Adhesive composition and adhesive sheet, and acrylic resin

Abstract

To provide an active energy ray-curable detachable adhesive composition from which an adhesive that has good adhesive force before irradiation with active energy rays, is excellent in heat resistance, is reduced in adhesive force after irradiation with active energy rays even when exposed to high temperature, and is excellent in detachability without adhesive residues can be obtained.SOLUTION: An adhesive composition contains an acrylic resin (A) having a structural site derived from (meth)acrylate (a1) represented by a specific structural formula.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to adhesive compositions and adhesive sheets, and more particularly to adhesive compositions used as adhesives for release-type adhesive sheets for temporary surface protection when processing workpieces such as semiconductor wafers, printed circuit boards, glass products, metal plates, and plastic plates, and in particular to active energy ray-curable release-type adhesive compositions and adhesive sheets. [Background technology]

[0002] Traditionally, in the fabrication and drilling processes of integrated circuits using semiconductor wafers, adhesive sheets for surface protection have been used to temporarily protect the surface of the workpiece to prevent contamination and damage. In recent years, due to the miniaturization of processing technology and the thinning of workpieces, there is a need for adhesive sheets with appropriate adhesion to the workpiece. At the same time, it is necessary to remove the adhesive sheet after it has served its purpose of surface protection, and it is required that it be removable with light force and without leaving any adhesive residue. Furthermore, in recent years, adhesive sheets for surface protection have been used not only for semiconductor wafers but also in the processing of various other materials.

[0003] Effective adhesive sheets for this purpose are active energy ray curable adhesive compositions that harden and reduce adhesive strength upon irradiation with active energy rays. For example, active energy ray curability is achieved by (1) blending at least one of a monomer and oligomer having an ethylenically unsaturated group with an acrylic resin, or by (2) using an ethylenically unsaturated group-containing acrylic resin in which the acrylic resin itself contains an ethylenically unsaturated group. In particular, ethylenically unsaturated group-containing acrylic resins, in which the acrylic resin itself contains an ethylenically unsaturated group, are advantageous in reducing adhesive residue after peeling because they contain fewer low-molecular-weight components even after hardening by active energy ray irradiation.

[0004] As an adhesive sheet used in the semiconductor wafer dicing process described above, for example, Patent Document 1 discloses an adhesive sheet in which an adhesive layer consisting of an adhesive and a radiation-polymerizable compound which is a urethane acrylate oligomer having a molecular weight of 3,000 to 10,000 is applied to the substrate surface, and it is stated that after radiation irradiation, the adhesive strength between the wafer chip and the adhesive sheet decreases, making it easy to pick up the wafer chip.

[0005] Furthermore, Patent Document 2 describes an adhesive composition using an ethylenically unsaturated acrylic resin, in which the acrylic resin itself contains ethylenically unsaturated groups. For example, it describes a re-peelable adhesive using an acrylic resin containing ethylenically unsaturated groups, obtained by urethane-forming an acrylic polymer copolymerized with 2-hydroxyethyl acrylate with 2-methacryloyloxyethyl isocyanate.

[0006] In recent years, in the manufacturing process of electronic components, components with adhesive tape attached are often exposed to high temperatures. Therefore, adhesive tapes used in the manufacturing process of electronic components are required to have heat resistance that can withstand high-temperature conditions. Patent document 3 discloses an energy-ray easily peelable adhesive composition containing an acrylic polymer, an energy-ray polymerizable oligomer, a polymerization initiator, and a crosslinking agent, wherein a polymerization initiator having specific physical properties is used.

[0007] Furthermore, as an adhesive composition containing an energy-ray curable polymer used in adhesive sheets for wafer processing, Patent Document 4 discloses an energy-ray curable adhesive composition containing an energy-ray curable polymer in which a radical generating group that initiates a polymerization reaction under excitation by energy rays and an energy-ray polymerizable group are bonded to the main chain or side chain. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 62-153376 [Patent Document 2] Japanese Patent Publication No. 2010-53346 [Patent Document 3] Japanese Patent Publication No. 2012-012506 [Patent Document 4] Japanese Patent Publication No. 2009-242733 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the technology disclosed in Patent Document 1, while reducing the adhesive strength of the release adhesive after curing, still has problems such as adhesive residue remaining on the workpiece during peeling, chips scattering during dicing, and chips peeling off during expansion in the semiconductor wafer dicing process, and has not yet been satisfactory.

[0010] Furthermore, in the technology disclosed in Patent Document 2 mentioned above, while peelability after curing by ultraviolet irradiation is good, adhesive residue may occur due to the photopolymerization initiator used to cure by active energy ray irradiation. Such adhesive residue is more likely to occur when a component to which an adhesive sheet has been attached is exposed to high temperatures, and then cured and peeled off by active energy ray irradiation.

[0011] While the technology disclosed in Patent Document 3 shows improvement in heat resistance, the adhesive strength before and after active energy ray irradiation is insufficient. Therefore, there is a need for a release-type adhesive that has sufficient adhesive strength before active energy ray irradiation, becomes slightly adhesive after active energy ray irradiation, and also has excellent heat resistance. Furthermore, when exposed to high temperatures, low molecular weight components in the resin composition may segregate at the interface between the adherend and the adhesive due to the heat. This can lead to phenomena such as low molecular weight components remaining on the adherend surface after peeling, which can alter the surface wettability and potentially affect the adherend's staining ability.

[0012] In the disclosed technology of Patent Document 4, when introducing a radical generating group into the main chain or side chain of an acrylic resin, a radical generating group-containing monomer obtained by reacting 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (manufactured by Ciba Specialty Chemicals, Irgacure 2959) with methacryloyloxyethyl isocyanate is used. However, when preparing the radical generating group-containing monomer, due to the primary hydroxyl group and tertiary hydroxyl group of 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, some diacrylate may be generated, leaving problems in production stability. Furthermore, since unreacted 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (Irgacure 2959) will remain, problems such as the adhesive strength after irradiation with active energy rays being less likely to decrease after being exposed to high temperatures occur, and further improvement is required.

[0013] Therefore, under such circumstances, the present invention aims to provide an active energy ray-curable release-type adhesive composition that can obtain an adhesive having good adhesive strength before irradiation with active energy rays, excellent heat resistance, and excellent peelability such that the adhesive strength is reduced, there is no glue residue, and there is no change in wettability even after being exposed to high temperatures and then irradiated with active energy rays.

Means for Solving the Problems

[0014] However, as a result of intensive research in view of such circumstances, the present inventor has found that, as an adhesive composition, by using a compound having a structure with specific photopolymerization initiation performance and containing an acrylic resin into which a specific structural site is introduced, an adhesive having good adhesive strength before irradiation with active energy rays and excellent heat resistance can be obtained, and even after being exposed to high temperatures, an adhesive composition that can obtain an adhesive having excellent peelability with reduced adhesive strength, no glue residue, and no change in wettability can be obtained, thus completing the present invention.

[0015] In other words, the present invention has the following embodiments [1] to [9]. [1] An adhesive composition containing an acrylic resin (A) having a structural site derived from (meth)acrylate (a1) represented by the following general formula (I). [ka] [2] The adhesive composition according to [1], wherein the acrylic resin (A) further comprises an ethylenically unsaturated group. [3] The adhesive composition according to [1] or [2], wherein the content of structural members derived from (meth)acrylate (a1) represented by the general formula (I) is 0.001 to 10% by weight relative to the acrylic resin (A). [4] The adhesive composition according to any one of [1] to [3], wherein the acrylic resin (A) has a structural site derived from a hydroxyl group-containing monomer (a3). [5] The adhesive composition according to any one of [2] to [4], wherein the acrylic resin (A) contains 5 to 250 mmol / 100 g of ethylenically unsaturated groups. [6] The adhesive composition according to any one of [1] to [5] further contains a crosslinking agent (C). [7] An adhesive sheet having an adhesive layer in which the adhesive composition described in any of [1] to [6] is crosslinked. [8] The adhesive sheet according to [7], wherein the adhesive layer is hardened by irradiation with active energy rays and becomes peelable. [9] An acrylic resin having a structural moiety derived from (meth)acrylate (a1) represented by the following general formula (I) and an ethylenically unsaturated group. [ka] [Effects of the Invention]

[0016] The adhesive composition of the present invention has good adhesive strength before irradiation with active energy rays, excellent heat resistance, and even when exposed to high temperatures, the adhesive strength decreases after irradiation with active energy rays, leaving no adhesive residue and exhibiting excellent release properties without any change in wettability.

[0017] Furthermore, when the acrylic resin of the present invention is used as an adhesive, it exhibits good adhesive strength before irradiation with active energy rays, excellent heat resistance, and even when exposed to high temperatures, the adhesive strength is reduced after irradiation with active energy rays, leaving no adhesive residue and exhibiting excellent release properties without any change in wettability. [Modes for carrying out the invention]

[0018] The following describes specific embodiments for carrying out the present invention, but the present invention is not limited to these. In this invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate. Furthermore, acrylic resins are resins obtained by polymerizing a polymerization component that contains at least one (meth)acrylate monomer. In this invention, the term "sheet" is not specifically distinguished from "film" or "tape," but rather encompasses all of these terms.

[0019] The adhesive composition of the present invention is primarily used in the adhesive layer of an adhesive sheet, which is intended to be peeled off after being bonded to a workpiece such as a metal plate, plastic plate, or semiconductor wafer. The adhesive sheet is formed by coating the adhesive composition onto a base sheet to create an adhesive layer, and after being bonded to a workpiece, the adhesive layer hardens and its adhesive strength decreases when irradiated with active energy rays, allowing it to be easily peeled off from the workpiece.

[0020] The adhesive composition of the present invention contains an acrylic resin (A) having a structural moiety derived from (meth)acrylate (a1) represented by the following general formula (I). The individual components of the adhesive composition of the present invention will be described below.

[0021] [Acrylic resin (A)] The acrylic resin (A) used in the present invention is typically obtained by copolymerizing a (meth)acrylate (a1) represented by the following general formula (I), an alkyl (meth)acrylate monomer (a2), preferably a hydroxyl group-containing monomer (a3), and optionally a functional group-containing monomer (a4) or other copolymerizable monomer (a5).

[0022] [(meth)acrylate (a1) represented by general formula (I)] The (meth)acrylate (a1) used in the present invention has a structure represented by the following general formula (I).

[0023] [ka]

[0024] In the above equation (I), R 1 This represents a hydrogen atom, a methyl group, or an ethyl group. Of these, a hydrogen atom or a methyl group is preferred, and a methyl group is particularly preferred.

[0025] In the above equation (I), R 2 This represents a linear or branched alkylene group having 1 to 5 carbon atoms. Among these, the ethylene group, propane-1,3-diyl group, butane-1,3-diyl group, and butane-1,4-diyl group are preferred in terms of polymerizability when obtaining acrylic resin (A) and reactivity with ethylenically unsaturated groups described later, with the ethylene group being more preferred.

[0026] In the above equation (I), R 3 , R 4 Each of these independently represents a linear or branched alkyl group having 1 to 5 carbon atoms. Also, R 3 and R 4may be bonded to each other to form a ring, and R 3 and R 4 The number of carbon atoms in the ring formed is preferably 5 to 8, more preferably 6. R 3 、R 4 、or R 3 and R 4 The cyclic group formed is preferably a methyl group, an ethyl group, or a cyclohexyl group in terms of reactivity with an ethylenically unsaturated group described later and ease of availability, more preferably a methyl group, and even more preferably both R 3 、R 4 are methyl groups.

[0027] The (meth)acrylate (a1) represented by the above general formula (I) has an intramolecular cleavage type active group represented by the following formula (Ia).

[0028]

Chemical formula

[0029] When the acrylic resin (A) used in the present invention is irradiated with active energy rays, the active group represented by the above formula (Ia) easily cleaves to generate radicals and acts as a photoinitiator. Therefore, it is not necessary to blend a photoinitiator in the adhesive composition of the present invention, and it is possible to suppress changes in glue residue and wettability caused by the photoinitiator, particularly changes in glue residue and wettability when exposed to high temperatures.

[0030] The content of the (meth)acrylate (a1) represented by the general formula (I) in the copolymer component of the acrylic resin (A) is usually 0.001 to 10% by weight, preferably 0.1 to 8% by weight, and particularly preferably 0.5 to 5% by weight. When the content of the (meth)acrylate (a1) represented by the general formula (I) is within the above range, the peelability after irradiation with active energy rays tends to be excellent.

[0031] [(Alkyl (meth)acrylate monomer (a2))] The above (meth)acrylate alkyl ester monomer (a2) typically has 1 to 20 carbon atoms in the alkyl group, preferably 1 to 12, particularly preferably 1 to 8, and even more preferably 1 to 6. If the number of carbon atoms is too large, adhesive residue tends to be more likely to occur on the workpiece.

[0032] Examples of the above-mentioned alkyl (meth)acrylate monomer (a2) include aliphatic alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate; and alicyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. These may be used individually or in combination of two or more. Among the alkyl ester monomers (a2) listed above, methyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred in terms of copolymerizability, adhesive properties, ease of handling, and availability of raw materials, with methyl (meth)acrylate and n-butyl (meth)acrylate being particularly preferred.

[0033] Furthermore, the content of the alkyl ester monomer (a2) in the copolymer component of the acrylic resin (A) is usually 30 to 99% by weight, preferably 40 to 90% by weight, and particularly preferably 50 to 80% by weight. If the content is too low, the adhesive strength before irradiation with active energy rays tends to decrease, and if it is too high, the adhesive strength before irradiation with active energy rays tends to become too high.

[0034] [Hydroxygroup-containing monomer (a3)] In the present invention, it is preferable to use a hydroxyl group-containing monomer (a3) ​​as a copolymer component of the acrylic resin (A). By using the above hydroxyl group-containing monomer (a3) ​​as a copolymer component of the acrylic resin (A), the acrylic resin (A) will have structural sites derived from the hydroxyl group-containing monomer (a3), i.e., hydroxyl groups. These hydroxyl groups serve as reaction sites when introducing ethylenically unsaturated groups, as described later, and also as reaction sites with the crosslinking agent (C), as described later.

[0035] The above hydroxyl group-containing monomer (a3) ​​is preferably a hydroxyl group-containing (meth)acrylate monomer, specifically, for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate, Examples include oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid; secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate. These may be used individually or in combination of two or more. Among the hydroxyl group-containing monomers mentioned above, primary hydroxyl group-containing monomers are preferred due to their excellent reactivity with the ethylenically unsaturated compounds and crosslinking agent (C) described later, and 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are particularly preferred.

[0036] The content of hydroxyl group-containing monomer (a3) ​​in the copolymer component of the above acrylic resin (A) is usually 0.1 to 60% by weight, preferably 1 to 50% by weight, more preferably 3 to 40% by weight, and particularly preferably 7 to 30% by weight. If the content is too high, crosslinking tends to progress before the drying process, which can easily lead to problems with coating properties. If the content is too low, the ethylenically unsaturated groups described later will also be reduced, resulting in insufficient reduction of adhesive strength and a tendency for contamination of the workpiece to increase.

[0037] [Functional group-containing monomer (a4)] The above-mentioned functional group-containing monomer (a4) is a monomer having a functional group, excluding the above-mentioned hydroxyl group-containing monomer (a3), and examples include carboxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, acetoacetyl group-containing monomers, and the like. These functional group-containing monomers can be used individually or in combination of two or more types.

[0038] The content of functional group-containing monomers (a4) in the copolymer component of acrylic resin (A) is usually 30% by weight or less, preferably 20% by weight or less, and more preferably 10% by weight or less. If the content is too high, the storage stability of the resin solution may decrease, such as gelling during storage, or crosslinking may progress before the drying process, which tends to cause problems with coating properties.

[0039] Examples of the above-mentioned carboxyl group-containing monomers include (meth)acrylic acid, (meth)acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide N-glycolic acid, and cinnamic acid. Among these, (meth)acrylic acid is preferred due to its copolymerizability.

[0040] The content of carboxyl group-containing monomers in the copolymer component of acrylic resin (A) is usually 30% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. If the content is too high, it tends to easily alter the workpiece, reduce storage stability, and crosslinking progresses before the drying process, which tends to cause problems with coating properties.

[0041] Examples of the above-mentioned amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate.

[0042] The content of amino group-containing monomers in the copolymer component of acrylic resin (A) is usually 30% by weight or less, preferably 25% by weight or less, and more preferably 20% by weight or less. If the content is too high, crosslinking tends to progress before the drying process, which can easily lead to problems with coating properties.

[0043] Examples of the above-mentioned amide group-containing monomers include (meth)acrylamide monomers such as ethoxymethyl(meth)acrylamide, n-butoxymethyl(meth)acrylamide, (meth)acrylamide, dimethyl(meth)acrylamide, diethyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, (meth)acrylamide, and N-methylol(meth)acrylamide.

[0044] The content of amide group-containing monomers in the copolymer component of acrylic resin (A) is usually 30% by weight or less, preferably 25% by weight or less, and more preferably 20% by weight or less. If the content is too high, crosslinking tends to progress before the drying process, which can easily lead to problems with coating properties.

[0045] Examples of the above-mentioned glycidyl group-containing monomers include glycidyl methacrylate and allyl glycidyl methacrylate.

[0046] The content of glycidyl group-containing monomers in the copolymer component of acrylic resin (A) is usually 20% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. If the content is too high, crosslinking tends to progress before the drying process, which can easily lead to problems with coating properties.

[0047] Examples of the above-mentioned sulfonic acid group-containing monomers include olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, 2-acrylamido-2-methylolpropanesulfonic acid, styrene sulfonic acid, or salts thereof.

[0048] The content of sulfonic acid group-containing monomers in the copolymer component of acrylic resin (A) is usually 10% by weight or less, preferably 5% by weight or less, and more preferably 1% by weight or less. If the content is too high, crosslinking tends to progress before the drying process, which can easily lead to problems with coating properties.

[0049] Examples of the above-mentioned acetoacetyl group-containing monomers include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate.

[0050] The content of acetoacetyl group-containing monomers in the copolymer component of acrylic resin (A) is usually 10% by weight or less, preferably 5% by weight or less, and more preferably 1% by weight or less. If the content is too high, crosslinking tends to progress before the drying process, which can easily lead to problems with coating properties.

[0051] [Other copolymerizable monomers (a5)] Examples of the above-mentioned other copolymerizable monomers (a5) include vinyl carboxylate monomers such as vinyl acetate, vinyl propionate, vinyl stearate, and vinyl benzoate; monomers containing aromatic rings such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, styrene, and α-methylstyrene; biphenyloxy structure-containing (meth)acrylic acid ester monomers such as biphenyloxyethyl (meth)acrylate; and 2-methoxyethyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate. Examples include monomers containing alkoxy or oxyalkylene groups, such as phosphates, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and polypropylene glycol mono(meth)acrylate; and acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, alkyl vinyl ethers, vinyltoluene, vinylpyridine, vinylpyrrolidone, dialkyl itaconate, dialkyl fumarate, allyl alcohol, acrylic chloride, methyl vinyl ketone, allyltrimethylammonium chloride, and dimethylallyl vinyl ketone. These may be used individually or in combination of two or more.

[0052] The content of other copolymerizable monomers (a5) in the copolymer component of the acrylic resin (A) is usually 40% by weight or less, preferably 30% by weight or less, and more preferably 25% by weight or less. If there is too much of the other copolymerizable monomers (a5), the adhesive properties tend to decrease.

[0053] In the present invention, a (meth)acrylic resin (A) is produced by polymerizing a (meth)acrylate (a1) represented by the above general formula (I), an alkyl (meth)acrylate monomer (a2), preferably a hydroxyl group-containing monomer (a3), and optionally a functional group-containing monomer (a4) and other copolymerizable monomers (a5) as copolymer components. Conventional known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization are typically used for this polymerization. Among these, production by solution radical polymerization is preferred because it allows for the safe, stable production of acrylic resin (A) with any monomer composition.

[0054] In the above solution radical polymerization, for example, monomer components such as (meth)acrylate (a1) represented by general formula (I), alkyl (meth)acrylate monomers (a2), hydroxyl group-containing monomers (a3), functional group-containing monomers (a4), and other copolymerizable monomers (a5), along with a polymerization initiator, are mixed or added dropwise to an organic solvent, and polymerization can be carried out under reflux or at a temperature of 50 to 98°C for about 0.1 to 20 hours.

[0055] Examples of organic solvents used in the above polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, aliphatic alcohols such as n-propyl alcohol and isopropyl alcohol, and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Furthermore, the amount of the above-mentioned organic solvent used is typically 10 to 900 parts by weight per 100 parts by weight of the copolymer component.

[0056] As the polymerization initiators mentioned above, conventional radical polymerization initiators can be used. Specifically, examples include azo polymerization initiators such as azobisisobutyronitrile and azobisdimethylvaleronitrile, and peroxide polymerization initiators such as benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, and cumene hydroperoxide. These may be used individually or in combination of two or more.

[0057] Acrylic resin (A) is obtained by the polymerization method described above. The above-mentioned acrylic resin (A) has a structural part derived from (meth)acrylate (a1) represented by the following general formula (I).

[0058] [ka]

[0059] In the above acrylic resin (A), the content of structural moieties derived from (meth)acrylate (a1) represented by the above general formula (I) is preferably 0.001 to 10% by weight, more preferably 0.01 to 8% by weight, particularly preferably 0.1 to 5% by weight, and even more preferably 0.5 to 5% by weight, relative to the acrylic resin (A). When the content of (meth)acrylate (a1) represented by the general formula (I) is within the above range, there is a tendency for excellent peelability after irradiation with active energy rays.

[0060] Furthermore, it is preferable that the acrylic resin (A) has a structural site derived from a hydroxyl group-containing monomer (a3), i.e., has a hydroxyl group, from the viewpoint of reactivity with the ethylenically unsaturated compound and the crosslinking agent (C) described later. The presence of a hydroxyl group in the acrylic resin (A) allows for a reaction with the ethylenically unsaturated compound, introducing an ethylenically unsaturated group into the acrylic resin (A). Additionally, the reaction with the crosslinking agent (C) forms a crosslinked structure, which tends to improve the adhesive strength before irradiation with active energy rays.

[0061] When the acrylic resin (A) has hydroxyl groups, the hydroxyl group content is usually 0.01 to 20% by weight, preferably 0.05 to 10% by weight, and more preferably 0.1 to 5% by weight, relative to the acrylic resin (A). If the hydroxyl group content is too low, the cohesive force of the adhesive decreases, which tends to cause adhesive residue. If the hydroxyl group content is too high, the flexibility and adhesive strength of the adhesive decreases, which tends to cause lifting between the adhesive and the workpiece.

[0062] The glass transition temperature (Tg) of the above acrylic resin (A) is preferably -60 to 0°C, more preferably -55 to -5°C, even more preferably -50 to -10°C, and especially preferably -40 to -20°C. If the glass transition temperature is too high, the tackiness tends to decrease, and if it is too low, the contamination of the workpiece tends to increase.

[0063] The glass transition temperature (Tg) mentioned above was calculated by applying the glass transition temperature and weight fraction of each monomer constituting the acrylic resin (A) as a homopolymer to Fox's formula below.

[0064]

number

[0065] Here, the glass transition temperature when the monomers constituting the acrylic resin (A) are homopolymers is usually measured by differential scanning calorimeter (DSC), and can be measured using methods compliant with JIS K 7121-1987 or JIS K 6240.

[0066] Furthermore, the weight-average molecular weight of the acrylic resin (A) is typically 100,000 to 2,000,000, preferably 150,000 to 1,500,000, particularly preferably 200,000 to 1,200,000, and especially preferably 300,000 to 1,000,000. If the weight-average molecular weight is too low, it tends to increase the likelihood of contamination of the workpiece, and if it is too high, it tends to decrease the coating properties and also tends to be disadvantageous in terms of cost.

[0067] Furthermore, the degree of dispersion (weight-average molecular weight / number-average molecular weight) of the acrylic resin (A) is preferably 20 or less, particularly preferably 10 or less, even more preferably 7 or less, and especially preferably 5 or less. If the degree of dispersion is too high, the contamination of the workpiece tends to increase. The lower limit of the degree of dispersion is usually 1.1, from the standpoint of manufacturing limitations.

[0068] The weight-average molecular weight of the above acrylic resin (A) is the weight-average molecular weight converted to the standard polystyrene molecular weight. The chromatograph was high-performance liquid chromatograph (Waters 2695 (main unit) and Waters 2414 (detector)) manufactured by Waters Japan, with a column: Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10⁶). 7 Separation range: 100~2×10 7 The number-average molecular weight is measured by using three tubes in series (theoretical plate count: 10,000 stages / tube, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm), and the number-average molecular weight can be obtained by the same method.

[0069] Furthermore, the viscosity of the acrylic resin (A) at 25°C is preferably 5 to 10,000 mPa·s, and more preferably 10 to 5,000 mPa·s. If the viscosity is outside this range, the coating properties tend to decrease. The viscosity is measured using an E-type viscometer.

[0070] The acrylic resin (A) described above may be used as is, but in the present invention, it is preferable that the acrylic resin (A) further has ethylenically unsaturated groups. When the acrylic resin (A) has ethylenically unsaturated groups, the ethylenically unsaturated groups polymerize and harden when irradiated with active energy rays, causing a decrease in adhesive strength. Therefore, when an adhesive composition containing the acrylic resin (A) is made into an adhesive sheet, it is possible to impart easy peelability.

[0071] A method for introducing ethylenically unsaturated groups into the above-mentioned acrylic resin (A) is to react the acrylic resin (A) with a compound containing ethylenically unsaturated groups, for example, (i) A method of reacting the hydroxyl group of an acrylic resin (A) with an isocyanate group-containing ethylenically unsaturated compound. (ii) A method of reacting the hydroxyl groups of an acrylic resin (A) with (meth)acrylic anhydride, (iii) A method of reacting a hydroxyl group of an acrylic resin (A) with an ethylenically unsaturated group-containing carboxylic acid. (iv) A method for reacting a carboxyl group in an acrylic resin (A) with a vinyl ether group-containing (meth)acrylic acid ester, These are some examples. Among them, method (i) is preferred in terms of reactivity. The preferred method (i) is described below.

[0072] In the method described in (i) above, the hydroxyl group derived from the hydroxyl group-containing monomer (a3) ​​in the acrylic resin (A) reacts with the isocyanate group of the isocyanate group-containing ethylenically unsaturated compound, thereby obtaining an acrylic resin containing ethylenically unsaturated groups, in which ethylenically unsaturated groups including ethylenically unsaturated bonds and urethane bonds are introduced into the acrylic resin (A).

[0073] [Isocyanate group-containing ethylenically unsaturated compounds] The above isocyanate group-containing ethylenically unsaturated compounds are monomers that have an isocyanate group and a polymerizable ethylenically unsaturated group. Examples of the above isocyanate group-containing ethylenically unsaturated compounds include 2-(meth)acryloyloxyethyl isocyanate, 3-(meth)acryloyloxy-n-propyl isocyanate, 2-(meth)acryloyloxyisopropyl isocyanate, 4-(meth)acryloyloxy-n-butyl isocyanate, 2-(meth)acryloyloxy-tert-butyl isocyanate, 2-(meth)acryloyloxybutyl-4-isocyanate, 2-(meth)acryloyloxybutyl-3-isocyanate, 2-(meth)acryloyloxybutyl-2-isocyanate, and 2-(meth)acryloyloxybutyl-1- Examples include isocyanates, 5-(meth)acryloyloxy-n-pentyl isocyanate, 6-(meth)acryloyloxy-n-hexyl isocyanate, 7-(meth)acryloyloxy-n-heptyl isocyanate, 2-(isocyanatoethyloxy)ethyl(meth)acrylate, 3-(meth)acryloyloxyphenyl isocyanate, 4-(meth)acryloyloxyphenyl isocyanate, 1,1-bis((meth)acryloyloxymethyl)methyl isocyanate, 1,1-bis((meth)acryloyloxymethyl)ethyl isocyanate, 2'-pentenoyl-4-oxyphenyl isocyanate, etc. These may be used individually or in combination of two or more. Among these compounds, (meth)acrylate monomers are particularly preferred due to their ease of synthesis and availability of raw materials. Furthermore, 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, 2-(isocyanatoethyloxy)ethyl methacrylate, 2-(isocyanatoethyloxy)ethyl acrylate, and 1,1-bis(acryloyloxymethyl)ethyl isocyanate are preferred.

[0074] The ratio of acrylic resin (A) and isocyanate group-containing ethylenically unsaturated compound used in the reaction between the two is appropriately set considering the ratio of hydroxyl groups to isocyanate groups, and varies depending on the type of compound. However, typically, the ratio is 10 to 100 mol%, preferably 15 to 95 mol%, and particularly preferably 20 to 90 mol%, of the isocyanate group-containing ethylenically unsaturated compound relative to 100 mol% of the hydroxyl group-containing monomer (a3) ​​in the acrylic resin (A).

[0075] Furthermore, the reaction of both compounds may be carried out in the presence of a reaction catalyst, and the reaction rate can be adjusted by controlling the amount of reaction catalyst added. As the above reaction catalyst, known reaction catalysts can be used. Specific examples of reaction catalysts include, for example, dibutyltin dilaurate, copper naphthenate, cobalt naphthenate, zinc naphthenate, triethylamine, 1,4-diazabicyclo[2.2.2]octane, zirconium acetylacetonate, titanium diisopropoxybis(ethylacetoacetate), and a mixture of bismastris(2-ethylhexanoate) and 2-ethylhexanoic acid. One of these reaction catalysts can be used alone, or two or more can be used in combination.

[0076] The reaction temperature for reacting the two compounds is preferably -10 to 100°C, and more preferably 30 to 80°C. The reaction time is preferably 30 minutes to 50 hours, and more preferably 1 hour to 20 hours.

[0077] When reacting the two compounds, a polymerization inhibitor may be added to the reaction system as needed. Commonly used polymerization inhibitors can be used, such as phenolic compounds and hydroquinone compounds. Specific examples of polymerization inhibitors include hydroquinone, methoxyhydroquinone, catechol, p-tert-butylcatechol, cresol, and 2,6-di-tert-butyl-4-methylphenol (BHT). These may be used individually or in combination of two or more. In addition, known additives may be added to the reaction of the two compounds, depending on the purpose.

[0078] The addition reaction rate, i.e., the urethane conversion rate, between the hydroxyl group derived from the hydroxyl group-containing monomer (a3) ​​of the above-mentioned acrylic resin (A) and the isocyanate group of the isocyanate group-containing ethylenically unsaturated compound is preferably 5 to 99%, and more preferably 10 to 90%. If the urethane conversion rate is too low, the adhesive strength tends not to decrease sufficiently after irradiation with active energy rays such as ultraviolet light, and if the urethane conversion rate is too high, the urethane reaction does not complete, and unreacted isocyanate group-containing ethylenically unsaturated compounds tend to remain.

[0079] The urethane conversion rate can be calculated, for example, from the ratio of isocyanate groups (moles) of an isocyanate-containing ethylenically unsaturated compound to the amount of hydroxyl groups (moles) of an acrylic resin (A). Furthermore, by confirming the disappearance of the isocyanate group peak through IR measurement, it can be determined that 100% of the added isocyanate groups have reacted. In addition, other methods for calculating the urethane content include: 1 One method involves calculating the integral value ratio of the structures derived from the hydroxyl group-containing monomer (a3) ​​before and after the urethane reaction, as measured by 1H-NMR.

[0080] In the above, method (i), which is a preferred embodiment for introducing ethylenically unsaturated groups into acrylic resin (A), was described. However, ethylenically unsaturated groups can also be introduced into acrylic resin (A) by following conventional methods in methods (ii) to (iv).

[0081] When the above-mentioned acrylic resin (A) has ethylenically unsaturated groups, the content of these groups is usually 5 to 250 mmol / 100g, and more preferably 30 to 200 mmol / 100g. If the content of ethylenically unsaturated groups is too low, the peelability by active energy ray irradiation tends to decrease, and if the content of ethylenically unsaturated groups is too high, the stain resistance of the processed workpiece after peeling tends to decrease.

[0082] The content of the above-mentioned ethylenically unsaturated groups can be determined from the following formula. Ethylene-unsaturated group content (mmol / 100g) = Number of hydroxyl groups (mmol) contained in 100g of acrylic resin (A) before addition of ethylenically unsaturated groups × Addition reaction rate (%) / Weight of 100g of acrylic resin (A) after addition of ethylenically unsaturated groups (g) × 100

[0083] When the above acrylic resin (A) has ethylenically unsaturated groups, the glass transition temperature (Tg) is preferably -60 to 0°C, more preferably -55 to -5°C, even more preferably -50 to -10°C, and especially preferably -40 to -20°C. If the glass transition temperature is too high, the tack tends to decrease, and if it is too low, the adhesion before irradiation with active energy rays tends to be too low. The above glass transition temperature (Tg) can be calculated by the method described above.

[0084] Furthermore, when the above-mentioned acrylic resin (A) has ethylenically unsaturated groups, the weight-average molecular weight is usually 100,000 to 2,000,000, preferably 150,000 to 1,500,000, particularly preferably 200,000 to 1,200,000, and especially preferably 200,000 to 1,000,000. If the weight-average molecular weight is too small, there is a tendency for contamination of the workpiece to increase, and if it is too large, the coating properties tend to decrease, and there is also a tendency for it to be disadvantageous in terms of cost.

[0085] Furthermore, when the acrylic resin (A) has ethylenically unsaturated groups, the degree of dispersion (weight-average molecular weight / number-average molecular weight) is preferably 20 or less, particularly preferably 10 or less, even more preferably 7 or less, and especially preferably 5 or less. If the degree of dispersion is too high, the contamination of the workpiece tends to increase. The lower limit of the degree of dispersion is usually 1.1, from the standpoint of manufacturing limitations.

[0086] Furthermore, the weight-average molecular weight and dispersion of the acrylic resin (A) described above, when it contains ethylenically unsaturated groups, can be measured according to the method described above.

[0087] When the above-mentioned acrylic resin (A) has ethylenically unsaturated groups, its viscosity at 25°C is preferably 5 to 10,000 mPa·s, and more preferably 10 to 5,000 mPa·s. If the viscosity is outside this range, the coating properties tend to decrease. The viscosity is measured using an E-type viscometer.

[0088] Furthermore, even if the acrylic resin (A) has ethylenically unsaturated groups, it is preferable that it has structural sites derived from hydroxyl group-containing monomers (a3), i.e., that it has hydroxyl groups, from the viewpoint of reactivity with the crosslinking agent (C) described later.

[0089] When the acrylic resin (A) has ethylenically unsaturated groups, the hydroxyl group content is usually 0.01 to 10% by weight, preferably 0.05 to 8% by weight, and more preferably 0.1 to 5% by weight. If the hydroxyl group content is too low, the cohesive force of the adhesive decreases, which tends to cause adhesive residue. If the hydroxyl group content is too high, the flexibility and adhesive strength of the adhesive decreases, which tends to cause lifting between the adhesive and the workpiece.

[0090] In the adhesive composition of the present invention, if the acrylic resin (A) has ethylenically unsaturated groups, irradiation with active energy rays causes polymerization and hardening of the ethylenically unsaturated groups, resulting in a decrease in adhesive strength and making it peelable. Furthermore, if the acrylic resin (A) does not have ethylenically unsaturated groups, it is preferable to include a photopolymerizable compound, particularly a urethane (meth)acrylate compound (B), in the adhesive composition. By including a photopolymerizable compound such as a urethane (meth)acrylate compound (B), it is possible to impart easy peelability when irradiated with active energy rays.

[0091] [Urethane (meth)acrylate compound (B)] The above-mentioned urethane (meth)acrylate compound (B) is a compound having a urethane bond and a (meth)acryloyl group.

[0092] The above-mentioned urethane (meth)acrylate compound (B) may be a urethane (meth)acrylate compound (B1) which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1) and a polyvalent isocyanate compound (b2), or it may be a urethane (meth)acrylate compound (B2) which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (b1), a polyvalent isocyanate compound (b2), and a polyol compound (b3). In particular, in the present invention, it is preferable to use a urethane (meth)acrylate compound (B1) in terms of peelability after irradiation with active energy rays. In this invention, one type of urethane (meth)acrylate compound (B) may be used, or two or more types may be used in combination.

[0093] The above hydroxyl group-containing (meth)acrylate compound (b1) is preferably one having one hydroxyl group, for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2-hydroxyethyl acryloyl phosphate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, dipropylene glycol (meth)acrylate, fatty acid-modified glycidyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-(meth)acrylate Examples include hydroxyl group-containing (meth)acrylate compounds containing one ethylenically unsaturated group, such as kryloyloxypropyl (meth)acrylate; hydroxyl group-containing (meth)acrylate compounds containing two ethylenically unsaturated groups, such as glycerin di(meth)acrylate and 2-hydroxy-3-acryloyloxypropyl methacrylate; and hydroxyl group-containing (meth)acrylate compounds containing three or more ethylenically unsaturated groups, such as pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, and ethylene oxide-modified dipentaerythritol penta(meth)acrylate. The above-mentioned hydroxyl group-containing (meth)acrylate compound (b1) can be used alone or in combination of two or more types.

[0094] Among these, hydroxyl group-containing (meth)acrylate compounds (b1) containing three or more ethylenically unsaturated groups are preferred due to their excellent reactivity and versatility, with pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate being particularly preferred.

[0095] Examples of the polyvalent isocyanate compounds (b2) include aromatic polyvalent isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate; and aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and lysine triisocyanate. Examples include cyanates; alicyclic polyvalent isocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate; or isocyanurates or polymer compounds of these polyvalent isocyanates, allophanate-type polyisocyanates, burette-type polyisocyanates, and water-dispersible polyisocyanates (for example, "Aquanate 100", "Aquanate 110", "Aquanate 200", "Aquanate 210", etc. manufactured by Nippon Polyurethane Industries Co., Ltd.). The above-mentioned polyvalent isocyanate compound (b2) can be used alone or in combination of two or more.

[0096] Among these, aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, and alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate are preferred due to their excellent reactivity and versatility. Particularly preferred are isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, and hexamethylene diisocyanate, and even more preferred are isophorone diisocyanate and hexamethylene diisocyanate.

[0097] The polyol compound (b3) can be any compound containing two or more hydroxyl groups, such as aliphatic polyols, alicyclic polyols, polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, polybutadiene polyols, polyisoprene polyols, (meth)acrylic polyols, and polysiloxane polyols. These can be used individually or in combination of two or more.

[0098] Among these, aliphatic polyols and alicyclic polyols are preferred in terms of cost, while polyester polyols, polyether polyols, and polycarbonate polyols are preferred in terms of versatility.

[0099] The weight-average molecular weight of the polyol compound (b3) is preferably 60 to 3000, particularly preferably 100 to 1000, and even more preferably 150 to 800. If the weight-average molecular weight of the polyol compound (b3) is too high, the resulting urethane (meth)acrylate compound (B2) and acrylic resin (A) will not mix uniformly, and adhesive residue will tend to remain on the workpiece. Conversely, if the weight-average molecular weight of the polyol compound (b3) is too low, cracks will tend to occur in the adhesive layer after irradiation with active energy rays.

[0100] The urethane (meth)acrylate compound (B) can be produced by reacting the above components using known reaction methods. Typically, in the case of urethane (meth)acrylate compounds (B1), the above-mentioned hydroxyl group-containing (meth)acrylate compound (b1) and polyvalent isocyanate compound (b2) can be charged together or separately into a reactor and urethaneized using known reaction methods. In the case of urethane (meth)acrylate compounds (B2), a polyol compound (b3) can also be charged together or separately into a reactor and urethaneized. Furthermore, when producing urethane (meth)acrylate compounds (B2), a method in which the polyol compound (b3) and polyvalent isocyanate compound (b2) are reacted beforehand to obtain a reaction product, and then the hydroxyl group-containing (meth)acrylate compound (b1) is reacted with the product. This method is useful in terms of the stability of the urethaneization reaction and the reduction of by-products.

[0101] The above urethane formation reaction is terminated when the residual isocyanate group content in the reaction system becomes 0.5% by weight or less, thereby yielding a urethane (meth)acrylate compound (B).

[0102] The urethane (meth)acrylate compound (B) obtained in this manner preferably has 4 to 20 ethylenically unsaturated groups, more preferably 4 to 18, and particularly preferably 6 to 15, from the viewpoint of exfoliation after irradiation with active energy rays. If there are too many ethylenically unsaturated groups, the crosslinking density after irradiation with active energy rays becomes too high, making the adhesive layer prone to cracking. Conversely, if there are too few crosslinking groups, a sufficient crosslinking density cannot be obtained, making it difficult to delaminate after irradiation with active energy rays.

[0103] The weight-average molecular weight of the above-mentioned urethane (meth)acrylate compound (B) is typically 500 to 10000, preferably 750 to 5000, and more preferably 1000 to 4000. If the weight-average molecular weight is too high, the viscosity of the urethane (meth)acrylate compound (B) increases, reducing its compatibility with the acrylic resin (A), and making it more likely for adhesive residue to remain on the workpiece. If the weight-average molecular weight is too low, the urethane (meth)acrylate compound (B) tends to bleed from the adhesive sheet, making it more likely for adhesive residue to remain.

[0104] The weight-average molecular weight of the above-mentioned urethane (meth)acrylate compound (B) is the weight-average molecular weight converted to the standard polystyrene molecular weight, and is measured using a high-performance liquid chromatograph (Waters, "ACQUITY APC system") with four columns in series: one ACQUITY APC XT 450, one ACQUITY APC XT 200, and two ACQUITY APC XT 45.

[0105] The viscosity of the urethane (meth)acrylate compound (B) used in this invention is preferably 500 to 100,000 mPa·s at 60°C, and particularly preferably 1,000 to 50,000 mPa·s. If the viscosity is outside this range, the coating properties tend to decrease. The viscosity can be measured using an E-type viscometer.

[0106] In the present invention, the content of the urethane (meth)acrylate compound (B) is usually preferably 5 to 100 parts by weight, more preferably 10 to 80 parts by weight, and particularly preferably 15 to 50 parts by weight, per 100 parts by weight of the acrylic resin (A). If the content of the urethane (meth)acrylate compound (B) is too low, the peelability after irradiation with active energy rays tends to decrease, and if it is too high, cracks tend to occur in the adhesive layer after irradiation with active energy rays.

[0107] [Crosslinking agent (C)] The resin composition of the present invention preferably further contains a crosslinking agent (C) to improve adhesion before irradiation with active energy rays. As described above, the crosslinking agent (C) reacts with the functional groups in the acrylic resin (A) to form a crosslinked structure, and examples include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, amine crosslinking agents, and metal chelate crosslinking agents. Among these, isocyanate crosslinking agents are preferred in terms of improving adhesion to the adherend and reactivity with the acrylic resin (A).

[0108] The above-mentioned isocyanate-based crosslinking agents contain at least two isocyanate groups and include, for example, aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret and isocyanurate forms thereof, as well as adducts resulting from reactions with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among these, aromatic polyisocyanates and adducts of aromatic polyisocyanates and trimethylolpropane are preferred in terms of drug resistance and reactivity with functional groups, and adducts of tolylene diisocyanate and trimethylolpropane are particularly preferred.

[0109] Examples of the epoxy crosslinking agents mentioned above include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.

[0110] Examples of the above-mentioned aziridine crosslinking agents include diphenylmethane-4,4'-bis(1-aziridine carboxamide), trimethylolpropane tri-β-aziridinyl propionate, tetramethylolmethane tri-β-aziridinyl propionate, toluene-2,4-bis(1-aziridine carboxamide), triethylene melamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine, and trimethylolpropane tri-β-(2-methylaziridine)propionate.

[0111] Examples of the melamine-based crosslinking agents mentioned above include melamine, methylolmelamine derivatives such as amino group-containing methylolmelamine, imino group-containing methylolmelamine, and hexamethylolmelamine obtained by condensing melamine with formaldehyde, partially or completely alkylated methylolmelamine obtained by reacting a methylolmelamine derivative with a lower alcohol such as methyl alcohol or butyl alcohol, and alkylated methylolmelamine such as imino group-containing partially or completely alkylated methylolmelamine.

[0112] Examples of the aldehyde-based crosslinking agents mentioned above include aldehyde compounds that release aldehydes in aqueous solutions such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, glyoxal, glutaraldehyde, dialdehyde starch, hexamethylenetetramine, 1,4-dioxan-2,3-diol, 1,3-bis(hydroxymethyl)-2-imidazolidin, dimethylolurea, N-methylolacrylamide, urea formalin resin, and melamine formalin resin, or aromatic aldehyde compounds such as benzaldehyde, 2-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, and m-hydroxybenzaldehyde.

[0113] Examples of the amine-based crosslinking agents mentioned above include 4,4'-methylene-bis(2-chloroaniline), modified 4,4'-methylene-bis(2-chloroaniline), and diethyltoluenediamine.

[0114] Examples of the above-mentioned metal chelating crosslinking agents include chelating compounds in which the metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc., and aluminum chelating compounds are preferred in terms of performance. Examples of aluminum chelating compounds include diisopropoxyaluminum monooleyl acetate, monoisopropoxyaluminum bisoleyl acetate, monoisopropoxyaluminum monooleate monoethyl acetate, diisopropoxyaluminum monolauryl acetate, diisopropoxyaluminum monostearyl acetate, and diisopropoxyaluminum monoisostearyl acetate.

[0115] The above crosslinking agent (C) may be used alone or in combination of two or more types.

[0116] The content of the crosslinking agent (C) is usually preferably 0.01 to 30 parts by weight, particularly preferably 0.2 to 10 parts by weight, and even more preferably 0.2 to 3 parts by weight, per 100 parts by weight of the acrylic resin (A). If the amount of crosslinking agent (C) is too small, the cohesive force of the adhesive decreases, which tends to cause adhesive residue. If the amount is too large, the flexibility and adhesive strength of the adhesive decreases, which tends to cause lifting between the adhesive and the workpiece.

[0117] [Other ingredients] The adhesive composition of the present invention may further contain, to the extent that it does not impair the effects of the present invention, for example, ethylenically unsaturated compounds, which is preferable in terms of peelability after irradiation with active energy rays. It may also further contain additives such as antistatic agents, antioxidants, polymerization inhibitors, plasticizers, fillers, pigments, diluents, anti-aging agents, ultraviolet absorbers, ultraviolet stabilizers, tackifying resins, and photopolymerization initiators. These additives can be used individually or in combination of two or more. Antioxidants, in particular, are effective in maintaining the stability of the adhesive layer. There are no particular restrictions on the content of antioxidants when they are included, but it is preferably 0.01 to 5% by weight. In addition to additives, small amounts of impurities contained in the raw materials for manufacturing the components of the adhesive composition may also be included.

[0118] Thus, the adhesive composition of the present invention is obtained by mixing an acrylic resin (A), preferably a crosslinking agent (C), and optionally a urethane (meth)acrylate compound (B) and other components.

[0119] The adhesive composition of the present invention is preferably used as an adhesive sheet to temporarily protect the surface of a workpiece, such as an electronic substrate, semiconductor wafer, glass product, metal plate, or plastic plate, when processing the workpiece. The adhesive sheet has an adhesive layer in which the adhesive composition is crosslinked. The adhesive sheet mentioned above will be explained below.

[0120] The above-mentioned adhesive sheet typically comprises a base sheet, an adhesive layer made of the adhesive composition of the present invention, and a release film. As a method for producing such an adhesive sheet, first, the adhesive composition of the present invention is applied directly to the release film or base sheet, either as is or with its concentration adjusted using a suitable organic solvent. Then, it is dried, for example, by heat treatment at 80-105°C for 0.5-10 minutes, and this is then attached to the base sheet or release film to obtain the adhesive sheet. Furthermore, aging may be performed after drying to balance the adhesive properties.

[0121] Examples of the above-mentioned base sheet include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymers; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyfluoroethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluoroethylene; polyamides such as nylon 6 and nylon 6,6; vinyl polymers such as polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; cellulose resins such as cellulose triacetate and cellophane; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; polystyrene; polycarbonate; polyarylate; polyimide; and other materials. Examples of the above-mentioned base sheet include sheets made from at least one synthetic resin selected from the group consisting of these materials, as well as metal foils of aluminum, copper, and iron; paper such as fine paper and glassine paper; and textiles and nonwoven fabrics made from glass fibers, natural fibers, synthetic fibers, etc. These base sheets can be used as single layers or as multi-layered structures made by laminating two or more types. Among these, sheets made of synthetic resin are preferred from the viewpoint of weight reduction and other factors.

[0122] Furthermore, as the release film, for example, various synthetic resin sheets, paper, textiles, nonwoven fabrics, etc., as exemplified in the base sheet, can be used, which have been treated with a release agent.

[0123] Furthermore, the coating method for the above-mentioned adhesive composition is not particularly limited as long as it is a general coating method, and examples include roll coating, die coating, gravure coating, comma coating, and screen printing.

[0124] The thickness of the adhesive layer of the above adhesive sheet is usually preferably 5 to 200 μm, and more preferably 5 to 30 μm.

[0125] The aging conditions described above typically involve a temperature of room temperature (23°C) to 70°C, and a duration of 1 to 30 days. Specifically, this can be done under conditions such as 1 to 20 days at 23°C, 3 to 10 days at 23°C, or 1 to 7 days at 40°C.

[0126] The gel fraction of the adhesive layer of the above adhesive sheet is preferably 10 to 99% by weight, particularly preferably 20 to 97% by weight, and even more preferably 40 to 95% by weight, from the viewpoint of adhesiveness. If the gel fraction is too low, the adhesive strength to the workpiece tends to decrease, and if it is too high, the adhesive strength to the workpiece also tends to decrease.

[0127] The above gel fraction serves as an indicator of the degree of crosslinking (degree of hardening) and can be calculated, for example, by the following method: After laminating an adhesive sheet onto a SUS mesh sheet (200 mesh) and wrapping the adhesive sheet, the sheet is immersed in a sealed container containing ethyl acetate for 24 hours. The gel fraction is then determined from the change in weight of the adhesive layer before and after immersion in ethyl acetate using the following formula. Gel fraction (weight %) = Weight (g) of the adhesive layer after ethyl acetate immersion Weight of the adhesive layer before ethyl acetate immersion (g) × 100

[0128] Furthermore, adjusting the gel fraction of the adhesive layer to the above range is achieved by adjusting the type and amount of crosslinking agent (C), among other things.

[0129] By irradiating the adhesive layer of the adhesive sheet of the present invention with active energy rays, the ethylenically unsaturated groups contained in the adhesive layer polymerize, causing the adhesive layer to harden and resulting in a decrease in adhesive strength, making it possible to peel it off.

[0130] As active energy rays, various types of light rays can be used, including far-ultraviolet, ultraviolet, near-ultraviolet, and infrared rays, as well as electromagnetic waves such as X-rays and gamma rays, electron beams, proton beams, and neutron beams. However, ultraviolet light is preferred due to its curing speed, ease of obtaining irradiation equipment, and cost.

[0131] The cumulative radiation dose when irradiating with the above ultraviolet light is typically 50-3000 mJ / cm².2 Preferably 100-1000 mJ / cm² 2 Furthermore, the irradiation time varies depending on the type of light source, the distance between the light source and the adhesive layer, the thickness of the adhesive layer, and other conditions, but it is usually only a few seconds, and in some cases even just a fraction of a second.

[0132] The adhesive strength of the above adhesive sheet varies depending on the type of base sheet, the type of workpiece, etc., but before irradiation with active energy rays, it is preferably 5.5 N / 25 mm or higher, and more preferably 6.0 N / 25 mm or higher. The upper limit of the adhesive strength before irradiation with active energy rays is usually 100 N / 25 mm. Furthermore, the adhesive strength after irradiation with active energy rays is preferably 0.3 N / 25 mm or less, and more preferably 0.1 N / 25 mm or less.

[0133] Furthermore, the adhesive sheet of the present invention is heated at 100°C for 30 minutes, and then irradiated with ultraviolet light (cumulative irradiation dose of 250 mJ / cm²). 2 The adhesive strength when the coating is applied is preferably 1 N / 25 mm or less, and more preferably 0.5 N / 25 mm or less.

[0134] Furthermore, the adhesive sheet of the present invention is heated at 120°C for 30 minutes, and then irradiated with ultraviolet light (cumulative irradiation dose of 250 mJ / cm²). 2 The adhesive strength when the coating is applied is preferably 1 N / 25 mm or less, and more preferably 0.5 N / 25 mm or less.

[0135] The adhesive composition of the present invention is useful as a release-type adhesive sheet because, for example, when an adhesive sheet using this composition as an adhesive layer is bonded to a workpiece, temporarily protecting the surface of the workpiece, and then irradiated with active energy rays, the adhesive layer hardens, reducing its adhesive strength and allowing it to be easily peeled off from the workpiece. Furthermore, because the adhesive sheet of the present invention has excellent heat resistance, even if it is subjected to a heating process of, for example, 100°C or higher, particularly 120°C or higher, after being attached to the surface of a workpiece, subsequent irradiation with active energy rays reduces its adhesive strength, leaves no adhesive residue, and exhibits excellent release properties without causing any change in wettability. [Examples]

[0136] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. Hereinafter, "parts" means by weight.

[0137] <(meth)acrylate(a1)> First, we prepared the following (a1-1) as the (meth)acrylate (a1) represented by the general formula (I) above.

[0138] (a1-1): 2-[4-(2-hydroxy-2-methyl-1-oxopropyl)phenoxy]ethyl methacrylate obtained in Synthesis Example 1 below: In formula (I), R 1 , R 3 , R 4 is a methyl group, R 2 A compound in which the group is an ethylene group.

[0139] (Synthesis Example 1: Synthesis of (meth)acrylate (a1-1)) Methacrylic anhydride (manufactured by Tokyo Chemical Industry Co., Ltd.) was subjected to vacuum distillation, and the fraction with a purity of 99.8% or higher was recovered to obtain the methacrylic anhydride distillate. Vacuum distillation was carried out by gradually raising the temperature from room temperature (25°C) to 90°C at a pressure of 30 Pa. Separately, 22.4 g (0.1 mol) of 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxymethylpropanone (manufactured by Tokyo Chemical Industry Co., Ltd.) and 30.4 g (0.3 mol) of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in 500 mL of methylene chloride (manufactured by Tokyo Chemical Industry Co., Ltd.). 23.1 g (0.15 mol) of the distillate of the above methacrylic anhydride was added dropwise at room temperature, and the mixture was stirred for 12 hours. The resulting reaction mixture was washed three times with 500 mL of deionized water, the organic phase was concentrated, and the solvent was removed by distillation. The residue was purified by column chromatography (ethyl acetate / hexane = 10 / 90 (volume ratio)) to obtain 21.6 g of the target compound (meth)acrylate (a1-1) (yield 74%).

[0140] 1 ¹H-NMR analysis confirmed that the obtained compound was 2-[4-(2-hydroxy-2-methyl-1-oxopropyl)phenoxy]ethyl methacrylate. 1 H-NMR (300MHz, chloroform-d): δ8.06(d,J=9.0Hz,2H),6.96(d,J=9.0Hz,2H),6.13(d,J=0.6Hz,1H),5. 59(s,1H),4.50(d,J=5.1Hz,2H),4.29(dd,J=5.5,4.1Hz,3H),1.94(dd,J=1.6,1.0Hz,3H),1.61(s,6H).

[0141] [Manufacturing of ethylenically unsaturated group-containing acrylic resin (A-1)] In a four-necked round-bottom flask equipped with a reflux condenser, stirrer, nitrogen gas inlet, and thermometer, 72 parts of ethyl acetate and 10 parts of toluene were charged, and the internal temperature was raised to the boiling point to initiate the reaction. Then, 1 part of the prepared (meth)acrylate (a1-1), 61 parts of n-butyl acrylate (BA), 10 parts of methyl methacrylate (MMA), 28 parts of 2-hydroxyethyl acrylate (HEA), and 0.075 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator were added dropwise over 2 hours. After reacting for 1 hour, 30 parts of an ethyl acetate solution containing 0.4% AIBN were added, and the reaction was carried out at reflux temperature for 2.5 hours. Another 30 parts of an ethyl acetate solution containing 0.4% AIBN were added, and the reaction was carried out at reflux temperature for another 2.5 hours before the reaction was stopped. The mixture was then diluted with ethyl acetate to obtain the acrylic resin (A1) solution. To the acrylic resin (A1) solution obtained above, 2-methacryloyloxyethyl isocyanate (hereinafter referred to as "MOI") (manufactured by Showa Denko Corporation) and dibutyltin dilaurate as a urethane catalyst were appropriately added, and the mixture was reacted at 50°C for 18 hours to obtain an ethylenically unsaturated group-containing acrylic resin (A-1) solution (solid content 40.5% by weight, viscosity 1900 mPa·s / 25°C, acrylic resin (A-1): weight-average molecular weight (Mw) 550,000, dispersion degree (Mw / Mn) 4.27). The urethane conversion rate by MOI was 80%, and the ethylenically unsaturated group content was 148 mmol / 100g.

[0142] [Manufacturing of ethylenically unsaturated group-containing acrylic resin (A-2)] The process for producing ethylenically unsaturated group-containing acrylic resin (A-1) was carried out in the same manner as described in Table 1, except that the monomer composition was changed as shown in Table 1, to obtain a solution of ethylenically unsaturated group-containing acrylic resin (A-2). The obtained ethylenically unsaturated group-containing acrylic resin (A-2) is shown in Table 1.

[0143] [Manufacturing of acrylic resin (A-3)] In a four-necked round-bottom flask equipped with a reflux condenser, stirrer, nitrogen gas inlet, and thermometer, 102 parts of ethyl acetate were charged, and the internal temperature was raised to the boiling point to initiate the reaction. Then, 2 parts of the prepared (meth)acrylate (a1-1), 56.8 parts of n-butyl acrylate (BA), 40 parts of methyl acrylate (MA), 1 part of 2-hydroxyethyl acrylate (HEA), 0.2 parts of N,N-dimethylaminoethyl acrylate (DMAEA), and 0.056 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator were added dropwise over 2 hours. After reacting for 1 hour, 20 parts of an ethyl acetate solution containing 0.2% AIBN were added, and the reaction was carried out at reflux temperature for 2 hours. Then, 20 parts of an ethyl acetate solution containing 0.12% AIBN were added, and the reaction was carried out at reflux temperature for 2 hours before the reaction was stopped. The mixture was then diluted with ethyl acetate to obtain the acrylic resin (A-3) solution.

[0144] [Production of ethylenically unsaturated group-containing acrylic resin (A'-1)] Using the radical-generating group-containing monomer (a') obtained by Comparative Synthesis Example 1 below, the same procedure was followed as for the production of ethylenically unsaturated group-containing acrylic resin (A-1), except that the monomer composition was changed as shown in Table 1, to obtain a solution of ethylenically unsaturated group-containing acrylic resin (A'-1). The obtained ethylenically unsaturated group-containing acrylic resin (A'-1) is shown in Table 1.

[0145] (Comparative synthesis example 1: Synthesis of radical-generating monomer (a')) 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (manufactured by Ciba Specialty Chemicals, Irgacure 2959) and methacryloyloxyethyl isocyanate were mixed in equimolar ratios and reacted to obtain a radical-generating monomer (a').

[0146] [Production of ethylenically unsaturated group-containing acrylic resins (A'-2) to (A'-4)] The production of ethylenically unsaturated group-containing acrylic resin (A-1) was carried out in the same manner as described in Table 1, except that the monomer composition was changed as shown in Table 1, to obtain solutions of ethylenically unsaturated group-containing acrylic resins (A'-2) to (A'-4). The obtained ethylenically unsaturated group-containing acrylic resins (A'-2) to (A'-4) are shown in Table 1.

[0147] Note that ethylenically unsaturated group-containing acrylic resins (A-1), (A-2), and acrylic resin (A-3) are acrylic resins used in the examples, while ethylenically unsaturated group-containing acrylic resins (A'-1) to (A'-4) are acrylic resins used in the comparative examples.

[0148] [Table 1]

[0149] [Urethane (meth)acrylate compound (B)] The following urethane (meth)acrylate compounds (B-1) were prepared. • Reaction product of isophorone diisocyanate and dipentaerythritol pentaacrylate [Ethylene unsaturated groups: 10, weight-average molecular weight: 2300]

[0150] [Crosslinking agent (C)] The following were prepared as crosslinking agents (C-1). • Coronate® L-55E (adduct body of tolylene diisocyanate and trimethylolpropane, manufactured by Tosoh Corporation)

[0151] [Ethylene-unsaturated monomers] The following ethylenically unsaturated monomers were prepared. • Dipentaerythritol hexaacrylate

[0152] [Photopolymerization initiator] The following were prepared as photopolymerization initiators. • Omnirad® 184 (1-hydroxycyclohexyl phenyl ketone, manufactured by IGM Resins)

[0153] <Examples 1-3, Comparative Examples 1-6> To 100 parts of the acrylic resin prepared as described above, a crosslinking agent, urethane acrylate, ethylenically unsaturated monomer, and photopolymerization initiator were added and mixed as shown in Table 2 below. This mixture was then diluted with ethyl acetate to a solid content concentration (resin content) of 30% by weight to obtain an active energy ray curable, peelable adhesive composition solution. The following adhesive sheets were prepared using the obtained adhesive composition solution, and the following evaluations were performed. The evaluation results are shown in Table 2 below.

[0154] <Adhesive sheet (S1) (for gel fraction measurement)> The adhesive composition solution obtained above was applied to a heavily peelable 38 μm polyester release sheet (manufactured by Mitsui Chemicals Tohcello Co., Ltd.: Lumirror® SP03-38BU) to a thickness of 25 μm after drying, dried at 100°C for 5 minutes, then laminated to a lightly peelable 38 μm polyester release sheet (manufactured by Mitsui Chemicals Tohcello Co., Ltd.: Lumirror® SP01-38BU), and aged for 4 days at 40°C to obtain an adhesive sheet (S1) for gel fraction measurement.

[0155] <Adhesive sheet (S2) (for measuring adhesive strength)> The adhesive composition solution obtained above was applied to an untreated 38 μm polyester sheet (manufactured by Mitsui Chemicals Tohcello Co., Ltd.: Lumirror® T60) so that the thickness after drying was 25 μm, dried at 100°C for 5 minutes, then laminated to a light-peel 38 μm polyester release sheet (manufactured by Mitsui Chemicals Tohcello Co., Ltd.: Lumirror® SP01-38BU), and aged for 4 days at 40°C to obtain an adhesive sheet (S2) for adhesive strength measurement.

[0156] [Gel fraction] After cutting the above adhesive sheet (S1) to 40mm x 40mm, the light-release 38μm polyester release sheet was peeled off, and the adhesive layer side was bonded to a 50mm x 100mm SUS mesh sheet (200 mesh). Next, the heavy-release 38μm polyester release sheet was peeled off, and the sample was wrapped by folding it back from the center along the longitudinal direction of the SUS mesh sheet. The sample was immersed in a sealed container containing 250g of ethyl acetate for 24 hours, and the gel fraction was determined from the weight change of the adhesive layer before and after immersion in ethyl acetate using the following formula. Gel fraction (weight %) = (Weight of the adhesive layer after ethyl acetate immersion (g)) (Weight of the adhesive layer before ethyl acetate immersion (g)) × 100

[0157] [Adhesion before irradiation with activated energy rays] A 25mm x 100mm test specimen was prepared from the above adhesive sheet (S2). The 38μm polyester release sheet was peeled off, and the specimen was pressed onto a stainless steel plate (SUS304BA plate: size 70mm x 150mm) by rolling a 2kg rubber roller back and forth twice under conditions of 23°C and 50%RH. After standing for 30 minutes under the same conditions, the 180° peel strength (N / 25mm) was measured at a peeling speed of 300mm / min.

[0158] [Adhesion after irradiation with active energy rays (irradiation with high-pressure mercury lamps)] A 25mm x 100mm test specimen was prepared from the above adhesive sheet (S2). The easily removable 38μm polyester release sheet was peeled off, and the specimen was pressed onto a stainless steel plate (SUS304BA plate: size 70mm x 150mm) by rolling a 2kg rubber roller back and forth twice under conditions of 23°C and 50%RH. The specimen was then left to stand for 30 minutes under the same conditions. Subsequently, ultraviolet irradiation (cumulative irradiation dose of 250mJ / cm²) was performed from the untreated 38μm polyester sheet side using one 80W high-pressure mercury lamp. 2 The following procedure was performed: the sample was taken, and the sample was left to stand for 30 minutes in an atmosphere of 23°C and 50%RH. Then, the 180° peel strength (N / 25mm) was measured at a peeling speed of 300 mm / min.

[0159] [Adhesion after heating and irradiation with activated energy rays (irradiation with high-pressure mercury lamp) (1)] A 25mm x 100mm test specimen was prepared from the above adhesive sheet (S2). The 38μm polyester release sheet was peeled off, and the specimen was pressed onto a stainless steel plate (SUS304BA plate: size 70mm x 150mm) by passing a 2kg rubber roller back and forth twice in an atmosphere of 23°C and 50%RH. After that, it was heat-treated at 100°C for 30 minutes. The stainless steel plate with the heat-treated adhesive sheet attached was left to stand for 1 hour in an atmosphere of 23°C and 50% relative humidity, and then ultraviolet irradiation (cumulative irradiation dose 250mJ / cm²) was applied from the untreated 38μm polyester sheet side using one 80W high-pressure mercury lamp. 2 The following procedure was performed: the sample was taken, and the sample was left to stand for 30 minutes in an atmosphere of 23°C and 50%RH. Then, the 180° peel strength (N / 25mm) was measured at a peeling speed of 300 mm / min.

[0160] [Adhesion after heating and irradiation with activated energy rays (irradiation with high-pressure mercury lamp) (2)] In the above-mentioned adhesion strength after heating and activation ray irradiation (1), the procedure was carried out in the same manner except that the heating treatment conditions were changed to heating at 120°C for 30 minutes, and the 180° peel strength (N / 25mm) was measured.

[0161] [Adhesion after irradiation with active energy rays (irradiation with LED)] In measuring the adhesive strength after the above-mentioned active energy ray irradiation (irradiation with a high-pressure mercury lamp), a Heraeus UV4300 LED was used to irradiate the untreated 38 μm polyester sheet side with ultraviolet light from a 365 nm lamp (cumulative irradiation dose of 1500 mJ / cm²). 2 The procedure was carried out similarly except for the application of ( ), and the 180-degree peel strength (N / 25mm) was measured.

[0162] [Evaluation of adhesive residue after heating and activation ray irradiation (irradiation with high-pressure mercury lamp) (1)] A 25mm x 100mm test piece cut from the adhesive sheet (S2) obtained above was attached to the surface of a stainless steel plate (SUS304BA plate: size 70mm x 150mm) free of foreign matter, and then heat-treated at 100°C for 30 minutes. After the heat-treated stainless steel plate with the adhesive sheet attached was left to stand for 1 hour in an atmosphere of 23°C and 50%RH, and then ultraviolet irradiation (cumulative irradiation dose 250mJ / cm²) was performed from the untreated 38μm polyester sheet side using one 80W high-pressure mercury lamp. 2 After applying the adhesive sheet and allowing it to stand for 30 minutes in an atmosphere of 23°C and 50% RH, the adhesive sheet was peeled off the surface of the stainless steel plate. The remaining adhesive residue on the peeled stainless steel plate was checked under 1000x magnification using a digital microscope (Hirox HR-2000) and evaluated according to the following criteria. (Evaluation Criteria) ○...No adhesive residue left behind ×...Glue residue present

[0163] [Evaluation of adhesive residue after heating and activation energy irradiation (irradiation with high-pressure mercury lamp) (2)] In the above evaluation of adhesive residue after heating and activation ray irradiation (1), the procedure was carried out in the same manner except that the heating treatment conditions were changed to heating at 120°C for 30 minutes. The adhesive residue was checked under 1000x magnification using a digital microscope (Hirox HR-2000) and evaluated according to the same criteria as above.

[0164] [Changes in wettability after heating and irradiation with activated energy rays (irradiation with high-pressure mercury lamp) (1)] A 25mm x 100mm test piece cut from the adhesive sheet (S2) obtained above was attached to the surface of a stainless steel plate (SUS304BA plate: size 70mm x 150mm) free of foreign matter, and then heat-treated at 100°C for 30 minutes. After the heat-treated stainless steel plate with the adhesive sheet attached was left to stand for 1 hour in an atmosphere of 23°C and 50%RH, and then ultraviolet irradiation (cumulative irradiation dose 250mJ / cm²) was performed from the untreated 38μm polyester sheet side using one 80W high-pressure mercury lamp. 2The following steps were performed: the stainless steel plate was left standing for 30 minutes at 23°C and 50% RH. After that, the adhesive sheet was peeled off the surface of the stainless steel plate, and the wettability of the surface of the stainless steel plate after peeling was evaluated using a DynePen manufactured by Pacific Chemical Co., Ltd. For the evaluation, a 2cm line was drawn inside the 2.5cm width of the adhesive sheet using a dye pen. After 2 seconds, the maximum die gauge of the dye pen that resulted in less than 10% ink repellency was identified. Dyes with a die gauge of 38mN / m were marked "○", and those with a die gauge less than 38mN / m were marked "×". The surface energy (corresponding to the Dyne pen gauge) of the stainless steel plate (SUS304BA plate: size 70mm x 150mm) itself is 38 mN / m.

[0165] [Changes in wettability after heating and irradiation with active energy rays (irradiation with high-pressure mercury lamps) (2)] In the above-mentioned change in wettability after heating and activation ray irradiation (irradiation with a high-pressure mercury lamp) (1), the procedure was carried out in the same manner except that the heating treatment conditions were changed to heating at 120°C for 30 minutes, and the wettability of the stainless steel plate surface was evaluated using the same criteria as above.

[0166] [Table 2]

[0167] Based on the above evaluation results, the adhesive composition containing an acrylic resin (A) having a structural part derived from (meth)acrylate (a1) represented by general formula (I) is effective as an active energy ray curable adhesive composition even without the addition of a photopolymerization initiator. In particular, as a release-type adhesive sheet, it exhibits good adhesive strength before active energy ray irradiation, excellent heat resistance, and even when exposed to high temperatures, the adhesive strength is reduced after active energy ray irradiation, there is no adhesive residue, and there is no change in wettability, resulting in excellent release properties. In contrast, the acrylic resins of Comparative Examples 1 to 3, in which structural parts derived from monomers different from general formula (I) were introduced, showed insufficient reduction of tackiness after UV irradiation, insufficient reduction of tackiness after UV irradiation following exposure to high temperatures, and inferior performance in evaluating adhesive residue after peeling. In the acrylic resins of Comparative Examples 4-6, a sufficient reduction in adhesive strength was observed after UV irradiation, but the evaluation of adhesive residue after peeling was inferior, and changes in wettability also occurred. This indicates that it is important to have a structural site derived from (meth)acrylate (a1) of general formula (I). [Industrial applicability]

[0168] The adhesive composition of the present invention can be suitably used as an adhesive sheet for temporary surface protection when processing electronic substrates, semiconductor wafers, glass products, metal plates, plastic plates, etc.

Claims

1. An adhesive composition containing an acrylic resin (A) having a structural moiety derived from a (meth)acrylate (a1) represented by the following general formula (I), and a structural moiety derived from a hydroxyl group-containing monomer (a3), The above acrylic resin (A) has an ethylenically unsaturated group, An active energy ray-curable, peelable adhesive composition for temporary surface protection when processing a workpiece, characterized in that the content of a structural part derived from (meth)acrylate (a1) represented by the following general formula (I) is 0.001 to 10% by weight relative to the acrylic resin (A). 【Chemistry 1】

2. An adhesive composition containing an acrylic resin (A) having a structural moiety derived from a (meth)acrylate (a1) represented by the following general formula (I), and a structural moiety derived from a hydroxyl group-containing monomer (a3), The above adhesive composition contains a urethane (meth)acrylate compound (B), and the acrylic resin (A) does not have an ethylenically unsaturated group. An active energy ray-curable release adhesive composition characterized in that the content of a structural moiety derived from (meth)acrylate (a1) represented by the following general formula (I) is 0.001 to 10% by weight relative to the acrylic resin (A). 【Chemistry 2】

3. The active energy ray curable release adhesive composition according to claim 1, characterized in that the ethylenically unsaturated group content in the acrylic resin (A) is 5 to 250 mmol / 100g.

4. Furthermore, the active energy ray curable release adhesive composition according to any one of claims 1 to 3 is characterized by containing a crosslinking agent (C).

5. An adhesive sheet characterized by having an adhesive layer in which the active energy ray curable peelable adhesive composition according to any one of claims 1 to 4 is crosslinked.

6. The adhesive sheet according to claim 5, characterized in that the adhesive layer is hardened and peelable by irradiation with active energy rays.

7. An acrylic resin having a structural moiety derived from (meth)acrylate (a1) represented by the following general formula (I), a structural moiety derived from a hydroxyl group-containing monomer (a3), and an ethylenically unsaturated group, The above ethylenically unsaturated group is derived from at least one ethylenically unsaturated group-containing compound selected from the group consisting of isocyanate group-containing ethylenically unsaturated compounds, (meth)acrylic anhydride, and ethylenically unsaturated group-containing carboxylic acids. An acrylic resin for temporary surface protection when processing a workpiece, characterized in that the content of structural parts derived from (meth)acrylate (a1) represented by the following general formula (I) is 0.001 to 10% by weight relative to the acrylic resin. 【Transformation 3】

8. The acrylic resin for temporary surface protection when processing a workpiece, as described in claim 7, characterized in that the above-mentioned ethylenically unsaturated group is derived from at least one (meth)acrylate monomer selected from the group consisting of 2-methacryloyloxyethyl isocyanate, 2-acryloyloxyethyl isocyanate, 2-(isocyanatoethyloxy)ethyl methacrylate, 2-(isocyanatoethyloxy)ethyl acrylate, 1,1-bis(acryloyloxymethyl)ethyl isocyanate, and ethylenically unsaturated group-containing carboxylic acid.

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