Adhesive sheet for processing workpiece, manufacturing method thereof, and manufacturing method of electronic device

Abstract

To provide an adhesive sheet for workpiece processing that is excellent in productivity and reduces an amount of adhesion of grinding debris, a method for manufacturing the same, and a method for manufacturing electronic devices that use the adhesive sheet for workpiece processing.SOLUTION: The present invention relates to an adhesive sheet for workpiece processing, which has a surface coating layer, a buffer layer, a base material, and an adhesive layer, in that order, and in which a static contact angle of diiodomethane at 23°C with respect to the surface coating layer is 43° or greater, and a method for manufacturing the same, as well as a method for manufacturing an electronic device apparatus using the adhesive sheet for workpiece processing.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an adhesive sheet for processing a workpiece, a method for producing the same, and a method for producing an electronic device. [Background technology]

[0002] 2. Description of the Related Art As information terminal equipment is rapidly becoming thinner, smaller and more multifunctional, electronic devices such as semiconductor devices mounted on these equipment are also required to be thinner and more dense. As a method for thinning electronic devices, a method of grinding the back surface of a workpiece such as a semiconductor wafer used in the electronic device has been used. The back surface of the workpiece is ground by attaching an adhesive sheet for back surface grinding (hereinafter also referred to as a "back grinding sheet") to the front surface of the workpiece, and the front surface of the workpiece is protected by the sheet. The back grinding sheet is peeled off and removed from the front surface of the workpiece after back surface grinding.

[0003] In recent years, as a grinding and singulation method for thinning a workpiece while suppressing damage to the workpiece, a first dicing method, a stealth first dicing method, etc. have been put into practical use. The first dicing method is a method in which a groove of a predetermined depth is formed on the surface of the workpiece with a dicing blade or the like, and the workpiece is then ground from the back side to the groove to singulate the workpiece into individual workpieces. The stealth first dicing method is a method in which a modified region is formed inside the workpiece by irradiation with laser light, and the workpiece is then ground from the back side and cut into individual workpieces by using the modified region as a splitting starting point. In these methods, a back grind sheet is also used to protect the surface of the workpiece.

[0004] When grinding the backside of a workpiece, the backgrind sheet attached to the workpiece is fixed on the side opposite to the side attached to the workpiece (hereinafter also referred to as the "backside") by a support device such as a chuck table. The workpiece fixed on the table of the support device via the backgrind sheet is ground on the backside while cooling water is supplied to the grinding surface to remove heat and grinding debris caused by grinding.

[0005] When grinding the back surface, if grinding chips are present between the back grinding sheet and the table of the support device, cracks may occur in the workpiece or the individual pieces of the workpiece, starting from the part where the grinding chips are present, due to the impact when fixing the workpiece to the table, the pressure and vibration during back surface grinding, etc. Since the grinding chips are contained in the cooling water and adhere to the back surface of the back grinding sheet, in order to suppress the occurrence of the above-mentioned cracks, it is necessary to reduce the amount of grinding chips adhering to the back surface of the back grinding sheet.

[0006] Patent Document 1 discloses an adhesive sheet for semiconductor processing that has a reduced amount of grinding debris adhesion and excellent transportability, the adhesive sheet having a surface coating layer, a buffer layer, a substrate, and an adhesive layer in this order, the surface coating layer being a layer formed from a surface coating layer-forming composition that contains a silicone compound. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2023-048103 A Summary of the Invention [Problem to be solved by the invention]

[0008] The adhesive sheet for semiconductor processing of Patent Document 1 makes it possible to suppress adhesion of grinding debris by providing a surface coating layer on one surface. The surface coating layer is formed by applying a solution of an active ingredient dissolved in an organic solvent to a specific member and then drying it. In order to improve the productivity of the adhesive sheet for processing a workpiece, it is desirable to increase the drying temperature for removing the organic solvent and shorten the drying time. However, according to the study by the present inventors, it has been found that when the drying temperature for removing the organic solvent is increased during the formation of the surface coating layer, the amount of adhesion of grinding dust cannot be sufficiently suppressed. Therefore, it has been difficult to improve the productivity of the adhesive sheet for processing a workpiece that can sufficiently suppress the amount of adhesion of grinding dust.

[0009] The present invention has been made in consideration of the above-mentioned situation, and aims to provide an adhesive sheet for workpiece processing that is highly productive and has a reduced amount of grinding debris adhesion, a manufacturing method thereof, and a manufacturing method for electronic device equipment using the adhesive sheet for workpiece processing. [Means for solving the problem]

[0010] As a result of intensive research, the inventors have found that the above-mentioned problems can be solved by an adhesive sheet for workpiece processing having, in this order, a surface coating layer, a buffer layer, a base material and an adhesive layer, the static contact angle of which with diiodomethane at 23°C is 43° or more, and have completed the present invention as described below.

[0011] That is, the present invention relates to the following [1] to

[10] . [1] A surface coating layer, a buffer layer, a substrate, and a pressure-sensitive adhesive layer, in this order; The adhesive sheet for workpiece processing, wherein the static contact angle of diiodomethane at 23°C with the surface coating layer is 43° or more. [2] The adhesive sheet for workpiece processing described in [1] above, wherein the surface coating layer is an organic layer containing a resin component. [3] The adhesive sheet for workpiece processing according to the above [2], wherein the resin component is a polymer of a compound having one or more ethylenically unsaturated bonds. [4] The adhesive sheet for workpiece processing according to the above [3], wherein the compound having one or more ethylenically unsaturated bonds is a styrene-based compound. [5] The pressure-sensitive adhesive sheet for workpiece processing according to any one of the above [1] to [4], wherein the surface coating layer has a thickness of 0.05 to 10 μm. [6] The pressure-sensitive adhesive sheet for workpiece processing according to any one of the above [1] to [5], wherein the buffer layer is a layer formed from a buffer layer-forming composition containing a urethane (meth)acrylate. [7] The adhesive sheet for workpiece processing according to any one of the above [1] to [6], which is used for grinding a workpiece. [8] A method for producing the adhesive sheet for workpiece processing according to any one of [2] to [4] above, A method for producing an adhesive sheet for workpiece processing, comprising a step of forming the surface coating layer by irradiating an energy ray to a composition for forming a surface coating layer, the composition containing the resin component, an energy ray-polymerizable multifunctional compound, and a photopolymerization initiator. [9] A step of attaching the adhesive sheet for workpiece processing according to any one of the above [1] to [7] to a surface of a workpiece with the adhesive layer as an attachment surface; A step of grinding the back surface of the workpiece while the surface coating layer side of the adhesive sheet for workpiece processing attached to the workpiece is fixed by a supporting device; A method for manufacturing an electronic device comprising the steps of:

[10] A process for forming a line to be divided, which is a process a for forming a groove on the surface of the workpiece, or a process b for forming a modified region inside the workpiece from the surface or back surface of the workpiece; A sheet attachment step of attaching the adhesive sheet for workpiece processing according to any one of the above [1] to [7] to the surface of the workpiece with the adhesive layer as an attachment surface after the step a, or before or after the step b; A grinding and singulation process in which the back surface of the workpiece is ground while the surface coating layer side of the adhesive sheet for workpiece processing attached to the workpiece is fixed by a supporting device, and the workpiece is singulated into a plurality of workpiece singulations starting from the grooves or the modified regions; A method for manufacturing an electronic device comprising the steps of: Effect of the Invention

[0012] According to the present invention, it is possible to provide an adhesive sheet for workpiece processing which is excellent in productivity and reduces the amount of adhesion of grinding debris, and a method for manufacturing electronic devices using the adhesive sheet for workpiece processing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In this specification, the lower limit and upper limit described in stages for the preferred numerical ranges can be combined independently. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0014] In this specification, the term "active ingredient" refers to the ingredients contained in the target composition excluding the diluent solvent.

[0015] In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid", and similar terms.

[0016] In this specification, the term "energy rays" refers to electromagnetic waves or charged particle beams having an energy quantum, and examples thereof include ultraviolet rays, radiation, electron beams, etc. Ultraviolet rays can be irradiated by using, for example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, etc. as an ultraviolet ray source. Electron beams can be irradiated by generating them using an electron beam accelerator, etc. In this specification, "energy ray polymerizable" means a property of being polymerized by irradiation with energy rays, "energy ray curable" means a property of being cured by irradiation with energy rays, and "non-energy ray curable" means a property of not having energy ray curability.

[0017] In this specification, the term "workpiece" refers to a plate-like body to which the adhesive sheet for workpiece processing of this embodiment is attached and which is then processed. Examples of the workpiece include a wafer, a panel level package, and a strip (rectangular substrate) sealed with a molded resin. Among these, a wafer is preferred from the viewpoint of facilitating the attainment of the effects of the present invention. The wafer may be, for example, a semiconductor wafer such as a silicon wafer, a gallium arsenide wafer, a silicon carbide wafer, a gallium nitride wafer, or an indium phosphide wafer, or an insulating wafer such as a glass wafer, a lithium tantalate wafer, or a lithium niobate wafer. It may also be a reconstructed wafer made of a resin and a semiconductor used in the manufacture of a fan-out package or the like. Among these, from the viewpoint of easily obtaining the effects of the present invention, the wafer is preferably a semiconductor wafer or an insulating wafer, more preferably a semiconductor wafer, and even more preferably a silicon wafer. A semiconductor wafer usually has circuits formed on its surface, such as wiring, capacitors, diodes, transistors, etc. These circuits can be formed by a conventional method such as an etching method or a lift-off method. The thickness of the work before machining is not particularly limited, but is usually 500 to 1,000 μm.

[0018] In this specification, the term "workpiece singulation" refers to a workpiece that has been divided. For example, if the workpiece is a semiconductor wafer, the workpiece singulation is a semiconductor chip, and if the workpiece is a panel level package or a strip (rectangular substrate) sealed with molded resin, the workpiece singulation is a semiconductor package.

[0019] In this specification, the term "electronic device" refers to, for example, a workpiece, a workpiece singulated product, an electronic component including the workpiece singulated product, and electronic equipment including the electronic component.

[0020] In this specification, the "front surface" of a workpiece refers to the surface on which a circuit is formed, and the "back surface" refers to the surface on which no circuit is formed.

[0021] The mechanism of action described in this specification is merely speculation and does not limit the mechanism by which the adhesive sheet for workpiece processing of the present invention exerts its effects.

[0022] [Adhesive sheet for workpiece processing] The adhesive sheet for workpiece processing of this embodiment (hereinafter also referred to as "adhesive sheet") is an adhesive sheet for workpiece processing which has a surface coating layer, a buffer layer, a base material and an adhesive layer, in that order, and the static contact angle of diiodomethane at 23°C with the surface coating layer is 43° or more.

[0023] The adhesive sheet of the present embodiment is attached to the surface of a workpiece and is used to perform a predetermined processing on the workpiece while protecting the surface. After the predetermined processing is performed on the workpiece, the adhesive sheet of the present embodiment is peeled off and removed from the workpiece.

[0024] The pressure-sensitive adhesive sheet of the present embodiment may or may not have layers other than the surface coating layer, the buffer layer, the substrate, and the pressure-sensitive adhesive layer. Examples of layers other than the surface coating layer, the buffer layer, the substrate, and the pressure-sensitive adhesive layer include an intermediate layer provided between the substrate and the pressure-sensitive adhesive layer, and a release sheet provided on the surface of the pressure-sensitive adhesive layer opposite the substrate. Hereinafter, each of the members constituting the pressure-sensitive adhesive sheet of this embodiment will be described in order.

[0025] <Surface coating layer> The surface coating layer is a layer provided on the side of the buffer layer opposite the base material, and is a layer that is fixed by a supporting device when the workpiece is processed.

[0026] (Contact angle of diiodomethane on the surface coating layer) The static contact angle of diiodomethane at 23° C. (hereinafter also simply referred to as “diiodomethane contact angle”) with the surface coating layer of the pressure-sensitive adhesive sheet of this embodiment is 43° or greater. If the diiodomethane contact angle of the surface coating layer is 43° or more, the amount of adhesion of grinding debris can be sufficiently suppressed even if the drying temperature for removing the organic solvent is increased when forming the surface coating layer, so that the adhesive sheet of this embodiment has excellent productivity and suppresses the amount of adhesion of grinding debris. The diiodomethane contact angle of the surface coating layer is preferably 45° or more, more preferably 48° or more, and even more preferably 50° or more, from the viewpoint of further reducing the amount of grinding debris attached. The upper limit of the diiodomethane contact angle of the surface coating layer is not particularly limited, but from the viewpoint of ease of production, etc., it may be, for example, 70° or less, 60° or less, or 55° or less. The diiodomethane contact angle of the surface coating layer is a value measured in accordance with JIS R 3257:1999, and specifically, can be measured by the method described in the examples.

[0027] The surface coating layer of the pressure-sensitive adhesive sheet of the present embodiment may be an inorganic layer or an organic layer; however, from the viewpoints of productivity and handleability of the pressure-sensitive adhesive sheet, it is preferably an organic layer, and more preferably an organic layer containing a resin component.

[0028] (Resin component) As the resin component, a thermoplastic resin is preferred from the viewpoint of reducing the amount of adhesion of grinding debris. The resin component may be used alone or in combination of two or more kinds.

[0029] [Thermoplastic resin] From the viewpoint of further reducing the amount of adhesion of grinding debris, the thermoplastic resin is preferably a polymer of a compound having one or more ethylenically unsaturated bonds (hereinafter, also referred to as "polymer (1)"). In addition, the "ethylenically unsaturated bond" in this embodiment means a carbon-carbon double bond capable of undergoing an addition reaction, and does not include a double bond in an aromatic ring.

[0030] The content of the structural unit derived from the compound having one or more ethylenically unsaturated bonds in the polymer (1) is not particularly limited, but is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. When the content of the structural unit derived from the compound having one or more ethylenically unsaturated bonds is equal to or more than the lower limit, the amount of adhesion of grinding dust tends to be further reduced. Furthermore, the content of structural units derived from a compound having one or more ethylenically unsaturated bonds in the polymer (1) may be 100% by mass, but may be, for example, 99.5% by mass or less, or 99% by mass or less, in order to contain structural units derived from other monomers.

[0031] Examples of compounds having one or more ethylenically unsaturated bonds include styrene-based compounds such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, chlorostyrene, and methoxystyrene; linear monoolefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene; linear non-conjugated dienes (non-conjugated diolefins) such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene; and conjugated dienes such as 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. (conjugated diolefins); cyclic monoolefins such as cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, and cyclooctene; cyclic diolefins such as cyclohexadiene, methylcyclohexadiene, cyclooctadiene, methylcyclooctadiene, and phenylcyclooctadiene; polycyclic olefins such as norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, and tetracyclo[7.4.0.110,13.02,7]trideca-2,4,6,11-tetraene; monomers having an oxygen atom and an ethylenically unsaturated bond such as maleic anhydride and vinyl acetate, and monomers having a nitrogen atom and an ethylenically unsaturated bond such as maleimide compounds and nitrile monomers.

[0032] Among the above options, it is preferable that the polymer (1) contains a structural unit derived from a styrene-based compound. Hereinafter, the polymer (1) containing a structural unit derived from a styrene-based compound is referred to as a "styrene-based resin."

[0033] The content of structural units derived from a styrene-based compound in the styrene-based resin is not particularly limited, but is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more. When the content of the structural units derived from a styrene-based compound in the styrene-based resin is equal to or more than the above lower limit, the heat resistance of the surface coating layer tends to be good. Furthermore, the content of structural units derived from styrene-based compounds in the styrene-based resin is not particularly limited, but is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. When the content of structural units derived from styrene-based compounds in the styrene-based resin is equal to or less than the above upper limit, the introduction of structural units other than the structural units derived from styrene-based compounds tends to make it easier to achieve a good balance between the amount of grinding debris attached and heat resistance.

[0034] Examples of the structural units other than the structural units derived from styrene-based compounds that the styrene-based resin may contain include structural units derived from compounds other than styrene-based compounds that are listed as the compounds having one or more ethylenically unsaturated bonds.Among these, it is more preferable that the styrene-based resin contains structural units derived from conjugated dienes. The structural unit derived from a conjugated diene is a structural unit formed by addition polymerization of the above-mentioned conjugated diene, a structural unit formed by hydrogenating a structural unit formed by addition polymerization of the above-mentioned conjugated diene, or the like. Examples of structural units formed by hydrogenating structural units formed by addition polymerization of conjugated dienes include ethylene-propylene units formed by hydrogenating structural units formed by addition polymerization of isoprene, and ethylene-butylene units formed by hydrogenating structural units formed by addition polymerization of 1,3-butadiene. When the styrene-based resin contains a structural unit derived from a conjugated diene, the content thereof in the styrene-based resin is not particularly limited, but is preferably 20 to 50 mass%, more preferably 25 to 45 mass%, and even more preferably 30 to 40 mass%. When the content of the structural unit derived from the conjugated diene in the styrene resin is equal to or more than the lower limit, the amount of grinding dust adhesion tends to be reduced. Also, when the content of the structural unit derived from the conjugated diene in the styrene resin is equal to or less than the upper limit, the transportability after processing of the workpiece tends to be improved.

[0035] As the styrene-based resin, from the viewpoint of the amount of grinding debris adhesion and heat resistance, one or more types selected from the group consisting of styrene-butadiene block copolymer, styrene-ethylene-propylene block copolymer, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer (hereinafter also referred to as "SEBS") and styrene-ethylene-propylene-styrene block copolymer (hereinafter also referred to as "SEPS") are preferred, and one or more types selected from the group consisting of styrene-ethylene-butylene-styrene block copolymer and styrene-ethylene-propylene-styrene block copolymer are more preferred.

[0036] Examples of the polymer (1) other than the styrene-based resin include homopolymers such as polyethylene, polypropylene, and polybutadiene; binary copolymers such as ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-maleic anhydride copolymers, ethylene-vinyl acetate copolymers, ethylene-(meth)acrylate copolymers, ethylene-tetracyclododecene copolymers, propylene-butene copolymers, propylene-maleic anhydride copolymers, propylene-vinyl acetate copolymers, propylene-(meth)acrylate copolymers, and propylene-tetracyclododecene copolymers; binary copolymers such as ethylene-maleic anhydride-vinyl acetate copolymers, ethylene-maleic anhydride-(meth)acrylate copolymers, and propylene-tetracyclododecene copolymers; and multipolymers such as propylene-(meth)acrylate copolymer, propylene-maleic anhydride-vinyl acetate copolymer, propylene-maleic anhydride-(meth)acrylate copolymer, propylene-vinyl acetate-(meth)acrylate copolymer, ethylene-propylene-maleic anhydride copolymer, ethylene-propylene-vinyl acetate copolymer, ethylene-propylene-(meth)acrylate copolymer, ethylene-butene-maleic anhydride copolymer, ethylene-butene-vinyl acetate copolymer, ethylene-butene-(meth)acrylate copolymer, propylene-butene-maleic anhydride copolymer, propylene-butene-vinyl acetate copolymer, propylene-butene-(meth)acrylate copolymer, and the like.

[0037] The mass average molecular weight (Mw) of the thermoplastic resin is not particularly limited, but is preferably 10,000 to 600,000, more preferably 15,000 to 500,000, and even more preferably 20,000 to 400,000. When the mass average molecular weight (Mw) of the thermoplastic resin is equal to or greater than the lower limit, the transportability after processing of the workpiece tends to be improved. Also, when the mass average molecular weight (Mw) of the thermoplastic resin is equal to or less than the upper limit, the solvent solubility of the thermoplastic resin is improved, and the formation of a surface coating layer by coating tends to be facilitated. In the present embodiment, the mass average molecular weight (Mw) refers to a value calculated in terms of standard polystyrene measured by gel permeation chromatography (GPC), specifically, a value measured by the method described in the examples.

[0038] The content of the resin component in the surface coating layer is not particularly limited, but is preferably 30 to 80 mass %, more preferably 40 to 70 mass %, and even more preferably 45 to 60 mass %, relative to the total amount (100 mass %) of the surface coating layer. When the content of the resin component is within the above range, the amount of adhesion of grinding debris tends to be further reduced.

[0039] (Hydrophobic treated silica) The surface coating layer preferably further contains hydrophobically treated silica together with the resin component. By including hydrophobically treated silica in the surface coating layer, the pressure-sensitive adhesive sheet of this embodiment tends to have a further reduced amount of adhesion of grinding debris. The hydrophobically treated silica may be used alone or in combination of two or more kinds.

[0040] Examples of hydrophobically treated silica include raw silica that has been surface-treated with a hydrophobizing agent. The raw silica to be hydrophobized may be, for example, wet-process silica produced by a wet process such as a precipitation process, a gel process, or a sol-gel process, or may be dry-process silica such as fumed silica, fused silica, etc. Among these, wet-process silica is preferred from the viewpoint of ease of hydrophobization, and precipitated silica is more preferred.

[0041] Examples of the hydrophobic treatment agent include organosilicon compounds, fatty acids, and fatty acid metal salts. The hydrophobizing agent may be used alone or in combination of two or more kinds.

[0042] Examples of methods for surface-treating raw silica with a hydrophobizing agent include a method in which the raw silica and the hydrophobizing agent are contacted in a solvent, a method in which the raw silica is contacted with vapor of the hydrophobizing agent carried by a carrier gas such as nitrogen, and a method in which an undiluted solution of the hydrophobizing agent is directly contacted with the raw silica.

[0043] The shape of the hydrophobized silica is not particularly limited, and examples thereof include spherical, irregular, etc. Among these, from the viewpoint of further reducing the amount of grinding debris attached, irregular shapes are preferred.

[0044] Examples of hydrophobically treated silica that are commercially available include the "AEROSIL (registered trademark) series" manufactured by Evonik, the "QSG series" manufactured by Shin-Etsu Chemical Co., Ltd., the "Nipsil (registered trademark) SS series" manufactured by Tosoh Silica Corporation, and the "SYLOPHOBIC (registered trademark) series" manufactured by Fuji Silysia Chemical Ltd.

[0045] When the surface coating layer contains hydrophobized silica, the content of the hydrophobized silica in the surface coating layer is not particularly limited, but is preferably 1 to 150 parts by mass, more preferably 10 to 120 parts by mass, even more preferably 30 to 90 parts by mass, and even more preferably 50 to 70 parts by mass, relative to 100 parts by mass of the resin component. When the content of the hydrophobized silica is equal to or more than the lower limit, the amount of grinding debris tends to be reduced. When the content of the hydrophobized silica is equal to or less than the upper limit, the film-forming property of the surface coating layer tends to be improved.

[0046] The surface coating layer may contain components other than the resin component and the hydrophobically treated silica. For example, from the viewpoint of achieving better adhesion to the buffer layer, the surface coating layer is preferably a layer formed by irradiating a composition containing a resin component, an energy ray-polymerizable multifunctional compound, and a photopolymerization initiator with energy rays. In the following description, the composition used to form the surface coating layer may be referred to as a "surface coating layer-forming composition."

[0047] (Energy ray polymerizable polyfunctional compound) The energy ray-polymerizable polyfunctional compound is a compound having two or more energy ray-polymerizable functional groups. The energy ray-polymerizable polyfunctional compound may be used alone or in combination of two or more kinds.

[0048] The energy ray-polymerizable polyfunctional compound preferably has 2 to 10 energy ray-polymerizable functional groups, more preferably 3 to 8 energy ray-polymerizable functional groups, and further preferably 4 to 7 energy ray-polymerizable functional groups. The energy ray-polymerizable functional group contained in the energy ray-polymerizable polyfunctional compound is preferably a (meth)acryloyl group.

[0049] The energy ray polymerizable polyfunctional compound is preferably a polyfunctional (meth)acrylate monomer. Examples of the polyfunctional (meth)acrylate monomer include bifunctional (meth)acrylate monomers such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphoric acid di(meth)acrylate, di(acryloxyethyl)isocyanurate, allylated cyclohexyl di(meth)acrylate, and isocyanuric acid ethylene oxide-modified diacrylate; trimethylolpropane tri(meth)acrylate, di Examples of the copolymer include pentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, bis(acryloxyethyl)hydroxyethyl isocyanurate, isocyanuric acid ethylene oxide modified triacrylate, ε-caprolactone modified tris(acryloxyethyl)isocyanurate, diglycerol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, propionic acid modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone modified dipentaerythritol hexa(meth)acrylate. Among these, dipentaerythritol hexa(meth)acrylate and dipentaerythritol penta(meth)acrylate are preferred, and dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate are more preferred.

[0050] When the composition for forming the surface coating layer contains an energy ray-polymerizable multifunctional compound, the content of the energy ray-polymerizable multifunctional compound is preferably 10 to 60 parts by mass, more preferably 15 to 50 parts by mass, and even more preferably 20 to 40 parts by mass, per 100 parts by mass of the resin component. When the content of the energy ray polymerizable polyfunctional compound is equal to or more than the lower limit, the surface coating layer tends to have excellent adhesion to the buffer layer. When the content of the energy ray polymerizable polyfunctional compound is equal to or less than the upper limit, the balance between the adhesion to the buffer layer and the amount of grinding dust adhesion tends to be good.

[0051] (Photopolymerization initiator) Examples of the photopolymerization initiator include a benzoin compound, an acetophenone compound, an acylphosphinoxide compound, a titanocene compound, a thioxanthone compound, a peroxide compound, and further a photosensitizer such as an amine or quinone. More specifically, examples of the photopolymerization initiator include 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl} -2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, etc. Among these, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one are preferred from the viewpoint of improving the productivity of the adhesive sheet for workpiece processing that can sufficiently suppress the amount of adhesion of grinding debris. The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0052] The molecular weight of the photopolymerization initiator is preferably 255 or more, more preferably 260 or more, further preferably 265 or more, and particularly preferably 270 or more. When the molecular weight of the photopolymerization initiator is equal to or greater than the above lower limit, the diiodomethane contact angle of the formed surface coating layer is set to 43° or more, and the adhesive sheet of this embodiment tends to have a reduced amount of adhesion of grinding debris. The molecular weight of the photopolymerization initiator is preferably 400 or less, more preferably 380 or less, and further preferably 360 or less. When the molecular weight of the photopolymerization initiator is equal to or less than the upper limit, the solvent solubility of the photopolymerization initiator is improved, and the preparation of the composition for forming the surface coating layer becomes easy.

[0053] When the composition for forming the surface coating layer contains a photopolymerization initiator, the content thereof is not particularly limited, but from the viewpoint of homogeneously and sufficiently proceeding with the energy ray polymerization reaction, it is preferably 0.01 to 40 parts by mass, more preferably 0.1 to 30 parts by mass, even more preferably 1 to 20 parts by mass, and particularly preferably 5 to 10 parts by mass relative to 100 parts by mass of the energy ray-polymerizable polyfunctional compound.

[0054] (Other Ingredients) The surface coating layer may contain other components in addition to those described above, provided that the effects of the present invention are not impaired. Examples of other components include resins other than those described above, and additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes.

[0055] (Thickness of surface coating layer) The thickness of the surface coating layer is not particularly limited, but is preferably 0.05 to 10 μm, more preferably 0.2 to 7 μm, and further preferably 1 to 4 μm. When the thickness of the surface coating layer is equal to or greater than the lower limit, a uniform layer can be formed, and the amount of grinding debris attached tends to be reduced. When the thickness of the surface coating layer is equal to or less than the upper limit, the effect of the buffer layer, which absorbs unevenness of foreign matter on the chuck table, tends to be easily obtained.

[0056] <Buffer layer> The buffer layer is a layer provided between the substrate and the surface coating layer, and serves to absorb vibrations, shocks, etc. that occur during back grinding and prevent cracks from occurring in the workpiece. Furthermore, by providing the buffer layer, it is possible to absorb unevenness such as foreign matter present on the table of the supporting device, thereby improving the holding ability of the adhesive sheet by the supporting device.

[0057] (Buffer layer forming composition) The buffer layer can be formed from a buffer layer-forming composition. From the viewpoint of obtaining physical properties suitable for a buffer layer, the buffer layer is preferably a layer obtained by curing, with energy rays, a buffer layer-forming composition containing an energy ray-polymerizable compound. The buffer layer forming composition preferably contains a urethane (meth)acrylate (a1) as an energy ray polymerizable compound. By containing the urethane (meth)acrylate (a1) in the buffer layer forming composition, the storage modulus of the buffer layer tends to be adjusted to a good range. From the same viewpoint, the buffer layer-forming composition more preferably contains, in addition to the urethane (meth)acrylate (a1), one or more compounds selected from the group consisting of polymerizable compounds (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms and polymerizable compounds (a3) ​​having a functional group, and further preferably contains, in addition to the urethane (meth)acrylate (a1), a polymerizable compound (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms and a polymerizable compound (a3) ​​having a functional group. In this specification, the number of ring atoms refers to the number of atoms constituting the ring itself of a compound having a structure in which atoms are bonded in a ring, and does not include atoms that do not constitute the ring (for example, hydrogen atoms bonded to atoms constituting the ring) and atoms contained in the substituent when the ring is substituted with a substituent.

[0058] [Urethane (meth)acrylate (a1)] The urethane (meth)acrylate (a1) is a compound having a (meth)acryloyl group and a urethane bond, and has the property of being polymerized by irradiation with energy rays. The urethane (meth)acrylate (a1) may be used alone or in combination of two or more kinds.

[0059] The mass average molecular weight (Mw) of the urethane (meth)acrylate (a1) is not particularly limited, but is preferably from 1,000 to 100,000, more preferably from 2,000 to 60,000, and even more preferably from 3,000 to 20,000.

[0060] The number of (meth)acryloyl groups that the urethane (meth)acrylate (a1) has in one molecule is not particularly limited, but is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2.

[0061] The urethane (meth)acrylate (a1) can be obtained, for example, by reacting a polyol compound with a polyisocyanate compound to obtain an isocyanate-terminated urethane prepolymer, and then reacting the resulting prepolymer with a (meth)acrylate having a hydroxy group.

[0062] The polyol compound is not particularly limited as long as it is a compound having two or more hydroxy groups. Specific examples of the polyol compound include alkylene diols, polyether polyols, polyester polyols, polycarbonate polyols, etc. Among these, polyester polyols are preferred. The polyol compound may be any of a difunctional diol, a trifunctional triol, and a polyol having 4 or more functional groups, but a difunctional diol is preferred, and a polyester type diol is more preferred. The polyol compounds may be used alone or in combination of two or more kinds.

[0063] Examples of polyisocyanate compounds include aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, norbornane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and ω,ω'-diisocyanate dimethylcyclohexane; and aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, tolidine diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate. Among these, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred. The polyisocyanate compounds may be used alone or in combination of two or more kinds.

[0064] The (meth)acrylate having a hydroxy group to be reacted with the isocyanate-terminated urethane prepolymer is not particularly limited as long as it is a compound having a hydroxy group and a (meth)acryloyl group in at least one molecule. Examples of (meth)acrylates having a hydroxy group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 5-hydroxycyclooctyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; hydroxyl group-containing (meth)acrylamides such as N-methylol (meth)acrylamide; and reaction products obtained by reacting diglycidyl esters of vinyl alcohol, vinylphenol, and bisphenol A with (meth)acrylic acid; and the like. Among these, hydroxyalkyl (meth)acrylates are preferred, and 2-hydroxyethyl (meth)acrylate is more preferred. The (meth)acrylate having a hydroxy group may be used alone or in combination of two or more kinds.

[0065] The conditions for reacting the isocyanate-terminated urethane prepolymer with the (meth)acrylate having a hydroxy group are not particularly limited, but may be, for example, conditions in which the reaction is carried out at 60 to 100°C for 1 to 4 hours in the presence of an organic solvent, a catalyst, etc., which are added as necessary.

[0066] The content of the urethane (meth)acrylate (a1) in the buffer layer-forming composition is not particularly limited, but is preferably 10 to 70 mass %, more preferably 20 to 60 mass %, and even more preferably 30 to 50 mass %, relative to the total amount (100 mass %) of the active ingredients of the buffer layer-forming composition.

[0067] [Polymerizable compound (a2) having an alicyclic group or heterocyclic group having 6 to 20 ring atoms] When the buffer layer-forming composition contains a polymerizable compound (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms (hereinafter also referred to as "polymerizable compound (a2) having an alicyclic group or a heterocyclic group"), the film-forming property of the buffer layer-forming composition tends to be improved. Examples of atoms forming the ring structure of the heterocyclic group include carbon atoms, nitrogen atoms, oxygen atoms, and sulfur atoms. The polymerizable compound (a2) having an alicyclic group or a heterocyclic group may be used alone or in combination of two or more kinds.

[0068] The polymerizable compound (a2) having an alicyclic group or a heterocyclic group is preferably a compound having a (meth)acryloyl group. The number of (meth)acryloyl groups contained in one molecule of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group is not particularly limited, but is preferably one or more, more preferably one or two, and even more preferably one.

[0069] The alicyclic or heterocyclic group of the polymerizable compound (a2) having an alicyclic or heterocyclic group has 6-20, preferably 6-18, more preferably 6-16, and further preferably 7-12 ring atoms.

[0070] Examples of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group include alicyclic group-containing (meth)acrylates such as isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, cyclohexyl (meth)acrylate, and adamantane (meth)acrylate; heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate; and the like. Among these, alicyclic group-containing (meth)acrylates are preferred, and isobornyl (meth)acrylate is more preferred.

[0071] The content of the polymerizable compound (a2) having an alicyclic group or a heterocyclic group in the buffer layer-forming composition is not particularly limited, but is preferably 10 to 70 mass %, more preferably 20 to 60 mass %, and even more preferably 30 to 50 mass %, relative to the total amount (100 mass %) of the active ingredients of the buffer layer-forming composition.

[0072] [Polymerizable compound (a3) ​​having a functional group] By including the polymerizable compound (a3) ​​having a functional group in the buffer layer forming composition, the viscosity of the buffer layer forming composition tends to be adjusted to an appropriate range. The polymerizable compound (a3) ​​having a functional group may be used alone or in combination of two or more kinds.

[0073] Examples of the functional group contained in the polymerizable compound (a3) ​​having a functional group include a hydroxyl group, an epoxy group, an amide group, and an amino group. The number of functional groups contained in one molecule of the polymerizable compound (a3) ​​having a functional group is 1 or more, preferably 1 to 3, more preferably 1 or 2, and further preferably 1.

[0074] The polymerizable compound (a3) ​​having a functional group is preferably a compound having a (meth)acryloyl group in addition to the functional group. The number of (meth)acryloyl groups that the functional group-containing polymerizable compound (a3) ​​has in one molecule is not particularly limited, but is preferably one or more, more preferably one or two, and even more preferably one.

[0075] Examples of the polymerizable compound (a3) ​​having a functional group include a hydroxyl group-containing polymerizable compound, an epoxy group-containing polymerizable compound, an amide group-containing polymerizable compound, and an amino group-containing polymerizable compound.

[0076] Examples of hydroxyl group-containing polymerizable compounds include hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate; vinyl ether compounds such as hydroxyethyl vinyl ether and hydroxybutyl vinyl ether; and the like.

[0077] Examples of the epoxy group-containing polymerizable compound include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0078] Examples of amide group-containing polymerizable compounds include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, and N-vinylformamide.

[0079] Examples of the amino group-containing polymerizable compound include amino group-containing (meth)acrylates such as primary amino group-containing (meth)acrylates, secondary amino group-containing (meth)acrylates, and tertiary amino group-containing (meth)acrylates.

[0080] Among these, hydroxyl group-containing (meth)acrylates are preferred, and hydroxyl group-containing (meth)acrylates having an aromatic ring, such as 2-hydroxy-3-phenoxypropyl (meth)acrylate, are more preferred.

[0081] The content of the polymerizable compound (a3) ​​having a functional group in the buffer layer-forming composition is not particularly limited, but is preferably 5 to 40 mass %, more preferably 10 to 30 mass %, and even more preferably 15 to 25 mass %, relative to the total amount (100 mass %) of the active ingredients of the buffer layer-forming composition.

[0082] [Other polymerizable compounds] The buffer layer-forming composition may contain other polymerizable compounds in addition to the components (a1) to (a3) ​​as long as the effects of the present invention are not impaired. Examples of other polymerizable compounds include alkyl (meth)acrylates having an alkyl group having 1 to 20 carbon atoms; vinyl compounds such as styrene, N-vinylpyrrolidone, and N-vinylcaprolactam; and the like. The other polymerizable compounds may be used alone or in combination of two or more kinds. The content of other polymerizable compounds in the buffer layer-forming composition is not particularly limited, but is preferably 0 to 20 mass%, more preferably 0 to 10 mass%, and even more preferably 0 to 2 mass%, relative to the total amount (100 mass%) of active ingredients in the buffer layer-forming composition.

[0083] [Photopolymerization initiator] The buffer layer-forming composition containing an energy ray-polymerizable compound preferably further contains a photopolymerization initiator from the viewpoint of reducing the polymerization time and the amount of energy ray irradiation caused by energy ray irradiation. The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0084] Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and further photosensitizers such as amines and quinones. More specifically, examples of the photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. Among these, 1-hydroxycyclohexyl phenyl ketone is preferred.

[0085] The content of the photopolymerization initiator in the composition for forming the buffer layer is not particularly limited, but from the viewpoint of allowing the energy ray curing reaction to proceed uniformly and sufficiently, the content is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.3 to 5 parts by mass relative to 100 parts by mass of the energy ray-polymerizable compound.

[0086] (Other Ingredients) The buffer layer-forming composition may contain other components within the range that does not impair the effects of the present invention. Examples of other components include resin components other than the above-mentioned resins, other additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, and dyes, etc.

[0087] (Young's modulus of the buffer layer) The Young's modulus of the buffer layer at 23° C. is smaller than that of the substrate at 23° C., specifically, preferably less than 1,200 MPa, more preferably less than 1,000 MPa, and even more preferably less than 900 MPa. The Young's modulus of the buffer layer at 23° C. is preferably 50 MPa or more, more preferably 100 MPa or more. When the Young's modulus of the buffer layer at 23°C is equal to or less than the upper limit, the effect of absorbing vibrations, shocks, etc. occurring during back grinding and the retention of the adhesive sheet tend to be improved. Also, when the Young's modulus of the buffer layer at 23°C is equal to or more than the lower limit, the buffer layer tends to be prevented from excessively deforming when the workpiece is processed. The Young's modulus of the buffer layer at 23° C. can be measured in accordance with JIS K 7127:1999 at a test speed of 200 mm / min.

[0088] (Stress relaxation rate of the buffer layer) The stress relaxation rate of the buffer layer is not particularly limited, but is preferably 70 to 100%, more preferably 75 to 100%, and further preferably 78 to 98%. When the stress relaxation rate of the buffer layer is within the above range, the effect of absorbing vibrations, shocks, etc. that occur during back grinding and the retention of the adhesive sheet tend to be improved. The stress relaxation rate of the buffer layer was measured by cutting a 200 μm thick buffer layer into a 15 mm × 140 mm test piece, gripping both ends of the test piece by 20 mm, and stretching it by 10% at 200 mm / min, and measuring the stress A (N / m 2 ), and stress B (N / m 2 ) is calculated using the following formula: Stress relaxation rate (%) = 100 × (AB) / A (%)

[0089] (Thickness of the buffer layer) The thickness of the buffer layer is not particularly limited, but is preferably 5 to 70 μm, more preferably 7 to 50 μm, and further preferably 10 to 40 μm. When the thickness of the buffer layer is equal to or greater than the lower limit, the effect of absorbing vibrations, shocks, etc. that occur during back grinding and the retention of the adhesive sheet tend to be enhanced. Also, when the thickness of the buffer layer is equal to or less than the upper limit, the buffer layer tends to be prevented from being excessively deformed when the workpiece is processed.

[0090] <Adhesive layer> The adhesive layer is a layer provided on the side of the substrate opposite the buffer layer, and is a layer to be attached to the workpiece. The adhesive layer is preferably a layer formed from an energy ray curable adhesive. By forming the adhesive layer from an energy ray curable adhesive, the adhesive layer can provide sufficient adhesion to protect the work surface well before energy ray curing, and the peeling force is reduced after energy ray curing, making it easy to peel off from the work.

[0091] Examples of the energy ray-curable adhesive include the following X-type adhesive composition, Y-type adhesive composition, and XY-type adhesive composition. X-type adhesive composition: an energy ray-curable adhesive composition containing a non-energy ray-curable adhesive resin (hereinafter also referred to as "adhesive resin I") and an energy ray-curable compound other than the adhesive resin. Y-type adhesive composition: an energy ray-curable adhesive composition containing an energy ray-curable adhesive resin (hereinafter also referred to as "adhesive resin II") in which an unsaturated group has been introduced into the side chain of a non-energy ray-curable adhesive resin, and containing no energy ray-curable compound other than the adhesive resin XY-type adhesive composition: an energy ray-curable adhesive composition containing the above-mentioned energy ray-curable adhesive resin II and an energy ray-curable compound other than the adhesive resin. Among these, the energy ray curable adhesive is preferably an XY type adhesive composition. By using an XY type adhesive composition, there is a tendency that the adhesive has sufficient adhesion before curing, while the peel force against the workpiece can be sufficiently reduced after curing.

[0092] The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer may be a layer formed from a non-energy ray-curable pressure-sensitive adhesive that does not cure even when irradiated with energy rays. An example of a non-energy ray-curable pressure-sensitive adhesive is one that contains pressure-sensitive adhesive resin I but does not contain pressure-sensitive adhesive resin II or an energy ray-curable compound.

[0093] Next, each component constituting the pressure-sensitive adhesive layer will be described in more detail. In the following description, the term "adhesive resin" is used to refer to one or both of adhesive resin I and adhesive resin II. In addition, in the following description, when simply referring to an "adhesive composition", this concept includes an X-type adhesive composition, a Y-type adhesive composition, an XY-type adhesive composition, and adhesive compositions other than these.

[0094] Examples of adhesive resins include acrylic resins, urethane resins, rubber resins, silicone resins, etc. Among these, acrylic resins are preferred.

[0095] (Acrylic resin) The acrylic resin preferably contains a structural unit derived from an alkyl (meth)acrylate. The alkyl(meth)acrylate may, for example, be an alkyl(meth)acrylate having an alkyl group with 1 to 20 carbon atoms. The alkyl group in the alkyl (meth)acrylate may be linear or branched.

[0096] From the viewpoint of further improving the adhesive strength of the pressure-sensitive adhesive layer, the acrylic resin preferably contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 4 or more carbon atoms. The structural unit derived from an alkyl (meth)acrylate in which the alkyl group contained in the acrylic resin has 4 or more carbon atoms may be of one type alone or of two or more types. The alkyl group in the alkyl (meth)acrylate having 4 or more carbon atoms preferably has 4-12 carbon atoms, more preferably 4-8 carbon atoms, and further preferably 4-6 carbon atoms. Examples of alkyl(meth)acrylates having an alkyl group with 4 or more carbon atoms include butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, etc. Among these, butyl(meth)acrylate is preferred, and butyl acrylate is more preferred. When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 4 or more carbon atoms, the content thereof in the acrylic resin is preferably 30 to 90 mass %, more preferably 40 to 80 mass %, and even more preferably 45 to 60 mass %, from the viewpoint of further improving the adhesive strength of the pressure-sensitive adhesive layer.

[0097] From the viewpoint of improving the storage modulus G' and adhesive properties of the adhesive layer, it is preferable that the acrylic resin contains a structural unit derived from an alkyl(meth)acrylate having an alkyl group with 4 or more carbon atoms, as well as a structural unit derived from an alkyl(meth)acrylate having an alkyl group with 1 to 3 carbon atoms. The structural unit derived from an alkyl (meth)acrylate in which the alkyl group contains 1 to 3 carbon atoms contained in the acrylic resin may be of one type alone or of two or more types. Examples of alkyl(meth)acrylates having an alkyl group with 1 to 3 carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, isopropyl(meth)acrylate, n-propyl(meth)acrylate, etc. Among these, methyl(meth)acrylate and ethyl(meth)acrylate are preferred, methyl(meth)acrylate is more preferred, and methyl methacrylate is even more preferred. When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate in which the alkyl group has 1 to 3 carbon atoms, the content thereof in the acrylic resin is preferably 1 to 35 mass%, more preferably 5 to 30 mass%, and even more preferably 15 to 25 mass%.

[0098] The acrylic resin preferably further contains a structural unit derived from a functional group-containing monomer. By including a constituent unit derived from a functional group-containing monomer in the acrylic resin, it is possible to introduce a functional group that acts as a crosslinking origin that reacts with a crosslinking agent, or a functional group that reacts with an unsaturated group-containing compound to introduce an unsaturated group into the side chain of the acrylic resin. The structural unit derived from the functional group-containing monomer contained in the acrylic resin may be of one type alone or two or more types.

[0099] Examples of functional group-containing monomers include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, etc. Among these, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are more preferred. Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and the like. Examples of carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids and anhydrides thereof such as fumaric acid, itaconic acid, maleic acid and citraconic acid; and 2-carboxyethyl methacrylate.

[0100] When the acrylic resin contains a structural unit derived from a functional group-containing monomer, the content thereof in the acrylic resin is not particularly limited, but is preferably 5 to 45 mass %, more preferably 15 to 40 mass %, and even more preferably 25 to 35 mass %.

[0101] In addition to the above-mentioned structural units, the acrylic resin may contain structural units derived from other monomers copolymerizable with the acrylic monomer. The structural unit derived from the other monomer contained in the acrylic resin may be of one type alone or of two or more types. Examples of other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

[0102] The acrylic resin may further include an energy ray-polymerizable unsaturated group introduced therein in order to impart energy ray-curing properties. The unsaturated group can be introduced, for example, by reacting the functional group of the acrylic resin containing a constituent unit derived from a functional group-containing monomer with the reactive substituent reactive with the functional group and the reactive substituent of a compound having an unsaturated group (hereinafter also referred to as "unsaturated group-containing compound"). The unsaturated group-containing compound may be used alone or in combination of two or more kinds. Examples of the unsaturated group contained in the unsaturated group-containing compound include a (meth)acryloyl group, a vinyl group, an allyl group, etc. Among these, a (meth)acryloyl group is preferred. Examples of reactive substituents that the unsaturated group-containing compound has include an isocyanate group and a glycidyl group. Examples of the unsaturated group-containing compound include (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, and glycidyl (meth)acrylate.

[0103] When an acrylic resin containing a constituent unit derived from a functional group-containing monomer is reacted with an unsaturated group-containing compound, the ratio of functional groups reactive with the unsaturated group-containing compound to the total number of functional groups in the acrylic resin is not particularly limited, but is preferably 60 to 98 mol %, more preferably 70 to 95 mol %, and even more preferably 80 to 93 mol %. When the ratio of functional groups that react with the unsaturated group-containing compound is within the above range, sufficient energy ray curability can be imparted to the acrylic resin, and the functional groups that have not reacted with the unsaturated group-containing compound can be reacted with a crosslinking agent to crosslink the acrylic resin.

[0104] The mass average molecular weight (Mw) of the acrylic resin is not particularly limited, but is preferably 300,000 to 1,500,000, more preferably 350,000 to 1,000,000, and further preferably 400,000 to 600,000. When the mass average molecular weight (Mw) of the acrylic resin is within the above range, the adhesive strength and cohesive strength of the pressure-sensitive adhesive layer tend to be better.

[0105] (Energy ray curable compound) The energy ray-curable compound contained in the X-type or XY-type pressure-sensitive adhesive composition is preferably a monomer or oligomer having an unsaturated group in the molecule and capable of being cured by irradiation with energy rays. Examples of the energy ray curable compound include polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate; oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate; etc. Among these, urethane (meth)acrylate oligomers are preferred from the viewpoint of having a relatively high molecular weight and being less likely to reduce the elastic modulus of the pressure-sensitive adhesive layer.

[0106] The molecular weight of the energy ray-curable compound is not particularly limited, but is preferably 100 to 12,000, more preferably 200 to 10,000, even more preferably 400 to 8,000, and still more preferably 600 to 6,000. When the energy ray-curable compound is an oligomer, the above molecular weight means the mass average molecular weight (Mw).

[0107] The content of the energy ray curable compound in the X-type adhesive composition is not particularly limited, but is preferably 40 to 200 parts by mass, more preferably 50 to 150 parts by mass, and even more preferably 60 to 90 parts by mass, relative to 100 parts by mass of the adhesive resin. When the content of the energy ray-curable compound in the X-type pressure-sensitive adhesive composition is within the above range, the balance between the adhesive strength before energy ray irradiation and the releasability after energy ray irradiation tends to be good.

[0108] The content of the energy ray-curable compound in the XY-type pressure-sensitive adhesive composition is not particularly limited, but is preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, and even more preferably 3 to 15 parts by mass, relative to 100 parts by mass of the pressure-sensitive adhesive resin. When the content of the energy ray curable compound in the XY type pressure-sensitive adhesive composition is within the above range, the balance between the adhesive strength before the energy ray irradiation and the peelability after the energy ray irradiation tends to be good. Note that, since the adhesive resin in the XY type pressure-sensitive adhesive composition is energy ray curable, even if the content of the energy ray curable compound is small, the peel strength after the energy ray irradiation tends to be sufficiently reduced.

[0109] (Crosslinking agent) The pressure-sensitive adhesive composition preferably further contains a crosslinking agent. The crosslinking agent crosslinks the adhesive resins together by reacting with a functional group derived from a functional group-containing monomer contained in the adhesive resin, for example. The crosslinking agent may be used alone or in combination of two or more kinds.

[0110] Examples of the crosslinking agent include isocyanate-based crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, and adducts thereof, epoxy-based crosslinking agents such as ethylene glycol glycidyl ether, aziridine-based crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphatriazine, and chelate-based crosslinking agents such as aluminum chelate. Among these, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing the cohesive force to further improve the adhesive force and of easy availability.

[0111] When the pressure-sensitive adhesive composition contains a crosslinking agent, the content is not particularly limited, but from the viewpoint of allowing the crosslinking reaction to proceed appropriately, the content is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 4 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin.

[0112] (Photopolymerization initiator) When the pressure-sensitive adhesive is an energy ray-curable pressure-sensitive adhesive, the pressure-sensitive adhesive composition preferably further contains a photopolymerization initiator. By containing the photopolymerization initiator in the energy ray-curable pressure-sensitive adhesive, the curing reaction of the energy ray-curable pressure-sensitive adhesive tends to proceed sufficiently even with relatively low-energy energy rays such as ultraviolet rays. The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0113] Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphinoxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and further photosensitizers such as amines and quinones. More specific examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0114] When the pressure-sensitive adhesive composition contains a photopolymerization initiator, the content thereof is not particularly limited, but from the viewpoint of allowing the energy ray curing reaction to proceed uniformly and sufficiently, it is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass relative to 100 parts by mass of the pressure-sensitive adhesive resin.

[0115] (Other additives) The pressure-sensitive adhesive composition may contain other additives within the range that does not impair the effects of the present invention. Examples of other additives include antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, dyes, etc.

[0116] (Organic solvent) The pressure-sensitive adhesive composition may be in the form of a solution by diluting it with an organic solvent, from the viewpoint of further improving the coatability onto a substrate, a release sheet, or the like. Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexane, n-hexane, toluene, xylene, n-propanol, and isopropanol. The organic solvent may be used alone or in combination of two or more kinds. The organic solvent may be the same as that used during synthesis of the adhesive resin, or one or more organic solvents other than the organic solvent used during synthesis may be added.

[0117] The storage modulus G' of the pressure-sensitive adhesive layer at 23° C. is not particularly limited, but is preferably from 0.05 to 0.5 MPa, more preferably from 0.1 to 0.4 MPa, and even more preferably from 0.12 to 0.3 MPa. When the storage modulus G' of the adhesive layer at 23°C is within the above range, even if the workpiece surface is uneven, an adhesive layer with excellent conformability to the uneven shape is obtained, and the surface of the workpiece tends to be better protected during processing. When the pressure-sensitive adhesive layer is formed from an energy ray-curable pressure-sensitive adhesive, the storage modulus G' of the pressure-sensitive adhesive layer means the storage modulus G' before curing by irradiation with energy rays. The storage modulus G' of the adhesive layer at 23°C can be measured by a torsional shear method using a viscoelasticity measuring device at a frequency of 1 Hz and a measurement temperature of 23°C, using a 3 mm thick adhesive layer cut into a circular specimen with a diameter of 8 mm.

[0118] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 80 μm, and even more preferably 15 to 60 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, excellent adhesion is obtained, and the surface of the workpiece tends to be better protected during processing. Also, when the thickness of the adhesive layer is equal to or less than the upper limit, the generation of tape waste during cutting of the adhesive sheet is suppressed, and damage to the workpiece tends to be better prevented.

[0119] <Base material> Examples of the substrate include various resin films. Examples of the resin constituting the resin film include polyethylene such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE); polyolefin such as polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-norbornene copolymer, and norbornene resin; ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, and ethylene-(meth)acrylic acid ester copolymer; polyvinyl chloride such as polyvinyl chloride and vinyl chloride copolymer; polyester such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and wholly aromatic polyester; polyurethane, polyimide, polyamide, polycarbonate, fluororesin, polyacetal, modified polyphenylene oxide, polyphenylene sulfide, polysulfone, polyether ketone, and acrylic polymer; and the like. The substrate may be a single-layer film of a resin film made of one or more resins selected from these resins, or a laminate film of two or more of these resin films laminated together, or a modified film such as a crosslinked film or ionomer film of the above resin. Among these resin films, the substrate is preferably one or more selected from polyester film, polyamide film, polyimide film, and biaxially oriented polypropylene film, more preferably polyester film, and further preferably polyethylene terephthalate film.

[0120] The Young's modulus of the substrate is not particularly limited, but is preferably 1,000 MPa or more, more preferably 1,800 to 30,000 MPa, and even more preferably 2,500 to 6,000 MPa. When the Young's modulus of the substrate is equal to or greater than the lower limit, the vibration suppression effect during processing of the workpiece tends to be improved, whereas when the Young's modulus of the substrate is equal to or less than the upper limit, the workability when attaching the substrate to the workpiece and the workability when peeling the substrate from the workpiece tend to be improved. The Young's modulus of the substrate can be measured in accordance with JIS K 7127:1999 at a test speed of 200 mm / min.

[0121] The thickness of the substrate is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 100 μm, and further preferably 30 to 70 μm. When the thickness of the substrate is equal to or greater than the lower limit, the substrate tends to have sufficient strength to function as a support for the PSA sheet, whereas when the thickness of the substrate is equal to or less than the upper limit, the substrate tends to have appropriate flexibility and improve handleability. The "thickness of the substrate" means the thickness of the entire substrate, and when the substrate is a substrate made of multiple layers, means the total thickness of all layers constituting the substrate.

[0122] The substrate may contain a plasticizer, a lubricant, an infrared absorbing agent, an ultraviolet absorbing agent, a filler, a colorant, an antistatic agent, an antioxidant, a catalyst, and the like, as long as the effects of the present invention are not impaired. The substrate may be transparent or opaque and may be pigmented or vapor deposited as desired. From the viewpoint of improving adhesion to other layers, the substrate may be one that has been subjected to a surface treatment such as a corona treatment on at least one side, or may be provided with a coating layer for the purpose of improving adhesion.

[0123] <Release sheet> The pressure-sensitive adhesive sheet of the present embodiment may have a release sheet attached to at least one of the surface of the pressure-sensitive adhesive layer and the surface of the surface coating layer. The release sheet is releasably attached to the surface of the pressure-sensitive adhesive sheet before use to protect the surface, and is peeled off and removed when the pressure-sensitive adhesive sheet is used. The release sheet may be a release sheet which has been treated for release on one side, or may be a release sheet which has been treated for release on both sides. A preferred example of the release sheet is a release sheet in which a release agent is applied to a release sheet substrate. The release sheet substrate is preferably a resin film, and examples of the resin film include polyester films such as polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film; polyolefin films such as polypropylene film and polyethylene film; and the like. Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins; long-chain alkyl-based resins, alkyd-based resins, and fluorine-based resins. The thickness of the release sheet is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 100 μm, and even more preferably 20 to 50 μm.

[0124] <Total thickness of adhesive sheet> The total thickness of the pressure-sensitive adhesive sheet of the present embodiment is not particularly limited, but is preferably 30 to 300 μm, more preferably 40 to 220 μm, and even more preferably 45 to 160 μm. When the total thickness of the adhesive sheet is equal to or greater than the lower limit, the adhesive performance of the adhesive layer and the shock absorbing performance of the buffer layer are appropriately maintained, and the adhesive sheet tends to be able to fully function as an adhesive sheet for processing a workpiece. Also, when the total thickness of the adhesive sheet is equal to or less than the upper limit, the peeling force required to peel the workpiece from the adhesive sheet tends to be small. In this embodiment, the "total thickness of the adhesive sheet" means the thickness from the surface of the surface coating layer of the adhesive sheet to the surface of the adhesive layer, and when a release sheet is provided, the thickness of the release sheet is not included in the total thickness.

[0125] <Method of manufacturing adhesive sheet> The method for producing the pressure-sensitive adhesive sheet of the present embodiment is not particularly limited, and the sheet can be produced by a known method. The pressure-sensitive adhesive sheet of the present embodiment can be manufactured, for example, by a method including a step of forming a pressure-sensitive adhesive layer on one side of a substrate (hereinafter also referred to as a "pressure-sensitive adhesive layer forming step"), a step of forming a buffer layer on the other side of the substrate (hereinafter also referred to as a "buffer layer forming step"), and a step of forming a surface coat layer on the side of the buffer layer opposite the substrate (hereinafter also referred to as a "surface coat layer forming step"). The order of these steps is not particularly limited, and when they can be performed simultaneously, they may be performed simultaneously.

[0126] Examples of methods for forming the adhesive layer, the buffer layer, or the surface coating layer include a method in which an adhesive composition, a composition for forming a buffer layer, or a composition for forming a surface coating layer is applied to a predetermined position by a known method, and then, if necessary, energy ray irradiation, heating and drying, etc. are performed.

[0127] Examples of methods for applying the pressure-sensitive adhesive composition, the composition for forming a buffer layer, or the composition for forming a surface coating layer include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0128] The pressure-sensitive adhesive layer forming step may be, for example, a method in which a pressure-sensitive adhesive layer formed on a release sheet is bonded to the surface of a substrate, or a method in which a pressure-sensitive adhesive layer is formed by directly applying a pressure-sensitive adhesive composition to the surface of a substrate. In the buffer layer forming step, the buffer layer forming composition may be applied onto a release sheet, or may be applied directly onto the surface of the substrate. When the buffer layer forming composition is applied onto a release sheet, a layer formed from the buffer layer forming composition on the release sheet (hereinafter also referred to as "buffer layer forming composition layer") is then attached to the surface of the substrate. The buffer layer forming composition layer on the release sheet may be the buffer layer itself, or when the buffer layer forming composition has curing properties, it may be an uncured or semi-cured product of the buffer layer forming composition having curing properties. When the buffer layer forming composition has an uncured or semi-cured product formed on the substrate, the buffer layer forming composition is then subjected to a treatment for completely curing.

[0129] In the surface coating layer forming step, the composition for forming the surface coating layer may be applied onto a release sheet, or may be applied directly onto the surface of the buffer layer. The drying temperature after application of the composition for forming a surface coating layer is preferably 105 to 150°C, more preferably 110 to 140°C, and even more preferably 115 to 130°C, from the viewpoints of productivity and quality stability of the pressure-sensitive adhesive sheet. Furthermore, the drying time after application of the composition for forming a surface coating layer is preferably 0.1 to 60 minutes, more preferably 0.3 to 30 minutes, and even more preferably 0.5 to 5 minutes, from the viewpoints of productivity and quality stability of the pressure-sensitive adhesive sheet.

[0130] When the surface coat layer forming composition is applied onto a release sheet, a layer formed from the surface coat layer forming composition on the release sheet (hereinafter also referred to as "surface coat layer forming composition layer") is then attached to the surface of the buffer layer. The surface coat layer forming composition layer on the release sheet may be the surface coat layer itself, or when the surface coat layer forming composition is curable, it may be an uncured or semi-cured product of the surface coat layer forming composition having curability. When the surface coat layer forming composition is formed on the buffer layer with an uncured or semi-cured product, the surface coat layer forming composition is then subjected to a treatment for completely curing.

[0131] The buffer layer forming step and the surface coat layer forming step may be a method in which the surface coat layer and the buffer layer are provided in this order on a release sheet, and then the buffer layer is attached to the surface of the substrate.

[0132] When the buffer layer forming composition contains an energy ray-polymerizable compound, the buffer layer forming step preferably includes a step of irradiating the buffer layer forming composition with energy rays. When the buffer layer-forming composition contains an energy ray-polymerizable compound, the curing treatment by energy ray irradiation may be carried out once or may be carried out in a plurality of separate steps. When the curing treatment by energy ray irradiation is carried out in one step, a coating film of the buffer layer-forming composition may be formed on the substrate, and then the buffer layer-forming composition may be completely cured by energy ray irradiation, or the buffer layer-forming composition may be completely cured on a release sheet and then bonded to the substrate. When the composition for forming a surface coating layer is an organic layer containing a resin component and contains an energy ray polymerizable multifunctional compound, the surface coating layer formation process preferably includes a step of forming the surface coating layer by irradiating the composition for forming a surface coating layer containing the above-mentioned resin component, the energy ray polymerizable multifunctional compound, and a photopolymerization initiator with energy rays. The timing of irradiating the composition for forming a surface coating layer with energy rays is not particularly limited, and may be either before or after laminating the composition for forming a surface coating layer onto the buffer layer or the composition layer for forming a buffer layer. When the curing treatment of the buffer layer-forming composition is carried out in a plurality of times, after forming a coating film of the buffer layer-forming composition on the release sheet, the buffer layer-forming composition may not be completely cured on the release sheet, but may be cured to a semi-cured state, and then laminated to the surface coat layer-forming composition layer provided on the release sheet, and then irradiated with energy rays again to completely cure the buffer layer-forming composition. When the surface coat layer-forming composition contains an energy ray-polymerizable polyfunctional compound, the surface coat layer-forming composition may be cured simultaneously by irradiating with energy rays to completely cure the buffer layer-forming composition. The energy rays irradiated in the curing treatment of the buffer layer forming composition and the surface coat layer forming composition are preferably ultraviolet rays. When the buffer layer-forming composition and the surface coating layer-forming composition are irradiated with energy rays to harden them, the buffer layer-forming composition and the surface coating layer-forming composition may be in a state exposed to the outside, but it is preferable to irradiate the energy rays in a state where both sides are covered with a member such as a release sheet or a substrate and are not exposed to the outside.

[0133] <Applications of adhesive sheets> Examples of processing of a workpiece that is performed with the adhesive sheet of this embodiment attached include backgrinding, in which one side of the workpiece is ground with the adhesive sheet attached to the other side, dicing, in which the workpiece is divided into individual pieces with the adhesive sheet attached to one side of the workpiece, transporting the workpiece, picking up the individual pieces of the workpiece, etc. Among these, the adhesive sheet of the present embodiment is suitable for grinding a workpiece, more suitable for back-grinding a workpiece, and even more suitable for back-grinding in which the back surface of the workpiece is ground with the adhesive sheet of the present embodiment attached to the circuit-forming surface of the workpiece. In particular, the adhesive sheet of the present embodiment has the effect of suppressing the occurrence of cracks when thinning the workpiece, and is therefore suitable for processes such as a first dicing method and a stealth first dicing method.

[0134] [Method of manufacturing electronic device] The method for manufacturing an electronic device according to the present embodiment includes the steps of: A step of attaching the adhesive sheet for work processing of this embodiment to a surface of a workpiece with the adhesive layer as an attachment surface; A step of grinding the back surface of the workpiece while the surface coating layer side of the adhesive sheet for workpiece processing attached to the workpiece is fixed by a supporting device; The present invention relates to a method for manufacturing an electronic device, comprising the steps of:

[0135] In addition, the method for manufacturing an electronic device according to the present embodiment includes the steps of: A process for forming a line to be divided is a process a for forming a groove on a surface of a workpiece, or a process b for forming a modified region inside the workpiece from the surface or back surface of the workpiece; After the step a, or before or after the step b, a sheet attachment step of attaching the adhesive sheet for work processing of the present embodiment to the surface of the work with the adhesive layer as an attachment surface; A grinding and singulation process in which the back surface of the workpiece is ground while the surface coating layer side of the adhesive sheet for workpiece processing attached to the workpiece is fixed by a supporting device, and the workpiece is singulated into a plurality of workpiece singulations starting from the grooves or the modified regions; The method for producing an electronic device preferably includes the steps of: Furthermore, the manufacturing method of the electronic device of this embodiment may include a peeling step of peeling the adhesive sheet for work processing of this embodiment from the multiple workpieces after the grinding and singulation step. The method for manufacturing an electronic device having the above step a is a process corresponding to a first dicing method, and the method for manufacturing an electronic device having the above step b is a process corresponding to a stealth first dicing method. Each step of the method for manufacturing an electronic device according to this embodiment will be described in detail below.

[0136] <Division line formation process> The division line forming step is a step a of forming a groove on the surface of the workpiece, or a step b of forming a modified region inside the workpiece from the surface or rear surface of the workpiece.

[0137] Step a is a step of forming grooves on the surface of the workpiece, and is carried out before the adhesive sheet is attached to the surface of the workpiece. The grooves formed on the surface of the workpiece in process a are shallower than the thickness of the workpiece. After process a, the back surface of the workpiece is ground down to the grooves formed in process a, and the workpiece is divided into a plurality of workpiece pieces. Therefore, in process a, the grooves are formed along the dividing lines when the workpiece is divided into individual pieces. The grooves can be formed by dicing using a conventionally known wafer dicing device or the like.

[0138] Step b is a step of forming a modified region inside the workpiece from the front or back surface of the workpiece, and may be performed before or after the adhesive sheet is attached to the front surface of the workpiece. In step b, the modified region is formed inside the workpiece by irradiating a laser focused on the inside of the workpiece. The modified region is a brittle part of the workpiece, and is a region that becomes the starting point for dividing the workpiece when the workpiece becomes thin by back grinding or when a grinding force is applied. Therefore, the modified region is formed along the dividing line when the workpiece is divided into individual pieces. The laser irradiation may be performed from the front side or the back side of the workpiece. When the step b is performed after the sheet attachment step, the workpiece may be irradiated with the laser through the adhesive sheet.

[0139] <Sheet attachment process> The sheet attachment step is a step of attaching an adhesive sheet to the surface of a workpiece with the adhesive layer serving as an attachment surface after step a or before or after step b. The method for attaching the pressure-sensitive adhesive sheet is not particularly limited, and for example, a conventionally known method using a laminator or the like can be applied.

[0140] <Grinding and Slicing Process> The grinding and singulation process is a process in which, while the surface coating layer side of the adhesive sheet attached to the workpiece is fixed by a support device, the back surface of the workpiece is ground to singulate the workpiece into multiple workpieces starting from the groove or the modified area. The workpiece to which the adhesive sheet is attached and in which the grooves or modified regions are formed is fixed on the surface coating layer side of the adhesive sheet by a supporting device. The supporting device is not particularly limited, but is preferably a device that sucks and holds a fixed object such as a chuck table.

[0141] Next, the back surface of the fixed workpiece is ground to separate the workpiece into a plurality of workpiece pieces. In the back grinding, when a groove is formed in the workpiece by the step a, the workpiece is ground at least to a position where the grinding surface reaches the bottom of the groove. By this back grinding, the groove becomes a cut that penetrates the workpiece, and the workpiece is divided by the cut and is divided into individual workpiece pieces. On the other hand, when a modified region is formed on the workpiece by step b, the grinding surface may reach the modified region, but may not reach the modified region strictly. That is, the workpiece may be ground to a position close to the modified region so that the workpiece is destroyed and divided into individual pieces starting from the modified region. For example, the workpiece may be ground to a position close to the modified region without being divided into individual pieces, and then a pick-up tape may be attached to the workpiece and the pick-up tape may be stretched to divide the workpiece into individual pieces.

[0142] The shape of the individual workpieces may be square or an elongated shape such as a rectangle. The thickness of the individual workpieces is not particularly limited, but is preferably 5 to 100 μm, more preferably 7 to 70 μm, and further preferably 10 to 45 μm. The size of the individual workpieces is not particularly limited, but is preferably 50 mm. 2 Less than 30 mm, more preferably 2 Less than 10 mm, more preferably 2 is less than.

[0143] <Peeling process> The peeling step is a step of peeling the adhesive sheet from the plurality of workpiece individual pieces after the grinding and singulation step. When the adhesive layer of the adhesive sheet is formed from an energy ray-curable adhesive, the adhesive is cured by irradiating it with energy rays, reducing the peel strength of the adhesive layer, and then the adhesive sheet is peeled off. A pick-up tape may be used to peel off the adhesive sheet. The pick-up tape is, for example, composed of a substrate and an adhesive sheet having an adhesive layer provided on one surface of the substrate. When using the pick-up tape, first, the pick-up tape is attached to the back side of the individualized workpiece, and the position and direction are adjusted so that the workpiece can be picked up. At this time, it is preferable that the ring frame arranged on the outer periphery of the workpiece is also attached to the pick-up tape, and the outer periphery of the pick-up tape is fixed to the ring frame. Next, the adhesive sheet is peeled off from the multiple workpieces fixed on the pick-up tape. Thereafter, a plurality of workpieces on the pick-up tape may be picked up and fixed onto a substrate or the like to manufacture an electronic device. EXAMPLES

[0144] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Measurement and evaluation methods for various physical properties are as follows.

[0145] [Mass average molecular weight (Mw)] The mass average molecular weight (Mw) was measured using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8220") under the following conditions, and calculated in terms of standard polystyrene. (Measurement conditions) Columns: "TSK guard column HXL-H", "TSK gel GMHXL (x2)", "TSK gel G2000HXL" (all manufactured by Tosoh Corporation) Column temperature: 40℃ Developing solvent: Tetrahydrofuran ·Flow rate: 1.0mL / min

[0146] [Measuring the thickness of adhesive sheets, etc.] The total thickness of the adhesive sheet, the thickness of each layer, and the thickness of the test piece made from these were measured using a constant pressure thickness measuring device (manufactured by Techclock Corporation, product name "PG-02") At this time, measurements were taken at 10 random points, and the average value was calculated. The total thickness of the adhesive sheet is determined by measuring the thickness of the adhesive sheet with a release sheet and subtracting the thickness of the release sheet from the measured thickness. The thickness of the buffer layer is the thickness of the substrate with the buffer layer subtracted by the thickness of the substrate. The thickness of the surface coating layer is the thickness of the surface coating layer with the release sheet subtracted by the thickness of the release sheet. The thickness of the pressure-sensitive adhesive layer is the total thickness of the pressure-sensitive adhesive sheet minus the thicknesses of the surface coating layer, the buffer layer and the substrate.

[0147] [Measurement of diiodomethane contact angle of surface coating layer] The diiodomethane contact angle of the surface coating layer was measured in accordance with JIS R 3257: 1999. Specifically, the release sheet on the surface coating layer side of the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples was peeled off, and diiodomethane was dropped onto the exposed surface of the surface coating layer, and the static contact angle was measured under the following conditions using a fully automatic contact angle measuring meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701"). ·Measurement temperature: 23℃ ·Droplet volume: 2μl ·Measurement time: 1 second after dropping Image analysis method: θ / 2 method

[0148] [Evaluation of the amount of grinding debris attached to the surface coating layer] The adhesive sheets having release sheets on both sides produced in the examples and comparative examples were cut into a size of 5 cm square in plan view, and the release sheet on the surface coating layer side was peeled off to expose the surface coating layer to prepare a test piece. One of the four corners of the test piece was fixed and hung, and immersed in grinding water containing 5 mass% of silicon wafer grinding dust for 10 minutes. The test piece was taken out of the grinding water, left hanging at 23 ° C for 24 hours to dry, and then the surface coating layer of the test piece was visually observed and the amount of grinding dust adhesion was evaluated according to the following criteria. In the following evaluation criteria, the "grinding dust adhesion part" means an island-shaped grinding dust adhesion part formed by drying droplets of grinding water attached to the surface coating layer. A: There is one area on the surface coating layer where grinding chips have adhered, or there is no grinding chips attached to the surface that can be distinguished from the area where grinding chips have adhered. B: There are 2 to 5 areas where grinding chips are attached on the surface coating layer. C: There are six or more locations on the surface coating layer where grinding dust is attached, but the entire surface of the surface coating layer is not covered with grinding dust. D: Grinding debris adheres to the entire surface of the surface coating layer.

[0149] [Preparation of urethane acrylate oligomer for use in buffer layer] Manufacturing Example 1 A bifunctional urethane acrylate oligomer having a mass average molecular weight (Mw) of 5,000 was obtained by reacting a terminal isocyanate urethane prepolymer obtained by reacting a polyester diol with isophorone diisocyanate with 2-hydroxyethyl acrylate.

[0150] [Preparation of energy ray-curable acrylic resin for use in adhesive layer] Manufacturing Example 2 52 parts by mass of n-butyl acrylate, 20 parts by mass of methyl methacrylate, and 28 parts by mass of 2-hydroxyethyl acrylate were copolymerized to obtain an acrylic polymer, which was then reacted with 2-methacryloyloxyethyl isocyanate so as to be added to 90 mol% of the total hydroxyl groups of the acrylic polymer, to obtain an energy beam-curable acrylic resin having a mass average molecular weight (Mw) of 500,000.

[0151] [Manufacturing of adhesive sheets] Examples 1 to 4, Comparative Examples 1 to 2 Next, a pressure-sensitive adhesive sheet was produced by the method described below. Note that the amount of each component in the following description all means the amount of active ingredient.

[0152] (1) Preparation of the substrate As a substrate, a polyethylene terephthalate film (Young's modulus: 2,500 MPa) having a thickness of 50 μm was prepared.

[0153] (2) Preparation of the composition for forming the surface coating layer Each component shown in Table 1 was dissolved in toluene so that the active ingredient concentration became 10 mass %, to prepare a composition for forming a surface coating layer.

[0154] (3) Preparation of buffer layer forming composition A composition for forming a buffer layer was prepared by blending 40 parts by mass of the urethane acrylate oligomer obtained in Production Example 1, 40 parts by mass of isobornyl acrylate, 20 parts by mass of 2-hydroxy-3-phenoxypropyl acrylate, 2.0 parts by mass of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and 0.2 parts by mass of a phthalocyanine pigment.

[0155] (4) Preparation of Pressure Sensitive Adhesive Composition A pressure-sensitive adhesive composition was prepared by blending 100 parts by mass of the energy ray-curable acrylic resin obtained in Production Example 2, 6 parts by mass of a multifunctional urethane acrylate (manufactured by Mitsubishi Chemical Corporation, product name "Shikoh UT-4332", mass average molecular weight (Mw) 4,700) as an energy ray-curable compound, 0.375 parts by mass of an isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, product name "Coronate L"), and 1 part by mass of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photopolymerization initiator, and diluting the mixture with an organic solvent.

[0156] (5) Preparation of adhesive sheet The composition for forming a buffer layer obtained above was applied to one surface of the substrate described above so that the thickness of the buffer layer formed would be 20 μm, and then the composition was exposed to light with an illumination intensity of 30 mW / cm 2 , irradiation amount 60mJ / cm 2 The buffer layer-forming composition was semi-cured by irradiating it with ultraviolet light under the conditions of (a) to (c), thereby forming a layer of the buffer layer-forming composition semi-cured on one surface of the substrate. In addition, the composition for forming a surface coating layer obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") using a Mayer bar so that the thickness of the surface coating layer formed was 2 μm, and then the composition was heated and dried at 120°C for 1 minute to form a composition layer for forming a surface coating layer on the release sheet. The layer of the composition for forming a surface coating layer on the release sheet and the layer of the semi-cured composition for forming a buffer layer formed on one side of the substrate were laminated together, and then the laminate was subjected to irradiation with an illuminance of 160 mW / cm 2 , irradiation amount 500mJ / cm2 The buffer layer-forming composition and the surface coat layer-forming composition were cured by irradiating ultraviolet light under the above conditions, thereby obtaining a laminate having a buffer layer and a surface coat layer in this order on one surface of the substrate. In addition, the adhesive composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Corporation, product name "SP-PET381031") so that the thickness after drying was 20 μm, and then the applied film was heated and dried to produce a release sheet with an adhesive layer. The adhesive layer of the release sheet with adhesive layer was attached to the side of the substrate of the laminate on which the buffer layer was not provided, thereby obtaining an adhesive sheet having release sheets on both sides and having a surface coating layer, a buffer layer, a substrate and an adhesive layer in that order.

[0157] Table 1 shows the evaluation results of the pressure-sensitive adhesive sheets obtained in the respective Examples and Comparative Examples.

[0158] [Table 1]

[0159] (Resin component) S2104: Hydrogenated styrene-based thermoplastic elastomer (SEPS), styrene content: 65% by mass, manufactured by Kuraray Co., Ltd., product name "Septon (registered trademark) 2104"

[0160] Energy ray polymerizable polyfunctional compound: mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate, manufactured by Nippon Kayaku Co., Ltd., product name "KAYARAD DPHA" Hydrophobized silica: Amorphous precipitated silica that has been hydrophobized.

[0161] (Photopolymerization initiator) Omnirad 651: 2,2-dimethoxy-2-phenylacetophenone, molecular weight 256.3, from IGM Resins BV Omnirad 907: 2-Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, molecular weight 279.4, from IGM Resins BV Omnirad 127: 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, molecular weight 340.4, from IGM Resins BV Omnirad 1173: 2-hydroxy-2-methyl-1-phenylpropanone, molecular weight 164.2, from IGM Resins BV Omnirad 184: 1-Hydroxycyclohexyl-phenyl ketone, molecular weight 204.3, manufactured by IGM Resins BV

[0162] From Table 1, the adhesive sheets of Examples 1 to 4, in which the diiodomethane contact angle of the surface coating layer is 43° or more, had a sufficiently reduced amount of grinding dust adhesion, even though the composition for forming the surface coating layer was dried at high temperature for a short time when forming the surface coating layer. From this result, it can be seen that the adhesive sheet for workpiece processing of this embodiment has excellent productivity and suppresses the amount of grinding dust adhesion. On the other hand, the adhesive sheets of Comparative Examples 1 and 2, in which the diiodomethane contact angle of the surface coating layer is less than 43°, did not sufficiently reduce the amount of grinding dust adhesion.

Claims

1. The film has a surface coating layer, a buffer layer, a substrate, and a pressure-sensitive adhesive layer in this order, The pressure-sensitive adhesive sheet for workpiece processing, wherein the static contact angle of diiodomethane at 23° C. with the surface coating layer is 43° or more.

2. The adhesive sheet for workpiece processing according to claim 1 , wherein the surface coating layer is an organic layer containing a resin component.

3. 3. The adhesive sheet for workpiece processing according to claim 2, wherein the resin component is a polymer of a compound having one or more ethylenically unsaturated bonds.

4. The adhesive sheet for workpiece processing according to claim 3 , wherein the compound having one or more ethylenically unsaturated bonds is a styrene-based compound.

5. The adhesive sheet for workpiece processing according to any one of claims 1 to 4, wherein the surface coating layer has a thickness of 0.05 to 10 µm.

6. The adhesive sheet for workpiece processing according to any one of claims 1 to 4, wherein the buffer layer is a layer formed from a buffer layer-forming composition containing urethane (meth)acrylate.

7. The adhesive sheet for workpiece processing according to any one of claims 1 to 4, which is used for grinding a workpiece.

8. A method for producing the adhesive sheet for workpiece processing according to any one of claims 2 to 4, A method for producing an adhesive sheet for workpiece processing, comprising a step of forming the surface coating layer by irradiating an energy ray to a composition for forming a surface coating layer, the composition containing the resin component, an energy ray-polymerizable multifunctional compound, and a photopolymerization initiator.

9. A step of attaching the adhesive sheet for workpiece processing according to any one of claims 1 to 4 to a surface of a workpiece with the adhesive layer as an attachment surface; A step of grinding the back surface of the workpiece while the surface coating layer side of the adhesive sheet for workpiece processing attached to the workpiece is fixed by a supporting device; A method for manufacturing an electronic device comprising the steps of:

10. A process for forming a line to be divided is a process a for forming a groove on a surface of a workpiece, or a process b for forming a modified region inside the workpiece from the surface or back surface of the workpiece; A sheet attachment step of attaching the adhesive sheet for work processing according to any one of claims 1 to 4 to the surface of the workpiece with the adhesive layer as an attachment surface after the step a, or before or after the step b; A grinding and singulation process in which the back surface of the workpiece is ground while the surface coating layer side of the adhesive sheet for workpiece processing attached to the workpiece is fixed by a supporting device, and the workpiece is singulated into a plurality of workpiece singulations starting from the grooves or the modified regions; A method for manufacturing an electronic device comprising the steps of:

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