JP2020114935A - Acrylic adhesive composition, and adhesive and adhesive sheet obtained using the same, and polarizing plate with adhesive layer - Google Patents

Abstract

To provide an adhesive which is an acrylic resin, has a sufficient pot life even when an acrylic resin containing a hydroxyl group is used, and can suppress degradation of an easily hydrolyzable film such as a TAC film and deterioration of an adhesive by acid under high temperature and high humidity conditions.SOLUTION: An acrylic adhesive composition is an adhesive composition containing a hydroxyl group-containing acrylic resin (A), a tertiary amine compound (B), a crosslinking agent (C), and an ionic compound (D), where the tertiary amine compound (B) is a tertiary amine compound of which at least one of three substituents is a substituent having at least one of an aromatic ring structure, an alicyclic structure and a branched alkyl structure, and the crosslinking agent (C) is at least one of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. The content of the ionic compound (D) is 2-10 pts.wt. relative to the acrylic resin (A) 100 pts.wt.SELECTED DRAWING: None

Description

The present invention relates to an acrylic pressure-sensitive adhesive composition, and more specifically, it is possible to obtain a pressure-sensitive adhesive that has a sufficient pot life and can suppress deterioration of the pressure-sensitive adhesive due to hydrolysis of a base material or acid. The present invention relates to an acrylic pressure-sensitive adhesive composition.

BACKGROUND ART Conventionally, pressure-sensitive adhesive sheets having an acrylic pressure-sensitive adhesive provided on one side or both sides of a substrate have been used for various purposes. As a base material used for these pressure-sensitive adhesive sheets, metal thin films, non-woven fabrics, plastic films and the like are used.
In recent years, in applications such as displays, window films, and masking films that require transparency, pressure-sensitive adhesive sheets in which an acrylic pressure-sensitive adhesive is provided on a transparent plastic film have been used. Although a pressure-sensitive adhesive sheet obtained by providing an acrylic pressure-sensitive adhesive on such a plastic film substrate can be used under normal circumstances without problems, the substrate and the acrylic pressure-sensitive adhesive are hydrolyzed under high temperature and high humidity conditions. However, there is a problem that the film is deteriorated and the adhesive is deteriorated.

Here, Patent Document 1 describes that in an acrylic pressure-sensitive adhesive, a carboxyl group derived from a monomer in the acrylic resin serves as a catalyst to promote hydrolysis of a triacetyl cellulose (TAC) film, and an isocyanate-based adhesive is used. In an acrylic pressure-sensitive adhesive containing a cross-linking agent, by blending a tertiary amine having an alkyl group with 6 to 12 carbon atoms, it is possible to achieve both suppression of hydrolysis of the TAC film and extension of pot life. Have been described.

JP-A-9-87600

However, the pressure-sensitive adhesive described in Patent Document 1 uses an acrylic resin having a carboxyl group as a functional group serving as a reaction point of a crosslinking agent, and thus uses an acrylic resin having no hydroxyl group. In the case of using an acrylic resin that has only a carboxyl group, although the pot life will be satisfied, the reworkability will decrease due to the adhesive strength becoming too high over time, and the holding power and resistance to moist heat and whitening will increase. There was a problem that it was inferior to.
On the other hand, when an acrylic resin having a hydroxyl group is used, as described in Patent Document 1, even if a long-chain alkylamine is contained in the acrylic adhesive, sufficient pot life cannot be obtained. There was a problem.

Therefore, there is a demand for a pressure-sensitive adhesive that has a sufficient pot life even when an acrylic resin containing a hydroxyl group is used and that can suppress hydrolysis of the base film and deterioration of the pressure-sensitive adhesive.

Therefore, in the present invention, under such a background, the acrylic adhesive has a sufficient pot life even when an acrylic resin containing a hydroxyl group is used, and further, under high temperature and high humidity conditions, TAC An object of the present invention is to provide a pressure-sensitive adhesive that can suppress deterioration of a base film that is susceptible to hydrolysis such as a film and deterioration of the pressure-sensitive adhesive due to acid.

However, as a result of earnest studies in view of such circumstances, the present inventor has made a pressure-sensitive adhesive composition containing a hydroxyl group-containing acrylic resin contain a tertiary amine compound having a specific structure and a specific amount of an ionic compound. Thus, the present inventors have completed the present invention by finding that a pressure-sensitive adhesive having a sufficient pot life and further suppressing hydrolysis of the TAC film and deterioration of the pressure-sensitive adhesive can be obtained.

That is, the gist of the present invention is a pressure-sensitive adhesive composition containing a hydroxyl group-containing acrylic resin (A), a tertiary amine compound (B), a cross-linking agent (C) and an ionic compound (D). The amine compound (B) is a tertiary amine compound in which at least one of the three substituents is a substituent having at least one of an aromatic ring structure, an alicyclic structure and a branched alkyl structure, and the crosslinking agent (C) is an isocyanate-based compound. An acrylic pressure-sensitive adhesive composition which is at least one of a crosslinking agent and an epoxy-based crosslinking agent, and has an ionic compound (D) content of 2 to 10 parts by weight based on 100 parts by weight of the acrylic resin (A). is there.

Furthermore, the present invention relates to a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a pressure-sensitive adhesive layer-attached polarizing plate using the above acrylic pressure-sensitive adhesive composition.

The acrylic pressure-sensitive adhesive composition of the present invention has a sufficient pot life, and when used as a pressure-sensitive adhesive used for a plastic film substrate, it is a plastic film substrate (particularly a TAC film) under a high temperature and high humidity environment. It has excellent performance in suppressing the hydrolysis of plastic film that deteriorates due to hydrolysis, etc., and in suppressing the deterioration of the pressure-sensitive adhesive, and that it does not peel off even under high temperature, high temperature and high humidity environments. Obtainable.

The present invention will be 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.
Further, the pressure-sensitive adhesive has a tack at 25° C. or lower (room temperature) and adheres to an adherend with a light pressure such that it is pressed by hand.

The acrylic pressure-sensitive adhesive composition of the present invention comprises at least a hydroxyl group-containing acrylic resin (A), a tertiary amine compound (B) having a specific structure, and an isocyanate crosslinking agent and an epoxy crosslinking agent as the crosslinking agent (C). One type and an ionic compound (D) are contained as an essential component.

<Acrylic resin (A)>
The hydroxyl group-containing acrylic resin (A) used in the present invention contains a hydroxyl group-containing monomer as an essential component, and if necessary, an alkyl (meth)acrylate-based monomer, a polar group-containing monomer other than the hydroxyl group-containing monomer, and other polymerizable compounds. It is obtained by polymerizing a polymerization component that appropriately contains a monomer as a polymerization component.

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 (meth)acrylate monomers such as (meth)acrylate, caprolactone modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, oxyalkylene modified (meth)acrylates such as diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate Monomers, other, primary hydroxyl group-containing (meth)acrylate monomers such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol(meth)acrylamide, hydroxyethylacrylamide;
Secondary hydroxyl group-containing (meth)acrylate monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate;
Examples thereof include tertiary hydroxyl group-containing (meth)acrylate monomers such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate. These may be used alone or in combination of two or more.

Among them, a primary hydroxyl group-containing (meth)acrylate monomer is preferable in terms of excellent reactivity with a crosslinking agent (C) described below and improved resistance to moist heat whitening, and further 2-hydroxyethyl (meth) Acrylate and 4-hydroxybutyl(meth)acrylate are preferable because they contain few impurities such as di(meth)acrylate and are easy to manufacture.

As the hydroxyl group-containing monomer used in the present invention, it is also preferable to use a di(meth)acrylate content ratio of 0.5% or less, more preferably 0.2% or less, particularly preferably 0. It is preferable to use 1% or less.

The content ratio of the hydroxyl group-containing monomer is preferably 0.1 to 50% by weight, particularly preferably 1 to 30% by weight, further preferably 5 to 25% by weight, based on the whole copolymerization component. is there.
If the content ratio is too low, the resistance to moist heat and whitening tends to decrease, and if it is too high, the storage stability when used as an adhesive decreases, the reworkability decreases, and the pot life shortens. Tend.

In the present invention, it is preferable to contain an alkyl (meth)acrylate-based monomer as a copolymerization component, and as the alkyl (meth)acrylate-based monomer, for example, the carbon number of the alkyl group is usually 1 to 24 (preferably 1 to 4). 18, particularly preferably 1 to 12, more preferably 1 to 8.), specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-. Butyl (meth)acrylate, tert-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isodecyl (meth) Examples thereof include acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate and the like. These may be used alone or in combination of two or more.

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

The content ratio of the alkyl (meth)acrylate-based monomer is preferably 90% by weight or less, particularly preferably 20 to 90% by weight, and more preferably 25 to 85, based on the whole copolymerization component. %, particularly preferably 30 to 80% by weight.
If the content ratio is too large, the change of the acrylic resin when the alkyl chain is hydrolyzed becomes large, and the adhesive tends to be deteriorated. If the amount is too small, it tends to be difficult to balance the adhesive physical properties.

Examples of the polar group-containing monomer other than the hydroxyl group-containing monomer include a carboxyl group-containing monomer and a nitrogen atom-containing monomer.

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, dimer acid of (meth)acrylic acid such as β-carboxyethyl (meth)acrylate, and the like. From the viewpoint of stability, (meth)acrylic acid is preferable.

The content ratio of the carboxyl group-containing monomer is preferably 10% by weight or less, particularly preferably 0.1 to 5% by weight, further preferably 0.5 to 1% by weight, based on the whole copolymer component. ..
If the content ratio is too large, the interaction with the tertiary amine compound (B) becomes large, the storage stability is lowered, and corrosion tends to occur easily when bonded to a metal or a metal oxide. If the content ratio is low, the durability tends to decrease and the aging time tends to increase.

Examples of the nitrogen atom-containing monomer include amino group-containing monomers and amide group-containing monomers.
Examples of the amino group-containing monomer include primary amino group-containing (meth)acrylate monomers such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; secondary amino groups such as t-butylaminoethyl (meth)acrylate. Containing (meth)acrylate monomers; tertiary amino group-containing (meth)acrylate monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate.
Examples of the amide group-containing monomer include (meth)acrylamide; methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, isopropoxymethyl (meth)acrylamide, n-butoxymethyl (meth). Examples thereof include alkoxyalkyl (meth)acrylamide monomers such as acrylamide and isobutoxymethyl (meth)acrylamide; dialkyl (meth)acrylamide monomers such as dimethyl (meth)acrylamide and diethyl (meth)acrylamide.
Examples of the other nitrogen-containing monomers include acryloylmorpholine and vinyl-containing nitrogen-containing monomers such as vinylimidazole.
These may be used alone or in combination of two or more.

Among the nitrogen-containing monomers, the amide group-containing monomer is preferable in terms of stability of the resin solution, suppression of migration of the antistatic agent, suppression of alteration of the pressure-sensitive adhesive, and difficulty in shortening pot life. Particularly preferred are dialkyl(meth)acrylamide-based monomers and alkoxyalkyl(meth)acrylamide-based monomers, and specifically, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, dipropyl(meth)acrylamide, n-methoxy(meth). ) Acrylamide, n-ethoxy(meth)acrylamide, n-butoxyacrylamide.

Examples of the other copolymerizable monomer include an alicyclic structure-containing monomer, an aromatic ring-containing monomer, an alkoxy group- and oxyalkylene group-containing monomer, and the like.

Examples of the alicyclic structure-containing monomer include cyclohexyl (meth)acrylate, isobornyl acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, Examples thereof include (meth)acrylates having an alicyclic structure such as dicyclopentenyloxyethyl (meth)acrylate and 2-adamantyl (meth)acrylate. These may be used alone or in combination of two or more.

Examples of the aromatic ring-containing monomer include phenyl (meth)acrylate; benzyl (meth)acrylate; phenoxyalkyl (meth)acrylate such as phenoxyethyl (meth)acrylate and phenoxypropyl (meth)acrylate; phenoxydiethylene glycol (meth)acrylate. , Phenoxydialkylene glycol (meth)acrylate such as phenoxydipropylene glycol (meth)acrylate; phenoxypolyethylene glycol (meth)acrylate; phenoxypolyethylene glycol-polypropylene glycol-(meth)acrylate. These may be used alone or in combination of two or more.

Examples of the alkoxy group- and oxyalkylene group-containing monomers include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, and 2-butoxyethyl (meth)acrylate. Are listed.

In the present invention, from the viewpoint that the birefringence of the acrylic resin (A) can be efficiently adjusted, it is preferable to contain an aromatic ring-containing monomer as the other copolymerizable monomer, and among them, the copolymerizability and the adhesive physical properties are preferable. And phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, and phenoxydialkylene (meth) acrylate are preferable, and the monomer remaining during the polymerization is contained in the pressure-sensitive adhesive layer when the pressure-sensitive adhesive composition is dried. Benzyl (meth)acrylate is particularly preferable because it does not remain and does not cause odor or outgas.

The content ratio of the aromatic ring-containing monomer is preferably 1 to 50% by weight, particularly preferably 5 to 40% by weight, further preferably 10 to 30% by weight, based on the whole copolymerization component. If the content ratio is too small, the pressure-sensitive adhesive tends to be deteriorated or the display unevenness of the liquid crystal display tends to become large, and if it is too small, the display unevenness of the liquid crystal display tends to become large.

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, it is appropriately selected in an organic solvent. There are methods such as a copolymerization component and a polymerization initiator which are mixed or added dropwise and polymerized under predetermined polymerization conditions. Among them, solution radical polymerization and bulk polymerization are preferable, and particularly preferable in that an acrylic resin can be stably obtained. Solution radical polymerization.

Examples of the organic solvent used in the above 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, isopropyl alcohol. Examples thereof include aliphatic alcohols such as acetone, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.
Among these organic solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are used because of the ease of polymerization reaction, the effect of chain transfer, the ease of drying when coating the adhesive, and the 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 usual radical polymerization initiators. Azo initiators such as 4,4′-azobis(4-cyanovaleric acid) and 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 and used according to the monomer to be used. These polymerization initiators can be used alone or in combination of two or more kinds.

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

The acrylic resin (A) has a weight average molecular weight of 200,000 to 2,500,000, preferably 600,000 to 1,800,000, and particularly preferably 800,000 to 1,600,000. If the weight average molecular weight is too small, the durability and reworkability tend to be deteriorated, and if it is too large, the pot life tends to be shortened and it is necessary to dilute with a large amount of solvent at the time of coating.

The dispersity (weight average molecular weight/number average molecular weight) of the acrylic resin (A) is preferably 15 or less, particularly preferably 10 or less, and further preferably 6 or less. If the dispersity is too high, the cohesive force tends to decrease, and the durability or the reworkability tends to decrease. The lower limit is usually 1.

The weight average molecular weight of the acrylic resin (A) is a weight average molecular weight in terms of standard polystyrene molecular weight, and is based on high performance liquid chromatography (manufactured by Japan Waters, "Waters 2695 (main body)" and "Waters 2414 (detection)". ))), column: 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, packing material: styrene-divinyl) The number average molecular weight can be measured by the same method by using three series of benzene copolymer and filler particle size: 10 μm. The dispersity is calculated from the weight average molecular weight and the number average molecular weight.

The glass transition temperature (Tg) of the acrylic resin (A) is preferably −100 to 25° C., particularly preferably −60 to 0° C., and further preferably −55 to −20° C. If the glass transition temperature is too high, the tack is lowered and it becomes difficult to bond them together, or zipping tends to occur when reworking from a release film or an adherend, and if it is too low, heat resistance is lowered. Tend.

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）
即ち、アクリル系樹脂を構成するそれぞれのモノマーのホモポリマーとした際のガラス転移温度および重量分率を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 from the following Fox equation.

Tg: glass transition temperature (K) of copolymer
Tga: glass transition temperature (K) of homopolymer of monomer A Wa: weight fraction of monomer A Tgb: glass transition temperature of homopolymer of monomer B (K) Wb: weight fraction of monomer B Tgn: homopolymer of monomer N Polymer glass transition temperature (K) Wn: Weight fraction of monomer N (Wa+Wb+...+Wn=1)
That is, it is a value calculated by applying the glass transition temperature and the weight fraction when the homopolymer of each monomer constituting the acrylic resin is applied to the Fox equation.
The glass transition temperature of the homopolymer of the monomer that constitutes the acrylic resin is usually measured by a differential scanning calorimeter (DSC) and conforms to JIS K7121-1987 and JIS K6240. Can be measured by the method.

<Tertiary amine compound (B)>
The tertiary amine compound (B) used in the present invention is a tertiary amine compound in which at least one of the three substituents is a substituent having at least one of an aromatic ring structure, an alicyclic structure and a branched alkyl structure.
By using the compound having such a structure, the steric hindrance of the substituent becomes large, and the tertiary amine compound cannot approach the hydroxyl group of the acrylic resin, the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent, which is more excellent. It is possible to obtain the effect peculiar to the present invention that it has a pot life and can suppress hydrolysis of the base film and deterioration of the pressure-sensitive adhesive.

Examples of the aromatic ring structure include a structure having one aromatic ring such as a phenyl group, a phenoxy group, a phenoxyalkyl group and a benzyl group, or two structures having an ether bond such as a naphthyl group, a biphenyl group and a phenoxybenzyl group. Structures having two or more aromatic rings such as the above-mentioned compounds having an aromatic ring are mentioned. In addition, these aromatic rings may have a substituent other than hydrogen.

The alicyclic structure, for example, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group and the like, cycloalkyl group having a monocyclic structure, norbornyl group, isobornyl group, adamantyl group and the like, Examples thereof include a cycloalkyl group having one or more alicyclic structures. In addition, these alicyclic rings may have a substituent other than hydrogen.

Examples of the branched alkyl structure include 1-methylethyl group, 1-methylpropyl group, 1-methylbutyl group, 1-methyloctyl group, 1-methylnonyl group, 2-methylpropyl group, 2-methylbutyl group, 2- An alkyl group having one branch such as a methyloctyl group, a 2-ethylbutyl group, a 2-ethylhexyl group, a 2-ethyloctyl group, a 2-ethyldecyl group, a 10-methylundecyl group; a 1,1-dimethylethyl group, 1 An alkyl group having two or more branches such as 1,1-dimethylpropyl group, 1,1-dimethylbutyl group, 1,1-methylethylbutyl group, 5,5-dimethylhexyl group and 1-methyl2-methylbutylamine Can be mentioned.

In the present invention, the tertiary amine compound (B) only needs to have at least one of an aromatic ring structure, an alicyclic structure and a branched alkyl structure in at least one of the three substituents, and preferably has a long pot life. It is preferable that two or more of the three substituents have at least one of an aromatic ring structure, an alicyclic structure, and a branched alkyl structure, and further, all three substituents are aromatic in that the pot life becomes longer. It preferably has at least one of a ring structure, an alicyclic structure, and a branched alkyl structure.

Here, when only one of the three substituents of the tertiary amine compound (B) has at least one of an aromatic ring, an alicyclic ring and a branched alkyl, the remaining two are linear alkyl groups. It is preferable in terms of compatibility with the acrylic resin (A), and particularly, it is preferable that the two linear alkyl groups each have 4 to 30 carbon atoms, and particularly preferably 5 to 18 carbon atoms. Is preferably 6 to 12. If the carbon number of the alkyl group is too short, the pot life tends to be short, and if it is too long, the compatibility with the acrylic resin (A) tends to be low.

Moreover, when two of the three substituents of the tertiary amine compound (B) have at least one of an aromatic ring, an alicyclic ring and a branched alkyl, the remaining one has compatibility with the acrylic resin (A). In view of this, a straight-chain alkyl group is preferable, and particularly, the straight-chain alkyl group preferably has 2 to 30 carbon atoms, particularly preferably 4 to 18 carbon atoms, and further preferably 6 to 12 carbon atoms. It is preferable. If the carbon number of the alkyl group is too short, the pot life tends to be short, and if it is too long, the compatibility with the acrylic resin (A) tends to be low.

In the present invention, at least one of the three substituents is a branched alkyl group because the tertiary amine compound (B) has excellent compatibility with the acrylic resin (A) and has a long pot life. Is preferred, and particularly preferably two or more are branched alkyl groups, and more preferably all are branched alkyl groups.

The branched alkyl group preferably has 3 to 30 carbon atoms, particularly preferably 6 to 18 carbon atoms, and further preferably 8 to 12 carbon atoms. If the carbon number is too short, it tends to volatilize during drying or the pot life tends to be shortened, and if it is too long, the compatibility with the acrylic resin (A) tends to decrease or the durability tends to decrease.

Among them, the branched alkyl group is preferably an alkyl group having a branch at the carbon atom within the 8th position from the nitrogen atom, particularly preferably within the 6th position, more preferably within the 4th position, and particularly preferably within the 2nd position. An alkyl group having a branch at a carbon atom within is preferable.

In the present invention, among the tertiary amine compounds (B), R1 to R3 of the general formula (I) may not have an aromatic ring because they are less likely to be colored and are less likely to be crystalline. preferable.

The tertiary amine compound (B) of the present invention preferably has a molecular weight of 85 to 1,500, particularly preferably 250 to 1,500, further preferably 350 to 800, and particularly preferably 350 to 600. ..
If such a molecular weight is too low, it will volatilize during drying to lower the hydrolysis suppressing effect and the deterioration suppressing effect of the pressure-sensitive adhesive, or the durability tends to decrease when used as a pressure-sensitive adhesive when attached to an adherend, If the molecular weight is too high, the compatibility tends to decrease, and the surface of the pressure-sensitive adhesive layer tends to bleed, so that the durability tends to decrease.

The melting point of the tertiary amine compound (B) of the present invention is preferably 100°C or lower, and particularly preferably 50°C or lower. If the melting point is too high, the pressure-sensitive adhesive tends to precipitate at low temperature.

As the tertiary amine compound (B) used in the present invention, specifically, tri(1,1-dimethylethyl)amine, tri(2-ethylhexyl)amine, tri(2-ethyloctyl)amine, tri(2 -Ethyldecyl)amine, tri(2-ethyldodecyl)amine, tri(isooctyl)amine and the like are preferably used.
Among these, tri(2-ethylhexyl)amine (molecular weight 354, melting point: liquid at 25° C.) is particularly preferable in terms of excellent pot life and compatibility with an acrylic resin.

The content of the tertiary amine compound (B) is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the acrylic resin (A). It is more preferably 0.5 to 3 parts by weight. If the content is too small, the effect of suppressing the hydrolysis of the TAC film and the deterioration of the pressure-sensitive adhesive may not be sufficiently obtained, and if the content is too high, bleeding out or the adhesive strength may be deteriorated and peeling tends to occur.

<Crosslinking agent (C)>
In the present invention, the crosslinking agent (C) contains at least one of an isocyanate type crosslinking agent and an epoxy type crosslinking agent.

Examples of the above-mentioned isocyanate cross-linking 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 the polyol compound, burettes and isocyanurates of these polyisocyanate compounds.

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

These may be used alone or in combination of two or more.
Among them, the isocyanate cross-linking agent is preferable from the viewpoint of improving the adhesiveness with the base material and the reactivity with the acrylic resin, and particularly, the pot life, the compatibility with the acrylic resin, and the balance of the durability. A tolylene diisocyanate-based cross-linking agent is preferable from the standpoint of superiority, and an adduct of 2,4-tolylene diisocyanate with trimethylolpropane is more preferable.

The content of the cross-linking agent (C) is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and particularly preferably 100 parts by weight of the acrylic resin (A). Is 0.12 to 1.5 parts by weight. If the content of the cross-linking agent (C) is too small, the durability and reworkability tend to deteriorate, and if it is too large, it becomes too hard and the adhesiveness tends to decrease, resulting in easy peeling from the adherend. ..

In the present invention, a cross-linking agent other than the cross-linking agent (C) may be contained within a range that does not lose the effect of the present invention, and examples thereof include a metal chelate cross-linking agent, an aziridine cross-linking agent, a melamine cross-linking agent, and an aldehyde. You may contain a system type crosslinking agent, an amine type crosslinking agent, etc.

<Ionic compound (D)>
In the present invention, the pressure-sensitive adhesive composition further contains an ionic compound (D) as an antistatic agent, which is preferable in applications where antistatic performance is required.
Examples of the ionic compound (D) used in the present invention include metal salts consisting of metal cations and anions such as lithium salts, sodium salts and potassium salts, imidazolium salts, ammonium salts, pyridinium salts, pyrrolidinium salts and piperidinium salts. An organic salt consisting of the organic cation and anion is preferred.

Further, from the viewpoint of excellent antistatic performance, an ionic compound composed of a fluorine atom-containing anion is preferable.

Further, an ionic compound composed of a nitrogen-containing cation such as an ammonium salt, an imidazolium salt, a pyridinium salt, a piperidinium salt or a pyrrolidinium salt is preferable because of its excellent compatibility with the tertiary amine compound (B), and ammonium is particularly preferable. Salts are preferred, especially ammonium salts consisting of tetraalkylammonium cations.

Specific examples of the ionic compound (D) used in the present invention include trioctylmethylammonium N,N-bis(trifluoromethanesulfonyl)imide, tributylmethylammonium N,N-bis(trifluoromethanesulfonyl)imide, Tetraoctylammonium N,N-bis(trifluoromethanesulfonyl)imide, tetrabutylammonium N,N-bis(trifluoromethanesulfonyl)imide, trimethylphenylammonium N,Nbis(fluorosulfonyl)imide, triethylphenylammonium N,Nbis (Fluorosulfonyl)imide, tributylphenylammonium N,N bis(fluorosulfonyl)imide, trioctylphenylammonium N,N bis(fluorosulfonyl)imide, 1-hexyl-4-methylpyridinium N,N-bis(trifluoromethanesulfonyl) ), etc., among which, quaternary ammonium cation N,N-bis(fluorosulfonyl)imide is preferable, and particularly tributylmethylammonium N,N-bis(trifluoromethanesulfonyl)imide has antistatic property and hydrolytic property. It is preferable in terms of the balance of the effect of suppressing decomposition.

The content of the ionic compound (D) is 2 to 10 parts by weight, preferably 2 to 8 parts by weight, particularly preferably 2 to 5 parts by weight, based on 100 parts by weight of the acrylic resin (A). .. If the content is too small, antistatic performance tends to be difficult to obtain, and if it is too large, hydrolysis of TAC or deterioration of the pressure-sensitive adhesive tends to occur.

<Silane coupling agent (E)>
It is preferable that the pressure-sensitive adhesive composition of the present invention contains a silane coupling agent (E) from the viewpoint that when used on an adherend such as a metal or glass, it is possible to suppress a decrease in the pressure-sensitive adhesive force under a humid heat environment. ..

The silane coupling agent is an organosilicon compound that has at least one reactive functional group and at least one silicon-bonded alkoxy group in the structure.
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 balance between durability and reworkability From the viewpoint, a mercapto group and an epoxy group are preferable.

The alkoxy group bonded to the silicon atom preferably contains an alkoxy group having 1 to 8 carbon atoms from the viewpoint of durability and storage stability, and a methoxy group and an ethoxy group are particularly preferable.

The content of the alkoxy group bonded to the silicon atom of the silane coupling agent (E) is preferably 5 to 80% by weight, particularly preferably 7 to 50% by weight, and further preferably 8 to 30% by weight. .. If the content is too small, the adhesion between the glass and the pressure-sensitive adhesive tends to decrease, and the durability tends to decrease. If the content is too large, the reworkability tends to decrease.

The reactive functional group equivalent of the silane coupling agent (E) is preferably 50 to 1000 g/mol, particularly preferably 100 to 850 g/mol, and further preferably 300 to 650 g/mol. If the reactive functional group equivalent is too small, the reworkability tends to decrease, and if it is too large, the durability under moist heat resistance tends to decrease.

The silane coupling agent (E) may have a substituent other than the reactive functional group and the alkoxy group bonded to the silicon atom, such as an alkyl group and a phenyl group.

The weight average molecular weight of the silane coupling agent (E) is preferably 500 or more, particularly preferably 1,000 to 20,000, and further preferably 2,000 to 15,000. If the weight average molecular weight is too small, the long-term reworkability tends to deteriorate, and if it is too large, the compatibility tends to decrease and bleeding out tends to occur, and the durability tends to decrease.

The above weight average molecular weight is a weight average molecular weight in terms of standard polystyrene molecular weight and is measured by the following method.
Device: Gel Permeation Chromatography Detector: Differential Refractive Index Detector RI (RI-8020 manufactured by Tosoh Corporation, sensitivity 32)
Column: Tosoh TSKguardcolumn H _HR- H (1) (φ6 mm×4 cm), (TSKgelGMH _HR- N (2) (φ7.8 mm×30 cm), Filler material: Styrene-divinylbenzene copolymer Solvent: Tetrahydrofuran (THF)
Column temperature: 23°C Flow rate: 1.0 mL/min

As the silane coupling agent (E), for example,
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4 epoxycyclohexyl) A monomer type epoxy group-containing silane coupling agent that is a silane compound such as ethyltrimethoxysilane, or part of the silane compound is hydrolytically polycondensed, or the silane compound and methyltriethoxysilane, ethyltriethoxysilane, An oligomer type epoxy group-containing silane coupling agent which is a silane compound co-condensed with an alkyl group-containing silane compound such as methyltrimethoxysilane and ethyltrimethoxysilane;
A monomer type mercapto group-containing silane coupling agent which is a silane compound such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, and 3-mercaptopropylmethyldimethoxysilane, and the above. A silane compound in which a part of the silane compound is hydrolytically polycondensed or the silane compound and an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane are co-condensed. A certain oligomeric mercapto group-containing silane coupling agent;
(Meth) such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane Acryloyl group-containing silane coupling agent;
N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, Amino group-containing silane coupling agent such as 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine and N-phenyl-3-aminopropyltrimethoxysilane;
Isocyanate group-containing silane coupling agent such as 3-isocyanatopropyltriethoxysilane;
Vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; and the like.
These may be used alone or in combination of two or more.

Among these, epoxy group-containing silane coupling agent, mercapto group-containing silane coupling agent is preferably used, it is also possible to use the epoxy group-containing silane coupling agent and the mercapto group-containing silane coupling agent together, It is preferable because the improvement and the adhesive strength do not increase too much.

The silane coupling agent (E) may be a monomer type silane coupling agent or an oligomer type silane coupling agent partially hydrolyzed and polycondensed, but it is excellent in durability and reworkability, It is preferable to use the oligomer type silane coupling agent because it is less likely to volatilize during drying after coating the agent.

As the silane coupling agent (E) used in the present invention, specifically, all commercially available products, "X-41-1059A" (weight average molecular weight: 2,270, manufactured by Shin-Etsu Chemical Co., Ltd., contained) Functional 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 equivalent weight: 350 g/mol), "X-41-1805" (weight average) Molecular weight: 3,450, containing functional group; mercapto group, containing silicon atom-bonded alkoxy group; methoxy group and ethoxy group, content of silicon atom-bonded alkoxy group; 50% by weight, functional group equivalent; 800 g/mol), "X- 24-9579A" (weight average molecular weight: 2,370, contained functional group; mercapto group, contained silicon atom-bonded alkoxy group; methoxy group, functional group equivalent; 510 g/mol), "X-24-9589" (weight average molecular weight : 4,700, containing functional group; epoxy group, containing silicon atom-bonded alkoxy group; ethoxy group, functional group equivalent; 680 g/mol), "X-24-9590" (weight average molecular weight: 13,700, containing functional group Epoxy group, contained silicon atom-bonded alkoxy group; Amount of methoxy group, contained silicon atom-bonded alkoxy group; 9.5% by weight, functional group equivalent; 592 g/mol), "X-41-1818" (weight average molecular weight: 2) , 350, contained functional group; mercapto group, contained silicon atom-bonded alkoxy group; ethoxy group, amount of contained silicon atom-bonded alkoxy group; 60% by weight, functional group equivalent; 850 g/mol). Among these, "X-41-1059A", "X-41-1805", "X-24-9579A", and "X-24-9590" are preferable from the viewpoint of durability.

The content of the silane coupling agent (E) is preferably 0.01 to 1.0 part by weight, particularly preferably 0.03 to 0. 0, based on 100 parts by weight of the acrylic resin (A). 5 parts by weight, more preferably 0.05 to 0.3 parts by weight. If the content is too small, the durability tends to decrease, and if it is too large, the silane coupling agent bleeds and the durability tends to decrease.

Further, in the pressure-sensitive adhesive composition of the present invention, as long as the effect of the present invention is not impaired, as other components, resin components other than acrylic resin, acrylic monomers, polymerization inhibitors, antioxidants, corrosion inhibitors Various additives such as radical generators, peroxides and radical scavengers, metal and resin particles and the like can be added. In addition to the above, a small amount of impurities and the like contained in the raw materials for manufacturing the constituent components of the pressure-sensitive adhesive composition may be contained.

The content of the above 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). If the content is too large, the compatibility with the acrylic resin (A) decreases, and the durability tends to decrease.

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 cross-linking with a cross-linking agent (C), and by further forming a pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive on a substrate film or the like, a pressure-sensitive adhesive can be obtained. You can get a sheet.
In the pressure-sensitive adhesive sheet, it is preferable to further provide a release film on the surface of the pressure-sensitive adhesive layer opposite to the base film.

The method for producing the pressure-sensitive adhesive sheet,
[1] A method in which a pressure-sensitive adhesive composition is applied onto a base film, dried, and then a release sheet is attached to the base film, and treatment is performed by at least one of aging at room temperature or in a heated state,
[2] There is a method in which the pressure-sensitive adhesive composition is applied onto a release sheet, dried, and then a substrate film is attached, and treatment is performed by at least one of aging at room temperature or in a heated state.
Among these, the method [2] of aging at room temperature is preferable in that the base film is not damaged by heat and the adhesiveness between the base film and the pressure-sensitive adhesive layer is excellent.

Such aging treatment is performed as a reaction time of chemical crosslinking of the pressure-sensitive adhesive to balance the pressure-sensitive adhesive properties, and the aging condition is as follows: temperature is usually room temperature to 70° C., time is usually 1 day 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, and 40° C. for 1 to 7 days.

In applying the above-mentioned pressure-sensitive adhesive composition, it is preferable to dilute the pressure-sensitive adhesive composition with a solvent before coating, and the dilution concentration is preferably 5 to 60% by weight, particularly preferably 10% as the heating residue concentration. ~30% by weight. Further, the solvent is not particularly limited as long as it can dissolve the pressure-sensitive adhesive composition, for example, methyl acetate, ethyl acetate, methyl acetoacetate, ester solvents such as 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 in terms of solubility, drying property, price, and the like.

The application of the pressure-sensitive adhesive composition is carried out by a conventional method such as roll coating, die coating, gravure coating, comma coating or screen printing.

Moreover, the thickness of the pressure-sensitive adhesive layer in the obtained pressure-sensitive adhesive sheet is preferably 5 to 100 μm, particularly preferably 10 to 50 μm, and further preferably 10 to 30 μm.
If the pressure-sensitive adhesive layer is too thin, the thickness accuracy tends to be low or the adhesive force tends to be low, and if it is too thick, the pressure-sensitive adhesive sheet tends to stick out from the end when it is rolled.

The gel fraction of the pressure-sensitive adhesive layer produced by the above method is preferably from 30 to 95%, particularly preferably from 50 to 90%, further preferably from 70 to 85, from the viewpoint of low stain resistance and holding power. %. If the gel fraction is too low, the cohesive force will be low, and there will be a tendency for adhesive residue when reworking or for the holding power to be low. If it is too high, the adhesive force will be too low and peeling will tend to occur.

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

The pressure-sensitive adhesive layer produced by the above method preferably has a moderately tacky feel when touched with a finger, and since it has good wettability when actually attached to an adherend, workability tends to increase, which is preferable. ..
The tack is measured by a ball tack at an inclination angle of 30° specified in JIS Z0237 (2009). The ball tack is preferably 1 or more, more preferably 3 or more. If the ball tack is too low, it tends to be difficult to adhere the adhesive sheet to the adherend.

The pressure-sensitive adhesive sheet of the present invention, which has a release sheet directly or after the release sheet is peeled off, is used by sticking the pressure-sensitive adhesive layer surface to the surface of an adherend.

The pressure-sensitive adhesive obtained from the acrylic pressure-sensitive adhesive composition of the present invention is preferably used as a pressure-sensitive adhesive for a polarizing plate, and the effect of the present invention is remarkably obtained.
The polarizing plate with the pressure-sensitive adhesive layer of the present invention can be produced, for example, by transferring and laminating the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet of the present invention onto the polarizing plate.

The pressure-sensitive adhesive composition of the present invention has a sufficient pot life, and the pressure-sensitive adhesive obtained using this can suppress hydrolysis of the TAC film under high temperature and high humidity environment and deterioration of the pressure-sensitive adhesive. In addition, peeling and foaming do not occur, the reworkability is excellent, and the wet heat resistance and whitening resistance are also excellent. Therefore, it can be suitably used as a pressure-sensitive adhesive for a polarizing plate used for bonding a polarizing plate (protective film) and a liquid crystal cell (glass substrate).

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 thereof is not exceeded. In the examples, “part” and “%” mean weight basis.
In addition, the weight average molecular weight and the dispersity of the acrylic resin (A) in the following examples were measured according to the methods described above.
The glass transition temperature of the acrylic resin (A) was calculated using the Fox equation described above, and the glass transition temperature of the homopolymer of the monomers constituting the acrylic resin (A) is usually measured by DSC. The following literature values and catalog values were used.

<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 blowing port and a thermometer, 70.3 parts of normal butyl acrylate (a1), 8 parts of 2-hydroxyethyl acrylate (a2), acrylic acid ( a3) 0.7 parts, benzyl acrylate (a5) 21 parts, ethyl acetate 54.9 parts Acetone 42 parts, and azobisisobutyronitrile (AIBN) 0.013 parts as a polymerization initiator are charged, and azobisisobutyro After the reaction was carried out at the reflux temperature for 3.25 hours while adding the nitrile acetic acid solution dropwise, the mixture was diluted with ethyl acetate and the acrylic resin (A-1) (weight average molecular weight 1.59 million, dispersity 4.5) solution (solid content 21 0.3% and a viscosity of 7,400 mPa·s/25° C.) were obtained.

<Tertiary amine compound (B)>
The following were prepared as the tertiary amine compound (B).
[Tertiary amine compound whose substituents are all branched alkyl groups]
(B-1) Tris(2-ethylhexyl)amine (Wako Pure Chemical Industries, Ltd., molecular weight 354, liquid at 25° C.)
[Tertiary amine compound having no specific structure]
(B′-1) tri-n-octylamine (manufactured by Wako Pure Chemical Industries, Ltd., molecular weight 354, melting point −34.6° C. (Wako Pure Chemical Industries SDS reference value))
(B'-2) tri-n-dodecylamine (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 522, melting point 16°C (Tokyo Chemical Industry SDS reference value))

<Crosslinking agent (C)>
The following were prepared as a cross-linking agent.
(C-1): Tolylene diisocyanate trimethylolpropane adduct (“Coronate L55E” manufactured by Tosoh Corporation) [isocyanate-based cross-linking agent]

<Ionic compound (D)>
The following ionic compound (D) was prepared as an antistatic agent.
(D-1): Salt of quaternary ammonium cation and N,N-bis(fluorosulfonyl)imide anion (“MP-446” manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., melting point 37° C.)
(D-2): tributylmethylammonium, N,N-bis(trifluoromethanesulfonyl)imide (“FC-4400” manufactured by 3M, molecular weight 482, melting point 27.5° C.)

<Silane coupling agent (E)>
The following were prepared as silane coupling agents.
(E-1): X-41-1059A: X-24-9590 = 1:2 compound X-41-1059A (Shin-Etsu Chemical Co., Ltd., epoxy-based oligomer type silane coupling agent).
X-24-9590 (Shin-Etsu Chemical Co., Ltd., epoxy oligomer type silane coupling agent)

<Examples 1 to 3 and Comparative Examples 1 to 3>
Each of the compounding components prepared and prepared as described above was compounded as shown in Table 1 below, and this was adjusted to a solid content concentration of 15% with ethyl acetate to obtain a pressure-sensitive adhesive composition.

[Pot life]
The viscosity of the pressure-sensitive adhesive composition obtained above was measured with a B-type viscometer immediately after blending, 20 hours after blending, and 30 hours after blending, and the state of the liquid was visually confirmed.
The coatability of the pressure-sensitive adhesive composition after 30 hours of formulation was evaluated, and the pot life was evaluated according to the following criteria. The results are shown in Table 2.
(Evaluation criteria)
O: Coating was possible without streaks.
Δ: Coating was possible, but many coating streaks were seen.
X: It could not be applied.

[Preparation of sheet with adhesive layer]
The obtained pressure-sensitive adhesive composition was applied to a 38 μm polyester release sheet (Cerapile WZ manufactured by Toray Industries, Inc.) so that the thickness after drying would be 25 μm, and dried at 100° C. for 3 minutes, and then used as a polyester film (PET). The release sheet and the adhesive layer side opposite to the release sheet are attached to one TAC film surface of a polarizing plate in which triacetyl cellulose (TAC) films are respectively laminated, and cured for 7 days in an environment of 23°C x 50% RH to obtain adhesion. A polarizing plate with an agent layer was obtained (layer structure; release sheet/adhesive layer/TAC film/polarizer/PET film).

(Performance control performance of adhesive)
Using the obtained pressure-sensitive adhesive layer-attached polarizing plate, the deterioration inhibiting performance of the pressure-sensitive adhesive was evaluated as described below. The results are shown in Table 2.
The polarizing plate with the pressure-sensitive adhesive layer was cut into 16 cm×9.5 cm, the release sheet was peeled off, and the pressure-sensitive adhesive layer surface was pressed against non-alkali glass (“Eagle XG” manufactured by Corning Co., Ltd.: thickness 0.7 mm) to form a 2 kg roller. After reciprocating two times to bond them together, an autoclave treatment (0.5 Mpa×50° C.×20 minutes) was performed to prepare a test sample for the pressure-sensitive adhesive deterioration suppressing performance. The obtained test sample was allowed to stand in an environment of 80° C.×90% RH, and the deterioration suppressing performance was evaluated by measuring the time until the deterioration of the pressure-sensitive adhesive layer occurred.
(Evaluation criteria)
◯: The adhesive was not deteriorated after 360 hours had passed.
X: The adhesive had deteriorated after 360 hours had passed.

From the results in Table 2, Examples 1 and 2 using a tertiary amine having a specific structure as the tertiary amine compound have a large steric hindrance of the substituent of the tertiary amine and have a sufficient pot life. I understand. Furthermore, no alteration of the pressure-sensitive adhesive layer was observed.
On the other hand, in Comparative Examples 1 to 3 in which the tertiary amine compound having no specific structure, which was substituted with the linear alkyl group, was used, steric hindrance was obtained even if the carbon number of the substituent was relatively long. Is small and does not have a sufficient pot life.

The pressure-sensitive adhesive composition of the present invention has a sufficient pot life, and the pressure-sensitive adhesive obtained using the same suppresses hydrolysis of the base film in a high temperature and high humidity environment and deterioration of the pressure-sensitive adhesive by an acid. Therefore, it can be preferably used as a pressure-sensitive adhesive for surface protection and a pressure-sensitive adhesive for labels, especially as a pressure-sensitive adhesive for polarizing plates.

Claims (9)

A pressure-sensitive adhesive composition containing a hydroxyl group-containing acrylic resin (A), a tertiary amine compound (B), a crosslinking agent (C) and an ionic compound (D),
The tertiary amine compound (B) is a tertiary amine compound in which at least one of the three substituents is a substituent having at least one of an aromatic ring structure, an alicyclic structure and a branched alkyl structure,
The crosslinking agent (C) is at least one of an isocyanate crosslinking agent and an epoxy crosslinking agent,
Content of an ionic compound (D) is 2-10 weight part with respect to 100 weight part of acrylic resin (A), The acrylic adhesive composition characterized by the above-mentioned. The acrylic pressure-sensitive adhesive composition according to claim 1, wherein at least one of the three substituents of the tertiary amine compound (B) is a branched alkyl group. The acrylic resin (A) is an acrylic resin obtained by copolymerizing a copolymerization component containing 0.1 to 50% by weight of a hydroxyl group-containing monomer, and the acrylic pressure-sensitive adhesive according to claim 1 or 2. Agent composition. The acrylic resin (A) is an acrylic resin obtained by copolymerizing a copolymerization component containing 1 to 50% by weight of an aromatic ring-containing monomer, and the acrylic resin according to claim 1. Adhesive composition. 5. The acrylic resin (A) is an acrylic resin obtained by copolymerizing a copolymerization component having an alkyl (meth)acrylate monomer content of 90% by weight or less. The acrylic pressure-sensitive adhesive composition described. Content of a tertiary amine compound (B) is 0.01-10 weight part with respect to 100 weight part of acrylic resin (A), The acrylic pressure-sensitive adhesive in any one of Claims 1-5. Agent composition. A pressure-sensitive adhesive, wherein the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 6 is crosslinked with a crosslinking agent (C). A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive according to claim 7. A polarizing plate with a pressure-sensitive adhesive layer, comprising the pressure-sensitive adhesive according to claim 7.