Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

Abstract

To provide an adhesive composition and an adhesive sheet which have sufficient adhesive strength and high tackiness and exhibit good re-releasability even on a highly polar adherend such as SUS and a steel plate, which are likely to leave adhesive residue when peeling and have sufficient re-releasability even after long-term storage under high temperature or moisture-heat conditions in a state of being adhered and further to provide an adhesive composition and an adhesive sheet which have less protrusion of the adhesive from the sheet even under high temperature and high load conditions in a state of being adhered and can be stored by overlapping heavy adherends such as a steel plate even under high temperatures.SOLUTION: There is provided an adhesive composition which comprises an acrylic acid ester copolymer which is a copolymer of a monomer mixture comprising an alkyl (meth)acrylate monomer having an alkyl group having 1 to 12 carbon atoms (A), a monomer having an acid group (B) and a monomer having a hydroxyl group (C) and an isocyanate-based curing agent, wherein the percentage content of the monomer having an acid group (B) is 0.01 mass% or more and 6 mass% or less in 100 mass% of the monomer mixture, the percentage content of the monomer having a hydroxyl group (C) is 0.05 mass% or more and 10 mass% or less in 100 mass% of the monomer mixture and the gel fraction is 55% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet. [Background technology]

[0002] Adhesive sheets with adhesive layers formed from adhesives are easier to handle than adhesives, and are therefore used in a wide range of fields as display labels and fixing tapes. They are broadly divided into strong adhesive types that permanently fix objects, and removable adhesive types that allow the adhesive sheet to be peeled off after use. There are various resin-based adhesives, with acrylic being the most 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.

[0003] Patent Document 1 discloses a removable acrylic pressure-sensitive adhesive composition characterized by an acrylic pressure-sensitive adhesive layer formed by crosslinking an acrylic polymer, which is composed of a (meth)acrylic ester ester having an alkyl group containing 4 to 12 carbon atoms as the main monomer, copolymerized with at least 3 to 20% by weight of a carboxyl-containing radically polymerizable monomer, with a gel fraction of 80% by weight or more, using a crosslinker having a functional group reactive with a carboxyl group in the molecule. Patent Document 2 also discloses a removable pressure-sensitive adhesive sheet characterized by a pressure-sensitive adhesive layer formed by coating one surface of a substrate with a pressure-sensitive adhesive composition comprising heat-expandable microspheres, an acrylic pressure-sensitive adhesive having a weight-average molecular weight of 100,000 to 300,000 and an acid value of 30 or more that is reactive with the crosslinker, a tackifier resin having a softening point of 90°C or higher and a solubility parameter (SP value) of 8.9 or higher, and a crosslinker. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-328016 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-160765 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the pressure-sensitive adhesive composition of Patent Document 1 has the problem that when the pressure-sensitive adhesive sheet is peeled off after being stored for a long period of time under high temperature or humid heat conditions while attached to an adherend, the pressure-sensitive adhesive remains on the adherend. Also, the pressure-sensitive adhesive sheet of Patent Document 2 has the problem that it is difficult to ensure sufficient removability under room temperature conditions, and there are problems with peeling due to a decrease in adhesive strength under high temperature conditions, and with insufficient removability after long-term storage at high temperatures.

[0006] The problem that the present invention aims to solve is to provide a pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet that have sufficient adhesive strength and high tackiness, exhibit good removability even when applied to highly polar adherends such as SUS or steel plates that tend to leave adhesive residue when removed, and that retain sufficient removability even when stored in an applied state under high temperature or humid heat conditions for long periods of time; and a pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet that have little adhesive protrusion from the sheet even when applied to heavy adherends such as steel plates under high temperature and high load conditions, and that can be stored stacked on top of each other even at high temperatures. [Means for solving the problem]

[0007] In order to solve the above problems, the present inventors have developed a compound having an alkyl group with 1 to 12 carbon atoms (methacrylamide). ) An acrylic acid ester copolymer, which is a copolymer of a monomer mixture consisting of an acrylic acid alkyl ester monomer (A), a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group. The inventors have discovered a pressure-sensitive adhesive composition which contains a polymer and an isocyanate-based curing agent, in which the content of the monomer (B) having an acidic group is 0.01% by mass or more and 6% by mass or less, and the content of the monomer (C) having a hydroxyl group is 0.05% by mass or more and 10% by mass or less, in 100% by mass of the monomer mixture, and which has a gel fraction of 55% or more.

[0008] That is, the present invention relates to the following [1] to [4].

[0009] [1] (Meth)acrylic acid alkyl ester monomer having an alkyl group carbon number of 1 to 12 The present invention relates to a pressure-sensitive adhesive composition comprising an acrylic acid ester copolymer, which is a copolymer of a monomer mixture consisting of (A), a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group, and an isocyanate-based curing agent, wherein 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 (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.

[0010] [2] (Meth)acrylic acid alkyl ester monomer having an alkyl group carbon number of 1 to 12 - The pressure-sensitive adhesive composition according to the above item [1], wherein the content of (meth)acrylic acid alkyl ester monomer (a1) in which the alkyl group has 8 to 12 carbon atoms is 55 mass % or more based on 100 mass % of (A).

[0011] [3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the ratio (P) of the loss modulus at 25°C to the loss modulus at 150°C measured at 1 Hz, as represented by Equation 1, is 0.02 or more and 0.3 or less. P = (loss modulus at 150°C when measured at 1 Hz) / (loss modulus at 25°C when measured at 1 Hz) Loss modulus) (Equation 1)

[0012] [4] A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive composition according to any one of [1] to [3] above. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet that have sufficient adhesive strength and high tackiness, exhibit good removability even when the composition is stored in an attached state under high temperature or humid heat conditions for an extended period of time, even on highly polar adherends such as SUS or steel plates that tend to leave residual adhesive when removed, and that exhibit sufficient removability even when stored in an attached state under high temperature or humid heat conditions.It is also possible to provide a pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet that have little adhesive protrusion from the sheet when attached under high temperature and high load conditions, and that can be stored on top of heavy adherends such as steel plates even at high temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. It goes without saying that other embodiments are also included within the scope of the present invention as long as they are consistent with the spirit of the present invention. Furthermore, in this specification, a numerical range specified using "to" includes the numerical values before and after "to" as the range's lower and upper limits.

[0015] In this specification, unless otherwise specified, the terms "(meth)acrylic acid" and "(meth)acrylate" refer to "acrylic acid or methacrylic acid" and "acrylate or methacrylate," respectively. Furthermore, the term "(meth)acrylic acid ester monomer" refers collectively to "acrylic acid ester monomer" and "methacrylic acid ester monomer." Furthermore, the term "(meth)acrylic acid alkyl ester monomer" refers to a (meth)acrylic acid alkyl ester monomer having 1 to 12 carbon atoms in the alkyl group. The termonomer (A) is simply referred to as the monomer (A), and the monomer (B) having an acidic group is simply referred to as the monomer (B). -(B), and the monomer (C) having a hydroxyl group may be simply referred to as monomer (C).

[0016] In this specification, "Mw" refers to the weight-average molecular weight in terms of polystyrene obtained by gel permeation chromatography (GPC). "Mn" refers to the number-average molecular weight in terms of polystyrene obtained by GPC. These can be measured by the method described in the "Examples" section.

[0017] Unless otherwise noted, the various components appearing in this specification may be used independently as a single type or as a mixture of two or more types.

[0018] <Acrylate ester copolymer> The acrylic acid ester copolymer means a polymer of a monomer having an ethylenically unsaturated bond, such as a (meth)acrylic acid ester monomer. The acrylic acid ester copolymer of the present invention has at least an alkyl group having 1 to 12 carbon atoms. The copolymer is a copolymer of a monomer mixture consisting of a (meth)acrylic acid alkyl ester monomer (A), a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group, wherein 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 0.05% by mass or more and 10% by mass or less in 100% by mass of the monomer mixture.

[0019] The monomer is a (meth)acrylate alkyl ester having an alkyl group with 1 to 12 carbon atoms. They are classified into monomers (A), monomers with acidic groups (B), monomers with hydroxyl groups (C), and other monomers. The monomers that make up the acrylic copolymer are monomers (A), (B), and (C), which are essential components, and other monomers may be used as needed.

[0020] [Monomer (A)] Monomer (A) is an alkyl (meth)acrylate having an alkyl group with 1 to 12 carbon atoms. It is an ester monomer. (Meth)acrylate alkyl group has 1 to 12 carbon atoms. The alkyl ester monomers are classified into (meth)acrylic acid alkyl ester monomers (a1) having an alkyl group with 8 to 12 carbon atoms and (meth)acrylic acid alkyl ester monomers (a2) having an alkyl group with 1 to 7 carbon atoms. It is preferable to use (meth)acrylic acid alkyl ester monomers (a1) having an alkyl group with 8 to 12 carbon atoms, and it is more preferable to use (a1) and (a2) in combination. By using (meth)acrylic acid alkyl ester monomers (a1) having an alkyl group with 8 to 12 carbon atoms, it is possible to achieve both high levels of tackiness and removability.

[0021] Examples of the monomer (a1) include octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, and lauryl (meth)acrylate. Among these, 2-ethylhexyl acrylate and lauryl (meth)acrylate are most preferred. This is preferable from the viewpoint of releasability.

[0022] The content of 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 acid ester copolymer. There is no particular upper limit, but if one is to be set, 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.

[0023] Examples of the monomer (a2) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and isobutyl (meth)acrylate. Examples include butyl acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, etc. Among these, butyl acrylate and (iso)butyl acrylate are preferred because they exhibit good adhesive strength to various adherends.

[0024] [Monomer (B)] Monomer (B) is a monomer having an acidic group. By using monomer (B), it is possible to exhibit good adhesive strength and cohesive strength to various adherends.

[0025] Examples of the monomer (B) include (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, and 2-(meth)acryloyloxyethyl phthalic acid. Examples of suitable carboxylic acids include carboxylic acids having an unsaturated bond such as acrylic acid, crotonic acid, maleic acid, itaconic acid, fumaric acid, citraconic acid, and mesaconic acid, and 2-(meth)acryloyloxyethyl acid phosphate. From the viewpoints of the cohesive strength of the resulting pressure-sensitive adhesive composition and copolymerizability with other monomers, (meth)acrylic acid and 2-carboxyethyl (meth)acrylate are preferred.

[0026] The content of the monomer (B) is 0.01% by mass or more and 6% by mass or less, preferably 0.1% by mass or more and 4% by mass or less, more preferably 0.5% by mass or more and 3.5% by mass or less, and more preferably 1% by mass or more and 3% by mass or less, based on 100% by mass of the monomer mixture constituting the acrylic acid ester copolymer. A content of 0.05% by mass or less of the monomer (B) is particularly preferred. When the content of the monomer (B) is 0.05% by mass or more, high adhesive strength and cohesive strength can be imparted. Furthermore, when the content of the monomer (B) is 6% by mass or less, adhesion of the pressure-sensitive adhesive composition to the adherend can be suppressed even after the pressure-sensitive adhesive sheet is peeled from the adherend.

[0027] [Monomer (C)] Monomer (C) is a monomer having a hydroxyl group. By using monomer (C), it becomes a reaction site with the isocyanate-based curing agent, and it is possible to impart good removability even under high temperature or humid heat conditions.

[0028] Examples of monomers having a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate, and hydroxy(meth)acrylamides such as hydroxymethyl acrylamide and hydroxyethyl acrylamide. From the viewpoint of reactivity with isocyanate-based curing agents and the resulting cohesive strength, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0029] The content of monomer (C) is 0.05% by mass or more and 10% by mass or less, preferably 0.07% by mass or more and 1.8% by mass or less, and more preferably 0.08% by mass or more and 1% by mass or less, based on 100% by mass of the monomer mixture constituting the acrylic acid ester copolymer. A content of monomer (C) of 0.05% by mass or more can impart high cohesive strength during the curing agent reaction. A content of monomer (B) of 10% by mass or less can suppress a significant increase in the viscosity of the solution after the curing agent is added, and can impart good removability.

[0030] [Other monomers] The other monomer is a monomer other than the monomer (A), the monomer (B), and the monomer (C). The other monomer is not particularly limited, and a monomer copolymerizable with the monomer (A), the monomer (B), and the monomer (C) can be appropriately selected. For example, acetic acid Examples of the monomer include vinyl carboxylate monomers such as vinyl, vinyl propionate, and vinyl butyrate; other vinyl monomers such as styrene and acrylonitrile; monomers having an alicyclic structure such as isobornyl (meth)acrylate and cyclohexyl (meth)acrylate; monomers having an aromatic ring such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and biphenyl (meth)acrylate; monomers having an alkoxy (poly)alkylene oxide such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and ethoxypolypropylene glycol (meth)acrylate; acid anhydrides having a polymerizable unsaturated bond in the molecule such as maleic anhydride and itaconic anhydride; monomers having an amino group; other monomers having a nitrogen atom; monomers having an epoxy group; and monomers having an isocyanato group.

[0031] Examples of the monomer having an amino group include monoalkylaminoester (meth)acrylates such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate.

[0032] Other monomers having a nitrogen atom include (meth)acrylamide, N-vinylpyrrolidone, and acryloylmorpholine.

[0033] Examples of the monomer having an epoxy group include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and 6-methyl-3,4-epoxycyclohexylmethyl (meth)acrylate.

[0034] An example of a monomer having an isocyanato group is 2-isocyanatoethyl (meth)acrylate.

[0035] [Method of producing acrylic ester copolymer] The method for producing the acrylic acid ester copolymer is not particularly limited, and can be obtained, for example, by polymerizing the above-mentioned monomer mixture using a known radical polymerization reaction. The reaction can be carried out in the absence of a solvent, but it is preferable to use a solvent from the viewpoints of synthesis stability and handling. Furthermore, it is preferable to use a radical polymerization initiator (hereinafter sometimes abbreviated as "polymerization initiator") from the viewpoint of molecular weight control. In addition, known additives such as chain transfer agents may be used. As the solvent, the solvents described below can be used.

[0036] Examples of the polymerization initiator include benzoyl peroxide, tert-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyneodecanoate, tert-butylperoxypivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, and diacetyl peroxide. Organic peroxides such as cyclohexane-1-carbonitrile, 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-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), 2,2'-azobis[2-(2- Examples of the azo compounds include azo compounds such as (imidazolin-2-yl)propane.

[0037] 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, 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, and β-pinene are preferred because the resulting polymer has a low odor.

[0038] The weight-average molecular weight Mw of the acrylic acid ester copolymer, as calculated using standard polystyrene standards by gel permeation chromatography (GPC), is preferably 200,000 to 2,000,000, more preferably 300,000 to 1,000,000, even 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 strength can be obtained. When the weight-average molecular weight is 2,000,000 or less, an increase in viscosity can be suppressed, and good coating suitability can be obtained.

[0039] The molecular weight dispersity Mw / Mn of the acrylic acid ester copolymer, as calculated using standard polystyrene standards by gel permeation chromatography (GPC), is preferably 2.0 to 12, more preferably 4 to 10. When the molecular weight dispersity is within the above range, both adhesive strength and cohesive strength can be achieved. Here, Mn means number average molecular weight.

[0040] The glass transition temperature (Tg) of the acrylic acid ester copolymer is not particularly limited, but is preferably −70 to −25° C., and more preferably −65 to −30° C. If the glass transition temperature is −70° C. or higher, sufficient cohesive strength can be obtained. If the glass transition temperature is −25° C. or lower, good adhesive strength can be exhibited.

[0041] In the present invention, the glass transition temperature (Tg) of the acrylic acid 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 represents the Tg (unit: K) of the acrylic acid ester copolymer (A), Tgi (i = 1, 2, ... n) represents the Tg (unit: K) when radical polymerizable monomer i forms a homopolymer, and Wi (i = 1, 2, ... n) represents the mass fraction of radical polymerizable monomer i in all monomer components. Note that the Tg of the homopolymer uses published values such as literature values and catalog values.] The above formula (2) is a calculation formula when the acrylic acid ester copolymer (A) is composed of n types of monomer components, namely, Monomer 1, Monomer 2, . . . , Monomer n.

[0042] <Isocyanate-based curing agent> The pressure-sensitive adhesive composition of the present invention contains an isocyanate-based curing agent as a curing agent, which forms crosslinks with the hydroxyl-containing monomer (C) contained in the acrylic ester copolymer, thereby exhibiting high adhesive strength and cohesive strength.

[0043] Examples of the isocyanate curing agent include adducts of diisocyanates such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate with polyol compounds such as trimethylolpropane. Examples of suitable diisocyanates include compounds having three or more isocyanate groups in the molecule, such as diisocyanates, their biuret derivatives, and their isocyanurates, as well as adducts of the above diisocyanates with any of polyols such as polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols; or compounds having two isocyanate groups in the molecule, such as their allophanate derivatives. Among these, trimethylolpropane adducts of tolylene diisocyanate, trimethylolpropane adducts of xylylene diisocyanate, and trimethylolpropane adducts of hexamethylene diisocyanate are preferred because their adhesive properties can be easily adjusted, and trimethylolpropane adducts of tolylene diisocyanate are particularly preferred. The number of isocyanate groups is an average number.

[0044] The content of the isocyanate curing agent is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 1 to 9 parts, and particularly preferably 1.5 to 7 parts, relative to 100 parts by mass of the acrylic acid ester copolymer. When the content of the isocyanate curing agent is 0.1 part by mass or more, sufficient cohesive strength is obtained, and when it is 10 parts by mass or less, zipping during peeling can be suppressed.

[0045] The pressure-sensitive adhesive composition of the present invention can further contain a curing agent other than the isocyanate-based curing agent. Examples of the other curing agent include a metal chelate-based curing agent, an epoxy-based curing agent, and an aziridine-based curing agent. By including such a curing agent, the cohesive strength of the pressure-sensitive adhesive composition is further increased, and the heat resistance is improved.

[0046] Known metal chelate curing agents can be used, and examples thereof include coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium with ligands such as acetylacetone and ethyl acetoacetate. 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 acetoacetic ester.

[0047] Examples of the metal chelate curing agent include aluminum alkoxides such as aluminum isopropylate, monosec-butoxyaluminum diisopropylate, aluminum sec-butylate, and aluminum ethylate; aluminum chelates such as ethyl acetoacetate aluminum diisopropylate, aluminum tris(ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum monoacetylacetate bis(ethyl acetoacetate), and aluminum tris(acetylacetonate); titanium alkoxides such as titanium tetraisopropoxide, titanium tetra-normal butoxide, titanium butoxy dimer, and titanium tetra-2-ethylhexoxide; titanium chelates such as titanium isopropoxybis(acetylacetonate), titanium tetraacetylacetonate, titanium diisopropoxybis(ethylacetoacetate), titanium phosphate ester complexes, and titanium octylene glycolate; zirconium alkoxides such as zirconium tetra-normal propoxide and zirconium tetra-normal butoxide; zirconium chelates such as zirconium tetraacetylacetonate, zirconium tributoxymonoacetylacetonate, zirconium tetraacetylacetonate, and zirconium dibutoxybis(ethylacetoacetate); Examples include zirconium acylate such as zirconium stearate.

[0048] Among these, alkyl acetoacetate aluminum diisopropylate and aluminum monoacetylacetate bis(ethoxylated methyl acrylate) are preferred from the viewpoints of crosslinkability, adhesive strength, transparency, and storage stability. ethyl acetoacetate), and aluminum tris(acetylacetonate) are preferred.

[0049] Examples of epoxy curing agents include bisphenol A-epichlorohydrin type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidylaminophenylmethane.

[0050] Aziridine hardeners include, for example, N,N'-diphenylmethane-4,4'-bis(1-aziridine) lysinecarboxite), N,N'-toluene-2,4-bis(1-aziridinecarboxite), bisisophthaloyl-1-(2-methylaziridine), tri-1-aziridinylphosphine oxide, N,N'-hexamethylene-1,6-bis(1-aziridinecarboxite), 2,2'-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate], trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, and tris-2,4,6-(1-aziridinyl)-1,3,5-triazine.

[0051] The content of the other curing agent is not particularly limited, but is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the acrylic acid ester copolymer.

[0052] A known catalytic inhibitor may be added to the pressure-sensitive adhesive composition of the present invention for the purpose of improving the pot life of the pressure-sensitive adhesive. Specific examples of the catalytic inhibitor include keto-enol tautomer-forming compounds, etc. Keto-enol tautomer-forming compounds are compounds that can form keto-enol tautomers, and preferred are acetylacetone, acetoacetic esters, malonic esters, etc.

[0053] Examples of acetoacetate esters include methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, butyl acetoacetate, isobutyl acetoacetate, and tert-butyl acetoacetate.

[0054] 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 it is easily volatilized when dried.

[0055] The content of the catalytic inhibitor is preferably 0.05 to 10.0 parts by mass, more preferably 0.1 to 5.0 parts by mass, relative to 100 parts by mass of the acrylic acid ester copolymer. When the amount of the catalyst action inhibitor is 0.05 parts by mass or more, a good pot life is obtained, and when it is 10.0 parts by mass or less, good initial curing properties are obtained.

[0056] <Solvent> The pressure-sensitive 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 dilution solvent to adjust the viscosity during the production of the pressure-sensitive adhesive composition. The solvent can be selected from the viewpoints of leveling property and drying property during coating, as well as the effect on the environment and the human body. The solvent may be an aliphatic hydrocarbon, an alicyclic hydrocarbon, an aromatic hydrocarbon, an ester ... Preferred are esters, ketones, alcohols, and the like.

[0057] Examples of the solvent include ester-based solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone-based solvents such as acetone, methyl ethyl ketone, methyl butyl ketone, and cyclohexanone; hydrocarbon-based solvents such as toluene, xylene, and anisole; and alcohol-based solvents such as methanol, ethanol, normal propanol, and isopropanol. From the viewpoint of the pot life of the PSA composition, it is preferable that the PSA composition contains an ester-based solvent and / or an alcohol-based solvent.

[0058] The amount of solvent used is preferably 10 parts by weight or more, more preferably 30 parts by weight or more, per 100 parts by weight of the acrylic acid ester copolymer. There is no particular upper limit, but from the viewpoint of coatability, it is preferably 2000 parts by weight or less.

[0059] <Tackifying resin> The pressure-sensitive adhesive composition of the present invention can further contain a tackifier resin. The tackifier resin can be used in any manner, such as by using it during solution polymerization or by blending it with an acrylic ester copolymer. When used during solution polymerization, the tackifier resin acts as a chain transfer agent, making it easier to adjust the molecular weight of the acrylic ester copolymer. Furthermore, when blended with an acrylic ester copolymer, the adhesive strength can be further improved.

[0060] The softening point of the tackifier resin is preferably from 70°C to 170°C, more preferably from 75°C to 160°C, and even more preferably from 100°C to 150°C. When the softening point of the tackifier resin is within the above range, it becomes easier to achieve high levels of both adhesive strength and cohesive strength. The softening point is the softening temperature measured according to the dry bulb method specified in JIS SK5902.

[0061] Examples of tackifying resins include, but are not limited to, rosin-based resins, polymerized rosin-based resins, rosin ester-based resins, polymerized rosin ester-based resins, terpene-based resins, terpene-phenol-based resins, coumarone-based resins, coumarone-indene-based resins, styrene-based resins, xylene-based resins, phenol-based resins, and petroleum-based resins. Among these, rosin-based resins, polymerized rosin-based resins, rosin ester-based resins, polymerized rosin ester-based resins, petroleum resins, and styrene-based resins are preferred because they have good compatibility with the acrylic ester copolymer (A) and can further improve adhesive performance. One type of tackifying resin may be used alone, or two or more types may be used in combination.

[0062] The content of the tackifier resin is preferably 1 to 60 parts by mass, more preferably 1.5 to 20 parts by mass, and even more preferably 2 to 10 parts by mass, relative to 100 parts by mass of the acrylic ester copolymer. Adding 1 part by mass or more of the tackifier resin can increase the adhesive strength, while adding 60 parts by mass or less can maintain removability.

[0063] <Plasticizer> The pressure-sensitive adhesive composition of the present invention may further contain a plasticizer, if necessary, for the purpose of suppressing zipping during peeling. The plasticizer is not particularly limited, but an organic acid ester is preferred from the viewpoint of compatibility with the acrylic acid ester copolymer, etc.

[0064] Examples of esters of monobasic or polybasic acids with alcohols include isostearyl laurate, isopropyl myristate, isocetyl myristate, octyldodecyl myristate, isostearyl palmitate, isocetyl stearate, octyldodecyl oleate, dibutyl phthalate, dioctyl phthalate, diheptyl phthalate, diisopropyl ... Examples of the alkyl acrylate copolymer include benzyl, butyl benzyl phthalate, diisodecyl adipate, diisostearyl adipate, dibutyl sebacate, diisocetyl sebacate, tributyl acetylcitrate, tributyl trimellitate, trioctyl trimellitate, trihexyl trimellitate, trioleyl trimellitate, and triisocetyl trimellitate.

[0065] Other examples of esters of acids and alcohols include esters of unsaturated or branched fatty acids such as myristoleic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid with alcohols such as ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitan.

[0066] Examples of esters of monobasic acids or polybasic acids with polyalkylene glycols include polyethylene glycol dihexylate, polyethylene glycol di-2-ethylhexylate, polyethylene glycol dilaurate, polyethylene glycol dioleate, and dipolyethylene glycol methyl ether adipate.

[0067] Examples of the phosphate ester plasticizer include tricresyl phosphate (TCP), triphenyl phosphate (TPP), tri-2-ethylhexyl phosphate (TOP), trixylenyl phosphate (TXP), and triethyl phosphate (TEP).

[0068] Examples of epoxy plasticizers include epoxidized soybean oil, epoxidized linseed oil, epoxidized octyl stearate, epoxidized fatty acid butyl, and epoxidized linseed oil fatty acid butyl.

[0069] The molecular weight (formula weight or Mn) of the plasticizer is preferably 250 to 1000, more preferably 400 to 900, and particularly preferably 500 to 850. If the molecular weight is 250 or more, the adhesive layer will have good heat resistance, and if the molecular weight is 1000 or less, a sufficient zipping suppression effect will be obtained.

[0070] The content of the plasticizer is not particularly limited, but is preferably 0.01 to 30 parts by mass, and more preferably 4 to 20 parts by mass, per 100 parts by mass of the acrylic ester copolymer. If the content of the plasticizer is 0.01 part by mass or more, a sufficient effect of suppressing zipping during peeling can be obtained, and if it is 30 parts by mass or less, a decrease in adhesive strength can be suppressed.

[0071] <Antioxidants> The pressure-sensitive adhesive composition of the present invention may further contain an antioxidant, if necessary. Examples of antioxidants include radical scavengers and peroxide decomposers. Examples of radical scavengers include phenolic compounds and amine compounds. Examples of peroxide decomposers include sulfur compounds and phosphorus compounds.

[0072] 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-dimethyl ethyl)-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, and tocopherol.

[0073] Examples of sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate, dimyristyl 3,3'-thiodipropionate, and distearyl 3,3'-thiodipropionate.

[0074] Examples of phosphorus compounds include triphenyl phosphite, diphenyl isodecyl phosphite, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenylditridecyl)phosphite, cyclic neopentanetetraylbis(octadecylphosphite), tris(nonylphenyl)phosphite, tris(mononylphenyl)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-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, tris(2,4-di-tert-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,4-di-tert-butylphenyl)phosphite, cyclic neopentanetetraylbis(2,6-di-tert-butyl-4-methylphenyl)phosphite, and 2,2-methylenebis(4,6-di-tert-butylphenyl)octylphosphite.

[0075] By using an antioxidant, thermal deterioration of the acrylic acid ester copolymer can be prevented, and the heat resistance can be improved. The amount of antioxidant added is not particularly limited, and is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts by mass, and even more preferably 0.2 to 2 parts by mass, per 100 parts by mass of the acrylic acid ester copolymer.

[0076] As the antioxidant, a phenolic compound, which is a radical scavenger, is preferred from the viewpoints of transparency and polymerization inhibition effect. The phenolic compound can effectively prevent residual monomer components from generating low molecular weight components over time during the synthesis of the acrylic ester copolymer (A), which reduces heat resistance.

[0077] The pressure-sensitive adhesive composition of the present invention may further contain known additives, such as catalysts, antistatic agents (AS agents), ultraviolet absorbers, light stabilizers, lubricants, corrosion inhibitors, heat stabilizers, weathering stabilizers, hydrolysis inhibitors, antifungal 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, and dielectric property adjusters, as needed.

[0078] <Adhesive composition> The pressure-sensitive adhesive composition of the present invention is a (meth)alkyl (meth)alkyl (meth)acrylate composition having an alkyl group with 1 to 12 carbon atoms. an acrylic ester copolymer, which is a copolymer of a monomer mixture consisting of an acrylic ester monomer (A), a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group; and an isocyanate-based curing agent. 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, the content of the monomer (C) having a hydroxyl group is 0.05% by mass or more and 10% by mass or less in 100% by mass of the monomer mixture, and the gel fraction is 55% or more.

[0079] <Gel fraction> The gel fraction is a value calculated by the following formula (3). (Gel fraction) = {(W2 - W0 - W3) / (W1 - W0 - W3)} × 100 (Equation 3) W0: Weight of wire mesh W1: Weight of wire mesh + test piece W2: Weight of wire mesh and test specimen after drying W3: Weight of the test piece substrate The method for measuring the gel fraction will be described in detail in the Examples section.

[0080] The pressure-sensitive adhesive composition of the present invention has a gel fraction of 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. A gel fraction of 55% or more allows the composition to exhibit good removability even after storage at high temperatures.

[0081] <Viscoelasticity> The storage modulus (G'), loss modulus (G'') and loss tangent (tanδ) of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention were measured for temperature dependency using a TA Instruments viscoelasticity measuring device "Ares-G2" under conditions of a frequency of 1 Hz, a strain of 0.1%, and a temperature of -50°C to 200°C (heating rate of 10°C / min), and the values at 25°C and 150°C were used.

[0082] The pressure-sensitive adhesive composition of the present invention has a ratio (P) of the loss modulus at 25°C to the loss modulus at 150°C when measured at 1 Hz, represented by Formula 1, of 0.02 to 0.3, preferably 0.03 to 0.15, more preferably 0.04 to 0.07, and particularly preferably 0.05 to 0.06. When the value of (P) is within this range, good adhesive strength and tack can be exhibited when applied, good removability can be exhibited even when applied for long periods at high temperatures, and adhesive bleeding can be suppressed even when a load is applied at high temperatures. (P) = (loss modulus at 150°C when measured at 1 Hz) / (25°C when measured at 1 Hz) Loss modulus in °C (Equation 1)

[0083] The storage modulus (G') at 25°C of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is preferably from 15,000 Pa to 90,000 Pa, and more preferably from 30,000 Pa to 65,000 Pa. A storage modulus of 15,000 Pa or more ensures sufficient cohesive strength, while a storage modulus of 90,000 Pa or less ensures good adhesive strength during use.

[0084] The storage modulus (G') at 150°C of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is preferably 10,000 Pa or more and 50,000 Pa or less. A storage modulus of 15,000 Pa or more allows for a pressure-sensitive adhesive with little extrusion even at high temperatures, while a storage modulus of 50,000 Pa or less allows for good adhesive strength even at high temperatures.

[0085] The loss modulus (G'') at 25°C of the pressure-sensitive adhesive layer formed from the pressure-sensitive 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 more preferably 15,000 Pa or more and 30,000 Pa or less. When it is 10,000 Pa or more, sufficient adhesive strength and tack can be obtained, and when it is 40,000 Pa or less, good removability during use can be obtained. can be obtained.

[0086] The loss modulus (G'') at 150°C of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention is not particularly limited, but is preferably from 800 Pa to 8,000 Pa, and more preferably from 900 Pa to 2,500 Pa. A loss modulus of 800 Pa or more ensures sufficient adhesive strength and tack even at high temperatures, and a loss modulus of 8,000 Pa or less ensures good removability even at high temperatures.

[0087] <Method of manufacturing pressure-sensitive adhesive composition> The method for producing the pressure-sensitive 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-based curing agent, a solvent, and, if necessary, optional components to the acrylic acid ester copolymer.

[0088] The pressure-sensitive adhesive composition of the present invention preferably has a nonvolatile content of 30 to 75 mass %, more preferably 38 to 65 mass %, and even more preferably 40 to 60 mass %. By setting the nonvolatile content of the pressure-sensitive adhesive composition to a high level, the solvent content can be relatively reduced, thereby reducing drying costs during coating and reducing the burden on the environment and the human body.

[0089] The viscosity of the pressure-sensitive adhesive composition at 25°C is preferably 1,000 to 20,000 mPa·s, more preferably 1,500 to 10,000 mPa·s, and even more preferably 2,500 to 7,000 mPa·s. When the viscosity of the pressure-sensitive adhesive composition is in the above range, the coating properties are improved, and a pressure-sensitive adhesive layer with a smooth surface is easily obtained. The viscosity is measured in an atmosphere of 25°C using a BL-type viscometer with a #3 rotor at a rotation speed of 12 rpm, after 1 minute of rotation. The viscosity measured is:

[0090] <Adhesive sheet> The pressure-sensitive adhesive sheet comprises a substrate and a pressure-sensitive adhesive layer made of a cured product of the pressure-sensitive adhesive composition of the present invention. The pressure-sensitive adhesive layer can be formed on one or both sides of the substrate. If necessary, the exposed surface of the pressure-sensitive adhesive layer can be covered with a release sheet. The release sheet is peeled off when the pressure-sensitive adhesive sheet is attached to an adherend.

[0091] When applying the pressure-sensitive adhesive composition, the viscosity can be adjusted using the above-mentioned solvent, or the viscosity can be reduced by heating the pressure-sensitive adhesive composition.

[0092] The substrate is not particularly limited, and examples thereof include a resin sheet, paper, and metal foil. The substrate may be a laminated sheet in which any one or more layers are laminated on at least one surface of the substrate. The surface of the substrate on which the adhesive layer is to be formed may be subjected to an easy-adhesion treatment such as a corona discharge treatment or application of an anchor coating agent, as necessary.

[0093] The constituent resin of the resin sheet is not particularly limited, and examples thereof include ester-based resins such as polyethylene terephthalate (PET); olefin-based resins such as polyethylene (PE) and polypropylene (PP); vinyl-based resins such as polyvinyl chloride; amide-based resins such as nylon 66; urethane-based resins (including foams); and combinations of these. The thickness of the resin sheets excluding the polyurethane sheet is not particularly limited, but is preferably 15 to 300 μm. The thickness of the polyurethane sheet (including the foam) is not particularly limited, but is preferably 20 to 50,000 μm.

[0094] The paper is not particularly limited, and examples thereof include plain paper, coated paper, and art paper. The metals constituting the metal foil are not particularly limited, and may be aluminum, copper, or a combination thereof. etc.

[0095] The release sheet is not particularly limited, and any known release sheet can be used, which is obtained by applying a release agent or other known release treatment to the surface of a base sheet such as a resin sheet or paper.

[0096] The pressure-sensitive adhesive sheet can be produced 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 application method, a known method 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, or a gravure coater method. The coating layer is then 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, but is preferably about 60 to 150°C. The thickness of the pressure-sensitive 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. In this manner, a single-sided PSA sheet can be produced. By carrying out the above operation on both sides, a double-sided PSA sheet can be produced.

[0097] Conversely to the above method, the pressure-sensitive adhesive composition of the present invention may be applied to the surface of a release sheet to form a coating layer comprising the pressure-sensitive adhesive composition of the present invention, and then the coating layer may be dried and cured to form a pressure-sensitive adhesive layer comprising a cured product of the pressure-sensitive adhesive composition of the present invention, and a substrate sheet may be laminated on the exposed surface of the pressure-sensitive adhesive layer.

[0098] The method for producing a pressure-sensitive adhesive sheet preferably includes a coating step of coating a substrate with a pressure-sensitive adhesive, a heating step of subjecting the formed coating layer to a heat-drying treatment to form a pressure-sensitive adhesive layer containing a cured product of the pressure-sensitive adhesive composition, a winding step of winding the obtained pressure-sensitive adhesive sheet around a core to form a pressure-sensitive adhesive sheet roll, and a curing step of curing the pressure-sensitive adhesive sheet roll. [Example]

[0099] Synthesis examples, examples according to the present invention, and comparative examples are described below. In the following description, unless otherwise specified, "parts" means parts by mass, "%" means % by mass, and "RH" means relative humidity.

[0100] [Measurement of weight average molecular weight (Mw)] The weight average molecular weight (Mw) was measured by gel permeation chromatography (GPC) under the following conditions. Note that Mw is a polystyrene equivalent value. <Measurement conditions> Equipment: Shimadzu Corporation, LC-GPC system "Prominence" Column: Four Tosoh GMHXL columns and one Tosoh HXL-H column connected in series. Detector: Differential refractive index detector (RID-10A), Solvent: tetrahydrofuran (THF), Flow rate: 1mL / min, Solvent temperature: 40°C, Sample concentration: 0.2%, Sample injection volume: 100 μL

[0101] <Production of acrylic ester copolymer> (Synthesis Example 1) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 2-Hydroxyethyl methacrylate 0.4 parts, ethyl acetate 35 parts, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged into vessel A equipped with a stirrer, and then charged into vessel B. 17.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. Simultaneously, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 790,000.

[0102] (Synthesis Example 2) A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube (hereinafter, sometimes simply referred to as "reaction vessel") was charged with 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 4-hydroxybutyl acrylate, 35 parts of ethyl acetate, and 2,2'-azobisisopropyl acrylate. After charging 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 4-hydroxybutyl acrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged into vessel A equipped with a stirrer, and vessel B was charged with 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 4-hydroxybutyl acrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN). 17.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature 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 non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic ester copolymer was was 770,000.

[0103] (Synthesis Example 3) A reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 30 parts of 2-ethylhexyl acrylate, 0.84 parts of 2-carboxyethyl acrylate, 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 vessel was replaced with nitrogen gas. Furthermore, a mixture of 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.0 parts of 2,2'-azobisisobutyronitrile (AIBN) was added to a vessel A equipped with a stirrer. 2 parts of butyl acrylate, 16.4 parts of butyl acrylate, 1.96 parts of 2-carboxyethyl acrylate, and 5 parts of ethyl acetate were charged into vessel A. The contents of vessel A were then added dropwise to vessel B over 2 hours using a dropping pump while stirring under a nitrogen atmosphere. At the same time, the contents of vessel B were added to vessel A over 2 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 820,000.

[0104] (Synthesis Example 4) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of isobutylnitrile (AIBN), the air in the reaction vessel was purged with nitrogen gas. Further, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged into a vessel A equipped with a stirrer, and then the mixture was transferred to a vessel B. 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. The reaction vessel was then heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction. The contents of vessel A were then added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were simultaneously fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a nonvolatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 880,000.

[0105] (Synthesis Example 5) A reaction vessel (hereinafter simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 12 parts of 2-ethylhexyl acrylate, 7.5 parts of isononyl acrylate, 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 in the reaction vessel was replaced with nitrogen gas. Further, a mixture of 28 parts of 2-ethylhexyl acrylate, 17.5 parts of isononyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 2,2'-azo 0.02 parts of bisisobutyronitrile (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 vessel B. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the solution was cooled and diluted with ethyl acetate to obtain an acrylic acid ester copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic acid ester copolymer was 810,000. there were.

[0106] (Synthesis Example 6) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (A After charging 0.02 parts of 2-ethylhexyl acrylate, the air in the reaction vessel was replaced with nitrogen gas. Furthermore, a container A equipped with a stirrer was charged with 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'-azobisulfite. 0.02 parts of isobutyronitrile (AIBN) was charged, and 19.15 parts of butyl acrylate, 0.05 parts of acrylic acid, and 5 parts of ethyl acetate were charged into vessel B. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic acid ester copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic acid ester copolymer was 800,000. It was.

[0107] (Synthesis Example 7) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (A After charging 0.02 parts of 2-ethylhexyl acrylate and 15 parts of lauryl methacrylate into a vessel A equipped with a stirrer, the air in the vessel was replaced with nitrogen gas. parts, 2-hydroxyethyl methacrylate 0.4 parts, ethyl acetate 20 parts, 2,2'-azobi 0.02 parts of isobutyronitrile (AIBN) was charged, and 18.4 parts of butyl acrylate, 0.8 parts of acrylic acid, and 5 parts of ethyl acetate were charged into vessel B. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic acid ester copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic acid ester copolymer was 800,000. .

[0108] (Synthesis Example 8) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (A After charging 0.02 parts of 2-ethylhexyl acrylate, the air in the reaction vessel was replaced with nitrogen gas. Furthermore, a container A equipped with a stirrer was charged with 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'-azobisulfite. 0.02 parts of isobutyronitrile (AIBN) was charged, and 18.2 parts of butyl acrylate, 1 part of acrylic acid, and 5 parts of ethyl acetate were charged into vessel B. The contents of the reaction vessel were then heated to 80°C under a nitrogen atmosphere while stirring to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were simultaneously fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a nonvolatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 800,000.

[0109] (Synthesis Example 9) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.84 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and in vessel B, To the reaction vessel were charged 16.4 parts of butyl acrylate, 1.96 parts of acrylic acid, and 5 parts of ethyl acetate. The contents of the reaction vessel were then heated to 80°C under a nitrogen atmosphere while stirring to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were simultaneously fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 810,000.

[0110] (Synthesis Example 10) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 1.05 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and in vessel B, 15.7 parts of butyl acrylate, 2.45 parts of acrylic acid, and 5 parts of ethyl acetate were then charged. The reaction vessel was heated to 80°C under a nitrogen atmosphere while stirring, and the reaction was initiated. The contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the solution was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 820,000.

[0111] (Synthesis Example 11) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 1.65 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 13 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and in vessel B, To the reaction vessel were charged 15.7 parts of butyl acrylate, 3.85 parts of acrylic acid, and 5 parts of ethyl acetate. The contents of the reaction vessel were then heated to 80°C under a nitrogen atmosphere while stirring to initiate the reaction. The contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 850,000.

[0112] (Synthesis Example 12) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.02 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.03 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and the vessel was To vessel B, 17.95 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. Simultaneously, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 790,000.

[0113] (Synthesis Example 13) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.04 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel A equipped with a stirrer, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.03 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and the vessel was To the reactor B, 17.93 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the contents of the reactor were heated to 80°C under a nitrogen atmosphere while stirring to start the reaction, and the contents of the reactor A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of the reactor B were added dropwise to the reactor. The mixture was fed to reactor A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylate copolymer was 790,000.

[0114] (Synthesis Example 14) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.08 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and the vessel was To vessel B, 17.85 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. Simultaneously, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 780,000.

[0115] (Synthesis Example 15) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.5 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged into vessel A equipped with a stirrer, and then charged into vessel B. 17.1 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. Simultaneously, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate ester copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate ester copolymer was 790,000.

[0116] (Synthesis Example 16) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.8 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, 35 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 0.7 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged into vessel A equipped with a stirrer, and then charged into vessel B. 16.5 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to start the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to give an acrylic acid solution with a non-volatile content of 35%. An ester copolymer solution was obtained, and the weight average molecular weight (Mw) of the acrylic acid ester copolymer was 790,000.

[0117] (Synthesis Example 17) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, 2,2'-azobisisobutyric acid, 1 part of 2-ethylhexyl acrylate, 1 part of 2-hydroxyethyl methacrylate ... After charging 0.02 parts of azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and in vessel B, acrylic acid 35 parts, lauryl methacrylate 11 parts, 2 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged. 16 parts of butyl acetate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylate copolymer was 810,000. It was.

[0118] (Synthesis Example 18) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 65 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in a vessel A equipped with a stirrer, 15 parts of 2-ethylhexyl acrylate, 5 parts of lauryl methacrylate, 32.2 parts of butyl acrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 20 parts of ethyl acetate, 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN), 0.02 parts of azobis ... Container A was charged with 0.02 parts of butyl acrylate, and Container B was charged with 15 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate. The reaction vessel was then heated to 80°C with stirring under a nitrogen atmosphere to initiate the reaction, and the contents of Container A were added dropwise over 2 hours using a dropping pump. Simultaneously, the contents of Container B were fed to Container A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature 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 non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylic ester copolymer was 830,000.

[0119] (Synthesis Example 19) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 65 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel A equipped with a stirrer, 15 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 22.2 parts of butyl acrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 10 parts of ethyl acetate, and 2,2'-azobisisobutyronitrile (AIBN) were charged. 0.02 parts of butyl acrylate, 15 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into vessel A. The reaction vessel was then heated to 80°C with stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 800,000.

[0120] (Synthesis Example 20) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 65 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in a vessel A equipped with a stirrer, 22.2 parts of 2-ethylhexyl acrylate, 15 parts of lauryl methacrylate, 15 parts of butyl acrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 10 parts of ethyl acetate, and 2,2'-azobisisobutyronitrile (AIBN) were charged. 0.02 parts of butyl acrylate, 15 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged into vessel A. The reaction vessel was then heated to 80°C with stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 770,000.

[0121] (Synthesis Example 21) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 40 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of azobisisobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, 34 parts of 2-ethylhexyl acrylate, 5 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 35 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged into vessel A equipped with a stirrer, and then the mixture was charged into vessel B. 28.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. Simultaneously, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 700,000.

[0122] (Synthesis Example 22) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 45 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and in vessel B, 10.2 parts of butyl acrylate, 1.4 parts of acrylic acid, and 5 parts of ethyl acetate were charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. Simultaneously, the contents of vessel B were fed to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 720,000.

[0123] (Synthesis Example 23) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 30 parts of 2-ethylhexyl acrylate, 0.6 parts of acrylic acid, 0.4 parts of 2-hydroxyethyl methacrylate, 40 parts of ethyl acetate, 2,2'-azobis(isothiazolinone) After charging 0.02 parts of isobutyronitrile (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged, and in vessel B, 16 parts of 2-ethylhexyl acrylate, 36 parts of lauryl methacrylate, 0.4 parts of 2-hydroxyethyl methacrylate, 5 parts of ethyl acetate, and 0.02 parts of 2,2'-azobisisobutyronitrile (AIBN) were charged. 10 parts lauryl acrylate, 5.2 parts butyl acrylate, 1.4 parts acrylic acid, and 5 parts ethyl acetate were charged. The reaction vessel was then heated to 80°C with stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. At the same time, the contents of vessel B were simultaneously added to vessel A over 2.0 hours with stirring. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a nonvolatile content of 35%. The weight-average molecular weight (Mw) of the acrylate copolymer was 800,000.

[0124] (Synthesis Example 24) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 13.5 parts of 2-ethylhexyl acrylate, 1.5 parts of lauryl methacrylate, 14.2 parts of butyl acrylate, 0.6 parts of acrylic acid, 0.24 parts of 2-hydroxyethyl methacrylate, 50 parts of ethyl acetate, and 2,2'-azobisisobutyronitrile were added. After charging 0.02 parts of AIBN, the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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, 0.56 parts of 2-hydroxyethyl methacrylate, 30 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (A 0.02 parts of ethanol (IBN) was then charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic acid ester copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic acid ester copolymer was 830,000.

[0125] (Synthesis Example 25) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 8.4 parts of 2-ethylhexyl acrylate, 0.9 parts of lauryl methacrylate, 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'-azobisisopropyl acrylate, 1 part of 2-ethylhexyl acrylate, 1 part of 2-hydroxyethyl methacrylate, 1 part of 2-ethylhexyl acrylate, 1 part of 2-ethylhexyl meth ... After charging 0.02 parts of isobutyl acrylate (AIBN), the air in the reaction vessel was replaced with nitrogen gas. Furthermore, in vessel 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. The reaction vessel was heated to 80°C under a nitrogen atmosphere while stirring, and the contents of vessel 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 acid ester copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylic acid ester copolymer was 700,000.

[0126] (Comparative Synthesis Example 1) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 13.5 parts of 2-ethylhexyl acrylate, 1.5 parts of lauryl methacrylate, 14 parts of butyl acrylate, 0.8 parts of acrylic acid, 60 parts of ethyl acetate, 2, After charging 0.02 parts of 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, 33.2 parts of butyl acrylate, 3.5 parts of lauryl methacrylate, 2.0 parts of acrylic acid, 30 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (AIBN) 0.02 parts of acetone was charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise using a dropping pump over 2 hours. The polymerization reaction was carried out at reflux temperature under a nitrogen atmosphere for 8 hours. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylate copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylate copolymer was 810,000.

[0127] (Comparative Synthesis Example 2) A reaction vessel (hereinafter simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 13.5 parts of 2-ethylhexyl acrylate, 1.5 parts of lauryl methacrylate, 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). After the addition, the air in the reaction vessel was replaced with nitrogen gas. Further, in a vessel 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, 30 parts of ethyl acetate, 2,2' 0.02 parts of azobisisobutyronitrile (AIBN) was then charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic acid ester copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic acid ester copolymer was The figure was 810,000.

[0128] (Comparative Synthesis Example 3) A reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 13.5 parts of 2-ethylhexyl acrylate, 1.5 parts of lauryl methacrylate, 10.5 parts of butyl acrylate, 2.7 parts of acrylic acid, 1.8 parts of 2-hydroxyethyl methacrylate, 55 parts of ethyl acetate, 2,2'-azobisisobutyronitrile ( After charging 0.02 parts of 2-ethylhexyl acrylate, the air in the reaction vessel was replaced with nitrogen gas. Further, in vessel 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, 4.2 parts of 2-hydroxyethyl methacrylate, 15 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (A 0.02 parts of ethanol (IBN) was charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise using a dropping pump over 2 hours. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic acid ester copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic acid ester copolymer was 880,000.

[0129] (Comparative Synthesis Example 4) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 13.5 parts of 2-ethylhexyl acrylate, 1.5 parts of lauryl methacrylate, 9.3 parts of butyl acrylate, 1.2 parts of acrylic acid, 4.5 parts of 2-hydroxyethyl methacrylate, 55 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (A After charging 0.02 parts of 2,2'-azobisisobutyronitrile (A), the air in the reaction vessel was replaced with nitrogen gas. Further, in a vessel 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, 10.5 parts of 2-hydroxyethyl methacrylate, 10 parts of ethyl acetate, and 2,2'-azobisisobutyronitrile (A Next, 0.02 parts of 8-IBN was added to the reaction vessel under a nitrogen atmosphere while stirring. The mixture was heated to 0°C to initiate the reaction, and the contents of vessel 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 acid ester copolymer solution with a non-volatile content of 35%. The weight-average molecular weight (Mw) of the acrylic acid ester copolymer was 850,000.

[0130] (Comparative Synthesis Example 5) Into a reaction vessel (hereinafter sometimes simply referred to as "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, 13.5 parts of 2-ethylhexyl acrylate, 1.5 parts of lauryl methacrylate, 7.8 parts of butyl acrylate, 2.7 parts of acrylic acid, 4.5 parts of 2-hydroxyethyl methacrylate, 55 parts of ethyl acetate, 2,2'-azobisisobutyronitrile (A After charging 0.02 parts of 2,2'-azobisisobutyronitrile (A), the air in the reaction vessel was replaced with nitrogen gas. Further, in a vessel 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, 10.5 parts of 2-hydroxyethyl methacrylate, 10 parts of ethyl acetate, and 2,2'-azobisisobutyronitrile (A 0.02 parts of ethanol (IBN) was then charged. Next, the reaction vessel was heated to 80°C while stirring under a nitrogen atmosphere to initiate the reaction, and the contents of vessel A were added dropwise over 2 hours using a dropping pump. The polymerization reaction was carried out for 8 hours at reflux temperature under a nitrogen atmosphere. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic acid ester copolymer solution with a non-volatile content of 35%. The weight average molecular weight (Mw) of the acrylic acid ester copolymer was 870,000.

[0131] [Table 1]

[0132] The abbreviations in Table 1 are as follows: 2EHA: 2-ethylhexyl acrylate INA: Isononyl acrylate LMA: Lauryl methacrylate EA: Ethyl acrylate BA: butyl acrylate AA: acrylic acid BCEA: 2-carboxyethyl acrylate HEMA: 2-hydroxyethyl methacrylate 4HBA: 4-hydroxybutyl acrylate

[0133] Example 1 <Production of Pressure-Sensitive Adhesive Composition> 100 parts of acrylic acid ester copolymer (Synthesis Example 1) was mixed with 2.5 parts of TDI-TMP as an isocyanate curing agent in terms of non-volatile content, and further mixed with 100 parts of acrylic acid ester copolymer (Synthesis Example 1) as a solvent. Ethyl acetate was then added so that the nonvolatile content was 30%, and the mixture was mixed uniformly to obtain a pressure-sensitive adhesive composition.

[0134] <Manufacturing of adhesive sheets> The resulting adhesive composition was applied to the release-treated surface of a 38 μm-thick release sheet (made of polyethylene terephthalate) (hereinafter referred to as "release film substrate") so that the thickness after drying would be 25 μm, and the coating was dried in a hot air oven at 100°C for 90 seconds to produce an adhesive layer. After drying, the coating was laminated onto a 50 μm-thick substrate (made of polyethylene terephthalate) and further aged at 23°C and 50% RH for 7 days to obtain an adhesive sheet.

[0135] (Examples 2 to 32, Comparative Examples 1 to 7) Each pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet were produced in the same manner as the pressure-sensitive adhesive sheet of Example 1, except that the acrylic acid ester copolymer and various additives were changed to the compositions and amounts (parts by mass) shown in Table 2. However, Examples 5, 21, 22, and 27 to 32 are reference examples.

[0136] [Table 2]

[0137] [Table 3]

[0138] The materials used are as follows: <Isocyanate-based curing agent> TDI-TMP: Adduct of tolylene diisocyanate and trimethylolpropane <Other hardeners> Azd: Aziridine-based curing agent, Chemitite PZ-33, manufactured by Nippon Shokubai Co., Ltd. <Plasticizer> ATBC: acetyl tributyl citrate

[0139] [Evaluation items and evaluation methods] The resulting pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets were evaluated by the following methods.

[0140] (gel fraction) After coating, the adhesive sheet was aged for 7 days in an atmosphere of 23°C and 50% RH, and then a test piece 30 mm wide and 100 mm long was cut from the sheet. The release sheet was peeled off from the test piece, and the exposed adhesive layer was attached to a 300-mesh stainless steel wire mesh. The wire mesh was folded to prevent the test piece from peeling off, and the test piece was immersed in ethyl acetate and left to stand at 50°C for 24 hours. After immersion, the wire mesh was removed, 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 (Equation 3) W0: Weight of wire mesh W1: Weight of wire mesh + test piece W2: Weight of wire mesh and test specimen after drying W3: Weight of the test piece substrate

[0141] (viscoelasticity) The adhesive composition obtained above was coated onto the release-treated surface of a 38 μm-thick release sheet (made of polyethylene terephthalate) (hereinafter referred to as the "release film substrate") so that the dried thickness would be 25 μm. The coated film was then dried in a hot air oven at 100°C for 90 seconds to produce an adhesive layer. After drying, the coated film was laminated onto another 75 μm-thick release sheet (made of polyethylene terephthalate) (hereinafter referred to as the "release film substrate") and aged for 7 days in an atmosphere of 23°C and 50% RH to produce an adhesive layer sandwiched between two release sheets in a "release sheet / adhesive layer / release sheet" configuration. Next, one release sheet was peeled off, and the lamination was repeated so that the adhesive layers overlapped, resulting in an adhesive layer with a thickness of 1 mm. After removing air bubbles in an autoclave, the coated film was cut into an 8 mm-diameter cylindrical shape to prepare a test specimen for measuring the storage modulus. The release sheets on both sides were peeled off, and viscoelasticity was measured. The storage modulus (G'), loss modulus (G") and loss tangent (tanδ) of the pressure-sensitive adhesive layer were measured for temperature dependence using a TA Instruments viscoelasticity measuring device "Ares-G2" at a frequency of 1 Hz, strain of 0.1%, and temperature of -50°C to 200°C (heating rate of 10°C / min). The loss modulus (G") values obtained at 25°C and 150°C were used to calculate the value of P according to the following formula (1). P = (loss modulus at 150°C when measured at 1 Hz) / (loss modulus at 25°C when measured at 1 Hz) Loss modulus) (Equation 1)

[0142] (Adhesive strength) After curing for 5 hours in an atmosphere of 23°C and 50% RH, a test piece measuring 25 mm in width and 150 mm in length was cut from the pressure-sensitive adhesive sheet. The release sheet was peeled off from the cut-out pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive layer was attached to the surface of a stainless steel plate (SUS304) and pressed with a 2 kg roll once. The test piece was then left in an atmosphere of 23°C and 50% RH for 24 hours. Next, the adhesive strength (adhesive strength before heating) was measured using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.) in accordance with JIS Z0237 at a peel speed of 300 mm / min and a peel angle of 180°. The evaluation criteria are as follows: [Evaluation criteria] ◎: 3N / 25mm or more, excellent. ○: 1N / 25mm or more, less than 3N / 25mm, good. △: 0.6N / 25mm or more and less than 1N / 25mm, practical. ×: Less than 0.6N / 25mm, not practical.

[0143] (Ball tuck) The resulting adhesive sheet was prepared to a size of 25 mm wide and 250 mm long. The release sheet was peeled off from the adhesive sheet, and the sheet was fixed with the adhesive side facing up on an inclined plate with an inclination angle of 30 degrees. A PET film for the runway was attached to the top, and a steel board was attached to the sample with a runway of 10 cm and an adhesive surface of 10 cm. A ball (1 / 32 to 32 / 32 inches) was rolled across the adhesive surface, and the diameter number of the ball that stopped near the center of the adhesive surface was recorded. Measurements were carried out in an atmosphere of 23°C and 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.

[0144] (Removal test) After aging for 7 days in an atmosphere of 23°C and 50% RH, test pieces measuring 25 mm in width and 150 mm in length were cut from the pressure-sensitive adhesive sheet. The release sheet was peeled from the cut-out pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive layer was attached to the surface of a stainless steel plate (SUS304) and pressed back and forth with a 2 kg roll. The test pieces were then stored for 10 days in environments of 23°C and 50% RH, 40°C, 60°C, and 55°C and 80% RH. After 10 days, the test pieces were left at 23°C and 50% RH for 3 hours. Then, the adhesive strength (adhesive strength before heating) was measured using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.) in accordance with JIS Z 0237 at a peel speed of 300 mm / min and a peel angle of 180°. The condition of the stainless steel plate after the measurement was observed. The evaluation criteria are as follows. [Evaluation criteria] ◎: No adhesive adhered to the stainless steel plate, excellent. ○: Adhesion of adhesive to stainless steel plate is more than 0% and less than 3% of the adhesion area, good. △: Adhesion of adhesive to stainless steel plate is 3% or more but less than 5% of the adhesion area, usable. ×: Adhesive adhesion to the stainless steel plate is 5% or more of the attachment area, cannot be used.

[0145] (Extrusion test) After curing for 5 hours or 7 days in an atmosphere of 23°C and 50% RH, the adhesive sheets were prepared in a size of 10 mm wide x 10 mm long. The release sheet was peeled off from the adhesive sheet, and the sheet was sandwiched between 38 μm thick release sheets (made of polyethylene terephthalate) on the top and bottom. The sheet was then pressed in a press tester at 60°C and 50 kg / cm. 2 After the test, the sample was removed and the width of the glue protruding from the edge of the test piece (maximum value) was measured. Evaluation criteria ◎: Protrusion is less than 0.2 mm. Very good. ○: Protrusion is 0.2 to less than 0.4 mm. Good. △: Protrusion is 0.4 to less than 0.6 mm. Practical use is possible. ×: Overhang of 0.6 mm or more. Not practical.

[0146] (Storage stability) After blending the curing agent, the pressure-sensitive adhesive composition was mixed uniformly and allowed to stand in an atmosphere of 23°C and 50% RH, and the rate of increase in viscosity was calculated using the following formula (4). (Viscosity increase rate) = {(Viscosity 7 days after mixing the hardener) / (Viscosity 1 hour after mixing the hardener)} ×100} (Formula 4) [Evaluation criteria] ◎: Viscosity increase rate is less than 150%, excellent. ○: Viscosity increase rate is 150% or more and less than 160%, good. △: Viscosity increase rate is 160% or more but less than 170%, suitable for practical use. ×: Viscosity increase rate is 170% or more, not usable.

[0147] The adhesive composition includes an acrylic ester copolymer, which is a copolymer of a monomer mixture consisting of (meth)acrylic ester monomer (A) having 1 to 12 carbon atoms in the alkyl group, monomer (B) having an acidic group, and monomer (C) having a hydroxyl group, and an isocyanate-based curing agent, and the content of monomer (B) having an acidic group is 100% by mass of the monomer mixture. , and the content of the monomer (C) having a hydroxyl group is 0.05% by mass or more and 10% by mass or less in 100% by mass of the monomer mixture, and the gel fraction is 55% or more. All of the pressure-sensitive adhesive compositions of the present invention have good adhesive properties, good removability after long-term storage under various conditions, little adhesive extrusion under high temperature and high load, and pressure-sensitive adhesive sheets with excellent storage stability after blending with a curing agent were produced.

Claims

1. The composition includes an acrylic acid ester copolymer, which is a copolymer of a monomer mixture including a (meth)acrylic acid alkyl ester monomer (A) having 1 to 12 carbon atoms in the alkyl group, a monomer (B) having an acidic group, and a monomer (C) having a hydroxyl group, and an isocyanate-based curing agent; the content of the (meth)acrylic acid alkyl ester monomer (a1) having an alkyl group with a carbon number of 8 to 12 is 55% by mass or more and 90% by mass or less in 100% by mass of the (meth)acrylic acid alkyl ester monomer (A) having an alkyl group with a carbon number of 1 to 12, 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 content of the hydroxyl group-containing monomer (C) is 0.05% by mass or more and 10% by mass or less, based on 100% by mass of the monomer mixture; the isocyanate-based curing agent contains a trimethylolpropane adduct of tolylene diisocyanate; The gel fraction is 55% or more, The (meth)acrylic acid alkyl ester monomer (a1) having an alkyl group with 8 to 12 carbon atoms contains 2-ethylhexyl acrylate and lauryl methacrylate. Pressure-sensitive adhesive composition.

2. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the ratio (P) of the loss modulus at 25°C to the loss modulus at 150°C measured at 1 Hz, as represented by Equation 1, is 0.02 or more and 0.3 or less. P = (loss modulus at 150°C when measured at 1 Hz) / (loss modulus at 25°C when measured at 1 Hz) (Equation 1)

3. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the ratio (P) of the loss modulus at 25°C to the loss modulus at 150°C measured at 1 Hz, as represented by Equation 1, is 0.03 or more and 0.15 or less. P = (loss modulus at 150°C when measured at 1 Hz) / (loss modulus at 25°C when measured at 1 Hz) (Equation 1)

4. A pressure-sensitive adhesive sheet comprising a substrate 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.

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