JP2007138015A - Adhesive and adhesive sheet using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive which is excellent in low temperature characteristics and is excellent in balance characteristics between high adhesive force and high cohesive power, and to provide an adhesive sheet which uses the same and is excellent in processability. <P>SOLUTION: This adhesive comprises a copolymer (a) which is produced by copolymerizing iso-butyl methacrylate in an amount of 8 to 35 wt.% per 100 wt.% of the total amount of monomers with one or more copolymerization monomers, and has at least one kinds of carboxy groups and hydroxy groups and a weight-average mol.wt. of 400,000 to 1,200,000, and a cross-linking agent having at least one of carboxy group and hydroxy group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive capable of forming a pressure-sensitive adhesive sheet excellent in processability, and a pressure-sensitive adhesive sheet using the pressure-sensitive adhesive.

Conventionally, various adhesives are used for various applications. Acrylic adhesives are widely used because of their excellent weather resistance, durability, heat resistance, transparency, and the like.
Among them, a solvent-type acrylic pressure-sensitive adhesive, particularly an acrylic pressure-sensitive adhesive used in combination with a crosslinking agent, is widely used in pressure-sensitive adhesive sheets because it can easily control the adhesive force.

The pressure-sensitive adhesive sheet in the present invention is a general term for so-called pressure-sensitive adhesive coated products, and includes various forms such as a tape and a label in addition to a relatively large sheet. The adhesive strength required for each application is different, but the cohesive strength of the adhesive layer is required to be sufficiently large when processed into various forms.
When processing a relatively large pressure-sensitive adhesive sheet according to various forms such as a label and a tape, it is processed by various processing methods such as punching, slitting, and cutting. For example, the punching process refers to a process of punching a small piece of a desired shape, that is, a relatively small pressure-sensitive adhesive sheet, from a relatively large pressure-sensitive adhesive sheet using a punching die with a blade having a desired shape. Slit processing is a processing method in which a blade is inserted into a wide adhesive sheet and cut into a desired width.
The cutting process refers to the sheet substrate and adhesive layer, and cuts patterns such as desired characters, pictures, patterns, and drawings into the sheet substrate and the adhesive layer. It is the processing method which forms the pattern affixed on a body on a peelable sheet. In this processing method, the sheet-like base material and the pressure-sensitive adhesive layer are usually used after being removed from the peelable sheet except for the pattern to be attached to the adherend.
There is also a process of obtaining a narrow pressure-sensitive adhesive sheet by winding a wide pressure-sensitive adhesive sheet into a roll and then cutting it into a roll.
Each of these processing methods is a method of cutting and processing by inserting a blade into an adhesive sheet in common even if each method is different.

  However, since acrylic adhesives generally have a weak cohesive force, they may cause problems such as protrusion of the adhesive layer and blade contamination when the above processing is performed. In order to solve these problems, there are known methods for curing acrylic resins with functional groups introduced with various crosslinking agents, methods for increasing the glass transition temperature of acrylic resins, and methods for increasing the molecular weight of acrylic resins. Yes. However, these methods have a large temperature dependence of physical properties, such as a decrease in adhesive strength and a decrease in tack, and a decrease in low-temperature physical properties, making it difficult to balance high adhesive strength and high cohesive strength to a high degree. There was a difficulty.

  As a method for improving the punching workability, for example, Patent Document 1 proposes to use a polyethylene terephthalate foam. As a method for improving the cutting property, for example, Patent Document 2 proposes adding a filler to a resin of a film base material. However, this is not a means for fundamentally solving the sticking out of the pressure-sensitive adhesive layer and blade contamination.

  As a method for improving the cohesive force of the acrylic pressure-sensitive adhesive layer, for example, Patent Document 3 proposes using polyester having a polycarbonate structure in order to improve the adhesive force and cohesive force of the pressure-sensitive adhesive. However, with this technique, it has been difficult to balance low-temperature characteristics even though the adhesive force and cohesive force can be improved.

Patent Document 4 proposes a pressure-sensitive adhesive that uses alkyl methacrylate as the re-peeling adhesive for the purpose of suppressing an increase in peel strength with time, and uses 43 parts by weight of iso-butyl methacrylate in Example 2. ing. However, according to the calculation method of the glass transition temperature described in this specification, the composition of this example is as high as −6.1 ° C., and has low tack and adhesive strength. Although it has sufficient adhesive strength for re-peeling, it is not suitable for the pressure-sensitive adhesive and pressure-sensitive adhesive sheet that are excellent in low-temperature characteristics and excellent in balance characteristics between high adhesive strength and high cohesive strength.
JP-A-8-60104 Japanese Patent Laid-Open No. 5-65349 JP 2000-230164 A JP 2002-363521 A

  An object of this invention is to provide the adhesive sheet which is excellent in low-temperature characteristics, and was excellent in the balance characteristic of high adhesive force and high cohesive force, and the adhesive sheet excellent in workability using the same.

  The first invention is obtained by copolymerizing 8 to 35% by weight of iso-butyl methacrylate with 100% by weight of the total amount of monomers and another copolymerizable monomer, having at least one of a carboxyl group or a hydroxyl group, and having a weight average The present invention relates to a pressure-sensitive adhesive containing a copolymer (a) having a molecular weight of 400,000 to 1,200,000 and a crosslinking agent having a functional group capable of reacting with at least one of a carboxyl group and a hydroxyl group.

  The second invention is a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive according to the first invention is laminated on at least one surface of a sheet-like base material (however, a polyester-based material is used as the sheet-like base material) Except when a film is used and the pressure-sensitive adhesive layer is laminated on both sides thereof).

  By using the pressure-sensitive adhesive of the present invention, it is possible to provide a pressure-sensitive adhesive sheet that is excellent in low-temperature characteristics, has a balance between high adhesive strength and high cohesive strength, and has excellent workability.

  The pressure-sensitive adhesive of the present invention is obtained by copolymerizing 8 to 35% by weight of iso-butyl methacrylate and another copolymerizable monomer in 100% by weight of the total amount of monomers, and has at least one of a carboxyl group or a hydroxyl group, and has a weight. It is a pressure-sensitive adhesive containing a copolymer (a) having an average molecular weight of 400,000 to 1,200,000 and a crosslinking agent having a functional group capable of reacting with at least one of a carboxyl group or a hydroxyl group.

  Iso-butyl methacrylate, which is an essential component of the monomer constituting the copolymer (a) used in the present invention, improves the coating strength of the pressure-sensitive adhesive layer with a small amount of use compared to other acrylic copolymerizable monomers. Is possible. Therefore, by using iso-butyl methacrylate, it is possible to improve the cohesive force of the pressure-sensitive adhesive layer without reducing the basic adhesive physical properties required for the pressure-sensitive adhesive sheet, such as tackiness and tackiness. As a result, when processed as an adhesive sheet, the workability can be greatly improved.

Even when normal-butyl methacrylate, which is the structural isomer, is used instead of iso-butyl methacrylate, the cohesive force cannot be improved, and an adhesive sheet with excellent processability cannot be obtained.
Even if iso-butyl acrylate is used in place of iso-butyl methacrylate, the improvement of cohesion cannot be expected.

It is important that the copolymer (a) used in the present invention has at least one of a carboxyl group or a hydroxyl group as a functional group involved in the reaction with a crosslinking agent described later. In order for the copolymer (a) to have at least one of a carboxyl group or a hydroxyl group, a monomer having at least one of a carboxyl group or a hydroxyl group is used as a monomer that can be copolymerized with iso-butyl methacrylate.
Examples of the copolymerizable monomer having at least one of a carboxyl group and a hydroxyl group include alkenyl group-containing compounds, α, β-unsaturated carboxylic acid esters and α, β-unsaturated carboxylic acids having at least one of a carboxyl group and a hydroxyl group. Is mentioned.
Examples of the monomer having at least one carboxyl group in addition to the radical polymerizable unsaturated group include (meth) acrylic acid, itaconic anhydride, itaconic acid, crotonic acid, maleic anhydride, maleic acid, 2- (meta ) Acrylyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid and the like.
Examples of the monomer having at least one hydroxyl group in addition to the radical polymerizable unsaturated group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. , 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylhexyl) -methyl acrylate, chloro- 2-hydroxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate, caprolactone-modified (meth) acrylates, polyethylene glycol (meth) acrylates, polypropylene glycol (meth) acrylate Relate, and the like can be mentioned.

Examples of other copolymerizable monomers used in obtaining the copolymer (a) used in the present invention include compounds having a polymerizable double bond in the molecule called α, β-unsaturated compound. Acrylic monomers are preferred from the viewpoints of copolymerization with tert-butyl methacrylate and adhesive properties.
For example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl acrylate, t- (meth) acrylate Butyl, n-amyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, (meth) acrylic acid Alkyl (meth) acrylates such as decyl, dodecyl (meth) acrylate, octadecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate;
(Meth) acrylic acid cyclic esters such as cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate;
Allyl (meth) acrylate, 1-methylallyl (meth) acrylate, 2-methylallyl (meth) acrylate, 1-butenyl (meth) acrylate, 2-butenyl (meth) acrylate, (meth) acrylic acid 3- Butenyl, 1,3-methyl-3-butenyl (meth) acrylate, 2-chloroallyl (meth) acrylate, 3-chloroallyl (meth) acrylate, o-allylphenyl (meth) acrylate, (meth) acrylic acid 2- (allyloxy) ethyl, allyl lactyl (meth) acrylate, citronellyl (meth) acrylate, geranyl (meth) acrylate, rosinyl (meth) acrylate, cinnamyl (meth) acrylate, vinyl (meth) acrylate, etc. Unsaturated group-containing (meth) acrylic acid esters;
Heterocycle-containing (meth) acrylic acid esters such as (meth) acrylic acid glycidyl, (meth) acrylic acid (3,4-epoxycyclohexyl) methyl, (meth) acrylic acid tetrahydrofurfuryl;
Amino groups such as N-methylaminoethyl (meth) acrylate, N-tributylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and N, N-diethylaminoethyl (meth) acrylate Containing (meth) acrylic acid esters;
Alkoxysilyl such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltriisopropoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane Group-containing (meth) acrylic acid esters;
(Meth) acrylic acid derivatives such as (meth) acrylic acid methoxyethyl, ethylene oxide adducts of (meth) acrylic acid;
(Meth) acrylic acid perfluoroalkyl esters such as (meth) acrylic acid perfluoroethyl, (meth) acrylic acid perfluoropropyl, (meth) acrylic acid perfluorobutyl, (meth) acrylic acid perfluorooctyl;
Trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, 1,1,1-trishydroxymethylethane diacrylate, 1,1,1-trishydroxymethylethane triacrylate, 1,1, 1-trishydroxymethylpropane polyfunctional (meth) acrylic acid esters such as triacrylic acid;
Perfluoromethyl (meth) acrylate, trifluoromethyl methyl (meth) acrylate, 2-trifluoromethyl ethyl (meth) acrylate, diperfluoromethyl methyl (meth) acrylate, 2-par (meth) acrylate Fluoroethylethyl, 2-perfluoromethyl-2-perfluoroethylmethyl (meth) acrylate, triperfluoromethylmethyl (meth) acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth) acrylate Fluorine-containing (meth) acrylic acid esters such as 2-perfluorohexylethyl (meth) acrylate, 2-perfluorodecylethyl (meth) acrylate, 2-perfluorohexadecylethyl (meth) acrylate;
Examples thereof include, but are not limited to, acrylic monomers. These may use only 1 type or may use multiple types together.

Other monomers such as vinyl monomers copolymerizable with acrylic monomers can also be used.
For example, aromatic vinyl systems such as styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 1-butylstyrene, chlorostyrene, styrenesulfonic acid and sodium salts thereof monomer;
Trialkyloxysilyl group-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane;
silicon-containing vinyl monomers such as γ- (methacryloyloxypropyl) trimethoxysilane;
Nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile;
Amide group-containing vinyl monomers such as acrylamide and methacrylamide;
Vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, vinyl cinnamate;
Fluorine-containing monomers such as perfluoroethylene, perfluoropropylene, vinylidene fluoride;
However, it is not particularly limited to these. These may use only 1 type or may use multiple types together.

The copolymer (a) used in the present invention radically polymerizes iso-butyl methacrylate, a monomer having at least one of a carboxyl group or a hydroxyl group, and, if necessary, another copolymerizable monomer in an organic solvent. Can be obtained.
The amount of iso-butyl methacrylate used is important to be 8 to 35% by weight, preferably 10 to 25% by weight, based on a total of 100% by weight of monomers used for polymerization. If iso-butyl methacrylate is less than 8% by weight, the pressure-sensitive adhesive layer cannot be expected to improve the cohesive strength, and a pressure-sensitive adhesive sheet with excellent processability cannot be obtained. On the other hand, when the amount of iso-butyl methacrylate is more than 35% by weight, the adhesive strength and tack are lowered, and the adhesion to the substrate tends to be lowered.

The monomer having a carboxyl group used for obtaining the copolymer (a) is a copolymer of 1 to 10% by weight out of a total of 100% by weight of the monomers to be polymerized from the viewpoint of adhesive strength and cohesive strength as an adhesive. It is preferable to do.
If the monomer having a carboxyl group is less than 1% by weight, it is difficult to obtain a sufficient adhesive force, the cohesive force of the adhesive layer tends to be lowered, and an adhesive sheet having excellent processability is hardly obtained. On the other hand, if the monomer having a carboxyl group is used in an amount of more than 10% by weight, the adhesion to the tack or the substrate tends to be lowered. More preferably, it is 2 to 6% by weight.
The monomer having a hydroxyl group used for obtaining the copolymer (a) is mainly used when an isocyanate compound is used as a cross-linking agent, and 0.01% of the total 100% by weight of monomers used for polymerization. It is preferred to copolymerize ~ 5% by weight. If it is less than 0.01% by weight, it is difficult to obtain sufficient adhesive force, the cohesive force of the adhesive layer tends to decrease, and an adhesive sheet having excellent processability cannot be obtained. On the other hand, if the monomer having a hydroxyl group is used in an amount of more than 5% by weight, the adhesion to the tack and the substrate tends to be lowered. More preferably, it is 0.05 to 2% by weight.
A monomer containing a carboxyl group or a monomer containing a hydroxyl group can be used alone or in combination.

The copolymer (a) used in the present invention is composed of 2-ethylhexyl acrylate and acrylic which can form a homopolymer having a glass transition temperature (Tg) of −50 ° C. or lower among the other copolymerizable monomers described above. An acrylic acid ester having an alkyl side chain such as n-butyl acid, octyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, etc. is used in an amount of 55 to 91% by weight in 100% by weight of the copolymerizable monomer. It is preferable that these may be used alone or in combination.
The copolymer (a) used in the present invention is an alkenyl group-containing compound or α, β- which can form a homopolymer having a Tg in the range of −30 to 120 ° C. among the other copolymerizable monomers described above. Unsaturated carboxylic acid esters can be used as appropriate.

It is preferable to copolymerize iso-butyl methacrylate and the various monomers described above so that a copolymer (a) having a glass transition temperature (Tg) of −70 to −5 ° C. can be formed. More preferably, it is −55 to −15 ° C.
In the case of a pressure-sensitive adhesive using a copolymer having a Tg of less than −70 ° C., the cohesive force of the formed pressure-sensitive adhesive layer is reduced, making it difficult to obtain a pressure-sensitive adhesive sheet with excellent processability.
On the other hand, in the case of a pressure-sensitive adhesive using a polymer having a glass transition temperature exceeding −5 ° C., the low-temperature characteristics of the pressure-sensitive adhesive sheet are deteriorated, and sufficient adhesive force and tack cannot be obtained, and the adhesion to the substrate is decreased. There is a possibility that.

As an organic solvent used when polymerizing the copolymer (a), ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone and the like are used. These polymerization solvents may be used as a mixture of two or more.
Examples of the polymerization initiator used when polymerizing the copolymer (a) include benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, t-butyl peroxybenzoate, and t-butyl peroxy. Organic peroxide polymerization initiators such as neodecanoate and t-butylperoxy 2-ethylhexanoate; 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobiscyclohexane Although radical polymerization initiators, such as azo polymerization initiators, such as carbonitrile, are mentioned, it is not specifically limited. Only one kind of these polymerization initiators may be used, or two or more kinds may be appropriately mixed and used. What is necessary is just to set the usage-amount of a polymerization initiator according to a composition, reaction conditions, etc. of the monomer with which it superposes | polymerizes, and it does not specifically limit.

Further, when the copolymer (a) is polymerized, a chain transfer agent can also be used.
Examples of chain transfer agents that can be used include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, dodecyl mercaptan, thioglycolic acid esters such as octyl thioglycolate, nonyl thioglycolate, and 2-ethylhexyl thioglycolate. 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, and the like. In particular, when thioglycolic acid esters, 2,4-diphenyl-4-methyl-1-pentene, and 1-methyl-4-isopropylidene-1-cyclohexene are used, the resulting copolymer has a low odor. preferable.
In addition, when using a chain transfer agent, it is used in about 0.001-3 weight part with respect to a total of 100 weight part of the monomer to superpose | polymerize.
Moreover, a polymerization reaction is normally performed over 2-8 hours on 40-100 degreeC temperature conditions.

It is important that the weight average molecular weight of the copolymer (a) is 400,000 to 1,200,000, and preferably 700,000 to 1,000,000. When the weight average molecular weight is less than 400,000, even if a crosslinking agent is added, the cohesive force of the pressure-sensitive adhesive layer is insufficient, and a pressure-sensitive adhesive sheet with excellent processability cannot be obtained. Moreover, when it exceeds 1,200,000, sufficient adhesive force and tack cannot be obtained, and the adhesiveness with respect to a base material will fall.
In addition, the pressure-sensitive adhesive in the present invention may be blended with a pressure-sensitive adhesive resin having a composition or molecular weight other than the range specified in the present invention, as long as the object of the present invention is not impaired.

The pressure-sensitive adhesive of the present invention contains the copolymer (a) as a so-called main ingredient and a crosslinking agent.
A crosslinking agent has a functional group which can react with at least one of the carboxyl group or hydroxyl group which the said copolymer (a) has. Examples of such a crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, an aziridine crosslinking agent, an amine crosslinking agent, a carbodiimide compound, an oxazoline compound, and a melamine compound. By using the crosslinking agent, the cohesive force of the pressure-sensitive adhesive layer can be further improved. Only one kind of these crosslinking agents may be used, or two or more kinds may be used in combination.

Here, examples of the isocyanate-based crosslinking agent include aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, and alicyclic polyisocyanate.
Aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-triisocyanate. Range isocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 " -Triphenylmethane triisocyanate etc. can be mentioned.
Aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate. 2,4,4-trimethylhexamethylene diisocyanate and the like.
Examples of the araliphatic polyisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene, , 4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like.
Examples of alicyclic polyisocyanates include 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl- Examples include 2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4′-methylene bis (cyclohexyl isocyanate), 1,4-bis (isocyanate methyl) cyclohexane and the like.

In addition, a trimethylolpropane adduct of the above polyisocyanate, a trimer having an isocyanurate ring, etc. can be used in combination. Polyphenylmethane polyisocyanate (PAPI), naphthylene diisocyanate, and these polyisocyanate modified products can be used. As the polyisocyanate-modified product, a carbodiimide group, a uretdione group, a uretoimine group, a burette group reacted with water, a group of isocyanurate groups, or a modified product having two or more of these groups can be used. A reaction product of a polyol and a diisocyanate can also be used as a polyisocyanate.
These polyisocyanate compounds include 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), xylylene diisocyanate, 4,4′-methylenebis. From the viewpoint of weather resistance, it is particularly preferable to use a non-yellowing or hardly yellowing polyisocyanate compound such as (cyclohexyl isocyanate) (hydrogenated MDI).

Examples of epoxy crosslinking agents include bisphenol A-epichlorohydrin type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol. Diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) And cyclohexane.

  Examples of metal chelate-based crosslinking agents include chelate compounds composed of acetylacetone and acetone esters of divalent or higher metals such as aluminum, copper, iron, tin, zinc, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Is mentioned.

  Examples of the aziridine-based crosslinking agent include trimethylolpropane-tri-β-aziridinylpropionate, bisisophthaloyl-1- (2-methylaziridine), and the like.

  As the amine-based crosslinking agent, any polyamine having two or more primary amino groups can be used without particular limitation. A polyamine having two or more primary amino groups that are not directly bonded to the aromatic ring, that is, the primary amino group is directly bonded to an aliphatic functional group or an alicyclic functional group because of its excellent curing speed. Aliphatic polyamines are preferred. The aliphatic polyamine may contain an aromatic ring in its skeleton as long as the aromatic ring is not directly bonded to the primary amino group.

Aliphatic polyamines include 2,5-dimethyl-2,5-hexamethylenediamine, mensendiamine, 1,4-bis (2-amino-2-methylpropyl) piperazine, and propylene branched carbon at both ends of the molecule. Polypropylene glycol to which an amino group is bonded [a diamine having a propylene skeleton, such as “Jefamine D230” and “Jefamine D400” manufactured by Sun Techno Chemical Co., Ltd.], and a triamine having a propylene skeleton, such as “Jeffamine T403”. ], Ethylenediamine, propylenediamine, butylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, trimethylhexamethylenediamine, N-aminoethylpiperazine, 1,2-diaminopropane, iminobispropyl Amines such as amine, methyliminobispropylamine, H ₂ N (CH ₂ CH ₂ O) ₂ (CH ₂ ) ₂ NH ₂ [“Jefamine EDR148” (diamine with ethylene glycol skeleton) manufactured by Sun Techno Chemical Co.] Polyether skeleton diamine, 1,5-diamino-2-methylpentane ("MPMD" manufactured by DuPont Japan), metaxylylenediamine (MXDA), polyamidoamine (Sanwa Chemical) "X2000"), isophoronediamine, 1,3-bisaminomethylcyclohexane ("1,3BAC" manufactured by Mitsubishi Gas Chemical Company), 1-cyclohexylamino-3-aminopropane, 3-aminomethyl-3,3,5 -Trimethyl-cyclohexylamine, dimethyleneamine having a norbornane skeleton (“NBDA” manufactured by Mitsui Chemicals) and the like.
Among these, since the curing rate is particularly high, 1,3-bisaminomethylcyclohexane, dimethyleneamine having a norbornane skeleton, metaxylylenediamine, H ₂ N (CH ₂ CH ₂ O) ₂ (CH ₂ ) ₂ NH ₂ (ethylene glycol skeleton diamine), propylene skeleton diamine, propylene skeleton triamine, and polyamidoamine (trade name: X2000).
Ketimines, which are the reaction products of these polyamines and ketones, are also included in the amine compounds, and from the viewpoints of stability, reactivity adjustment and overcoatability, acetophenone or propiophenone and 1,3-bisaminomethylcyclohexane Obtained from acetophenone or propiophenone and dimethyleneamine (NBDA) having a norbornane skeleton; obtained from acetophenone or propiophenone and metaxylylenediamine; acetophenone or propiophenone; Those obtained from Jeffamine EDR148, Jeffamine D230 and Jeffamine D400, which are diamines having an ethylene glycol skeleton or propylene skeleton, or Jeffamine T403, which is a triamine having a propylene skeleton, etc. It is below.

As the carbodiimide compound, a compound having two or more carbodiimide groups (—N═C═N—) in the molecule is preferably used, and known polycarbodiimides can be used.
As the carbodiimide compound, high molecular weight polycarbodiimide produced by decarboxylation condensation reaction of diisocyanate in the presence of a carbodiimidization catalyst can also be used.
Examples of such compounds include those obtained by decarboxylation condensation reaction of the following diisocyanates. As the diisocyanate, 4,4′-diphenylmethane diisocyanate, 3,3′-dimethoxy-4,4′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate, 3,3′-dimethyl-4,4′-diphenyl ether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4′- One kind of dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate or a mixture thereof can be used. As the carbodiimidization catalyst, 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl- Phosphorene oxides such as 2-phospholene-1-oxide or their 3-phospholene isomers can be used.

  As the oxazoline compound, a compound having two or more oxazoline groups in the molecule is preferably used. Specifically, 2'-methylenebis (2-oxazoline), 2,2'-ethylenebis (2-oxazoline), 2 2,2'-ethylenebis (4-methyl-2-oxazoline), 2,2'-propylenebis (2-oxazoline), 2,2'-tetramethylenebis (2-oxazoline), 2,2'-hexamethylene Bis (2-oxazoline), 2,2'-octamethylenebis (2-oxazoline), 2,2'-p-phenylenebis (2-oxazoline), 2,2'-p-phenylenebis (4,4 ' -Dimethyl-2-oxazoline), 2,2'-p-phenylenebis (4-methyl-2-oxazoline), 2,2'-p-phenylenebis (4-phenyl- -Oxazoline), 2,2'-m-phenylenebis (2-oxazoline), 2,2'-m-phenylenebis (4-methyl-2-oxazoline), 2,2'-m-phenylenebis (4 4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis (4-phenylenebis-2-oxazoline), 2,2'-o-phenylenebis (2-oxazoline), 2,2'- o-phenylenebis (4-methyl-2-oxazoline), 2,2'-bis (2-oxazoline), 2,2'-bis (4-methyl-2-oxazoline), 2,2'-bis (4 -Ethyl-2-oxazoline), 2,2'-bis (4-phenyl-2-oxazoline) and the like. Alternatively, it may be a copolymer of vinyl compounds such as 2-isopropenyl-2-oxazoline and 2-isopropenyl-4,4-dimethyl-2-oxazoline, and other monomers copolymerizable therewith.

  The melamine compound is a compound having a triazine ring in the molecule, and examples thereof include melamine, benzoguanamine, cyclohexanecarboguanamine, methylguanamine, vinylguanamine, hexamethoxymethylmelamine, tetramethoxymethylbenzoguanamine and the like. Further, these low condensation products, alkyl etherified formaldehyde resins, and aminoplast resins may be used.

The amount of the crosslinking agent used may be determined in consideration of the type of the copolymer (a), adhesive physical properties, etc., and is not particularly limited, but by adjusting the amount of the crosslinking agent, The crosslinking density (gel fraction) of the pressure-sensitive adhesive layer can be adjusted to an appropriate value. In other words, the use amount of the crosslinking agent preferably contains a crosslinking agent as appropriate so that the gel fraction of the pressure-sensitive adhesive layer is in the range of 30 to 80%, and the gel fraction is in the range of 40 to 60%. More preferably. When the gel fraction of the pressure-sensitive adhesive layer is less than 30%, a pressure-sensitive adhesive sheet with excellent processability cannot be obtained when processed as a pressure-sensitive adhesive sheet. On the other hand, when the gel fraction of the pressure-sensitive adhesive layer exceeds 80%, sufficient adhesive force and tack cannot be obtained, and the adhesion to the substrate is lowered.
In addition, the addition method which adds a crosslinking agent to a copolymer (a) is not specifically limited.
In addition, the pressure-sensitive adhesive in the present invention is a tackifier resin, a silane coupling agent, a weathering stabilizer, a plasticizer, which is blended in a conventional acrylic pressure-sensitive adhesive as desired, as long as the object of the present invention is not impaired. Various additive components such as a softening material, a dye, a pigment, and an inorganic filler can be contained.

  Examples of the tackifier include terpene resin, aliphatic petroleum resin, aromatic petroleum resin, coumarone-indene resin, phenol resin, terpene-phenol resin, rosin derivative (rosin, polymerized rosin, hydrogenated rosin, and glycerin thereof. All existing ones such as esters with pentaerythritol, resin acid dimers, etc.) can be used. As the plasticizer, known materials such as phthalates and phosphates can be used.

Next, the pressure-sensitive adhesive sheet of the present invention will be described.
The pressure-sensitive adhesive sheet of the present invention is obtained by laminating a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present invention on at least one surface of a sheet-like substrate.
As a sheet-like base material, there are a non-peelable type and a peelable type. Accordingly, the pressure-sensitive adhesive sheet of the present invention has the following aspects.
A so-called single-sided pressure-sensitive adhesive sheet in which a non-peelable sheet-like substrate / pressure-sensitive adhesive layer / peelable sheet-like substrate is laminated in order.
A so-called double-sided pressure-sensitive adhesive sheet in which a peelable sheet-like substrate / pressure-sensitive adhesive layer / non-peelable sheet-like substrate / pressure-sensitive adhesive layer / peelable sheet-like substrate are sequentially laminated.
A so-called coreless double-sided pressure-sensitive adhesive sheet, in which a peelable sheet-like base material / adhesive layer / peelable sheet-like base material is sequentially laminated.
However, the case where a polyester film is used as the sheet-like substrate and the pressure-sensitive adhesive layer is laminated on both surfaces thereof is excluded.

  Among the sheet-like substrates constituting the pressure-sensitive adhesive sheet of the present invention, for example, a polyolefin resin such as polyethylene, a polyester resin such as polyethylene terephthalate, a vinyl acetate resin, a polyimide resin, Plastic film made of plastics such as fluororesin and cellophane; Kraft paper, Japanese paper, etc .; Rubber sheet made of natural rubber, butyl rubber, etc .; Foam sheet made by foaming polyurethane, polychloroprene rubber, etc .; Aluminum foil, copper Metal foil, such as foil; These composites etc. are mentioned. Moreover, surface treatments, such as a corona treatment, may be given to the single side | surface or both surfaces.

  The peelable sheet-like substrate is also referred to as a separator. Examples of such a peelable sheet-like substrate include glassine paper, kraft paper, clay coat paper, paper laminated with a film such as polyethylene, polyvinyl alcohol and acrylic. Papers coated with resins such as acid ester copolymers, synthetic resin films such as polyester and polypropylene, etc., which include a release resin such as fluorine resin or silicone resin, can be mentioned, but are particularly limited is not.

The pressure-sensitive adhesive sheet of the present invention can be obtained by various methods.
For example, an adhesive solution is applied and dried on one surface of a non-peelable sheet-like base material, and the peelable sheet-like base material is overlaid on the surface of the formed pressure-sensitive adhesive layer, or the peelable sheet-like base material It can be obtained by applying and drying a pressure-sensitive adhesive solution on one surface and overlaying a non-peelable sheet-like substrate on the surface of the formed pressure-sensitive adhesive layer.
The application apparatus used when applying the adhesive solution to various sheet-like base materials is a commonly used application apparatus and is not particularly limited. For example, a roll knife coater, a die coater, a roll coater, Examples include bar coaters, gravure roll coaters, reverse roll coaters, dipping, blade coaters.
The drying conditions may be any conditions as long as the solvent of the pressure-sensitive adhesive solution is dried and removed during drying, and the functional group of the copolymer (a) reacts with the crosslinking agent to form a crosslinked structure. . For example, 60 to 120 ° C. and about 1 to 5 minutes are preferable, but not limited thereto. After drying, aging is performed with the pressure-sensitive adhesive layer sandwiched between sheet-like substrates, and the crosslinking reaction can further proceed.
In the pressure-sensitive adhesive sheet of the present invention, the thickness of the pressure-sensitive adhesive layer after drying is preferably 1 to 200 μm, and more preferably 10 to 50 μm.

Next, although an example of the present invention is shown and explained in detail, the present invention is not limited by these. In the examples, “part” means “part by weight” and “%” means “% by weight”.
Example 1
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 78 parts of n-butyl acrylate, 10 parts of iso-butyl methacrylate, 5 parts of methyl acrylate, 2.5 parts of 2-ethylhexyl acrylate , 3.4 parts of acrylic acid, 1 part of vinyl acetate, 0.1 part of 2-hydroxyethyl acrylate, 72 parts of ethyl acetate, 0.13 part of 2,2′-azobis (2-methylbutyronitrile) After the air in the reaction vessel was replaced with nitrogen gas, the reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the reaction solution was diluted with ethyl acetate to obtain an acrylic copolymer solution having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 720,000. To 100 parts by weight of the obtained acrylic copolymer solution, 0.75 part of an isocyanate crosslinking agent (“Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd., non-volatile content: 75%) was added and stirred uniformly. A solution was obtained.
The obtained pressure-sensitive adhesive solution was applied onto a commercially available separator so that the dry coating thickness was 30 μm, and dried at 100 ° C. for 2 minutes. The pressure-sensitive adhesive layer surface and a polyester film (trade name “Toyobo Ester”, A pressure-sensitive adhesive sheet was prepared by laminating 50 μm in thickness, manufactured by Toyobo Co., Ltd.

(Example 2)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 68.9 parts of n-butyl acrylate, 15 parts of iso-butyl methacrylate, 5 parts of methyl acrylate, 5 parts of 2-ethylhexyl acrylate , 4 parts of acrylic acid, 2 parts of vinyl acetate, 0.1 part of 2-hydroxyethyl acrylate, 67 parts of ethyl acetate and 0.13 part of 2,2′-azobis (2-methylbutyronitrile) After replacing the air inside with nitrogen gas, the reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the solution was diluted with ethyl acetate to obtain a solution of an acrylic copolymer having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 750,000. To 100 parts by weight of the obtained acrylic copolymer solution, 0.75 part of an isocyanate crosslinking agent (“Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd., non-volatile content: 75%) was added and stirred uniformly. A solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Example 3)
A pressure-sensitive adhesive solution was prepared in the same manner as in Example 2 except that 0.11 part of aluminum tris (acetyl acetate) was used as the metal chelate cross-linking agent instead of the isocyanate cross-linking agent, and a pressure-sensitive adhesive sheet was prepared.

Example 4
A pressure-sensitive adhesive solution was obtained in the same manner as in Example 2 except that 0.021 part of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine was used as the epoxy crosslinking agent instead of the isocyanate crosslinking agent. Was prepared to produce an adhesive sheet.

(Example 5)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 68.9 parts of n-butyl acrylate, 20 parts of iso-butyl methacrylate, 5 parts of 2-ethylhexyl acrylate, 4 parts of acrylic acid , 2 parts of vinyl acetate, 0.1 part of 2-hydroxyethyl acrylate, 67 parts of ethyl acetate and 0.13 part of 2,2′-azobis (2-methylbutyronitrile) were charged, and the air in the reaction vessel was nitrogen After replacing with gas, the reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the solution was diluted with ethyl acetate to obtain a solution of an acrylic copolymer having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 750,000. To 100 parts by weight of the resulting acrylic copolymer solution, 0.021 part of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine as an epoxy cross-linking agent was added and stirred uniformly to obtain an adhesive. An agent solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Comparative Example 1)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introducing tube, 82.3 parts of n-butyl acrylate, 5.7 parts of methyl methacrylate, 5 parts of methyl acrylate, 2-ethylhexyl acrylate 5 parts, 3.4 parts of acrylic acid, 1 part of vinyl acetate, 0.1 part of 2-hydroxyethyl acrylate, 72 parts of ethyl acetate, 0.13 part of 2,2′-azobis (2-methylbutyronitrile) After replacing the air in the reaction vessel with nitrogen gas, the reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the reaction solution was diluted with ethyl acetate to obtain an acrylic copolymer solution having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 730,000. To 100 parts by weight of the resulting acrylic copolymer solution, 0.021 part of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine as an epoxy cross-linking agent was added and stirred uniformly to obtain an adhesive. An agent solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Comparative Example 2)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 70 parts of n-butyl acrylate, 19.9 parts of ethyl acrylate, 10 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, 100 parts of ethyl acetate and 0.13 part of 2,2′-azobis (2-methylbutyronitrile) were charged, and the air in the reaction vessel was replaced with nitrogen gas. The reaction solution was reacted at reflux temperature for 8 hours. After completion of the reaction, the solution was diluted with ethyl acetate to obtain an acrylic copolymer solution having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 900,000. To 100 parts by weight of the resulting acrylic copolymer solution, 0.021 part of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine as an epoxy cross-linking agent was added and stirred uniformly to obtain an adhesive. An agent solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Comparative Example 3)
In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device, nitrogen introduction tube, 74.9 parts of n-butyl acrylate, 21 parts of normal-butyl methacrylate, 5.9 parts of 2-ethylhexyl acrylate, acrylic acid 4 parts, 2-hydroxyethyl acrylate 0.1 part, ethyl acetate 67 parts, 2,2′-azobis (2-methylbutyronitrile) 0.13 part are charged, and the air in the reaction vessel is replaced with nitrogen gas. Then, this reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the solution was diluted with ethyl acetate to obtain an acrylic copolymer solution having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 770,000. To 100 parts by weight of the resulting acrylic copolymer solution, 0.021 part of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine as an epoxy cross-linking agent was added and stirred uniformly to obtain an adhesive. An agent solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Comparative Example 4)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 79.5 parts of n-butyl acrylate, 5 parts of iso-butyl methacrylate, 3 parts of 2-ethylhexyl acrylate, 9 parts of methyl acrylate , 3.4 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, 82 parts of ethyl acetate and 0.13 part of 2,2′-azobis (2-methylbutyronitrile) Was replaced with nitrogen gas, and the reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic copolymer solution having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 780,000. To 100 parts by weight of the resulting acrylic copolymer solution, 0.021 part of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine as an epoxy cross-linking agent was added and stirred uniformly to obtain an adhesive. An agent solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Comparative Example 5)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 70 parts of n-butyl acrylate, 10 parts of iso-butyl methacrylate, 5 parts of methyl acrylate, 2.5 parts of 2-ethylhexyl acrylate , 3.4 parts of acrylic acid, 1 part of vinyl acetate, 0.1 part of 2-hydroxyethyl acrylate, 120 parts of toluene, 0.25 part of 2,2′-azobis (2-methylbutyronitrile), and this reaction After the air in the vessel was replaced with nitrogen gas, the reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic copolymer solution having a nonvolatile content concentration of about 30% and a weight average molecular weight Mw of about 210,000. To 100 parts by weight of the obtained acrylic copolymer solution, 0.04 part of N, N, N ′, N′-tetraglycidyl-m-xylylenediamine as an epoxy cross-linking agent was added and stirred uniformly. An agent solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Comparative Example 6)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, 78 parts of n-butyl acrylate, 10 parts of iso-butyl methacrylate, 5 parts of methyl acrylate, 2.5 parts of 2-ethylhexyl acrylate , 3.4 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, 20 parts of acetone, 13 parts of ethyl acetate, 0.1 part of 2,2′-azobis (2-methylbutyronitrile) After the air in the vessel was replaced with nitrogen gas, the reaction solution was reacted at reflux temperature for 8 hours in a nitrogen atmosphere with stirring. After completion of the reaction, the reaction mixture was diluted with ethyl acetate to obtain an acrylic copolymer solution having a nonvolatile content concentration of about 10% and a weight average molecular weight Mw of about 1,500,000. To 100 parts by weight of the obtained acrylic copolymer solution, 0.3 part of an isocyanate crosslinking agent (“Coronate L” manufactured by Nippon Polyurethane Industry Co., Ltd., non-volatile content: 75%) was added and stirred uniformly to obtain an adhesive. A solution was obtained.
Using the obtained adhesive solution, an adhesive sheet was prepared in the same manner as in Example 1.

(Comparative Example 7)
From 55 parts 2-ethylhexyl acrylate, 43 parts iso-butyl methacrylate, 1 part acrylic acid, 1 part 2-hydroxyethyl acrylate to a reaction vessel equipped with a stirrer, thermometer, reflux condenser, dropping device and nitrogen inlet tube An emulsion obtained by emulsifying the resulting monomer mixture with 2.5 parts of an anionic reactive emulsifier ("Aqualon BC-2020" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 144 parts of water was added, and the atmosphere was replaced with nitrogen for 2 hours. Subsequently, after raising the temperature to 55 ° C., 0.03 part of 2,2′-azobis (2-amidinopropane) hydrochloride was added and polymerization was performed for 8 hours. Thereafter, the mixture was cooled to room temperature and neutralized with 10% aqueous ammonia to obtain an acrylic copolymer dispersion. A water-soluble epoxy crosslinking agent ("Denacol EX-614B" manufactured by Nagase Kasei Kogyo Co., Ltd.) is used for 100 parts by weight of the solid content of this acrylic copolymer dispersion, and the number of epoxy groups is acrylic copolymer. A water-dispersed pressure-sensitive adhesive composition was prepared by adding 2.4 parts so as to be equivalent to the number of carboxyl groups in the coalescence.
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using the obtained pressure-sensitive adhesive composition.

The types of copolymerizable monomers constituting the copolymer (a) in Table 1 are indicated by the following abbreviations.
BA: normal-butyl acrylate (molecular weight = 128, homopolymer Tg = −54 ° C.)
iBMA: iso-butyl methacrylate (molecular weight = 142, homopolymer Tg = 67 ° C.)
nBMA: normal-butyl methacrylate (molecular weight = 142, homopolymer Tg = 20 ° C.)
EA: ethyl acrylate (molecular weight = 100, homopolymer Tg = −22 ° C.)
MA: methyl acrylate (molecular weight = 86, homopolymer Tg = 8 ° C.)
MMA: Methyl methacrylate (molecular weight = 100, homopolymer Tg = 105 ° C.)
2EHA: 2-ethylhexyl acrylate (molecular weight = 184, homopolymer Tg = −85 ° C.)
VAC: vinyl acetate (molecular weight = 86, homopolymer Tg = 29 ° C.)
AA: acrylic acid (molecular weight = 72, homopolymer Tg = 106 ° C.)
HEA: 2-hydroxyethyl acrylate (molecular weight = 116, Tg of homopolymer = −15 ° C.)

(Weight average molecular weight)
It is a weight average molecular weight in terms of polystyrene determined by GPC measurement, and the measurement conditions are as follows.
Equipment: HCL8820GPC manufactured by Tosoh Corporation
Column: Three TSKgel GMH _XL manufactured by Tosoh Corporation are connected and used.
Solvent: Tetrahydrofuran Flow rate: 0.5 ml / min
Temperature: 40 ° C
Sample concentration: 0.2 wt%
Sample injection volume: 100 μl

[Glass transition temperature (Tg)]
The Tg of the acrylic copolymer in the present invention is theoretically derived from the following formula [I].
Tg = [M1 / (M1 + M2 +... + Mn) × Tg1] + [M2 / (M1 + M2 +... + Mn) × Tg2] +... + [Mn / (M1 + M2 +... + Mn) × Tgn ] [I]
Where M1 = (weight% of monomer 1) / (molecular weight of monomer 1), Tg1: glass transition temperature (° C.) of homopolymer of monomer 1;
M2 = (% by weight of monomer 2) / (molecular weight of monomer 2), Tg2: glass transition temperature of homopolymer of monomer 2 (° C.),
Mn = (% by weight of monomer n) / (molecular weight of monomer n), Tgn: glass transition temperature (° C.) of homopolymer of monomer n.
(Here, the total amount of monomers used for copolymerization is 100% by weight.)

[Measurement of physical properties of adhesive sheet]
About the adhesive sheet obtained by the Example and the comparative example, it was made to pass in 23 degreeC-50% RH atmosphere for 7 days, and after aging the adhesive layer, the test shown below was done. The results are shown in Table 1.

〔Adhesive force〕
This was performed according to JIS Z 0237. Cut out a 25 mm wide test piece from each adhesive sheet, peel off the separator, attach it to a stainless steel plate at 5 ° C. or 23 ° C.-50% atmosphere, leave it in the same environment for 20 minutes, respectively, The peel strength (N / inch) when peeled at an angle of 180 ° at a tensile speed of 300 mm / min was measured with a tensile tester.

[Retention force]
Cut out a 25mm wide test piece from each adhesive sheet, peel off the separator, apply it to a stainless steel plate (attachment area: 25mm x 25mm), apply a 1kg load to the test piece in an environment of 80 ° C, and leave it for 1 hour. Then, the displacement of the sticking position was measured (mm). In the case of falling within 1 hour, the time until dropping was determined.

[Ball tack]
This was performed according to JIS Z 0237. The inclination angle of the pressure-sensitive adhesive sheet was 30 °, and the measurement was performed in an atmosphere of 23 ° C.-50%.

  As a method for evaluating the cohesive force, a stress-strain curve measurement was performed separately from the holding force to measure the coating film strength of the pressure-sensitive adhesive layer. Generally, the greater the stress value with respect to strain, the greater the strength of the coating film. That is, it is generally known that the greater the stress value, the greater the cohesive force of the pressure-sensitive adhesive layer.

[Preparation of sample for stress-strain curve measurement]
The pressure-sensitive adhesive solution and the pressure-sensitive adhesive dispersion prepared in Examples and Comparative Examples were applied on a commercially available separator so that the dry coating thickness was 30 μm and dried at 100 ° C. for 2 minutes. A commercially available separator was bonded to prepare an adhesive sheet. After aging in a 23 ° C.-50% RH atmosphere for 7 days, an adhesive layer was laminated to obtain a test sample consisting of only an adhesive layer having a thickness of 120 μm.
[Measurement of stress-strain curve]
The obtained test sample (test sample consisting only of the pressure-sensitive adhesive layer) was adjusted to a tensile tester (EZTest, manufactured by Shimadzu Corporation) with a width of 20 mm and a gauge distance of 25 mm and fixed, and measurement at 23 ° C.-50% RH A stress value (N) at 600% strain obtained by pulling at 100 mm / min in an atmosphere was determined.

[Punching workability]
Using a punching machine TH-2000 (manufactured by Mochizuki Seisakusho), the adhesive sheet was punched continuously for 50 shots in a circle with a diameter of 10 mm, and the punching processability was evaluated.
The evaluation criteria for punching workability are shown below.
○: No glue adheres to the blade, and the punched circular part of the release paper can be peeled cleanly and lightly.
Δ: Adhesive adheres to the blade, or there is a little resistance when peeling off the punched circular paper.
X: The glue is very attached to the blade, or the resistance when peeling the punched circular part of the release paper is large.

[Cutting]
Using a cutting machine (CG-50 manufactured by Mimaki Co., Ltd.), cut the adhesive sheet from the Toyo Ink Manufacturing and polyester film side with a size of 30 mm square, and turn over phenomenon (whether the polyester film floats or turns over) ) Was then confirmed, and then the scraping (removal of unnecessary parts other than characters) was performed one day after cutting.
The evaluation criteria for the turnover phenomenon are shown below.
○ ... There was no turning-up phenomenon.
Δ: Although there was a slight turning phenomenon, it was at a practical level.
X: There was a turning phenomenon.
The evaluation criteria for the blur removal property are shown below.
○: All character patterns remain.
Δ: Some character patterns do not remain.
X: Most character patterns do not remain.

  The above evaluation results are shown in Table 1.

From Table 1, as can be seen from the physical property results of the stress-strain curve, the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive of the present invention containing a specific copolymer containing iso-butyl methacrylate as an essential component is shown in FIG. As the amount of methacrylate used increases, the strength of the coating film is improved. As a result, it can be seen that the punching workability and cutting property are good, and the adhesive strength is also a good value.
Comparative Examples 1 and 3 are adhesives containing a copolymer formed only from a monomer not containing iso-butyl methacrylate, even though they have a Tg comparable to that of the copolymer used in Example 1. This is the case when an agent is used. As can be seen by comparing Example 1 with Comparative Examples 1 and 3, it is possible to use a pressure-sensitive adhesive containing a copolymer formed from a monomer mixture containing iso-butyl methacrylate, rather than the effect of Tg. Contributes to improved punchability and cutting performance.
Moreover, even if it is a copolymer formed from the monomer mixture containing iso-butylmethacrylate, if the weight average molecular weight is too small as shown in Comparative Example 5, the punching processability and scraping ability are inferior. On the other hand, even in the case of a copolymer formed from a monomer mixture containing iso-butyl methacrylate, if the weight average molecular weight is too large as shown in Comparative Example 6, the scraping phenomenon is good, but the curling phenomenon is not good. It turns out that it is inferior or the adhesive strength is lowered, and physical properties at a practical level cannot be obtained.

Claims (2)

It is formed by copolymerizing 8 to 35% by weight of iso-butyl methacrylate and other copolymerizable monomer in 100% by weight of the total amount of monomers, has at least one of a carboxyl group or a hydroxyl group, and has a weight average molecular weight of 400,000 to 120. A pressure-sensitive adhesive comprising a copolymer (a) which is tens of thousands and a crosslinking agent having a functional group capable of reacting with at least one of a carboxyl group or a hydroxyl group. A pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive according to claim 1 is laminated on at least one surface of a sheet-like base material (however, a polyester-based film is used as a sheet-like base material on both sides thereof) Excluding the case where the pressure-sensitive adhesive layer is laminated).