Expansion method of adhesive sheet

Abstract

The present invention relates to a method for expanding an adhesive sheet, which is an adhesive sheet having a substrate and an adhesive layer, wherein at least one layer of the adhesive sheet is an adhesive sheet containing thermally expandable particles, and the adhesive layer is used as the adhesive surface, and the adhesive sheet is adhered to one side (Wα) of an object (W) to cause it to expand locally, and includes steps 1 and 2.

Description

[Technical Field]

[0001] This invention relates to a method for expanding adhesive sheets. [Previous Technology]

[0002] Adhesive sheets are not only used for semi-permanent fixing of components, but are also used as temporary fixing sheets to temporarily fix components (hereinafter referred to as "attached objects") that will be processed or inspected during the processing or inspection of building materials, interior materials, electronic components, etc. For example, in the manufacturing method of semiconductor devices, semiconductor wafers are processed by back-side grinding, monolithization, etc. However, in order to protect the circuit surface of the semiconductor wafer, these processes are carried out in a state where temporary fixing sheets are adhered to the circuit surface of the semiconductor wafer.

[0003] Temporary fixing sheets typically use a substrate having an adhesive layer and supporting the adhesive layer. The adhesive layer of the temporary fixing sheet is adhered to the object to be bonded, and after specific processing, the temporary fixing sheet is peeled off from the surface of the object to be bonded.

[0004] However, the surface of the object to which the temporary fixing sheet is adhered does not necessarily have to be flat. For example, the temporary fixing sheet may be adhered to a surface with protrusions. When the surface of the object to which the temporary fixing sheet is adhered is not flat, the surface of the substrate side opposite to the adhesive side of the temporary fixing sheet will be affected by the surface shape of the object to which it is adhered, and sometimes it may not be flat.

[0005] For example, in recent years, as a technology for miniaturizing semiconductor device modules, a flip-chip bonding technology has been put into practical use, in which a semiconductor wafer (hereinafter also referred to as "bumped wafer") with a plurality of bumps with a height of about tens to hundreds of μm formed on the circuit surface is back-grinded and monolithically bonded to the wiring substrate.

[0006] When a temporary fixing sheet is attached to the bump forming surface of a wafer with bumps, the portion of the temporary fixing sheet covering the bump expands more than the other portion, resulting in a bump on the substrate side of the substrate opposite to the attachment surface. When this surface with the bump is fixed, and the back side of the semiconductor wafer is ground, the resulting semiconductor wafer has poor thickness uniformity.

[0007] To alleviate the above-mentioned problems, a temporary fixing sheet adhered to a surface with protrusions sometimes has an intermediate layer embedded in the protrusions. Patent Document 1 discloses a temporary fixing tape, which is used for grinding a substrate. It comprises a supporting substrate and an adhesive layer laminated on one side of the supporting substrate. The supporting substrate has a first layer supporting the substrate and a second layer with buffering properties located between the first layer and the adhesive layer. When the substrate, at least one surface with protrusions, is joined to the adhesive layer, the front end of the protrusion penetrates the adhesive layer and is located within the second layer. After irradiation by the energy beam, the adhesive force of the adhesive layer is set to F1 [N / 25mm], and the adhesive force of the second layer is set to F2 [N / 25mm], characterized by satisfying the relationship F1 > F2. [Prior Art Documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-77799 [Summary of the Invention]

[0009] [The problem the invention aims to solve]

[0010] According to the temporary fixing tape of Patent Document 1, the protrusions provided on the surface of the substrate penetrate the adhesive layer and become located in the second layer, which is equivalent to the intermediate layer. In this way, a thin layer of uniform thickness can be formed on the entire substrate in order to apply uniform pressing pressure.

[0011] As described in Patent Document 1, an intermediate layer is formed on a temporary fixing sheet, and the method of embedding the protrusion of the adhered object into the intermediate layer can suppress the tendency for protrusions to occur on the substrate side surface of the temporary fixing sheet. However, for example, when the height of the protrusion is large, or when the area of ​​the protrusion is wide, the method of embedding the protrusion into the intermediate layer alone is sometimes insufficient to suppress the occurrence of protrusions. Furthermore, when improving embedding, the mechanical strength of the intermediate layer decreases, the protection around the protrusion is insufficient, or after peeling, a portion of the intermediate layer adheres to the periphery of the protrusion. In addition, embedding the intermediate layer itself is difficult when the surface of the adhered object is a gently curved surface. To solve these problems, a method is desired that after the adhered object is bonded, the surface shape of the bonded sheet is adjusted to the desired shape, but such a method has not yet been established.

[0012] This invention was made in view of the above-mentioned facts. The object of this invention is to provide a method for expanding an adhesive sheet that, after being adhered to an object, can cause localized expansion. [Means for solving the problem]

[0013] As a result of careful examination, the inventors discovered that by using an adhesive sheet having a substrate and an adhesive layer and by performing specific steps, the above-mentioned problems can be solved, and the following invention is completed.

[0014] That is, the present invention relates to the following [1]~

[13] . [1] An expansion method for an adhesive sheet, comprising an adhesive sheet having a substrate and an adhesive layer, wherein the adhesive sheet contains at least one layer of a thermally expandable layer containing thermally expandable particles, and the adhesive layer is used as the adhesive surface, and is adhered to a surface (Wα) of a substrate (W), thereby causing it to expand locally, and comprising the following steps 1 and 2: Step 1: a step of contacting a cooling material with a region (A) of a portion of the surface (Sα) on the substrate side of the adhesive sheet; Step 2: while the cooling material is in contact with the region (A), by heating the substrate (W) to above the expansion initiation temperature (t) of the thermally expandable particles, the adhesive sheet is heated from the substrate (W) side, and by the cooling effect of the cooling material, the expansion of the portion of the surface of the adhesive sheet having the region (A) is suppressed, while the portion of the surface having the region (A) is expanded. [2] The expansion method of the adhesive sheet as described in [1] above, wherein the thermal conductivity of the aforementioned cooling material at 20°C is 50 W / m·K or higher. [3] The expansion method of the adhesive sheet as described in [1] or [2] above, wherein the aforementioned cooling material is a metal. [4] The expansion method of the adhesive sheet as described in any one of [1] to [3] above, wherein the thickness of the aforementioned cooling material is 100 times or more the thickness of the aforementioned thermally expandable layer. [5] The expansion method of the adhesive sheet as described in any one of [1] to [4] above, wherein the thickness of the aforementioned adhesive layer is 1 to 80 μm. [6] The expansion method of the adhesive sheet as described in any one of [1] to [5] above, wherein the content of the aforementioned thermally expandable particles is 0.05 to 25% by mass relative to the total mass (100% by mass) of the aforementioned thermally expandable layer. [7] The expansion method of the adhesive sheet as described in any of [1] to [6] above, wherein the expansion initiation temperature (t) of the aforementioned thermally expandable particles is 50°C or higher but less than 125°C. [8] The expansion method of the adhesive sheet as described in any of [1] to [7] above, wherein the aforementioned adhesive sheet further has an intermediate layer between the aforementioned substrate and the aforementioned adhesive layer. [9] The expansion method of the adhesive sheet as described in [8] above, wherein the thickness of the aforementioned intermediate layer is 10 to 500 μm.

[10] The expansion method of the adhesive sheet as described in [8] or [9] above, wherein the aforementioned intermediate layer is the aforementioned thermally expandable layer.

[11] The expansion method of the adhesive sheet as described in any of [1] to

[10] above, wherein the aforementioned heating of the aforementioned adhered object (W) in step 2 is performed by heating the side (Wβ) opposite to the aforementioned surface (Wα) of the adhered object (W).

[12] The method for expanding the adhesive sheet as described in any of [1] to

[11] above, wherein the aforementioned adhesive sheet is an adhesive sheet for semiconductor processing and the aforementioned adhered object (W) is a semiconductor wafer.

[13] The method for expanding the adhesive sheet as described in

[12] above, wherein the aforementioned semiconductor wafer is a semiconductor wafer with protrusions. [Effects of the invention].

[0015] According to the present invention, an expansion method can be provided for an adhesive sheet that can be locally expanded after being adhered to an object.

Implementation Method

[0017] [Form of Invention]

[0018] In this specification, the preferred numerical range is described in stages as a lower limit and an upper limit, which can be combined independently. For example, the description "preferably 10~90, more preferably 30~60" can be combined with "preferably lower limit (10)" and "more preferably upper limit (60)" to become "10~60".

[0019] In this specification, for example, "(meth)acrylic acid" means both "acrylic acid" and "methacrylic acid", and so on.

[0020] In this specification, "energy line" refers to a line of electromagnetic waves or charged particles that possesses energy quanta, such as ultraviolet rays, radiation, and electron beams. Ultraviolet rays can be obtained by irradiation using electrodeless lamps, high-pressure mercury lamps, metal halide lamps, UV-LEDs, etc., which serve as ultraviolet light sources. Electron beams can be obtained by irradiation using electron beam accelerators, etc.

[0021] In this specification, "layer" refers to either a "non-thermally expandable layer" or a "thermally expandable layer," as determined below. When the layer being judged contains thermally expandable particles, the layer is heated for 3 minutes at the expansion initiation temperature (t) of the thermally expandable particles. If the volume change rate calculated by the following formula is less than 5%, the layer is judged to be a "non-thermally expandable layer," and if it is 5% or more, the layer is judged to be a "thermally expandable layer." Volume change rate (%) = {(volume of the aforementioned layer after heat treatment - volume of the aforementioned layer before heat treatment) / volume of the aforementioned layer before heat treatment} × 100 Furthermore, a layer that does not contain thermally expandable particles is defined as a "non-thermally expandable layer." In this specification, when the "layer" is a non-thermally expandable layer, the volume change rate (%) of the non-thermally expandable layer calculated by the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and still more preferably less than 0.01%. Furthermore, in this specification, when the "layer" is a non-thermally expandable layer, the non-thermally expandable layer preferably does not contain thermally expandable particles; however, it may contain thermally expandable particles without departing from the purpose of this invention. When the non-thermally expandable layer contains thermally expandable particles, the lower the content, the better. Relative to the total mass (100% by mass) of the non-thermally expandable layer, it is preferably less than 3% by mass, more preferably less than 1% by mass, even more preferably less than 0.1% by mass, even more preferably less than 0.01% by mass, and still more preferably less than 0.001% by mass.

[0022] In this specification, the “circuit side” of a semiconductor wafer refers to the side on which a circuit is formed, and the “back side” of a semiconductor wafer refers to the side on which no circuit is formed.

[0023] In this specification, "semiconductor device" means an entire device that can generate functions by utilizing the characteristics of semiconductors. Examples include wafers with integrated circuits, thinned wafers with integrated circuits, chips with integrated circuits, thinned chips with integrated circuits, electronic components including such chips, and electronic machines having such electronic components.

[0024] In this specification, the thickness of each layer is the thickness at 23°C, which can be measured by the method described in the examples.

[0025] The mechanisms described in this specification are speculative and not limited to the mechanisms that enable the effects of the present invention.

[0026] [Expansion Method of Adhesive Sheet] One aspect of the present invention is an expansion method of an adhesive sheet having a substrate and an adhesive layer. The adhesive sheet contains at least one layer that is a thermally expandable layer containing thermally expandable particles. The adhesive sheet is adhered to one side (Wα) of an object (W) with the aforementioned adhesive layer as the adhesive surface, and then locally expands. The method includes the following steps 1 and 2. Step 1: The step of bringing the cooling material into contact with a portion (A) of the surface (Sα) of the aforementioned substrate side of the adhesive sheet. Step 2: With the cooling material in contact with the aforementioned region (A), the aforementioned adherend (W) is heated to above the expansion initiation temperature (t) of the aforementioned thermally expandable particles, and the aforementioned adhesive sheet is heated from the adherend (W) side. By means of the cooling effect of the aforementioned cooling material, the expansion of the portion of the surface of the aforementioned adhesive sheet having the aforementioned region (A) is suppressed, while the portion of the surface having the aforementioned region (A) is expanded.

[0027] Hereinafter, the adhesive sheet used in the expansion method of the adhesive sheet of the present invention will be described first, and then the steps included in the expansion method of the adhesive sheet of the present invention will be described in detail.

[0028] <Adhesive Sheet> One embodiment of the adhesive sheet of the present invention is an adhesive sheet having a substrate and an adhesive layer, wherein at least one layer of the adhesive sheet is a thermally expandable layer containing thermally expandable particles. One embodiment of the adhesive sheet of the present invention is adhered to one side (Wα) of an object to be adhered to (W).

[0029] FIG1(a) shows an adhesive sheet 10a of one embodiment of the present invention, which has a substrate 1 and an adhesive layer 2 laminated together. The adhesive sheet of one embodiment of the present invention, such as adhesive sheet 10a, may also have only a substrate and an adhesive layer, but may have other layers if necessary. Examples of other layers include, for instance, an intermediate layer disposed between the substrate and the adhesive layer, and a release sheet disposed on the side opposite to the substrate of the adhesive layer. FIG1(b) shows an adhesive sheet 10b of one embodiment of the present invention having an intermediate layer 3 as another layer. FIG1(c) and (d) show adhesive sheets 10c and 10d of adhesive sheets 10a and 10b, respectively, in which a release sheet 4 is laminated on the adhesive surface of the adhesive layer 2.

[0030] Next, the preferred state of each layer of the adhesive sheet of the present invention will be described.

[0031] (Thermal Expansion Layer) At least one layer in the adhesive sheet of one embodiment of the present invention is a thermal expansion layer containing thermal expansion particles. The thermal expansion layer of the adhesive sheet of one embodiment of the present invention can be categorized as follows: for example, when the adhesive sheet of one embodiment of the present invention contains only a substrate and an adhesive layer, at least one of the substrate and adhesive layers is a thermal expansion layer; when the adhesive sheet of one embodiment of the present invention has layers other than a substrate and an adhesive layer, those other layers can be thermal expansion layers. The adhesive sheet of one embodiment of the present invention may have two or more thermal expansion layers, but it is preferable to have only one layer. When the adhesive sheet of one embodiment of the present invention has two or more thermal expansion layers, the thermal expansion layers may have layers other than thermal expansion layers between them, or the thermal expansion layers may not have layers other than thermal expansion layers between them. When the adhesive sheet of one embodiment of the present invention has a substrate, an intermediate layer, and an adhesive layer, it is preferably selected from the group consisting of a substrate, an intermediate layer, and an adhesive layer, in which one or more layers are thermally expandable layers. A configuration where the intermediate layer is a thermally expandable layer is more preferred, and a configuration where the intermediate layer is a thermally expandable layer and the substrate and adhesive layers are non-thermally expandable layers is even more preferred. When the intermediate layer is a thermally expandable layer and the substrate and adhesive layers are non-thermally expandable layers, the unevenness caused by the thermally expandable particles after thermal expansion is unlikely to be exposed on the surface of the adhesive layer or the substrate. This tends to improve the adhesion to the adhered object (W) or the retention provided by the support device such as a chuck table.

[0032] The thickness of the thermally expandable layer is not particularly limited. It can be appropriately determined based on the fact that any one of the layers in the adhesive sheet of the present invention is a thermally expandable layer. Furthermore, in this specification, when referred to only as "thickness of the thermally expandable layer," this refers to the total thickness of all the thermally expandable layers in the adhesive sheet of the present invention. For example, if the adhesive sheet of the present invention has a substrate, an intermediate layer, and an adhesive layer, and only one of these layers is a thermally expandable layer, then the thickness of that layer is the thickness of the thermally expandable layer. Furthermore, if the adhesive sheet of the present invention has a substrate, an intermediate layer, and an adhesive layer, and two or more of these layers are thermally expandable layers, then the total thickness of those two or more layers is the thickness of the thermally expandable layer.

[0033] [Thermal Expansion Particles] Thermal expansion particles are particles that expand upon heating. One type of thermal expansion particle may be used alone, or two or more types may be used together.

[0034] The expansion initiation temperature (t) of the thermally expandable particles is preferably 50°C or higher, but not exceeding 125°C; more preferably 55-120°C; even more preferably 60-115°C; even more preferably 70-110°C; and still more preferably 75-105°C. When the expansion initiation temperature (t) of the thermally expandable particles is 50°C or higher, the tendency for unintentional expansion can be easily suppressed. Furthermore, when the expansion initiation temperature (t) of the thermally expandable particles is not exceeding 125°C, the heating temperature during heat-peeling can be lowered. Also, in this specification, the expansion initiation temperature (t) of the thermally expandable particles refers to the value measured according to the following method.

[0035] [Method for Determining the Expansion Initiation Temperature (t) of Thermally Expandable Particles] A sample was prepared in an aluminum cup with a diameter of 6.0 mm (inner diameter 5.65 mm) and a depth of 4.8 mm. 0.5 mg of the thermally expandable particle to be tested was added, and an aluminum cap (diameter 5.6 mm, thickness 0.1 mm) was attached to the cup. Using a dynamic viscoelasticity measuring device, the height of the sample was measured from the top of the aluminum cap with a force of 0.01 N applied by a pressure bar. Then, the sample was heated from 20°C to 300°C at a heating rate of 10°C / min with a force of 0.01 N applied by the pressure bar. The displacement of the pressure bar in the vertical direction was measured, and the displacement initiation temperature in the positive direction was set as the expansion initiation temperature (t).

[0036] As a thermally expandable particle, it is preferably a microcapsule-type foaming agent consisting of an outer shell made of thermoplastic resin and an inner encapsulated component that vaporizes when heated to a specific temperature. Examples of thermoplastic resins constituting the outer shell of the microcapsule-type foaming agent include, for example, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polyvinyl chloride, or copolymers obtained by polymerizing two or more monomers forming the constituent units contained in such thermoplastic resins.

[0037] As the outer shell of the microencapsulated foaming agent, examples of low-boiling-point liquids include propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, n-heptane, n-octane, cyclopropane, cyclobutane, and petroleum ether. Among these, from the viewpoint of suppressing unintentional expansion and lowering the heating temperature during heat-induced peeling, when the expansion initiation temperature (t) of the thermally expandable particles is set to 50°C or higher but less than 125°C, the encapsulation components are preferably propane, isobutane, n-pentane, or cyclopropane. These encapsulation components can be used individually or in combination of two or more. The expansion initiation temperature (t) of the thermally expandable particles can be adjusted by appropriately selecting the types of encapsulation components.

[0038] The average particle size of the thermally expandable particles before expansion at 23°C is preferably 3~100 μm, more preferably 4~70 μm, even more preferably 6~60 μm, and still more preferably 10~50 μm. Furthermore, the average particle size of the thermally expandable particles before expansion is the volume median particle size (D50), which, in the particle distribution of the thermally expandable particles before expansion measured using a laser diffraction particle size distribution measuring device (e.g., Malvern, product name "Master Sizer 3000"), corresponds to the particle size that represents 50% of the cumulative volume frequency calculated from the smaller particle size of the thermally expandable particles before expansion.

[0039] The 90% particle size (D90) of the thermally expandable particles before expansion at 23°C is preferably 10~150 μm, more preferably 15~100 μm, even more preferably 20~90 μm, and even more preferably 25~80 μm. Furthermore, the 90% particle size (D90) of the thermally expandable particles before expansion refers to the particle size that corresponds to 90% of the cumulative volume frequency calculated from the smaller particle size of the thermally expandable particles before expansion, as measured using a laser diffraction particle size distribution measuring device (e.g., Malvern, product name "Master Sizer 3000").

[0040] The maximum volume expansion rate when the thermally expandable particles used in one state of the present invention are heated to a temperature above the expansion initiation temperature (t) is preferably 1.5 to 200 times, more preferably 2 to 150 times, even more preferably 2.5 to 120 times, and even more preferably 3 to 100 times.

[0041] Relative to the total mass (100% by mass) of the thermally expandable layer, the content of thermally expandable particles is preferably 0.05 to 25% by mass, more preferably 0.1 to 15% by mass, even more preferably 0.2 to 10% by mass, and still more preferably 0.3 to 5% by mass. When the content of thermally expandable particles is 0.05% by mass or more, the expansion amount of the portion to be expanded in the adhesive sheet tends to be easily and sufficiently obtained. Furthermore, when the content of thermally expandable particles is 25% by mass or less, the unevenness of the thermally expandable particles before thermal expansion becomes less likely to be exposed on the surface of the adhesive layer or the substrate, and the adhesion to the adhered object (W) or the retention of the support device such as the cutting disc tends to become better.

[0042] (Substrate) The substrate used in one embodiment of the present invention is not particularly limited as long as it is made of a material that can support the adhered object (W).

[0043] The substrate is preferably a non-adhesive substrate. The probe tack value of the substrate surface is usually less than 50mN / 5mmφ, preferably less than 30mN / 5mmφ, more preferably less than 10mN / 5mmφ, and even more preferably less than 5mN / 5mmφ. Furthermore, in this specification, the probe tack value of the substrate surface is measured by the following method. <Probe Tack Value> The substrate to be tested is cut into squares with 10mm sides, and after standing for 24 hours in an environment of 23°C and 50%RH (relative humidity), it is used as a test sample. Using an adhesion tester (manufactured by Nippon Special Test Instruments Co., Ltd., product name "NTS-4800") in an environment of 23°C and 50%RH (relative humidity), the probe tack value on the surface of the test sample can be measured according to JIS Z0237:1991. Specifically, a stainless steel probe with a diameter of 5 mm is brought into contact with the surface of the test sample under a load of 0.98 N / cm2 for 1 second. The force required for the probe to leave the surface of the test sample at a speed of 10 mm / s is then measured. The obtained value can be used as the probe viscosity value of the test sample.

[0044] The material of the substrate may include, for example, resin, metal, and paper. Examples of resins include, for example, polyolefin resins such as polyethylene and polypropylene; vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; polycarbonate; polyurethane resins such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polyurethane; polyetheretherketone; polyether sulfide; polyphenylene sulfide; polyetherimide and polyimide resins; polyamide resins; acrylic resins; and fluorine resins. Examples of metals include, for example, aluminum, tin, chromium, and titanium. Examples of paper materials include, for example, thin paper, medium-quality paper, high-quality paper, impregnated paper, cast-coated paper, coated paper, tracing paper, and cellophane. Among these, polyester resins such as polyethylene terephthalate (hereinafter also referred to as "PET"), polybutylene terephthalate, and polyethylene naphthalate are preferred.

[0045] Such forming materials may consist of one type or two or more types. Examples of substrates using two or more forming materials include, for example, thermoplastic resin laminated paper such as polyethylene, or a metal film formed on the surface of a resin film or sheet containing resin. Furthermore, examples of methods for forming the metal layer include, for example, PVD methods such as vacuum evaporation, sputtering, or ion plating, where the metal is deposited; or methods such as bonding a metal foil composed of the metal using a common adhesive.

[0046] Furthermore, from the viewpoint of improving the interlayer adhesion between the substrate and other layers of the laminate, when the substrate contains resin, the surface of the substrate may be subjected to surface treatments such as oxidation, texturing, easy-adhesion treatment, or primer treatment.

[0047] The substrate may contain substrate additives when necessary. Examples of substrate additives include, for instance, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, lubricants, anti-caking agents, and colorants. Furthermore, one or more of these substrate additives may be used alone or in combination.

[0048] When the substrate contains a thermally expandable layer (hereinafter also referred to as "thermally expandable substrate"), the substrate can be formed by a substrate composition containing resin and thermally expandable particles. The preferred form of the type and content of thermally expandable particles is the same as the preferred form of the type and content of thermally expandable particles in the description of the thermally expandable layer above.

[0049] The type of resin contained in the substrate composition is preferably a carbamate resin or an olefin resin, more preferably a carbamate resin, and even more preferably an acrylic-modified polyurethane. When the substrate composition contains acrylic-modified polyurethane, in addition to the acrylic-modified polyurethane and thermally expandable particles, the substrate composition further contains energy-line polymerizable monomers, photopolymerization initiators, etc., and may also be a solvent-free resin composition. The solvent-free resin composition is solvent-free, but the energy-line polymerizable monomer is one that helps improve plasticity. For the solvent-free resin composition, by irradiating with energy lines, the acrylic-modified polyurethane, energy-line polymerizable monomers, etc., polymerize, and a thermally expandable substrate can be formed. The energy-line polymerizable monomers and photopolymerization initiators may be the same as those that may be contained in the intermediate layer composition described later.

[0050] The substrate may also be a substrate laminate containing a thermally expandable substrate and a non-thermally expandable layer (hereinafter also referred to as "non-thermally expandable substrate"). When the substrate is the aforementioned substrate laminate, the thermally expandable substrate is disposed on the adhesive layer side, and the non-thermally expandable substrate may be disposed on the opposite side of the adhesive layer. When the non-thermally expandable substrate is disposed on the opposite side of the adhesive layer, the unevenness caused by the expanding thermally expandable particles is difficult to be exposed on the surface opposite to the adhesive layer, and the retention of the substrate by the support device such as the cutting disc is more likely to become a good feature. When the non-thermally expandable substrate is disposed on the adhesive layer side, the tendency of the thermally expandable substrate to expand unintentionally can be easily controlled by frictional heat during the processing of the adhered object (W).

[0051] The thickness of the substrate is preferably 5 to 500 μm, more preferably 15 to 300 μm, and even more preferably 20 to 200 μm. When the substrate thickness is 5 μm or more, the tendency to improve the deformation resistance of the adhesive sheet is easily increased. Furthermore, when the substrate thickness is 500 μm or less, the tendency to improve the workability of the adhesive sheet is easily increased. Also, the substrate thickness refers to the overall thickness of the substrate. For example, the thickness of a substrate composed of multiple layers refers to the total thickness of all layers constituting the substrate.

[0052] (Intermediate Layer) In one embodiment of the adhesive sheet of the present invention, it is preferable to further include an intermediate layer between the substrate and the adhesive layer. Because the adhesive sheet of one embodiment of the present invention has an intermediate layer, the adherend (W) can also have protrusions. Since the intermediate layer can embed the protrusions of the adherend (W), the tendency for protrusions on the substrate side surface caused by the protrusions can be easily suppressed. The composition of the intermediate layer is not particularly limited, but the intermediate layer is preferably formed from an intermediate layer composition containing resin.

[0053] The resin contained in the composition of the intermediate layer may include urethane (meth) acrylate, acrylic resin, etc.

[0054] [Aminocarbamate (meth)acrylate] Aminocarbamate (meth)acrylate is a compound having at least a (meth)acrylic group and an aminocarbamate bond, and has the property of being polymerized by irradiation with an energy line. Intermediate layer compositions containing aminocarbamate (meth)acrylate tend to have improved flexibility in the resulting intermediate layer. One type of aminocarbamate (meth)acrylate may be used alone, or two or more may be used in combination.

[0055] The urethane (meth) acrylate may be a monofunctional urethane (meth) acrylate or a polyfunctional urethane (meth) acrylate, but is preferably a polyfunctional urethane (meth) acrylate, and more preferably a difunctional urethane (meth) acrylate.

[0056] The mass average molecular weight (Mw) of the urethane (meth) acrylate is preferably 10,000 to 100,000, more preferably 20,000 to 90,000, even more preferably 25,000 to 70,000, and still more preferably 30,000 to 60,000.

[0057] Aminocarbamate (meth)acrylate, for example, a terminal isocyanate aminocarbamate prepolymer obtained by reacting a polyol compound with a polyvalent isocyanate compound, can be obtained by reacting it with a (meth)acrylate having hydroxyl groups.

[0058] Polyol compounds, for example, include alkyl polyols, ether polyols, ester polyols, ester-amine polyols, ester-ether polyols, carbonate polyols, etc. A single polyol compound may be used alone, or two or more may be used in combination.

[0059] Examples of polyisocyanates include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Furthermore, these polyisocyanates can be trimethylolpropane addition-type modifiers, water-reacting biuret-type modifiers, or isocyanurate-type modifiers containing an isocyanurate ring. A single polyisocyanate can be used alone, or two or more can be used in combination.

[0060] Among hydroxyl-containing (meth)acrylates are examples 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, etc. Hydroxyl-containing (meth)acrylates may be used alone or in combination with two or more.

[0061] The content of urethane (meth) acrylate in the intermediate layer composition is preferably 20 to 90% by mass, more preferably 35 to 80% by mass, and even more preferably 50 to 70% by mass, relative to the total amount (100% by mass) of the active ingredient in the intermediate layer composition.

[0062] [Acrylic resin] Acrylic resins that can be used as resins contained in compositions for intermediate layers may be listed as being the same as acrylic resins that can be used as adhesive resins for adhesive layers as described later.

[0063] The intermediate layer composition is preferably a polymeric monomer containing other than the above-mentioned carbamate (meth) acrylate and carbamate (meth) acrylate.

[0064] [Polymerizable Monomer] The polymerizable monomer is preferably a polymerizable compound other than a methacrylate, and is a compound that can be polymerized with other components by irradiation with an energy beam. Specifically, the polymerizable monomer is preferably a compound having at least one (meth)acrylic group. One polymerizable monomer may be used alone, or two or more monomers may be used in combination.

[0065] Examples of polymerizable monomers include, for example, (meth)acrylates having an alkyl group having 1 to 30 carbon atoms; (meth)acrylates having functional groups such as hydroxyl, amide, amino, epoxy, etc.; (meth)acrylates having an alicyclic structure; (meth)acrylates having an aromatic structure; (meth)acrylates having a heterocyclic structure; vinyl compounds such as styrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-vinylmethylamine, N-vinylpyrrolidone, N-vinylcaprolactam, etc.; allyl compounds such as allyl glycidyl ether; etc.

[0066] (Meth)acrylates having an alkyl group having 1 to 30 carbon atoms, for example, meth(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate, n-pentyl(meth)acrylate, n-hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, nonyl(meth)acrylate, decyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, hexadecyl(meth)acrylate, octadecyl(meth)acrylate, eicosyl(meth)acrylate, etc. The alkyl (meth)acrylate having a carbon number of 1 to 30 is preferably 4 to 24, more preferably 8 to 18, and even more preferably 10 to 14.

[0067] Examples of (meth)acrylates having a functional group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc., in which the hydroxyl group contains (meth)acrylate; (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, etc. Compounds containing amide groups, such as N-hydroxymethylpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; (meth)acrylates containing amino groups, such as (meth)acrylates containing primary amino groups, (meth)acrylates containing secondary amino groups, and (meth)acrylates containing tertiary amino groups; and (meth)acrylates containing epoxy groups, such as glycidyl (meth)acrylates and methyl glycidyl (meth)acrylates.

[0068] Examples of (meth)acrylates having an alicyclic structure include isocamphenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenoxy (meth)acrylate, cyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, and adamantane (meth)acrylate. Among these, isocamphenyl (meth)acrylate and trimethylcyclohexyl (meth)acrylate are preferred.

[0069] Examples of (meth)acrylates having an aromatic structure include phenylhydroxypropyl (meth)acrylate, benzyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate. Examples of (meth)acrylates having a heterocyclic structure include tetrahydrofurfuryl (meth)acrylate and morpholine (meth)acrylate.

[0070] Among the above selections of polymerizable monomers, the intermediate layer composition preferably contains alkyl (meth)acrylates having 1 to 30 carbon atoms and (meth)acrylates having an alicyclic structure. The content of the alkyl (meth)acrylates having 1 to 30 carbon atoms in the intermediate layer composition is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, relative to the total amount (100% by mass) of the active ingredient in the intermediate layer composition. The content of the (meth)acrylates having an alicyclic structure in the intermediate layer composition is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 30% by mass, relative to the total amount (100% by mass) of the active ingredient in the intermediate layer composition.

[0071] The total content of polymerizable monomers in the intermediate layer composition is preferably 8 to 70% by mass, more preferably 15 to 50% by mass, and even more preferably 30 to 40% by mass, relative to the total amount (100% by mass) of the active ingredient in the intermediate layer composition.

[0072] The ratio of the content of urethane (meth) acrylate to the content of polymerizable monomer in the intermediate layer composition (urethane (meth) acrylate / polymerizable monomer) is based on mass and is preferably 20 / 80 to 90 / 10, more preferably 40 / 60 to 80 / 20, and even more preferably 60 / 40 to 70 / 30.

[0073] [Photopolymerization Initiator] The intermediate layer composition preferably further includes urethane (meth)acrylate, polymerizable monomers, and a photopolymerization initiator. Because the intermediate layer composition contains a photopolymerization initiator, the curing reaction can be sufficiently carried out by irradiation with a relatively low-energy beam. One type of photopolymerization initiator may be used alone, or two or more may be used in combination.

[0074] Photopolymerization initiators may include, for example, photopolymerization initiators of benzoin compounds, acetophenone compounds, phosphine oxide compounds, dicene compounds, thioxanone compounds, peroxide compounds, etc., and photosensitizers such as amines or quinones. More specifically, examples may include, for example, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, etc.

[0075] The content of the photopolymerization initiator in the intermediate layer composition is preferably 0.05 to 15 parts by weight relative to 100 parts by weight of the total amount of urethane (meth) acrylate and polymerizable monomers, more preferably 0.5 to 10 parts by weight, and even more preferably 1 to 5 parts by weight.

[0076] [Chain Transfer Agent] The intermediate layer composition preferably further contains urethane (meth)acrylate, polymerizable monomers, and a chain transfer agent. Because the intermediate layer composition contains a chain transfer agent, even after curing, a greater proportion of components with shorter molecular chains may remain, resulting in a flexible polymer after curing. One type of chain transfer agent may be used alone, or two or more may be used in combination.

[0077] Chain transfer agents may include, for example, compounds containing thiol groups. Examples of compounds containing thiol groups include nonylthiol, 1-dodecylthiol, 1,2-ethanedithiol, 1,3-propanedithiol, triazine thiol, triazine dithiol, triazine trithiol, 1,2,3-propane trithiol, tetraethylene glycol-bis(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetramercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), tris[(3-mercaptopropoxy)-ethyl]-isocyanurate, 1,4-bis(3-mercaptobutoxy)butane, pentaerythritol tetra(3-mercaptobutyrate), 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, etc. Of these, pentaerythritol tetra(3-mercaptobutyrate) is preferred.

[0078] The content of the chain transfer agent in the intermediate layer composition is preferably 0.1 to 10 parts by mass relative to 100 parts by mass of the total amount of urethane (meth) acrylate and polymerizable monomer, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass.

[0079] [Thermal Expansion Particles] When the intermediate layer is a thermal expansion layer containing thermal expansion particles, the intermediate layer can be formed by a composition containing thermal expansion particles. The preferred state of the type and content of thermal expansion particles is the same as the preferred state of the type and content of thermal expansion particles in the above description of thermal expansion layers.

[0080] [Intermediate Layer Additives] The intermediate layer composition may contain intermediate layer additives in addition to the above-mentioned components, without impairing the effects of the present invention. Examples of intermediate layer additives include antioxidants, softeners (plasticizers), fillers, rust inhibitors, pigments, dyes, and adhesives. Furthermore, each of these intermediate layer additives may be used individually or in combination of two or more. When the intermediate layer composition contains these intermediate layer additives, the content of each intermediate layer additive is, independently, relative to 100 parts by weight of the total amount of urethane (meth)acrylate and polymerizable monomers, preferably 0.0001 to 20 parts by weight, more preferably 0.001 to 10 parts by weight.

[0081] The intermediate layer composition used in one embodiment of the present invention may contain a solvent, preferably a solvent-free resin composition containing urethane (meth)acrylate and polymerizable monomers, without containing a solvent, within the scope of not impairing the effects of the present invention. Although the solvent-free resin composition does not contain a solvent, the aforementioned polymerizable monomers help to improve the plasticity of the resin. For the solvent-free resin composition, the urethane (meth)acrylate, polymerizable monomers, etc., are polymerized by irradiation energy lines to form the intermediate layer.

[0082] [Thickness of the Intermediate Layer] In the adhesive sheet of one embodiment of the present invention, the thickness of the intermediate layer is preferably 10-500 μm, more preferably 20-350 μm, and even more preferably 30-200 μm. When the thickness of the intermediate layer is 10 μm or more, it tends to easily embed the protrusions of the adhered object (W). Furthermore, when the thickness of the intermediate layer is 500 μm or less, it tends to improve the operability of the adhesive sheet. Also, the thickness of the intermediate layer refers to the overall thickness of the intermediate layer. For example, the thickness of an intermediate layer composed of multiple layers refers to the total thickness of all the layers constituting the intermediate layer.

[0083] (Adhesive layer) The adhesive layer is a layer disposed on the side opposite to the substrate of the intermediate layer, and is adhered to one side (Wα) of the adhered object (W).

[0084] The adhesive layer is preferably a layer with energy-line curing properties. Because the adhesive layer has energy-line curing properties, before energy-line curing, it has sufficient adhesion and can achieve good adhesion to the substrate (W). After energy-line curing, the peeling force is reduced and it can be easily peeled off from the substrate (W).

[0085] The adhesive layer may be formed from an adhesive composition comprising an adhesive resin. Examples of adhesive compositions include, for example, type X adhesive compositions, type Y adhesive compositions, and type XY adhesive compositions described below. Type X adhesive composition: an energy-curing adhesive composition containing a non-energy-curing adhesive resin (hereinafter also referred to as "adhesive resin I") and an energy-curing compound other than an adhesive resin. Type Y adhesive composition: an energy-curing adhesive resin (hereinafter also referred to as "adhesive resin II") containing unsaturated groups introduced into the side chains of a non-energy-curing adhesive resin, and an energy-curing adhesive composition containing no energy-curing compound other than an adhesive resin. Type XY adhesive composition: an energy-curing adhesive composition containing the above-mentioned energy-curing adhesive resin II and an energy-curing compound other than an adhesive resin. Among these, the energy-curing adhesive is preferably of type XY.

[0086] Next, the components constituting the adhesive layer will be described in more detail. In the following description, "adhesive resin" is used to refer to one or both of adhesive resin I and adhesive resin II.

[0087] The adhesive resin may be an adhesive resin without functional groups, but it is more preferably an adhesive resin with functional groups. Because the adhesive resin has functional groups, it can, for example, exhibit reactivity with the crosslinking agent described later, and energy-line curing properties. Examples of functional groups possessed by the adhesive resin include, for example, unsaturated groups with energy-line polymerizability such as (meth)acrylic, vinyl, and allyl groups; hydroxyl, carboxyl, amino, and epoxy groups. Among these, (meth)acrylic and hydroxyl groups are preferred. The adhesive resin may have one type of functional group or two or more types of functional groups.

[0088] Adhesive resins include, for example, acrylic resins, carbamate resins, rubber resins, and polysiloxane resins. Among these, acrylic resins are preferred.

[0089] [Acrylic Resin] An acrylic resin is not particularly limited as long as it contains a polymer with acrylic monomers as monomer components, but it is preferable to contain constituent units derived from alkyl (meth)acrylates. Examples of alkyl (meth)acrylates include alkyl (meth)acrylates with 1 to 20 carbon atoms. The alkyl group in the alkyl (meth)acrylate can be linear or branched.

[0090] From the viewpoint of further improving the adhesion of the adhesive layer, acrylic resins preferably contain alkyl (meth)acrylate constituent units from which the alkyl group has 4 or more carbon atoms. The alkyl (meth)acrylate constituent units from which the alkyl group has 4 or more carbon atoms contained in the acrylic resin can be one type or two or more types. The alkyl (meth)acrylate having 4 or more carbon atoms preferably has 4 to 12 carbon atoms, more preferably 4 to 8, and even more preferably 4 to 6. Examples of alkyl (meth)acrylates having 4 or more carbon atoms include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, etc. Of these, 2-ethylhexyl (meth)acrylate is preferred, and more preferably 2-ethylhexyl acrylate. The view that the content of alkyl (meth)acrylates with 4 or more carbon atoms in the alkyl group further improves the adhesive strength of the adhesive layer is derived from the fact that the content of alkyl monomers constituting acrylic resins is preferably 30-90% by mass, more preferably 40-80% by mass, and even more preferably 50-70% by mass.

[0091] Acrylic resins, from the viewpoint of providing good elastic modulus and adhesive properties of the adhesive layer, preferably contain constituent units of alkyl (meth)acrylates with 4 or more carbon atoms derived from alkyl groups and constituent units of alkyl (meth)acrylates with 1 to 3 carbon atoms derived from alkyl groups. The constituent units of alkyl (meth)acrylates with 1 to 3 carbon atoms derived from the acrylic resin can be one type or two or more types. Examples of alkyl (meth)acrylates with 1 to 3 carbon atoms include methacrylate, ethyl methacrylate, isopropyl methacrylate, and n-propyl methacrylate. Among these, methacrylate and ethyl methacrylate are preferred, and methyl methacrylate and ethyl acrylate are more preferred. The content of the constituent units of alkyl (meth)acrylates having 1 to 3 carbon atoms in the alkyl group is derived from the constituent units of the acrylic monomers constituting the acrylic resin, preferably 1 to 35% by mass, more preferably 5 to 30% by mass, and even more preferably 15 to 25% by mass.

[0092] The acrylic resin preferably further contains constituent units derived from monomers containing functional groups. Because the acrylic resin contains constituent units derived from monomers containing functional groups, functional groups that can serve as crosslinking initiation points for reaction with crosslinking agents, or react with compounds containing unsaturated groups, can introduce unsaturated functional groups into the side chains of the acrylic resin. The constituent units derived from monomers containing functional groups contained in the acrylic resin can be one type or two or more types.

[0093] Monomers containing functional groups include, for example, monomers containing hydroxyl groups, monomers containing carboxyl groups, monomers containing amino groups, and monomers containing epoxy groups. Monomers containing hydroxyl groups include, for example, 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; etc. Monomers containing carboxyl groups include, for example, vinyl unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; vinyl unsaturated dicarboxylic acids such as fumaric acid, ecacinic acid, maleic acid, and citrate, and their anhydrides; 2-carboxyethyl methacrylate; etc. Among these, monomers containing hydroxyl groups are preferred, 2-hydroxyethyl (meth)acrylate is more preferred, and 2-hydroxyethyl methacrylate is even more preferred.

[0094] The content of the constituent units of the monomer containing the functional group is derived from the constituent units of the acrylic monomer constituting the acrylic resin, preferably 1 to 35% by mass, more preferably 5 to 30% by mass, and even more preferably 15 to 25% by mass.

[0095] In addition to the constituent units mentioned above, acrylic resins may also contain constituent units derived from other monomers that can copolymerize with acrylic monomers. The constituent units derived from other monomers contained in acrylic resins may be one or more. Examples of other monomers include styrene, α-methylstyrene, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, and acrylamide.

[0096] To further impart energy-line curing properties to acrylic resins, unsaturated groups with energy-line polymerization properties may be introduced. Unsaturated groups can be introduced, for example, by reacting the functional group of an acrylic resin containing a monomer with a functional group with a reactive substituent having reactivity with that functional group and a reactive substituent of a compound containing an unsaturated group (hereinafter also referred to as "a compound containing an unsaturated group"). A compound containing an unsaturated group may be used alone or in combination with two or more. Examples of unsaturated groups in a compound containing an unsaturated group include (meth)acrylic, vinyl, allyl, etc. Among these, (meth)acrylic is preferred. Examples of reactive substituents in a compound containing an unsaturated group include isocyanate groups, glycidyl groups, etc. Compounds containing unsaturated groups include, for example, 2-(meth)acryloxyethyl isocyanate, (meth)acrylyl isocyanate, glycidyl (meth)acrylate, etc. Among these, 2-(meth)acryloxyethyl isocyanate is preferred, and more preferably 2-methacryloxyethyl isocyanate.

[0097] When an acrylic resin containing constituent units derived from monomers containing functional groups reacts with a compound containing unsaturated groups, the ratio of functional groups in the acrylic resin that react with the compound containing unsaturated groups is not particularly limited, but is preferably 30-90 mol%, more preferably 40-80 mol%, and even more preferably 50-70 mol%. When the ratio of functional groups that react with the compound containing unsaturated groups is within the above range, the acrylic resin can be endowed with sufficient energy line curing properties, and the acrylic resin can be cross-linked by reacting the functional groups that have not reacted with the compound containing unsaturated groups with a cross-linking agent.

[0098] The mass-average molecular weight (Mw) of the acrylic resin is not particularly limited, but is preferably 300,000 to 1,500,000, more preferably 450,000 to 1,000,000, and even more preferably 600,000 to 900,000. When the mass-average molecular weight (Mw) of the acrylic resin is within the above range, the adhesive layer tends to have better adhesion and cohesion.

[0099] The content of acrylic resin in the adhesive composition is, relative to the total amount (100% by mass) of the effective components of the adhesive composition, preferably 70-99% by mass, more preferably 80-98% by mass, and even more preferably 90-97% by mass.

[0100] [Crosslinking Agent] When the adhesive composition contains an adhesive resin with functional groups, it is preferable to further contain a crosslinking agent. The crosslinking agent is a substance that reacts with an adhesive resin with functional groups, using the functional group as the starting point for crosslinking, allowing the adhesive resins to crosslink with each other. One type of crosslinking agent may be used alone, or two or more may be used in combination.

[0101] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, and metal chelate-based crosslinking agents. Among these crosslinking agents, isocyanate-based crosslinking agents are preferred from the viewpoint of easily achieving improved cohesion and adhesion.

[0102] Isocyanate crosslinking agents include, for example, aromatic polyisocyanates such as methylbenzene diisocyanate, diphenylmethane diisocyanate, and xylene diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane-4,4'-diisocyanate, dicycloheptane triisocyanate, pentosan diisocyanate, pentosan diisocyanate, methyl pentosan diisocyanate, methylene bis(cyclohexyl isocyanate), 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, and hydrogenated xylene diisocyanate; noncyclic aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; and polyvalent isocyanate compounds. Furthermore, isocyanates are crosslinking agents, and examples include, for instance, trimethylolpropane addition-type modifiers of polyisocyanate compounds, biuret-type modifiers reacting with water, and isocyanurate-type modifiers containing isocyanurate rings. Among these, trimethylolpropane addition-type modifiers of polyisocyanate compounds are preferred, more preferably trimethylolpropane addition-type modifiers of aromatic polyisocyanate compounds, and even more preferably trimethylolpropane addition-type modifiers of methylphenyl diisocyanate.

[0103] The content of crosslinking agent in the adhesive composition is appropriately adjusted by the number of functional groups possessed by the adhesive resin. It is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 7 parts by weight, and even more preferably 0.05 to 5 parts by weight, relative to 100 parts by weight of the adhesive resin.

[0104] [Photopolymerization initiator] The adhesive composition preferably further includes a photopolymerization initiator. The energy-line curing adhesive, due to the presence of the photopolymerization initiator, tends to undergo sufficient energy-line curing reaction even under relatively low-energy energy rays such as ultraviolet light. One type of photopolymerization initiator may be used alone, or two or more may be used in combination.

[0105] Examples of photopolymerization initiators include 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzylphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, bibenzyl, diacetyl, β-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, etc. Among these, 2,2-dimethoxy-2-phenylacetophenone is preferred.

[0106] The content of photopolymerization initiator in the adhesive composition is preferably 0.01 to 10 parts by weight relative to 100 parts by weight of the total amount of adhesive resin, more preferably 0.03 to 5 parts by weight, and even more preferably 0.05 to 3 parts by weight.

[0107] [Adhesion-enhancing agent] From the viewpoint of improving adhesion, the adhesive composition may further contain an adhesion-enhancing agent. An adhesion-enhancing agent may be used alone or in combination with two or more. Examples of adhesion-enhancing agents include, for instance, C5-based petroleum resins obtained by copolymerizing C5 fractions of rosin-based resins, terpene-based resins, styrene-based resins, and pentene, isoprene, piperine, and 1,3-pentadiene produced by the thermal decomposition of naphtha; C9-based petroleum resins obtained by copolymerizing C9 fractions of indene, vinyltoluene, and others produced by the thermal decomposition of naphtha; and hydrogenated resins of these, etc. When the adhesive composition contains an adhesion-enhancing agent, the content of the adhesion-enhancing agent relative to the total amount (100% by mass) of the effective components of the adhesive composition is preferably 0.01 to 65% by mass, more preferably 0.1 to 50% by mass, and even more preferably 1 to 40% by mass.

[0108] [Energy-line curing compound] The adhesive composition may further contain an energy-line curing compound other than the components mentioned above in order to adjust the cohesiveness of the adhesive layer. One energy-line curing compound may be used alone, or two or more may be used in combination. Examples of energy-line curing compounds include monomers or oligomers that can be polymerized and cured by energy-line irradiation. Examples of energy-line curing compounds include, for example, polyvalent (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate; oligomers such as urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, and epoxy (meth)acrylate; etc. Of these, from the viewpoint of curability, dipentaerythritol hexa(meth)acrylate is preferred, and more preferably dipentaerythritol hexaacrylate. When the adhesive composition contains an energy-curing compound, the content of the energy-curing compound is not particularly limited, but is preferably 10 to 100 parts by weight relative to 100 parts by weight of the adhesive resin, more preferably 20 to 70 parts by weight, and even more preferably 30 to 40 parts by weight.

[0109] [Thermal Expansion Particles] When the adhesive layer is a thermal expansion layer containing thermal expansion particles, the adhesive layer can be formed by an adhesive composition containing thermal expansion particles. The preferred state of the type and content of thermal expansion particles is the same as that of the preferred state of the type and content of thermal expansion particles in the above description of thermal expansion layers.

[0110] [Adhesive Additives] In one embodiment of the present invention, the adhesive composition may, in addition to the components described above, contain adhesive additives commonly used in adhesives, without impairing the effects of the present invention. Examples of such adhesive additives include, for instance, antioxidants, softeners (plasticizers), rust inhibitors, pigments, dyes, retarders, reaction promoters (catalysts), and ultraviolet absorbers. Furthermore, each of these adhesive additives may be used individually or in combination of two or more. When the adhesive composition contains such adhesive additives, the content of each adhesive additive is independently 0.0001 to 20 parts by weight relative to 100 parts by weight of the adhesive resin, more preferably 0.001 to 10 parts by weight.

[0111] [Thickness of Adhesive Layer] The thickness of the adhesive layer is preferably 1~80μm, more preferably 2~60μm, and even more preferably 3~40μm. When the thickness of the adhesive layer is 1μm or more, good adhesion can be obtained, and there is a tendency to easily obtain sufficient adhesion to the substrate (W). Furthermore, when the thickness of the adhesive layer is 80μm or less, it is easier to suppress the occurrence of tape debris when cutting the adhesive sheet.

[0112] (Method for manufacturing adhesive sheet) The method for manufacturing one aspect of the adhesive sheet of the present invention is not particularly limited and can be manufactured by conventional methods.

[0113] One embodiment of the adhesive sheet of the present invention can be manufactured, for example, by a method including step a of preparing a substrate and step b of forming an adhesive layer. Furthermore, when the adhesive sheet of one embodiment of the present invention has an intermediate layer, in addition to the above-described steps a and b, the adhesive sheet of one embodiment of the present invention having an intermediate layer can be manufactured by a method including step c of forming an intermediate layer. The steps will be described below.

[0114] [Step a] Step a is the step of preparing the substrate. The substrate of the adhesive sheet of one embodiment of the present invention can be formed using commercially available and conventional methods. When the substrate is a substrate laminate containing a thermally expandable substrate and a non-thermally expandable substrate, the substrate laminate can be formed, for example, by coating one side of the non-thermally expandable substrate with the aforementioned solvent-free resin composition for forming a thermally expandable substrate, and then by irradiation with an energy line. The method of coating the solvent-free resin composition can be a conventional method, such as spin coating, spray coating, bar coating, doctor blade coating, roller coating, doctor blade coating, die coating, gravure coating, etc.

[0115] [Step b] Step b is the step of forming the adhesive layer. The method of forming the adhesive layer can be, for example, by directly applying the adhesive composition to the surface of the laminated layer and then drying it; or by applying the adhesive composition to the release surface of the release sheet, drying it to form the adhesive layer, and then adhering the adhesive layer to the surface of the laminated layer. The laminated adhesive layer is determined according to the composition of the desired adhesive sheet, for example, a thermally expandable substrate, a non-thermally expandable substrate, an intermediate layer, etc. The method of applying the adhesive composition can be the same as the method of applying a solvent-free resin composition described above. The drying conditions for the adhesive composition can be adjusted appropriately according to the type and content of the solvent in the adhesive composition.

[0116] [Step c] Step c is the step of forming an intermediate layer. The method for forming the intermediate layer may be, for example, to directly coat the intermediate layer composition onto the surface of the substrate and then irradiate it with energy lines to harden it; or it may be to coat the intermediate layer composition onto the release treatment surface of a release sheet, irradiate it with energy lines to form the intermediate layer, and then adhere the intermediate layer to one side of the substrate. The method of coating the intermediate layer composition may be the same as the method described above for coating a solvent-free resin composition.

[0117] From the viewpoint that the intermediate layer composition can be irradiated with an energy line only once, but it is easier to control the degree of hardening of the intermediate layer, it is preferable to irradiate it multiple times. When the energy line is ultraviolet light, the conditions for the first ultraviolet irradiation are as follows: the ultraviolet irradiation intensity is preferably 30~500 mW / cm2, more preferably 50~340 mW / cm2, and the ultraviolet irradiation dose is preferably 100~2,500 mJ / cm2, more preferably 150~2,000 mJ / cm2. The conditions for the second ultraviolet irradiation are as follows: the ultraviolet irradiation intensity is preferably 100~1,000 mW / cm2, more preferably 200~500 mW / cm2, and the ultraviolet irradiation dose is preferably 300~5,000 mJ / cm2, more preferably 500~3,000 mJ / cm2. The second ultraviolet irradiation should ideally be performed under conditions where the illuminance and irradiation intensity are greater than those of the first irradiation. Irradiation with energy lines is best performed with the coating film in an oxygen-free state. Methods for oxygen-freeing the coating film include, for example, attaching a release liner to the coating film.

[0118] As described above, after the intermediate layer is formed on the substrate, an adhesive layer is deposited on the intermediate layer by step b, thereby manufacturing an adhesive sheet having a substrate, an intermediate layer and an adhesive layer in sequence.

[0119] [Inflating Method of Adhesive Sheet] Next, after describing the adhered object (W) in the expanding method of adhesive sheet of the present invention, the steps of the expanding method of adhesive sheet of the present invention will be described in sequence.

[0120] <Adhesive (W)> The adhesive (W) is not particularly limited, and examples include building materials, interior materials, electronic components, etc., that can be temporarily fixed with a thin sheet. Among these, the adhesive (W) is preferably an electronic component, and more preferably a semiconductor wafer. That is, the adhesive sheet used in the adhesive sheet expansion method of one embodiment of the present invention is preferably a semiconductor processing adhesive sheet for semiconductor wafer processing. Furthermore, the adhesive sheet expansion method of one embodiment of the present invention is preferably applicable to a method for manufacturing a semiconductor device that processes a semiconductor wafer using a semiconductor processing adhesive sheet.

[0121] A semiconductor wafer is a substrate used for semiconductor wafers, for example, forming circuits, bumps, etc. Examples of substrates used for semiconductor wafers include silicon wafers; wafers made of gallium arsenide, silicon carbide, sapphire, lithium tantalate, lithium niobate, gallium nitride, indium phosphate, etc.; and glass wafers.

[0122] The shape of a semiconductor wafer in a planar view is not particularly limited, and it is usually a circular plate shape. The size of the circular plate-shaped semiconductor wafer can be selected appropriately according to the equipment and manufacturing method used in each step. Examples include 8-inch (200mm) diameter and 12-inch (300mm) diameter wafers.

[0123] The thickness of the semiconductor wafer is not particularly limited, but from the viewpoint of the operability and processability of the semiconductor wafer, it is preferably 100~1,000 μm, more preferably 200~900 μm, and even more preferably 300~800 μm. However, when the semiconductor wafer has protrusions, the above-mentioned thickness of the semiconductor wafer does not include the thickness of the protrusions.

[0124] The adherend (W) may also have a protrusion on one side (Wα). Examples of adherends (W) with protrusions include semiconductor wafers having circuits, bumps, etc. Among these, adherends (W) with protrusions are preferably semiconductor wafers with bumps as protrusions. Examples of bumps include bumps made of metals such as gold, silver, copper, nickel, tin, lead, and alloys containing these metals. The shape of the bumps is not particularly limited, and examples include spherical, cylindrical, elliptical cylindrical, ellipsoidal, conical, elliptical conical, cubic, cuboid, trapezoidal, etc. The number of bumps formed on the semiconductor wafer is not particularly limited and can be varied according to design requirements.

[0125] The height of the protrusion of the adhered material (W) is not particularly limited, but from the viewpoint that it significantly demonstrates the effect of the expansion method of the adhesive sheet of the present invention, it is preferably 10 to 500 μm, more preferably 15 to 400 μm, and even more preferably 20 to 300 μm.

[0126] FIG2 is an example of an adherend (W) with protrusions, showing a schematic plan view of a semiconductor wafer W (hereinafter also referred to as "bumped wafer W") having bumps as protrusions. The surface Wα of the bumped wafer W is formed with a plurality of devices 6 divided by a predetermined dividing line 5. Each device 6 forms a circuit (not shown), and as shown in the enlarged view of FIG2, a plurality of bumps 7 forming protrusions are formed. The surface Wα of the bumped wafer W has a device region 8 where the plurality of devices 6 are arranged via the predetermined dividing line 5 and a device non-forming region 9 for the residual portion when it becomes a monolithic wafer.

[0127] Next, referring to the drawings, the steps of one embodiment of the method of the present invention will be described. Furthermore, in the drawings used in the following description, for ease of understanding of the features of the present invention, important parts are enlarged or simplified. Therefore, the size ratios, numbers, etc., of each component are not necessarily the same as in reality. Furthermore, the following description uses a wafer with bumps as the adherend (W), where the adhesive sheet of this embodiment is adhered to the wafer with bumps, and local expansion is caused to planarize the substrate-side surface of the adhesive sheet. However, the expansion method of the adhesive sheet of the present invention is not limited to these embodiments.

[0128] <Adhesion Step> When implementing the expansion method of the adhesive sheet of the present invention, before step 1, the adhesive sheet of the present invention is adhered to the surface (Wα) of one side of the object (W) with the aforementioned adhesive layer as the adhesive surface.

[0129] Figures 3(a) and (b) are cross-sectional views illustrating the steps of attaching an adhesive sheet 10 to a surface Wα of a bumped wafer W according to one embodiment of the present invention. Figure 3(a) is a cross-sectional view corresponding to the bumped wafer W shown in Figure 2. That is, the bumped wafer W has a plurality of devices 6 separated by a predetermined dividing line 5 on surface Wα3, a plurality of bumps 7 formed on each device 6, a device region 8, and a device non-forming region 9. Figure 3(b) shows the state in which the adhesive sheet 10 is attached to surface Wα of the bumped wafer W. Furthermore, the illustrations of each layer of the adhesive sheet 10 are omitted, but the adhesive sheet 10 is attached to surface Wα with an adhesive layer as the adhesive surface, and the surface opposite to the adhesive surface is the substrate side surface Sα. The adhesive sheet 10 can be any adhesive sheet used in the expansion method of the adhesive sheet of one embodiment of the present invention, such as the adhesive sheet 10a and adhesive sheet 10b described above. As shown in FIG3(b), the substrate side surface Sα of the adhesive sheet 10 of the wafer W to which the bumps are attached forms a protrusion 11 caused by the bumps 7 and a non-protrusion 12 other than the protrusion 11. In the embodiment of FIG3(b), the area of ​​the adhesive sheet 10 covering the device region 8 shown in FIG3(a) becomes the protrusion 11, and the portion covering the non-device forming region 9 shown in FIG3(a) becomes the non-protrusion 12.

[0130] In the pasting step, there are no particular limitations on the method of pasting the sheet. For example, a laminating machine or other conventional methods can be used.

[0131] <Step 1> Step 1 is the step of bringing a portion (A) of the surface (Sα) of the aforementioned adhesive sheet on the substrate side into contact with the cooling material.

[0132] Region (A) is a portion of the surface (Sα) on the substrate side, and is the area in contact with the cooling material. That is, for the adhesive sheet, expansion is typically suppressed in the portion of the surface having region (A). Region (A) is the surface shape of the adhesive sheet after it is adhered to the substrate (W), and can be arbitrarily set according to the purpose of the expansion method of the adhesive sheet in one embodiment of the present invention.

[0133] (Cooling material) The cooling material used in step 1 is a region (A) of a portion of the surface (Sα) of the substrate side of the adhesive sheet. When heating is performed in step 2, the cooling effect is used to suppress the thermal expansion of the adhesive sheet on the surface having region (A).

[0134] The material of the cooling material is not particularly limited as long as it has a cooling effect, but it is preferably a heat conductor. When the cooling material is a heat conductor, the area (A) of the adhesive sheet that contacts the heat conductor generates heat conduction to the heat conductor, and the cooling effect of the part of the surface with area (A) can be obtained.

[0135] As a heat conductor used as a cooling material, in order to improve the cooling effect, it may have an artificial cooling mechanism for example, such as one that allows internal refrigerant to circulate. However, from the point of view of economy and production, it may also be that it does not have an artificial cooling mechanism. That is, the heat conductor itself may not be intentionally cooled. In this case, the heat absorbed by the heat conduction system at the point of contact with the area (A) of the adhesive sheet is naturally dissipated from the surface of the heat conductor itself, thus achieving a cooling effect.

[0136] The heat conductor is preferably a metal. Examples of metals include single metals such as copper, silver, gold, iron, zinc, lead, tin, nickel, chromium, and aluminum; and alloys such as stainless steel and brass. Among these, copper and aluminum are preferred from the viewpoint of versatility and thermal conductivity, with copper being more preferred.

[0137] From the viewpoint of improving cooling effect, the thermal conductivity of the heat conductor at 20°C is preferably 50 W / m·K or higher, more preferably 100 W / m·K or higher, and even more preferably 200 W / m·K or higher. Furthermore, from the viewpoint of general applicability, the thermal conductivity of the cooling material of the heat conductor at 20°C can be 1,000 W / m·K or lower, 700 W / m·K or lower, or 500 W / m·K or lower.

[0138] The cooling material, as the surface (Sα) in contact with the substrate side (hereinafter also referred to as "surface (Cα)"), is preferably planar. When the cooling material is planar as a surface (Cα), the shape and size of the surface are not particularly limited. For example, it can be a planar diagram, and its shape and size are roughly the same as the area of ​​the adhesive sheet whose expansion is to be suppressed (hereinafter also referred to as "expansion suppression area"). The shape and size of the surface (Cα) of the cooling material are roughly the same as the shape and size of the expansion suppression area. By matching the shape of the surface (Cα) with the shape of the expansion suppression area, it is easy to selectively suppress the thermal expansion of the adhesive sheet on the surface with the expansion suppression area. That is, at this time, the surface of the expansion suppression area becomes the area (A) in step 1.

[0139] The shape and size of the surface (Cα) of the cooling material are not limited to the above-described forms. For example, it may be smaller than the area of ​​the expansion suppression region. When the thermal conductivity of the cooling material is high, it becomes easier to achieve a cooling effect in a region that is wider than the area (A) in which the surface (Cα) of the cooling material contacts. Therefore, even if the surface (Cα) of the cooling material has a smaller area than the area of ​​the expansion suppression region, it can suppress the tendency of thermal expansion of the expansion suppression region. In addition, for example, when the expansion suppression region is a protrusion on the surface of the substrate on which the sheet is adhered, if the area of ​​the surface (Cα) of the cooling material is larger than the area above the protrusion, it can contact the entire area above the protrusion. By increasing the area of ​​the surface (Cα) of the cooling material, the cooling effect of the part in contact with the surface (Cα) of the cooling material tends to be improved.

[0140] From the viewpoint of achieving sufficient cooling effect, the thickness of the cooling material is preferably 100 times or more, more preferably 500 times or more, and even more preferably 1,000 times or more. Furthermore, from an operability perspective, the thickness of the cooling material can also be less than 10,000 times, less than 6,000 times, or less than 3,000 times the thickness of the thermal expansion layer.

[0141] FIG4 is a cross-sectional view illustrating the step of contacting the upper surface of the protrusion 11 with the cooling material 13 among the protrusion 11 formed on the substrate-side surface Sα of the adhesive sheet 10 and the non-protrusion 12 other than the protrusion. That is, in the view of FIG4, the upper surface of the protrusion 11 corresponds to region (A). In FIG4, the cooling material 13 is in contact with the entire upper surface of the protrusion 11, and the size of the surface Cα of the substrate-side surface Sα of the cooling material 13 in contact with it is approximately the same as the size of the protrusion 11.

[0142] <Step 2> Step 2 is a step in which, while in contact with the aforementioned cooling material, the aforementioned adhered material (W) is heated to above the expansion initiation temperature (t) of the aforementioned thermally expandable particles, and the aforementioned adhesive sheet is heated from the side of the aforementioned adhered material (W). By means of the cooling effect of the aforementioned cooling material, the expansion of the portion of the surface having the aforementioned region (A) in the aforementioned adhesive sheet is suppressed, while the portion of the surface having the region other than the aforementioned region (A) is expanded.

[0143] In step 2, the adhesive sheet adhered to the adhered object (W) is heated from the adhered object (W) side by heating the adhered object (W) to above the expansion initiation temperature (t) of the thermally expanding particles. For example, the method of heating the adhered object (W) can be to heat the side (Wβ) opposite to the previously described side (Wα) of the adhered object (W). If a portion of the aforementioned side (Wα) is exposed, the exposed side (Wα) can also be heated. For an adhered object (W) with excellent thermal conductivity, heating can be performed by heating only a portion of it, thereby heating the entire adhered object (W) through heat conduction. From the viewpoint of easily controlling the heating location and heating temperature, the method of heating the adhered object (W) is preferably to bring the adhered object (W) into contact with the heated heat conductor, and more preferably to bring the side (Wβ) of the adhered object (W) into contact with the heated heat conductor. From the viewpoint of uniform heating, the method of bringing the adhered object (W) into contact with a heat conductor to be heated is preferably a method of bringing the adhered object (W) into contact with a heat conductor having a smooth surface, and even more preferably a method of bringing it into contact with a heating plate. Examples of heating plates include metal plates and ceramic plates.

[0144] The surface temperature at which the adherend (W) contacts the heated heat conductor is at or above the expansion initiation temperature (t) of the thermally expanding particles, preferably "above the expansion initiation temperature (t)," more preferably "expansion initiation temperature (t) + 2°C" or more, even more preferably "expansion initiation temperature (t) + 4°C" or more, and still more preferably "expansion initiation temperature (t) + 5°C" or more. Furthermore, from the viewpoint of energy saving and suppressing thermal changes of the adherend (W) during heat-induced peeling, the surface temperature of the heated heat conductor is preferably "expansion initiation temperature (t) + 50°C" or less, more preferably "expansion initiation temperature (t) + 40°C" or less, and even more preferably "expansion initiation temperature (t) + 30°C" or less. Furthermore, from the viewpoint of suppressing thermal changes in the adhered material (W), the surface temperature of the heated heat conductor that brings the adhered material (W) into contact with it is preferably below 130°C, more preferably below 120°C, and even more preferably below 115°C, within the range above the expansion initiation temperature (t).

[0145] Figures 5(a) and (b) illustrate the step of heating the surface Wβ, opposite to the surface Wα of the wafer W with the attached bump, to above the expansion initiation temperature (t) of the thermally expanding particles while the cooling material 13 is in contact with the surface of the protrusion 11. As shown in Figure 5(a), the adhesive sheet 10 is heated by contacting the surface Wβ of the wafer W with the attached bump with the heating plate 14. At this time, the portion of the adhesive sheet 10 with the surface of the protrusion 11 in contact with the cooling material 13 is thermally expanded by the cooling effect of the cooling material 13. However, the portion of the surface of the adhesive sheet 10 without the protrusion 12 in contact with the cooling material 13 cannot exert the cooling effect of the cooling material 13, and thus thermal expansion occurs. The result is shown in Figure 5(b). The height of the non-convex portion 12' that expands in Figure 5(a) is close to the height of the convex portion 11' in Figure 5(a). The height difference between the convex portion 11 and the non-convex portion 12 is reduced, and the surface Sα on the substrate side is flattened.

[0146] The amount of expansion of the portion of the surface having the non-convex portion 12 in step 2 can be adjusted, for example, by the content of thermally expandable particles in the thermally expandable layer. That is, if the height difference between the convex and non-convex portions is large before step 2, the expansion amount can be increased by increasing the content of thermally expandable particles in the thermally expandable layer. Conversely, if the height difference between the convex and non-convex portions is small before step 2, the expansion amount can be reduced by decreasing the content of thermally expandable particles in the thermally expandable layer.

[0147] As described above, in the method for expanding the adhesive sheet according to one aspect of the present invention, the adhesive sheet can be partially expanded after being adhered to the substrate. The substrate (W) with the partially expanded adhesive sheet is then, if necessary, supplied for processing, inspection, etc. Processing can include, for example, grinding of the substrate (W), monolithization, etc. Inspection can include, for example, defect inspection using an optical microscope, laser (e.g., waste inspection, surface scratch inspection, wiring pattern inspection, etc.), visual surface inspection, etc. Among these, the substrate (W) with the partially expanded adhesive sheet is preferably supplied for processing, and more preferably for grinding of the substrate (W). Grinding of the substrate (W) is preferably back-side grinding of a semiconductor wafer, more preferably back-side grinding of a semiconductor wafer with protrusions, and even more preferably back-side grinding of a semiconductor wafer with bumps.

[0148] Figure 6 is a cross-sectional view illustrating the steps of thinning a bump-attached wafer W with the substrate-side surface Sα of the adhesive sheet 10 fixed thereon. In Figure 6, the substrate-side surface Sα of the adhesive sheet 10 is fixed to a support device 15 such as a dicing disc, and the bump-attached wafer W has its backside Wβ ground to the desired thickness using a grinder 16. The substrate-side surface Sα of the adhesive sheet 10 has excellent flatness, thus providing uniform pressing pressure across the entire backside of the semiconductor wafer, allowing the semiconductor wafer to be thinned uniformly.

[0149] After the above processing, the adhesive sheet can be peeled off from the processed adhered object (W). When the adhesive layer of the adhesive sheet is formed by an energy-curing adhesive, the adhesive is hardened by irradiation with energy lines, reducing the peeling force of the adhesive layer and thus peeling off the adhesive sheet. [Example]

[0150] The following embodiments illustrate the present invention in more detail, but the present invention is not limited to the following embodiments. Furthermore, the physical property values ​​in each embodiment are values ​​measured by the following methods.

[0151] [Mass Average Molecular Weight (Mw)] Determined using a gel permeation chromatography apparatus (manufactured by Tosoh Corporation, product name "HLC-8020") under the following conditions. Values ​​are converted to standard polystyrene. (Determination Conditions) ･Column: "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL", "TSK gel G1000HXL" (all manufactured by Tosoh Corporation) connected in sequence. ･Column temperature: 40℃ ･Developing solvent: tetrahydrofuran ･Flow rate: 1.0 mL / min

[0152] [Thickness of each layer] The thickness was measured at 23°C using a constant pressure thickness gauge (model: "PG-02J", according to standard specifications: JIS K6783, Z1702, Z1709) manufactured by Teclock Co., Ltd.

[0153] [Average particle size (D50), 90% particle size (D90) of thermally expandable particles] The particle distribution of thermally expandable particles before expansion at 23°C was measured using a laser diffraction particle size distribution measuring device (e.g., Malvern, product name "Mastersizer 3000"). Then, the cumulative volume frequency calculated from the smaller particle size of the particle distribution corresponds to the 50% and 90% particle sizes, respectively, and is used as the "average particle size (D50) of thermally expandable particles" and the "90% particle size (D90) of thermally expandable particles".

[0154] [Manufacturing of Adhesive Sheets] Manufacturing Examples 1-3 [Manufacturing of Adhesive Sheets 1-3] Adhesive sheets 1-3 are manufactured by the method shown below. Furthermore, in the following description, the descriptions of the copolymer composition such as "X / Y / Z = A / B / C" indicate that the copolymer is a copolymer of monomer X, monomer Y, and monomer Z, obtained by copolymerizing A parts by mass of monomer X, B parts by mass of monomer Y, and C parts by mass of monomer Z.

[0155] (Formulation of intermediate layer components) 65 parts by weight of urethane acrylate oligomer (manufactured by Arkema Co., Ltd., trade name "CN9021 NS"), 25 parts by weight of isobornyl acrylate, 10 parts by weight of dodecyl acrylate, 3.4 parts by weight of photopolymerization initiator (manufactured by IGM Resins BV, trade name "Omnirad 1173", 2-hydroxy-2-methyl-1-phenylpropane-1-one), and chain transfer agent (manufactured by Showa Denko Co., Ltd., trade name "KarenzMT"). PE1”, pentaerythritol tetra(3-mercaptobutyrate) 1.0 parts by weight and relative to the total mass (100% by weight) of the formed intermediate layer, were mixed with thermally expandable particles (manufactured by Nouryon, product name "Expancel (registered trademark) 031-40" (DU type), expansion initiation temperature (t) = 88°C, average particle size (D50) = 12.6 μm, 90% particle size (D90) = 26.2 μm) as listed in Table 1 to obtain a solvent-free resin composition for the intermediate layer.

[0156] (Preparation of the substrate for the intermediate layer) The intermediate layer composition obtained above is coated onto a PET film (manufactured by Toyobo Co., Ltd., trade name "Cosmo Shine A4160", thickness 50μm) of the substrate using a doctor blade method, so that the thickness of the formed intermediate layer is 100μm, forming an intermediate layer composition layer. Next, on the exposed surface of the formed intermediate layer composition layer, a PET release film (manufactured by Lintec Co., Ltd., trade name "SP-PET381130", thickness 38μm) is laminated to block oxygen from the intermediate layer composition layer. Next, after the first ultraviolet irradiation using a high-pressure mercury lamp with an illuminance of 80 mW / cm2 and an irradiation dose of 200 mJ / cm2, a second ultraviolet irradiation using a high-pressure mercury lamp with an illuminance of 330 mW / cm2 and an irradiation dose of 1,260 mJ / cm2 was carried out, the intermediate layer was hardened to produce a substrate with a release sheet attached to the intermediate layer.

[0157] (Preparation of adhesive composition) A polymer was prepared by reacting 100 parts by weight of an acrylic copolymer (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., in which 2-ethylhexyl acrylate (2EHA) / ethyl acrylate (EA) / methyl methacrylate (MMA) / 2-hydroxyethyl acrylate (HEA) = 60 / 15 / 5 / 20 (mass ratio), wherein 2-methacryloxyethyl isocyanate (MOI) was added to 60 moles of the hydroxyl groups of the acrylic copolymer; mass average molecular weight (Mw) 800,000); 1.1 parts by weight of trimethylolpropane adduct methylphenyl diisocyanate (manufactured by Tosoh Corporation, trade name "coronateL") as a crosslinking agent; and 2,2-dimethoxy-2-phenylacetophenone (IGM Resins) as a photopolymerization initiator. 2.2 parts by weight of BV (trade name "Omnirad 651") were added, and toluene was added to adjust the concentration of solid components to 30% by weight. The mixture was stirred for 30 minutes to prepare the adhesive composition.

[0158] (Preparation of adhesive layer with release film) Next, the prepared adhesive composition is coated on a PET release film (manufactured by Lintec Corporation, trade name "SP-PET381130", thickness 38μm), dried, and an adhesive layer with a thickness of 10μm is formed on the release film to obtain an adhesive layer with release film.

[0159] (Preparation of adhesive sheet) Remove the release film of the substrate with intermediate layer obtained above, and attach the adhesive layer of the adhesive layer with release film obtained above to the exposed surface of the intermediate layer to obtain adhesive sheets 1 to 3 having substrate, intermediate layer, adhesive layer and release sheet in sequence.

[0160] Manufacturing Example 4 [Manufacturing of Adhesive Sheet 4] In Manufacturing Example 1, except that thermally expandable particles were not mixed with the composition in the intermediate layer, adhesive sheet 4 was obtained in the same way as in Manufacturing Example 1.

[0161] [Implementation of the method for expanding the adhesive sheet] Examples 1-3, Comparative Example 1 (1. Formation of the protrusion) An adhesive sheet (125 μm thick), cut into a circle with a diameter of 60 mm and attached to a PET substrate, is adhered to the center of one side of a circular silicon wafer (200 mm in diameter, 740 μm thick) as a protrusion. This forms a protrusion with a height of 125 μm in the center of the silicon wafer.

[0162] (2. Fabrication of a silicon wafer with an adhesive sheet) Next, the release film is removed from the adhesive sheet obtained in each manufacturing example, exposing the adhesive layer on the surface as the bonding surface. Using a BG tape laminator (manufactured by Lintec Corporation, product name "RAD 3510F / 12"), the work tray is heated to 65°C while the wafer is bonded at a lamination speed of 5 mm / sec and a lamination pressure of 0.3 MPa. Through the above steps, a silicon wafer with an adhesive sheet attached to the entire surface of the silicon wafer on which the protrusion is formed is obtained before thermal expansion. Furthermore, when the silicon wafer with the attached sheet is used as a planar view below, the area containing the protrusion is sometimes called the "protrusion forming area", and the area without the protrusion is called the "protrusion non-forming area". Furthermore, the silicon wafer with the attached sheet before thermal expansion is referred to as the "wafer with attached sheet (1)".

[0163] (3. Thickness Measurement of the Wafer (1) with Adhesive Sheets) Next, the silicon wafer side surface of the wafer (1) with adhesive sheets is placed on a flat surface, and the substrate side surface is arranged to become the contact surface of the constant pressure thickness measuring device. The thickness of four points is measured for both the protrusion forming area and the non-protrusion forming area. The thickness measurement points are four points that are concentric with the protrusion forming area and are equally spaced on a circumference with a diameter of about 1 / 2. The thickness measurement points are four points that are concentric with the non-protrusion forming area and are equally spaced on a circumference with a diameter of about 2 / 3. Table 1 shows the average thickness of the protrusion forming area and the average thickness of the non-protrusion forming area in the wafer (1) with adhesive sheets. As shown in Table 1, the thickness of the area where the protrusion is formed is greater than the thickness of the area where the protrusion is not formed, indicating that a protrusion is formed on the surface of the substrate side of the adhesive sheet.

[0164] (4. Heat expansion treatment of the adhesive sheet) Next, with the substrate side surface of the adhesive sheet facing up, the wafer (1) with the adhesive sheet is placed on a flat surface. A cylindrical copper (60 mm in diameter and 200 mm in thickness) serving as a cooling material is deposited on the wafer (1) with its bottom surface facing up on the substrate side surface, aligned with the protrusion formation area. Then, the wafer (1) with the copper-coated adhesive sheet is placed on the heating plate with the silicon wafer side surface in contact with the heating plate and the substrate side surface of the copper-coated adhesive sheet facing up not in contact with the heating plate. It is heated for 2 minutes at 110°C, above the expansion initiation temperature of the thermally expanding particles. Then, it is left to stand in a standard environment (23°C, 50%RH) for 60 minutes to obtain the wafer with the adhesive sheet after heat expansion. Hereinafter, the wafer with the attached thin film after heating and expansion is referred to as "wafer with attached thin film (2)".

[0165] (5. Thickness measurement of the wafer (2) with the attached sheet) Next, the thickness of the wafer (2) with the attached sheet was measured using the same method as described in "3. Thickness measurement of the wafer (1) with the attached sheet". Table 1 shows the average thickness of the protrusion forming region and the average thickness of the non-protrusion forming region in the wafer (2) with the attached sheet.

[0166]

[0167] As shown in Table 1, in Examples 1-3, the thickness difference [(B)-(A)] in the wafer (2) with the attached sheet after the heat expansion treatment is less than the thickness difference [(B)-(A)] in the wafer (1) with the attached sheet before the heat expansion treatment, indicating that the attached sheet expands locally. Furthermore, in Examples 1-3, it can be seen that the thickness difference decreases depending on the content of thermally expandable particles, so the expansion amount of the area to be expanded can be adjusted by adjusting the content of thermally expandable particles. [Simplified Explanation of the Diagram]

[0016] [Fig. 1] A cross-sectional view showing an example of the structure of the adhesive sheet. [Fig. 2] A plan view illustrating a semiconductor wafer with protrusions. [Fig. 3] A cross-sectional view illustrating an example of the adhesive sheet bonding step. [Fig. 4] A cross-sectional view illustrating an example of the steps of the adhesive sheet expansion method of the present invention. [Fig. 5] A cross-sectional view illustrating an example of the steps of the adhesive sheet expansion method of the present invention. [Fig. 6] A cross-sectional view illustrating an example of the steps of thinning a semiconductor wafer.

Claims

1. A method for expanding an adhesive sheet, comprising an adhesive sheet having a substrate and an adhesive layer, wherein the adhesive sheet contains at least one layer that is a thermally expandable layer containing thermally expandable particles, the method comprising attaching the adhesive sheet to a surface (Wα) of a substrate (W) with the aforementioned adhesive layer as the adhesive surface, and causing it to expand locally, and comprising the following steps 1 and 2: Step 1: making a cooling material contact a region (A) of a portion of the surface (Sα) on the substrate side of the adhesive sheet; Step 2: while the cooling material is in contact with the aforementioned region (A), heating the substrate (W) to above the expansion initiation temperature (t) of the aforementioned thermally expandable particles, thereby heating the adhesive sheet from the substrate (W) side, and using the cooling effect of the aforementioned cooling material to suppress the expansion of the portion of the surface of the adhesive sheet having the aforementioned region (A), while causing the portion of the surface of the adhesive sheet other than the aforementioned region (A) to expand. The content of the aforementioned thermally expandable particles is 0.05 to 25% of the total mass (100% by mass) of the aforementioned thermally expandable layer.

2. The expansion method of the adhesive sheet as claimed in claim 1, wherein the aforementioned cooling material has a thermal conductivity of 50 W / m·K or higher at 20°C.

3. The method for expanding the adhesive sheet as claimed in claim 1 or 2, wherein the aforementioned cooling material is metal.

4. The expansion method of the adhesive sheet as claimed in claim 1 or 2, wherein the thickness of the aforementioned cooling material is more than 100 times the thickness of the aforementioned thermally expandable layer.

5. The method for expanding the adhesive sheet as claimed in claim 1 or 2, wherein the thickness of the aforementioned adhesive layer is 1 to 80 μm.

6. The expansion method of the adhesive sheet as claimed in claim 1 or 2, wherein the expansion initiation temperature (t) of the aforementioned thermally expandable particles is above 50°C but below 125°C.

7. The method for expanding the adhesive sheet as claimed in claim 1 or 2, wherein the adhesive sheet further comprises an intermediate layer between the substrate and the adhesive layer.

8. The method for expanding the adhesive sheet as described in claim 7, wherein the thickness of the aforementioned intermediate layer is 10 to 500 μm.

9. The method for expanding the adhesive sheet as claimed in claim 7, wherein the aforementioned intermediate layer is the aforementioned thermally expandable layer.

10. The method for expanding the adhesive sheet as claimed in claim 1 or 2, wherein the heating of the aforementioned adhesive (W) in step 2 is performed by heating the side (Wβ) opposite to the aforementioned surface (Wα) of the aforementioned adhesive (W).

11. The method for expanding the adhesive sheet as claimed in claim 1 or 2, wherein the aforementioned adhesive sheet is an adhesive sheet for semiconductor processing, and the aforementioned adhered object (W) is a semiconductor wafer.

12. The method for expanding the adhesive sheet as claimed in claim 11, wherein the aforementioned semiconductor wafer is a semiconductor wafer having protrusions.

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