Adhesive composition and adhesive sheet

Abstract

The present invention provides an adhesive composition containing a (meth) acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C), wherein the (meth) acrylic resin (A) contains 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 an adhesive composition, an adhesive sheet, and an integrated dicing / die bonding film containing a (meth)acrylic resin. Background Art

[0002] Various adhesive sheets have been used in semiconductor manufacturing processes. Specifically, there are protective sheets (back grinding tapes) used to protect semiconductor wafers during back grinding (back grinding) and fixing sheets (dicing tapes) used in the process of cutting (dicing) semiconductor wafers into small components. These adhesive sheets are removable adhesive sheets that are attached to the semiconductor wafer as an adherend and are peeled off from the adherend after the specified processing steps are completed.

[0003] As the adhesive composition used in the adhesive layer of a removable adhesive sheet, it is known to have a composition comprising a resin having an ethylenically unsaturated group that can be cured by UV (ultraviolet) curing introduced into the side chain of a (meth) acrylic resin. Such an adhesive composition is cured by UV irradiation with a cross-linking reaction, and adhesion is reduced. For example, a method for manufacturing an adhesive sheet is described in patent document 1 (Japanese Patent Application Publication No. 2014-62210), which comprises reacting a compound having an isocyanate group such as a (meth) acrylic polymer having two or more hydroxyl groups in a side chain with (meth) acrylic acid 2-isocyanatoethyl ester in the presence of a first catalyst to form a process for forming a (meth) acrylic polymer having a carbamate bond.

[0004] Prior art literature

[0005] Patent Literature

[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] In a removable adhesive sheet, the dicing tape constituting a dicing / chip bonding integrated film that integrates the dicing tape and the chip bonding agent (adhesive layer) is also required to have high adhesion to the adhesive layer and the ability to be easily peeled off from the adhesive layer without residual adhesive after UV irradiation, which are characteristics that are not required for other removable adhesive sheets. However, as in Patent Document 1, when a compound having an isocyanate group is used to introduce an ethylenically unsaturated group into the side chain of a (meth) acrylic resin, a dimer of the isocyanate compound is generated during the synthesis to form an impurity, and there is a problem that the dimer has an adverse effect on the reduction of the adhesion after UV (ultraviolet) curing. As a result, the peelability from the adhesive layer after the processing step is completed is insufficient, and therefore it is expected to be improved. The present disclosure provides an adhesive composition, which has sufficient adhesion to an adherend such as an adhesive layer, and the adhesion is sufficiently reduced due to UV irradiation after the processing step is completed, and has improved peelability from the adherend.

[0009] Means of solving the problem

[0010] The present disclosure includes the following aspects.

[0011] [1] An adhesive composition comprising a (meth)acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C), wherein the (meth)acrylic resin (A) contains structural units of the following formulas (1) to (3), and optionally the following formula (4);

[0012]

[0013] 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, wherein R 3 represents a hydrogen atom or a methyl group, 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, R 6 represents a group having 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, wherein R 7 represents a hydrogen atom or a methyl group, R 8 It represents an epoxy group-containing group.

[0014] [2] The adhesive composition according to [1], wherein the (meth)acrylic resin (A) has an ethylenically unsaturated group equivalent of 350 to 4000 g / mol.

[0015] [3] The adhesive composition according to [1] or [2], wherein the total proportion of the structural units of the formulae (2) to (4) is 1 to 50 mol% based on all the structural units of the (meth)acrylic resin (A).

[0016] [4] The adhesive composition according to any one of [1] to [3], wherein in the (meth)acrylic resin (A), the total proportion of the structural units of formulae (2) and (3) relative to the total of the structural units of formulae (2) to (4) is 50 to 100 mol%.

[0017] [5] The adhesive composition according to any one of [1] to [4], wherein the (meth)acrylic resin (A) has a glass transition temperature (Tg) of -80°C to 0°C.

[0018] [6] The adhesive composition according to any one of [1] to [5], wherein the residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid is a (meth)acryloyloxy group.

[0019] [7] The adhesive composition according to any one of [1] to [6], wherein each carbon atom of the residue having a hydroxyl group or a carboxyl group of an unsaturated monocarboxylic acid after removing a hydrogen atom in the formulas (2) and (3) has one or two hydrogen atoms.

[0020] [8] The adhesive composition according to any one of [1] to [7], wherein the (meth)acrylic resin (A) has a hydroxyl value of 1 to 60 mgKOH / g.

[0021] [9] The adhesive composition according to any one of [1] to [8], wherein the (meth)acrylic resin (A) has a weight average molecular weight of 100,000 to 1,000,000.

[0022]

[10] The adhesive composition according to any one of [1] to [9], wherein the crosslinking agent (C) is a polyisocyanate.

[0023]

[11] An ultraviolet curable adhesive layer, which is a thermally cured product of the adhesive composition according to any one of [1] to

[10] .

[0024]

[12] A pressure-sensitive adhesive sheet comprising the ultraviolet-curable pressure-sensitive adhesive layer according to

[11] and a base material layer.

[0025]

[13] A dicing / die bonding integrated film comprising a base material layer, the ultraviolet curable adhesive layer described in

[11] , and an adhesive layer laminated in this order.

[0026]

[14] A method for manufacturing a semiconductor device, comprising the step of performing semiconductor dicing using the dicing / die bonding integrated film described in

[13] .

[0027] Effects of the Invention

[0028] According to the present disclosure, a PSA composition having excellent adhesive strength and excellent releasability when the PSA sheet is peeled from an adherend after UV irradiation can be provided. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below.

[0030] In this specification, when “to” is used for a numerical range, the numerical values at both ends are respectively an upper limit and a lower limit, and are included in the numerical range.

[0031] In this specification, (meth)acrylic refers to "acrylic" or "methacrylic." (meth)acrylate refers to "acrylate" or "methacrylate," and (meth)acryloyloxy refers to "acryloyloxy" or "methacryloyloxy."

[0032] In this specification, the "structural unit" refers to 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.

[0033] <Adhesive Composition>

[0034] The adhesive composition according to one embodiment includes a (meth)acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C).

[0035] <(Meth)acrylic Resin (A)>

[0036] The (meth)acrylic resin (A) according to one embodiment contains structural units of the following formulae (1) to (3) and optionally the following formula (4).

[0037]

[0038] 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, wherein R 3 represents a hydrogen atom or a methyl group, 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, R 6represents a group having 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, wherein R 7 represents a hydrogen atom or a methyl group, R 8 It represents an epoxy group-containing group.

[0039] [Structural unit of formula (1)]

[0040] The (meth)acrylic resin (A) contains a structural unit of the following formula (1). The structural unit of formula (1) contributes to imparting adhesive strength.

[0041]

[0042] 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. 2 It 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 unit of formula (1) may be more than one type. R of each structural unit 1 The R of each structural unit can be different. 2 They may also be different.

[0043] Specific examples of the monomer forming the structural unit of formula (1) include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and decyl (meth)acrylate. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate are preferred from the perspectives of ease of synthesis of the (meth)acrylic resin (A), adhesive properties, and releasability after UV irradiation. 2-ethylhexyl (meth)acrylate is more preferred from the perspective of releasability after UV irradiation.

[0044] The monomers forming the structural unit of formula (1) may be used alone or in combination of two or more.

[0045] The proportion of the structural unit of formula (1) relative to the total structural units of the (meth)acrylic resin (A) is preferably 50 to 99 mol%, more preferably 60 to 98 mol%, and even more preferably 70 to 95 mol%. When the structural unit of formula (1) accounts for 50 mol% or more, sufficient adhesion to the adherend can be achieved before UV irradiation. When the structural unit of formula (1) accounts for 99 mol% or less, sufficient proportions of the structural units of formulae (2) and (3) below can be ensured, thereby achieving sufficient photocurability as an adhesive composition and achieving desired releasability after UV irradiation.

[0046] [Structural unit of formula (2)]

[0047] The (meth)acrylic resin (A) contains a structural unit of the following formula (2). Thus, the hydroxyl moiety is cross-linked with the cross-linking agent (C), and a UV-curable adhesive layer can be formed by thermal curing. Furthermore, the ethylenically unsaturated groups introduced into the side chains can impart photocurability to the adhesive composition, reducing the adhesive strength after UV irradiation and improving the peelability from the adherend.

[0048]

[0049] In formula (2), R 3 represents a hydrogen atom or a methyl group, 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. From the perspective 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 a carboxyl group of an unsaturated monocarboxylic acid preferably has one or two hydrogen atoms. The structural unit of formula (2) may be more than one. R of each structural unit 3 The R of each structural unit can be different. 4 They may also be different.

[0050] As a component of R 4 Specific examples of the residue formed by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid include the residue formed by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid such as (meth)acrylic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, crotonic acid, propiolic acid, cinnamic acid, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, monomethyl fumarate, and monoethyl itaconate. Among them, the residue formed by removing a hydrogen atom from the carboxyl group of (meth)acrylic acid, i.e., the (meth)acryloyloxy group, is preferred from the perspective of ease of synthesis of the (meth)acrylic resin.

[0051] Specific examples of the structural unit of formula (2) include structural units of the following formula (2-1-1) and the following formula (2-1-2).

[0052]

[0053] 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 (wherein R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group.

[0054]

[0055] 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.

[0056] In formula (2-1-1), R 10 The divalent linking group represented by the present invention includes an alkylene group having 1 to 20 carbon atoms, -R 55 -OR 56 -(where R 55 and R 56 Each independently represents an alkylene group having 1 to 10 carbon atoms) etc. 10 The alkylene group having 1 to 20 carbon atoms represented by , includes methylene, ethylene, butylene, etc. Among them, alkylene groups having 1 to 10 carbon atoms are preferred from the viewpoint of adhesion to the adherend, and methylene and ethylene are more preferred. 55 and R 56 The alkylene group having 1 to 10 carbon atoms represented by includes methylene, ethylene, butylene, etc. Among them, an alkylene group having 1 to 6 carbon atoms is preferred from the viewpoint of photocurability. 10, preferably an alkylene group having 1 to 10 carbon atoms, and -R 55 -OR 56 -, more preferably methylene, ethylene, and -(CH2) n -O-(CH2) y -(n is an integer of 1 to 6, and y is an integer of 1 to 2). n is preferably an integer of 2 to 6, and y is preferably an integer of 1 to 2.

[0057] In formula (2-1-1), 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. 11 、R 12 、R 14 and R 15 The alkyl group having 1 to 6 carbon atoms represented by is methyl. From the viewpoint of heat resistance, R 11 and R 12 From the perspective of heat resistance, R 14 is a hydrogen atom or a methyl group. 15 A hydrogen atom.

[0058] 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 -OR 58 -(where R 57 and R 58 each independently represents an alkylene group having 1 to 10 carbon atoms), -R 59 -CO-OR 60 -CO-、-R 61 -CO-OR 62 -(where R 59 ~R 62 Each independently represents an alkylene group having 1 to 10 carbon atoms) etc. 13 The alkylene group having 1 to 20 carbon atoms represented by R includes methylene, ethylene, butylene and the like. 13 From the viewpoint of photocurability, a single bond and an alkylene group having 1 to 6 carbon atoms are preferred, and a single bond is more preferred.

[0059] 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. 16The alkyl group having 1 to 6 carbon atoms represented by R is methyl and ethyl. 16 A hydrogen atom.

[0060] In formula (2-1-2), R 18 ~R 24 The specific examples and preferred examples are the same as those of R in formula (2-1-1) 10 ~R 16 The same respectively.

[0061] Specific examples of methods for forming a structural unit of formula (2-1-1) or formula (2-1-2) include forming a 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. The monomers forming the structural unit of formula (4-1) may be used alone or in combination of two or more, and the unsaturated monocarboxylic acids to be reacted may be used alone or in combination of two or more.

[0062] Specific examples of the structural unit of formula (2) include the structural unit of the following formula (2-2).

[0063]

[0064] 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 represents 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.

[0065] As R 38 The divalent linking group represented by the present invention includes, for example, an alkylene group having 1 to 20 carbon atoms, -R 63 -OR 64 -(where R 63 and R 64 each independently represents an alkylene group having 1 to 10 carbon atoms), -R 65 -O-(where R 65 represents an alkylene group having 1 to 10 carbon atoms), -COO-, and combinations thereof. 38The alkylene group having 1 to 20 carbon atoms includes methylene, ethylene, butylene, cyclohexylene, etc. Among them, alkylene groups having 1 to 10 carbon atoms are preferred from the perspective of adhesion to the adherend, and methylene and ethylene are more preferred. 63 and R 64 The alkylene group having 1 to 10 carbon atoms represented by includes methylene, ethylene, butylene, etc. Among them, an alkylene group having 1 to 6 carbon atoms is preferred from the viewpoint of photocurability. 65 The alkylene group having 1 to 10 carbon atoms represented by includes methylene, ethylene, butylene, etc. Among them, an alkylene group having 1 to 6 carbon atoms is preferred from the viewpoint of photocurability. 38 , preferably a single bond, an alkylene group having 1 to 10 carbon atoms, and -R 65 -O-, more preferably a single bond, methylene, ethylene, and -(CH2) m -O- (m is an integer from 1 to 3).

[0066] In formula (2-2), R 39 、R 41 and R 42 Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. 39 、R 41 and R 42 The alkyl group having 1 to 6 carbon atoms represented by is methyl. From the viewpoint of heat resistance, R 39 is a hydrogen atom. From the perspective of heat resistance, R 41 is a hydrogen atom or a methyl group. 42 A hydrogen atom.

[0067] In formula (2-2), R 40 and R 43 The specific examples and preferred examples are the same as those of R in formula (2-1-1) 13 and R 16 The same respectively.

[0068] In formula (2-2), X1 represents a saturated hydrocarbon ring. The number of carbon atoms in the saturated hydrocarbon ring is preferably 4 to 20, more preferably 5 to 10, and even more preferably 5 to 8. The saturated hydrocarbon ring may be a monocyclic ring or a condensed ring. Preferred saturated hydrocarbon rings include cyclohexyl, cyclopentyl, and tricyclodecanyl.

[0069] From the viewpoint of heat resistance, the structural unit of formula (2) preferably includes a structural unit of formula (2-2).

[0070] Specifically, a method for forming a structural unit of formula (2-2) includes introducing a structural unit of formula (4-2) below, 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 forming the structural unit of formula (4-2) may be used alone or in combination of two or more, and the unsaturated monocarboxylic acids to be reacted may be used alone or in combination of two or more.

[0071] The proportion of the structural unit of formula (2) relative to the total structural units of the (meth)acrylic resin (A) is preferably 0.1 to 40 mol%, more preferably 0.5 to 18 mol%, and even more preferably 1 to 15 mol%. When the structural unit of formula (2) is 0.1 mol% or more, the thermosetting property of the adhesive composition is sufficient. As a result, sufficient adhesive strength to the adherend and cohesive strength of the adhesive composition 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 good adhesive strength can be obtained.

[0072] [Structural unit of formula (3)]

[0073] The (meth)acrylic resin (A) contains a structural unit of the following formula (3). The two ethylenically unsaturated groups introduced into the side chain can impart photocurability to the adhesive composition, thereby reducing the adhesive strength of the adhesive composition after UV irradiation and improving the peelability from the adherend.

[0074]

[0075] In formula (3), R 5 represents a hydrogen atom or a methyl group, R 6 represents a group having a residue after removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid on a carbon atom, and a residue after removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid on a carbon atom adjacent to the carbon atom. In view of heat resistance, each carbon atom having a residue after removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid preferably has one or two hydrogen atoms. The structural unit of formula (3) may be more than one. R of each structural unit 5 The R of each structural unit can be different. 6 They may also be different.

[0076] As a component of R 6Specific examples of the residue formed by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid include the residue formed by removing a hydrogen atom from the carboxyl group of an unsaturated monocarboxylic acid such as (meth)acrylic acid, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, crotonic acid, propiolic acid, cinnamic acid, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, monomethyl fumarate, and monoethyl itaconate. Among them, the residue formed by removing a hydrogen atom from the carboxyl group of (meth)acrylic acid, i.e., the (meth)acryloyloxy group, is preferred from the perspective of ease of synthesis of the (meth)acrylic resin.

[0077] Specific examples of the structural unit of formula (3) include the structural unit of the following formula (3-1).

[0078]

[0079] 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 (wherein R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group.

[0080] In formula (3-1), R 26 ~R 32 The specific examples and preferred examples are the same as those of R in formula (2-1-1) 10 ~R 16 In formula (3-1), R 33 ~R 36 The specific examples and preferred examples are the same as those of R in formula (2-1) 13 ~R 16 The same respectively.

[0081] Specifically, a method for forming a structural unit of formula (3-1) includes reacting the hydroxyl group of the structural unit of formula (2-1-1) or formula (2-1-2) with an unsaturated monocarboxylic acid anhydride to introduce a residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid. The unsaturated monocarboxylic acid anhydride to be reacted may be used alone or in combination of two or more. Examples of the unsaturated monocarboxylic acid anhydride include (meth)acrylic anhydride.

[0082] Specific examples of the structural unit of formula (3) include the structural unit of the following formula (3-2).

[0083]

[0084] 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 (wherein R represents an alkyl group having 1 to 6 carbon atoms), or a phenyl group, and X2 represents a saturated hydrocarbon ring.

[0085] In formula (3-2), R 45 ~R 50 The specific examples and preferred examples are the same as those of R in formula (2-2) 38 ~R 43 In formula (3-2), R 51 ~R 54 The specific examples and preferred examples are the same as those of R in formula (2-2) 40 ~R 43 In formula (3-2), specific examples and preferred examples of X2 are the same as those of X1 in formula (2-2).

[0086] Specifically, a method for forming a structural unit of formula (3-2) includes reacting the hydroxyl group of the structural unit of formula (2-2) with an unsaturated monocarboxylic acid anhydride to introduce a residue obtained by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid. The unsaturated monocarboxylic acid anhydride to be reacted may be used alone or in combination of two or more. Examples of the unsaturated monocarboxylic acid anhydride include (meth)acrylic anhydride.

[0087] The proportion of the structural unit of formula (3) relative to the total structural units of the (meth)acrylic resin (A) is preferably 0.1 to 30 mol%, more preferably 0.2 to 28 mol%, and even more preferably 0.5 to 26 mol%. When the structural unit of formula (3) is 0.1 mol% or more, the photocurability can be sufficiently improved. As a result, the adhesive strength of the adhesive composition can be sufficiently reduced during UV irradiation, and the peelability from the adherend is improved. When the structural unit of formula (3) is 30 mol% or less, the adhesive strength is good.

[0088] [Structural unit of formula (4)]

[0089] The (meth)acrylic resin (A) may contain a structural unit of the following formula (4). To reduce residual monomers during the synthesis of the (meth)acrylic resin (A), namely, residual unsaturated monocarboxylic acids and unsaturated monocarboxylic anhydrides used to introduce the structural units of the above formulas (2) and (3), it is preferred to contain a certain amount of the structural unit of the following formula (4). On the other hand, to reduce the deterioration of the adhesive composition over time, it is preferred to minimize the content of the structural unit of formula (4).

[0090]

[0091] In formula (4), R 7 represents a hydrogen atom or a methyl group, R 8 Represents a group containing an epoxy group. The structural unit of formula (4) may be more than one. R of each structural unit 7 The R of each structural unit can be different. 8 They may also be different.

[0092] Specific examples of the structural unit of formula (4) include structural units of the following formula (4-1) and the following formula (4-2).

[0093]

[0094] 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 represents 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, R 72 represents an alicyclic epoxy group.

[0095] In formula (4-1), R 67 、R 68 and R 69The specific examples and preferred examples are the same as those of R in formula (2-1-1) 10 、R 11 and R 12 The same respectively.

[0096] Specific examples of monomers that form the structural unit of formula (4-1) include glycidyl (meth)acrylate and hydroxybutyl (meth)acrylate glycidyl ether. From the perspective of ease of reaction with unsaturated monocarboxylic acids when forming the structural units of formulae (2-1-1), (2-1-2), and (3-1), glycidyl (meth)acrylate and hydroxybutyl (meth)acrylate glycidyl ether are preferred.

[0097] The monomers forming the structural unit of formula (4-1) may be used alone or in combination of two or more.

[0098] In formula (4-2), R 71 The specific examples and preferred examples are the same as those of R in formula (2-2) 38 same.

[0099] In formula (4-2), R 72 represents an alicyclic epoxy group, and specific examples thereof include 3,4-epoxycyclohexyl, epoxycyclopentyl, 3,4-epoxytricyclo[5.2.1.0 2,6 ]Decylenyl, etc.

[0100] Specific examples of monomers that form the structural unit of formula (4-2) include 3,4-epoxycyclohexylmethyl (meth)acrylate (e.g., Sicromer (trademark) A200 and M100 manufactured by Daisy Corporation), (meth)acrylates having a lactone adduct of a 3,4-epoxycyclohexyl group, mono(meth)acrylates of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, epoxides of dicyclopentenyl (meth)acrylate, and epoxides of dicyclopentenyloxyethyl (meth)acrylate. Among these, 3,4-epoxycyclohexylmethyl (meth)acrylate is preferred from the perspective of ease of reaction with unsaturated monocarboxylic acids when forming the structural units of formula (2-2) and formula (3-2). Monomers that form the structural unit of formula (4-2) may be used alone or in combination of two or more.

[0101] The proportion of the structural unit of formula (4) relative to the total structural units of the (meth)acrylic resin (A) is preferably 0 to 10 mol%, more preferably 0 to 5 mol%, and even more preferably 0 to 1 mol%. When the proportion of the structural unit of formula (4) is 10 mol% or less, sufficient heat resistance and storage stability can be achieved, the adhesive strength is sufficiently reduced after UV irradiation, and peeling can be achieved without contaminating the adherend.

[0102] Based on the total structural units of the (meth)acrylic resin (A), the total proportion of the structural units of formulae (2) to (4) is preferably 1 mol% or more, more preferably 2 mol% or more, and further preferably 5 mol% or more. Based on the total structural units of the (meth)acrylic resin (A), the total proportion of the structural units of formulae (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 may be combined arbitrarily. Based on the total structural units of the (meth)acrylic resin (A), the total proportion of the structural units of formulae (2) to (4) is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, and further preferably 5 to 30 mol%. If the total proportion of the structural units of formulae (2) to (4) is 1 mol% or more, sufficient photocurability and the desired peelability after UV irradiation can be obtained. When the total proportion of the structural units of formulae (2) to (4) is 50 mol% or less, the pickup property is good.

[0103] The total proportion of the structural units of formulae (2) and (3) is preferably 50 mol% or more, more preferably 55 mol% or more, and further preferably 60 mol% or more relative to the total of the structural units of formulae (2) to (4). The total proportion of the structural units of formulae (2) and (3) is preferably 100 mol% or less, more preferably 95 mol% or less, and further preferably 90 mol% or less relative to the total of the structural units of formulae (2) to (4). These upper and lower limits may be combined arbitrarily. The total proportion of the structural units of formulae (2) and (3) is preferably 50 to 100 mol%, more preferably 55 to 95 mol%, and further preferably 60 to 90 mol% relative to the total of the structural units of formulae (2) to (4). If the total proportion of the structural units of formulae (2) and (3) is 50 mol% or more, sufficient photocurability and the desired peelability after UV irradiation can be obtained.

[0104] [Physical Properties of (Meth)Acrylic Resin (A)]

[0105] The ethylenically unsaturated group equivalent of (meth) acrylic resin (A) is preferably 350 g / mol or more, more preferably 400 g / mol or more, and further preferably 450 g / mol or more. The ethylenically unsaturated group equivalent of (meth) acrylic resin (A) is preferably 4000 g / mol or less, more preferably 3000 g / mol or less, and further preferably 2000 g / mol or less. These upper and lower limits can be combined arbitrarily. The ethylenically unsaturated group equivalent of (meth) acrylic resin (A) is preferably 350 to 4000 g / mol, more preferably 400 to 3000 g / mol, and further preferably 450 to 2000 g / mol. When the ethylenically unsaturated group equivalent is 350 g / mol or more, the pickup property is good. When the ethylenically unsaturated group equivalent is 4000 g / mol or less, the adhesion before UV irradiation is good.

[0106] In this specification, the ethylenically unsaturated group equivalent weight of a (meth)acrylic resin refers to the mass (g / mol) of the (meth)acrylic resin per 1 mol of ethylenically unsaturated bonds. In one embodiment, the ethylenically unsaturated group equivalent weight of a (meth)acrylic resin is a calculated value based on the charge amount, assuming 100% reaction of each raw material used in the production of the (meth)acrylic resin. The ethylenically unsaturated group equivalent weight of a (meth)acrylic resin can be calculated based on the amount of halogen bonds to the (meth)acrylic resin. The amount of halogen bonds to the (meth)acrylic resin can be evaluated in accordance with JIS K 0070:1992.

[0107] The glass transition temperature (Tg) of the (meth)acrylic resin (A) 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 (A) is preferably 0°C or lower, more preferably -10°C or lower, and further preferably -20°C or lower. These upper and lower limits may be combined arbitrarily. The glass transition temperature (Tg) of the (meth)acrylic resin (A) 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 pickup property is good. If the glass transition temperature is 0°C or lower, the adhesion before UV irradiation is good.

[0108] In this specification, "glass transition temperature (Tg)" refers to the endothermic onset temperature due to the glass transition observed by differential scanning calorimetry (DSC) of a 10 mg sample at a heating rate of 10°C / min from -100°C to 200°C. If two or more endothermic onset temperatures are observed, Tg is the simple average of these two or more endothermic onset temperatures.

[0109] The weight average molecular weight of the (meth)acrylic resin (A) is preferably 100,000 or more, more preferably 200,000 or more, and further preferably 300,000 or more. The weight average molecular weight of the (meth)acrylic resin (A) is preferably 1000,000 or less, more preferably 900,000 or less, and further preferably 800,000 or less. These upper and lower limits may be combined arbitrarily. The weight average molecular weight of the (meth)acrylic resin (A) is preferably 100,000 to 1000,000, 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 more, the cohesion before UV irradiation is good. If the weight average molecular weight is 1000,000 or less, the workability during coating is good.

[0110] In this specification, the "weight average molecular weight" is a value determined by measuring at room temperature (23° C.) using gel permeation chromatography (GPC) under the following conditions and using a standard polystyrene calibration curve.

[0111] Device: Shodex (trademark) GPC-101 (Showa Denko K.K.)

[0112] Column: Shodex (trademark) LF-804 (Showa Denko K.K.)

[0113] Column temperature: 40°C

[0114] Sample: 0.2 mass% tetrahydrofuran solution of the sample

[0115] Flow rate: 1mL / min

[0116] Eluent: tetrahydrofuran

[0117] Detector: Shodex (trademark) RI-71S (Showa Denko K.K.)

[0118] The hydroxyl value of the (meth)acrylic resin (A) 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 (A) 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 limits may be combined arbitrarily. The hydroxyl value of the (meth)acrylic resin (A) 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 (C). When the hydroxyl value is 60 mgKOH / g or less, the peelability after UV irradiation is good.

[0119] In this specification, the hydroxyl value is the mass (mg) of potassium hydroxide required to neutralize acetic acid bonded to the hydroxyl groups when 1 g of the resin is acetylated according to JIS K 0070:1992.

[0120] [Method for producing (meth)acrylic resin (A)]

[0121] The (meth)acrylic resin (A) can be obtained, for example, by the following steps:

[0122] (i) polymerizing a monomer having an epoxy group with other monomers to obtain a copolymer;

[0123] step (ii) of adding an unsaturated monocarboxylic acid to the epoxy group of the copolymer; and

[0124] A step (iii) of adding unsaturated monocarboxylic acid anhydride to the hydroxyl group generated by the ring-opening of the epoxy group in the addition reaction of the step (ii) and simultaneously adding unsaturated monocarboxylic acid derived from the free unsaturated monocarboxylic acid anhydride to the remaining epoxy group.

[0125] [Step (i) of polymerizing monomers to obtain a copolymer]

[0126] 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 reaction in steps (ii) and (iii), solution polymerization is preferably used from the perspective of the ease of the reaction.

[0127] As the monomer, an alkyl (meth)acrylate, an epoxy group-containing (meth)acrylate, and optionally other monomers can be used.

[0128] (Alkyl (meth)acrylate)

[0129] As the alkyl (meth)acrylate, there is no particular limitation as long as it is a monomer that forms a structural unit of formula (1). As specific examples thereof, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, etc. can be cited. Among them, from the perspective of the ease of synthesis of the (meth)acrylic resin (A), as well as the adhesive properties and the peelability after UV irradiation, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred, and from the perspective of the peelability after UV irradiation, 2-ethylhexyl (meth)acrylate is more preferred. The alkyl (meth)acrylate can be used alone or in combination of two or more.

[0130] (Epoxy-containing (meth)acrylate)

[0131] As the (meth)acrylate containing an epoxy group, there is no particular limitation as long as it is a monomer that forms a structural unit of formula (4). Specific examples thereof include glycidyl (meth)acrylate, hydroxybutyl (meth)acrylate glycidyl ether, 3,4-epoxycyclohexylmethyl (meth)acrylate (for example, Sicromer (trademark) A200 and M100 manufactured by Daicel Co., Ltd.), (meth)acrylate having a lactone adduct of 3,4-epoxycyclohexyl group, mono(meth)acrylate of 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, epoxide of dicyclopentenyl (meth)acrylate, epoxide of dicyclopentenyloxyethyl (meth)acrylate, etc. Among them, glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, and hydroxybutyl (meth)acrylate glycidyl ether are preferred from the perspective of ease of reaction with unsaturated monocarboxylic acid. The epoxy group-containing (meth)acrylate may be used alone or in combination of two or more.

[0132] (Other monomers)

[0133] The other monomers are not particularly limited as long as they do not have a carboxyl group, form a structural unit other than those of formulae (1) to (4), and are copolymerizable with the aforementioned alkyl (meth)acrylates and epoxy-containing (meth)acrylates. Specific examples include alicyclic (meth)acrylates, aromatic ring-containing (meth)acrylates, hydroxyl-containing (meth)acrylates, and amide-containing (meth)acrylates.

[0134] Examples of the alicyclic ring-containing (meth)acrylate include cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, norbornyl (meth)acrylate, 5-ethylnorbornyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate.

[0135] Examples of the (meth)acrylate 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, biphenyloxyethyl (meth)acrylate, naphthyl (meth)acrylate, and anthracene (meth)acrylate.

[0136] Examples of the hydroxyl group-containing (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate.

[0137] Examples of the amide group-containing (meth)acrylate include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, and anthracenyl(meth)acrylamide.

[0138] The content of the alkyl (meth)acrylate in all monomers is preferably 50 to 99 mol %, more preferably 60 to 98 mol %, and even more preferably 70 to 95 mol %.

[0139] The content of the epoxy group-containing (meth)acrylate in all monomers is preferably 1 to 50 mol%, more preferably 2 to 40 mol%, and even more preferably 5 to 30 mol%.

[0140] (Free radical polymerization initiator)

[0141] The polymerization is preferably carried out in the presence of a free radical polymerization initiator. Examples of the free radical polymerization initiator include conventional organic free radical polymerization initiators, specifically, 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, and oil-soluble 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, and 1,1-bis(tert-butylperoxy)cyclododecane.

[0142] The radical polymerization initiator may be used alone or in combination of two or more.

[0143] The amount of the radical polymerization initiator used is preferably 0.001 to 5 parts by mass, more preferably 0.005 to 3 parts by mass, and even more preferably 0.01 to 1 part by mass, relative to 100 parts by mass of the total amount of the monomers.

[0144] (Solvent)

[0145] As the solvent used in solution polymerization, a common solvent can be used. Examples of the solvent include esters such as ethyl acetate, propyl acetate, and butyl acetate; aromatic hydrocarbons such as toluene, xylene, and benzene; aliphatic hydrocarbons such as hexane and heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone; glycols such as ethylene glycol, propylene glycol, and dipropylene glycol; glycol ethers such as methyl cellosolve, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; and glycol esters such as ethylene glycol diacetate and propylene glycol monomethyl ether acetate. These solvents can be used alone or in combination of two or more.

[0146] (Reaction Conditions)

[0147] The polymerization reaction temperature also depends on the type of free radical polymerization initiator used, but is generally 30°C to 130°C, preferably 40°C to 120°C, and more preferably 50°C to 110°C. A polymerization temperature of 30°C or higher allows for a sufficient reaction rate. A polymerization temperature of 130°C or lower reduces the risk during production.

[0148] The polymerization reaction time also depends on the type of monomers and free radical polymerization initiator used, and is generally 3 to 30 hours, preferably 4 to 20 hours, and more preferably 5 to 15 hours. If the reaction time is 3 hours or longer, a copolymer can be produced from the monomers with an appropriate degree of polymerization, and if the reaction time is 30 hours or shorter, production can be carried out efficiently.

[0149] [Step (ii) of adding an unsaturated monocarboxylic acid to the epoxy group of the copolymer, and step (iii) of adding an unsaturated monocarboxylic anhydride]

[0150] Steps (ii) and (iii) may be performed sequentially or simultaneously. From the perspective of operational simplicity, it is preferred that steps (ii) and (iii) be performed simultaneously.

[0151] (Unsaturated monocarboxylic acid)

[0152] For unsaturated monocarboxylic acid, as long as it is a monocarboxylic acid with an ethylenically unsaturated group, there is no particular restriction. As its specific example, (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 listed. Wherein, from the perspective of the ease of synthesis of (meth) acrylic resin (A), (meth) acrylic acid is preferred. The unsaturated monocarboxylic acid can be used alone or in combination of two or more.

[0153] (Unsaturated monocarboxylic anhydride)

[0154] There are no particular restrictions on the unsaturated monocarboxylic anhydride as long as it is a monocarboxylic anhydride having an ethylenically unsaturated group. Specific examples thereof include (meth)acrylic anhydride. The unsaturated monocarboxylic anhydride may be used alone or in combination of two or more.

[0155] The addition rate of the unsaturated monocarboxylic acid to the epoxy groups of the epoxy-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. From the perspective of 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-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-containing (meth)acrylate present in the copolymer is calculated from the feed amount.

[0156] Regarding the ratio of unsaturated monocarboxylic acid to unsaturated monocarboxylic anhydride, the unsaturated monocarboxylic acid is preferably 5 to 130 mol, more preferably 10 to 120 mol, and even more preferably 15 to 110 mol per 100 mol of the unsaturated monocarboxylic anhydride. If the unsaturated monocarboxylic acid is 130 mol or less per 100 mol of the unsaturated monocarboxylic anhydride, adhesion to the adherend is improved. If the unsaturated monocarboxylic acid is 5 mol or more per 100 mol of the unsaturated monocarboxylic anhydride, releasability after UV irradiation is improved.

[0157] (catalyst)

[0158] In the addition reaction in steps (ii) and (iii), a known catalyst may be used as needed. As the catalyst, a known catalyst may be used without particular limitation, and examples thereof include triphenylphosphine, tri(p-tolyl)phosphine, and tri(2,6-dimethoxyphenyl)phosphine. The catalyst may be used alone or in combination of two or more.

[0159] When a catalyst is used, the amount of the catalyst used is preferably 2.5 to 10 mol, more preferably 3.0 to 9.0 mol, and even more preferably 3.5 to 8.0 mol per 100 mol of the epoxy-containing (meth)acrylate used in the production of the copolymer. When the amount of the catalyst used is 2.5 mol or more, the addition reaction can be accelerated. On the other hand, when the amount of the catalyst used is 10 mol or less, gelation during the addition reaction can be suppressed.

[0160] (Polymerization Inhibitor)

[0161] In the addition reaction in steps (ii) and (iii), a known polymerization inhibitor may be used as needed. As the polymerization inhibitor, a known polymerization inhibitor may be used without particular limitation, and examples thereof include 4-methoxyphenol, hydroquinone, p-hydroxyanisole, 2,6-di-tert-butylphenol, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), and phenothiazine. The polymerization inhibitor may be used alone or in combination of two or more.

[0162] When a polymerization inhibitor is used, the amount used is preferably 0.005 to 5 parts by mass, more preferably 0.03 to 3 parts by mass, and even more preferably 0.05 to 1.5 parts by mass, relative to 100 parts by mass of the copolymer. When the amount of the polymerization inhibitor is 0.005 parts by mass or greater, gelation during the addition reaction can be prevented. On the other hand, when the amount of the polymerization inhibitor is 5 parts by mass or less, sufficient exposure sensitivity of the (meth)acrylic resin (A) can be achieved during UV irradiation.

[0163] (Solvent)

[0164] As the solvent, a common solvent can be used. As the solvent, for example, the same solvent as that used in the solution polymerization of step (i) can be used. Alcohols such as toluene or 1-methoxy-2-propanol that easily undergo chain transfer reactions can also be used. The solvent can be used alone or in combination of two or more.

[0165] (Reaction Conditions)

[0166] The addition reaction temperature is preferably 25°C to 130°C, particularly preferably 40°C to 120°C. A temperature of 25°C or higher allows for a sufficient reaction rate. A temperature of 130°C or lower prevents crosslinking of double bonds due to thermal radical polymerization, thereby preventing the formation of a gel. The addition reaction time is preferably 2 to 24 hours, more preferably 2 to 12 hours.

[0167] During the addition reaction, a gas having a polymerization inhibitory effect may be introduced into the reaction system. By introducing a gas having a polymerization inhibitory effect into the reaction system, gelation during the addition reaction can be prevented.

[0168] Examples of the gas having a polymerization inhibitory effect include gases containing oxygen to a degree that does not reach the explosion range of substances in the system, such as air.

[0169] It is more preferable to use a gas having a polymerization inhibitory effect and a polymerization inhibitor in combination, because this allows the amount of the polymerization inhibitor to be used to be reduced or the polymerization inhibitory effect to be enhanced.

[0170] <Photopolymerization initiator (B)>

[0171] Examples of the photopolymerization initiator (B) include benzophenone, benzyl, benzoin, ω-bromoacetophenone, chloroacetone, acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzoin methyl ether, benzyl alcohol, benzophenone ... Carbonyl photopolymerization initiators such as benzoin isobutyl ether, benzoin n-butyl ether, benzyl methyl ketone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, methyl benzoylformate, 4'-dimethylaminoacetophenone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one.

[0172] Examples of the photopolymerization initiator (B) include sulfide-based photopolymerization initiators such as diphenyl disulfide, dibenzyl disulfide, tetraethylthiuram disulfide, and tetramethylammonium monosulfide; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2,4,6-trimethylbenzoylphenylethoxyphosphine 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.

[0173] Among these photopolymerization initiators (B), carbonyl photopolymerization initiators and acylphosphine oxides are preferred from the viewpoint of solubility in the adhesive composition, and at least one selected from 1-hydroxycyclohexyl phenyl ketone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide is more preferred.

[0174] The photopolymerization initiator (B) may be used alone or in combination of two or more.

[0175] The amount of the photopolymerization initiator (B) is preferably 0.1 to 5.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the (meth) acrylic resin (A). When the amount of the photopolymerization initiator (B) relative to 100 parts by mass of the (meth) acrylic resin (A) is 0.1 parts by mass or more, the adhesive composition can be cured at a sufficiently fast curing speed during UV irradiation, thereby being able to sufficiently reduce the adhesive force of the ultraviolet-curable adhesive layer after UV irradiation. When the amount of the photopolymerization initiator (B) relative to 100 parts by mass of the (meth) acrylic resin (A) is 5.0 parts by mass or less, when an adhesive sheet having an ultraviolet-curable adhesive layer as a thermosetting material of the adhesive composition is adhered to an adherend and then peeled off, the adhesive layer is not likely to remain on the adherend. When the adhesive composition is used as an adhesive layer of a dicing / die bonding integrated film, the peeling property and pick-up property of the adhesive layer after UV irradiation are good. Even if the content of the photopolymerization initiator (B) exceeds 5.0 parts by mass per 100 parts by mass of the (meth)acrylic resin (A), no effect commensurate with the content of the photopolymerization initiator (B) is observed. Therefore, by setting the content to 5.0 parts by mass or less, the pressure-sensitive adhesive composition can be produced economically.

[0176] <Crosslinking agent (C)>

[0177] The crosslinking agent (C) is a compound without an ethylenically unsaturated bond and has two or more functional groups reactive with the hydroxyl groups contained in the (meth)acrylic resin (A). The crosslinking agent (C) improves the balance between the adhesive strength before and after UV irradiation.

[0178] Examples of the functional group reactive with a hydroxyl group include an isocyanate group, an epoxy group, a carboxyl group, an acid anhydride group, and an aziridine group. From the viewpoint of reactivity, an isocyanate group and an epoxy group are preferred, and an isocyanate group is particularly preferred.

[0179] Examples of the crosslinking agent (C) include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hydrogenated toluene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isocyanurate of hexamethylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, toluene diisocyanate adduct of trimethylolpropane, trimethylolpropane, and the like. Polyisocyanates such as propane-xylene diisocyanate adducts, triphenylmethane triisocyanate, and methylenebis(4-phenylmethane) triisocyanate; 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, bisphenol A-epichlorohydrin type epoxy resins, N,N'-[1,3-phenylenebis(methylene)]bis[bis(oxiran-2-ylmethyl)amine], ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, and trimethylolpropane Polyepoxides such as alkyl triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether; tetramethylolmethane-tri-β-aziridinyl propionate, trimethylolpropane-tri-β-aziridinyl propionate, N,N'-diphenylmethane-4,4'-bis(1-aziridine carboxamide), N,N'-hexamethylene-1,6-bis(1-aziridine carboxamide), ethylene glycol-bis-[3-(2-aziridine) propionate], trimethylolpropane-tris[3-(2-aziridine) propionate] [3-(1-aziridinyl)propionate], trimethylolpropane-tris[3-(1-aziridinyl)propionate], trimethylolpropane-tris[3-(2-methyl-1-aziridinyl)propionate], tetramethylolmethane-tris[3-(2-aziridinyl)propionate], pentaerythritol-tris[3-(1-aziridinyl)propionate]; and melamine compounds such as hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentoxymethylmelamine, and hexhexyloxymethylmelamine.

[0180] Among these crosslinking agents (C), at least one selected from polyisocyanates and polyepoxy compounds is preferably used, and polyisocyanates are more preferably used, from the viewpoint of good reactivity with the (meth)acrylic resin (A).

[0181] The cross-linking agent (C) may be used alone or in combination of two or more.

[0182] The amount of the crosslinking agent (C) is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, further preferably 0.1 to 10 parts by mass, and even more preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the (meth)acrylic resin (A). If the amount of the crosslinking agent (C) is 0.1 parts by mass or more relative to 100 parts by mass of the (meth)acrylic resin (A), a crosslinked structure with the (meth)acrylic resin (A) is fully formed during heating, resulting in good strength of the ultraviolet-curable adhesive layer before UV irradiation. If the amount of the crosslinking agent (C) is 30 parts by mass or less relative to 100 parts by mass of the (meth)acrylic resin (A), the adhesive strength of the adhesive composition before UV irradiation is good.

[0183] (Other ingredients)

[0184] The pressure-sensitive adhesive composition may contain other components in addition to the (meth)acrylic resin (A), the photopolymerization initiator (B), and the crosslinking agent (C), as needed. Examples of other components include a tackifier, a solvent, and various additives.

[0185] (Thickener)

[0186] As the tackifier, any conventionally known tackifier can be used without particular limitation. Examples of the tackifier include terpene tackifying resins, phenolic tackifying resins, rosin tackifying resins, aliphatic petroleum resins, aromatic petroleum resins, copolymeric petroleum resins, alicyclic petroleum resins, xylene resins, epoxy tackifying resins, polyamide tackifying resins, ketone tackifying resins, and elastomer tackifying resins. These tackifiers can be used alone or in combination of two or more.

[0187] When a tackifier is mixed, the amount thereof added is preferably 30 parts by mass or less, more preferably 5 to 20 parts by mass, relative to 100 parts by mass of the (meth)acrylic resin (A).

[0188] (Solvent)

[0189] The solvent can be used to dilute the adhesive composition for the purpose of adjusting the viscosity of the adhesive composition. For example, when the adhesive composition is applied, the solvent can be used to adjust the viscosity of the adhesive composition to an appropriate viscosity.

[0190] Examples of the solvent include organic solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone, ethyl acetate, propyl acetate, tetrahydrofuran, dioxane, cyclohexanone, hexane, toluene, xylene, n-propanol, and isopropanol. These solvents may be used alone or in combination of two or more.

[0191] (additive)

[0192] Examples of additives include plasticizers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers such as benzotriazoles, ultraviolet absorbers, polymerization inhibitors, phosphates and other flame retardants, surfactants, and antistatic agents.

[0193] UV-curable adhesive layer

[0194] The ultraviolet curing adhesive layer is a thermosetting material of the adhesive composition. There are no particular restrictions on the conditions for thermosetting. Usually, after applying the adhesive composition, it is thermoset by heat drying and / or aging. The conditions for heat drying are usually 25 to 180°C, preferably 60 to 150°C, and generally for 1 to 20 minutes, preferably 1 to 10 minutes. By heat drying within the above range, the solvent can be removed when the adhesive composition contains a solvent. There are no particular restrictions on the conditions for aging the heat-dried sheet in an oven for a certain period of time. Usually, it is 25 to 100°C, preferably 30 to 80°C, and generally for 1 to 30 days, preferably 1 to 14 days. By aging under the above conditions, the (meth) acrylic resin (A) can be crosslinked using the crosslinking agent (C), and the gel fraction of the adhesive layer can be adjusted to the desired range.

[0195] The thickness of the ultraviolet curable pressure-sensitive adhesive layer can be appropriately adjusted depending on the intended use.

[0196] <Adhesive Sheet>

[0197] The pressure-sensitive adhesive sheet includes an ultraviolet-curable pressure-sensitive adhesive layer and a base layer.

[0198] (Base material layer)

[0199] As the substrate layer, for example, known inorganic substrates and polymer sheets and polymer films can be used without particular limitation. Specifically, crystalline polypropylene, amorphous polypropylene, high-density polyethylene, medium-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, low-density linear polyethylene, polybutene, polymethylpentene and other polyolefins, ethylene-vinyl acetate copolymers, ionomer resins, ethylene-(methyl) acrylic acid copolymers, ethylene-(methyl) acrylic ester (random, alternating) copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, polyurethanes, polyethylene terephthalate, polyesters such as polyethylene naphthalate, polycarbonate, polyimide, polyetheretherketone, polyimide, polyetherimide, polyamide, fully aromatic polyamide, polyphenylene sulfide, aromatic polyamide (paper), glass, glass cloth, fluororesin, polyvinyl chloride, polyvinylidene chloride, cellulose resin, silicone resin and mixtures formed by mixing plasticizers therein and curing materials formed by crosslinking them by electron beam irradiation.

[0200] In the case where the adhesive composition is used for cutting / chip bonding integrated film, for the substrate layer, it is preferably possible to implement an expansion process under low temperature conditions, preferably having a surface with at least one resin selected from polyethylene, polypropylene, polyethylene-polypropylene random copolymer and polyethylene-polypropylene block copolymer as the main component, and the surface is in contact with the adhesive layer. For these resins, it is also a good substrate from the aspects of Young's modulus, stress relaxation and melting point characteristics and price aspects, waste recycling after use, etc. The substrate layer can be a single layer, or it can have a multilayer structure formed by laminating layers of different materials as needed. In order to control the adhesion with the adhesive layer, the surface of the substrate layer can be subjected to surface roughening treatments such as matte treatment and corona treatment.

[0201] [Method for producing adhesive sheet]

[0202] The pressure-sensitive adhesive sheet can be produced, for example, by the method described below.

[0203] First, a PSA solution is prepared by dissolving or dispersing the PSA composition in a solvent. Alternatively, the PSA composition may be used directly as the PSA solution.

[0204] Next, an adhesive solution is applied to a substrate and, if it contains a solvent, is heated and dried to remove the solvent, thereby forming an adhesive layer. A release sheet is then attached to the adhesive layer as needed. The resulting sheet is then aged in an oven for a predetermined period of time, as needed, to form a cross-linked structure, thereby producing an adhesive sheet.

[0205] The adhesive sheet can also be manufactured by the method shown below. An adhesive solution is applied to a release sheet, and the solution is removed by heating and drying in the presence of a solvent to form an adhesive layer. Then, a release sheet having an adhesive layer is placed on a substrate with the adhesive layer facing the substrate, and the adhesive layer is transferred to the substrate. Furthermore, the obtained sheet is aged in an oven for a certain period of time as needed to form a cross-linked structure, thereby obtaining an adhesive sheet.

[0206] In the above method, a dicing die bonding film can be obtained by using a substrate having an adhesive layer as the substrate and applying an adhesive composition onto the adhesive layer, or laminating the adhesive layers so that the adhesive layers face each other. A dicing die bonding film can also be obtained by applying an adhesive composition onto an adhesive layer having a cross-linked structure formed by the above method.

[0207] As a method for coating the adhesive solution on the substrate (or release sheet), a known method can be used. Specifically, a method using a commonly used coater such as a gravure roll coater, a reverse roll coater, a lick coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, or a direct coater can be used.

[0208] There are no particular restrictions on the conditions for heat drying the applied adhesive solution, but generally, heat drying is performed at 25 to 180°C, preferably 60 to 150°C, for 1 to 20 minutes, preferably 1 to 10 minutes. By heat drying within the above range, the solvent contained in the adhesive solution can be removed. There are no particular restrictions on the conditions for aging the heat-dried sheet in an oven for a certain period of time, but generally, it is aged at 25 to 100°C, preferably 30 to 80°C, for 1 to 30 days, preferably 1 to 14 days. By aging under the above conditions, the (meth) acrylic resin (A) can be crosslinked using the crosslinking agent (C), and the gel fraction of the adhesive layer can be adjusted to the desired range.

[0209] [Applications of adhesive sheets]

[0210] For adhesive sheet, it can be used as a removable adhesive sheet, for example, when manufacturing electronic components. Specifically, the removable adhesive sheet is used in each process when manufacturing electronic components, fixes the adherend, implements various processing steps, and is irradiated with UV (ultraviolet rays) and peeled off from the adherend. Therefore, the adhesive sheet can be used as a back grinding tape, a cutting tape, etc. when processing semiconductor wafers. The adhesive sheet can also be used as a supporting tape for fragile components such as ultra-thin glass substrates, easy-to-warp components such as FPC substrates, etc. In particular, the adhesive sheet has excellent adhesion to the adhesive layer and excellent peelability after UV irradiation, and is therefore suitable for the cutting tape used when manufacturing cutting / chip bonding integrated films.

[0211] When the adhesive sheet is used as a dicing tape for a wafer, the adhesive sheet is pasted on a wafer having a plurality of components before the dicing process. Next, the wafer is cut and divided (cut) into individual components to form component chips. Then, the adhesive sheet pasted on each component chip is irradiated with UV. Thus, the UV-curable adhesive layer is irradiated with UV through the substrate of the adhesive sheet, and the unsaturated bonds in the adhesive layer form a three-dimensional cross-linked structure and solidify. As a result, the adhesive force of the adhesive layer is reduced. Then, the adhesive sheet is peeled off from each component chip.

[0212] Examples of the light source used for UV irradiation include a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, and a black light lamp.

[0213] The UV irradiation dose applied to the adhesive sheet is preferably 50 to 3,000 mJ / cm2 , more preferably 100 to 600 mJ / cm 2 If the UV radiation dose irradiated to the adhesive sheet is 50mJ / cm 2 The UV curable adhesive layer can be cured at a sufficiently fast curing speed by UV irradiation, thereby sufficiently reducing the adhesive force of the adhesive layer after UV irradiation. 2 Therefore, the UV irradiation dose to the adhesive sheet was set to 3,000 mJ / cm 2 Hereinafter, the influence of UV irradiation on the adherend can be reduced, and the pressure-sensitive adhesive sheet can be peeled off economically.

[0214] Example

[0215] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0216] The raw materials used for the synthesis of the (meth)acrylic resins (A) and (cA) are shown below.

[0217] Methyl acrylate, Nippon Shokubai Co., Ltd.

[0218] n-Butyl acrylate, Osaka Organic Chemical Industry Co., Ltd.

[0219] 2-Ethylhexyl acrylate, Osaka Organic Chemical Industry Co., Ltd.

[0220] Glycidyl methacrylate, NOF Corporation

[0221] 4-Hydroxybutyl acrylate glycidyl ether, Mitsubishi Chemical Corporation

[0222] 3,4-Epoxycyclohexylmethyl methacrylate, Daicel Co., Ltd.

[0223] Acrylic acid 3,4-epoxy tricyclic [5.2.1.0 2,6 ] Decyloxyethyl ester, acrylic acid, Nippon Shokubai Co., Ltd.

[0224] 2-hydroxyethyl acrylate, Nippon Shokubai Co., Ltd.

[0225] Methacrylic acid, Nippon Shokubai Co., Ltd.

[0226] Methacrylic anhydride, Edotron Co., Ltd.

[0227] KALENS (trademark) MOI: 2-isocyanatoethyl methacrylate, Showa Denko K.K.

[0228] Free radical polymerization initiator:

[0229] 2,2'-Azobis(isobutyronitrile), Fujifilm Wako Pure Chemical Industries, Ltd.

[0230] catalyst:

[0231] Triphenylphosphine, Hokuko Chemical Industry Co., Ltd.

[0232] Dioctyltin dilaurate, Nitto Kasei Co., Ltd.

[0233] [Synthesis example 1]

[0234] 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 and reflux were started. 90 parts by mass of 2-ethylhexyl acrylate and 10 parts by mass of glycidyl methacrylate were mixed to prepare a monomer mixture. 0.10 parts by mass of 2,2'-azobis(isobutyronitrile) as a polymerization initiator was added dropwise to the reaction apparatus. After the addition was completed, the mixture was kept at 85°C for 4 hours. Next, 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 parts by mass of triphenylphosphine as a catalyst, and the mixture was kept at 120°C for 4 hours. The disappearance of methacrylic acid was confirmed by acid value measurement. Through the above steps, a propylene glycol monomethyl ether solution of (meth)acrylic resin (A1) (solid content: 40% by mass) was obtained.

[0235] [Synthesis Examples 2 to 4]

[0236] The same operation as in Synthesis Example 1 was carried out except that the compositions shown in Table 1 were used to obtain propylene glycol monomethyl ether solutions (solid content: 40% by mass) of (meth)acrylic resins (A2) to (A4).

[0237] [Comparative Synthesis Example 1]

[0238] 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 and reflux were 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. 0.10 parts by mass of 2,2'-azobis(isobutyronitrile) was added as a polymerization initiator to the monomer mixture, which was added dropwise to the reaction apparatus. After the addition was completed, the mixture was maintained at 85°C for 4 hours. Next, the reaction temperature was raised to 120°C, and 20.00 parts by mass of 3,4-epoxycyclohexylmethyl methacrylate and 1.00 parts by mass of triphenylphosphine as a catalyst were added, and the mixture was maintained at 120°C for 4 hours. Through the above steps, a propylene glycol monomethyl ether solution of (meth)acrylic resin (cA1) (solids content: 40% by mass) was obtained.

[0239] [Comparative Synthesis Example 2]

[0240] 32 parts by mass of ethyl acetate was added to a reaction apparatus equipped with a stirrer, temperature regulator, reflux condenser, dropping funnel, and thermometer, and heating and reflux were initiated. 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, to which 0.10 parts by mass of 2,2'-azobis(isobutyronitrile) as a polymerization initiator had been added, was added dropwise to the reaction apparatus. After the addition was complete, the mixture was maintained under heating and reflux for 4 hours. Next, the reaction temperature was lowered to 60°C, and a mixture of 20.00 parts by mass of 2-isocyanatoethyl methacrylate and 0.10 parts by mass of dibutyltin dilaurate as a urethanization catalyst was added dropwise. After the addition was complete, the reaction system was maintained at 60°C for 4 hours to eliminate the isocyanate groups. Through the above steps, an ethyl acetate solution of (meth)acrylic resin (cA2) (40% solids) was obtained.

[0241]

[0242] The raw materials used to prepare the adhesive composition are shown below.

[0243] Photopolymerization initiator (B):

[0244] TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (IGM, trade name: Omnirad TPO)

[0245] Crosslinking agent (C)

[0246] L-45E: Trimethylolpropane toluene diisocyanate adduct (Tosoh Corporation, trade name: Coronato L-45E)

[0247] [Preparation of Adhesive Composition]

[0248] To 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, ethyl acetate was added as a diluent to adjust the contents of the (meth)acrylic resins (A1) to (A4) and (cA1) and (cA2) to 30% by mass. Using these solutions, pressure-sensitive adhesive compositions were obtained by the following method.

[0249] In a room shielded from active radiation, the (meth)acrylic resin (A), photopolymerization initiator (B), and crosslinking agent (C) shown in Table 2 were added to a plastic container at the contents (parts by mass) shown in Table 2, respectively, and stirred to obtain adhesive compositions (1) to (4) and (c1) and (c2). The values for (meth)acrylic resin (A) in Table 2 represent the solid content of the solution used, i.e., the amount (parts by mass) of the (meth)acrylic resin used.

[0250] [Example 1] Preparation of adhesive sheet

[0251] As a separator, a silicone-based light-peel PET film (Toyobo Co., Ltd., trade name: E7006, thickness 25 μm) was prepared. The adhesive composition (1) was applied to the surface subjected to a release treatment using an applicator so that the thickness after curing was 20 μm. The film was then heated and dried at 100°C for 2 minutes to form an adhesive layer. Next, a 90 μm thick PO film was prepared as a sheet substrate. The PO film was attached to the adhesive layer using a rubber roller so that the corona-treated surface of the PO film adhered to the exposed surface of the adhesive layer. The film was aged in an oven at 40°C for 3 days to crosslink and cure the adhesive layer, thereby obtaining the adhesive sheet of Example 1.

[0252] [Examples 2 to 4 and Comparative Examples 1 and 2] Preparation of PSA Sheets

[0253] PSA sheets of Examples 2 to 4 and Comparative Examples 1 and 2 were obtained by performing the same operation as in Example 1 except that the PSA composition described in Table 2 was used instead of PSA composition (1).

[0254] [Production of Dicing / Chip Bonding Integrated Film]

[0255] The adhesive layer was protected on both sides by cover films on a 25 μm or 10 μm thick die bonding film (DAF) (FH-D25T-50, Showa Denko Materials Co., Ltd.). The cover film on one side was peeled off to expose the adhesive layer. This adhesive layer was then bonded to the UV-curable adhesive layer of the adhesive sheets of Examples 1 to 4 and Comparative Examples 1 and 2, which had been prepared by peeling off a light-peel PET film to expose the UV-curable adhesive layer. The film was then left at room temperature for one day to produce a dicing / die bonding integrated film.

[0256] [evaluate]

[0257] (1) Determination of adhesion (30° peel strength) before UV irradiation

[0258] As described below, the adhesion of the adhesive sheet of the embodiment and the comparative example to the die bonding film (DAF) was evaluated by measuring the 30° peel strength. A sample with a width of 25 mm and a length of 100 mm was cut out from the dicing / die bonding integrated film. The cover film on the side of the dicing / die bonding integrated film where the adhesive sheet was not attached was peeled off, and the adhesive layer was attached to a polycarbonate plate using a double-sided tape to obtain a sample for adhesion measurement. The peel strength of the adhesive sheet to the die bonding film was measured using a tensile testing machine (VPA-H200, Kyowa Interface Science Co., Ltd.). The measurement conditions were set to a peeling angle of 30° and a tensile speed of 600 mm / min. It should be noted that the storage of the sample and the measurement of the peel strength were carried out in an environment with a temperature of 23°C and a relative humidity of 40%. The results are shown in Table 2.

[0259] (2) Determination of adhesion (30° peel strength) after UV irradiation

[0260] For the dicing die bonding integrated film, the irradiation dose was 300 mJ / cm from the substrate side of the adhesive sheet. 2 The adhesive sheet was irradiated with ultraviolet light (UV) under conditions of 100°F to obtain a sample for measuring the adhesive strength after UV irradiation. UV irradiation was performed using a conveyor-type UV irradiation device (Igrapix Co., Ltd., 2 kW lamp, 80 W / cm). The peel strength of the adhesive sheet to the die-bonding film was then measured using the same method as for measuring the adhesive strength (30° peel strength) before UV irradiation. The results are shown in Table 2.

[0261] (3) Pickup

[0262] (i) Preparation of Samples for Pickup Evaluation

[0263] Protective tape (BG tape) was applied to the surface of a silicon wafer (12 inches in diameter, 775 μm thick). Stealth dicing of the silicon wafer was then performed. Specifically, a modified layer was formed within the silicon wafer by irradiating the surface of the silicon wafer opposite the side with the BG tape (the back side) with a laser under the following conditions.

[0264] <Invisible cutting conditions>

[0265] ·Stealth cutting device: DFL7361 (Doshiko Co., Ltd.)

[0266] Laser oscillator type: Q-switched semiconductor excited solid-state laser

[0267] Wavelength: 1342nm

[0268] Frequency: 90kHz

[0269] Output power: 1.7W

[0270] ·Number of channels: 2

[0271] Chip size: 10mm×10mm

[0272] Cutting speed: 700mm / s

[0273] The stealth-diced silicon wafer was ground to a thickness of 30 μm using a grinding and polishing device (DGP8761, Desco Co., Ltd.). The adhesive layer of the dicing / die bonding integrated film was attached to the ground silicon wafer under the following conditions, with the substrate side of the adhesive sheet facing the dicing ring. The BG tape was then peeled from the surface of the silicon wafer.

[0274] <Paste conditions>

[0275] · Pasting device: DFM2800 (Decosco Co., Ltd.)

[0276] Paste temperature: 70℃

[0277] Pasting speed: 10mm / s

[0278] Paste tension level: Level 6

[0279] Next, a die separation machine (DDS2300, DISCO Co., Ltd.) was used to cool and expand the wafer under the following conditions. The base layer (PO film) of the dicing / die-bonding integrated film was then heat-shrunk under the following conditions. These steps separated the silicon wafer and adhesive layer into multiple chips (10 mm x 10 mm) with adhesive sheets.

[0280] Cooling expansion conditions

[0281] Cooling temperature: -15℃

[0282] Cooldown: 120 seconds

[0283] Lifting amount: 12mm

[0284] Lifting speed: 200mm / s

[0285] Holding time after lifting: 3 seconds

[0286] <Heat Shrinkage Conditions>

[0287] Heater temperature: 220℃

[0288] Heater rotation speed: 5° / second

[0289] Lifting amount: 8mm

[0290] ·Tape cooling waiting time: 10 seconds

[0291] After the silicon wafer and the adhesive layer were separated into individual pieces, the UV-curable adhesive layer was irradiated with ultraviolet light from the substrate side of the adhesive sheet under the following conditions. This cured the UV-curable adhesive layer and reduced its adhesive strength to the adhesive layer.

[0292] <Ultraviolet irradiation conditions>

[0293] Ultraviolet irradiance: 100mW / cm 2

[0294] UV exposure: 150mJ / cm 2

[0295] (Pickup performance evaluation)

[0296] 100 chips with adhesive sheets were picked up under the following conditions and evaluated according to the following criteria. The results are shown in Table 2.

[0297] Pickup Conditions

[0298] ·Die bonding device: DB-830P (Fujitsu Co., Ltd.)

[0299] Ejector pin: EJECTOR NEEDLE SEN2-83-05 (diameter: 0.7 mm, tip shape: hemisphere with a radius of 350 μm, MicroMechanics Co., Ltd.)

[0300] ·Top height: 250μm

[0301] Lifting speed: 1mm / s

[0302] Number of ejector pins: 9

[0303] <Evaluation Criteria>

[0304] A: The success rate of picking up is 100%.

[0305] B: The success rate of picking up is 80% or more and less than 100%.

[0306] C: The success rate of picking up is 60% or more and less than 80%.

[0307]

[0308] The adhesive strength of Examples 1 to 4 before UV irradiation was good, and the adhesive strength after UV irradiation was sufficiently reduced, and the pick-up property was good, which was A. On the other hand, in Comparative Example 1, the adhesive strength after UV irradiation was not sufficiently reduced, and the success rate of picking up was low. This is considered to be because the carboxyl group derived from acrylic acid in the (meth) acrylic resin used in Comparative Example 1 increased the adhesive strength to the adherend, but on the other hand, it had an adverse effect on the peelability after UV irradiation. In Comparative Example 2, the adhesive strength after UV irradiation was also not sufficiently reduced, and the success rate of picking up was low. This is considered to be mainly due to the use of 2-isocyanatoethyl methacrylate in the synthesis of the (meth) acrylic resin used in Comparative Example 2. That is, it is considered that by using 2-isocyanatoethyl methacrylate in the addition reaction, a dimer is generated as an impurity, which causes the wettability of the adhesive layer to the adherend to be improved, or the dimer migrates to the adherend side. As a result, it is considered that the transferred dimer cross-links with the (meth)acrylic resin of the pressure-sensitive adhesive layer after UV irradiation, and thus adversely affects the releasability and pickup properties after UV irradiation.

[0309] Industrial applicability

[0310] The present invention provides an adhesive composition that has sufficient adhesive strength to an adherend and, after processing, sufficiently reduces its adhesive strength by UV irradiation, thereby improving its releasability from the adherend. The adhesive layer formed from the thermosetting adhesive composition can be preferably used as a removable adhesive sheet, particularly as an adhesive layer in a dicing / die bonding integrated film.

Claims

1. An adhesive composition comprising a (meth)acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C), wherein the (meth)acrylic resin (A) contains structural units of the following formulas (1) to (3), and optionally the following formula (4); 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, wherein R 3 represents a hydrogen atom or a methyl group, 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, R 6 represents a group having 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, wherein R 7 represents a hydrogen atom or a methyl group, R 8 It represents an epoxy group-containing group. 2 . The adhesive composition according to claim 1 , wherein the (meth)acrylic resin (A) has an ethylenically unsaturated group equivalent weight of 350 g / mol to 4000 g / mol. 3 . The adhesive composition according to claim 1 , wherein the total proportion of the structural units of formulae (2) to (4) is 1 to 50 mol % based on all structural units of the (meth)acrylic resin (A).

4. The adhesive composition according to claim 1 or 2, wherein the (meth)acrylic resin (A) comprises 50 to 100 mol% of the total proportion of the structural units of formulae (2) and (3) relative to the total of the structural units of formulae (2) to (4). 5 . The adhesive composition according to claim 1 , wherein the (meth)acrylic resin (A) has a glass transition temperature (Tg) of −80° C. to 0° C. 6 . The adhesive composition according to claim 1 , wherein the residue formed by removing a hydrogen atom from the carboxyl group of the unsaturated monocarboxylic acid is a (meth)acryloyloxy group.

7. The adhesive composition according to claim 1 or 2, wherein each carbon atom having a hydroxyl group or a residue obtained by removing a hydrogen atom from a carboxyl group of an unsaturated monocarboxylic acid in the formula (2) and (3) has one or two hydrogen atoms. 8 . The adhesive composition according to claim 1 , wherein the (meth)acrylic resin (A) has a hydroxyl value of 1 to 60 mgKOH / g. 9 . The adhesive composition according to claim 1 , wherein the (meth)acrylic resin (A) has a weight average molecular weight of 100,000 to 1,000,000. 10 . The adhesive composition according to claim 1 , wherein the crosslinking agent (C) is a polyisocyanate. 11 . An ultraviolet curable adhesive layer, which is a thermally cured product of the adhesive composition according to claim 1 or 2. 12 . A pressure-sensitive adhesive sheet comprising the ultraviolet-curable pressure-sensitive adhesive layer according to claim 11 and a base layer.

13. A dicing / chip bonding integrated film, wherein: A base material layer, the ultraviolet curable pressure-sensitive adhesive layer according to claim 11, and an adhesive layer are laminated in this order. 14 . A method for manufacturing a semiconductor device, comprising the step of dicing a semiconductor using the dicing and die-bonding integrated film according to claim 13 .

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