JP2018044070A - Adhesive composition for polarizing plate, adhesive for polarizing plate, polarizing plate with adhesive layer, and polarizing plate with adhesive layer with release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition for a polarizing plate, which gives an adhesive layer having excellent ageing characteristics and releasing property for a release film and excellent reworkability and durability when used for bonding a polarizing plate and a liquid crystal cell.SOLUTION: The adhesive composition for a polarizing plate comprises an acrylic resin (A) and an oligomer type silane coupling agent (B) having each at least one reactive functional group and at least one silicon atom-bonded alkoxy group in the structure. The acrylic resin (A) contains a structural unit derived from a tertiary amino group-containing monomer (a1) by 0.003 to 0.25 wt.%; and the oligomer type silane coupling agent (B) contains a silicon atom-bonded alkoxy group by 20 to 45 wt.%.SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition for a polarizing plate, a pressure-sensitive adhesive for a polarizing plate, a polarizing plate with a pressure-sensitive adhesive layer, and a polarizing plate with a pressure-sensitive adhesive layer with a release film. It is related with the adhesive composition for polarizing plates which can obtain the adhesive layer excellent in this.

  Liquid crystal display devices are widely used as image display devices for liquid crystal televisions, computer displays, mobile phones, digital cameras, and the like. Such a liquid crystal display device has a configuration in which polarizing plates are laminated on both surfaces of a glass substrate (liquid crystal cell) in which liquid crystal is sealed, and various optical elements such as a retardation plate are further laminated as necessary. .

  In the production of a liquid crystal display device, a pressure-sensitive adhesive layer is usually provided on a release-treated film, and the pressure-sensitive adhesive layer side opposite to the release film is attached to the polarizing plate to produce a polarizing plate with a pressure-sensitive adhesive layer. Then, when bonding with a liquid crystal cell after that, a release film is peeled off and an adhesive layer and the glass substrate of a liquid crystal cell are stuck, and it manufactures.

  As the above-mentioned pressure-sensitive adhesive, a pressure-sensitive adhesive containing an acrylic resin having a monomer containing a carboxyl group as a copolymerization component has been used since it has excellent durability and aging characteristics (see, for example, Patent Document 1). However, in recent years, liquid crystal cells have become highly functional, and patterning of metals such as copper and metal oxides such as ITO has been performed to provide a touch function for the contact portion of the adhesive. If an adhesive made of an adhesive composition containing an acidic group is used as a base, it may cause corrosion or deterioration of the wiring and the like, which may cause problems in the final product. Adhesives made of acrylic resins that are not used have come to be used preferably.

  However, in the pressure-sensitive adhesive composition that does not contain an acrylic resin using a carboxyl group-containing monomer, the catalytic effect of the carboxyl group cannot be obtained, so the progress of the crosslinking reaction is slow, and the time taken for the pressure-sensitive adhesive properties to stabilize There is a problem that the aging characteristics become worse.

  On the other hand, it is known that by using a tertiary amino group-containing monomer as a polymerization component of an acrylic resin, the tertiary amino group-containing monomer can act as a catalyst, improve cross-linking stability, and have excellent aging characteristics. (For example, refer to Patent Document 2).

JP 2008-156513 A JP 2009-167386 A

  However, in the pressure-sensitive adhesive composition using the tertiary amino group-containing acrylic resin, the aging characteristics are improved, but when an oligomer type silane coupling agent is blended in the composition, the release film and the pressure-sensitive adhesive are used. There was a problem that the adhesiveness of the layer became high and a large peeling force was required when peeling the release film from the pressure-sensitive adhesive layer.

This is because the reactive functional group of the oligomer type silane coupling agent in the pressure-sensitive adhesive layer and the residual reactive functional group on the surface of the release film (for example, the residual active hydrogen or residual vinyl group of the raw material used for the release film, Reaction with hydroxyl groups, alkoxy groups, etc.) is partly promoted by the catalytic action of the amino group contained in the acrylic resin, and the adhesiveness between the pressure-sensitive adhesive layer and the release film is improved. As a result, the release film It is presumed that this is because the peel strength of the film increases.
In addition, since the oligomer type silane coupling agent has a large number of functional groups in a single molecule, it is easy to take a cross-linked structure compared to the monomer type silane coupling agent, and the release force of the release film due to the above reaction is reduced. It is estimated that the increase will be greater.

  In recent years, since the polarizing film constituting the polarizing plate has been thinned, there is no stiffness of the film, and when the release film has a large peeling force, it becomes difficult to peel off when the release film is peeled off from the adhesive layer. When the mold film is peeled off, the polarizing plate fixed to the adsorbing mat of the laminating apparatus tends to float or the adhesive is missing.

  Therefore, in the present invention, under such a background, even if an oligomer type silane coupling agent is used, the aging characteristics and the release film are excellent in releasability, and the reworkability and durability when the polarizing plate and the liquid crystal cell are bonded together. It aims at providing the adhesive composition for polarizing plates which can obtain the adhesive layer which is excellent also in the property.

  However, as a result of intensive studies in view of such circumstances, the present inventors have found that a tertiary amino group-containing monomer in an acrylic resin in an adhesive composition containing an acrylic resin and an oligomer-type silane coupling agent. Paying attention to the content of the structural unit derived from and the content of the silicon-bonded alkoxy group of the oligomer type silane coupling agent, the content is higher than the content in the acrylic resin usually used in the pressure-sensitive adhesive for polarizing plates. By using an acrylic resin with a low content of structural units derived from a secondary amino group-containing monomer, and using an oligomeric silane coupling agent with a silicon atom-bonded alkoxy group content in a specific range as an oligomeric silane coupling agent , Excellent in both aging characteristics and release film release properties, and polarizing plate and glass substrate etc. It found that pressure-sensitive adhesive layer excellent in durability can be obtained, and have completed the present invention.

That is, the gist of the present invention is a polarizing plate containing an acrylic resin (A) and an oligomer type silane coupling agent (B) containing at least one reactive functional group and one silicon-bonded alkoxy group in the structure. The acrylic resin (A) is an acrylic resin containing 0.003 to 0.25% by weight of a structural unit derived from the tertiary amino group-containing monomer (a1), The oligomer-type silane coupling agent (B) is an oligomer-type silane coupling agent having a silicon atom-bonded alkoxy group content of 20 to 45% by weight. is there.
Furthermore, the present invention also relates to an adhesive for polarizing plates, a polarizing plate with an adhesive layer, and a polarizing plate with an adhesive layer with a release film.

  The pressure-sensitive adhesive obtained by using the pressure-sensitive adhesive composition of the present invention is excellent in aging characteristics and peelability of a release film, and is excellent in reworkability and durability when a polarizing plate and a liquid crystal cell are bonded together. . Therefore, by using this pressure-sensitive adhesive composition for polarizing plates, a liquid crystal display device can be efficiently produced, and a liquid crystal display device having excellent durability can be obtained.

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

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

<Acrylic resin (A)>
The acrylic resin (A) used in the present invention is an acrylic resin containing 0.003 to 0.25% by weight of a structural unit derived from the tertiary amino group-containing monomer (a1). It is obtained by copolymerizing a copolymer component containing 0.003 to 0.25% by weight of the amino group-containing monomer (a1). The copolymer component of the acrylic resin (A) includes a functional group-containing monomer (a2) (except for (a1)), a (meth) acrylic acid alkyl ester monomer (a3), and the like, if necessary. The copolymerizable ethylenically unsaturated monomer (a4) may be included.

Examples of the tertiary amino group-containing monomer (a1) include ethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) ) Acrylate and the like.
These may be used alone or in combination of two or more.

  Among the tertiary amino group-containing monomers (a1), dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylate are preferable, and dimethylaminoethyl (meth) acrylate is particularly preferable because of excellent aging characteristics.

  The content of the tertiary amino group-containing monomer (a1) is preferably 0.003 to 0.25% by weight, particularly preferably 0.005 to 0.15% by weight, based on the entire copolymerization component. More preferably, it is 0.006 to 0.08% by weight. When the content is too small, the aging characteristics are not improved, and when the content is too large, the pot life tends to be shortened.

  The structural unit (a1) derived from the tertiary amino group-containing monomer reacts with the later-described crosslinking agent (C) and the mercapto group of the silane coupling agent when the oligomer type silane coupling agent is a mercapto group. Promotes and efficiently forms a thiourethane bond, whereby the acrylic resin and the silane coupling agent are bonded via the isocyanate crosslinking agent. Therefore, in the present invention, the acrylic resin (A) contains a tertiary amino group even in the case of using an acrylic resin having only a hydroxyl group that is difficult to act with a general silane coupling agent and having no carboxyl group. By having the structural unit (a1) derived from the monomer, the acrylic resin reacts with the silane coupling agent, and the coupling effect by the silane coupling agent, that is, the adhesion between the pressure-sensitive adhesive layer and the liquid crystal cell is more effective. Can be obtained.

Examples of the functional group-containing monomer (a2) include monomers having a functional group that reacts with a cross-linking agent (C) described later, such as a hydroxyl group-containing monomer, a carboxyl group-containing monomer, an acetoacetyl group-containing monomer, and an isocyanate group-containing monomer. And glycidyl group-containing monomers.
Among these, a hydroxyl group-containing monomer and a carboxyl group-containing monomer are preferable in that a crosslinking reaction can be efficiently performed, and it is particularly preferable to use a hydroxyl group-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, 8-hydroxyoctyl ( Hydroxyalkyl esters of acrylic acid such as (meth) acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylate, oxyalkylene-modified monomers such as diethylene glycol (meth) acrylate and polyethylene glycol (meth) acrylate, 2- Primary hydroxyl group-containing monomers such as acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol (meth) acrylamide, and hydroxyethylacrylamide; Secondary hydroxyl group-containing monomers such as hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-chloro 2-hydroxypropyl (meth) acrylate; 2,2-dimethyl 2-hydroxyethyl (meth) acrylate, etc. And tertiary hydroxyl group-containing monomers.
These may be used alone or in combination of two or more.

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

  Examples of the carboxyl group-containing monomer include acrylic acid dimers such as (meth) acrylic acid and β-carboxyethyl acrylate, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N -Glycolic acid, cinnamic acid and the like.

  Examples of the acetoacetyl group-containing monomer include 2- (acetoacetoxy) ethyl (meth) acrylate and allyl acetoacetate.

  Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

  Examples of the glycidyl group-containing monomer include glycidyl (meth) acrylate, allyl glycidyl (meth) acrylate, and the like.

The content of the functional group-containing monomer (a2) is preferably 1 to 20% by weight, particularly preferably 2 to 15% by weight, more preferably 4 to 10% by weight, based on the entire copolymerization component. .
If the content is too small, the heat-and-moisture whitening resistance tends to decrease, and if the content is too large, the pot life tends to decrease.

When the hydroxyl group-containing monomer is used as the functional group-containing monomer (a2), the hydroxyl group-containing monomer content is preferably 3 to 15% by weight, particularly preferably 6. 5 to 11% by weight, more preferably 7 to 9% by weight.
If the content is too small, durability, particularly durability at high temperatures, is reduced, or there are few reactive sites with the isocyanate group of the crosslinking agent, so it takes time until the crosslinking reaction is completed and the physical properties are stabilized. Aging characteristics tend to decrease. If the amount is too large, the hydrophilicity of the pressure-sensitive adhesive increases, and the wet heat durability tends to decrease, or the pot life tends to be shortened.

In the case where a carboxyl group-containing monomer is used as the functional group-containing monomer (a2), the content of the carboxyl group-containing monomer is preferably 0 to 0.1% by weight with respect to the entire copolymerization component. Preferably it is 0-0.07 weight%, More preferably, it is 0-0.05 weight%.
When there is too much this content, there exists a possibility that a pot life may fall, or the metal or metal oxide of a to-be-adhered body may be corroded or deteriorated.

In the present invention, it is preferable to further contain a (meth) acrylic acid alkyl ester monomer (a3) as a copolymerization component. As the (meth) acrylic acid alkyl ester monomer (a3), for example, an alkyl group carbon The number is usually 1 to 20 (preferably 1 to 18, particularly preferably 1 to 12, more preferably 1 to 6), and specifically, methyl (meth) acrylate, ethyl (meta ) Acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , N-octyl (meth) acrylate, isodecyl (meth) acrylate, lauric (Meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, and the like.
These may be used alone or in combination of two or more.

  Among these, (meth) acrylic acid alkyl ester monomers having 1 to 6 carbon atoms in the alkyl group are preferred, and n-methyl acrylate, n-ethyl acrylate, and n-butyl acrylate are preferred in terms of versatility and adhesive properties. Particularly preferred.

The content of the (meth) acrylic acid alkyl ester monomer (a3) is preferably 55 to 97% by weight, particularly preferably 60 to 90% by weight, more preferably 70 to 85% by weight based on the entire copolymerization component. %.
If the content is too small or too large, it tends to be difficult to balance the physical properties of the adhesive.

Examples of the other copolymerizable ethylenically unsaturated monomer (a4) include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and orthophenylphenoxyethyl. Aromatic ring-containing monomers such as (meth) acrylate; cyclohexyl (meth) acrylate, cyclohexyloxyalkyl (meth) acrylate, t-butylcyclohexyloxyethyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) ) Acrylates 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 And ether chain-containing monomers such as octoxypolyethyleneglycol-polypropyleneglycol-mono (meth) acrylate, lauroxypolyethyleneglycolmono (meth) acrylate, stearoxypolyethyleneglycolmono (meth) acrylate, and the like.
These may be used alone or in combination of two or more.

In terms of easy adjustment of the refractive index and birefringence, an aromatic ring-containing monomer is preferably used as the other copolymerizable ethylenically unsaturated monomer (a4), and benzyl (meth) acrylate is particularly preferable. .
In addition, it is easy to adjust the refractive index and birefringence, and is excellent in adhesion to the adherend, so that a (meth) acrylic acid alkyl ester monomer having an alkyl group having 1 to 6 carbon atoms and benzyl ( It is preferable to use (meth) acrylate together.

The content of the other copolymerizable ethylenically unsaturated monomer (a4) is preferably 0 to 20% by weight, particularly preferably 5 to 18% by weight, more preferably based on the entire copolymerization component. Is 12 to 17% by weight.
If the content is too large or too small, the light leakage resistance tends to decrease.

  The acrylic resin (A) used in the present invention includes a tertiary amino group-containing monomer (a1), a functional group-containing monomer (a2) as necessary, a (meth) acrylic acid alkyl ester monomer (a3), and others. The copolymerizable component containing the copolymerizable ethylenically unsaturated monomer (a4) can be appropriately selected and polymerized.

  As a method for polymerizing the acrylic resin (A), conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization and the like can be used. For example, in an organic solvent, a copolymerization component, polymerization An initiator is mixed or dropped and polymerized under predetermined polymerization conditions. Of these, solution radical polymerization and bulk polymerization are preferable, and solution radical polymerization is particularly preferable.

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

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

  The acrylic resin (A) used in the present invention is an acrylic resin containing 0.003 to 0.25% by weight of a structural unit derived from the tertiary amino group-containing monomer (a1).

The content of the structural unit derived from the tertiary amino group-containing monomer (a1) contained in the acrylic resin (A) is preferably 0.005 to 0.15% by weight, particularly preferably 0.006. -0.08% by weight.
If the number of structural units derived from the tertiary amino group-containing monomer (a1) is too small, the aging characteristics are deteriorated, and if it is too large, the peeling force is increased or the pot life is decreased.

Moreover, it is preferable to contain the structural unit derived from a hydroxyl-containing monomer, As the content, it is preferable that it is 3 to 15 weight%, Especially preferably, it is 6.5 to 11 weight%, More preferably, it is 7 to 9 % By weight.
If the number of structural units derived from a hydroxyl group-containing monomer is too small, the aging characteristics are lowered, the heat durability is lowered, if too much, the release film is peeled off, or the polarizing plate and the liquid crystal cell are bonded together. Wet heat durability decreases.

The acrylic resin (A) has a weight average molecular weight of preferably 800,000 to 1,500,000, particularly preferably 1,050,000 to 1,400,000, and more preferably 1.1 million to 1,300,000.
If the weight average molecular weight is too small, the durability tends to decrease. If the weight average molecular weight is too large, the viscosity is high, so that a large amount of a diluent solvent is required during production, and the drying property tends to decrease.

  The degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 15 or less, particularly preferably 10 or less, more preferably 5 or less, and still more preferably 4.5 or less. . If the degree of dispersion is too high, the cohesive force tends to decrease. The lower limit of the degree of dispersion is usually 2.

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

The glass transition temperature (Tg) of the acrylic resin (A) is preferably −80 to 0 ° C., particularly preferably −60 to −15 ° C., and further 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：共重合体のガラス転移温度（Ｋ）
Ｔga：モノマーＡのホモポリマーのガラス転移温度（Ｋ） Ｗａ：モノマーＡの重量分率
Ｔgb：モノマーＢのホモポリマーのガラス転移温度（Ｋ） Ｗｂ：モノマーＢの重量分率
Ｔgn：モノマーＮのホモポリマーのガラス転移温度（Ｋ） Ｗｎ：モノマーＮの重量分率
（Ｗａ＋Ｗｂ＋・・・＋Ｗｎ＝１） The glass transition temperature is calculated from the following Fox equation.

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

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

<Oligomer type silane coupling agent (B)>
The silane coupling agent is an organosilicon compound containing one or more reactive functional groups and silicon-bonded alkoxy groups in the structure.
In the present invention, an oligomer type silane coupling agent (B) having a silicon atom-bonded alkoxy group content of 20 to 45% by weight is used as the silane coupling agent.

  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, and an isocyanate group. Among these, a mercapto group is preferred from the viewpoint of durability. Is preferred.

  The silicon-bonded alkoxy group preferably contains an alkoxy group having 1 to 8 carbon atoms from the viewpoint of durability and storage stability, particularly preferably contains a methoxy group or an ethoxy group, and the ethoxy group and methoxy group. More preferably it contains both groups.

  The oligomer type silane coupling agent (B) may have an organic functional group other than the reactive functional group and the silicon atom-bonded alkoxy group, such as an alkyl group and a phenyl group.

The silicon-bonded alkoxy group content of the oligomer type silane coupling agent (B) is required to be 20 to 45% by weight, preferably 25 to 43% by weight, particularly preferably 28 to 40% by weight, Preferably it is 29 to 35% by weight.
If the silicon atom-bonded alkoxy group content is too small, the adhesion with the adherend is reduced, sufficient durability cannot be obtained, and if too large, the adhesion with the release film is too high, The peelability of the release film is reduced.

Moreover, it is preferable that the functional group equivalent of an oligomer type silane coupling agent (B) is 200-700 g / mol from an adhesive point, Especially preferably, it is 300-500 g / mol, More preferably, it is 400-480 g / mol. mol.
When the functional group equivalent is too small, the reaction point is small and the effect of the silane coupling agent is not sufficiently obtained, and the adhesion with the adherend tends to be lowered. Therefore, there is a tendency that the release film reacts with the remaining reactive functional groups on the surface and the like, and the release film is poorly peeled.

Further, the oligomer type silane coupling agent (B) has a viscosity (25 ° C.) of ^{2 to} 50 mPa · s (mm ² / s) from the viewpoint of being less volatile and improving the durability of the pressure-sensitive adhesive. It is preferably 3 to 35 mm ² / s, more preferably 4 to 10 mm ² / s.

The oligomer type silane coupling agent (B) is an oligomer type organosilicon compound (organosiloxane compound) such as a dimer or trimer obtained by hydrolysis and polycondensation of a part of the organosilicon compound. Mercapto group-containing oligomer type silane coupling agents in which a part of mercapto group-containing silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyldimethoxymethylsilane and the like are hydrolyzed and polycondensed, A mercapto group-containing oligomer type silane coupling which is a cocondensate of the mercapto group-containing silane compound with an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane. Agent; γ-Glyci Xylpropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, methyltri (glycidyl) silane, β- (3,4 epoxy) An epoxy group-containing oligomer type silane coupling agent in which a part of an epoxy group-containing silane compound such as cyclohexyl) ethyltrimethoxysilane or β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane is hydrolyzed and polycondensed, or the above epoxy An epoxy group-containing oligomer type silane coupling agent, which is a cocondensate of a group-containing silane compound with an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane; or The epoxy group-containing oligomeric silane coupling agent ether-modified part of the epoxy group-containing oligomeric silane coupling agent; and the like.
From these, it may be appropriately selected and used so that the silicon atom-bonded alkoxy group content is satisfied, and one kind may be used alone, or two or more kinds may be used in combination.

As the oligomer type silane coupling agent (B) used in the present invention, specifically, any commercially available product is “X-41-1810” (containing functional group; mercapto group, contained) manufactured by Shin-Etsu Chemical Co., Ltd. Silicon atom-bonded alkoxy group; methoxy group, content of silicon atom-bonded alkoxy group; 30% by weight, functional group equivalent; 450 g / mol, viscosity at 25 ° C .; 5 mm ² / s), “X-41-1059A” Group, epoxy group, contained silicon atom-bonded alkoxy group; methoxy group and ethoxy group, contained silicon atom-bonded alkoxy group amount: 42% by weight, functional group amount; 350 g / mol, 25 ° C. viscosity; 30 mm ² / s), etc. That's fine.

As content of an oligomer type silane coupling agent (B), it is preferable that it is 0.01-0.3 weight part with respect to 100 weight part of acrylic resin (A), Most preferably, it is 0.03-. The amount is 0.25 parts by weight, more preferably 0.05 to 0.15 parts by weight.
If the content is too small, the durability tends to decrease. If the content is too large, the peelability of the release film decreases or the silane coupling agent bleeds and the durability tends to decrease.

  In addition, silane coupling agents other than the oligomer type silane coupling agent (B) used in the present invention (for example, a monomer type silane coupling agent or a silicon atom bond defined in the present invention, as long as the effects of the present invention are not impaired). An oligomer type silane coupling agent that does not satisfy the alkoxy group content can be used. However, if the content of the silane coupling agent is too large, the durability tends to decrease due to bleeding. The amount is preferably 0.5 parts by weight or less, particularly preferably 0.3 parts by weight or less, and still more preferably 0.2 parts by weight or less with respect to 100 parts by weight of the acrylic resin (A).

<Crosslinking agent (C)>
Examples of the crosslinking agent (C) used in the present invention include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents. Can be mentioned.

  Examples of the isocyanate crosslinking agent include tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, tetra Xylylene diisocyanate compounds such as methyl xylylene diisocyanate; aromatic isocyanate compounds such as 1,5-naphthalene diisocyanate and triphenylmethane triisocyanate; hexamethylene diisocyanate, isophorone diisocyanate, and these isocyanate compounds and trimethylolpropane Examples thereof include adducts with polyol compounds such as burettes and isocyanurates of these polyisocyanate compounds.

  Examples of the epoxy crosslinking 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. , Trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether and the like.

  Examples of the aziridine-based crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N, N′-diphenylmethane-4,4. '-Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like can be mentioned.

  Examples of the melamine-based crosslinking agent include hexamethoxymethyl melamine, hexaethoxymethyl melamine, hexapropoxymethyl melamine, hexaptoxymethyl melamine, hexapentyloxymethyl melamine, hexahexyloxymethyl melamine, and melamine resin. .

  Examples of the aldehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleindialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde and the like.

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

  Examples of the metal chelate-based crosslinking 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 said crosslinking agent (C) may be used independently and may use 2 or more types together.
Among the crosslinking agents (C), an isocyanate-based crosslinking agent is preferably used from the viewpoint of improving the adhesion to the substrate and the reactivity with the base polymer.
Among the isocyanate-based crosslinking agents, the tolylene diisocyanate-based crosslinking agent is preferable from the viewpoint of excellent pot life, compatibility with the resin, and durability, and an adduct of 2,4-tolylene diisocyanate with trimethylolpropane. Is particularly preferred.

The content of the crosslinking agent (C) is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 0.5 parts by weight, with respect to 100 parts by weight of the acrylic resin (A). Particularly preferred is 0.12 to 0.20 parts by weight.
If the content of such a crosslinking agent is too small, the durability tends to decrease, and if it is too large, the stress relaxation property decreases and the substrate tends to warp, or a long-term aging tends to be required. is there.

<Antistatic agent (D)>
The acrylic pressure-sensitive adhesive composition of the present invention preferably further contains an antistatic agent (D) from the viewpoint of electrostatic countermeasures, and the antistatic agent (D) is an ionicity composed of a metal salt and / or an organic salt. It is preferable to contain at least one selected from compounds.
Examples of the metal salt include alkali metal salts such as lithium salt, sodium salt, calcium salt and potassium salt.
Examples of organic salts include onium salts such as ammonium salts, imidazolium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, phosphonium salts, and sulfonium salts.
Among these, the antistatic agent (D) is composed of a nitrogen-containing cation such as an ammonium salt, an imidazolium salt, a pyridinium salt, a piperidinium salt, or a pyrrolidinium salt from the viewpoint of compatibility with a resin and corrosion resistance. It is preferable to contain an ionic compound composed of an onium salt or a phosphonium salt, particularly preferably an ammonium salt, and more preferably an ammonium salt composed of an ammonium cation and a trifluoromethanesulfonylimide anion.

  The content of these antistatic agents (D) is preferably 0.5 to 10 parts by weight, more preferably 2 to 5 parts by weight, and particularly preferably 3 to 4 parts by weight. If the content is too small, the antistatic performance cannot be obtained, and display unevenness due to static electricity tends to occur. If the content is too large, the polarization degree of the polarizing plate decreases, the heat-and-whitening resistance decreases, There is a tendency for durability to fall out.

  Furthermore, in the pressure-sensitive adhesive composition of the present invention, as long as the effects of the present invention are not impaired, as other components, a resin component, an acrylic monomer, a polymerization inhibitor, an antioxidant, a corrosion inhibitor, a crosslinking accelerator, Various additives such as radical generators, peroxides, radical scavengers, metals, 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 the acrylic resin (A). When there is too much this content, compatibility with acrylic resin (A) will fall, and there exists a tendency for durability to fall.

Thus, the pressure-sensitive adhesive composition of the present invention can be obtained.
The pressure-sensitive adhesive composition of the present invention can be made into a pressure-sensitive adhesive by crosslinking with a crosslinking agent, and further, by laminating and forming a pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive on a polarizing plate (optical laminate), A polarizing plate with an adhesive layer can be obtained.
The pressure-sensitive adhesive layer-attached polarizing plate is preferably further provided with a release film on the surface opposite to the pressure-sensitive adhesive layer of the polarizing plate.

As the release film, a condensation reaction type silicone release agent (for example, polydimethylsiloxane having hydroxyl groups at both ends as a base polymer, polymethylhydrosiloxane siloxane as a crosslinking agent, and tin-based catalyst as a catalyst is common. ), Addition-reactive silicone release agents (for example, those in which part of the methyl group of polydimethylsiloxane having hydroxyl groups at both ends is substituted with vinyl groups as the base polymer, and polymethylhydrogenene as the crosslinking agent) Siloxane, and those using platinum-based catalysts as catalysts) are generally used. Although not particularly limited, an addition reaction type silicone release agent is used from the viewpoint of quality stability. Is preferred.
Specific examples include commercially available “Film Bina” manufactured by Fujimori Kogyo Co., Ltd., “Separator SP-PET” manufactured by Mitsui Chemicals Tosero Co., Ltd., and the like.

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

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

  Note that the pressure-sensitive adhesive composition of the present invention has excellent aging characteristics, cross-linking proceeds in a short time, and the gel fraction increases and stabilizes. Therefore, even if the aging treatment time is short, the pressure-sensitive adhesive properties are excellent. An adhesive can be obtained. Therefore, the aging treatment period can be shortened compared to the conventional case, which is very advantageous in terms of productivity. In addition, since the physical properties of the adhesive are stabilized in a short time, for example, when the film with the pressure-sensitive adhesive layer is stored in a roll, the particles of the anti-block layer of the protective film are transferred to the pressure-sensitive adhesive. Scratches can also be suppressed.

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

A coating solution obtained by diluting the pressure-sensitive adhesive composition with a solvent needs to have stability over time (pot life), and the viscosity change rate after 24 hours calculated by the following formula 1 is usually 1.0 to 1.5. It is preferable that it is, and it is more preferable that it is 1.0-1.2. When the rate of change in viscosity after 24 hours is greater than 1.5, the viscosity of the coating solution increases, and when running for a long time, uneven coating such as streaks tends to occur on the coated surface over time compared to the initial time. There is.
[Formula 1]
Viscosity change rate = viscosity of coating solution after 24 hours / viscosity of coating solution immediately after preparation

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

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

Moreover, 5-200 micrometers is preferable, as for the thickness of the adhesive layer in the polarizing plate with an adhesive layer obtained, 10-100 micrometers is especially preferable, Furthermore, 10-30 micrometers is preferable.
If the thickness of the pressure-sensitive adhesive layer is too thin, the pressure-sensitive adhesive for polarizing plates does not have sufficient stress relaxation properties, and the durability tends to decrease. There is a tendency to decrease.

  The gel fraction of the pressure-sensitive adhesive layer produced by the above method is preferably 30 to 95%, particularly preferably 40 to 85%, more preferably 60 from the viewpoint of durability performance and suppression of decrease in polarization degree. ~ 80%. If the gel fraction is too low, foaming during heating, particularly reworkability, tends to occur, and if it is too high, floating and peeling tend to occur.

  The gel fraction is a measure of the degree of crosslinking (curing degree), and is calculated, for example, by the following method. That is, the pressure-sensitive adhesive is picked from a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed on a base material, wrapped in a 200-mesh SUS wire mesh, immersed in ethyl acetate at 23 ° C. for 24 hours, and placed in the wire mesh. The weight percentage of the remaining insoluble pressure-sensitive adhesive component is defined as the gel fraction.

  In addition, in adjusting the gel fraction of the adhesive for polarizing plates to the said range, it is achieved by adjusting the kind and quantity of a crosslinking agent, etc.

Regarding the gel fraction of the pressure-sensitive adhesive layer produced by the above-mentioned method, the gel fraction of the pressure-sensitive adhesive layer that has passed 3 hours after the application and drying of the pressure-sensitive adhesive composition solution is defined as “initial gel fraction Gi” at room temperature (23 The gel fraction of the sample aged for 3 days under “° C.” is “gel fraction Gt after aging”, and the gel fraction of the sample aged for 7 days further at room temperature (23 ° C.) is “gel fraction after aging”. In the case of “Ga”,
The initial gel fraction Gi of the pressure-sensitive adhesive layer is preferably from 0 to 80%, more preferably from 30 to 80%, from the viewpoint of quality stability (there is no contamination such as dents or paste protruding). More preferably, it is 50 to 80%. When the gel fraction Gi is too low, the cohesive force of the pressure-sensitive adhesive layer is weakened, and contamination due to dents or the like or protrusion of glue tends to occur.

  Further, the gel fraction Ga of the pressure-sensitive adhesive layer after aging for 3 days is preferably 55 to 95%, more preferably 65 to 90%, further preferably 70 from the viewpoint of durability performance and light leakage prevention performance. ~ 85%. If the gel fraction Ga is too low, the cohesive force of the pressure-sensitive adhesive layer becomes weak and tends to generate bubbles at high temperatures. If it is too high, the pressure-sensitive adhesive layer becomes hard, There is a tendency that the adhesiveness of the resin is lowered and peeling easily occurs.

  Furthermore, the change rate ((Ga−Gt) / Ga) of the gel fraction (Ga) of the pressure-sensitive adhesive layer after aging for 3 days and the gel fraction (Gt) of the pressure-sensitive adhesive layer after aging for 7 days is usually 40%. Less than 10%, preferably less than 10%. When the change rate ((Ga-Gt) / Ga) of the gel fraction Ga after the aging is too high, the aging period until the physical properties of the pressure-sensitive adhesive layer are stabilized tends to be long, and the productivity tends to decrease.

  The adhesive force after 20 days of the pressure-sensitive adhesive layer of the polarizing plate with the pressure-sensitive adhesive layer produced by the above method, that is, the pressure-sensitive adhesive force (reworkability) when peeling the polarizing plate again is, for example, when sticking to a glass substrate. It preferably has an adhesive strength of 22 N / 25 mm or less, particularly preferably 18 N / 25 mm or less, and more preferably 15 N / 25 mm or less.

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

  The peeling force from the pressure-sensitive adhesive layer of the release film of the polarizing plate with the pressure-sensitive adhesive layer produced by the above method is preferably 0.02 to 0.13 N / 25 mm, particularly preferably 0.03 to 0. .10 N / 25 mm, more preferably 0.05 to 0.09 N / 25 mm. If the release force of the release film is too small, the release film will naturally peel off from the adhesive during processing or transport, and the product will tend to be defective.If it is too large, the panel manufacturer will remove the release film from the adhesive layer. When peeling, it becomes difficult to peel off, and there is a tendency that productivity is deteriorated such that the polarizing plate fixed to the adsorption mat is lifted or the adhesive is missing together with peeling of the release film.

  In addition, the peeling force of the release film of the polarizing plate with an adhesive layer manufactured by the said method is computed as follows. About a polarizing plate with an adhesive layer, it is cut to a width of 25 mm, the opposite side of the release film is fixed to a glass plate with a double-sided tape, and the release angle is attached to the adhesive layer. The peel test is performed at 180 degrees and a peel speed of 300 mm / min.

  The antistatic performance of the polarizing plate with the pressure-sensitive adhesive layer produced by the above method is as follows. After the polarizing plate with the pressure-sensitive adhesive layer is produced, the polarizing plate with the pressure-sensitive adhesive layer is allowed to stand at 23 ° C. × 50% RH for 24 hours The “initial surface resistance value Ri” obtained by peeling the release film and measuring the surface resistance value of the pressure-sensitive adhesive layer using a surface resistivity measuring device described later is preferably 1.0 × 10 12 Ω. / □, more preferably less than 1.0 × 10 11 Ω / □, and even more preferably less than 5.0 × 10 9 Ω / □. If the initial surface resistance Ri is too high, the polarizing plate is charged due to friction with the backlight of the liquid crystal display panel, etc., and there is a tendency to cause a display defect.

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

  First, various acrylic resins were prepared as follows. In addition, regarding the measurement of the weight average molecular weight of acrylic resin and the gel fraction of an adhesive, it measured according to the above-mentioned method.

<Preparation of acrylic resin (A)>
[Production of acrylic resin (A-1)]
In a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 0.2 parts of dimethylaminoethyl acrylate [DMAEA] (a1), 2-hydroxyethyl acrylate [HEA] ( a2) 8 parts, 91.8 parts of butyl acrylate [BA] (a3), 47.2 parts of ethyl acetate as a solvent, 42 parts of acetone, 0.013 parts of azobisisobutyronitrile [AIBN] as a polymerization initiator While appropriately adding AIBN and ethyl acetate, reacting at reflux temperature for 3.25 hours and then diluting with ethyl acetate, acrylic resin (A-1) (weight average molecular weight 1.1 million, dispersity 4.0) Solution was obtained.

[Manufacture of acrylic resin (A-2)]
In a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 0.2 parts of dimethylaminoethyl acrylate [DMAEA] (a1), 2-hydroxyethyl acrylate [HEA] ( a2) 3.5 parts, 96.3 parts of butyl acrylate [BA] (a3), 47.2 parts of ethyl acetate as a solvent, 42 parts of acetone, 0.013 parts of azobisisobutyronitrile [AIBN] as a polymerization initiator The reaction was carried out at reflux temperature for 3.25 hours while appropriately adding AIBN and ethyl acetate, and diluted with ethyl acetate to obtain an acrylic resin (A-1) (weight average molecular weight 1.470,000, dispersity 3. A solution of 2) was obtained.

[Production of acrylic resin (A-3)]
To a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 0.05 part of dimethylaminoethyl acrylate [DMAEA] (a1), 2-hydroxyethyl acrylate [HEA] ( a2) 8 parts, butyl acrylate [BA] (a3) 91.95 parts, 47.2 parts of ethyl acetate as a solvent, 42 parts of acetone, 0.013 part of azobisisobutyronitrile [AIBN] as a polymerization initiator While appropriately adding AIBN and ethyl acetate, reacting at reflux temperature for 3.25 hours and then diluting with ethyl acetate, acrylic resin (A-1) (weight average molecular weight 1.1 million, dispersity 4.0) Solution was obtained.

[Preparation of acrylic resin (A-4)]
In a four-necked round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 8 parts of 2-hydroxyethyl acrylate [HEA] (a2) and 92 parts of butyl acrylate [BA] (a3) , 47.2 parts of ethyl acetate as a solvent, 42 parts of acetone, 0.013 part of azobisisobutyronitrile [AIBN] as a polymerization initiator, and 3.25 at a reflux temperature while appropriately adding AIBN and ethyl acetate. After the time reaction, the reaction mixture was diluted with ethyl acetate to obtain a solution of acrylic resin (A-4) (weight average molecular weight 1.34 million, dispersity 4.5).

  Regarding the acrylic resins (A-1) to (A-4) produced as described above, the content of the raw material monomer component, the weight average molecular weight and the degree of dispersion are shown in Table 1 below.

<Oligomer type silane coupling agent (B)>
The following were prepared as oligomer type silane coupling agents.
(B-1): Oligomer type silane coupling agent “X-41-1059A” manufactured by Shin-Etsu Chemical Co., Ltd. (containing functional group; epoxy group, containing silicon atom-bonded alkoxy group; methoxy group and ethoxy group, containing silicon atom bond) Alkoxy group amount: 42% by weight, functional group amount: 350 g / mol, viscosity at 25 ° C .; 30 mm ² / s (manufacturer catalog value))
(B-2): Oligomer type silane coupling agent “X-41-1810” manufactured by Shin-Etsu Chemical Co., Ltd. (containing functional group; mercapto group, containing silicon atom-bonded alkoxy group; methoxy group, containing silicon atom-bonded alkoxy group amount) 30% by weight, functional group equivalent; 450 g / mol, viscosity at 25 ° C .; 5 mm ² / s (manufacturer catalog value))

Moreover, the following were prepared as silane coupling agents other than the oligomer type silane coupling agent (B) used in the present invention.
(B-3): Oligomer type silane coupling agent that does not satisfy the silicon-bonded alkoxy group content defined in the present invention “X-41-1805” manufactured by Shin-Etsu Chemical Co., Ltd. (containing functional group; mercapto group, containing silicon atom) Bonded alkoxy group; methoxy group and ethoxy group, contained silicon atom-bonded alkoxy amount; 50% by weight, functional group equivalent; 800 g / mol, viscosity at 25 ° C .; 20 mm ² / s (manufacturer catalog value))
(B-4): Monomer type silane coupling agent “KBM-403” manufactured by Shin-Etsu Chemical Co., Ltd. (containing functional group; epoxy group, containing silicon atom-bonded alkoxy group; methoxy group)

<Crosslinking agent (C)>
The following were prepared as a crosslinking agent.
(C-1): Trimethylolpropane adduct of tolylene diisocyanate (55% ethyl acetate solution) (manufactured by Nippon Polyurethane Industry Co., Ltd., “Coronate L-55E”)

<Antistatic agent (D)>
The following were prepared as antistatic agents.
(D-1): Methyltri-n-butylammonium bis (trifluoromethanesulfonyl) imide (“FC-4400” manufactured by 3M Corporation, melting point 27.5 ° C. (manufacturer published value))

<Examples 1-4, Comparative Examples 1-4>
Each of the ingredients prepared and prepared as described above was blended as shown in Table 2 below to obtain a pressure-sensitive adhesive composition, which was adjusted to a solid content concentration of 13% with ethyl acetate, and pressure-sensitive adhesive composition A solution was obtained.

<Aging characteristics>
[Preparation of gel fraction measurement sample]
The pressure-sensitive adhesive composition solutions of the above Examples and Comparative Examples were each applied to a polyester release film (“SP-PET 01BU” manufactured by Mitsui Chemicals, Inc., thickness 38 μm) so that the thickness after drying would be 25 μm. After coating and drying at 100 ° C. for 3 minutes, the formed adhesive composition layer was coated with a polarizing plate (protective film 1 / PVA / protective film 2 configuration, protective film 1: TAC film manufactured by Fuji Film Co., Ltd., protective film) 2: COP film manufactured by Nippon Zeon Co., Ltd., PVA: PVA film dyed with stretched iodine-based pigment), which was affixed to the protective film 2 side and aged for 3 days under the condition of 23 ° C. × 65% RH Was used as a sample for measuring “gel fraction Gt after 3 days” and a sample for measuring “gel fraction Ga after aging” was aged for 7 days.

  The gel fraction was measured by stripping the pressure-sensitive adhesive layer from a pressure-sensitive adhesive sheet (without a release film) formed by forming a pressure-sensitive adhesive layer on a polarizing plate serving as a base material. Wrapped with a SUS wire mesh and immersed in ethyl acetate at 23 ° C. for 24 hours, the weight percentage of the insoluble adhesive component remaining in the wire mesh was defined as “gel fraction”.

Regarding the gel fraction obtained by the above method, the change rate of the gel fraction (Gt) of the adhesive layer after aging for 3 days and the gel fraction (Ga) of the adhesive layer after aging for 7 days ((Ga- From Gt) / Ga), the aging characteristics were evaluated as follows.
The higher the initial gel fraction, the better the aging characteristics, and the smaller the change rate of the gel fraction, the better the aging characteristics.

(Evaluation criteria)
○ ・ ・ ・ Change rate of gel fraction is less than 10% Δ ・ ・ ・ Change rate of gel fraction is 10% or more and less than 40% × ・ ・ ・ Change rate of gel fraction is 40% or more

  Next, the pressure-sensitive adhesive composition solutions of the examples and comparative examples are respectively applied to polyester release sheets (“SP-PET 01BU” manufactured by Mitsui Chemicals, Inc., thickness: 38 μm) so that the thickness after drying becomes 25 μm. After coating at 100 ° C. for 3 minutes, the formed pressure-sensitive adhesive composition layer was coated with a polarizing plate (protective film 1 / PVA / protective film 2 structure, protective film 1: TAC film manufactured by Fuji Film Co., Ltd. Protective film 2: COP film manufactured by Nippon Zeon Co., Ltd., PVA: PVA film dyed with stretched iodine pigment), and aged for 7 days under conditions of 23 ° C. × 65% RH The polarizing plate with an adhesive layer with a release film was obtained.

  Using the polarizing plate with the release layer-attached pressure-sensitive adhesive layer obtained above, the release film was evaluated for peelability, reworkability, durability, and antistatic performance. These results are also shown in Table 3 below. In addition, the polarizing plate with an adhesive layer was cut and used so that it might become 0 degree | times (parallel) with respect to the extending | stretching axis | shaft of a polarizing plate.

<Releasability of release film>
A polarizing film with a release film and a pressure-sensitive adhesive layer is cut to a width of 25 mm, the opposite surface of the release film is fixed to a glass plate with a double-sided tape, and the release film is peeled at a 180 degree peel angle and peel speed. The peelability was evaluated as follows from the peel force applied when peeled at 300 mm / min.
(Evaluation criteria)
○ ... 0.01-0.13N / 25mm
X ... larger than 0.13N / 25mm

<Reworkability>
A polarizing plate with a release film-attached adhesive layer is cut to a width of 25 mm, the release sheet is peeled off, and the pressure-sensitive adhesive layer side is pressed against a non-alkali glass plate (Corning Co., Ltd., “Eagle XG”). A polarizing plate and a glass plate were bonded. Then, after autoclaving (50 ° C., 0.5 MPa, 20 minutes), after leaving at 23 ° C. and 50% RH for 20 days, a 180 ° peel test was performed, and the reworkability was evaluated as follows.
○ ... 20N / 25mm or less × ... 20N / 25mm or more

<Durability>
The release film of the polarizing plate with the pressure-sensitive adhesive layer with release film is peeled off, and the pressure-sensitive adhesive layer side is pressed against a non-alkali glass plate (Corning Co., Ltd., “Eagle XG”). After pasting, an autoclave treatment (50 ° C., 0.5 MPa, 20 minutes) was performed, and then the following durability test was performed. Evaluation was performed as follows depending on the presence or absence of foaming, peeling, and the like. In addition, the size of the test piece used for the test is 200 mm × 150 mm (punching).

(1) Heat resistance test The evaluation was as follows in an endurance test at 80 ° C for 240 hours.
(2) Moisture and heat resistance test The durability was evaluated as follows in an endurance test of 60 ° C x 90% RH x 240 hours.
(3) High heat resistance test The evaluation was as follows in an endurance test at 100 ° C for 240 hours.

(Evaluation criteria)
For each of the tests (1), (2), and (3), the presence or absence of defects (foaming, streaks, floating, peeling) was evaluated by optical microscope observation and visual observation. The evaluation criteria are as follows.
(Evaluation criteria)
◎ ・ ・ ・ No defects were observed in the optical microscope observation.
○: In the optical microscope observation, defects were observed at the edge within 0.5 mm from the edge of the polarizing plate.
Δ: On the edge within 0.5 mm from the edge of the polarizing plate, a defect of about 1 mm that can be visually confirmed was observed.
X ... The defect which can be visually confirmed was seen inside 0.5 mm from the edge part of a polarizing plate (near center). Or peeling of 1 mm or more was observed.

  Table 4 below summarizes the results.

  From the results of Table 4, acrylic resin (A) comprising a copolymer component containing amino group-containing monomer (a1) in a specific range, and oligomer type silane coupling agent having a silicon atom-bonded alkoxy group content in a specific range In Examples 1 to 4 using the pressure-sensitive adhesive composition containing (B), both the aging characteristics and the peelability of the release film are excellent, and the reworkability and durability of the pressure-sensitive adhesive layer are further improved. Can also be seen as excellent.

On the other hand, in Comparative Example 1 using an oligomer type silane coupling agent having a silicon atom-bonded alkoxy group content less than that of the present invention, the aging characteristics are excellent, but the release film has satisfactory peelability. You can see that it is not.
Further, in Comparative Example 2 using a monomer type silane coupling agent instead of the oligomer type silane coupling agent, both the aging characteristics and the release property of the release film are satisfied. It can be seen that even if an acrylic resin containing a group-containing monomer is used, there is no problem of a decrease in peelability of the release film, but the reworkability of the pressure-sensitive adhesive layer is poor.
Moreover, in the comparative examples 3 and 4 which use acrylic resin which does not contain an amino group containing monomer (a1), it turns out that the rate of change of the gel fraction after aging is large and is inferior to an aging characteristic.

  The pressure-sensitive adhesive obtained by using the pressure-sensitive adhesive composition of the present invention is excellent in aging characteristics and peelability of a release film, and is excellent in reworkability and durability when a polarizing plate and a liquid crystal cell are bonded together. is there. Therefore, a liquid crystal display device can be efficiently produced by using this pressure-sensitive adhesive composition, and a liquid crystal display device having excellent durability can be obtained. Therefore, it is useful as a pressure-sensitive adhesive for polarizing plates.

Claims (10)

A pressure-sensitive adhesive composition for a polarizing plate containing an acrylic resin (A) and an oligomer type silane coupling agent (B) containing at least one reactive functional group and one silicon-bonded alkoxy group in the structure. ,
The acrylic resin (A) is an acrylic resin containing 0.003 to 0.25% by weight of a structural unit derived from the tertiary amino group-containing monomer (a1),
The pressure-sensitive adhesive composition for a polarizing plate, wherein the oligomer type silane coupling agent (B) is an oligomer type silane coupling agent having a silicon atom-bonded alkoxy group content of 20 to 45% by weight.   The pressure-sensitive adhesive composition for a polarizing plate according to claim 1, wherein the acrylic resin (A) is an acrylic resin containing 3 to 15% by weight of a structural unit derived from a hydroxyl group-containing monomer.   The polarized light according to claim 1 or 2, wherein the content of the oligomer type silane coupling agent (B) is 0.01 to 0.3 parts by weight with respect to 100 parts by weight of the acrylic resin (A). Adhesive composition for board.   The functional group equivalent of an oligomer type silane coupling agent (B) is 200-700 g / mol, The adhesive adhesive composition for polarizing plates in any one of Claims 1-3 characterized by the above-mentioned. The pressure-sensitive adhesive for polarizing plates according to any one of claims 1 to 4, wherein the oligomer type silane coupling agent (B) has a viscosity (25 ° C) of ^{2 to} 50 mPa · s (mm ² / s). Agent composition.   Furthermore, a system crosslinking agent (C) is contained, The adhesive composition for polarizing plates in any one of Claims 1-5 characterized by the above-mentioned.   A pressure-sensitive adhesive for polarizing plates, wherein the pressure-sensitive adhesive composition for polarizing plates according to claim 6 is crosslinked with a crosslinking agent (C).   The polarizing plate with an adhesive layer formed by laminating | stacking the adhesive layer containing the adhesive for polarizing plates of Claim 7 on a polarizing plate.   A polarizing plate with a release film and a pressure-sensitive adhesive layer, comprising a polarizing plate / adhesive layer / release film, wherein the pressure-sensitive adhesive layer is the pressure-sensitive adhesive for polarizing plates according to claim 7.   The peeling force from the adhesive layer of a release film is 0.02-0.13N / 25mm, The polarizing plate with an adhesive layer with a release film of Claim 9 characterized by the above-mentioned.