / 25 mm.

The 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) and leaving it at 23 ° C. × 50% RH for 24 hours, 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, a cycloolefin-based film, and the like. 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 adhering 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) and the silane coupling agent (B) 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)]
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 condenser, a stirrer, a nitrogen gas inlet and a thermometer. 73.3 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% 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 20.9%). , Viscosity 4,770 mPa · s / 25 ° C., Acrylic resin (A-1): Glass transition temperature −43 ° C., Weight average molecular weight 1.29 million, Dispersity 4.3) was 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, 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.

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

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

・ (B1-2):
(Manufactured by Shinetsu Chemical Industry Co., Ltd., "X-24-9589", weight average molecular weight: 4,700, alkoxy group content: 14.5% (measured value), reactive functional group: epoxy group, epoxy equivalent: 1, 509 g / mol, containing alkoxy group: ethoxy group: ethoxy group and propenyloxy group)

The alkoxy group content of "X-24-9589" was measured by the following method, and the alkoxy group content was calculated.
1. 1. About 50 mg of the measurement sample was weighed in a vial, and 1 mL of d-chloroform was added to dissolve the sample to prepare a 5% (w / v) chloroform solution. This was placed in a sample tube for NMR measurement, and ^{1 1 HNMR measurement was performed under the following conditions.} The obtained ^{1 1} HNMR spectrum is shown in FIG.
≪Measurement conditions≫
Measuring device: Bruker Ascend ^TM 400
Probe: cryo probe Pulse program: Single pulse Measurement temperature: 23 ° C (296K)
Number of integrations: 16 times Pulse delay time: 10 sec
2. Calculation of alkoxy group content
¹ Regarding signals A to F in the HNMR spectrum, A (6.2,6.0 ppm): propenyloxy group, B (3.6 ppm): ethylene oxide chain, C (3.4 ppm): ethylene oxide chain terminal methoxy group, D ( 3.1,2.8,2.6ppm): Epoxide group, E (1.2ppm): ethoxy group, F (0.1ppm): Methyl group, and the alkoxy group content is based on the integrated value of these signals. Asked.
The number of organic substituents (epoxide group, methyl group) is X, the number of alkoxy groups (ethoxy group, propenyloxy group) is R, and the main chain (−SiO−) is (X + R) / 2. did.

・ (B'-1)
(Manufactured by Shinetsu Chemical Industry Co., Ltd., "X-41-1059A", weight average molecular weight: 2,270 alkoxy group content: 42%, reactive functional group: epoxy group, epoxy equivalent: 350 g / mol, contained alkoxy group: methoxy Group, ethoxy group)

・ (B'-2)
(Manufactured by Shin-Etsu Chemical Industry Co., Ltd., "X-41-1805", weight average molecular weight: 3,450, alkoxy group content: 50%, reactive functional group: mercapto group, mercapto equivalent: 800 g / mol, contained alkoxy group: Methoxy group, ethoxy group)

・ (B'-3)
(Manufactured by Shin-Etsu Chemical Industry Co., Ltd., "X-41-1810", weight average molecular weight: 640, alkoxy group content: 30%, reactive functional group: mercapto group, mercapto equivalent: 450 g / mol, contained alkoxy group: methoxy group )

・ (B'-4)
3-glycidoxypropyltrimethoxysilane (manufactured by Shinetsu Chemical Industry Co., Ltd., "KBM-403", molecular weight: 236.6, alkoxy group content: 39% (calculated value), reactive functional group: epoxy group, epoxy equivalent : 236.6 g / mol (calculated value) containing alkoxy group: methoxy group)
Regarding the alkoxy group content of B'-4, 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). The epoxy equivalent was calculated as the molecular weight per 1 mol of epoxy group.

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

<Antistatic agent (D)>
The following antistatic agents (D) were prepared.
(D-1): Tri-n-butylmethylammonium N, N-bis (trifluoromethanesulfonyl) imide (manufactured by 3M Ltd., "FC-4400", melting point 27.5 ° C.)

(D-2): An ionic compound composed of an aromatic ring-containing ammonium cation and bis (fluorosulfonylimide) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "MP-446", melting point 37 ° C.)

(D-3): Lithium N, N-bis (trifluoromethanesulfonyl) imide (Morita Chemical Industries, Ltd., "Li-TFSI", melting point 232 to 234 ° C.)

<Examples 1 to 12, Comparative Examples 1 to 9>
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 below.

[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. ).
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 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). 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 for 1, 20 and 50 days in an environment of 23 ° C. × 50% RH, and then. The adhesive strength at the time of peeling at a peeling angle of 180 ° and a peeling speed of 300 mm / min was measured and evaluated according to the following criteria.
(Evaluation criteria)
・ 1 day later A ・ ・ ・ 5N / 25mm or less B ・ ・ ・ 5N / 25mm or more, 10N / 25mm or less C ・ ・ ・ 10N / 25mm or less, or adhesive residue is generated or the base material is broken ・ 20 days later A ・ ・・ 5N / 25mm or less B ・ ・ ・ 5N / 25mm or more, 10N / 25mm or less C ・ ・ ・ 10N / 25mm or more, 15N / 25mm or less D ・ ・ ・ 15N / 25mm or more, 20N / 25mm or less E ・ ・ ・ 20N / Over 25 mm, or adhesive residue is generated, or the substrate is broken. 50 days later A: 5N / 25 mm or less B: 5N / 25 mm or more, 10N / 25 mm or less C: 10N / 25 mm or more, 15N / 25 mm D ... 15N / 25mm or more, 20N / 25mm or less E ... 20N / 25mm or more, adhesive residue is generated, or the substrate is broken

〔durability〕
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 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 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. × 500 hours).
(Evaluation criteria)
○ ・ ・ ・ No firing or floating at the edges of the polarizing plate × ・ ・ ・ Foaming or floating at the edges of the polarizing plate [Moisture heat whitening resistance]
The obtained 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 surface 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 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. The haze 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 3% △ ・ ・ ・ 3% 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 3% × ・ ・ ・ 3% 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 above-mentioned polarizing plate with an adhesive layer [I] 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 resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) The surface resistivity of the pressure-sensitive adhesive layer was measured using the apparatus name "Hiresta-UP MCP-HT450").

From the above results, it can be obtained from an acrylic pressure-sensitive adhesive composition using an acrylic resin (A) containing a larger amount of hydroxyl group-containing monomer and an oligomer-type silane coupling agent (B1) having an alkoxy group content of 15% by weight or less. It can be seen that Examples 1 to 12 using the pressure-sensitive adhesive are excellent in long-term reworkability and moisture-heat bleaching resistance.

On the other hand, it can be obtained from an acrylic pressure-sensitive adhesive composition using an acrylic resin (A'-1, A'-2) that does not contain a large amount of hydroxyl group-containing monomers and a silane coupling agent having an alkoxy group content of more than 15% by weight. In Comparative Examples 1 and 2 using the adhesive, it can be seen that although the long-term reworkability is excellent, the moisture-heat bleaching resistance is inferior.
Further, Comparative Example 3 using a pressure-sensitive adhesive obtained from an acrylic pressure-sensitive adhesive composition using an acrylic resin (A) containing a larger amount of hydroxyl group-containing monomer and a silane coupling agent having an alkoxy group content of more than 15% by weight. From 9 to 9, it can be seen that although the moisture heat whitening resistance is excellent, the long-term reworkability is inferior.

The silane coupling agent is hydrolyzed by the moisture in the pressure-sensitive adhesive system and is bonded to the glass surface via a silanol group to improve the adhesion. An acrylic resin containing a large amount of hydroxyl group-containing monomers to the extent that it has good moisture-resistant heat-whitening resistance easily takes in moisture in the environment and is easily affected by hydrolysis. Therefore, the long-term reworkability tends to be lower than usual. In Comparative Examples 1 and 2 using an acrylic resin containing not a large amount of hydroxyl group-containing monomers, long-term reworkability was not an issue even if a silane coupling agent having an alkoxy group content of more than 15% by weight was used. Understand. On the other hand, in Examples 1 to 12, an oligomer-type silane coupling agent (B1) having an alkoxy group content of 15% by weight or less even when an acrylic resin containing a large amount of polar monomers to a degree of good moisture-heat whitening resistance is used. ) Is used, so it can be seen that it is excellent in long-term reworkability and durability.

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 12, 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 for a long period of time when used as a pressure-sensitive adhesive for bonding a polarizing plate (protective film) and a liquid crystal cell (glass) in the manufacture of a liquid crystal display device. A pressure-sensitive adhesive that exhibits properties and has excellent moisture-heat whitening resistance can be obtained even when a polarizing plate using a low-polarity film such as a cycloolefin-based film as a protective film is used. It is useful as a pressure-sensitive adhesive for optical members for bonding constituent optical components, and particularly as a pressure-sensitive adhesive for a polarizing plate for bonding a polarizing plate and a glass substrate of a liquid crystal cell.

Claims (8)

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) is an acrylic resin containing 5 to 50% by weight of a structural unit derived from a hydroxyl group-containing monomer.
An acrylic pressure-sensitive adhesive composition, wherein the silane coupling agent (B) contains an oligomer-type silane coupling agent (B1) having an alkoxy group content of 15% by weight or less. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein the oligomer-type silane coupling agent (B1) has a reactive functional group equivalent of 1,600 g / mol or less. The acrylic pressure-sensitive adhesive composition according to claim 1 or 2, wherein the oligomer-type 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 3, further containing a cross-linking agent (C). The acrylic resin composition according to any one of claims 1 to 4, 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 5 with a cross-linking agent (C). A pressure-sensitive adhesive for a polarizing plate, which comprises using the pressure-sensitive adhesive according to claim 6. An image display device according to claim 6, wherein a polarizing plate and a liquid crystal cell are bonded together.

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