Adhesive composition, method for producing same, adhesive sheet, dicing tape, dicing / die bonding integrated film, and method for producing (METH)acrylic resin

Abstract

Provided is an adhesive composition. The adhesive composition contains a (meth)acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C). The (meth)acrylic resin (A) has a structural unit (M-1) that has a hydroxy group, a structural unit (M-2) that has an ethylenically unsaturated group, and a structural unit (M-3) that has a carboxy group. The (meth)acrylic resin (A) has a weight average molecular weight of 200,000-650,000. The (meth)acrylic resin (A) has an acid value of 5-50 mg KOH / g.

Description

Pressure-sensitive adhesive composition and method for producing the same, pressure-sensitive adhesive sheet, dicing tape, integrated dicing and die-bonding film, and method for producing (meth)acrylic resin

[0001] The present disclosure relates to a pressure-sensitive adhesive composition and a method for producing the same, a pressure-sensitive adhesive sheet, a dicing tape, a dicing and die-bonding integrated film, and a method for producing a (meth)acrylic resin.

[0002] Conventionally, pressure-sensitive adhesive sheets have been used in the manufacturing process of semiconductor devices, etc. Examples of such pressure-sensitive adhesive sheets include dicing tape used in the process of cutting and dividing a semiconductor wafer into semiconductor chips (dicing). Such pressure-sensitive adhesive sheets are releasable pressure-sensitive adhesive sheets that are attached to a semiconductor wafer as an adherend and are peeled off from the adherend after a predetermined processing step is 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 that has an ethylenically unsaturated group in the molecule and that hardens when irradiated with ultraviolet (UV) light (see, for example, Patent Document 1).

[0004] JP 2014-62210 A

[0005] Removable pressure-sensitive adhesive sheets are required to have sufficient adhesive strength to adherends when subjected to predetermined processing steps. However, conventional pressure-sensitive adhesive sheets do not have sufficient adhesive strength, and there is still room for improvement.

[0006] A main object of the present disclosure is to provide a pressure-sensitive adhesive composition that can provide a pressure-sensitive adhesive sheet having high adhesive strength.

[0007] As a result of extensive research, the inventors of the present disclosure have discovered that the adhesive strength of the pressure-sensitive adhesive sheet can be improved by adjusting the weight-average molecular weight and acid value of the (meth)acrylic resin within a predetermined range, and have thus completed the invention of the present disclosure.

[0008] The present disclosure provides a pressure-sensitive adhesive composition according to any one of [1] to [4], a pressure-sensitive adhesive sheet according to [5], a dicing tape according to [6], a dicing and die-bonding integrated film according to [7], a method for producing a (meth)acrylic resin according to [8] and [9], and a method for producing a pressure-sensitive adhesive composition according to

[10] . [1] A pressure-sensitive adhesive composition comprising: a (meth)acrylic resin (A); a photopolymerization initiator (B); and a crosslinking agent (C), wherein the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group, the weight-average molecular weight of the (meth)acrylic resin (A) being 200,000 to 650,000, and the acid value of the (meth)acrylic resin (A) being 5 to 50 mgKOH / g. [2] The pressure-sensitive adhesive composition according to [1], wherein the (meth)acrylic resin (A) further has a structural unit derived from an alkyl (meth)acrylate. [3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the (meth)acrylic resin (A) has an ethylenically unsaturated group equivalent of 100 to 5,000 g / mol. [4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the (meth)acrylic resin (A) has a hydroxyl value of 0.01 to 50 mgKOH / g. [5] A pressure-sensitive adhesive sheet comprising: a base layer; and a pressure-sensitive adhesive layer provided on the base layer; wherein the pressure-sensitive adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B); the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group; the weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000; and the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g.[6] A dicing tape comprising: a base layer; and a pressure-sensitive adhesive layer provided on the base layer; wherein the pressure-sensitive adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B); the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group; the weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000; and the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g. [7] A dicing and die bonding integrated film comprising, in this order: a base layer; a pressure-sensitive adhesive layer; and an adhesive layer; wherein the pressure-sensitive adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B); the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group; the weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000; and the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g. [8] A method for producing a (meth)acrylic resin, comprising the step of adding an isocyanato group-containing ethylenically unsaturated compound (a) in the presence of a catalyst to some of the hydroxy groups of a copolymer having a structural unit derived from an ethylenically unsaturated compound (m-1) having a hydroxy group and a structural unit derived from an ethylenically unsaturated compound (m-3) having a carboxy group, to obtain a (meth)acrylic resin (A), wherein the (meth)acrylic resin (A) has a weight-average molecular weight of 200,000 to 650,000, and an acid value of 5 to 50 mgKOH / g. [9] A method for producing a (meth)acrylic resin according to [8], wherein the catalyst contains at least one metal selected from the group consisting of tin, zirconium, and bismuth.

[10] A method for producing a pressure-sensitive adhesive composition, comprising the step of mixing the (meth)acrylic resin (A) obtained by the production method according to [8] or [9] with a photopolymerization initiator (B) and a crosslinking agent (C).

[0009] According to the present disclosure, a pressure-sensitive adhesive composition capable of providing a pressure-sensitive adhesive sheet having high adhesive strength and a method for producing the same are provided. Also, according to the present disclosure, a pressure-sensitive adhesive sheet, a dicing tape, and a dicing / die-bonding integrated film using the pressure-sensitive adhesive composition are provided. Furthermore, according to the present disclosure, a method for producing a (meth)acrylic resin suitable for use in the pressure-sensitive adhesive composition is provided.

[0010] Hereinafter, embodiments of the present disclosure will be described in detail, but the present disclosure is not limited to the embodiments described below.

[0011] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described in this specification, the upper limit or lower limit of that numerical range may be replaced with a value shown in the examples. Furthermore, upper and lower limits described individually can be combined in any way.

[0012] In this specification, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0013] In this specification, the term "(meth)acrylate" refers to at least one of an acrylate and its corresponding methacrylate. The same applies to other similar expressions such as "(meth)acryloyl" and "(meth)acrylic acid."

[0014] In this specification, the term "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.

[0015] In this specification, "A or B" means that either A or B is contained, or both are contained. Furthermore, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more. When a composition contains multiple substances corresponding to each component, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0016] In this specification, the term "ethylenically unsaturated group" refers to a group having a double bond formed between carbon atoms excluding carbon atoms forming an aromatic ring, and the term "ethylenically unsaturated compound" refers to a compound having an ethylenically unsaturated bond.

[0017] [Adhesive Composition] The adhesive composition of one embodiment contains a (meth)acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C), and may further contain other components added as needed. The adhesive composition containing the (meth)acrylic resin (A) is suitable for use in removable adhesive sheets, particularly dicing tapes and dicing / die bonding integrated films.

[0018] (Meth)acrylic Resin (A) The (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group. The (meth)acrylic resin (A) may further have a structural unit (M-4) other than the structural units (M-1), (M-2), and (M-3).

[0019] <Structural Unit (M-1) Having a Hydroxy Group> The structural unit (M-1) is a structural unit that does not have an ethylenically unsaturated group and has a hydroxy group. Specifically, in the production method described below, the structural unit (M-1) corresponds to the portion of the structural unit derived from the ethylenically unsaturated compound (m-1) having a hydroxy group, where the hydroxy group remains unreacted. When the (meth)acrylic resin (A) has the structural unit (M-1), a pressure-sensitive adhesive sheet having sufficient adhesive strength can be obtained. In addition, crosslinking points with the crosslinking agent (C) described below can be secured, thereby improving the strength of the pressure-sensitive adhesive layer. The structural unit (M-1) may be used alone or in combination of two or more types.

[0020] The structural unit (M-1) may be a structural unit derived from an ethylenically unsaturated compound (m-1) having a hydroxy group (hereinafter, sometimes referred to as "compound (m-1)"). The compound (m-1) is not particularly limited as long as it is a compound having a hydroxy group and one ethylenically unsaturated 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; (meth)acrylates having an aromatic ring and a hydroxy group such as hydroxyphenyl (meth)acrylate and 2-hydroxy-3-phenoxypropyl (meth)acrylate; and hydroxystyrene. Among these, from the viewpoint of curability when combined with the crosslinking agent (C) described below, the compound (m-1) may be a hydroxyalkyl (meth)acrylate, a hydroxyalkyl (meth)acrylate in which the hydroxyalkyl group has 1 to 6 carbon atoms, a hydroxyalkyl (meth)acrylate in which the linear alkyl group has a hydroxy group at the terminal, or at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0021] The content of the structural unit (M-1) may be 0.1 mol% or more, 0.5 mol% or more, or 1 mol% or more, and may be 20 mol% or less, 15 mol% or less, or 10 mol% or less, based on all structural units of the (meth)acrylic resin (A). When the content of the structural unit (M-1) is 0.1 mol% or more, based on all structural units of the (meth)acrylic resin (A), the (meth)acrylic resin (A) tends to be sufficiently thermoset by a crosslinking reaction caused by heating. In addition, the adhesive strength of the resulting pressure-sensitive adhesive sheet is improved, and when the pressure-sensitive adhesive sheet is used as a dicing tape or a dicing / die-bonding integrated film, the dicing properties tend to be improved. Furthermore, sufficient strength of the pressure-sensitive adhesive layer is obtained, which tends to prevent contamination of the adherend when the pressure-sensitive adhesive sheet is peeled off. When the content of the structural unit (M-1) is 20 mol% or less based on all structural units of the (meth)acrylic resin (A), the amount of hydroxy groups contained in the pressure-sensitive adhesive layer after thermal curing is sufficiently reduced, and the resulting pressure-sensitive adhesive sheet tends to have good water resistance. Therefore, when the pressure-sensitive adhesive sheet is used as a dicing tape or a dicing / die-bonding integrated film, the pressure-sensitive adhesive sheet tends to have excellent water resistance even in processes using water such as cutting water, and to have good dicing properties.

[0022] <Structural Unit (M-2) Having an Ethylenically Unsaturated Group> The structural unit (M-2) is a structural unit having an ethylenically unsaturated group. The structural unit (M-2) may be a structural unit derived from a (meth)acrylate (m-2) having an ethylenically unsaturated group other than a (meth)acryloyloxy group, or a structural unit derived from a compound having a (meth)acryloyloxy group. When the (meth)acrylic resin (A) has the structural unit (M-2), the adhesive strength can be reduced by UV irradiation after the pressure-sensitive adhesive sheet is attached to an adherend, making it possible to easily peel the sheet from the adherend. When the pressure-sensitive adhesive sheet is used as a dicing tape or a dicing / die-bonding integrated film, the dicing properties are good and excellent pick-up properties tend to be obtained after UV irradiation. The structural unit (M-2) may be used alone or in combination of two or more types.

[0023] In one embodiment, the structural unit (M-2) is a structural unit derived from a (meth)acrylate (m-2) (hereinafter, sometimes referred to as "compound (m-2)") having an ethylenically unsaturated group other than a (meth)acryloyloxy group. Examples of the compound (m-2) include alkenyl (meth)acrylates such as vinyl (meth)acrylate, allyl (meth)acrylate, isopropenyl (meth)acrylate, and 2-butenyl (meth)acrylate; and (meth)acrylates containing an unsaturated alicyclic skeleton such as dicyclopentenyloxyethyl (meth)acrylate and dicyclopentenyl (meth)acrylate. Among these, from the viewpoint of reaction control, the compound (m-2) may be an alkenyl (meth)acrylate, or may be at least one selected from the group consisting of allyl (meth)acrylate, isopropenyl (meth)acrylate, and 2-butenyl (meth)acrylate, or may be isopropenyl (meth)acrylate.

[0024] In one embodiment, the structural unit (M-2) is a structural unit in which an isocyanato group of an isocyanato group-containing ethylenically unsaturated compound (a) (hereinafter, sometimes referred to as "compound (a)") is added to the hydroxy group of a structural unit derived from the ethylenically unsaturated compound (m-1) having a hydroxy group. The compound (a) is not particularly limited as long as it does not have a hydroxy group and has one 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), the compound (a) may be a (meth)acryloyloxyalkyl isocyanate or 2-isocyanatoethyl (meth)acrylate.

[0025] When an isocyanato group of the compound (a) is introduced into a portion of the hydroxy group of a structural unit derived from an ethylenically unsaturated compound (m-1) having a hydroxy group, the addition rate of the compound (a) relative to the number of moles of the hydroxy group may be 40 mol% or more, 50 mol% or more, 60 mol% or more, or 70 mol% or more. The addition rate of the compound (a) may preferably be 99 mol% or less, 95 mol% or less, 92 mol% or less, or 90 mol% or less. When the addition rate of the compound (a) is 40 mol% or more, sufficient releasability is obtained after UV irradiation of the pressure-sensitive adhesive sheet, and when the pressure-sensitive adhesive sheet is used as a dicing tape or a dicing / die-bonding integrated film, good pick-up properties tend to be obtained. When the addition rate of the compound (a) is 99 mol% or less, the (meth)acrylic resin (A) tends to be sufficiently thermoset by the crosslinking reaction due to heating. In addition, the adhesive strength of the resulting pressure-sensitive adhesive sheet tends to be good. Therefore, when the pressure-sensitive adhesive sheet is used as a dicing tape or a dicing / die bonding integrated film, the dicing property tends to be good. Furthermore, sufficient strength of the pressure-sensitive adhesive layer is obtained, and contamination of the adherend when the pressure-sensitive adhesive sheet is peeled off tends to be prevented.

[0026] The content of the structural unit (M-2), based on the total structural units of the (meth)acrylic resin (A), may be 1 mol% or more, 5 mol% or more, or 10 mol% or more, and may be 40 mol% or less, 30 mol% or less, or 25 mol% or less. When the content of the structural unit (M-2), based on the total structural units of the (meth)acrylic resin (A), is 1 mol% or more, sufficient peelability is obtained after UV irradiation of the pressure-sensitive adhesive sheet, and when the pressure-sensitive adhesive sheet is used as a dicing tape or a dicing / die-bonding integrated film, good pick-up properties tend to be obtained. When the content of the structural unit (M-2), based on the total structural units of the (meth)acrylic resin (A), is 40 mol% or less, compatibility with common organic solvents tends to be good.

[0027] <Structural Unit (M-3) Having a Carboxy Group> The structural unit (M-3) is a structural unit having a carboxy group. When the (meth)acrylic resin (A) has the structural unit (M-3), a pressure-sensitive adhesive sheet having sufficient adhesive strength can be obtained. The structural unit (M-3) may be used alone or in combination of two or more types.

[0028] The structural unit (M-3) may be a structural unit derived from an ethylenically unsaturated compound (m-3) having a carboxy group (hereinafter, may be referred to as "compound (m-3)"). The compound (m-3) is not particularly limited as long as it is a compound having a carboxy group and one ethylenically unsaturated group. Specific examples include unsaturated monobasic acids such as (meth)acrylic acid, crotonic acid, and vinylbenzoic acid; and unsaturated dibasic acids such as itaconic acid. Among these, the compound (m-3) may be (meth)acrylic acid from the viewpoint of ease of synthesis of the (meth)acrylic resin (A).

[0029] The content of the structural unit (M-3) may be 1 mol% or more, 1.5 mol% or more, or 1.8 mol% or more, and may be 16 mol% or less, 14 mol% or less, or 12 mol% or less, based on all structural units of the (meth)acrylic resin (A). When the content of the structural unit (M-3) is 1 mol% or more, based on all structural units of the (meth)acrylic resin (A), the acid value tends to be easily adjusted to above the lower limit of a predetermined range, and the adhesive strength of the resulting pressure-sensitive adhesive sheet tends to be good. When the content of the structural unit (M-3) is 16 mol% or less, based on all structural units of the (meth)acrylic resin (A), the acid value tends to be easily adjusted to below the upper limit of a predetermined range, and a decrease in the adhesive strength of the pressure-sensitive adhesive sheet due to an excessive increase in the cohesive strength of the (meth)acrylic resin (A) tends to be suppressed.

[0030] <Structural Unit (M-4) Other Than Structural Unit (M-1), Structural Unit (M-2), and Structural Unit (M-3)> The structural unit (M-4) may be a structural unit derived from a compound copolymerizable with the compounds (m-1), (m-2), and (m-3) (hereinafter, sometimes referred to as "compound (m-4)"). Examples of the compound (m-4) include alkyl(meth)acrylates; dienes such as butadiene and dicyclopentadiene; styrenes; unsaturated dicarboxylic acid diesters; and other vinyl compounds. Among these, the compound (m-4) may be an alkyl(meth)acrylate from the viewpoint of reaction control.

[0031] Examples of the alkyl (meth)acrylate include linear or branched 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. Among these, from the viewpoint of reactivity, the alkyl(meth)acrylate may be a linear or branched alkyl(meth)acrylate in which the alkyl group has 1 to 10 carbon atoms, or may be a linear or branched alkyl(meth)acrylate in which the alkyl group has 4 to 8 carbon atoms.

[0032] Specific examples of styrenes include styrene and α-, o-, m-, or p-alkyl derivatives of styrene.

[0033] Specific examples of the unsaturated dicarboxylic acid diester include diethyl citraconate, diethyl maleate, diethyl fumarate, and diethyl itaconate.

[0034] 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[4.4.0.1 ２，５ .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 ７，１０ ] 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.

[0035] The content of the structural unit (M-4) may be 40 mol% or more, 50 mol% or more, or 60 mol% or more, and may be 90 mol% or less, 85 mol% or less, or 80 mol% or less, based on all structural units of the (meth)acrylic resin (A).

[0036] The weight average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000, and the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g. When the weight average molecular weight and acid value of the (meth)acrylic resin (A) satisfy these conditions, the adhesive strength of the pressure-sensitive adhesive sheet can be sufficiently improved.

[0037] The weight average molecular weight (Mw) of the (meth)acrylic resin (A) is 200,000 or more, and may be 250,000 or more, 300,000 or more, 350,000 or more, 400,000 or more, or 450,000 or more. When the weight average molecular weight (Mw) is 200,000 or more, the cohesive strength of the (meth)acrylic resin (A) is improved, and the adhesive strength of the pressure-sensitive adhesive sheet tends to be improved. In addition, there is a tendency to be able to prevent adhesive residue when the pressure-sensitive adhesive sheet is peeled from the adherend. The weight average molecular weight (Mw) of the (meth)acrylic resin (A) is 650,000 or less, and may be 600,000 or less. When the weight average molecular weight (Mw) is 650,000 or less, the cohesive strength of the (meth)acrylic resin (A) is not too high, and it easily penetrates into the interface with the adherend, and the adhesive strength of the pressure-sensitive adhesive sheet tends to be improved.

[0038] In this specification, the "weight average molecular weight (Mw)" refers to a value measured using 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 (Resonac Inc.) Column: Shodex™ LF-804 (Resonac Inc.) 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 (Resonac Inc.)

[0039] The weight average molecular weight (Mw) of the (meth)acrylic resin (A) can be adjusted by adjusting, for example, the reaction concentration, reaction solvent, reaction temperature, reaction time, the type of polymerization initiator, the amount of polymerization initiator used, etc.

[0040] The acid value of the (meth)acrylic resin (A) is 5 mgKOH / g or more, and may be 10 mgKOH / g or more, 15 mgKOH / g or more, or 18 mgKOH / g or more. When the acid value is 5 mgKOH / g or more, the chemical affinity with the adherend surface increases, and the adhesive strength of the pressure-sensitive adhesive sheet tends to be improved. The acid value of the (meth)acrylic resin (A) is 50 mgKOH / g or less, and may be 45 mgKOH / g or less, 42 mgKOH / g or less, or 40 mgKOH / g or less. When the acid value is 50 mgKOH / g or less, the cohesive strength increases within a range that does not impair the wettability to the adherend surface, and sufficient adhesive strength tends to be exhibited.

[0041] In this specification, the term "acid value" refers to the mass (mg) of potassium hydroxide required to neutralize the acid (carboxy group) contained in 1 g of a sample. The "acid value" can be calculated from the amount required for neutralization by titrating a sample with an ethanolic potassium hydroxide solution (neutralization titration method) in accordance with JIS K2501:2003.

[0042] The acid value of the (meth)acrylic resin (A) can be adjusted, for example, by adjusting the content of the structural unit (M-3).

[0043] The hydroxyl value of the (meth)acrylic resin (A) may be, for example, 0.01 to 50 mgKOH / g. When the hydroxyl value of the (meth)acrylic resin (A) is within this range, the effects of the present disclosure tend to be more easily achieved. The hydroxyl value of the (meth)acrylic resin (A) may be 1 mgKOH / g or more, 2.5 mgKOH / g or more, or 5 mgKOH / g or more, and may be 40 mgKOH / g or less, 30 mgKOH / g or less, or 25 mgKOH / g or less.

[0044] In this specification, the term "hydroxyl value" refers to the mass (mg) of potassium hydroxide required to neutralize acetic acid bonded to hydroxy groups when 1 g of a sample is acetylated. The "hydroxyl value" can be calculated from the amount required for neutralization by titrating an acetylated sample with an ethanolic potassium hydroxide solution (neutralization titration method) in accordance with JIS K0070:1992.

[0045] The ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) may be, for example, 100 to 5000 g / mol. When the ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) is within this range, the adhesive strength can be more sufficiently reduced by irradiating the PSA sheet with UV light after it has been attached to an adherend, and the sheet tends to be easily peeled from the adherend. The ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) may be 200 g / mol or more, 250 g / mol or more, or 500 g / mol or more, and may be 4000 g / mol or less, 3000 g / mol or less, or 2000 g / mol or less.

[0046] The "ethylenically unsaturated group equivalent" is the mass of the (meth)acrylic resin (A) per mole of ethylenically unsaturated bond. The ethylenically unsaturated group equivalent of the (meth)acrylic resin (A) is a calculated value calculated from the charged amounts of each raw material used in the production of the (meth)acrylic resin (A), assuming that 100% of the raw materials have 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 K0070:1992.

[0047] The glass transition temperature (Tg) of the (meth)acrylic resin (A) may be −80° C. to 0° C., −70° C. to −10° C., or −60° C. to −20° C. When the glass transition temperature (Tg) of the (meth)acrylic resin (A) is in such a range, the effects of the present disclosure tend to be easily obtained.

[0048] The "glass transition temperature (Tg)" is measured by taking a 10 mg sample and using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min. In the obtained DSC curve, a stepwise change in specific heat capacity accompanying the glass transition is observed. In accordance with JIS K 7121:2012, the midpoint glass transition temperature (Tmg) calculated from the baselines before and after the change region is defined as Tg.

[0049] The content of the (meth)acrylic resin (A) may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 97% by mass or more, based on the total solid content of the pressure-sensitive adhesive composition. When the content of the (meth)acrylic resin (A) is 50% by mass or more, the adhesive strength of the resulting pressure-sensitive adhesive sheet is good, and when the pressure-sensitive adhesive sheet is used as a dicing tape or a dicing / die-bonding integrated film, the dicing properties tend to be good. The content of the (meth)acrylic resin (A) may be 99% by mass or less, based on the total solid content of the pressure-sensitive adhesive composition.

[0050] The (meth)acrylic resin (A) can be obtained by synthesis using a known method. Examples of synthesis methods include solution polymerization, suspension polymerization, emulsion polymerization, bulk polymerization, precipitation polymerization, gas-phase polymerization, plasma polymerization, and supercritical polymerization. Examples of polymerization reaction types include radical polymerization, cationic polymerization, anionic polymerization, living radical polymerization, living cationic polymerization, living anionic polymerization, coordination polymerization, and immortal polymerization, as well as ATRP (atom transfer radical polymerization) and RAFT (reversible addition-fragmentation chain transfer polymerization). Among these, synthesis by radical polymerization using a solution polymerization method has advantages such as good economy, high reactivity, and ease of polymerization control, as well as the ability to use the resin solution obtained by polymerization as is for blending.

[0051] Here, a method for producing the (meth)acrylic resin (A) or a copolymer (a precursor of the (meth)acrylic resin (A)) by radical polymerization using a solution polymerization method will be described.

[0052] In one embodiment, the (meth)acrylic resin (A) can be obtained by a method including a step of polymerizing monomers including the compound (m-1), the compound (m-2), and the compound (m-3), and, if necessary, the compound (m-4).

[0053] To obtain such a (meth)acrylic resin (A), a known radical polymerization initiator can be used. Examples of the radical polymerization initiator include azo-based polymerization initiators such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4,4-trimethylpentane), and dimethyl-2,2'-azobis(2-methylpropionate); and 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.

[0054] Among these, the radical polymerization initiator is preferably an azo-based polymerization initiator from the viewpoints of the 10-hour half-life temperature and solubility in organic solvents, and may be at least one selected from the group consisting of 2,2'-azobis(isobutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(N-butyl-2-methylpropionamide).

[0055] The amount of the radical polymerization initiator used may be 0.01 to 5 parts by mass, 0.02 to 4 parts by mass, or 0.03 to 3 parts by mass, relative to 100 parts by mass of the total of the monomers.

[0056] The solvent used in solution polymerization is not particularly limited as long as it can dissolve the (meth)acrylic resin (A). Examples of the solvent include known organic solvents such as 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; glycol esters such as ethylene glycol diacetate and propylene glycol monomethyl ether acetate. Furthermore, polymerization can also be carried out using supercritical carbon dioxide or the like as a solvent.

[0057] The reaction temperature can be set appropriately depending on the type of radical polymerization initiator used, etc. The reaction temperature may be, for example, 40 to 125°C or 60 to 120°C. The reaction time can also be set appropriately depending on the type of radical polymerization initiator used, etc. The reaction time may be, for example, 1 to 24 hours or 3 to 15 hours.

[0058] In one embodiment, the (meth)acrylic resin (A) can be obtained by a method including: a step (hereinafter sometimes referred to as "step (A)") of polymerizing monomers including the compound (m-1) and the compound (m-3), and, if necessary, the compound (m-4), to obtain a copolymer having structural units derived from the compound (m-1) and structural units derived from the compound (m-3); and a step (hereinafter sometimes referred to as "step (B)") of adding the compound (a) to a portion of the hydroxy groups in the obtained copolymer (a precursor of the (meth)acrylic resin (A)) in the presence of a catalyst.

[0059] In step (A), the radical polymerization initiator, solvent, etc. used in producing the copolymer may be the same as those described above. In step (A), conditions such as reaction temperature, reaction time, and polymerization method can be appropriately set in the same manner as those described above.

[0060] Step (B) is a step in which, in the presence of a catalyst, compound (a) is added to some of the hydroxy groups (in the side chains) of the copolymer obtained in step (A). If compound (a) is added to all of the hydroxy groups of the copolymer obtained in step (A), the resulting (meth)acrylic resin (A) will no longer contain hydroxy groups, resulting in insufficient adhesive strength as a pressure-sensitive adhesive sheet. In addition, if compound (a) is added to all of the hydroxy groups of the copolymer obtained in step (A), there will be no reaction sites with the crosslinking agent (C) described below. Therefore, compound (a) is added only to some of the hydroxy groups. Specifically, when hydroxy groups are taken as 100 mol %, the hydroxy groups to which compound (a) is added may be 40 to 99 mol %.

[0061] Since the (meth)acrylic resin (A) has an ethylenically unsaturated group derived from the compound (a) in its 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 crosslinking density can be efficiently improved by UV irradiation. Therefore, when the (meth)acrylic resin (A) is used as a material for a pressure-sensitive adhesive composition, the adhesive strength after UV irradiation can be significantly reduced. Therefore, pressure-sensitive adhesive sheets using the (meth)acrylic resin (A) tend to have excellent peelability from adherends. In addition, pressure-sensitive adhesive compositions produced using the (meth)acrylic resin (A) tend to have excellent adhesion to adhesive layers. Therefore, pressure-sensitive adhesive compositions produced using the (meth)acrylic resin (A) can be suitably used for pressure-sensitive adhesive layers of dicing tapes and integrated dicing and die-bonding films.

[0062] As a method for adding the compound (a) to the hydroxy group, for example, a method of reacting the copolymer obtained in the step (A) with the compound (a) in the presence of a catalyst can be mentioned.

[0063] The reaction between an isocyanato group and a hydroxy group is a urethanization reaction. Therefore, a known urethanization catalyst used in urethanization reactions can be used as the catalyst. In one embodiment, the catalyst may be a catalyst containing at least one metal selected from the group consisting of tin, zirconium, and bismuth. In one embodiment, the catalyst may be an amine catalyst.

[0064] Examples of catalysts containing tin (tin-based catalysts) include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin didecanate, dioctyltin didecanate, and tin 2-ethylhexanoate.

[0065] Examples of catalysts containing zirconium (zirconium-based catalysts) include normal propyl zirconate, normal butyl zirconate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium ethylacetoacetate, and zirconium dibutoxybis(ethylacetoacetate).

[0066] Examples of catalysts containing bismuth (bismuth-based catalysts) include bismuth octoate (bismuth 2-ethylhexanoate, etc.), bismuth neodecanoate, and bismuth naphthenate.

[0067] Examples of the amine catalyst include triethylenediamine, bis(dimethylaminoethyl)ether, di(N,N-dimethylaminoethyl)amine, and 1-isobutyl-2-methylimidazole.

[0068] The amount of the catalyst used may be 0.01 to 10 parts by mass, 0.02 to 5 parts by mass, or 0.03 to 1 part by mass, per 100 parts by mass of the copolymer and compound (a) combined.

[0069] When compound (a) is added to a hydroxy group, a known polymerization inhibitor may be used as needed. 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.

[0070] When a polymerization inhibitor is used, the amount of the polymerization inhibitor used may be 0.005 to 5 parts by mass, 0.03 to 3 parts by mass, or 0.05 to 1.5 parts by mass, relative to 100 parts by mass of the copolymer and compound (a) combined.

[0071] In the reaction between the copolymer and compound (a), the reaction temperature may be 25°C to 130°C or 40°C to 90°C. A reaction temperature of 25°C or higher tends to provide a sufficient reaction rate. A reaction temperature of 130°C or lower tends to prevent double bonds from being crosslinked by thermal radical polymerization, thereby preventing the formation of a gel. The reaction time may be, for example, 1 to 24 hours or 3 to 15 hours.

[0072] In the reaction between the copolymer and the compound (a), a gas having a polymerization inhibitory effect may be introduced into the reaction system, which tends to prevent gelation during the reaction.

[0073] 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.

[0074] The combined use of a gas having a polymerization-inhibiting effect and a polymerization inhibitor is advantageous in that the amount of polymerization inhibitor used can be reduced and the polymerization-inhibiting effect can be enhanced.

[0075] 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.

[0076] Examples of the photopolymerization initiator (B) include sulfide-based photopolymerization initiators such as diphenyl disulfide, dibenzyl disulfide, tetraethylthiuram disulfide, and tetramethylammonium monosulfide; acylphosphine oxide-based photopolymerization initiators 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.

[0077] Among these, the photopolymerization initiator (B) may be at least one selected from the group consisting of carbonyl-based photopolymerization initiators and acylphosphine oxide-based photopolymerization initiators, and may be at least one selected from the group consisting of 1-hydroxycyclohexyl phenyl ketone and 2,4,6-trimethylbenzoyldiphenylphosphine oxide, from the viewpoint of solubility in the pressure-sensitive adhesive composition.

[0078] The photopolymerization initiator (B) may be present in an amount of 0.1 to 5.0 parts by mass or 0.3 to 2.0 parts by mass relative to 100 parts by mass of the (meth)acrylic resin (A). When the photopolymerization initiator (B) is present in an amount of 0.1 parts by mass or more relative to 100 parts by mass of the (meth)acrylic resin (A), the crosslinking density of the thermoset product of the pressure-sensitive adhesive composition containing the reaction product of the (meth)acrylic resin (A) and the crosslinking agent (C) can be improved at a sufficiently fast curing rate upon UV irradiation. When the thermoset product of the pressure-sensitive adhesive composition is used in a pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer after UV irradiation tends to be sufficiently reduced. When the photopolymerization initiator (B) is present in an amount of 5.0 parts by mass or less relative to 100 parts by mass of the (meth)acrylic resin (A), the adhesive strength and water resistance of the pressure-sensitive adhesive layer prior to UV irradiation tend to be sufficiently maintained, which is also economically advantageous.

[0079] Crosslinking Agent (C) The crosslinking agent (C) is a compound that does not have an ethylenically unsaturated bond and has two or more functional groups that react with the hydroxy groups contained in the (meth)acrylic resin (A). By heating, the functional groups of the crosslinking agent (C) react with the hydroxy groups of the (meth)acrylic resin (A), thereby obtaining a thermoset product of the pressure-sensitive adhesive composition containing the reaction product of the (meth)acrylic resin (A) and the crosslinking agent (C). When the thermoset product of the pressure-sensitive adhesive composition is used in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet that exhibits a good balance between adhesive strength before and after UV irradiation tends to be obtained.

[0080] In the crosslinking agent (C), examples of the functional group reactive with a hydroxy group include an isocyanato group, an epoxy group, a carboxy group, an acid anhydride group, an aziridinyl group, etc. From the viewpoint of reactivity, the functional group may be an isocyanato group or an epoxy group, or may be an isocyanato group.

[0081] Examples of the crosslinking agent (C) include polyisocyanates such as 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, tolylene diisocyanate adduct of trimethylolpropane, xylylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, and polymeric (methylene diphenyl diisocyanate); 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, bisphenol A-ethylenediisocyanate, and the like. Polyepoxy compounds such as picrohydrin-type epoxy resins, N,N'-[1,3-phenylenebis(methylene)]bis[bis(oxiran-2-ylmethyl)amine], ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, and diglycerol polyglycidyl ether; melamine compounds such as hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, and hexahexyloxymethylmelamine;Tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, ethylene glycol-bis-[3-(2-aziridinyl)propionate], trimethylolpropane-tris[3-(2-aziridinyl)propionate], trimethylolpropane-tris[3-(1-aziridinyl)propionate], trimethylolpropane-tris[3-(2 and aziridinyl compounds such as N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), tetramethylolmethane-tris[3-(2-aziridinyl)propionate], tetramethylolmethane-tris[3-(2-aziridinyl)propionate], pentaerythritol-tris[3-(1-aziridinyl)propionate], N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide);

[0082] Among these, the crosslinking agent (C) may be one selected from the group consisting of polyisocyanates and polyepoxy compounds, and may be polyisocyanate, since it has good reactivity with the (meth)acrylic resin (A).

[0083] The crosslinking agent (C) may be present in an amount of 0.1 to 30 parts by mass, 0.1 to 20 parts by mass, 0.1 to 10 parts by mass, or 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) is 0.1 parts by mass or more relative to 100 parts by mass of the (meth)acrylic resin (A), a three-dimensional crosslinked structure is sufficiently formed in the thermoset product of the pressure-sensitive adhesive composition containing the reaction product of the (meth)acrylic resin (A) and the crosslinking agent (C) upon UV irradiation, and when the thermoset product of the pressure-sensitive adhesive composition is used in a pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer after UV irradiation tends to be sufficiently reduced. When the content 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 thermosetting adhesive composition containing the reaction product of the (meth)acrylic resin (A) and the crosslinking agent (C) has a good balance of properties with the cured product after UV irradiation, and when used as a dicing tape or a dicing / die bonding integrated film, it tends to exhibit good adhesive strength and water resistance. When the thermosetting adhesive composition is used in the adhesive layer, the adhesive strength of the adhesive layer before UV irradiation tends to be good.

[0084] Other Components 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 necessary. Examples of other components include a tackifier, a solvent, and various additives.

[0085] Any conventionally known tackifier can be used without any particular limitation, and examples of such 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.

[0086] When a tackifier is contained, the content thereof may be 30 parts by mass or less, and may be 5 to 20 parts by mass, based on 100 parts by mass of the (meth)acrylic resin (A).

[0087] The 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 applied, the solvent can be used to adjust the viscosity of the PSA composition to an appropriate level. As the solvent, the solvent used in synthesizing the (meth)acrylic resin (A) may be used as is, or another solvent may be added to the solvent.

[0088] Examples of the solvent include known organic solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone, ethyl acetate, propyl acetate, butyl acetate, tetrahydrofuran, dioxane, cyclohexanone, hexane, toluene, xylene, n-propanol, and isopropyl alcohol.

[0089] Examples of additives include plasticizers, surface lubricants, leveling agents, softeners, antioxidants, antiaging agents, UV absorbers, polymerization inhibitors, light stabilizers such as benzotriazole-based ones, flame retardants such as phosphate ester-based ones, surfactants, and antistatic agents.

[0090] The pressure-sensitive adhesive composition can be produced, for example, by a method including a step of mixing a (meth)acrylic resin (A), a photopolymerization initiator (B), a crosslinking agent (C), and other components that are added as needed.

[0091] The method for mixing the components is not particularly limited, and any known method can be used. Mixing can be carried out using a stirring device equipped with stirring blades such as a homodisper or paddle blade.

[0092] A thermoset product of the pressure-sensitive adhesive composition containing the reaction product of the (meth)acrylic resin (A) and the crosslinking agent (C) and the photopolymerization initiator (B) can be produced, for example, by a method including a step of applying the pressure-sensitive adhesive composition to a substrate or a release sheet and thermally curing the composition.

[0093] The pressure-sensitive adhesive composition obtained above may be used as it is, or may be used after adjusting the viscosity by adding a solvent.

[0094] The process of applying a pressure-sensitive adhesive composition to a substrate or a release sheet and thermally curing it involves, for example, applying the pressure-sensitive adhesive composition to a substrate, and if a solvent is contained, heating and drying to remove the solvent, thereby forming a layer containing the pressure-sensitive adhesive composition. Thereafter, if necessary, a release sheet is laminated onto the layer containing the pressure-sensitive adhesive composition. Furthermore, if necessary, the resulting sheet is cured in an oven for a certain period of time, thereby forming a crosslinked structure (a reaction product of the (meth)acrylic resin (A) and the crosslinking agent (C)) in the layer containing the pressure-sensitive adhesive composition, thereby obtaining a layer (pressure-sensitive adhesive layer) containing a thermally cured product of the pressure-sensitive adhesive composition.

[0095] The pressure-sensitive adhesive composition can be applied to a substrate (or a release sheet) by a known method, specifically by using a conventional coater (e.g., a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater, a direct coater, etc.).

[0096] The conditions for heat-drying the applied pressure-sensitive adhesive composition are not particularly limited and can be set as desired. The heat-drying temperature may be, for example, 25 to 180°C or 60 to 150°C. The heat-drying time may be, for example, 1 to 20 minutes or 1 to 10 minutes. By performing heat-drying under such conditions, the solvent contained in the pressure-sensitive adhesive composition can be removed. The conditions for curing the heat-dried sheet in an oven for a certain period of time are not particularly limited and can be set as desired. The curing temperature may be 25 to 100°C or 30 to 80°C. The curing time may be, for example, 1 to 30 days or 1 to 14 days. By performing curing under such conditions, the (meth)acrylic resin (A) and the crosslinking agent (C) are reacted (crosslinked) to obtain a thermoset pressure-sensitive adhesive composition.

[0097] [Adhesive Sheet] An adhesive sheet according to one embodiment includes a substrate layer and an adhesive layer provided on the substrate layer. The adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B). The adhesive layer may be formed by thermally curing an adhesive composition containing the (meth)acrylic resin (A), the photopolymerization initiator (B), and the crosslinking agent (C).

[0098] The substrate is not particularly limited and can be appropriately selected depending on the application. The substrate may be a resin film. Examples of resin materials constituting the resin film include polyvinyl chloride, polyvinylidene chloride, polyolefin (PO), polyester, polyurethane, polycarbonate, polyether ether ketone, polyimide, polyetherimide, polyamide, wholly aromatic polyamide (aramid), polyphenyl sulfide, fluororesin, cellulose-based resin, and silicone resin.

[0099] Examples of polyolefins include polyethylenes (PE) such as low-density polyethylene, linear polyethylene, medium-density polyethylene, high-density polyethylene, and very low-density polyethylene; polypropylenes (PP) such as random copolymer polypropylene, block copolymer polypropylene, and homopolypropylene; polybutene; polymethylpentene; ethylene-vinyl acetate copolymer; ionomer resins; ethylene-(meth)acrylic acid copolymers; ethylene-(meth)acrylic acid ester copolymers; ethylene-butene copolymers; and ethylene-hexene copolymers.

[0100] Examples of polyester include polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT).

[0101] Among these, the resin material constituting the resin film may be one or more selected from the group consisting of PE, PP, and PET, since a pressure-sensitive adhesive sheet having appropriate flexibility can be obtained. The resin material constituting the resin film may be used alone or in combination of two or more. When used as a dicing tape, the resin material constituting the resin film may be polyolefin.

[0102] The substrate may have a single layer structure or a multilayer structure. Since the thermosetting product of the pressure-sensitive adhesive composition on the substrate is a UV-curable type, the substrate may be UV-transparent. When the substrate is a resin film, the substrate may be a non-stretched film, a uniaxially stretched film, or a biaxially stretched film.

[0103] The substrate may be subjected to a surface treatment to enhance adhesion, such as physical treatments such as corona discharge treatment, plasma treatment, sand matting, ozone exposure, flame exposure, high-voltage shock exposure, and ionizing radiation treatment; chemical treatments such as chromic acid treatment; and primer treatment.

[0104] The substrate may be a PO film. PO film has low heat resistance and is not suitable for the above-mentioned heat drying temperature. Therefore, a pressure-sensitive adhesive composition may be applied to a release sheet, and after the solvent is removed by heat drying, a layer containing the pressure-sensitive adhesive composition may be transferred to the PO film. Specifically, a pressure-sensitive adhesive composition may be applied to a release-treated surface of a silicone-based light-release PET film, and the film may be heat-dried. The PO film may be attached to the layer containing the pressure-sensitive adhesive composition using a rubber roller so that the corona-treated surface of the PO film is adhered to the exposed surface of the layer containing the pressure-sensitive adhesive composition.

[0105] The release sheet is not particularly limited, and for example, a sheet generally used for pressure-sensitive adhesives can be used without any restrictions. Specific examples include the same resin films as those used for the substrate. From the viewpoint of ease of handling, the resin material constituting the release sheet may be one selected from the group consisting of PE, PP, and PET.

[0106] The release sheet may be subjected to a release treatment on its surface to impart light releasability, specifically, a silicone release treatment or the like.

[0107] The thickness of the pressure-sensitive adhesive layer may be 5 to 100 μm, 10 to 50 μm, or 10 to 30 μm. When the thickness of the pressure-sensitive adhesive layer is 5 μm or more, sufficient adhesive properties tend to be exhibited and coating is easy. When the thickness of the pressure-sensitive adhesive layer is 100 μm or less, the generation of bubbles during heat drying and residual solvent tend to be suppressed.

[0108] The pressure-sensitive adhesive sheet can be used as a removable pressure-sensitive adhesive sheet, for example, when manufacturing electronic components. Specifically, the removable pressure-sensitive adhesive sheet can be used as a surface protection tape for protecting the surface of an adherend in each process of manufacturing electronic components. It can also be used in each process of manufacturing electronic components, where the adherend is fixed and subjected to various processing steps, and then UV irradiation is used to peel it from the adherend. Therefore, the pressure-sensitive adhesive sheet can be used as a backgrinding tape, dicing tape, dicing / die bonding integrated film, etc. when processing semiconductor wafers. The pressure-sensitive adhesive sheet can also be suitably used as a support tape for fragile members such as ultrathin glass substrates and easily warped members such as FPC boards (flexible printed circuit boards). In particular, the pressure-sensitive adhesive sheet has sufficient adhesive strength to the adherend, making it suitable for use in dicing tape and dicing / die bonding integrated film.

[0109] [Dicing Tape] A dicing tape according to one embodiment includes a base layer and a pressure-sensitive adhesive layer provided on the base layer. The pressure-sensitive adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B). The pressure-sensitive adhesive layer may be formed by thermally curing a pressure-sensitive adhesive composition containing the (meth)acrylic resin (A), the photopolymerization initiator (B), and the crosslinking agent (C).

[0110] An exemplary method of using the pressure-sensitive adhesive sheet as a dicing tape for a semiconductor wafer is described below. Prior to the dicing process, the pressure-sensitive adhesive sheet is attached to a semiconductor wafer on which multiple components are formed. Next, the semiconductor wafer is cut and separated (diced) into individual components to form semiconductor chips. The pressure-sensitive adhesive sheet attached to each semiconductor chip is then irradiated with UV light. This allows UV to be irradiated onto the pressure-sensitive adhesive layer through the substrate of the pressure-sensitive adhesive sheet, and the ethylenically unsaturated bonds in the thermoset product of the pressure-sensitive adhesive composition form a three-dimensional crosslinked structure, further hardening the thermoset product of the pressure-sensitive adhesive composition. As a result, the adhesive strength of the pressure-sensitive adhesive layer is reduced, and the pressure-sensitive adhesive sheet is peeled off from each semiconductor chip.

[0111] The dicing tape can be produced, for example, by forming a pressure-sensitive adhesive layer on a substrate. The pressure-sensitive adhesive layer can be formed, for example, by the same method as described above.

[0112] The substrate may be suitable for the expanding step that is carried out subsequent to the dicing step, and may be a polyolefin film.

[0113] When a polyolefin film is used, heating during the formation of the pressure-sensitive adhesive layer may cause problems in terms of heat resistance. Therefore, the dicing tape may be obtained by a method including the steps of: applying a pressure-sensitive adhesive composition onto a release sheet to obtain a layer containing the pressure-sensitive adhesive composition; thermally curing the layer containing the pressure-sensitive adhesive composition to obtain a layer containing a thermoset product of the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer); and laminating a substrate on the layer containing a thermoset product of the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer).

[0114] The thickness of the adhesive layer may be 5 to 100 μm, 10 to 50 μm, or 10 to 30 μm. When the thickness of the adhesive layer is 5 μm or more, sufficient adhesive properties tend to be exhibited and coating is easy. When the thickness of the adhesive layer is 100 μm or less, the generation of bubbles during heat drying, residual solvent, etc. tend to be suppressed. In particular, when the thickness of the adhesive layer is 10 to 30 μm, sufficient peelability and severability (cuttability) tend to be obtained.

[0115] [Dicing and die bonding integrated film] An embodiment of the dicing and die bonding integrated film includes a base layer, a pressure-sensitive adhesive layer, and an adhesive layer in this order. The pressure-sensitive adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B). The pressure-sensitive adhesive layer may be formed by thermally curing a pressure-sensitive adhesive composition containing the (meth)acrylic resin (A), the photopolymerization initiator (B), and the crosslinking agent (C).

[0116] The dicing and die bonding integrated film can be obtained, for example, by laminating a dicing tape and a die bonding film. The dicing tape can be produced, for example, by the same method as the above-mentioned production method.

[0117] Examples of methods for producing a dicing / die-bonding integrated film include the following: applying a pressure-sensitive adhesive composition onto a release sheet to obtain a layer containing the pressure-sensitive adhesive composition; thermally curing the layer containing the pressure-sensitive adhesive composition to obtain a layer containing a thermoset product of the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer); laminating a substrate on the layer containing a thermoset product of the pressure-sensitive adhesive composition (pressure-sensitive adhesive layer) to obtain a dicing tape; and laminating the dicing tape and the die-bonding film together.

[0118] The thickness of the adhesive layer may be 5 to 100 μm, 10 to 50 μm, or 10 to 30 μm. When the thickness of the adhesive layer is 5 μm or more, sufficient adhesive properties tend to be exhibited and coating is easy. When the thickness of the adhesive layer is 100 μm or less, the generation of bubbles during heat drying, residual solvent, etc. tend to be suppressed. In particular, when the thickness of the adhesive layer is 10 to 30 μm, sufficient peelability and severability (cuttability) tend to be obtained.

[0119] The lamination of the dicing tape and the die bonding film can be carried out, for example, by preparing a die bonding film and pressing it to the dicing tape. The die bonding film can be obtained, for example, by applying an adhesive composition to a release sheet to form an adhesive layer. The lamination temperature may be, for example, 30 to 50°C. The lamination pressure (linear pressure) may be, for example, 0.1 to 20 kgf / cm.

[0120] The heat-cured product of the pressure-sensitive adhesive composition contains a reaction product of an ethylenically unsaturated group-containing (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B). Therefore, the heat-cured product of the pressure-sensitive adhesive composition can be further cured (further improving the crosslink density) by UV irradiation.

[0121] 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.

[0122] The UV irradiation dose applied to the heat-cured product of the pressure-sensitive adhesive composition is 50 to 3000 mJ / cm ２ or 100 to 600 mJ / cm ２ The UV irradiation dose applied to the heat-cured product of the pressure-sensitive adhesive composition may be 50 mJ / cm ２ When the UV irradiation dose is 3000 mJ / cm or more, the crosslink density of the thermoset product of the pressure-sensitive adhesive composition can be improved at a sufficiently high curing rate by UV irradiation. Therefore, when the thermoset product of the pressure-sensitive adhesive composition is used as a pressure-sensitive adhesive layer, the adhesive strength of the pressure-sensitive adhesive layer after UV irradiation tends to be sufficiently reduced. When the thermoset product of the pressure-sensitive adhesive composition is used as a resist, the strength tends to be improved. The UV irradiation dose irradiated to the thermoset product of the pressure-sensitive adhesive composition is 3000 mJ / cm ２ When the temperature is equal to or lower than this, it tends to be possible to economically further cure the thermoset product of the pressure-sensitive adhesive composition while reducing the effects of UV irradiation on the adherend.

[0123] Hereinafter, the present disclosure will be described more specifically with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0124] In synthesizing the (meth)acrylic resin (A) and the (meth)acrylic resin (cA), the following raw materials were used. Compound (m-1) m-1A: 2-hydroxyethyl acrylate (Osaka Organic Chemical Industry Ltd.) m-1B: 4-hydroxybutyl acrylate (Osaka Organic Chemical Industry Ltd.) Compound (m-3) m-3A: acrylic acid (Nippon Shokubai Co., Ltd.) m-3B: methacrylic acid (Nippon Shokubai Co., Ltd.) Compound (m-4) m-4A: 2-ethylhexyl acrylate (Toagosei Co., Ltd.) m-4B: n-butyl acrylate (Toagosei Co., Ltd.) Radical polymerization initiator AIBN: 2,2'-azobis(isobutyronitrile) (Fujifilm Wako Pure Chemical Industries, Ltd.) Compound (a) a-A: 2-isocyanatoethyl methacrylate (Karenz MOI, Resonac Co., Ltd.) a-B: 2-isocyanatoethyl acrylate (Karenz AOI-VM, Resonac Co., Ltd.) Catalysts Catalyst A: dibutyltin dilaurate (Neostan U-810, Nitto Kasei Kogyo Co., Ltd.) Catalyst B: zirconium tetraacetylacetonate (Orgatix ZC-700, Matsumoto Fine Chemical Co., Ltd.) Catalyst C: bismuth octylate (Pucat 25, Nippon Chemical Industry Co., Ltd.)

[0125] The weight average molecular weight (Mw), acid value, hydroxyl value, and glass transition temperature (Tg) of the (meth)acrylic resin (A) and the (meth)acrylic resin (cA) were calculated by measuring them using the above-mentioned methods. The ethylenically unsaturated group equivalents of the (meth)acrylic resin (A) and the (meth)acrylic resin (cA) were calculated from the amounts charged as described above.

[0126] The following materials were used in producing the pressure-sensitive adhesive sheet: Photopolymerization initiator (B) B-1: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (L-TPO, BASF) Crosslinking agent (C) C-1: tolylene diisocyanate adduct of trimethylolpropane (Coronate L, Tosoh Corporation)

[0127] Synthesis Example 1 Synthesis of (meth)acrylic resin (A-1) A mixed solution was prepared by mixing 100 parts by mass of ethyl acetate; 259.9 parts by mass of 2-ethylhexyl acrylate (m-4A, 66.2 mol %), 56.6 parts by mass of 2-hydroxyethyl acrylate (m-1A, 22.9 mol %), and 16.6 parts by mass of acrylic acid (m-3A, 10.9 mol %) monomers; and 0.1 part by mass of 2,2′-azobis(isobutyronitrile) (AIBN) as a radical polymerization initiator relative to a total of 100 parts by mass of the monomers.

[0128] A four-neck flask equipped with a stirrer, dropping funnel, condenser, and nitrogen inlet tube was charged with 200 parts by mass of ethyl acetate as a solvent and heated to 80°C under a nitrogen gas atmosphere. While maintaining the reaction temperature at 80°C ± 2°C, the mixed solution prepared above was added dropwise uniformly to the four-neck flask over 2 hours. After completion of the dropwise addition, stirring was continued at 80°C ± 2°C for an additional 6 hours to carry out polymerization, yielding a copolymer as a precursor to the (meth)acrylic resin (A-1). Separately, a mixed solution was prepared by mixing 65.6 parts by mass of 2-isocyanatoethyl methacrylate (a-A, equivalent to 19.9 mol% relative to 100 mol% of the total of the monomers); 0.2 parts by mass of dibutyltin dilaurate (catalyst A) relative to 100 parts by mass of the copolymer and 2-isocyanatoethyl methacrylate (a-A); and 100 parts by mass of ethyl acetate. The temperature of the reaction system was lowered to 60°C, and the resulting mixed solution was added dropwise through the dropping funnel. After the dropwise addition was completed, the reaction system was maintained at 70°C for 6 hours to eliminate the isocyanato groups of 2-isocyanatoethyl methacrylate (a-A). 200 parts by mass of ethyl acetate was added to obtain a solution containing (meth)acrylic resin (A-1) (resin concentration: 40% by mass). The weight average molecular weight (Mw), acid value, hydroxyl value, ethylenically unsaturated group equivalent, and glass transition temperature (Tg) of (meth)acrylic resin (A-1) are shown in Table 1.

[0129] Synthesis Examples 2 to 6 and Comparative Synthesis Examples 1 to 5 Synthesis of (meth)acrylic resins (A-2) to (A-6) and (meth)acrylic resins (cA-1) to (cA-5) Solutions containing (meth)acrylic resins (A-2) to (A-6) and (meth)acrylic resins (cA-1) to (cA-5) of Synthesis Examples 2 to 6 and Comparative Synthesis Examples 1 to 5 were obtained in the same manner as in Synthesis Example 1, except that the raw materials shown in Tables 1 and 2 were used as monomers (compound (m-1), compound (m-3), and compound (m-4)), radical polymerization initiator, compound (a), and catalyst in the amounts shown in Tables 1 and 2, and the amount of ethyl acetate was adjusted so that the resin concentration was 40% by mass. Note that in Tables 1 and 2, the amount of radical polymerization initiator used is the value relative to 100 parts by mass of the total of the monomers, and the amount of catalyst used is the value relative to 100 parts by mass of the total of the copolymer and compound (a). Tables 1 and 2 show the weight average molecular weight (Mw), acid value, hydroxyl value, ethylenically unsaturated group equivalent, and glass transition temperature (Tg) of each (meth)acrylic resin.

[0130]

[0131]

[0132] Example 1 Preparation of Pressure-Sensitive Adhesive Composition In a room shielded from actinic rays, the (meth)acrylic resin (A-1), L-TPO (B-1) as the photopolymerization initiator (B), and Coronate L (C-1) as the crosslinking agent (C) were added to a plastic container in the amounts (parts by mass) shown in Table 3, and the mixture was stirred to obtain the pressure-sensitive adhesive composition of Example 1. The numerical value for (meth)acrylic resin (A-1) in Table 3 is the amount (parts by mass) of a solution containing (meth)acrylic resin (A-1) in which the content of (meth)acrylic resin (A-1) is 40% by mass. The numerical values ​​for the photopolymerization initiator (B) and the crosslinking agent (C) are the amounts (parts by mass) used relative to 100 parts by mass of the solution containing the (meth)acrylic resin (A-1) (this corresponds to the addition of 2.5 parts by mass of the photopolymerization initiator (B) and 1.5 parts by mass of the crosslinking agent (C) relative to 100 parts by mass of the solid content of the (meth)acrylic resin (A-1)).

[0133] <Preparation of Pressure-Sensitive Adhesive Sheet (Dicing Tape)> The pressure-sensitive adhesive composition of Example 1 was directly applied to a release sheet (polyethylene terephthalate (PET) film (E7006, Toyobo Co., Ltd.), thickness 25 μm) so that the film thickness after heat curing would be 20 μm, and the applied film was dried by heating at 100° C. for 2 minutes to prepare a layer containing the pressure-sensitive adhesive composition. Thereafter, a substrate film (polyolefin (PO) film (FUNCRARE PO #90, Gunze Co., Ltd.), thickness 90 μm) was attached to the layer containing the pressure-sensitive adhesive composition, and this was cured in an oven at 40° C. for 3 days to crosslink and cure the pressure-sensitive adhesive composition in the layer containing the pressure-sensitive adhesive composition to form a pressure-sensitive adhesive layer, thereby obtaining the pressure-sensitive adhesive sheet (dicing tape) of Example 1 comprising a substrate layer and a pressure-sensitive adhesive layer provided on the substrate layer.

[0134] <Evaluation of Pressure-Sensitive Adhesive Sheet> (Measurement of Peel Strength (180° Peel Strength) Before UV Irradiation) The pressure-sensitive adhesive sheet of Example 1 was cut into a size of 25 mm long and 100 mm wide, and the release sheet was peeled off to expose the pressure-sensitive adhesive layer. Next, the pressure-sensitive adhesive sheet was attached to a glass plate so that the exposed pressure-sensitive adhesive layer (measurement surface) was in contact with the glass plate, and a 2 kg rubber roller (width: approximately 50 mm) was rolled back and forth once to obtain a sample for measuring peel strength before UV irradiation. The obtained measurement sample was left for 30 minutes in an environment of 23°C and 50% humidity. Thereafter, a tensile test was performed in the 180° direction at a peel rate of 300 mm / min in accordance with JIS Z0237:2009 using a tensile tester (Texture Analyzer, Eiko Seiki Co., Ltd.) in an environment of 23°C and 50% humidity, and the peel strength (N / 25 mm) of the pressure-sensitive adhesive sheet against the glass plate before UV irradiation was measured. The results are shown in Table 3.

[0135] (Measurement of peel strength (180° peel strength) after UV irradiation) A sample identical to that used for measuring peel strength before UV irradiation was prepared, and the UV irradiation dose was 300 mJ / cm from the pressure-sensitive adhesive sheet side. ２The sample was irradiated with UV under the conditions of (a) to (c) to obtain a sample for measuring the peel strength after UV irradiation. A conveyor-type ultraviolet irradiation device (Eye Graphics Co., Ltd., 2 kW lamp, 80 W / cm) was used for UV irradiation. The peel strength (N / 25 mm) of the pressure-sensitive adhesive sheet against the glass plate after UV irradiation was measured for the obtained measurement sample in the same manner as the peel strength (180° peel strength) before UV irradiation. The results are shown in Table 3.

[0136] (Evaluation of chipping) The release sheet was peeled from the pressure-sensitive adhesive sheet of Example 1, exposing the adhesive layer surface, and laminated to a semiconductor wafer (mirror wafer, size 8 inches, thickness 50 μm) at 70°C. Thereafter, using a fully automatic dicer DFD6361 (Disco Corporation), dicing was performed to chips 5 mm square. The cutting method was single cut, and a dicing blade NBC-ZH-127F-SE-27HCBB (Disco Corporation) was used. The blade rotation speed was 4000 rpm, the cutting speed was 50 mm / sec, and the blade height was set so that the cutting depth into the semiconductor wafer was 30 μm. After dicing, the pressure-sensitive adhesive sheet was visually observed to check for the presence or absence of chips that had fallen off the pressure-sensitive adhesive sheet, and chipping was evaluated based on the following criteria. The results are shown in Table 3. The confirmation of chip detachment was carried out only for chips that were diced according to the intended shape (5 mm square), and chips that were not diced into a square shape because they were located on the periphery of the semiconductor wafer were excluded. A: No chips were found to have fallen off. B: One or more chips were found to have fallen off.

[0137] (Evaluation of Pick-up Properties) After dicing, the adhesive layer was irradiated with UV from the base layer side of the adhesive sheet at 500 mJ / cm2 using an air-cooled high-pressure mercury lamp (80 W / cm, irradiation distance 10 cm). Then, a pick-up test was performed on 20 chips using a die bonder (CPS-100FM, NEC Machinery Co., Ltd. (now Canon Machinery Inc.)) to determine the pick-up success rate. The pick-up properties were evaluated based on the following criteria. The results are shown in Table 3. A: The pick-up success rate was 100% when the push-up amount was 300 μm or less. B: The pick-up success rate was less than 100% when the push-up amount was 300 μm or less.

[0138] (Evaluation of Package Reliability) A substrate (LN001E-001PCB(Au)AUS308, Cima Electronics Co., Ltd.) was prepared as a substrate, in which a circuit pattern was formed on the copper foil (thickness 18 μm) of a copper foil-clad laminate (HL832NX-A, Mitsubishi Gas Chemical Company, Inc.), and a layer of solder resist (PSR-4000AUS308, Taiyo Ink Mfg. Co., Ltd.) was formed on this circuit pattern. Subsequently, dicing was performed in the same manner as in (Evaluation of Chip Flying), and the picked-up chip was bonded to the above substrate using an adhesive (LOCTITE ABLESTIK TIK2025JH, Henkel), and the resulting chip was heat-cured at 175° C. for 30 minutes. Next, using an encapsulation device (MPC-06M TriAlPress, Apic Yamada Co., Ltd.), a layer of encapsulating resin (KE-G1250, Kyocera Chemical Co., Ltd. (now Kyocera Corporation)) was formed on the bonded chip. The encapsulating resin was cured to form a 400 μm thick encapsulating layer, thereby obtaining a encapsulating substrate. The encapsulating resin was pre-cured by applying a pressure of 7 MPa to the encapsulating resin heated to 175°C for 2 minutes, and then heated at 175°C for 5 hours.

[0139] The pressure-sensitive adhesive sheet of Example 1 was attached to the obtained sealing substrate, and then the sealing substrate was diced using a dicing machine (DFD6361, Disco Corporation) with the blade rotation speed of the dicing blade set to 4000 rpm under the same conditions as in (evaluation of chip flying). As a result, semiconductor packages were obtained that were separated into pieces measuring 15 mm x 15 mm.

[0140] The obtained semiconductor packages were left to absorb moisture for 168 hours under conditions of a temperature of 85°C and a relative humidity of 60%, and then subjected to IR reflow at a maximum heating temperature of 260°C for a heating time of 5 minutes. Five of the semiconductor packages that had undergone IR reflow were randomly selected and observed for the presence or absence of package cracks using a scanning ultrasonic flaw detector (HYE-FOCUS, Hitachi Construction Machinery Finetech Co., Ltd. (now Hitachi Construction Machinery Co., Ltd.). Package reliability was evaluated based on the following criteria. The results are shown in Table 3. A: No package cracks were observed in any of the five semiconductor packages. B: Package cracks were observed in at least one semiconductor package.

[0141] [Examples 2 to 6 and Comparative Examples 1 to 5] Pressure-sensitive adhesive compositions of Examples 2 to 6 and Comparative Examples 1 to 5 were prepared in the same manner as Example 1, except that the materials shown in Tables 3 and 4 were used in the amounts shown in Tables 3 and 4. Subsequently, pressure-sensitive adhesive sheets (dicing tapes) of Examples 2 to 6 and Comparative Examples 1 to 5 were produced in the same manner as Example 1 using each pressure-sensitive adhesive composition. The pressure-sensitive adhesive sheets of Examples 2 to 6 and Comparative Examples 1 to 5 were evaluated in the same manner as Example 1. The results are shown in Tables 3 and 4.

[0142]

[0143]

[0144] As shown in Tables 3 and 4, the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of the Examples were superior in terms of peel strength (180° peel strength) before UV irradiation compared to the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of the Comparative Examples. The pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of the Examples were also found to be superior in terms of various evaluations. These results confirmed that the pressure-sensitive adhesive composition of the present disclosure can provide a pressure-sensitive adhesive sheet with high adhesive strength.

Claims

1. A pressure-sensitive adhesive composition comprising a (meth)acrylic resin (A), a photopolymerization initiator (B), and a crosslinking agent (C), wherein the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group, the weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000, and the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic resin (A) further has a structural unit derived from an alkyl (meth)acrylate.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the (meth)acrylic resin (A) has an ethylenically unsaturated group equivalent of 100 to 5000 g / mol.

4. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the (meth)acrylic resin (A) has a hydroxyl value of 0.01 to 50 mgKOH / g.

5. A pressure-sensitive adhesive sheet comprising: a base layer; and a pressure-sensitive adhesive layer provided on the base layer; wherein the pressure-sensitive adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B); the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group; the weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000; and the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g.

6. A dicing tape comprising: a base layer; and an adhesive layer provided on the base layer; wherein the adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B); the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group; the weight average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000; and the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g.

7. A dicing and die bonding integrated film comprising, in this order: a base layer; a pressure-sensitive adhesive layer; and an adhesive layer; wherein the pressure-sensitive adhesive layer contains a reaction product of a (meth)acrylic resin (A) and a crosslinking agent (C), and a photopolymerization initiator (B); wherein the (meth)acrylic resin (A) has a structural unit (M-1) having a hydroxy group, a structural unit (M-2) having an ethylenically unsaturated group, and a structural unit (M-3) having a carboxy group; wherein the weight-average molecular weight of the (meth)acrylic resin (A) is 200,000 to 650,000; and wherein the acid value of the (meth)acrylic resin (A) is 5 to 50 mgKOH / g.

8. A method for producing a (meth)acrylic resin, comprising the step of adding an isocyanato group-containing ethylenically unsaturated compound (a) in the presence of a catalyst to some of the hydroxy groups of a copolymer having structural units derived from an ethylenically unsaturated compound (m-1) having a hydroxy group and structural units derived from an ethylenically unsaturated compound (m-3) having a carboxy group, to obtain a (meth)acrylic resin (A), wherein the (meth)acrylic resin (A) has a weight average molecular weight of 200,000 to 650,000, and an acid value of 5 to 50 mgKOH / g.

9. The method for producing a (meth)acrylic resin according to claim 8, wherein the catalyst contains at least one metal selected from the group consisting of tin, zirconium, and bismuth.

10. A method for producing a pressure-sensitive adhesive composition, comprising a step of mixing the (meth)acrylic resin (A) obtained by the production method according to claim 8 or 9, a photopolymerization initiator (B), and a crosslinking agent (C).

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