Adhesive composition and adhesive sheet

Abstract

Provided are an adhesive composition with which it is possible to suppress the occurrence of adhesive residue and tape lifting and is particularly suitable in semiconductor, etc., production processes, and an adhesive sheet using the same. This adhesive composition contains a (meth)acrylic polymer (A) containing an alkyl (meth)acrylate monomer (a), a carboxylic acid-containing vinyl monomer (b), and a hydroxyl group-containing vinyl monomer (c) as constituent units, and a crosslinking agent (B), wherein (a) contains butyl acrylate, and the contents of the butyl acrylate, acrylic acid, and methacrylic acid are within fixed ranges. Also provided is an adhesive sheet using the same.

Description

Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive composition for use in sheet members such as tapes and films, and a pressure-sensitive adhesive sheet using the same.

[0002] In the electrical, electronics, and mobile industries, adhesive tapes are widely used in place of adhesives to secure components, etc., from the perspective of workability and the working environment. Acrylic adhesives are particularly popular, as they have superior heat resistance and weather resistance compared to rubber adhesives, and also offer a high degree of design freedom.

[0003] Conventionally, in the manufacturing process of semiconductors and the like, removable pressure-sensitive adhesive sheets have been used to temporarily hold or protect various components when processing the components. These pressure-sensitive adhesive sheets contain acrylic pressure-sensitive adhesive compositions. In the manufacturing process, the components are often exposed to high temperatures while the pressure-sensitive adhesive sheet is attached to them, so the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet often adheres to the components, leaving adhesive residue when the pressure-sensitive adhesive sheet is peeled off, which can cause contamination or damage. Therefore, there is a demand for pressure-sensitive adhesive sheets that leave little adhesive residue after peeling.

[0004] As an example of a pressure-sensitive adhesive sheet used in the manufacturing process of semiconductors and the like, Patent Document 1 discloses a pressure-sensitive adhesive composition containing an acrylic resin (A), an isocyanate-based crosslinking agent (B), a metal-based crosslinking catalyst (C), and a crosslinking retarder (D), wherein the glass transition temperature of the acrylic resin (A) is higher than −50° C. This technology aims to provide a pressure-sensitive adhesive composition that has a sufficient pot life, excellent quick-curing properties, shows little increase in adhesive strength after use under high-temperature conditions, can be peeled off with little force and at high speed, and is less likely to cause contamination when peeled off from an adherend, and can be used for masking films and the like.

[0005] JP 2019-143078 A

[0006] There is a particular demand for improved performance for adhesives and adhesive sheets used in the manufacturing process of precision semiconductors, etc. In particular, there is a strong demand for adhesives that leave even less adhesive residue than conventional adhesives, so that they do not leave any adhesive residue when peeled off after molding epoxy resins used as sealing materials. Furthermore, when the component is a silicon wafer, there is a strong demand for adhesives that are resistant to lifting, so that the tape does not lift off the silicon wafer when heated in a state where it is laminated to an adhesive sheet.

[0007] The present invention has been made in view of the above background, and an object of the present invention is to provide a pressure-sensitive adhesive composition that can suppress the occurrence of adhesive residue and tape lifting, and is particularly suitable for manufacturing processes for semiconductors and the like, and a pressure-sensitive adhesive sheet using the same.

[0008] The present invention includes the following aspects: [1] A pressure-sensitive adhesive composition comprising a (meth)acrylic polymer (A) containing, as structural units, an alkyl (meth)acrylate monomer (a), a carboxylic acid-containing vinyl monomer (b), and a hydroxyl group-containing vinyl monomer (c), and a crosslinking agent (B), wherein the alkyl (meth)acrylate monomer (a) contains butyl acrylate, and the content of the butyl acrylate is 82% by mass or more relative to 100% by mass of the total of (a), (b), and (c), and the carboxylic acid-containing vinyl monomer (b) contains acrylic acid or methacrylic acid, and the content of acrylic acid is 5% by mass or more and 12% by mass or the content of methacrylic acid is 1% by mass or more and 5% by mass or less relative to 100% by mass of the total of (a), (b), and (c), or when both acrylic acid and methacrylic acid are contained, the total content of acrylic acid and methacrylic acid is 0.5% by mass or more and 12% by mass or less. [2] The pressure-sensitive adhesive composition according to [1], further comprising a thermally expandable filler (C). [3] The weight-average molecular weight of the (meth)acrylic polymer (A) is 1.5 × 10 ５ Above 6.0 x 10 ５[4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the (meth)acrylic polymer (A) has a glass transition temperature of -55°C or higher and -38°C or lower. [5] The pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the hydroxyl group-containing vinyl monomer (c) is 2-hydroxyethyl acrylate and / or 4-hydroxybutyl acrylate. [6] The pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the crosslinking agent (B) is an isocyanate-based crosslinking agent and / or an epoxy-based crosslinking agent. [7] A pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition according to any one of [1] to [6], comprising: a pressure-sensitive adhesive layer (X) having a structure in which the (meth)acrylic polymer (A) is crosslinked by the crosslinking agent (B); and a substrate (Y) supporting the pressure-sensitive adhesive layer (X).

[0009] According to the present invention, it is possible to obtain a pressure-sensitive adhesive composition that can suppress the occurrence of adhesive residue and tape lifting and is particularly suitable for manufacturing processes such as semiconductors, and a pressure-sensitive adhesive sheet using the same.

[0010] The pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet according to the present invention will be described below with reference to embodiments, although the present invention is not limited to the following embodiments.

[0011] (Pressure-sensitive adhesive composition) The pressure-sensitive adhesive composition of the present embodiment is a pressure-sensitive adhesive composition comprising: a (meth)acrylic polymer (A) containing, as constituent units, an alkyl (meth)acrylate monomer (a), a carboxylic acid-containing vinyl monomer (b), and a hydroxyl group-containing vinyl monomer (c); and a crosslinking agent (B), wherein (a) contains butyl acrylate, and the content of the butyl acrylate is 82 mass% or more relative to 100 mass% of the total of (a), (b), and (c); and (b) contains acrylic acid or methacrylic acid, and the content of acrylic acid is 5 mass% or more and 12 mass% or the content of methacrylic acid is 1 mass% or more and 12 mass% or less relative to 100 mass% of the total of (a), (b), and (c); or when both acrylic acid and methacrylic acid are contained, the total content of acrylic acid and methacrylic acid is 0.5 mass% or more and 12 mass% or less.

[0012] In the following description, "(meth)acrylic" is a general term for acrylic and methacrylic.

[0013] ((Meth)acrylic polymer (A) component) ((meth)acrylic acid alkyl ester monomer (a) component) The (meth)acrylic acid alkyl monomer component in this embodiment includes butyl acrylate. Here, the butyl acrylate is n-butyl acrylate. The content of the butyl acrylate in the (meth)acrylic polymer (A) is 82% by mass or more relative to 100% by mass of the total of (a), (b), and (c). The upper limit of the butyl acrylate content is not particularly limited, but is, for example, 99% by mass or less, preferably 98.5% by mass or less, relative to 100% by mass of the total of (a), (b), and (c). Note that by ensuring that the amount of n-butyl acrylate in the (meth)acrylic acid alkyl monomer component (a) is 82% by mass or more, it becomes easier to set the glass transition temperature of the acrylic polymer (A) within a suitable range, which in turn contributes to suppressing adhesive residue and tape lift.

[0014] In addition to n-butyl acrylate, examples of the alkyl (meth)acrylate monomer component of the present embodiment include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, etc. Two or more different compounds of these may be used.

[0015] (Carboxylic Acid-Containing Vinyl Monomer (b) Component) The carboxylic acid-containing vinyl monomer (b) is a component that mainly contributes to improving high-temperature retention and load-bearing capacity by imparting an appropriate proportion of carboxyl groups to the pressure-sensitive adhesive composition. Specific examples of the carboxylic acid-containing vinyl monomer (b) include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 2-carboxy-1-butene, 2-carboxy-1-pentene, 2-carboxy-1-hexene, and 2-carboxy-1-heptene. Two or more of these may be used in combination. The component (b) of the present embodiment contains, among these, acrylic acid or methacrylic acid. That is, it is preferable that either acrylic acid or methacrylic acid is contained, and it is also preferable that both acrylic acid and methacrylic acid are contained.

[0016] The content of the carboxylic acid-containing vinyl monomer component (b) is, relative to the total of (a), (b), and (c) (100% by mass): When the component (b) contains acrylic acid, the content of acrylic acid is 3% by mass or more and 15% by mass or less, preferably 7% by mass or more and 11% by mass or less. When the component (b) contains methacrylic acid, the content of methacrylic acid is 1% by mass or more and 5% by mass or less, preferably 2% by mass or more and 4% by mass or less. When the component (b) contains both acrylic acid and methacrylic acid, the total content of acrylic acid and methacrylic acid is 0.5% by mass or more and 12% by mass or less, preferably 0.5% by mass or more and 2% by mass or less.

[0017] (Hydroxyl Group-Containing Vinyl Monomer Component (c)) The hydroxyl group-containing vinyl monomer component (c) is a component that mainly contributes to improving application properties and retention by imparting an appropriate proportion of hydroxyl groups to the pressure-sensitive adhesive composition. Specific examples of the hydroxyl group-containing vinyl monomer component (c) include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Two or more of these may be used in combination. Of these, 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate is preferred.

[0018] The content of the hydroxyl group-containing vinyl monomer (c) is preferably 0.5% by mass or more and 5.0% by mass or less, more preferably 1.0% by mass or more and 3.0% by mass or less, based on 100% by mass of the total of (a), (b), and (c).

[0019] (Other Monomer Components) The (meth)acrylic polymer (A) may contain other copolymerizable monomer components as appropriate. For example, it may contain vinyl acetate as a monomer component. The content of vinyl acetate may be 1% by mass or more and 10% by mass or less, relative to 100% by mass of the total of (a), (b), and (c). The content is preferably 1% by mass or more and 5% by mass or less.

[0020] The (meth)acrylic polymer (A) has a weight average molecular weight of 1.5×10 ５ Above 6.0 x 10 ５ It is preferably 2.0 × 10 or less. More preferably, it is 2.0 × 10 ５ Above 5.0 x 10 ５ The weight-average molecular weight of the pressure-sensitive adhesive composition can provide a good balance of adhesiveness, high-temperature retention, load-bearing capacity, and impact resistance, and can also provide good stickiness. The weight-average molecular weight can be measured, for example, by a method using a GPC method (polystyrene equivalent value).

[0021] The glass transition temperature of the (meth)acrylic polymer (A) is preferably −55° C. or higher and −38° C. or lower. The glass transition temperature can be the theoretical Tg calculated by a method using the FOX formula, as described in, for example, JP-A-2019-151837.

[0022] (Crosslinking Agent (B)) The pressure-sensitive adhesive composition of the present embodiment further contains a crosslinking agent (B). Examples of the crosslinking agent (curing agent) include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, as well as urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. Of these, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents are preferred. These crosslinking agents may be used alone or in combination. For example, an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent may be used in combination.

[0023] Specific examples of isocyanate-based crosslinking agents include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and xylylene diisocyanate; and trimethylolpropane / tolylene diisocyanate ternary isocyanates. Examples of the isocyanate adduct include a trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), a trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HL"), and an isocyanurate of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HX"), and an HDI (hexamethylene diisocyanate)-based polyisocyanate (manufactured by Asahi Kasei Corporation, trade name "Duranate D101E"). The content of the isocyanate-based crosslinking agent is typically from 0.1 to 20 parts by mass, more preferably from 0.5 to 10 parts by mass, even more preferably from 0.5 to 7 parts by mass, and particularly preferably from 0.5 to 5 parts by mass, relative to 100 parts by mass of the acrylic pressure-sensitive adhesive composition (A).

[0024] Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "Tetrad C"), N,N,N',N'-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "Tetrad X"), 1,6-hexanediol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolite 1600"), neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolite 1500NP"), and ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolite 40"). E"), propylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolite 70P"), polyethylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name "Epiol E-400"), polypropylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name "Epiol P-200"), sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol EX-611"), glycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol EX-314"), pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol" EX-512"), sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. The content of the epoxy crosslinking agent is from 0.01 to 10 parts by mass, more preferably from 0.03 to 7 parts by mass, and particularly preferably from 0.05 to 6 parts by mass, relative to 100 parts by mass of the acrylic pressure-sensitive adhesive composition (A).

[0025] Examples of metal chelate crosslinking agents that can be used include metal chelate compounds whose metal atoms are aluminum, zirconium, titanium, zinc, iron, tin, etc. Metal chelate crosslinking agents form crosslinking points by coordinating carboxylate ions in a polymer with metal ions. Among these, aluminum chelate compounds and titanium chelate compounds are preferred. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethyl acetoacetate, diisopropoxyaluminum monolauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, diisopropoxyaluminum monoisostearyl acetoacetate, and monoisopropoxyaluminum mono-N-lauroyl-β-alanate monolauryl acetoacetate. Examples of titanium chelate compounds include titanium tetra-n-butylate, titanium tetra-2-ethylhexanoate, titanium tetraacetylacetonate, titanium diisopropoxybis(ethylacetoacetate), titanium tetra-n-butylate, titanium tetra-2-ethylhexanoate, titanium tetraacetylacetonate, titanium diisopropoxybis(ethylacetoacetate), titanium octylene glycolate, and the like. Other examples of the metal chelate compound include zirconium tetraacetylacetonate, zirconium tributoxymonoacetylacetonate, etc. The above metal chelate crosslinking agents may be used alone or in combination of two or more.The content of the metal chelate crosslinking agent is typically 0.01 parts by mass or more and 10 parts by mass or less, more preferably 0.01 parts by mass or more and 1 part by mass or less, and even more preferably 0.02 parts by mass or more and 0.1 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0026] (Tackifier (C)) A tackifier (C) may be added to the pressure-sensitive adhesive composition as needed for the purpose of adjusting adhesive strength, etc. Specific examples of the tackifier (C) include tackifier resins such as rosin-based resins, terpene-based resins, petroleum-based resins, alkylphenol resins, alkylphenol-modified resins (manufactured by Fudow Corporation, trade name "Nikanol GHP-150", etc.), styrene-based resins, xylene-based resins, and other resins. Two or more of these may be used in combination. Of these, petroleum-based resins, rosin-based resins, and xylene-based resins are particularly preferred.

[0027] The softening point of the tackifier (C) is preferably 100° C. or higher, more preferably 135° C. or higher. This softening point is a value measured in accordance with JIS K 2531 (ring and ball method).

[0028] Examples of rosin-based resins include hydrogenated resins, disproportionated resins, and polymerized ester resins. Examples of terpene-based resins include terpene phenol resins, α-pinene resins, and β-pinene resins. Examples of petroleum-based resins include aliphatic resins and aromatic resins.

[0029] The proportion of the tackifier (C) relative to 100 parts by mass of the (meth)acrylic polymer (A) can be selected from preferably 0 parts by mass or more and 15 parts by mass or less, more preferably 0 parts by mass or more and 12 parts by mass or less. If the amount of the tackifier added is more than 15 parts by mass, high-temperature retention may be reduced. When a tackifier is used, the lower limit of the content is not particularly limited and can be set appropriately, but can be 1 part by mass or more relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0030] (Thermally Expandable Filler (D)) The pressure-sensitive adhesive composition of the present embodiment may further contain a thermally expandable filler (D). Examples of the thermally expandable filler include thermally expandable microcapsules and chemical foaming agents. The thermally expandable filler (D) can be appropriately selected from known thermally expandable microspheres, and a microencapsulated thermally expandable filler (D) is preferred. Examples of such thermally expandable fillers (D) include those in which a gasifying agent such as a liquid low-boiling hydrocarbon such as isobutane, propane, or pentane is encapsulated in a thermoplastic polymer shell. When such a thermally expandable filler (D) is heated, the polymer shell softens, the encapsulated liquid low-boiling hydrocarbon is gasified, and the filler expands due to the resulting pressure. Examples of materials for forming the thermoplastic polymer shell include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone.

[0031] Specific examples of the thermally expandable filler (D) include microspheres manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. (trade names: F-20D, F-30D, F-40D, FN-100D, FN-100MD, FN-100SD, FN-100SSD, FN-180D, FN-180SD, FN-180SSD, F-190D, F-260D), microspheres manufactured by Kureha Corporation (trade names: H850D, H880D, S2340D, S2640D), and thermally expandable graphite manufactured by Air Water (trade names: 50LTE-U, MZ-260, CA-60, SS-3, SS-3LA).

[0032] The content of the thermally expandable filler (D) is typically 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 25 parts by mass or less, and even more preferably 3 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). By including the thermally expandable filler, it becomes possible to perform thermal foam peeling by high-temperature heating when peeling off the tape after the manufacturing process of a semiconductor or the like.

[0033] (Other Additives, Pigments, etc.) The pressure-sensitive adhesive composition of the present embodiment may contain other additives as needed. Specific examples of other additives include inorganic fillers, antioxidants, flame retardants, UV absorbers, light stabilizers, antistatic agents, light-shielding fillers, softeners, plasticizers, dispersants, thickeners, pigments, etc. The proportion of these additives relative to 100 parts by mass of the (meth)acrylic polymer (A) can be selected from the range of 0.1 parts by mass to 100 parts by mass.

[0034] Specific examples of inorganic fillers include silica, calcium carbonate, alumina, calcium oxide, magnesium oxide, silica, zinc oxide, and titanium oxide.Specific examples of light-shielding fillers include carbon black, carbon nanotubes, aniline black, acetylene black, ketjen black, iron black, and black inorganic fillers. Specific examples of pigments include organic pigments such as benzidine yellow, Hansa yellow, lithol red, alizarin lake, Pigment Scarlet 3B, Brilliant Carmine 6B, Permanent Red F-5R, Permanent Red 4R, Rhodamine Lake B, Rhodamine Lake Y, Lake Red C, Para Red, Peacock Blue Lake, Phthalocyanine Blue, aniline black, Permanent Yellow HR, PV Violet BL, quinacridone, perinone, anthraquinone, Cromophtal Yellow 6G, Cromophtal Yellow 3G, and Cromophtal Yellow GR; and inorganic pigments such as zinc white, lithopone, white lead, cadmium yellow, yellow lead, titanium yellow, zinc chromate, yellow ochre, chrome vermilion, red pigments, umber, yellow iron oxide, red iron oxide, cadmium red, red lead, iron blue, ultramarine, cobalt blue, chrome oxide green, and mineral violet.

[0035] (Adhesive composition for high-temperature adhesion applications) The adhesive composition of the present embodiment preferably leaves little adhesive residue when peeled off after being attached to an adherend and exposed to a high-temperature environment. "Less adhesive residue when peeled off after being exposed to a high-temperature environment" preferably means that when an adhesive sheet having the adhesive composition applied to a substrate is attached to an SUS (stainless steel) adherend, heated at 100°C or higher for 1 hour or more, and subjected to a peel test at a peel angle of 180° and a peel speed of 300 mm / min, no adhesive residue is visually observed.

[0036] The pressure-sensitive adhesive composition of this embodiment preferably has lift-off resistance after being applied to an adherend and exposed to a high-temperature environment. Having lift-off resistance means that lift-off is unlikely to occur after exposure to the high-temperature environment. The lift-off resistance is measured by applying the pressure-sensitive adhesive sheet to an adherend, pressing the pressure-sensitive adhesive sheet with a 2 kg roller on a hot plate at 60°C, and leaving the bonded sample of the pressure-sensitive adhesive sheet and adherend for 30 minutes on a hot plate with a plate surface temperature of 175°C for 10 minutes, and measuring the lift-off area of ​​the pressure-sensitive adhesive sheet from the adherend. The adherend is particularly preferably a silicon wafer.

[0037] (Adhesive Sheet) The adhesive sheet of the present embodiment comprises an adhesive layer (X) formed from an adhesive composition and having a structure in which the (meth)acrylic polymer (A) is crosslinked with the crosslinking agent (B), and a substrate (Y) supporting the adhesive layer (X). The adhesive sheet broadly refers to a sheet-like form, and for example, a form having a large longitudinal dimension may be called an adhesive tape, and a thin film-like form may be called an adhesive film.

[0038] The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of this embodiment is formed by adding a crosslinking agent (B) to the (meth)acrylic polymer (A). The pressure-sensitive adhesive layer preferably has a gel fraction of 60% or less. If the gel fraction is too high, the adhesive strength may decrease. The gel fraction is the ratio of insoluble matter when the pressure-sensitive adhesive layer after crosslinking is immersed in toluene for 1 day, and is calculated by the following formula: Gel fraction (%) = (C / A) x 100% A: initial mass of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet C: mass of the pressure-sensitive adhesive layer after immersing the pressure-sensitive adhesive sheet in an excess amount of toluene for 24 hours, removing the sheet, and drying it at 130°C for 2 hours

[0039] The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present embodiment preferably contains the (meth)acrylic polymer (A), a crosslinking agent (B), and a tackifier resin (C).

[0040] The pressure-sensitive adhesive sheet of this embodiment has multiple layers, at least one of which is a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing the (meth)acrylic polymer (A) of this embodiment. For example, it may be a single-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer (X) on one side of a substrate (Y), or a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers (X) on both sides of a substrate (Y). In the case of a double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layers on both sides may be pressure-sensitive adhesive layers (X) formed from a pressure-sensitive adhesive composition containing the (meth)acrylic polymer (A) of this embodiment, or only one side may be a pressure-sensitive adhesive layer (Y) formed from a pressure-sensitive adhesive composition containing the (meth)acrylic polymer (A) of this embodiment. When the pressure-sensitive adhesive sheet includes three or more pressure-sensitive adhesive layers, at least one of the pressure-sensitive adhesive layers may be a pressure-sensitive adhesive layer (X) formed from a pressure-sensitive adhesive composition containing the (meth)acrylic polymer (A) of this embodiment.

[0041] The adhesive sheet may also be a substrateless adhesive sheet consisting only of the adhesive layer, with no substrate (Y). In this case, during the production of the substrateless adhesive sheet, both sides of the adhesive layer are covered with release liners before use, and the release liners are peeled off when used. After peeling, the adhesive sheet can be used by being attached to the substrate (Y) or other sheet-like article, and any adhesive sheet that can suppress the occurrence of adhesive residue or tape lifting can be formed as desired.

[0042] The thickness of the pressure-sensitive adhesive layer (Y) is preferably 5 μm or more and 150 μm or less, more preferably 10 μm or more and 100 μm or less, and particularly preferably 20 μm or more and 80 μm or less. If the pressure-sensitive adhesive layer is moderately thick, the degree of deformability of the pressure-sensitive adhesive layer increases, and the pressure-sensitive adhesive layer can sufficiently follow dimensional changes of the member and suppress the occurrence of wrinkles in the member. On the other hand, if the pressure-sensitive adhesive layer is moderately thin, it can be suitably used in applications requiring thinness (for example, applications for liquid crystal displays).

[0043] The type of substrate (Y) is not particularly limited, and any known substrate may be used. Specific examples include polyester films such as polyimide (PI) film, polyamide (PA) film, polyphenylene sulfide (PPS) film, polyether ether ketone (PEEK) film, polyethylene terephthalate (PET) film, polybutylene terephthalate (PBT) film, and polyethylene naphthalate film (PEN); and olefin films such as polyethylene and polypropylene. Among these, substrates made of polyimide film or polyester film are preferred. When visibility is required for the substrate, a colored substrate may be used. Colored substrates can be obtained, for example, by mixing a pigment into the resin constituting the substrate, or by providing a printed layer, coating layer, laminate layer, or other colored layer on the substrate.

[0044] The thickness of the substrate (Y) is preferably 1 μm or more and 125 μm or less, more preferably 10 μm or more and 75 μm or less, and particularly preferably 20 μm or more and 60 μm or less. If the substrate is appropriately thin, it can be suitably used in applications requiring thinness (for example, applications in PCs and portable devices such as displays).

[0045] The thickness of the pressure-sensitive adhesive sheet of this embodiment is preferably 7 μm or more and 280 μm or less, more preferably 30 μm or more and 180 μm or less, and particularly preferably 50 μm or more and 150 μm or less. If the pressure-sensitive adhesive sheet is appropriately thin, it can be suitably used in applications requiring thinness (for example, applications in PCs and mobile devices such as displays).

[0046] The pressure-sensitive adhesive layer (X) in the pressure-sensitive adhesive sheet of this embodiment can be formed by applying a pressure-sensitive adhesive composition to a substrate (Y) and heating it as necessary. Furthermore, when the heat resistance of the substrate (Y) is low, the pressure-sensitive adhesive layer can be formed by applying the pressure-sensitive adhesive composition to the release surface of a release liner such as release paper or release film and heating it. The pressure-sensitive adhesive layer (X) formed in this manner can also be attached to one or both surfaces of the substrate (Y). For applying the pressure-sensitive adhesive composition, a coating device such as a roll coater, die coater, lip coater, gravure coater, or knife coater can be used. When the (meth)acrylic polymer (A) is crosslinked by the crosslinking agent (B), the crosslinking reaction by heating proceeds and the solvent in the pressure-sensitive adhesive composition can also be removed.

[0047] [Effects of this embodiment] According to this embodiment, it is possible to obtain a pressure-sensitive adhesive composition that can suppress the occurrence of adhesive residue and tape lifting, and that is particularly suitable for manufacturing processes of semiconductors and the like, and a pressure-sensitive adhesive sheet using the same.

[0048] The pressure-sensitive adhesive sheet of this embodiment is less likely to leave adhesive residue after heating, which has the effect of preventing adhesive residue from remaining on the sealing material when the sealing material, an epoxy resin, is peeled off after molding. Furthermore, because it is less likely to lift when heated, it has the effect of preventing tape lift even when heated in a state in which the tape is attached to a silicon wafer. By achieving both of these effects, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape can be obtained that are suitable for use in processes that include a heating step, particularly in semiconductor manufacturing processes.

[0049] Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made.

[0050] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0051] <Preparation of (Meth)acrylic Polymer (A)> A reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube was charged with the components shown in the amounts (% by mass) of each Example and Comparative Example in Tables 1 to 4, an appropriate amount of ethyl acetate as a diluent solvent, 0.06 parts by mass of n-dodecanethiol as a chain transfer agent per 100 parts by mass of the total amount of monomers, and 0.1 parts by mass of 2,2'-azobis(2-methylbutyronitrile) as a radical polymerization initiator per 100 parts by mass of the total amount of monomers. Nitrogen gas was sealed into the reactor, and the polymerization reaction was carried out under a nitrogen gas stream with stirring at 68°C for 3 hours, and then at 78°C for 3 hours. The mixture was then cooled to room temperature, and ethyl acetate was added to adjust the concentration. This yielded a (meth)acrylic polymer (A) with a solids concentration of 40% by mass. The numerical value next to each component in the table is the amount (mass %) used (for example, BA 82 indicates that the content of n-butyl acrylate is 82 mass % relative to the total mass of the composition), and the abbreviations for each component are as follows: <(Meth)acrylic acid alkyl ester monomer (a) (-R)> - "2-EHA": 2-ethylhexyl acrylate - "BA": n-butyl acrylate - "EA": ethyl acrylate - "MA": methyl acrylate <Carboxylic acid-containing vinyl monomer (b) (-COOH)> - "AA": acrylic acid - "MAA": methacrylic acid <Hydroxyl group-containing vinyl monomer (-OH)> - "2-HEA": 2-hydroxyethyl acrylate - "4-HBA": 4-hydroxybutyl acrylate

[0052] <Preparation of Pressure-Sensitive Adhesive Composition and Fabrication of Pressure-Sensitive Adhesive Tape> [Preparation of Sample for Evaluating Lifting Resistance] A pressure-sensitive adhesive composition was prepared by adding 1 part by mass of a crosslinking agent and 5 parts by mass of a thermally expandable filler to 100 parts by mass of the solid content of the (meth)acrylic polymer (A) having the component ratios shown in the above Examples and Comparative Examples, and mixing them. The crosslinking agent and thermally expandable filler used were as follows. Crosslinking agent: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "Tetrad C"), which is an epoxy-based curing agent. Thermally expandable filler: S2640D (manufactured by Kureha Corporation).

[0053] Each of the resulting PSA compositions was then applied to the corona-treated surface of a 50 μm-thick polyester film (substrate (Y)) that had been corona-discharge-treated, so that the resulting thickness after drying would be 50 μm. The solvent (ethyl acetate) was then removed, the film was dried, and a crosslinking reaction was carried out at a temperature of 110° C. to form a PSA layer (X). This was then bonded to the silicone-release-treated surface of a 50 μm-thick polyester film that had been silicone-release-treated, and stored in an environment at 40° C. for 72 hours to obtain a sample for evaluating lift-off resistance.

[0054] [Preparation of Samples for Evaluating Adhesive Residue] 7 parts by mass of crosslinker were added to 100 parts by mass of the solids content of (meth)acrylic polymer (A) having the component ratios described in the Examples and Comparative Examples, and mixed to prepare pressure-sensitive adhesive compositions. The crosslinker used was as follows: Crosslinker: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., product name "Tetrad C"), an epoxy-based curing agent. Note that the samples for evaluating adhesive residue were evaluated in an environmental environment at 200°C to clarify the differences between the Examples and Comparative Examples. Because heating to 200°C causes some of the thermally expandable filler to foam, no thermally expandable filler was used. Furthermore, because the temperature conditions were more severe at 200°C, the amount of crosslinker was increased to 7 parts by mass, which was higher than the amount used for the samples for evaluating lift resistance, and the differences in the effects of the Examples and Comparative Examples were confirmed.

[0055] Each of the resulting pressure-sensitive adhesive compositions was then applied to a 25 μm-thick polyimide film (Kapton 100H, manufactured by DuPont-Toray Co., Ltd.) so that the thickness after drying would be 50 μm. The solvent (ethyl acetate) was then removed, the film was dried, and a crosslinking reaction was carried out at a temperature of 110° C. to form a pressure-sensitive adhesive layer. This was then bonded to the treated surface of a 50 μm-thick silicone-treated polyester film, and stored in an environment at a temperature of 40° C. for 72 hours to obtain a sample for evaluating adhesive residue.

[0056] The weight-average molecular weight (Mw) and theoretical Tg of each (meth)acrylic polymer are shown in Tables 1 to 4. The weight-average molecular weight (Mw) is a value obtained by measuring the molecular weight of the (meth)acrylic polymer in terms of standard polystyrene by GPC using the following measuring device and conditions: Device: LC-2000 series (manufactured by JASCO Corporation) Column: Shodex KF-806M x 2, Shodex KF-802 x 1 Eluent: tetrahydrofuran (THF) Flow rate: 1.0 mL / min Column temperature: 40°C Injection volume: 100 μL Detector: refractometer (RI) Measurement sample: An acrylic polymer was dissolved in THF to prepare a solution with an acrylic polymer concentration of 0.5 wt%, and dust was removed by filtration. The theoretical Tg is a value calculated using the FOX formula.

[0057] The evaluation method was as follows. (Adhesive Residue) Each of the pressure-sensitive adhesive sheets was attached to a 1.5 mm to 2.0 mm thick SUS304 steel plate (hereinafter referred to as "SUS") as specified in JIS G 4305, finished with No. 280 waterproof abrasive paper as specified in JIS R 6253, as an adherend (pressure-bonding conditions: a 2 kg roller whose surface was covered with a 6 mm thick rubber layer and had a spring hardness of 80±5 Hs as specified in JIS K 6253, was used, moving back and forth at a speed of 300 mm / min), and heated for 2 hours in an environment at a temperature of 200°C. A peel test was carried out in an environment at a temperature of 23°C and a relative humidity of 65% RH, with a peel angle of 180° and a peel speed of 300 mm / min, to confirm the condition of the SUS adherend. The evaluation criteria were as follows: ⊚: no residue was found on the adherend; ◯: no residue was found with the naked eye, but residue was found by touch; ×: residue was found with the naked eye.

[0058] (Lifting Resistance) The method for evaluating lifting resistance to a silicon wafer was as follows: a silicon wafer (Dainichi Shoji Co., Ltd. dummy silicon wafer, diameter 150±0.2 mm, one-sided mirror-etched, thickness 550-600 μm) was used as an adherend, and the pressure-sensitive adhesive sheet was pressed onto a hot plate with a plate surface temperature of 60 ° C. by reciprocating once at a speed of 300 mm / min using the 2 kg roller described above. After 30 minutes of pressure-bonding, the sample was left on a hot plate heated to 175 ° C. for 10 minutes, and the lifted area of ​​the pressure-sensitive adhesive sheet from the adherend at that time was measured. The lifted area was measured by magnifying and observing with a 20x lens using an optical microscope (Keyence Corporation, product name: VHX-8000). During observation, adjustments were made so that there was no tilt in the longitudinal direction of the pressure-sensitive adhesive sheet, and so that the focus was on the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet in the circumferential direction. Then, a magnified image of the surface of the adhesive layer at a position approximately 100 mm from one end of the adhesive sheet in the longitudinal direction was taken. The obtained results were then subjected to density filtering using the area measurement mode of the attached image analysis software. The lifted area was confirmed from the obtained results. The evaluation criteria were: lifted area = (adhesive sheet lifted / adhesive sheet area) x 100, with lifted areas of less than 1% being evaluated as pass (◎) and lifted areas of 1% or more being evaluated as fail (×).

[0059] The evaluation results are shown in Tables 1 to 4. The above-mentioned samples for evaluating adhesive residue and samples for evaluating lifting resistance were prepared using (meth)acrylic polymers (A) prepared with the components of Examples 1 to 11 and Comparative Examples 1 to 10 shown in the tables. For the components of each Example and Comparative Example, the samples for evaluating adhesive residue were used to evaluate heat resistance and lifting resistance, respectively, to evaluate lifting.

[0060]

[0061]

[0062]

[0063]

[0064] As shown in the table, when the BA content of the (a) component was 82% by mass or more (Example 1), the AA content of the (b) component was 5% by mass (Example 3) to 12% by mass (Example 6), the MAA content was 1% by mass or more (Example 6), or the sum of AA and MAA was 0.5% by mass or more (Example 9), good results were obtained for both adhesive residue and lifting, with a rating of ◯ or ⊚ and a rating of ⊚. Furthermore, in all of Examples 1 to 9, the thermally expandable filler expanded by heating to 250°C, allowing thermal foaming and peeling. On the other hand, Comparative Examples 2 and 3, in which the BA content was below the lower limit of the range of this embodiment, and Comparative Example 7, in which the AA content was low below the lower limit, good results were obtained for lifting, but poor adhesive residue. Comparative Example 8, in which the MAA content was above the upper limit, and Comparative Example 9, in which the BA, AA, and MAA contents were below the lower limits, good results were obtained for adhesive residue, but poor results were obtained for lifting. Furthermore, in Comparative Example 1 (80 parts by mass), Comparative Example 4 (22.3% by mass), Comparative Example 5 (44.5% by mass), and Comparative Example 6 (0% by mass), in which the BA of component (a) was less than the lower limit, good results were not obtained in either adhesive residue or lifting. These results demonstrate that good results can be obtained in both adhesive residue and lifting at the content of this embodiment.

[0065] While preferred embodiments of the present invention have been described and illustrated, it should be understood that these are exemplary of the present invention and should not be considered limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the present invention is not to be deemed limited by the foregoing description, but is limited only by the scope of the appended claims.

[0066] According to the present invention, it is possible to obtain a pressure-sensitive adhesive composition that can suppress the occurrence of adhesive residue and tape lifting and is particularly suitable for manufacturing processes such as semiconductors, and a pressure-sensitive adhesive sheet using the same.

Claims

1. A pressure-sensitive adhesive composition comprising: a (meth)acrylic polymer (A) containing, as structural units, an alkyl (meth)acrylate monomer (a), a carboxylic acid-containing vinyl monomer (b), and a hydroxyl group-containing vinyl monomer (c); and a crosslinking agent (B), wherein the alkyl (meth)acrylate monomer (a) contains butyl acrylate, and the content of the butyl acrylate is 82% by mass or more relative to 100% by mass of the total of (a), (b), and (c), and the carboxylic acid-containing vinyl monomer (b) contains acrylic acid or methacrylic acid, and the content of acrylic acid is 5% to 12% by mass or the content of methacrylic acid is 1% to 5% by mass, relative to 100% by mass of the total of (a), (b), and (c), or when both acrylic acid and methacrylic acid are contained, the total content of acrylic acid and methacrylic acid is 0.5% to 12% by mass.

2. The pressure-sensitive adhesive composition according to claim 1, further comprising a thermally expandable filler (C).

3. The weight average molecular weight of the (meth)acrylic polymer (A) is 1.5 × 10 ５ Above 6.0 x 10 ５ The pressure-sensitive adhesive composition according to claim 1, wherein:

4. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic polymer (A) has a glass transition temperature of -55°C or higher and -38°C or lower.

5. The pressure-sensitive adhesive composition according to claim 1, wherein the hydroxyl group-containing vinyl monomer (c) is 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate.

6. The pressure-sensitive adhesive composition according to claim 1, wherein the crosslinking agent (B) is an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent.

7. A pressure-sensitive adhesive sheet comprising: a pressure-sensitive adhesive layer (X) formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 6, the pressure-sensitive adhesive layer (X) having a structure in which the (meth)acrylic polymer (A) is crosslinked with the crosslinking agent (B); and a substrate (Y) supporting the pressure-sensitive adhesive layer (X).

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