Adhesive sheet

Abstract

Provided is an adhesive sheet that has moderate adhesiveness to a sealing resin for sealing a semiconductor chip and a semiconductor chip, can be easily peeled from the sealing resin, and is difficult to produce a residue at the time of peeling. The adhesive sheet of the present invention has a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer containing an acrylic adhesive, the acrylic adhesive containing a base polymer having an acid value of 16 mgKOH / g or less. In one embodiment, the above-described adhesive sheet has the above-described substrate, the above-described adhesive layer disposed on one side of the substrate, and a second adhesive layer disposed on the side of the substrate opposite the adhesive layer.

Description

Technical Field

[0001] This invention relates to adhesive sheets. Background Technology

[0002] In recent years, during the manufacturing of semiconductor components containing semiconductor chips, resin sealing is sometimes performed on the semiconductor chips to prevent damage and expansion of metal wiring. In the resin sealing process, from an operability perspective, the semiconductor chips are sometimes sealed onto an adhesive sheet. For example, to prevent movement of the semiconductor chips, multiple semiconductor chips are arranged on a pre-defined adhesive sheet as a temporary fixing material, and the semiconductor chips are sealed onto the adhesive sheet in one step. Then, in a predetermined subsequent process, the adhesive sheet is peeled off from the resin used to seal the semiconductor chips.

[0003] In the process described above, if conventional adhesive sheets are used, there is a problem of residual adhesive being generated in the structure when the adhesive sheet is peeled off from the structure containing the sealing resin and the semiconductor chip.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-308116

[0007] Patent Document 2: Japanese Patent Application Publication No. 2001-313350

[0008] Patent Document 3: Japanese Patent Application Publication No. 2018-193563 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] The present invention was made to solve the above-mentioned prior art problems, and its object is to provide an adhesive sheet that has moderate adhesion to a sealing resin used to seal a semiconductor chip and the semiconductor chip, can be easily peeled off from the sealing resin, and does not easily produce adhesive residue during peeling.

[0011] Solution for solving the problem

[0012] The adhesive sheet of the present invention comprises a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer comprising an acrylic adhesive comprising a base polymer with an acid value of less than 16 mg KOH / g.

[0013] In one embodiment, the adhesive sheet comprises: the substrate, the adhesive layer disposed on one side of the substrate, and a second adhesive layer disposed on the side of the substrate opposite to the adhesive layer.

[0014] In one embodiment, the ratio of the shear adhesion force B at 150°C when the silicon chip is attached to the adhesive layer to the adhesion force A at 23°C when the adhesive layer is attached to polyethylene terephthalate (shear adhesion force B / adhesion force A) is 32.0 g / (N / 20 mm) or more.

[0015] In one embodiment, the base polymer is a crosslinked acrylic polymer.

[0016] In one embodiment, the gelation rate of the adhesive layer is 75% or higher.

[0017] In one embodiment, the acrylic adhesive comprises a crosslinking agent, wherein the amount of the crosslinking agent is 0.08 molar equivalents to 2 molar equivalents relative to the carboxyl groups of the acrylic polymer.

[0018] In one embodiment, the crosslinking agent is an epoxy-based crosslinking agent.

[0019] In one embodiment, the amount of nitrogen generated during the heat treatment of the adhesive layer is 0.05 wt% to 1.0 wt%.

[0020] In one embodiment, the thickness of the adhesive layer is 1 μm to 300 μm.

[0021] In one embodiment, the adhesive sheet is a temporary fixing material used in the resin sealing process of a semiconductor chip.

[0022] In one embodiment, the adhesive sheet is used when the sealing resin is cured on the adhesive sheet.

[0023] The effects of the invention

[0024] According to the present invention, an adhesive sheet is provided that has moderate adhesion to a sealing resin used for sealing a semiconductor chip and the semiconductor chip, can be easily peeled off from the sealing resin, and does not easily produce adhesive residue during peeling. Attached Figure Description

[0025] Figure 1 This is a cross-sectional schematic diagram of an adhesive sheet according to one embodiment of the present invention.

[0026] Figure 2 This is a cross-sectional schematic diagram of an adhesive sheet according to another embodiment of the present invention. Detailed Implementation

[0027] A. Overview of Adhesive Sheets

[0028] Figure 1This is a cross-sectional schematic diagram of an adhesive sheet according to one embodiment of the present invention. The adhesive sheet 100 includes a substrate 10 and an adhesive layer (first adhesive layer) 20 disposed on at least one side of the substrate 10.

[0029] The adhesive sheet of the present invention can be suitably used as a temporary fixing material for resin sealing of semiconductor chips. More specifically, the adhesive sheet of the present invention can be used as a temporary fixing material for resin sealing of semiconductor chips when semiconductor chips are arranged on an adhesive layer of the adhesive sheet, covered with resin (usually an epoxy resin), and the semiconductor chips are resin sealed by curing the sealing resin. After the semiconductor chip is resin sealed, the adhesive sheet can be peeled off from the structure composed of the sealing resin and the semiconductor chip during specified subsequent processes (e.g., back-side grinding of the sealing resin, patterning, bumping, chip forming (cutting)). The epoxy equivalent of the sealing resin is, for example, 50 g / eq to 500 g / eq.

[0030] The aforementioned adhesive layer comprises an acrylic adhesive. This acrylic adhesive contains a base polymer with an acid value of less than 16 mg KOH / g. This means that the adhesive layer has few residual carboxyl groups. In this invention, by reducing the residual carboxyl groups in the adhesive layer, the compatibility between the sealing resin and the adhesive layer components can be reduced, resulting in the prevention of residue when the adhesive sheet is peeled from the sealing resin. Furthermore, by reducing the residual carboxyl groups in the adhesive layer, the cohesive strength of the acrylic adhesive can be increased, resulting in superior adhesion even at high temperatures (e.g., under the heating conditions of the resin sealing process), enabling the semiconductor chip to be fixed with high fixation force during resin sealing. Obtaining an adhesive sheet with excellent fixation at high temperatures, prevention of residue, and excellent peelability is one of the significant achievements of this invention.

[0031] Figure 2 This is a cross-sectional schematic diagram of an adhesive sheet according to another embodiment of the present invention. The adhesive sheet 200 further comprises a second adhesive layer on the side of the substrate 10 opposite to the adhesive layer 20. That is, the adhesive sheet 200 sequentially comprises the adhesive layer 20, the substrate 10, and the second adhesive layer 30. By providing the second adhesive layer 30, when performing resin sealing on the base, the second adhesive layer 30 can be attached to the base side, thereby providing good fixation for the adhesive sheet 200.

[0032] In one embodiment, the second adhesive layer comprises thermally expandable microspheres. These microspheres are capable of expanding at a specified temperature. When an adhesive layer containing such thermally expandable microspheres is heated above the specified temperature, the microspheres expand, creating unevenness on the adhesive surface (i.e., the surface of the second adhesive layer), resulting in reduced or absent adhesive force. If a second adhesive layer containing thermally expandable microspheres is formed, the desired adhesion is exhibited when the adhesive sheet is fixed (e.g., fixed to a pedestal), and when the adhesive sheet is peeled off (e.g., peeled from the pedestal), the adhesive force is reduced or absent by heating, exhibiting good peelability.

[0033] The adhesive strength A of the adhesive sheet of the present invention at 23°C when the adhesive layer is attached to polyethylene terephthalate is preferably 0.05 N / 20 mm to 1 N / 20 mm, more preferably 0.05 N / 20 mm to 10 N / 20 mm, further 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 this range, an adhesive sheet that can preferably fix the adhered object (e.g., a semiconductor chip) and leaves minimal adhesive residue upon peeling can be obtained. It should be noted that, in this specification, "adhesive force at 23°C when the adhesive layer is applied to polyethylene terephthalate" refers to the adhesive force measured by applying the adhesive layer of an adhesive sheet (20mm wide × 100mm long) to a polyethylene terephthalate film (25μm thick) (adhesive conditions: 2kg roller passes back and forth once) and placing the sample at an ambient temperature of 23°C for 30 minutes, and then subjecting the sample to a tensile test (peeling speed: 300mm / min, peeling angle 180°).

[0034] The shear bond strength B of the adhesive sheet of the present invention at 150°C when a silicon chip is attached to the adhesive layer is preferably 500g or more, more preferably 700g to 1500g, and even more preferably 800g to 1200g. Within this range, the acrylic adhesive has high cohesive strength and exhibits preferred adhesive strength even at high temperatures (e.g., heating processes used to cure sealing resins), and can prevent displacement of the adhered object (e.g., a semiconductor chip) disposed on the adhesive sheet. The shear bond strength can be measured as follows: after vertically attaching the mirror surface of a silicon chip (size: 5mm × 5mm) to the adhesive layer without touching the chip corners, heating at 130°C for 30 minutes to ensure close adhesion between the silicon chip and the adhesive surface, and then applying an external force at a shear rate of 500 μm / sec along the direction horizontal to the chip at the measurement temperature (150°C for shear bond strength B measurement), the maximum destructive load is read from the resulting load-displacement curve.

[0035] The ratio of the shear adhesion force B (hereinafter also referred to as shear adhesion force B) at 150°C when the silicon chip is attached to the adhesive layer to the adhesive force A (hereinafter also referred to as adhesive force A) at 23°C when the adhesive layer is attached to polyethylene terephthalate (shear adhesion force B / adhesive force A) is preferably 32.0 g / (N / 20 mm) or more, more preferably 150 g / (N / 20 mm) or more, further preferably 1600 g / (N / 20 mm) or more, and particularly preferably 4000 g / (N / 20 mm) or more. Within this range, residual adhesive during peeling and displacement of the adhered objects (especially displacement at high temperatures) can be prevented.

[0036] The shear adhesion force of the adhesive sheet of the present invention at 190°C when a silicon chip is attached to the adhesive layer is preferably 300g to 1000g, more preferably 350g to 750g, and even more preferably 400g to 600g. Within this range, when the adhesive sheet has a second adhesive layer containing thermally expandable microspheres, when the second adhesive layer side exhibits peelability, i.e., when heated to cause the thermally expandable microspheres to expand, the adhered object on the adhesive layer can be preferably fixed.

[0037] The thickness of the adhesive sheet of the present invention is preferably 3μm to 300μm, more preferably 5μm to 150μm, and even more preferably 10μm to 100μm.

[0038] B. Adhesive layer

[0039] As described above, the adhesive layer comprises an acrylic adhesive. This acrylic adhesive comprises a base polymer with an acid value of 16 mg KOH / g or less. The acid value of this base polymer is preferably 10 mg KOH / g or less, more preferably 7.5 mg KOH / g or less, and even more preferably 5 mg KOH / g or less. Within such a range, the effects of the present invention are significant. The lower the acid value of the base polymer, the more preferred; a lower limit is, for example, 0 mg KOH / g.

[0040] In this specification, the acid value of the aforementioned base polymer is determined by the following method using the adhesive layer as a sample. More specifically, the acid value of the base polymer is as follows: the adhesive layer is swollen with chloroform, excess methanol is added, and the mixture is separated into soluble components (sol) and insoluble components (gel). The mixture is filtered through filter paper, and the insoluble components are recovered. This operation is repeated three times, and the acid value of the dried insoluble components is measured. This acid value can be determined by potentiometric titration according to JIS K 2501. The acid value of the base polymer can be determined by adding a crosslinking agent that can react with the carboxyl groups of the base polymer to consume the carboxyl groups and crosslink the base polymer, thereby setting its amount within an appropriate range. It should be noted that in this specification, the "base polymer" contained in the acrylic adhesive in the adhesive layer refers to the polymer formed by crosslinking the prepolymer (uncrosslinked polymer).

[0041] The gelation rate of the aforementioned adhesive layer is preferably 75% or more, more preferably 85% or more, and even more preferably 90% or more. Within this range, an adhesive layer formed by adjusting the carboxyl group content of the base polymer can be obtained through crosslinking. A higher gelation rate of the adhesive layer is more preferred, with an upper limit of, for example, 99%. It should be noted that the gelation rate is calculated by immersing the crosslinked adhesive layer in toluene for 7 days and then drying it, using (dry weight after immersion / dry weight before immersion) × 100.

[0042] The amount of nitrogen generated during the heat treatment of the adhesive layer 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 generated during the heat treatment of the adhesive layer is within this range, the carboxyl groups of the base polymer are cross-linked and consumed, resulting in low compatibility with the sealing resin and the formation of an adhesive layer with minimal residue. Regarding the amount of nitrogen generated during the heat treatment of the adhesive layer, for a sample in which approximately 5.0 mg to 10.0 mg of the adhesive layer is placed on a ceramic plate and measured using a microbalance, the amount of nitrogen generated by heating under conditions of 800°C in a thermal decomposition furnace / 900°C in an oxidation furnace is determined using a TN (micro total nitrogen analysis) device.

[0043] 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.

[0044] The elastic modulus of the aforementioned adhesive layer at 25°C based on nanoindentation 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 based on nanoindentation refers to the elastic modulus obtained by continuously measuring the loading load and indentation depth of the indenter when it is pressed into the sample from loading to unloading, and calculating the loading load-indentation depth curve. In this specification, the elastic modulus based on nanoindentation refers to the elastic modulus measured under the following conditions: load: 1 mN, loading / unloading speed: 0.1 mN / s, holding time: 1 s, as described above.

[0045] The tensile modulus of the 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. Within this range, an adhesive sheet with appropriate adhesive strength can be obtained. It should be noted that the tensile modulus can be measured according to JIS K 7161:2008.

[0046] The preferred probe adhesion value for the above adhesive layer is... The above, or more preferably The above, further preferred The above. If this range is maintained, it can prevent the position of the object (e.g., a semiconductor chip) mounted on the adhesive sheet from shifting. The conditions for measuring the probe adhesive force are set as follows: probe processing speed: 30 mm / min, test speed: 30 mm / min, adhesion load: 100 gf, adhesion holding time: 1 second, probe area:

[0047] The sp value of the above-mentioned basic polymer is preferably 7 (cal / cm). 3 ) 1 / 2 ~10 (cal / cm) 3 ) 1 / 2 More preferably 7 (cal / cm) 3 ) 1 / 2 ~9 (cal / cm) 3 ) 1 / 2 A further preferred value is 7 (cal / cm³). 3 ) 1 / 2 ~8 (cal / cm) 3 ) 1 / 2 If it falls within this range, an adhesive sheet with appropriate adhesion and minimal adhesive residue upon peeling can be obtained.

[0048] (Acrylic adhesives)

[0049] Examples of acrylic adhesives include those that use an acrylic polymer (homopolymer or copolymer) with one or more alkyl (meth)acrylates as monomer components as a prepolymer, and a crosslinked product of the prepolymer as a base polymer. In one embodiment, the base polymer has a crosslinked structure based on an acrylic polymer and an epoxy crosslinking agent.

[0050] Specific examples of the aforementioned alkyl methacrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecanyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, and other C1-20 alkyl methacrylates. Preferably, alkyl (meth)acrylates having a straight-chain or branched alkyl group having 4 to 20 carbon atoms (more preferably 6 to 20, particularly preferably 8 to 18) are used, and 2-ethylhexyl (meth)acrylate is even more preferred.

[0051] For the purpose of modifying cohesion, heat resistance, crosslinking, etc., the above-mentioned acrylic polymers (prepolymers) may, as needed, contain units corresponding to other monomer components that can copolymerize with the above-mentioned alkyl methacrylates. Examples of such monomer components include: acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and other carboxyl-containing monomers; maleic anhydride, itaconic anhydride, and other anhydride monomers; hydroxyl-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 methyl methacrylate (4-hydroxymethylcyclohexyl)methacrylate; styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, and (meth)acrylic acid... Monomers containing sulfonic acid groups, such as methacrylamide propanesulfonic acid, sulfonylpropyl (meth)acrylate, and methacryloyloxynaphthalenesulfonic acid; (N-substituted) amide monomers, such as (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxymethylpropane (meth)acrylamide; (meth)acrylate aminoethyl ester monomers, such as N,N-dimethylaminoethyl (meth)acrylate and tert-butylaminoethyl (meth)acrylate; (meth)acrylate alkoxyalkyl ester monomers, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; N- Maleimide monomers such as cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers such as N-methylitconimide, N-ethylitconimide, N-butylitconimide, N-octylitconimide, N-2-ethylhexylitconimide, N-cyclohexylitconimide, and N-laurylitconimide; succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; vinyl acetate, vinyl propionate, etc. Vinyl monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazolium, vinyloxazole, vinylmorpholine, N-vinylcarboxylic amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy-containing acrylic monomers such as glycidyl acrylate; diol-based acrylate monomers such as polyethylene glycol acrylate, polypropylene glycol acrylate, methoxyethylene glycol acrylate, and methoxypolypropylene glycol acrylate.Acrylate monomers containing heterocyclic rings, halogen atoms, or silicon atoms, such as tetrahydrofurfuryl methacrylate, fluoromethacrylates, and organosilicon methacrylates; multifunctional monomers such as hexanediol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, pentaerythritol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, epoxy acrylates, polyester acrylates, and urethane acrylates; olefin monomers such as isoprene, butadiene, and isobutylene; and vinyl ether monomers such as vinyl ethers. These monomer components can be used alone or in combination of two or more.

[0052] In one embodiment, the aforementioned acrylic polymer (prepolymer) further comprises structural units derived from hydroxyl-containing monomers. By using acrylic polymers with structural units derived from hydroxyl-containing monomers, the interaction with the sealing resin is less compared to acrylic polymers containing structural units derived from carboxyl-containing monomers, thus suppressing residue. The content of the structural units derived from hydroxyl-containing monomers relative to all structural units constituting the acrylic polymer is preferably 0.1% to 20% by weight, more preferably 0.5% to 10% by weight, and particularly preferably 1% to 7% by weight.

[0053] The aforementioned acrylic adhesives may contain any suitable additives as needed. Examples of such additives include crosslinking agents, tackifiers, plasticizers (e.g., trimellitate plasticizers, pyromellitic ester plasticizers, etc.), pigments, dyes, fillers, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, peel modifiers, softeners, surfactants, flame retardants, antioxidants, etc.

[0054] Examples of crosslinking agents contained in the aforementioned acrylic adhesives include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, 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.

[0055] In one embodiment, the amount of crosslinking agent mixed with the acrylic polymer (prepolymer) is preferably 0.08 molar equivalents to 2 molar equivalents, more preferably 0.3 molar equivalents to 1.6 molar equivalents, relative to the carboxyl groups of the acrylic polymer (prepolymer). Within this range, an adhesive sheet with fewer residual carboxyl groups in the adhesive layer can be obtained. Here, the amount of crosslinking agent mixed with the acrylic polymer refers to the content of crosslinking agent before crosslinking.

[0056] Specific examples of the isocyanate-based crosslinking agents contained in the aforementioned acrylic adhesives 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-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenyl diisocyanate; isocyanate adducts such as trimethylolpropane / toluene 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 esters of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "CORONATE HX"). The amount of isocyanate-based crosslinking agent can be set to any suitable amount according to the desired adhesive strength, typically 0.1 to 20 parts by weight, and more preferably 1 to 10 parts by weight, relative to 100 parts by weight of the acrylic polymer. Within this range, adhesive sheets with fewer residual carboxyl groups in the adhesive layer can be obtained. Here, the amount of crosslinking agent refers to the content of crosslinking agent before crosslinking of the acrylic polymer.

[0057] In one embodiment, an epoxy-based crosslinking agent is preferably used as the crosslinking agent. Using an epoxy-based crosslinking agent allows for the formation of an adhesive layer with high cohesive strength, which more effectively prevents the adhesion of the objects from shifting.

[0058] Examples of epoxy crosslinking agents contained in the aforementioned acrylic adhesives include: N,N,N',N'-tetraglycidyl-m-phenylenediamine, diglycidyl-aniline, 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 "EPOLIGHT 1600"), neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "EPOLIGHT 1500NP"), ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "EPOLIGHT 40E"), propylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "EPOLIGHT 70P"), and polyethylene glycol diglycidyl ether (manufactured by Nippon Yushi Co., Ltd., trade name "EPIOL"). E-400”), polypropylene glycol diglycidyl ether (manufactured by Nippon Yushi Co., Ltd., 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 anhydride polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, epoxy resins with two or more epoxy groups in the molecule, etc. The amount of epoxy crosslinking agent can be set to any suitable amount according to the desired adhesive strength, typically 0.01 to 50 parts by weight, more preferably 1 to 30 parts by weight, further preferably 2 to 20 parts by weight, and particularly preferably 3 to 15 parts by weight relative to 100 parts by weight of the acrylic polymer. Within this range, adhesive sheets with fewer residual carboxyl groups in the adhesive layer can be obtained. Here, the amount of crosslinking agent refers to the content of crosslinking agent before crosslinking of the acrylic polymer.

[0059] In one embodiment, an epoxy-based crosslinking agent containing nitrogen atoms can be used as the crosslinking agent. Using a crosslinking agent containing nitrogen atoms promotes the crosslinking reaction through catalysis, which is advantageous from the perspective of easily achieving high gelation of the adhesive.

[0060] As the tackifier contained in the above-mentioned acrylic adhesive, any suitable tackifier can be used. For example, a tackifying resin can be used as the tackifier. Specific examples of such tackifying resins include: rosin-based tackifying resins (e.g., unmodified rosin, modified rosin, rosin phenol-based resins, rosin ester-based resins, etc.), terpene-based tackifying resins (e.g., terpene-based resins, terpene phenol-based resins, styrene-modified terpene-based resins, aromatic-modified terpene-based resins, hydrogenated terpene-based resins), hydrocarbon-based tackifying resins (e.g., aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene-based resins, xylene-based resins, etc.), aliphatic / aromatic petroleum resins, aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, coumarone-indene-based resins, etc.), phenol-based tackifying resins (e.g., alkylphenol-based resins, xylene-formaldehyde-based resins, methylphenol, phenolic varnish, etc.), ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastic system tackifying resins, etc. The preferred tackifiers are rosin-based, terpene-based, or hydrocarbon-based tackifiers (such as styrene-based resins). Tackifiers can be used alone or in combination of two or more types. The amount of the tackifier added relative to 100 parts by weight of the base polymer is preferably 5 to 100 parts by weight, more preferably 8 to 50 parts by weight.

[0061] Preferably, a resin with a high softening point or glass transition temperature (Tg) is used as the aforementioned tackifying resin. Using a resin with a high softening point or glass transition temperature (Tg) allows for the formation of an adhesive layer exhibiting high adhesion even under high-temperature conditions (e.g., high-temperature environments during semiconductor chip sealing processes). 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.

[0062] A low-polarity tackifying resin is preferably used as the aforementioned tackifying resin. Using a low-polarity tackifying resin allows for the formation of an adhesive layer with low affinity for the sealing material. Examples of low-polarity tackifying resins include aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene-based resins, xylene-based resins, etc.), aliphatic / aromatic petroleum resins, aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, and other hydrocarbon-based tackifying resins. Tackifiers with 5 to 9 carbon atoms are preferred. This is because such tackifiers 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.

[0063] The acid value of the aforementioned 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 for the sealing material can be formed. The hydroxyl value of the aforementioned 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 for the sealing material can be formed.

[0064] C. Substrate

[0065] Examples of substrates include resin sheets, nonwoven fabrics, paper, metal foils, woven fabrics, rubber sheets, foam sheets, and laminates thereof (especially laminates containing resin sheets). Examples of resins constituting 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), fluorinated resins, and polyetheretherketone (PEEK). Examples of nonwoven fabrics include nonwoven fabrics based on heat-resistant natural fibers such as Manila hemp; and synthetic resin nonwoven fabrics such as polypropylene resin nonwoven fabrics, polyethylene resin nonwoven fabrics, and ester-based resin nonwoven fabrics. Examples of metal foils include copper foil, stainless steel foil, and aluminum foil. As for paper, examples include Japanese paper and kraft paper.

[0066] The thickness of the substrate can be set to any appropriate thickness according to the desired strength or flexibility, as well as the intended use. The thickness of the substrate is preferably less than 1000 μm, more preferably 1 μm to 1000 μm, further preferably 1 μm to 500 μm, particularly preferably 3 μm to 300 μm, and most preferably 5 μm to 250 μm.

[0067] The aforementioned 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 primer-based coating treatment.

[0068] Examples of organic coating materials include those described in Plastic Hard Coating Materials II (CMC Publication, (2004)). Urafra-based polymers are preferred, and polyurethane acrylate, polyester urethane, or precursors thereof are more preferred. This is because coating / applying to the substrate is simple, and a variety of materials are available industrially and inexpensive. The urethane-based polymer is, for example, a polymer formed from a reaction mixture of an isocyanate monomer and a monomer containing an alcoholic hydroxyl group (e.g., a hydroxyl-containing acrylic compound or a hydroxyl-containing ester compound). The organic coating material may contain chain extenders such as polyamines, anti-aging agents, oxidation stabilizers, etc., as optional additives. The thickness of the organic coating layer is not particularly limited, but is suitable for about 0.1 μm to 10 μm, preferably about 0.1 μm to 5 μm, and more preferably about 0.5 μm to 5 μm.

[0069] D. Second adhesive layer

[0070] The second adhesive layer described above can be an adhesive layer composed of any suitable adhesive. In one embodiment, as described above, the second adhesive layer further comprises thermally expandable microspheres.

[0071] The adhesive contained in the second adhesive layer described above can be a curing adhesive (e.g., an active energy radiation curing adhesive) or a pressure-sensitive adhesive. Examples of pressure-sensitive adhesives include acrylic adhesives and rubber-based adhesives. Details of the adhesive contained in the second adhesive layer can be found in Japanese Patent Application Publication No. 2018-009050. The entire contents of that publication are incorporated herein by reference.

[0072] As the aforementioned thermally expandable microspheres, any suitable thermally expandable microspheres can be used, as long as they are capable of expanding or foaming upon heating. For example, microspheres containing a substance that readily expands upon heating enclosed in an elastic shell can be used. Such thermally expandable microspheres can be manufactured using any suitable method, such as the coacervate method, interfacial polymerization, etc.

[0073] Examples of substances that readily expand upon heating include: propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, heptane, octane, petroleum ether, halides of methane, tetraalkylsilanes, and other low-boiling-point liquids; azodicarbonamide that vaporizes through thermal decomposition; and so on.

[0074] Examples of materials constituting the aforementioned shell include polymers composed of nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, and fumaric acid; carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid; vinylidene chloride; vinyl acetate; (meth)acrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 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 can be homopolymers or copolymers. Examples of such copolymers include vinylidene chloride-methyl methacrylate-acrylonitrile copolymer, methyl methacrylate-acrylonitrile-methacrylonitrile copolymer, methyl methacrylate-acrylonitrile copolymer, acrylonitrile-methacrylonitrile-itaconic acid copolymer, etc.

[0075] As the aforementioned thermally expandable microspheres, inorganic or organic foaming agents can be used. Examples of inorganic foaming agents include ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and various azides. In addition, examples of organic blowing agents include: chlorofluorocarbon compounds such as trichloromonofluoromethane and dichloromonofluoromethane; azo compounds such as azobisisobutyronitrile, azodicarbonamide, and barium azodicarbonate; hydrazine compounds such as p-toluenesulfonyl hydrazine, diphenyl sulfone-3,3′-disulfonyl hydrazine, 4,4′-oxobis(benzenesulfonyl hydrazine), and allylbis(sulfonyl hydrazine); aminourea compounds such as p-toluenesulfonamide and 4,4′-oxobis(benzenesulfonamide); triazole compounds such as 5-morpholino-1,2,3,4-thiatriazole; N,N′-dinitrospentamethylenetetramine and N,N′-dimethyl-N,N′-dinitrosterephthalamide; and other N-nitroso compounds.

[0076] The aforementioned thermally expandable microspheres can also be commercially available products. Specific examples of commercially available thermally expandable microspheres include those manufactured by Matsumoto Oils & Fats Co., Ltd. under the trade name "Matsumoto microsphere" (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), Japan. Products manufactured by Fillite Co., Ltd. under the brand name "Expacel" (grades: 053-40, 031-40, 920-40, 909-80, 930-120), by Kureha Chemical Industry Co., Ltd. under the brand name "DYFOAM" (grades: H750, H850, H1100, S2320D, S2640D, M330, M430, M520), and by Sekisui Chemical Industry Co., Ltd. under the brand name "Advacell" (grades: EML101, EMH204, EHM301, EHM302, EHM303, EM304, EHM401, EM403, EM501), etc.

[0077] The particle size of the aforementioned 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, if the average particle size of the aforementioned thermally expandable microspheres before heating is expressed as the average particle size, it is preferably 6 μm to 45 μm, more preferably 15 μm to 35 μm. The aforementioned particle size and average particle size are values ​​obtained by particle size distribution measurement using laser scattering.

[0078] The aforementioned thermally expandable microspheres preferably possess moderate strength that does not break even with a volume expansion rate of at least 5 times, more preferably at least 7 times, and even more preferably at least 10 times. When using such thermally expandable microspheres, adhesive forces can be efficiently reduced through heat treatment.

[0079] The content ratio of thermally expandable microspheres in the adhesive layer can be appropriately set according to the desired reduction in adhesive strength, etc. The content ratio of thermally expandable microspheres relative to 100 parts by weight of the base polymer forming the second adhesive layer 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.

[0080] When the adhesive layer comprises thermally expandable microspheres, the arithmetic mean 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 adhered object can be obtained. Such an adhesive layer with excellent surface smoothness can be obtained, for example, by making the thickness of the adhesive layer within the above-mentioned range.

[0081] When the aforementioned adhesive layer contains thermally expandable microspheres, the adhesive layer preferably comprises an adhesive made of a base polymer with a dynamic storage modulus at 80°C ranging from 5 kPa to 1 MPa (more preferably from 10 kPa to 0.8 MPa). With such an adhesive layer, an adhesive sheet can be formed that exhibits moderate adhesion before heating and whose adhesive strength is easily reduced by heating. It should be noted that the dynamic storage modulus can be measured using a dynamic viscoelasticity measuring device (e.g., the trade name "ARES" manufactured by Rheometrics) under measurement conditions of a frequency of 1 Hz and a heating rate of 10°C / min.

[0082] E. Method for manufacturing adhesive sheets

[0083] The adhesive sheet of the present invention can be manufactured by any suitable method. Examples of methods for manufacturing the adhesive sheet of the present invention include: directly coating a composition comprising an acrylic adhesive onto a substrate; or transferring a coating layer formed by coating a composition comprising an acrylic adhesive onto any suitable substrate to the substrate. The composition comprising the acrylic adhesive may contain any suitable solvent.

[0084] When forming an adhesive layer containing thermally expandable microspheres, the adhesive layer can be formed by coating a composition containing thermally expandable microspheres, an adhesive, and any suitable solvent onto a substrate. Alternatively, the thermally expandable microspheres can be embedded into the adhesive using a laminator or the like after the thermally expandable microspheres are sprinkled onto the adhesive coating layer, thereby forming an adhesive layer containing thermally expandable microspheres.

[0085] As a coating method for the aforementioned adhesives and compositions, any suitable coating method can be employed. For example, drying can be performed after coating to form each layer. Examples of coating methods include those using multi-functional coating machines, die-casting machines, gravure coating machines, applicators, etc. Examples of drying methods include natural drying and heat drying. The heating temperature during heat drying can be set to any suitable temperature depending on the characteristics of the substance being dried.

[0086] Example

[0087] The present invention is illustrated below by way of examples, but the present invention is not limited to these examples. The evaluation methods in the examples are shown below. In addition, in the examples, unless otherwise specified, "parts" and "%" are based on weight.

[0088] (1) Acid value

[0089] The acid value of the base polymer constituting the adhesive layer is determined by the following method.

[0090] After swelling a specified amount of adhesive layer with chloroform, excess methanol is added to separate the soluble component (sol) and the insoluble component (gel). The mixture is filtered with filter paper and the insoluble component is recovered (this operation is performed a total of 3 times). The insoluble component (gel) obtained after drying is used as the test sample.

[0091] For this test sample, according to JIS K 2501, the acid value was determined by potentiometric titration using an AT-500N potentiometric titration apparatus (manufactured by Kyoto Electronics Industry Co., Ltd.) and glass electrodes H-171 and R-173 (manufactured by Kyoto Electronics Industry Co., Ltd.). This acid value was then used as the acid value of the base polymer.

[0092] Regarding the order of determination, the sample and 200 mL of mixed solvent were added to a 300 mL Erlenmeyer flask for swelling and titration. A blank test was also performed using the same method, and the acid value was calculated using the following formula (1).

[0093] Acid value (mgKOH / g)=(V1-V0)×f×0.1×56.11 / S···(1)

[0094] S: Mass of the sample taken (g)

[0095] V0: The volume (mL) of titrant required for the blank test.

[0096] V1: The volume (mL) of titrant required for this experiment.

[0097] f: Coefficient of the titrant (f = 1.002)

[0098] It should be noted that the measurement conditions in the above measurements are as follows.

[0099] • Titration solution: 0.1 mol / L KOH alcoholic solution (commercially available)

[0100] • Mixed solvent: Toluene: Water: Isopropanol = 500: 5: 495

[0101] (2) Adhesion

[0102] The SUS304 board is attached to the entire side of the adhesive sheet (20mm wide x 140mm long) opposite to the adhesive layer using double-sided adhesive tape (manufactured by Nitto Denko Co., Ltd., trade name "No. 531") and a 2kg hand roller.

[0103] Next, a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S-10", thickness: 25μm, width: 30mm) is applied to the entire surface of the adhesive layer (temperature: 23℃, humidity: 65%, 2kg roller for 1 round trip).

[0104] The evaluation specimens obtained as described above were used for tensile testing. A tensile testing machine manufactured by Shimadzu Corporation, under the trade name "Shimadzu Autograph AG-120kN," was used. After placing the evaluation specimens in the tensile testing machine, the machine was placed at an ambient temperature of 23°C for 30 minutes, and then the tensile test was started. The tensile test conditions were set as follows: peel angle: 180°, peel speed (tensile speed): 300 mm / min. The load at which the adhesive sheet was peeled from the PET film was measured, and the maximum load at this point was taken as the adhesive force of the adhesive sheet.

[0105] (3) Shear adhesion

[0106] For the adhesive sheets (size: 20mm × 20mm) obtained in Examples 1-7 and Comparative Examples, using double-sided adhesive tape No. 585 manufactured by Nitto Denko Corporation, the side opposite to the adhesive layer (the second adhesive layer in Example 7) was adhered to the specified base (20mm × 20mm silicon chip) and fixed. Using tweezers, a 5mm × 5mm silicon chip (mirror finish) was vertically adhered to the adhesive surface layer without touching the chip corners. Then, the surface was heated at 130°C for 30 minutes to ensure a tight bond between the silicon chip and the adhesive surface, thus creating an evaluation sample.

[0107] For the evaluation sample, at the test temperatures (150℃, 190℃), a Nordson Dage 4000 was used. A test terminal was set on the side of a 5mm × 5mm silicon chip at a height of 250μm from the bonding surface, and an external force was applied along the horizontal direction of the chip at a shear rate of 500μm / sec. The maximum breaking load was read from the resulting load-displacement curve and taken as the shear bond strength.

[0108] (4) Gel content

[0109] Approximately 0.5 g of the adhesive layer (weight W1) was wrapped in a porous polytetrafluoroethylene membrane (weight W2) with an average pore size of 0.2 μm to form a purse-like package, and the opening was secured with kite string (weight W3). The package was immersed in 50 mL of toluene and kept at room temperature (25°C) for 7 days until only the sol component of the adhesive layer dissolved to the outside of the membrane. The package was then 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 measured. The gelation rate was then calculated by substituting the values ​​into the following formula.

[0110] gelation rate (%) = [(W4 - W2 - W3) / W1] × 100

[0111] (5) Nitrogen production

[0112] The amount of nitrogen generated during the heat treatment of the adhesive layer was determined using a TN (trace total nitrogen) analyzer for evaluation samples where the adhesive layer was placed on a ceramic plate and measured using a microbalance. It should be noted that the ceramic plate used was a pre-introduced and air-fired ceramic plate. The measurement was performed twice, and the average value was calculated.

[0113] It should be noted that the measurement conditions in the above measurements are as follows.

[0114] • Temperature: 800℃ for pyrolysis furnace, 900℃ for oxidation furnace

[0115] • Carrier gas: O2 (300 mL / min), Ar (300 mL / min)

[0116] Standard sample: pyridine / toluene solution

[0117] • Detector: Reduced-pressure chemiluminescence detector

[0118] • Range: High concentration

[0119] (6) Evaluation of residual adhesive

[0120] In the examples and comparative examples, a frame-like spacer (inner dimensions 25mm × 95mm) with a thickness of 0.3mm was disposed on the adhesive layer of the adhesive sheet (size: 50mm × 125mm). Granular epoxy resin-based sealing material (manufactured by Sumitomo Bakelite Co., Ltd., G730) was sprinkled on the inside of the spacer, so that the cured resin thickness was 0.3mm. Then, an organosilicon-treated release liner was covered. Next, the evaluation sample was compressed at 130°C for 600 seconds using a vacuum compression molding machine. Then, it was heated at 140°C for 1 hour to cure it, forming a sealing resin on the adhesive layer of the adhesive sheet, thus forming a structure.

[0121] The structure obtained as described above was cooled, and then the adhesive sheet was peeled off from the structure using a tensile testing machine. After placing the structure in the tensile testing machine, it was placed at an ambient temperature of 23°C or 80°C for 30 minutes, and then tensile tests were conducted at each temperature. The tensile test conditions were set as follows: peel angle: 180°, peel speed (tensile speed): 300 mm / min. After peeling the adhesive sheet from the sealing resin, the residual adhesive on the bonding surface of the structure was visually observed and evaluated according to the following conditions.

[0122] ◎: No residual adhesive was observed on either epoxy resin-based sealant at ambient temperatures of 23℃ and 80℃.

[0123] 〇: No residual adhesive was observed on epoxy resin sealants at an ambient temperature of 80°C.

[0124] ×: Residual adhesive was observed on epoxy resin sealant at an ambient temperature of 80℃.

[0125] [Example 1]

[0126] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with 2-ethylhexyl acrylate structural units: acrylic acid structural units = 95:5 (by weight)), 3 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD C"), 10 parts by weight of rosin phenolic tackifying resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "Sumilite Resin PR-12603"), and 100 parts by weight of toluene.

[0127] The adhesive layer forming composition is coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 5 μm).

[0128] The resulting adhesive sheets were used for the evaluations described above (1) to (6). The results are shown in Table 1.

[0129] [Example 2]

[0130] An adhesive layer forming composition was prepared by setting the amount of epoxy crosslinking agent to 5 parts by weight and without mixing with rosin phenol tackifying resin. Otherwise, an adhesive sheet was obtained in the same manner as in Example 1. The obtained adhesive sheets were subjected to the above evaluations (1) to (6). The results are shown in Table 1.

[0131] [Example 3]

[0132] An adhesive layer forming composition was prepared by mixing 5 parts by weight of an epoxy crosslinking agent, and an adhesive sheet was obtained in the same manner as in Example 1. The obtained adhesive sheets were subjected to the above evaluations (1) to (6). The results are shown in Table 1.

[0133] [Example 4]

[0134] An adhesive layer forming composition was prepared by mixing 10 parts by weight of an epoxy crosslinking agent, and an adhesive sheet was obtained in the same manner as in Example 1. The obtained adhesive sheets were subjected to the above evaluations (1) to (6). The results are shown in Table 1.

[0135] [Example 5]

[0136] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer B (a copolymer of 2-ethylhexyl acrylate and hydroxyethyl acrylate, with 2-ethylhexyl acrylate structural units: hydroxyethyl acrylate structural units = 100:4 (by weight)), 3 parts by weight of isocyanate crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name "CORONATE L"), 10 parts by weight of rosin phenolic tackifying resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "Sumilite Resin PR-12603"), and 100 parts by weight of toluene.

[0137] The adhesive layer forming composition is coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 5 μm).

[0138] [Example 6]

[0139] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with 2-ethylhexyl acrylate structural units: acrylic acid structural units = 95:5 (by weight)), 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 phenolic tackifying resin (manufactured by YASUHARA CHEMICAL CO.,LTD., trade name "YS Polystar S145"), and 100 parts by weight of toluene.

[0140] The adhesive layer forming composition is coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 10 μm).

[0141] The resulting adhesive sheets were used for the evaluations described above (1) to (6). The results are shown in Table 1.

[0142] [Example 7]

[0143] In Example 3, a second adhesive layer (45 μm thick) was formed by coating the side of the polyethylene terephthalate film opposite to the adhesive layer with a mixture of an acrylic copolymer C (a copolymer of 2-ethylhexyl acrylate, ethyl acrylate, methyl methacrylate and hydroxyethyl acrylate, with a 2-ethylhexyl acrylate structural unit: ethyl acrylate structural unit: methyl methacrylate structural unit: acrylic structural unit = 30:70:5:4 (weight ratio)), 30 parts by weight of thermally expandable microspheres (manufactured by Matsumoto Oils & Fats Co., Ltd., trade name "Matsumoto mircosphere F-190D"), 1.4 parts by weight of an isocyanate crosslinking agent (manufactured by Tosoh Co., Ltd., trade name "CORONATE L"), 10 parts by weight of a tackifier (manufactured by YASUHARA CHEMICAL CO.,LTD., trade name "Mightyace G125"), and 100 parts by weight of toluene. This resulted in a double-sided adhesive sheet. The adhesive layer of the obtained double-sided adhesive sheet was used for the above evaluation (1) to (6). The results are shown in Table 1.

[0144] [Comparative Example 1]

[0145] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of an acrylic copolymer (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with 2-ethylhexyl acrylate structural units: acrylic acid structural units = 95:5 (by weight)), 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 phenolic tackifying resin (manufactured by YASUHARA CHEMICAL CO.,LTD., trade name "YS Polystar S145"), and 100 parts by weight of toluene.

[0146] The adhesive layer forming composition is coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 10 μm).

[0147] [Table 1]

[0148]

[0149] Explanation of reference numerals in the attached figures

[0150] 10 Substrate

[0151] 20 Adhesive layers

[0152] 30 Second adhesive layer

[0153] 100 and 200 adhesive sheets

Claims

1. An adhesive sheet comprising a substrate and an adhesive layer disposed on at least one side of the substrate, The adhesive layer contains an acrylic adhesive. This acrylic adhesive contains a base polymer with an acid value of less than 16 mg KOH / g. The base polymer has a crosslinked structure based on an acrylic polymer containing structural units derived from carboxyl-containing monomers and an epoxy crosslinking agent containing N atoms. The ratio of shear adhesion force B at 150°C when the adhesive layer is attached to the silicon chip to adhesion force A at 23°C when the adhesive layer is attached to polyethylene terephthalate (shear adhesion force B / adhesion force A) is 4000 g / (N / 20 mm) to 8618 g / (N / 20 mm).

2. The adhesive sheet according to claim 1, comprising: the substrate, the adhesive layer disposed on one side of the substrate, and a second adhesive layer disposed on the side of the substrate opposite to the adhesive layer.

3. The adhesive sheet according to claim 1 or 2, wherein, The gelation rate of the adhesive layer is above 75%.

4. The adhesive sheet according to claim 1 or 2, wherein, The amount of the epoxy crosslinking agent containing N atoms is 0.08 molar equivalents to 2 molar equivalents relative to the carboxyl group of the acrylic polymer.

5. The adhesive sheet according to claim 1 or 2, wherein, The amount of nitrogen generated during the heat treatment of the adhesive layer is 0.05wt%~1.0wt%.

6. The adhesive sheet according to claim 1 or 2, wherein, The thickness of the adhesive layer is 1μm to 300μm.

7. The adhesive sheet according to claim 1 or 2, which is a temporary fixing material used in the resin sealing process of a semiconductor chip.

8. The adhesive sheet according to claim 7, used when curing a sealing resin on the adhesive sheet.

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