Adhesive sheet and method for manufacturing semiconductor device

Abstract

The present invention relates to an adhesive sheet which has a multilayer structure wherein: an adhesive layer (X1), a thermally expandable base material layer (Y1) and a thermally non-expandable base material layer (Y2) are sequentially arranged in this order; the thermally expandable base material layer (Y1) contains thermally expandable particles in a resin base material; and the resin base material has a Young's modulus of 2.05 MPa or less at 120°C. The present invention also relates to a method for producing a semiconductor device, said method using this adhesive sheet.

Description

[Technical field]

[0001] The present invention relates to an adhesive sheet and a method for manufacturing a semiconductor device using the adhesive sheet. [Background technology]

[0002] Pressure-sensitive adhesive sheets are not only used to semi-permanently fix components, but are also used as temporary fixing sheets for temporarily fixing target components (hereinafter also referred to as "adherend") when processing or inspecting building materials, interior materials, electronic components, etc. For example, in the manufacturing process of semiconductor devices, temporary fixing sheets are used when processing semiconductor wafers.

[0003] In the manufacturing process of a semiconductor device, a semiconductor wafer is processed into a semiconductor chip through a grinding process in which the thickness is reduced by grinding, a singulation process in which the wafer is cut and separated, and the like. At this time, the semiconductor wafer is subjected to a predetermined process while being temporarily fixed to the temporary fixing sheet. The semiconductor chip obtained by the predetermined process is separated from the temporary fixing sheet, and then, as necessary, an expanding process in which the spacing between the semiconductor chips is increased, a rearrangement process in which the multiple semiconductor chips with the increased spacing are arranged, an inversion process in which the front and back of the semiconductor chips are inverted, and the like are appropriately performed, and then the semiconductor chip is mounted on a substrate. In each of the above processes, a temporary fixing sheet suitable for each purpose can be used.

[0004] Patent Document 1 discloses a heat-peelable adhesive sheet for temporary fixing when cutting electronic components, which has a heat-expandable adhesive layer containing heat-expandable microspheres on at least one side of a substrate. The document describes that the heat-peelable adhesive sheet can ensure a predetermined contact area with the adherend when cutting the electronic components, thereby exhibiting adhesion that can prevent adhesion problems such as chipping, while after use, it can be easily peeled off by heating to expand the heat-expandable microspheres, thereby reducing the contact area with the adherend. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3594853 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the adhesive layer contains heat-expandable particles, as in the adhesive sheet disclosed in Patent Document 1, there is a concern that the surface of the adherend may be contaminated after peeling by heating due to, for example, adhesion of residue from the heat-expandable particles to the surface of the adherend, or adhesion of part of the adhesive layer to the surface of the adherend due to deformation or alteration of the adhesive layer caused by the expansion of the heat-expandable particles (so-called "glue residue").

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide an adhesive sheet that can easily peel off a temporarily fixed adherend by heating and that can suppress contamination of the adherend surface after peeling, and a method for manufacturing a semiconductor device using the adhesive sheet. [Means for solving the problem]

[0008] The present inventors have discovered that the above problems can be solved by configuring an adhesive sheet having a laminated structure in which (1) an adhesive layer, a heat-expandable base layer, and a non-heat-expandable base layer are arranged in this order, and (2) the heat-expandable base layer is composed of a resin base material having a specific Young's modulus and containing heat-expandable particles, thereby completing the present invention.

[0009] That is, the present invention relates to the following [1] to

[15] . [1] A laminate structure in which a pressure-sensitive adhesive layer (X1), a heat-expandable base layer (Y1), and a non-heat-expandable base layer (Y2) are arranged in this order, The thermally expandable substrate layer (Y1) comprises a resin substrate containing thermally expandable particles, The pressure-sensitive adhesive sheet, wherein the resin substrate has a Young's modulus at 120° C. of 2.05 MPa or less. [2] The pressure-sensitive adhesive sheet according to the above [1], wherein the resin substrate contains one or more resins selected from the group consisting of acrylic urethane resins and olefin resins. [3] The pressure-sensitive adhesive sheet according to the above [1] or [2], wherein the resin substrate is formed from a resin composition (y-1) containing a resin that is cured by irradiation with energy rays. [4] The pressure-sensitive adhesive sheet according to any one of the above [1] to [3], wherein the resin substrate has a Young's modulus at 120° C. of 0.1 MPa or more. [5] The pressure-sensitive adhesive sheet according to any one of the above [1] to [4], wherein the expansion starting temperature (t) of the thermally expandable particles is 50°C or higher and lower than 125°C. [6] The pressure-sensitive adhesive sheet according to any one of the above [1] to [5], wherein the pressure-sensitive adhesive layer (X1) has a thickness at 23° C. of 3 to 10 μm. [7] The pressure-sensitive adhesive sheet according to any one of the above [1] to [6], wherein the content of the thermally expandable particles is 1 to 30 mass % relative to the total mass (100 mass %) of the thermally expandable base layer (Y1). [8] The pressure-sensitive adhesive sheet according to any one of the above [1] to [7], wherein the non-thermally expandable base layer (Y2) has a Young's modulus at 120° C. of 500 MPa or more. [9] The pressure-sensitive adhesive sheet according to any one of the above [1] to [8], wherein the non-thermally expandable base layer (Y2) is a polyethylene terephthalate film.

[10] The pressure-sensitive adhesive sheet according to any one of the above [1] to [9], further comprising a pressure-sensitive adhesive layer (X2) on the surface of the non-thermally expandable base layer (Y2) opposite to the surface on which the heat-expandable base layer (Y1) is laminated.

[11] The pressure-sensitive adhesive sheet according to the above-mentioned

[10] , wherein the pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer that is cured by irradiation with energy rays, thereby reducing its adhesive strength.

[12] A processing and inspection object is attached to the adhesive sheet according to any one of [1] to

[11] above, A method for manufacturing a semiconductor device, comprising a step of subjecting the processed and inspected object to one or more of processing and inspection, and then heating the adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) of the thermally expandable particles.

[13] A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to

[10] or

[11] above, in which the thermally expandable particles have an expansion onset temperature (t) of 50°C or higher and lower than 125°C, the method comprising the following steps 1A to 3A, a first separation step as described below, and a second separation step as described below. Step 1A: A step of attaching an object to be processed to the adhesive layer (X2) of the adhesive sheet, and attaching a support to the adhesive layer (X1) of the adhesive sheet. Step 2A: A step of subjecting the object to one or more treatments selected from a grinding treatment and a singulation treatment. Step 3A: A step of attaching a thermosetting film to the surface of the object to be processed opposite to the pressure-sensitive adhesive layer (X2) that has been subjected to the treatment. First separation step: a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion starting temperature (t) and lower than 125° C. to separate the pressure-sensitive adhesive layer (X1) from the support. Second separation step: a step of separating the pressure-sensitive adhesive layer (X2) from the object to be processed.

[14] A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to

[10] or

[11] above, in which the thermally expandable particles have an expansion onset temperature (t) of 50°C or higher and lower than 125°C, the method comprising the following steps 1B to 3B, a first separation step as described below, and a second separation step as described below. Step 1B: A step of attaching an object to be processed to the adhesive layer (X1) of the adhesive sheet, and attaching a support to the adhesive layer (X2) of the adhesive sheet. Step 2B: subjecting the object to one or more treatments selected from a grinding treatment and a singulation treatment. Step 3B: A step of attaching a thermosetting film to the surface of the object to be processed opposite to the pressure-sensitive adhesive layer (X1) that has been subjected to the treatment. First separation step: a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion starting temperature (t) and lower than 125° C. to separate the pressure-sensitive adhesive layer (X1) from the object to be processed. Second separation step: a step of separating the pressure-sensitive adhesive layer (X2) from the support

[15] Using the adhesive sheet described in

[11] above, The method for producing a semiconductor device according to the above-mentioned

[13] or

[14] , wherein the second separation step includes a step of curing the adhesive layer (X2) by irradiating the adhesive layer (X2) with energy rays. Effect of the Invention

[0010] According to the present invention, it is possible to provide an adhesive sheet that can easily peel off a temporarily fixed adherend by heating and that can suppress contamination of the adherend surface after peeling, and a method for manufacturing a semiconductor device using the adhesive sheet. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing an example of the configuration of a pressure-sensitive adhesive sheet of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing another example of the configuration of the pressure-sensitive adhesive sheet of the present invention. [Diagram 3] 1A to 1C are cross-sectional views illustrating an example of a process for producing a semiconductor device according to the present invention. [Figure 4] 1A to 1C are cross-sectional views illustrating an example of a process for producing a semiconductor device according to the present invention. [Diagram 5] 1A to 1C are cross-sectional views illustrating an example of a process for producing a semiconductor device according to the present invention. [Figure 6] 1A to 1C are cross-sectional views illustrating an example of a process for producing a semiconductor device according to the present invention. [Figure 7] 1A to 1C are cross-sectional views illustrating an example of a process for producing a semiconductor device according to the present invention. [Figure 8] 1A to 1C are cross-sectional views illustrating an example of a process for producing a semiconductor device according to the present invention. [Figure 9] 1A to 1C are cross-sectional views illustrating an example of a process for producing a semiconductor device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In this specification, the term "active ingredient" refers to the ingredients contained in the target composition excluding diluent solvents. In this specification, the mass average molecular weight (Mw) is a value calculated as standard polystyrene measured by gel permeation chromatography (GPC), and specifically, is a value measured based on the method described in the examples.

[0013] In this specification, for example, "(meth)acrylic acid" refers to both "acrylic acid" and "methacrylic acid", and similar terms. In this specification, the lower limit and upper limit described in stages for the preferred numerical range (e.g., the range of the content, etc.) can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0014] In this specification, the term "energy rays" refers to electromagnetic waves or charged particle beams having an energy quantum, and examples thereof include ultraviolet rays, radiation, electron beams, etc. Ultraviolet rays can be irradiated by using, for example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, etc. as an ultraviolet ray source. Electron beams can be irradiated by generating them using an electron beam accelerator, etc. In this specification, the term "energy ray polymerizable" refers to a property of being polymerized by irradiation with energy rays.

[0015] In this specification, whether a "layer" is a "non-thermally expandable layer" or a "thermally expandable layer" is determined as follows. If the layer to be judged contains thermally expandable particles, the layer is heat-treated for 3 minutes at the expansion start temperature (t) of the thermally expandable particles. If the volume change rate calculated from 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 layer after heat treatment - volume of the layer before heat treatment) / volume of the layer before heat treatment} x 100 A layer that does not contain thermally expandable particles is referred to as a "non-thermally expandable layer."

[0016] In this specification, the "front surface" of a semiconductor wafer and a semiconductor chip refers to the surface on which circuits are formed (hereinafter also referred to as the "circuit surface"), and the "back surface" of a semiconductor wafer and a semiconductor chip refers to the surface on which circuits are not formed.

[0017] [Adhesive sheet] A pressure-sensitive adhesive sheet according to one embodiment of the present invention has a laminated structure in which a pressure-sensitive adhesive layer (X1), a thermally expandable base layer (Y1) and a non-thermally expandable base layer (Y2) are arranged in this order, the thermally expandable base layer (Y1) comprises a resin base material containing thermally expandable particles, and the resin base material has a Young's modulus at 120°C of 2.05 MPa or less. In this specification, the resin substrate, i.e., a resin substrate that becomes a thermally expandable substrate layer (Y1) by containing thermally expandable particles and has a Young's modulus of 2.05 MPa or less at 120°C, may be referred to as "resin substrate (Y')". Here, the resin substrate (Y1') corresponds to a substrate having the same structure as the thermally expandable substrate layer (Y1) except that it does not contain thermally expandable particles. That is, the thermally expandable substrate layer (Y1) can be said to be a substrate consisting of the resin substrate (Y1') and the thermally expandable particles contained in the resin substrate (Y1'). Moreover, the "resin substrate" is a substrate that contains at least a resin, and may contain components other than the resin, such as additives for the substrate, as described below.

[0018] In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the heat-expandable particles contained in the heat-expandable base layer (Y1) are heated to a temperature equal to or higher than the expansion initiation temperature (t) to expand the heat-expandable particles, which favorably forms unevenness on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1), thereby greatly reducing the contact area between the pressure-sensitive adhesive surface and an adherend attached to the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1). This can significantly reduce the adhesion between the pressure-sensitive adhesive sheet and the adherend. Therefore, in the pressure-sensitive adhesive sheet of one embodiment of the present invention, when peeling by heating, the pressure-sensitive adhesive sheet can be peeled off from the adherend without applying a force to peel off the pressure-sensitive adhesive sheet. Specifically, in a laminate in which the pressure-sensitive adhesive sheet is attached to an adherend, when peeling by heating, the pressure-sensitive adhesive sheet can be peeled off by facing the pressure-sensitive adhesive sheet side downward and allowing the pressure-sensitive adhesive sheet to fall from the adherend by gravity. Furthermore, since the thermally expandable particles are contained in the thermally expandable base layer (Y1), contamination of the adherend surface caused by the thermally expandable particles is suppressed. In this specification, the state in which the pressure-sensitive adhesive sheet is peeled off or falls off from the adherend without the application of a force to peel the pressure-sensitive adhesive sheet is referred to as "self-peeling." Furthermore, such a property is referred to as "self-removal property."

[0019] In the pressure-sensitive adhesive sheet of one embodiment of the present invention, the thermally expandable base layer (Y1) contains thermally expandable particles in a resin base material (Y1'), and the Young's modulus of the resin base material (Y1') at 120°C is adjusted to 2.05 MPa or less. Therefore, when peeled off by heating, the expansion of the thermally expandable particles is not excessively suppressed by the resin base material (Y1') containing the thermally expandable particles, and unevenness is well formed on the adhesive surface of the pressure-sensitive adhesive layer (X1). As a result, the pressure-sensitive adhesive sheet of one embodiment of the present invention has excellent self-peeling properties. On the other hand, if the Young's modulus of the resin substrate (Y1') at 120°C exceeds 2.05 MPa, the expansion of the heat-expandable particles is suppressed by the surrounding resin substrate (Y1'), making it difficult to form unevenness on the adhesive surface of the pressure-sensitive adhesive layer (X1), and sufficient self-peelability may not be obtained.

[0020] In the pressure-sensitive adhesive sheet of one embodiment of the present invention, the Young's modulus of the resin substrate (Y1') at 120°C is 2.05 MPa or less, preferably 2.00 MPa or less, more preferably 1.95 MPa or less, even more preferably 1.90 MPa or less, still more preferably 1.85 MPa or less, and even more preferably 1.80 MPa or less, from the viewpoint of facilitating the formation of irregularities on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1). Also, the Young's modulus of the resin substrate (Y1') at 120°C is preferably 0.01 MPa or more, more preferably 0.1 MPa or more, even more preferably 0.2 MPa or more, still more preferably 0.5 MPa or more, even more preferably 0.8 MPa or more, and even more preferably 1.1 MPa or more, from the viewpoint of improving the sheet shape retention after thermal expansion. In this specification, "sheet shape retention" refers to the property that, when the adhesive sheet of one embodiment of the present invention is thermally expanded, the occurrence of curling in the adhesive sheet is suppressed, and the shape of the adhesive sheet prior to thermal expansion is macroscopically maintained. The Young's modulus of the resin substrate (Y1') at 120°C can be adjusted to within the above range, for example, by appropriately adjusting the type and blending ratio of the material (i.e., the material other than the thermally expandable particles used to form the thermally expandable substrate layer (Y1)) used to form the resin substrate (Y1'), or by appropriately adjusting the curing conditions when a curing reaction is used. In this specification, the Young's modulus of the resin substrate (Y1') at 120° C. is measured by the method described in the examples described later.

[0021] [Adhesive sheet composition] The pressure-sensitive adhesive sheet of one embodiment of the present invention may have a laminated structure in which a pressure-sensitive adhesive layer (X1), a heat-expandable base layer (Y1), and a non-heat-expandable base layer (Y2) are arranged in this order, but the pressure-sensitive adhesive sheet of one embodiment of the present invention may have only the pressure-sensitive adhesive layer (X1), the heat-expandable base layer (Y1), and the non-heat-expandable base layer (Y2), or may have other layers as necessary. For example, when the pressure-sensitive adhesive sheet of one embodiment of the present invention is used for one or more selected from processing and inspection of an adherend, from the viewpoint of improving the processability and inspectability of the adherend, it is preferable that the pressure-sensitive adhesive sheet further comprises a pressure-sensitive adhesive layer (X2) on the surface of the non-expandable base layer (Y2) opposite to the surface on which the thermally expandable base layer (Y1) is laminated. With this configuration, the adherend can be attached to either one of the pressure-sensitive adhesive layer (X1) or the pressure-sensitive adhesive layer (X2), and a support can be attached to the other pressure-sensitive adhesive layer. By fixing the adherend to the support via the adhesive sheet, when the adherend is subjected to one or more of processing and inspection, vibration of the adherend, displacement, and damage when the adherend is fragile can be suppressed, thereby improving processing accuracy and processing speed as well as inspection accuracy and inspection speed. In the following description, unless otherwise specified, the term "double-sided pressure-sensitive adhesive sheet" refers to a pressure-sensitive adhesive sheet having a laminated structure in which a pressure-sensitive adhesive layer (X1), a heat-expandable base layer (Y1), a non-heat-expandable base layer (Y2), and a pressure-sensitive adhesive layer (X2) are arranged in this order.

[0022] The pressure-sensitive adhesive sheet of one embodiment of the present invention may have a release material on the adhesive surface of the pressure-sensitive adhesive layer (X1). When the pressure-sensitive adhesive sheet of one embodiment of the present invention has a double-sided pressure-sensitive adhesive sheet configuration, at least one of the pressure-sensitive adhesive layers (X1) and (X2) may have a release material on the adhesive surface.

[0023] Next, the configuration of the pressure-sensitive adhesive sheet according to one embodiment of the present invention will be described in more detail with reference to the drawings.

[0024] An example of a pressure-sensitive adhesive sheet according to the present invention is a pressure-sensitive adhesive sheet 1a having a laminated structure in which a pressure-sensitive adhesive layer (X1), a thermally expandable base layer (Y1), and a non-thermally expandable base layer (Y2) are arranged in this order, as shown in FIG. 1(a). The pressure-sensitive adhesive sheet of one embodiment of the present invention may further have a release material 10 on the adhesive surface of the pressure-sensitive adhesive layer (X1), as in the pressure-sensitive adhesive sheet 1b shown in FIG. 1(b).

[0025] An example of a pressure-sensitive adhesive sheet according to another embodiment of the present invention is one having the configuration of the double-sided pressure-sensitive adhesive sheet described above. An example of an adhesive sheet having such a configuration is an adhesive sheet 2a having a laminated structure in which an adhesive layer (X1), a heat-expandable base layer (Y1), a non-heat-expandable base layer (Y2), and an adhesive layer (X2) are arranged in this order, as shown in FIG. 2(a). Also, as shown in FIG. 2(b) in double-sided adhesive sheet 2b, the adhesive layer (X1) may further have a release material 10a on its adhesive surface, and the adhesive layer (X2) may further have a release material 10b on its adhesive surface.

[0026] In the double-sided adhesive sheet 2b shown in Fig. 2(b), if the peeling force when peeling the release material 10a from the adhesive layer (X1) is similar to the peeling force when peeling the release material 10b from the adhesive layer (X2), when attempting to peel both release materials outward, a phenomenon may occur in which the adhesive layer is divided and peeled off along with the two release materials. From the viewpoint of suppressing such a phenomenon, it is preferable to use two types of release materials for the two release materials 10a and 10b, which are designed to have different peeling forces from the adhesive layers to which they are attached.

[0027] A further embodiment of the pressure-sensitive adhesive sheet of the present invention may be a double-sided pressure-sensitive adhesive sheet having a configuration in which a release material having a release treatment applied to both sides is laminated onto one adhesive surface of the pressure-sensitive adhesive layer (X1) and the pressure-sensitive adhesive layer (X2) in the double-sided pressure-sensitive adhesive sheet 2a shown in FIG. 2(a) and is wound into a roll.

[0028] The pressure-sensitive adhesive sheet of one embodiment of the present invention may or may not have another layer between at least one of the layers between the pressure-sensitive adhesive layer (X1) and the heat-expandable base layer (Y1) and between the heat-expandable base layer (Y1) and the non-heat-expandable base layer (Y2). Furthermore, when the pressure-sensitive adhesive sheet of one embodiment of the present invention is the above-mentioned double-sided pressure-sensitive adhesive sheet, at least one of the following may or may not have another layer between the pressure-sensitive adhesive layer (X1) and the heat-expandable base layer (Y1), between the heat-expandable base layer (Y1) and the non-heat-expandable base layer (Y2), and between the non-heat-expandable base layer (Y2) and the pressure-sensitive adhesive layer (X2). However, in the pressure-sensitive adhesive sheet of one embodiment of the present invention, from the viewpoint of effectively transmitting deformation of the heat-expandable base layer (Y1) due to the expansion of the heat-expandable particles to the pressure-sensitive adhesive layer (X1), it is preferable that the pressure-sensitive adhesive layer (X1) and the heat-expandable base layer (Y1) are directly laminated to each other.

[0029] Next, regarding the pressure-sensitive adhesive sheet of one embodiment of the present invention, the heat-expandable particles necessary for forming unevenness on the adhesive surface of the pressure-sensitive adhesive layer (X1) by heating will be explained, and then the pressure-sensitive adhesive layer (X1), the heat-expandable base layer (Y1), the non-heat-expandable base layer (Y2), and the pressure-sensitive adhesive layer (X2) will be explained.

[0030] <Thermal expansion particles> The thermally expandable particles used in the pressure-sensitive adhesive sheet of one embodiment of the present invention may be any particles that expand when heated, and the expansion initiation temperature (t) is appropriately selected depending on the application of the pressure-sensitive adhesive sheet.

[0031] Incidentally, in recent years, when mounting a semiconductor chip on a substrate, a process has been adopted in which the semiconductor chip is attached to the substrate via a thermosetting film-like adhesive called a die attach film (hereinafter also referred to as "DAF"). The DAF is attached to one side of a semiconductor wafer or a plurality of individualized semiconductor chips, and is divided into the same shape as the semiconductor chips at the same time as the semiconductor wafer is individualized or after being attached to the semiconductor chips. The individualized semiconductor chips with DAF are attached (die-attached) to a substrate from the DAF side, and then the DAF is thermally cured to fix the semiconductor chip and the substrate. At this time, the DAF needs to maintain its pressure-sensitive or heat-adhesive properties until it is attached to the substrate. However, when the semiconductor chip with DAF is used as the adherend of the heat-peelable adhesive sheet, the heat applied when expanding the thermally expandable particles may cause the DAF to harden before die-attaching, and the adhesive strength of the DAF to the substrate may decrease. It is desirable to suppress the decrease in adhesive strength of the DAF, since it leads to a decrease in the reliability of the bonding between the semiconductor chip and the substrate. In other words, it is desirable to suppress the thermal change of the adherend when peeling off by heating. From this viewpoint, in the pressure-sensitive adhesive sheet of one embodiment of the present invention, the expansion initiation temperature (t) of the thermally expandable particles is preferably less than 125°C, more preferably 120°C or less, even more preferably 115°C or less, still more preferably 110°C or less, and even more preferably 105°C or less.

[0032] In addition, when heat-expandable particles having a low expansion start temperature are used for a heat-peelable pressure-sensitive adhesive sheet, the heat-expandable particles may expand due to a rise in temperature when grinding the adherend, etc. Such unintended expansion of the heat-expandable particles may lead to unintended separation or displacement of the adherend, and is therefore desirably suppressed. From this viewpoint, in the pressure-sensitive adhesive sheet of one embodiment of the present invention, the expansion initiation temperature (t) of the thermally expandable particles is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, and even more preferably 70°C or higher. In this specification, the expansion starting temperature (t) of the thermally expandable particles means a value measured based on the following method.

[0033] (Method for measuring the expansion start temperature (t) of thermally expandable particles) A sample is prepared by adding 0.5 mg of the thermally expandable particles to be measured to an aluminum cup having a diameter of 6.0 mm (inner diameter 5.65 mm) and a depth of 4.8 mm, and placing an aluminum lid (diameter 5.6 mm, thickness 0.1 mm) on top of it. Using a dynamic viscoelasticity measuring device, the height of the sample is measured while a force of 0.01 N is applied to the sample from above the aluminum lid using a pressure gauge. Then, while a force of 0.01 N is applied using the pressure gauge, the sample is heated from 20°C to 300°C at a temperature increase rate of 10°C / min, the amount of displacement of the pressure gauge in the vertical direction is measured, and the temperature at which displacement in the forward direction begins is taken as the expansion start temperature (t).

[0034] The thermally expandable particles are preferably microencapsulated foaming agents that are composed of an outer shell made of a thermoplastic resin and an encapsulated component that is encapsulated in the outer shell and vaporizes when heated to a predetermined temperature. Examples of the thermoplastic resin constituting the outer shell of the microencapsulated foaming agent include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone.

[0035] Examples of the encapsulated component, which is the component encapsulated in the outer shell of the microencapsulated foaming agent, include low-boiling point liquids such as 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 viewpoints of suppressing thermal changes in the adherend during heat peeling and suppressing unintended expansion of the heat-expandable particles due to temperature rise when the adherend is ground, etc., when the expansion initiation temperature (t) of the heat-expandable particles is 50°C or higher and lower than 125°C, the encapsulated components are preferably propane, isobutane, n-pentane, and cyclopropane. These encapsulation components may be used alone or in combination of two or more. The expansion starting temperature (t) of the thermally expandable particles can be adjusted by appropriately selecting the type of encapsulated component.

[0036] The average particle size of the thermally expandable particles used in one embodiment of the present invention before expansion at 23° C. is preferably 3 to 100 μm, more preferably 4 to 70 μm, even more preferably 6 to 60 μm, and even more preferably 10 to 50 μm. The average particle size of the thermally expandable particles before expansion is the volume median particle size (D 50 ) and refers to the particle size at which the cumulative volume frequency, calculated from the smaller particle size of the heat-expandable particles before expansion, corresponds to 50% in the particle distribution of the heat-expandable particles before expansion measured using a laser diffraction particle size distribution measuring device (for example, product name "Mastersizer 3000" manufactured by Malvern).

[0037] The 90% particle diameter (D 90 ) is preferably 10 to 150 μm, more preferably 15 to 100 μm, even more preferably 20 to 90 μm, and still more preferably 25 to 80 μm. The 90% particle size (D 90 ) means the particle size at which the cumulative volume frequency, calculated from the smaller particle size of the heat-expandable particles before expansion, corresponds to 90% in the particle distribution of the heat-expandable particles before expansion, measured using a laser diffraction particle size distribution measuring device (for example, Malvern, product name "Mastersizer 3000").

[0038] The maximum volume expansion rate of the thermally expandable particles used in one embodiment of the present invention when heated to a temperature equal to or higher than 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.

[0039] <Adhesive layer (X1)> The pressure-sensitive adhesive layer (X1) may be a heat-expandable layer or a non-heat-expandable layer, but is preferably a non-heat-expandable layer. When the pressure-sensitive adhesive layer (X1) is a non-thermally expandable layer, the volume change rate (%) of the pressure-sensitive adhesive layer (X1) calculated from the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and even more preferably less than 0.01%. The pressure-sensitive adhesive layer (X1) preferably does not contain thermally expandable particles, but may contain thermally expandable particles within a range that does not contradict the object of the present invention. When the pressure-sensitive adhesive layer (X1) contains thermally expandable particles, the lower the content, the better, and the content is preferably less than 3 mass%, more preferably less than 1 mass%, even more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably less than 0.001 mass%, based on the total mass (100 mass%) of the pressure-sensitive adhesive layer (X1).

[0040] The pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of one embodiment of the present invention can be formed from a pressure-sensitive adhesive composition (x-1) containing a pressure-sensitive adhesive resin. Hereinafter, each component contained in the pressure-sensitive adhesive composition (x-1) will be described.

[0041] (Adhesive resin) The adhesive resin may be a polymer that has adhesiveness by itself and has a mass average molecular weight (Mw) of 10,000 or more. The mass average molecular weight (Mw) of the adhesive resin is preferably from 10,000 to 2,000,000, more preferably from 20,000 to 1,500,000, and even more preferably from 30,000 to 1,000,000, from the viewpoint of improving the adhesive strength of the adhesive layer (X1).

[0042] Specific examples of adhesive resins include rubber-based resins such as acrylic resins, urethane resins, and polyisobutylene resins, polyester resins, olefin resins, silicone resins, and polyvinyl ether resins. These adhesive resins may be used alone or in combination of two or more kinds. Furthermore, when these adhesive resins are copolymers having two or more types of structural units, the form of the copolymer is not particularly limited and may be any of a block copolymer, a random copolymer, and a graft copolymer.

[0043] The pressure-sensitive adhesive resin may be an energy ray-curable pressure-sensitive adhesive resin having a polymerizable functional group introduced into its side chain. Examples of the polymerizable functional group include those having a carbon-carbon double bond such as a (meth)acryloyl group, a vinyl group, and an allyl group. Among the above-mentioned energy rays, ultraviolet rays, which are easy to handle, are preferable as the energy ray.

[0044] Here, in one aspect of the present invention, from the viewpoint of expressing excellent adhesive strength in the pressure-sensitive adhesive layer (X1) and adjusting the Young's modulus of the pressure-sensitive adhesive layer (X1) within the above range, it is preferable that the pressure-sensitive adhesive resin contains an acrylic resin.

[0045] The content of the acrylic resin in the pressure-sensitive adhesive resin is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, still more preferably 70 to 100% by mass, and even more preferably 85 to 100% by mass with respect to the total amount (100% by mass) of the pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition (x-1) or the pressure-sensitive adhesive layer (X1).

[0046] (Acrylic resin) In one aspect of the present invention, examples of the acrylic resin that can be used as the pressure-sensitive adhesive resin include polymers containing structural units derived from alkyl (meth)acrylates having a linear or branched alkyl group, polymers containing structural units derived from (meth)acrylates having a cyclic structure, and the like.

[0047] The mass average molecular weight (Mw) of the acrylic resin is preferably 100,000 to 1,500,000, more preferably 200,000 to 1,300,000, still more preferably 350,000 to 1,200,000, and even more preferably 500,000 to 1,100,000.

[0048] The acrylic resin used in one embodiment of the present invention is preferably an acrylic copolymer (A1) having a structural unit (a1) derived from an alkyl (meth)acrylate (a1') (hereinafter also referred to as "monomer (a1')") and a structural unit (a2) derived from a functional group-containing monomer (a2') (hereinafter also referred to as "monomer (a2')").

[0049] The number of carbon atoms in the alkyl group of the monomer (a1') is preferably 1 to 24, more preferably 1 to 12, even more preferably 2 to 10, and even more preferably 4 to 8, from the viewpoint of imparting excellent adhesive strength to the pressure-sensitive adhesive layer (X1). The alkyl group contained in the monomer (a1') may be a linear alkyl group or a branched alkyl group.

[0050] Examples of the monomer (a1') include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate. These monomers (a1') may be used alone or in combination of two or more. As monomer (a1'), butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred.

[0051] The content of the structural unit (a1) is preferably 50 to 99.9 mass%, more preferably 60 to 99.0 mass%, even more preferably 70 to 97.0 mass%, and still more preferably 80 to 95.0 mass%, based on all structural units (100 mass%) of the acrylic copolymer (A1).

[0052] Examples of the functional group contained in the monomer (a2') include a hydroxyl group, a carboxyl group, an amino group, and an epoxy group. That is, examples of the monomer (a2') include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, and epoxy group-containing monomers. These monomers (a2') may be used alone or in combination of two or more. Among these, as the monomer (a2'), hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred, and hydroxyl group-containing monomers are more preferred.

[0053] Examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and hydroxyl group-containing compounds such as unsaturated alcohols such as vinyl alcohol and allyl alcohol.

[0054] Examples of carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid, and citraconic acid, and their anhydrides, 2-(acryloyloxy)ethyl succinate, and 2-carboxyethyl (meth)acrylate.

[0055] The content of the structural unit (a2) is preferably 0.1 to 30 mass%, more preferably 0.5 to 20 mass%, even more preferably 1.0 to 15 mass%, and still more preferably 3.0 to 10 mass%, based on all structural units (100 mass%) of the acrylic copolymer (A1).

[0056] The acrylic copolymer (A1) may further contain a structural unit (a3) ​​derived from a monomer (a3') other than the monomers (a1') and (a2'). In the acrylic copolymer (A1), the total content of the structural units (a1) and (a2) is preferably 70 to 100 mass%, more preferably 80 to 100 mass%, even more preferably 90 to 100 mass%, and still more preferably 95 to 100 mass%, based on all structural units (100 mass%) of the acrylic copolymer (A1).

[0057] Examples of the monomer (a3') include olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; diene monomers such as butadiene, isoprene, and chloroprene; (meth)acrylates having a cyclic structure such as cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and imide (meth)acrylate; styrene, α-methylstyrene, vinyl toluene, vinyl formate, vinyl acetate, acrylonitrile, (meth)acrylamide, (meth)acrylonitrile, (meth)acryloylmorpholine, and N-vinylpyrrolidone.

[0058] The acrylic copolymer (A1) may be an energy ray-curable acrylic copolymer having a polymerizable functional group introduced into at least one of the main chain and the side chain. The polymerizable functional group and the energy ray are as described above. The polymerizable functional group can be introduced by reacting an acrylic copolymer having the above-mentioned structural units (a1) and (a2) with a polymerizable compound (Xa) having a polymerizable functional group and a substituent capable of bonding to a functional group possessed by the structural unit (a2) of the acrylic copolymer. Examples of the polymerizable compound (Xa) include 2-(meth)acryloyloxyethyl isocyanate, meta-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acryloyl isocyanate, allyl isocyanate, glycidyl (meth)acrylate, and (meth)acrylic acid.

[0059] The content of the adhesive resin in the adhesive composition (x-1) is preferably 35 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 60 to 100 mass%, and still more preferably 70 to 99.5 mass%, relative to the total amount (100 mass%) of the active ingredients of the adhesive composition (x-1).

[0060] The pressure-sensitive adhesive composition (x-1) may contain, together with the pressure-sensitive adhesive resin, a monomer or oligomer that can be polymerized and cured by irradiation with energy rays as an energy ray-curable compound. Examples of such energy ray-curable compounds include polyfunctional (meth)acrylate monomers such as trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol (meth)acrylate; and oligomers such as polyfunctional urethane (meth)acrylate, polyfunctional polyester (meth)acrylate, polyfunctional polyether (meth)acrylate, and polyfunctional epoxy (meth)acrylate. Among these, polyfunctional urethane (meth)acrylate oligomers are preferred from the viewpoint of having a relatively high molecular weight and being less likely to reduce the elastic modulus of the pressure-sensitive adhesive layer (X1). The molecular weight of the energy ray-curable compound (in the case of an oligomer, the mass average molecular weight (Mw)) is preferably 100 to 12,000, more preferably 200 to 10,000, even more preferably 400 to 8,000, and still more preferably 600 to 6,000.

[0061] (Crosslinking agent) In one embodiment of the present invention, when the pressure-sensitive adhesive composition (x-1) contains a pressure-sensitive adhesive resin having a functional group, such as the above-mentioned acrylic copolymer (A1), it is preferable that the pressure-sensitive adhesive composition (x-1) further contains a crosslinking agent. The crosslinking agent reacts with an adhesive resin having a functional group, and crosslinks the adhesive resins together using the functional group as the crosslinking starting point.

[0062] Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, and a metal chelate-based crosslinking agent. These crosslinking agents may be used alone or in combination of two or more. Among these crosslinking agents, isocyanate-based crosslinking agents are preferred from the viewpoints of increasing cohesive strength and improving adhesive strength, and of ease of availability. Examples of the isocyanate-based crosslinking agent include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane-4,4'-diisocyanate, bicycloheptane triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, methylene bis(cyclohexyl isocyanate), 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate, and hydrogenated xylylene diisocyanate; and acyclic aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; and other polyvalent isocyanate compounds. Further, examples of the isocyanate-based crosslinking agent include a trimethylolpropane adduct type modified product of the polyisocyanate compound, a biuret type modified product obtained by reacting the polyisocyanate compound with water, and an isocyanurate type modified product containing an isocyanurate ring. Among these, from the viewpoint of suppressing a decrease in the elastic modulus of the pressure-sensitive adhesive layer (X1) during heating and suppressing adhesion of residue derived from the pressure-sensitive adhesive layer (X1) to the adherend, it is preferable to use an isocyanurate-type modified product containing an isocyanurate ring, it is more preferable to use an isocyanurate-type modified product of an acyclic aliphatic polyisocyanate, and it is even more preferable to use an isocyanurate-type modified product of hexamethylene diisocyanate.

[0063] The content of the crosslinking agent is appropriately adjusted depending on the number of functional groups possessed by the adhesive resin, but is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass, relative to 100 parts by mass of the adhesive resin having functional groups.

[0064] (tackifier) In one embodiment of the present invention, the pressure-sensitive adhesive composition (x-1) may further contain a tackifier from the viewpoint of further improving adhesive strength. In this specification, the term "tackifier" refers to a component that auxiliary improves the adhesive strength of an adhesive resin and has a mass average molecular weight (Mw) of less than 10,000, and is distinguished from the adhesive resin described above. The mass average molecular weight (Mw) of the tackifier is less than 10,000, preferably 400 to 9,000, more preferably 500 to 8,000, and even more preferably 800 to 5,000.

[0065] Examples of tackifiers include rosin-based resins, terpene-based resins, styrene-based resins, C5 petroleum resins obtained by copolymerizing C5 fractions such as pentene, isoprene, piperine, and 1,3-pentadiene produced by thermal decomposition of petroleum naphtha, C9 petroleum resins obtained by copolymerizing C9 fractions such as indene and vinyltoluene produced by thermal decomposition of petroleum naphtha, and hydrogenated resins obtained by hydrogenating these.

[0066] The softening point of the tackifier is preferably 60 to 170°C, more preferably 65 to 160°C, and further preferably 70 to 150°C. In this specification, the "softening point" of a tackifier refers to a value measured in accordance with JIS K2531. The tackifier may be used alone or in combination with two or more types having different softening points, structures, etc. When two or more tackifiers are used, it is preferable that the weighted average of the softening points of the multiple tackifiers falls within the above range.

[0067] The content of the tackifier is preferably 0.01 to 65% by mass, more preferably 0.1 to 50% by mass, still more preferably 1 to 40% by mass, and even more preferably 2 to 30% by mass with respect to the total amount (100% by mass) of the active ingredients of the pressure-sensitive adhesive composition (x-1).

[0068] (Photoinitiator) In one aspect of the present invention, when the pressure-sensitive adhesive composition (x-1) contains an energy-ray curable pressure-sensitive adhesive resin as the pressure-sensitive adhesive resin, it is preferable to further contain a photoinitiator. By using a pressure-sensitive adhesive composition containing an energy-ray curable pressure-sensitive adhesive resin and a photoinitiator, the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition can sufficiently proceed with the curing reaction even by irradiation with relatively low-energy energy rays, and it is possible to adjust the adhesive force to a desired range. Examples of the photoinitiator used in one aspect of the present invention include 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, 8-chloroanthraquinone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the like. These photoinitiators may be used alone or in combination of two or more.

[0069] The content of the photoinitiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and still more preferably 0.05 to 2 parts by mass with respect to 100 parts by mass of the energy-ray curable pressure-sensitive adhesive resin.

[0070] (Additives for pressure-sensitive adhesives) In one aspect of the present invention, the pressure-sensitive adhesive composition (x-1) may contain additives for pressure-sensitive adhesives used in general pressure-sensitive adhesives in addition to the above-mentioned additives as long as the effects of the present invention are not impaired. Examples of such adhesive additives include antioxidants, softeners (plasticizers), rust inhibitors, pigments, dyes, retarders, reaction accelerators (catalysts), and ultraviolet absorbers. These pressure-sensitive adhesive additives may be used alone or in combination of two or more kinds.

[0071] When these adhesive additives are contained, the content of each adhesive additive is preferably 0.0001 to 20 parts by mass, and more preferably 0.001 to 10 parts by mass, based on 100 parts by mass of the adhesive resin.

[0072] (Thickness of adhesive layer (X1) at 23°C) In one embodiment of the present invention, the thickness of the pressure-sensitive adhesive layer (X1) at 23°C is preferably 3 to 10 μm, more preferably 3 to 8 μm, and even more preferably 3 to 7 μm, from the viewpoints of exhibiting good adhesive strength and forming good unevenness on the adhesive surface of the pressure-sensitive adhesive layer (X1) when the thermo-expandable particles are expanded by heating. By adjusting the thickness of the pressure-sensitive adhesive layer (X1) to within the above range, the pressure-sensitive adhesive layer (X1) can be easily formed, and also unevenness can be favorably formed on the adhesive surface of the pressure-sensitive adhesive layer (X1). The thickness of the pressure-sensitive adhesive layer (X1) at 23° C. is a value measured by the method described in the Examples section below.

[0073] <Thermal Expandable Base Layer (Y1)> The thermally expandable base layer (Y1) comprises a resin base material (Y1') containing thermally expandable particles, and is a layer provided between the pressure-sensitive adhesive layer (X1) and the non-thermally expandable base material layer (Y2). The thermally expandable substrate layer (Y1) is preferably a non-adhesive substrate. In the present invention, whether a substrate is non-adhesive or not is determined as follows: if the probe tack value of the surface of the substrate in question, measured in accordance with JIS Z0237:1991, is less than 50 mN / 5 mmφ, the substrate is determined to be a "non-adhesive substrate." The probe tack value on the surface of the thermally expandable substrate layer (Y1) is usually less than 50 mN / 5 mmφ, preferably less than 30 mN / 5 mmφ, more preferably less than 10 mN / 5 mmφ, and even more preferably less than 5 mN / 5 mmφ. In this specification, the probe tack value on the surface of a substrate means a value measured by the following method. <Probe tack value> The substrate to be measured is cut into a square with sides of 10 mm, and then left to stand for 24 hours in an environment of 23°C and 50% RH (relative humidity) to serve as a test sample. The probe tack value on the surface of the test sample is measured in accordance with JIS Z0237:1991 using a tack tester (manufactured by Nippon Tokushu Sokki Co., Ltd., product name "NTS-4800") in an environment of 23°C and 50% RH (relative humidity). Specifically, a stainless steel probe with a diameter of 5 mm is tacked for 1 second with a contact load of 0.98 N / cm. 2 After contacting the probe with the surface of the test sample at a speed of 10 mm / sec, the force required to separate the probe from the surface of the test sample is measured, and the obtained value can be used as the probe tack value of the test sample.

[0074] The content of the thermally expandable particles in the thermally expandable base layer (Y1) is preferably 1 to 40 mass%, more preferably 5 to 35 mass%, even more preferably 10 to 30 mass%, and still more preferably 15 to 25 mass%, relative to the total mass (100 mass%) of the thermally expandable base layer (Y1).

[0075] In order to improve the interlayer adhesion between the thermally expandable base layer (Y1) and another layer to be laminated therewith, the surface of the thermally expandable base layer (Y1) may be subjected to a surface treatment such as an oxidation method or a roughening method, an easy-adhesion treatment, or a primer treatment. Examples of the oxidation method include corona discharge treatment, plasma discharge treatment, chromic acid treatment (wet), hot air treatment, ozone, and ultraviolet irradiation treatment, and examples of the roughening method include sandblasting and solvent treatment.

[0076] The thermally expandable substrate layer (Y1) is preferably formed from a resin composition (y-1) containing a resin and thermally expandable particles. A preferred embodiment of the resin composition (y-1) will be described below. The following description of the components other than the thermally expandable particles that may be contained in the resin composition (y-1) can be read as the components that may be contained in the resin substrate (Y1').

[0077] The resin composition (y-1) may contain additives for substrates as necessary, within the range that does not impair the effects of the present invention. Examples of the additives for the substrate include ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, slip agents, antiblocking agents, and colorants. These additives for substrates may be used alone or in combination of two or more kinds. When these base material additives are contained, the content of each base material additive is preferably 0.0001 to 20 parts by mass, and more preferably 0.001 to 10 parts by mass, based on 100 parts by mass of the resin.

[0078] The thermally expandable particles contained in the resin composition (y-1) which is the material for forming the thermally expandable base layer (Y1) are as described above. The content of the thermally expandable particles is preferably 1 to 40 mass%, more preferably 5 to 35 mass%, even more preferably 10 to 30 mass%, and still more preferably 15 to 25 mass%, relative to the total amount (100 mass%) of the active ingredients of the resin composition (y-1).

[0079] The resin contained in the resin composition (y-1) which is the material for forming the thermally expandable base layer (Y1) may be a non-adhesive resin or an adhesive resin. In other words, even if the resin contained in the resin composition (y-1) is a sticky resin, in the process of forming the thermally expandable base layer (Y1) from the resin composition (y-1), the sticky resin undergoes a polymerization reaction with a polymerizable compound, the resulting resin becomes a non-sticky resin, and the thermally expandable base layer (Y1) containing the resin becomes non-sticky.

[0080] The mass average molecular weight (Mw) of the resin contained in the resin composition (y-1) is preferably from 1,000 to 1,000,000, more preferably from 1,000 to 700,000, and even more preferably from 1,000 to 500,000. Furthermore, when the resin is a copolymer having two or more types of constitutional units, the form of the copolymer is not particularly limited, and may be any of a block copolymer, a random copolymer, and a graft copolymer.

[0081] The resin content is preferably 50 to 99 mass%, more preferably 60 to 95 mass%, even more preferably 65 to 90 mass%, and still more preferably 70 to 85 mass%, based on the total amount (100 mass%) of the active ingredients of the resin composition (y-1).

[0082] The resin contained in the resin composition (y-1) preferably contains at least one selected from the group consisting of acrylic urethane resins and olefin resins, from the viewpoint of facilitating the formation of irregularities on the adhesive surface of the adhesive layer (X1) and improving the sheet shape retention after thermal expansion. That is, the thermally expandable substrate layer (Y1) and the resin substrate (Y1') preferably contain at least one selected from the group consisting of acrylic urethane resins and olefin resins. As the acrylic urethane resin, the following resin (U1) is preferable. - Acrylic urethane resin (U1) obtained by polymerizing urethane prepolymer (UP) and a vinyl compound containing a (meth)acrylic acid ester. In this specification, a prepolymer refers to a compound obtained by polymerizing a monomer, which can be further polymerized to form a polymer.

[0083] (Acrylic urethane resin (U1)) The urethane prepolymer (UP) which becomes the main chain of the acrylic urethane resin (U1) may be a reaction product of a polyol and a polyisocyanate. The urethane prepolymer (UP) is preferably obtained by further carrying out a chain extension reaction using a chain extender.

[0084] Examples of polyols that can be used as raw materials for the urethane prepolymer (UP) include alkylene polyols, ether polyols, ester polyols, ester amide polyols, ester-ether polyols, and carbonate polyols. These polyols may be used alone or in combination of two or more kinds. The polyol used in one embodiment of the present invention is preferably a diol, more preferably an ester type diol, an alkylene type diol, or a carbonate type diol, and further preferably an ester type diol or a carbonate type diol.

[0085] Examples of the ester-type diol include condensation polymers of one or more selected from diols such as alkane diols (e.g., 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol); alkylene glycols (e.g., ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol); and one or more selected from dicarboxylic acids (e.g., phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4-diphenyldicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, HET acid, maleic acid, fumaric acid, itaconic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, and methylhexahydrophthalic acid) and their anhydrides. Specific examples thereof include polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyhexamethylene isophthalate diol, polyneopentyl adipate diol, polyethylene propylene adipate diol, polyethylene butylene adipate diol, polybutylene hexamethylene adipate diol, polydiethylene adipate diol, poly(polytetramethylene ether) adipate diol, poly(3-methylpentylene adipate) diol, polyethylene azelate diol, polyethylene sebacate diol, polybutylene azelate diol, polybutylene sebacate diol, and polyneopentyl terephthalate diol.

[0086] Examples of alkylene diols include alkane diols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol; alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; polyalkylene glycols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol; and polyoxyalkylene glycols such as polytetramethylene glycol.

[0087] Examples of carbonate diols include 1,4-tetramethylene carbonate diol, 1,5-pentamethylene carbonate diol, 1,6-hexamethylene carbonate diol, 1,2-propylene carbonate diol, 1,3-propylene carbonate diol, 2,2-dimethylpropylene carbonate diol, 1,7-heptamethylene carbonate diol, 1,8-octamethylene carbonate diol, and 1,4-cyclohexane carbonate diol.

[0088] Examples of polyisocyanates that can be used as a raw material for the urethane prepolymer (UP) include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. These polyisocyanates may be used alone or in combination of two or more. Furthermore, these polyisocyanates may be trimethylolpropane adduct-type modified products, biuret-type modified products obtained by reacting with water, or isocyanurate-type modified products containing an isocyanurate ring.

[0089] Among these, the polyisocyanate used in one embodiment of the present invention is preferably a diisocyanate, and more preferably at least one selected from 4,4'-diphenylmethane diisocyanate (MDI), 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), hexamethylene diisocyanate (HMDI), and alicyclic diisocyanates.

[0090] Examples of alicyclic diisocyanates include 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl-2,6-cyclohexane diisocyanate, with isophorone diisocyanate (IPDI) being preferred.

[0091] In one embodiment of the present invention, the urethane prepolymer (UP) that becomes the main chain of the acrylic urethane resin (U1) is preferably a straight-chain urethane prepolymer that is a reaction product of a diol and a diisocyanate and has ethylenically unsaturated groups at both ends. As a method for introducing ethylenically unsaturated groups into both ends of the linear urethane prepolymer, a method of reacting the NCO groups at the ends of the linear urethane prepolymer obtained by reacting a diol with a diisocyanate compound with a hydroxyalkyl (meth)acrylate can be mentioned.

[0092] Examples of hydroxyalkyl (meth)acrylates include 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.

[0093] The vinyl compound which becomes the side chain of the acrylic urethane resin (U1) contains at least a (meth)acrylic acid ester. The (meth)acrylic acid ester is preferably at least one selected from alkyl (meth)acrylates and hydroxyalkyl (meth)acrylates, and more preferably an alkyl (meth)acrylate and a hydroxyalkyl (meth)acrylate are used in combination.

[0094] When an alkyl (meth)acrylate and a hydroxyalkyl (meth)acrylate are used in combination, the mixing ratio of the hydroxyalkyl (meth)acrylate per 100 parts by mass of the alkyl (meth)acrylate is preferably 0.1 to 100 parts by mass, more preferably 0.5 to 30 parts by mass, even more preferably 1.0 to 20 parts by mass, and even more preferably 1.5 to 10 parts by mass.

[0095] The alkyl group in the alkyl (meth)acrylate preferably has 1-24 carbon atoms, more preferably 1-12 carbon atoms, even more preferably 1-8 carbon atoms, and even more preferably 1-3 carbon atoms.

[0096] In addition, the hydroxyalkyl (meth)acrylate may be the same as the hydroxyalkyl (meth)acrylate used for introducing ethylenically unsaturated groups into both ends of the above-mentioned linear urethane prepolymer.

[0097] Examples of vinyl compounds other than (meth)acrylic acid esters include aromatic hydrocarbon vinyl compounds such as styrene, α-methylstyrene, and vinyl toluene; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; and polar group-containing monomers such as vinyl acetate, vinyl propionate, (meth)acrylonitrile, N-vinylpyrrolidone, (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, and metha(acrylamide). These may be used alone or in combination of two or more.

[0098] The content of the (meth)acrylic acid ester in the vinyl compound is preferably 40 to 100 mass%, more preferably 65 to 100 mass%, even more preferably 80 to 100 mass%, and still more preferably 90 to 100 mass%, relative to the total amount (100 mass%) of the vinyl compound.

[0099] The total content of the alkyl (meth)acrylate and the hydroxyalkyl (meth)acrylate in the vinyl compound is preferably 40 to 100 mass%, more preferably 65 to 100 mass%, even more preferably 80 to 100 mass%, and still more preferably 90 to 100 mass%, based on the total amount (100 mass%) of the vinyl compound.

[0100] The acrylic urethane resin (U1) used in one embodiment of the present invention can be obtained by mixing a urethane prepolymer (UP) with a vinyl compound containing a (meth)acrylic acid ester and polymerizing the two. The polymerization is preferably carried out further by adding a radical initiator.

[0101] In the acrylic urethane resin (U1) used in one embodiment of the present invention, the content ratio [(u11) / (u12)] of the structural unit (u11) derived from the urethane prepolymer (UP) to the structural unit (u12) derived from a vinyl compound is, in mass ratio, preferably 10 / 90 to 80 / 20, more preferably 20 / 80 to 70 / 30, even more preferably 30 / 70 to 60 / 40, and still more preferably 35 / 65 to 55 / 45.

[0102] (Olefin resin) As the resin contained in the resin composition (y-1), the olefin resin, which is suitable as the resin, is a polymer having at least a structural unit derived from an olefin monomer. As the above olefin monomer, α-olefins having 2 to 8 carbon atoms are preferable, and specifically, ethylene, propylene, butylene, isobutylene, 1-hexene, etc. can be mentioned. Among these, ethylene and propylene are preferable.

[0103] Specific olefin resins include, for example, ultra-low density polyethylene (VLDPE, density: 880 kg / m 3 or more and less than 910 kg / m 3 ), low density polyethylene (LDPE, density: 910 kg / m 3 or more and less than 915 kg / m 3 ), medium density polyethylene (MDPE, density: 915 kg / m 3 or more and less than 942 kg / m 3 ), high density polyethylene (HDPE, density: 942 kg / m 3 or more), polyethylene resins such as linear low density polyethylene; polypropylene resin (PP); polybutene resin (PB); ethylene-propylene copolymer; olefin elastomer (TPO); poly(4-methyl-1-pentene) (PMP); ethylene-vinyl acetate copolymer (EVA); ethylene-vinyl alcohol copolymer (EVOH); olefinic terpolymers such as ethylene-propylene-(5-ethylidene-2-norbornene); etc. can be mentioned.

[0104] In one aspect of the present invention, the olefin resin may be a modified olefin resin subjected to one or more modifications selected from acid modification, hydroxyl group modification, and acrylic modification.

[0105] For example, examples of acid-modified olefin resins obtained by subjecting an olefin resin to acid modification include modified polymers obtained by graft polymerizing an unsaturated carboxylic acid or an anhydride thereof onto the above-mentioned unmodified olefin resin. Examples of the unsaturated carboxylic acid or anhydride thereof include maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, (meth)acrylic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic acid anhydride, and tetrahydrophthalic anhydride. The unsaturated carboxylic acid or anhydride thereof may be used alone or in combination of two or more kinds.

[0106] Examples of acrylic-modified olefin resins obtained by subjecting olefin resins to acrylic modification include modified polymers obtained by graft polymerizing alkyl (meth)acrylate as a side chain onto the above-mentioned unmodified olefin resin as the main chain. The alkyl group in the alkyl (meth)acrylate preferably has 1-20 carbon atoms, more preferably 1-16 carbon atoms, and even more preferably 1-12 carbon atoms. Examples of the alkyl (meth)acrylate include the same compounds as those selectable as the monomer (a1') described above.

[0107] Examples of hydroxyl-modified olefin resins obtained by subjecting olefin resins to hydroxyl group modification include modified polymers obtained by graft polymerizing a hydroxyl-containing compound onto the above-mentioned unmodified olefin resins that form the main chain. Examples of the hydroxyl group-containing compound include the same hydroxyl group-containing compounds as those mentioned above.

[0108] (Resins other than acrylic urethane resins and olefin resins) In one embodiment of the present invention, the resin composition (y-1) may contain a resin other than the acrylic urethane resin and the olefin resin, as long as the effects of the present invention are not impaired. Examples of such resins include vinyl resins such as polyvinyl chloride, polyvinylidene chloride, and polyvinyl alcohol; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; polycarbonate; polyurethanes not falling under acrylic urethane resins; polysulfone; polyetheretherketone; polyethersulfone; polyphenylene sulfide; polyimide resins such as polyetherimide and polyimide; polyamide resins; acrylic resins; fluorine-based resins, etc.

[0109] However, from the viewpoint of facilitating the formation of irregularities on the adhesive surface of the adhesive layer (X1) and improving the sheet shape maintainability after thermal expansion, it is preferable that the content of resins other than acrylic urethane resins and olefin resins in the resin composition (y-1) is less. The content of resins other than acrylic urethane resins and olefin resins is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, still more preferably less than 10 parts by mass, even more preferably less than 5 parts by mass, and still more preferably less than 1 part by mass, with respect to 100 parts by mass of the total amount of resins contained in the resin composition (y-1).

[0110] (Solvent-free resin composition (y-1a)) As one aspect of the resin composition (y-1) used in one aspect of the present invention, there is provided a solvent-free resin composition (y-1a) which is prepared by blending an oligomer having an ethylenically unsaturated group with a mass average molecular weight (Mw) of 50,000 or less, an energy ray-polymerizable monomer, and the above-described thermally expandable particles, and does not contain a solvent. In the solvent-free resin composition (y-1a), although no solvent is blended, the energy ray-polymerizable monomer contributes to the improvement of the plasticity of the oligomer. By irradiating the solvent-free resin composition (y-1a) with energy rays, oligomers having ethylenically unsaturated groups, energy ray-polymerizable monomers, etc. are polymerized, and the thermally expandable base material layer (Y1) is formed.

[0111] The type, shape and amount (content) of the thermally expandable particles to be blended in the solventless resin composition (y-1a) are as described above.

[0112] The mass average molecular weight (Mw) of the oligomer contained in the solventless resin composition (y-1a) is 50,000 or less, preferably 1,000 to 50,000, more preferably 2,000 to 40,000, even more preferably 3,000 to 35,000, and still more preferably 4,000 to 30,000.

[0113] The oligomer may be any resin contained in the above-mentioned resin composition (y-1) that has an ethylenically unsaturated group with a mass average molecular weight of 50,000 or less. The above-mentioned urethane prepolymer (UP) is preferred, and a linear urethane prepolymer having ethylenically unsaturated groups at both ends is more preferred. As the oligomer, a modified olefin resin having an ethylenically unsaturated group can also be used.

[0114] The total content of the oligomer and the energy ray polymerizable monomer in the solventless resin composition (y-1a) is preferably 50 to 99 mass%, more preferably 60 to 95 mass%, even more preferably 65 to 90 mass%, and still more preferably 70 to 85 mass%, based on the total amount (100 mass%) of the solventless resin composition (y-1a).

[0115] Examples of energy ray polymerizable monomers include alicyclic polymerizable compounds such as isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, cyclohexyl (meth)acrylate, adamantane (meth)acrylate, and tricyclodecane acrylate; aromatic polymerizable compounds such as phenylhydroxypropyl acrylate, benzyl acrylate, and phenol ethylene oxide modified acrylate; and heterocyclic polymerizable compounds such as tetrahydrofurfuryl (meth)acrylate, morpholine acrylate, N-vinylpyrrolidone, and N-vinylcaprolactam. These energy ray polymerizable monomers may be used alone or in combination of two or more kinds.

[0116] The content ratio of the oligomer to the energy ray polymerizable monomer in the solventless resin composition (y-1a) [oligomer / energy ray polymerizable monomer], in mass ratio, is preferably 20 / 80 to 90 / 10, more preferably 30 / 70 to 85 / 15, and even more preferably 35 / 65 to 80 / 20.

[0117] In one embodiment of the present invention, the solventless resin composition (y-1a) preferably further contains a photopolymerization initiator. By including a photopolymerization initiator, the curing reaction can be sufficiently promoted even by irradiation with energy rays having a relatively low energy.

[0118] Examples of the photopolymerization initiator include the same ones as the photopolymerization initiator that may be contained in the pressure-sensitive adhesive composition (x-1). These photopolymerization initiators may be used alone or in combination of two or more kinds.

[0119] The amount of the photopolymerization initiator added is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 4 parts by mass, and even more preferably 0.02 to 3 parts by mass, based on the total amount (100 parts by mass) of the oligomer and the energy ray polymerizable monomer.

[0120] (Young's modulus adjustment component) The resin composition (y-1) for forming the thermally expandable substrate layer (Y1) may contain a Young's modulus adjusting component for adjusting the Young's modulus at 120° C. of the resin substrate (Y1′). An example of the Young's modulus adjusting component is a component that, when the resin substrate (Y1') does not contain a Young's modulus adjusting component and the Young's modulus at 120°C of the resulting resin substrate (Y1') exceeds 2.05 MPa, is added as a raw material to adjust the Young's modulus at 120°C of the resulting resin substrate (Y1') to 2.05 MPa or less. The Young's modulus adjusting component is not particularly limited as long as it can adjust the Young's modulus at 120°C to a desired range, and examples thereof include monomers, oligomers, polymers, etc., which adjust the orientation, crystallinity, rigidity, etc. of the resin substrate (Y1'). The Young's modulus adjusting component may adjust the Young's modulus by reacting with other components forming the resin base material (Y1'), or may adjust the Young's modulus by being present without reacting with other components forming the resin base material (Y1'). For example, when adjusting the Young's modulus at 120°C to a lower value, the Young's modulus adjusting component that reacts with other components can be selected from those that have low crystallinity, high flexibility, or reduce the crosslinking points of the resin substrate (Y1'). Furthermore, as the Young's modulus adjusting component that does not react with other components, a component that has low reactivity or compatibility with other components can be selected. Specific examples of the Young's modulus adjusting component include, for example, the monomers listed as the raw material monomer (a1') of the adhesive resin contained in the adhesive layer (X1), and energy ray polymerizable monomers that can be contained in the solventless resin composition (y-1a), and among these, one that can exert the above-mentioned effect can be appropriately selected. The amount of the Young's modulus adjusting component used may be appropriately adjusted depending on the type of the Young's modulus adjusting component, the type of resin other than the Young's modulus adjusting component, and the like.

[0121] (Thickness of the thermally expandable base layer (Y1)) In one aspect of the present invention, the thickness of the thermally expandable base material layer (Y1) is preferably 10 to 1000 μm, more preferably 20 to 500 μm, still more preferably 25 to 400 μm, and even more preferably 30 to 300 μm.

[0122] <Non-thermally expandable base material layer (Y2)> The non-thermally expandable base material layer (Y2) of the pressure-sensitive adhesive sheet according to one aspect of the present invention is provided on the surface of the thermally expandable base material layer (Y1) opposite to the laminated surface of the pressure-sensitive adhesive layer (X1). In the pressure-sensitive adhesive sheet according to one aspect of the present invention, the Young's modulus of the non-thermally expandable base material layer (Y2) at 120°C is preferably higher than the Young's modulus of the thermally expandable base material layer (Y1) at 120°C. Thereby, when the thermally expandable particles are expanded, unevenness is more likely to be formed on the surface of the thermally expandable base material layer (Y1) on the pressure-sensitive adhesive layer (X1) side than on the surface of the thermally expandable base material layer (Y1) on the non-thermally expandable base material layer (Y2) side, and unevenness is favorably formed on the adhesive surface of the pressure-sensitive adhesive layer (X1). From such a viewpoint, the Young's modulus of the non-thermally expandable base material layer (Y2) at 120°C is preferably 500 MPa or more, more preferably 600 MPa or more, still more preferably 700 MPa or more, and even more preferably 800 MPa or more. Also, it is usually 10,000 MPa or less.

[0123] The non-thermally expandable base material layer (Y2) is preferably a non-adhesive base material. The probe tack value on the surface of the non-thermally expandable base material layer (Y2) is usually less than 50 mN / 5 mmφ, preferably less than 30 mN / 5 mmφ, more preferably less than 10 mN / 5 mmφ, and still more preferably less than 5 mN / 5 mmφ.

[0124] Examples of the material for forming the non-thermally expandable base material layer (Y2) include resins, metals, paper materials, etc., and can be appropriately selected according to the use of the pressure-sensitive adhesive sheet according to one aspect of the present invention.

[0125] Examples of resins include 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; urethane resins such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polysulfone; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide resins such as polyetherimide and polyimide; polyamide resins; acrylic resins; and fluorine-based resins. Examples of metals include aluminum, tin, chromium, and titanium. Examples of paper materials include thin paper, medium-quality paper, fine paper, impregnated paper, coated paper, art paper, parchment paper, and glassine paper. Among these, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are preferred.

[0126] These forming materials may be composed of one kind or two or more kinds in combination. Examples of the non-thermally expandable base layer (Y2) using two or more forming materials in combination include a paper material laminated with a thermoplastic resin such as polyethylene, and a resin film or sheet containing a resin and having a metal film formed on the surface thereof. Examples of methods for forming the metal layer include a method of depositing the above-mentioned metal by a PVD method such as vacuum deposition, sputtering, or ion plating, or a method of attaching a metal foil made of the above-mentioned metal using a general adhesive.

[0127] In addition, from the viewpoint of improving the interlayer adhesion between the non-thermally expandable base layer (Y2) and other layers to be laminated therewith, when the non-thermally expandable base layer (Y2) contains a resin, the surface of the non-thermally expandable base layer (Y2) may also be subjected to a surface treatment such as an oxidation method or a roughening method, an easy-adhesion treatment, or a primer treatment, as in the case of the above-mentioned heat-expandable base layer (Y1).

[0128] When the non-thermally expandable substrate layer (Y2) contains a resin, it may contain, together with the resin, the above-mentioned substrate additives which may also be contained in the resin composition (y-1).

[0129] The non-thermally expandable base layer (Y2) is a non-thermally expandable layer determined based on the above-mentioned method. Therefore, the volume change rate (%) of the non-thermally expandable base layer (Y2) calculated from the above formula is less than 5%, but is preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and even more preferably less than 0.01%.

[0130] The non-thermally expandable base layer (Y2) may contain thermally expandable particles as long as the volume change rate is within the above range. For example, by selecting the resin contained in the non-thermally expandable base layer (Y2), it is possible to adjust the volume change rate to the above range even if the layer contains thermally expandable particles. However, the content of the thermally expandable particles in the non-thermally expandable base layer (Y2) is preferably as small as possible. The specific content of the thermally expandable particles is usually less than 3 mass%, preferably less than 1 mass%, more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably less than 0.001 mass%, based on the total mass (100 mass%) of the non-thermally expandable base layer (Y2). It is even more preferable that the thermally expandable particles are not contained.

[0131] (Storage modulus E'(23) of non-thermally expandable base layer (Y2) at 23°C) The storage modulus E'(23) of the non-thermally expandable base layer (Y2) at 23°C is preferably 5.0 x 10 7 ~5.0×10 9Pa, more preferably 5.0×10 8 ~4.5×10 9 Pa, more preferably 1.0×10 9 ~4.0×10 9 It is Pa. The storage modulus E'(23) of the non-thermally expandable base layer (Y2) is 5.0×10 7 On the other hand, when the storage modulus E'(23) of the non-thermally expandable base layer (Y2) is 5.0×10 Pa or more, the deformation resistance of the pressure-sensitive adhesive sheet is easily improved. 9 When the elastic modulus is not more than 1 Pa, the handleability of the pressure-sensitive adhesive sheet is easily improved. In this specification, the storage modulus E'(23) of the non-thermally expandable base layer (Y2) means a value measured by the method described in the Examples.

[0132] (Thickness of non-thermally expandable base layer (Y2)) The thickness of the non-thermally expandable base layer (Y2) is preferably 5 to 500 μm, more preferably 15 to 300 μm, and even more preferably 20 to 200 μm. If the thickness of the non-thermally expandable base layer (Y2) is 5 μm or more, the deformation resistance of the pressure-sensitive adhesive sheet is easily improved. On the other hand, if the thickness of the non-thermally expandable base layer (Y2) is 500 μm or less, the handleability of the pressure-sensitive adhesive sheet is easily improved. In this specification, the thickness of the non-thermally expandable base layer (Y2) means a value measured by the method described in the examples.

[0133] <Adhesive layer (X2)> The pressure-sensitive adhesive layer (X2) is a layer that is optionally provided on the surface of the non-thermally expandable base layer (Y2) opposite to the surface on which the thermally expandable base layer (Y1) is laminated. The pressure-sensitive adhesive layer (X2) may be a heat-expandable layer or a non-heat-expandable layer, but is preferably a non-heat-expandable layer. When the pressure-sensitive adhesive layer (X2) is a non-thermally expandable layer, the volume change rate (%) of the pressure-sensitive adhesive layer (X2) calculated from the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and even more preferably less than 0.01%. The pressure-sensitive adhesive layer (X2) preferably does not contain any thermally expandable particles, but may contain thermally expandable particles as long as this does not contradict the object of the present invention. When the pressure-sensitive adhesive layer (X2) contains thermally expandable particles, the smaller the content, the better, and the content is preferably less than 3 mass%, more preferably less than 1 mass%, even more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably less than 0.001 mass%, relative to the total mass (100 mass%) of the pressure-sensitive adhesive layer (X2).

[0134] The adhesive layer (X2) is preferably an adhesive layer that is cured by irradiation with energy rays to reduce its adhesive strength. This allows the adhesive surface of the adhesive layer (X1) to have its adhesive strength reduced by heating, and the adhesive surface of the adhesive layer (X2) to have its adhesive strength reduced by irradiation with energy rays, making it possible to make the adhesive layers have different mechanisms of action for reducing their adhesive strengths. Therefore, when performing a process for reducing the adhesive strength of one of the adhesive layers, it is possible to prevent the adhesive strength of the other adhesive layer from being unintentionally reduced.

[0135] The pressure-sensitive adhesive layer (X2) is preferably formed from a pressure-sensitive adhesive composition (x-2) containing a pressure-sensitive adhesive resin. Each component contained in the pressure-sensitive adhesive composition (x-2) will be described below.

[0136] (Adhesive composition (x-2)) The pressure-sensitive adhesive composition (x-2) contains a pressure-sensitive adhesive resin, and may contain, as necessary, a crosslinking agent, a tackifier, a polymerizable compound, a polymerization initiator, and other pressure-sensitive adhesive additives used in general pressure-sensitive adhesives other than the above-mentioned components.

[0137] (Adhesive resin) The adhesive resin may be a polymer that has adhesiveness by itself and has a mass average molecular weight (Mw) of 10,000 or more. The mass average molecular weight (Mw) of the adhesive resin is preferably from 10,000 to 2,000,000, more preferably from 20,000 to 1,500,000, and even more preferably from 30,000 to 1,000,000, from the viewpoint of further improving the adhesive strength of the adhesive layer (X2).

[0138] The adhesive resin may be the same as that contained in the adhesive composition (x-1). These adhesive resins may be used alone or in combination of two or more kinds. Furthermore, when these adhesive resins are copolymers having two or more types of constitutional units, the copolymer may be in the form of any one of a block copolymer, a random copolymer, and a graft copolymer.

[0139] The adhesive resin contained in the adhesive composition (x-2) is preferably an adhesive resin having an energy ray-polymerizable functional group in a side chain, from the viewpoint of making the resulting adhesive layer (X2) into an adhesive layer whose adhesive strength decreases upon curing by energy ray irradiation. Examples of the energy ray-polymerizable functional group include those having a carbon-carbon double bond, such as a (meth)acryloyl group, a vinyl group, and an allyl group. Of the above-mentioned energy rays, ultraviolet rays are preferred because they are easy to handle.

[0140] When the pressure-sensitive adhesive composition (x-2) is a pressure-sensitive adhesive composition that is cured by irradiation with energy rays, the pressure-sensitive adhesive composition preferably further contains a photopolymerization initiator. By including a photopolymerization initiator, the polymerization of the energy ray-polymerizable component can be promoted more efficiently. Examples of the photopolymerization initiator include the same ones as the photopolymerization initiator that may be contained in the pressure-sensitive adhesive composition (x-1). The content of the photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.05 to 2 parts by mass, based on 100 parts by mass of the total amount of the adhesive resin having an energy ray-polymerizable functional group.

[0141] From the viewpoint of exhibiting excellent adhesive strength, the adhesive resin preferably contains an acrylic resin. The content of the acrylic resin in the pressure-sensitive adhesive composition (x-2) is preferably 30 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 70 to 100 mass%, and still more preferably 85 to 100 mass%, relative to the total amount (100 mass%) of the pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition (x-2).

[0142] The content of the adhesive resin in the adhesive composition (x-2) is preferably 35 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 60 to 98 mass%, and still more preferably 70 to 95 mass%, relative to the total amount (100 mass%) of the active ingredients of the adhesive composition (x-2).

[0143] (Crosslinking agent) In one embodiment of the present invention, when the pressure-sensitive adhesive composition (x-2) contains a pressure-sensitive adhesive resin having a functional group, it is preferable that the pressure-sensitive adhesive composition (x-2) further contains a crosslinking agent. The crosslinking agent reacts with an adhesive resin having a functional group, and crosslinks the adhesive resins together using the functional group as the crosslinking starting point.

[0144] Examples of the crosslinking agent that may be contained in the pressure-sensitive adhesive composition (x-2) include the same crosslinking agents as those that may be contained in the pressure-sensitive adhesive composition (x-1). From the viewpoints of increasing the cohesive strength and improving the adhesive strength, and of ease of availability, an isocyanate-based crosslinking agent is preferred.

[0145] The content of the crosslinking agent is appropriately adjusted depending on the number of functional groups possessed by the adhesive resin, but is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and even more preferably 0.05 to 5 parts by mass, relative to 100 parts by mass of the adhesive resin having functional groups.

[0146] (tackifier) In one embodiment of the present invention, the pressure-sensitive adhesive composition (x-2) may further contain a tackifier from the viewpoint of further improving adhesive strength. As the tackifier that may be contained in the pressure-sensitive adhesive composition (x-2), one similar to the tackifier that may be contained in the pressure-sensitive adhesive composition (x-1) can be used.

[0147] (Adhesive additives) Examples of the pressure-sensitive adhesive additives include the same ones as the pressure-sensitive adhesive additives that may be contained in the pressure-sensitive adhesive composition (x-1).

[0148] The pressure-sensitive adhesive composition (x-2) can be produced by mixing a pressure-sensitive adhesive resin and, if necessary, a crosslinking agent, a tackifier, pressure-sensitive adhesive additives, and the like.

[0149] (Thickness of adhesive layer (X2) at 23°C) The thickness of the pressure-sensitive adhesive layer (X2) at 23° C. is preferably from 5 to 150 μm, more preferably from 8 to 100 μm, even more preferably from 12 to 70 μm, and even more preferably from 15 to 50 μm. If the thickness of the pressure-sensitive adhesive layer (X2) at 23° C. is 5 μm or more, sufficient adhesive strength is easily obtained, and unintended peeling from the adherend during temporary fixing, displacement of the adherend, etc. tend to be suppressed. On the other hand, if the thickness of the pressure-sensitive adhesive layer (X2) at 23° C. is 150 μm or less, handling of the pressure-sensitive adhesive sheet tends to be easier.

[0150] <Removal material> As the release material, a release sheet having undergone a double-sided release treatment, a release sheet having undergone a single-sided release treatment, etc., may be used, and examples thereof include a release material having a release agent applied onto a base material for the release material. Examples of the substrate for the release material include plastic films, papers, etc. Examples of the plastic films include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin; olefin resin films such as polypropylene resin and polyethylene resin; and examples of the papers include fine paper, glassine paper, and craft paper.

[0151] Examples of the release agent include rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, butadiene-based resins, long-chain alkyl-based resins, alkyd-based resins, fluorine-based resins, etc. The release agent may be used alone or in combination of two or more kinds.

[0152] The thickness of the release material is preferably 10 to 200 μm, more preferably 20 to 150 μm, and further preferably 35 to 80 μm.

[0153] [Method of manufacturing adhesive sheet] The method for producing the pressure-sensitive adhesive sheet according to one embodiment of the present invention is not particularly limited, and examples thereof include a method for producing a pressure-sensitive adhesive sheet comprising the following steps (1a) to (3a). Step (1a): A step of applying a pressure-sensitive adhesive composition (x-1) onto a release-treated surface of a release material to form a pressure-sensitive adhesive layer (X1). Step (2a): A step of applying a resin composition (y-1) to one side of a non-thermally expandable base layer (Y2) to form a base laminate in which the non-thermally expandable base layer (Y2) and the thermally expandable base layer (Y1) are laminated together. Step (3a): A step of bonding the adhesive surface of the pressure-sensitive adhesive layer (X1) formed in step (1a) to the surface of the thermally expandable base material layer (Y1) side of the base material laminate formed in step (2a).

[0154] Another method for producing a pressure-sensitive adhesive sheet according to an embodiment of the present invention includes a method for producing a double-sided pressure-sensitive adhesive sheet, which includes the above steps (4a) to (5a) in addition to the above steps (1a) to (3a). Step (4a): A step of applying a pressure-sensitive adhesive composition (x-2) onto the release-treated surface of a release material to form a pressure-sensitive adhesive layer (X2). Step (5a): A step of bonding the adhesive surface of the adhesive layer (X2) formed in step (4a) to the surface of the non-thermally expandable base layer (Y2) of the adhesive sheet formed in step (3a).

[0155] In the above-mentioned method for producing a pressure-sensitive adhesive sheet, the resin composition (y-1), the pressure-sensitive adhesive composition (x-1), and the pressure-sensitive adhesive composition (x-2) may be further mixed with a dilution solvent to form a solution. Examples of the coating method include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0156] In addition, in the process of drying the coating film formed from the resin composition (y-1), the pressure-sensitive adhesive composition (x-1), and the pressure-sensitive adhesive composition (x-2), the drying temperature is preferably lower than the expansion initiation temperature (t) of the heat-expandable particles, from the viewpoint of suppressing the expansion of the heat-expandable particles.

[0157] [Applications and usage of adhesive sheets] The pressure-sensitive adhesive sheet of one embodiment of the present invention can easily peel off the temporarily fixed adherend by heating, and can suppress the contamination of the adherend surface after peeling, and can be applied to all kinds of uses.Specifically, it is suitable for, for example, a dicing sheet used when dicing an adherend such as a semiconductor wafer, a back grinding sheet used in the process of grinding an adherend, an expand tape used to expand the distance between adherends such as semiconductor chips that are divided by dicing, a transfer tape used to turn over an adherend such as a semiconductor chip, a temporary fixing sheet for inspecting an object to be inspected, etc.

[0158] The adherend to which the pressure-sensitive adhesive sheet of one embodiment of the present invention can be applied is not particularly limited, but examples thereof include semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, sapphire substrates, displays, and panel substrates. In the pressure-sensitive adhesive sheet of one embodiment of the present invention, when the expansion onset temperature (t) of the thermally expandable particles is set to less than 125°C, heat peeling is possible at low temperatures, making the sheet suitable for temporarily fixing adherends that are susceptible to thermal changes, such as semiconductor chips with DAFs. Furthermore, in the pressure-sensitive adhesive sheet of one embodiment of the present invention, when the expansion initiation temperature (t) of the heat-expandable particles is set to 50°C or higher, unintended expansion of the heat-expandable particles due to temperature rise, for example when grinding an adherend, can be suppressed, making the sheet suitable for use as a backgrind sheet in the process of grinding an adherend.

[0159] The heating temperature when the pressure-sensitive adhesive sheet of one embodiment of the present invention is heat-peeled from the adherend is equal to or higher than the expansion start temperature (t) of the thermally expandable particles, preferably "a temperature higher than the expansion start temperature (t)", more preferably "expansion start temperature (t) + 2°C" or higher, even more preferably "expansion start temperature (t) + 4°C" or higher, and even more preferably "expansion start temperature (t) + 5°C" or higher. From the viewpoint of energy saving and suppressing thermal changes in the adherend during heat-peeling, the heating temperature is preferably "expansion start temperature (t) + 50°C" or lower, more preferably "expansion start temperature (t) + 40°C" or lower, and even more preferably "expansion start temperature (t) + 20°C" or lower. Furthermore, from the viewpoint of suppressing thermal changes in the adherend, the heating temperature during heat peeling is within the range of the expansion onset temperature (t) or higher, and is preferably less than 125°C, more preferably 120°C or lower, even more preferably 115°C or lower, still more preferably 110°C or lower, and even more preferably 105°C or lower.

[0160] The heating method is not particularly limited as long as it can heat the material to a temperature equal to or higher than the temperature at which the thermally expandable particles expand, and for example, an electric heater, dielectric heating, magnetic heating, heating by electromagnetic waves such as infrared rays such as near infrared rays, mid infrared rays, and far infrared rays, etc. The heating method may be any of contact heating methods such as a heating roller or a heating press, or non-contact heating methods such as an atmospheric heating device or infrared irradiation.

[0161] [Method of manufacturing semiconductor device] The present invention also provides a method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet of one aspect of the present invention. One embodiment of the method for manufacturing a semiconductor device of the present invention is an embodiment in which an adhesive sheet of one embodiment of the present invention is used as a temporary fixing sheet for processing and / or inspecting an adherend (hereinafter also referred to as the "first embodiment of the method for manufacturing a semiconductor device"). In this specification, the "semiconductor device" refers to all devices that can function by utilizing semiconductor characteristics. For example, it includes wafers with integrated circuits, thinned wafers with integrated circuits, chips with integrated circuits, thinned chips with integrated circuits, electronic components including these chips, and electronic devices equipped with such electronic components, etc.

[0162] <Manufacturing Method of Semiconductor Device of the First Aspect> As a more specific aspect of the manufacturing method of the semiconductor device of the first aspect, there is provided a manufacturing method of a semiconductor device including a step of attaching a processing and inspection object to the adhesive sheet of an aspect of the present invention, performing one or more selected from processing and inspection on the processing and inspection object, and then heating the adhesive sheet to a temperature equal to or higher than the expansion start temperature (t). Examples of the processing and inspection object include semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, LED elements, sapphire substrates, displays, substrates for panels, etc. The processing performed on the processing and inspection object is not particularly limited, and examples include grinding processing, singulation processing, etc. The inspection performed on the processing and inspection object is not particularly limited, and examples include defect inspection using an optical microscope, laser (e.g., dust inspection, surface defect inspection, wiring pattern inspection, etc.), visual surface inspection, etc.

[0163] In the manufacturing method of the semiconductor device of the first aspect, the adhesive layer of the adhesive sheet to which the processing and inspection object is attached may be the adhesive layer (X1), and when the adhesive sheet is a double-sided adhesive sheet, it may be the adhesive layer (X2). In addition, when the adhesive sheet is a double-sided adhesive sheet, it is preferable to attach the processed inspection object to one of the adhesive layers and attach the support to the other adhesive layer. By fixing the processed inspection object to the support via the adhesive sheet, vibration, positional deviation, and damage to the fragile processed inspection object can be suppressed when performing at least one of processing and inspection, and processing accuracy and processing speed, as well as inspection accuracy and inspection speed can be improved. At this time, the support may be attached to the adhesive layer (X1) and the processed inspection object may be attached to the adhesive layer (X2), or the processed inspection object may be attached to the adhesive layer (X1) and the support may be attached to the adhesive layer (X2). In the case where the support is attached to the adhesive layer (X1) and the processing test object is attached to the adhesive layer (X2), the support is attached to the adhesive layer (X1) which has excellent peelability after heat treatment, so that even if the support is made of a hard material, the adhesive sheet and the support can be heat peeled off without bending. In addition, the composition of the adhesive layer (X2) can be selected appropriately depending on the type of the processing test object, and for example, if the adhesive layer (X2) is an adhesive layer whose adhesive strength decreases by energy ray irradiation, the processing object can be peeled off without contaminating it with residues derived from the thermally expandable particles. On the other hand, in the case where the processed and inspected object is attached to the adhesive layer (X1) and the support is attached to the adhesive layer (X2), since the processed and inspected object is attached to the adhesive layer (X1) which has excellent peelability after heat treatment, when the processed and inspected object is heated and peeled off after processing, there is no need to pick up the processed and inspected objects individually, and they can be easily peeled off all at once, resulting in excellent productivity of the semiconductor device. Furthermore, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used as a temporary fixing sheet for inspecting processed and inspected objects, the inspection can be performed with a plurality of processed and inspected objects attached to the adhesive layer (X1) of the pressure-sensitive adhesive sheet. After the inspection, for example, a portion of the pressure-sensitive adhesive sheet to which the plurality of processed and inspected objects are attached can be locally heated to selectively heat-peel off a specific processed and inspected object attached to that portion. In this case, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be heat-peel off at a low temperature, so that the heat-peel off operation is easy to perform and energy-saving, and even if the processed and inspected object is easily thermally changed, the thermal change of the processed and inspected object due to heating during heat-peel off can be suppressed.

[0164] <Second embodiment of the method for manufacturing a semiconductor device> The second embodiment of the method for manufacturing a semiconductor device can be a manufacturing method (hereinafter also referred to as "manufacturing method A") that uses a double-sided pressure-sensitive adhesive sheet in which the expansion onset temperature (t) of the thermally expandable particles is 50°C or higher and lower than 125°C as the pressure-sensitive adhesive sheet of one embodiment of the present invention, and includes the following steps 1A to 3A, a first separation step, and a second separation step. Step 1A: A step of attaching an object to be processed to the adhesive layer (X2) and attaching a support to the adhesive layer (X1) Step 2A: A step of subjecting the object to one or more treatments selected from a grinding treatment and a singulation treatment. Step 3A: A step of attaching a thermosetting film to the surface of the object to be processed opposite to the adhesive layer (X2) that has been subjected to the above-mentioned treatment. First separation step: a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion starting temperature (t) and lower than 125° C. to separate the pressure-sensitive adhesive layer (X1) from the support. Second separation step: a step of separating the pressure-sensitive adhesive layer (X2) from the object to be processed

[0165] Hereinafter, the method for manufacturing a semiconductor device including steps 1A to 3A, a first separation step, and a second separation step will be described with reference to the drawings. In the following description, an example in which a semiconductor wafer is used as the processing object will be mainly described, but the same applies to other processing objects. Examples of other processing objects include the same objects as those listed above as processing and inspection objects.

[0166] (Process 1A) Step 1A is a step of attaching an object to be processed to the adhesive layer (X2) of the adhesive sheet, and attaching a support to the adhesive layer (X1). FIG. 3 shows a cross-sectional view illustrating a process of attaching a semiconductor wafer W to the adhesive layer (X2) of the adhesive sheet 2a and attaching a support 3 to the adhesive layer (X1). The semiconductor wafer W is attached so that the front surface W1, which is the circuit surface, faces the adhesive layer (X2). The semiconductor wafer W may be a silicon wafer, or may be a wafer made of gallium arsenide, silicon carbide, sapphire, lithium tantalate, lithium niobate, gallium nitride, indium phosphide, or the like, or a glass wafer. The thickness of the semiconductor wafer W before grinding is usually 500 to 1000 μm. The circuits on the surface W1 of the semiconductor wafer W can be formed by a conventional method such as an etching method or a lift-off method.

[0167] The material of the support 3 may be appropriately selected in consideration of the required characteristics such as mechanical strength and heat resistance depending on the type of workpiece and the processing content. Examples of materials for the support 3 include metal materials such as SUS; non-metallic inorganic materials such as glass and silicon wafers; resin materials such as epoxy resin, ABS resin, acrylic resin, engineering plastic, super engineering plastic, polyimide resin, and polyamideimide resin; and composite materials such as glass epoxy resin. Of these, SUS, glass, and silicon wafers are preferred. Examples of the engineering plastics include nylon, polycarbonate (PC), and polyethylene terephthalate (PET). Examples of the super engineering plastics include polyphenylene sulfide (PPS), polyethersulfone (PES), and polyetheretherketone (PEEK).

[0168] The support 3 is preferably attached to the entire adhesive surface of the adhesive layer (X1). Therefore, the surface area of ​​the support 3 attached to the adhesive surface of the adhesive layer (X1) is preferably equal to or larger than the surface area of ​​the adhesive surface of the adhesive layer (X1). In addition, the surface of the support 3 attached to the adhesive surface of the adhesive layer (X1) is preferably flat. The shape of the support 3 is not particularly limited, but is preferably a plate shape. The thickness of the support 3 may be appropriately selected in consideration of the required characteristics, but is preferably from 20 μm to 50 mm, more preferably from 60 μm to 20 mm.

[0169] (Process 2A) Step 2A is a step of subjecting the object to one or more treatments selected from a grinding treatment and a singulation treatment. Examples of one or more processes selected from grinding processes and dicing processes include grinding processes using a grinder or the like; dicing processes by blade dicing method, laser dicing method, and Stealth Dicing (registered trademark) method; grinding processes and dicing processes by blade tip dicing method and stealth tip dicing method; and the like. Among these, the grinding process and singulation process using the stealth tip dicing method, the grinding process and singulation process using the blade tip dicing method, and the grinding process and singulation process using the stealth tip dicing method are preferred, and the grinding process and singulation process using the blade tip dicing method and the grinding process and singulation process using the stealth tip dicing method are more preferred.

[0170] The stealth dicing method is a method in which a modified region is formed inside a semiconductor wafer by irradiation with laser light, and the semiconductor wafer is divided into individual pieces using the modified region as a dividing starting point. The modified region formed in the semiconductor wafer is a part embrittled by multiphoton absorption, and when the semiconductor wafer is expanded, stress is applied parallel to the wafer surface and in the direction in which the wafer is expanded, so that cracks extend from the modified region toward the front and back surfaces of the semiconductor wafer, and the semiconductor wafer is divided into individual pieces. That is, the modified region is formed along the dividing line when the wafer is divided into individual pieces. The modified region is formed inside the semiconductor wafer by irradiating the semiconductor wafer with a laser beam focused on the inside of the semiconductor wafer. The incident surface of the laser beam may be the front or back surface of the semiconductor wafer. The incident surface of the laser beam may be the surface to which an adhesive sheet is attached, and in this case, the laser beam is irradiated to the semiconductor wafer through the adhesive sheet.

[0171] The blade tip dicing method is also called the DBG method (Dicing Before Grinding). The blade tip dicing method is a method in which a groove is formed in advance in a semiconductor wafer along a line to be divided, the semiconductor wafer is then back-ground until the grinding surface reaches at least the groove, and the semiconductor wafer is thinned and divided into individual pieces. The groove that the grinding surface reaches becomes a cut that penetrates the semiconductor wafer, and the semiconductor wafer is divided by the cut and divided into individual semiconductor chips. The pre-formed groove is usually provided on the surface (circuit surface) of the semiconductor wafer, and can be formed, for example, by dicing using a conventionally known wafer dicing device equipped with a dicing blade.

[0172] The stealth dicing method is also called the SDBG method (Stealth Dicing Before Grinding). The stealth dicing method is a method of forming a modified region inside a semiconductor wafer by irradiation with laser light, and dividing the semiconductor wafer into individual pieces using the modified region as a dividing starting point, as in the stealth dicing method. However, the stealth dicing method is different from the stealth dicing method in that the semiconductor wafer is thinned by grinding, and the semiconductor wafer is divided into individual pieces into semiconductor chips. Specifically, the semiconductor wafer having a modified region is thinned by back grinding, and at the same time, a crack is extended from the modified region toward the adhesive surface of the semiconductor wafer by the pressure applied to the semiconductor wafer, and the semiconductor wafer is divided into individual pieces into semiconductor chips. The grinding thickness after forming the modified region may be a thickness that reaches the modified region, but even if it does not strictly reach the modified region, it may be ground to a position close to the modified region and then broken by the processing pressure of a grinding wheel or the like.

[0173] When the semiconductor wafer W is diced into individual pieces by a blade tip dicing method, it is preferable to form grooves in advance on the surface W1 of the semiconductor wafer W to be attached to the adhesive layer (X2) in step 1A. On the other hand, when the semiconductor wafer W is diced into individual pieces by a stealth first dicing method, the semiconductor wafer W to be attached to the adhesive layer (X2) in step 1A may be irradiated with laser light to form a modified region in advance, or the semiconductor wafer W attached to the adhesive layer (X2) may be irradiated with laser light to form a modified region.

[0174] FIG. 4 shows a cross-sectional view illustrating a process of forming a plurality of modified regions 5 using a laser light irradiation device 4 on a semiconductor wafer W attached to an adhesive layer (X2). The semiconductor wafer W is irradiated with the laser light from the back surface W2 side thereof, and a plurality of modified regions 5 are formed inside the semiconductor wafer W at approximately equal intervals.

[0175] 5(a) and (b) are cross-sectional views illustrating a process of thinning the semiconductor wafer W and dicing it into a plurality of semiconductor chips CP. 5(a), the back surface W2 of the semiconductor wafer W on which the modified region 5 is formed is ground by a grinder 6, and at that time, the pressure applied to the semiconductor wafer W causes a fracture starting from the modified region 5. As a result, as shown in FIG 5(b), the semiconductor wafer W is thinned and divided into a plurality of semiconductor chips CP. The semiconductor wafer W on which the modified region 5 has been formed has its back surface W2 ground, for example, in a state in which the support 3 supporting the semiconductor wafer W is fixed on a fixed table such as a chuck table.

[0176] The thickness of the semiconductor chips CP after grinding is preferably 5 to 100 μm, more preferably 10 to 45 μm. When the grinding process and the singulation process are performed by the stealth tip dicing method, it becomes easy to make the thickness of the semiconductor chips CP obtained by grinding 50 μm or less, more preferably 10 to 45 μm. The size of the semiconductor chip CP after grinding in plan view is preferably 600 mm 2 Less than 400mm, more preferably 2 Less than 300 mm, more preferably 2 Note that the plan view refers to a view in the thickness direction. The shape of the semiconductor chip CP after separation in a plan view may be square or an elongated shape such as a rectangle. In addition, since the pressure-sensitive adhesive sheet used in the semiconductor device manufacturing method of the second embodiment has a thermally expandable particle with an expansion start temperature (t) of 50° C. or higher, it is possible to prevent the thermally expandable particle from unintentionally expanding due to a temperature rise during grinding, etc. Therefore, unintentional separation, positional displacement, etc. of the processed object are suppressed.

[0177] (Process 3A) Step 3A is a step of attaching a thermosetting film to the surface of the object that has been subjected to the above-mentioned treatment, opposite to the pressure-sensitive adhesive layer (X2). Figure 6 shows a cross-sectional view illustrating the process of attaching a thermosetting film 7 having a support sheet 8 to the side opposite the adhesive layer (X2) of multiple semiconductor chips CP obtained by the above-mentioned processing.

[0178] The thermosetting film 7 is a film having thermosetting properties obtained by forming a resin composition containing at least a thermosetting resin, and is used as an adhesive when mounting a semiconductor chip CP on a substrate. The thermosetting film 7 may contain, if necessary, a curing agent for the thermosetting resin, a thermoplastic resin, an inorganic filler, a curing accelerator, and the like. As the thermosetting film 7, for example, a thermosetting film generally used as a die bonding film, a die attach film, or the like can be used. The thickness of the thermosetting film 7 is not particularly limited, but is usually 1 to 200 μm, preferably 3 to 100 μm, and more preferably 5 to 50 μm. The support sheet 8 may be any one that can support the thermosetting film 7, and examples thereof include resins, metals, paper materials, and the like mentioned as the non-thermally expandable base material layer (Y2) of the adhesive sheet according to one aspect of the present invention.

[0179] As a method of attaching the thermosetting film 7 to a plurality of semiconductor chips CP, for example, a method by lamination can be mentioned. The lamination may be performed while heating or without heating. When performing the lamination while heating, the heating temperature is preferably "a temperature lower than the expansion start temperature (t)", more preferably "the expansion start temperature (t) - 5°C" or lower, still more preferably "the expansion start temperature (t) - 10°C" or lower, and even more preferably "the expansion start temperature (t) - 15°C" or lower, from the viewpoints of suppressing the expansion of the thermally expandable particles and suppressing the thermal change of the adherend.

[0180] (First separation step) The first separation step is a step of heating the adhesive sheet to a temperature equal to or higher than the expansion start temperature (t) and lower than 125°C to separate the adhesive layer (X1) from the support. FIG. 7 shows a cross-sectional view for explaining a step of heating the adhesive sheet 2a to separate the adhesive layer (X1) from the support 3.

[0181] The heating temperature in the first separation step is equal to or higher than the expansion start temperature (t) of the thermally expandable particles, and in the range of less than 125° C., is preferably “a temperature higher than the expansion start temperature (t)”, more preferably “expansion start temperature (t)+2° C.” or higher, even more preferably “expansion start temperature (t)+4° C.” or higher, and even more preferably “expansion start temperature (t)+5° C.” In addition, from the viewpoints of energy saving and suppressing thermal changes in the adherend during heat peeling, the heating temperature in the first separation step is, in the range of less than 125° C., preferably “expansion start temperature (t)+50° C.” or lower, more preferably “expansion start temperature (t)+40° C.” or lower, and even more preferably “expansion start temperature (t)+20° C.” or lower. From the viewpoint of suppressing thermal changes of the adherend, the heating temperature in the first separation step is within the range of the expansion onset temperature (t) or higher, and is preferably 120°C or lower, more preferably 115°C or lower, even more preferably 110°C or lower, and still more preferably 105°C or lower.

[0182] (Second separation step) The second separation step is a step of separating the pressure-sensitive adhesive layer (X2) from the object to be processed. FIG. 8 shows a cross-sectional view illustrating a step of separating the adhesive layer (X2) from the multiple semiconductor chips CP. The method for separating the adhesive layer (X2) from the semiconductor chips CP may be appropriately selected depending on the type of adhesive layer (X2). For example, when the adhesive layer (X2) is an adhesive layer whose adhesive strength is reduced by energy ray irradiation, the adhesive layer (X2) may be irradiated with energy ray to reduce the adhesive strength, and then the semiconductor chips CP may be separated from each other.

[0183] Through the above steps 1A to 3A, the first separation step, and the second separation step, a plurality of semiconductor chips CP attached onto the thermosetting film 7 are obtained. Next, it is preferable to divide the thermosetting film 7 to which the multiple semiconductor chips CP are attached into pieces having the same shape as the semiconductor chips CP to obtain semiconductor chips CP with the thermosetting film 7. As a method for dividing the thermosetting film 7, for example, a method such as laser dicing using a laser beam, expanding, or melting can be applied. FIG. 9 shows a semiconductor chip CP with a thermosetting film 7, which is divided into the same shape as the semiconductor chip CP.

[0184] The semiconductor chip CP with the thermosetting film 7 is further subjected to an expanding process for widening the gap between the semiconductor chips CP, a rearrangement process for arranging the semiconductor chips CP with the widened gaps, an inversion process for inverting the semiconductor chips CP, etc. as necessary, and then attached (die-attached) to a substrate from the side of the thermosetting film 7. The semiconductor chip and the substrate can then be fixed together by thermally curing the thermosetting film.

[0185] The second embodiment of the method for producing a semiconductor device may be a production method including the following steps 1B to 3B, the following first separation step, and the following second separation step (hereinafter also referred to as "production method B"). Step 1B: A step of attaching an object to be processed to the adhesive layer (X1) of the adhesive sheet and attaching a support to the adhesive layer (X2) of the adhesive sheet Step 2B: subjecting the object to one or more treatments selected from a grinding treatment and a singulation treatment. Step 3B: A step of attaching a thermosetting film to the surface of the object to be processed opposite to the pressure-sensitive adhesive layer (X1) that has been subjected to the treatment. First separation step: a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion starting temperature (t) and lower than 125° C. to separate the pressure-sensitive adhesive layer (X1) from the object to be processed. Second separation step: a step of separating the pressure-sensitive adhesive layer (X2) from the support

[0186] Steps 1B to 3B are explained by replacing the pressure-sensitive adhesive layer (X1) in the explanation of steps 1A to 3A with the pressure-sensitive adhesive layer (X2) and the pressure-sensitive adhesive layer (X2) with the pressure-sensitive adhesive layer (X1).

[0187] The first separation step is a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion starting temperature (t) and lower than 125° C. to separate the pressure-sensitive adhesive layer (X1) from the object to be processed. The heating conditions, such as the heating temperature of the pressure-sensitive adhesive sheet, in the first separation step are the same as those described in the production method A. The first separation step provides a plurality of semiconductor chips attached to the thermosetting film. Thereafter, in the same manner as in the above-described manufacturing method A, the thermosetting film is divided to provide semiconductor chips with the thermosetting film.

[0188] The second separation step is a step of separating the pressure-sensitive adhesive layer (X2) from the support. The method for separating the pressure-sensitive adhesive layer (X2) from the support may be appropriately selected depending on the type of the pressure-sensitive adhesive layer (X2). For example, when the pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer whose adhesive strength is reduced by energy ray irradiation, the pressure-sensitive adhesive layer (X2) may be irradiated with energy ray to reduce the adhesive strength, and then the pressure-sensitive adhesive layer (X2) may be separated from the support.

[0189] <Another embodiment of the method for manufacturing a semiconductor device> The method for manufacturing a semiconductor device of the present invention is not limited to the method for manufacturing a semiconductor device of the first and second aspects described above, and may be a method for manufacturing a semiconductor device of an aspect other than the first and second aspects.

[0190] An example of a method for manufacturing a semiconductor device of another embodiment is a method in which an object to be processed that is attached to another sheet is separated from the another sheet by using the pressure-sensitive adhesive sheet of one embodiment of the present invention. For example, a plurality of semiconductor chips spaced apart on the expanding tape are attached to the adhesive surface of the expanding tape, but the task of picking up these chips one by one is cumbersome. According to a method for manufacturing a semiconductor device of one aspect of the present invention, the adhesive layer (X1) of the adhesive sheet of one aspect of the present invention is attached to the exposed surfaces of the plurality of semiconductor chips attached to the expanding tape, and then the expanding tape is peeled off from the plurality of semiconductor chips, thereby allowing the plurality of semiconductor chips to be separated from the expanding tape all at once. Through the above steps, a plurality of semiconductor chips are obtained that are attached to the pressure-sensitive adhesive sheet of one embodiment of the present invention. The plurality of semiconductor chips can then be easily separated by heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion start temperature (t) of the thermally expandable particles. In this case, the pressure-sensitive adhesive sheet of one embodiment of the present invention is capable of thermal peeling at low temperatures, and therefore is excellent in workability and energy saving in the thermal peeling operation, and can suppress thermal changes in the adherend due to heating during thermal peeling, even if the object to be processed is susceptible to thermal changes. The separated semiconductor chips may be transferred to another adhesive sheet, or after being separated, may be subjected to a rearrangement step in which the semiconductor chips are aligned. EXAMPLES

[0191] The present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples. The physical properties in each Production Example and Example were measured by the following methods.

[0192] [Mass average molecular weight (Mw)] Measurements were carried out using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020") under the conditions below, and values ​​measured in terms of standard polystyrene were used. (Measurement conditions) Column: "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL", and "TSK gel G1000HXL" (all manufactured by Tosoh Corporation) connected in series Column temperature: 40℃ Developing solvent: Tetrahydrofuran ·Flow rate: 1.0mL / min

[0193] [Thickness of each layer] The measurements were performed using a constant pressure thickness gauge manufactured by Tecrock Corporation (model number: "PG-02J", standard specifications: compliant with JIS K6783, Z1702, Z1709).

[0194] [Average particle diameter of thermal expansion particles (D 50 ), 90% particle size (D 90 )] The particle size distribution of the thermally expandable particles before expansion at 23° C. was measured using a laser diffraction particle size distribution measuring device (for example, product name "Mastersizer 3000" manufactured by Malvern). The particle sizes corresponding to 50% and 90% of the cumulative volume frequency calculated from the smaller particle size of the particle distribution were defined as the "average particle size of the thermal expansion particles (D 50 )" and "90% particle size of thermal expansion particles (D 90 )".

[0195] In the following Production Examples and Examples, the details of the materials used to form each layer are as follows.

[0196] <Adhesive resin> Acrylic copolymer (A1): A solution containing an acrylic copolymer with Mw of 600,000 having structural units derived from raw monomers consisting of n-butyl acrylate (BA) / methyl methacrylate (MMA) / acrylic acid (AA) / 2-hydroxyethyl acrylate (HEA) = 86 / 8 / 1 / 5 (mass ratio), dilution solvent: ethyl acetate, solid concentration: 40 mass% Acrylic copolymer (A2): A solution containing an energy beam-curable acrylic copolymer with Mw of 500,000, which is obtained by reacting an acrylic copolymer having constituent units derived from raw monomers consisting of n-butyl acrylate (BA) / methyl methacrylate (MMA) / 2-hydroxyethyl acrylate (HEA) = 52 / 20 / 28 (mass ratio) with 2-methacryloyloxyethyl isocyanate (MOI) so that the addition rate relative to the total hydroxyl groups in the acrylic copolymer is 80% on a molar basis. Dilution solvent: ethyl acetate, solid content concentration: 35 mass% Acrylic copolymer (A3): A solution containing an energy beam-curable acrylic copolymer with Mw of 500,000, which is obtained by reacting an acrylic copolymer having constituent units derived from raw monomers consisting of n-butyl acrylate (BA) / methyl methacrylate (MMA) / 2-hydroxyethyl acrylate (HEA) = 52 / 20 / 28 (mass ratio) with 2-methacryloyloxyethyl isocyanate (MOI) so that the addition rate to the total hydroxyl groups in the acrylic copolymer is 90% on a molar basis. Dilution solvent: ethyl acetate, solid content concentration: 35 mass%

[0197] <Crosslinking agent> Isocyanate-based crosslinking agent (i): manufactured by Tosoh Corporation, product name "Coronate HX", a solution containing an isocyanurate-type modified product of hexamethylene diisocyanate, solid content: 75% by mass Isocyanate-based crosslinking agent (ii): Tosoh Corporation, product name "Coronate L", solution containing trimethylolpropane-modified tolylene diisocyanate, solid content: 75% by mass

[0198] <Energy ray curable compound> Energy ray curable compound (i): Nippon Synthetic Chemical Industry Co., Ltd., product name "Shiko UT-4332", multifunctional urethane acrylate

[0199] <Photopolymerization initiator> Photopolymerization initiator (i): Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide Photopolymerization initiator (ii): 1-hydroxycyclohexyl phenyl ketone

[0200] <Additives> Phthalocyanine pigments

[0201] <Thermal expansion particles> Thermally expansive particles: AkzoNobel, product name "Expancel (registered trademark) 031-40" (DU type), expansion start temperature (t) = 88°C, average particle diameter (D 50 )=12.6μm, 90% particle diameter (D 90 )=26.2μm

[0202] <Removal material> Heavy release film: Lintec Corporation, product name "SP-PET38 2150", a polyethylene terephthalate (PET) film with a release layer formed from a silicone release agent on one side, thickness: 38 μm Light release film: Lintec Corporation, product name "SP-PET38 1031", a release layer formed from a silicone release agent on one side of the PET film, thickness: 38μm

[0203] Production Example 1: Formation of adhesive layer (X1) 100 parts by mass of the solid content of the acrylic copolymer (A1) was mixed with 0.74 parts by mass (solid content ratio) of an isocyanate-based crosslinking agent (i), diluted with toluene, and stirred uniformly to prepare a pressure-sensitive adhesive composition (x-1) with a solid content concentration (active ingredient concentration) of 25% by mass. The prepared pressure-sensitive adhesive composition (x-1) was then applied onto the release surface of the heavy release film to form a coating film, and the coating film was dried at 100°C for 60 seconds to form a pressure-sensitive adhesive layer (X1) having a thickness of 5 µm.

[0204] Manufacturing Example 2: Formation of adhesive layer (X2) 100 parts by mass of the solid content of the acrylic copolymer (A2) was mixed with 4.2 parts by mass (solid content ratio) of the energy ray curable compound (i), 0.74 parts by mass (solid content ratio) of the isocyanate-based crosslinking agent (ii), and 1 part by mass (solid content ratio) of the photopolymerization initiator (i), diluted with toluene, and stirred uniformly to prepare a pressure-sensitive adhesive composition (x-2) with a solid content concentration (active ingredient concentration) of 30% by mass. The prepared pressure-sensitive adhesive composition (x-2) was then applied onto the release surface of the light release film to form a coating film, and the coating film was dried at 100°C for 60 seconds to form a pressure-sensitive adhesive layer (X2) having a thickness of 20 µm.

[0205] Production Example 3: Formation of adhesive layer (X2) 100 parts by mass of the solid content of the acrylic copolymer (A3), 12 parts by mass (solid content ratio) of the energy ray curable compound (i), 1.1 parts by mass (solid content ratio) of the isocyanate crosslinking agent (ii), and 1 part by mass (solid content ratio) of the photopolymerization initiator (i) were mixed, diluted with toluene, and uniformly stirred to prepare a pressure-sensitive adhesive composition (x-2) with a solid content concentration (active ingredient concentration) of 30% by mass. The pressure-sensitive adhesive composition (x-2) was applied onto the release surface of a light release film to form a coating film, and the coating film was dried at 100°C for 60 seconds to form a pressure-sensitive adhesive layer (X2) with a thickness of 20 μm.

[0206] Examples 1 to 7 and Comparative Examples 1 to 3: Formation of Adhesive Sheets (1) Preparation of Solvent-Free Resin Composition (y-1a) An isocyanate-terminated urethane prepolymer was obtained by reacting an ester-type diol with isophorone diisocyanate (IPDI) to give a linear urethane prepolymer having ethylenically unsaturated groups at both ends, which is an oligomer having a mass average molecular weight (Mw) of 5,000. Then, 40 parts by mass (solid content ratio) of isobornyl acrylate (IBXA) and 20 parts by mass (solid content ratio) of phenyl hydroxypropyl acrylate (HPPA) were blended as energy ray polymerizable monomers into 40 parts by mass (solid content ratio) of the urethane prepolymer synthesized above, and 2.0 parts by mass (solid content ratio) of photopolymerization initiator (ii), 0.2 parts by mass (solid content ratio) of a phthalocyanine pigment as an additive, and 20 parts by mass of a monomer shown in Table 1 as a Young's modulus adjusting component were further blended relative to the total amount (100 parts by mass) of the urethane prepolymer and the energy ray polymerizable monomer to prepare an energy ray curable composition. Then, the energy ray curable composition was mixed with thermally expandable particles to prepare a solventless resin composition (y-1a) containing no solvent. The content of the thermally expandable particles was 20% by mass relative to the total amount (100% by mass) of the solventless resin composition (y-1a).

[0207] (2) Formation of a base laminate by laminating a thermally expandable base layer (Y1) and a non-thermally expandable base layer (Y2) A PET film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4300", thickness: 50 μm) was used as the non-thermally expandable substrate layer (Y2), and a solventless resin composition (y-1a) was applied to one side of the PET film to form a coating film. Then, using an ultraviolet irradiation device (manufactured by iGraphics Co., Ltd., product name "ECS-401GX") and a high pressure mercury lamp (manufactured by iGraphics Co., Ltd., product name "H04-L41"), ultraviolet rays were irradiated under the irradiation conditions shown in Table 1, the coating film was cured, and a thermally expandable base layer (Y1) having a thickness of 100 μm was formed on the PET film as the non-thermally expandable base layer (Y2). Note that the above illuminance and light quantity during ultraviolet irradiation were values ​​measured using an illuminance / actinometer (manufactured by EIT Co., Ltd., product name "UV Power Puck II").

[0208] (3) Formation of adhesive sheet The adhesive surface of the pressure-sensitive adhesive layer (X1) formed in Production Example 1 was bonded to the surface of the thermally expandable base layer (Y1) of the base laminate formed in (2) above. Next, the adhesive surface of the pressure-sensitive adhesive layer (X2) formed in Production Example 2 was bonded to the PET film surface of the base laminate. As a result, a pressure-sensitive adhesive sheet having the following configuration was produced. <Heavy release film> / <Adhesive layer (X1), thickness: 5μm> / <Heat-expandable base layer (Y1), thickness: 100μm> / <Non-heat-expandable base layer (Y2), thickness: 50μm> / <Adhesive layer (X2), thickness: 20μm> / <Light release film>

[0209] Example 8: Formation of an adhesive sheet A pressure-sensitive adhesive sheet having the following configuration was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive layer (X2) formed in Production Example 3 was used as the pressure-sensitive adhesive layer (X2). <Heavy release film> / <Adhesive layer (X1), thickness: 5μm> / <Heat-expandable base layer (Y1), thickness: 100μm> / <Non-heat-expandable base layer (Y2), thickness: 50μm> / <Adhesive layer (X2), thickness: 20μm> / <Light release film>

[0210] [Evaluation of Young's modulus of resin substrate (Y1') at 120°C] The Young's modulus at 120° C. of the resin substrate (Y1') constituting the thermally expandable substrate layer (Y1) (that is, the substrate obtained by removing the thermally expandable particles from the thermally expandable substrate layer (Y1)) was evaluated by the following procedure. (1) Preparation of evaluation samples In the preparation of the solventless resin composition (y-1a) in each of the examples and comparative examples, except that no thermally expandable particles were added, a solventless resin composition (y-1a') not containing thermally expandable particles was prepared in the same manner as in each of the examples and comparative examples. The solventless resin composition (y-1a') obtained above was applied to a PET-based release film (manufactured by Lintec Corporation, product name "SP-PET38 1031", thickness: 38 μm) to form a coating film. Then, using an ultraviolet irradiation device (manufactured by iGraphics Co., Ltd., product name "ECS-401GX") and a high-pressure mercury lamp (manufactured by iGraphics Co., Ltd., product name "H04-L41"), ultraviolet light was irradiated under the irradiation conditions shown in Table 1 to harden the coating film and form a resin substrate (Y1') with a thickness of 150 μm, which was used as the evaluation sample. (2) Tensile test The tensile test was performed in accordance with JIS K 7127: 1999. However, the preparation of the evaluation samples and the measurement conditions were as follows. The evaluation sample thus prepared was cut into a size of 15 mm x 140 mm, the PET release film was removed, and tensile labels were attached to the 20 mm portions of both ends to prepare a dumbbell-shaped sample of 15 mm x 100 mm. The sample was left to stand at 120°C for 3 minutes in a thermostatic Tensilon (Tensilon "RTG-1210" manufactured by A&D Co., Ltd., and thermostatic bath "TKC-R3T-GS" manufactured by Mita Sangyo Co., Ltd.), and then subjected to a tensile test at a speed of 200 mm / min to measure the Young's modulus.

[0211] [Evaluation of Young's modulus of non-thermally expandable base layer (Y2) at 120°C] The PET film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4300", thickness: 50 μm) used as the non-thermally expandable base layer (Y2) was used as an evaluation sample, and was measured in the same manner as in "(2) Tensile test" in [Evaluation of Young's modulus of resin base material (Y1') at 120°C] above. As a result, the Young's modulus of the PET film, which is the non-thermally expandable base layer (Y2), at 120°C was 902 MPa.

[0212] [Storage modulus E'(23) of non-thermally expandable base layer (Y2) at 23°C] The non-thermally expandable base layer (Y2) cut to a size of 30 mm length x 5 mm width was used as a test sample, and the storage modulus E' at 23°C was measured using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, product name "DMAQ800") under the conditions of a test start temperature of 0°C, a test end temperature of 200°C, a heating rate of 3°C / min, a vibration frequency of 1 Hz, and an amplitude of 20 μm. As a result, the storage modulus E' (23) at 23°C of the PET film, which is the non-thermally expandable base layer (Y2), was 2.27×10 9 It was Pa.

[0213] [Evaluation of self-peeling properties] Two soda-lime glass plates measuring 30 mm × 30 mm × 1.1 mm were prepared. Hereinafter, the two soda-lime glass plates are referred to as "glass plate G1" and "glass plate G2," respectively. The adhesive sheet prepared in each example was cut to 30 mm x 30 mm, the heavy release film was removed from the adhesive layer (X1) on the thermally expandable base layer (Y1) side of the cut adhesive sheet, and a glass plate G1 was attached. Next, the light release film was removed from the adhesive layer (X2) on the non-thermally expandable base layer (Y2) side, and a glass plate G2 was attached, and then pressed for 30 seconds with a vacuum laminator (manufactured by Nikko Materials Co., Ltd., product name "V-130") at 60°C and 0.2 MPa to prepare a test sample. The test sample was then placed on a hot plate and heated for 1 minute at 110° C., which is equal to or higher than the expansion start temperature of the thermally expandable particles. The test sample was placed on the hot plate so that the glass plate G2 side was in contact with the hot plate. After heating at 110°C for 1 minute, the state of peeling of glass plate G1 from the adhesive sheet was checked, and the percentage (%) of the peeled area of ​​glass plate G1 (peeled area x 100 / total area of ​​adhesive sheet) was calculated and evaluated based on the following criteria. (Evaluation criteria for self-peeling properties) A: The entire surface of the glass plate G1 is peeled off from the adhesive sheet. B: The area of ​​glass plate G1 that had peeled off was 30% or more but less than 100%. C: The area of ​​the glass plate G1 that peeled off was less than 30%.

[0214] [Evaluation of sheet shape retention after thermal expansion] The sheet shape retention after thermal expansion was evaluated by visually checking the shape of the PSA sheet after the above-mentioned "evaluation of self-removal property". After the evaluation of self-removal property was performed, the PSA sheets were classified into those in which no curling was confirmed and those in which part of the PSA sheet peeled off from the glass plate G2 and the peeled part curled. For cases where part of the adhesive sheet peeled off from glass plate G2 and curled, the maximum height of the peeled and floating part of the adhesive sheet was measured using the surface of glass plate G2 as the base and evaluated based on the following criteria. (Evaluation criteria for sheet shape retention) A: No curling was visually confirmed, or curling was visually confirmed and the above-mentioned maximum height of the adhesive sheet was less than three times the thickness of the adhesive sheet before thermal expansion. B: Curling was confirmed by visual inspection, and the above-mentioned maximum height of the adhesive sheet was three times or more the thickness of the adhesive sheet before thermal expansion.

[0215] The evaluation results are shown in Tables 1 and 2.

[0216] [Table 1]

[0217] [Table 2]

[0218] It can be seen from Tables 1 and 2 that the pressure-sensitive adhesive sheets of Examples 1 to 7 and Example 8 have good self-removal properties because the Young's modulus of the resin substrate (Y1') at 120°C is 2.05 MPa or less. Among them, the pressure-sensitive adhesive sheets of Examples 1 to 6 and Example 8 also had excellent sheet shape retention after thermal expansion. In contrast, the pressure-sensitive adhesive sheets of Comparative Examples 1 to 3 have poor self-removal properties because the Young's modulus of the resin substrate (Y1') at 120°C is greater than 2.05 MPa. [Explanation of symbols]

[0219] 1a, 1b, 2a, 2b Adhesive sheet 10, 10a, 10b Release material 3 Support 4. Laser light irradiation device 5. Modification Area 6. Grinder 7 Thermosetting Film 8 Support Sheet W Semiconductor wafer W1 Circuit side of semiconductor wafer W2 Back side of semiconductor wafer CP Semiconductor Chip (X1) Adhesive layer (X1) (X2) Adhesive layer (X2) (Y1) Thermally expandable base layer (Y1) (Y2) Non-thermally expandable base layer (Y2)

Claims

1. a laminated structure in which a pressure-sensitive adhesive layer (X1), a thermally expandable base layer (Y1), and a non-thermally expandable base layer (Y2) are arranged in this order, The thermally expandable substrate layer (Y1) comprises a resin substrate containing thermally expandable particles, The pressure-sensitive adhesive sheet, wherein the resin substrate has a Young's modulus at 120°C of 0.8 MPa or more and 2.05 MPa or less.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the resin substrate comprises at least one resin selected from the group consisting of acrylic urethane resins and olefin resins.

3. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the resin substrate is formed from a resin composition (y-1) containing a resin that is cured by irradiation with energy rays.

4. An adhesive sheet described in any one of claims 1 to 3, wherein the thickness of the thermally expandable substrate layer (Y1) is 10 to 1000 μm.

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the thermally expandable particles have an expansion initiation temperature (t) of 50°C or higher and lower than 125°C.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer (X1) has a thickness at 23°C of 3 to 10 µm.

7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the content of the thermally expandable particles is 1 to 30 mass% relative to the total mass (100 mass%) of the thermally expandable base layer (Y1).

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the non-thermally expandable base layer (Y2) has a Young's modulus at 120°C of 500 MPa or more.

9. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, wherein the non-thermally expandable base layer (Y2) is a polyethylene terephthalate film.

10. The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, further comprising a pressure-sensitive adhesive layer (X2) on a surface of the non-thermally expandable base layer (Y2) opposite to the surface on which the thermally expandable base layer (Y1) is laminated.

11. The pressure-sensitive adhesive sheet according to claim 10 , wherein the pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer that is cured by irradiation with energy rays and has a reduced adhesive strength.

12. A processing and inspection object is attached to the adhesive sheet according to any one of claims 1 to 11, A method for manufacturing a semiconductor device, comprising a step of subjecting the processed and inspected object to one or more selected from processing and inspection, and then heating the adhesive sheet to a temperature equal to or higher than the expansion starting temperature (t) of the thermally expandable particles.

13. 12. A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to claim 10 or 11, wherein the thermally expandable particles have an expansion initiation temperature (t) of 50° C. or higher and lower than 125° C., the method comprising the steps 1A to 3A, a first separation step, and a second separation step. Step 1A: A step of attaching an object to be processed to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet and attaching a support to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet Step 2A: A step of subjecting the object to one or more treatments selected from a grinding treatment and a singulation treatment. Step 3A: A step of attaching a thermosetting film to the surface of the object to be processed opposite to the pressure-sensitive adhesive layer (X2) that has been subjected to the treatment. First separation step: a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) and lower than 125° C. to separate the pressure-sensitive adhesive layer (X1) from the support. Second separation step: a step of separating the pressure-sensitive adhesive layer (X2) from the object to be processed

14. 12. A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to claim 10 or 11, wherein the thermally expandable particles have an expansion initiation temperature (t) of 50° C. or higher and lower than 125° C., the method comprising the steps 1B to 3B, a first separation step, and a second separation step. Step 1B: A step of attaching an object to be processed to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet and attaching a support to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet Step 2B: A step of subjecting the object to one or more treatments selected from a grinding treatment and a singulation treatment. Step 3B: A step of attaching a thermosetting film to the surface of the object to be processed opposite to the pressure-sensitive adhesive layer (X1) that has been subjected to the treatment. First separation step: a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion starting temperature (t) and lower than 125° C. to separate the pressure-sensitive adhesive layer (X1) from the object to be processed. Second separation step: a step of separating the pressure-sensitive adhesive layer (X2) from the support

15. Using the pressure-sensitive adhesive sheet according to claim 11, The method for manufacturing a semiconductor device according to claim 13 or 14, wherein the second separation step includes a step of curing the adhesive layer (X2) by irradiating the adhesive layer (X2) with energy rays.

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