JP2023177416A - Adhesive composition and adhesive sheet - Google Patents

Abstract

【assignment】
It has sufficient adhesive strength and high tackiness, and shows good re-peelability even on highly polar adherends such as SUS and steel plates, where adhesive tends to remain when peeled, and can withstand high temperature or moist heat conditions when attached. The adhesive composition and adhesive sheet have sufficient removability even when stored for a long time, and the adhesive does not protrude from the sheet even under high temperature and high load conditions when attached. To provide an adhesive composition and an adhesive sheet that allow heavy adherends such as steel plates to be stacked and stored even at high temperatures.
[Solution]
Acrylic is a copolymer of a monomer mixture consisting of a (meth)acrylic acid alkyl ester monomer (A) whose alkyl group has 1 to 12 carbon atoms, a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group. The content of the monomer (B) containing an acid ester copolymer and an isocyanate curing agent and having an acidic group is 0.01% by mass or more and 6% by mass or less based on 100% by mass of the monomer mixture. The content of the monomer (C) is 0.05% by mass or more and 10% by mass or less based on 100% by mass of the monomer mixture, and the adhesive composition has a gel fraction of 55% or more.
[Selection diagram] None

Description

The present invention relates to an adhesive composition and an adhesive sheet.

Adhesive sheets with an adhesive layer formed from adhesives are easier to handle than adhesives, so they are used in a wide range of fields as display labels and fixing tapes. There are two main types: force type and removable type, in which the adhesive sheet is peeled off after use. There are various resin-based adhesives, among which acrylic adhesives are widely used. Acrylic adhesives have the advantage that basic adhesive properties such as adhesive strength and tack can be easily controlled by adjusting the monomer composition and compatible additives.

As a removable acrylic adhesive, Patent Document 1 discloses that the main monomer is (meth)acrylic acid acrylic ester whose alkyl group has 4 to 12 carbon atoms, and at least 3 of the total monomers are used as a removable acrylic adhesive. An acrylic polymer copolymerized with ~20% by weight of a radically polymerizable monomer containing carboxyl groups is crosslinked to a gel fraction of 80% by weight or more using a crosslinking agent that has a functional group that reacts with carboxyl groups in the molecule. A pressure-sensitive adhesive composition characterized by an acrylic pressure-sensitive adhesive layer is disclosed. Further, Patent Document 2 describes thermally expandable microspheres on one side of a base material, an acrylic adhesive with a weight average molecular weight of 100,000 to 300,000, an acid value of 30 or more that can react with a crosslinking agent, and a softening point of 90. ℃ or higher and a solubility parameter value (SP value) of 8.9 or higher, a removable adhesive comprising an adhesive layer formed by applying an adhesive composition comprising a tackifying resin and a crosslinking agent. The sheet is disclosed.

Japanese Patent Application Publication No. 2000-328016 Japanese Patent Application Publication No. 2003-160765

However, the adhesive composition of Patent Document 1 has a problem in that when the adhesive sheet is peeled off after being stored for a long period of time under high temperature or moist heat conditions while being attached to an adherend, the adhesive remains on the adherend. there were. In addition, the adhesive sheet of Patent Document 2 has difficulty in ensuring sufficient removability under room temperature conditions, and has problems with peeling due to decreased adhesive strength under high temperature conditions and long-term storage under high temperature conditions. There was a problem in that the subsequent removability was not sufficient.

Therefore, the problem to be solved by the present invention is to have sufficient adhesive strength, high tackiness, and good removability even for highly polar adherends such as SUS and steel plates, where adhesive tends to remain during peeling. Adhesive compositions and adhesive sheets that exhibit sufficient removability even when affixed and stored under high temperature or humid heat conditions for long periods of time; To provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet, which have a small amount of pressure-sensitive adhesive protruding from the sheet, and which allow heavy adherends such as steel plates to be stored stacked on top of each other even at high temperatures.

In order to solve the above problems, the present inventors have discovered a (meth)acrylic acid alkyl ester monomer (A) in which the alkyl group has 1 to 12 carbon atoms, a monomer (B) having an acidic group, and a monomer (B) having a hydroxyl group. The content of monomer (B) containing an acrylic ester copolymer which is a copolymer of a monomer mixture consisting of C) and an isocyanate curing agent and having an acidic group is 0.01% by mass in 100% by mass of the monomer mixture. The content of the monomer (C) having a hydroxyl group is 0.05% by mass or more and 10% by mass or less based on 100% by mass of the monomer mixture, and the gel fraction is 55% or more. We have discovered a certain adhesive composition.

That is, the present invention relates to the following [1] to [4].

[1] Copolymer of a monomer mixture consisting of a (meth)acrylic acid alkyl ester monomer (A) whose alkyl group has 1 to 12 carbon atoms, a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group The content of the monomer (B) containing an acrylic ester copolymer and an isocyanate curing agent and having an acidic group is 0.01% by mass or more and 6% by mass or less based on 100% by mass of the monomer mixture. The content of the monomer (C) having a hydroxyl group is 0.05% by mass or more and 10% by mass or less based on 100% by mass of the monomer mixture, and the adhesive composition has a gel fraction of 55% or more.

[2] (Meth)acrylic acid alkyl ester monomer (A) whose alkyl group has 1 to 12 carbon atoms (meth)acrylic acid alkyl ester monomer (A) whose alkyl group has 8 to 12 carbon atoms; The present invention relates to the pressure-sensitive adhesive composition according to [1] above, wherein the content of a1) is 55% by mass or more.

[3] The above-mentioned [1] wherein the ratio (P) of the loss modulus at 25 °C and the loss modulus at 150 °C when measured at 1 Hz, expressed by formula 1, is 0.02 or more and 0.3 or less. ] or [2].

P=(loss modulus at 150°C when measured at 1Hz)/(loss modulus at 25°C when measured at 1Hz) (Formula 1)

[4] A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive composition according to any one of [1] to [3] above.

According to the present invention, the present invention has sufficient adhesive strength and high tackiness, and exhibits good removability even on highly polar adherends such as SUS and steel plates, where adhesive tends to remain when peeled, and can be applied easily. Adhesive compositions and adhesive sheets that have sufficient removability even when stored under high temperature or humid heat conditions for long periods of time, as well as adhesive compositions and adhesive sheets that have sufficient removability even when stored under high temperature or humid heat conditions. It is possible to provide a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet that have little oozing out of the adhesive and that allow heavy adherends such as steel plates to be stacked and stored even at high temperatures.

The details of the present invention will be explained below. It goes without saying that other embodiments are also included in the scope of the present invention as long as they meet the spirit of the present invention. Furthermore, in this specification, numerical ranges specified using "~" include the numerical values written before and after "~" as the lower limit and upper limit ranges.

In this specification, "(meth)acrylic acid" and "(meth)acrylate" refer to "acrylic acid or methacrylic acid" and "acrylate or methacrylate," respectively, unless otherwise specified. shall be. Moreover, "(meth)acrylic acid ester monomer" refers to a general term for "acrylic acid ester monomer" and "methacrylic acid ester monomer." In addition, a (meth)acrylic acid alkyl ester monomer (A) in which the alkyl group has 1 to 12 carbon atoms is simply a monomer (A), a monomer having an acidic group (B) is simply a monomer (B), a monomer having a hydroxyl group (C) may be simply referred to as monomer (C).

In this specification, "Mw" is the weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) measurement. "Mn" is the number average molecular weight in terms of polystyrene determined by GPC measurement. These can be measured by the method described in the [Example] section.

Unless otherwise noted, the various components appearing in this specification may be used individually or in combination of two or more.

<Acrylic acid ester copolymer>
The acrylic ester copolymer means a polymer of a monomer having an ethylenically unsaturated bond such as a (meth)acrylic ester monomer.
The acrylic ester copolymer of the present invention comprises a (meth)acrylic acid alkyl ester monomer (A) in which the alkyl group has at least 1 to 12 carbon atoms, a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group. ), the content of the monomer (B) having an acidic group is 0.01% by mass or more and 6% by mass or less based on 100% by mass of the monomer mixture, and the content of the monomer (B) having a hydroxyl group is 0.01% by mass or more and 6% by mass or less. The content of C) is 0.05% by mass or more and 10% by mass or less in 100% by mass of the monomer mixture.

Monomers are classified into (meth)acrylic acid alkyl ester monomers (A) in which the alkyl group has 1 to 12 carbon atoms, monomers having acidic groups (B), monomers having hydroxyl groups (C), and other monomers. The monomers constituting the acrylic copolymer include monomers (A), (B), and (C) as essential components, and other monomers may be used as necessary.

[Monomer (A)]
Monomer (A) is a (meth)acrylic acid alkyl ester monomer in which the alkyl group has 1 to 12 carbon atoms. As the (meth)acrylic acid alkyl ester monomer in which the alkyl group has 1 to 12 carbon atoms, the (meth)acrylic acid alkyl ester monomer (a1) in which the alkyl group has 8 to 12 carbon atoms and the (meth)acrylic acid alkyl ester monomer (a1) in which the alkyl group has 8 to 12 carbon atoms are It is classified into 1 to 7 (meth)acrylic acid alkyl ester monomers (a2). It is preferable to use a (meth)acrylic acid alkyl ester monomer (a1) whose alkyl group has 8 to 12 carbon atoms, and it is more preferable to use (a1) and (a2) together. By using the (meth)acrylic acid alkyl ester monomer (a1) whose alkyl group has 8 to 12 carbon atoms, both tack and removability can be achieved at a high level.

Monomer (a1) includes octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, and isodecyl (meth)acrylate. Examples include lauryl (meth)acrylate. Among these, 2-ethylhexyl acrylate and lauryl (meth)acrylate are preferred from the viewpoint of removability.

The content of the monomer (a1) is not particularly limited, but is preferably 55% by mass or more, more preferably 65% by mass or more based on 100% by mass of the monomer mixture constituting the acrylic ester copolymer. There is no particular restriction on the upper limit, but if it is forced, it is preferably 90% by mass or less, more preferably 80% by mass or less. By setting it within this range, both high tackiness and removability can be achieved.

Monomers (a2) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, ( Examples include hexyl meth)acrylate and heptyl (meth)acrylate. Among these, butyl acrylate and (iso)butyl acrylate are preferred because they exhibit good adhesion to various adherends.

[Monomer (B)]
Monomer (B) is a monomer having an acidic group. By using the monomer (B), it is possible to exhibit good adhesive force and cohesive force to various adherends.

Examples of the monomer (B) include (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl-succinic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, - Carboxylic acids with unsaturated bonds such as (meth)acryloyloxyethyl-phthalic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, citraconic acid, mesaconic acid, and 2-(meth)acryloyloxyethyl acid phos (meth)acrylic acid and 2-carboxyethyl (meth)acrylate are preferred from the viewpoint of cohesive strength of the resulting pressure-sensitive adhesive composition and copolymerizability with other monomers.

The content of monomer (B) shall be 0.01% by mass or more and 6% by mass or less, and 0.1% by mass or more and 4% by mass or less based on 100% by mass of the monomer mixture constituting the acrylic ester copolymer. It is preferably 0.5% by mass or more and 3.5% by mass or less, more preferably 1% by mass or more and 3% by mass or less. When the content of the monomer (B) is 0.05% by mass or more, high adhesive force and cohesive force can be imparted. Moreover, since the content of the monomer (B) is 6% by mass or less, even after the adhesive sheet is peeled from the adherend, adhesion of the adhesive composition to the adherend can be suppressed.

[Monomer (C)]
Monomer (C) is a monomer having a hydroxyl group. By using the monomer (C), it becomes a reaction site with the isocyanate curing agent and can provide good removability even under high temperature or moist heat conditions.

Examples of monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-hydroxybutyl (meth)acrylate. Examples include hydroxyalkyl (meth)acrylates such as meth)acrylate and 4-hydroxybutyl(meth)acrylate, and hydroxy(meth)acrylamides such as hydroxymethylacrylamide and hydroxyethylacrylamide. 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of reactivity with the isocyanate curing agent and cohesive force obtained.

The content of the monomer (C) is 0.05% by mass or more and 10% by mass or less, and 0.07% by mass or more and 1.8% by mass or less based on 100% by mass of the monomer mixture constituting the acrylic ester copolymer. It is preferably at least 0.08% by mass and at most 1% by mass. When the content of the monomer (C) is 0.05% by mass or more, high cohesive force can be imparted during the curing agent reaction. When the content of the monomer (B) is 10% by mass or less, it is possible to suppress a significant increase in the viscosity of the solution after mixing the curing agent, and it is possible to impart good removability.

[Other monomers]
Other monomers are monomers other than monomer (A), monomer (B), and monomer (C). Other monomers are not particularly limited, and monomers copolymerizable with monomer (A), monomer (B), and monomer (C) can be selected as appropriate; examples include vinyl acetate, vinyl propionate, and vinyl butyrate. other vinyl monomers such as styrene, acrylonitrile, monomers with alicyclic structure such as isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate , monomers with aromatic rings such as benzyl (meth)acrylate, biphenyl (meth)acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxypolypropylene Monomers with alkoxy(poly)alkylene oxides such as glycol (meth)acrylate, acid anhydrides with polymerizable unsaturated bonds in the molecule such as maleic anhydride and itaconic anhydride, monomers with amino groups, other nitrogen Examples include monomers having atoms, monomers having epoxy groups, and monomers having isocyanato groups.

Examples of monomers having an amino group include monoalkylamino esters such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate. Examples include (meth)acrylate.

Other nitrogen atom-containing monomers include (meth)acrylamide, N-vinylpyrrolidone, acryloylmorpholine, and the like.

Examples of monomers having an epoxy group include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 6-methyl-3,4-epoxycyclohexylmethyl (meth)acrylate. etc.

Examples of the monomer having an isocyanato group include 2-isocyanatoethyl (meth)acrylate.

[Method for producing acrylic ester copolymer]
There are no particular restrictions on the method for producing the acrylic ester copolymer, and the acrylic ester copolymer can be obtained, for example, by polymerizing the above monomer mixture using a known radical polymerization reaction. Although the reaction may be carried out without a solvent, it is preferable to use a solvent from the viewpoint of synthesis stability and handling. Moreover, from the viewpoint of molecular weight control, it is preferable to use a radical polymerization initiator (hereinafter sometimes abbreviated as "polymerization initiator"). In addition, known additives such as chain transfer agents may also be used.
As the solvent, the solvents described below can be used.

Examples of the polymerization initiator include benzoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, and di(2-ethoxyethyl)peroxydicarbonate. , tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxy neodecanoate, tert-butyl peroxy bivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, Organic peroxides such as diacetyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane 1-carbonitrile) ), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropylene) pionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), 2,2'-azobis[2-(2-imidazoline-2 -yl)propane] and the like.

Examples of chain transfer agents include alkyl mercaptans such as octyl mercaptan, nonyl mercaptan, decyl mercaptan, and dodecyl mercaptan; thioglycolic acid esters such as octyl thioglycolate, nonyl thioglycolate, and 2-ethylhexyl thioglycolate; Examples include 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, α-pinene, and β-pinene. In particular, thioglycolic acid esters, 2,4-diphenyl-4-methyl-1-pentene, 1-methyl-4-isopropylidene-1-cyclohexene, α-pinene, β-pinene, etc. are It is preferable because it has low odor.

The weight average molecular weight Mw of the acrylic ester copolymer is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,000,000, as calculated by gel permeation chromatography (GPC) in terms of standard polystyrene. It is more preferably 400,000 to 900,000, and particularly preferably 500,000 to 800,000. When the weight average molecular weight is 200,000 or more, sufficient cohesive force can be obtained. When the weight average molecular weight is 2 million or less, increase in viscosity can be suppressed and good coating suitability can be obtained.

The molecular weight dispersity Mw/Mn of the acrylic acid ester copolymer is preferably 2.0 to 12, more preferably 4 to 10, as measured by gel permeation chromatography (GPC) in terms of standard polystyrene. When the degree of molecular weight dispersion is within the above range, both adhesive force and cohesive force can be achieved. In addition, Mn means number average molecular weight.

The glass transition temperature (Tg) of the acrylic ester copolymer is not particularly limited, but is preferably -70 to -25°C, more preferably -65 to -30°C. When the glass transition temperature is −70° C. or higher, sufficient cohesive force can be obtained. When the glass transition temperature is −25° C. or lower, good adhesive strength can be exhibited.

In the present invention, the glass transition temperature (Tg) of the acrylic ester copolymer (A) is a value calculated based on the following formula (2) (Fox formula).
1/Tg=W1/Tg1+W2/Tg2+...+Wn/Tgn (Formula 2)
[In formula (1), Tg is the Tg (unit: K) of the acrylic ester copolymer (A), and Tgi (i = 1, 2, ... n) is the radically polymerizable monomer i forming a homopolymer. Tg (unit: K) and Wi (i=1, 2, . . . n) represent the mass fraction of the radically polymerizable monomer i in all monomer components. Note that for the Tg of the homopolymer, published values such as literature values and catalog values are used. ]
The above formula (2) is a calculation formula when the acrylic ester copolymer (A) is composed of n types of monomer components: monomer 1, monomer 2, . . . , monomer n.

<Isocyanate curing agent)>
The adhesive composition of the present invention contains an isocyanate curing agent as a curing agent. The isocyanate curing agent can exhibit high adhesive strength and cohesive strength by forming a crosslinking point with the hydroxyl group-containing monomer (C) contained in the acrylic ester copolymer.

Examples of the isocyanate 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 diisocyanate. Isocyanates, adducts of diisocyanates such as polymethylene polyphenylisocyanate, and polyol compounds such as trimethylolpropane, burettes thereof, isocyanurates thereof, and the above diisocyanates, polyether polyols, polyester polyols, acrylic polyols Compounds having three or more isocyanate groups in the molecule, such as adducts with any one of polyols such as , polybutadiene polyol, and polyisoprene polyol; or compounds having two or more isocyanate groups in the molecule, such as allophanate bodies Examples include compounds having the following. Among these, trimethylolpropane adducts of tolylene diisocyanate, trimethylolpropane adducts of xylylene diisocyanate, and trimethylolpropane adducts of hexamethylene diisocyanate are preferred because the adhesive properties can be easily adjusted. Particularly preferred are propane adducts. Note that the number of isocyanate groups is the average number.

The content of the isocyanate curing agent is not particularly limited, but it is preferably 0.1 to 10 parts by mass, more preferably 1 to 9 parts, 1. Particularly preferred is 5 to 7 parts. When the content of the isocyanate curing agent is 0.1 parts by mass or more, sufficient cohesive force can be obtained, and when the content is 10 parts by mass or less, zipping during peeling can be suppressed.

The pressure-sensitive adhesive composition of the present invention may further contain other curing agents other than isocyanate-based curing agents. Examples of other curing agents include metal chelate curing agents, epoxy curing agents, and aziridine curing agents. By including these curing agents, the cohesive force of the adhesive composition is further increased and the heat resistance is improved.

Known metal chelate curing agents can be used, such as polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium, acetylacetone, acetoacetic acid, etc. Examples include coordination compounds with a ligand such as ethyl. From the viewpoint of long-term storage stability, the polyvalent metal is preferably aluminum, and the ligand is preferably at least one of acetylacetone and acetoacetate.

Examples of metal chelate curing agents include aluminum alkoxides such as aluminum isopropylate, monosec-butoxyaluminum diisopropylate, aluminum sec-butyrate, and aluminum ethylate;
Aluminum chelates such as ethyl acetoacetate aluminum diisopropylate, aluminum tris (ethylacetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum monoacetylacetate bis (ethylacetoacetate), aluminum tris (acetylacetonate),
Titanium alkoxides such as titanium tetraisopropoxide, titanium tetra-normal butoxide, titanium butoxy dimer, titanium tetra-2-ethylhexoxide,
Titanium chelates such as titanium isopropoxy bis (acetylacetonate), titanium tetraacetylacetonate, titanium diisopropoxy bis (ethylacetoacetate), phosphate ester titanium complex, titanium octylene glycolate,
Zirconium alkoxides such as zirconium tetranormal propoxide, zirconium tetranormal butoxide,
Zirconium chelates such as zirconium tetraacetylacetonate, zirconium tributoxy monoacetylacetonate, zirconium tetraacetylacetonate, zirconium dibutoxybis(ethylacetoacetate),
Examples include zirconium acylates such as zirconium stearate.

Among these, preferred are alkyl acetoacetate aluminum diisopropylate, aluminum monoacetylacetate bis(ethylacetoacetate), and aluminum tris(acetylacetonate) from the viewpoint of crosslinkability, adhesive strength, transparency, and storage stability.

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

Examples of aziridine curing agents include N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxite), N,N'-toluene-2,4-bis(1-aziridinecarboxite), and bisisophthalocarbonate. yl-1-(2-methylaziridine), tri-1-aziridinylphosphine oxide, N,N'-hexamethylene-1,6-bis(1-aziridinecarboxite), 2,2'-bishydroxymethyl Butanol-tris[3-(1-aziridinyl)propionate], trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethanetri-β-aziridinylpropionate, and tris-2,4,6 -(1-aziridinyl)-1,3,5-triazine and the like.

The content of the other curing agent is not particularly limited, but is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the acrylic ester copolymer.

A known catalytic action inhibitor may be added to the adhesive composition of the present invention for the purpose of improving the pot life of the adhesive.
Specific examples of the catalytic action inhibitor include compounds that form keto-enol tautomers. The keto-enol tautomer-forming compound is a compound capable of forming a keto-enol tautomer, and acetylacetone, acetoacetate, malonic acid ester, etc. are preferable.

Examples of acetoacetate include methyl acetoacetate, ethyl acetoacetate, and isopropyl acetoacetate. Examples include butyl acetoacetate, isobutyl acetoacetate, tert-butyl acetoacetate, and the like.

Examples of malonic acid esters include dimethyl malonate, diethyl malonate, and dibutyl malonate.
Among these, acetylacetone is preferred as the keto-enol tautomer-forming compound because of its ease of volatilization during drying.

The content of the catalytic action inhibitor is preferably 0.05 to 10.0 parts by mass, and preferably 0.1 to 5.0 parts by mass, based on 100 parts by mass of the acrylic ester copolymer. The amount is more preferably 0.5 to 3.0 parts by mass. When the amount of the catalytic action inhibitor is 0.05 parts by mass or more, the pot life is good, and when it is 10.0 parts by mass or less, good initial curability is obtained.

<Solvent>
The adhesive composition of the present invention may contain a solvent.
The timing of blending the solvent is not particularly limited, and it may be used during the production of the acrylic ester copolymer, or may be used as a diluting solvent to adjust the viscosity during the production of the adhesive composition. The solvent can be selected from the viewpoints of leveling properties and drying properties during coating, as well as effects on the environment and the human body. Preferred solvents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, esters, ketones, and alcohols.

Examples of the solvent include ester solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone, methyl butyl ketone, and cyclohexanone; hydrocarbon solvents such as toluene, xylene, and anisole; Examples include alcohol solvents such as methanol, ethanol, normal propanol, and isopropanol, but from the viewpoint of the pot life of the adhesive composition, it is preferable to include an ester solvent and/or an alcohol solvent.

The amount of the solvent to be used is preferably 10 parts by weight or more, more preferably 30 parts by weight or more, based on 100 parts by weight of the acrylic ester copolymer. The upper limit is not particularly limited, but from the viewpoint of coatability, it is preferably 2000 parts by mass or less.

<Tackifying resin>
The adhesive composition of the present invention can further contain a tackifying resin. The tackifying resin can be used by any method such as a method used during solution polymerization or a method of blending it into an acrylic ester copolymer. When the tackifier resin is used during solution polymerization, it acts as a chain transfer agent, making it easier to adjust the molecular weight of the acrylic ester copolymer. Moreover, when it is blended with an acrylic acid ester copolymer, the adhesive strength can be further improved.

The softening point of the tackifying resin is preferably 70°C to 170°C, more preferably 75°C to 160°C, and even more preferably 100°C to 150°C.
When the softening point of the tackifying resin is within the above range, it becomes easy to achieve both high levels of adhesive force and cohesive force. Note that the softening point is a softening temperature measured according to the dry bulb method specified in JIS SK5902.

Examples of tackifying resins include, but are not limited to, rosin resins, polymerized rosin resins, rosin ester resins, polymerized rosin ester resins, terpene resins, terpene phenol resins, coumaron resins, and coumarons. Examples include indene resins, styrene resins, xylene resins, phenol resins, petroleum resins, and the like. Among these, rosin resin, polymerized rosin resin, rosin ester resin, polymerized rosin ester resin, petroleum resin, Styrenic resins are preferred. The tackifying resins may be used alone or in combination of two or more.

The content of the tackifying resin is preferably 1 to 60 parts by weight, more preferably 1.5 to 20 parts by weight, and even more preferably 2 to 10 parts by weight, based on 100 parts by weight of the acrylic ester copolymer. By adding 1 part by mass or more of the tackifying resin, it is possible to increase the adhesive strength, and by adding the tackifying resin to 60 parts by mass or less, removability can be maintained.

<Plasticizer>
For the purpose of suppressing zipping during peeling, the adhesive composition of the present invention may further contain a plasticizer, if necessary. The plasticizer is not particularly limited, but organic acid esters are preferred from the viewpoint of compatibility with the acrylic ester copolymer.

Examples of esters of monobasic acids or polybasic acids and alcohols include isostearyl laurate, isopropyl myristate, isocetyl myristate, octyldodecyl myristate, isostearyl palmitate, isocetyl stearate, octyldodecyl oleate, and phthalate. dibutyl acid, dioctyl phthalate, diheptyl phthalate, dibenzyl phthalate, butylbenzyl phthalate, diisodecyl adipate, diisostearyl adipate, dibutyl sebacate, diisocetyl sebacate, tributyl acetyl citrate, tributyl trimellitate, trimellit Examples include trioctyl acid, trihexyl trimellitate, trioleyl trimellitate, and triisocetyl trimellitate.

Examples of esters of other acids and alcohols include unsaturated fatty acids or branched acids such as myristoleic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid, and ethylene glycol, propylene glycol, and glycerin. , trimethylolpropane, pentaerythritol, and esters with alcohols such as sorbitan.

Examples of esters of monobasic acids or polybasic acids and polyalkylene glycols include polyethylene glycol dihexylate, polyethylene glycol di-2-ethylhexylate, polyethylene glycol dilaurate, polyethylene glycol dioleate, and dipolyethylene glycol methyl adipate. Examples include ether.

Examples of phosphate ester plasticizers include tricresyl phosphate (TCP), triphenyl phosphate (TPP), tri-2-ethylhexyl phosphate (TOP), tricylenyl phosphate (TXP), and triethyl phosphate (TEP). can be mentioned.

Examples of the epoxy plasticizer include epoxidized soybean oil, epoxidized linseed oil, epoxidized octyl stearate, epoxidized butyl fatty acid, and epoxidized butyl fatty acid in linseed oil.

The molecular weight (formula weight or Mn) of the plasticizer is preferably 250 to 1000, more preferably 400 to 900, particularly preferably 500 to 850. If the molecular weight is 250 or more, the heat resistance of the adhesive layer will be good, and if the molecular weight is 1000 or less, a sufficient zipping suppressing effect will be obtained.

The content of the plasticizer is not particularly limited, but is preferably from 0.01 to 30 parts by weight, more preferably from 4 to 20 parts by weight, based on 100 parts by weight of the acrylic ester copolymer. If the content of the plasticizer is 0.01 parts by mass or more, a sufficient effect of suppressing zipping during peeling can be obtained, and if the content is 30 parts by mass or less, a decrease in adhesive strength can be suppressed.

<Antioxidant>
The adhesive composition of the present invention may further contain an antioxidant, if necessary.
Examples of antioxidants include radical scavengers and peroxide decomposers. Examples of the radical scavenger include phenolic compounds and amine compounds. Examples of peroxide decomposers include sulfur-based compounds and phosphorus-based compounds.

Examples of phenolic compounds include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearin-β-(3,5 -di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2- [β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, benzenepropanoic acid, 3,5- Bis(1,1-dimethylethyl)-4-hydroxy-, C7-C9 side chain alkyl ester, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1, 3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl) -4'-hydroxyphenyl)propionate] methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid] glycol ester, 1,3,5-tris(3 ',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, tocopherol, and the like.

Examples of the sulfur-based antioxidant include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, and distearyl 3,3'-thiodipropionate.

Examples of phosphorus compounds include triphenyl phosphite, diphenylisodecyl phosphite, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenylditridecyl) phosphite, and cyclic neopentanetetrayl. Bis(octadecyl phosphite), tris(nonylphenyl) phosphite, tris(monononylphenyl) phosphite, tris(dinonylphenyl) phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa- 10-phosphaphenanthrene-10-oxide, 10-(3,5-di-tert-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10 -Desyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, tris(2,4-di-tert-butylphenyl)phosphite, cyclic neopentanetetrayl bis(2,4-di-tert -butylphenyl) phosphite, cyclic neopentanetetrayl bis(2,6-di-tert-butyl-4-methylphenyl) phosphite, and 2,2-methylenebis(4,6-di-tert-butylphenyl) ) Octyl phosphite and the like.

By using an antioxidant, thermal deterioration of the acrylic ester copolymer can be prevented and heat resistance can be improved.
The amount of the antioxidant added is not particularly limited, and is preferably 0.01 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, and 0.2 to 3 parts by weight, based on 100 parts by weight of the acrylic ester copolymer. 2 parts by mass is more preferred.

As the antioxidant, a phenolic compound, which is a radical scavenger, is preferable from the viewpoint of transparency and polymerization inhibiting effect. The phenolic compound can effectively suppress the monomer components remaining during the synthesis of the acrylic acid ester copolymer (A) from producing low molecular weight components over time and reducing heat resistance.

The adhesive composition of the present invention further includes a catalyst, an antistatic agent (AS agent), an ultraviolet absorber, a light stabilizer, a lubricant, a corrosion inhibitor, a heat stabilizer, a weather stabilizer, a hydrolysis inhibitor, and a Mildew agents, thickeners, fillers (talc, calcium carbonate, titanium oxide, etc.), silane coupling agents, polymerization inhibitors, antifoaming agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, waxes , emulsions, magnetic materials, dielectric property modifiers, and other known additives may be blended as necessary.

≪Adhesive composition≫
The adhesive composition of the present invention consists of a (meth)alkyl acrylate monomer (A) in which the alkyl group has 1 to 12 carbon atoms, a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group. It contains an acrylic ester copolymer, which is a copolymer of a monomer mixture, and an isocyanate curing agent. Further, the content of the monomer (B) having an acidic group is 0.01% by mass or more and 6% by mass or less in 100% by mass of the monomer mixture, and the content of the monomer (C) having a hydroxyl group is 0.01% by mass or more and 6% by mass or less in 100% by mass of the monomer mixture. In mass%, it is 0.05% by mass or more and 10% by mass or less, and the gel fraction is 55% or more.

<Gel fraction>
The gel fraction is a value calculated by the following formula (3).
(Gel fraction) = {(W2-W0-W3)/(W1-W0-W3)}×100 (Formula 3)
W0: Weight of wire mesh W1: Weight of wire mesh + test piece W2: Weight of wire mesh + test piece after drying W3: Weight of base material of test piece Details of the method for measuring the gel fraction are described in the Examples column. .

The gel fraction of the adhesive composition of the present invention is 55% or more and 100% or less, preferably 70% or more and 98% or less, and more preferably 80% or more and 95% or less. When the gel fraction is 55% or more, good removability can be exhibited even after storage at high temperatures.

<Viscoelasticity>
The storage modulus (G'), loss modulus (G''), and loss tangent (tan δ) of the adhesive layer formed from the adhesive composition of the present invention were measured using a viscoelasticity measuring device manufactured by TA Instruments Co., Ltd. Temperature dependence measurements were carried out using "Ares-G2" under the conditions of frequency: 1 Hz, strain 0.1%, temperature: -50°C to 200°C (heating rate 10°C/min), 25°C, 150°C. The value in °C was used.

The adhesive composition of the present invention has a ratio (P) of the loss modulus at 25°C and the loss modulus at 150°C when measured at 1 Hz, which is expressed by Formula 1, and has a value of 0.02 or more and 0.3 or less. and is preferably 0.03 or more and 0.15 or less, more preferably 0.04 or more and 0.07 or less, particularly preferably 0.05 or more and 0.06 or less. By having a value of (P) within this range, it is possible to develop good adhesive strength and tack when pasting, and also to exhibit good removability even after being pasted for a long time under high temperature conditions, and to be able to exhibit good removability even under high temperature conditions under load. Even if it gets wet, it can prevent the adhesive from seeping out.

(P) = (loss modulus at 150°C when measured at 1Hz)/(loss modulus at 25°C when measured at 1Hz) (Formula 1)

The storage modulus (G') at 25°C of the adhesive layer formed from the adhesive composition of the present invention is not particularly limited, but is preferably 15,000 Pa or more and 90,000 Pa or less, and 30,000 Pa or more and 65,000 Pa or less. More preferred. If it is 15,000 Pa or more, sufficient cohesive force can be obtained, and if it is 90,000 Pa or less, good adhesive force can be obtained during use.

The storage modulus (G') at 150°C of the adhesive layer formed from the adhesive composition of the present invention is not particularly limited, but is preferably 10,000 Pa or more and 50,000 Pa or less. When the pressure is 15,000 Pa or more, an adhesive with little oozing out can be obtained even under high temperatures, and when the pressure is 50,000 Pa or less, good adhesive strength can be obtained even under high temperatures.

The loss modulus (G'') at 25°C of the adhesive layer formed from the adhesive composition of the present invention is not particularly limited, but is preferably 10,000 Pa or more and 40,000 Pa or less, and 15,000 Pa or more and 30,000 Pa or less. is more preferable. When the pressure is 10,000 Pa or more, sufficient adhesive force and tack can be obtained, and when the pressure is 40,000 Pa or less, good removability during use can be obtained.

The loss modulus (G'') at 150°C of the adhesive layer formed from the adhesive composition of the present invention is not particularly limited, but is preferably 800 Pa or more and 8,000 Pa or less, more preferably 900 Pa or more and 2,500 Pa or less. When the pressure is 800 Pa or more, sufficient adhesive strength and tack can be obtained even at high temperatures, and when the pressure is 8,000 Pa or less, good removability can be obtained even at high temperatures.

<Method for manufacturing adhesive composition>
The method for producing the adhesive composition of the present invention is not particularly limited.
The pressure-sensitive adhesive composition of the present invention can be produced by adding and mixing an isocyanate curing agent, a solvent, and optional components as necessary to the acrylic ester copolymer.

The adhesive composition of the present invention preferably has a nonvolatile content concentration of 30 to 75% by mass, more preferably 38 to 65% by mass, and even more preferably 40 to 60% by mass. By setting the nonvolatile content concentration of the adhesive composition to be high, the content of the solvent can be relatively suppressed, so that drying costs during coating can be suppressed, and the burden on the environment and the human body can be suppressed.

The viscosity of the adhesive composition at 25° C. is preferably 1,000 to 20,000 mPa·s, more preferably 1,500 to 10,000 mPa·s, and 2,500 to 7,000 mPa·s. is even more preferable. When the viscosity of the pressure-sensitive adhesive composition is within the above range, coating properties are improved and a pressure-sensitive adhesive layer with a smooth surface can be easily obtained. Note that the viscosity is the viscosity measured 1 minute after the start of rotation using a BL type viscometer in an atmosphere of 25° C. with a #3 rotor and a rotation speed of 12 rpm.

≪Adhesive sheet≫
The pressure-sensitive adhesive sheet includes a base material and a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive composition of the present invention. The adhesive layer can be formed on one or both sides of the base material. If necessary, the exposed surface of the adhesive layer can be covered with a release sheet. Note that the release sheet is peeled off when the adhesive sheet is attached to the adherend.

When applying the adhesive composition, the viscosity can be adjusted using the above-mentioned solvent, or the viscosity can be lowered by heating the adhesive composition.

The base material is not particularly limited, and examples include resin sheets, paper, and metal foils. The base material may be a laminated sheet in which one or more arbitrary layers are laminated on at least one surface of the base material. The surface of the base material on which the adhesive layer is to be formed may be subjected to adhesion-facilitating treatment such as corona discharge treatment and application of an anchor coating agent, if necessary.

The constituent resin of the resin sheet is not particularly limited, and may include ester resins such as polyethylene terephthalate (PET); olefin resins such as polyethylene (PE) and polypropylene (PP); vinyl resins such as polyvinyl chloride; Examples include amide resin; urethane resin (including foam); combinations thereof, and the like.
The thickness of the resin sheet excluding the polyurethane sheet is not particularly limited, and is preferably 15 to 300 μm. The thickness of the polyurethane sheet (including foam) is not particularly limited, and is preferably 20 to 50,000 μm.

The paper is not particularly limited, and examples include plain paper, coated paper, and art paper.
The constituent metal of the metal foil is not particularly limited, and examples thereof include aluminum, copper, and combinations thereof.

The release sheet is not particularly limited, and any known release sheet that has been subjected to a known release treatment such as coating a release agent on the surface of a base sheet such as a resin sheet or paper can be used.

The adhesive sheet can be manufactured by a known method.
First, the pressure-sensitive adhesive composition of the present invention is applied to the surface of a substrate to form a coating layer made of the pressure-sensitive adhesive composition of the present invention. As the coating method, known methods can be applied, such as a roll coater method, a comma coater method, a die coater method, a reverse coater method, a silk screen method, and a gravure coater method.
Next, the coating layer is dried and cured to form a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive composition of the present invention. The heat drying temperature is not particularly limited, and is preferably about 60 to 150°C. The thickness of the adhesive layer (thickness after drying) varies depending on the application, but is preferably 0.1 to 200 μm.
Next, if necessary, a release sheet is attached to the exposed surface of the adhesive layer by a known method.
A single-sided adhesive sheet can be manufactured in the manner described above.
By performing the above operation on both sides, a double-sided pressure-sensitive adhesive sheet can be manufactured.

Contrary to the above method, the pressure-sensitive adhesive composition of the present invention is applied to the surface of a release sheet to form a coating layer made of the pressure-sensitive adhesive composition of the present invention, and then the coating layer is dried and cured. Then, a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive composition of the present invention may be formed, and a base sheet may be laminated on the exposed surface of the pressure-sensitive adhesive layer.

The method for producing a pressure-sensitive adhesive sheet preferably includes a coating step of coating a pressure-sensitive adhesive onto a base material, and heating and drying the formed coating layer to form a pressure-sensitive adhesive layer containing a cured product of the pressure-sensitive adhesive composition. The method includes a heating step, a winding step of winding the obtained adhesive sheet around a core to form an adhesive sheet roll, and a curing step of curing the adhesive sheet roll.

Synthesis examples, examples according to the present invention, and comparative examples will be described below. In the following description, unless otherwise specified, "parts" means parts by mass, "%" means % by mass, and "RH" means relative humidity.

[Measurement of weight average molecular weight (Mw)]
The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC). The measurement conditions were as follows. Note that Mw is a polystyrene equivalent value.
<Measurement conditions>
Equipment: Shimadzu Corporation, LC-GPC system “Prominence”,
Column: 4 Tosoh GMHXL, 1 Tosoh HXL-H connected in series,
Detector: differential refractive index detector (RID-10A),
Solvent: tetrahydrofuran (THF),
Flow rate: 1 mL/min,
Solvent temperature: 40°C,
Sample concentration: 0.2%,
Sample injection volume: 100μL

<Production of acrylic ester copolymer>
(Synthesis example 1)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 17.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 790,000.

(Synthesis example 2)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"), 30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and acrylic acid were added. After charging 0.4 parts of 4-hydroxybutyl acid, 35 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 4-hydroxybutyl acrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 17.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 770,000.

(Synthesis example 3)
30 parts of 2-ethylhexyl acrylate and 0.0 parts of 2-carboxyethyl acrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 84 parts of 2-hydroxyethyl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Replaced with. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 16.4 parts of butyl acrylate, 1.96 parts of 2-carboxyethyl acrylate, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and then the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 820,000.

(Synthesis example 4)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 parts of lonitrile (AIBN) was charged, and 7.2 parts of butyl acrylate, 10 parts of ethyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and then the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 880,000.

(Synthesis example 5)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"), 12 parts of 2-ethylhexyl acrylate, 7.5 parts of isononyl acrylate, After charging 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), The air was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 28 parts of 2-ethylhexyl acrylate, 17.5 parts of isononyl acrylate, 15 parts of lauryl methacrylate, 0.4 part of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, 2 , 0.02 parts of 2'-azobisisobutyronitrile (AIBN), and 17.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and then the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Further, the weight average molecular weight (Mw) of the acrylic ester copolymer was 810,000.

(Synthesis example 6)
30 parts of 2-ethylhexyl acrylate and 0.0 parts of 2-hydroxyethyl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 4 parts of ethyl acetate, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 19.15 parts of butyl acrylate, 0.05 part of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 800,000.

(Synthesis example 7)
30 parts of 2-ethylhexyl acrylate and 0.0 parts of 2-hydroxyethyl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 4 parts of ethyl acetate, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 18.4 parts of butyl acrylate, 0.8 part of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 800,000.

(Synthesis example 8)
30 parts of 2-ethylhexyl acrylate and 0.0 parts of 2-hydroxyethyl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 4 parts of ethyl acetate, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 18.2 parts of butyl acrylate, 1 part of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 800,000.

(Synthesis example 9)
30 parts of 2-ethylhexyl acrylate, 0.84 part of acrylic acid, and methacrylic acid were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 16.4 parts of butyl acrylate, 1.96 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Further, the weight average molecular weight (Mw) of the acrylic ester copolymer was 810,000.

(Synthesis example 10)
30 parts of 2-ethylhexyl acrylate, 1.05 parts of acrylic acid, and methacrylic acid were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 15.7 parts of butyl acrylate, 2.45 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 820,000.

(Synthesis example 11)
30 parts of 2-ethylhexyl acrylate, 1.65 parts of acrylic acid, and methacrylic acid were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 13 parts of lauryl methacrylate, 0.4 part of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 15.7 parts of butyl acrylate, 3.85 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 850,000.

(Synthesis example 12)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.02 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.03 part of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 17.95 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 790,000.

(Synthesis example 13)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.04 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.03 part of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 17.93 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 790,000.

(Synthesis example 14)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.08 parts of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.07 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 17.85 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 780,000.

(Synthesis example 15)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.5 part of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 17.1 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 790,000.

(Synthesis example 16)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.8 parts of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.7 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 16.5 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 790,000.

(Synthesis example 17)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 4 parts of 2-hydroxyethyl acid, 35 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 11 parts of lauryl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutyronitrile were added. (AIBN), and 16 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Further, the weight average molecular weight (Mw) of the acrylic ester copolymer was 810,000.

(Synthesis example 18)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 65 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 15 parts of 2-ethylhexyl acrylate, 5 parts of lauryl methacrylate, 32.2 parts of butyl acrylate, 0.4 part of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, 2 , 0.02 parts of 2'-azobisisobutyronitrile (AIBN), and 15 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Further, the weight average molecular weight (Mw) of the acrylic ester copolymer was 830,000.

(Synthesis example 19)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 65 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 15 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 22.2 parts of butyl acrylate, 0.4 part of 2-hydroxyethyl methacrylate, 10 parts of ethyl acetate, 2 , 0.02 parts of 2'-azobisisobutyronitrile (AIBN), and 15 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 800,000.

(Synthesis example 20)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 65 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 22.2 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 15 parts of butyl acrylate, 0.4 part of 2-hydroxyethyl methacrylate, 10 parts of ethyl acetate, 2 , 0.02 parts of 2'-azobisisobutyronitrile (AIBN), and 15 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 770,000.

(Synthesis example 21)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 parts of 2-hydroxyethyl acid, 40 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 34 parts of 2-ethylhexyl acrylate, 5 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 28.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 700,000.

(Synthesis example 22)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 part of 2-hydroxyethyl acid, 45 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 15 parts of 2-ethylhexyl acrylate, 42 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 part of lonitrile (AIBN) was charged, and 10.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic acid ester copolymer was 720,000.

(Synthesis example 23)
30 parts of 2-ethylhexyl acrylate, 0.6 part of acrylic acid, and methacrylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 0.4 parts of 2-hydroxyethyl acid, 40 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 16 parts of 2-ethylhexyl acrylate, 36 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 5 parts of ethyl acetate, and 2,2'-azobisisobutylene were added. 0.02 parts of lonitrile (AIBN) was charged, and 10 parts of lauryl methacrylate, 5.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into container B. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of container B were supplied to container A while stirring for 2.0 hours. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 800,000.

(Synthesis example 24)
13.5 parts of 2-ethylhexyl acrylate and 1.5 parts of lauryl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). 14.2 parts of butyl acrylate, 0.6 parts of acrylic acid, 0.24 parts of 2-hydroxyethyl methacrylate, 50 parts of ethyl acetate, 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) After charging the reactor, the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 31.5 parts of 2-ethylhexyl acrylate, 3.5 parts of lauryl methacrylate, 33 parts of butyl acrylate, 1.4 parts of acrylic acid, and 0.2 parts of 2-hydroxyethyl methacrylate were added. 56 parts of ethyl acetate, 30 parts of ethyl acetate, and 0.02 part of 2,2'-azobisisobutyronitrile (AIBN) were charged. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Further, the weight average molecular weight (Mw) of the acrylic ester copolymer was 830,000.

(Synthesis example 25)
8.4 parts of 2-ethylhexyl acrylate and 0.9 parts of lauryl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). 14 parts of butyl acrylate, 6 parts of ethyl acrylate, 0.6 parts of acrylic acid, 0.3 parts of 2-hydroxyethyl methacrylate, 50 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (AIBN) ) After charging 0.02 parts, the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 19.6 parts of 2-ethylhexyl acrylate, 32.9 parts of butyl acrylate, 2.1 parts of lauryl methacrylate, 14 parts of ethyl acrylate, 1.4 parts of acrylic acid, 0.7 parts of 2-hydroxyethyl methacrylate, 30 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 700,000.

(Comparative synthesis example 1)
13.5 parts of 2-ethylhexyl acrylate and 1.5 parts of lauryl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 14 parts of butyl acrylate, 0.8 parts of acrylic acid, 60 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen. Replaced with gas. Furthermore, in a container A equipped with a stirrer, 31.5 parts of 2-ethylhexyl acrylate, 33.2 parts of butyl acrylate, 3.5 parts of lauryl methacrylate, 2.0 parts of acrylic acid, 30 parts of ethyl acetate, 2 , 0.02 part of 2'-azobisisobutyronitrile (AIBN) was charged. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Further, the weight average molecular weight (Mw) of the acrylic ester copolymer was 810,000.

(Comparative synthesis example 2)
13.5 parts of 2-ethylhexyl acrylate and 1.5 parts of lauryl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). After charging 14 parts of butyl acrylate, 0.6 parts of 2-hydroxyethyl methacrylate, 60 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), The air was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 31.5 parts of 2-ethylhexyl acrylate, 34 parts of butyl acrylate, 3.5 parts of lauryl methacrylate, 1.4 parts of 2-hydroxyethyl methacrylate, and 30 parts of ethyl acetate. , 0.02 part of 2,2'-azobisisobutyronitrile (AIBN) were charged. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Further, the weight average molecular weight (Mw) of the acrylic ester copolymer was 810,000.

(Comparative synthesis example 3)
13.5 parts of 2-ethylhexyl acrylate and 1.5 parts of lauryl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). 10.5 parts of butyl acrylate, 2.7 parts of acrylic acid, 1.8 parts of 2-hydroxyethyl methacrylate, 55 parts of ethyl acetate, 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) After charging the reactor, the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 31.5 parts of 2-ethylhexyl acrylate, 24.5 parts of butyl acrylate, 3.5 parts of lauryl methacrylate, 6.3 parts of acrylic acid, and 2-hydroxyethyl methacrylate. 4.2 parts of ethyl acetate, 15 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 880,000.

(Comparative synthesis example 4)
13.5 parts of 2-ethylhexyl acrylate and 1.5 parts of lauryl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). 9.3 parts of butyl acrylate, 1.2 parts of acrylic acid, 4.5 parts of 2-hydroxyethyl methacrylate, 55 parts of ethyl acetate, 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) After charging the reactor, the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 31.5 parts of 2-ethylhexyl acrylate, 21.7 parts of butyl acrylate, 3.5 parts of lauryl methacrylate, 2.8 parts of acrylic acid, and 2-hydroxyethyl methacrylate. 10.5 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic ester copolymer was 850,000.

(Comparative synthesis example 5)
13.5 parts of 2-ethylhexyl acrylate and 1.5 parts of lauryl methacrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube (hereinafter sometimes simply referred to as the "reaction vessel"). 7.8 parts of butyl acrylate, 2.7 parts of acrylic acid, 4.5 parts of 2-hydroxyethyl methacrylate, 55 parts of ethyl acetate, 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) After charging the reactor, the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in a container A equipped with a stirrer, 31.5 parts of 2-ethylhexyl acrylate, 18.2 parts of butyl acrylate, 3.5 parts of lauryl methacrylate, 6.3 parts of acrylic acid, and 2-hydroxyethyl methacrylate were added. 10.5 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged. Next, the inside of the reaction container was heated to 80° C. while stirring under a nitrogen atmosphere to start the reaction, and the contents of container A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out at reflux temperature for 8 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic ester copolymer solution with a nonvolatile content of 35%. Moreover, the weight average molecular weight (Mw) of the acrylic acid ester copolymer was 870,000.

The abbreviations listed in Table 1 are shown below.
2EHA: 2-ethylhexyl acrylate INA: Isononyl acrylate LMA: Lauryl methacrylate EA: Ethyl acrylate
BA: Butyl acrylate
AA: acrylate BCEA: 2-carboxyethyl acrylate HEMA: 2-hydroxyethyl methacrylate 4HBA: 4-hydroxybutyl acrylate

(Example 1)
<Manufacture of adhesive composition>
To 100 parts of acrylic acid ester copolymer (synthesis example 1), 2.5 parts of TDI-TMP was added as an isocyanate curing agent in terms of non-volatile content, and ethyl acetate was added as a solvent with a non-volatile content of 30%. The adhesive composition was obtained by adding the following ingredients and mixing them uniformly to obtain a pressure-sensitive adhesive composition.

<Manufacture of adhesive sheet>
The resulting pressure-sensitive adhesive composition was applied to the release-treated surface of a 38-μm-thick releasable sheet (made of polyethylene terephthalate, hereinafter referred to as "releasable film base material") in the manner described above so that the thickness after drying would be 25 μm. The obtained adhesive composition was applied and dried in a hot air oven at 100° C. for 90 seconds to prepare an adhesive layer. After drying, it was laminated onto a 50 μm thick base material (made of polyethylene terephthalate) and further cured at 23° C. and 50% RH for 7 days to obtain an adhesive sheet.

(Examples 2 to 32, Comparative Examples 1 to 7)
The respective adhesive compositions and adhesive sheets were prepared in the same manner as for the adhesive sheet of Example 1, except that the acrylic ester copolymer and various additives were changed to the composition and blending amount (parts by mass) shown in Table 2. Manufactured.

The materials used are as follows.
<Isocyanate curing agent>
TDI-TMP: Adduct of tolylene diisocyanate and trimethylolpropane <Other curing agents>
Azd: Aziridine curing agent, Chemitite PZ-33, manufactured by Nippon Shokubai Co., Ltd. <Plasticizer>
ATBC: acetyl tributyl citrate

[Evaluation items and evaluation method]
The obtained adhesive composition and adhesive sheet were evaluated by the following method.

(gel fraction)
After coating, a test piece with a width of 30 mm and a length of 100 mm was cut out from the adhesive sheet that was cured for 7 days in an atmosphere of 23° C. and 50% RH. The release sheet was peeled off from the test piece, the exposed adhesive layer was pasted on a 300 mesh stainless steel wire mesh, the wire mesh was folded to prevent the test piece from peeling off, the test piece was immersed in ethyl acetate with the test piece wrapped, It was left standing at ℃ for 24 hours. After immersion, the wire mesh was taken out, washed with a small amount of ethyl acetate, dried at 100° C. for 30 minutes, and then weighed. The gel fraction was calculated using the following formula (3).
(Gel fraction) = {(W2-W0-W3)/(W1-W0-W3)}×100 (Formula 3)
W0: Weight of wire mesh W1: Weight of wire mesh + test piece W2: Weight of wire mesh + test piece after drying W3: Weight of base material of test piece

(viscoelasticity)
The adhesive composition obtained above was applied onto the release-treated surface of a 38 μm thick releasable sheet (made of polyethylene terephthalate, hereinafter referred to as "releasable film base material") so that the thickness after drying was 25 μm. The adhesive layer was prepared by drying in a hot air oven at 100° C. for 90 seconds. After drying, it was laminated onto another releasable sheet (made of polyethylene terephthalate) with a thickness of 75 μm (hereinafter referred to as "releasable film base material"), and cured for 7 days in an atmosphere of 23°C and 50% RH. An adhesive layer sandwiched between two releasable sheets having the following structure was created: /adhesive layer/releasable sheet. Next, one of the releasable sheets was peeled off, and lamination was repeated so that the adhesive layers overlapped to obtain an adhesive layer with a thickness of 1 mm. After removing air bubbles in an autoclave, a test piece for measuring storage elastic modulus was prepared by cutting out a cylinder with a diameter of 8 mm, and the release sheets on both sides were peeled off, and the viscoelasticity was measured. The storage modulus (G'), loss modulus (G''), and loss tangent (tan δ) of the adhesive layer were measured using a viscoelasticity measuring device "Ares-G2" manufactured by TA Instruments Co., Ltd. at a frequency of 1 Hz. Temperature dependence measurements were carried out under the following conditions: , strain 0.1%, temperature: -50°C to 200°C (heating rate 10°C/min). Using the obtained loss modulus (G'') values at 25° C. and 150° C., the value of P was calculated from the following (Equation 1).
P=(loss modulus at 150°C when measured at 1Hz)/(loss modulus at 25°C when measured at 1Hz) (Formula 1)

(Adhesive force)
A test piece with a width of 25 mm and a length of 150 mm was cut from the adhesive sheet after curing for 5 hours in an atmosphere of 23° C. and 50% RH. The adhesive layer exposed by peeling off the releasable sheet from the cut-out adhesive sheet was adhered to the surface of a stainless steel plate (SUS304), and the adhesive layer was pressed with a 2 kg roll back and forth once. Thereafter, it was left in an atmosphere of 23° C. and 50% RH for 24 hours. Next, in accordance with JIS Z0237, the adhesive strength (adhesive strength before heating) was measured using a tensile tester (Tensilon, manufactured by Orientech Co., Ltd.) at a peeling rate of 300 mm/min and a peeling angle of 180°. The evaluation criteria are as follows.
[Evaluation criteria]
◎: 3N/25mm or more, excellent.
○: 1N/25mm or more and less than 3N/25mm, good.
△: 0.6N/25mm or more and less than 1N/25mm, practical.
×: Less than 0.6N/25mm, impractical.

(ball tuck)
The obtained pressure-sensitive adhesive sheet was prepared in a size of 25 mm in width and 250 mm in length. The releasable sheet was peeled off from the adhesive sheet, and it was fixed on an inclined plate with an inclined angle of 30 degrees with the adhesive side facing up. A steel ball (1/32 to 32/32 inches) is pasted on the top of the sample for the run-up track, and the run-up track is 10 cm long, and the glue surface is 10 cm. Recorded. The measurements were carried out at 23°C under an atmosphere of 50% relative humidity.
Evaluation criteria under an atmosphere of 23° C. and 50% relative humidity ◎: Ball diameter is 11 or more. Very good.
○: Ball diameter is 8 to 10. Good.
△: Ball diameter is 5 to 7. Practical.
×: Ball diameter is 4 or less. Not practical.

(Repeel test)
A test piece with a width of 25 mm and a length of 150 mm was cut from the adhesive sheet after curing for 7 days in an atmosphere of 23° C. and 50% RH. The adhesive layer exposed by peeling off the releasable sheet from the cut-out adhesive sheet was adhered to the surface of a stainless steel plate (SUS304), and the adhesive layer was pressed with a 2 kg roll back and forth once. Thereafter, it was stored for 10 days in an environment of 23° C.-50% RH, 40° C., 60° C., and 55° C.-80% RH. After 10 days, the test piece was left at 23°C - 50% RH for 3 hours, and then tested in accordance with JIS Z0237 using a tensile tester (Tensilon, manufactured by Orientec) at a peeling rate of 300 mm/min and a peeling angle of 180°. The adhesive strength (adhesive strength before heating) was measured under the following conditions, and the state of the stainless steel plate after the measurement was observed. The evaluation criteria are as follows.
[Evaluation criteria]
◎: No adhesive attached to stainless steel plate, excellent.
○: Adhesion of the adhesive to the stainless steel plate is more than 0% and less than 3% of the pasting area, good.
△: Adhesion of adhesive to stainless steel plate is 3% or more and less than 5% of the pasting area, practical.
×: Adhesion of adhesive to stainless steel plate exceeds 5% of pasting area, unusable.

(Protrusion test)
After curing in an atmosphere of 23° C. and 50% RH for 5 hours or 7 days, a pressure-sensitive adhesive sheet with a width of 10 mm and a length of 10 mm was prepared. Peel off the release sheet from the adhesive sheet, sandwich the top and bottom with a release sheet (made of polyethylene terephthalate) with a thickness of 38 μm, and apply a pressure of 50 kg/cm ² at 60°C using a press tester for 2 hours. I left it alone. After the test was completed, the sample was taken out and the width (maximum value) of the glue protruding from the edge of the test piece was measured.
Evaluation criteria ◎: Protrusion is less than 0.2 mm. Very good.
○: Protrusion is 0.2 or more and less than 0.4 mm. Good.
Δ: Protrusion is 0.4 or more and less than 0.6 mm. Practical.
×: Protrusion is 0.6 mm or more. Not practical.

(Storage stability)
After blending the curing agent, the uniformly mixed adhesive composition was left standing in an atmosphere of 23° C. and 50% RH, and the rate of increase in viscosity was calculated from the following formula (4).
(Rate of increase in viscosity) = {(Viscosity 7 days after mixing the curing agent)/(Viscosity 1 hour after mixing the curing agent) x 100} (Formula 4)
[Evaluation criteria]
◎: Increase rate of viscosity is less than 150%, excellent.
○: Increase rate of viscosity is 150% or more and less than 160%, good.
Δ: Viscosity increase rate is 160% or more and less than 170%, practical.
×: Viscosity increase rate is 170% or more, unusable.

Acrylic acid, which is a copolymer of a monomer mixture consisting of a (meth)acrylic acid ester monomer (A) whose alkyl group has 1 to 12 carbon atoms, a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group. It is an adhesive composition containing an ester copolymer and an isocyanate curing agent, and the content of the monomer (B) having an acidic group is 0.01% by mass or more and 6% by mass or less based on 100% by mass of the monomer mixture. The adhesive composition of the present invention, wherein the content of the monomer (C) having a hydroxyl group is 0.05% by mass or more and 10% by mass or less based on 100% by mass of the monomer mixture, and the gel fraction is 55% or more. All products have good adhesive physical properties, have good removability after long-term storage under various conditions, have little adhesive extrusion under high temperature and high load, and have good storage stability after adding a hardening agent. We were also able to produce an excellent adhesive sheet.

(Examples 2 to 32, Comparative Examples 1 to 7)
The respective adhesive compositions and adhesive sheets were prepared in the same manner as for the adhesive sheet of Example 1, except that the acrylic ester copolymer and various additives were changed to the composition and blending amount (parts by mass) shown in Table 2. Manufactured.
However, Examples 5, 21, 22, 27 to 32 are reference examples.

Claims (4)

Acrylic is a copolymer of a monomer mixture consisting of a (meth)acrylic acid alkyl ester monomer (A) whose alkyl group has 1 to 12 carbon atoms, a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group. The content of the monomer (B) containing an acid ester copolymer and an isocyanate curing agent and having an acidic group is 0.01% by mass or more and 6% by mass or less based on 100% by mass of the monomer mixture. A pressure-sensitive adhesive composition in which the content of the monomer (C) is 0.05% by mass or more and 10% by mass or less based on 100% by mass of the monomer mixture, and the gel fraction is 55% or more. (meth)acrylic acid alkyl ester monomer (A) whose alkyl group has 1 to 12 carbon atoms (meth)acrylic acid alkyl ester monomer (a1) whose alkyl group has 8 to 12 carbon atoms in 100% by mass; The adhesive composition according to claim 1, wherein the content is 55% by mass or more. The adhesive according to claim 1, wherein the ratio (P) of the loss modulus at 25°C and the loss modulus at 150°C when measured at 1 Hz, expressed by Formula 1, is 0.02 or more and 0.3 or less. agent composition.
P=(loss modulus at 150°C when measured at 1Hz)/(loss modulus at 25°C when measured at 1Hz) (Formula 1) A pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive composition according to any one of claims 1 to 3.