(METH) acrylic resin

Abstract

The present invention provides a (meth) acrylic resin containing structural units represented by formula (2) and formula (3). (In formula (2), R3 represents a hydrogen atom or a methyl group, and R4 represents a group having a hydroxyl group on a carbon atom and a residue having a hydrogen atom removed from a carboxyl group of an unsaturated monocarboxylic acid on a carbon atom adjacent to the carbon atom; in formula (3), R5 represents a hydrogen atom or a methyl group, and R6 represents a group having a residue on a carbon atom obtained by removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid, and having a residue on a carbon atom adjacent to the carbon atom obtained by removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid. # imgabs0 #

Description

Technical Field

[0001] The present disclosure relates to (meth)acrylic resins suitable for adhesive compositions. Background Art

[0002] Conventionally, various adhesive sheets have been used in semiconductor manufacturing processes and the like. Specifically, there are protective sheets (back grinding tapes) used for protecting wafers in the back grinding process of semiconductor wafers, and fixing sheets (dicing tapes) used in the process of cutting and dividing (dicing) semiconductor wafers into element chips. These adhesive sheets are re - peelable adhesive sheets that are adhered to semiconductor wafers as adherends and peeled off from the adherends after a specified processing step.

[0003] As an adhesive composition used in the adhesive layer of a re - peelable adhesive sheet, a composition containing a resin in which an ethylenically unsaturated group capable of being UV (ultraviolet) - cured is introduced into the side chain of a (meth)acrylic resin is known. Such an adhesive composition is cured by a cross - linking reaction upon UV irradiation, and the adhesive strength decreases. For example, Patent Document 1 (Japanese Patent Application Laid - Open No. 2014 - 62210) describes a method for manufacturing an adhesive sheet, which includes a step of reacting a (meth)acrylic polymer having two or more hydroxyl groups in the side chain with a compound having an isocyanate group such as 2 - isocyanatoethyl (meth)acrylate in the presence of a first catalyst to form a (meth)acrylic polymer having a urethane bond.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid - Open No. 2014 - 62210 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, when an ethylenically unsaturated group is introduced into the side chain of a (meth)acrylic resin using a compound having an isocyanate group as in Patent Document 1, a dimer of the isocyanate compound is generated as an impurity during synthesis, and there is a problem that this dimer has a negative impact on the decrease in adhesive strength after UV (ultraviolet) curing. As a result, the peelability after the processing step is insufficient when peeling off from the adherend, and thus improvement is desired. The present disclosure provides a (meth)acrylic resin suitable for an adhesive that has sufficient adhesive strength to an adherend, the adhesive strength is sufficiently reduced by UV irradiation after the processing step, and has improved peelability from the adherend.

[0009] Means for Solving the Problems

[0010] The content of the present disclosure includes the following solutions.

[0011] [1] A (meth)acrylic resin containing structural units of the following formulas (1) to (3), and optionally containing structural units of the following formula (4).

[0012]

[0013] In formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents an alkyl group having 1 to 20 carbon atoms; in formula (2), R 3 represents a hydrogen atom or a methyl group, and R 4 represents a group having a hydroxyl group on a carbon atom and a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on the carbon atom adjacent to the carbon atom; in formula (3), R 5 represents a hydrogen atom or a methyl group, and R 6 represents a group having a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on a carbon atom and a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on the carbon atom adjacent to the carbon atom; in formula (4), R 7 represents a hydrogen atom or a methyl group, and R 8 represents a group containing an epoxy group.

[0014] [2] The (meth)acrylic resin according to [1], wherein the structural unit of formula (2) is a structural unit of the following formula (2-1-1) or the following formula (2-1-2), and the structural unit of formula (3) is a structural unit of the following formula (3-1);

[0015]

[0016] In formula (2-1-1), R 9 represents a hydrogen atom or a methyl group, R 10 represents a divalent linking group, R 11 , R 12 , R 14 and R 15 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 13 represents a single bond or a divalent linking group, and R 16 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, and R in -COOR represents an alkyl group having 1 to 6 carbon atoms;

[0017]

[0018] In formula (2-1-2), R 17 represents a hydrogen atom or a methyl group, and R 18 represents a divalent linking group,19 , R 20 , R 22 and R 23 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 21 represents a single bond or a divalent linking group, and R 24 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, and R in the -COOR represents an alkyl group having 1 to 6 carbon atoms;

[0019]

[0020] In formula (3-1), R 25 represents a hydrogen atom or a methyl group, and R 26 represents a divalent linking group, and R 27 , R 28 , R 30 , R 31 , R 34 and R 35 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 29 and R 33 each independently represents a single bond or a divalent linking group, and R 32 and R 36 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, and R in the -COOR represents an alkyl group having 1 to 6 carbon atoms.

[0021] [3] The (meth)acrylic resin according to [1], wherein the structural unit of formula (2) is the structural unit of the following formula (2-2), and the structural unit of formula (3) is the structural unit of the following formula (3-2);

[0022]

[0023] In formula (2-2), R 37 represents a hydrogen atom or a methyl group, and R 38 represents a single bond or a divalent linking group, and R 39 , R 41 and R 42 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 40 represents a single bond or a divalent linking group, and R 43 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, and R in the -COOR represents an alkyl group having 1 to 6 carbon atoms, and X1 represents a saturated hydrocarbon ring;

[0024]

[0025] In formula (3-2), R44 represents a hydrogen atom or a methyl group, R 45 represents a single bond or a divalent linking group, R 46 , R 48 , R 49 , R 52 and R 53 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 47 and R 51 each independently represents a single bond or a divalent linking group, R 50 and R 54 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, wherein R in -COOR represents an alkyl group having 1 to 6 carbon atoms, and X2 represents a saturated hydrocarbon ring.

[0026] [4] The (meth)acrylic resin according to any one of [1] to [3], having an ethylenically unsaturated group equivalent of 350 to 4000 g / mol.

[0027] [5] The (meth)acrylic resin according to any one of [1] to [4], wherein, based on all the structural units of the (meth)acrylic resin, the total proportion of the structural units of the formulas (2) to (4) is 1 to 50 mol%.

[0028] [6] The (meth)acrylic resin according to any one of [1] to [5], wherein the total proportion of the structural units of the formulas (2) and (3) relative to the total of the structural units of the formulas (2) to (4) is 50 to 100 mol%.

[0029] [7] The (meth)acrylic resin according to any one of [1] to [6], having a glass transition temperature (Tg) of -80°C to 0°C.

[0030] [8] The (meth)acrylic resin according to any one of [1] to [7], wherein the residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid is (meth)acryloyloxy.

[0031] [9] The (meth)acrylic resin according to any one of [1] to [8], wherein each carbon atom having a hydroxyl group or a residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid in the formulas (2) and (3) has one or two hydrogen atoms.

[0032]

[10] The (meth)acrylic resin according to any one of [1] to [9], having a hydroxyl value of 1 to 60 mgKOH / g.

[0033]

[11] The (meth)acrylic resin according to any one of [1] to

[10] has a weight average molecular weight of 100,000 to 1,000,000.

[0034] Advantageous Effects of the Invention

[0035] According to the present disclosure, a (meth)acrylic resin suitable for an adhesive having excellent adhesiveness and excellent peelability when peeling the adhesive sheet from an adherend after UV irradiation can be provided. Detailed Description of the Invention

[0036] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments shown below.

[0037] In this specification, when a numerical range is expressed using "~", the numerical values at both ends are the upper limit value and the lower limit value, respectively, and are included in the numerical range.

[0038] In this specification, "(meth)acrylic" means "acrylic" or "methacrylic". "(Meth)acrylate" means "acrylate" or "methacrylate", and "(meth)acryloyloxy" means "acryloyloxy" or "methacryloyloxy".

[0039] In this specification, a "structural unit" means a unit derived from a polymerizable compound used as a monomer or a unit obtained by further modifying a unit derived from a polymerizable compound used as a monomer.

[0040] <(Meth)acrylic resin>

[0041] The (meth)acrylic resin of one embodiment contains structural units represented by the following formulas (1) to (3), and optionally contains a structural unit represented by the following formula (4).

[0042]

[0043] In formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents an alkyl group having 1 to 20 carbon atoms; in formula (2), R 3 represents a hydrogen atom or a methyl group, and R 4 represents a group having a hydroxyl group on a carbon atom and a residue obtained by removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid on a carbon atom adjacent to the carbon atom; in formula (3), R 5 represents a hydrogen atom or a methyl group, and R 6 represents a residue obtained by removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid on a carbon atom and a residue obtained by removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid on a carbon atom adjacent to the carbon atom; in formula (4), R 7represents a hydrogen atom or a methyl group, R 8 represents a group containing an epoxy group.

[0044] [Structural unit of formula (1)]

[0045] The (meth)acrylic resin contains a structural unit of the following formula (1). The structural unit of formula (1) helps to impart adhesiveness as an adhesive.

[0046]

[0047] In formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents an alkyl group having 1 to 20 carbon atoms. R 2 is preferably a linear or branched-chain alkyl group, more preferably a linear or branched-chain alkyl group having 1 to 10 carbon atoms, and further preferably a linear or branched-chain alkyl group having 4 to 8 carbon atoms. The structural units of formula (1) may not be of one kind. The R 1 of each structural unit may be different from each other, and the R 2 of each structural unit may also be different from each other.

[0048] Specific examples of the monomer that forms the structural unit of formula (1) include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and decyl (meth)acrylate. Among them, from the viewpoints of the ease of synthesis of the (meth)acrylic resin, the adhesive properties when used as an adhesive, and the peelability after UV irradiation, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred, and 2-ethylhexyl (meth)acrylate is more preferred from the viewpoint of the peelability after UV irradiation when used as an adhesive.

[0049] The monomers that form the structural unit of formula (1) can be used alone or in combination of two or more.

[0050] The proportion of the structural unit of formula (1) relative to all the structural units of the (meth)acrylic resin is preferably 50 to 99 mol%, more preferably 60 to 98 mol%, and further preferably 70 to 95 mol%. When the structural unit of formula (1) is 50 mol% or more, sufficient adhesiveness to the adherend can be obtained before UV irradiation. If the structural unit of formula (1) is 99 mol% or less, a sufficient proportion of the structural units of the following formula (2) and formula (3) can be ensured, so sufficient photocurability can be obtained when used as an adhesive, and thus the desired peelability can be obtained after UV irradiation.

[0051] [Structural unit of formula (2)]

[0052] (Meth)acrylic resins contain a structural unit represented by the following formula (2). Thus, when used as an adhesive composition containing a crosslinking agent, through thermal curing, the hydroxyl groups crosslink with the crosslinking agent, and an adhesive layer can be formed. In addition, by introducing an ethylenically unsaturated group into the side chain, photocurability can be imparted to the adhesive, and after UV irradiation, the adhesive strength as an adhesive is reduced, and the peelability from the adherend is improved.

[0053]

[0054] In formula (2), R 3 represents a hydrogen atom or a methyl group, and R 4 represents a group having a hydroxyl group on a carbon atom and a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on the carbon atom adjacent to the carbon atom having the hydroxyl group. From the viewpoint of heat resistance, the carbon atom having a hydroxyl group preferably has one hydrogen atom, and the carbon atom having a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid preferably has one or two hydrogen atoms. The structural units of formula (2) may not be of one kind. The R 3 of each structural unit may be different from each other, and the R 4 of each structural unit may also be different from each other.

[0055] Specific examples of the residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid that constitutes R 4 include residues obtained by removing a hydrogen atom from the carboxyl group of unsaturated monocarboxylic acids such as (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, crotonic acid, propiolic acid, cinnamic acid, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, monomethyl fumarate, and monoethyl itaconate. Among them, from the viewpoint of the ease of synthesis of (meth)acrylic resins, a residue obtained by removing a hydrogen atom from the carboxyl group of (meth)acrylic acid, i.e., (meth)acryloyloxy, is preferred.

[0056] Specific examples of the structural unit of formula (2) include the structural units represented by the following formula (2-1-1) and the following formula (2-1-2).

[0057]

[0058] In formula (2-1-1), R 9 represents a hydrogen atom or a methyl group, R 10 represents a divalent linking group, and R 11 , R 12 , R 14 and R 15 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 13represents a single bond or a divalent linking group, R 16 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR (wherein R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group.

[0059]

[0060] In formula (2-1-2), R 17 represents a hydrogen atom or a methyl group, R 18 represents a divalent linking group, R 19 , R 20 , R 22 and R 23 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 21 represents a single bond or a divalent linking group, R 24 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR (wherein R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group.

[0061] In formula (2-1-1), as the divalent linking group represented by R 10 there may be mentioned an alkylene group having 1 to 20 carbon atoms, -R 55 -O-R 56 -(wherein R 55 and R 56 each independently represents an alkylene group having 1 to 10 carbon atoms), etc. As the alkylene group having 1 to 20 carbon atoms represented by R 10 there may be mentioned a methylene group, an ethylene group, a butylene group, etc. Among them, from the viewpoint of adhesion to the adherend, an alkylene group having 1 to 10 carbon atoms is preferred, and a methylene group and an ethylene group are more preferred. As the alkylene group having 1 to 10 carbon atoms represented by R 55 and R 56 there may be mentioned a methylene group, an ethylene group, a butylene group, etc. Among them, from the viewpoint of photocurability, an alkylene group having 1 to 6 carbon atoms is preferred. As R 10 , an alkylene group having 1 to 10 carbon atoms, and -R 55 -O-R 56 - are preferred, and a methylene group, an ethylene group, and -(CH2) n -O-(CH2) y -(n is an integer from 1 to 6, y is an integer from 1 to 2). n is preferably an integer from 2 to 6, and y is preferably an integer from 1 to 2.

[0062] In formula (2-1-1), R 11 , R 12 , R 14 and R 15Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. As R 11 , R 12 , R 14 and R 15 , examples of the alkyl group having 1 to 6 carbon atoms include a methyl group. From the viewpoint of heat resistance, it is preferable that both R 11 and R 12 are hydrogen atoms. From the viewpoint of heat resistance, it is preferable that R 14 is a hydrogen atom or a methyl group. From the viewpoint of photocurability, it is preferable that R 15 is a hydrogen atom.

[0063] In formula (2-1-1), R 13 represents a single bond or a divalent linking group. Examples of the divalent linking group include an alkylene group having 1 to 20 carbon atoms, -R 57 -O-R 58 - (wherein, R 57 and R 58 each independently represent an alkylene group having 1 to 10 carbon atoms), -R 59 -CO-O-R 60 -CO-, -R 61 -CO-O-R 62 - (wherein, R 59 to R 62 each independently represent an alkylene group having 1 to 10 carbon atoms), etc. Examples of the alkylene group having 1 to 20 carbon atoms represented by R 13 include a methylene group, an ethylene group, a butylene group, etc. As R 13 , from the viewpoint of photocurability, a single bond and an alkylene group having 1 to 6 carbon atoms are preferable, and a single bond is more preferable.

[0064] In formula (2-1-1), R 16 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR (wherein, R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group. Examples of the alkyl group having 1 to 6 carbon atoms represented by R 16 include a methyl group and an ethyl group. From the viewpoint of photocurability, it is preferable that R 16 is a hydrogen atom.

[0065] In formula (2-1-2), the specific examples and preferred examples of R 18 to R 24 are the same as those of R 10 to R 16 in formula (2-1-1), respectively.

[0066] As a method for forming the structural unit of formula (2-1-1) or formula (2-1-2), specifically, a method of forming the structural unit of formula (4-1) described below, and then reacting the epoxy group of formula (4-1) with the carboxyl group of an unsaturated monocarboxylic acid to form a residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid can be cited. The monomers for forming the structural unit of formula (4-1) can be used alone or in combination of two or more, and the unsaturated monocarboxylic acids for the reaction can also be used alone or in combination of two or more.

[0067] As a specific example of the structural unit of formula (2), the structural unit of the following formula (2-2) can also be cited.

[0068]

[0069] In formula (2-2), R 37 represents a hydrogen atom or a methyl group, R 38 represents a single bond or a divalent linking group, R 39 , R 41 and R 42 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 40 represents a single bond or a divalent linking group, R 43 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR (wherein R represents an alkyl group having 1 to 6 carbon atoms) or a phenyl group, and X1 represents a saturated hydrocarbon ring.

[0070] As the divalent linking group represented by R 38 , for example, an alkylene group having 1 to 20 carbon atoms, -R 63 -O-R 64 - (wherein R 63 and R 64 each independently represent an alkylene group having 1 to 10 carbon atoms), -R 65 -O- (wherein R 65 represents an alkylene group having 1 to 10 carbon atoms), -COO-, and combinations thereof can be cited. As the alkylene group having 1 to 20 carbon atoms constituting R 38 , methylene, ethylene, butylene, cyclohexylene, etc. can be cited. Among them, from the viewpoint of adhesion to the adherend, an alkylene group having 1 to 10 carbon atoms is preferred, and methylene and ethylene are more preferred. As the alkylene group having 1 to 10 carbon atoms represented by R 63 and R 64 , methylene, ethylene, butylene, etc. can be cited. Among them, from the viewpoint of photocurability, an alkylene group having 1 to 6 carbon atoms is preferred. As R 65The alkylene group having 1 to 10 carbon atoms represented can include methylene, ethylene, butylene, etc. Among them, from the aspect of photocurability, an alkylene group having 1 to 6 carbon atoms is preferred. As R 38 , a single bond, an alkylene group having 1 to 10 carbon atoms, and -R 65 -O- are preferred, and a single bond, methylene, ethylene, and -(CH2) m -O- (where m is an integer from 1 to 3) are more preferred.

[0071] In formula (2-2), R 39 , R 41 and R 42 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. As the alkyl group having 1 to 6 carbon atoms represented by R 39 , R 41 and R 42 , methyl can be cited. From the aspect of heat resistance, it is preferred that R 39 is a hydrogen atom. From the aspect of heat resistance, it is preferred that R 41 is a hydrogen atom or a methyl group. From the aspect of photocurability, it is preferred that R 42 is a hydrogen atom.

[0072] In formula (2-2), the specific examples and preferred examples of R 40 and R 43 are the same as those of R 13 and R 16 in formula (2-1-1) respectively.

[0073] In formula (2-2), X1 represents a saturated hydrocarbon ring. The number of carbon atoms of the saturated hydrocarbon ring is preferably 4 to 20, more preferably 5 to 10, and further preferably 5 to 8. The saturated hydrocarbon ring can be a monocyclic ring or a fused ring. As the saturated hydrocarbon ring, cyclohexyl, cyclopentyl, and tricyclodecyl are preferred.

[0074] From the aspect of heat resistance, the structural unit of formula (2) preferably includes the structural unit of formula (2-2).

[0075] As a method for forming the structural unit of formula (2-2), specifically, there can be cited a method of introducing the structural unit of the following formula (4-2), and then reacting the epoxy group of formula (4-2) with the carboxyl group of an unsaturated monocarboxylic acid to form a residue after removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid. The monomers for forming the structural unit of formula (4-2) can be used alone or in combination of two or more, and the unsaturated monocarboxylic acids for the reaction can also be used alone or in combination of two or more.

[0076] The proportion of the structural unit of formula (2) relative to all the structural units of the (meth)acrylic resin is preferably 0.1 to 40 mol%, more preferably 0.5 to 18 mol%, and still more preferably 1 to 15 mol%. When the structural unit of formula (2) is 0.1 mol% or more, sufficient thermal curability can be obtained when used together with a crosslinking agent. As a result, sufficient adhesiveness to the adherend and cohesion of the adhesive can be obtained. If the structural unit of formula (2) is 40 mol% or less, a sufficient proportion of the structural unit of formula (1) can be ensured, and thus good adhesiveness can be obtained.

[0077] [Structural unit of formula (3)]

[0078] (The (meth)acrylic resin contains the structural unit of the following formula (3). By introducing two ethylenically unsaturated groups into the side chain, photocurability can be imparted to the adhesive, the adhesiveness as the adhesive can be reduced after UV irradiation, and the peelability from the adherend can be improved.

[0079]

[0080] In formula (3), R 5 represents a hydrogen atom or a methyl group, and R 6 represents a group having a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on a carbon atom and having a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on the carbon atom adjacent to the said carbon atom. From the viewpoint of heat resistance, each carbon atom having a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid preferably has one or two hydrogen atoms. The structural unit of formula (3) may not be a single kind. R 5 of each structural unit may be different respectively, and R 6 of each structural unit may also be different respectively.

[0081] As a specific example of the residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid constituting R 6 , residues obtained by removing a hydrogen atom from the carboxyl groups of unsaturated monocarboxylic acids such as (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, crotonic acid, propiolic acid, cinnamic acid, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, monomethyl fumarate, monoethyl itaconate, etc. can be cited. Among them, from the viewpoint of the ease of synthesis of the (meth)acrylic resin, the residue obtained by removing a hydrogen atom from the carboxyl group of (meth)acrylic acid, i.e., (meth)acryloyloxy, is preferred.

[0082] As a specific example of the structural unit of formula (3), the structural unit of the following formula (3-1) can be cited.

[0083]

[0084] In formula (3-1), R 25 represents a hydrogen atom or a methyl group, and R 26 represents a divalent linking group, and R 27 , R 28 , R 30 , R 31 , R 34 and R 35 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 29 and R 33 each independently represent a single bond or a divalent linking group, and R 32 and R 36 each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR (wherein R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group.

[0085] In formula (3-1), the specific examples and preferred examples of R 26 to R 32 are the same as those of R 10 to R 16 in formula (2-1-1) respectively. In formula (3-1), the specific examples and preferred examples of R 33 to R 36 are the same as those of R 13 to R 16 in formula (2-1) respectively.

[0086] As a method for forming the structural unit of formula (3-1), specifically, a method of reacting the hydroxyl group of the structural unit of the above formula (2-1-1) or formula (2-1-2) with an unsaturated monocarboxylic anhydride to introduce a residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid can be cited. The unsaturated monocarboxylic anhydride used in the reaction can be used alone or in combination of two or more. As the unsaturated monocarboxylic anhydride, (meth)acrylic anhydride can be cited.

[0087] As a specific example of the structural unit of formula (3), the structural unit of the following formula (3-2) can also be cited.

[0088]

[0089] In formula (3-2), R 44 represents a hydrogen atom or a methyl group, and R 45 represents a single bond or a divalent linking group, and R 46 , R 48 , R 49 , R 52 and R 53 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R 47 and R 51each independently represents a single bond or a divalent linking group, R 50 and R 54 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR (wherein R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group, and X2 represents a saturated hydrocarbon ring.

[0090] In formula (3-2), the specific examples and preferred examples of R 45 to R 50 are the same as those of R 38 to R 43 in formula (2-2), respectively. In formula (3-2), the specific examples and preferred examples of R 51 to R 54 are the same as those of R 40 to R 43 in formula (2-2), respectively. In formula (3-2), the specific examples and preferred examples of X2 are the same as those of X1 in formula (2-2).

[0091] As a method for forming the structural unit of formula (3-2), specifically, a method of reacting the hydroxyl group of the structural unit of the above formula (2-2) with an unsaturated monocarboxylic anhydride to introduce a residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid can be mentioned. The unsaturated monocarboxylic anhydride used in the reaction can be used alone or in combination of two or more. As the unsaturated monocarboxylic anhydride, (meth)acrylic anhydride can be mentioned.

[0092] The proportion of the structural unit of formula (3) relative to all the structural units of the (meth)acrylic resin is preferably 0.1 to 30 mol%, more preferably 0.2 to 28 mol%, and still more preferably 0.5 to 26 mol%. When the structural unit of formula (3) is 0.1 mol% or more, sufficient photocurability can be obtained when used as an adhesive composition together with a photoinitiator. As a result, the adhesive strength of the adhesive composition can be sufficiently reduced during UV irradiation, and the peelability from the adherend after UV irradiation is improved. When the structural unit of formula (3) is 30 mol% or less, the adhesive strength is good.

[0093] [Structural unit of formula (4)]

[0094] The (meth)acrylic resin may contain the structural unit of the following formula (4). From the aspect of reducing the residual monomers during the synthesis of the (meth)acrylic resin, that is, the residual unsaturated monocarboxylic acid and unsaturated monocarboxylic anhydride used to introduce the structural units of the above formulas (2) and (3), it is preferable to contain a certain amount of the structural unit of the following formula (4). On the other hand, from the aspect of reducing the deterioration of the adhesive over time, it is preferable to reduce the content of the structural unit of formula (4) as much as possible.

[0095]

[0096] In formula (4), R 7 represents a hydrogen atom or a methyl group, and R 8 represents a group containing an epoxy group. The structural unit of formula (4) may not be a single type. The R 7 of each structural unit may be different respectively, and the R 8 of each structural unit may also be different respectively.

[0097] As specific examples of the structural unit of formula (4), the structural units of the following formula (4-1) and the following formula (4-2) can be cited.

[0098]

[0099] In formula (4-1), R 66 represents a hydrogen atom or a methyl group, R 67 represents a divalent linking group, R 68 and R 69 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. In formula (4-2), R 70 represents a hydrogen atom or a methyl group, R 71 represents a single bond or a divalent linking group, and R 72 represents an alicyclic epoxy group.

[0100] In formula (4-1), the specific examples and preferred examples of R 67 , R 68 and R 69 are the same as R 10 , R 11 and R 12 in formula (2-1-1) respectively.

[0101] As specific examples of the monomer for forming the structural unit of formula (4-1), glycidyl (meth)acrylate, glycidyl hydroxybutyl (meth)acrylate, etc. can be cited. From the aspect of the ease of reaction with unsaturated monocarboxylic acids when forming the structural units of formula (2-1-1), formula (2-1-2) and formula (3-1), glycidyl (meth)acrylate and glycidyl hydroxybutyl (meth)acrylate are preferred.

[0102] The monomers for forming the structural unit of formula (4-1) can be used alone or in combination of two or more.

[0103] In formula (4-2), the specific examples and preferred examples of R 71 are the same as R 38 in formula (2-2).

[0104] In formula (4-2), R 72represents an alicyclic epoxy group, and specific examples thereof include 3,4-epoxycyclohexyl, epoxycyclopentyl, 3,4-epoxytricyclo[5.2.1.0 2,6 decyl, etc.

[0105] Specific examples of the monomer forming the structural unit of formula (4-2) include 3,4-epoxycyclohexylmethyl (meth)acrylate (for example, Cyclomer (trademark) A200 and M100 manufactured by Daicel Corporation), (meth)acrylate of lactone adduct having 3,4-epoxycyclohexyl, mono(meth)acrylate of 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexanecarboxylate, epoxide of dicyclopentenyl (meth)acrylate, epoxide of dicyclopentenoxyethyl (meth)acrylate, etc. Among them, 3,4-epoxycyclohexylmethyl (meth)acrylate is preferred in view of the ease of reaction with unsaturated monocarboxylic acid when forming the structural units of formula (2-2) and formula (3-2). The monomers forming the structural unit of formula (4-2) can be used alone or in combination of two or more.

[0106] The proportion of the structural unit of formula (4) relative to all the structural units of the (meth)acrylic resin is preferably 0 to 10 mol%, more preferably 0 to 5 mol%, and further preferably 0 to 1 mol%. If the structural unit of formula (4) is 10 mol% or less, sufficient heat resistance and storage stability can be obtained, and when used as an adhesive, the adhesive strength can be sufficiently reduced after UV irradiation, and the adherend can be peeled off without contamination.

[0107] Based on all the structural units of the (meth)acrylic resin, the total proportion of the structural units of formula (2) to (4) is preferably 1 mol% or more, more preferably 2 mol% or more, and further preferably 5 mol% or more. Based on all the structural units of the (meth)acrylic resin, the total proportion of the structural units of formula (2) to (4) is preferably 50 mol% or less, more preferably 40 mol% or less, and further preferably 30 mol% or less. These upper and lower limits can be arbitrarily combined. Based on all the structural units of the (meth)acrylic resin, the total proportion of the structural units of formula (2) to (4) is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, and further preferably 5 to 30 mol%. When the total proportion of the structural units of formula (2) to (4) is within the above range, sufficient photocurability when used as an adhesive and the desired peelability after UV irradiation can be obtained.

[0108] The total proportion of the structural units of formulas (2) and (3) is preferably 50 mol% or more, more preferably 55 mol% or more, and still more preferably 60 mol% or more, relative to the total of the structural units of formulas (2) to (4). The total proportion of the structural units of formulas (2) and (3) is preferably 100 mol% or less, more preferably 95 mol% or less, and still more preferably 90 mol% or less, relative to the total of the structural units of formulas (2) to (4). These upper and lower limits can be combined arbitrarily. The total proportion of the structural units of formulas (2) and (3) is preferably 50 to 100 mol%, more preferably 55 to 95 mol%, and still more preferably 60 to 90 mol%, relative to the total of the structural units of formulas (2) to (4). When the total proportion of the structural units of formulas (2) and (3) is 50 mol% or more, sufficient photocurability when used as an adhesive and the desired peelability after UV irradiation can be obtained.

[0109] [Physical property values of (meth)acrylic resins]

[0110] The vinyl unsaturated group equivalent of the (meth)acrylic resin is preferably 350 g / mol or more, more preferably 400 g / mol or more, and still more preferably 450 g / mol or more. The vinyl unsaturated group equivalent of the (meth)acrylic resin is preferably 4000 g / mol or less, more preferably 3000 g / mol or less, and still more preferably 2000 g / mol or less. These upper and lower limits can be combined arbitrarily. The vinyl unsaturated group equivalent of the (meth)acrylic resin is preferably 350 to 4000 g / mol, more preferably 400 to 3000 g / mol, and still more preferably 450 to 2000 g / mol. When the vinyl unsaturated group equivalent is 350 g / mol or more, the desired peelability after irradiating the adhesive with UV can be obtained. When the vinyl unsaturated group equivalent is 4000 g / mol or less, the adhesion before UV irradiation is good.

[0111] In this specification, the vinyl unsaturated group equivalent of the (meth)acrylic resin refers to the mass (g / mol) of the (meth)acrylic resin corresponding to 1 mole of vinyl unsaturated bonds. The vinyl unsaturated group equivalent of the (meth)acrylic resin in one embodiment is a calculated value obtained by assuming 100% reaction of each raw material used in the production of the (meth)acrylic resin and calculating from the feed amount. The vinyl unsaturated group equivalent of the (meth)acrylic resin can be calculated from the amount of halogen bonded to the (meth)acrylic resin. The amount of halogen bonded to the (meth)acrylic resin can be evaluated in accordance with JIS K 0070:1992.

[0112] The glass transition temperature (Tg) of the (meth)acrylic resin is preferably -80°C or higher, more preferably -70°C or higher, and further preferably -65°C or higher. The glass transition temperature (Tg) of the (meth)acrylic resin is preferably 0°C or lower, more preferably -10°C or lower, and further preferably -20°C or lower. These upper and lower limit values can be arbitrarily combined. The glass transition temperature (Tg) of the (meth)acrylic resin is preferably -80°C to 0°C, more preferably -70°C to -10°C, and further preferably -65°C to -20°C. If the glass transition temperature is -80°C or higher, the water resistance and chemical resistance are good. If the glass transition temperature is 0°C or lower, the adhesion before UV irradiation is good.

[0113] In this specification, the "glass transition temperature (Tg)" means that 10 mg of a sample is collected, and differential scanning calorimetry is performed using a differential scanning calorimeter (DSC) while changing the temperature of the sample from -100°C to 200°C at a heating rate of 10°C / minute, and the endothermic start temperature based on the glass transition is observed. In the case where two or more endothermic start temperatures are observed, Tg is the simple average of the two or more endothermic start temperatures.

[0114] The weight average molecular weight of the (meth)acrylic resin is preferably 100,000 or higher, more preferably 200,000 or higher, and further preferably 300,000 or higher. The weight average molecular weight of the (meth)acrylic resin is preferably 1,000,000 or lower, more preferably 900,000 or lower, and further preferably 800,000 or lower. These upper and lower limit values can be arbitrarily combined. The weight average molecular weight of the (meth)acrylic resin is preferably 100,000 to 1,000,000, more preferably 200,000 to 900,000, and further preferably 300,000 to 800,000. If the weight average molecular weight is 100,000 or higher, the cohesiveness before UV irradiation is good. If the weight average molecular weight is 1,000,000 or lower, the operability during coating is good.

[0115] In this specification, the "weight average molecular weight" is a value obtained by performing measurement at room temperature (23°C) under the following conditions using gel permeation chromatography (GPC: gel permeation chromatography) and using a standard polystyrene standard curve.

[0116] Apparatus: Shodex (trademark) GPC-101 (Showa Denko K.K.)

[0117] Column: Shodex (trademark) LF-804 (Showa Denko K.K.)

[0118] Column temperature: 40°C

[0119] Sample: 0.2 mass% tetrahydrofuran solution of the sample

[0120] Flow rate: 1 mL / minute

[0121] Eluent: Tetrahydrofuran

[0122] Detector: Shodex (trademark) RI-71S (Showa Denko K.K.)

[0123] The hydroxyl value of the (meth)acrylic resin is preferably 1 mgKOH / g or more, more preferably 2 mgKOH / g or more, and further preferably 3 mgKOH / g or more. The hydroxyl value of the (meth)acrylic resin is preferably 60 mgKOH / g or less, more preferably 50 mgKOH / g or less, and further preferably 40 mgKOH / g or less. These upper and lower limit values can be arbitrarily combined. The hydroxyl value of the (meth)acrylic resin is preferably 1 to 60 mgKOH / g, more preferably 2 to 50 mgKOH / g, and further preferably 3 to 40 mgKOH / g. When the hydroxyl value is 1 mgKOH / g or more, the desired cohesive force can be obtained when reacting with the crosslinking agent. When the hydroxyl value is 60 mgKOH / g or less, the peelability after UV irradiation is good.

[0124] In this specification, the hydroxyl value is the mass (mg) of potassium hydroxide required to neutralize acetic acid bonded to a hydroxyl group when acetylating 1 g of the resin in accordance with JIS K 0070:1992.

[0125] <Manufacturing method of (meth)acrylic resin>

[0126] For the (meth)acrylic resin, for example, it can be obtained through the following steps:

[0127] Step (i) of polymerizing a monomer having an epoxy group with other monomers to obtain a copolymer;

[0128] Step (ii) of adding an unsaturated monocarboxylic acid to the epoxy group of the copolymer;

[0129] Step (iii) of adding an unsaturated monocarboxylic anhydride to the hydroxyl group formed by ring-opening of the epoxy group through the addition reaction in step (ii) above, and at the same time adding an unsaturated monocarboxylic acid derived from the free unsaturated monocarboxylic anhydride to the remaining epoxy group.

[0130] [Step (i) of polymerizing monomers to obtain a copolymer]

[0131] As the polymerization method, solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, alternating copolymerization, etc. can be used. Among these polymerization methods, considering the addition reactions in steps (ii) and (iii), solution polymerization is preferably used in terms of the ease of reaction.

[0132] As the monomer, an alkyl (meth)acrylate, an epoxy group-containing (meth)acrylate, and optionally other monomers can be used.

[0133] ((meth)acrylate

[0134] As the alkyl (meth)acrylate, there is no particular limitation as long as it is a monomer that forms the structural unit of formula (1). Specific examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, etc. Among them, from the viewpoints of the ease of synthesis of the (meth)acrylic resin, the adhesive properties when used as an adhesive, and the peelability after UV irradiation, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred, and 2-ethylhexyl (meth)acrylate is more preferred from the viewpoint of the peelability after UV irradiation when used as an adhesive. The alkyl (meth)acrylate can be used alone or in combination of two or more.

[0135] (epoxy group-containing (meth)acrylate)

[0136] As the epoxy group-containing (meth)acrylate, there is no particular limitation as long as it is a monomer that forms the structural unit of formula (4). Specific examples thereof include glycidyl (meth)acrylate, glycidyl ether of hydroxybutyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate (for example, Cyclomer (trademark) A200 and M100 manufactured by Daicel Corporation), (meth)acrylate having an adduct of lactone with 3,4-epoxycyclohexyl, mono(meth)acrylate of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, epoxide of dicyclopentenyl (meth)acrylate, epoxide of dicyclopentenoxyethyl (meth)acrylate, etc. Among them, from the viewpoint of the ease of reaction with an unsaturated monocarboxylic acid, glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and glycidyl ether of hydroxybutyl (meth)acrylate are preferred. The epoxy group-containing (meth)acrylate can be used alone or in combination of two or more.

[0137] (other monomers)

[0138] As other monomers, as long as they do not have a carboxyl group, form structural units other than those of formulas (1) to (4), and can copolymerize with the above-mentioned (meth)acrylic acid alkyl ester and the (meth)acrylic acid ester containing an epoxy group, there are no particular limitations. Specifically, examples thereof include (meth)acrylic acid esters containing an alicyclic ring, (meth)acrylic acid esters containing an aromatic ring, (meth)acrylic acid esters containing a hydroxyl group, (meth)acrylic acid esters containing an amide group, and the like.

[0139] Examples of the (meth)acrylic acid ester containing an alicyclic ring include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, norbornyl (meth)acrylate, 5-ethylnorbornyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, and the like.

[0140] Examples of the (meth)acrylic acid ester containing an aromatic ring include benzyl (meth)acrylate, triphenylmethyl (meth)acrylate, phenyl (meth)acrylate, cumyl (meth)acrylate, 4-phenoxyphenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, phenoxyethyl biphenyl (meth)acrylate, naphthyl (meth)acrylate, anthryl (meth)acrylate, and the like.

[0141] Examples of the (meth)acrylic acid ester containing a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and the like.

[0142] Examples of the (meth)acrylic acid ester containing an amide group include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, anthryl(meth)acrylamide, and the like.

[0143] The content of the (meth)acrylic acid alkyl ester in all the monomers is preferably 50 to 99 mol%, more preferably 60 to 98 mol%, and still more preferably 70 to 95 mol%.

[0144] The content of the (meth)acrylic acid ester containing an epoxy group in all the monomers is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, and still more preferably 5 to 30 mol%.

[0145] (Free radical polymerization initiator)

[0146] The polymerization is preferably carried out in the presence of a radical polymerization initiator. As the radical polymerization initiator, for example, conventional organic radical polymerization initiators can be cited. Specifically, for example, azo-based polymerization initiators such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4,4-trimethylpentane), dimethyl-2,2'-azobis(2-methylpropionate); and peroxide-based polymerization initiators such as benzoyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)-cyclododecane and other oil-soluble polymerization initiators.

[0147] The radical polymerization initiator can be used alone or in combination of two or more.

[0148] Regarding the usage amount of the radical polymerization initiator, it is preferably 0.001 to 5 parts by mass, more preferably 0.005 to 3 parts by mass, and further preferably 0.01 to 1 part by mass relative to 100 parts by mass of the total amount of the monomers.

[0149] (Solvent)

[0150] As the solvent used in solution polymerization, ordinary solvents can be used. As the solvent, for example, esters such as ethyl acetate, propyl acetate, butyl acetate; aromatic hydrocarbons such as toluene, xylene, benzene; aliphatic hydrocarbons such as hexane, heptane; cycloaliphatic hydrocarbons such as cyclohexane, methylcyclohexane; ketones such as methyl ethyl ketone, methyl isobutyl ketone; diols such as ethylene glycol, propylene glycol, dipropylene glycol; glycol ethers such as methyl cellosolve, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether; and glycol esters such as ethylene glycol diacetate, propylene glycol monomethyl ether acetate can be cited. The solvents can be used alone or in combination of two or more.

[0151] (Reaction conditions)

[0152] The reaction temperature of the polymerization also depends on the type of the radical polymerization initiator used and is usually 30°C to 130°C, preferably 40°C to 120°C, and more preferably 50°C to 110°C. If the temperature during polymerization is 30°C or higher, a sufficient reaction rate can be obtained. If the temperature during polymerization is 130°C or lower, the risk during production is small.

[0153] The reaction time of the polymerization also depends on the types of monomers and free radical polymerization initiators used, and is generally 3 hours to 30 hours, preferably 4 hours to 20 hours, more preferably 5 hours to 15 hours. If the reaction time is more than 3 hours, copolymers can be produced from monomers with appropriate degrees of polymerization. If the reaction time is less than 30 hours, the production can be effectively carried out.

[0154] [Step (ii) of adding an unsaturated monocarboxylic acid to the epoxy groups of the copolymer, and step (iii) of adding an unsaturated monocarboxylic anhydride]

[0155] Steps (ii) and (iii) can be carried out sequentially or simultaneously. Considering the simplicity of operation, it is preferred to carry out steps (ii) and (iii) simultaneously.

[0156] (Unsaturated monocarboxylic acid)

[0157] There is no particular limitation on the unsaturated monocarboxylic acid as long as it is a monocarboxylic acid having an ethylenic unsaturated group. Specific examples thereof include (meth)acrylic acid, 2-(meth)acryloyloxyethyl succinic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, crotonic acid, propiolic acid, cinnamic acid, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, monomethyl fumarate, monoethyl itaconate, etc. Among them, (meth)acrylic acid is preferred in terms of the ease of synthesis of (meth)acrylic resins. The unsaturated monocarboxylic acid can be used alone or in combination of two or more.

[0158] (Unsaturated monocarboxylic anhydride)

[0159] There is no particular limitation on the unsaturated monocarboxylic anhydride as long as it is a monocarboxylic anhydride having an ethylenic unsaturated group. Specific examples thereof include (meth)acrylic anhydride. The unsaturated monocarboxylic anhydride can be used alone or in combination of two or more.

[0160] The addition rate of the unsaturated monocarboxylic acid to the epoxy groups of the epoxy group-containing (meth)acrylate present in the copolymer is preferably 50% or more, more preferably 60% or more, and further preferably 70% or more. If the addition rate is 50% or more, good peelability can be obtained after UV irradiation. Considering the heat resistance, the higher the addition rate, the more preferred. In one embodiment, the addition rate of the unsaturated monocarboxylic acid to the epoxy groups of the epoxy group-containing (meth)acrylate present in the copolymer is 100%. The upper limit of the addition rate can be, for example, 99% or 98%. The addition rate of the unsaturated monocarboxylic acid to the epoxy groups of the epoxy group-containing (meth)acrylate present in the copolymer is calculated from the feed amount.

[0161] Regarding the ratio of the unsaturated monocarboxylic acid to the unsaturated monocarboxylic anhydride, relative to 100 mol of the unsaturated monocarboxylic anhydride, the unsaturated monocarboxylic acid is preferably 5 to 130 mol, more preferably 10 to 120 mol, and still more preferably 15 to 110 mol. If the unsaturated monocarboxylic acid is 130 mol or less relative to 100 mol of the unsaturated monocarboxylic anhydride, the adhesion to the adherend is improved. If the unsaturated monocarboxylic acid is 5 mol or more relative to 100 mol of the unsaturated monocarboxylic anhydride, the peelability after UV irradiation is improved.

[0162] (Catalyst)

[0163] In the addition reactions in steps (ii) and (iii), a known catalyst can be used as needed. As the catalyst, known catalysts can be used without particular limitation, and examples include triphenylphosphine, tris(p-tolyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine, etc. The catalyst can be used alone or in combination of two or more.

[0164] When using a catalyst, regarding the amount of the catalyst used, relative to 100 mol of the epoxy group-containing (meth)acrylate used in the production of the copolymer, it is preferably 2.5 to 10 mol, more preferably 3.0 to 9.0 mol, and still more preferably 3.5 to 8.0 mol. If the amount of the catalyst used is 2.5 mol or more, the addition reaction can be promoted. On the other hand, if the amount of the catalyst used is 10 mol or less, gelation during the addition reaction can be suppressed.

[0165] (Polymerization inhibitor)

[0166] In the addition reactions in steps (ii) and (iii), a known polymerization inhibitor can be used as needed. As the polymerization inhibitor, known polymerization inhibitors can be used without particular limitation, and examples include 4-methoxyphenol, hydroquinone, p-methoxyphenol, 2,6-di-tert-butylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), and phenothiazine. The polymerization inhibitor can be used alone or in combination of two or more.

[0167] When using a polymerization inhibitor, regarding the amount of the polymerization inhibitor used, relative to 100 parts by mass of the copolymer, it is preferably 0.005 to 5 parts by mass, more preferably 0.03 to 3 parts by mass, and still more preferably 0.05 to 1.5 parts by mass. If the amount of the polymerization inhibitor used is 0.005 parts by mass or more, gelation during the addition reaction can be prevented. On the other hand, when the amount of the polymerization inhibitor used is 5 parts by mass or less, sufficient exposure sensitivity of the (meth)acrylic resin can be obtained during UV irradiation.

[0168] (Solvent)

[0169] As the solvent, ordinary solvents can be used. As the solvent, for example, the same solvent as that used in the solution polymerization of step (i) can be used. Toluene, which is prone to chain transfer reactions, or alcohols such as 1-methoxy-2-propanol can also be used. The solvent can be used alone or in combination of two or more.

[0170] (Reaction conditions)

[0171] The temperature of the addition reaction is preferably 25°C to 130°C, particularly preferably 40°C to 120°C. If the temperature of the addition reaction is 25°C or higher, a sufficient reaction rate can be obtained. If the temperature of the addition reaction is 130°C or lower, crosslinking of the double bond part due to thermal free radical polymerization and generation of gel-like substances can be prevented. The time of the addition reaction is preferably 2 to 24 hours, more preferably 2 to 12 hours.

[0172] When carrying out the addition reaction, a gas having an inhibitory effect on polymerization can be introduced into the reaction system. By introducing a gas having an inhibitory effect on polymerization into the reaction system, gelation during the addition reaction can be prevented.

[0173] As the gas having an inhibitory effect on polymerization, a gas containing oxygen in an amount that does not reach the explosion range of the substances in the system, such as air, can be cited.

[0174] If a gas having an inhibitory effect on polymerization and an inhibitor are used in combination, the amount of the inhibitor used can be reduced or the inhibitory effect can be enhanced, so it is more preferable.

[0175] [Usage method of (meth)acrylic resin]

[0176] The (meth)acrylic resin in one embodiment can be mixed with a photoinitiator, a crosslinking agent, and other components added as needed to be used as an adhesive composition. The adhesive composition containing the (meth)acrylic resin is suitable for re-peelable adhesive sheets such as surface protection tapes, process protection tapes, back grinding tapes, and dicing / chip bonding integrated films, and is particularly suitable for dicing / chip bonding integrated films.

[0177] The method of mixing the components contained in the adhesive composition is not particularly limited. Mixing can be carried out using, for example, a homogenizer or a stirring device equipped with stirring blades such as paddle blades.

[0178] (Photoinitiator)

[0179] Examples of the photopolymerization initiator include thioether-based photopolymerization initiators such as diphenyl disulfide, dibenzyl disulfide, tetraethylthiuram disulfide, and tetramethylammonium monosulfide; acylphosphine oxides such as 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2,4,6-trimethylbenzoyl phenylethoxyphosphine oxide; quinone-based photopolymerization initiators such as benzoquinone and anthraquinone; sulfonyl chloride-based photopolymerization initiators; and thioxanthone-based photopolymerization initiators such as thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone.

[0180] Among these photopolymerization initiators, acylphosphine oxides are preferred in view of solubility in the adhesive composition, and 2,4,6-trimethylbenzoyl diphenylphosphine oxide is more preferred.

[0181] The photopolymerization initiator may be used alone or in combination of two or more.

[0182] With respect to 100 parts by mass of the (meth)acrylic resin, the photopolymerization initiator is preferably 0.1 to 5.0 parts by mass, more preferably 0.5 to 2.0 parts by mass. When the content of the photopolymerization initiator is 0.1 part by mass or more with respect to 100 parts by mass of the (meth)acrylic resin, the adhesive composition can be cured at a sufficiently fast curing rate upon UV irradiation, and thus the adhesive force of the adhesive layer after UV irradiation can be sufficiently reduced. When the content of the photopolymerization initiator is 5.0 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic resin, in the case of peeling the adhesive sheet having an adhesive layer containing the adhesive composition from the adherend, the adhesive layer is not likely to remain on the adherend. Even when the content of the photopolymerization initiator exceeds 5.0 parts by mass with respect to 100 parts by mass of the (meth)acrylic resin, no effect commensurate with the content of the photopolymerization initiator is observed. Therefore, by setting the content to 5.0 parts by mass or less, the adhesive composition can be economically produced.

[0183] (Crosslinking agent)

[0184] By mixing a crosslinking agent, an adhesive composition having good balance between the adhesive force before UV irradiation and the adhesive force after UV irradiation can be obtained. The crosslinking agent is a compound having no ethylenically unsaturated bond and having two or more functional groups capable of reacting with the hydroxyl groups contained in the (meth)acrylic resin. Examples of the functional group having reactivity with a hydroxyl group include an isocyanate group, an epoxy group, a carboxyl group, an acid anhydride group, and an aziridinyl group. In view of reactivity, an isocyanate group and an epoxy group are preferred, and an isocyanate group is particularly preferred.

[0185] Examples of the crosslinking agent include polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hydrogenated toluene diisocyanate, 1,3-benzenedimethylene diisocyanate, 1,4-benzenedimethylene diisocyanate, diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isocyanurate of hexamethylene diisocyanate, tetramethylbenzenedimethylene diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate adduct of trimethylolpropane, benzenedimethylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, and methylenebis(4-phenylmethane)triisocyanate; polyepoxides such as 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, bisphenol A-epichlorohydrin type epoxy resin, N,N'-[1,3-phenylenebis(methylene)]bis[bis(oxirane-2-ylmethyl)amine], ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, and diglycerol polyglycidyl ether; aziridine compounds such as tetramethylolmethane-tris(β-aziridinylpropionate), trimethylolpropane-tris(β-aziridinylpropionate), N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), ethylene glycol-bis-[3-(2-aziridinyl)propionate], trimethylolpropane-tris[3-(2-aziridinyl)propionate], trimethylolpropane-tris[3-(1-aziridinyl)propionate], trimethylolpropane-tris[3-(2-methyl-1-aziridinyl)propionate], tetramethylolmethane-tris[3-(2-aziridinyl)propionate], and pentaerythritol-tris[3-(1-aziridinyl)propionate]; and melamine compounds such as hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, and hexah exyloxymethylmelamine.

[0186] Among these crosslinking agents, from the viewpoint of good reactivity with the (meth)acrylic resin, at least one selected from polyisocyanates and polyepoxides is preferably used, and polyisocyanates are more preferably used.

[0187] The crosslinking agent can be used alone or in combination of two or more.

[0188] With respect to 100 parts by mass of the (meth)acrylic resin, the crosslinking agent is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, still more preferably 0.1 to 10 parts by mass, and even more preferably 0.1 to 5 parts by mass. If the content of the crosslinking agent is 0.1 part by mass or more with respect to 100 parts by mass of the (meth)acrylic resin, a crosslinked structure with the (meth)acrylic resin is sufficiently formed during heating, so that the strength of the ultraviolet curable adhesive layer before UV irradiation is good. If the content of the crosslinking agent is 30 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic resin, the adhesiveness of the adhesive composition before UV irradiation is good.

[0189] Examples

[0190] Hereinafter, the present invention will be described more specifically by way of examples and comparative examples, but the present invention is not limited by the following examples.

[0191] The raw materials used in the synthesis of the (meth)acrylic resins (A) and (cA) are as follows.

[0192] Methyl acrylate, Nippon Shokubai Co., Ltd.

[0193] n-Butyl acrylate, Osaka Organic Chemical Industry Co., Ltd.

[0194] 2-Ethylhexyl acrylate, Osaka Organic Chemical Industry Co., Ltd.

[0195] Glycidyl methacrylate, NOF Corporation

[0196] 4-Hydroxybutyl acrylate glycidyl ether, Mitsubishi Chemical Corporation

[0197] 3,4-Epoxycyclohexylmethyl methacrylate, Daicel Corporation

[0198] 3,4-Epoxytricyclo[5.2.1.0 2,6 decoxyethyl acrylate, acrylic acid, Nippon Shokubai Co., Ltd.

[0199] 2-Hydroxyethyl acrylate, Nippon Shokubai Co., Ltd.

[0200] Methacrylic acid, Nippon Shokubai Co., Ltd.

[0201] Methacrylic anhydride, Evonik Japan Co., Ltd.

[0202] Karezs (trademark) MOI: 2-Isocyanatoethyl methacrylate, Showa Denko K.K.

[0203] Free radical polymerization initiator:

[0204] 2,2'-Azobis(isobutyronitrile), FUJIFILM Wako Pure Chemical Corporation

[0205] Catalyst:

[0206] Triphenylphosphine, Kitakyo Chemical Industry Co., Ltd.

[0207] Dioctyltin dilaurate, Nitto Kasei Co., Ltd.

[0208] [Synthesis Example 1] (Example 1)

[0209] 32 parts by mass of propylene glycol monomethyl ether was added to a reaction apparatus equipped with a stirrer, a temperature regulator, a reflux condenser, a dropping funnel, and a thermometer, and heating under reflux was started. 90 parts by mass of 2-ethylhexyl acrylate and 10 parts by mass of glycidyl methacrylate were mixed to prepare a monomer mixture. The monomer mixture containing 0.10 part by mass of 2,2'-azobis(isobutyronitrile) as a polymerization initiator was added dropwise to the reaction apparatus. After the addition was completed, it was maintained at 85 °C for 4 hours. Then, the reaction temperature was raised to 120 °C, 3.00 parts by mass of methacrylic acid and 5.00 parts by mass of methacrylic anhydride were added together with 1.00 part by mass of triphenylphosphine as a catalyst, and it was maintained at 120 °C for 4 hours. The disappearance of methacrylic acid was confirmed by measuring the acid value. Through the above steps, a propylene glycol monomethyl ether solution (solid content 40 mass%) of (meth)acrylic resin (A1) was obtained.

[0210] [Synthesis Examples 2-4] (Examples 2-4)

[0211] Using the compositions shown in Table 1, otherwise, the same operations as in Synthesis Example 1 were carried out to obtain propylene glycol monomethyl ether solutions (solid content 40 mass%) of (meth)acrylic resins (A2)-(A4).

[0212] [Comparative Synthesis Example 1] (Comparative Example 1)

[0213] 32 parts by mass of propylene glycol monomethyl ether was added to a reaction apparatus equipped with a stirrer, a temperature regulator, a reflux condenser, a dropping funnel, and a thermometer, and heating under reflux was started. 20 parts by mass of n-butyl acrylate, 70 parts by mass of 2-ethylhexyl acrylate, and 10 parts by mass of acrylic acid were mixed to prepare a monomer mixture. The monomer mixture containing 0.10 part by mass of 2,2'-azobis(isobutyronitrile) as a polymerization initiator was added dropwise to the reaction apparatus. After the addition was completed, it was maintained at 85 °C for 4 hours. Then, the reaction temperature was raised to 120 °C, 20.00 parts by mass of cyclohexylmethyl 3,4-epoxycyclohexene carboxylate was added together with 1.00 part by mass of triphenylphosphine as a catalyst, and it was maintained at 120 °C for 4 hours. Through the above steps, a propylene glycol monomethyl ether solution (solid content 40 mass%) of (meth)acrylic resin (cA1) was obtained.

[0214] [Comparative Synthesis Example 2](Comparative Example 2)

[0215] 32 parts by mass of ethyl acetate was added to a reaction apparatus equipped with a stirrer, a temperature regulator, a reflux condenser, a dropping funnel, and a thermometer, and heating under reflux was started. 20 parts by mass of methyl acrylate, 12 parts by mass of n-butyl acrylate, 50 parts by mass of 2-ethylhexyl acrylate, and 18 parts by mass of 2-hydroxyethyl acrylate were mixed to prepare a monomer mixture. The monomer mixture containing 0.10 part by mass of 2,2'-azobis(isobutyronitrile) as a polymerization initiator was dropped into the reaction apparatus. After completion of the dropping, the mixture was kept under heating under reflux for 4 hours. Then, the reaction temperature was lowered to 60°C, and a mixture of 20.00 parts by mass of 2-isocyanatoethyl methacrylate and 0.10 part by mass of dibutyltin dilaurate as a urethanization catalyst was dropped. After completion of the dropping, the reaction system was kept at 60°C for 4 hours to allow the isocyanate groups to disappear. Through the above steps, an ethyl acetate solution (solid content: 40 mass%) of a (meth)acrylic resin (cA2) was obtained.

[0216]

[0217] The raw materials for preparing the adhesive composition are shown below.

[0218] Photoinitiator:

[0219] TPO: 2,4,6-trimethylbenzoyl diphenylphosphine oxide (manufactured by IGM, trade name: Omnirad TPO)

[0220] Crosslinking agent (C)

[0221] L-45E: Toluene diisocyanate adduct of trimethylolpropane (manufactured by Tosoh Corporation, trade name: Coronate L-45E),

[0222] [Preparation of Adhesive Composition]

[0223] Ethyl acetate as a diluting solvent was added to the solutions containing the (meth)acrylic resins (A1) to (A4) and (cA1) and (cA2) obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Examples 1 and 2, respectively, and the contents of the (meth)acrylic resins (A1) to (A4) and (cA1) and (cA2) were adjusted to 30 mass% respectively. Using this solution, an adhesive composition was obtained by the method shown below.

[0224] In a room where actinic rays are blocked, in a plastic container, a (meth)acrylic resin, a photopolymerization initiator, and a crosslinking agent shown in Table 2 were added in the amounts (parts by mass) shown in Table 2 and stirred to obtain adhesive compositions (B1) to (B4), (cB1), and (cB2). The values of the (meth)acrylic resin in Table 2 are the solids of the solution used, that is, the amount used (parts by mass) of the (meth)acrylic resin.

[0225] [Example 5] Production of an adhesive sheet

[0226] As a separator, a silicone-based lightly peeling PET film (Toray Industries, Inc., trade name: E7006, thickness 25 μm) was prepared. For the surface subjected to the release treatment, the adhesive composition (B1) was applied using a coater so that the cured thickness reached 20 μm, and dried by heating at 100 °C for 2 minutes to form an adhesive layer. Next, as a sheet-like substrate, a PO film with a thickness of 90 μm was prepared. The PO film was pasted onto the adhesive layer using a rubber roller in such a manner that the corona-treated surface of the PO film was adhered to the exposed surface of the adhesive layer. It was cured in an oven at 40 °C for 3 days to crosslink and cure the adhesive layer, and the adhesive sheet of Example 5 was obtained.

[0227] [Examples 6 to 8 and Comparative Examples 3 and 4] Production of an adhesive sheet

[0228] Except for using the adhesive compositions described in Table 2 instead of the adhesive composition (B1), the same operations as in Example 5 were carried out to obtain the adhesive sheets of Examples 6 to 8 and Comparative Examples 3 and 4.

[0229] [Production of a dicing / chip bonding integrated film]

[0230] The cover film on one side of a chip bonding film (DAF) (FH-D25T-50, Showa Denko Materials Co., Ltd.) with a film thickness of 25 μm or 10 μm whose both sides of the adhesive layer were protected by cover films was peeled off to expose the adhesive layer. The adhesive layer was adhered to the adhesive layers of the adhesive sheets of Examples 5 to 8 and Comparative Examples 3 and 4 from which the lightly peeling PET films were peeled off to expose the adhesive layers using a rubber roller. It was left at room temperature for 1 day to obtain a dicing / chip bonding integrated film.

[0231] [Evaluation]

[0232] (1) Measurement of the adhesive force (30° peel strength) before UV irradiation

[0233] As described below, the adhesive strength of the adhesive sheet to the chip bonding film in the examples and comparative examples was evaluated by measuring the 30° peel strength. Specimens with a width of 25 mm and a length of 100 mm were cut from the dicing / chip bonding integrated film. The cover film on the side of the dicing / chip bonding integrated film where the adhesive sheet was not pasted was peeled off, and the adhesive layer was pasted onto a polycarbonate plate using double-sided tape to obtain a sample for measuring the adhesive strength. A tensile testing machine (VPA-H200, Kyowa Interface Science Co., Ltd.) was used to measure the peel strength of the adhesive sheet from the chip bonding film. The measurement conditions were set as a peel angle of 30° and a tensile speed of 600 mm / min. It should be noted that the storage of the specimens and the measurement of the peel strength were carried out in an environment of 23°C and a relative humidity of 40%. The results are shown in Table 2.

[0234] (2) Measurement of Adhesive Strength (30° Peel Strength) after UV Irradiation

[0235] For the dicing / chip bonding integrated film, ultraviolet light (UV) was irradiated from the surface on the substrate side of the adhesive sheet under the condition of an irradiation dose of 300 mJ / cm 2 to obtain a sample for measuring the adhesive strength after UV irradiation. The UV irradiation was performed using a conveyor belt type ultraviolet irradiation device (Eye Graphics Co., Ltd., 2KW lamp, 80W / cm). Then, the peel strength of the adhesive sheet from the chip bonding film was measured using the same method as that for the measurement of the adhesive strength (30° peel strength) before UV irradiation. The results are shown in Table 2.

[0236] (3) Pick-up Property

[0237] (i) Preparation of Specimens for Evaluating Pick-up Property

[0238] A protective tape (BG tape) was pasted on the surface of a silicon wafer (diameter: 12 inches, thickness: 775 μm). Then, the silicon wafer was subjected to stealth dicing. That is, by irradiating the surface (back surface) of the silicon wafer on the side opposite to the side where the BG tape was pasted with a laser under the following conditions, a modified layer was formed inside the silicon wafer.

[0239] <Stealth Dicing Conditions>

[0240] · Stealth dicing device: DFL7361 (DISCO Corporation)

[0241] · Laser oscillator model: Q-switch semiconductor-excited solid-state laser

[0242] · Wavelength: 1342 nm

[0243] · Frequency: 90 kHz

[0244] · Output power: 1.7 W

[0245] · Number of passes: 2

[0246] · Chip size: 10 mm × 10 mm

[0247] · Cutting speed: 700 mm / s

[0248] The silicon wafer after invisible cutting is ground to a thickness of 30 μm. Grinding is performed using a grinding and polishing apparatus (DGP8761, DISCO Corporation). The adhesive layer of the cut / chip bonding integrated film is pasted onto the ground silicon wafer with the surface on the substrate side of the adhesive sheet facing the cutting ring under the following conditions. Then, the BG tape is peeled off from the surface of the silicon wafer.

[0249] <Pasting conditions>

[0250] · Pasting apparatus: DFM2800 (DISCO Corporation)

[0251] · Pasting temperature: 70 °C

[0252] · Pasting speed: 10 mm / s

[0253] · Pasting tension level: Level 6

[0254] Next, cooling expansion is performed using a chip dicing machine (DDS2300, DISCO Corporation) under the following conditions. Then, the substrate layer (PO film) of the cut / chip bonding integrated film is heat-shrunk under the following conditions. Through these processes, the silicon wafer and the adhesive layer are singulated into multiple chips with adhesive sheets (size 10 mm × 10 mm).

[0255] <Cooling expansion conditions>

[0256] · Cooling temperature: -15 °C

[0257] · Cooling time: 120 seconds

[0258] · Lift amount: 12 mm

[0259] · Lift speed: 200 mm / s

[0260] · Holding time after lift: 3 seconds

[0261] <Heat shrinkage conditions>

[0262] · Heater temperature: 220 °C

[0263] · Heater rotation speed: 5 ° / s

[0264] · Lift amount: 8 mm

[0265] · Tape cooling waiting time: 10 seconds

[0266] After monolithicizing the silicon wafer and the adhesive layer, the adhesive layer is irradiated with ultraviolet light from the surface on the base material side of the adhesive sheet under the following conditions. Thereby, the adhesive layer is cured and the adhesive force to the adhesive layer is reduced.

[0267] <Ultraviolet irradiation conditions>

[0268] ·Illuminance of ultraviolet light: 100 mW / cm 2

[0269] ·Exposure amount of ultraviolet light: 150 mJ / cm 2

[0270] (Pick-up evaluation)

[0271] Pick up 100 chips with adhesive sheets under the following conditions and evaluate them according to the following criteria. The results are shown in Table 2.

[0272] <Pick-up conditions>

[0273] ·Chip bonding device: DB-830P (Fast Forward Technology Co., Ltd.)

[0274] ·Ejector pin: EJECTOR NEEDLE SEN2-83-05 (diameter: 0.7 mm, tip shape: hemisphere with a radius of 350 μm, Micro Mechanics Co., Ltd.)

[0275] ·Ejection height: 250 μm

[0276] ·Ejection speed: 1 mm / second

[0277] ·Number of ejector pins: 9

[0278] <Evaluation criteria>

[0279] A: The success rate of pick-up is 100%.

[0280] B: The success rate of pick-up is 80% or more and less than 100%.

[0281] C: The success rate of pick-up is 60% or more and less than 80%.

[0282]

[0283] The adhesiveness before UV irradiation in Examples 5 to 8 was good, the adhesiveness decreased sufficiently after UV irradiation, and the pick-up property was good, being A. On the other hand, in Comparative Example 3, the adhesiveness after UV irradiation did not decrease sufficiently, and the success rate of pick-up was low. It is considered that this is because the carboxyl group derived from acrylic acid in the (meth)acrylic resin used in Comparative Example 3 increased the adhesiveness to the adherend, and on the other hand, had an adverse effect on the peelability after UV irradiation. In Comparative Example 4, similarly, the adhesiveness after UV irradiation did not decrease sufficiently, and the success rate of pick-up was low. It is considered that the main reason therefor is 2-isocyanatoethyl methacrylate used in the synthesis of the (meth)acrylic resin used in Comparative Example 4. That is, it is considered that by using 2-isocyanatoethyl methacrylate in the addition reaction, a dimer as an impurity is generated, causing a phenomenon of improving the wettability of the adhesive layer to the adherend or the migration of the dimer to the adherend side. As a result, it is considered that after UV irradiation, the transferred dimer crosslinks with the (meth)acrylic resin of the adhesive layer, etc., having an adverse effect on the peelability and pick-up property after UV irradiation.

[0284] Industrial applicability

[0285] According to the present invention, a (meth)acrylic resin suitable for an adhesive composition can be provided. An adhesive layer formed from an adhesive composition produced using the (meth)acrylic resin can preferably be used as an adhesive layer of a re-peelable adhesive sheet, particularly a cutting / chip bonding integrated film.

Claims

1. A (meth)acrylic resin which contains structural units of the following formulas (1) to (3) and optionally contains structural units of the following formula (4). In formula (1), R 1 represents a hydrogen atom or a methyl group, and R 2 represents an alkyl group having 1 to 20 carbon atoms; in formula (2), R 3 represents a hydrogen atom or a methyl group, and R 4 represents a group having a hydroxyl group on a carbon atom and a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on a carbon atom adjacent to the carbon atom having the hydroxyl group; in formula (3), R 5 represents a hydrogen atom or a methyl group, and R 6 represents a group having a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on a carbon atom and a residue obtained by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid on a carbon atom adjacent to the carbon atom having the residue; in formula (4), R 7 represents a hydrogen atom or a methyl group, and R 8 represents a group containing an epoxy group.

2. The (meth)acrylic resin according to claim 1, wherein the structural unit of formula (2) is a structural unit of the following formula (2-1-1) or the following formula (2-1-2), and the structural unit of formula (3) is a structural unit of the following formula (3-1). In formula (2-1-1), R 9 represents a hydrogen atom or a methyl group, R 10 represents a divalent linking group, R 11 , R 12 , R 14 and R 15 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 13 represents a single bond or a divalent linking group, R 16 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, where R in -COOR represents an alkyl group having 1 to 6 carbon atoms; In formula (2-1-2), R 17 represents a hydrogen atom or a methyl group, R 18 represents a divalent linking group, R 19 , R 20 , R 22 and R 23 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 21 represents a single bond or a divalent linking group, R 24 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, and R in -COOR represents an alkyl group having 1 to 6 carbon atoms; In formula (3-1), R 25 represents a hydrogen atom or a methyl group, R 26 represents a divalent linking group, R 27 , R 28 , R 30 , R 31 , R 34 and R 35 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 29 and R 33 each independently represents a single bond or a divalent linking group, R 32 and R 36 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, and R in -COOR represents an alkyl group having 1 to 6 carbon atoms.

3. The (meth)acrylic resin according to claim 1, wherein the structural unit of formula (2) is a structural unit of the following formula (2-2), and the structural unit of formula (3) is a structural unit of the following formula (3-2). In formula (2-2), R 37 represents a hydrogen atom or a methyl group, R 38 represents a single bond or a divalent linking group, R 39 , R 41 and R 42 each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 40 represents a single bond or a divalent linking group, R 43 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, where R in -COOR represents an alkyl group having 1 to 6 carbon atoms, and X1 represents a saturated hydrocarbon ring; In formula (3-2), R 44 represents a hydrogen atom or a methyl group, R 45 represents a single bond or a divalent linking group, R 46 , R 48 , R 49 , R 52 and R 53 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R 47 and R 51 each independently represents a single bond or a divalent linking group, R 50 and R 54 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, -COOR or a phenyl group, wherein R in -COOR represents an alkyl group having 1 to 6 carbon atoms, and X2 represents a saturated hydrocarbon ring.

4. The (meth)acrylic resin according to any one of claims 1 to 3, wherein the vinyl unsaturated group equivalent is 350 to 4000 g / mol.

5. The (meth)acrylic resin according to any one of claims 1 to 3. Based on all the structural units of the (meth)acrylic resin, the total proportion of the structural units of formulas (2) to (4) is 1 to 50 mol%.

6. The (meth)acrylic resin according to any one of claims 1 to 3. The proportion of the total of the structural units of formulas (2) and (3) relative to the total of the structural units of formulas (2) to (4) is 50 to 100 mol%.

7. The (meth)acrylic resin according to any one of claims 1 to 3, having a glass transition temperature (Tg) of -80°C to 0°C.

8. The (meth)acrylic resin according to any one of claims 1 to 3, wherein the residue after removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid is (meth)acryloyloxy.

9. The (meth)acrylic resin according to any one of claims 1 to 3, wherein each carbon atom having a hydroxyl group in formulas (2) and (3) or the residue after removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid has one or two hydrogen atoms.

10. The (meth)acrylic resin according to any one of claims 1 to 3, having a hydroxyl value of 1 to 60 mgKOH / g.

11. The (meth)acrylic resin according to any one of claims 1 to 3, having a weight average molecular weight of 100,000 to 1,000,000.

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