Adhesive sheet

Abstract

The present invention provides an adhesive sheet which exhibits adequate adhesiveness to a semiconductor chip and a sealing resin that seals the semiconductor chip, and which is not likely to leave adhesive residue when removed, while being able to be easily removed from the sealing resin.　An adhesive sheet according to the present invention is provided with a base material and an adhesive layer that is arranged on at least one side of the base material; the adhesive layer contains an acrylic adhesive; and the acrylic adhesive contains a base polymer that has an acid value of 16 mgKOH / g or less. According to one embodiment of the present invention, the adhesive sheet is provided with the base material, the adhesive layer that is arranged on one side of the base material, and a second adhesive layer that is arranged on the reverse side of the base material from the adhesive layer.

Description

[Technical Field]

[0001] This invention relates to an adhesive sheet. [Background technology]

[0002] In recent years, in the manufacturing of semiconductor components including semiconductor chips, semiconductor chips are sometimes encapsulated in resin to prevent damage to the chips and to expand metal wiring. In the resin encapsulation process, semiconductor chips are sometimes encapsulated on an adhesive sheet from the viewpoint of workability. For example, to prevent the movement of semiconductor chips, multiple semiconductor chips are placed on an adhesive sheet that serves as a predetermined temporary fixing material, and the semiconductor chips are encapsulated together on the adhesive sheet. Subsequently, in a predetermined post-processing step, the adhesive sheet is peeled off from the resin that encapsulated the semiconductor chips.

[0003] In the process described above, using a conventional adhesive sheet presents a problem in that adhesive residue is left on the structure when the adhesive sheet is peeled off from the structure containing the sealing resin and semiconductor chip. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2001-308116 [Patent Document 2] Japanese Patent Publication No. 2001-313350 [Patent Document 3] Japanese Patent Publication No. 2018-193563 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention was made to solve the above-mentioned conventional problems, and its objective is to provide an adhesive sheet that has appropriate adhesion to a sealing resin for sealing semiconductor chips and to semiconductor chips, can be easily peeled off from the sealing resin, and does not leave adhesive residue when peeled off. [Means for solving the problem]

[0006] The adhesive sheet of the present invention comprises a base material and an adhesive layer disposed on at least one side of the base material, wherein the adhesive layer contains an acrylic adhesive, and the acrylic adhesive contains a base polymer having an acid value of 16 mg KOH / g or less. In one embodiment, the adhesive sheet comprises a base material, an adhesive layer disposed on one side of the base material, and a second adhesive layer disposed on the opposite side of the base material from the adhesive layer. In one embodiment, the ratio of the shear adhesive strength B at 150°C when a silicone chip is attached to the adhesive layer to the adhesive strength A at 23°C when the adhesive layer is attached to polyethylene terephthalate (shear adhesive strength B / adhesion strength A) is 32.0 g / (N / 20 mm) or more. In one embodiment, the base polymer is a crosslinked acrylic polymer. In one embodiment, the gel fraction of the adhesive layer is 75% or more. In one embodiment, the acrylic adhesive contains a crosslinking agent, and the amount of the crosslinking agent relative to the carboxyl groups of the acrylic polymer is 0.08 molar equivalents to 2 molar equivalents. In one embodiment, the crosslinking agent is an epoxy-based crosslinking agent. In one embodiment, the amount of nitrogen gas generated when the adhesive layer is heat-treated is 0.05 wt% to 1.0 wt%. In one embodiment, the thickness of the adhesive layer is 1 μm to 300 μm. In one embodiment, the adhesive sheet is a temporary fixing material used in the resin encapsulation process of a semiconductor chip. In one embodiment, the adhesive sheet is used when curing the sealing resin on the adhesive sheet. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an adhesive sheet that has appropriate adhesion to a sealing resin for sealing a semiconductor chip and to the semiconductor chip, can be easily peeled off from the sealing resin, and does not leave adhesive residue when peeled off. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of an adhesive sheet according to another embodiment of the present invention. [Modes for carrying out the invention]

[0009] A. Overview of adhesive sheets Figure 1 is a schematic cross-sectional view of an adhesive sheet according to one embodiment of the present invention. The adhesive sheet 100 comprises a base material 10 and an adhesive layer (first adhesive layer) 20 disposed on at least one side of the base material 10.

[0010] The adhesive sheet of the present invention can be suitably used as a temporary fixing material when resin-encapsulating semiconductor chips. More specifically, the adhesive sheet of the present invention can be used as a temporary fixing material for semiconductor chips when resin-encapsulating semiconductor chips by arranging semiconductor chips on the adhesive layer of the adhesive sheet, covering the semiconductor chips with a resin (usually an epoxy resin), and curing the encapsulating resin. After resin-encapsulating the semiconductor chips, the adhesive sheet can be peeled off from the structure composed of the encapsulating resin and the semiconductor chips during predetermined post-processing steps (e.g., back surface grinding of the encapsulating resin, pattern formation, bump formation, chipping (cutting)). The epoxy equivalent of the encapsulating resin is, for example, 50 g / eq to 500 g / eq.

[0011] The above adhesive layer contains an acrylic adhesive. The acrylic adhesive contains a base polymer with an acid value of 16 mgKOH / g or less. This means that there are few residual carboxyl groups in the components of the adhesive layer. In the present invention, by reducing the residual carboxyl groups in the components of the adhesive layer, the compatibility between the encapsulation resin and the adhesive layer components can be reduced. As a result, it is possible to prevent adhesive residue when peeling the adhesive sheet from the encapsulation resin. Also, by reducing the residual carboxyl groups in the components of the adhesive layer, the cohesive force of the acrylic adhesive can be increased. As a result, it has a preferable adhesive force even at high temperatures (for example, in the heating environment during the resin encapsulation process), and when resin encapsulating, the semiconductor chip can be fixed with a high fixing force. Obtaining an adhesive sheet that has excellent fixability at high temperatures and is free of adhesive residue and has excellent peelability is one of the great achievements of the present invention.

[0012] Figure 2 is a schematic cross-sectional view of an adhesive sheet according to another embodiment of the present invention. The adhesive sheet 200 further includes a second adhesive layer on the side opposite to the adhesive layer 20 of the base material 10. That is, the adhesive sheet 200 includes the adhesive layer 20, the base material 10, and the second adhesive layer 30 in this order. By providing the second adhesive layer 30, when resin encapsulation is performed on a pedestal, the second adhesive layer 30 side can be adhered to the pedestal, and the adhesive sheet 200 can be arranged with good fixability.

[0013] In one embodiment, the second adhesive layer contains thermally expandable microspheres. The thermally expandable microspheres can expand at a predetermined temperature. An adhesive layer containing such thermally expandable microspheres expands the thermally expandable microspheres by heating to a predetermined temperature or higher, causing unevenness on the adhesive surface (that is, the surface of the second adhesive layer), and the adhesive force decreases or disappears. If a second adhesive layer containing thermally expandable microspheres is formed, the necessary adhesiveness is exhibited when fixing the adhesive sheet (for example, fixing it to a pedestal), and when peeling the adhesive sheet (for example, peeling it from the pedestal), the adhesive force decreases or disappears due to heating, and good peelability is exhibited.

[0014] The adhesive sheet of the present invention preferably has an adhesive force A at 23°C when the adhesive layer is adhered to polyethylene terephthalate, which is 0.05 N / 20 mm to 1 N / 20 mm, more preferably 0.05 N / 20 mm to 10 N / 20 mm, still more preferably 0.05 N / 20 mm to 5 N / 20 mm, particularly preferably 0.1 N / 20 mm to 2 N / 20 mm, and most preferably 0.1 N / 20 mm to 1 N / 20 mm. Within such a range, the adherend (e.g., semiconductor chip) can be preferably fixed, and an adhesive sheet with little adhesive residue upon peeling can be obtained. In this specification, the "adhesive force at 23°C when the adhesive layer is adhered to polyethylene terephthalate" refers to the adhesive force measured by bonding the adhesive layer of the adhesive sheet (width 20 mm × length 100 mm) to a polyethylene terephthalate film (thickness 25 μm) (bonding condition: one reciprocation of a 2 kg roller), leaving it for 30 minutes at an environmental temperature of 23°C, and then subjecting the sample to a tensile test (peeling speed: 300 mm / min, peeling angle 180°).

[0015] The adhesive sheet of the present invention preferably has a shear adhesive force B at 150°C when a silicon chip is adhered to the adhesive layer, which is 500 g or more, more preferably 700 g to 1500 g, still more preferably 800 g to 1200 g. Within such a range, the cohesive force of the acrylic adhesive is high, and it has a preferable adhesive force even at a high temperature (e.g., a heating step for curing a sealing resin), and it can prevent the displacement of the adherend (e.g., semiconductor chip) disposed on the adhesive sheet. The shear adhesive force can be measured by vertically attaching the mirror surface of a silicon chip (size: 5 mm × 5 mm) to the adhesive layer without applying the chip angle, heating it at 130°C for 30 minutes to make it adhere to the silicon chip adhesive surface, and then reading the maximum breaking load from the load-displacement curve obtained by applying an external force in the horizontal direction with the chip at a shear speed of 500 μm / sec at the measurement temperature (in the case of measuring the shear adhesive force B, 150°C).

[0016] The ratio (shear adhesive strength B / adhesive strength A) of the shear adhesive strength B at 150°C when a silicone chip is attached to the adhesive layer to the adhesive strength A at 23°C when the adhesive layer is attached to polyethylene terephthalate is preferably 32.0 g / (N / 20 mm) or more, more preferably 150 g / (N / 20 mm) or more, even more preferably 1600 g / (N / 20 mm) or more, and particularly preferably 4000 g / (N / 20 mm) or more. Within this range, adhesive residue during peeling can be prevented, and displacement of the adherend (especially displacement at high temperatures) can be prevented.

[0017] The adhesive sheet of the present invention has a shear adhesive strength at 190°C when a silicon chip is attached to the adhesive layer, preferably 300g to 1000g, more preferably 350g to 750g, and even more preferably 400g to 600g. Within this range, when the adhesive sheet comprises a second adhesive layer containing thermally expandable microspheres, the adherend on the adhesive layer can be preferably fixed when the second adhesive layer is made to exhibit peelability, that is, when the thermally expandable microspheres are heated to expand.

[0018] The thickness of the adhesive sheet of the present invention is preferably 3 μm to 300 μm, more preferably 5 μm to 150 μm, and even more preferably 10 μm to 100 μm.

[0019] B.Adhesive layer As described above, the adhesive layer contains an acrylic adhesive. The acrylic adhesive contains a base polymer with an acid value of 16 mgKOH / g or less. The acid value of the base polymer is preferably 10 mgKOH / g or less, more preferably 7.5 mgKOH / g or less, and even more preferably 5 mgKOH / g or less. Within this range, the effects of the present invention become remarkable. A lower acid value of the base polymer is preferable, and its lower limit is, for example, 0 mgKOH / g.

[0020] In this specification, the acid value of the base polymer is measured by the following method using the adhesive layer as a sample. More specifically, the acid value of the base polymer is determined by swelling the adhesive layer with chloroform, adding excess methanol to separate it into soluble (sol) and insoluble (gel) components, filtering it through filter paper, and recovering the insoluble component. This operation is repeated a total of three times, and the acid value of the insoluble component obtained after drying is measured. This oxidation can be measured by potentiometric titration in accordance with JIS K 2501. The acid value of the base polymer can be adjusted to an appropriate range by adding a crosslinking agent that can react with the carboxyl groups of the base polymer, thereby crosslinking the base polymer while consuming the carboxyl groups. In this specification, "base polymer" contained in the acrylic adhesive in the adhesive layer refers to a polymer formed by crosslinking a prepolymer (uncrosslinked polymer).

[0021] The gel fraction of the adhesive layer described above is preferably 75% or more, more preferably 85% or more, and even more preferably 90% or more. Within this range, an adhesive layer can be obtained in which the amount of carboxyl groups of the base polymer is preferably adjusted by crosslinking. A higher gel fraction of the adhesive layer is preferable, but its upper limit is, for example, 99%. The gel fraction is determined by immersing the crosslinked adhesive layer in toluene for 7 days, drying it, and then calculating (dry weight after immersion / dry weight before immersion) × 100.

[0022] The amount of nitrogen gas generated when the above adhesive layer is heat-treated is preferably 0.05 wt% to 1.0 wt%, more preferably 0.07 wt% to 0.8 wt%, and even more preferably 0.15 wt% to 0.7 wt%. When the amount of nitrogen gas generated when the adhesive layer is heat-treated is within this range, the carboxyl groups of the base polymer are consumed by crosslinking, resulting in an adhesive layer with low compatibility with the sealing resin and minimal adhesive residue. The amount of nitrogen gas generated when the adhesive layer is heat-treated can be determined by taking a sample of approximately 5.0 mg to 10.0 mg of the adhesive layer, placing it on a ceramic board, weighing it with a microbalance, and heating it under the conditions of a pyrolysis furnace at 800°C / oxidation furnace at 900°C, and then using a TN (Trace Total Nitrogen Analysis) device to determine the amount of nitrogen gas generated.

[0023] The thickness of the adhesive layer is preferably 1 μm to 300 μm, more preferably 2 μm to 300 μm, even more preferably 3 μm to 150 μm, even more preferably 4 μm to 100 μm, and even more preferably 5 μm to 50 μm.

[0024] The elastic modulus of the adhesive layer measured by nanoindentation at 25°C is preferably less than 100 MPa, more preferably 0.1 MPa to 50 MPa, and even more preferably 0.1 MPa to 10 MPa. Within this range, an adhesive sheet with appropriate adhesive strength can be obtained. The elastic modulus measured by nanoindentation refers to the elastic modulus obtained from the load-indentation depth curve, which is obtained by continuously measuring the load applied to the indenter and the indentation depth during loading and unloading when the indenter is pressed into the sample. In this specification, the elastic modulus measured by nanoindentation refers to the elastic modulus measured as described above, with the measurement conditions being load: 1 mN, loading / unloading speed: 0.1 mN / s, and holding time: 1 s.

[0025] The tensile elastic modulus of the above adhesive layer at 25°C is preferably less than 100 MPa, more preferably 0.1 MPa to 50 MPa, and even more preferably 0.1 MPa to 10 MPa. If it is within such a range, an adhesive sheet having appropriate adhesiveness can be obtained. The tensile elastic modulus can be measured according to JIS K 7161:2008.

[0026] The probe tack value of the above adhesive layer is preferably 50 N / 5 mmφ or more, more preferably 75 N / 5 mmφ or more, and even more preferably 100 N / 5 mmφ or more. If it is within such a range, displacement of an adherend (for example, a semiconductor chip) disposed on the adhesive sheet can be prevented. The measurement conditions of the probe tack value are: probe processing speed: 30 mm / min, test speed: 30 mm / min, adhesion load: 100 gf, adhesion holding time: 1 second, probe area: 5 mmφ SUS.

[0027] The sp value of the above base polymer is preferably 7 (cal / cm 3 ) 1 / 2 ~10 (cal / cm 3 ) 1 / 2 and more preferably 7 (cal / cm 3 ) 1 / 2 ~9 (cal / cm 3 ) 1 / 2 and even more preferably 7 (cal / cm 3 ) 1 / 2 ~8 (cal / cm 3 ) 1 / 2 If it is within such a range, an adhesive sheet having appropriate adhesiveness and little adhesive residue at the time of peeling can be obtained.

[0028] (Acrylic adhesive) Examples of the above-mentioned acrylic adhesives include acrylic adhesives in which an acrylic polymer (homopolymer or copolymer) using one or more alkyl (meth)acrylate esters as monomer components is used as a prepolymer, and a crosslinked prepolymer is used as the base polymer. In one embodiment, the base polymer has a crosslinked structure of an acrylic polymer and an epoxy crosslinking agent.

[0029] Specific examples of the above alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, (meth Examples of C1-20 alkyl esters of (meth)acrylate include nonyl acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Preferably, these are alkyl (meth)acrylates having a linear or branched alkyl group with 4 to 20 carbon atoms (more preferably 6 to 20, particularly preferably 8 to 18), and more preferably 2-ethylhexyl (meth)acrylate.

[0030] The above-mentioned acrylic polymer (prepolymer) may, if necessary, contain units corresponding to other monomer components copolymerizable with the above-mentioned alkyl (meth)acrylate, for the purpose of modifying properties such as cohesiveness, heat resistance, and crosslinkability. Examples of such monomeric components include carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride monomers such as maleic anhydride and eicotanoic anhydride; hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl methacrylate; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; (meth (N-substituted)amide monomers such as acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide; (meth)acrylate aminoalkyl monomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate; (meth)acrylate alkoxyalkyl monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide; itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-laurylitaconimide;Succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; vinyl monomers such as vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinyl carboxylic acid amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and (meth)acrylic acid Examples include glycol-based acrylic ester monomers such as methoxypolypropylene glycol phosphate; acrylic acid ester monomers having heterocyclic rings, halogen atoms, silicon atoms, etc., such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; polyfunctional monomers such as hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate; olefin-based monomers such as isoprene, butadiene, and isobutylene; and vinyl ether-based monomers such as vinyl ether. These monomer components may be used individually or in combination of two or more.

[0031] In one embodiment, the acrylic polymer (prepolymer) further comprises structural units derived from hydroxyl group-containing monomers. By using an acrylic polymer containing structural units derived from hydroxyl group-containing monomers, the interaction with the sealing resin is reduced compared to an acrylic polymer containing structural units derived from carboxyl group-containing monomers, thus suppressing adhesive residue. The content of structural units derived from hydroxyl group-containing monomers is preferably 0.1% to 20% by weight, more preferably 0.5% to 10% by weight, and particularly preferably 1% to 7% by weight, relative to the total structural units constituting the acrylic polymer.

[0032] The above-mentioned acrylic adhesive may contain any suitable additives as needed. Examples of such additives include crosslinking agents, tackifiers, plasticizers (e.g., trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers, etc.), pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, release modifiers, softeners, surfactants, flame retardants, antioxidants, and the like.

[0033] Examples of crosslinking agents included in the above-mentioned acrylic adhesives 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.

[0034] In one embodiment, the amount of crosslinking agent relative to the carboxyl groups of the acrylic polymer (prepolymer) is preferably 0.08 to 2 molar equivalents, and more preferably 0.3 to 1.6 molar equivalents. Within this range, an adhesive sheet with a low amount of residual carboxyl groups in the adhesive layer can be obtained. The amount of crosslinking agent referred to here means the amount of crosslinking agent before the acrylic polymer is crosslinked.

[0035] Specific examples of the isocyanate crosslinking agents contained in the above-mentioned acrylic adhesive 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; isocyanate adducts such as trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HL"), and isocyanurate derivative of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HX"); and the like. The amount of isocyanate-based crosslinking agent can be set to any appropriate amount depending on the desired adhesive strength, typically 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight, per 100 parts by weight of acrylic polymer. Within this range, an adhesive sheet with a low amount of residual carboxyl groups in the adhesive layer can be obtained. The amount of crosslinking agent used here refers to the amount of crosslinking agent before the acrylic polymer is crosslinked.

[0036] In one embodiment, an epoxy-based crosslinking agent is preferably used as the crosslinking agent. By using an epoxy-based crosslinking agent, a highly cohesive adhesive layer can be formed, which can more effectively prevent displacement of the adherend.

[0037] Examples of the epoxy crosslinking agent included in the above-mentioned acrylic adhesive include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C"), 1,6-hexanediol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolite 1600"), and neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolite 1500NP"). ), ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., product name "Epolite 40E"), propylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., product name "Epolite 70P"), polyethylene glycol diglycidyl ether (manufactured by Nippon Oil & Fats Co., Ltd., product name "Epiol E-400"), polypropylene glycol diglycidyl ether (manufactured by Nippon Oil & Fats Co., Ltd., product name "Epiol P-200"), sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Co., Ltd., product name "Denacol") Examples include EX-611), glycerol polyglycidyl ether (manufactured by Nagase ChemteX, trade name "Denacol EX-314"), pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX, trade name "Denacol EX-512"), sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipic acid ester, diglycidyl o-phthalate 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 amount of epoxy crosslinking agent can be set to any appropriate amount depending on the desired adhesive strength, typically 0.01 to 50 parts by weight, more preferably 1 to 30 parts by weight, even more preferably 2 to 20 parts by weight, and particularly preferably 3 to 15 parts by weight, per 100 parts by weight of acrylic polymer. Within this range, an adhesive sheet with a small amount of residual carboxyl groups in the adhesive layer can be obtained. The amount of crosslinking agent referred to here means the amount of crosslinking agent before the acrylic polymer is crosslinked.

[0038] In one embodiment, a crosslinking agent containing nitrogen atoms is used as the epoxy crosslinking agent. Using a crosslinking agent containing nitrogen atoms is advantageous because the crosslinking reaction is promoted by catalytic action, making it easier to achieve high gelation of the adhesive.

[0039] Any suitable tackifier can be used as the tackifier included in the acrylic adhesive described above. For example, a tackifying resin can be used as the tackifier. Specific examples of the tackifying resin include rosin-based tackifying resins (e.g., unmodified rosin, modified rosin, rosin-phenol resins, rosin-ester resins, etc.), terpene-based tackifying resins (e.g., terpene resins, terpene-phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, hydrogenated terpene resins), hydrocarbon-based tackifying resins (e.g., aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene resins, xylene resins, etc.), aliphatic-aromatic petroleum resins, aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone-indene resins, etc.), phenol-based tackifying resins (e.g., alkylphenol resins, xylene-formaldehyde resins, resol, novolac, etc.), ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, elastomer-based tackifying resins, and the like. Preferably, the tackifier is a rosin-based tackifier, a terpene-based tackifier, or a hydrocarbon-based tackifier (such as a styrene-based resin). The tackifier may be used alone or in combination of two or more types. The amount of the tackifier added is preferably 5 to 100 parts by weight, and more preferably 8 to 50 parts by weight, per 100 parts by weight of the base polymer.

[0040] Preferably, a resin with a high softening point or glass transition temperature (Tg) is used as the tackifying resin. By using a resin with a high softening point or glass transition temperature (Tg), an adhesive layer that exhibits high tackiness can be formed even in high-temperature environments (for example, high-temperature environments in semiconductor chip encapsulation processing). The softening point of the tackifier is preferably 100°C to 180°C, more preferably 110°C to 180°C, and even more preferably 120°C to 180°C. The glass transition temperature (Tg) of the tackifier is preferably 100°C to 180°C, more preferably 110°C to 180°C, and even more preferably 120°C to 180°C.

[0041] Preferably, a low-polarity tackifying resin is used as the tackifying resin. Using a low-polarity tackifying resin makes it possible to form an adhesive layer with low affinity to the sealing material. Examples of low-polarity tackifying resins include aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene resins, xylene resins, etc.), aliphatic-aromatic petroleum resins, aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, and other hydrocarbon tackifying resins. Among these, tackifying agents having 5 to 9 carbon atoms are preferred. This is because such tackifying agents are low-polarity, have excellent compatibility with acrylic polymers, do not undergo phase separation over a wide temperature range, and can form an adhesive layer with excellent stability.

[0042] The acid value of the tackifying resin is preferably 40 or less, more preferably 20 or less, and even more preferably 10 or less. Within this range, an adhesive layer with low affinity to the sealing material can be formed. The hydroxyl value of the tackifying resin is preferably 60 or less, more preferably 40 or less, and even more preferably 20 or less. Within this range, an adhesive layer with low affinity to the sealing material can be formed.

[0043] C. Base material Examples of the above-mentioned substrates include resin sheets, nonwoven fabrics, paper, metal foils, woven fabrics, rubber sheets, foamed sheets, and laminates thereof (especially laminates including resin sheets). Examples of resins that make up resin sheets include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), fully aromatic polyamide (aramid), polyimide (PI), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), fluororesins, and polyether ether ketone (PEEK). Examples of nonwoven fabrics include nonwoven fabrics made from heat-resistant natural fibers such as nonwoven fabrics containing Manila hemp; and synthetic resin nonwoven fabrics such as polypropylene resin nonwoven fabrics, polyethylene resin nonwoven fabrics, and ester resin nonwoven fabrics. Examples of metal foils include copper foil, stainless steel foil, and aluminum foil. Examples of paper include Japanese paper (washi) and kraft paper.

[0044] The thickness of the above-mentioned substrate can be set to any appropriate thickness depending on the desired strength or flexibility, as well as the intended use. The thickness of the substrate is preferably 1000 μm or less, more preferably 1 μm to 1000 μm, even more preferably 1 μm to 500 μm, particularly preferably 3 μm to 300 μm, and most preferably 5 μm to 250 μm.

[0045] The above-mentioned substrate may be subjected to surface treatment. Examples of surface treatments include corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, ionizing radiation treatment, and coating treatment with a primer.

[0046] Examples of the above-mentioned organic coating materials include those described in Plastic Hard Coat Materials II (CMC Publishing, (2004)). Preferably, urethane polymers, more preferably polyacrylic urethane, polyester urethane, or precursors thereof are used. This is because coating and application to the substrate is simple, and a wide variety of types are available industrially and are inexpensive to obtain. The urethane polymer is, for example, a polymer consisting of a reaction mixture of isocyanate monomer and alcoholic hydroxyl group-containing monomer (e.g., hydroxyl group-containing acrylic compound or hydroxyl group-containing ester compound). The organic coating material may contain optional additives such as chain extenders such as polyamines, antioxidants, and oxidation stabilizers. The thickness of the organic coating layer is not particularly limited, but for example, about 0.1 μm to 10 μm is suitable, about 0.1 μm to 5 μm is preferred, and about 0.5 μm to 5 μm is more preferred.

[0047] D. Second adhesive layer The second adhesive layer described above may be an adhesive layer composed of any suitable adhesive. In one embodiment, as described above, the second adhesive layer further includes thermally expandable microspheres.

[0048] The adhesive contained in the second adhesive layer described above may be a curing type adhesive (for example, an active energy ray curing type adhesive) or a pressure-sensitive adhesive. Examples of pressure-sensitive adhesives include acrylic adhesives and rubber adhesives. Details of the adhesive contained in the second adhesive layer can be found in, for example, Japanese Patent Application Publication No. 2018-009050. The entire description of that publication is incorporated herein by reference.

[0049] Any suitable thermally expandable microsphere can be used as the above-mentioned thermally expandable microsphere, as long as it is a microsphere that can expand or foam upon heating. For example, a microsphere can be used in which a substance that expands easily upon heating is encapsulated within an elastic shell. Such thermally expandable microspheres can be manufactured by any suitable method, such as coacervation or interfacial polymerization.

[0050] Examples of substances that expand easily upon heating include low-boiling-point liquids such as propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, heptane, octane, petroleum ether, methane halides, and tetraalkylsilanes; and azodicarbonamides that gasify upon thermal decomposition.

[0051] Examples of materials constituting the above shell include polymers composed of nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, and fumaronitrile; carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid; vinylidene chloride; vinyl acetate; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and β-carboxyethyl acrylate; styrene monomers such as styrene, α-methylstyrene, and chlorostyrene; and amide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide. Polymers composed of these monomers may be homopolymers or copolymers. Examples of the copolymer include vinylidene chloride-methyl methacrylate-acrylonitrile copolymer, methyl methacrylate-acrylonitrile-methacrylonitrile copolymer, methyl methacrylate-acrylonitrile copolymer, and acrylonitrile-methacrylonitrile-itaconic acid copolymer.

[0052] As the above-mentioned thermally expandable microspheres, inorganic or organic blowing agents may be used. Examples of inorganic blowing agents include ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydrate, and various azides. Examples of organic blowing agents include: salt fluoride alkane compounds such as trichloromonofluoromethane and dichloromonofluoromethane; azo compounds such as azobisisobutyronitrile, azodicarbonamide, and barium azodicarboxylate; hydrazine compounds such as p-toluenesulfonyl hydrazide, diphenylsulfon-3,3'-disulfonyl hydrazide, 4,4'-oxybis(benzenesulfonyl hydrazide), and allylbis(sulfonyl hydrazide); semicarbazide compounds such as p-toluenesulfonyl semicarbazide and 4,4'-oxybis(benzenesulfonyl semicarbazide); triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; and N-nitroso compounds such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosotelephthalamide.

[0053] The above-mentioned thermally expandable microspheres may be commercially available products. Specific examples of commercially available thermally expandable microspheres include "Matsumoto Microspheres" (grades: F-30, F-30D, F-36D, F-36LV, F-50, F-50D, F-65, F-65D, FN-100SS, FN-100SSD, FN-180SS, FN-180SSD, F-190D, F-260D, F-2800D) manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., and "Expancel" (grade: 053) manufactured by Nippon Philite Co., Ltd. Examples include -40, 031-40, 920-40, 909-80, 930-120), Kureha Chemical Industries' "Daiform" (grades: H750, H850, H1100, S2320D, S2640D, M330, M430, M520), and Sekisui Chemical Co., Ltd.'s "Advancell" (grades: EML101, EMH204, EHM301, EHM302, EHM303, EM304, EHM401, EM403, EM501).

[0054] The particle size of the above-mentioned thermally expandable microspheres before heating is preferably 0.5 μm to 80 μm, more preferably 5 μm to 45 μm, even more preferably 10 μm to 20 μm, and particularly preferably 10 μm to 15 μm. Therefore, the average particle size of the above-mentioned thermally expandable microspheres before heating is preferably 6 μm to 45 μm, and more preferably 15 μm to 35 μm. The above-mentioned particle size and average particle size are values ​​obtained by particle size distribution measurement using the laser scattering method.

[0055] The above-mentioned heat-expandable microspheres preferably have moderate strength that prevents them from bursting until their volume expansion coefficient is preferably 5 times or more, more preferably 7 times or more, and even more preferably 10 times or more. When such heat-expandable microspheres are used, the adhesive strength can be efficiently reduced by heat treatment.

[0056] The proportion of thermally expandable microspheres in the adhesive layer can be appropriately set according to the desired degree of reduction in adhesive strength, etc. The proportion of thermally expandable microspheres is, for example, 1 to 150 parts by weight, preferably 10 to 130 parts by weight, and more preferably 25 to 100 parts by weight, per 100 parts by weight of the base polymer forming the second adhesive layer.

[0057] When the adhesive layer contains thermally expandable microspheres, the arithmetic surface roughness Ra of the adhesive layer before the thermally expandable microspheres expand (i.e., before heating) is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. Within this range, an adhesive sheet with excellent adhesion to the adherend can be obtained. Such an adhesive layer with excellent surface smoothness can be obtained, for example, by setting the thickness of the adhesive layer within the above range.

[0058] When the adhesive layer contains thermally expandable microspheres, it is preferable that the adhesive layer contains an adhesive composed of a base polymer having a dynamic storage modulus at 80°C in the range of 5 kPa to 1 MPa (more preferably 10 kPa to 0.8 MPa). Such an adhesive layer can form an adhesive sheet that has appropriate tackiness before heating and whose tackiness decreases easily upon heating. The dynamic storage modulus can be measured using a dynamic viscoelasticity measuring device (for example, a product name "ARES" manufactured by Rheometrics) under measurement conditions of a frequency of 1 Hz and a heating rate of 10°C / min.

[0059] E. Method for manufacturing adhesive sheets The adhesive sheet of the present invention can be manufactured by any suitable method. Examples of such methods include directly coating a substrate with a composition containing an acrylic adhesive, or coating a suitable substrate with a composition containing an acrylic adhesive and transferring the resulting coating layer to the substrate. The composition containing the acrylic adhesive may contain any suitable solvent.

[0060] When forming an adhesive layer containing thermally expandable microspheres, the adhesive layer can be formed by coating a substrate with a composition containing thermally expandable microspheres, an adhesive, and any suitable solvent. Alternatively, the thermally expandable microspheres may be sprinkled onto an adhesive coating layer, and then the thermally expandable microspheres may be embedded in the adhesive using a laminator or the like to form an adhesive layer containing thermally expandable microspheres.

[0061] Any suitable coating method can be used for coating the above-mentioned adhesive and each composition. For example, the coating can be dried after application to form each layer. Examples of coating methods include coating using a multi-coater, die coater, gravure coater, applicator, etc. Examples of drying methods include natural drying and heat drying. In the case of heat drying, the heating temperature can be set to any suitable temperature depending on the properties of the substance to be dried. [Examples]

[0062] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows. In the examples, unless otherwise specified, "parts" and "%" are based on weight.

[0063] (1) Acid value The acid value of the base polymer constituting the adhesive layer was measured by the following method. A predetermined amount of adhesive layer was swollen with chloroform, then excess methanol was added to separate it into soluble (sol) and insoluble (gel) components. The mixture was filtered through filter paper to recover the insoluble component (this process was repeated a total of three times), and the resulting insoluble component (gel) was dried and used as the measurement sample. For the sample in question, the acid value was measured by potentiometric titration in accordance with JIS K 2501, using a potentiometric titrator AT-500N (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) and glass electrodes H-171 and R-173 (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) as electrodes. This value was then defined as the acid value of the base polymer. The measurement procedure involved adding the sample to be measured and 200 mL of mixed solvent to a 300 mL Erlenmeyer flask, allowing it to swell, and then titrating. A blank test was performed in the same manner, and the acid value was calculated using the following formula (1). Acid value (mgKOH / g)=(V1-V0)×f×0.1×56.11 / S (1) S; Mass of the collected sample (g) V0; Amount of titrant (mL) required for the blank test. V1; Amount of titration solution required in this test (mL) f; Factor of the titrator (f=1.002) The measurement conditions used in the above measurements were as follows: • Titrate: 0.1 mol / L KOH alcohol solution (commercially available) Mixed solvent; Toluene:Water:Isopropanol = 500:5:495 (2) Adhesive strength A SUS304 plate was attached to the entire surface of the side of an adhesive sheet (20mm wide x 140mm long) opposite the adhesive layer, using double-sided adhesive tape (manufactured by Nitto Denko, product name "No. 531") and a 2kg hand roller. Next, a polyethylene terephthalate film (manufactured by Toray Industries, Ltd., product name "Lumirror S-10", thickness: 25 μm, width: 30 mm) was applied to the entire surface of the adhesive layer (temperature: 23°C, humidity: 65%, 2 kg roller, one pass). The evaluation samples obtained as described above were subjected to tensile testing. A Shimadzu Autograph AG-120kN, manufactured by Shimadzu Corporation, was used as the tensile testing machine. After setting the evaluation samples in the tensile testing machine, they were left for 30 minutes at an ambient temperature of 23°C before the tensile test was started. The conditions for the tensile test were a peel angle of 180° and a peel speed (tensile speed) of 300 mm / min. The load when the adhesive sheet was peeled from the PET film was measured, and the maximum load at that time was defined as the adhesive strength of the adhesive sheet. (3) Shear bond strength The adhesive sheets (size: 20mm x 20mm) obtained in Examples 1-7 and the Comparative Example were attached and fixed to a predetermined base (20mm x 20mm silicone chip) using double-sided tape No. 585 manufactured by Nitto Denko Corporation, with the side opposite to the adhesive layer (in Example 7, the side with the second adhesive layer) facing the adhesive layer. A 5mm x 5mm silicone chip (mirror surface) was then attached perpendicularly to the adhesive surface of the adhesive sheet using tweezers, ensuring that the chip's corners did not touch the adhesive surface layer. Subsequently, the sample was heated at 130°C for 30 minutes to allow the silicone chip to adhere to the adhesive surface, and an evaluation sample was prepared. For the evaluation samples, under measurement temperatures (150°C, 190°C), a Nordson dage4000 was used. The measurement terminal was set on the side of a 5mm x 5mm silicon chip at a height of 250μm from the bonding surface, and an external force was applied horizontally to the chip at a shear rate of 500μm / sec. The maximum breaking load was read from the resulting load-displacement curve and defined as the shear adhesive strength. (4) Gel fraction Approximately 0.5 g of the adhesive layer (weight W1) was taken and wrapped in a drawstring-like shape with a porous polytetrafluoroethylene membrane (weight W2) having an average pore size of 0.2 μm, and the opening was tied with string (weight W3). This package was immersed in 50 mL of toluene and kept at room temperature (25°C) for 7 days to allow only the sol component of the adhesive layer to dissolve outside the membrane. Then the package was removed, the toluene adhering to the outer surface was wiped off, and the package was dried at 130°C for 2 hours. The weight of the package (W4) was then measured. The gel fraction was then determined by substituting each value into the following formula. Gel fraction (%) = [(W4 - W2 - W3) / W1] × 100 (5) Nitrogen gas generation The amount of nitrogen gas generated during the heat treatment of the adhesive layer was determined using a TN (Trace Total Nitrogen Analysis) instrument on evaluation samples obtained by taking a sample of the adhesive layer, placing it on a ceramic board, and weighing it with a microbalance. The ceramic board used was pre-heated in the instrument. Two measurements were performed, and the average value was calculated. The measurement conditions used in the above measurements were as follows: ·Temperature: Pyrolysis furnace 800℃, oxidation furnace 900℃ Carrier gas: O2 (300 mL / min), Ar (300 mL / min) • Standard sample: Pyridine / toluene solution • Detector: Depressurized chemiluminescence detector • Range: High concentration (6) Evaluation of adhesive residue In the examples and comparative examples, a frame-shaped spacer (internal dimensions 25 mm x 95 mm) with a thickness of 0.3 mm was placed on the adhesive layer of the adhesive sheet (size: 50 mm x 125 mm). Granular epoxy resin-based encapsulant (Sumitomo Bakelite Co., Ltd., G730) was sprinkled inside the spacer so that the resin thickness after curing would be 0.3 mm. A silicone-treated release liner was then placed over it. Next, the evaluation sample was compressed and molded at 130°C for 600 seconds using a vacuum compression molding machine, and then heated at 140°C for 1 hour to cure, forming a encapsulating resin on the adhesive layer of the adhesive sheet and creating a structure. The structure obtained as described above was cooled, and then the adhesive sheet was peeled off the structure using a tensile testing machine. After setting the structure in the tensile testing machine, it was left for 30 minutes at an ambient temperature of 23°C or 80°C, and then the tensile test was started at each temperature. The conditions for the tensile test were: peel angle: 180°, peel speed (tensile speed): 300 mm / min. After peeling the adhesive sheet from the sealing resin, the adhesive residue on the adhesive surface of the structure was visually observed and evaluated under the following conditions. ◎: No adhesive residue was observed on the epoxy resin-based sealant at both ambient temperatures of 23°C and 80°C. ○: No adhesive residue was observed on the epoxy resin-based sealant under ambient temperatures of 80°C. ×: Adhesive residue was observed on the epoxy resin-based sealant at an ambient temperature of 80°C.

[0064] [Example 1] A composition for forming an adhesive layer was prepared by mixing 100 parts by weight of acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with a ratio of 95:5 (weight ratio) of 2-ethylhexyl acrylate units to acrylic acid units). 3 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, trade name "Tetrad C"), 10 parts by weight of rosinphenol-based tackifying resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "Sumilide Resin PR-12603"), and 100 parts by weight of toluene. The adhesive layer-forming composition was coated onto one side of a polyethylene terephthalate film (manufactured by Toray Industries, Ltd., product name "Lumirror S10", thickness 38 μm) as a base material to obtain an adhesive sheet consisting of a base material and an adhesive layer (thickness 5 μm). The obtained adhesive sheets were subjected to the evaluations (1) to (6) described above. The results are shown in Table 1.

[0065] [Example 2] An adhesive sheet was obtained in the same manner as in Example 1, except that the amount of epoxy crosslinking agent was 5 parts by weight and the adhesive layer forming composition was prepared without the rosinphenol-based tackifying resin. The obtained adhesive sheet was subjected to the above evaluations (1) to (6). The results are shown in Table 1.

[0066] [Example 3] An adhesive sheet was obtained in the same manner as in Example 1, except that the composition for forming the adhesive layer was prepared with an epoxy crosslinking agent of 5 parts by weight. The obtained adhesive sheet was subjected to the evaluations (1) to (6) described above. The results are shown in Table 1.

[0067] [Example 4] An adhesive sheet was obtained in the same manner as in Example 1, except that the composition for forming the adhesive layer was prepared with an epoxy crosslinking agent of 10 parts by weight. The obtained adhesive sheet was subjected to the evaluations (1) to (6) described above. The results are shown in Table 1.

[0068] [Example 5] A composition for forming an adhesive layer was prepared by mixing 100 parts by weight of acrylic copolymer B (a copolymer of 2-ethylhexyl acrylate and hydroxyethyl acrylate, with 2-ethylhexyl acrylate constituent units and hydroxyethyl acrylate constituent units = 100:4 (weight ratio)), 3 parts by weight of isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate L"), 10 parts by weight of rosinphenol-based tackifying resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "Sumilide Resin PR-12603"), and 100 parts by weight of toluene. The adhesive layer-forming composition was coated onto one side of a polyethylene terephthalate film (manufactured by Toray Industries, Ltd., product name "Lumirror S10", thickness 38 μm) as a base material to obtain an adhesive sheet consisting of a base material and an adhesive layer (thickness 5 μm).

[0069] [Example 6] A composition for forming an adhesive layer was prepared by mixing 100 parts by weight of acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with a ratio of 95:5 (weight ratio) of 2-ethylhexyl acrylate units to acrylic acid units). 5 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C"), 10 parts by weight of terpene phenol-based tackifying resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "YS Polystar S145"), and 100 parts by weight of toluene. The adhesive layer-forming composition was coated onto one side of a polyethylene terephthalate film (manufactured by Toray Industries, Ltd., product name "Lumirror S10", thickness 38 μm) as a base material to obtain an adhesive sheet consisting of a base material and an adhesive layer (thickness 10 μm). The obtained adhesive sheets were subjected to the evaluations (1) to (6) described above. The results are shown in Table 1.

[0070] [Example 7] In Example 3, an adhesive layer-forming composition was prepared by mixing 100 parts by weight of acrylic copolymer C (a copolymer of 2-ethylhexyl acrylate, ethyl acrylate, methyl methacrylate, and hydroxyethyl acrylate, where 2-ethylhexyl acrylate units, ethyl acrylate units, methyl methacrylate units, and acrylic acid units = 30:70:5:4 (weight ratio)), 30 parts by weight of thermally expandable microspheres (manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., product name "Matsumoto Microsphere F-190D"), 1.4 parts by weight of isocyanate crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), 10 parts by weight of tackifier (manufactured by Yasuhara Chemical Co., Ltd., product name "Mighty Ace G125"), and 100 parts by weight of toluene, and applied to the side of the polyethylene terephthalate film of the adhesive sheet opposite to the adhesive layer to form a second adhesive layer (thickness 45 μm) and obtain a double-sided adhesive sheet. The adhesive layer of the obtained double-sided adhesive sheet was subjected to the evaluations (1) to (6) described above. The results are shown in Table 1.

[0071] [Comparative Example 1] A composition for forming an adhesive layer was prepared by mixing 100 parts by weight of an acrylic copolymer (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with a ratio of 95:5 (weight ratio) of 2-ethylhexyl acrylate units to acrylic acid units). 0.5 parts by weight of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C"), 10 parts by weight of a terpene phenol-based tackifying resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "YS Polystar S145"), and 100 parts by weight of toluene. The adhesive layer-forming composition was coated onto one side of a polyethylene terephthalate film (manufactured by Toray Industries, Ltd., product name "Lumirror S10", thickness 38 μm) as a base material to obtain an adhesive sheet consisting of a base material and an adhesive layer (thickness 10 μm).

[0072] [Table 1] [Explanation of symbols]

[0073] 10 Base material 20 Adhesive layer 30 Second adhesive layer 100, 200 adhesive sheets

Claims

1. The system comprises a base material and an adhesive layer disposed on at least one side of the base material, The adhesive layer contains an acrylic adhesive, The acrylic adhesive contains a base polymer with an acid value of 16 mg KOH / g or less. The base polymer has a crosslinked structure comprising an acrylic polymer containing structural units derived from carboxyl group-containing monomers and an epoxy crosslinking agent containing N atoms. The amount of nitrogen gas generated when the adhesive layer is heat-treated is 0.05 wt% to 1.0 wt%, The gel fraction of the adhesive layer is 85% or more. The ratio of the shear adhesive strength B at 150°C when a silicone chip is attached to the adhesive layer to the adhesive strength A at 23°C when the adhesive layer is attached to polyethylene terephthalate (shear adhesive strength B / adhesive strength A) is between 4000 g / (N / 20 mm) and 8618 g / (N / 20 mm). Adhesive sheet.

2. The adhesive sheet according to claim 1, comprising the aforementioned base material, the adhesive layer disposed on one side of the base material, and a second adhesive layer disposed on the opposite side of the base material from the adhesive layer.

3. The adhesive sheet according to claim 1 or 2, wherein the amount of the crosslinking agent blended with respect to the carboxyl groups of the acrylic polymer is 0.08 molar equivalents to 2 molar equivalents.

4. The adhesive sheet according to any one of claims 1 to 3, wherein the thickness of the adhesive layer is 1 μm to 300 μm.

5. An adhesive sheet according to any one of claims 1 to 4, which is a temporary fixing material used in the resin encapsulation process of semiconductor chips.

6. The adhesive sheet according to claim 5, used when curing a sealing resin on the adhesive sheet.

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