Active energy ray-curable release-type adhesive composition, active energy ray-curable release-type adhesive sheet, and active energy ray-curable release-type adhesive

Abstract

To provide an adhesive composition that has favorable peelability (light adhesion) after active energy ray irradiation and can form an adhesive layer having high elongation at break.SOLUTION: An active energy ray-curable peelable adhesive composition contains an ethylenically unsaturated group-containing acrylic resin (A) having an ethylenically unsaturated group-containing structural site (α) with a number average molecular weight of 1000-300,000 in a side chain.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active energy ray-curable release-type pressure-sensitive adhesive composition containing an ethylenically unsaturated group-containing acrylic resin having an ethylenically unsaturated group-containing structural moiety in its side chain, an active energy ray-curable release-type pressure-sensitive adhesive sheet using the same, and an active energy ray-curable release-type pressure-sensitive adhesive, and in particular to an active energy ray-curable release-type pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, and pressure-sensitive adhesive that are useful as pressure-sensitive adhesive sheets for temporary surface protection of substrates such as metal plates and plastic plates, and as pressure-sensitive adhesive sheets for fixing semiconductors used in semiconductor manufacturing processes such as dicing and back-grinding processes for semiconductor devices such as semiconductor wafers. [Background technology]

[0002] BACKGROUND ART Active energy ray-curable resin compositions that are cured by irradiation with active energy rays such as ultraviolet rays and electron beams are used in applications such as adhesives, pressure-sensitive adhesives, paints, inks, coating materials, and photo-fabrication materials.

[0003] The active energy ray-curable resin composition is also used as an adhesive layer in a surface-protecting adhesive sheet that temporarily protects the surface of a workpiece to prevent contamination and damage to the workpiece during processing such as drilling holes in substrates such as metal plates and plastic plates, and is also used as an adhesive layer in a semiconductor-fixing adhesive sheet that is used when subjecting semiconductor devices such as semiconductor wafers to semiconductor manufacturing processes such as dicing processes. Hereinafter, the workpiece, including substrates and semiconductor devices, will also be referred to as a "workpiece," and surface-protecting adhesive sheets and semiconductor-fixing adhesive sheets will also be collectively referred to as "adhesive sheets."

[0004] The above-mentioned adhesive sheets are required to have an appropriate adhesive strength to the workpiece due to recent trends in finer processing techniques and thinner workpieces, but since the adhesive sheet needs to be peeled off after it has completed its role of protecting the surface of the workpiece and fixing it, it is required that the adhesive sheet can be peeled off with light force without leaving any adhesive residue after being irradiated with active energy rays.

[0005] Such active energy ray-curable resin compositions exhibit active energy ray curability by, for example, blending at least one of a monomer and an oligomer having an ethylenically unsaturated group with an acrylic resin, or by incorporating an ethylenically unsaturated group into the acrylic resin itself. Among these, ethylenically unsaturated group-containing acrylic resins, in which the acrylic resin itself contains an ethylenically unsaturated group, have a small amount of low-molecular-weight components even after curing by active energy ray irradiation, and are therefore advantageous in reducing adhesive residue after peeling.

[0006] For example, Patent Document 1 discloses an adhesive sheet used in the dicing process of semiconductor wafers, which is formed by applying an adhesive layer composed of an adhesive and a radiation-polymerizable compound, which is a urethane acrylate oligomer having a molecular weight of 3,000 to 10,000, to a substrate surface, and describes that the adhesive strength between the wafer chip and the adhesive sheet decreases after radiation exposure, allowing the wafer chip to be easily picked up.

[0007] Furthermore, Patent Document 2 describes a pressure-sensitive adhesive composition using an ethylenically unsaturated group-containing acrylic resin, in which the acrylic resin itself contains an ethylenically unsaturated group, such as a removable pressure-sensitive adhesive using an acrylic resin containing an ethylenically unsaturated group, which is obtained by subjecting an acrylic polymer copolymerized with 2-hydroxyethyl acrylate to a urethanization reaction with 2-methacryloyloxyethyl isocyanate. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 153376 / 1983 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-53346 Summary of the Invention [Problem to be solved by the invention]

[0009] However, although the technology disclosed in Patent Document 1 reduces the adhesive strength of the peelable adhesive after hardening, there are problems such as the adhesive remaining on the wafer chip when peeled, the wafer chip scattering during dicing, and the wafer chip peeling off and falling off during expansion, and further improvements are required.

[0010] Furthermore, the technology disclosed in Patent Document 2 above has good releasability after curing by ultraviolet irradiation, but the adhesive tends to become hard after curing, which reduces the elongation of the adhesive layer and makes expanding difficult.

[0011] In recent years, there has been an increasing demand for contamination resistance, such as not leaving adhesive residue on the workpiece when peeled off after curing by ultraviolet irradiation. In order to improve such contamination resistance, the elongation of the pressure-sensitive adhesive layer after curing is important, and it is desirable for the pressure-sensitive adhesive layer to have a high breaking elongation.

[0012] Therefore, under such circumstances, the present invention aims to provide a pressure-sensitive adhesive composition that has excellent releasability (slight adhesion) after irradiation with active energy rays and is capable of forming a pressure-sensitive adhesive layer having high elongation at break. [Means for solving the problem]

[0013] However, the present inventors have discovered that in an active energy ray-curable peelable pressure-sensitive adhesive composition containing an ethylenically unsaturated group-containing acrylic resin, by incorporating a relatively high molecular weight ethylenically unsaturated group-containing structural moiety in the side chain of the acrylic resin, it is possible to form a pressure-sensitive adhesive layer that has excellent peelability (slight adhesion) after exposure to active energy rays and also has high elongation at break, and have completed the present invention.

[0014] That is, the present invention provides a polymerizable composition containing an ethylenically unsaturated group-containing acrylic resin (A) having an ethylenically unsaturated group-containing structural moiety (α) in a side chain and having a number average molecular weight of 1,000 to 300,000. The ethylenically unsaturated group-containing structural moiety (α) is a structural moiety derived from a hydroxyl group-containing macromonomer (α1), and is an ethylenically unsaturated group-containing structural moiety formed by a reaction between a hydroxyl group derived from the hydroxyl group-containing macromonomer (α1) and an isocyanate group of an isocyanate group-containing ethylenically unsaturated compound (α2). The first aspect of the present invention is an active energy ray-curable peelable pressure-sensitive adhesive composition.

[0015] A second aspect of the present invention is an active energy ray-curable peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the active energy ray-curable peelable pressure-sensitive adhesive composition according to the first aspect is crosslinked. [Effects of the Invention]

[0017] According to the active energy ray-curable peel-type pressure-sensitive adhesive composition of the present invention, it is possible to form a pressure-sensitive adhesive layer that has excellent releasability (slight adhesion) after irradiation with active energy rays and also has high breaking elongation. In the active energy ray-curable peel-type pressure-sensitive adhesive sheet of the present invention having such a pressure-sensitive adhesive layer, because the pressure-sensitive adhesive layer has high breaking elongation after irradiation with active energy rays, even if the exposure dose of active energy rays is insufficient and the pressure-sensitive adhesive layer is not sufficiently cured, adhesive residue is less likely to adhere to the workpiece such as a wafer when the pressure-sensitive adhesive sheet is peeled off, and the occurrence of adhesive residue can be suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments for carrying out the present invention will be specifically described, but the present invention is not limited to these. Some terms used in this specification will be explained. "(Meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate, respectively. The term "acrylic resin" refers to a resin obtained by polymerizing a polymerization component containing at least one type of (meth)acrylate monomer. The term "sheet" is not particularly distinguished from "film" or "tape" and is used to include these terms.

[0019] The "number average molecular weight (Mn)" is the number average molecular weight converted to 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. "Weight average molecular weight (Mw)" is the weight average molecular weight converted to standard polystyrene molecular weight. The sample was analyzed using a high performance liquid chromatograph (Waters Japan, "Waters 2695 (main unit)" and "Waters 2414 (detector)") with a column: Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 7 Separation range: 100 to 2 × 10 7 The measurement is performed using three columns in series (theoretical plate number: 10,000 columns / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm). The "dispersity" is determined by the weight average molecular weight (Mw) / number average molecular weight (Mn).

[0020] The "glass transition temperature" is calculated from the types and mass fractions of the monomer units constituting the copolymer using the Fox equation below. In this specification, the glass transition temperature calculated using the Fox equation is also referred to as the "calculated glass transition temperature." 1 / (273+Tg)=Σ{Wi / (273+Tgi)} In the formula, Tg is the glass transition temperature (°C) of the copolymer, Wi is the weight fraction of monomer units derived from monomer i constituting the copolymer, and Tgi is the glass transition temperature (°C) of a homopolymer of monomer i. Tgi is usually measured using a differential scanning calorimeter (DSC) and can be measured by a method conforming to JIS K7121-1987 or JIS K 6240. Furthermore, if the value of Tgi is listed in the Polymer Handbook [Polymer Handbook, J. Brandrup, Interscience, 1989], this value can also be used to determine the value.

[0021] <Active energy ray-curable peel-type pressure-sensitive adhesive composition> The active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention (hereinafter sometimes simply referred to as "pressure-sensitive adhesive composition") is suitably used to form a pressure-sensitive adhesive layer on one side of a substrate sheet. The pressure-sensitive adhesive layer is formed, for example, by coating the pressure-sensitive adhesive composition on a substrate sheet and crosslinking the composition, thereby obtaining a pressure-sensitive adhesive sheet. After the pressure-sensitive adhesive sheet is attached to a workpiece such as a metal plate, a plastic plate, or a semiconductor wafer, the pressure-sensitive adhesive layer is cured by irradiation with active energy rays, thereby reducing the adhesive strength of the pressure-sensitive adhesive layer, and the sheet can be easily peeled off from the workpiece.

[0022] The pressure-sensitive adhesive composition of the present invention contains an ethylenically unsaturated group-containing acrylic resin (A), which has an ethylenically unsaturated group-containing structural moiety (α) having a number average molecular weight of 1,000 to 300,000 on a side chain of the acrylic resin. The ethylenically unsaturated group-containing acrylic resin (A), which is a constituent of the pressure-sensitive adhesive composition of the present invention, will be described below.

[0023] [Ethylenically unsaturated group-containing acrylic resin (A)] The ethylenically unsaturated group-containing acrylic resin (A) used in the present invention is not particularly limited as long as it has an ethylenically unsaturated group-containing structural moiety (α) having a number average molecular weight of 1,000 to 300,000 on the side chain of the acrylic resin.

[0024] Examples of the ethylenically unsaturated group-containing structural moiety (α) include the following structural moieties (1) to (3), of which the structural moiety (1) is preferred from the standpoint of ease of reaction. (1) A structural moiety derived from a hydroxyl group-containing macromonomer (α1), which is an ethylenically unsaturated group-containing structural moiety formed by a reaction between a hydroxyl group derived from the hydroxyl group-containing macromonomer (α1) and an isocyanate group of an isocyanate group-containing ethylenically unsaturated compound (α2). (2) A structural moiety derived from an acid-containing macromonomer, which is an ethylenically unsaturated group-containing structural moiety obtained by reacting a carboxy group derived from the acid-containing macromonomer with a vinyl ether group of a vinyl ether group-containing ethylenically unsaturated compound. (3) A structural moiety derived from an acid-containing macromonomer, which is an ethylenically unsaturated group-containing structural moiety obtained by reacting a carboxy group derived from the acid-containing macromonomer with a glycidyl ether group of a glycidyl ether group-containing ethylenically unsaturated compound.

[0025] The method for preparing the structural moiety (1) above is not particularly limited. For example, a graft copolymer of an acrylic resin is formed using a hydroxyl group-containing macromonomer (α1) having a predetermined number average molecular weight as at least a polymerization component, and then the hydroxyl group derived from the hydroxyl group-containing macromonomer (α1) is reacted with the isocyanate group of an isocyanate group-containing ethylenically unsaturated compound (α2) to introduce the ethylenically unsaturated group-containing structural moiety (α), thereby obtaining an ethylenically unsaturated group-containing acrylic resin (A). The polymerization components for forming the graft copolymer may contain other monomers in addition to the hydroxyl-containing macromonomer (α1). Examples of the other monomers include (meth)acrylic acid alkyl esters (α3), hydroxyl-containing monomers (α4) (excluding the hydroxyl-containing macromonomer (α1)), and other copolymerizable monomers (α5). Among these, it is preferable to contain the hydroxyl-containing monomer (α4). The ethylenically unsaturated group-containing acrylic resin (A) having the structural moiety (α) of (1) above will be described in more detail below. First, the hydroxyl group-containing macromonomer (α1) will be described.

[0026] [Hydroxyl group-containing macromonomer (α1)] The hydroxyl group-containing macromonomer (α1) is a high molecular weight monomer having a hydroxyl group in the side chain and a polymerizable functional group, and it is particularly preferred that the macromonomer has a polymerizable unsaturated group at the end of the polymer chain.

[0027] The polymer chain (main chain) portion constituting the hydroxyl group-containing macromonomer (α1) is not particularly limited as long as it is a hydroxyl group-containing monomer having a hydroxyl group in the side chain, but a polymer chain connected by a carbon-carbon bond is preferred, and a macromonomer containing a hydroxyl group-containing (meth)acrylate monomer as a constituent unit is preferred in terms of compatibility with the other copolymerization components (α3) to (α5) and polymerizability.

[0028] Examples of the hydroxyl group-containing (meth)acrylate monomers include (meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate; 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. Among these, primary hydroxyl group-containing monomers are preferred, and 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are more preferred, in view of their excellent reactivity with the crosslinking agent (B) described below.

[0029] The content of the structural moiety derived from a hydroxyl group-containing monomer such as the hydroxyl group-containing (meth)acrylate monomer in the hydroxyl group-containing macromonomer (α1) is preferably 1 to 100 wt %, more preferably 10 to 90 wt %, and particularly preferably 15 to 70 wt %. This range is preferable because it results in excellent curability with active energy rays such as ultraviolet rays and good elongation at break.

[0030] The number average molecular weight (Mn) of the hydroxyl group-containing macromonomer (α1) is preferably 1,000 to 300,000, more preferably 2,000 to 100,000, and particularly preferably 4,000 to 20,000. If Mn is equal to or greater than the lower limit, improvement in breaking elongation is easily achieved, which is preferable. On the other hand, if Mn is equal to or less than the upper limit, copolymerization with the monomer easily proceeds, facilitating stable production, which is preferable.

[0031] The glass transition temperature (Tg) of the hydroxyl group-containing macromonomer (α1) is preferably from -100 to 150°C, more preferably from -70 to 130°C, and particularly preferably from -50 to 120°C, from the viewpoint of durability.

[0032] Examples of raw material monomers other than the hydroxyl group-containing monomer for obtaining the hydroxyl group-containing macromonomer (α1) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-lauryl (meth)acrylate, and n-stearyl (meth)acrylate. Acrylic (meth)acrylate; (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl maleate, 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxypropyl copolymer Carboxy group-containing vinyl monomers such as cinnamic acid, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, and monomethyl itaconate; acid anhydride group-containing vinyl monomers such as maleic anhydride and itaconic anhydride; epoxy group-containing vinyl monomers such as glycidyl (meth)acrylate, glycidyl α-ethyl acrylate, and 3,4-epoxybutyl (meth)acrylate; amino group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate. ) Acrylate vinyl monomers; vinyl monomers containing an amide group, such as (meth)acrylamide, Nt-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetone acrylamide, maleic acid amide, and maleimide; vinyl monomers such as styrene, α-methylstyrene, vinyl toluene, (meth)acrylonitrile, vinyl chloride, vinyl acetate, and vinyl propionate;Examples of the divinylbenzene include divinylbenzene, ethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and allyl (meth)acrylate. As the raw material monomer other than the hydroxyl group-containing monomer, one selected from the raw material monomers mentioned above can be used alone, or two or more selected from the raw material monomers mentioned above can be used in combination.

[0033] As the raw material monomer other than the hydroxyl group-containing monomer, alkyl(meth)acrylate is preferred, and particularly (meth)alkyl acrylate in which the alkyl has 1 to 8 carbon atoms is preferred, and further, methyl(meth)acrylate and butyl(meth)acrylate are preferred in terms of compatibility and copolymerizability with the other copolymerization components (α3) to (α5).

[0034] Furthermore, as the raw material monomer, one monomer selected from the group consisting of a carboxy group-containing vinyl monomer, an acid anhydride group-containing vinyl monomer, an amino group-containing (meth)acrylate vinyl monomer, and an amide group-containing vinyl monomer can be used alone or in combination of two or more types.

[0035] The hydroxyl group-containing macromonomer (α1) may be one produced by a known method, or may be a commercially available product. Examples of known production methods include a production method using a cobalt chain transfer agent, a method using an α-substituted unsaturated compound such as α-methylstyrene dimer as a chain transfer agent, a method of chemically bonding a polymerizable group, and a method using thermal decomposition.

[0036] Among these, the method for producing the hydroxyl group-containing macromonomer (α1) is preferably a method using a cobalt chain transfer agent, since it requires fewer production steps and uses a catalyst with a high chain transfer constant.

[0037] Methods for producing the hydroxyl group-containing macromonomer (α1) using a cobalt chain transfer agent include, for example, bulk polymerization, solution polymerization, and aqueous dispersion polymerization. Examples of aqueous dispersion polymerization include suspension polymerization and emulsion polymerization. Among these polymerization methods, aqueous dispersion polymerization is preferred because of its simple recovery process.

[0038] The content of the hydroxyl group-containing macromonomer (α1) is preferably 0.1 to 50% by weight, more preferably 1 to 30% by weight, and particularly preferably 5 to 25% by weight, based on the polymerization components constituting the ethylenically unsaturated group-containing acrylic resin (A). Within this content range, the properties of the hydroxyl group-containing macromonomer (α1) can be expressed, and copolymerization with the monomers can proceed easily, facilitating stable production. This is preferable.

[0039] [(Meth)acrylic acid alkyl ester (α3)] The (meth)acrylic acid alkyl ester (α3) refers to a monomer having an alkyl group and a polymerizable functional group. Examples of such (meth)acrylic acid alkyl ester (α3) include those having an alkyl group with typically 1 to 20 carbon atoms (preferably 1 to 18, more preferably 1 to 12, and particularly preferably 1 to 8), preferably aliphatic (meth)acrylic acid alkyl esters. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, and stearyl (meth)acrylate. Monomers selected from these can be used alone or in combination of two or more.

[0040] Among these (meth)acrylic acid alkyl esters (α3), methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred, and n-butyl (meth)acrylate is particularly preferred, in terms of excellent adhesive properties and excellent stability during polymerization.

[0041] The content of the (meth)acrylic acid alkyl ester (α3) is preferably 10% by weight or more, more preferably 30% by weight or more, particularly preferably 50 to 95% by weight, and even more preferably 60 to 90% by weight, based on the polymerization components constituting the ethylenically unsaturated group-containing acrylic resin (A). If the content is too low, the adhesive properties and durability tend to decrease.

[0042] [Hydroxyl group-containing monomer (α4)] The hydroxyl group-containing monomer (α4) refers to a monomer having a hydroxyl group and a polymerizable functional group, and is preferably a (meth)acrylate-based monomer. Examples of the (meth)acrylate hydroxyl group-containing monomer (α4) include acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethyl phthalate, N-methylol (meth)acrylamide, and hydroxyethyl acrylamide; secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro 2-hydroxypropyl (meth)acrylate; and hydroxyl group-containing monomers such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate.

[0043] Among the above hydroxyl group-containing monomers (α4), primary hydroxyl group-containing monomers are preferred because of their excellent reactivity with crosslinking agents, 2-hydroxyethyl (meth)acrylate is preferred because of its stability during polymerization, and 4-hydroxybutyl (meth)acrylate is preferred because of its rapid reactivity with crosslinking agents and short aging time. Furthermore, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred because they contain fewer impurities such as di(meth)acrylates and are easy to produce.

[0044] It is also preferable to use the hydroxyl group-containing monomer (α4) having a content of di(meth)acrylate as an impurity of 0.5% by weight or less, more preferably 0.2% by weight or less, and particularly preferably 0.15% by weight or less. Specifically, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate having such impurity amounts are particularly preferred.

[0045] From the viewpoints of availability and ease of copolymerization, the number average molecular weight of the hydroxyl group-containing monomer (α4) is preferably less than 1,000, and more preferably not more than 200. The lower limit of the number average molecular weight is usually 50.

[0046] The hydroxyl group-containing monomer (α4) is preferably contained in an amount of 30% by weight or less, more preferably 0.01 to 30% by weight, particularly preferably 0.1 to 20% by weight, even more preferably 1 to 15% by weight, and even more preferably 3 to 10% by weight, based on the polymerization components constituting the ethylenically unsaturated group-containing acrylic resin (A).

[0047] [Other copolymerizable monomers (α5)] The other copolymerizable monomer (α5) is a copolymerizable ethylenically unsaturated monomer, and is preferably a (meth)acrylate-based monomer. Examples of the other copolymerizable monomer (α5) of the (meth)acrylate-based monomer include aromatic ring-containing monomers such as benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, and orthophenylphenoxyethyl (meth)acrylate; alicyclic ring-containing monomers such as cyclohexyl (meth)acrylate, cyclohexyloxyalkyl (meth)acrylate, t-butylcyclohexyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and 3-methoxybutyl (meth)acrylate; Examples of the monomer include ether chain-containing monomers such as acrylate, 2-butoxyethyl (meth)acrylate, 2-butoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, octoxypolyethylene glycol-polypropylene glycol-mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, and stearoxypolyethylene glycol mono(meth)acrylate.

[0048] Further, copolymerizable monomers having a polar group other than a hydroxyl group, such as carboxyl group-containing monomers and nitrogen atom-containing monomers, can also be used. Examples of the carboxy group-containing monomer include (meth)acrylic acid and dimer acids of acrylic acid such as β-carboxyethyl acrylate, and among these, (meth)acrylic acid is preferred in terms of resistance to moist heat and stability during polymerization.

[0049] Examples of the nitrogen atom-containing monomer include amino group-containing monomers, amide group-containing monomers, and other nitrogen atom-containing monomers.

[0050] Examples of the amino group-containing monomer include primary amino group-containing monomers such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; secondary amino group-containing monomers such as t-butylaminoethyl (meth)acrylate; and tertiary amino group-containing monomers such as ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. Among the above amino group-containing monomers, tertiary amino group-containing monomers are preferred in terms of their high crosslinking promoting effect and high storage stability of the resin.

[0051] Examples of the amide group-containing monomer include (meth)acrylamide; alkoxyalkyl (meth)acrylamide-based monomers such as methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylamide, isopropoxymethyl (meth)acrylamide, n-butoxymethyl (meth)acrylamide, and isobutoxymethyl (meth)acrylamide; dialkyl (meth)acrylamide-based monomers such as dimethyl (meth)acrylamide and diethyl (meth)acrylamide; hydroxyl group-containing amide monomers such as N-(hydroxymethyl)acrylamide; and heterocyclic amide monomers such as (meth)acryloylmorpholine. Among the above amide group-containing monomers, (meth)acryloylmorpholine, alkoxyalkyl(meth)acrylamide-based monomers, and dialkyl(meth)acrylamide-based monomers are preferred in terms of the stability of the resin solution.

[0052] One selected from the above other copolymerizable monomers (α5) can be used alone, or two or more can be used in combination. The content of the other copolymerizable monomer (α5) is preferably 25% by weight or less based on the polymerizable components in order not to impair the effects of the present invention.

[0053] When forming an acrylic resin graft copolymer using at least a hydroxyl-containing macromonomer (α1) as a polymerization component, polymerization is carried out by, for example, mixing or dropping the polymerization components and a polymerization initiator into an organic solvent using polymerization components containing at least the hydroxyl-containing macromonomer (α1). The polymerization components may also contain (meth)acrylic acid alkyl ester (α3), hydroxyl-containing monomer (α4), and other copolymerizable monomers (α5). Among these monomers, (meth)acrylic acid alkyl ester (α3) is preferred in terms of ease of polymerization and adjustment of adhesive properties, and hydroxyl-containing monomer (α4) is preferred in terms of compatibility with the hydroxyl-containing macromonomer (α1).

[0054] The polymerization reaction can be carried out by a known polymerization method such as solution radical polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. Among these, solution radical polymerization and bulk polymerization are preferred, and solution radical polymerization is more preferred.

[0055] In the solution radical polymerization method, for example, the polymerization components and a polymerization initiator are mixed or dropped into an organic solvent, and the mixture is subjected to reflux or generally at 50 to 98° C. for about 0.1 to 20 hours.

[0056] Examples of the organic solvent used in the 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.

[0057] Among these organic solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are preferably used, and more preferably ethyl acetate, acetone, and methyl ethyl ketone, because of their ease of polymerization reaction, chain transfer effect, ease of drying when applying the adhesive, and high safety. One selected from these organic solvents can be used alone, or two or more selected from these organic solvents can be used in combination. The amount of these organic solvents used is usually 10 to 900 parts by weight per 100 parts by weight of the polymerization components.

[0058] Examples of polymerization initiators used in such solution radical polymerization methods include azo-based polymerization initiators such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 4,4'-azobis(4-cyanovaleric acid), and 2,2'-azobis(methylpropionic acid), which are common radical polymerization initiators; and organic peroxides such as benzoyl peroxide, lauryl peroxide, di-t-butyl peroxide, and cumene hydroperoxide. These polymerization initiators can be selected individually or in combination with one another to suit the monomers used. The amount of these polymerization initiators used is usually 0.01 to 5% by weight based on the polymerization components.

[0059] The weight-average molecular weight of the graft copolymer obtained by the above polymerization method is usually 100,000 to 2,000,000, preferably 150,000 to 1,500,000, more preferably 200,000 to 1,200,000, and particularly preferably 300,000 to 1,000,000. If the weight-average molecular weight is too small, the polymer tends to be more susceptible to contamination of workpieces, whereas if it is too large, the polymer tends to be less coatable and is disadvantageous in terms of cost.

[0060] The dispersity (weight average molecular weight / number average molecular weight) of the graft copolymer is preferably 20 or less, more preferably 10 or less, particularly preferably 7 or less, and even more preferably 5 or less. If the dispersity is too high, contamination of the workpiece tends to increase. The lower limit of the dispersity is usually 1.1 due to production limitations.

[0061] The viscosity of the graft copolymer at 25°C is preferably 5 to 50,000 mPa·s, and more preferably 10 to 10,000 mPa·s. If the viscosity is outside this range, the coating properties tend to decrease. The viscosity is measured using an E-type viscometer.

[0062] The glass transition temperature (Tg) of the graft copolymer is usually 40° C. or lower, preferably −60 to 20° C., more preferably −50 to −5° C., and particularly preferably −40 to −10° C. If the glass transition temperature is too high, the adhesiveness tends to decrease, and if it is too low, the contamination of the workpiece tends to increase.

[0063] [Isocyanate group-containing ethylenically unsaturated compound (α2)] The graft copolymer of the acrylic resin obtained through the above polymerization step is reacted with an isocyanate group-containing ethylenically unsaturated compound (α2) to carry out urethanization. The isocyanate group-containing ethylenically unsaturated compound (α2) refers to a monomer having an isocyanate group and a polymerizable functional group. Examples of the isocyanate group-containing ethylenically unsaturated compound (α2) 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-isocyanate. -isocyanate, 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. One compound selected from these compounds can be used alone, or two or more can be used in combination. Among these compounds, (meth)acrylate monomers are particularly preferred in terms of ease of synthesis and availability of raw materials, and 2-(meth)acryloyloxyethyl isocyanate, 2-(meth)acryloyloxyethyl isocyanate, 2-(isocyanatoethyloxy)ethyl (meth)acrylate, 2-(isocyanatoethyloxy)ethyl (meth)acrylate, and 1,1-bis((meth)acryloyloxymethyl)ethyl isocyanate are more preferred.

[0064] When the graft copolymer is reacted with the isocyanate group-containing ethylenically unsaturated compound (α2), the hydroxyl group derived from the hydroxyl group-containing macromonomer (α1) contained in the graft copolymer reacts with the isocyanate group of the ethylenically unsaturated compound (α2), forming an ethylenically unsaturated group-containing structural moiety containing an ethylenically unsaturated bond and a urethane bond within the molecule.

[0065] The ratio of the two compounds used in the reaction is appropriately determined taking into consideration the ratio of hydroxyl groups to isocyanate groups, and varies depending on the types of the two compounds.

[0066] The reaction of the two compounds may be carried out in the presence of a reaction catalyst, and the reaction rate can be adjusted by the amount of the reaction catalyst added. As the reaction catalyst, a known reaction catalyst can be used. Specific examples of the reaction catalyst include 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 bismuth tris(2-ethylhexanoate) and 2-ethylhexanoic acid. One selected from these reaction catalysts can be used alone, or two or more can be used in combination.

[0067] The reaction temperature when reacting the two compounds is preferably −10 to 100° C., more preferably 0 to 80° C. The reaction time is preferably 30 minutes to 50 hours, more preferably 1 hour to 20 hours.

[0068] When the two compounds are reacted, a polymerization inhibitor may be added to the reaction system, if necessary. As the polymerization inhibitor, a commonly used one can be used, for example, a phenol-based compound, a hydroquinone-based compound, etc. Specific examples of the polymerization inhibitor include hydroquinone, methoxyhydroquinone, catechol, p-tert-butylcatechol, cresol, 2,6-di-tert-butyl-4-methylphenol (BHT), etc. In addition, when reacting the two compounds, known additives may be added depending on the purpose.

[0069] The ethylenically unsaturated group-containing acrylic resin (A) in the present invention has, in its side chain, an ethylenically unsaturated group-containing structural moiety (α) having a number average molecular weight of 1,000 to 300,000. For example, in the case of the structural moiety (1) above, specifically, an ethylenically unsaturated group-containing structural moiety formed by the reaction of a hydroxyl group derived from a hydroxyl group-containing macromonomer (α1) with an isocyanate group of an isocyanate group-containing ethylenically unsaturated compound (α2), the number average molecular weight of the structural moiety (1) above is the sum of the number average molecular weights of the hydroxyl group-containing macromonomer (α1) and the isocyanate group-containing ethylenically unsaturated compound (α2). The number average molecular weight of the ethylenically unsaturated group-containing structural moiety (α) is preferably 2,000 to 250,000, more preferably 3,000 to 100,000, particularly preferably 4,000 to 50,000, and even more preferably 5,000 to 30,000. If the number average molecular weight of the ethylenically unsaturated group-containing structural moiety (α) is too low, it tends to be difficult to improve the elongation at break, while if the number average molecular weight is too high, it tends to be difficult to produce stably due to a decrease in copolymerizability with other monomers. In addition, the number average molecular weight of the ethylenically unsaturated group-containing structural moiety (α), if it is the structural moiety (1) above, can be appropriately set by adjusting the number average molecular weight of the hydroxyl group-containing macromonomer (α1) or the isocyanate group-containing ethylenically unsaturated compound (α2).

[0070] The addition reaction rate between the hydroxyl groups derived from the hydroxyl group-containing macromonomer (α1) contained in the graft copolymer and the isocyanate groups of the isocyanate group-containing ethylenically unsaturated compound (α2), i.e., the urethanization rate, is preferably 5 to 99 mol%, more preferably 10 to 90 mol%. If the urethanization rate is too low, the adhesive strength after irradiation with active energy rays such as ultraviolet rays tends to be difficult to sufficiently reduce, while if the urethanization rate is too high, the urethane reaction tends to be incomplete, leaving unreacted isocyanate group-containing ethylenically unsaturated compound (α2).

[0071] The ethylenically unsaturated group-containing acrylic resin (A) typically has an ethylenically unsaturated group content of 5 to 250 mmol / 100 g, preferably 10 to 200 mmol / 100 g, and more preferably 15 to 100 mmol / 100 g. If the ethylenically unsaturated group content is too low, the releasability upon irradiation with active energy rays tends to decrease, while if the ethylenically unsaturated group content is too high, the stain resistance of the workpiece after release tends to decrease.

[0072] The content of the ethylenically unsaturated group in the ethylenically unsaturated group-containing acrylic resin (A) can be calculated from the following formula. Ethylenically unsaturated group content (mmol / 100g) = Amount of hydroxyl groups contained in 100 g of ethylenically unsaturated group-containing acrylic resin (A) (mmol%) × Urethane conversion rate (%) / 100

[0073] The ethylenically unsaturated group-containing acrylic resin (A) used in the present invention preferably contains a hydroxyl group that reacts with the crosslinking agent (B) described below, thereby forming a crosslinked structure, thereby improving the adhesive strength before irradiation with active energy rays. The hydroxyl group content in the ethylenically unsaturated group-containing acrylic resin (A) is usually 0.01 to 20% by weight, preferably 0.05 to 10% by weight, and more preferably 0.1 to 5% by weight. If the hydroxyl group content is too low, the cohesive strength of the adhesive will decrease, which will tend to cause adhesive residue, while if the hydroxyl group content is too high, the flexibility and adhesive strength of the adhesive will decrease, which will tend to cause lifting from the workpiece.

[0074] [Crosslinking agent (B)] The pressure-sensitive adhesive composition of the present invention preferably further contains a crosslinking agent (B) in order to improve the adhesive strength before irradiation with active energy rays. The crosslinking agent (B) reacts with the functional groups in the ethylenically unsaturated group-containing acrylic resin (A) to form a crosslinked structure, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, amine-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, it is preferable to use an isocyanate-based crosslinking agent in terms of reactivity with the ethylenically unsaturated group-containing acrylic resin (A).

[0075] The isocyanate crosslinking agent contains at least two isocyanate groups, and examples thereof include tolylene diisocyanate crosslinking agents such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate; xylylene diisocyanate crosslinking agents such as 1,3-xylylene diisocyanate; diphenylmethane crosslinking agents such as diphenylmethane-4,4-diisocyanate; and aromatic isocyanate crosslinking agents such as naphthalene diisocyanate crosslinking agents such as 1,5-naphthalene diisocyanate; isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, and isopropylidenedicyclohexyl-4,4 alicyclic isocyanate crosslinking agents such as 1,3-diisocyanate, 1,3-diisocyanatomethylcyclohexane, and norbornane diisocyanate; aliphatic isocyanate crosslinking agents such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; and adducts, biurets, and isocyanurates of the above-mentioned isocyanate compounds.

[0076] Among these isocyanate-based crosslinking agents, tolylene diisocyanate-based crosslinking agents are preferred in terms of pot life and durability, xylylene diisocyanate-based crosslinking agents or isocyanurate skeleton-containing isocyanate-based crosslinking agents are preferred in terms of shortening the aging time, and aromatic-free isocyanate-based crosslinking agents are preferred in terms of yellowing resistance. Specifically, among these, adducts and nurates of any of the isocyanates selected from tolylene diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate with trimethylolpropane are preferred in terms of an excellent balance of durability, pot life, and crosslinking speed.

[0077] Examples of the epoxy crosslinking agent 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, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, and diglycerol polyglycidyl ether.

[0078] Examples of the aziridine crosslinking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide).

[0079] Examples of the melamine-based crosslinking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins.

[0080] Examples of the aldehyde crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleic dialdehyde, glutaric dialdehyde, formaldehyde, acetaldehyde, and benzaldehyde.

[0081] Examples of the amine-based crosslinking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resins, and polyamides.

[0082] Examples of the metal chelate crosslinking agent include acetylacetone and acetoacetyl ester coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

[0083] One selected from these crosslinking agents can be used alone, or two or more selected from these crosslinking agents can be used in combination.

[0084] The content of the crosslinking agent (B) is usually preferably 0.005 to 30 parts by weight, more preferably 0.01 to 10 parts by weight, particularly preferably 0.03 to 5 parts by weight, and even more preferably 0.05 to 3 parts by weight, per 100 parts by weight of the ethylenically unsaturated group-containing acrylic resin (A). If the amount of crosslinking agent (B) is too small, the cohesive strength of the adhesive will decrease, which will tend to cause adhesive residue, while if the amount of crosslinking agent (B) is too large, the flexibility and adhesive strength of the adhesive will decrease, which will tend to cause lifting from the workpiece.

[0085] [Photopolymerization initiator (C)] The pressure-sensitive adhesive composition of the present invention preferably further contains a photopolymerization initiator (C) from the viewpoints of improving the curability upon irradiation with active energy rays and improving the releasability after irradiation with active energy rays. As the photopolymerization initiator (C), a compound that generates radicals by the action of active energy rays can be used, and examples thereof include the following photopolymerization initiators. alkylphenones such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer; benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenones such as benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, and (4-benzoylbenzyl)trimethylammonium chloride; thioxanthones such as 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one mesochloride; Acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Among these, alkylphenones, particularly 1-hydroxycyclohexylphenyl ketone, and acylphosphonoxides, particularly 2,4,6-trimethylbenzoyl-diphenylphosphine oxide are preferred. One selected from these photopolymerization initiators can be used alone, or two or more selected from these photopolymerization initiators can be used in combination.

[0086] The content of the photopolymerization initiator (C) is usually preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, and particularly preferably 0.5 to 10 parts by weight, per 100 parts by weight of the ethylenically unsaturated group-containing acrylic resin (A). If the content of the photopolymerization initiator (C) is too low, the releasability after irradiation with active energy rays tends to decrease, whereas if it is too high, contamination of the workpiece tends to increase.

[0087] Furthermore, as an auxiliary agent for these photopolymerization initiators (C), it is also possible to use in combination, for example, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, etc. One selected from these auxiliary agents can be used alone, or two or more can be used in combination.

[0088] [Other ingredients] The pressure-sensitive adhesive composition of the present invention may contain other components within the range that does not impair the effects of the present invention. For example, an ethylenically unsaturated compound may be further contained for the purpose of improving releasability after irradiation with active energy rays. The pressure-sensitive adhesive composition of the present invention may also contain additives such as antistatic agents, antioxidants, plasticizers, fillers, pigments, diluents, antioxidants, UV absorbers, UV stabilizers, and tackifying resins. One selected from these additives may be used alone, or two or more may be used in combination. Antioxidants are particularly effective in maintaining the stability of the pressure-sensitive adhesive layer. When an antioxidant is contained, its content is not particularly limited, but is preferably 0.01 to 5 wt % in the pressure-sensitive adhesive composition. In addition to the additives, small amounts of impurities contained in the raw materials for producing the components of the pressure-sensitive adhesive composition may also be contained.

[0089] Thus, the pressure-sensitive adhesive composition of the present invention can be obtained by containing at least the ethylenically unsaturated group-containing acrylic resin (A), preferably the crosslinking agent (B) and / or the photopolymerization initiator (C), and optionally other components.

[0090] The pressure-sensitive adhesive composition of the present invention does not require the crosslinking agent (B) as an essential component, but the inclusion of the crosslinking agent (B) facilitates crosslinking, allowing the pressure-sensitive adhesive composition to more easily exhibit its performance as a pressure-sensitive adhesive. Furthermore, the pressure-sensitive adhesive composition of the present invention does not require the photopolymerization initiator (C) as an essential component, but the inclusion of the photopolymerization initiator (C) facilitates polymerization of the ethylenically unsaturated groups in the ethylenically unsaturated-group-containing acrylic resin (A) upon irradiation with active energy rays, making the pressure-sensitive adhesive more likely to cure, and thus reducing the adhesive strength, allowing the pressure-sensitive adhesive composition to more easily exhibit its releasability.

[0091] The pressure-sensitive adhesive composition of the present invention is preferably used as a pressure-sensitive adhesive sheet for temporary surface protection of substrates such as metal plates and plastic plates, and members such as processed glass products, or as a pressure-sensitive adhesive layer in a pressure-sensitive adhesive sheet for fixing semiconductors used when subjecting semiconductor devices such as semiconductor wafers and electronic substrates to semiconductor manufacturing processes such as dicing processes. The active energy ray-curable peelable pressure-sensitive adhesive sheet (hereinafter sometimes simply referred to as "pressure-sensitive adhesive sheet"), which is the second aspect of the present invention, will be described below.

[0092] <Active energy ray curable peel-off adhesive sheet> The pressure-sensitive adhesive sheet of the present invention typically comprises a substrate sheet, a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of the present invention, and a release film. To produce such a pressure-sensitive adhesive sheet, the pressure-sensitive adhesive composition of the present invention is first applied directly to a release film or a substrate sheet, either as is or after dissolving in an appropriate organic solvent to adjust the concentration. The composition is then dried, for example, by heat treatment at 80 to 105°C for 0.5 to 10 minutes, and then attached to a substrate sheet or a release film to obtain a pressure-sensitive adhesive sheet. To balance the adhesive properties, further aging may be performed after drying.

[0093] Examples of the substrate sheet include synthetic resin sheets; metal foils made of aluminum, copper, iron, etc.; paper such as fine paper and glassine paper; woven fabrics and nonwoven fabrics made of glass fiber, natural fiber, synthetic fiber, etc. Examples of materials for the synthetic resin sheet include polyester resins such as polyethylene naphthate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymer; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyethylene fluoride resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyethylene fluoride; 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; and polyimide. These substrate sheets can be used as a single layer or as a multi-layered body in which two or more types are laminated. Among these, synthetic resin sheets are preferred from the viewpoint of weight reduction and the like.

[0094] Furthermore, as the release film, for example, various synthetic resin sheets, paper, woven fabrics, nonwoven fabrics, etc. exemplified above as the base sheet can be used which have been subjected to a release treatment.

[0095] The method for applying the pressure-sensitive adhesive composition is not particularly limited, and any common application method can be used, such as roll coating, die coating, gravure coating, comma coating, and screen printing.

[0096] The thickness of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is usually preferably 10 to 200 μm, and more preferably 15 to 100 μm.

[0097] The aging conditions are generally a temperature of room temperature (23°C) to 70°C, and a time of 1 to 30 days. Specifically, the aging can be carried out 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.

[0098] The gel fraction of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is preferably 10 to 99 wt % from the viewpoint of adhesiveness, more preferably 20 to 97 wt %, and particularly preferably 50 to 90 wt %. If the gel fraction is too low, the adhesive strength to the workpiece tends to decrease, while if the gel fraction is too high, the adhesive strength to the workpiece tends to decrease.

[0099] The gel fraction is a measure of the degree of crosslinking (degree of hardening) and is calculated, for example, by the following method: The pressure-sensitive adhesive sheet is attached to a SUS mesh sheet (200 mesh), the pressure-sensitive adhesive sheet is wrapped, and then immersed in a sealed container containing ethyl acetate for 24 hours, and the gel fraction is calculated from the change in weight of the pressure-sensitive adhesive layer before and after immersion in ethyl acetate using the following formula. Gel fraction (%) = (weight (g) of adhesive layer after immersion in ethyl acetate) / Weight of adhesive layer before immersion in ethyl acetate (g) × 100

[0100] The gel fraction of the pressure-sensitive adhesive layer can be adjusted to fall within the above range by adjusting the type and amount of the crosslinking agent, for example.

[0101] When the pressure-sensitive adhesive sheet of the present invention is irradiated with active energy rays, the pressure-sensitive adhesive layer is cured, the adhesive strength is reduced, and the sheet becomes peelable. As the active energy rays, generally usable are light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays, electromagnetic waves such as X-rays and gamma rays, as well as electron beams, proton beams, neutron beams, etc. Among these, ultraviolet rays are preferred in view of curing speed, ease of availability of irradiation equipment, cost, etc.

[0102] The cumulative dose of ultraviolet light is usually 50 to 3,000 mJ / cm 2 , preferably 100 to 1,000 mJ / cm 2 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 is usually several seconds, and in some cases may be a fraction of a second.

[0103] The adhesive strength of the adhesive layer of the pressure-sensitive adhesive sheet varies depending on the type of substrate sheet, the type of workpiece, etc., but is preferably 0.1 to 30 N / 25 mm, more preferably 0.5 to 20 N / 25 mm, before irradiation with active energy rays.

[0104] The term "the pressure-sensitive adhesive sheet of the present invention is releasable" means that the pressure-sensitive adhesive layer has an adhesive strength sufficient to be peeled off from the workpiece together with the substrate sheet upon irradiation with active energy rays, and that even when the pressure-sensitive adhesive sheet is attached to an uneven surface and the contact area between the pressure-sensitive adhesive sheet and the adherend differs between the uneven and other areas, the difference in adhesive strength between the uneven and other areas upon peeling is small. For example, this means that the coefficient of variation, as explained in the examples, is preferably less than 20, more preferably 14 or less.

[0105] The adhesive sheet of the present invention is useful as an adhesive sheet for temporary surface protection of a substrate, or as an adhesive sheet for fixing a semiconductor when a semiconductor device is subjected to a semiconductor manufacturing process. After completing these roles, if necessary, the adhesive layer can be hardened by irradiating it with active energy rays, reducing the adhesive strength, and the sheet can be easily peeled off from the workpiece.

[0106] Next, the active energy ray-curable peelable pressure-sensitive adhesive (hereinafter sometimes simply referred to as "pressure-sensitive adhesive"), which is the third aspect of the present invention, will be described.

[0107] <Active energy ray curable peel-off adhesive> The pressure-sensitive adhesive of the present invention contains an ethylenically unsaturated group-containing acrylic resin, a crosslinking agent (B) and a photopolymerization initiator (C). The ethylenically unsaturated group-containing acrylic resin is not particularly limited as long as it is an acrylic resin containing an ethylenically unsaturated group in its side chain, and may be not only the ethylenically unsaturated group-containing acrylic resin (A) contained in the pressure-sensitive adhesive composition according to the first aspect of the present invention, but also an ethylenically unsaturated group-containing acrylic resin having an ethylenically unsaturated group-containing structural moiety in its side chain and having a number average molecular weight outside the range of 1,000 to 300,000, and further the ethylenically unsaturated group-containing structural moiety may be not only any of the structural moieties (1) to (3) below but also another structural moiety. (1) A structural moiety derived from a hydroxyl group-containing macromonomer (α1), which is an ethylenically unsaturated group-containing structural moiety formed by a reaction between a hydroxyl group derived from the hydroxyl group-containing macromonomer (α1) and an isocyanate group of an isocyanate group-containing ethylenically unsaturated compound (α2). (2) A structural moiety derived from an acid-containing macromonomer, which is an ethylenically unsaturated group-containing structural moiety obtained by reacting a carboxy group derived from the acid-containing macromonomer with a vinyl ether group of a vinyl ether group-containing ethylenically unsaturated compound. (3) A structural moiety derived from an acid-containing macromonomer, which is an ethylenically unsaturated group-containing structural moiety obtained by reacting a carboxy group derived from the acid-containing macromonomer with a glycidyl ether group of a glycidyl ether group-containing ethylenically unsaturated compound. In the present invention, among the above, the ethylenically unsaturated group-containing acrylic resin (A) is preferred in terms of low reaction temperature and ease of production.

[0108] The crosslinking agent (B) and the photopolymerization initiator (C) may be the same as or similar to those explained in the pressure-sensitive adhesive composition according to the first aspect of the present invention. The contents of the crosslinking agent (B) and the photopolymerization initiator (C) in the pressure-sensitive adhesive of the present invention are the same as or similar to the contents explained for the pressure-sensitive adhesive composition that is the first aspect of the present invention.

[0109] The pressure-sensitive adhesive of the present invention satisfies the following requirement [I], and thereby can form a pressure-sensitive adhesive layer that has excellent releasability (slight adhesiveness) after irradiation with active energy rays and also has high elongation at break. [I] A pressure-sensitive adhesive sheet having a crosslinked pressure-sensitive adhesive layer with a thickness of 300 μm is exposed to a cumulative irradiation dose of 1000 mJ / cm using one 80 W high-pressure mercury lamp. 2 After being left to stand for 30 minutes in an atmosphere of 23°C and 50% RH, the breaking elongation measured with a tensile tester at a tensile speed of 300 mm / min is 90 to 300%. The breaking elongation is preferably from 100 to 280%, more preferably from 110 to 270%, and particularly preferably from 130 to 250%. If the breaking elongation is too high, the adhesive will not separate from the adherend indefinitely, and the adhesive strength will tend to be too high, whereas if it is too low, adhesive residue will tend to occur. The breaking elongation can be adjusted by the degree of crosslinking of the pressure-sensitive adhesive layer. The method for measuring the breaking elongation will be explained in detail in the examples below.

[0110] The pressure-sensitive adhesive of the present invention, like the pressure-sensitive adhesive composition according to the first aspect of the present invention, is suitably used for producing a pressure-sensitive adhesive layer in a pressure-sensitive adhesive sheet according to the second aspect of the present invention. However, the pressure-sensitive adhesive of the present invention is not limited to pressure-sensitive adhesive sheets, and can be used in a variety of other applications. [Example]

[0111] 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 as long as it does not depart from the gist of the present invention. In the following, "parts" are by weight. First, the following raw material monomers were prepared, and various ethylenically unsaturated group-containing acrylic resins were prepared as follows.

[0112] The following macromonomers were prepared as raw materials for preparing the acrylic resin.

[0113] (Macromonomer 1) A polymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), an acrylic macromonomer containing hydroxyl groups in the side chains (manufactured by Mitsubishi Chemical Corporation, MMA:HEMA (weight ratio) = 75.5:24.5, number average molecular weight 10,400, dispersity 1.73, calculated glass transition temperature 66.3°C)

[0114] (Macromonomer 2) A polymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), an acrylic macromonomer containing hydroxyl groups in the side chains (manufactured by Mitsubishi Chemical Corporation, MMA:HEMA (weight ratio) = 75.5:24.5, number average molecular weight 4200, dispersity 1.5, calculated glass transition temperature 66.3°C)

[0115] (Macromonomer 3) A polymer of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA), an acrylic macromonomer containing hydroxyl groups in the side chains (manufactured by Mitsubishi Chemical Corporation, MMA:HEMA (weight ratio) = 75.5:24.5, number average molecular weight 22600, dispersity 1.75, calculated glass transition temperature 66.3°C)

[0116] (Macromonomer 4) A polymer of methyl methacrylate (MMA), an acrylic macromonomer that does not contain hydroxyl groups in the side chain (manufactured by Mitsubishi Chemical Corporation, number average molecular weight 10300, dispersity 1.91, calculated glass transition temperature 105°C)

[0117] [Production of ethylenically unsaturated group-containing acrylic resin [I]] A four-neck round-bottom flask equipped with a reflux condenser, stirrer, nitrogen gas inlet, and thermometer was charged with 20 parts of the prepared macromonomer 1 (α1), 79 parts of n-butyl acrylate (BA), 1 part of 2-hydroxyethyl methacrylate (HEMA), 56 parts of ethyl acetate, 21 parts of acetone, and 0.075 parts of azobisisobutyronitrile (AIBN) as a polymerization initiator. The internal temperature was raised to the boiling point to initiate the reaction and heated for 2 hours. Next, 10 parts of a 0.6% ethyl acetate solution of 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN) was added, and the reaction was continued at reflux for 2.5 hours. Another 10 parts of a 0.6% ethyl acetate solution of ADVN was added, and the reaction was continued at reflux for 2.5 hours. The reaction was then stopped and the mixture was diluted with ethyl acetate to obtain an acrylic resin [I'] (graft copolymer; the same applies below) solution (calculated glass transition temperature: -36 °C). To the acrylic resin [I'] solution obtained above, 2-methacryloyloxyethyl isocyanate (hereinafter referred to as "MOI") (manufactured by Showa Denko K.K.) and dibutyltin dilaurate as a urethanization catalyst were added appropriately, and the reaction was carried out at 50°C for 18 hours to obtain an ethylenically unsaturated group-containing acrylic resin [I] solution (solid content 35.5%, viscosity 1700 mPa·s / 25°C, acrylic resin [I]: weight average molecular weight (Mw) 520,000, dispersity (Mw / Mn) 4.95). The urethanization rate by MOI was 50 mol%, and the ethylenically unsaturated group content was 21.8 mmol / 100 g.

[0118] [Production of ethylenically unsaturated group-containing acrylic resins [II] to [VII]] Acrylic resins [II'] to [VII'] were obtained in the same manner as in the production method for the acrylic resin [I'], except that the copolymerization component compositions were as shown in Table 1. Then, MOI was reacted in the same manner as in the production method for the acrylic resin [I], to obtain ethylenically unsaturated group-containing acrylic resins [II] to [VII]. The measurement results are shown in Table 1. The ethylenically unsaturated group-containing acrylic resins [I] to [V] are acrylic resins used in the examples, and the ethylenically unsaturated group-containing acrylic resins [VI] and [VII] are acrylic resins used in the comparative examples.

[0119] [Table 1]

[0120] [Crosslinking agent (B)] The following crosslinking agent (B-1) was prepared. Coronate (registered trademark) L-55E (adduct of tolylene diisocyanate and trimethylolpropane, manufactured by Tosoh Corporation)

[0121] [Photopolymerization initiator (C)] The following photopolymerization initiator (C-1) was prepared. Omnirad® 184 (1-hydroxycyclohexyl phenyl ketone, manufactured by IGM Resins)

[0122] <Examples 1 to 9 and Comparative Examples 1 to 4> To 100 parts of the ethylenically unsaturated group-containing acrylic resin ([I] to [VII]) prepared as described above, an isocyanate-based crosslinking agent ("Coronate (registered trademark) L-55E" manufactured by Tosoh Corporation) was added in the amount shown in Table 2 below, and 1 part of a photopolymerization initiator ("Omnirad (registered trademark) 184" manufactured by IGM Resins) was mixed. This was then adjusted with ethyl acetate to a solids concentration (resin content) of 30% by weight, thereby obtaining an active energy ray-curable peel-type pressure-sensitive adhesive composition solution. The resulting active energy ray-curable peel-type pressure-sensitive adhesive composition solution was used to prepare the following pressure-sensitive adhesive sheets, which were then evaluated as follows: The evaluation results are shown in Table 2 below.

[0123] <Adhesive sheet (S1) (for gel fraction measurement)> The pressure-sensitive adhesive composition solution obtained above was applied to a heavy release 38 μm polyester release sheet (manufactured by Mitsui Chemicals Tocello Inc.: Lumirror (registered trademark) SP03-38BU) so that the thickness after drying would be 25 μm, and after drying at 100°C for 5 minutes, this was laminated to a light release 38 μm polyester release sheet (manufactured by Mitsui Chemicals Tocello Inc.: Lumirror (registered trademark) SP01-38BU) and aged in an environment of 40°C for 4 days to obtain a pressure-sensitive adhesive sheet (S1) for gel fraction measurement.

[0124] <Adhesive sheet (S2) (for measuring adhesive strength)> The adhesive composition solution obtained above was applied to an untreated 38 μm polyester sheet (Lumirror (registered trademark) T60, manufactured by Mitsui Chemicals Tocello Inc.) so that the thickness after drying would be 25 μm, and after drying at 100°C for 5 minutes, this was laminated to a light-release 38 μm polyester release sheet (Lumirror (registered trademark) SP01-38BU, manufactured by Mitsui Chemicals Tocello Inc.) and aged for 4 days in an environment of 40°C to obtain an adhesive sheet (S2) for adhesive strength measurement.

[0125] [Gel fraction] The pressure-sensitive adhesive sheet (S1) was cut to 40 mm x 40 mm, and the light-release 38 μm polyester-based release sheet was peeled off. The pressure-sensitive adhesive layer was then attached to a 50 mm x 100 mm SUS mesh sheet (200 mesh). Next, the heavy-release 38 μm polyester-based release sheet was peeled off, and the SUS mesh sheet was folded back from the center in the longitudinal direction to encase the sample. The sample was then immersed in a sealed container containing 250 g of ethyl acetate for 24 hours. The gel fraction was calculated from the change in weight of the pressure-sensitive adhesive layer before and after immersion in ethyl acetate using the following formula. Gel fraction (wt%) = (weight (g) of the adhesive layer after immersion in ethyl acetate) / Weight of adhesive layer before immersion in ethyl acetate (g) × 100

[0126] [Adhesive strength before irradiation with active energy rays] A 25mm x 100mm test piece was prepared from the above pressure-sensitive adhesive sheet (S2), and the 38µm polyester release sheet with a light release property was peeled off. The test piece was then pressed onto a stainless steel plate (SUS304BA plate) using a 2kg rubber roller, which was rolled back and forth twice in an atmosphere of 23°C and 50% RH. After leaving the test piece in the same atmosphere for 30 minutes, the 180-degree peel strength (N / 25mm) was measured at a peel speed of 300mm / min.

[0127] [Adhesive strength after irradiation with active energy rays] A 25mm x 100mm test piece was prepared from the pressure-sensitive adhesive sheet (S2), the 38μm polyester release sheet was peeled off, and the piece was pressed onto a stainless steel plate (SUS304BA plate) by rolling a 2kg rubber roller back and forth twice in an atmosphere of 23°C and 50%RH, and left in the same atmosphere for 30 minutes. Using one 80W high-pressure mercury lamp, ultraviolet light was irradiated from the untreated 38μm polyester sheet side (cumulative exposure dose 250mJ / cm). 2 After standing for 30 minutes in an atmosphere of 23°C and 50% RH, the 180° peel strength (N / 25 mm) was measured at a peel rate of 300 mm / min.

[0128] [Breaking elongation of pressure-sensitive adhesive layer] A plurality of the pressure-sensitive adhesive sheets (S1) were laminated together until the thickness of the pressure-sensitive adhesive layer reached 300 μm, and then cut into 10 mm × 50 mm pieces. The pieces were then irradiated with an 80 W high-pressure mercury lamp at an accumulated irradiation dose of 1000 mJ / cm. 2 After leaving the sample for 30 minutes in an atmosphere of 23°C and 50% RH, the heavy-release 38 μm polyester release sheet was peeled off to prepare a test specimen. The test specimen was measured for breaking elongation at 23°C using a tensile tester (Shimadzu Corporation, product name "Autograph AG-X") in accordance with JIS K71 61:2014 using the following procedure. Both ends of the test piece in the longitudinal direction were gripped with grippers so that the distance between the grippers was 20 mm, and the test piece was pulled at a speed of 300 mm / min until it broke. The length of the test piece at the time of break (L mm) was measured and calculated using the following formula. The evaluation criteria are as follows. Breaking elongation (%) = [(length of test piece at break L) / 20] x 100 (Evaluation criteria) ◎ 150% or more ○ Between 90% and 150% × Less than 90%

[0129] [Coefficient of variation] First, an acrylic plate with a pattern of 1 mm diameter x 24 ± 2 μm deep holes spaced 2.5 mm apart was used as the adherend. Next, a 25 mm x 120 mm test piece was prepared from the pressure-sensitive adhesive sheet (S2), and the 38 μm polyester release sheet with a light release property was peeled off. The acrylic plate was then pressed and attached by rolling a 2 kg rubber roller back and forth twice in an atmosphere of 23°C and 50% RH, and left in the same atmosphere for 30 minutes. An 80 W high-pressure mercury lamp was used to irradiate ultraviolet light from the acrylic plate side (cumulative exposure dose 250 mJ / cm). 2 ) and left to stand for 30 minutes in an atmosphere of 23°C and 50% RH. Thereafter, the adhesive strength was measured by measuring the 180-degree peel strength (N / 25mm) at 700 points spaced at 0.05mm intervals over a 35mm distance from the peel start point to the 95mm position at a peel speed of 300mm / min. The coefficient of variation was calculated using the values ​​obtained from the 700 points using the formula below, and the results were evaluated as follows: Coefficient of variation = (standard deviation of 700 points) / average of 700 points (Evaluation criteria) ○ Less than 20 × 20 or more

[0130] [Table 2]

[0131] The pressure-sensitive adhesives of Examples 1 to 9, which contain an ethylenically unsaturated group-containing acrylic resin (A) having an ethylenically unsaturated group-containing structural moiety (α) in the side chain of the acrylic resin, showed a decrease in adhesive strength after irradiation with active energy rays compared to the adhesive strength before irradiation, and exhibited excellent releasability (slight adhesiveness). Furthermore, the pressure-sensitive adhesives after irradiation with active energy rays were flexible, had good elongation, and exhibited high elongation at break. Furthermore, the coefficient of variation was small, and the pressure-sensitive adhesives exhibited good releasability even from uneven adherends.

[0132] On the other hand, the adhesives of Comparative Examples 1 to 4, which have an ethylenically unsaturated group-containing structural moiety in the side chain of the acrylic resin but have a small molecular weight of the ethylenically unsaturated group-containing structural moiety, had good peelability (slight adhesiveness) after irradiation with active energy rays, but the adhesives after irradiation with active energy rays had low elongation at break. This raises concerns about adhesive residue remaining when peeled, and does not satisfy the object of the present invention. Furthermore, Comparative Example 1 is not satisfactory in terms of the coefficient of variation, and does not have good releasability. [Industrial Applicability]

[0133] The active energy ray-curable peel-type pressure-sensitive adhesive composition of the present invention can be suitably used as a pressure-sensitive adhesive sheet for temporary surface protection of substrates such as metal plates and plastic plates, or as a pressure-sensitive adhesive sheet for fixing semiconductors used when subjecting semiconductor devices such as semiconductor wafers to semiconductor manufacturing processes such as dicing processes.

Claims

1. The composition contains an ethylenically unsaturated group-containing acrylic resin (A) having an ethylenically unsaturated group-containing structural moiety (α) in a side chain and having a number average molecular weight of 1,000 to 300,000, an active energy ray-curable peel-type pressure-sensitive adhesive composition, characterized in that the ethylenically unsaturated group-containing structural moiety (α) is a structural moiety derived from a hydroxyl group-containing macromonomer (α1), and is an ethylenically unsaturated group-containing structural moiety formed by a reaction between a hydroxyl group derived from the hydroxyl group-containing macromonomer (α1) and an isocyanate group of an isocyanate group-containing ethylenically unsaturated compound (α2).

2. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the hydroxyl group-containing macromonomer (α1) has a number average molecular weight of 1,000 to 300,000.

3. 3. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the hydroxyl group-containing macromonomer (α1) has a structural moiety derived from a hydroxyl group-containing monomer, and the content of the structural moiety derived from the hydroxyl group-containing monomer in the hydroxyl group-containing macromonomer (α1) is 1 to 100% by weight.

4. The active energy ray-curable peel-type pressure-sensitive adhesive composition according to any one of claims 1 to 3, characterized in that the ethylenically unsaturated group-containing acrylic resin (A) has a structural moiety derived from a hydroxyl group-containing monomer.

5. The active energy ray-curable peel-type pressure-sensitive adhesive composition according to any one of claims 1 to 4, characterized in that the content of the ethylenically unsaturated group in the ethylenically unsaturated group-containing acrylic resin (A) is 5 to 250 mmol / 100 g.

6. The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of claims 1 to 5, further comprising a crosslinking agent (B).

7. The active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of claims 1 to 6, further comprising a photopolymerization initiator (C).

8. An active energy ray-curable peelable pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed by crosslinking the active energy ray-curable peelable pressure-sensitive adhesive composition according to any one of claims 1 to 7.

9. 9. The active energy ray-curable peelable pressure-sensitive adhesive sheet according to claim 8, wherein the pressure-sensitive adhesive layer is cured and becomes peelable by irradiation with active energy rays.

10. 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the ethylenically unsaturated group-containing structural moiety (α) is a structural moiety derived from an acid-containing macromonomer, and is either (1) an ethylenically unsaturated group-containing structural moiety formed by a reaction between a carboxy group derived from the acid-containing macromonomer and a vinyl ether group of a vinyl ether group-containing ethylenically unsaturated compound, or (2) an ethylenically unsaturated group-containing structural moiety formed by a reaction between a carboxy group derived from the acid-containing macromonomer and a glycidyl ether group of a glycidyl ether group-containing ethylenically unsaturated compound.

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