TWI859916B - Adhesive Sheet - Google Patents

Abstract

The present invention provides an adhesive sheet that can be used as a temporary fixing material when a semiconductor chip is sealed with a resin, and can prevent the sealing resin from having a poor appearance after the adhesive sheet is peeled off. 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 adhesive, and the adhesive comprising a base polymer having an Sp value of 19.5 (J/cm ³ ) ^1/2 to 25 (J/cm ³ ) ^1/2 .

Description

Adhesive Sheet

The present invention relates to an adhesive sheet.

In recent years, in the manufacture of semiconductor parts including semiconductor chips, there are cases where the semiconductor chips are resin-sealed in order to prevent damage to the semiconductor chips, expand metal wiring, etc. In the resin sealing step, from the perspective of workability, there are cases where the semiconductor chips are resin-sealed on an adhesive sheet. For example, in order to prevent the semiconductor chips from moving, a plurality of semiconductor chips are arranged on a specific adhesive sheet that serves as a temporary fixing material, and the semiconductor chips are resin-sealed together on the adhesive sheet. Thereafter, in a specific subsequent step, the above-mentioned adhesive sheet is peeled off from the resin that seals the semiconductor chips.

In the above-mentioned steps, if the previous adhesive sheet is used, there is a problem that after the adhesive sheet is peeled off, the sealing resin surface that was in contact with the adhesive sheet will become uneven in appearance. Prior art literature Patent literature

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

[The problem the invention is trying to solve]

The present invention is completed to solve the above-mentioned previous problems, and its purpose is to provide an adhesive sheet that can be used as a temporary fixing material when the semiconductor chip is resin-sealed, and can prevent the appearance of the sealing resin from being poor after the adhesive sheet is peeled off. [Technical means to solve the problem]

The adhesive sheet of the present invention comprises a substrate and an adhesive layer disposed on at least one side of the substrate, wherein the adhesive layer comprises an adhesive, and the adhesive comprises a base polymer having an Sp value of 19.5 (J/cm ³ ) ^1/2 to 25 (J/cm ³ ) ^1/2 . 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. In one embodiment, the adhesive is an acrylic adhesive. In one embodiment, the acrylic adhesive contains a base polymer having an alkyl ester with a carbon number of 6 or less as a side chain, and the content ratio of the structural unit having an alkyl ester with a carbon number of 6 or less as a side chain is 50% by weight or more relative to the total structural units constituting the acrylic polymer. In one embodiment, the contact angle of the adhesive layer to 4-tert-butylphenyl glycidyl ether is 47° or less. In one embodiment, when the epoxy resin is cured on the adhesive layer, the adhesion to the epoxy resin at 23°C is preferably 8 N/20 mm or more. In one embodiment, when the adhesive layer is attached to a silicon wafer, the shear adhesion at 150°C is 400 g or more. [Effect of the invention]

According to the present invention, an adhesive sheet can be provided, which can be used as a temporary fixing material when a semiconductor chip is resin-sealed, and can prevent the appearance of the sealing resin from being poor after the adhesive sheet is peeled off.

A. Overview of Adhesive Sheet FIG1 is a schematic cross-sectional view of an adhesive sheet according to an 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 .

The adhesive sheet of the present invention can be used as a temporary fixing material when performing resin sealing on a semiconductor chip. In more detail, regarding the adhesive sheet of the present invention, a semiconductor chip is arranged on the adhesive layer of the adhesive sheet, and the semiconductor chip is coated with a resin (usually an epoxy resin), and the sealing resin is hardened, thereby being used as a temporary fixing material for the semiconductor chip when performing resin sealing on the semiconductor chip. After the semiconductor chip is resin-sealed, when a specific subsequent step (for example, back grinding of the sealing resin, pattern formation, bump formation, and wafering (cutting)) is performed, the above-mentioned adhesive sheet can be peeled off from the structure including the sealing resin and the semiconductor chip.

The adhesive layer contains an adhesive. The adhesive contains a base polymer having an Sp value of 19.5 (J/cm ³ ) ^1/2 to 25 (J/cm ³ ) ^1/2 . In the present invention, by using a base polymer having an Sp value in this range, an adhesive layer having a higher affinity with the sealing resin can be formed. If an adhesive sheet having such an adhesive layer is bonded to a sealing resin and provided to a resin sealing step, a mixed layer containing adhesive layer components and sealing resin components is well formed between the sealing resin and the adhesive layer of the adhesive sheet by heating and pressurizing during this step. As a result, after the operation of stripping the adhesive sheet from the sealing resin, the surface of the sealing resin to which the adhesive sheet was attached can be prevented from having a poor appearance (flow marks). In one embodiment, one reason why the adhesive layer of the adhesive sheet is stripped from the substrate and remains in the sealing resin during the operation of stripping the adhesive sheet is the formation of a mixed layer. As a result, the above-mentioned effect of preventing flow marks becomes significant. In addition, the adhesion of the wiring formed in the structure including the semiconductor chip can be improved. Furthermore, after stripping, the step difference between the surface of the sealing resin and the semiconductor chip can also be reduced.

Previously, it was believed that the main cause of flow marks was the uneven thickness of the mixed layer formed by mixing the low molecular weight components of the sealing resin and the adhesive components of the adhesive layer. As an adhesive sheet for temporary fixation of the resin seal, the industry is researching and developing an adhesive sheet having an adhesive layer with a lower affinity with the sealing resin (for example, an adhesive layer containing an adhesive with a lower Sp value). On the other hand, the present invention is based on a completely different concept from the previous adhesive sheets, that is, it is characterized in that flow marks can be prevented by forming an adhesive layer with a higher affinity with the sealing resin.

FIG2 is a schematic cross-sectional view of an adhesive sheet of another embodiment of the present invention. The adhesive sheet 200 has a second adhesive layer 30 on the side of the substrate 10 opposite to the adhesive layer 20. That is, the adhesive sheet 200 has the adhesive layer 20, the substrate 10, and the second adhesive layer 30 in sequence. By having the second adhesive layer 30, when performing resin sealing on the base, the second adhesive layer 30 side can be attached to the base, and the adhesive sheet 200 can be arranged with good fixity.

In one embodiment, the second adhesive layer includes heat-expandable microspheres. The heat-expandable microspheres are expandable at a specific temperature. With respect to the adhesive layer including such heat-expandable microspheres, by heating to a temperature above a specific temperature, the heat-expandable microspheres will expand, thereby generating irregularities on the adhesive surface (i.e., the surface of the second adhesive layer), and the adhesive force is reduced or disappears. If a second adhesive layer including heat-expandable microspheres is formed, the desired adhesiveness is exhibited when the adhesive sheet is fixed (for example, fixed to a base), and when the adhesive sheet is peeled off (for example, when peeled off from a base), the adhesive force is reduced or disappears due to heating, and good peeling properties are exhibited.

Regarding the adhesive sheet of the present invention, the adhesive force 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 0.1 N/20 mm to 10 N/20 mm, further preferably 0.1 N/20 mm to 5 N/20 mm, particularly preferably 0.2 N/20 mm to 2 N/20 mm, and most preferably 0.2 N/20 mm to 1 N/20 mm. If it is within this range, the adherend (e.g., semiconductor chip) can be well fixed, and an adhesive sheet with less paste residue when peeled can be obtained. Furthermore, in this specification, the so-called "adhesion at 23°C when the adhesive layer is bonded to polyethylene terephthalate" refers to the adhesion measured by bonding the adhesive layer of an adhesive sheet (20 mm wide × 100 mm long) to a polyethylene terephthalate film (25 μm thick) (bonding conditions: 2 kg roller reciprocating once) at an ambient temperature of 23°C for 30 minutes and then subjecting the sample to a tensile test (peeling speed: 300 mm/min, peeling angle 180°).

Regarding the adhesive sheet of the present invention, when the epoxy resin is cured on the adhesive layer, the adhesive force to the epoxy resin at 23°C is preferably 8 N/20 mm or more, more preferably 8 N/20 mm to 20 N/20 mm, and further preferably 8 N/20 mm to 15/20 mm. "When the epoxy resin is cured on the adhesive layer, the adhesive force to the epoxy resin at 23°C" is an indicator of the close contact between the adhesive sheet and the sealing resin. If the adhesive force is within the above range, an adhesive sheet suitable for use as a temporary fixing material when performing resin sealing on a semiconductor chip can be obtained. Furthermore, in this specification, the term "adhesion to the epoxy resin at 23°C when the epoxy resin is cured on the adhesive layer" means the peeling force when the epoxy resin is peeled off from the adhesive layer of a sample obtained by coating the epoxy resin before curing (e.g., Sumitomo Bakelite Co., Ltd., trade name "G730") on the adhesive layer and then curing the epoxy resin. The adhesion (peeling force) is measured by subjecting the above-mentioned sample of 20 mm width × 100 mm length to a tensile test (peeling speed: 300 mm/min, peeling angle 180°).

Regarding the adhesive sheet of the present invention, when the adhesive layer is attached to a silicon chip, the shear bonding force at 150°C is preferably 400 g or more, more preferably 400 g to 2000 g, and further preferably 700 g to 1500 g. If it is within this range, the cohesive force of the adhesive is high, and it has good adhesion even at high temperatures (for example, a heating step for hardening the sealing resin), and can prevent the position of the adherend (for example, a semiconductor chip) arranged on the adhesive sheet from shifting. In addition, it can prevent the formation of a gap (gap between the adhesive sheet/sealing resin) into which the sealing resin can penetrate. Shear adhesion can be measured in the following way: after attaching the mirror surface of a silicon wafer (size: 5 mm×5 mm) vertically to the adhesive layer without the wafer corners touching, heat it at 130℃ for 30 minutes to make the silicon wafer close to the adhesive surface. Then, apply an external force in a direction horizontal to the wafer at a shear rate of 500 μm/sec in an environment of 150℃. Read the maximum breaking load from the load-displacement curve obtained in this way.

The thickness of the adhesive sheet of the present invention is preferably 3 μm to 300 μm, more preferably 20 μm to 200 μm, and even more preferably 50 μm to 150 μm.

B. Adhesive layer The thickness of the adhesive layer is preferably 1 μm to 300 μm, more preferably 2 μm to 300 μm, further preferably 2 μm to 200 μm, further preferably 3 μm to 100 μm, further preferably 4 μm to 80 μm, and particularly preferably 5 μm to 50 μm. If it is within this range, an adhesive layer with a flat surface can be obtained, and an adhesive sheet that is not prone to flow marks can be obtained.

The contact angle of the adhesive layer to 4-tert-butylphenyl glycidyl ether is preferably 47° or less, more preferably 25° to 47°, and further preferably 28° to 45°. If it is within this range, an adhesive layer having a high affinity with the sealing resin can be formed.

The elastic modulus of the adhesive layer obtained by the nano-indentation method at 25°C is preferably less than 100 MPa, more preferably 0.1 MPa to 50 MPa, and further preferably 0.1 MPa to 10 MPa. If it is within this range, an adhesive sheet with appropriate adhesion can be obtained. The elastic modulus obtained by the nano-indentation method refers to the elastic modulus obtained by continuously measuring the load and the penetration depth of the pressure head when the pressure head is pressed into the sample during loading and unloading, and the load-indentation depth curve obtained. In this specification, the elastic modulus obtained by 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.

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 further preferably 0.1 MPa to 10 MPa. If it is within this range, an adhesive sheet with appropriate adhesive force can be obtained. In addition, the tensile modulus can be measured according to JIS K 7161:2008.

The probe viscosity of the above adhesive layer is preferably 50 g/5 mm Above, preferably 75 g/5 mm Above, preferably 100 g/5 mm If it is within this range, the position of the adherend (such as a semiconductor chip) placed on the adhesive sheet can be prevented from shifting. The measurement conditions for the probe viscosity value are set as probe processing speed: 30 mm/min, test speed: 30 mm/min, close contact load: 100 gf, close contact holding time: 1 second, probe area: 5 mm SUS.

<Adhesive> As the adhesive constituting the above-mentioned adhesive layer, any appropriate adhesive can be used as long as the effect of the present invention can be obtained. As the adhesive, for example, acrylic adhesives, rubber adhesives, and silicone adhesives can be exemplified. Among them, acrylic adhesives are preferably used. In addition, active energy ray-curing adhesives can also be used as adhesives. The above-mentioned adhesive contains a base polymer having an sp value within the above-mentioned range. Furthermore, the so-called base polymer refers to a polymer that can be the cause of the adhesive showing adhesiveness.

As mentioned above, the Sp value of the base polymer is 19.5 (J/cm ³ ) ^1/2 to 25 (J/cm ³ ) ^1/2 . The Sp value of the base polymer is preferably 20 (J/cm ³ ) ^1/2 to 24 (J/cm ³ ) ^1/2 , and more preferably 20.5 (J/cm ³ ) ^1/2 to 23.5 (J/cm ³ ) ^1/2 . Within this range, the effect of the present invention becomes significant. The Sp value of the base polymer can be calculated by the method of Fedors (Hideki Yamamoto, "Sp Value Foundation, Application and Calculation Method", Information Agency Co., Ltd., published on April 3, 2006, pages 66-67). Specifically, the sp value is calculated by the following formula based on the vaporization energy Δe (cal) of each atom or atomic group forming the polymer at 25°C and the molar volume ΔV (cm ³ ) of each atom or atomic group forming the polymer at 25°C. Sp value = (ΣΔe/ΣΔv) ^1/2 In the case where the polymer is a copolymer, the Sp value is calculated by multiplying the Sp values of the homopolymers of each structural unit constituting the copolymer, and the Sp values are multiplied by the molar fraction of each structural unit, and the results are accumulated to calculate.

(Acrylic adhesive) Examples of the acrylic adhesive include acrylic adhesives using an acrylic polymer (homopolymer or copolymer) as a base polymer and using one or more (meth) alkyl esters of acrylic acid as monomer components.

Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, 2- ... C1-20 alkyl (meth)acrylates such as nonyl (meth)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, eicosyl (meth)acrylate, etc. Among them, alkyl (meth)acrylates having a linear or branched alkyl group with a carbon number of 1 to 16 (more preferably 1 to 12, particularly preferably 1 to 6) are preferred.

The above-mentioned acrylic polymer is preferably an alkyl ester having a carbon number of 6 or less, more preferably an alkyl ester having a carbon number of 4 or less, and further preferably an alkyl ester having a carbon number of 2 or less as a side chain. If an acrylic polymer having a shorter side chain is used, an adhesive layer having a higher affinity with the sealing material can be formed. In the above-mentioned acrylic polymer, the content ratio of the structural unit having an alkyl ester having a carbon number of 6 or less (preferably 4 or less, and more preferably 2 or less) as a side chain relative to the total structural unit constituting the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, further preferably 60% to 100% by weight, particularly preferably 60% to 90% by weight, and most preferably 60% to 80% by weight. If it is within this range, an adhesive layer with high affinity to the sealing material can be formed.

The acrylic adhesive may include a plurality of acrylic polymers, but the content of the acrylic polymer having an alkyl ester with a carbon number of 6 or less (preferably 4 or less, more preferably 2 or less) as a side chain is preferably 30 to 100 parts by weight, more preferably 70 to 100 parts by weight, and further preferably 90 to 100 parts by weight, relative to 100 parts by weight of the total acrylic polymer. In one embodiment, the content of the acrylic polymer having an alkyl ester with a carbon number of 6 or less as a side chain is 100 parts by weight relative to 100 parts by weight of the total acrylic polymer.

The acrylic polymer is intended to improve cohesive force, heat resistance, crosslinking properties, etc., and may contain units corresponding to other monomer components that can be copolymerized with the alkyl (meth)acrylate, if necessary. Examples of such monomer components include: monomers containing a carboxyl group, 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 itaconic anhydride; hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, and hydroxyoctyl (meth)acrylate. ) hydroxydecyl acrylate, (meth)hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl methacrylate and other hydroxyl group-containing monomers; styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, (meth)acrylatesulfopropyl, (meth)acryloyloxynaphthalenesulfonic acid and other sulfonic acid group-containing monomers; (meth)acrylamide, N,N-dimethyl (methyl) (N-substituted) amide monomers such as acrylamide, N-butyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxymethylpropane (meth)acrylamide; (meth)acrylic acid aminoalkyl ester monomers such as (meth)acrylic acid aminoethyl ester, (meth)acrylic acid N,N-dimethylaminoethyl ester, and (meth)acrylic acid tert-butylaminoethyl ester; (meth)acrylic acid methoxyethyl ester, (meth)acrylic acid (Meth)acrylate monomers such as ethoxyethyl ester; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; N-methyliconimide, N-ethyliconimide, N-butyliconimide, N-octyliconimide, N-2-ethylhexyliconimide, N-cyclohexyliconimide, N- Iconimide monomers such as lauryl iconimide; N-(meth)acryloxymethylenebutaneimide, N-(meth)acryl-6-oxyhexamethylenebutaneimide, N-(meth)acryl-8-oxyoctamethylenebutaneimide and other butaneimide monomers; vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, Vinyl monomers such as vinylpyrimidine, vinylpiperidinium, vinylpyridine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylisocyanate, N-vinylcaprolactam, styrene, α-methylstyrene, N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy-containing acrylic monomers such as glycidyl (meth)acrylate; polyethylene glycol (meth)acrylate, polypropylene glycol Diol acrylate monomers such as (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate; acrylate monomers having a heterocyclic ring, a halogen atom, a silicon atom, etc. such as tetrahydrofurfuryl (meth)acrylate, fluoro(meth)acrylate, 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, trihydroxymethylpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate; olefin monomers such as isoprene, butadiene, isobutylene; vinyl ether monomers such as vinyl ether, etc. The monomer components can be used alone or in combination of two or more. Among the above, carboxyl-containing monomers (especially acrylic acid) or hydroxyl-containing monomers (especially hydroxyethyl (meth)acrylate) are more preferred. The content of structural units derived from carboxyl-containing monomers is preferably 40% by weight or less, more preferably 0.1% by weight to 10% by weight, more preferably 0.5% by weight to 5% by weight, and particularly preferably 1% by weight to 4% by weight relative to the total structural units constituting the acrylic polymer. In addition, the content of structural units derived from hydroxyl-containing monomers is preferably 0.09% by weight to 40% by weight, more preferably 0.1% by weight to 20% by weight, more preferably 0.5% by weight to 10% by weight, and particularly preferably 1% by weight to 7% by weight relative to the total structural units constituting the acrylic polymer.

The acrylic adhesive may contain any appropriate additives as required. Examples of such additives include: crosslinking agents, adhesion promoters, plasticizers (e.g., trimellitic acid ester plasticizers, pyromellitic acid ester plasticizers, etc.), pigments, dyes, fillers, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, stripping modifiers, softeners, surfactants, flame retardants, antioxidants, etc.

Examples of the crosslinking agent included in the acrylic adhesive include, in addition to isocyanate crosslinking agents, epoxy crosslinking agents, melamine crosslinking agents, and peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and amine crosslinking agents, among which isocyanate crosslinking agents or epoxy crosslinking agents are preferred.

Specific examples of the isocyanate crosslinking agent contained in the acrylic adhesive include: low-order aliphatic polyisocyanates such as butyl diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentyl diisocyanate, cyclohexyl diisocyanate, and isophorone diisocyanate; aromatic isocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylyl diisocyanate; trihydroxymethylpropane/toluene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), trihydroxymethylpropane/hexamethyl diisocyanate trimer adduct (N ... Industry, trade name "Coronate HL"), isocyanurate of hexamethylene diisocyanate (Nippon Polyurethane Industry, trade name "Coronate HX") and other isocyanate adducts. The content of the isocyanate crosslinking agent can be set to any appropriate amount according to the required adhesion, and is typically 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the base polymer.

Examples of the epoxy crosslinking agent included in the acrylic adhesive include N,N,N',N'-tetraglycidyl-m-xylylenediamine, 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 "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"), polyethylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name "EPIOL E-400"), polypropylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name "EPIOL P-200"), sorbitol polyglycidyl ether (manufactured by Nagase ChemteX, trade name "Denacol 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, trihydroxymethylpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tri(2-hydroxyethyl)isocyanuric acid triglycidyl ester, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, epoxy resins having two or more epoxy groups in the molecule, etc. The content of the epoxy crosslinking agent can be set to any appropriate amount according to the required adhesion, and is typically 0.01 to 10 parts by weight, and more preferably 0.03 to 5 parts by weight, relative to 100 parts by weight of the base polymer.

Any appropriate tackifier may be used as the tackifier contained in the acrylic adhesive. For example, a tackifier resin may be used as the tackifier. Specific examples of the tackifier resin include rosin-based tackifier resins (e.g., unmodified rosin, modified rosin, rosin phenol-based resins, rosin ester-based resins, etc.), terpene-based tackifier 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 tackifier resins (e.g., aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., phenylene-based resins), The adhesive imparting resins include ethylene-based resins, xylene-based resins, etc.), aliphatic-aromatic petroleum resins, aliphatic-aliphatic cyclopentane-based petroleum resins, hydrogenated hydrocarbon resins, benzofuran-based resins, benzofuran-indene-based resins, etc.), phenol-based adhesive imparting resins (for example, alkylphenol-based resins, xylene-formaldehyde-based resins, resole-based phenol-formaldehyde resins, novolac-based phenol-formaldehyde varnishes, etc.), ketone-based adhesive imparting resins, polyamide-based adhesive imparting resins, epoxy-based adhesive imparting resins, and elastic system adhesive imparting resins. Among them, rosin-based adhesive-imparting resins, terpene-based adhesive-imparting resins or hydrocarbon-based adhesive-imparting resins (styrene-based resins, etc.) are preferred. Adhesive-imparting agents can be used alone or in combination of two or more. The amount of the adhesive-imparting agent added is preferably 5 to 100 parts by weight, more preferably 10 to 50 parts by weight, relative to 100 parts by weight of the base polymer.

It is preferred to use a resin with a high softening point or glass transition temperature (Tg) as the above-mentioned adhesion-imparting resin. If a resin with a high softening point or glass transition temperature (Tg) is used, an adhesive layer that can exhibit high adhesion can be formed even in a high temperature environment (for example, a high temperature environment during the process of sealing a semiconductor chip). The softening point of the adhesion-imparting agent is preferably 100°C to 180°C, more preferably 110°C to 180°C, and further preferably 120°C to 180°C. The glass transition temperature (Tg) of the adhesion agent is preferably 100°C to 180°C, more preferably 110°C to 180°C, and further preferably 120°C to 180°C.

The above-mentioned acrylic adhesive may further contain a reaction aid. By adding a reaction aid, it is expected that the effect of preventing the residue of the paste caused by the coagulation and destruction of the adhesive when the adhesive sheet is peeled off after the resin sealing can be further improved. When using an isocyanate-based crosslinking agent, for example, tin-based organic compounds, titanium-based organic compounds, iron-based organic compounds, amine (TEDA, etc.)-based organic compounds, etc. can be used as a reaction aid. As specific examples of tin-based organic compounds, there can be cited: "OL-1" manufactured by Tokyo Fine Chemical Co., Ltd., "Tetraethylenediamine" manufactured by Tosoh Corporation, etc. When using an epoxy-based crosslinking agent, for example, imidazoles or phosphorus-based organic compounds can be used. The content of the reaction aid is preferably 0.001 to 0.5 parts by weight, more preferably 0.005 to 0.1 parts by weight, and further preferably 0.01 to 0.07 parts by weight, relative to 100 parts by weight of the base polymer.

(Rubber-based adhesive) As the above-mentioned rubber-based adhesive, any appropriate adhesive may be used as long as the effect of the present invention can be obtained. As the above-mentioned rubber adhesive, for example, it is preferred to use a rubber adhesive using the following components as a base polymer: natural rubber; polyisoprene rubber, butadiene rubber, styrene-butadiene (SB) rubber, styrene-isoprene (SI) rubber, styrene-isoprene-styrene block copolymer (SIS) rubber, styrene-butadiene-styrene block copolymer (SBS) rubber, styrene-ethylene-butylene-styrene block copolymer (SEBS) rubber, styrene-ethylene-propylene-styrene block copolymer (SEPS) rubber, styrene-ethylene-propylene block copolymer (SEP) rubber, recycled rubber, butyl rubber, polyisobutylene rubber, or synthetic rubbers such as modified products thereof. The sp value of these base polymers (rubbers) is relatively low. If these base polymers are used, an adhesive layer with low affinity to the sealing material can be formed.

As the base polymer constituting the above-mentioned rubber-based adhesive, polyisobutylene rubber, polyisoprene rubber or butyl rubber is particularly preferably used. If these rubbers are used, an adhesive layer having excellent semiconductor chip retention and peeling properties at room temperature can be formed. In addition, an adhesive layer having low affinity with the sealing material can be formed.

As the base polymer constituting the above-mentioned rubber adhesive, styrene-ethylene-propylene block copolymer (SEP) rubber, styrene-ethylene-butylene-styrene block copolymer (SEBS) rubber, styrene-isoprene-styrene block copolymer (SIS) rubber, styrene-butadiene-styrene block copolymer (SBS) rubber, and propylene rubber can be used well. If these rubbers are used, an adhesive layer that can show high adhesion can be formed even in a high temperature environment (for example, in a high temperature environment during semiconductor chip sealing processing). In the base polymer (rubber) having structural units derived from styrene, the content ratio of the structural units derived from styrene is preferably 15% by weight or more relative to the total structural units in the base polymer.

The rubber adhesive may contain any appropriate additives as required. Examples of such additives include: crosslinking agents, vulcanizers, adhesion promoters, plasticizers, pigments, dyes, fillers, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, stripping modifiers, softeners, surfactants, flame retardants, antioxidants, etc.

As the above-mentioned adhesive impregnating agent contained in the above-mentioned rubber-based adhesive, any appropriate adhesive impregnating agent can be used. As the adhesive impregnating agent, for example, an adhesive impregnating resin can be used. As specific examples of the adhesive impregnating resin, there can be cited: rosin-based adhesive impregnating resins, rosin derivative resins, petroleum-based resins, terpene-based resins, and ketone-based resins. Relative to 100 parts by weight of the base polymer, the added amount of the above-mentioned adhesive impregnating agent is preferably 5 parts by weight to 100 parts by weight, and more preferably 10 parts by weight to 50 parts by weight.

Examples of the rosin resin included in the rubber adhesive include rosin gum, wood rosin, and tall rosin. As the rosin resin, stabilized rosin obtained by disproportionation or hydrogenation of any appropriate rosin may be used. Furthermore, as the rosin resin, polymerized rosin, which is a polymer (typically a dimer) of any appropriate rosin, or modified rosin obtained by modifying any appropriate rosin (for example, modification by unsaturated acid) may be used.

Examples of the rosin derivative resin contained in the rubber adhesive include esters of the above-mentioned rosin resins, phenol-modified rosin resins, and esters of phenol-modified rosin resins.

Examples of the petroleum-based resin contained in the rubber-based adhesive include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and hydrogenated products thereof.

Examples of the terpene resin contained in the rubber adhesive include α-pinene resin, β-pinene resin, aromatic modified terpene resin, terpene phenol resin, and the like.

Examples of the ketone resin contained in the rubber adhesive include ketone resins obtained by condensing ketones (such as aliphatic ketones and alicyclic ketones) with formaldehyde.

As the crosslinking agent contained in the above-mentioned rubber adhesive, for example, isocyanate crosslinking agents can be cited. As the vulcanizing agent contained in the above-mentioned rubber adhesive, for example, thiuram vulcanizing agents, quinone-like vulcanizing agents, and quinone dioxime vulcanizing agents can be cited. If the rubber adhesive contains a crosslinking agent and/or a vulcanizing agent, an adhesive layer with high cohesion and less residual paste can be formed. The total content of the crosslinking agent and the vulcanizing agent is typically 0.1 to 20 parts by weight, and more preferably 0.1 to 10 parts by weight, relative to 100 parts by weight of the base polymer.

In one embodiment, a rubber adhesive (Rub1) comprising the above-mentioned base polymer (rubber), a hydroxyl-containing polyolefin, and a crosslinking agent a that can react with the hydroxyl group of the hydroxyl polyolefin can be used. In the rubber adhesive, although the base polymer is not directly crosslinked, the base polymer and the crosslinked hydroxyl-containing polyolefin are entangled with each other to form a so-called pseudo crosslink. As a result, an adhesive layer with high cohesion and less residual paste can be formed. As the base polymer (rubber) used in the embodiment, it is preferably the above-mentioned synthetic rubber. In addition, as the crosslinking agent used in this embodiment, an isocyanate crosslinking agent is preferably used.

The amount of the hydroxyl-containing polyolefin is preferably 0.5 parts by weight or more, and more preferably 1.0 parts by weight or more, relative to 100 parts by weight of the base polymer (rubber), the hydroxyl-containing polyolefin, and the crosslinking agent a in total. If it is within this range, an adhesive layer with high cohesion can be formed. In addition, when the adhesive sheet has a substrate layer, the adhesion (grip) between the substrate layer and the adhesive layer can be improved. That is, if the amount of the hydroxyl-containing polyolefin is within the above range, an adhesive sheet with less paste residue can be obtained.

The amount of the crosslinking agent a is preferably 0.5 parts by weight or more, and more preferably 1.0 parts by weight or more, relative to 100 parts by weight of the base polymer (rubber), the hydroxyl-containing polyolefin, and the crosslinking agent a in total. If it is within this range, an adhesive layer with high cohesion can be formed. In addition, when the adhesive sheet has a substrate layer, the adhesion (gripping force) between the substrate layer and the adhesive layer can be improved. That is, if the amount of the crosslinking agent a is within the above range, an adhesive sheet with less paste residue can be obtained.

As the hydroxyl-containing polyolefin, it is preferred to use a resin having excellent compatibility with the synthetic rubber. Examples of the hydroxyl-containing polyolefin include polyethylene polyol, polypropylene polyol, polybutadiene polyol, hydrogenated polybutadiene polyol, polyisoprene polyol, and hydrogenated polyisoprene polyol. Among them, hydrogenated polyisoprene polyol, polyisoprene polyol, and polybutadiene polyol are preferred from the viewpoint of compatibility with the synthetic rubber.

The number average molecular weight (Mn) of the hydroxyl-containing polyolefin is preferably 500 to 500,000, more preferably 1,000 to 200,000, and even more preferably 1,200 to 150,000. The number average molecular weight can be measured according to ASTM D2503.

The hydroxyl value (mgKOH/g) of the hydroxyl-containing polyolefin is preferably 5 to 95, more preferably 10 to 80. The hydroxyl value can be measured according to JIS K1557:1970.

(Silicone-based adhesive) As the above-mentioned silicone-based adhesive, any appropriate adhesive can be used as long as the effect of the present invention can be obtained. As the above-mentioned silicone-based adhesive, for example, it is preferable to use a silicone-based adhesive using a silicone rubber or silicone resin containing an organic polysiloxane as a base polymer. As the base polymer constituting the silicone-based adhesive, a base polymer obtained by cross-linking the above-mentioned silicone rubber or silicone resin can also be used. Furthermore, in this specification, "silicone rubber" means a polymer composed of diorganosiloxane (D unit) as the main component connected in a straight chain (for example, the viscosity is 1000 Pa・s), and "silicone resin" means a polymer containing triorganosilhemioxane (M unit) and silicate (Q unit) as the main components ("Material Design and Functionalization of Adhesives (Films/Tapes)", Technology Information Association, issued on September 30, 2009).

As the above-mentioned silicone rubber, for example, an organic polysiloxane containing dimethyl siloxane as a structural unit can be exemplified. A functional group (such as a vinyl group) can be introduced into the organic polysiloxane as needed. The weight average molecular weight of the organic polysiloxane is preferably 100,000 to 1,000,000, more preferably 150,000 to 500,000. The weight average molecular weight can be measured by GPC (solvent: THF).

Examples of the silicone resin include organic polysiloxane (R is a monovalent hydrocarbon group or a hydroxyl group) containing at least one structural unit selected from the group consisting of an R ₃ SiO _1/2 structural unit, an SiO ₂ structural unit, an RSiO _3/2 structural unit, and an R ₂ SiO structural unit.

The silicone rubber and silicone resin can be used together. The weight ratio of silicone rubber to silicone resin in the silicone adhesive (rubber: resin) is preferably 100:0 to 100:220, more preferably 100:0 to 100:180, and further preferably 100:10 to 100:100. The silicone rubber and silicone resin can be included in the silicone adhesive as a simple mixture, or in the form of a partial condensation of silicone rubber and silicone resin. The rubber:resin ratio can also be determined from the ratio of Q unit (resin) to D unit (rubber) obtained by measuring the composition of the silicone adhesive using ²⁹ Si-NMR.

The silicone adhesive may contain any appropriate additives as required. Examples of such additives include: crosslinking agents, vulcanizing agents, adhesion promoters, plasticizers, pigments, dyes, fillers, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, stripping modifiers, softeners, surfactants, flame retardants, and antioxidants.

It is preferred that the silicone adhesive contains a crosslinking agent. Examples of the crosslinking agent include siloxane crosslinking agents and peroxide crosslinking agents. Any appropriate crosslinking agent may be used as a peroxide crosslinking agent. Examples of the peroxide crosslinking agent include benzoyl peroxide, tert-butyl perbenzoate, and diisopropylphenyl peroxide. Examples of the siloxane crosslinking agent include polyorganohydrosiloxane. The polyorganohydrosiloxane preferably has two or more hydrogen atoms bonded to silicon atoms. Furthermore, the polyorganohydrogensiloxane preferably has an alkyl group, a phenyl group, or a halogenated alkyl group as a functional group bonded to a silicon atom.

(Active energy ray hardening adhesive) As the above adhesive, an active energy ray hardening adhesive that can be hardened (high elastic modulus) by irradiation with active energy ray can also be used. If an active energy ray hardening adhesive is used, an adhesive sheet can be obtained that is low in elasticity, high in flexibility and excellent in operability when attached, and when it is necessary to peel it off, the adhesive force can be reduced by irradiation with active energy ray. Examples of active energy ray include: gamma ray, ultraviolet ray, visible light, infrared ray (heat ray), radio frequency wave, alpha ray, beta ray, electron beam, plasma flow, ionizing radiation and particle beam. Furthermore, in this specification, when referred to as "adhesive layer", it means the adhesive layer before the adhesive hardens and the adhesive force decreases.

Examples of the resin material constituting the active energy ray-curing adhesive include the resin materials described in Ultraviolet Curing System (Kato Kiyoshi, published by the Center for Integrated Technology (1989)), Photocuring Technology (Technical Information Association (2000)), Japanese Patent Publication No. 2003-292916, Japanese Patent No. 4151850, etc. More specifically, examples include: a resin material (R1) containing a polymer serving as a masterbatch and an active energy ray-reactive compound (monomer or oligomer), a resin material (R2) containing an active energy ray-reactive polymer, and the like.

Examples of the polymer used as the masterbatch include natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer rubber, recycled rubber, butyl rubber, polyisobutylene rubber, nitrile rubber (NBR) and other rubber-based polymers; silicone-based polymers; acrylic polymers, etc. These polymers can be used alone or in combination of two or more. As the polymer used as the masterbatch, from the viewpoint of affinity with the sealing material, the polymers exemplified as the base polymers of the acrylic adhesive, rubber adhesive or silicone adhesive can be used well.

Examples of the active energy ray-reactive compound include photoreactive monomers or oligomers having a functional group having a carbon-carbon multiple bond such as an acryloyl group, a methacryloyl group, a vinyl group, an allyl group, an ethynyl group, etc. Specific examples of the photoreactive monomer or oligomer include (meth)acryloyl group-containing compounds such as trihydroxymethylpropane tri(meth)acrylate, tetrahydroxymethylmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and polyethylene glycol di(meth)acrylate; dimers to pentamers of the (meth)acryloyl group-containing compounds, etc.

In addition, as the active energy ray-reactive compound, monomers such as butylene oxide, glycidyl methacrylate, acrylamide, vinyl siloxane, etc., or oligomers containing the monomers may also be used. The resin material (R1) containing the compounds can be cured by high energy rays such as ultraviolet rays and electron beams.

Furthermore, as the above-mentioned active energy ray-reactive compound, a mixture of an organic salt such as an onium salt and a compound having a plurality of heterocyclic rings in the molecule can also be used. When the mixture is irradiated with active energy rays (such as ultraviolet rays and electron beams), the organic salt will be dissociated to generate ions, which become starting species to cause the ring-opening reaction of the heterocyclic ring, and can form a stereonet structure. As the above-mentioned organic salts, for example, iodonium salts, phosphonium salts, antimony salts, coronium salts, and borate salts can be cited. As the heterocyclic ring in the above-mentioned compound having a plurality of heterocyclic rings in the molecule, for example, ethylene oxide, cyclohexane, cyclopentane, cyclothioethane, and aziridine can be cited.

In the resin material (R1) comprising the polymer serving as a masterbatch and the active energy ray reactive compound, the content ratio of the active energy ray reactive compound is preferably 0.1 to 500 parts by weight, more preferably 1 to 300 parts by weight, and further preferably 10 to 200 parts by weight, relative to 100 parts by weight of the polymer serving as a masterbatch. Within this range, an adhesive layer having a low affinity with the sealing material can be formed.

The above-mentioned resin material (R1) containing a polymer that serves as a masterbatch and an active energy ray-reactive compound may contain any appropriate additive as needed. As additives, for example, active energy ray polymerization initiators, active energy ray polymerization accelerators, crosslinking agents, plasticizers, and vulcanizers can be cited. As active energy ray polymerization initiators, any appropriate initiator can be used according to the type of active energy ray used. Active energy ray polymerization initiators can be used alone or in combination of two or more. In the resin material (R1) containing a polymer that serves as a masterbatch and an active energy ray-reactive compound, the content ratio of the active energy ray polymerization initiator is preferably 0.1 to 10 parts by weight, and more preferably 1 to 5 parts by weight, relative to 100 parts by weight of the polymer that serves as a masterbatch.

As the above-mentioned active energy line reactive polymer, for example, there can be cited polymers having functional groups having carbon-carbon multiple bonds such as acryl, methacryl, vinyl, allyl, ethynyl, etc. As specific examples of polymers having active energy line reactive functional groups, there can be cited polymers containing multifunctional (meth)acrylates, etc. The polymer containing multifunctional (meth)acrylates is preferably an alkyl ester having a carbon number of 4 or more, more preferably an alkyl ester having a carbon number of 6 or more, further preferably an alkyl ester having a carbon number of 8 or more, particularly preferably an alkyl ester having a carbon number of 8 to 20, and most preferably an alkyl ester having a carbon number of 8 to 18. If a polymer having a longer side chain is used, an adhesive layer with a lower affinity for the sealing material can be formed. In the polymer, the content ratio of the structural unit having an alkyl ester with a carbon number of 4 or more as a side chain is preferably 30 wt % or more, more preferably 50 wt % or more, further preferably 70 wt % to 100 wt %, particularly preferably 80 wt % to 100 wt % relative to the total structural units constituting the polymer. If it is within this range, an adhesive layer with low affinity to the sealing material can be formed.

The above-mentioned resin material (R2) containing an active energy ray-reactive polymer may further contain the above-mentioned active energy ray-reactive compound (monomer or oligomer). Moreover, the above-mentioned resin material (R2) containing an active energy ray-reactive polymer may contain any appropriate additive as needed. Specific examples of additives are the same as the additives that may be contained in the resin material (R1) containing a polymer that becomes a masterbatch and an active energy ray-reactive compound. In the resin material (R2) containing an active energy ray-reactive polymer, the content ratio of the active energy ray polymerization initiator relative to 100 parts by weight of the active energy ray-reactive polymer is preferably 0.1 parts by weight to 10 parts by weight, and more preferably 1 part by weight to 5 parts by weight.

C. Substrate Examples of the substrate include resin sheets, nonwoven fabrics, paper, metal foils, woven fabrics, rubber sheets, foam sheets, and laminates thereof (particularly laminates containing resin sheets). Examples of the resin constituting the resin sheet include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene naphthalate (PBT), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), wholly aromatic polyamide (aramid), polyimide (PI), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), fluorine-based resin, and polyetheretherketone (PEEK). Examples of nonwoven fabrics include nonwoven fabrics made of heat-resistant natural fibers such as Manila hemp nonwoven fabrics, 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 foils, stainless steel foils, and aluminum foils. Examples of paper include Japanese paper and kraft paper.

The thickness of the substrate can be set to any appropriate thickness according to the required strength or flexibility, the purpose of use, etc. The thickness of the substrate is preferably 1000 μm or less, 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.

The substrate may be subjected to a surface treatment, such as a corona treatment, a chromic acid treatment, an ozone exposure, a flame exposure, a high-voltage electric shock exposure, an ionizing radiation treatment, and a coating treatment using a primer.

As the above-mentioned organic coating material, for example, the materials described in Plastic Hard Coating Material II (CMC Publishing, (2004)) can be cited. It is preferred to use a urethane polymer, and it is more preferred to use polyacrylic urethane, polyester polyurethane or such precursors. The reason is that it is easy to apply and coat on the substrate, and there are many types to choose from in the industry, and it can be obtained more economically. The urethane polymer is, for example, a polymer of a reaction mixture containing an isocyanate monomer and an alcoholic hydroxyl-containing monomer (for example, a hydroxyl-containing acrylic compound or a hydroxyl-containing ester compound). The organic coating material may contain a chain extender such as polyamine, an anti-aging agent, and an oxidation stabilizer as an optional additive. The thickness of the organic coating layer is not particularly limited, and is, for example, preferably 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.

D. Second Adhesive Layer The second adhesive layer may include any suitable adhesive. In one embodiment, as described above, the second adhesive layer further includes thermally expandable microspheres.

The adhesive contained in the second adhesive layer may be a hardening adhesive (e.g., an active energy ray hardening adhesive) or a pressure-sensitive adhesive. Examples of pressure-sensitive adhesives include acrylic adhesives and rubber adhesives. The adhesives described in item B may be used.

As the heat-expandable microspheres, any appropriate heat-expandable microspheres can be used as long as they can expand or foam by heating. As the heat-expandable microspheres, for example, microspheres can be used in which a substance that easily expands by heating is enclosed in an elastic shell. Such heat-expandable microspheres can be produced by any appropriate method, such as a coacervation method, an interfacial polymerization method, etc.

Examples of substances that easily expand by 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 tetraalkylsilane; and azodicarboxamides that gasify by thermal decomposition.

As the material constituting the shell, for example, there can be cited polymers containing the following monomers: 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 citric acid; vinylidene chloride; vinyl acetate; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and β-carboxyethyl acrylate; styrene monomers such as styrene, α-methylstyrene, and chlorostyrene; amide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; etc. The polymer containing these monomers may be a homopolymer or a copolymer. Examples of the copolymer include vinylidene chloride-methyl methacrylate-acrylonitrile copolymer, methyl methacrylate-acrylonitrile-methacrylonitrile copolymer, methyl methacrylate-acrylonitrile copolymer, and acrylonitrile-methaconic acid copolymer.

The thermally expandable microspheres may be formed using an inorganic foaming agent or an organic foaming agent. Examples of the inorganic foaming agent include ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and various nitrogen azides. Examples of organic foaming agents include fluorinated alkane compounds such as trichloromonofluoromethane and dichloromonofluoromethane; azo compounds such as azobisisobutyronitrile, azodicarboxamide, and barium azodicarboxylate; hydrazine compounds such as p-toluenesulfonylhydrazine, diphenylsulfonium-3,3'-disulfonylhydrazine, 4,4'-oxybis(benzenesulfonylhydrazine), and allylbis(sulfonylhydrazine); amine urea compounds such as p-toluenesulfonylamine urea and 4,4'-oxybis(benzenesulfonylamine urea); triazole compounds such as 5-thiophene-1,2,3,4-thiatriazole; N-nitroso compounds such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide; and the like.

The heat-expandable microspheres can be commercially available. Specific examples of commercially available heat-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 & Pharmaceutical Co., Ltd. The product name "Expancel" manufactured by Fillite (grades: 053-40, 031-40, 920-40, 909-80, 930-120), "DAIFOAM" manufactured by Wu Yu Chemical Industry Co., Ltd. (grades: H750, H850, H1100, S2320D, S2640D, M330, M430, M520), "ADVANCELL" manufactured by Sekisui Chemical Industry Co., Ltd. (grades: EML101, EMH204, EHM301, EHM302, EHM303, EM304, EHM401, EM403, EM501), etc.

The particle size of the heat-expandable microspheres before heating is preferably 0.5 μm to 80 μm, more preferably 5 μm to 45 μm, further preferably 10 μm to 20 μm, and particularly preferably 10 μm to 15 μm. Therefore, in terms of average particle size, the particle size of the heat-expandable microspheres before heating is preferably 6 μm to 45 μm, more preferably 15 μm to 35 μm. The particle size and average particle size are values obtained by the particle size distribution measurement method in the laser scattering method.

The heat-expandable microspheres preferably have a moderate strength that does not break until the volume expansion rate reaches preferably 5 times or more, more preferably 7 times or more, and further preferably 10 times or more. When such heat-expandable microspheres are used, the adhesive force can be efficiently reduced by heat treatment.

The content ratio of the heat-expandable microspheres in the adhesive layer can be appropriately set according to the required adhesive force reduction, etc. The content ratio of the heat-expandable microspheres is, for example, 1 to 150 parts by weight, preferably 10 to 130 parts by weight, and further preferably 25 to 100 parts by weight, relative to 100 parts by weight of the base polymer forming the second adhesive layer.

In the case where the above-mentioned adhesive layer includes heat-expandable microspheres, the arithmetic surface roughness Ra of the adhesive layer before the heat-expandable microspheres expand (i.e., before heating) is preferably 500 nm or less, more preferably 400 nm or less, and further preferably 300 nm or less. If it is within this range, an adhesive sheet having excellent adhesion to an adherend can be obtained. Such an adhesive layer having excellent surface smoothness can be obtained, for example, by making the thickness of the adhesive layer within the above range, applying the adhesive layer and transferring it onto a separator when another adhesive layer is provided. Furthermore, as described in the above item A, when the adhesive sheet of the present invention further has another adhesive layer, the other adhesive layer may contain thermally expandable microspheres. When the other adhesive layer contains thermally expandable microspheres, the arithmetic surface roughness Ra of the adhesive layer is also preferably within the above range.

When the adhesive layer includes heat-expandable microspheres, the adhesive layer preferably contains an adhesive containing 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). If it is such an adhesive layer, an adhesive sheet can be formed that has moderate adhesiveness before heating and whose adhesiveness is easily reduced by heating. Furthermore, the dynamic storage modulus can be measured using a dynamic viscoelasticity measuring device (e.g., the product name "ARES" manufactured by Rheometrics) under measuring conditions of a frequency of 1 Hz and a heating rate of 10°C/min.

E. Method for producing adhesive sheet The adhesive sheet of the present invention can be produced by any appropriate method. For example, the adhesive sheet of the present invention can be produced by directly applying a composition containing an adhesive on a substrate, or by transferring a coating layer formed by applying a composition containing an adhesive on any appropriate substrate to a substrate. The composition containing an adhesive can contain any appropriate solvent.

When forming an adhesive layer containing heat-expandable microspheres, a composition containing heat-expandable microspheres, an adhesive and any appropriate solvent may be applied to a substrate to form the adhesive layer. Alternatively, heat-expandable microspheres may be sprinkled on the adhesive coating layer and then embedded in the adhesive using a laminating machine to form the adhesive layer containing heat-expandable microspheres.

As a coating method for the above-mentioned adhesive and each composition, any appropriate coating method can be adopted. For example, each layer can be formed by drying after coating. As a coating method, for example, a coating method using a multi-layer coater, a die coater, a gravure coater, and an applicator can be cited. As a drying method, for example, natural drying and heat drying can be cited. The heating temperature when heat drying is performed can be set to any appropriate temperature according to the characteristics of the substance to be dried. Example

The present invention is specifically described below by way of examples, but the present invention is not limited to these examples. The evaluation method in the examples is as follows. In addition, in the examples, unless otherwise specified, "parts" and "%" are based on weight.

(1) sp value The sp value of the polymer in the adhesive layer after the adhesive sheet is formed is calculated by the method of Fedors (Hideki Yamamoto, "The Fundamentals, Applications and Calculation Methods of sp Value", Information Agency Co., Ltd., published on April 3, 2006, pages 66-67). Specifically, the sp value is calculated by the following formula based on the evaporation energy Δe (cal) of each atom or atomic group forming the polymer at 25°C and the molar volume ΔV (cm ³ ) of each atom or atomic group forming the polymer at 25°C. Sp value = (ΣΔe/ΣΔv) ^1/2 In addition, when the polymer is a copolymer, its SP value is calculated by calculating the SP value of each homopolymer of each structural unit constituting the copolymer, multiplying these SP values by the molar fraction of each structural unit, and summing the results. In the above case, the analysis method of each structural unit (polymer composition analysis) can be obtained by appropriately taking only the adhesive layer from the adhesive sheet, immersing it in an organic solvent such as dimethylformamide (DMF), acetone, methanol, tetrahydrofuran (THF), etc., recovering the solvent-soluble portion, and obtaining it according to the analysis method of gel filtration chromatography (GPC), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), and mass analysis. (2) Contact angle The adhesive sheet is placed on a glass slide with the adhesive layer on top, and the contact angle of the adhesive layer surface to 4-tert-butylphenyl glycidyl ether is measured. 2 μl of 4-tert-butylphenyl glycidyl ether was dropped onto the surface of the adhesive layer, and the contact angle was measured after 5 seconds (N=5). The contact angle was measured using a contact angle meter (manufactured by Kyowa Interface Co., Ltd., trade name "CX-A") at 23°C and 50% RH. (3) Adhesion to sealing resin (adhesion to epoxy resin at 23°C when epoxy resin is cured on the adhesive layer) A 0.6 mmt frame-shaped spacer (inner size 100 mm×100 mm) was arranged on the adhesive layer surface of the adhesive sheet (size: 125 mm×125 mm) obtained in the embodiment and the comparative example. The thickness of the cured resin on the inner side of the spacer was 0.6 mmt. Granular epoxy sealing resin (G730 manufactured by Sumitomo Bakelite Co., Ltd.) was spread in the manner of mmt, covered with a silicone-treated peeling pad, and then the evaluation sample was compressed and formed at 150°C for 600 seconds and 0.3 MPa using a vacuum compression molding machine, and then heated at 150°C for 1 hour to harden it, so that the sealing resin was formed into an adhesive sheet to form a structure. The structure obtained as described above was cooled, and then a sample (20 mm wide × 100 mm long) was cut out from the structure, and the adhesive sheet was peeled off from the sample using a tensile testing machine. After the sample was set in the tensile testing machine, it was placed in an ambient temperature of 23°C (normal temperature) for 30 minutes. The test force when the tape was subsequently peeled off at room temperature (300 mm/min 180 degree peeling) was taken as the sealant resin adhesion. (4) Shear Adhesion Using double-sided tape No. 585 manufactured by Nitto Denko Co., Ltd., the adhesive sheet (size: 20 mm × 20 mm) obtained in the embodiment and comparative example was attached and fixed on a specific substrate (e.g., 20 mm × 20 mm silicon wafer) on the side opposite to the adhesive layer, and a 5 mm × 5 mm silicon wafer (mirror surface) was attached vertically to the adhesive layer surface of the adhesive sheet using tweezers in a manner that the wafer corners did not abut the adhesive surface layer. After that, the samples were heated at 130℃ for 30 minutes to make the silicon wafer close to the adhesive surface, and the evaluation samples were made. For the evaluation samples, the DAGE4000 manufactured by Nordson was used at an ambient temperature of 150℃, and the measuring terminal was set on the side of the 5 mm×5 mm silicon wafer at a height of 250 μm from the attachment surface. The external force was applied in the direction horizontal to the wafer at a shear rate of 500 μm/sec., and the maximum breaking load was read from the load-displacement curve obtained in this way, which was used as the shear bonding strength at an ambient temperature of 150℃. (5) Cross-sectional observation of sealing resin A glass filler-containing particle sealing resin (G730 manufactured by Sumitomo Bakelite) was dispersed on the surface of the adhesive layer of the adhesive sheet obtained in the Examples and Comparative Examples, and pressurized at 145°C × 10 min × 0.3 MPa to form a resin layer. After that, it was heated at 150°C × 4 h, returned to room temperature, and the tape was peeled off at room temperature (300 mm/min 180 degree peeling). Next, the part where the adhesive tape was attached to the resin was cut, and the cross section was sputter-plated with a Pt/Pd alloy, and then observed by SEM ("S-3400 N" manufactured by Hitachi, Ltd., applied voltage 10 kV, high vacuum, SE mode, 1000 times). The case where a layer without glass filler (adhesive layer, or a mixed phase containing adhesive layer components and resin layer components) was observed on the resin layer containing glass filler was set as 0, and the case where such a layer was not formed was set as ×.

[Example 1] 100 parts by weight of acrylic copolymer A (a copolymer of butyl acrylate (BA), methyl methacrylate (MMA), and hydroxyethyl acrylate (HEA), BA:MMA:HEA=65:30:5 (weight ratio)), 1.5 parts by weight of isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry, trade name "Coronate L"), and 0.01 parts by weight of reaction aid (manufactured by Tokyo Fine Chemical, trade name "OM-5") were mixed to prepare an adhesive layer-forming composition. The adhesive layer-forming composition was applied to one side of a polytetrafluoroethylene film (manufactured by Toray, trade name "Lumirror S10", thickness 38 μm) as a substrate to obtain an adhesive sheet comprising a substrate and an adhesive layer (thickness 5 μm). The obtained adhesive sheet was subjected to the above evaluations (1) to (4). The results are shown in Table 1.

[Example 2] An adhesive sheet was obtained in the same manner as in Example 1 except that no reaction aid was added and 10 parts by weight of a terpene phenol adhesive-imparting resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "SUMILITERESIN PR51732") was added to prepare a composition for forming an adhesive layer. The obtained adhesive sheet was subjected to the above-mentioned evaluations (1) to (4). The results are shown in Table 1.

[Example 3] Without adding a reaction aid, 20 parts by weight of a terpene phenol adhesive-imparting resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "YS POLYSTER S145") was formulated to prepare a composition for forming an adhesive layer. The thickness of the adhesive layer was set to 10 μm. An adhesive sheet was obtained in the same manner as in Example 1. The obtained adhesive sheet was subjected to the above-mentioned evaluations (1) to (4). The results are shown in Table 1.

[Example 4] Without adding a reaction aid, 20 parts by weight of a terpene phenol adhesive-imparting resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "YS POLYSTER T145") was formulated to prepare a composition for forming an adhesive layer. The thickness of the adhesive layer was set to 10 μm. An adhesive sheet was obtained in the same manner as in Example 1. The obtained adhesive sheet was subjected to the above-mentioned evaluations (1) to (4). The results are shown in Table 1.

[Example 5] 100 parts by weight of acrylic copolymer B (copolymer of 2-ethylhexyl acrylate (2EHA), butyl acrylate (BA), acrylic acid (AA), and hydroxyethyl acrylate (HEA), 2EHA:BA:AA:HEA=50:50:4:1 (weight ratio)), 5 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C"), and 20 parts by weight of terpene phenol adhesive imparting resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "SUMILITERESIN PR12603") were mixed to prepare a composition for forming an adhesive layer. The adhesive layer-forming composition was applied to one side of a polytetrafluoroethylene film (manufactured by Toray Industries, trade name "Lumirror S10", thickness 38 μm) as a substrate to obtain an adhesive sheet comprising a substrate and an adhesive layer (thickness 10 μm). The obtained adhesive sheet was subjected to the above evaluations (1) to (4). The results are shown in Table 1.

[Example 6] 100 parts by weight of acrylic copolymer C (copolymer of 2-ethylhexyl acrylate (2EHA), ethyl acrylate (EA), methyl methacrylate (MMA), and hydroxyethyl acrylate (HEA), 2EHA:EA:MMA:HEA=30:65:5:5 (weight ratio)), 0.05 parts by weight of reaction aid (manufactured by Tokyo Fine Chemical Co., Ltd., trade name "OL-1"), 3 parts by weight of isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), and 20 parts by weight of rosin adhesive imparting agent (manufactured by Arakawa Chemical Industries, Ltd., trade name "PENSEL D125") were mixed to prepare an adhesive layer-forming composition. The adhesive layer-forming composition was applied to one side of a polytetrafluoroethylene film (manufactured by Toray Industries, trade name "Lumirror S10", thickness 38 μm) as a substrate to obtain an adhesive sheet comprising a substrate and an adhesive layer (thickness 10 μm). The obtained adhesive sheet was subjected to the above evaluations (1) to (4). The results are shown in Table 1.

[Comparative Example 1] 100 parts by weight of acrylic copolymer D (copolymer of 2-ethylhexyl acrylate (2EHA) and hydroxyethyl acrylate (HEA), 2EHA:HEA=100:5 (weight ratio)), 0.05 parts by weight of reaction aid (manufactured by Tokyo Fine Chemical Co., Ltd., trade name "OL-1"), 1.5 parts by weight of isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), and 10 parts by weight of terpene phenol adhesive imparting resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name "SUMILITERESIN PR12603") were mixed to prepare a composition for forming an adhesive layer. The adhesive layer-forming composition was applied to one side of a polytetrafluoroethylene film (manufactured by Toray Industries, trade name "Lumirror S10", thickness 38 μm) as a substrate to obtain an adhesive sheet comprising a substrate and an adhesive layer (thickness 10 μm). The obtained adhesive sheet was subjected to the above evaluations (1) to (4). The results are shown in Table 1.

[Comparative Example 2] 100 parts by weight of acrylic copolymer E (copolymer of 2-ethylhexyl acrylate (2EHA) and acrylic acid (AA), 2EHA:AA=100:5 (weight ratio)), 0.5 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "Tetrad C"), and 10 parts by weight of terpene phenol adhesive imparting resin (manufactured by Yasuhara Chemical Co., Ltd., trade name "YS POLYSTER S145") were mixed to prepare an adhesive layer-forming composition. The adhesive layer-forming composition was applied to one side of a polytetrafluoroethylene film (manufactured by Toray Industries, Ltd., trade name "Lumirror S10", thickness 38 μm) as a substrate to obtain an adhesive sheet comprising a substrate and an adhesive layer (thickness 10 μm). The obtained adhesive sheet was submitted to the above evaluations (1) to (4). The results are shown in Table 1.

[Table 1] Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Embodiment 5 Embodiment 6 Comparison Example 1 Comparison Example 2 Adhesive composition (parts by weight) polymer Acrylic copolymer A 100 100 100 100 Acrylic copolymer B 100 Acrylic copolymer C 100 Acrylic copolymer D 100 Acrylic copolymer E 100 Reaction Aids OM-5 0.01 OL-1 0.05 0.05 Crosslinking agent Coronate L(isocyanate crosslinking agent) 1.5 1.5 1.5 1.5 3 1.5 Tetrad C (Epoxy crosslinking agent) 5 0.5 Adhesion agents SUMILITERESIN PR51732 10 YS POLYSTER S145 20 10 YS POLYSTER T145 20 SUMILITERESIN PR12603 20 10 PENSEL D125 20 Adhesive layer thickness (μm) 5 5 10 10 10 10 10 10 Reviews Sp value of base polymer [(J/cm ³ ) ^{1 /2} ] twenty one twenty one twenty one twenty one 19.8 20.7 19.2 19.2 Contact angle [°] 47.5 45.6 43.2 44.4 15.4 15.2 53.1 47.6 Adhesion to sealing resin [N/20 mm] 10.7 8.2 16.7 14.2 11.3 17.7 7.5 0.2 Shear adhesion [g] 831 540 884 902 951 685 371 226

Regarding Example 1 and Comparative Example 1, the SEM photograph of the observation surface in "(5) Cross-sectional observation of sealing resin" is shown in FIG3. In the cross-sectional sample produced according to the Example, a gray resin layer containing glass filler and a darker gray layer not containing glass filler (i.e., an adhesive layer containing a mixed layer) were observed. In contrast, only a gray resin layer containing glass filler was observed in the Comparative Example. Examples 2 to 6 also had the same results as Example 1. In addition, Comparative Example 2 had the same results as Comparative Example 1.

10: Base material 20: Adhesive layer 30: Second adhesive layer 100,200: Adhesive sheet

FIG1 is a schematic cross-sectional view of an adhesive sheet of one embodiment of the present invention. FIG2 is a schematic cross-sectional view of an adhesive sheet of another embodiment of the present invention. FIG3 is a SEM (Scanning Electron Microscope) photograph of the results of "cross-sectional observation of sealing resin" of the embodiment and the comparative example.

10: Base material

20: Adhesive layer

100: Adhesive sheet

Claims (8)

An adhesive sheet comprises a substrate, an adhesive layer disposed on at least one side of the substrate, and a second adhesive layer disposed on the side of the substrate opposite to the adhesive layer. The adhesive layer contains an adhesive, and the adhesive contains a base polymer with an Sp value of 19.5 (J/cm ³ ) ^1/2 to 25 (J/cm ³ ) ^1/2 . The second adhesive layer contains thermally expandable microspheres. The adhesive sheet of claim 1, wherein the Sp value of the base polymer is 20 (J/cm ³ ) ^1/2 to 24 (J/cm ³ ) ^1/2 . The adhesive sheet of claim 1 or 2, wherein the adhesive is an acrylic adhesive. As in the adhesive sheet of claim 1 or 2, wherein the acrylic adhesive contains a base polymer having an alkyl ester with a carbon number of 6 or less as a side chain as a base polymer, and the content ratio of the structural unit having an alkyl ester with a carbon number of 6 or less as a side chain is 50% by weight or more relative to the total structural units constituting the acrylic polymer. As in the adhesive sheet of claim 1 or 2, the acrylic adhesive contains a base polymer having an alkyl ester with a carbon number of 4 or less as a side chain as a base polymer, and the content ratio of the structural unit having an alkyl ester with a carbon number of 4 or less as a side chain is 50% by weight or more relative to the total structural units constituting the acrylic polymer. The adhesive sheet of claim 1 or 2, wherein the contact angle of the adhesive layer to 4-tert-butylphenyl glycidyl ether is 47° or less. The adhesive sheet of claim 1 or 2, wherein when the epoxy resin is cured on the adhesive layer, the adhesion to the epoxy resin at 23°C is preferably 8 N/20 mm or more. The adhesive sheet of claim 1 or 2, wherein when the adhesive layer is bonded to a silicon wafer, the shear adhesion at 150° C. is greater than 400 g.