JP7205144B2 - Adhesive composition, and adhesive and adhesive sheet using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition, and more particularly, it suppresses hydrolysis of a plastic film used as a substrate and/or an adherend even in a high-temperature and high-humidity environment, and further prevents whitening of the pressure-sensitive adhesive layer. The present invention relates to a pressure-sensitive adhesive composition for forming a pressure-sensitive adhesive having excellent transparency without occurrence of blemishes.

Films and plates made of polyester-based resins, triacetylcellulose-based resins, polyether-based resins, and the like have been conventionally used as substrates for pressure-sensitive adhesive sheets and tapes, adherends, and the like.

In addition, acrylic adhesives, which are mainly composed of acrylic resin, are used in a variety of applications, such as adhesives for curing sheets, adhesives for surface protection, adhesives for semiconductor processes, adhesives for bonding optical components, and adhesives for touch panel sensors. used for various purposes.

Furthermore, tapes and laminates using an acrylic pressure-sensitive adhesive and using the plastic film as a substrate or adherend are widely used.

For example, a polarizing plate with an adhesive layer, in which an acrylic resin adhesive is laminated on a polarizing plate using a triacetyl cellulose (TAC) film or a polyester film as a protective film, is used in liquid crystal displays, organic EL displays, and the like. ing.

Under such circumstances, Patent Document 1 proposes a pressure-sensitive adhesive containing a carbodiimide compound in an acrylic resin containing a carboxyl group, and describes that the pressure-sensitive adhesive is excellent in durability and the like.

JP 2017-179076 A

However, although the amount of the carbodiimide compound used in Patent Document 1 is effective for suppressing hydrolysis of the added resin, when it is added to the adhesive, the adhesive layer is made of a plastic film in contact. The amount is insufficient to suppress the hydrolysis of the base material and the adherend, and the problem remains that the hydrolysis cannot be sufficiently suppressed.
Further, when simply increasing the amount of the carbodiimide compound, hydrolysis can be suppressed, but a new problem arises in that the pressure-sensitive adhesive layer whitens in a high-temperature, high-humidity environment.

Therefore, in view of this background, the present invention provides crystals having excellent hydrolysis suppression performance against hydrolysis in substrates and adherends made of plastic films even when used in high-temperature and high-humidity environments. Furthermore, the pressure-sensitive adhesive layer does not turn white, and can be suitably used even when applied to a pressure-sensitive adhesive that can be applied to various uses, especially a substrate or an adherend that is susceptible to hydrolysis. An object of the present invention is to provide a pressure-sensitive adhesive composition capable of obtaining a pressure-sensitive adhesive suitable as a pressure-sensitive adhesive, for example, a pressure-sensitive adhesive for a polarizing plate.

However, as a result of intensive research in view of such circumstances, the present inventors have found that a carbodiimide compound having an oxyalkylene structure is used as a carbodiimide compound in a pressure-sensitive adhesive composition containing an acrylic resin. The present inventors have found that it is possible to form a pressure-sensitive adhesive that is excellent in suppressing hydrolysis and crystallization even in a high-temperature and high-humidity environment and that does not cause whitening of the pressure-sensitive adhesive layer, and completed the present invention.

That is, the gist of the present invention is that it contains an acrylic resin (A) and a carbodiimide compound (B) having an oxyalkylene structure, and the content of the carbodiimide compound (B) having an oxyalkylene structure is 100% of the acrylic resin (A). It relates to a pressure-sensitive adhesive composition characterized in that it is 1 to 30 parts by weight.

Furthermore, the present invention relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition of the present invention has excellent hydrolysis suppression performance against hydrolysis especially in plastic films constituting substrates and adherends even when used in a high-temperature and high-humidity environment, and crystallizes. Furthermore, the pressure-sensitive adhesive layer does not whiten, and the pressure-sensitive adhesive can be applied to various applications, especially when applied to a plastic film substrate or adherend that is susceptible to hydrolysis. It is possible to obtain a pressure-sensitive adhesive that can be used, for example, a pressure-sensitive adhesive that is suitable as a pressure-sensitive adhesive for polarizing plates, and is very useful.

The present invention will be described in detail below.
(Meth)acryl means acrylic or methacrylic, (meth)acryloyl means acryloyl or methacryloyl, and (meth)acrylate means acrylate or methacrylate, respectively. An acrylic resin is a resin obtained by polymerizing a polymerizable component containing at least one (meth)acrylate monomer.
The pressure-sensitive adhesive used in the present invention has tackiness at 25° C. (room temperature) and adheres to an adherend with light pressure such as pressing by hand.

The adhesive composition of the present invention comprises an acrylic resin (A) and a carbodiimide compound (B) having an oxyalkylene structure.

<Acrylic resin (A)>
Examples of the acrylic resin (A) used in the present invention include acrylic resins containing alkyl (meth)acrylate monomers (and other copolymerizable monomers) as polymerization components.

Examples of the alkyl (meth)acrylate-based monomer include (meth)acrylate-based monomers in which the number of carbon atoms in the alkyl group is usually 1 to 24, preferably 1 to 18, particularly preferably 1 to 12, and more preferably 1 to 8. Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate ) acrylates 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 preferred in terms of versatility and adhesive properties.

The content of the alkyl (meth)acrylate monomer is preferably 40% by weight or more, particularly preferably 40 to 99.9% by weight, more preferably 50 to 99.5% by weight, based on the total polymerization components. , particularly preferably 60 to 99% by weight. If the content of the alkyl (meth)acrylate monomer is too low, the adhesive properties tend to deteriorate. If the amount is too large, the number of reaction points with a cross-linking agent, which will be described later, will decrease, and the durability will tend to decrease.

The polymerizable component may further contain other polymerizable components (copolymerizable monomers). Examples of such polymerization components include, but are not limited to, functional group-containing monomers (e.g., hydroxyl group-containing monomers, carboxyl group-containing monomers, nitrogen-containing monomers, etc.), alkoxy group-containing monomers, aromatic monomers, and alicyclic structure-containing monomers. Examples include monomers and other ethylenically unsaturated group-containing monomers.
In the present invention, the acrylic resin (A) using a functional group-containing monomer as a copolymerizable monomer serves as a cross-linking point of the acrylic resin (A), improves the cohesive force, and It is preferable in terms of increasing the adhesion to the adherend and in terms of wet heat whitening resistance (wet heat whitening: a phenomenon in which the adhesive turns white after being exposed to a constant temperature and humidity environment), especially in terms of wet heat whitening resistance. It is preferred to use hydroxyl group-containing monomers.

As the hydroxyl group-containing monomer, for example,
(Meth) acrylic monomers having a hydroxyalkyl group [for example, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2,2-dimethyl-2-hydroxyethyl Hydroxyalkyl (meth)acrylate monomer such as (meth)acrylate],
lactone-modified monomers [for example, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate (for example, caprolactone-modified (meth)acrylic monomers)],
oxyalkylene-modified monomers [e.g., oxyalkylene-modified (meth)acrylic monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate (e.g., oxyalkylene-modified (meth)acrylate monomers)],
Monomers (hydroxyl group-containing (meth)acrylic monomers) such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, N-methylol(meth)acrylamide, and hydroxyethylacrylamide are included.
In addition, in the monomer (hydroxyl group-containing (meth)acrylic monomer), the hydroxyl group may be any one of primary to tertiary.
Examples of primary hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl. Hydroxyalkyl (meth)acrylate monomers such as (meth)acrylates, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, oxyalkylene-modified (meth)acrylates such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate Primary hydroxyl group-containing (meth)acrylic monomers such as acrylate monomers, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, N-methylol(meth)acrylamide, and hydroxyethylacrylamide are included.
Secondary hydroxyl group-containing monomers include, for example, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate and other secondary hydroxyl group-containing (meth) acrylics system monomers, and the like.
Tertiary hydroxyl group-containing monomers include, for example, tertiary hydroxyl group-containing (meth)acrylic monomers such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate.
These may be used alone or in combination of two or more.

Among the above hydroxyl group-containing monomers, a primary hydroxyl group-containing (meth) acrylate monomer is preferable in that it has excellent reactivity with a cross-linking agent, particularly a nitrogen-containing cross-linking agent described below, and improves wet heat whitening resistance, and further Preferably, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are used because they contain few impurities such as di(meth)acrylate and are easy to manufacture.
Further, 4-hydroxybutyl acrylate is most preferable in that it contains less acid impurities and suppresses hydrolysis of the base material.

In addition, as the hydroxyl group-containing monomer used in the present invention, it is also preferable to use one having a content of di(meth)acrylate, which is an impurity, of 0.5% or less, particularly 0.2% or less, and more preferably 0.5% or less. It is preferred to use 0.1% or less.

The content of the hydroxyl group-containing monomer is preferably 0.1 to 50% by weight, particularly preferably 1 to 30% by weight, based on the total polymerization components (or in all the polymerization components, the same shall apply hereinafter). and more preferably 5 to 25% by weight.
If the content is too small, the resistance to wet heat whitening tends to decrease. There is a tendency that there is no adhesive residue and that the adherend is not damaged).

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, dimer acids of (meth)acrylic acid such as β-carboxyethyl (meth)acrylate, etc. Among them, in terms of wet heat whitening resistance, during polymerization (Meth)acrylic acid is preferred in terms of stability.

The content of the carboxyl group-containing monomer is preferably 1% by weight or less, particularly preferably 0.5% by weight or less, more preferably 0.2% by weight or less, and still more preferably 0.2% by weight or less, based on the total polymerization components. is 0.1% by weight or less.
If the content is too high, the hydrolysis of the base material tends to be accelerated, or a side reaction with the carbodiimide compound (B) occurs, resulting in a decrease in durability.

Examples of the nitrogen-containing monomer include amino group-containing monomers and amide group-containing monomers.
Examples of amino group-containing monomers 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; group-containing (meth)acrylate-based monomers; tertiary amino group-containing (meth)acrylate-based monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate;

Examples of amide group-containing monomers include (meth)acrylamide; methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, isopropoxymethyl (meth)acrylamide, n-butoxymethyl ( Alkoxyalkyl (meth)acrylamide-based monomers such as meth)acrylamide and isobutoxymethyl (meth)acrylamide; Dialkyl (meth)acrylamide-based monomers such as dimethyl (meth)acrylamide and diethyl (meth)acrylamide; and the like.

Other nitrogen-containing monomers include nitrogen-containing monomers having a cyclic structure such as acryloylmorpholine and vinylimidazole.
These may be used alone or in combination of two or more.

Among the above nitrogen-containing monomers, dialkylacrylamide is preferable because it can suppress hydrolysis of the substrate or adherend, and dimethylacrylamide and diethylacrylamide are preferable because they have high polymerizability and amide group concentration and can suppress hydrolysis.

The content of the nitrogen-containing monomer is preferably 10% by weight or less, particularly preferably 8% by weight or less, and still more preferably 5% by weight or less, based on the total polymerization components. If the content is too high, the glass transition temperature of the acrylic resin (A) tends to be high, resulting in reduced reworkability and zipping.

Examples of the alkoxy group-containing monomer include alkoxyalkyl (meth)acrylate such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, and 2-butoxyethyl (meth)acrylate. meth)acrylates.

Examples of the alicyclic structure-containing monomer include cyclohexyl (meth)acrylate, isobornyl acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, Examples 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 monomers include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, and phenoxydipropylene glycol (meth)acrylate. , phenoxypolyethylene glycol (meth)acrylate, phenoxypolyethyleneglycol (meth)acrylate, phenoxypolypropylene glycol-(meth)acrylate having one aromatic ring; phenoxybenzyl (meth)acrylate, ethoxylated o-phenyl Examples include (meth)acrylates having two aromatic rings such as phenol (meth)acrylate. These may be used alone or in combination of two or more.

In the present invention, when adjusting the birefringence of the acrylic resin (A) to the positive side, benzyl (meth) acrylate, phenoxy (meth) ethyl acrylate, phenoxybenzyl (meth) acrylate, and phenoxy diethylene glycol (meth) acrylate are used. be able to.

As the polymerization method of the acrylic resin (A), conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization can be used. There is a method of mixing or dropping a polymerization component and a polymerization initiator and polymerizing under predetermined polymerization conditions. Among them, solution radical polymerization and bulk polymerization are preferred, and particularly preferably acrylic resin (A) can be stably obtained. It is solution radical polymerization at the point.

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. and 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 are preferred from the standpoint of ease of polymerization reaction, chain transfer effect, ease of drying when the adhesive composition is applied, and safety. Ketones are preferred, especially 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, lauroyl peroxide, di-t-butyl peroxide, cumene Examples 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.

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

The weight average molecular weight of the acrylic resin (A) is preferably 200,000 to 2,500,000, particularly preferably 400,000 to 2,000,000, more preferably 600,000 to 1,800,000, and particularly preferably 1,000,000. ~1.6 million. If the weight-average molecular weight is too small, the components in the hydrolyzed plastic substrate migrate faster, and crystals tend to precipitate more easily. A large amount of solvent is required, which tends to increase the energy required for drying.

Further, 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, further preferably 6 or less. If the degree of dispersion is too high, the cohesive force tends to decrease, resulting in a decrease in durability and a decrease in reworkability. The lower limit of the degree of dispersion is usually 1.

The weight average molecular weight of the above acrylic resin (A) is the weight average molecular weight in terms of standard polystyrene molecular weight, and high performance liquid chromatography (Japan Waters Co., Ltd., "Waters 2695 (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/line, packing material: styrene-divinyl Benzene copolymer, filler particle size: 10 µm), and the number average molecular weight can be measured in the same manner. Further, the dispersity is obtained from the weight average molecular weight and the number average molecular weight.

The glass transition temperature (Tg) of the acrylic resin (A) is preferably -100 to 25°C, particularly preferably -60 to 0°C, and still more preferably -55 to -10°C. If the glass transition temperature is too high, the tack tends to decrease, making it difficult to bond, or zipping tends to occur when reworking from the release film or adherend, and if it is too low, the heat resistance decreases. Tend.

The glass transition temperature is calculated from the following Fox formula.

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）

Tg: glass transition temperature of the copolymer (K)
Tga: glass transition temperature (K) of homopolymer of monomer A Wa: weight fraction of monomer A Tgb: glass transition temperature (K) of homopolymer of monomer B Wb: weight fraction of monomer B Tgn: homopolymer of monomer N Glass transition temperature of polymer (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 weight fraction of each homopolymer of each monomer constituting the acrylic resin to the Fox formula.
The glass transition temperature of a homopolymer of the monomers constituting the acrylic resin is usually measured by a differential scanning calorimeter (DSC), and is in accordance with JIS K7121-1987 and JIS K 6240. method can be measured.

<Carbodiimide compound (B)>
The carbodiimide compound (B) may be a compound having one or more carbodiimide groups [-N=C=N-], for example, a monofunctional carbodiimide compound having one carbodiimide group (monocarbodiimide compound, monomeric carbodiimide compound ), polyfunctional carbodiimide compounds having two or more carbodiimide groups (referred to as polycarbodiimide compounds), and the like. The polycarbodiimide compound may be a polymer-type carbodiimide compound or the like having a repeating structure of carbodiimide groups.

It is important that the carbodiimide compound (B) used in the present invention has an oxyalkylene structure (oxyalkylene skeleton). The skeleton or structure of the portion other than the carbodiimide group and the oxyalkylene structure in the carbodiimide compound (B) is not particularly limited. (e.g., cycloalkylene skeleton), aromatic structure (aromatic skeleton, e.g., arylene skeleton), or a combination thereof (e.g., arene dialkylene skeleton, cycloalkanedialkylene skeleton, etc.).

As described above, the polycarbodiimide compound has two or more carbodiimide groups, and a typical example is a polymer-type carbodiimide compound having a repeating structure of carbodiimide groups.

Such a carbodiimide compound may have, for example, a structure represented by the following formula.
-(N=C=N-R)n-
(Wherein, R represents a residue of a carbodiimide structure, and n represents an integer of 2 or more.)
As R, for example, an aliphatic structure (alicyclic skeleton, such as an alkylene skeleton), an alicyclic structure (alicyclic skeleton, such as a cycloalkylene skeleton), an aromatic structure (an aromatic skeleton, such as an arylene skeleton ), structures having a combination of these (eg, arenedialkylene skeleton, cycloalkanedialkylene skeleton, etc.), and the like.
Note that R may be the same or different depending on the number of n. That is, the carbodiimide compounds having the structures represented by the formulas above may have the same or different R's.
In the above formula, n may be 2 or more, preferably 2 to 30, more preferably 3 to 20, more preferably 5 to 15.

In the carbodiimide compound (B), the oxyalkylene structure includes, for example, an alkoxy group (alkoxy structure) such as a methoxy group and an ethoxy group, a polyoxyethylene structure, a polyoxypropylene structure, a polyoxypropylene structure such as a polyoxyethylene polyoxypropylene structure. An alkylene (polyoxyalkylene oxide) structure can be mentioned.
The carbodiimide compound (B) may have these oxyalkylene structures singly or in combination of two or more.
Among these, a polyoxyalkylene structure (especially a polyoxyethylene structure) is preferred because whitening is less likely to occur even when exposed to high temperature and high humidity.
The repeating number of the polyoxyalkylene structure is preferably 2-50, particularly preferably 5-20.
Within the above range, compatibility with the acrylic resin (A) tends to be good, and whitening of the pressure-sensitive adhesive layer when exposed to high-temperature and high-humidity conditions can be suppressed.

The position (bonding form) of the carbodiimide compound (B) is not particularly limited as long as it has an oxyalkylene structure. For example, the oxyalkylene structure may have a skeleton or structure other than the carbodiimide group, may be located at the end of the carbodiimide compound, or may be located at the main chain of the polycarbodiimide compound. It may also exist in a combined manner.

When located on the main chain, the oxyalkylene structure may be adjacent to (attached to) the repeating unit or may form a repeating unit together with the carbodiimide group.

A carbodiimide compound having an oxyalkylene structure may typically have an oxyalkylene structure adjacent to at least a repeating unit. Such a carbodiimide compound may have, for example, a structural unit represented by the following formula.
-N=C=N-R-X-
(Wherein, X represents an oxyalkylene structure, and R is the same as described above.)

In particular, a polycarbodiimide compound having an oxyalkylene structure may have, for example, a structural unit represented by the following formula.
-(N=C=N-R)nX-
(Wherein, n, R and X are the same as above.)

Specific carbodiimide compounds (B) include, for example, aliphatic monocarbodiimide compounds {e.g., dialkylcarbodiimides [e.g., diC _1-20 alkylcarbodiimides such as 1,3-dimethylcarbodiimide and 1,3-diisopropylcarbodiimide), etc. ] etc.}, alicyclic monocarbodiimide compounds {e.g., dicycloalkylcarbodiimide [e.g., di- _C4-10 cycloalkylcarbodiimide such as 1,3-dicyclohexylcarbodiimide] etc.}, aromatic monocarbodiimide compounds {e.g., diaryl Carbodiimides [for example, diphenylcarbodiimide, ditolylcarbodiimide, bis(2,6-dimethylphenyl)carbodiimide, bis(2,6-diisopropylphenyl)carbodiimide, bis(2,4,6-trimethylphenyl)carbodiimide, bis(2, 6-diethylphenyl)carbodiimide, diC _6-15 arylcarbodiimide such as N-phenyl-N′-tolylcarbodiimide], benzylisopropylcarbodiimide, etc.} monocarbodiimide compounds such as compounds having adjacent oxyalkylene structures;
Aliphatic polycarbodiimide compounds {e.g., polyalkylenecarbodiimide [e.g., polyhexamethylenecarbodiimide, poly(C _2-20 alkylenecarbodiimide) such as poly(3-methylhexamethylenecarbodiimide), etc.], etc.}, alicyclic polycarbodiimide compounds {e.g., polydicycloalkylalkanecarbodiimide [e.g., poly(di-C _4-10 cycloalkyl-C _1-10 alkanecarbodiimide) such as poly(4,4′-dicyclohexylmethanecarbodiimide)], etc.}, aromatic polycarbodiimide Compound {e.g., polyarylenecarbodiimide [e.g., poly(C6-15 _{arylenecarbodiimide} ) such as polyphenylenecarbodiimide, polytolylenecarbodiimide, poly(diisopropylphenylenecarbodiimide), etc.], polydiarylalkanecarbodiimide [e.g., poly(4,4 poly(diC _6-15 aryl-C _1-10 alkane carbodiimide) such as '-diphenylmethane carbodiimide), etc.], etc.), etc.), and polycarbodiimide compounds such as compounds having adjacent oxyalkylene structures (e.g., polymer-type polycarbodiimide compounds, etc.).

The carbodiimide compound (B) may be used alone or in combination of two or more.

Among these, a polymer-type carbodiimide compound having an oxyalkylene structure is preferable because, when used in a TAC film, the reaction product of the carbodiimide compound and acetic acid generated by hydrolysis of TAC is less likely to precipitate in the adhesive layer. In the polymer-type carbodiimide compound, the repeating number of the carbodiimide structure may be in the same range as n in the above formula, particularly preferably 2 to 30, more preferably 3 to 20, more preferably 5 to 15. is.

The weight average molecular weight of the carbodiimide compound (B) having an oxyalkylene structure used in the present invention is preferably 300 to 100,000, particularly preferably 500 to 50,000, and further preferably 1,000 to 20,000. If the weight-average molecular weight is too low, it tends to form a crystal structure when reacting with the acid generated from the substrate, and crystals tend to precipitate. If it is too high, compatibility with the acrylic resin (A) tends to decrease. be.

In the present invention, the carbodiimide group equivalent of the carbodiimide compound (B) having an oxyalkylene structure is preferably 1000 g/mol or less, particularly 800 g/mol or less, and further 500 g/mol or less. preferable. If the carbodiimide group equivalent is too high, the amount to be blended increases relative to the acrylic resin (A), so that the plasticizing effect tends to increase and the durability tends to decrease. Incidentally, the lower limit of the carbodiimide group equivalent is usually 70 g/mol.

It is important that the content of the carbodiimide compound (B) having an oxyalkylene structure is 1 to 30 parts by weight with respect to 100 parts by weight of the acrylic resin (A). It is preferably 1.5 to 25 parts by weight, more preferably 2 to 20 parts by weight, particularly preferably 2.5 to 15 parts by weight. If the content is too large, the durability tends to be lowered, and if it is too small, the effect of inhibiting hydrolysis tends to be lowered.

Moreover, it is preferable that the carbodiimide group amount (mmol) of the carbodiimide compound (B) having an oxyalkylene structure is equal to or greater than the carboxyl group amount (mmol) of the acrylic resin (A). In other words, when the amount of carboxyl groups in the acrylic resin (A) is αmmol and the amount of carbodiimide groups in the carbodiimide compound (B) is βmmol, β-α (mmol) is preferably 0 or more, and 0.05 to 0.05. 1000 mmol is particularly preferred, 0.10 to 100 mmol is more preferred, 0.15 to 70 mmol is preferred, and 0.20 to 50 mmol is even more preferred.
If the carbodiimide group content is too small relative to the carboxyl group content of the acrylic resin (A), the reaction may proceed gradually at room temperature, or under high temperature and high humidity conditions, the carbodiimide may be hydrolyzed before the base material is hydrolyzed. All of the groups tend to react, and the effect of suppressing hydrolysis tends to decrease.

Regarding the carbodiimide compound (B) having the above oxyalkylene structure, the residual isocyanate group is preferably 10% or less, particularly 5% or less, further 1% or less, and particularly 0.2% or less. is preferred. In particular, in the present invention, carbodiimide compounds containing no (substantially no) isocyanate groups can be preferably used. If there are too many isocyanate groups, the physical properties of the pressure-sensitive adhesive layer tend to be difficult to stabilize.

The carbodiimide compound (B) (e.g., polymeric carbodiimide compound) is preferably hydrophobic and has a solubility in water of preferably 10% by weight or less, particularly 5% by weight or less, and further 1% by weight or less. is preferred. If the solubility in water is too high, it tends to gradually diffuse from the pressure-sensitive adhesive layer in a hot and humid environment, resulting in a decrease in the effect of suppressing crystal precipitation accompanying hydrolysis.
In the present invention, the term "dissolution" refers to a state in which there is no turbidity and there is no separation. The lower limit of solubility is usually 0.00001% by weight of solubility in water.

As the carbodiimide compound (B), a commercially available product or a compound synthesized by a known method may be used.
Examples of commercially available products include "V-02B" and "V-04K" manufactured by Nisshinbo Chemical Co., Ltd.

A carbodiimide compound (another carbodiimide compound) other than the carbodiimide compound (B) is preferably added in an amount of 10% by weight or less, more preferably 5% by weight or less, based on the total composition as long as the object of the present invention is not impaired. They can also be used in combination.

Such other carbodiimide compounds include carbodiimide compounds having no oxyalkylene structure, such as the above monocarbodiimide compounds {for example, the above aliphatic monocarbodiimide compounds (e.g., 1,3-diisopropylcarbodiimide, 2,6-diisopropylcarbodiimide, etc.). , the above alicyclic monocarbodiimide compound, monomer type carbodiimide such as the above aromatic monocarbodiimide compound}, polycarbodiimide compound {e.g., the above aliphatic polycarbodiimide compound (e.g., aliphatic dicarbodiimide, etc.), the above alicyclic poly Carbodiimide compounds (e.g., alicyclic dicarbodiimides, etc.), polymer-type polycarbodiimide compounds (e.g., polymer-type dicarbodiimide compounds, etc.) such as the above aromatic polycarbodiimide compounds (e.g., aromatic dicarbodiimides, etc.), etc. be done.

Other carbodiimide compounds may be used alone or in combination of two or more.

<Crosslinking agent (C)>
In the present invention, it is preferable to further contain a cross-linking agent (C) because it tends to improve the elastic modulus when used as a pressure-sensitive adhesive and prevent migration of components contained in substrates and adherends.

Examples of the cross-linking agent (C) include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, aldehyde-based cross-linking agents, amine-based cross-linking agents, and metal chelate-based cross-linking agents. Among these, it is preferable to use an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, and especially an isocyanate-based cross-linking agent in terms of improving the adhesiveness to the substrate and being excellent in reactivity with the acrylic resin (A). .

Examples of the isocyanate-based cross-linking agents include tolylene diisocyanate-based cross-linking agents such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, xylylene diisocyanate-based cross-linking agents such as 1,3-xylylene diisocyanate, Diphenylmethane-based cross-linking agents such as diphenylmethane-4,4-diisocyanate; aromatic isocyanate-based cross-linking agents such as naphthalene diisocyanate-based cross-linking agents such as 1,5-naphthalenediisocyanate; Alicyclic isocyanate cross-linking agents such as -dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane, norbornane diisocyanate; hexamethylene diisocyanate, trimethylhexamethylene diisocyanate aliphatic isocyanate cross-linking agents; and adducts, burettes, and isocyanurates of the above isocyanate compounds.

Among these isocyanate-based cross-linking agents, tolylene diisocyanate-based cross-linking agents are preferable from the viewpoint of pot life and durability, and xylylene diisocyanate-based cross-linking agents or isocyanurate skeleton-containing isocyanate-based cross-linking agents are preferable from the viewpoint of shortening the aging time.
On the other hand, an aromatic-free isocyanate-based cross-linking agent [for example, selected from aliphatic isocyanate-based cross-linking agents such as hexamethylene diisocyanate, its adducts, burettes or isocyanurates, and alicyclic (alicyclic) isocyanate-based cross-linking agents at least one isocyanate-based cross-linking agent] is preferable from the viewpoints of yellowing resistance, suppression of hydrolysis of the substrate and/or adherend under high-temperature and high-humidity environments, suppression or prevention of whitening in the pressure-sensitive adhesive layer, and the like. Specifically, among these, tolylene diisocyanate, xylylene diisocyanate, adducts of hexamethylene diisocyanate and trimethylolpropane, and nurates are preferable in that they have an excellent balance of durability, pot life, and crosslinking speed. .

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

Examples of the aziridine-based cross-linking 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.

Examples of the melamine-based cross-linking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins. .

Examples of the aldehyde cross-linking agent include glyoxal, malondialdehyde, succindialdehyde, maleinedialdehyde, glutaredialdehyde, formaldehyde, acetaldehyde, and benzaldehyde.

Examples of the amine-based cross-linking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resins, and polyamides.

Examples of the metal chelate-based cross-linking agents 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. mentioned.

The cross-linking agent (C) may be used alone or in combination of two or more.

The content of the cross-linking agent (C) is preferably 0.01 to 10 parts by weight, particularly preferably 0.05 to 5 parts by weight, per 100 parts by weight of the acrylic resin (A). If the content is too low, the durability tends to be low, and adhesive residue tends to occur during rework. Tend.

<Ionic compound (D)>
The pressure-sensitive adhesive composition of the present invention preferably contains an ionic compound (D) in terms of antistatic performance.

In the present invention, the ionic compound (D) is a salt composed of a cation and an anion.
The cation may be any cation selected from inorganic cations and organic cations.

Examples of inorganic cations include nonmetallic inorganic cations such as phosphonium cations and sulfonium cations, and metallic inorganic cations such as lithium cations, sodium cations, calcium cations and potassium cations.

Examples of organic cations include cations having a nitrogen atom, such as quaternary ammonium cations, imidazolium cations, pyridinium cations, piperidinium cations, and pyrrolidinium cations.

Among these, metal cations, particularly alkali metal cations, are preferred for their excellent antistatic performance and wet heat whitening resistance. , organic cations and other non-metal cations are preferred, among which quaternary ammonium cations, particularly non-cyclic quaternary ammonium cations, imidazolium cations, pyridinium cations, piperidinium cations, pyrimidinium cations, pyrazolium cations, Nitrogen-containing cations such as pyrrolidinium-based cations, and nitrogen-containing cations such as quaternary ammonium cations are preferred.

Examples of the alkali metal cations include lithium cations, potassium cations, sodium cations, etc. Among them, lithium cations are preferable from the viewpoint of excellent durability, antistatic performance, and wet heat whitening resistance when used as an adhesive.

As the quaternary ammonium cation, specifically, for example,
Tetraalkylammonium cations such as tetramethylammonium cations, tetraethylammonium cations, tetrabutylammonium cations, tetrapentylammonium cations, tetrahexylammonium cations, tetraheptylammonium cations, in which the alkyl groups have the same alkyl chain length;
triethylmethylammonium cation, tributylmethylammonium cation, trimethylpropylammonium cation, trimethyldecylammonium cation, triethylmethylammonium cation, tributylethylammonium cation, N,N-dimethyl-N-ethyl-N-propylammonium cation, N,N- Dimethyl-N-ethyl-N-butylammonium cation, N,N-dimethyl-N-ethyl-N-pentylammonium cation, N,N-dimethyl-N-ethyl-N-hexylammonium cation, N,N-dimethyl- N-ethyl-N-heptylammonium cation, N,N-dimethyl-N-ethyl-N-nonylammonium cation, N,N-dimethyl-N,N-dipropylammonium cation, N,N-diethyl-N-propyl -N-butylammonium cation, N,N-dimethyl-N-propyl-N-pentylammonium cation, N,N-dimethyl-N-propyl-N-hexylammonium cation, N,N-dimethyl-N-propyl-N -heptylammonium cation, N,N-dimethyl-N-butyl-N-hexylammonium cation, N,N-diethyl-N-butyl-N-heptylammonium cation, N,N-dimethyl-N-pentyl-N-hexyl ammonium cation, N,N-dimethyl-N,N-dihexylammonium cation, trimethylheptylammonium cation, N,N-diethyl-N-methyl-N-propylammonium cation, N,N-diethyl-N-methyl-N- Pentylammonium cation, N,N-diethyl-N-methyl-N-heptylammonium cation, N,N-diethyl-N-propyl-N-pentylammonium cation, triethylpropylammonium cation, triethylpentylammonium cation, triethylheptylammonium cation , N,N-dipropyl-N-methyl-N-ethylammonium cation, N,N-dipropyl-N-methyl-N-pentylammonium cation, N,N-dipropyl-N-butyl-N-hexylammonium cation, N , N-dipropyl-N,N-dihexylammonium cation, N,N-dibutyl-N-methyl-N-pentylammonium cation, N,N-dibutyl-N-methyl-N-hexylammonium cation, trioctylmethyl tetraalkylammonium cations having alkyl groups with different alkyl chain lengths, such as ammonium cations, N-methyl-N-ethyl-N-propyl-N-pentylammonium cations;
In addition, substituents and ether bonds having aromatic rings such as glycidyltrimethylammonium cation, diallyldimethylammonium cation, benzotributylammonium cation, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium cation ammonium cations with substituents having

As the imidazolium-based cation, specifically, for example,
1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium Cation, 1-octyl-3-methylimidazolium cation, 1-decyl-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1,2- dimethyl-3-propylimidazolium cation, 1-ethyl-2,3-dimethylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, 1-hexyl-2,3-dimethylimidazolium cation, etc. mentioned.

Specific examples of pyridinium-based cations include:
1-octyl-2-methylpyridinium cation, 1-octyl-3-methylpyridinium cation, 1-octyl-4-methylpyridinium cation, 1-octylpyridinium cation, 2-ethylhexylpyridinium cation, 1-ethylpyridinium cation, 1- butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-hexyl-3-methylpyridinium cation, 1-butyl-3,4- dimethylpyridinium cation, 1,1-dimethylpyrrolidinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-methyl-1-propylpyrrolidinium cation and the like.

Specific examples of piperidinium-based cations include, for example,
1-methyl-1-ethylpiperidinium cation, 1-methyl-1-butylpiperidinium cation, 1-butyl-1-butylpiperidinium cation, 1-octyl-1-octylpiperidinium cation, 1- butyl-1-octylpiperidinium cation and the like.

Specifically, pyrimidinium-based cations include, for example,
1,3-dimethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3,4- Tetramethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3,5-tetramethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,3-dimethyl-1, 4-dihydropyrimidinium cation, 1,3-dimethyl-1,6-dihydropyrimidinium cation, 1,2,3-trimethyl-1,4-dihydropyrimidinium cation, 1,2,3-trimethyl- 1,6-dihydropyrimidinium cation, 1,2,3,4-tetramethyl-1,4-dihydropyrimidinium cation, 1,2,3,4-tetramethyl-1,6-dihydropyrimidinium A cation etc. are mentioned.

Specific examples of pyrazolium-based cations include, for example,
1-methylpyrazolium cation, 3-methylpyrazolium cation, 1-ethyl-2-methylpyrazolinium cation and the like.

Specifically, pyrrolidinium-based cations include, for example,
1-dimethylpyrrolidinium, 1-methyl-1-ethylpyrrolidinium, 1-methyl-1-propylpyrrolidinium, 1-methyl-1-butylpyrrolidinium, 1-methyl-1-pentylpyrrolidinium , 1-methyl-1-hexylpyrrolidinium, 1-methyl-1-heptylpyrrolidinium, 1-ethyl-1-propylpyrrolidinium, 1-ethyl-1-butylpyrrolidinium, 1-ethyl- 1-pentylpyrrolidinium, 1-ethyl-1-hexylpyrrolidinium, 1-ethyl-1-heptylpyrrolidinium, 1,1-dipropylpyrrolidinium, 1-propyl-1-butylpyrrolidinium and 1,1-dibutylpyrrolidinium.

In addition, other nitrogen-containing cations include 1-ethyl-2-phenylindole cation, 1,2-dimethylindole cation, 1-ethylcarbazole cation, 4-(2-ethoxyethyl)-4-methylmorpholinium cation, and the like. mentioned.

Among the above nitrogen-containing cations, a nitrogen-containing cation having a nitrogen atom substituted with at least one alkyl group is particularly preferable in terms of excellent compatibility with the acrylic resin (A) described below and high durability. .

Among the above, imidazolium-based cations, pyridinium cations, and ammonium-based cations are preferred from the viewpoint of an excellent balance between antistatic performance and hydrolysis resistance, and alkylammonium cations are particularly preferred. It is preferably a tetraalkylammonium cation in which each group is substituted with an alkyl group. Tetraalkylammonium cations having alkyl groups with different alkyl chain lengths are preferred because they are less likely to precipitate from the pressure-sensitive adhesive layer.

Among the above tetraalkylammonium cations, tetraalkylammonium cations having a total carbon number of 4 to 48 are preferred, tetraalkylammonium cations having a total carbon number of 8 to 32 are particularly preferred, and tetraalkylammonium cations having a total carbon number of 10 to 16 are particularly preferred. Certain tetraalkylammonium cations are preferred. If the total number of carbon atoms is too large or too small, the compatibility with the acrylic resin tends to decrease.

Examples of the anion include
tetrafluoroborate anion [BF ₄ ⁻ ],
hexafluorophosphate anion [PF ₆ ⁻ ],
hexafluoroarsenate anion [AsF ₆ ⁻ ],
hexafluoroantimonate anion [SbF ₆ ⁻ ],
hexafluoroniobate anion [NbF ₆ ⁻ ],
hexafluorotantalate anion [TaF ₆ ⁻ ],
fluorine-containing inorganic anions such as;
N,N-bis(fluorosulfonyl)imide anion [(SO ₂ F) ₂ N ⁻ ]
N,N-bis(trifluoromethanesulfonyl)imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ], N,N-bis(pentafluoroethanesulfonyl)imide anion [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ] , fluorine-containing imide anions such as trifluoroacetate anions [CF ₃ COO ⁻ ],
Trifluoromethanesulfonate anion [CF ₃ SO ₃ ⁻ ]
perfluorobutanesulfonate anion [C ₄ F ₉ SO ₃ ⁻ ],
perfluorobutanoate anion [C ₃ F ₇ COO ⁻ ],
tris(trifluoromethanesulfonyl)methanide anion [(CF ₃ SO ₂ ) ₃ C ⁻ ],
etc.

Among them, fluorine-containing imide anions are preferable, and particularly preferably N,N-bis(perfluoroalkane Specifically, N,N-bis(trifluoromethanesulfonyl)imide and N,N-bis(pentafluoroethanesulfonyl)imide are preferred.

The ionic compound (D) used in the present invention can be appropriately selected from the combination of the above cationic component and anionic component. , a combination of a quaternary ammonium cation and a fluorine-containing imide anion is preferred. Specific examples include tributylmethylammonium N,N-bis(trifluoromethanesulfonyl)imide and trioctylmethylammonium N,N-bis(trifluoromethanesulfonyl)imide.

Furthermore, the melting point of the ionic compound (D) used in the present invention is preferably 120°C or less, particularly preferably 0 to 100°C, particularly preferably 10 to 80°C, and further preferably 15 to 50°C. be. If the melting point is too high, the ionic compound tends to precipitate at low temperatures. If the melting point is too low, it tends to move easily in the adhesive layer and promote hydrolysis of the base material, and tends to cause a decrease in the degree of polarization in a moist and hot environment when used for a polarizing plate. be.

The melting point of the ionic compound (D) is usually measured by a differential scanning calorimeter (DSC) and described in the catalogs of each company.

The content of the ionic compound (D) is preferably 0.5 to 30 parts by weight, particularly preferably 1 to 15 parts by weight, more preferably 2 parts by weight with respect to 100 parts by weight of the acrylic resin (A). ~10 parts by weight. If the content of the ionic compound (D) is too low, there is a tendency that sufficient antistatic performance cannot be obtained, and if it is too high, hydrolysis of the plastic substrate or the adherend tends to occur easily.

<Silane coupling agent (E)>
It is also preferable that the pressure-sensitive adhesive composition of the present invention contain a silane coupling agent (E) from the viewpoint of suppressing a decrease in adhesive strength in a moist heat environment when used on an adherend such as metal or glass. .

The silane coupling agent (E) is an organosilicon compound containing in its structure at least one reactive functional group and at least one alkoxy group bonded to a silicon atom.
Examples of the reactive functional group include epoxy group, (meth)acryloyl group, mercapto group, hydroxyl group, carboxyl group, amino group, amide group, and isocyanate group. From the point of view, a mercapto group and an epoxy group are preferable.

From the standpoint of durability and storage stability, the silicon-bonded alkoxy group preferably contains an alkoxy group having 1 to 8 carbon atoms, and particularly preferably a methoxy group or an ethoxy group.

The content of silicon-bonded alkoxy groups in the silane coupling agent (E) is preferably 5 to 80% by weight, particularly preferably 7 to 50% by weight, more preferably 8 to 30% by weight. . If the content is too low, the adhesiveness between the glass and the pressure-sensitive adhesive tends to be low, and durability tends to be low.

The reactive functional group equivalent weight of the silane coupling agent (E) is preferably 50-1000 g/mol, particularly preferably 100-850 g/mol, and still more preferably 200-650 g/mol. If the reactive functional group equivalent is too small, the reworkability tends to be lowered, and if it is too large, the durability under moist heat resistance conditions tends to be lowered.

In addition, 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) (oligomeric or polymeric silane coupling agent, etc.) is preferably 200 or more, particularly preferably 500 to 20,000, more preferably 2,000 to 15, 000. If the weight average molecular weight is too small, the long-term reworkability tends to deteriorate. In addition, when it is too large, the compatibility tends to decrease, bleeding 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.
Apparatus: Gel permeation chromatography Detector: Differential refractive index detector RI (RI-8020 type manufactured by Tosoh Corporation, sensitivity 32)
Column: TSKguardcolumn HHR-H (1 piece) (φ6 mm × 4 cm) manufactured by Tosoh Corporation, (TSKgelGMHHR-N (2 pieces) (φ7.8 mm × 30 cm), packing material: styrene-divinylbenzene copolymer Solvent: tetrahydrofuran ( THF)
Column temperature: 23°C Flow rate: 1.0 mL/min

Examples of the silane coupling agent (E) include
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4 epoxycyclohexyl) A monomer type epoxy group-containing silane coupling agent which is a silane compound such as ethyltrimethoxysilane, a part of the silane compound undergoes hydrolytic condensation polymerization, the silane compound and methyltriethoxysilane, ethyltriethoxysilane, Oligomeric epoxy group-containing silane coupling agents, which are silane compounds obtained by cocondensation of alkyl group-containing silane compounds such as methyltrimethoxysilane and ethyltrimethoxysilane;
Monomeric mercapto group-containing silane coupling agents that are silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethyldimethoxysilane, and the above A silane compound obtained by cocondensation of the above silane compound and an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane and ethyltrimethoxysilane, in which a part of the silane compound is hydrolytically condensation polymerized. An oligomeric mercapto group-containing silane coupling agent which is;
(Meth), such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, etc. acryloyl group-containing silane coupling agent;
N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, amino group-containing silane coupling agents such as N-phenyl-3-aminopropyltrimethoxysilane;
an isocyanate group-containing silane coupling agent such as 3-isocyanatopropyltriethoxysilane;
vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane;
These may be used independently and may use 2 or more types together.

Among these, an epoxy group-containing silane coupling agent and a mercapto group-containing silane coupling agent are preferably used. It is preferable in terms of improvement and prevention of excessive increase in adhesive strength.

In addition, the silane coupling agent (E) may be a monomer type silane coupling agent or an oligomer (or polymer) type silane coupling agent partially hydrolyzed and polycondensed, but has excellent durability and reworkability. It is preferable to use an oligomeric silane coupling agent because it is less likely to volatilize when the adhesive is dried after coating.

Specifically, as the silane coupling agent (E) used in the present invention, all commercially available products are manufactured by Shin-Etsu Chemical Co., Ltd.
"X-41-1059A" (weight average molecular weight: 2,270, containing functional group; epoxy group, containing silicon atom-bonded alkoxy group; methoxy group and ethoxy group, amount of silicon atom-bonded alkoxy group; 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, containing silicon atom-bonded alkoxy group amount; 50% by weight, functional group equivalent weight; 800 g/mol),
"X-24-9579A" (weight average molecular weight: 2,370, containing functional group; mercapto group, containing 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, contained functional group; epoxy group, contained silicon atom-bonded alkoxy group; methoxy group, contained silicon atom-bonded alkoxy group content; 9.5% by weight, functional group equivalent ; 592 g/mol),
"X-41-1818" (weight average molecular weight: 2,350, containing functional group; mercapto group, containing silicon atom-bonded alkoxy group; ethoxy group, containing silicon atom-bonded alkoxy group content; 60% by weight, functional group equivalent: 850 g /mol)
etc. should be used. Among these, "X-41-1059A", "X-41-1805", "X-24-9579A" and "X-24-9590" are preferable in terms of the balance between durability and reworkability.

The content of the silane coupling agent (E) is preferably 0.001 to 5 parts by weight, particularly preferably 0.005 to 1 part by weight, with respect to 100 parts by weight of the acrylic resin (A). More preferably, it is 0.01 to 0.5 parts by weight. If the content is too small, the durability tends to decrease, and if it is too large, the silane coupling agent tends to bleed, resulting in a decrease in durability.

Furthermore, the pressure-sensitive adhesive composition of the present invention may contain, as other components, resin components other than acrylic resins, acrylic monomers, polymerization inhibitors, antioxidants, and corrosion inhibitors as long as the effects of the present invention are not impaired. , various additives such as radical generators, peroxides, radical scavengers, metals, resin particles, and the like. In addition to the above, it may contain a small amount of impurities contained in raw materials for manufacturing constituent components of the pressure-sensitive adhesive composition.

The content of the above other components is preferably 5 parts by weight or less, particularly preferably 1 part by weight or less, and still more preferably 0.5 parts by weight or less based on 100 parts by weight of the acrylic resin (A). . If the content is too large, the compatibility with the acrylic resin (A) tends to decrease, resulting in a decrease in durability.

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 (especially cross-linking with a cross-linking agent (C)), and a pressure-sensitive adhesive layer containing such a pressure-sensitive adhesive is laminated on a substrate such as a plastic film. By forming, a pressure-sensitive adhesive sheet can be obtained.
It is preferable that the pressure-sensitive adhesive sheet is further provided with a release film on the side of the pressure-sensitive adhesive layer opposite to the base film.

As a method for manufacturing the pressure-sensitive adhesive sheet,
[1] A method of applying and drying a pressure-sensitive adhesive composition on a base film, laminating a release sheet, and performing at least one of aging at room temperature or in a heated state,
[2] There is a method of coating a release sheet with a pressure-sensitive adhesive composition, drying it, laminating a base film, and subjecting it to at least one of aging at room temperature or in a heated state.
Among these methods, the method [2], in which aging is performed at room temperature, is preferable because the base film is not damaged by heat and the adhesion between the base film and the pressure-sensitive adhesive layer is excellent.

Such an aging treatment is carried out in order to balance the adhesive physical properties as the reaction time for chemical cross-linking of the adhesive. It is 1 to 30 days, specifically, for example, 1 to 20 days at 23° C., 3 to 10 days at 23° C., 1 to 7 days at 40° C., and the like.

When applying the pressure-sensitive adhesive composition, it is preferable to apply the pressure-sensitive adhesive composition after diluting it with a solvent. ~30% by weight. The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition. Ketone solvents such as methyl isobutyl ketone, aromatic solvents such as toluene and xylene, and alcohol solvents such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate and methyl ethyl ketone are preferably used in terms of solubility, drying property, price, and the like.

Application of the pressure-sensitive adhesive composition is carried out by conventional methods such as roll coating, die coating, gravure coating, comma coating and screen printing.

The thickness of the pressure-sensitive adhesive layer in the resulting pressure-sensitive adhesive sheet is preferably 5-100 μm, particularly preferably 10-50 μm, further preferably 10-30 μm.
If the pressure-sensitive adhesive layer is too thin, the thickness precision tends to be low and the adhesive strength tends to be low.

The gel fraction of the pressure-sensitive adhesive layer produced by the above method is preferably 30% or more, particularly preferably 40% or more, in terms of adhesion to the substrate, reworkability, and holding power. Preferably it is 60% or more. The upper limit of the gel fraction is usually 100%, preferably 95%. If the gel fraction is too low, the cohesive force tends to be low, and adhesive residue tends to be left during reworking, and the holding power tends to be low.

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

The pressure-sensitive adhesive layer produced by the above method preferably has a moderate tackiness when touched with a finger, because it has good wettability when actually applied to an adherend, and workability tends to increase, which is preferable. .
Tack is measured by ball tack at an inclination angle of 30° specified in JIS Z0237 (2009). 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 PSA sheet to an adherend when it is attached.

The surface resistance value of the pressure-sensitive adhesive layer (for example, the pressure-sensitive adhesive layer containing the ionic compound (D)) is preferably less than 1.0×10 ¹² Ω/cm ² , particularly preferably 1×10 less than ¹¹ Ω/cm ² . If the surface resistance value is too high, when the release film is peeled off or the pressure-sensitive adhesive sheet is peeled off from the adherend, it is likely to be electrically charged, causing dust to adhere to the pressure-sensitive adhesive layer. In that case, the liquid crystal tends to be affected and display defects tend to occur.

The pressure-sensitive adhesive sheet of the present invention is used either directly or, if it has a release sheet, after peeling off the release sheet, the pressure-sensitive adhesive layer surface is adhered to the surface of the adherend.

The pressure-sensitive adhesive obtained from the pressure-sensitive adhesive composition of the present invention can suppress deterioration of the pressure-sensitive adhesive even in a high-temperature and high-humidity environment.
Furthermore, the object of the present invention is remarkably achieved when a hydrolyzable plastic film (for example, a substrate and/or an adherend made of a hydrolyzable plastic film) is provided.

Therefore, it can be suitably used as an adhesive for various members such as surface protection films, display labels, curing tapes, optical films and polarizing plates, but it is preferably used as an adhesive for optical members used for laminating optical members. In particular, it is suitable for bonding a polarizing plate and glass, and is preferably used as an adhesive for polarizing plates (adhesive for use in polarizing plates).

Examples of the protective film that constitutes the polarizing plate include triacetyl cellulose film, acrylic film, polyethylene film, polypropylene film, cycloolefin film, etc. The present invention is applicable to the polarizing plate using any of the protective films. In particular, a polarizing plate laminated with a triacetyl cellulose film or a polyester film is preferable because the effect of the present invention can be easily obtained.

The pressure-sensitive adhesive layer-attached polarizing plate 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 a polarizing plate.

EXAMPLES The present invention will be described in more detail below 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, "parts" and "%" mean weight standards.

Further, the weight average molecular weight and degree of dispersion 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) is calculated using the above-mentioned Fox formula, and the glass transition temperature of the homopolymer of the monomers constituting the acrylic resin (A) is usually measured by DSC. The literature value and the catalog description value were used.

<Preparation of acrylic resin (A)>
[Acrylic resin (A-1)]
92 parts of normal butyl acrylate (BA), 8 parts of 4-hydroxybutyl acrylate (4HBA), 63 parts of ethyl acetate, and 42 parts of acetone and 0.012 parts of 2,2-azobisisobutyronitrile (AIBN) as a polymerization initiator were charged, and the temperature was raised to the boiling point to initiate the reaction, followed by 2,2-azobis-2,4-dimethylvalero. A mixed solution of 0.012 parts of nitrile (ADVN) and 30 parts of ethyl acetate was added dropwise and reacted at reflux temperature for 3.25 hours. A solution (solid content: 21.1%, viscosity: 5,320 mPa·s/25°C) was obtained.

<Carbodiimide compound (B)>
Polymer-type carbodiimide (B-1) having the following structure as the carbodiimide compound (B) having an oxyalkylene structure (carbodiimide group equivalent: 336 g/mol, type of oxyalkylene structure: polyethylene oxide structure, weight average molecular weight Mw: 2950) prepared.

（式中、ｎ＝９．３、ｍ＝１１．６）

(where n = 9.3, m = 11.6)

As a carbodiimide compound (B'-1) having no oxyalkylene structure, a compound having the following structure (carbodiimide group equivalent: 200 g/mol, weight average molecular weight Mw: 6812) was prepared.

（式中、ｌ＝３２．３）

(where l = 32.3)

The above structure and molecular weight were measured and identified by NMR under the following conditions.

measurement:
About 50 mg of the sample was dissolved in 1 mL of d-DMSO to prepare a 5 w/v% solution. NMR measurement was performed on this under the following conditions.
<Measurement conditions>
Measuring device: AscendTM400 manufactured by Bruker
Probe: cryo probe pulse program: zg45
Measurement temperature: 23°C (296K)
Accumulated times: 16 times D1: 10 sec

The presence or absence of an oxyalkylene structure was confirmed from the peaks obtained by the measurement.
Also, the average number of repeating units of the carbodiimide group and the oxyalkylene structural group was obtained from the assignment of each peak.

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

<Ionic compound (D)>
The following ionic compounds were prepared.
(D-1): 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): Epoxy oligomer type silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., "X-41-1059A")
(E-2): "X-41-1059A": "X-24-9590"("X-24-9590": manufactured by Shin-Etsu Chemical Co., Ltd., epoxy-based oligomeric silane coupling agent) = 1:2 formulation Stuff

<Examples 1-2, Comparative Examples 1-5>
The components prepared and prepared as described above were blended as shown in Table 1 below, and this was adjusted to a solid concentration of 12.5% with ethyl acetate to obtain a pressure-sensitive adhesive composition.
The following evaluation was performed using the obtained adhesive composition.

[Preparation of pressure-sensitive adhesive layer-attached polarizing plate [I]]
The resulting pressure-sensitive adhesive composition was applied to a 38 μm polyester release film ("Therapeal WZ" manufactured by Toray Industries, Inc.) so that the thickness after drying was 25 μm, dried at 100 ° C. for 3 minutes, and then applied to a polyester film (PET film) and a triacetyl cellulose film with a retardation function (retardation TAC film) are laminated on one side of the retardation TAC film surface of the polarizing plate, and the pressure-sensitive adhesive layer surface on the opposite side of the separator is attached, and the pressure is applied at 23 ° C. × 50%. After aging for 7 days in a RH environment, an adhesive layer-attached polarizing plate [I] was obtained (layer structure: release film/adhesive layer/retardation TAC film/polarizer/PET film).

[Preparation of pressure-sensitive adhesive layer-attached separator film [II]]
The resulting pressure-sensitive adhesive composition was applied to a 38 μm polyester release film (“Therapeel WZ” manufactured by Toray Industries, Inc.) so that the thickness after drying was 25 μm, dried at 100 ° C. for 3 minutes, and then coated with a 38 μm polyester release film. A mold film ("SP0338BU" manufactured by Mitsui Tocello Co., Ltd.) was laminated and cured for 7 days in an environment of 23 ° C. × 50% RH to obtain a separator film [II] with an adhesive layer (layer structure: light release film / adhesive layer/heavy release film).

[Crystal deposition time and evaluation of whitening of pressure-sensitive adhesive layer]
Using the obtained pressure-sensitive adhesive layer-attached polarizing plate [I], the effect of the pressure-sensitive adhesive for suppressing crystal precipitation was evaluated as follows.
The adhesive layer-attached polarizing plate [I] was cut to 16 cm × 9.5 cm, the release film was peeled off, and the adhesive layer surface was pressed against alkali-free glass ("Eagle XG" manufactured by Corning: thickness 0.7 mm). After sticking together by reciprocating twice with a 2 kg roller, autoclave treatment (0.5 Mpa x 50°C x 20 minutes) was performed to prepare a sample for testing the effect of suppressing crystal precipitation.
A test sample was placed under conditions of 80° C. and 90% RH, and the time until crystal precipitation was evaluated.
The whitening of the adhesive layer was evaluated by visually observing the adhesive layer after 650 hours under the conditions of 80° C. and 90% RH.

[Evaluation of antistatic performance]
After the pressure-sensitive adhesive layer-attached polarizing plate [I] obtained above was allowed to stand in an atmosphere of 23°C × 50% RH for 24 hours, the separator release film was peeled off, and a surface resistivity measuring device (Mitsubishi Chemical Analytech Co., Ltd. The surface resistivity of the pressure-sensitive adhesive layer was measured using a device name "Hiresta-UP MCP-HT450" manufactured by the company.

[Adhesive force]
The pressure-sensitive adhesive layer-attached polarizing plate [I] obtained above was cut to a width of 25 mm, the separator release film was removed, and a 2 kg roller was placed on an alkali-free glass ("Eagle XG" manufactured by Corning, Inc.: thickness 1.1 mm). After laminating and autoclave treatment (0.5 Mpa × 50 ° C. × 20 minutes), (1) 24 hours (1 day) in a 23 ° C. × 50% RH environment, (2) 480 hours ( 20 days), and the adhesive force was measured when peeled off at an angle of 180°.

[Gel fraction]
Using the adhesive layer-attached separator film [II] obtained above, the adhesive was collected by picking from the adhesive layer formed on the separator, and the adhesive was wrapped in a 200-mesh SUS wire mesh and placed in ethyl acetate. It was immersed at 23°C for 24 hours, and the weight percentage of the undissolved adhesive component remaining in the wire mesh was measured to determine the gel fraction.

The results of the above Examples and Comparative Examples are shown in Table 1 below. In the table, the number for each component indicates "parts by weight" unless otherwise specified.

From the above results, in Examples 1 and 2, in which an adhesive containing a relatively large amount of a carbodiimide compound having an oxyalkylene structure was used, crystal precipitation due to hydrolysis of the TAC film was suppressed, and whitening of the adhesive layer was also observed. It can be seen that there is no occurrence and the transparency is excellent.
On the other hand, in Comparative Examples 1 and 2 using a carbodiimide compound having no oxyalkylene structure, crystal precipitation could be suppressed, but the pressure-sensitive adhesive layer was whitened and inferior in transparency.
In addition, it can be seen that Comparative Examples 3 to 5, in which no carbodiimide compound is used or the amount used is small, is inferior in crystal precipitation suppressing performance.

The pressure-sensitive adhesive obtained using the pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive having hydrolysis resistance and durability, and further suppresses crystal precipitation in the pressure-sensitive adhesive layer under a high-temperature and high-humidity environment. is possible. Therefore, such adhesives can be suitably used as adhesives for various members such as surface protection films, display labels, curing tapes, optical films, and polarizing plates, and in particular, can be suitably used as adhesives for optical members. can. Furthermore, it is particularly useful as a pressure-sensitive adhesive for polarizing plates having protective films susceptible to hydrolysis, such as triacetyl cellulose films and polyester films.

Claims (8)

Contains an acrylic resin (A), a carbodiimide compound (B) having an oxyalkylene structure, and a cross-linking agent (C), wherein the content of the carbodiimide compound (B) having an oxyalkylene structure is 100 parts by weight of the acrylic resin (A) 1 to 30 parts by weight, and the acrylic resin (A) is an acrylic resin in which the content of the carboxyl group-containing monomer is 0.5% by weight or less with respect to the entire polymerization component. A pressure-sensitive adhesive composition for optical members . 2. The adhesive for optical members according to claim 1, wherein the acrylic resin (A) contains 0.1% by weight or less of the carboxyl group-containing monomer relative to the total polymerization components. agent composition. 3. The pressure-sensitive adhesive composition for optical members according to claim 1, wherein the carbodiimide group equivalent of the carbodiimide compound (B) having an oxyalkylene structure is 1000 g/mol or less. The adhesive for optical members according to any one of claims 1 to 3, wherein the content of the cross-linking agent (C) is 0.01 to 10 parts by weight with respect to 100 parts by weight of the acrylic resin (A). agent composition. 5. A pressure-sensitive adhesive for optical members, which is obtained by cross-linking the pressure-sensitive adhesive composition according to any one of claims 1 to 4. 6. The pressure-sensitive adhesive for optical members according to claim 5, which is used for a hydrolyzable plastic film. 7. The pressure-sensitive adhesive for optical members according to claim 5, which is used for a polarizing plate. A pressure-sensitive adhesive sheet for an optical member , comprising a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive according to any one of claims 5 to 7.