Method for producing (METH)acrylic resin and method for producing adhesive composition

Abstract

A method for producing a (meth)acrylic resin having an ethylenically unsaturated group comprising a step (i) that reversible addition-fragmentation chain transfer (RAFT) polymerizes a raw material monomer group (M) containing a hydroxy group-containing (meth)acrylate (m-1) and an alkyl (meth)acrylate (m-2) to obtain a copolymer (A-0) and a step (ii) that adds an isocyanate group-containing ethylenically unsaturated compound (a) to some of the side chain hydroxy groups of the copolymer (A-0) to obtain a (meth)acrylic resin.

Description

Method for producing (meth)acrylic resin and method for producing pressure-sensitive adhesive composition

[0001] The present disclosure relates to a method for producing a (meth)acrylic resin used in a pressure-sensitive adhesive composition, and a method for producing a pressure-sensitive adhesive composition.

[0002] Conventionally, various pressure-sensitive adhesive sheets have been used in semiconductor manufacturing processes, etc. Specific examples include protective sheets (backgrinding tapes) for protecting semiconductor wafers during the backgrinding (backgrinding) process, and fixing sheets (dicing tapes) used during the dicing process for cutting and dividing semiconductor wafers into small element pieces. These pressure-sensitive adhesive sheets are releasable pressure-sensitive 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] Known pressure-sensitive adhesive compositions used in the pressure-sensitive adhesive layer of removable pressure-sensitive adhesive sheets include those containing a resin in which a UV-curable ethylenically unsaturated group has been introduced into the side chain of a (meth)acrylic resin. Such pressure-sensitive adhesive compositions undergo a crosslinking reaction upon UV irradiation, curing and reducing adhesive strength. For example, Patent Document 1 (JP 2018-138682 A) describes a pressure-sensitive adhesive tape containing a living radical polymerization polymer having a molecular weight distribution (Mw / Mn) of 1.05 to 2.5, particularly a (meth)acrylic polymer in which a UV-curable polymerizable group has been introduced into the side chain of a polymer obtained by living radical polymerization using an organotellurium polymerization initiator.

[0004] Japanese Patent Application Laid-Open No. 2018-138682

[0005] To shorten the semiconductor manufacturing process, a dicing / die bond integrated film is used, which is a film that integrates a dicing tape, which is a releasable adhesive sheet, and a die bond (adhesive layer). This film is used, for example, by attaching the adhesive layer to the backside of a semiconductor wafer and attaching the adhesive layer derived from the dicing tape to a dicing ring. The semiconductor wafer is then diced with a dicing blade to obtain individual semiconductor chips. Therefore, the adhesive layer derived from the dicing tape is required to have high adhesion to the adhesive layer and dicing ring during the dicing process, while during the semiconductor chip pick-up process, it is required that there is no adhesive residue (glue residue) on each semiconductor chip, allowing easy pick-up of the semiconductor chips with adhesive pieces attached. If the adhesive layer has insufficient adhesion to the adhesive layer, the high-speed rotation of the dicing blade causes peeling between the adhesive layer and the adhesive layer, and the adhesive layer breaks, resulting in a phenomenon in which pieces of the adhesive layer fly off (DAF (die attach film) fly-off). If the adhesive strength of the adhesive layer to the dicing ring is insufficient, the dicing ring will peel off from the adhesive layer due to the flow of cutting water (ring peeling).

[0006] In recent years, stealth dicing has attracted attention as a dicing method that does not use a dicing blade. In stealth dicing, laser light is focused inside a wafer to form a starting point (modified layer) for division, a removable adhesive sheet is attached to the backside of the wafer, and the sheet is cooled and expanded to obtain individual semiconductor chips. When a dicing / die-bond integrated film is used in stealth dicing, the wafer and adhesive layer are separated by cooling and expanding. If the adhesive layer has insufficient adhesive strength even during the cooling and expanding process, the impact and stress during expansion can cause the outer periphery of the adhesive layer to break, resulting in scattering of chip fragments (DAF skipping), or peeling of the edge of the adhesive-attached chip from the adhesive layer (chip edge peeling), which can cause problems in subsequent processes.

[0007] Thus, the pressure-sensitive adhesive layer used in the dicing / die-bonding integrated film must have high adhesive strength to the adhesive layer and be easily peeled off from the adhesive layer without leaving any adhesive residue after UV irradiation, properties not required for other removable pressure-sensitive adhesive sheets. Therefore, it is difficult to apply the acrylic pressure-sensitive adhesives used in conventional removable pressure-sensitive adhesive sheets directly to the dicing / die-bonding integrated film.

[0008] The present disclosure provides a production method capable of obtaining a (meth)acrylic resin or a pressure-sensitive adhesive composition containing a (meth)acrylic resin, which can provide a pressure-sensitive adhesive layer that has sufficient adhesive strength to an adhesive layer, and that exhibits excellent releasability and is less likely to leave adhesive residue when the pressure-sensitive adhesive sheet is peeled from the adhesive layer after UV irradiation.

[0009] The present inventors have found that a polymer obtained by modifying a copolymer obtained by reversible addition-fragmentation chain transfer (RAFT) polymerization of a hydroxyl group-containing (meth)acrylate and an alkyl (meth)acrylate with an isocyanato group-containing ethylenically unsaturated compound is suitable for use in the pressure-sensitive adhesive layer of a dicing and die-bonding integrated film.

[0010] That is, the present disclosure includes the following aspects. [1] A method for producing a (meth)acrylic resin, comprising: a step (i) of polymerizing raw material monomers (M) containing a hydroxy group-containing (meth)acrylate (m-1) and an alkyl (meth)acrylate (m-2) by reversible addition-fragmentation chain transfer (RAFT) to obtain a copolymer (A-0); and a step (ii) of adding an isocyanato group-containing ethylenically unsaturated compound (a) to a portion of the side chain hydroxy groups of the copolymer (A-0) to obtain a (meth)acrylic resin (A) having an ethylenically unsaturated group. [2] A method for producing a (meth)acrylic resin according to [1], wherein the raw material monomers (M) further contain a carboxy group-containing monomer (m-3). [3] A method for producing a (meth)acrylic resin according to [1] or [2], wherein the molecular weight distribution (Mw / Mn) of the (meth)acrylic resin (A) having an ethylenically unsaturated group is 2.4 to 10.0. [4] A method for producing a pressure-sensitive adhesive composition, comprising a step (iii) of mixing an ethylenically unsaturated group-containing (meth)acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C), the method being obtainable by the method according to any one of [1] to [3]. [5] A method for producing a pressure-sensitive adhesive composition according to [4], wherein the crosslinking agent (C) is at least one selected from the group consisting of polyisocyanates and polyepoxy compounds. [6] A method for producing a pressure-sensitive adhesive layer, comprising a step of forming a crosslinked structure in the pressure-sensitive adhesive composition obtained by the method according to [4] or [5]. [7] A method for producing a pressure-sensitive adhesive sheet, comprising applying the pressure-sensitive adhesive composition obtained by the method according to [4] or [5] to a sheet-like substrate to produce a pressure-sensitive adhesive layer. [8] A method for producing a pressure-sensitive adhesive sheet, comprising a step of forming a crosslinked structure in the pressure-sensitive adhesive layer obtained by the method according to [7]. [9] A method for producing a dicing-die-bonding integrated film, comprising laminating an adhesive layer on the pressure-sensitive adhesive layer having a crosslinked structure, the pressure-sensitive adhesive layer obtained by the method according to [8].

[10] A method for producing a dicing and die bonding integrated film, comprising applying the pressure-sensitive adhesive composition obtained by the production method according to [4] or [5] to an adhesive layer.

[0011] By using the (meth)acrylic resin obtained by the method of the present disclosure in the pressure-sensitive adhesive layer of a dicing / die-bonding integrated film, it is possible to provide a pressure-sensitive adhesive layer that has sufficient adhesive strength to the adhesive layer, and that has excellent releasability and is less likely to leave adhesive residue when the pressure-sensitive adhesive sheet is peeled from the adhesive layer after UV irradiation.

[0012] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the embodiments described below.

[0013] In this specification, when "to" is used to describe a range of values, the numerical values ​​at both ends are the upper and lower limits, respectively, and are included in the range.

[0014] In this specification, "(meth)acrylic" means methacrylic or acrylic, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acryloyloxy" means acryloyloxy or methacryloyloxy.

[0015] In this specification, the "weight average molecular weight" and "number average molecular weight" refer to values ​​measured by gel permeation chromatography (GPC) at room temperature (23°C) under the following conditions and determined using a standard polystyrene calibration curve. Apparatus: Shodex™ GPC-101 (Showa Denko K.K.) Column: Shodex™ LF-804 (Showa Denko K.K.) Column temperature: 40°C Sample: 0.2% by mass solution of sample in tetrahydrofuran Flow rate: 1 mL / min Eluent: tetrahydrofuran Detector: Shodex™ RI-71S (Showa Denko K.K.)

[0016] In this specification, the term "glass transition temperature (Tg)" refers to the endothermic onset temperature due to glass transition observed when a 10 mg sample is collected and subjected to differential scanning calorimetry 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 / min. When two or more endothermic onset temperatures are observed, Tg is the simple average of the two or more endothermic onset temperatures.

[0017] [Method for producing (meth)acrylic resin (A) having an ethylenically unsaturated group] The method for producing a (meth)acrylic resin (A) having an ethylenically unsaturated group (hereinafter simply referred to as "(meth)acrylic resin (A)") includes step (i) of polymerizing raw material monomers (M) containing a hydroxy group-containing (meth)acrylate (m-1) and an alkyl (meth)acrylate (m-2) by reversible addition-fragmentation chain transfer (RAFT) to obtain a copolymer (A-0), and step (ii) of adding an isocyanato group-containing ethylenically unsaturated compound (a) to a portion of the side chain hydroxy groups of the copolymer (A-0) to obtain the (meth)acrylic resin (A). The raw material monomers (M) may contain a carboxy group-containing monomer (m-3).

[0018] <Step (i)> The copolymer (A-0) is obtained by RAFT polymerization of raw material monomers (M) containing a hydroxy group-containing (meth)acrylate (m-1), an alkyl (meth)acrylate (m-2), and optionally a carboxy group-containing monomer (m-3) in the presence of a reversible addition-fragmentation chain transfer agent (RAFT agent). In this specification, RAFT polymerization refers to radical polymerization carried out in the presence of a RAFT agent. RAFT polymerization is a type of living radical polymerization. Living radical polymerization is generally known as a polymerization method capable of producing polymers with narrow molecular weight distributions, and specific examples thereof include atom transfer radical polymerization, organotellurium-mediated radical polymerization, and RAFT polymerization. Of these, RAFT polymerization does not use halogens or heavy metals, and therefore has a low environmental impact and is suitable for semiconductor applications. Without being bound by any theory, the copolymer (A-0) obtained by RAFT polymerization has a more appropriate molecular weight distribution than other (meth)acrylic copolymers obtained by living radical polymerization, and therefore a pressure-sensitive adhesive composition produced using a (meth)acrylic resin (A) obtained from the copolymer (A-0) has excellent wettability to an adhesive layer and high adhesion to the adhesive layer. This is because the low-molecular-weight component of the (meth)acrylic resin (A) contributes to the wettability and fluidity of the pressure-sensitive adhesive composition. If the molecular weight distribution of the (meth)acrylic copolymer is too narrow, the fluidity of the resulting pressure-sensitive adhesive composition and its wettability to an adhesive layer are low, and sufficient adhesion cannot be obtained.

[0019] As the polymerization method, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, an alternating copolymerization method, etc. Among these polymerization methods, in consideration of the addition reaction in step (ii), it is preferable to use a solution polymerization method from the viewpoint of ease of reaction.

[0020] (Hydroxy Group-Containing (Meth)acrylate (m-1)) The hydroxy group-containing (meth)acrylate (m-1) is not particularly limited as long as it has a hydroxy group and a (meth)acryloyloxy group. Specific examples include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and (meth)acrylates having an aromatic ring and a hydroxy group, such as hydroxyphenyl (meth)acrylate and 2-hydroxy-3-phenoxypropyl (meth)acrylate. Among these, from the viewpoint of the releasability of the PSA sheet after UV irradiation, hydroxyalkyl(meth)acrylates are preferred, hydroxyalkyl(meth)acrylates in which the hydroxyalkyl group has 1 to 6 carbon atoms are more preferred, and 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate are even more preferred.

[0021] The content of the hydroxy group-containing (meth)acrylate (m-1) is preferably 5 to 50 mol%, more preferably 10 to 40 mol%, and even more preferably 15 to 35 mol%, relative to 100 mol% of the raw material monomer group (M). When the content of the hydroxy group-containing (meth)acrylate (m-1) is 5 mol% or more, the (meth)acrylic resin (A) has sufficient hydroxy groups, ensuring the amount of crosslinking with the crosslinking agent (C), thereby enabling a pressure-sensitive adhesive layer with sufficient cohesive strength to be obtained. In addition, reaction sites for introducing ethylenically unsaturated groups can be secured, resulting in better releasability when peeling the pressure-sensitive adhesive sheet from an adherend after UV irradiation. On the other hand, when the content of the hydroxy group-containing (meth)acrylate (m-1) is 50 mol% or less, the progression of unintended reactions in the pressure-sensitive adhesive composition can be suppressed, resulting in good storage stability.

[0022] (Alkyl (meth)acrylate (m-2)) The alkyl (meth)acrylate (m-2) is not particularly limited as long as it does not have a hydroxy group or a carboxy group, but has an alkyl group and a (meth)acryloyloxy group. Specific examples include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isoamyl (meth)acrylate, and dodecyl (meth)acrylate; and alicyclic alkyl (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, ethylcyclohexyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate. The alkyl group in the alkyl (meth)acrylate (m-2) may be substituted. Examples of the substituent include alkoxy groups such as a methoxy group and an ethoxy group. Among these, from the viewpoint of the releasability of the PSA sheet after UV irradiation, alkyl(meth)acrylates and alicyclic alkyl(meth)acrylates in which the alkyl group has 1 to 20 carbon atoms are preferred, and one or more selected from methyl(meth)acrylate, ethyl(meth)acrylate, 2-methoxyethyl(meth)acrylate, propyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, dodecyl(meth)acrylate, cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, and dicyclopentanyl(meth)acrylate are more preferred.

[0023] The content of the alkyl (meth)acrylate (m-2) is preferably 10 to 94 mol%, more preferably 30 to 85 mol%, and even more preferably 50 to 80 mol%, relative to 100 mol% of the raw material monomer group (M). When the content of the alkyl (meth)acrylate (m-2) is 10 mol% or more, excellent adhesiveness can be obtained. When the content of the alkyl (meth)acrylate (m-2) is 94 mol% or less, the content of hydroxy groups and ethylenically unsaturated groups in the (meth)acrylic resin (A) can be sufficiently ensured, thereby obtaining a pressure-sensitive adhesive layer with balanced physical properties in terms of the cohesive strength of the pressure-sensitive adhesive layer and the releasability of the pressure-sensitive adhesive sheet after UV irradiation.

[0024] (Carboxy Group-Containing Monomer (m-3)) The carboxy group-containing monomer (m-3) is not particularly limited as long as it is a monomer that does not have a hydroxy group and has a carboxy group and an ethylenically unsaturated group. Examples include unsaturated monobasic acids such as (meth)acrylic acid, crotonic acid, vinylbenzoic acid, and acrylic acid substituted with haloalkyl, alkoxyl, halogen, nitro, or cyano at the α-position, and unsaturated dibasic acids such as itaconic acid. Among these, (meth)acrylic acid is preferred because of the ease of producing the pressure-sensitive adhesive.

[0025] When a carboxy group-containing monomer (m-3) is used, the content of the carboxy group-containing monomer (m-3) is preferably 0.1 to 10 mol%, more preferably 0.5 to 8.0 mol%, and even more preferably 1.0 to 5.0 mol%, relative to 100 mol% of the raw material monomer group (M). When the content of the carboxy group-containing monomer (m-3) is 0.1 mol% or more, when the crosslinking agent (C) is a polyepoxy compound, a sufficient amount of crosslinking can be ensured, and sufficient cohesive strength of the adhesive can be obtained. When the content of the carboxy group-containing monomer (m-3) is 10 mol% or less, the content of hydroxy groups and ethylenically unsaturated groups in the (meth)acrylic resin (A) can be sufficiently ensured, thereby obtaining an adhesive layer with balanced physical properties in terms of the cohesive strength of the adhesive layer and the releasability of the adhesive sheet after UV irradiation.

[0026] In the raw material monomer group (M), the molar ratio of the hydroxy group-containing (meth)acrylate (m-1), the alkyl (meth)acrylate (m-2), and the carboxy group-containing monomer (m-3) is preferably (m-1):(m-2):(m-3)=10-70:30-90:0-10, and more preferably (m-1):(m-2):(m-3)=15-35:65-85:0-5.

[0027] (Other Monomers (m-4)) The raw material monomer group (M) may contain another monomer (m-4) in addition to (m-1) to (m-3). Specific examples include dienes such as butadiene and dicyclopentadiene, styrenes, unsaturated dicarboxylic acid diesters, and other vinyl compounds.

[0028] Specific examples of styrenes include styrene and α-, o-, m-, or p-alkyl derivatives of styrene.

[0029] Specific examples of the unsaturated dicarboxylic acid diester include diethyl citraconate, diethyl maleate, diethyl fumarate, and diethyl itaconate.

[0030] Specific examples of other vinyl compounds include norbornene (bicyclo[2.2.1]hept-2-ene), 5-methylbicyclo[2.2.1]hept-2-ene, 5-ethylbicyclo[2.2.1]hept-2-ene, tetracyclo[4.4.0.1]hept-2-ene, ２，５ .1 ７，１０ ] dodec-3-ene, 8-methyltetracyclo[4.4.0.1 ２，５ .1 ７，１０ ] dodec-3-ene, 8-ethyltetracyclo[4.4.0.1 ２，５ .1 ７，１０ ] dodec-3-ene, tricyclo[5.2.1.0 ２，６ ]dec-8-ene, tricyclo[5.2.1.0 ２，６ ]dec-3-ene, tricyclo[4.4.0.1 ２，５ ]undec-3-ene, tricyclo[6.2.1.0 １，８ ]undec-9-ene, tricyclo[6.2.1.0 １，８ ]undec-4-ene, tetracyclo[4.4.0.1２，５ .1 ７，１０ .0 １，６ ] dodec-3-ene, 8-methyltetracyclo[4.4.0.1 ２，５ .1 ７，１０ .0 １，６ ] dodec-3-ene, 8-ethylidenetetracyclo[4.4.0.1 ２，５ .1 ７，１２ ] dodec-3-ene, 8-ethylidenetetracyclo[4.4.0.1 ２，５ .1 ７，１０ .0 １，６ ] dodec-3-ene, pentacyclo[6.5.1.1 ３，６ .0 ２，７ .0 ９，１３ ]pentadec-4-ene, pentacyclo[7.4.0.1 ２，５ .1 ９，１２ .0 ８，１３ ] Pentadec-3-ene, (meth)acrylic acid anilide, vinylpyridine, vinyl acetate, and the like.

[0031] (Reversible Addition-Fragmentation Chain Transfer Agent (RAFT Agent)) As the RAFT agent, known agents can be used without any particular limitation. For example, sulfur-based compounds (trithiocarbonates, dithioesters, dithiocarbonates, and dithiocarbamates) represented by the following formula (1), formula (2), formula (3), or formula (4) are preferred.

[0032] <Trithiocarbonate> (In formula (1), R １ａ and R １ｂ are the same or different and represent a hydrogen atom, a hydrocarbon group, a carboxy group, or a cyano group; R １ｃ represents a cyano group, a saturated or unsaturated aliphatic hydrocarbon group which may be substituted with a cyano group or a carboxy group, or a phenyl group which may be substituted; R ２ represents a saturated or unsaturated aliphatic hydrocarbon group in which some of the hydrogen atoms may be substituted with carboxy groups, or an optionally substituted benzyl group.

[0033] <Dithioester> (In formula (2), R ３ａ and R ３ｂare the same or different and represent a hydrogen atom, a hydrocarbon group, or a cyano group; R ３ｃ represents a carboxy group, an acetoxymethyl group, or a hydrocarbon group which may be substituted with a cyano group or a carboxy group; R ４ represents a hydrocarbon group.)

[0034] <Dithiocarbonate> (In formula (3), R ５ａ and R ５ｂ are the same or different and represent a hydrogen atom, a hydrocarbon group, a carboxy group which may be substituted with a saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms, or a cyano group; R ５ｃ represents a hydrocarbon group which may be substituted with an alkoxy group, and R ６ represents a hydrocarbon group.)

[0035] <Dithiocarbamate> (In formula (4), R ７ａ and R ７ｂ are the same or different and represent a hydrogen atom or a hydrocarbon group; R ７ｃ represents a cyano group, and R ８ and R ９ are the same or different and represent a hydrocarbon group, or R ８ and R ９ may be bonded to form a saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms or a pyrazole ring which may be substituted with a chlorine atom.

[0036] In formula (1), R １ａ and R １ｂ Examples of the hydrocarbon group represented by the formula (1) include linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 20 carbon atoms, and among these, linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 12 carbon atoms are preferred. Examples of the hydrocarbon group include linear, branched, or cyclic saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl, dodecyl, and octadecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl; and arylalkyl groups having 7 to 10 carbon atoms, such as benzyl and phenethyl. In formula (1), R１ｃ Examples of the saturated or unsaturated aliphatic hydrocarbon group represented by the formula (1) include linear, branched, or cyclic, saturated or unsaturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, and among these, linear, branched, or cyclic, saturated or unsaturated aliphatic hydrocarbon groups having 1 to 12 carbon atoms are preferred. Examples of the aliphatic hydrocarbon group include linear, branched, or cyclic, saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl, dodecyl, and octadecyl groups. In formula (1), R １ｃ For example, 1 to 3 hydrogen atoms of the saturated or unsaturated aliphatic hydrocarbon group represented by the formula (1) may be substituted with a carboxy group or a cyano group, and the carboxy group may be further substituted with a saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms. １ｃ Examples of the substituent of the optionally substituted phenyl group represented by the formula (1) include a substituted carbamoyl group, an alkoxycarbonyl group having 2 to 5 carbon atoms which may be substituted with a hydroxy group, and an alkenyloxycarbonyl group having 3 to 5 carbon atoms. Examples of the substituent of the substituted carbamoyl group include a saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms which may be substituted with a hydroxy group or an acetyloxy group. In formula (1), R ２ Examples of the saturated or unsaturated aliphatic hydrocarbon group represented by the formula (1) include linear, branched, or cyclic saturated or unsaturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, and among these, aliphatic hydrocarbon groups having 1 to 12 carbon atoms are preferred. Examples of the aliphatic hydrocarbon group include linear, branched, or cyclic saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a cyclohexyl group, a dodecyl group, and an octadecyl group. In formula (1), R ２ In formula (1), for example, 1 to 3 hydrogen atoms of the saturated or unsaturated aliphatic hydrocarbon group represented by the formula (1) may be substituted with a carboxy group. ２Examples of the substituent of the optionally substituted benzyl group represented by the formula (I) include a substituted carbamoyl group, an alkoxycarbonyl group having 2 to 5 carbon atoms which may be substituted with a hydroxy group, and an alkenyloxycarbonyl group having 3 to 5 carbon atoms. Examples of the substituent of the substituted carbamoyl group include a saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms which may be substituted with a hydroxy group or an acetyloxy group. Among these, R １ａ and R １ｂ are the same or different and are a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, or a carboxy group, and R １ｃ is a hydrocarbon group having 1 to 4 carbon atoms or an optionally substituted phenyl group, and R ２ is a linear, branched or cyclic, saturated or unsaturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, or an optionally substituted benzyl group, and １ａ and R １ｂ is a hydrogen atom, a combination of a methyl group or an ethyl group with a carboxy group, or a hydrogen atom, and R １ｃ is a methyl group, an ethyl group, or an optionally substituted phenyl group, and R ２ More preferred are compounds of formula (1) in which is a linear saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms or an optionally substituted benzyl group.

[0037] In formula (2), R ３ａ , R ３ｂ , R ３ｃ and R ４ Examples of the hydrocarbon group represented by the formula (2) include linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 20 carbon atoms, and among these, linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 12 carbon atoms are preferred. Examples of the hydrocarbon group include linear, branched, or cyclic saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl, dodecyl, and octadecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl; and arylalkyl groups having 7 to 10 carbon atoms, such as benzyl and phenethyl. In formula (2), R３ｃ Examples of the hydrocarbon group represented by the formula (I) which may be substituted with a cyano group or a carboxy group include the above-mentioned hydrocarbon group in which 1 to 3 hydrogen atoms have been substituted with a cyano group or a carboxy group. ３ａ and R ３ｂ are the same or different and are linear saturated hydrocarbon groups having 1 to 4 carbon atoms, and R ３ｃ is an aryl group, and R ４ is an aryl group or a benzyl group, and ３ａ and R ３ｂ are the same or different and are a methyl group or an ethyl group, and R ３ｃ is a phenyl group, and R ４ More preferred are compounds of formula (2) in which is a phenyl group or a benzyl group.

[0038] In formula (3), R ５ａ , R ５ｂ , R ５ｃ and R ６ Examples of the hydrocarbon group represented by the formula (3) include linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 20 carbon atoms, and among these, linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 12 carbon atoms are preferred. Examples of the hydrocarbon group include linear, branched, or cyclic saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl, dodecyl, and octadecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl; and arylalkyl groups having 7 to 10 carbon atoms, such as benzyl and phenethyl. In formula (3), R ５ｃ Examples of the hydrocarbon group which may be substituted with an alkoxy group include the above hydrocarbon groups in which 1 to 3 hydrogen atoms have been substituted with alkoxy groups.

[0039] In formula (4), R ７ａ , R ７ｂ , R ８ and R ９Examples of the hydrocarbon group represented by the formula (I) include linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 20 carbon atoms, and among these, linear, branched, or cyclic, saturated or unsaturated hydrocarbon groups having 1 to 12 carbon atoms are preferred. Examples of the hydrocarbon group include linear, branched, or cyclic saturated aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclohexyl, dodecyl, and octadecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl; and arylalkyl groups having 7 to 10 carbon atoms, such as benzyl and phenethyl. R ８ and R ９ may form a pyrazole ring together with the nitrogen atom of formula (4). The pyrazole ring may be substituted with a saturated aliphatic hydrocarbon group having 1 to 3 carbon atoms or a chlorine atom.

[0040] When polymerization is carried out in the presence of a RAFT agent represented by any of the formulae (1) to (4), the polymerization proceeds while radical species undergo a chain reaction between a sulfur atom in the RAFT agent and a carbon atom adjacent to the sulfur atom. Among these, the RAFT agents represented by the formulae (1) and (2) are preferred from the viewpoint of ease of polymerization.

[0041] Many RAFT agents are commercially available, and those that are not commercially available can be easily synthesized by known or conventional methods.

[0042] Specific examples of RAFT agents include S-cyanomethyl-S-dodecyltrithiocarbonate, 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, bis{4-[ethyl-(2-hydroxyethyl)carbamoyl]benzyl}trithiocarbonate, 4-[(2-carboxyethylsulfanylthiocarbonyl)sulfanyl]-4-cyanopentanoic acid, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl] methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, S,S-dibenzyltrithiocarbonate, methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, 2-cyano-2-propyldodecyltrithiocarbonate, bis[4-(allyloxycarbonyl)benzyl]trithiocarbonate, bis[4-(2,3-dihydroxypropoxycarbonyl)benzyl]trithiocarbonate, bis{4-[ethyl-(2-acetyloxyethyl)carbamoyl]benzyl}trithiocarbonate, bis[4-(2-hydroxyethoxycarbonyl)benzyl]trithiocarbonate trithiocarbonates such as [(ethoxycarbonothioyl)thio]trithiocarbonate, etc.; dithioesters such as cyanoethyl dithiopropionate, benzyl dithiopropionate, benzyl dithiobenzoate, acetoxyethyl dithiobenzoate, 2-phenyl-2-propyldithiobenzoic acid, 2-cyano-2-propyldithiobenzoic acid, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, and S-(thiobenzoyl)thioglycolic acid; ethyl 2-[(ethoxycarbonothioyl)thio]propionate, O-ethyl-S-(2-propoxyethyl)dithiocarbonate, etc. dithiocarbonates such as 2-cyano-2-propyldiethyldithiocarbamate, 2'-cyanobutan-2'-yl 4-chloro-3,5-dimethylpyrazole-1-dithiocarbamate, 2'-cyanobutan-2'-yl 3,5-dimethylpyrazole-1-dithiocarbamate, cyanomethyl 3,5-dimethylpyrazole-1-dithiocarbamate, and cyanomethyl N-methyl-N-phenyldithiocarbamate.Of these, from the viewpoint of ease of polymerization of the (meth)acrylic resin (A), trithiocarbonates and dithioesters are preferred, and 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, 2-phenyl-2-propyldithiobenzoic acid, S,S-dibenzyltrithiocarbonate, and bis{4-[ethyl-(2-acetyloxyethyl)carbamoyl]benzyl}trithiocarbonate are more preferred.

[0043] The RAFT agents may be used alone or in combination of two or more.

[0044] (Radical Polymerization Initiator) RAFT polymerization is preferably carried out in the presence of a radical polymerization initiator. Examples of the radical polymerization initiator include ordinary organic radical polymerization initiators, and specific examples thereof include 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), and azo-based polymerization initiators such as dimethyl-2,2'-azobis(2-methylpropionate); and oil-soluble polymerization initiators such as peroxide-based polymerization initiators such as benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, and 1,1-bis(t-butylperoxy)cyclododecane.

[0045] The radical polymerization initiators may be used alone or in combination of two or more.

[0046] 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 raw material monomer group (M).

[0047] (Solvent) A common solvent can be used as the solvent used in RAFT polymerization. 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. The solvents may be used alone or in combination of two or more.

[0048] (Reaction Conditions) The reaction temperature for RAFT polymerization varies depending on the type of radical polymerization initiator used, but is usually 30°C to 130°C, preferably 40°C to 120°C, and more preferably 50°C to 110°C. When the temperature during RAFT polymerization is 30°C or higher, a sufficient reaction rate can be obtained. When the temperature during RAFT polymerization is 130°C or lower, there is little risk during production.

[0049] The reaction time for RAFT polymerization varies depending on the types of raw material monomer group (M), RAFT agent, and radical polymerization initiator used, but is usually 3 to 30 hours, preferably 4 to 20 hours, and more preferably 5 to 15 hours. When the reaction time is 3 hours or more, copolymer (A-0) can be produced from raw material monomer group (M) with an appropriate degree of polymerization, and when the reaction time is 30 hours or less, production can be carried out efficiently.

[0050] <Step (ii)> The (meth)acrylic resin (A) is obtained by adding an isocyanato group-containing ethylenically unsaturated compound (a) to some of the side chain hydroxy groups derived from the hydroxy group-containing (meth)acrylate (m-1) of the copolymer (A-0). Adding the isocyanato group-containing ethylenically unsaturated compound (a) to all of the side chain hydroxy groups of the copolymer (A-0) would eliminate sites for reaction with the crosslinking agent (C), described below, so addition is limited to some of the side chain hydroxy groups. Specifically, when the side chain hydroxy groups are taken as 100 mol %, it is preferable that 5.0 to 99 mol % of the side chain hydroxy groups be subjected to the addition reaction. The method for adding the isocyanato group-containing ethylenically unsaturated compound (a) is not particularly limited, and methods known in the technical field of this specification can be used. Since the (meth)acrylic resin (A) has an ethylenically unsaturated group in the side chain, the length of the molecular chain between crosslinking points is relatively short compared to a (meth)acrylic copolymer having an ethylenically unsaturated group introduced at the terminal, and the adhesive strength can be significantly reduced after UV irradiation. Therefore, a pressure-sensitive adhesive sheet using the (meth)acrylic resin (A) has excellent peelability from an adherend. In addition, since the (meth)acrylic resin (A) has an appropriate molecular weight distribution, a pressure-sensitive adhesive composition produced using the methacrylic resin (A) has excellent adhesion to an adhesive layer. Therefore, a pressure-sensitive adhesive composition produced using the (meth)acrylic resin (A) is suitable for use in the pressure-sensitive adhesive layer of a dicing / die-bonding integrated film.

[0051] The molecular weight distribution (Mw / Mn) of the (meth)acrylic resin (A) is preferably 2.4 or more, more preferably 2.5 or more, and even more preferably 3.0 or more. The molecular weight distribution of the (meth)acrylic resin (A) is preferably 10.0 or less, more preferably 6.0 or less, even more preferably 5.8 or less, and even more preferably 5.6 or less. Any combination of these lower and upper limits may be used. The molecular weight distribution of the (meth)acrylic resin (A) is preferably 2.4 to 10.0, more preferably 2.4 to 6.0, even more preferably 2.5 to 5.8, and even more preferably 3.0 to 5.6. A molecular weight distribution of 2.4 or more improves the wettability of the pressure-sensitive adhesive composition containing the (meth)acrylic resin (A), resulting in good adhesion to the adherend, particularly to the adhesive layer. When the molecular weight distribution is 10.0 or less, the (meth)acrylic resin (A) in the high molecular weight region falls within an appropriate range, making it easy to control the viscosity of the pressure-sensitive adhesive composition, and the (meth)acrylic resin (A) in the low molecular weight region falls within an appropriate range, reducing adhesive residue when the pressure-sensitive adhesive sheet is peeled from an adherend.

[0052] The weight-average molecular weight (Mw) of the (meth)acrylic resin (A) is preferably 100,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and even more preferably 300,000 or more. The weight-average molecular weight of the (meth)acrylic resin (A) is preferably 800,000 or less, more preferably 700,000 or less, and even more preferably 650,000 or less. Any combination of these lower and upper limits is acceptable. The weight-average molecular weight (Mw) of the (meth)acrylic resin (A) is preferably 100,000 to 800,000, more preferably 150,000 to 700,000, even more preferably 200,000 to 650,000, and even more preferably 300,000 to 650,000. A weight-average molecular weight of 100,000 or more improves releasability after UV irradiation. When the weight average molecular weight is 800,000 or less, the viscosity of the pressure-sensitive adhesive composition containing the (meth)acrylic resin (A) can be appropriately reduced, and the workability of the pressure-sensitive adhesive composition can be improved.

[0053] The ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) is preferably 100 to 3,000 g / mol, more preferably 300 to 2,500 g / mol, and even more preferably 500 to 2,000 g / mol. Within the above range, the amount of crosslinking of the pressure-sensitive adhesive composition upon UV irradiation is sufficient, resulting in excellent releasability when peeling a pressure-sensitive adhesive sheet produced using the (meth)acrylic resin (A) from an adherend, and excellent pick-up ability of fragmented elements. In this specification, the ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) refers to the mass of the (meth)acrylic resin (A) per mole of ethylenically unsaturated bonds. In one embodiment, the ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) is a calculated value calculated from the amounts of raw materials used in the production of the (meth)acrylic resin (A), assuming that 100% of each raw material was reacted. The ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) may be calculated from the amount of halogen bonded to the (meth)acrylic resin (A). The amount of halogen bonded to the (meth)acrylic resin (A) can be evaluated in accordance with JIS K 0070:1992.

[0054] 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 even more preferably −60° C. to −30° C. When the glass transition temperature (Tg) is −80° C. or higher, the cohesive strength of the pressure-sensitive adhesive composition is increased and adhesive residue is suppressed. When the glass transition temperature (Tg) is 0° C. or lower, sufficient fixation and adhesive strength can be obtained when processing the adherend.

[0055] When the raw material monomer group (M) contains a carboxy group-containing monomer (m-3), the acid value of the (meth)acrylic resin (A) is preferably 0.5 to 100 mgKOH / g, more preferably 1.0 to 50 mgKOH / g, and even more preferably 3.0 to 25 mgKOH / g. When the acid value is 0.5 mgKOH / g or more, a sufficient amount of crosslinking can be ensured when a polyepoxy compound is used as the crosslinking agent (C), and the cohesive strength of the pressure-sensitive adhesive layer can be sufficiently ensured. When the acid value is 100 mgKOH / g or less, the pressure-sensitive adhesive composition has good storage stability. In this specification, the acid value is a value measured in accordance with JIS K 0070:1992.

[0056] (Isocyanato Group-Containing Ethylenically Unsaturated Compound (a)) The isocyanato group-containing ethylenically unsaturated compound (a) is not particularly limited as long as it is a compound that does not have a hydroxy group or a carboxy group but has an isocyanato group and an ethylenically unsaturated group. Specific examples include (meth)acryloyloxyalkyl isocyanates such as 2-isocyanatoethyl (meth)acrylate, 2-isocyanatopropyl (meth)acrylate, 3-isocyanatopropyl (meth)acrylate, 2-isocyanato-1-methylethyl (meth)acrylate, 2-isocyanato-1,1-dimethylethyl (meth)acrylate, and 4-isocyanatocyclohexyl (meth)acrylate; 2-(2-isocyanatoethyloxy)ethyl (meth)acrylate; and 1,1-(bis(meth)acryloyloxymethyl)ethyl isocyanate. Among these, from the viewpoint of ease of synthesis of the (meth)acrylic resin (A), (meth)acryloyloxyalkyl isocyanate is preferred, and 2-isocyanatoethyl (meth)acrylate is more preferred.

[0057] The content of the isocyanato group-containing ethylenically unsaturated compound (a) is preferably 0.25 mol or more, more preferably 0.50 mol or more, and even more preferably 1.0 mol or more, per 100 mol of the raw material monomer group (M). The content of the isocyanato group-containing ethylenically unsaturated compound (a) is preferably 49 mol or less, more preferably 47 mol or less, and even more preferably 45 mol or less. Any combination of these lower and upper limits may be used. The content of the isocyanato group-containing ethylenically unsaturated compound (a) is preferably 0.25 to 49 mol, more preferably 0.50 to 47 mol, and even more preferably 1.0 to 45 mol, per 100 mol of the raw material monomer group (M). When the content of the isocyanato group-containing ethylenically unsaturated compound (a) is 0.25 mol or more, a sufficient amount of ethylenically unsaturated groups is introduced into the (meth)acrylic resin (A), thereby achieving better releasability when peeling the pressure-sensitive adhesive sheet from an adherend after UV irradiation. When the content of the isocyanato group-containing ethylenically unsaturated compound (a) is 49 moles or less, the content of hydroxy groups in the (meth)acrylic resin (A) can be sufficiently ensured, and the adhesive layer can obtain excellent cohesive strength. In addition, the amount of unreacted isocyanato group-containing ethylenically unsaturated compound (a) can be reduced, and therefore a pressure-sensitive adhesive sheet with little adhesive residue can be obtained.

[0058] (Catalyst) In the addition reaction in step (ii), a known catalyst can be used, if necessary. Examples of the catalyst include urethanization catalysts such as dibutyltin dilaurate, titanium diisopropoxybis(ethylacetoacetate), tetrakis(2,4-pentanedionato)zirconium, and bismuth tris(2-ethylhexanoate).

[0059] When a catalyst is used in step (ii), the amount of the catalyst used is preferably 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, and even more preferably 0.03 to 1 part by mass, per 100 parts by mass of the total of the copolymer (A-0) and the isocyanato group-containing ethylenically unsaturated compound (a).

[0060] (Polymerization inhibitor) In the addition reaction in step (ii), a known polymerization inhibitor can be used as necessary. The polymerization inhibitor can be any known one, and is not particularly limited. Examples of the polymerization inhibitor include 4-methoxyphenol, hydroquinone, methoquinone, 2,6-di-t-butylphenol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), and phenothiazine. The polymerization inhibitor may be used alone, or two or more types may be used in combination.

[0061] When a polymerization inhibitor is used in step (ii), the amount of the polymerization inhibitor 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 total of the copolymer (A-0) and the isocyanato group-containing ethylenically unsaturated compound (a). When 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 (A) during UV irradiation can be obtained.

[0062] (Reaction Conditions) The temperature of the addition reaction is preferably 25°C to 130°C, and particularly preferably 40°C to 120°C. When the temperature of the addition reaction is 25°C or higher, a sufficient reaction rate can be obtained. When the temperature of the addition reaction is 130°C or lower, crosslinking of double bonds due to thermal radical polymerization can be prevented, preventing the formation of a gelled product.

[0063] 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.

[0064] Examples of gases that have a polymerization-inhibiting effect include gases that contain oxygen to an extent that does not fall within the explosive range of the substances in the system, such as air.

[0065] It is more preferable to use a gas having a polymerization inhibitor effect in combination with a polymerization inhibitor, since this allows the amount of polymerization inhibitor used to be reduced and the polymerization inhibitor effect to be enhanced.

[0066] [Method for producing pressure-sensitive adhesive composition] The pressure-sensitive adhesive composition can be produced by a method including a step (iii) of mixing a (meth)acrylic resin (A), a photopolymerization initiator (B), a crosslinking agent (C), and other components added as needed. The pressure-sensitive adhesive composition containing the (meth)acrylic resin (A) is suitably used for removable pressure-sensitive adhesive sheets, in particular, dicing and die-bonding integrated films.

[0067] The method for mixing the components contained in the pressure-sensitive adhesive composition is not particularly limited, and mixing can be carried out using, for example, a stirring device equipped with stirring blades such as a homodisper or a paddle blade.

[0068] <Photopolymerization Initiator (B)> Examples of the photopolymerization initiator (B) include benzophenone, benzil, 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, and benzoin isopropyl alcohol. butyl ether, benzoin-n-butyl ether, benzyl methyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, methylbenzoyl formate, 4'-dimethylaminoacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and other carbonyl-based photopolymerization initiators.

[0069] 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; sulfochloride-based photopolymerization initiators; and thioxanthone-based photopolymerization initiators such as thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone.

[0070] Among these photopolymerization initiators (B), from the viewpoint of solubility in the pressure-sensitive adhesive composition, carbonyl-based photopolymerization initiators and acylphosphine oxides are preferred, and it is more preferred to use at least one selected from 1-hydroxycyclohexyl phenyl ketone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0071] The photopolymerization initiator (B) may be used alone or in combination of two or more kinds.

[0072] 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, per 100 parts by mass of the (meth)acrylic resin (A). When the content of the photopolymerization initiator (B) per 100 parts by mass of the (meth)acrylic resin (A) is 0.1 parts by mass or more, the pressure-sensitive adhesive composition can be cured at a sufficiently fast curing rate upon UV irradiation, and the adhesive strength of the pressure-sensitive adhesive layer after UV irradiation can be sufficiently reduced. When the content of the photopolymerization initiator (B) per 100 parts by mass of the (meth)acrylic resin (A) is 5.0 parts by mass or less, when a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is attached to an adherend and then peeled off, the pressure-sensitive adhesive layer is less likely to remain on the adherend. Even if the content of the photopolymerization initiator (B) exceeds 5.0 parts by mass relative to 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.

[0073] <Crosslinking agent (C)> By mixing the crosslinking agent (C), it is possible to obtain a pressure-sensitive adhesive composition having a good balance between adhesive strength before and after UV irradiation. The crosslinking agent (C) is a compound having no ethylenically unsaturated bond and having two or more functional groups that react with the hydroxy group and / or the carboxy group, which is an optional functional group, contained in the (meth)acrylic resin (A).

[0074] The crosslinking agent (C) is not particularly limited, but a compound having two or more functional groups reactive with a hydroxy group is preferred. When the (meth)acrylic resin (A) has a carboxy group, a compound having two or more functional groups reactive with a carboxy group may be used. Examples of functional groups reactive with a hydroxy group include an isocyanato group, an epoxy group, a carboxy group, an acid anhydride group, and an aziridinyl group. From the viewpoint of reactivity, an isocyanato group and an epoxy group are preferred, and an isocyanato group is particularly preferred. Examples of functional groups reactive with a carboxy group include an epoxy group, a hydroxy group, and an aziridinyl group. From the viewpoint of reactivity, an epoxy group and an aziridinyl group are preferred.

[0075] Examples of the crosslinking agent (C) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene 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, tetramethylxylylene ... Polyisocyanates such as tolylene diisocyanate adduct of trimethylolpropane, xylylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, methylenebis(4-phenylmethane)triisocyanate; 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, bisphenol A-epichlorohydrin type epoxy resin, N,N'-[1,3-phenylenebis(methylene)]bis[bis(oxiran-2-ylmethyl)amine], ethylene glycol polyepoxy compounds such as ethanol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, and diglycerol polyglycidyl ether; Aziridine compounds such as N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide); melamine compounds such as hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, and hexahexyloxymethylmelamine;Examples of aziridinyl compounds include 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], pentaerythritol tris[3-(1-aziridinyl)propionate], N,N'-diphenylmethane-4,4'-bis(1-aziridinylcarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinylcarboxamide);

[0076] Among these crosslinking agents (C), it is preferable to use at least one selected from the group consisting of polyisocyanates and polyepoxy compounds, and it is more preferable to use polyisocyanates, because they have good reactivity with the (meth)acrylic resin (A).

[0077] The crosslinking agent (C) may be used alone or in combination of two or more kinds.

[0078] The content of the crosslinking agent (C) is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, even more 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). When the content of the crosslinking agent (C) relative to 100 parts by mass of the (meth)acrylic resin (A) is 0.1 parts by mass or more, a three-dimensional crosslinked structure is sufficiently formed in the pressure-sensitive adhesive composition upon UV irradiation, thereby making it possible to sufficiently reduce the adhesive strength of the pressure-sensitive adhesive composition after UV irradiation. When the content of the crosslinking agent (C) relative to 100 parts by mass of the (meth)acrylic resin (A) is 30 parts by mass or less, the adhesive strength of the pressure-sensitive adhesive composition before UV irradiation is good.

[0079] (Other Components) In the method for producing a pressure-sensitive adhesive composition, components other than the (meth)acrylic resin (A), the photopolymerization initiator (B), and the crosslinking agent (C) may be mixed, if necessary. Examples of the other components include a tackifier, a solvent, and various additives.

[0080] (Tackifier) ​​Any conventionally known tackifier can be used without any particular limitation. Examples of tackifiers include terpene-based tackifier resins, phenol-based tackifier resins, rosin-based tackifier resins, aliphatic petroleum resins, aromatic petroleum resins, copolymer-based petroleum resins, alicyclic petroleum resins, xylene resins, epoxy-based tackifier resins, polyamide-based tackifier resins, ketone-based tackifier resins, and elastomer-based tackifier resins. These tackifiers may be used alone or in combination of two or more.

[0081] When a tackifier is mixed, the amount added is preferably 30 parts by mass or less, and more preferably 5 to 20 parts by mass, per 100 parts by mass of the (meth)acrylic resin (A).

[0082] (Solvent) A solvent can be used to dilute the PSA composition for the purpose of adjusting the viscosity of the PSA composition. For example, when the PSA composition is to be applied, the solvent can be used to adjust the viscosity of the PSA composition to an appropriate value.

[0083] Examples of the solvent that can be used include organic solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone, ethyl acetate, propyl acetate, tetrahydrofuran, dioxane, cyclohexanone, hexane, toluene, xylene, n-propanol, isopropyl alcohol, etc. These solvents may be used alone or in combination of two or more.

[0084] (Additives) Examples of additives include plasticizers, surface lubricants, leveling agents, softeners, antioxidants, antiaging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, benzotriazole-based light stabilizers and the like, phosphate ester-based and other flame retardants, surfactants, and antistatic agents.

[0085] [Method for Producing Pressure-Sensitive Adhesive Sheet] The pressure-sensitive adhesive sheet can be produced, for example, by the method described below.

[0086] First, a pressure-sensitive adhesive solution is prepared by dissolving or dispersing a pressure-sensitive adhesive composition in a solvent. The pressure-sensitive adhesive composition may be used as the pressure-sensitive adhesive solution as it is.

[0087] Next, the adhesive solution is applied to the substrate, and if a solvent is contained, the solution is heated and dried to remove the solvent, forming an adhesive layer. Thereafter, a release sheet is attached to the adhesive layer as needed. Furthermore, the resulting sheet is cured in an oven for a certain period of time as needed to form a crosslinked structure, thereby obtaining an adhesive sheet.

[0088] The pressure-sensitive adhesive sheet can also be produced by the following method. A pressure-sensitive adhesive solution is applied to a release sheet, and if a solvent is contained, the solution is heated and dried to remove the solvent, forming a pressure-sensitive adhesive layer. The release sheet having the pressure-sensitive adhesive layer is then placed on a substrate with the pressure-sensitive adhesive layer side facing the substrate, and the pressure-sensitive adhesive layer is transferred (adhered) onto the substrate. Furthermore, if necessary, the obtained sheet is cured in an oven for a certain period of time to form a crosslinked structure, thereby obtaining a pressure-sensitive adhesive sheet.

[0089] In the above method, a substrate having an adhesive layer is used as the substrate, and a pressure-sensitive adhesive composition is applied to the adhesive layer, or the adhesive layer and the pressure-sensitive adhesive layer are laminated so that they face each other, thereby obtaining a dicing / die-bonding integrated film.

[0090] The pressure-sensitive adhesive solution can be applied to the substrate (or release sheet) by any known method, specifically by using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, or direct coater.

[0091] The conditions for heat-drying the applied pressure-sensitive adhesive solution are not particularly limited, but are typically 25 to 180°C, preferably 60 to 150°C, for 1 to 20 minutes, preferably 1 to 10 minutes. Heat-drying within the above ranges allows the solvent contained in the pressure-sensitive adhesive solution to be removed. The conditions for curing the heat-dried sheet in an oven for a certain period of time are not particularly limited, but are typically 25 to 100°C, preferably 30 to 80°C, for 1 to 30 days, preferably 1 to 14 days. Curing under the above conditions allows the (meth)acrylic resin (A) to be crosslinked by the crosslinking agent (C), thereby adjusting the gel fraction of the pressure-sensitive adhesive layer to the desired range.

[0092] [Uses of the Pressure-Sensitive Adhesive Sheet] The pressure-sensitive adhesive sheet can be used as a removable pressure-sensitive adhesive sheet, for example, when manufacturing electronic components. Specifically, removable pressure-sensitive adhesive sheets are used in various processes when manufacturing electronic components, such as fixing an adherend and subjecting it to various processing steps, followed by irradiating it with UV (ultraviolet) light to remove it from the adherend. Therefore, the pressure-sensitive adhesive sheet can be used as a backgrinding tape, dicing tape, etc. when processing semiconductor wafers. The pressure-sensitive adhesive sheet can also be used as a support tape for fragile materials such as ultrathin glass substrates and materials that are prone to warping, such as FPC boards. In particular, the pressure-sensitive adhesive sheet has excellent adhesion to the adhesive layer and excellent releasability after UV irradiation, making it suitable as a dicing tape used when manufacturing a dicing / die-bonding integrated film.

[0093] When using an adhesive sheet as a wafer dicing tape, the adhesive sheet is attached to a wafer on which multiple components are formed before the dicing process. Next, the wafer is cut and separated (diced) into individual components to form element pieces (chips). Then, the adhesive sheet attached to each element piece is irradiated with UV light. This irradiates the adhesive layer through the base material of the adhesive sheet, and the unsaturated bonds in the adhesive form a three-dimensional crosslinked structure and harden. As a result, the adhesive strength of the adhesive layer is reduced. Then, the adhesive sheet is peeled off from each element piece.

[0094] Examples of light sources used for UV irradiation include high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, chemical lamps, and black lights.

[0095] The UV irradiation dose applied to the adhesive sheet is 50 to 3,000 mJ / cm ２ is preferably 100 to 600 mJ / cm ２ It is more preferable that the UV irradiation dose applied to the pressure-sensitive adhesive sheet is 50 mJ / cm. ２ When the UV irradiation dose is 3,000 mJ / cm or more, the pressure-sensitive adhesive layer can be cured at a sufficiently high curing rate by UV irradiation, and the adhesive strength of the pressure-sensitive adhesive layer after UV irradiation can be sufficiently reduced. ２ Even if the UV irradiation dose is increased to 3,000 mJ / cm, the effect is not commensurate with the increase. ２ By setting the temperature as follows, the pressure-sensitive adhesive sheet can be economically peeled off while reducing the effect of UV irradiation on the adherend.

[0096] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0097] The raw materials used in the synthesis of the (meth)acrylic resins (A) and (cA) are as follows: Hydroxy group-containing (meth)acrylate (m-1): 2-hydroxyethyl acrylate, Nippon Shokubai Co., Ltd., 2-hydroxyethyl methacrylate, Nippon Shokubai Co., Ltd., 4-hydroxybutyl acrylate, Osaka Organic Chemical Industry Ltd. Alkyl (meth)acrylate (m-2): 2-ethylhexyl acrylate, Osaka Organic Chemical Industry Ltd., n-butyl acrylate, Osaka Organic Chemical Industry Ltd., dodecyl acrylate, Osaka Organic Chemical Industry Ltd., 2-methoxyethyl acrylate, Osaka Organic Chemical Industry Ltd., ethyl acrylate, Nippon Shokubai Co., Ltd., methyl methacrylate, Nippon Shokubai Co., Ltd. Carboxy group-containing monomer (m-3): Acrylic acid, Nippon Shokubai Co., Ltd., methacrylic acid, Nippon Shokubai Co., Ltd. Radical polymerization initiator: 2,2'-azobis(isobutyronitrile), Fujifilm Wako Pure Chemical Industries, Ltd. RAFT agent: 2-(Dodecylsulfanylthiocarbonyl)sulfanyl)propanoic acid, Fujifilm Wako Pure Chemical Corporation, Bis{4-[ethyl-(2-hydroxyethyl)carbamoyl]benzyl}trithiocarbonate, Fujifilm Wako Pure Chemical Corporation, S,S-Dibenzyltrithiocarbonate, Fujifilm Wako Pure Chemical Corporation, 2-Phenyl-2-propyldithiobenzoic acid, Ouchi Shinko Chemical Industry Co., Ltd. Additive: 2-Methyl-2-n-butyltellanyl-ethyl propionate, Otsuka Chemical Co., Ltd. Isocyanato group-containing ethylenically unsaturated compound (a): Karenz™ MOI, 2-isocyanatoethyl methacrylate, Showa Denko K.K., AOI-VM™, 2-isocyanatoethyl acrylate, Showa Denko K.K.

[0098] Synthesis examples of (meth)acrylic resins (A) and (cA) are shown below. The weight-average molecular weight, molecular weight distribution, acid value, and glass transition temperature of (meth)acrylic resins (A) and (cA) were measured and calculated by the methods described above. The ethylenically unsaturated group equivalent of (meth)acrylic resins (A) and (cA) was calculated from the charged amount as described above. The hydroxyl value is the mass (mg) of potassium hydroxide required to neutralize the acetic acid bonded to the hydroxyl group when 1 g of resin is acetylated in accordance with JIS K 0070:1992. The weight-average molecular weight, molecular weight distribution, ethylenically unsaturated group equivalent, hydroxyl value, acid value, and glass transition temperature of (meth)acrylic resins (A) and (cA) are shown in Table 1.

[0099] Synthesis Example 1 (Example 1-1) A reaction apparatus equipped with a stirrer, temperature controller, reflux condenser, dropping funnel, and thermometer was charged with 132 parts by mass (71.6 mol) of 2-ethylhexyl acrylate, 33 parts by mass (28.4 mol) of 2-hydroxyethyl acrylate, 0.23 parts by mass of 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, 0.05 parts by mass of 2,2'-azobis(isobutyronitrile), and 471 parts by mass of ethyl acetate as a solvent. After heating to reflux was initiated, the reaction was allowed to proceed for 10 hours. Next, the temperature of the reaction mixture was lowered to 60°C, and a mixture of 24.7 parts by mass (15.9 mol) of 2-isocyanatoethyl methacrylate and 0.19 parts by mass of dibutyltin dilaurate as a urethanization catalyst was added dropwise through the dropping funnel. After completion of the dropwise addition, the reaction system was maintained at 70°C for 4 hours to eliminate the isocyanato groups. This gave a solution with a solid content of 35% by mass containing a (meth)acrylic resin (A1) having a weight average molecular weight of 300,000, a glass transition temperature of −50° C. and an ethylenically unsaturated group equivalent of 1,189 g / mol.

[0100] Synthesis Examples 2 to 4 (Examples 1-2 to 1-4) (Meth)acrylic resins (A2) to (A4) were obtained in the same manner as in Synthesis Example 1, except that the compositions shown in Table 1 were used.

[0101] Comparative Synthesis Example 1 (Comparative Example 1-1) A reaction apparatus equipped with a stirrer, temperature controller, reflux condenser, dropping funnel, and thermometer was charged with 132 parts by mass (71.6 mol) of 2-ethylhexyl acrylate, 33 parts by mass (28.4 mol) of 2-hydroxyethyl acrylate, 0.08 parts by mass of 2,2'-azobis(isobutyronitrile), and 471 parts by mass of ethyl acetate as a solvent. After heating and refluxing were initiated, the reaction was allowed to proceed for 10 hours. Next, the temperature of the reaction mixture was lowered to 60°C, and a mixture of 16.5 parts by mass (10.6 mol) of 2-isocyanatoethyl methacrylate and 0.18 parts by mass of dibutyltin dilaurate as a urethanization catalyst was added dropwise through the dropping funnel. After completion of the dropwise addition, the reaction system was maintained at 70°C for 4 hours to eliminate the isocyanato groups. This gave a solution with a solid content of 35% by mass containing a (meth)acrylic resin (cA1) having a weight average molecular weight of 600,000, a glass transition temperature of −45° C. and an ethylenically unsaturated group equivalent of 1,707 g / mol.

[0102] Comparative Synthesis Example 2 (Comparative Example 1-2) A (meth)acrylic resin (cA2) was obtained in the same manner as in Synthesis Example 1, except that 2-methyl-2-n-butyltellanyl-ethyl propionate was used instead of 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid and the composition shown in Table 1 was used.

[0103] Comparative Synthesis Example 3 (Comparative Example 1-3) A (meth)acrylic resin (cA3) was obtained in the same manner as in Synthesis Example 1, except that the composition shown in Table 1 was used.

[0104]

[0105] The raw materials used in preparing the pressure-sensitive adhesive composition are as follows: Photopolymerization initiator (B): TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (BASF, trade name: L-TPO) Crosslinking agent (C) L-45E: tolylene diisocyanate adduct of trimethylolpropane (Tosoh Corporation, trade name: Coronate L-45E) TETRAD-X: N,N'-[1,3-phenylenebis(methylene)]bis[bis(oxiran-2-ylmethyl)amine] (Mitsubishi Gas Chemical Company, Inc., trade name: TETRAD-X)

[0106] [Preparation of Pressure-Sensitive Adhesive Composition] Ethyl acetate, a dilution solvent, was added to the solutions containing the (meth)acrylic resins (A1) to (A4) and (cA1) to (cA3) obtained in Synthesis Examples 1 to 4 and Comparative Synthesis Examples 1 to 3, so that the contents of the (meth)acrylic resins (A1) to (A4) and (cA1) to (cA3) were 30 mass %. Using these solutions, pressure-sensitive adhesive compositions were obtained by the method described below.

[0107] In a room shielded from actinic radiation, the (meth)acrylic resin (A) or (cA), photopolymerization initiator (B), and crosslinking agent (C) shown in Table 2 were added to a plastic container in the amounts (parts by mass) shown in Table 2, and the mixture was stirred to obtain PSA compositions (B1) to (B4) and (cB1) to (cB3). The numerical values ​​for (meth)acrylic resins (A1) to (A4) and (meth)acrylic resins (cA1) to (cA3) in Table 2 represent the solids content of the solution used, i.e., the amount (parts by mass) of (meth)acrylic resins (A1) to (A4) and (cA1) to (cA3) used. The numerical value for photopolymerization initiator (B) represents the amount (parts by mass) of photopolymerization initiator (B) used per 100 parts by mass of (meth)acrylic resin (A) or (cA). The numerical value of the crosslinking agent (C) is the amount (parts by mass) of the crosslinking agent (C) used relative to 100 parts by mass of the (meth)acrylic resin (A) or (cA).

[0108] Example 2-1 Preparation of Pressure-Sensitive Adhesive Sheet A silicone-based light-release PET film (Toyobo Co., Ltd., product name: E7006, thickness: 25 μm) was prepared as a separator, and the pressure-sensitive adhesive composition (B1) was applied to the release-treated surface using an applicator so that the thickness after curing would be 20 μm. The film was then dried by heating at 100°C for 2 minutes to form a pressure-sensitive adhesive layer. Next, a 90 μm-thick PO film was prepared as a sheet-like substrate. The PO film was attached to the pressure-sensitive adhesive layer using a rubber roller so that the corona-treated surface of the PO film was adhered to the exposed surface of the pressure-sensitive adhesive layer. The film was then cured in an oven at 40°C for 3 days, and the pressure-sensitive adhesive layer was crosslinked and cured to obtain the pressure-sensitive adhesive sheet of Example 2-1.

[0109] [Examples 2-2 to 2-4 and Comparative Examples 2-1 to 2-3] Preparation of Pressure-Sensitive Adhesive Sheets Pressure-sensitive adhesive sheets of Examples 2-2 to 2-4 and Comparative Examples 2-1 to 2-3 were obtained in the same manner as in Example 2-1, except that the pressure-sensitive adhesive compositions shown in Table 2 were used instead of the pressure-sensitive adhesive composition (B1).

[0110]

[0111] [Preparation of a dicing / die bonding integrated film] The adhesive layer was exposed by peeling off the cover film on one side of a die bonding film (FH-D25T-50, Showa Denko Materials Co., Ltd.), both sides of which were protected by cover films. This adhesive layer was then bonded with the adhesive layer of each of the adhesive sheets of Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-3, in which the adhesive layer had been exposed by peeling off the light-release PET film, using a rubber roller. This was left at room temperature for one day, yielding a dicing / die bonding integrated film.

[0112] [Evaluation] (1) Measurement of Adhesion Strength (30° Peel Strength) Before UV Irradiation The adhesion strength of the pressure-sensitive adhesive sheets according to the Examples and Comparative Examples to a die bonding film was evaluated by measuring the 30° peel strength as follows. A sample measuring 25 mm wide and 100 mm long was cut from the integrated dicing and die bonding film. The cover film on the side of the integrated dicing and die bonding film to which the pressure-sensitive adhesive sheet was not attached was peeled off, and the adhesive layer was attached to a polycarbonate plate using double-sided tape to obtain a sample for adhesion measurement. The peel strength of the pressure-sensitive adhesive sheet to the die bonding film was measured using a tensile tester (VPA-H200, Kyowa Interface Science Co., Ltd.). The measurement conditions were a peel angle of 30° and a tensile speed of 600 mm / min. The sample storage and peel strength measurement were performed in an environment of 23°C and 40% relative humidity. The results are shown in Table 2.

[0113] (2) Measurement of adhesive strength (30° peel strength) after UV irradiation. The dicing and die bonding integrated film was exposed to an irradiation dose of 300 mJ / cm from the substrate side of the adhesive sheet. ２The adhesive sheet was irradiated with ultraviolet (UV) rays under the conditions of (a) to (c) to obtain a sample for measuring adhesive strength after UV irradiation. A conveyor-type UV irradiation device (Eye Graphics Co., Ltd., 2 kW lamp, 80 W / cm) was used for UV irradiation. The peel strength of the adhesive sheet against the die bonding film was then measured using the same method as for measuring adhesive strength before UV irradiation (30° peel strength). The results are shown in Table 2.

[0114] (3) Processability Evaluation (i) Preparation of a Sample for Processability Evaluation A protective tape (BG tape) was attached to the surface of a silicon wafer (diameter: 12 inches, thickness: 775 μm). The silicon wafer was then subjected to stealth dicing. That is, a modified layer was formed inside the silicon wafer by irradiating the surface (back surface) of the silicon wafer opposite to the side where the BG tape was attached with laser light under the following conditions. <Stealth dicing conditions> Stealth dicing device: DFL7361 (Disco Corporation) Laser oscillator type: Q-switched semiconductor pumped solid state laser Wavelength: 1342 nm Frequency: 90 kHz Output: 1.7 W Number of passes: 2 Chip size: 10 mm × 10 mm Dicing speed: 700 mm / sec

[0115] The silicon wafer after stealth dicing was polished to a thickness of 30 μm. A grinder polisher (DGP8761, Disco Corporation) was used for polishing. The adhesive layer of a dicing / die bonding integrated film was attached to the polished silicon wafer under the following conditions, with the substrate side of the dicing tape facing the dicing ring. The BG tape was then peeled off from the surface of the silicon wafer. <Attachment conditions> Attachment device: DFM2800 (Disco Corporation) Attachment temperature: 70°C Attachment speed: 10 mm / s Attachment tension level: Level 6

[0116] Next, a die separator (DDS2300, Disco Corporation) was used to cool and expand under the following conditions. Thereafter, the base material layer (PO film) of the dicing-die bonding integrated film was heat-shrunk under the following conditions. Through these processes, the silicon wafer and adhesive layer were singulated into multiple adhesive-piece chips (size 10 mm x 10 mm). <Cooling and expanding conditions> - Cooling temperature: -15°C - Cooling time: 120 seconds - Push-up amount: 12 mm - Push-up speed: 200 mm / sec - Holding time after push-up: 3 seconds <Heat shrinking conditions> - Heater temperature: 220°C - Heater rotation speed: 5° / sec - Push-up amount: 8 mm - Tape cooling waiting time: 10 seconds

[0117] After the silicon wafer and the adhesive layer were separated into individual pieces, the pressure-sensitive adhesive layer was irradiated with ultraviolet light from the substrate side of the pressure-sensitive adhesive sheet under the following conditions. This cured the pressure-sensitive adhesive layer, thereby reducing the adhesive strength of the adhesive layer. <UV Irradiation Conditions> UV Illuminance: 100 mW / cm ２ UV irradiation dose: 150 mJ / cm ２

[0118] (ii) Evaluation of processability (DAF skipping) After cooling expansion and heat shrinking, DAF skipping was evaluated according to the following criteria. The results are shown in Table 2. A: No DAF skipping occurred. B: No DAF skipping occurred, but peeling or lifting was observed at the interface between the adhesive layer and the pressure-sensitive adhesive layer. C: DAF skipping occurred in at least one location.

[0119] (Chip edge peeling) After cooling expansion and heat shrinking, peeling between the adhesive layer and the pressure-sensitive adhesive layer at the edge of the chip with adhesive piece was evaluated according to the following criteria. The results are shown in Table 2. A: No peeling was observed at the edge. B: Peeling was observed at a length of 1 mm or more but less than 2 mm from the edge. C: Peeling was observed at a length of 2 mm or more but less than 3 mm from the edge. D: Peeling was observed at a length of 3 mm or more from the edge.

[0120] (Separability of adhesive layer) The entire surface of the silicon wafer after cooling expansion and heat shrinking was observed under a microscope, and the separability of the adhesive layer was evaluated according to the following criteria. The results are shown in Table 2. A: The adhesive layer was completely separated. D: There was at least one part of the adhesive layer that was not separated.

[0121] (Kerf Width) The distance between the chips with adhesive pieces (kerf width) after singulation was measured using a microscope. The kerf width in the MD / TD directions was measured at two locations on the outer periphery of the silicon wafer (top, bottom, left, and right) and one location in the center (18 locations in total), and the average value was calculated. Evaluation was based on the following criteria. The results are shown in Table 2. S: The average kerf width was 100 μm or more and less than 150 μm. A: The average kerf width was 70 μm or more and less than 100 μm. B: The average kerf width was 50 μm or more and less than 70 μm.

[0122] (Pickup ability) After carrying out the above evaluation, 100 chips with adhesive pieces attached were picked up under the following conditions and evaluated according to the following criteria. The results are shown in Table 2. <Pickup conditions> Die bonder: DB-830P (Fasford Technology Co., Ltd.) Push-up pin: EJECTOR NEEDLE SEN2-83-05 (diameter: 0.7 mm, tip shape: hemisphere with radius of 350 μm, Micromechanics Co., Ltd.) Push-up height: 250 μm Push-up speed: 1 mm / sec Number of push-up pins: 9 <Evaluation criteria> A: The pickup success rate was 100%. B: The pickup success rate was 80% or more but less than 100%. C: The pickup success rate was 60% or more but less than 80%.

[0123] The integrated dicing and die bonding films produced using the pressure-sensitive adhesive sheets of Examples 2-1 to 2-3 all achieved good results in the processability evaluation. In particular, Examples 2-1, 2-2, and 2-4 received a kerf width rating of "S." Kerf width is one of the important factors in the stealth dicing process from the perspective of achieving excellent pickup performance. Meanwhile, the kerf width rating of all comparative examples was "B." In addition, chip edge peeling occurred after cooling expansion and heat shrinking in all comparative examples, and pickup failure also occurred. Comparative example 2-2, which used a (meth)acrylic resin obtained from a copolymer produced by organotellurium radical polymerization, received a D rating for adhesive layer severability due to a low level of low-molecular-weight components and insufficient propagation of fracture stress.

[0124] According to the present disclosure, a (meth)acrylic resin suitable for a pressure-sensitive adhesive composition is provided. A pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition produced using the (meth)acrylic resin can be preferably used as a removable pressure-sensitive adhesive sheet, particularly as a pressure-sensitive adhesive layer for a dicing / die-bonding integrated film.

Claims

1. a step (i) of polymerizing raw material monomers (M) containing a hydroxyl group-containing (meth)acrylate (m-1) and an alkyl (meth)acrylate (m-2) by reversible addition-fragmentation chain transfer (RAFT) polymerization to obtain a copolymer (A-0); (ii) a step of adding an isocyanato group-containing ethylenically unsaturated compound (a) to a portion of the side chain hydroxyl groups of the copolymer (A-0) to obtain an ethylenically unsaturated group-containing (meth)acrylic resin (A); (A) an ethylenically unsaturated group-containing (meth)acrylic resin obtained by a method for producing a (meth)acrylic resin comprising the steps of: A photopolymerization initiator (B); A crosslinking agent (C); a method for producing an integrated dicing and die bonding film, the method comprising: laminating an adhesive layer on a pressure-sensitive adhesive layer having a crosslinked structure formed thereon, the pressure-sensitive adhesive layer being obtained by a method for producing a pressure-sensitive adhesive sheet comprising a step of forming a crosslinked structure in a pressure-sensitive adhesive layer obtained by applying a pressure-sensitive adhesive composition obtained by a method for producing a pressure-sensitive adhesive composition comprising a step (iii) of mixing the above.

2. A process (i) for obtaining a copolymer (A-0) by polymerizing a raw material monomer group (M) containing a hydroxyl group-containing (meth)acrylate (m-1) and an alkyl (meth)acrylate (m-2) through reversible addition-fragmentation chain transfer (RAFT) polymerization; (ii) a step of adding an isocyanato group-containing ethylenically unsaturated compound (a) to a portion of the side chain hydroxyl groups of the copolymer (A-0) to obtain an ethylenically unsaturated group-containing (meth)acrylic resin (A); (A) an ethylenically unsaturated group-containing (meth)acrylic resin obtained by a method for producing a (meth)acrylic resin comprising the steps of: A photopolymerization initiator (B); A crosslinking agent (C); and applying to an adhesive layer a pressure-sensitive adhesive composition obtained by a pressure-sensitive adhesive composition producing method comprising the step (iii) of mixing the above.

3. The method for producing a dicing-die bonding integrated film according to claim 1 or 2, wherein the raw material monomer group (M) further contains a carboxyl group-containing monomer (m-3).

4. 3. The method for producing a dicing-die bonding integrated film according to claim 1, wherein the (meth)acrylic resin (A) having an ethylenically unsaturated group has a molecular weight distribution (Mw / Mn) of 2.4 to 10.

0.

5. 3. The method for producing a dicing-die bonding integrated film according to claim 1, wherein the crosslinking agent (C) is at least one selected from the group consisting of polyisocyanates and polyepoxy compounds.