JP7040661B1 - Adhesive composition and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet which exhibit high adhesive strength to both a high-polarity adherend and a low-polarity adherend even if they are thin films, and also have excellent holding power and curved surface adhesiveness. thing. SOLUTION: The copolymer (A) contains an copolymer (A) and a curing agent (B), and the copolymer (A) is an alkyl (meth) acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, and a reactive functional group. It is a copolymer of a monomer mixture containing a (meth) acrylate (a2) having an aliphatic ring structure and a (meth) acrylate (a3) having a carboxyl group, and has a carboxyl group (meth). ) The acrylate (a3) contains at least one of the (meth) acrylate (a3-1) represented by the general formula (1) and the (meth) acrylate (a3-2) represented by the general formula (2). It is solved by the pressure-sensitive adhesive composition characterized by the above. [Selection diagram] None

Description

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

The pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is used in a wide range of fields as a label and an adhesive application because it is easy to handle. In recent years, there has been a demand for thinning of the adhesive layer for various purposes from the viewpoint of cost reduction and reduction of environmental load, and from the viewpoint of reducing the weight and thinning of electronic devices. However, the adhesive strength of the pressure-sensitive adhesive sheet generally decreases as the film thickness of the pressure-sensitive adhesive layer decreases. Therefore, there is a strong demand for the development of an adhesive sheet having high adhesive strength even under thin film conditions. Furthermore, in order to be used in various applications, it exhibits strong adhesive strength to both high-polarity adherends such as stainless steel plates and low-polarity adherends such as polyolefins, and also has holding power and curved surface adhesiveness. It needs to be good.
Patent Document 1 discloses a pressure-sensitive adhesive sheet containing a certain amount of a monomer having a carboxyl group and having a thin-film pressure-sensitive adhesive film in which a weight average molecular weight and a gel fraction are defined.
Patent Document 2 discloses a pressure-sensitive adhesive containing an acrylic copolymer containing n-butyl (meth) acrylate and a synthetic hydrocarbon-based pressure-sensitive adhesive resin, and a thin-film pressure-sensitive adhesive sheet.

Japanese Unexamined Patent Publication No. 2019-77820 International Publication No. 2020/27180

However, although these conventional pressure-sensitive adhesive sheets have excellent adhesive strength to high-polarity adherends such as stainless steel plates, they do not have sufficient adhesive strength to low-polarity adherends such as polyolefins, especially in the case of thin film conditions. However, it is difficult to show high adhesive strength to both high-polarity adherends and low-polarity adherends, and in addition, the holding power and curved surface suitability cannot be satisfied at present. be.

INDUSTRIAL APPLICABILITY The present invention provides a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet which exhibit high adhesive strength to both high-polarity adherends and low-polarity adherends even if they are thin films, and also have excellent holding power and curved surface adhesiveness. With the goal.

（式中、Ｒ_１は水素原子またはメチル基、ｍは２～１０の整数、ｎは１～５の整数を示す。）

（式中、Ｒ_２は水素原子またはメチル基、Ｒ_３は２価の炭化水素基、ｐは１～５の整数を示す。） The pressure-sensitive adhesive of the present invention contains a copolymer (A) and a curing agent (B), and the copolymer (A) is an alkyl (meth) acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, which is a reaction. It is a copolymer of a monomer mixture containing a (meth) acrylate (a2) having an aliphatic ring structure and having a (meth) acrylate (a3) having a carboxyl group without having a sex functional group, and has a carboxyl group. The (meth) acrylate (a3) having is at least one of a (meth) acrylate (a3-1) represented by the general formula (1) and a (meth) acrylate (a3-2) represented by the general formula (2). It is characterized by including.

(In the formula, R ₁ is a hydrogen atom or a methyl group, m is an integer of 2 to 10, and n is an integer of 1 to 5.)

(In the formula, R ₂ is a hydrogen atom or a methyl group, R ₃ is a divalent hydrocarbon group, and p is an integer of 1 to 5.)

INDUSTRIAL APPLICABILITY According to the present invention, a pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that exhibit high adhesive strength to both high-polarity adherends and low-polarity adherends even if they are thin films, and also have excellent holding power and curved surface adhesiveness. Can be provided.

Before describing the present invention in detail, terms are defined. First, sheets, films and tapes are synonyms. (Meta) acrylic acid includes acrylic acid and methacrylic acid. (Meta) acrylates include acrylates and methacrylates. The monomer is a monomer having an ethylenically unsaturated double bond. The adherend is the other party to which the adhesive sheet is attached.
In the present specification, an alkyl (meth) acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, a (meth) acrylate (a2) having no reactive functional group and having an aliphatic ring structure, and the like. And (meth) acrylate having a carboxyl group (a3), (meth) acrylate having a hydroxyl group (a4), alkyl (meth) acrylate having an alkyl group having 4 to 7 carbon atoms (a-1), 8 to 12 carbon atoms. Alkyl (meth) acrylate (a-2) having an alkyl group of, (meth) acrylate represented by the formula (1) (a3-1), and (meth) acrylate represented by the formula (2) (a3-). 2) are (meth) acrylate (a1), (meth) acrylate (a2), (meth) acrylate (a3), (meth) acrylate (a4), (meth) acrylate (a-1), (meth), respectively. It may be referred to as acrylate (a-2), (meth) acrylate (a3-1), and (meth) acrylate (a3-2).
Unless otherwise specified, the various components appearing in the present specification may be used independently or in combination of two or more.

（式中、Ｒ_１は水素原子またはメチル基、ｍは２～１０の整数、ｎは１～５の整数を示す。）

（式中、Ｒ_２は水素原子またはメチル基、Ｒ_３は２価の炭化水素基、ｐは１～５の整数を示す。） << Adhesive composition >>
The pressure-sensitive adhesive composition of the present invention contains a copolymer (A) and a curing agent (B), and the copolymer (A) is an alkyl (meth) acrylate (a1) having an alkyl group having 4 to 12 carbon atoms. , A copolymer of a monomer mixture containing a (meth) acrylate (a2) having an aliphatic ring structure without a reactive functional group and a (meth) acrylate (a3) having a carboxyl group, and carboxyl. The (meth) acrylate (a3) having a group is the (meth) acrylate (a3-1) represented by the general formula (1) and the (meth) acrylate (a3-2) represented by the general formula (2). Includes at least one.

(In the formula, R ₁ is a hydrogen atom or a methyl group, m is an integer of 2 to 10, and n is an integer of 1 to 5.)

(In the formula, R ₂ is a hydrogen atom or a methyl group, R ₃ is a divalent hydrocarbon group, and p is an integer of 1 to 5.)

In the present invention, by using a (meth) acrylate having an aliphatic ring structure without having a reactive functional group, the polarity of the copolymer is lowered to improve the adhesion to a low-polarity adherend at the same time. By improving the compatibility with the low-polarity tackifier resin and using (meth) acrylate having a carboxyl group represented by the general formula (1) or the general formula (2), the pressure-sensitive adhesive layer has cohesive force and flexibility. By combining these, it exhibits high adhesive strength to both high-polarity adherends and low-polarity adherends even though it is a thin film, and also has both holding power and curved surface adhesiveness. can.

<Copolymer (A)>
The copolymer (A) is an alkyl (meth) acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, and a (meth) acrylate (a2) having no reactive functional group and having an aliphatic ring structure. , And (meth) acrylate (a3) having a carboxyl group as an essential monomer, and (meth) acrylate (a4) having a hydroxyl group as necessary, and a monomer mixture containing other monomers as optional monomers are polymerized. It is a polymer.

The acid value of the copolymer (A) is preferably 0.1 to 24.0 mgKOH / g, more preferably 0.2 to 20.0 mgKOH / g. When the acid value of the copolymer (A) is 0.1 to 24.0 mgKOH / g, the cohesive force and the flexibility of the pressure-sensitive adhesive layer can be imparted in a well-balanced manner, and the adhesive strength, the holding power, and the curved surface can be imparted. It becomes easier to achieve both adhesiveness.

[(Meta) Acrylate (a1)]
The (meth) acrylate (a1) is an alkyl (meth) acrylate having an alkyl group having 4 to 12 carbon atoms.
The content of the (meth) acrylate (a1) is preferably 60 to 99% by mass, more preferably 70 to 98% by mass in 100% by mass of the monomer mixture. By using 60 to 99% by mass, it becomes easier to achieve both adhesive strength, holding power, and curved adhesiveness.
The (meth) acrylate (a1) includes an alkyl (meth) acrylate (a-1) having an alkyl group having 4 to 7 carbon atoms and an alkyl (meth) acrylate (a-1) having an alkyl group having 8 to 12 carbon atoms. It is preferable to contain 2) in terms of both adhesive strength to a highly polar adherend and a low-polarity adherend, and compatibility with a tackifier resin.

The content ratio of the (meth) acrylate (a-1) to the (meth) acrylate (a-2) component is preferably (a-1) / (a-2) = 99/1 to 20/80 in terms of weight ratio. , 98/2 to 50/50, more preferably 95/5 to 60/40. By using this ratio, it is possible to achieve both adhesive strength against a highly polar adherend and adhesive strength against a low-polarity adherend, improve compatibility with the tackifier resin, and further improve the adhesive strength. Can be improved.

Examples of the alkyl (meth) acrylate (a-1) having an alkyl group having 4 to 7 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, and n-hexyl (meth) acrylate. .. Among these, n-butyl (meth) acrylate is preferable from the viewpoint of achieving both adhesive strength and holding power.

Examples of the alkyl (meth) acrylate (a-2) having an alkyl group having 8 to 12 carbon atoms include 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, and n-nonyl. Examples thereof include (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, and dodecyl (meth) acrylate. Among these, 2-ethylhexyl (meth) acrylate is preferable from the viewpoint of achieving both adhesive strength and holding power.

[(Meta) Acrylate (a2)]
The (meth) acrylate (a2) is a (meth) acrylate having no reactive functional group and having an aliphatic cyclic structure.
The content of the (meth) acrylate (a2) is preferably 1 to 20% by mass in 100% by mass of the monomer mixture, and more preferably 2 to 15% by mass. By using 1 to 20% by mass, it becomes easier to achieve both adhesive strength, holding power, and curved adhesiveness.

The (meth) acrylate (a2) is characterized by having no reactive functional group other than an acryloyl group, and examples of the reactive functional group include a carboxyl group, a hydroxyl group, an amino group, and an epoxy group.
Examples of the aliphatic cyclic structure include a cyclohexyl group, a dicyclopentenyl group, a dicyclopentenyl group, an isobornyl group and the like. From the viewpoint of improving the adhesive strength to the low-polarity adherend and the compatibility with the tackifier resin, it is preferable to have a dicyclopentenyl group, a dicyclopentenyl group, or an isobornyl group.

Examples of the (meth) acrylate (a2) include cyclohexyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, isobornyl (meth) acrylate and the like. Among these, dicyclopentenyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and isobornyl (meth) acrylate having a three-dimensional aliphatic cyclic structure have adhesive strength to a low-polarity adherend and a phase with a tack-imparting resin. It is preferable from the viewpoint of improving solubility, and isobornyl (meth) acrylate is more preferable.

[(Meta) Acrylate (a3)]
The (meth) acrylate (a2) is a (meth) acrylate having a carboxyl group, and is represented by the (meth) acrylate (a3-1) represented by the general formula (1) and the (meth) acrylate represented by the general formula (2). ) Includes at least one of the acrylates (a3-2).
Above all, it is more preferable to contain the (meth) acrylate (a3-2) represented by the formula (2) in terms of both high-polarity adherend and low-polarity adherend.

The content of the (meth) acrylate (a3) is preferably 0.1 to 10% by mass, more preferably 0.2 to 8% by mass in 100% by mass of the monomer mixture. By using 0.1 to 10% by mass, it becomes easier to achieve both adhesive strength, holding power, and curved adhesiveness.

（式中、Ｒ_１は水素原子またはメチル基、ｍは２～１０の整数、ｎは１～５の整数を示す。） ((Meta) Acrylate (a3-1))
The (meth) acrylate (a3-1) is a (meth) acrylate represented by the general formula (1).

(In the formula, R ₁ is a hydrogen atom or a methyl group, m is an integer of 2 to 10, and n is an integer of 1 to 5.)

In the general formula (1), m represents an integer of 2 to 10. m is an integer of 2 to 10, preferably an integer of 2 to 8, and more preferably an integer of 3 to 5, from the viewpoint of achieving both adhesive strength, holding power, and curved surface adhesiveness. n represents an integer of 1 to 5. The n is an integer of 1 to 5, preferably an integer of 2 to 4, from the viewpoint of achieving both adhesive strength, holding power, and curved surface adhesiveness.

The (meth) acrylate (a3-1) may be produced by a conventional method or may be appropriately selected from commercially available monomers.
Examples of the (meth) acrylate (a3-1) include β-carboxyethyl acrylate and ω-carboxypolycaprolactone mono (meth) acrylate. As these monomers, for example, those commercially available as trade names of "β-CEA" (manufactured by Daicel Ornex) and "Aronix M-5300" (manufactured by Toagosei Co., Ltd.) can be used.

（式中、Ｒ_２は水素原子またはメチル基、Ｒ_３は２価の炭化水素基、ｐは１～５の整数を示す。） ((Meta) acrylate (a3-2))
The (meth) acrylate (a3-2) is a (meth) acrylate represented by the general formula (2).

(In the formula, R ₂ is a hydrogen atom or a methyl group, R ₃ is a divalent hydrocarbon group, and p is an integer of 1 to 5.)

In the general formula (2), p represents an integer of 1 to 5. p is an integer of 1 to 5, but preferably an integer of 1 to 3 from the viewpoint of achieving both adhesive strength, holding power, and curved surface adhesiveness. R3 represents a divalent hydrocarbon group.
Examples of the hydrocarbon group include a saturated aliphatic hydrocarbon group such as an alkylene group, a saturated alicyclic hydrocarbon group such as a cycloalkylene group, an aromatic hydrocarbon group such as a phenylene group, an unsaturated aliphatic hydrocarbon group, or a non-saturated aliphatic hydrocarbon group. Saturated alicyclic hydrocarbon groups and the like can be mentioned.
Among these, a saturated aliphatic hydrocarbon group is preferable, an alkylene group is more preferable, and an alkylene group having 1 to 4 carbon atoms is further preferable, from the viewpoint of improving the adhesive strength by imparting flexibility.

The (meth) acrylate (a3-2) may be produced by a conventional method or may be appropriately selected from commercially available monomers.
Examples of the (meth) acrylate (a3-2) include 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) acryloyloxyethyl fumaric acid, 2- (meth) acryloyloxyethyl phthalic acid and the like. These monomers are, for example, products of "Light Ester HO-MS", "HOA-MS (N)", "Light Acrylate HOA-HH (N)" and "HOA-MPL (N)" (manufactured by Kyoeisha Chemical Co., Ltd.). Commercially available names can be used.

Even if the (meth) acrylate (a3) contains a (meth) acrylate (a3-1) and a (meth) acrylate (a3-3) having a carboxyl group other than the (meth) acrylate (a3-2). good.
Examples of the (meth) acrylate (a3-3) having a carboxyl group include (meth) acrylic acid and the like.

By using the (meth) acrylate (a3-1) or the (meth) acrylate (a3-2) as the (meth) acrylate (a3), the carbosyl group present at the end of the side chain and the (meth) acrylate (a2) It is possible to achieve both high-polarity and low-polarity adherends without interfering with the large adipose ring structure of origin from adhering to the highly polar or low-polarity adherends. Become.

Compared to (meth) acrylates, which have short side chains such as (meth) acrylic acid, (meth) acrylates (a3-1) and (meth) acrylates (a3-2) are the main chains of acrylic polymers. And the carboxyl group are separated from each other, and the large aliphatic ring structure derived from (meth) acrylate (a2) does not interfere with the structure, and the adhesion to the highly polar adherend can be improved. .. Further, when the side chain is not too long, it is possible to prevent the aliphatic cyclic structure derived from (meth) acrylate (a2) from adhering to the low-polarity adherend.

The smaller the content of the (meth) acrylate (a3) other than the (meth) acrylate (a3-1) and the (meth) acrylate (a3-2), the more preferable, but it is 40% by mass or less in the total 100% by mass. It is preferable, it is more preferably 30% by mass or less, and further preferably 20% by mass or less.
When it is 40% by mass or less, it is preferable because it is easy to achieve both a high-polarity adherend and a low-polarity adherend.

[(Meta) Acrylate (a4)]
The (meth) acrylate (a4) is a (meth) acrylate having a hydroxyl group.
The monomer mixture of the present invention can further contain a (meth) acrylate (a4) having a hydroxyl group.
It is preferable to contain the (meth) acrylate (a4) having a hydroxyl group because it is easy to develop a cohesive force and can have excellent holding power and curved surface adhesiveness.
The (meth) acrylate (a4) having a hydroxyl group is preferably used in an amount of 0.05 to 3% by mass, more preferably 0.1 to 2% by mass in 100% by mass of the monomer mixture. By using 0.05 to 3% by mass, the cohesive force of the pressure-sensitive adhesive layer is increased, and it becomes easier to improve the holding force and the adhesiveness to the curved surface.

The (meth) acrylate (a4) having a hydroxyl group includes, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and the like. Hydroxyalkyl (meth) acrylates such as acid 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, and polyethylene glycol mono ( Examples thereof include meth) acrylate, polypropylene glycol mono (meth) acrylic rate, glycol mono (meth) acrylate such as 1,4-cyclohexanedimethanol mono (meth) acrylate, and the like. Among these, 2-hydroxyethyl (meth) acrylate is preferable.

[Other monomers]
Other monomers include an alkyl (meth) acrylate (a1) having an alkyl group having 4 to 12 carbon atoms, a (meth) acrylate (a2) having no reactive functional group and having an aliphatic ring structure, and a carboxyl group. Other (meth) acrylates other than the (meth) acrylate (a3) having a hydroxyl group and the (meth) acrylate (a4) having a hydroxyl group, and a monomer other than the (meth) acrylate.
Other monomers can be used within a range that does not impair the adhesive strength, holding power, and curved surface adhesiveness of the pressure-sensitive adhesive. Specifically, alkyl (meth) acrylates having an alkyl group other than (meth) acrylate (a1), for example, a monomer having an amide bond, a monomer having an epoxy group, a monomer having an amino group, and a monomer having an aromatic ring. , Monomers having an alkoxy (poly) alkylene oxide, other vinyl monomers and the like.

Alkyl (meth) acrylate monomers other than (meth) acrylate (a1) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-octadecyl (meth). Examples thereof include acrylate and isooctadecyl (meth) acrylate.
When an alkyl (meth) acrylate monomer other than the (meth) acrylate (a1) is used, the content thereof is preferably 0.1 to 20% by weight based on 100% by weight of the monomer mixture.

The compounds having an amide bond include, for example, (meth) acrylamide, N-methylacrylamide, N-isopropylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, N, N-dimethylaminopropyl (meth) acrylamide, and di. Examples thereof include (meth) acrylamide compounds such as acetone acrylamide and N- (butoxymethyl) acrylamide; and heterocycle-containing compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, and acryloylmorpholin.
Examples of the monomer having an epoxy group include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and 3,4-epoxycyclohexylmethyl (meth) acrylate.
The monomer having an amino group is a monoalkylamino (meth) such as monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, and monoethylaminopropyl (meth) acrylate. Examples include acrylate.
When a monomer having an amide bond, a monomer having an epoxy group and a monomer having an amino group are used, the content thereof is preferably 0.1 to 1% by weight in 100% by weight of the monomer mixture.

Examples of the monomer having an aromatic ring include phenoxyethyl acrylate, benzyl acrylate, phenoxydiethylene glycol (meth) acrylate, and ethylene oxide-modified nonylphenol (meth) acrylate.
When a monomer having an aromatic ring is used, the content thereof is preferably 0.1 to 10% by weight based on 100% by weight of the monomer mixture.

The monomer having an alkoxy (poly) alkylene oxide is, for example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-phenoxyethyl acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, methoxypolypropylene glycol ( Examples thereof include meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, and phenoxypolyethylene glycol (meth) acrylate.
When a monomer having an alkoxy (poly) alkylene oxide is used, the content thereof is preferably 0.1 to 10% by weight based on 100% by weight of the monomer mixture.

Other vinyl monomers include, but are not limited to, vinyl acetate, acrylonitrile, and the like.
When other vinyl monomers are used, the content thereof is preferably 0.1 to 10% by weight based on 100% by weight of the monomer mixture.

[Manufacturing of copolymer (A)]
The copolymer (A) can be obtained, for example, by adding a polymerization initiator to a monomer mixture and subjecting it to solution polymerization. The solvent used for the solution polymerization is, for example, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, isopropanol and the like. Is preferable, and ethyl acetate is more preferable.

For solution polymerization, it is preferable to add about 0.001 to 1 part by weight of a polymerization initiator to 100 parts by weight of the monomer mixture. Usually, the polymerization can be carried out under a nitrogen stream at a temperature of about 50 ° C. to 90 ° C. for 6 hours to 20 hours. Further, at the time of polymerization, a chain transfer agent can be used to appropriately adjust the weight average molecular weight of the copolymer.

In the present invention, the weight average molecular weight of the copolymer (A) is preferably 300,000 to 1,500,000, more preferably 500,000 to 1,300,000, still more preferably 600,000 to 1,200,000. By setting Mw in the range of 300,000 to 1,500,000, it becomes easy to achieve both adhesive strength, holding power, and curved surface adhesiveness. In the present invention, the weight average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

Chain transfer agents include, for example, n-dodecyl mercaptan, mercaptoisobutyl alcohol, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, glycidyl mercaptan, α-methylstyrene. Dimer, carbon tetrachloride, chloroform, hydroquinone and the like can be mentioned. As the chain transfer agent, about 0.01 to 1 part by weight can be used with respect to 100 parts by weight of the monomer mixture.

The polymerization initiator is generally an azo compound or an organic peroxide.
The azo compound is, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis (
2-Methylbutyronitrile), 1,1'-azobis (cyclohexane1-carbonitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,)
4-Dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2) -Hydroxymethylpropionitrile) and 2,2'-azobis (2- (2- (2-)
Imidazoline-2-yl) propane) and the like.
Organic peroxides include, for example, benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxydicarbonate. , T-Butylperoxyneodecanoate, t-Butylperoxyvivarate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

<Curing agent (B)>
The pressure-sensitive adhesive of the present invention needs to further contain a curing agent (B). By including a curing agent, the cohesive force can be improved, and the holding force and the curved surface adhesiveness can be improved to a practical level.
Examples of the curing agent (B) include isocyanate-based curing agents, epoxy-based curing agents, aziridine-based curing agents, metal chelate-based curing agents, amine-based curing agents, amino resin-based curing agents, and the like.
Among these, it is preferable to use at least one selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent, and a metal chelate-based curing agent, because the holding power and the adhesiveness to the curved surface can be further improved.

Examples of the isocyanate-based curing agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate. , And an adduct of a diisocyanate such as polymethylene polyphenyl isocyanate and a polyol compound such as trimethylolpropane, and a buretto body thereof, and an isocyanurate form thereof, and the diisocyanate, a polyether polyol, a polyester polyol, an acrylic polyol, and a polybutadiene. Compounds having three or more isocyanate groups in the molecule such as an adduct with any of polyols such as polyols and polyisoprene polyols; tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated 2 in molecules such as xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylenepolyphenyl isocyanate, and hexamethylene diisocyanate allophanate. Compounds having an isocyanate group; and the like. Among these, the trimethylolpropane adduct body of tolylene diisocyanate is preferable because the adhesive physical properties can be easily adjusted. The number of isocyanate groups is an average number.

Examples of the epoxy-based curing agent include bisphenol A-epichlorohydrin-type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, and 1,6-hexanediol diglycidyl. Ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, N, N, N', N'-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane, And N, N, N', N'-tetraglycidylaminophenylmethane and the like.

Examples of the metal chelate-based curing agent include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium and zirconium, and a coordination compound of acetylacetone or ethyl acetoacetate. Can be mentioned.

Of the curing agents (B), the isocyanate-based curing agent preferably contains 0.1 to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer. The epoxy-based curing agent preferably contains 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the acrylic copolymer. The metal chelate-based curing agent preferably contains 0.1 to 2 parts by weight. By using an amount in the above range and the curing agent (B), it becomes easy to achieve both adhesive strength and holding power.

<Adhesive-imparting resin>
The pressure-sensitive adhesive composition of the present invention may further contain a pressure-sensitive adhesive resin.
Examples of the tackifier resin include a rosin-based tackifier resin, a synthetic hydrocarbon-based tackifier resin, a terpene-based tackifier resin, a terpenephenol-based tackifier resin, and the like. It is preferable to contain at least one selected from the tackifier resin and the terpene phenolic tackifier resin. By including these adhesive-imparting resins, the adhesive strength can be further improved.
Furthermore, by using a rosin-based tackifier resin and a synthetic hydrocarbon-based tackifier resin in combination, it becomes easier to achieve both compatibility and adhesive strength to a highly polar adherend and a low-polarity adherend. preferable.

The rosin-based tackifier resin includes rosin esters obtained by esterifying unmodified rosins of gum rosin, tall oil rosin, and wood rosin with alcohol, and modified rosins such as disproportionated rosin modified from unmodified rosin, polymerized rosin, and hydrogenated rosin. , Disproportionate rosin ester obtained by further esterifying these modified rosins with alcohol or the like, modified rosin ester such as polymerized rosin ester or hydrogenated rosin ester, rosin phenol obtained by adding phenol to unmodified rosin, and the like are preferable. Among these, rosin ester and modified rosin ester are preferable because the adhesive strength and transparency are further improved. In the rosin ester and the modified rosin ester, some of the hydroxyl groups such as alcohol used for esterification may remain unreacted. Examples of the alcohol used for esterification include monofunctional alcohols such as methanol, bifunctional alcohols such as ethylene glycol, trifunctional alcohols such as glycerin, and tetrafunctional alcohols such as pentaerythritol, which are in phase with acrylic copolymers. Considering the solubility, alcohols having trifunctionality or less are preferable.

Examples of the synthetic hydrocarbon-based pressure-sensitive adhesive-imparting resin include kumaron-based resin, kumaron-inden-based resin, styrene-based resin, xylene-based resin, phenol-based resin, and petroleum-based resin. Among these, styrene-based resins are preferable because they have good compatibility with acrylic polymers and can further improve the adhesive performance.

As the pressure-sensitive adhesive resin used in the pressure-sensitive adhesive of the present invention, a rosin-based pressure-sensitive adhesive resin and a synthetic hydrocarbon-based pressure-sensitive adhesive resin are preferable from the viewpoint of achieving both a high-polarity adherend and a low-polarity adherend. , Synthetic hydrocarbon-based tackifier resins are more preferred.

The softening point of the tackifier resin is preferably 80 ° C. or higher, more preferably 90 ° C. or higher. The upper limit of the softening point is preferably 170 ° C, more preferably 160 ° C, and even more preferably 155 ° C. When the softening point of the tackifying resin is 80 to 170 ° C., it becomes easy to achieve both adhesive strength and holding power at a high level. The softening point is the softening temperature measured according to the dry-bulb method specified in JIS K5902.

The tackifier resin is preferably used in an amount of 10 to 50 parts by mass, more preferably 15 to 40 parts by mass, based on 100 parts by mass of the copolymer (A). By using 10 to 50 parts by mass of the tackifying resin, it is possible to more easily achieve both adhesive strength, cohesive strength, and curved surface adhesiveness.

<Polyolefin>
The pressure-sensitive adhesive composition of the present invention may further contain a polyolefin. By containing polyolefin, the adhesive strength to a low-polarity adherend made of polyolefin can be improved.

Polyolefins are classified into chlorinated polyolefins (hereinafter referred to as chlorinated polyolefins) and non-chlorinated polyolefins (hereinafter referred to as non-chlorinated polyolefins). Chlorinated polyolefins are classified into, for example, chlorinated polypropylene and acids. Examples thereof include modified chlorinated polypropylene, acrylic modified chlorinated polypropylene, chlorinated polyethylene, chlorinated ethylene vinyl acetate copolymer and the like. Among these, chlorinated polypropylene, acid-modified chlorinated polypropylene, and acrylic-modified chlorinated polypropylene are preferable, and chlorinated polypropylene is more preferable, because they have excellent solubility and high adhesiveness to a polyolefin-made adherend. The chlorine content of the chlorinated polyolefin is preferably 20% or more to 45% or less, and more preferably 28% or more to 45% or less, from the viewpoint of having a high effect of improving the adhesive strength on the low-polarity adherend made of polyolefin.

Examples of the non-chlorinated polyolefin include polyethylene, polypropylene, α-olefin-propylene copolymer, ethylene-vinyl acetate copolymer, polybutene, maleated polypropylene, maleated polybutene, polybutadiene and its hydride, polyisoprene and its hydride. Examples thereof include maleinated polybutadiene, maleated polyisoprene, polybutadiene polyol and its hydride, polyisoprene polyol and its hydride, and lubricating oil such as process oil and liquid paraffin.
Among these, α-olefin-polypropylene copolymer, maleated polypropylene, polybutene, and lubricating oil are preferable because of their excellent solubility and high adhesiveness to the polyolefin-made adherend. As the lubricating oil, paraffin-based lubricating oil, naphthen-based lubricating oil and the like are preferable.
As the polyolefin used in the pressure-sensitive adhesive of the present invention, chlorinated polyolefin is preferable from the viewpoint of excellent solubility and high adhesive force to a polyolefin-made adherend, and chlorinated polypropylene is more preferable.

The polyolefin is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass with respect to 100 parts by mass of the copolymer (A). By using 0.01 to 10 parts by mass of polyolefin, it is possible to more easily achieve both adhesive force, cohesive force and curved surface adhesiveness to a low-polarity adherend.

The pressure-sensitive adhesive of the present invention further comprises, as optional components, a flame retardant aid, a heat-resistant stabilizer, a weather-resistant stabilizer, an antiaging agent, an ultraviolet absorber, a leveling agent, an antistatic agent, a slip agent, an anti-blocking agent, and an anti-fog agent. It can contain lubricants, dyes, waxes, emulsions, magnetic materials, and dielectric property modifiers.

《Adhesive sheet》
The pressure-sensitive adhesive sheet of the present invention preferably includes a base material and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present invention. As another embodiment, a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the core material, or a cast pressure-sensitive adhesive sheet composed of only the pressure-sensitive adhesive layer without a base material and a core material is also preferable. The pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive onto a substrate and drying it. Alternatively, it can be formed by applying an adhesive on a peelable sheet, drying it to form an adhesive layer, and then laminating the base materials. It is usual to attach a peelable sheet to the surface of the pressure-sensitive adhesive layer that does not come into contact with the base material and store it.

When applying the pressure-sensitive adhesive, the viscosity can be adjusted by adding the solvent described in solution polymerization.

As the base material, for example, cellophane, plastic, rubber, foam, cloth, rubberized cloth, resin-impregnated cloth, glass, wood and the like are preferable. The shape of the base material can be selected from a plate shape and a film shape, but a film shape that is easy to handle is preferable. As the base material, a single body or a laminated body of two or more kinds can be used.

The plastic may be, for example, a polyolefin such as polyvinyl alcohol, triacetyl cellulose, polypropylene, polyethylene, polycycloolefin, ethylene-vinyl acetate copolymer; polyester such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polycarbonate, polynorbornene. , Polyarylate, Polyacrylic, Polyphenylene Sulfidem, Polyester, Polyester, Polyester; and the like.

The method of applying the adhesive is not particularly limited, and examples thereof include a Meyer bar, an applicator, a brush, a spray, a roller, a gravure coater, a die coater, a lip coater, a comma coater, a knife coater, a reverse coater, and a spin coater. Be done. It is preferable to carry out a drying step at the time of coating. The drying device is not particularly limited, and examples thereof include a hot air dryer, an infrared heater, and a decompression method. The drying temperature is usually about 60 to 160 ° C.
The thickness of the pressure-sensitive adhesive layer is preferably 1 to 20 μm, more preferably 1 to 15 μm, and even more preferably 1 to 10 μm. The pressure-sensitive adhesive composition of the present invention can be excellent in all of adhesive strength, holding power, and curved surface adhesiveness even in a thin film of 1 to 20 μm.

The pressure-sensitive adhesive sheet of the present invention can be used for various purposes regardless of the adherend from high polarity to low polarity such as plastics such as polyolefin, glass, cardboard, and metal. In particular,

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the Examples. In the embodiment, "part" means "part by weight" and "%" means "% by weight".
The blending amount in the table is a part by weight, and is a non-volatile content conversion value except for the solvent. The blanks in the table indicate that they are not mixed.

The weight average molecular weight (Mw) and acid value of the copolymer were measured by the following methods.
<Measurement of weight average molecular weight (Mw)>
GPC was used for the measurement of the weight average molecular weight. GPC is a liquid chromatography in which a substance dissolved in a solvent (THF; tetrahydrofuran) is separated and quantified by the difference in its molecular size, and the weight average molecular weight is determined in terms of polystyrene.
Device name: LC-GPC system "Prominence" manufactured by Shimadzu Corporation
Column: 4 GMHXL manufactured by Tosoh Co., Ltd. and 1 HXL-H manufactured by Tosoh Co., Ltd. were connected in series.
Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 ml / min
Column temperature: 40 ° C

<Measurement of acid value>
Precisely weigh 1 g of the sample in an Erlenmeyer flask with a stopper, add 100 ml of a toluene / ethanol (volume ratio: toluene / ethanol = 2/1) mixture to dissolve it, and then add it to a 0.1 N-alcoholic potassium hydroxide solution. And titrated. The acid value (unit: mgKOH / g) was calculated by the following formula. The acid value was the value of the dried sample.
Acid value = {(5.61 × a × F) / S} / (nonvolatile content concentration / 100)
S: Sample collection amount (g)
a: Consumption of 0.1N-alcoholic potassium hydroxide solution (ml)
F: Factor of 0.1N-alcoholic potassium hydroxide solution

(Manufacturing of copolymer (A-1))
20 parts of 2-ethylhexyl acrylate, n-butyl acrylate in a reaction vessel (hereinafter, simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube under a nitrogen atmosphere. 70.8 parts, Isobornyl acrylate 5 parts, 2-Hydroxyethyl acrylate 0.2 parts, ω-carboxypolycaprolactone monoacrylate (Aronix M-5300, manufactured by Toa Synthetic Co., Ltd.) 2 parts, 2-acryloyloxyethyl succinic acid (HOA-MS (N) manufactured by Kyoeisha Chemical Co., Ltd.), 70 parts of ethyl acetate, and 0.015 parts of 2,2'-azobisisobutyronitrile were charged. Heating was carried out with stirring to confirm the start of the polymerization reaction, and the reaction was carried out at the reflux temperature for 2 hours. Then, 0.03 part of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Then, the reaction vessel was cooled and 130 parts of ethyl acetate was added to obtain a copolymer (A-1) solution having a weight average molecular weight of 900,000.

(Manufacturing of copolymers (A-2 to 11, A'-1 to 4))
Copolymers (A-2 to 11, A'-1 to 4) were obtained in the same manner as the copolymer (A-1) except that the type and blending amount of the monomers were changed to those shown in Table 1.

(Manufacturing of copolymer (A-12))
20 parts of 2-ethylhexyl acrylate, n-butyl acrylate in a reaction vessel (hereinafter, simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube under a nitrogen atmosphere. 70.8 parts, isobornyl acrylate 5 parts, 2-hydroxyethyl acrylate 0.2 parts, 2-acryloyloxyethyl succinic acid (manufactured by Kyoeisha Chemical Co., Ltd., HOA-MS (N)) 4 parts, ethyl acetate 35 parts, 35 parts of methyl ethyl ketone and 0.015 parts of 2,2'-azobisisobutyronitrile were charged. Heating was carried out with stirring to confirm the start of the polymerization reaction, and the reaction was carried out at the reflux temperature for 2 hours. Then, 0.03 part of 2,2'-azobisisobutyronitrile was added to the reaction solution, and the reaction was continued for 6 hours. Then, the reaction vessel was cooled and 130 parts of ethyl acetate was added to obtain a copolymer (A-12) solution having a weight average molecular weight of 400,000.

The abbreviations in Table 1 are listed below.
2EHA: 2-Ethylhexyl acrylate BA: n-butyl acrylate CHA: Cyclohexyl acrylate IBXA: Isobornyl acrylate DCPA: Dicyclopentanyl acrylate M-5300: ω-carboxypolycaprolactone monoacrylate (manufactured by Toagosei Co., Ltd., Aronix M-5300) )
β-CEA: β-carboxyethyl acrylate (manufactured by Dycel Ornex, β-CEA)
HOA-MS (N): 2-acryloyloxyethyl succinic acid (manufactured by Kyoeisha Chemical Co., Ltd., HOA-MS (N))
HOA-HH: 2-acryloyloxyethyl hexahydrophthalic acid (manufactured by Kyoeisha Chemical Co., Ltd., light acrylate HOA-HH)
AA: Acrylic acid HEA: 2-Hydroxyethyl acrylate

(Example 1)
For 100 parts of the copolymer (A-1), 1.0 part of trimethylolpropane adduct of tolylene diisocyanate as a curing agent (nonvolatile content equivalent) and Pencel D-125 (Arakawa Chemical), which is a rosin-based tackifier resin. 10 parts of FTR6100 (manufactured by Mitsui Chemicals Co., Ltd.), which is a synthetic hydrocarbon-based tackifier resin, 1 part of Supercron 360T (manufactured by Nippon Paper Co., Ltd.), which is a polyolefin, and ethyl acetate are added as a solvent. The non-volatile content was adjusted to 30% to obtain a pressure-sensitive adhesive composition.

The obtained pressure-sensitive adhesive composition is coated on a removable sheet (made of polyethylene terephthalate) having a thickness of 38 μm with a comma coater so that the thickness after drying becomes 10 μm, and dried at 100 ° C. for 2 minutes. This formed a pressure-sensitive adhesive layer. Next, a 25 μm-thick base material (made of polyethylene terephthalate, hereinafter referred to as PET sheet) is attached to this pressure-sensitive adhesive layer and aged for one week at a temperature of 23 ° C. and a relative humidity of 50%. An adhesive sheet having a structure of "adhesive layer / PET sheet" was obtained.

(Examples 2 to 25, Comparative Examples 1 to 4)
The pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets of Examples 2 to 25 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1 except that the composition and the blending amount were changed as shown in Tables 2 and 3.

<< Evaluation of adhesive sheet >>
The obtained adhesive sheet was evaluated by the following method. The results are shown in Tables 2 and 3.
(1) Adhesive strength The obtained adhesive sheet was prepared to have a width of 25 mm and a length of 100 mm. In an atmosphere of 23 ° C. and 50% relative humidity, the peelable sheet was peeled off from the pressure-sensitive adhesive sheet, the exposed pressure-sensitive adhesive layer was attached to a stainless steel (SUS) plate, and pressure-bonded once with a 2 kg roll. After leaving it for 24 hours, the adhesive strength was measured in a 180 ° peel test in which the material was peeled off at a speed of 300 mm / min in the 180 degree direction using a tensile tester, and evaluation was performed based on the following evaluation criteria. (Compliant with JIS Z 0237: 2000)
A: "Adhesive strength is 12N or more, which is very good."
B: "Adhesive strength is 10N or more and less than 12N, which is good."
C: "Adhesive strength is 6N or more and less than 10N, and it is practical."
D: "Adhesive strength is less than 6N, so it is not practical."
The adhesive strength of the polypropylene (PP) plate was measured in the same manner as described above, and the evaluation was performed based on the following evaluation criteria.
A: "Adhesive strength is 12N or more, which is very good."
B: "Adhesive strength is 10N or more and less than 12N, which is good."
C: "Adhesive strength is 6N or more and less than 10N, and it is practical."
D: "Adhesive strength is less than 6N, so it is not practical."

(2) Holding power The obtained adhesive sheet was cut into a size of 25 mm in width and 100 mm in length and used as a sample. Next, in an atmosphere of 23 ° C. and 50% relative humidity, the release sheet was peeled off from the sample in accordance with JIS Z 0237, and the exposed adhesive layer having a tip width of 25 mm and a length of 25 mm was attached to a polished stainless steel (SUS) plate. After wearing and crimping once with a 2 kg roll, a load of 1 kg was applied in an atmosphere of 70 ° C. and the mixture was held for 70,000 seconds. The evaluation indicates the number of seconds when the sample falls from the SUS plate. When the sample does not fall, it indicates the number of mm in which the adhesive tip of the adhesive layer and the SUS plate is displaced downward due to the load. The evaluation criteria are shown below.
A: "Sample displacement is less than 0.05 mm, which is very good."
B: "The deviation of the sample is 0.05 mm or more and less than 0.2 mm, which is good."
C: "The deviation of the sample is 0.2 mm or more and there is no drop, so it is practical."
D: "Sample dropped, not practical."

(3) Curved surface adhesiveness The obtained adhesive sheet was placed in a constant temperature and humidity chamber at 23 ° C. and a relative humidity of 50%, and a measurement sample having a width of 15 mm and a length of 25 mm was prepared. The peeling sheet was peeled off from the measurement sample, and the exposed pressure-sensitive adhesive layer was attached to a 10 mmφ cylindrical polypropylene (PP) resin in the circumferential direction and left to stand for 72 hours. After that, the sample was left to stand in an atmosphere of 80 ° C. for 24 hours, and then the peeled state of the end portion of the pasted measurement sample was visually observed and evaluated according to the following criteria.
A: "There is no peeling at the end, which is very good."
B: "Peeling at the end is less than 3 mm in length, which is good."
C: "Peeling of the terminal part is 3 mm or more and less than 8 mm in length, and it is practical."
D: "The peeling of the end part is 8 mm or more in length, so it is not practical."

The abbreviations in Tables 2 and 3 are listed below.
<Adhesive-imparting resin>
D-125: Pencel D-125 (manufactured by Arakawa Chemical Co., Ltd., rosin-based adhesive resin)
FTR6100: FTR6100 (manufactured by Mitsui Chemicals, Inc., synthetic hydrocarbon-based tackifier resin (styrene-based tackifier resin))
T115: YS Polystar T115 (manufactured by Yasuhara Chemical Co., Ltd., terpene phenol-based adhesive-imparting resin)
PX1000: YS resin PX1000 (manufactured by Yasuhara Chemical Co., Ltd., terpene-based adhesive-imparting resin)
<Polyolefin>
360T: Supercron 360T (manufactured by Nippon Paper Industries, chlorinated polypropylene, chlorine content 31%)
930: Supercron 930 (manufactured by Nippon Paper Industries, chlorinated polypropylene, chlorine content 21%)
<Curing agent>
TDI / TMP: Trimethylolpropane adduct of toluene diisocyanate (nonvolatile content 37.5%)
TETRAD-X: N, N, N', N'-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Gas Chemical Company, Inc.)
Aluminum Chelate A: Aluminum Tris Acetylacetone (manufactured by Kawaken Fine Chemical Co., Ltd.)
Chemitite PZ-33: Trimethylolpropanetris [3- (aziridine-1-yl) propionate] (manufactured by Nippon Shokubai Co., Ltd.)

As shown in Tables 2 and 3, the adhesive sheet of the present invention has excellent adhesive strength to both a stainless steel plate which is a high-polarity adherend and a polypropylene plate which is a low-polarity adherend, and further has excellent holding power and curved surface adhesiveness. It was confirmed that it was excellent. On the other hand, in the comparative example adhesive sheet, one of the items is defective, which is practically problematic and impractical.

Claims (8)

The copolymer (A) is an alkyl (meth) acylate (a1) having an alkyl group having 4 to 12 carbon atoms, which contains a copolymer (A), a curing agent (B) , and a polyolefin, and a reactive functional group. It is a copolymer of a monomer mixture containing a (meth) acrylate (a 2) having an aliphatic ring structure and a (meth) acrylate (a 3) having a carboxyl group.
The content of the alkyl (meth) acrylate (a1) is 70 to 99% by mass in 100% by mass of the monomer mixture.
The (meth) acrylate (a3) having a carboxyl group is represented by the (meth) acrylate (a3-1) represented by the general formula (1) and the (meth) acrylate represented by the general formula (2) (a3-2). A pressure-sensitive adhesive composition comprising at least one of the above.

(In the formula, R ₁ is a hydrogen atom or a methyl group, m is an integer of 2 to 10, and n is an integer of 1 to 5.)

(In the formula, R ₂ is a hydrogen atom or a methyl group, R ₃ is a divalent hydrocarbon group, and p is an integer of 1 to 5.) The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylate (a3) contains a (meth) acrylate (a 3-2) represented by the general formula (2). The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the copolymer (A) has an acid value in the range of 0.1 to 24.0 mgKOH / g. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the monomer mixture further contains a (meth) acrylate (a4) having a hydroxyl group. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the curing agent (B) contains at least one selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent, and a metal chelate-based curing agent. Further, the tackifier resin is included, and the tackifier resin includes at least one selected from the group consisting of a rosin-based tackifier resin, a synthetic hydrocarbon-based tackifier resin, and a terpenephenol-based tackifier resin. 5 The pressure-sensitive adhesive composition according to any one of the above items. An adhesive sheet provided with an adhesive layer formed from the adhesive composition according to any one of claims 1 to 6 . The pressure-sensitive adhesive sheet according to claim 7 , wherein the pressure-sensitive adhesive layer has a thickness of 1 to 20 μm.