Adhesive sheet for workpiece processing, method for manufacturing same, and method for manufacturing electronic device

Abstract

The present invention addresses the problem of providing: an adhesive sheet for workpiece processing, which has excellent productivity and in which the amount of abrasive dust adhering is suppressed; a method for manufacturing the adhesive sheet; and a method for manufacturing an electronic device using the adhesive sheet for workpiece processing. [Solution] The adhesive sheet for workpiece processing has a surface coating layer, a buffer layer, a base material, and an adhesive layer in this order, and has a static contact angle of 43 DEG or more at 23 DEG C of diiodomethane with respect to the surface coating layer, a method for manufacturing the same, and a method for manufacturing an electronic device using the adhesive sheet for workpiece processing.

Description

Technical Field

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

[0002] As information terminal devices are rapidly becoming thinner, smaller, and more multifunctional, electronic devices such as semiconductor devices mounted on these devices are also being required to be thinner and more dense.

[0003] As a method for reducing the thickness of electronic devices, a method of grinding the back side of a workpiece such as a semiconductor wafer used in the electronic device has been developed. The back side grinding of the workpiece is performed by attaching a workpiece processing adhesive sheet for back side grinding (hereinafter also referred to as a "back grinding sheet") to the surface of the workpiece and protecting the surface of the workpiece with the sheet. The back grinding sheet can be peeled off and removed from the surface of the workpiece after back side grinding.

[0004] In recent years, as a method of grinding and singulation that reduces the thickness of the workpiece while suppressing damage to the workpiece, the cutting-first method and the invisible cutting-first method have been put into practical use. The cutting-first method is a method in which a groove of a given depth is formed on the surface of the workpiece by a cutting knife or the like, and then the workpiece is ground from the back side until the groove is reached, thereby singulating the workpiece into a singulated object. In addition, the invisible cutting-first method is a method in which a modified area is formed inside the workpiece by laser irradiation, and then the workpiece is ground from the back side, and the modified area is used as the starting point for segmentation to cut it off, thereby singulating it into a semiconductor chip. In these methods, a back grinding sheet for protecting the surface of the workpiece is also used.

[0005] When back grinding is performed on a workpiece, the back grinding sheet adhered to the workpiece is fixed by a support device such as a chuck table so that the surface opposite to the surface adhered to the workpiece (hereinafter also referred to as "back surface") is fixed. Furthermore, the back surface of the workpiece fixed to the table of the support device via the back grinding sheet is ground while cooling water for removing heat and grinding chips generated by grinding is supplied to the grinding surface.

[0006] When back grinding is performed, if grinding chips exist between the back grinding sheet and the worktable of the support device, cracks may sometimes be generated in the workpiece or the workpiece monolith starting from the portion where the grinding chips exist due to the impact when the workpiece is fixed to the worktable, the pressure and vibration during back grinding, etc. Grinding chips adhere to the back side of the back grinding sheet in a state of being contained in cooling water, so in order to suppress the occurrence of the above-mentioned cracks, it is necessary to reduce the amount of grinding chips adhered to the back side of the back grinding sheet.

[0007] Patent document 1 discloses an adhesive sheet for semiconductor processing that reduces the amount of grinding chips attached and has excellent transportability. The adhesive sheet has a surface coating layer, a buffer layer, a substrate and an adhesive layer in sequence, and the surface coating layer is a layer formed from a surface coating layer forming composition containing an organic silicon compound.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2023-048103 Summary of the invention

[0011] Problems to be solved by the invention

[0012] The adhesive sheet for semiconductor processing of Patent Document 1 can suppress adhesion of grinding chips by providing a surface coating layer on one surface.

[0013] The surface coating layer can be formed by applying a solution obtained by dissolving an active ingredient in an organic solvent on a given component and then drying it. In order to improve the productivity of the adhesive sheet for workpiece processing, it is desired to increase the drying temperature for removing the organic solvent and shorten the drying time. However, according to the research of the present inventors, it has been found that when forming the surface coating layer, if the drying temperature for removing the organic solvent is increased, the amount of grinding shavings attached cannot be fully suppressed. Therefore, it is difficult to improve the productivity of the adhesive sheet for workpiece processing that can fully suppress the amount of grinding shavings attached.

[0014] The present invention has been made in view of the above background, and an object of the present invention is to provide an adhesive sheet for workpiece processing which has excellent productivity and reduces the amount of adhesion of grinding chips, a method for producing the same, and a method for producing an electronic device using the adhesive sheet for workpiece processing.

[0015] Solutions to the problem

[0016] The present inventors have conducted intensive studies and have found that the above-mentioned problems can be solved by an adhesive sheet for workpiece processing having a surface coating layer having a static contact angle of diiodomethane at 23°C of 43° or more, a buffer layer, a substrate and an adhesive layer in sequence, thereby completing the following present invention.

[0017] That is, the present invention relates to the following [1] to

[10] .

[0018] [1] An adhesive sheet for workpiece processing, comprising, in order, a surface coating layer, a buffer layer, a substrate and an adhesive layer,

[0019] The static contact angle of diiodomethane with respect to the surface coating layer at 23° C. is 43° or more.

[0020] [2] The adhesive sheet for workpiece processing according to [1] above, wherein

[0021] The surface coating layer is an organic layer containing a resin component.

[0022] [3] The adhesive sheet for workpiece processing according to [2] above, wherein

[0023] The resin component is a polymer of a compound having one or more ethylenically unsaturated bonds.

[0024] [4] The adhesive sheet for workpiece processing according to [3] above, wherein

[0025] The compound having one or more ethylenically unsaturated bonds is a styrene compound.

[0026] [5] The adhesive sheet for workpiece processing according to any one of [1] to [4] above, wherein

[0027] The thickness of the surface coating layer is 0.05 to 10 μm.

[0028] [6] The adhesive sheet for workpiece processing according to any one of [1] to [5] above, wherein

[0029] The buffer layer is a layer formed from a buffer layer-forming composition containing urethane (meth)acrylate.

[0030] [7] The adhesive sheet for workpiece processing according to any one of [1] to [6] above, which is used for grinding a workpiece.

[0031] [8] A method for producing an adhesive sheet for workpiece processing, which is a method for producing the adhesive sheet for workpiece processing described in any one of [2] to [4] above, the method comprising:

[0032] A step of forming the surface coating layer by irradiating a composition for forming a surface coating layer containing the resin component, an energy-ray-polymerizable polyfunctional compound, and a photopolymerization initiator with energy rays.

[0033] [9] A method for manufacturing an electronic device, the method comprising:

[0034] A step of attaching the pressure-sensitive adhesive sheet for workpiece processing according to any one of [1] to [7] above to a surface of a workpiece with the pressure-sensitive adhesive layer as an attachment surface; and

[0035] A step of grinding the back surface of the workpiece in a state where the surface coating layer side of the workpiece processing pressure-sensitive adhesive sheet adhered to the workpiece is fixed by a supporting device.

[0036]

[10] A method for manufacturing an electronic device, the method comprising:

[0037] a step of forming a planned dividing line, which 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 back surface of the workpiece;

[0038] a sheet sticking step of sticking the workpiece processing adhesive sheet described in any one of [1] to [7] to the surface of the workpiece with the adhesive layer as the sticking surface after the step a or before or after the step b; and

[0039] The grinding and singulation step grinds the back side of the workpiece while the surface coating layer side of the workpiece processing adhesive sheet adhered to the workpiece is fixed by a supporting device, and singulates the workpiece into a plurality of workpiece singulation products starting from the groove or the modified region.

[0040] Effects of the Invention

[0041] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet for processing a workpiece which has excellent productivity and reduces the amount of adhesion of grinding chips, and a method for producing an electronic device using the pressure-sensitive adhesive sheet for processing a workpiece. DETAILED DESCRIPTION

[0042] In this specification, regarding the preferred numerical range, the lower limit and upper limit described in a hierarchical manner can be combined independently. For example, according to the description of "preferably 10 to 90, more preferably 30 to 60", "preferably the lower limit (10)" and "more preferably the upper limit (60)" can be combined to obtain "10 to 60".

[0043] In the present specification, the "active ingredient" refers to the ingredients contained in the target composition excluding the diluent solvent.

[0044] In this specification, for example, "(meth)acrylic acid" means both "acrylic acid" and "methacrylic acid", and the same applies to other similar terms.

[0045] In this specification, "energy ray" means a ray having energy particles in an electromagnetic wave or a charged particle beam, and examples thereof include ultraviolet rays, radiation, electron beams, etc. For example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, etc. can be used as an ultraviolet light source to irradiate ultraviolet rays. As for an electron beam, an electron beam generated by an electron beam accelerator, etc. can be irradiated.

[0046] In this specification, "energy ray polymerizable" means the property of being polymerized by irradiation with energy rays. In addition, "energy ray curable" means the property of being cured by irradiation with energy rays, and "non-energy ray curable" means the property of not being energy ray curable.

[0047] In this specification, the "workpiece" refers to a plate-shaped body that is processed by attaching the pressure-sensitive adhesive sheet for processing a workpiece according to the present embodiment.

[0048] Examples of the workpiece include a wafer, a panel level package, and a tape (long substrate) sealed with a mold resin. Among them, a wafer is preferred because the effects of the present invention can be easily obtained.

[0049] 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, an indium phosphide wafer, or an insulator wafer such as a glass wafer, a lithium tantalate wafer, or a lithium niobate wafer. In addition, a reconstructed wafer formed of a resin and a semiconductor for use in fan-out packaging or the like may also be used. Among them, from the viewpoint of easily obtaining the effects of the present invention, the wafer is preferably a semiconductor wafer or an insulator wafer, more preferably a semiconductor wafer, and even more preferably a silicon wafer.

[0050] Circuits such as wiring, capacitors, diodes, transistors, etc. are generally formed on the surface of a semiconductor wafer. These circuits can be formed by conventionally known methods such as etching and lift-off.

[0051] The thickness of the workpiece before processing is not particularly limited, but is usually 500 to 1000 μm.

[0052] In this specification, "workpiece monolithic object" refers to an object obtained by dividing a workpiece. For example, when the workpiece is a semiconductor wafer, the workpiece monolithic object is a semiconductor chip, and when the workpiece is a strip (long strip substrate) that has been subjected to panel-level packaging or molded resin sealing, the workpiece monolithic object is a semiconductor package.

[0053] In this specification, the term “electronic device” includes, for example, a workpiece, a workpiece singulated product, an electronic component including the workpiece singulated product, and electronic devices including the electronic component.

[0054] In this specification, the “front surface” of a workpiece refers to a surface on which a circuit is formed, and the “rear surface” refers to a surface on which no circuit is formed.

[0055] The mechanism of action described in this specification is a guess, and does not limit the mechanism for achieving the effect of the pressure-sensitive adhesive sheet for workpiece processing of the present invention.

[0056] [Adhesive sheets for workpiece processing]

[0057] 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 substrate and an adhesive layer in sequence, and the static contact angle of diiodomethane with respect to the above-mentioned surface coating layer at 23°C is 43° or more.

[0058] The adhesive sheet of this embodiment is attached to the surface of a workpiece to protect the surface and perform a predetermined process on the workpiece. After the predetermined process is performed on the workpiece, the adhesive sheet of this embodiment is peeled off and removed from the workpiece.

[0059] The adhesive sheet of this embodiment may have layers other than the surface coating layer, the buffer layer, the substrate and the adhesive layer, or may not have these layers. As layers other than the surface coating layer, the buffer layer, the substrate and the adhesive layer, for example, an intermediate layer provided between the substrate and the adhesive layer, a release sheet provided on the side of the adhesive layer opposite to the substrate, etc. may be cited.

[0060] Hereinafter, each member constituting the pressure-sensitive adhesive sheet according to the present embodiment will be described in sequence.

[0061] <Surface coating layer>

[0062] The surface coating layer is a layer provided on the side of the buffer layer opposite to the substrate, and is fixed by a support device when the workpiece is processed.

[0063] (Contact angle of diiodomethane of surface coating layer)

[0064] The static contact angle of diiodomethane at 23° C. with respect to the surface coating layer of the pressure-sensitive adhesive sheet of the present embodiment (hereinafter, also simply referred to as “diiodomethane contact angle”) is 43° or more.

[0065] If the diiodomethane contact angle of the surface coating layer is 43° or more, the amount of grinding debris adhesion can be sufficiently suppressed even if the drying temperature for removing the organic solvent is increased when the surface coating layer is formed. Therefore, the pressure-sensitive adhesive sheet of this embodiment has excellent productivity and the amount of grinding debris adhesion is suppressed.

[0066] From the viewpoint of further reducing the amount of grinding debris adhesion, 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.

[0067] 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.

[0068] The diiodomethane contact angle of the surface coating layer is a value measured in accordance with JIS R 3257:1999, and can be specifically measured by the method described in Examples.

[0069] The surface coating layer of the pressure-sensitive adhesive sheet of the present embodiment may be an inorganic layer or an organic layer, but is preferably an organic layer, more preferably an organic layer containing a resin component, from the viewpoint of productivity and handling of the pressure-sensitive adhesive sheet.

[0070] (Resin component)

[0071] As the resin component, a thermoplastic resin is preferred from the viewpoint of reducing the amount of grinding debris adhesion.

[0072] The resin components may be used alone or in combination of two or more.

[0073] [Thermoplastic resin]

[0074] As the thermoplastic resin, from the viewpoint of further reducing the amount of grinding debris adhesion, a polymer of a compound having one or more ethylenically unsaturated bonds (hereinafter also referred to as “polymer (1)”) is preferred.

[0075] It should be noted that the "ethylenically unsaturated bond" in the present embodiment refers to a carbon-carbon double bond that can undergo an addition reaction, and double bonds of an aromatic ring are not included.

[0076] 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 above the above lower limit, there is a tendency that the amount of grinding dust adhesion can be further reduced.

[0077] The content of the structural unit derived from the compound having one or more ethylenically unsaturated bonds in the polymer (1) may be 100% by mass, but may be 99.5% by mass or less, or 99% by mass or less, for example, in order to contain structural units derived from other monomers.

[0078] Examples of the compound having one or more ethylenically unsaturated bonds include styrene compounds such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, chlorostyrene, and methoxystyrene; chain monoolefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 2-methyl-1-propylene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 5-methyl-1-hexene; and chain non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, and 5-methyl-1,4-hexadiene. olefins (non-conjugated dienes); conjugated dienes (conjugated dienes) such as 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, etc.; cyclic monoolefins such as cyclobutene, cyclopentene, methylcyclopentene, cyclohexene, methylcyclohexene, cycloheptene, cyclooctene, etc.; cyclic dienes such as cyclohexadiene, methylcyclohexadiene, cyclooctadiene, methylcyclooctadiene, phenylcyclooctadiene, etc.; norbornene, dicyclopentadiene, tetracyclododecene, ethyltetracyclododecene, ethylidenetetracyclododecene, tetracyclo[7.4.0.1 10,13 .0 2,7 ] Polycyclic olefins such as tridecan-2,4,6,11-tetraene; monomers having oxygen atoms and ethylenically unsaturated bonds such as maleic anhydride and vinyl acetate; monomers having nitrogen atoms and ethylenically unsaturated bonds such as maleimide compounds and nitrile monomers; etc.

[0079] Among the above options, the polymer (1) preferably 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".

[0080] The content of the structural unit derived from the 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.

[0081] When the content of the structural unit derived from the styrene-based compound in the styrene-based resin is at least the above lower limit, the heat resistance of the surface coating layer tends to be good.

[0082] The content of the structural unit derived from the styrene-based compound 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.

[0083] When the content of the structural unit derived from the styrene compound in the styrene resin is at most the upper limit, the balance between the amount of grinding debris adhesion and the heat resistance tends to be improved by introducing structural units other than the structural unit derived from the styrene compound.

[0084] As structural units other than structural units derived from styrene compounds that may be contained in the styrene resin, for example, structural units derived from compounds other than styrene compounds listed as the above-mentioned compounds having one or more ethylenically unsaturated bonds can be cited. Among them, it is more preferred that the styrene resin contains structural units derived from conjugated dienes.

[0085] The structural unit derived from a conjugated diene refers to a structural unit formed by addition polymerization of the conjugated diene, a structural unit formed by hydrogenating a structural unit formed by addition polymerization of the conjugated diene, and the like.

[0086] Examples of the structural unit formed by hydrogenating the structural unit formed by addition polymerization of the conjugated diene include an ethylene-propylene unit formed by hydrogenating the structural unit formed by addition polymerization of isoprene, and an ethylene-butene unit formed by hydrogenating the structural unit formed by addition polymerization of 1,3-butadiene.

[0087] 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% by mass, more preferably 25 to 45% by mass, and even more preferably 30 to 40% by mass.

[0088] When the content of the structural unit derived from the conjugated diene in the styrene resin is above the above lower limit, there is a tendency to further reduce the amount of grinding shavings attached. In addition, when the content of the structural unit derived from the conjugated diene in the styrene resin is below the above upper limit, there is a tendency that the handling property after the workpiece processing becomes good.

[0089] As the styrene-based resin, from the viewpoint of the amount of grinding chip adhesion and heat resistance, it is preferably one or more selected from styrene-butadiene block copolymers, styrene-ethylene-propylene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylene-butylene-styrene block copolymers (hereinafter also referred to as "SEBS") and styrene-ethylene-propylene-styrene block copolymers (hereinafter also referred to as "SEPS"), and more preferably one or more selected from styrene-ethylene-butylene-styrene block copolymers and styrene-ethylene-propylene-styrene block copolymers.

[0090] 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; and ethylene-maleic anhydride-vinyl acetate copolymers, ethylene-maleic anhydride-(meth)acrylate copolymers, and ethylene-vinyl acetate copolymers. -(meth)acrylate copolymers, propylene-maleic anhydride-vinyl acetate copolymers, propylene-maleic anhydride-(meth)acrylate copolymers, propylene-vinyl acetate-(meth)acrylate copolymers, ethylene-propylene-maleic anhydride copolymers, ethylene-propylene-vinyl acetate copolymers, ethylene-propylene-(meth)acrylate copolymers, ethylene-butene-maleic anhydride copolymers, ethylene-butene-vinyl acetate copolymers, ethylene-butene-(meth)acrylate copolymers, propylene-butene-maleic anhydride copolymers, propylene-butene-vinyl acetate copolymers, propylene-butene-(meth)acrylate copolymers and other multipolymers; and the like.

[0091] The weight 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 further preferably 20,000 to 400,000.

[0092] When the weight average molecular weight (Mw) of the thermoplastic resin is above the above lower limit, there is a tendency that the handling property after workpiece processing becomes better. In addition, when the weight average molecular weight (Mw) of the thermoplastic resin is below the above upper limit, there is a tendency that the solvent solubility of the thermoplastic resin is improved and the formation of the surface coating layer based on coating becomes easy.

[0093] In addition, in this embodiment, the weight average molecular weight (Mw) is a value measured by gel permeation chromatography (GPC) method and is a value measured by the method described in the example.

[0094] The content of the resin component in the surface coating layer is not particularly limited, but is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and even more preferably 45 to 60% by mass relative to the total amount (100% by mass) of the surface coating layer.

[0095] When the content of the resin component is within the above range, there is a tendency that the amount of adhesion of grinding chips can be further reduced.

[0096] (Silica treated with hydrophobic treatment)

[0097] It is preferred that the surface coating layer contains not only the resin component but also hydrophobized silica.

[0098] When the surface coating layer contains hydrophobized silica, the amount of grinding debris adhering to the pressure-sensitive adhesive sheet of the present embodiment tends to be further reduced.

[0099] The hydrophobized silica may be used alone or in combination of two or more.

[0100] Examples of hydrophobized silica include silica obtained by surface-treating raw silica with a hydrophobized treatment agent.

[0101] The raw silica to be hydrophobized can be, for example, wet-process silica manufactured by a wet method such as a precipitation method, a gel method, a sol-gel method, or dry-process silica such as fumed silica and fused silica. Among them, from the viewpoint of easy hydrophobization, wet-process silica is preferred, and precipitated silica is more preferred.

[0102] Examples of the hydrophobizing agent include organic silicon compounds, fatty acids, and fatty acid metal salts.

[0103] The hydrophobizing agent may be used alone or in combination of two or more.

[0104] Examples of methods for surface treating raw silica with a hydrophobizing agent include a method of contacting raw silica with a hydrophobizing agent in a solvent, a method of contacting raw silica with vapor of a hydrophobizing agent carried by a carrier gas such as nitrogen, and a method of directly contacting a stock solution of a hydrophobizing agent with raw silica.

[0105] The shape of the hydrophobized silica is not particularly limited, and examples thereof include spherical shapes and irregular shapes, among which an irregular shape is preferred from the viewpoint of further reducing the amount of grinding debris attached.

[0106] As silica subjected to hydrophobization treatment, for example, “AEROSIL (registered trademark) series” manufactured by Evonik, “QSG series” manufactured by Shin-Etsu Chemical Co., Ltd., “Nipsil (registered trademark) SS series” manufactured by Tosoh Silicon Chemical Co., Ltd., and “SYLOPHOBIC (registered trademark) series” manufactured by Fuji Silysia Chemical Co., Ltd. are commercially available.

[0107] 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, further preferably 30 to 90 parts by mass, and further preferably 50 to 70 parts by mass, relative to 100 parts by mass of the resin component.

[0108] When the content of hydrophobized silicon dioxide is above the lower limit, there is a tendency to further reduce the amount of grinding debris attached. In addition, when the content of hydrophobized silicon dioxide is below the upper limit, there is a tendency to improve the film-forming property of the surface coating layer.

[0109] The surface coating layer may contain components other than the resin component and the hydrophobized silica.

[0110] For example, from the viewpoint of achieving better adhesion with the cushion layer, the surface coating layer is preferably a layer formed by irradiating a composition containing a resin component and an energy-ray-polymerizable polyfunctional compound and a photopolymerization initiator with energy rays.

[0111] In addition, in the following description, the composition for forming a surface coating layer may be referred to as a "surface coating layer-forming composition".

[0112] (Energy beam polymerizable multifunctional compound)

[0113] The energy-ray-polymerizable multifunctional compound is a compound having two or more energy-ray-polymerizable functional groups.

[0114] The energy beam polymerizable multifunctional compound may be used alone or in combination of two or more.

[0115] The number of energy-ray polymerizable functional groups contained in the energy-ray polymerizable polyfunctional compound is preferably 2 to 10, more preferably 3 to 8, and even more preferably 4 to 7.

[0116] As the energy-ray polymerizable functional group which the energy-ray polymerizable polyfunctional compound has, a (meth)acryloyl group is preferable.

[0117] As the energy-ray-polymerizable polyfunctional compound, a polyfunctional (meth)acrylate monomer is preferred.

[0118] Examples of the multifunctional (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, hydroxypivalate neopentyl glycol di(meth)acrylate, dicyclopentyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphoric acid di(meth)acrylate, di(acryloyloxyethyl) isocyanurate, allylated cyclohexyl di(meth)acrylate, and isocyanuric acid ethylene oxide-modified diacrylate; and tris(hydroxymethyl)acrylate. The present invention also includes propylene oxide modified trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, tri(acryloxyethyl)isocyanurate, bis(acryloxyethyl)hydroxyethylisocyanurate, isocyanuric acid ethylene oxide modified triacrylate, ε-caprolactone modified tri(acryloxyethyl)isocyanurate, diglycerol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, propionic acid modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, caprolactone modified dipentaerythritol hexa(meth)acrylate, etc. Among them, dipentaerythritol hexa(meth)acrylate and dipentaerythritol penta(meth)acrylate are preferred, and dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate are more preferred.

[0119] When the surface coating layer forming composition contains an energy ray polymerizable polyfunctional compound, the content of the energy ray polymerizable polyfunctional compound is preferably 10 to 60 parts by mass, more preferably 15 to 50 parts by mass, and further preferably 20 to 40 parts by mass, relative to 100 parts by mass of the resin component.

[0120] When the content of the energy-ray polymerizable multifunctional compound is above the above lower limit, there is a tendency that the adhesion between the surface coating layer and the buffer layer becomes excellent. In addition, when the content of the energy-ray polymerizable multifunctional compound is below the above upper limit, there is a tendency that the balance between the adhesion to the buffer layer and the amount of grinding chips attached is easily improved.

[0121] (Photopolymerization Initiator)

[0122] Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specifically, examples include 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, 2-hydroxy-1-{4-[4-(2-

[0013] The present invention relates to an adhesive sheet for processing a workpiece, wherein the adhesive sheet comprises an alkylene oxide, ...

[0123] The photopolymerization initiator may be used alone or in combination of two or more.

[0124] The molecular weight of the photopolymerization initiator is preferably 255 or more, more preferably 260 or more, further preferably 265 or more, particularly preferably 270 or more.

[0125] When the molecular weight of the photopolymerization initiator is equal to or greater than the above lower limit, the formed surface coating layer tends to have a diiodomethane contact angle of 43° or more, and the adhesive sheet of the present embodiment tends to have a reduced amount of attached grinding dust.

[0126] The molecular weight of the photopolymerization initiator is preferably 400 or less, more preferably 380 or less, and even more preferably 360 or less.

[0127] When the molecular weight of the photopolymerization initiator is not more than the above upper limit, the solubility of the photopolymerization initiator in a solvent is improved, and the surface coating layer-forming composition can be easily prepared.

[0128] When the surface coating layer forming composition contains a photopolymerization initiator, the content thereof is not particularly limited, but is preferably 0.01 to 40 parts by mass, more preferably 0.1 to 30 parts by mass, further 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 multifunctional compound, from the viewpoint of allowing the energy-ray polymerization reaction to proceed uniformly and sufficiently.

[0129] (Other ingredients)

[0130] The surface coating layer may also contain other components other than the above within the scope that does not damage the effect of the present invention. As other components, for example, resins other than the above; additives such as antistatic agents, antioxidants, softeners, fillers, rust inhibitors, pigments, dyes, etc.;

[0131] (Thickness of surface coating layer)

[0132] 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 even more preferably 1 to 4 μm.

[0133] When the thickness of the surface coating layer is above the above lower limit, there is a tendency to form a uniform layer and further reduce the amount of grinding chips attached. In addition, when the thickness of the surface coating layer is below the above upper limit, there is a tendency to easily obtain the effect of the buffer layer such as absorbing the concavo-convex of foreign matter on the chuck worktable.

[0134] <Buffer layer>

[0135] The buffer layer is a layer provided between the substrate and the surface coating layer, and is a layer that absorbs vibrations and impacts generated during back grinding and prevents cracks in the workpiece. Furthermore, by providing the buffer layer, it is also possible to absorb unevenness such as foreign matter present on the worktable of the support device, thereby improving the holding performance of the support device on the adhesive sheet.

[0136] (Composition for forming buffer layer)

[0137] The buffer layer can be formed from a buffer layer-forming composition.

[0138] From the viewpoint of obtaining physical properties suitable for a buffer layer, the buffer layer is preferably a layer formed by energy-ray curing a buffer layer-forming composition containing an energy-ray polymerizable compound.

[0139] The buffer layer-forming composition preferably contains urethane (meth)acrylate (a1) as an energy-beam-polymerizable compound. When the buffer layer-forming composition contains urethane (meth)acrylate (a1), the storage modulus of the buffer layer tends to be adjusted to a good range.

[0140] In addition, from the same point of view, the composition for forming a buffer layer preferably contains, in addition to the carbamate (meth) acrylate (a1), one or more selected from 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, and it is further preferred that, in addition to the carbamate (meth) acrylate (a1), it also contains 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.

[0141] It should be noted that, in this specification, the number of ring atoms refers to the number of atoms constituting the ring itself in a compound having a structure in which atoms are bonded in a ring shape, and atoms not constituting the ring (for example, hydrogen atoms bonded to atoms constituting the ring) and atoms contained in the substituent when the ring is substituted by a substituent are not included in the number of ring atoms.

[0142] [Urethane (meth)acrylate (a1)]

[0143] Urethane (meth)acrylate (a1) is a compound having a (meth)acryloyl group and a urethane bond, and has a property of being polymerized by irradiation with energy rays.

[0144] The urethane (meth)acrylate (a1) may be used alone or in combination of two or more.

[0145] The weight average molecular weight (Mw) of the urethane (meth)acrylate (a1) is not particularly limited, but is preferably 1,000 to 100,000, more preferably 2,000 to 60,000, and even more preferably 3,000 to 20,000.

[0146] The number of (meth)acryloyl groups in one molecule of the urethane (meth)acrylate (a1) is not particularly limited, but is preferably 1 to 4, more preferably 1 to 3, and even more preferably 1 or 2.

[0147] The urethane (meth)acrylate (a1) can be obtained, for example, by reacting a terminal isocyanate urethane prepolymer obtained by reacting a polyol compound with a polyisocyanate compound with a (meth)acrylate having a hydroxyl group.

[0148] The polyol compound is not particularly limited as long as it is a compound having two or more hydroxyl groups.

[0149] Specific examples of the polyol compound include alkylene glycol, polyether polyol, polyester polyol, polycarbonate polyol, etc. Among them, polyester polyol is preferred.

[0150] The polyol compound may be any of a bifunctional diol, a trifunctional triol, and a tetrafunctional or higher polyol, and is preferably a bifunctional diol, and more preferably a polyester diol.

[0151] The polyol compound may be used alone or in combination of two or more.

[0152] Examples of the polyisocyanate compound 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; aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, xylylene diisocyanate, dimethylbiphenyl diisocyanate, tetramethylene xylylene diisocyanate, and naphthalene-1,5-diisocyanate; and the like. Among them, isophorone diisocyanate, hexamethylene diisocyanate, and xylylene diisocyanate are preferred.

[0153] The polyisocyanate compounds may be used alone or in combination of two or more.

[0154] The (meth)acrylate having a hydroxyl group to be reacted with the terminal isocyanate urethane prepolymer is not particularly limited as long as it is a compound having a hydroxyl group and a (meth)acryloyl group in at least one molecule.

[0155] Examples of (meth)acrylates having a hydroxyl 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-phenoxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol mono(meth)acrylate, and polypropylene glycol mono(meth)acrylate; hydroxyl group-containing (meth)acrylamide such as N-methylol (meth)acrylamide; reactants obtained by reacting vinyl alcohol, vinyl phenol, and (meth)acrylic acid with diglycidyl ester of bisphenol A; and the like. Among these, hydroxyalkyl (meth)acrylates are preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.

[0156] The (meth)acrylate having a hydroxyl group may be used alone or in combination of two or more.

[0157] The conditions for reacting the terminal isocyanate urethane prepolymer with the (meth)acrylate having a hydroxyl group are not particularly limited, and for example, the conditions may be set to react at 60 to 100° C. for 1 to 4 hours in the presence of an organic solvent, a catalyst, etc. added as needed.

[0158] The content of the urethane (meth)acrylate (a1) in the buffer layer-forming composition is not particularly limited, but is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 30 to 50% by mass, relative to the total amount (100% by mass) of the active ingredients in the buffer layer-forming composition.

[0159] [Polymerizable compound (a2) having an alicyclic group or a heterocyclic group having 6 to 20 ring atoms]

[0160] When the buffer layer forming composition contains a polymerizable compound (a2) having an alicyclic group or heterocyclic group having 6 to 20 ring atoms (hereinafter also referred to as "polymerizable compound (a2) having an alicyclic group or heterocyclic group"), the film-forming property of the buffer layer forming composition tends to be improved.

[0161] Examples of the atom that forms the ring structure of the heterocyclic group include a carbon atom, a nitrogen atom, an oxygen atom, and a sulfur atom.

[0162] The polymerizable compound (a2) having an alicyclic group or a heterocyclic group may be used alone or in combination of two or more.

[0163] The polymerizable compound (a2) having an alicyclic group or a heterocyclic group is preferably a compound having a (meth)acryloyl group.

[0164] The number of (meth)acryloyl groups 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.

[0165] The polymerizable compound (a2) having an alicyclic group or a heterocyclic group has 6 to 20, preferably 6 to 18, more preferably 6 to 16, and even more preferably 7 to 12 ring atoms in the alicyclic group or the heterocyclic group.

[0166] 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 adamantyl (meth)acrylate; and heterocyclic group-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate. Among them, alicyclic group-containing (meth)acrylates are preferred, and isobornyl (meth)acrylate is more preferred.

[0167] 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% by mass, more preferably 20 to 60% by mass, and further preferably 30 to 50% by mass, relative to the total amount (100% by mass) of the active ingredients of the buffer layer forming composition.

[0168] [Polymerizable compound having a functional group (a3)]

[0169] By making the composition for buffer layer forming contain the polymerizable compound (a3) ​​which has a functional group, the viscosity of the composition for buffer layer forming can be adjusted to an appropriate range.

[0170] The polymerizable compound (a3) ​​having a functional group may be used alone or in combination of two or more.

[0171] Examples of the functional group possessed by the polymerizable compound (a3) ​​having a functional group include a hydroxyl group, an epoxy group, an amide group, and an amino group.

[0172] The number of functional groups contained in the polymerizable compound (a3) ​​having a functional group in one molecule is 1 or more, preferably 1 to 3, more preferably 1 or 2, and even more preferably 1.

[0173] The polymerizable compound (a3) ​​having a functional group is preferably a compound having a (meth)acryloyl group in addition to a functional group.

[0174] The number of (meth)acryloyl groups in one molecule of the polymerizable compound (a3) ​​having a functional group is not particularly limited, but is preferably one or more, more preferably one or two, and even more preferably one.

[0175] 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.

[0176] Examples of the hydroxyl-containing polymerizable compound include hydroxyl-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.

[0177] Examples of the epoxy group-containing polymerizable compound include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

[0178] Examples of the amide group-containing polymerizable compound 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.

[0179] Examples of the amino group-containing polymerizable compound include amino group-containing (meth)acrylates such as primary amino group-containing (meth)acrylate, secondary amino group-containing (meth)acrylate, and tertiary amino group-containing (meth)acrylate.

[0180] Among these compounds, 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.

[0181] 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% by mass, more preferably 10 to 30% by mass, and further preferably 15 to 25% by mass, relative to the total amount (100% by mass) of the active ingredients in the buffer layer forming composition.

[0182] [Other polymerizable compounds]

[0183] The buffer layer-forming composition may contain other polymerizable compounds in addition to the components (a1) to (a3) ​​within a range not impairing the effects of the present invention.

[0184] 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-vinyl pyrrolidone, and N-vinyl caprolactam; and the like.

[0185] The other polymerizable compounds may be used alone or in combination of two or more.

[0186] 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 the active ingredients in the buffer layer forming composition.

[0187] [Photopolymerization initiator]

[0188] From the viewpoint of reducing the polymerization time and energy ray irradiation dose by energy ray irradiation, the buffer layer-forming composition containing an energy ray polymerizable compound preferably further contains a photopolymerization initiator.

[0189] The photopolymerization initiator may be used alone or in combination of two or more.

[0190] Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specifically, examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, diacetyl, 8-chloroanthraquinone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. Among them, 1-hydroxycyclohexyl phenyl ketone is preferred.

[0191] The content of the photopolymerization initiator in the buffer layer forming composition is not particularly limited, but is preferably 0.05 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and still more preferably 0.3 to 5 parts by mass, relative to 100 parts by mass of the energy-ray polymerizable compound, from the viewpoint of making the energy-ray curing reaction uniform and sufficient.

[0192] (Other ingredients)

[0193] The composition for forming a buffer layer may also contain other components within the scope that does not damage the effect 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, dyes, etc.; and the like.

[0194] (Young's modulus of buffer layer)

[0195] The Young's modulus of the buffer layer at 23°C is lower than that of the substrate at 23°C, and specifically, is preferably lower than 1,200 MPa, more preferably lower than 1,000 MPa, and further preferably lower 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.

[0196] When the Young's modulus of the buffer layer at 23°C is below the upper limit, there is a tendency to improve the effect of absorbing vibrations and impacts generated during back grinding and the retention of the adhesive sheet. On the other hand, when the Young's modulus of the buffer layer at 23°C is above the lower limit, there is a tendency to suppress excessive deformation of the buffer layer during processing of the workpiece.

[0197] The Young's modulus of the cushion layer at 23° C. can be measured based on JIS K 7127:1999 under the condition of a test speed of 200 mm / min.

[0198] (Stress relaxation rate of buffer layer)

[0199] The stress relaxation rate of the buffer layer is not particularly limited, but is preferably 70 to 100%, more preferably 75 to 100%, and even more preferably 78 to 98%.

[0200] When the stress relaxation rate of the buffer layer is within the above range, the effect of absorbing vibrations, shocks, etc. generated during back grinding and the retention of the adhesive sheet tend to be improved.

[0201] The stress relaxation rate of the buffer layer was determined as follows: a buffer layer with a thickness of 200 μm was cut into 15 mm × 140 mm pieces and used as test pieces. The stress A (N / m 2 ), and the stress B (N / m 2 ) is calculated by the following formula.

[0202] Stress relaxation rate (%) = 100 × (A-B) / A (%)

[0203] (Thickness of buffer layer)

[0204] The thickness of the buffer layer is not particularly limited, but is preferably 5 to 70 μm, more preferably 7 to 50 μm, and even more preferably 10 to 40 μm.

[0205] When the thickness of the buffer layer is above the lower limit, there is a tendency to improve the effect of absorbing vibrations and impacts generated during back grinding and the retention of the adhesive sheet. In addition, when the thickness of the buffer layer is below the upper limit, there is a tendency to suppress excessive deformation of the buffer layer during processing of the workpiece.

[0206] <Adhesive Layer>

[0207] The adhesive layer is a layer provided on the side of the substrate opposite to the cushion layer, and is a layer to be attached to the workpiece.

[0208] The adhesive layer is preferably a layer formed of an energy-ray curable adhesive. By forming the adhesive layer of an energy-ray curable adhesive, the workpiece surface can be well protected by sufficient adhesion before energy-ray curing, and the peeling force can be reduced after energy-ray curing, thereby achieving easy peeling from the workpiece.

[0209] Examples of the energy-ray-curable adhesive include the following X-type adhesive composition, Y-type adhesive composition, and XY-type adhesive composition.

[0210] 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

[0211] Y-type adhesive composition: An energy-ray-curable adhesive composition containing an energy-ray-curable adhesive resin having an unsaturated group introduced into the side chain of a non-energy-ray-curable adhesive resin (hereinafter also referred to as "adhesive resin II"), and containing no energy-ray-curable compound other than the adhesive resin

[0212] 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

[0213] Among them, 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 adhesiveness is sufficient before curing, and the peeling force with respect to the workpiece can be sufficiently reduced after curing.

[0214] The adhesive forming the adhesive layer may be a layer formed of a non-energy ray-curable adhesive that does not cure even when irradiated with energy rays.

[0215] Examples of the non-energy ray-curable adhesive include an adhesive that contains an adhesive resin I but does not contain an adhesive resin II and an energy ray-curable compound.

[0216] Next, each component constituting the pressure-sensitive adhesive layer will be described in more detail.

[0217] In the following description, the term "adhesive resin" is used as a term meaning one or both of adhesive resin I and adhesive resin II. In addition, in the following description, when simply referred to as "adhesive composition", it is considered to include the concept of X-type adhesive composition, Y-type adhesive composition, XY-type adhesive composition and adhesive compositions other than these.

[0218] Examples of the adhesive resin include acrylic resins, urethane resins, rubber resins, silicone resins, etc. Among them, acrylic resins are preferred.

[0219] (Acrylic resin)

[0220] The acrylic resin preferably contains a structural unit derived from an alkyl (meth)acrylate.

[0221] Examples of the alkyl (meth)acrylate include alkyl (meth)acrylates having an alkyl group with 1 to 20 carbon atoms.

[0222] The alkyl group of the (meth)acrylic acid alkyl ester may be linear or branched.

[0223] 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 having an alkyl group with 4 or more carbon atoms.

[0224] The structural unit derived from an alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms contained in the acrylic resin may be one kind alone or two or more kinds.

[0225] The alkyl (meth)acrylate having 4 or more carbon atoms has an alkyl group having preferably 4 to 12 carbon atoms, more preferably 4 to 8 carbon atoms, and even more preferably 4 to 6 carbon atoms.

[0226] Examples of the (meth)acrylic acid alkyl esters 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, and dodecyl (meth)acrylate. Among them, butyl (meth)acrylate is preferred, and butyl acrylate is more preferred.

[0227] When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate having an alkyl group with 4 or more carbon atoms, the content thereof is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 45 to 60% by mass in the acrylic resin from the viewpoint of further improving the adhesive strength of the pressure-sensitive adhesive layer.

[0228] From the viewpoint of improving the storage modulus G' and adhesive properties of the pressure-sensitive adhesive layer, the acrylic resin preferably contains structural units derived from a (meth)acrylic acid alkyl ester having 4 or more carbon atoms in the alkyl group and structural units derived from a (meth)acrylic acid alkyl ester having 1 to 3 carbon atoms in the alkyl group.

[0229] The structural unit derived from an alkyl (meth)acrylate having an alkyl group with 1 to 3 carbon atoms contained in the acrylic resin may be one kind alone or two or more kinds.

[0230] Examples of the (meth)acrylic acid alkyl esters 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 them, methyl (meth)acrylate and ethyl (meth)acrylate are preferred, methyl (meth)acrylate is more preferred, and methyl methacrylate is further preferred.

[0231] When the acrylic resin contains a structural unit derived from an alkyl (meth)acrylate having 1 to 3 carbon atoms in the alkyl group, the content of the structural unit in the acrylic resin is preferably 1 to 35 mass %, more preferably 5 to 30 mass %, and even more preferably 15 to 25 mass %.

[0232] The acrylic resin preferably further contains a structural unit derived from a functional group-containing monomer.

[0233] By making the acrylic resin contain a structural unit derived from a functional group-containing monomer, a functional group serving as a crosslinking starting point for reacting with a crosslinking agent or a functional group capable of reacting with an unsaturated group-containing compound to introduce an unsaturated group into the side chain of the acrylic resin can be introduced.

[0234] The structural unit derived from the functional group-containing monomer contained in the acrylic resin may be one kind alone or two or more kinds.

[0235] Examples of the functional group-containing monomer include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, etc. Among them, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are more preferred.

[0236] Examples of the hydroxyl-containing monomer 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.

[0237] Examples of the carboxyl group-containing monomer include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid, and citraconic acid, and their anhydrides; and 2-carboxyethyl methacrylate.

[0238] When the acrylic resin contains a structural unit derived from a functional group-containing monomer, the content thereof is not particularly limited, but is preferably 5 to 45% by mass, more preferably 15 to 40% by mass, and further preferably 25 to 35% by mass in the acrylic resin.

[0239] The acrylic resin may contain a structural unit derived from other monomers copolymerizable with the acrylic monomer in addition to the above-mentioned structural units.

[0240] The structural unit derived from other monomers contained in the acrylic resin may be one kind alone or two or more kinds thereof.

[0241] Examples of other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

[0242] In order to further impart energy ray curability, an unsaturated group having energy ray polymerizability may be introduced into the acrylic resin.

[0243] The unsaturated group can be introduced by reacting, for example, a functional group of an acrylic resin containing a structural unit derived from a functional group-containing monomer with a reactive substituent having a reactive substituent with the functional group and a reactive substituent of a compound having an unsaturated group (hereinafter also referred to as an "unsaturated group-containing compound"). The unsaturated group-containing compound may be used alone or in combination of two or more.

[0244] 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 them, a (meth)acryloyl group is preferred.

[0245] Examples of the reactive substituent that the unsaturated group-containing compound has include an isocyanate group and a glycidyl group.

[0246] As an unsaturated group-containing compound, (meth)acryloyloxyethyl isocyanate, (meth)acryloyl isocyanate, glycidyl (meth)acrylate, etc. are mentioned, for example.

[0247] When an acrylic resin containing a structural unit derived from a functional group-containing monomer is reacted with an unsaturated group-containing compound, the ratio of the 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 further preferably 80 to 93 mol %.

[0248] When the ratio of the functional group reactive 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 group that has not reacted with the unsaturated group-containing compound can react with the crosslinking agent to crosslink the acrylic resin.

[0249] The weight 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 even more preferably 400,000 to 600,000.

[0250] When the weight average molecular weight (Mw) of the acrylic resin is within the above range, the adhesive force and cohesive force of the pressure-sensitive adhesive layer tend to be further improved.

[0251] (Energy ray curable compound)

[0252] The energy-ray-curable compound contained in the X-type or XY-type adhesive composition is preferably a monomer or oligomer having an unsaturated group in the molecule and being curable by irradiation with energy rays.

[0253] Examples of the energy-ray curable compound include: poly (meth)acrylate monomers such as trimethylolpropane tri (meth)acrylate, pentaerythritol tetra (meth)acrylate, dipentaerythritol hexa (meth)acrylate, 1,4-butanediol 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 them, urethane (meth)acrylate oligomers are preferred from the viewpoint that the molecular weight is relatively high and the elastic modulus of the adhesive layer is not easily reduced.

[0254] The molecular weight of the energy-beam curable compound is not particularly limited, but is preferably 100 to 12,000, more preferably 200 to 10,000, further preferably 400 to 8,000, and further preferably 600 to 6,000. When the energy-beam curable compound is an oligomer, the molecular weight refers to the weight average molecular weight (Mw).

[0255] 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, based on 100 parts by mass of the adhesive resin.

[0256] 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.

[0257] The content of the energy-ray curable compound in the XY-type 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, based on 100 parts by mass of the adhesive resin.

[0258] When the content of the energy-ray curable compound in the XY-type adhesive composition is within the above range, there is a tendency that the balance between the adhesive force before energy-ray irradiation and the peeling property after energy-ray irradiation becomes good. It should be noted that, since the adhesive resin in the XY-type adhesive composition is energy-ray curable, there is a tendency that the peeling force can be sufficiently reduced after energy-ray irradiation even if the content of the energy-ray curable compound is small.

[0259] (Crosslinking agent)

[0260] The pressure-sensitive adhesive composition preferably further contains a cross-linking agent.

[0261] The crosslinking agent is a component that crosslinks the adhesive resins by reacting with a functional group derived from a functional group-containing monomer contained in the adhesive resin, for example.

[0262] The cross-linking agent may be used alone or in combination of two or more.

[0263] Examples of the crosslinking agent include isocyanate crosslinking agents such as toluene diisocyanate, hexamethylene diisocyanate, and adducts thereof; epoxy crosslinking agents such as ethylene glycol glycidyl ether; aziridine crosslinking agents such as hexa[1-(2-methyl)-aziridinyl]triphosphate triazine; chelate crosslinking agents such as aluminum chelate; etc. Among them, isocyanate crosslinking agents are preferred from the viewpoint of increasing cohesive force and further increasing adhesive force, and from the viewpoint of easy availability.

[0264] When the adhesive composition contains a crosslinking agent, the content thereof is not particularly limited, but 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 adhesive resin, from the viewpoint of allowing the crosslinking reaction to proceed appropriately.

[0265] (Photopolymerization Initiator)

[0266] When the adhesive is an energy-ray curable adhesive, the adhesive composition preferably further contains a photopolymerization initiator. When the energy-ray curable adhesive contains a photopolymerization initiator, there is a tendency that the curing reaction of the energy-ray curable adhesive can be fully carried out even with energy rays with relatively low energy such as ultraviolet rays.

[0267] The photopolymerization initiator may be used alone or in combination of two or more.

[0268] Examples of the photopolymerization initiator include benzoin compounds, acetophenone compounds, acylphosphine oxide compounds, titanocene compounds, thioxanthone compounds, peroxide compounds, and photosensitizers such as amines and quinones. More specifically, examples include 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, diacetyl, 8-chloroanthraquinone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0269] When the adhesive composition contains a photopolymerization initiator, the content thereof is not particularly limited, but 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 adhesive resin from the viewpoint of allowing the energy ray curing reaction to proceed uniformly and sufficiently.

[0270] (Other additives)

[0271] The 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 preventives, pigments, dyes, and the like.

[0272] (Organic Solvent)

[0273] From the viewpoint of further improving the coating properties on a substrate, a release sheet, etc., the pressure-sensitive adhesive composition may be diluted with an organic solvent to be in the form of a solution.

[0274] Examples of the organic solvent include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, Alkane, cyclohexane, n-hexane, toluene, xylene, n-propanol, isopropanol, etc.

[0275] The organic solvent may be used alone or in combination of two or more.

[0276] The organic solvent used in the synthesis of the adhesive resin may be used as it is, or one or more organic solvents other than the organic solvent used in the synthesis may be added.

[0277] The storage modulus G' of the adhesive layer at 23°C is not particularly limited, but is preferably 0.05 to 0.5 MPa, more preferably 0.1 to 0.4 MPa, and further preferably 0.12 to 0.3 MPa.

[0278] When the storage elastic modulus G' of the adhesive layer at 23°C is within the above range, even when the workpiece surface has irregularities, an adhesive layer having excellent conformability to the irregularities can be obtained, and the workpiece surface tends to be more well protected during processing.

[0279] In addition, when the adhesive layer is formed of an energy-ray-curable adhesive, the storage elastic modulus G' of the adhesive layer means the storage elastic modulus G' before being cured by irradiation with energy rays.

[0280] The storage modulus G' of the adhesive layer at 23°C can be measured by cutting a 3 mm thick adhesive layer into a circular piece with a diameter of 8 mm as a test piece and measuring it by a torsional shear method using a viscoelasticity measuring apparatus at a frequency of 1 Hz and a measuring temperature of 23°C.

[0281] 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.

[0282] When the thickness of the adhesive layer is above the lower limit, there is a tendency that excellent adhesion can be obtained and the surface of the workpiece can be better protected during processing. In addition, when the thickness of the adhesive layer is below the upper limit, there is a tendency that the generation of scraps when the adhesive sheet is cut can be suppressed and the damage of the workpiece can be better prevented.

[0283] <Base Material>

[0284] As the substrate, various resin films can be cited, for example. As the resin constituting the resin film, for example, polyethylene such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE); polyolefins such as polypropylene, polybutene, polybutadiene, polymethylpentene, ethylene-norbornene copolymer, and norbornene resin; ethylene copolymers such as 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; polyesters such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and wholly aromatic polyester; polyurethane, polyimide, polyamide, polycarbonate, fluororesin, polyacetal, modified polyphenylene ether, polyphenylene sulfide, polysulfone, polyether ketone, and acrylic polymer; and the like.

[0285] The substrate may be a single layer film of a resin film formed of one or more resins selected from these resins, or a laminated film formed by laminating two or more of these resin films. In addition, it may also be a modified film such as a crosslinked film or ionomer film of the above resins.

[0286] Among these resin films, the substrate is preferably at least one selected from a polyester film, a polyamide film, a polyimide film, and a biaxially oriented polypropylene film, more preferably a polyester film, and still more preferably a polyethylene terephthalate film.

[0287] 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 further preferably 2,500 to 6,000 MPa.

[0288] When the Young's modulus of the substrate is above the above lower limit, there is a tendency that the vibration suppression effect during workpiece processing is further improved. In addition, when the Young's modulus of the substrate is below the above upper limit, there is a tendency that the workability when pasted to the workpiece and the workability when peeled off from the workpiece become good.

[0289] In addition, the Young's modulus of the base material can be measured based on JIS K 7127:1999 under the condition of a test speed of 200 mm / min.

[0290] The thickness of the substrate is not particularly limited, but is preferably 10 to 200 μm, more preferably 25 to 100 μm, and even more preferably 30 to 70 μm.

[0291] When the thickness of the substrate is above the lower limit, there is a tendency to obtain sufficient strength for functioning as a support of the adhesive sheet. In addition, when the thickness of the substrate is below the upper limit, there is a tendency to obtain appropriate flexibility and improve handleability.

[0292] In addition, the "thickness of a substrate" refers to the thickness of the entire substrate, and when the substrate is a substrate composed of multiple layers, it refers to the total thickness of all layers constituting the substrate.

[0293] The base material may contain a plasticizer, a lubricant, an infrared absorber, an ultraviolet absorber, a filler, a colorant, an antistatic agent, an antioxidant, a catalyst, etc. within a range not impairing the effects of the present invention.

[0294] The substrate may be transparent or opaque, and may be colored or vapor-deposited as desired.

[0295] From the viewpoint of improving adhesion with other layers, at least one surface of the substrate may be subjected to a surface treatment such as a corona treatment, or a coating layer may be provided for the purpose of improving adhesion.

[0296] <Peel Sheet>

[0297] The adhesive sheet of this embodiment may have a release sheet attached to at least one of the surface of the adhesive layer and the surface coating layer. The release sheet is attached to the surface of the adhesive sheet before use in a releasable manner to protect the surface, and is peeled off and removed when the adhesive sheet is used.

[0298] The release sheet may be a release sheet subjected to a single-side release treatment or a release sheet subjected to a double-side release treatment.

[0299] Preferred examples of the release sheet include a release sheet obtained by coating a release agent on a release sheet substrate.

[0300] 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; and polyolefin films such as polypropylene film and polyethylene film.

[0301] Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins; long-chain alkyl resins, alkyd resins, and fluorine resins.

[0302] 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.

[0303] <Total Thickness of Adhesive Sheet>

[0304] 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.

[0305] When the total thickness of the adhesive sheet is above the lower limit, the adhesive performance of the adhesive layer and the impact absorption performance of the buffer layer can be appropriately maintained, and the function of the adhesive sheet for workpiece processing can be fully exerted. In addition, when the total thickness of the adhesive sheet is below the upper limit, the peeling force when peeling the workpiece from the adhesive sheet can be reduced.

[0306] It should be noted that in the present embodiment, the “total thickness of the PSA sheet” refers to the thickness from the surface of the surface coating layer of the PSA sheet to the surface of the PSA layer. If a release sheet is provided, the thickness of the release sheet is not included in the total thickness.

[0307] <Method for producing adhesive sheet>

[0308] The pressure-sensitive adhesive sheet of the present embodiment may be produced by any known method without particular limitation.

[0309] The adhesive sheet of the present embodiment can be manufactured, for example, by a method including the following steps: a step of forming an adhesive layer on one side of a substrate (hereinafter, also referred to as an "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 coating layer on the side of the buffer layer opposite to the substrate (hereinafter, also referred to as a "surface coating layer forming step"). It should be noted that the order of these steps is not particularly limited, and they can be implemented simultaneously if they can be implemented simultaneously.

[0310] Examples of methods for forming an adhesive layer, a cushion layer or a surface coating layer include a method in which an adhesive composition, a cushion layer-forming composition or a surface coating layer-forming composition is applied to a predetermined position by a known method and then, if necessary, energy ray irradiation, heat drying or the like is performed.

[0311] Examples of methods for applying the adhesive composition, the buffer layer forming composition or the surface coating layer forming composition include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating and gravure coating.

[0312] The adhesive layer forming step may be, for example, a method of laminating the adhesive layer formed on a release sheet to the surface of a substrate, or a method of forming the adhesive layer by directly applying an adhesive composition on the surface of the substrate.

[0313] In the buffer layer forming process, the buffer layer forming composition can be coated on a release sheet or directly coated on the surface of the substrate. In the case where the buffer layer forming composition is coated on a release sheet, the layer formed by the buffer layer forming composition on the release sheet (hereinafter, also referred to as "buffer layer forming composition layer") is then pasted on the surface of the substrate. The buffer layer forming composition layer on the release sheet can be the buffer layer itself, and in the case where the buffer layer forming composition is a curable composition, it can also be an uncured or semi-cured material of the curable buffer layer forming composition. In the case where an uncured or semi-cured material of the buffer layer forming composition is formed on the substrate, a treatment is subsequently implemented to fully cure the buffer layer forming composition.

[0314] In the surface coating layer forming step, the surface coating layer forming composition may be applied onto a release sheet or may be directly applied onto the surface of the cushion layer.

[0315] From the viewpoint of productivity and quality stability of the pressure-sensitive adhesive sheet, the drying temperature after coating the surface coating layer-forming composition is preferably 105 to 150°C, more preferably 110 to 140°C, and even more preferably 115 to 130°C.

[0316] From the viewpoint of productivity and quality stability of the pressure-sensitive adhesive sheet, the drying time after applying the surface coating layer-forming composition is preferably 0.1 to 60 minutes, more preferably 0.3 to 30 minutes, and even more preferably 0.5 to 5 minutes.

[0317] When the composition for forming a surface coating layer is applied to a release sheet, the layer formed by the composition for forming a surface coating layer on the release sheet (hereinafter, also referred to as "the composition layer for forming a surface coating layer") is then attached to the surface of the buffer layer. The composition layer for forming a surface coating layer on the release sheet may be the surface coating layer itself, or, when the composition for forming a surface coating layer is a curable composition, may be an uncured or semi-cured product of the composition for forming a surface coating layer having curability. When an uncured or semi-cured product of the composition for forming a surface coating layer is formed on the buffer layer, a treatment for completely curing the composition for forming a surface coating layer is subsequently implemented.

[0318] The buffer layer forming step and the surface coating layer forming step may be a method of sequentially providing a surface coating layer and a buffer layer on a release sheet and then bonding the buffer layer to the surface of the substrate.

[0319] 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.

[0320] When the buffer layer-forming composition contains an energy-ray polymerizable compound, the curing treatment by irradiation with energy rays may be performed once or in multiple times.

[0321] When the curing treatment based on energy ray irradiation is performed in a one-time manner, the buffer layer forming composition can be completely cured by irradiating energy rays after a coating film of the buffer layer forming composition is formed on the substrate, or the buffer layer forming composition can be completely cured on a release sheet and then bonded to the substrate.

[0322] The composition for forming a surface coating layer is an organic layer containing a resin component. When it contains an energy-ray polymerizable multifunctional compound, the surface coating layer forming process preferably includes: a process of forming the above-mentioned surface coating layer by irradiating energy rays to the surface coating layer forming composition containing the above-mentioned resin component, the energy-ray polymerizable multifunctional compound and the photopolymerization initiator.

[0323] The timing of irradiating the surface coating layer forming composition with energy rays is not particularly limited, and may be any timing before or after laminating the surface coating layer forming composition on the buffer layer or the buffer layer forming composition layer.

[0324] In the case of curing the buffer layer forming composition in multiple times, after forming a coating film of the buffer layer forming composition on the release sheet, the buffer layer forming composition is not completely cured on the release sheet, but is cured to a semi-cured state and then attached to the surface coating layer forming composition layer provided on the release sheet, and then irradiated with energy rays again, thereby completely curing the buffer layer forming composition. In the case where the surface coating layer forming composition contains an energy ray polymerizable multifunctional compound, energy rays can be irradiated to completely cure the buffer layer forming composition, thereby simultaneously curing the surface coating layer forming composition.

[0325] In addition, as energy rays irradiated in the curing treatment of the buffer layer forming composition and the surface coating layer forming composition, ultraviolet rays are preferable.

[0326] When the buffer layer forming composition and the surface coating layer forming composition are irradiated with energy rays to cure them, the buffer layer forming composition and the surface coating layer forming composition may be in a state of being exposed to the outside, but it is preferred that the energy rays be irradiated in a state where both sides are covered by components such as a release sheet and a substrate and are not exposed to the outside.

[0327] <Application of adhesive sheet>

[0328] Examples of the processing of the workpiece performed with the adhesive sheet of the present embodiment affixed thereto include back grinding for grinding one side of the workpiece with the adhesive sheet affixed to the other side, cutting for singulating the workpiece with the adhesive sheet affixed to one side of the workpiece, conveying of the workpiece, picking up of singulated workpieces, etc.

[0329] Among them, the adhesive sheet of this embodiment is suitable for grinding of workpieces, more suitable for back grinding of workpieces, and further suitable for back grinding of grinding the back of a workpiece while the adhesive sheet of this embodiment is attached to the circuit forming surface of the workpiece. In particular, the adhesive sheet of this embodiment has the effect of suppressing the generation of cracks when the workpiece is thinned, and is therefore suitable for processes such as the first cutting method and the invisible first cutting method.

[0330] [Method for manufacturing electronic device]

[0331] The method for manufacturing an electronic device of this embodiment includes:

[0332] A step of attaching the workpiece processing adhesive sheet of the present embodiment to the surface of the workpiece using the adhesive layer as an attachment surface; and

[0333] A step of grinding the back surface of the workpiece in a state where the surface coating layer side of the workpiece processing pressure-sensitive adhesive sheet adhered to the workpiece is fixed by a supporting device.

[0334] In addition, it is preferred that the method for manufacturing the electronic device of the present embodiment includes:

[0335] a step of forming a planned dividing line, which 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 back surface of the workpiece;

[0336] a sheet sticking step of sticking the workpiece processing adhesive sheet of the present embodiment to the surface of the workpiece with the adhesive layer as a sticking surface after the step a or before or after the step b; and

[0337] The grinding and singulation step grinds the back side of the workpiece while the surface coating layer side of the workpiece processing adhesive sheet adhered to the workpiece is fixed by a supporting device, and singulates the workpiece into a plurality of workpiece singulation products starting from the groove or the modified region.

[0338] Furthermore, the method for manufacturing an electronic device of the present embodiment may include a peeling step of peeling the workpiece processing pressure-sensitive adhesive sheet of the present embodiment from the plurality of workpieces after the grinding and singulation steps.

[0339] It should be noted that the method for manufacturing an electronic device having the above step a is a process equivalent to the pre-cut method, and the method for manufacturing an electronic device having the above step b is a process equivalent to the stealth pre-cut method.

[0340] Hereinafter, each step of the method for manufacturing the electronic device according to the present embodiment will be described in detail.

[0341] <Parting Planned Line Forming Step>

[0342] The planned dividing line forming step is step a of forming a groove on the surface of the workpiece, or step b of forming a modified region inside the workpiece from the surface or back surface of the workpiece.

[0343] Step a is a step of forming grooves on the surface of the workpiece, and is performed before attaching the adhesive sheet to the surface of the workpiece.

[0344] The groove formed on the surface of the workpiece in step a is a groove whose depth is shallower than the thickness of the workpiece. After step a, the workpiece is back-ground to the position of the groove formed in step a, thereby being divided into a plurality of workpiece singulations. Therefore, in step a, the grooves are formed along the dividing lines when the workpiece is divided and singulated.

[0345] The grooves can be formed by dicing using a conventionally known wafer dicing device or the like.

[0346] Step b is a step of forming a modified region inside the workpiece from the surface or back surface of the workpiece, and may be performed before or after the adhesive sheet is attached to the surface of the workpiece.

[0347] In step b, a modified region is formed inside the workpiece by irradiating a laser focused inside the workpiece. The modified region is a portion of the workpiece that has become brittle, and is a region where the workpiece becomes thinner due to back grinding or is damaged due to the force applied by grinding, thereby becoming the starting point for the workpiece to be singulated. Therefore, the modified region is formed along the dividing line when the workpiece is divided and singulated.

[0348] The laser irradiation may be performed from the front side of the workpiece or from the back side. When the step b is performed after the sheet attaching step, the laser irradiation may be performed on the workpiece through the adhesive sheet.

[0349] <Sheet pasting process>

[0350] The sheet sticking step is a step of sticking the adhesive sheet with the adhesive layer as the sticking surface to the surface of the workpiece after step a or before or after step b.

[0351] The method for attaching the pressure-sensitive adhesive sheet is not particularly limited, and a conventionally known method using, for example, a laminator can be employed.

[0352] <Grinding and Singulation Process>

[0353] The grinding and singulation step is a step of grinding the back side of the workpiece while fixing the surface coating layer side of the adhesive sheet adhered to the workpiece by a supporting device, and singulating it into a plurality of workpiece singulation products starting from the above grooves or the above modified regions.

[0354] The workpiece having the adhesive sheet attached thereto and having the grooves or modified regions formed thereon is fixed by a support device on the surface coating layer side of the adhesive sheet. The support device is not particularly limited, but is preferably a device that holds the object by suction, such as a chuck table.

[0355] Next, the back surface of the fixed workpiece is ground to separate the workpiece into a plurality of workpiece separate pieces.

[0356] In the case where a groove is formed in the workpiece by step a, the workpiece is ground at least to a position where the grinding surface reaches the bottom of the groove. By the back grinding, the groove becomes a cut that penetrates the workpiece, and the workpiece is divided and singulated into individual workpiece singulation objects by the cut.

[0357] On the other hand, when a modified region is formed in the workpiece by step b, the grinding surface may reach the modified region, but it may not strictly reach the modified region. That is, it is sufficient to grind to a position close to the modified region so that the workpiece is broken and singulated starting from the modified region. For example, after grinding to a position close to the modified region without singulating the workpiece, a pick-up tape may be attached to the workpiece, and the semiconductor chip may be singulated by stretching the pick-up tape.

[0358] The shape of the singulated workpiece may be a square, or a rectangular or other elongated shape.

[0359] The thickness of the workpiece singulated products after singulation is not particularly limited, but is preferably 5 to 100 μm, more preferably 7 to 70 μm, and even more preferably 10 to 45 μm.

[0360] The size of the workpiece after singulation is not particularly limited, but is preferably less than 50 mm. 2 , more preferably less than 30mm 2 , and preferably less than 10 mm 2 .

[0361] <Peeling process>

[0362] The peeling step is a step of peeling the adhesive sheet from the plurality of workpiece singulation products after the grinding and singulation steps.

[0363] When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is formed of an energy-ray-curable pressure-sensitive adhesive, the pressure-sensitive adhesive is cured by irradiating energy rays to reduce the peeling force of the pressure-sensitive adhesive layer, and then the pressure-sensitive adhesive sheet is peeled.

[0364] In addition, when peeling off the adhesive sheet, you may use a pick-up tape. For example, the pick-up tape can be composed of an adhesive sheet including a substrate and an adhesive layer provided on one side of the substrate.

[0365] When using a pick-up tape, firstly, the pick-up tape is attached to the back side of the workpiece singulation after singulation, and the position and direction are aligned so that it can be picked up. At this time, it is preferred that the annular frame arranged on the outer peripheral side of the workpiece singulation is also attached to the pick-up tape, and the outer peripheral edge of the pick-up tape is fixed to the annular frame. Then, the adhesive sheet is peeled off from the plurality of workpiece singulations fixed on the pick-up tape.

[0366] Then, after picking up the plurality of singulated workpieces on the pickup belt, the singulated workpieces can be fixed on a substrate or the like, thereby manufacturing an electronic device.

[0367] Example

[0368] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods of various physical properties are as follows.

[0369] [Weight average molecular weight (Mw)]

[0370] The weight average molecular weight (Mw) was measured using a gel permeation chromatography apparatus (manufactured by Tosoh Corporation, product name "HLC-8220") under the following conditions and determined by conversion with standard polystyrene.

[0371] (Measurement conditions)

[0372] ·Chromatographic columns: "TSK guard column HXL-H", "TSK gel GMHXL (×2)", "TSK gelG2000HXL" (all manufactured by Tosoh Corporation)

[0373] Column temperature: 40℃

[0374] Elution solvent: tetrahydrofuran

[0375] Flow rate: 1.0mL / min

[0376] [Measurement of thickness of adhesive sheets, etc.]

[0377] The total thickness of the PSA sheet, the thickness of each layer, and the thickness of a test piece prepared therefrom were measured using a constant pressure thickness gauge (manufactured by TECLOCK Co., Ltd., trade name "PG-02"), at which time 10 random points were measured and the average value was calculated.

[0378] The total thickness of the PSA sheet is a value obtained by measuring the thickness of the PSA sheet with a release sheet and subtracting the thickness of the release sheet from the measured thickness.

[0379] The thickness of the buffer layer is a value obtained by subtracting the thickness of the substrate from the thickness of the substrate with the buffer layer.

[0380] The thickness of the surface coating layer is a value obtained by subtracting the thickness of the release sheet from the thickness of the surface coating layer with the release sheet.

[0381] The thickness of the PSA layer is a value obtained by subtracting the thicknesses of the surface coating layer, the cushion layer, and the substrate from the total thickness of the PSA sheet.

[0382] [Measurement of diiodomethane contact angle of surface coating layer]

[0383] The diiodomethane contact angle of the surface coating layer was measured based on JIS R 3257: 1999. Specifically, the release sheet on the surface coating layer side of the pressure-sensitive adhesive sheet produced in the Examples and Comparative Examples was peeled off, and the static contact angle when diiodomethane was dropped onto the surface of the exposed surface coating layer was measured under the following conditions using a fully automatic contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DM-701").

[0384] ·Measurement temperature: 23℃

[0385] Drop volume: 2μl

[0386] ·Measurement time: 1 second after dropping

[0387] Image analysis method: θ / 2 method

[0388] [Evaluation of the amount of grinding debris attached to the surface coating layer]

[0389] The adhesive sheet with release sheets on both sides manufactured in the embodiments and comparative examples was cut into a size of 5 cm square when viewed from above, and the release sheet on the surface coating layer side was peeled off to prepare a test piece in which the surface coating layer was exposed. Any one of the four corners of the test piece was fixed and hung, and immersed in grinding water containing 5% by mass of grinding chips of silicon wafers for 10 minutes. The test piece was taken out of the grinding water, kept hanging and allowed to stand at 23°C for 24 hours to dry, and then the surface coating layer of the test piece was observed with the naked eye, and the amount of grinding chips attached was evaluated according to the following criteria. It should be noted that in the following evaluation criteria, the "grinding chip attachment portion" refers to the island-shaped grinding chip attachment portion formed by drying the droplets of grinding water attached to the surface coating layer.

[0390] A: There is one grinding chip adhesion portion on the surface coating layer, or grinding chips are not adhered to such an extent that the grinding chip adhesion portion can be recognized.

[0391] B: There are 2 to 5 grinding debris adhesion areas on the surface coating layer.

[0392] C: There are 6 or more grinding debris adhering portions on the surface coating layer, but the grinding debris is not adhering to the entire surface of the surface coating layer.

[0393] D: Grinding chips adhere to the entire surface of the surface coating layer.

[0394] [Preparation of urethane acrylate oligomer for buffer layer]

[0395] Production Example 1

[0396] An isocyanate-terminated urethane prepolymer obtained by reacting polyester diol with isophorone diisocyanate and 2-hydroxyethyl acrylate were reacted to obtain a bifunctional urethane acrylate oligomer having a weight average molecular weight (Mw) of 5,000.

[0397] [Preparation of Energy-By-Ray Curable Acrylic Resin for Adhesive Layer]

[0398] Production Example 2

[0399] An acrylic polymer was obtained by copolymerizing 52 parts by mass of n-butyl acrylate, 20 parts by mass of methyl methacrylate, and 28 parts by mass of 2-hydroxyethyl acrylate. Then, 2-methacryloyloxyethyl isocyanate was reacted in a manner such that 90 mol % of the hydroxyl groups in all the hydroxyl groups of the acrylic polymer were added, thereby obtaining an energy-ray-curable acrylic resin having a weight average molecular weight (Mw) of 500,000.

[0400] [Manufacturing of adhesive sheet]

[0401] Examples 1 to 4, Comparative Examples 1 to 2

[0402] Next, a pressure-sensitive adhesive sheet was produced by the following method. It should be noted that the amount of each component in the following description refers to the amount of active ingredient in the composition.

[0403] (1) Preparation of substrate

[0404] As a substrate, a polyethylene terephthalate film (Young's modulus: 2,500 MPa) having a thickness of 50 μm was prepared.

[0405] (2) Preparation of composition for forming surface coating layer

[0406] Each component shown in Table 1 was dissolved in toluene so that the active ingredient concentration became 10 mass %, thereby obtaining a composition for forming a surface coating layer.

[0407] (3) Preparation of buffer layer forming composition

[0408] A buffer layer-forming composition was prepared by mixing 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.

[0409] (4) Preparation of adhesive composition

[0410] An adhesive composition was prepared by mixing 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, trade name "Shikou UT-4332", weight average molecular weight (Mw) 4,700) as an energy-ray-curable compound, 0.375 parts by mass of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate L"), and 1 part by mass of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide as a photopolymerization initiator, and diluting with an organic solvent.

[0411] (5) Preparation of adhesive sheet

[0412] The buffer layer-forming composition obtained above was applied to one side of the substrate so that the thickness of the formed buffer layer was 20 μm, and then the substrate was exposed to light at an illuminance of 30 mW / cm 2 , irradiation dose 60mJ / cm 2 The composition for forming a buffer layer was semi-cured by irradiating the substrate with ultraviolet rays under the conditions of , and a layer in which the composition for forming a buffer layer was semi-cured was formed on one side of the substrate.

[0413] In addition, the surface coating layer forming composition obtained above was applied to the release-treated surface of a release sheet (manufactured by Lintec Co., Ltd., trade name "SP-PET381031") using a Meyer rod so that the thickness of the formed surface coating layer reached 2 μm, and then heated and dried at 120° C. for 1 minute to form a surface coating layer forming composition layer on the release sheet.

[0414] After the surface coating layer-forming composition layer on the release sheet was laminated to a layer formed on one side of the substrate by semi-curing the buffer layer-forming composition, the surface coating layer-forming composition layer was laminated to a layer formed by semi-curing the buffer layer-forming composition. 2 、Irradiation 500mJ / cm 2 The composition for forming a buffer layer and the composition for forming a surface coating layer were cured by irradiating with ultraviolet rays under the conditions of , thereby obtaining a laminate having a buffer layer and a surface coating layer in this order on one side of the substrate.

[0415] The PSA composition obtained above was applied to the release-treated surface of a release sheet (trade name "SP-PET381031" manufactured by Lintec Corporation) to a thickness of 20 μm after drying, and then heated and dried to prepare a release sheet with a PSA layer.

[0416] The adhesive layer of the release sheet with an adhesive layer is attached to the side of the substrate of the laminated body not provided with a cushion layer, thereby obtaining an adhesive sheet having release sheets on both sides and having a surface coating layer, a cushion layer, a substrate and an adhesive layer in this order.

[0417] Table 1 shows the evaluation results of the pressure-sensitive adhesive sheets obtained in each of the Examples and Comparative Examples.

[0418] Table 1

[0419]

[0420] (Resin component)

[0421] S2104: Hydrogenated styrene-based thermoplastic elastomer (SEPS), styrene content: 65% by mass, manufactured by Kuraray Co., Ltd., trade name "SEPTON (registered trademark) 2104"

[0422] Energy-beam-polymerizable multifunctional compound: A mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate, manufactured by Nippon Kayaku Co., Ltd., trade name "KAYARAD DPHA"

[0423] ·Hydrophobic treated silica: Amorphous precipitated silica that has been hydrophobized

[0424] (Photopolymerization Initiator)

[0425] Omnirad 651: 2,2-dimethoxy-2-phenylacetophenone, molecular weight 256.3, manufactured by IGM Resins B.V.

[0426] Omnirad 907: 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, molecular weight 279.4, manufactured by IGM Resins BV

[0427] Omnirad 127: 2-Hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, molecular weight 340.4, manufactured by IGM Resins BV

[0428] Omnirad 1173: 2-Hydroxy-2-methyl-1-phenylpropanone, molecular weight 164.2, manufactured by IGM Resins B.V.

[0429] OmnirAD 184: 1-Hydroxycyclohexylphenylketone, molecular weight 204.3, manufactured by IGM Resins BV

[0430] According to Table 1, for the adhesive sheets of Examples 1 to 4 in which the diiodomethane contact angle of the surface coating layer was 43° or more, the amount of grinding dust adhesion was sufficiently reduced even though the surface coating layer-forming composition was dried at high temperature in a short time when the surface coating layer was formed.

[0431] The workpiece processing adhesive sheet of the embodiment has excellent productivity and reduces the amount of grinding debris attached. 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°, do not sufficiently reduce the amount of grinding debris attached.

Claims

1. An adhesive sheet for workpiece processing, which comprises a surface coating layer, a buffer layer, a substrate and an adhesive layer in sequence, The static contact angle of diiodomethane with respect to the surface coating layer at 23° C. 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. 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 compound.

5. The adhesive sheet for workpiece processing according to any one of claims 1 to 4, wherein The thickness of the surface coating layer is 0.05-10 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 claim 1 , which is used for grinding a workpiece.

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

9. A method for manufacturing an electronic device, the method comprising: A step of attaching the workpiece processing adhesive sheet according to any one of claims 1 to 4 to a surface of a workpiece using the adhesive layer as an adhesive surface; and A step of grinding the back surface of the workpiece in a state where the surface coating layer side of the workpiece processing pressure-sensitive adhesive sheet adhered to the workpiece is fixed by a supporting device.

10. A method for manufacturing an electronic device, the method comprising: a planned dividing line forming step, which is step a of forming a groove on the surface of the workpiece, or step b of forming a modified region inside the workpiece from the surface or back surface of the workpiece; a sheet sticking step of sticking the workpiece processing adhesive sheet according to any one of claims 1 to 4 to the surface of the workpiece with the adhesive layer as a sticking surface after the step a or before or after the step b; and The grinding and singulation step grinds the back side of the workpiece while the surface coating layer side of the workpiece processing adhesive sheet adhered to the workpiece is fixed by a supporting device, and singulates the workpiece into a plurality of workpiece singulation products starting from the groove or the modified region.

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