Adhesive sheet

Abstract

The present invention was made in view of the current situation and provides an adhesive sheet that has a sufficiently high adhesion to DAF before the adhesive layer is irradiated with light, and the adhesion becomes sufficiently low after the adhesive layer is irradiated with light, whether the DAF is immediately attached to the adhesive layer or after long-term storage following the attachment of the DAF to the adhesive layer. According to the present invention, an adhesive sheet is provided, comprising a substrate layer and an adhesive layer disposed on the substrate layer, wherein the adhesive layer is formed of a (meth)acrylic resin composition, the (meth)acrylic resin composition comprising 100 parts by weight of a (meth)acrylic resin and 1 to 15 parts by weight of a photopolymerization initiator, the (meth)acrylic resin being a reaction product of 100 parts by weight of a (meth)acrylic copolymer and 1 to 10 parts by weight of a curing agent, the (meth)acrylic copolymer being a reaction product of a reactive functional group of a (meth)acrylic base copolymer and an isocyanate group of a (meth)acrylic ester containing an isocyanate group, wherein the isocyanate group is in an amount of 0.3 to 0.9 equivalents relative to the reactive functional group, the (meth)acrylic base copolymer being a polymer of a mixture of (meth)acrylic monomers, and the ratio of monomers containing reactive functional groups in the (meth)acrylic monomer mixture being 20 to 50. The ratio of the low molecular weight components (with a weight average molecular weight of 200,000 to 800,000 and a molecular weight of less than 30,000) in the above-mentioned (meth)acrylic acid copolymer is 7 to 20 by mass.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet. Prior Art

[0002] Patent Document 1 describes adhesive sheets used in the manufacture of electronic components by dicing wafers. These sheets combine the functions of a dicing adhesive sheet with the adhesive layer, by laminating a die-bonding film to a lead frame. By laminating the die-bonding film, the adhesive application step after dicing is eliminated in the manufacture of electronic components. [Prior Art Literature] [Patent Document]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-102267 Summary of the Invention

[0004] [Problems to be solved by the invention]

[0005] For adhesive sheets used for such applications, it is ideal that the die bonding film (hereinafter, DAF) does not peel off from the adhesive layer during dicing; that the DAF can be easily peeled off from the adhesive layer if light irradiation is performed after dicing; and that the DAF can also be easily peeled off from the adhesive layer after being attached to the adhesive layer and then stored for a long period of time.

[0006] The present invention is made in view of this situation and provides an adhesive sheet whose adhesion to DAF is sufficiently high before the adhesive layer is irradiated with light, and whose adhesion becomes sufficiently low after the adhesive layer is irradiated with light, whether just after the DAF is attached to the adhesive layer or after the DAF is attached to the adhesive layer and then stored for a long time. [Technical means to solve the problem]

[0007] According to the present invention, the following inventions are provided. [1] An adhesive sheet comprising a substrate layer and an adhesive layer disposed on the substrate layer, wherein the adhesive layer is formed from a (meth)acrylic resin composition, wherein the (meth)acrylic resin composition comprises 100 parts by mass of a (meth)acrylic resin and 1 to 15 parts by mass of a photopolymerization initiator, wherein the (meth)acrylic resin is a reaction product of 100 parts by mass of a (meth)acrylic copolymer and 1 to 10 parts by mass of a curing agent, wherein the (meth)acrylic copolymer is a reaction product of a reactive functional group of a (meth)acrylic base copolymer and an isocyanate group of an isocyanate-containing (meth)acrylate, wherein the isocyanate group is 0.3 to 0.9 equivalents relative to the reactive functional group, and wherein the (meth)acrylic base copolymer is a polymer of a (meth)acrylic monomer mixture, wherein the ratio of the monomer containing the reactive functional group in the (meth)acrylic monomer mixture is 20 to 50. mol%, the weight average molecular weight of the (meth)acrylic acid copolymer is 200,000 to 800,000, and the ratio of the low molecular weight component with a molecular weight of 30,000 or less is 7 to 20% by mass. [2] The adhesive sheet as described in [1], wherein a die bonding film is bonded to the adhesive layer. [3] The adhesive sheet as described in [1] or [2], wherein the ratio of the above-mentioned low molecular weight component is 10-15% by mass. [Effects of the Invention]

[0008] After diligent research, the inventors discovered that the adhesive sheet of the present invention has sufficiently high adhesion to DAF before the adhesive layer is irradiated with light, and that the adhesion becomes sufficiently low after the adhesive layer is irradiated with light, whether just after the DAF is attached to the adhesive layer or after long-term storage after the DAF is attached to the adhesive layer, thereby completing the present invention. Simple diagram description

[0009] FIG. 1 shows the layer structure of an adhesive sheet 10 according to one embodiment of the present invention. FIG. 2 shows the layer structure of the adhesive sheet 10 with DAF 5 obtained by laminating DAF 5 to the adhesive layer 2 . FIG3 shows a bonded structure 11 obtained by attaching a semiconductor wafer 4 to an adhesive sheet 10 with DAF 5 attached thereto. Implementation Method

[0010] The following describes embodiments of the present invention. The various features described in the following embodiments can be combined with each other. Furthermore, each feature independently establishes the invention. In this specification, "(meth)acrylic acid" refers to methacrylic acid or acrylic acid, and "(meth)acrylate" refers to methacrylate or acrylate.

[0011] 1. Adhesive sheet 10 As shown in FIG. 1 , an adhesive sheet 10 according to one embodiment of the present invention includes a base material layer 1 and an adhesive layer 2 disposed thereon.

[0012] 1-1. Base material layer 1 The substrate layer 1 can have any composition and thickness as long as it can support the adhesive layer 2. The substrate layer 1 preferably comprises a thermoplastic resin. The composition of the thermoplastic resin is not particularly limited. Examples of the thermoplastic resin include ionomer resins formed by crosslinking the carboxyl groups of single components and / or composites such as ethylene-methacrylic acid-acrylate terpolymers, ethylene-methacrylic acid copolymers, and ethylene-acrylic acid copolymers with metal ions such as sodium ions, lithium ions, and magnesium ions; soft polypropylene resins formed by blending polypropylene resins with styrene-butadiene copolymer rubber, styrene-butadiene-styrene block copolymer rubber, styrene-isoprene-styrene block copolymer rubber, and ethylene-propylene rubber; low-density polyethylene; ethylene-propylene block copolymers; ethylene-propylene random copolymers; ethylene-vinyl acetate copolymers; ethylene-methacrylic acid copolymers; ethylene-1-octene copolymers; and polybutene. Among these, ionomer resins are preferred.

[0013] The weight average molecular weight (Mw) of the thermoplastic resin is preferably 10,000 to 1,000,000, and more preferably 50,000 to 500,000. The weight average molecular weight (Mw) is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0014] The thickness of the substrate layer is preferably 20-200 μm, more preferably 50-150 μm, and even more preferably 70-100 μm. Specific examples of the thickness include 20, 50, 70, 100, 150, and 200 μm, and may also be within a range between any two of the values ​​exemplified herein.

[0015] 1-2. Adhesive layer 2 Adhesive layer 2 is used to adhere DAF 5. Adhesive layer 2 is formed from a (meth)acrylic resin composition. The (meth)acrylic resin composition comprises 100 parts by mass of a (meth)acrylic resin and 1-15 parts by mass of a photopolymerization initiator. As described below, the (meth)acrylic resin contains (meth)acrylic groups, which are photopolymerized by light (ultraviolet light or visible light (e.g., wavelength 200-700 nm, preferably 250-500 nm, more preferably 300-450 nm). Irradiation with 100 nm (100 nm) of light can further polymerize the (meth)acrylic resin, curing the adhesive layer 2. Curing the adhesive layer 2 reduces its adhesion, facilitating the removal of the DAF 5. If the amount of photopolymerization initiator is too low, the reduction in adhesion due to light irradiation is likely to be insufficient. If the amount of photopolymerization initiator is too high, the adhesion after light irradiation (hereinafter referred to as "adhesion after long-term storage") after the DAF is attached to the adhesive layer and then stored for a long period of time is likely to be high. The amount of photopolymerization initiator per 100 parts by mass of the (meth)acrylic resin can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 parts by mass, and can also be within a range between any two of the values ​​listed here.

[0016] The photopolymerization initiator is not particularly limited as long as it initiates polymerization by irradiation with ultraviolet rays, and examples thereof include photoradical polymerization initiators. Examples of the photoradical polymerization initiator include: benzoin ketal such as 2,2-dimethoxy-1,2-diphenylethane-1-one; α-hydroxyketones such as 1-hydroxycyclohexylphenyl ketone; α-aminoketones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butane-1-one; oxime esters such as 1-[4-(phenylthio)phenyl]-1,2-octanedione-2-(benzoyl)oxime; and bis(2,4,6-trimethylbenzyl)phenylphosphine oxide. Phosphine oxide; 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer; benzophenone compounds such as benzophenone and N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone; quinone compounds such as 2-ethylanthraquinone; benzoin ethers such as benzoin methyl ether; benzoin compounds such as benzoin; benzoyl compounds such as benzoyl dimethyl ketal; acridine compounds such as 9-phenylacridine; N-phenylglycine, coumarin, etc. These may be used alone or in combination with a suitable sensitizer. As photopolymerization initiators, a combination of two or more (two or more) having different maximum absorption wavelengths may also be used.

[0017] <Details of (meth)acrylic resin and hardener> The (meth)acrylic resin is a reaction product of 100 parts by mass of a (meth)acrylic copolymer and 1-10 parts by mass of a hardener. The hardener is a compound that can cure the (meth)acrylic copolymer through a cross-linking reaction. If the hardener content is too low, the adhesion between the adhesive layer 2 and the DAF 5 will significantly decrease, resulting in incomplete peeling after light exposure. If the hardener content is too high, the adhesion between the adhesive layer 2 and the DAF 5 will significantly decrease, potentially causing the DAF 5 to bulge on the adhesive layer 2 or hindering the reactivity of the photopolymerization initiator due to the hardener, making it difficult to reduce the peeling force. The content of the hardener relative to 100 parts by mass of the (meth)acrylic copolymer can be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by mass, and can also be within a range between any two of these values.

[0018] Preferably, the (meth)acrylic copolymer has reactive functional groups (such as epoxy and hydroxyl groups) that react with isocyanate groups, and the hardener is a compound having two or more isocyanate groups per molecule. In this case, the (meth)acrylic copolymer crosslinks and hardens due to the reaction between the reactive functional groups and the isocyanate groups. Examples of compounds having two or more isocyanate groups in one molecule include isocyanate compounds such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-phenylenediisocyanate, 1,4-xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and lysine isocyanate.

[0019] <Details of (meth)acrylic acid copolymer> The (meth)acrylic copolymer is a reaction product of the reactive functional groups (epoxy, hydroxyl, etc.) of the (meth)acrylic base copolymer and the isocyanate groups of the isocyanate-containing (meth)acrylate. The isocyanate-containing (meth)acrylate is a compound containing both isocyanate and (meth)acryloyl groups. The isocyanate-containing (meth)acrylate is bonded to the (meth)acrylic base copolymer via the isocyanate groups and the reactive functional groups, forming a (meth)acrylic copolymer containing (meth)acryloyl groups. These (meth)acryloyl groups are used for photopolymerization prior to DAF stripping. Examples of isocyanate-containing (meth)acrylates include 2-methacryloyloxyethyl isocyanate (e.g., "Karenz MOI" manufactured by Showa Denko Co., Ltd.).

[0020] The equivalent of isocyanate groups relative to the reactive functional groups is 0.3-0.9. Therefore, the reactive functional groups of the (meth)acrylic base copolymer are not completely consumed in the reaction with the isocyanate-containing (meth)acrylate, but rather 10-70% remain. The remaining reactive functional groups are used to react with the hardener. If the equivalent number of isocyanate groups is too low, curing during photopolymerization may be insufficient, and adhesion may not be sufficiently reduced. If the equivalent number of isocyanate groups is too high, the number of reactive functional groups reactive with the hardener is too low, resulting in insufficient crosslinking of the (meth)acrylic base copolymer and insufficient molecular weight increase, which in turn reduces the elastic modulus of the adhesive (i.e., increases flexibility). This improves the adhesion between the adhesive layer 2 and the DAF 5, making it difficult to peel. Furthermore, the presence of a large amount of low-molecular-weight components in the adhesive layer 2 increases their migration into the DAF5, which can significantly increase the adhesive strength after long-term storage. Furthermore, insufficient crosslinking between the (meth)acrylic base copolymers can lead to adhesive residue on the DAF5 surface when the adhesive layer 2 is peeled off (i.e., low-molecular-weight components tend to remain).

[0021] The equivalent number of the isocyanate group relative to the reactive functional group is, for example, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, or 0.90 equivalents, or may be within a range between any two of the values ​​exemplified herein.

[0022] The (meth)acrylic acid copolymer has a weight-average molecular weight of 200,000 to 800,000, and the ratio of low-molecular-weight components with a molecular weight of 30,000 or less is 7 to 20% by mass, preferably 10 to 15% by mass. If the weight-average molecular weight is too low or the ratio of low-molecular-weight components is too high, the adhesion tends to increase after long-term storage. On the other hand, if the weight-average molecular weight is too high or the ratio of low-molecular-weight components is too low, the adhesion tends to increase after light irradiation. The weight-average molecular weight can be, for example, 200,000, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 800,000, or can be within a range between any two of the values ​​listed here. The ratio of low-molecular-weight components can be, for example, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20% by mass, or can be within a range between any two of the values ​​listed here. The weight average molecular weight and the ratio of low molecular weight components can be adjusted by changing the amount of polymerization initiator or chain transfer agent added or the polymerization conditions (temperature, time, etc.) during the polymerization of the (meth)acrylic base copolymer.

[0023] <Details of (meth)acrylic acid base copolymer> The (meth)acrylic base copolymer is a polymer of a (meth)acrylic monomer mixture, wherein the ratio of the reactive functional group-containing monomer in the (meth)acrylic monomer mixture is 20-50 mol%. If this ratio is too low, the number of (meth)acrylic groups introduced into the (meth)acrylic copolymer via bonding with the isocyanate-containing (meth)acrylate becomes too small, and the reduction in adhesion due to light irradiation is likely to be insufficient. If this ratio is too high, the water solubility becomes too high, necessitating the use of a water-soluble solvent such as an alcohol. However, such a water-soluble solvent tends to deactivate the isocyanate-containing (meth)acrylate, resulting in a too small number of (meth)acrylic groups introduced into the (meth)acrylic copolymer, and the reduction in adhesion due to light irradiation is likely to be insufficient.

[0024] A (meth)acrylic monomer mixture is a mixture of (meth)acrylic monomers. A (meth)acrylic monomer is a compound having a (meth)acrylic group, preferably a (meth)acrylic ester. The ratio of the (meth)acrylic monomer in the (meth)acrylic monomer mixture is, for example, 60-100% by mass, such as 60, 65, 70, 75, 80, 85, 90, 95, or 100% by mass, and may also be within a range between any two of the values ​​exemplified herein. The (meth)acrylic monomer mixture is preferably composed solely of (meth)acrylic monomers, but may also contain other monomers. Examples of other monomers include olefins such as ethylene and propylene, aliphatic vinyl esters such as vinyl acetate, and aromatic vinyls such as styrene.

[0025] The reactive functional group-containing monomers are monomers containing reactive functional groups (such as epoxy and hydroxyl groups). Preferably, the reactive functional group-containing monomers are acrylic monomers. The reactive functional groups of the reactive functional group-containing monomers are introduced into the (meth)acrylic base copolymer for reaction with the isocyanate-containing (meth)acrylate and the hardener. The ratio of the reactive functional group-containing monomers in the acrylic monomer mixture can be, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 mol%, and can also be within a range between any two of the values ​​listed above.

[0026] Examples of monomers having a hydroxyl group as a reactive functional group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Examples of monomers having an epoxy group as a reactive functional group include (meth)acrylates having an epoxy group such as glycidyl (meth)acrylate and 3,4-epoxycyclohexyl (meth)acrylate.

[0027] Examples of (meth)acrylic monomers other than monomers containing reactive functional groups include linear or branched alkyl (meth)acrylates and alicyclic (meth)acrylates. Examples of linear or branched alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, and tridecyl (meth)acrylate. Examples of alicyclic (meth)acrylates include cyclohexyl (meth)acrylate, isobutyl (meth)acrylate, and dicyclopentyl (meth)acrylate.

[0028] <Formation Method and Thickness of Adhesive Layer 2> The adhesive layer 2 can be formed by applying an adhesive comprising a (meth)acrylic resin composition onto the substrate layer 1 using a conventional coating method such as notch wheel coating, gravure coating, roller coating, or screen coating, or by transferring an adhesive layer formed by coating on a release film onto the substrate layer 1.

[0029] The thickness of the adhesive layer 2 is preferably 40 μm or less, more preferably 30 μm or less. The thickness is, for example, 5 to 40 μm, such as 5, 10, 15, 20, 25, 30, 35, or 40 μm, or can be within a range between any two of the values ​​exemplified herein.

[0030] <daf5> As shown in Figure 2, DAF5 is bonded to adhesive layer 2. DAF5 is formed by forming an adhesive into a film. Specific DAF5 compositions include single components, mixtures, copolymers, and laminates of acrylate copolymers, polyamides, polyethylene, polysulfones, epoxy resins, polyimides, polyamides, polysilicones, phenols, rubbers, fluororubbers, and fluororesins. For improved bonding reliability between the lead frame and the wafer, compositions containing epoxy resin are preferred.

[0031] 1-3. Application Regarding the adhesive sheet 10 , DAF 5 may be attached to the adhesive layer 2 to form the adhesive sheet 10 with DAF 5 for use in manufacturing semiconductor components.

[0032] 1-4. Method for manufacturing adhesive sheet 10 The adhesive sheet 10 can be manufactured by forming the adhesive layer 2 on the base material layer 1. The adhesive sheet 10 with the DAF 5 attached thereto can be manufactured by laminating the DAF 5 on the adhesive layer 2.

[0033] The (meth)acrylic resin composition constituting the adhesive layer 2 can be produced by the following method.

[0034] First, a (meth)acrylic acid base copolymer is polymerized using a (meth)acrylic acid monomer mixture containing 20-50 mol% of a monomer containing a reactive functional group. The amount of polymerization initiator added during polymerization is, for example, 0.01, 0.02, 0.025, 0.03, 0.04, or 0.05% by weight relative to the total weight of the monomer mixture, or can be within a range between any two of the values ​​listed above. AIBN (Azobisisobutyronitrile) or the like can be used as the polymerization initiator.

[0035] Next, the (meth)acrylic copolymer is produced by mixing the reactive functional groups (epoxy, hydroxyl, etc.) of the (meth)acrylic base copolymer with the isocyanate groups of the isocyanate-containing (meth)acrylate at an equivalent ratio of 1:0.3 to 0.9, and reacting them. The polymerization of the (meth)acrylic base copolymer and the addition of the isocyanate-containing (meth)acrylate are performed under conditions where the weight-average molecular weight of the (meth)acrylic copolymer is 200,000 to 800,000, and the proportion of low-molecular-weight components with a molecular weight of 30,000 or less is 7 to 20% by mass.

[0036] Next, 100 parts by mass of the (meth)acrylic copolymer and 1 to 10 parts by mass of a curing agent are mixed and reacted to produce a (meth)acrylic resin.

[0037] Next, 100 parts by mass of a (meth)acrylic resin and 1 to 15 parts by mass of a photopolymerization initiator are mixed to produce a (meth)acrylic resin composition.

[0038] 2. Manufacturing methods of semiconductor components A method for manufacturing a semiconductor component according to one embodiment of the present invention includes a laminating step, a dicing step, a light irradiation step, and a picking step. Each step is described in detail below.

[0039] 2-1. Attachment steps In the attaching step, as shown in FIG3 , the semiconductor wafer 4 is attached to the DAF 5 of the adhesive sheet 10 . Thus, a bonded body 11 is obtained in which the semiconductor wafer 4 is attached to the adhesive sheet 10 .

[0040] 2-2. Cutting steps In the dicing step, semiconductor wafer 4 is separated while attached to DAF 5 to form semiconductor chips. It is preferred that DAF 5 be separated at the same time. The dicing method is not particularly limited and can be performed using blade dicing, laser dicing, stealth dicing, or other methods.

[0041] 2-3. Light irradiation step In the light irradiation step, the adhesive layer 2 is irradiated with light to photopolymerize and harden the adhesive layer 2. This can reduce the adhesive strength of the adhesive layer 2 and facilitate the peeling of the DAF 5.

[0042] 2-4. Picking steps In the pickup step, the semiconductor wafer is picked up. At this time, the DAF 5 is peeled off from the adhesive layer 2 and picked up together with the semiconductor wafer. [Example]

[0043] 1. Manufacturing of Adhesive Sheet 10 In the Examples and Comparative Examples shown in Tables 1 to 3, adhesive sheets 10 were produced by forming an adhesive layer 2 on a substrate layer 1. An ionomer (Trade No.: Himilan 1650) manufactured by Dow Mitsui Polychemicals was used as substrate layer 1. It had an MFR (Melt Flow Rate) of 1.5 g / 10 min, a density of 950 kg / m³, and a thickness of 80 μm. Adhesive layer 2 was formed to a thickness of 10 μm using a (meth)acrylic resin composition produced using the method described below.

[0044] <Production of (meth)acrylic resin composition> (Example 1) Polymerization of (meth)acrylic acid based copolymers First, a monomer mixture prepared by mixing 2-ethylhexyl acrylate (hereinafter, "2-EHA") and 2-hydroxyethyl acrylate (hereinafter, "2-HEA") at a molar ratio of 8:2 was added to a glass flask. Next, a polymerization initiator (AIBN) was added to the monomer mixture so that its concentration became 0.025% by mass. Next, a solvent (toluene) was added so that the solid content of the monomer mixture became 50% by mass, and the mixture was stirred for about 30 minutes (stirring speed: 200 rpm) until uniform dispersion was achieved, thereby obtaining a diluted mixed solution. Next, place a syringe needle into the diluted mixed solution and introduce nitrogen gas for 5 minutes while stirring. Next, immediately after nitrogen is introduced, a balloon filled with nitrogen is connected to the mouth of the glass flask and sealed. Next, a polymerization reaction was carried out in a nitrogen atmosphere at 65° C. for 24 hours to obtain a (meth)acrylic acid (hereinafter, “MA”) base copolymer.

[0045] ·Manufacturing of MA copolymer Next, the MA base copolymer obtained in the above step was diluted with toluene to a solid content of 20% by mass and stirred. Next, 0.8 equivalents of 2-methacryloyloxyethyl isocyanate (hereinafter, "MOI") were added to the monomer mixture with respect to 2-HEA, and the mixture was stirred. Next, nitrogen was introduced for about 5 minutes, and then 0.5% by mass of an addition catalyst (bismuth carboxylate) was added, and the mixture was stirred under a nitrogen atmosphere. Then, the mixture was heated to 40°C and reacted for 24 hours to obtain MA copolymer.

[0046] ·Manufacturing of MA resin Next, the MA copolymer and the hardener were mixed and reacted so that the amount of hardener was 3 parts by mass per 100 parts by mass of the MA copolymer, thereby obtaining an MA resin. Takenate (registered trademark) D-101E (45EA) (trimethylolpropane adduct of 2,4-toluene diisocyanate) manufactured by Mitsui Chemicals was used as the hardener.

[0047] ·Manufacturing of MA resin composition Next, the MA resin and the photopolymerization initiator were mixed so that the amount of the photopolymerization initiator was 3 parts by mass relative to 100 parts by mass of the MA resin, thereby obtaining an MA resin composition.

[0048] (Examples 2-4, 7-13, Comparative Examples 1-2, Comparative Examples 5-9) An MA resin composition was obtained in the same manner as Example 1, except that the molar ratio of 2-EHA to 2-HEA, the amount of MOI added, the amount of hardener added, and the amount of photopolymerization initiator added were changed to those shown in Tables 1 to 3. In Example 4, the solvent was changed to methanol.

[0049] (Examples 5-6, Comparative Examples 3-4) MA resin compositions were obtained in the same manner as in Example 3, except that the addition amount of the polymerization initiator was changed to 0.05 mass % (Example 5), 0.01 mass % (Example 6), 0.25 mass % (Comparative Example 3), and 0.006 mass % (Comparative Example 4) in Examples 5-6 and Comparative Examples 3-4, respectively.

[0050] [Table 1] Table 1 Example 1 2 3 4 5 6 MA resin composition MA resin MA copolymer MA base copolymer 2-EHA:2-HEA (mol ratio) 8:2 7:3 6:4 5:5 6:4 6:4 MOI Equivalent (relative to OH group) 0.8 0.8 0.8 0.3 0.8 0.8 Weight average molecular weight (10,000) 50 50 50 50 20 80 Low molecular weight ratio (mass %) 13 13 13 13 20 7 hardener parts by mass 3 3 3 3 3 3 Photopolymerization initiator parts by mass 3 3 3 3 3 3 Adhesion strength to SUS (Steel Use Stainless, Japanese stainless steel standard) before light exposure ○ ○ ○ ○ ○ ○ Adhesion to DAF before light exposure ○ ○ ○ ○ ○ ○ After light irradiation △ ○ ○ △ ○ △ DAF adhesion after lamination and storage After light irradiation △ ○ ○ △ △ △

[0051] [Table 2] Table 2 Example 7 8 9 10 11 12 13 MA resin composition MA resin MA copolymer MA base copolymer 2-EHA:2-HEA (mol ratio) 6:4 6:4 6:4 6:4 6:4 6:4 6:4 MOI Equivalent (relative to OH group) 0.4 0.65 0.9 0.8 0.8 0.8 0.8 Weight average molecular weight (10,000) 50 50 50 50 50 50 50 Low molecular weight ratio (mass %) 13 13 13 13 13 13 13 hardener parts by mass 3 3 3 3 3 1 10 Photopolymerization initiator parts by mass 3 3 3 1 15 3 3 Adhesion to SUS before light exposure ○ ○ ○ ○ ○ ○ △ Adhesion to DAF before light exposure ○ ○ ○ ○ ○ ○ △ After light irradiation △ ○ ○ △ ○ △ △ DAF adhesion after lamination and storage After light irradiation △ ○ ○ △ △ △ △

[0052] [Table 3] Table 3 Comparative Example 1 2 3 4 5 6 7 8 9 MA resin composition MA resin MA copolymer MA base copolymer 2-EHA:2-HEA (mol ratio) 9.5:0.5 4:6 6:4 6:4 6:4 6:4 6:4 6:4 6:4 MOI Equivalent (relative to OH group) 0.8 0.1 0.8 0.8 0.2 0.8 0.8 0.8 0.8 Weight average molecular weight (10,000) 50 50 10 120 50 50 50 50 50 Low molecular weight ratio (mass %) 13 13 32 2 13 13 13 13 13 hardener parts by mass 3 3 3 3 3 3 3 0.5 15 Photopolymerization initiator parts by mass 3 3 3 3 3 0.5 25 3 3 Adhesion to SUS before light exposure ○ ○ ○ ○ ○ ○ ○ ○ × Adhesion to DAF before light exposure ○ ○ ○ ○ ○ ○ ○ ○ × After light irradiation × × ○ × × × ○ × × DAF adhesion after lamination and storage After light irradiation × × × × × × × × ×

[0053] 2. Manufacturing of DAF5 55 parts by mass of YDCN-703 (manufactured by Tohto Kasei Co., Ltd., trade name, cresol novolac-type epoxy resin, epoxy group equivalent weight 210, molecular weight 1200, softening point 80°C) as an epoxy resin, 45 parts by mass of Milex XLC-LL (manufactured by Mitsui Chemicals, Inc., trade name, hydroxyl group equivalent weight 175, water absorption 1.8%, mass loss upon heating at 350°C 4%) as a phenolic resin, 1.7 parts by mass of NUCA-189 (manufactured by Nippon Unicar Co., Ltd., trade name, γ-mercaptopropyltrimethoxysilane) and 3.2 parts by mass of NUCA-1160 (manufactured by Nippon Unicar Co., Ltd., trade name, γ-ureidopropyltriethoxysilane) as silane coupling agents, and AEROSIL as a filler. To 32 parts by mass of R972 (a silica filler whose surface is coated with dimethyldichlorosilane and hydrolyzed in a reactor at 400°C to modify it with organic groups such as methyl groups, manufactured by Japan Aerotech Co., Ltd., with an average particle size of 0.016 μm) was added cyclohexanone, stirred, and mixed. The mixture was then milled for 90 minutes using a bead mill. To the resulting mixture were added 280 parts by mass of HTR-860P-3 (manufactured by Nagase Chemicals Co., Ltd., with a weight-average molecular weight of 800,000 and containing 3% by mass of glycidyl acrylate or glycidyl methacrylate) as an acrylic rubber and 0.5 parts by mass of Curezol 2PZ-CN (manufactured by Shikoku Chemicals Co., Ltd., with 1-cyanoethyl-2-phenylimidazole) as a curing accelerator. The mixture was stirred and vacuum degassed to obtain a varnish for forming an adhesive layer. The obtained adhesive layer-forming varnish was applied to a release-treated polyethylene terephthalate (PET) film to a predetermined thickness and then dried by heating at 140°C for 5 minutes to form a 20 μm thick B-stage adhesive layer, thereby obtaining DAF5 laminated on the PET film.

[0054] 3. Manufacturing of adhesive sheet 10 with DAF5 The adhesive layer 2 of the adhesive sheet 10 was laminated to DAF5. Lamination was performed in a clean room (temperature 23°C, humidity 50%) using a laminator, without heating the rollers (i.e., at 23°C). To maintain a constant adhesion between the DAF5 and the adhesive layer 2, the sheet was then stored in a refrigerator at 4°C for one day, yielding an adhesive sheet 10 with DAF5 attached.

[0055] 4. Weight average molecular weight and low molecular weight ratio The weight average molecular weight and low molecular weight ratio of MA copolymer were measured using the following method.

[0056] <Weight Average Molecular Weight> 10 mg of the MA copolymers from Examples and Comparative Examples were dissolved in 10 mL of tetrahydrofuran (THF, stabilizer-free, manufactured by Wako Pharmaceutical Co., Ltd.) and filtered through a 0.50 μm PTFE membrane filter for analysis. The following are the conditions for determining the weight-average molecular weight.

[0057] (Analysis device) Gel permeation chromatography analyzer (DGU-20AC, etc., manufactured by Shimadzu Corporation ) (Measurement conditions) Standard material: Shodex STANDARD (Model: SM-105, manufactured by Showa Denko Co., Ltd.) Sample injection volume: 20 μL Mobile phase:THF Flow rate: 1 mL / min Column: Shim-pack GPC-80M (300 mm × 8.0 mm I.D.) Column temperature: 40℃ Detector: Refractive Index Detector (RID)

[0058] <Low molecular weight ratio> The low molecular weight ratio (the ratio of low molecular weight components with a molecular weight of 30,000 or less) is calculated based on the area ratio in the molecular weight distribution diagram obtained when measuring the weight average molecular weight.

[0059] 5. Evaluation The adhesive sheets 10 of the Examples and Comparative Examples were evaluated in the following manner. The results are shown in Tables 1 to 3. All Examples achieved favorable results in all evaluation criteria. On the other hand, all Comparative Examples achieved unfavorable results in at least one evaluation criteria.

[0060] <Determination of SUS Adhesion Resistance> A SUS plate having a width of 50 mm, a length of 150 mm, and a thickness of 2 mm was attached to the adhesive sheet 10 cut into a width of 10 mm and a length of 200 mm using a roller to obtain a measurement sample.

[0061] Next, the adhesive sheet 10 was pulled against the SUS plate using a VPA-3 free-angle adhesion and film peeling analyzer (manufactured by Kyowa Interface Science Co., Ltd.) at a temperature of 25±5°C, a humidity of 55±10%, a peel angle of 30°, and a peel speed of 300 mm / min. The peel strength (low-angle (30°) peel strength) was measured. Three identical measurements were performed, and the average value was designated as the SUS adhesion resistance. Evaluation was then conducted according to the following criteria. ○: 1 N / 25 mm or more △: 0.5 N / 25 mm or more, less than 1 N / 25 mm ×: Less than 0.5 N / 25 mm

[0062] <Measurement of DAF Adhesion> A first support film (EC tape, manufactured by OJI TAC Co., Ltd.) was attached to the DAF5 side of a DAF5-attached adhesive sheet 10 cut to a width of 25 mm and a length of 120 mm using a roller. A second support film was then fixed to the edge of the first support film to obtain a measurement sample.

[0063] Next, the test sample prepared above was placed in a VPA-3 flexible-angle adhesive and film peeling analyzer (manufactured by Kyowa Interface Science Co., Ltd.). Specifically, the substrate layer 1 was fixed to the analyzer's moving stage, and the end of the second support film was fixed to a fixed plate. The moving stage was then moved at a temperature of 25±5°C, a humidity of 55±10%, a peel angle of 30°, and a peel speed of 600 mm / min. The peel force (low-angle (30°) peel strength) when peeling the adhesive layer 2 from the DAF 5 was measured. Six identical measurements were performed, and the average value was defined as the adhesion to the DAF before light irradiation. Evaluation was performed according to the following criteria. ○: 10 N / 25 mm or more △: 5 N / 25 mm or more, less than 10 N / 25 mm ×: less than 5 N / 25 mm

[0064] Further, for the measurement sample, using an ultraviolet irradiation device (manufactured by Cosmo Giken Co., Ltd., model CUS0031-20A / b, metal halide lamp, 3 kw), irradiate from the substrate layer side at an irradiation temperature of 40°C or lower, an irradiation intensity of 70 mW / cm2, and a cumulative light quantity of 110 mJ / cm2. After the adhesive layer 2 is hardened, measure the peel strength 6 times using the same method as above, set the average value as the adhesion force to DAF after light irradiation, and evaluate according to the following criteria. ○: 0.7 N / 25 mm or less △: Exceeding 0.7 N / 25 mm and 1.0 N / 25 mm or less ×: Exceeding 1.0 N / 25 mm <Adhesion force after DAF bonding and storage> After manufacturing the adhesive sheet 10 with DAF5, leave it standing in an environment of 23°C and 50% humidity for 6 weeks. Thereafter, using the same method as above, measure the peel strength 6 times after light irradiation, and set the average value as the adhesion force after DAF bonding and storage. ○: 0.7 N / 25 mm or less △: Exceeding 0.7 N / 25 mm and 1.0 N / 25 mm or less ×: Exceeding 1.0 N / 25 mm

[0065] 1: Substrate layer 2: Adhesive layer 4: Semiconductor wafer 5: Die bonding film 10: Adhesive sheet 11: Bonded body

Claims

1. An adhesive sheet comprising a substrate layer and an adhesive layer disposed on the substrate layer, wherein the adhesive layer is formed of a (meth)acrylic resin composition, the (meth)acrylic resin composition comprising 100 parts by weight of a (meth)acrylic resin and 1 to 15 parts by weight of a photopolymerization initiator, wherein the (meth)acrylic resin is a reaction product of 100 parts by weight of a (meth)acrylic copolymer and 1 to 10 parts by weight of a curing agent, wherein the (meth)acrylic copolymer is a reaction product of a reactive functional group of a (meth)acrylic base copolymer and an isocyanate group of a (meth)acrylic ester containing an isocyanate group, wherein the isocyanate group is in an amount of 0.3 to 0.9 equivalents relative to the reactive functional group, wherein the (meth)acrylic base copolymer is a polymer of a mixture of (meth)acrylic monomers, and the ratio of monomers containing reactive functional groups in the (meth)acrylic monomer mixture is 30 to 50 mol%. The weight average molecular weight of the above-mentioned (meth)acrylic acid copolymer is 200,000 to 800,000, and the ratio of low molecular weight components with a molecular weight of less than 30,000 is 7 to 20 by mass.

2. The adhesive sheet of claim 1, wherein a grain bonding film is adhered to the adhesive layer.

3. The adhesive sheet as requested in item 1 or 2, wherein the ratio of the aforementioned low molecular weight component is 10 to 15 by mass.

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