Adhesive sheet and method for manufacturing semiconductor device

Abstract

An adhesive sheet having a laminated structure including an adhesive layer (X1) and a base material layer (Y), wherein the adhesive layer (X1) and / or the base material layer (Y) is a heat-expandable layer that contains heat-expandable particles, the arithmetic mean waviness (Wa) of the adhesive layer (X1) on a surface (SX1) on the opposite side of the surface facing the base material layer (Y) is 0.090 μm or less. A method for producing a semiconductor device using said 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] PSA sheets are not only used to semi-permanently fix components, but are also used as temporary fixing sheets for temporarily fixing components (hereinafter also referred to as "adherends") that are to be processed, inspected, etc. 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 semiconductor devices, semiconductor wafers are processed into semiconductor chips through processes such as a grinding process in which the wafer is thinned by grinding and a singulation process in which the wafer is cut and separated into individual pieces. At this time, the semiconductor wafer undergoes a predetermined process while temporarily fixed to a temporary fixing sheet. The semiconductor chips obtained by the predetermined process are separated from the temporary fixing sheet and, as necessary, undergo an expanding process to increase the spacing between the semiconductor chips, a rearrangement process to arrange the semiconductor chips with the increased spacing, and an inversion process to invert the semiconductor chips, before being mounted on a substrate. A temporary fixing sheet suitable for each application can be used in each of the above processes. Single-sided or double-sided pressure-sensitive adhesive sheets are used as such temporary fixing sheets. In the case of double-sided pressure-sensitive adhesive sheets, the object to be processed may be attached to one side, and the other side may be attached to a support, and the predetermined process may be performed.

[0004] Patent Document 1 discloses a heat-peelable pressure-sensitive adhesive sheet for temporary fixing electronic components during cutting, which comprises a substrate and a heat-expandable pressure-sensitive adhesive layer containing heat-expandable microspheres provided on at least one side thereof. The document describes that the heat-peelable pressure-sensitive adhesive sheet can ensure a predetermined contact area with the adherend during cutting of the electronic components, thereby exhibiting adhesion sufficient to prevent adhesion problems such as chipping, while after use, heating the sheet to expand the heat-expandable microspheres reduces the contact area with the adherend, allowing for easy peeling. [Prior art documents] [Patent documents]

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

[0006] When a temporary fixing sheet is used in a manner in which a workpiece is attached to one side thereof and a support is attached to the other side thereof, and a predetermined processing is performed on the workpiece, hard materials may be attached to both sides of the temporary fixing sheet. In this case, for example, when attaching the hard support to the temporary fixing sheet attached to the hard workpiece, it becomes necessary to attach the temporary fixing sheet and the support while maintaining the attached surfaces thereof in a substantially parallel state. A method of attaching a temporary fixing sheet to an adherend while maintaining a substantially parallel state is more likely to result in air pockets at the adhesive interface between the temporary fixing sheet and the adherend than a method of attaching the temporary fixing sheet while bending it. Air pockets at the adhesive interface can cause vibration and misalignment of the adherend, which can lead to reduced processing accuracy, such as cracks and chips, when processing the object to be processed. On the other hand, when attaching an adherend to a temporary fixing sheet, it is desirable to perform attachment under as mild conditions as possible from the standpoint of productivity and preventing damage and deterioration of the adherend due to pressure and heat application, and harsh attachment conditions should be avoided in order to improve attachment properties. Therefore, excellent attachment properties are required of the temporary fixing sheet itself, but the heat-peelable pressure-sensitive adhesive sheet of Patent Document 1 does not fully meet this requirement.

[0007] The present invention has been made in view of the above problems, and has an object to provide a pressure-sensitive adhesive sheet with excellent adhesion properties and a method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet. [Means for solving the problem]

[0008] The present inventors focused on the arithmetic mean waviness (Wa) of the surface of the pressure-sensitive adhesive sheet and discovered that the above-mentioned problems could be solved by adjusting this to a specific range, which led to the completion of the present invention.

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

[13] . [1] A laminated structure including a pressure-sensitive adhesive layer (X1) and a base layer (Y), at least one of the pressure-sensitive adhesive layer (X1) and the base layer (Y) is a heat-expandable layer containing heat-expandable particles, The pressure-sensitive adhesive layer (X1) has a surface (S X1 ) has an arithmetic mean waviness (Wa) of 0.090 μm or less. [2] The pressure-sensitive adhesive sheet according to the above [1], wherein the thickness of the heat-expandable layer before thermal expansion is 30 to 300 μm. [3] The pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the content of the heat-expandable particles in the heat-expandable layer is 1 to 25 mass % relative to the total mass (100 mass %) of the heat-expandable layer. [4] The pressure-sensitive adhesive sheet according to any one of the above [1] to [3], wherein the expansion starting temperature (t) of the heat-expanding particles is 50°C or higher and lower than 125°C. [5] The pressure-sensitive adhesive sheet according to any one of the above [1] to [4], wherein the base layer (Y) is a base laminate in which a heat-expandable base layer (Y1) containing heat-expandable particles and a non-heat-expandable base layer (Y2) are laminated together, and the pressure-sensitive adhesive sheet has a laminate structure in which the pressure-sensitive adhesive layer (X1), the heat-expandable base layer (Y1), and the non-heat-expandable base layer (Y2) are arranged in this order. [6] The pressure-sensitive adhesive sheet according to any one of the above [1] to [5], further comprising a pressure-sensitive adhesive layer (X2), and having a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are arranged in this order. [7] The pressure-sensitive adhesive sheet according to the above [6], wherein the pressure-sensitive adhesive layer (X2) is an energy ray-curable pressure-sensitive adhesive layer that is cured by irradiation with energy rays and has a reduced adhesive strength. [8] A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to [6] or [7] above, comprising the following steps 1A, 2A, 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) 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. 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) of the heat-expanding particles 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 [9] The expansion starting temperature (t) of the thermally expandable particles is 50°C or higher and lower than 125°C; After the step 2A, a step 3A is included in which a thermosetting film is attached to a surface of the object that has been subjected to the treatment, the surface being opposite to the pressure-sensitive adhesive layer (X2), the first separation step is 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; The method for manufacturing a semiconductor device according to [8] above.

[10] In the step 1A, the step of attaching the support to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet is carried out by attaching the support to the surface (S X1 ) and the surface of the support to which the adhesive sheet is attached (S s ) is maintained in a substantially parallel state, the surface (S X1 ) on the surface (S s The method for manufacturing a semiconductor device according to the above [8] or [9], wherein the step of attaching

[11] A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to [6] or [7] above, comprising the following steps 1B, 2B, a first separation step, and a second separation step: 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: A step of subjecting the object to one or more treatments selected from a grinding treatment and a singulation 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) of the heat-expanding particles 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

[12] The expansion starting temperature (t) of the thermally expandable particles is 50°C or higher and lower than 125°C; after step 2B, step 3B of attaching a thermosetting film to a surface of the object that has been subjected to the treatment, opposite to the pressure-sensitive adhesive layer (X1), 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 method for manufacturing a semiconductor device according to

[11] above.

[13] In the step 1B, the step of attaching the object to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet is performed by applying pressure-sensitive adhesive layer (X1) to the surface (S X1 ) and the surface (S w ) is maintained in a substantially parallel state, the surface (S X1 ) to the surface (S w The method for manufacturing a semiconductor device according to

[11] or

[12] above, wherein the step of attaching [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet with excellent adhesion properties and a method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet. [Brief explanation 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. [Figure 2] FIG. 3 is a cross-sectional view showing another example of the configuration of the pressure-sensitive adhesive sheet of the present invention. [Figure 3] 1A to 1C are cross-sectional views illustrating an example of a process for manufacturing a semiconductor device according to the present invention. [Figure 4] 1A to 1C are cross-sectional views illustrating an example of a process for manufacturing a semiconductor device according to the present invention. [Figure 5] 1A to 1C are cross-sectional views illustrating an example of a process for manufacturing a semiconductor device according to the present invention. [Figure 6] 1A to 1C are cross-sectional views illustrating an example of a process for manufacturing a semiconductor device according to the present invention. [Figure 7] 1A to 1C are cross-sectional views illustrating an example of a process for manufacturing a semiconductor device according to the present invention. [Figure 8] 1A to 1C are cross-sectional views illustrating an example of a process for manufacturing a semiconductor device according to the present invention. [Figure 9] 1A to 1C are cross-sectional views illustrating an example of a process for manufacturing a semiconductor device according to the present invention. [Figure 10] 1 is a three-dimensional surface shape image of the pressure-sensitive adhesive sheet produced in Example 1. [Figure 11] 1 is a three-dimensional surface shape image of the adhesive sheet produced in Comparative Example 9. [Figure 12] 1 is an example of a photograph of the appearance of a test sample corresponding to a rating of A in the application evaluation. [Figure 13] 1 is an example of a photograph of the appearance of a test sample corresponding to an F rating in the application evaluation. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this specification, the term "active ingredient" refers to the components contained in the target composition excluding the diluent solvent. In this specification, the mass average molecular weight (Mw) is a value calculated as a 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 the same applies to other similar terms. Furthermore, in this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in stages 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 that have an energy quantum, and examples thereof include ultraviolet rays, radioactive rays, and electron beams. Ultraviolet rays can be irradiated using, for example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, or the like as an ultraviolet light source. Electron beams can be irradiated using those generated by an electron beam accelerator, or the like. In this specification, "energy ray polymerizable" means a property of being polymerized by irradiation with energy rays, and "energy ray curable" means a property of being cured 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 starting temperature (t) of the thermally expandable particles. If the volume change rate calculated using 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} × 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 a circuit is 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 no circuit is formed.

[0017] In this specification, the thickness of each layer is the thickness at 23° C., and refers to the value measured by the method described in the examples.

[0018] In this specification, the adhesive strength of each layer refers to the adhesive strength to the mirror surface of a silicon mirror wafer, measured at a pulling rate of 300 mm / min using the 180° peel method in accordance with JIS Z0237:2000 under an environment of 23°C and 50% RH (relative humidity).

[0019] [Adhesive sheet] The pressure-sensitive adhesive sheet of one embodiment of the present invention comprises: It has a laminated structure including a pressure-sensitive adhesive layer (X1) and a base layer (Y), at least one of the pressure-sensitive adhesive layer (X1) and the base layer (Y) is a heat-expandable layer containing heat-expandable particles, The pressure-sensitive adhesive layer (X1) has a surface (S X1 ) The arithmetic mean waviness (Wa) is 0.090 μm or less.

[0020] In one embodiment of the pressure-sensitive adhesive sheet of the present invention, the heat-expandable particles contained in the heat-expandable layer, which is at least one of the pressure-sensitive adhesive layer (X1) and the base layer (Y), are heated to a temperature equal to or higher than the expansion initiation temperature (t) to expand, thereby forming irregularities on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1), and significantly 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 significantly reduces the adhesion between the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1) and the adherend, allowing the pressure-sensitive adhesive sheet to be easily separated from the adherend. In addition, the pressure-sensitive adhesive sheet according to one embodiment of the present invention has a surface (S1) of the pressure-sensitive adhesive layer (X1) opposite to the surface facing the base layer (Y). X1 When the arithmetic mean waviness (Wa) of the above-mentioned adhesive tape is 0.090 μm or less, excellent adhesion can be achieved. The arithmetic mean roughness (Ra) of the adhesive surface is often noted as a factor affecting the adhesion of a pressure-sensitive adhesive sheet. However, according to the inventors' studies, it has been found that for pressure-sensitive adhesive sheets containing thermally expandable particles, particularly when the application surfaces are maintained in a substantially parallel state, simply reducing the arithmetic mean roughness (Ra) does not necessarily result in sufficient adhesion. This is thought to be because, although increasing the microscopic smoothness as determined by the arithmetic mean roughness (Ra) improves local adhesion, pressure-sensitive adhesive sheets containing thermally expandable particles have slight waviness on the adhesive surface, possibly due to the presence of the thermally expandable particles, which causes air pockets at the adhesive interface. On the other hand, the pressure-sensitive adhesive sheet of one embodiment of the present invention is thought to exhibit excellent application properties by suppressing the occurrence of air pockets by adjusting the arithmetic mean waviness (Wa), which represents the macroscopic surface shape, to a specific range of 0.090 μm or less.

[0021] <Adhesive sheet composition> In the pressure-sensitive adhesive sheet of one embodiment of the present invention, at least one of the pressure-sensitive adhesive layer (X1) and the base layer (Y) may be a heat-expandable layer containing heat-expandable particles. An example of a pressure-sensitive adhesive sheet in which the base layer (Y) is a heat-expandable layer containing heat-expandable particles is a pressure-sensitive adhesive sheet in which the base layer (Y) is a base laminate in which a heat-expandable base layer (Y1) containing heat-expandable particles and a non-heat-expandable base layer (Y2) are laminated together, and the pressure-sensitive adhesive sheet has 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. Hereinafter, a pressure-sensitive adhesive sheet having this configuration may be referred to as a "first embodiment of a pressure-sensitive adhesive sheet." Furthermore, in the pressure-sensitive adhesive sheet of one embodiment of the present invention, when the pressure-sensitive adhesive layer (X1) is a heat-expandable layer containing heat-expandable particles, the pressure-sensitive adhesive sheet may have a laminated structure including the pressure-sensitive adhesive layer (X1) that is a heat-expandable layer and a base layer (Y). Hereinafter, a pressure-sensitive adhesive sheet having such a configuration may be referred to as a "pressure-sensitive adhesive sheet of a second embodiment."

[0022] The pressure-sensitive adhesive sheet of one embodiment of the present invention may have a laminated structure including a pressure-sensitive adhesive layer (X1) and a base layer (Y), but may also have layers other than the pressure-sensitive adhesive layer (X1) and the base layer (Y) depending on the application. For example, when the pressure-sensitive adhesive sheet of one embodiment of the present invention is used to process an object to be processed, from the viewpoint of improving the processability of the object to be processed, the pressure-sensitive adhesive sheet of one embodiment of the present invention preferably further comprises a pressure-sensitive adhesive layer (X2), and has a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are arranged in this order (i.e., the structure of a double-sided pressure-sensitive adhesive sheet). With this structure, the object to be processed can be attached to either 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 object to the support via the pressure-sensitive adhesive sheet, vibration of the object to be processed, positional displacement, damage to fragile objects, etc. can be suppressed when processing the object to be processed, and processing accuracy and processing speed can be improved. 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 base layer (Y), and a pressure-sensitive adhesive layer (X2) are arranged in this order.

[0023] 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). Furthermore, when the pressure-sensitive adhesive sheet of one embodiment of the present invention has a double-sided pressure-sensitive adhesive sheet configuration, a release material may be present on the adhesive surface of at least one of the pressure-sensitive adhesive layer (X1) and the pressure-sensitive adhesive layer (X2).

[0024] 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.

[0025] An example of a pressure-sensitive adhesive sheet according to the present invention is a pressure-sensitive adhesive sheet 1a having a pressure-sensitive adhesive layer (X1) on a substrate layer (Y), as shown in Fig. 1(a). The pressure-sensitive adhesive sheet 1a has a surface (S) of the pressure-sensitive adhesive layer (X1) on the side opposite to the surface facing the substrate layer (Y) that has an arithmetic mean waviness (Wa) of 0.090 µm or less. X1 ) 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).

[0026] Another embodiment of the pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive sheet having the above-described double-sided pressure-sensitive adhesive sheet configuration. An example of a pressure-sensitive adhesive sheet having such a configuration is a double-sided pressure-sensitive adhesive sheet 2a having a configuration in which a base layer (Y) is sandwiched between a pressure-sensitive adhesive layer (X1) and a pressure-sensitive adhesive layer (X2), as shown in Figure 2(a). The double-sided pressure-sensitive adhesive sheet 2a has a surface (S1) of the pressure-sensitive adhesive layer (X1) on the side opposite to the surface facing the base layer (Y) that has an arithmetic mean waviness (Wa) of 0.090 µm or less. X1 ) Furthermore, as shown in Figure 2(b), the double-sided adhesive sheet 2b may have a release material 10a on the adhesive surface of the adhesive layer (X1), and a release material 10b on the adhesive surface of the adhesive layer (X2).

[0027] 2(b), if the peel force when peeling release material 10a from the adhesive layer (X1) and the peel force when peeling release material 10b from the adhesive layer (X2) are similar, attempting to peel both release materials outward may result in the adhesive layer being torn apart and peeled away along with the two release materials. From the perspective of preventing this phenomenon, it is preferable to use two types of release materials for the two release materials 10a, 10b, which are designed to have different peel forces from the adhesive layers to which they are attached.

[0028] Another embodiment of the pressure-sensitive adhesive sheet may be a double-sided pressure-sensitive adhesive sheet 2a shown in Figure 2(a) in which a release material that has been subjected to a release treatment on both sides is laminated on one adhesive surface of the pressure-sensitive adhesive layer (X1) and the pressure-sensitive adhesive layer (X2), and the sheet is then wound into a roll.

[0029] The pressure-sensitive adhesive sheet of one embodiment of the present invention may or may not have another layer between the substrate layer (Y) and the pressure-sensitive adhesive layer (X1). Furthermore, when the pressure-sensitive adhesive sheet of one embodiment of the present invention is the double-sided pressure-sensitive adhesive sheet, in addition to the above, it may or may not have another layer between the substrate layer (Y) and the pressure-sensitive adhesive layer (X2). However, in the pressure-sensitive adhesive sheet of the first embodiment, a non-heat-expandable base layer (Y2) is preferably laminated directly on the surface of the heat-expandable base layer (Y1) opposite the pressure-sensitive adhesive layer (X1) from the viewpoint of suppressing expansion on that surface. Also, in the pressure-sensitive adhesive sheet of the second embodiment, a layer capable of suppressing expansion on the surface opposite the adhesive surface of the pressure-sensitive adhesive layer (X1) is preferably laminated directly, and a base layer (Y) is more preferably laminated directly.

[0030] <Arithmetic mean waviness (Wa)> The pressure-sensitive adhesive sheet of one embodiment of the present invention has a surface (S1) of the pressure-sensitive adhesive layer (X1) opposite to the surface facing the base layer (Y). X1 ) The arithmetic mean waviness (Wa) is 0.090 μm or less. The surface (S X1 When the arithmetic mean waviness (Wa) of the adhesive tape is 0.090 μm or less, excellent adhesion can be achieved. On the other hand, the surface (S X1 If the arithmetic mean waviness (Wa) of the adhesive tape exceeds 0.090 μm, sufficient adhesiveness may not be obtained. In this specification, the arithmetic mean waviness (Wa) is measured in accordance with JIS B0601:2013, and more specifically, is measured by the method described in the examples below. The surface (S X1 From the viewpoint of further improving the adhesion of the pressure-sensitive adhesive sheet, the arithmetic mean waviness (Wa) of the surface (S X1 ) is not particularly limited, and may be 0 μm, but from the viewpoint of maintaining a good balance with the easy releasability of the pressure-sensitive adhesive layer (X1), it is preferably 0.010 μm or more, more preferably 0.020 μm or more, even more preferably 0.030 μm or more, and still more preferably 0.040 μm or more. The surface (S X1 The arithmetic mean waviness (Wa) of the thermally expandable layer (X1) can be adjusted to fall within the above range by, for example, adjusting the thickness of the pressure-sensitive adhesive layer (X1) and the base layer (Y), the content of the thermally expandable particles in the thermally expandable layer, and the manufacturing conditions of the pressure-sensitive adhesive composition (x-1) that is the material for forming the pressure-sensitive adhesive layer (X1) and the resin composition (y-1) that is the material for forming the base layer (Y), which will be described later.

[0031] <Thermal expansion particles> The thermally expandable particles used in the pressure-sensitive adhesive sheet of one embodiment of the present invention may be particles that expand when heated, and the expansion initiation temperature (t) is appropriately selected depending on the application of the pressure-sensitive adhesive sheet.

[0032] 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"). A DAF is attached to one side of a semiconductor wafer or a plurality of singulated semiconductor chips, and is divided into pieces of the same shape as the semiconductor chips either simultaneously with singulation of the semiconductor wafer or after being attached to the semiconductor chips. The singulated semiconductor chips with DAFs are attached (die-attached) to a substrate from the DAF side, and then the DAF is thermally cured to bond the semiconductor chip to the substrate. The DAF must maintain its pressure-sensitive or heat-sensitive adhesive properties until it is attached to the substrate. However, when a semiconductor chip with a DAF is used as an adherend for a heat-peelable adhesive sheet, heating during expansion of the thermally expandable particles can cause the DAF to harden before die-attachment, reducing the adhesive strength of the DAF to the substrate. It is desirable to suppress the reduction in adhesive strength of the DAF, as this reduces the reliability of the bond between the semiconductor chip and the substrate. In other words, it is desirable to suppress thermal changes in the adherend during heat-peel. From this perspective, 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.

[0033] Furthermore, if heat-expandable particles with a low expansion initiation temperature are used in a heat-peelable pressure-sensitive adhesive sheet, the heat-expandable particles may expand due to a temperature rise when the adherend is ground, etc. Such unintended expansion of the heat-expandable particles may lead to unintended separation or displacement of the adherend, and therefore should be suppressed. From this perspective, 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.

[0034] (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 with a diameter of 6.0 mm (inner diameter 5.65 mm) and a depth of 4.8 mm, and then placing an aluminum lid (diameter 5.6 mm, thickness 0.1 mm) on top. 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 probe. Then, while a force of 0.01 N is being applied using the pressure probe, 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 probe in the vertical direction is measured, and the temperature at which displacement in the forward direction begins is taken as the expansion initiation temperature (t).

[0035] 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 thermoplastic resins that constitute the outer shell of the microencapsulated foaming agent include polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone, and copolymers obtained by polymerizing two or more types of monomers that form the structural units contained in these thermoplastic resins.

[0036] Examples of the encapsulated component, which is the component encapsulated in the outer shell of the microencapsulated blowing 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 thermal peeling and suppressing unintended expansion of the heat-expanding particles due to temperature increases when the adherend is ground, when the expansion starting temperature (t) of the heat-expanding particles is set to 50°C or higher but lower than 125°C, the encapsulated components are preferably propane, isobutane, n-pentane, and cyclopropane. These encapsulated 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.

[0037] 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 still 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 thermally expandable particles before expansion corresponds to 50% in the particle distribution of the thermally expandable particles before expansion measured using a laser diffraction particle size distribution analyzer (for example, Malvern's product name "Mastersizer 3000").

[0038] 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 even more preferably 25 to 80 μm. The 90% particle diameter (D 90 ) means the particle size at which the cumulative volume frequency calculated from the smaller particle size of the thermally expandable particles before expansion corresponds to 90% in the particle distribution of the thermally expandable particles before expansion, measured using a laser diffraction particle size distribution analyzer (for example, Malvern's product name "Mastersizer 3000").

[0039] 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.

[0040] The content of the thermally expandable particles in the thermally expandable layer is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and still more preferably 4% by mass or more, based on the total mass (100% by mass) of the thermally expandable layer. The content of the thermally expandable particles in the thermally expandable layer is preferably 25% by mass or less, more preferably 23% by mass or less, even more preferably 22% by mass or less, and still more preferably 21% by mass or less, based on the total mass (100% by mass) of the thermally expandable layer. When the content of the thermally expandable particles is 1% by mass or more, the peelability during heat peeling tends to be improved. Also, when the content of the thermally expandable particles is 25% by mass or less, the occurrence of irregularities caused by the thermally expandable particles before thermal expansion is suppressed, and the surface (S x1 ) can be further reduced, and the application property tends to be improved.

[0041] <Thickness of the thermal expansion layer> In one embodiment of the present invention, the thickness of the heat-expandable layer before thermal expansion is preferably 30 to 300 μm, more preferably 40 to 270 μm, even more preferably 50 to 240 μm, and still more preferably 55 to 220 μm. When the thickness of the heat-expandable layer before thermal expansion is 30 μm or more, the occurrence of irregularities due to the heat-expandable particles before thermal expansion is suppressed, and the surface (S x1 ) can be further reduced, and the adhesiveness tends to be improved. Furthermore, if the thickness of the heat-expandable layer before thermal expansion is 300 μm or less, the pressure-sensitive adhesive sheet tends to be easier to handle.

[0042] Next, preferred embodiments of each layer of the pressure-sensitive adhesive sheet according to one embodiment of the present invention will be described. Preferred embodiments of the pressure-sensitive adhesive sheet of the first embodiment and the pressure-sensitive adhesive sheet of the second embodiment will be described below, but the present invention is not limited to these embodiments.

[0043] [Adhesive sheet of the first embodiment] The pressure-sensitive adhesive sheet of the first embodiment is a pressure-sensitive adhesive sheet having 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. In the pressure-sensitive adhesive sheet of the first embodiment, the heat-expanding particles are contained in the base layer (Y), and therefore the unevenness caused by the heat-expanding particles is not formed on the surface (S x1 Furthermore, since the pressure-sensitive adhesive layer (X1) does not need to contain thermally expandable particles, there is a high degree of freedom in designing the thickness, resin composition, etc., and this tends to further reduce the arithmetic mean waviness (Wa) and improve application properties.

[0044] <Adhesive layer (X1)> The pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of the first embodiment 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 still more preferably less than 0.01%. The pressure-sensitive adhesive layer (X1) in the pressure-sensitive adhesive sheet of the first embodiment preferably does not contain heat-expanding particles, but may contain heat-expanding particles within a range that does not contradict the object of the present invention. When the pressure-sensitive adhesive layer (X1) contains heat-expanding particles, the lower the content, the better, and is preferably less than 3 mass%, more preferably less than 1 mass%, even more preferably less than 0.1 mass%, still 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 (X1).

[0045] The pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of the first embodiment can be formed from a pressure-sensitive adhesive composition (x-1) containing a pressure-sensitive adhesive resin. Each component contained in the pressure-sensitive adhesive composition (x-1) will be described below.

[0046] (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).

[0047] 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. 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.

[0048] In one embodiment of the present invention, the adhesive resin preferably contains an acrylic resin, from the viewpoint of imparting excellent adhesive strength to the adhesive layer (X1).

[0049] The content of the acrylic resin in the adhesive resin 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 adhesive resin contained in the adhesive composition (x-1) or the adhesive layer (X1).

[0050] In one embodiment of the present invention, examples of acrylic resins that can be used as adhesive resins include polymers containing structural units derived from alkyl (meth)acrylates having a linear or branched alkyl group, and polymers containing structural units derived from (meth)acrylates having a cyclic structure.

[0051] 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, even more preferably 350,000 to 1,200,000, and still more preferably 500,000 to 1,100,000.

[0052] The acrylic resin used in one embodiment of the present invention is more 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′)”).

[0053] 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 adhesive layer (X1). The alkyl group contained in the monomer (a1') may be a linear alkyl group or a branched alkyl group.

[0054] Examples of the monomer (a1') include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-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 the monomer (a1'), n-butyl acrylate and 2-ethylhexyl acrylate are preferred.

[0055] 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).

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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 even more preferably 3.0 to 10 mass%, based on all structural units (100 mass%) of the acrylic copolymer (A1).

[0060] 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).

[0061] 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, vinyltoluene, vinyl formate, vinyl acetate, acrylonitrile, (meth)acrylamide, (meth)acrylonitrile, (meth)acryloylmorpholine, and N-vinylpyrrolidone.

[0062] 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).

[0063] (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 preferably further contains a crosslinking agent. The crosslinking agent reacts with the adhesive resin having a functional group, and crosslinks the adhesive resins together using the functional group as the crosslinking starting point.

[0064] 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 crosslinking agent include polyvalent isocyanate compounds such as 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, methylenebis(cyclohexylisocyanate), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, and hydrogenated xylylene diisocyanate; and acyclic aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. Further, examples of the isocyanate crosslinking agent include a trimethylolpropane adduct modified product of the polyisocyanate compound, a biuret modified product obtained by reacting the polyisocyanate compound with water, and an isocyanurate 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 residues derived from the pressure-sensitive adhesive layer (X1) to the adherend, it is preferable to use a trimethylolpropane adduct-type modified polyisocyanate compound, it is more preferable to use a trimethylolpropane adduct-type modified aromatic polyisocyanate compound, and it is even more preferable to use a trimethylolpropane adduct-type modified tolylene diisocyanate.

[0065] The content of the crosslinking agent is adjusted appropriately 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 per 100 parts by mass of the adhesive resin having functional groups.

[0066] (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.

[0067] Examples of tackifiers include rosin resins, terpene resins, styrene 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.

[0068] The softening point of the tackifier is preferably 60 to 170°C, more preferably 65 to 160°C, and even more preferably 70 to 150°C. In this specification, the "softening point" of a tackifier means a value measured in accordance with JIS K 2531. The tackifier may be used alone or in combination with two or more types that differ in softening point, structure, etc. When two or more types of tackifiers are used, it is preferable that the weighted average of the softening points of the multiple tackifiers falls within the above range.

[0069] The content of the tackifier is preferably 0.01 to 65 mass%, more preferably 0.1 to 50 mass%, even more preferably 1 to 40 mass%, and still more preferably 2 to 30 mass%, relative to the total amount (100 mass%) of the active ingredients of the pressure-sensitive adhesive composition (x-1).

[0070] (adhesive additives) In one embodiment of the present invention, the pressure-sensitive adhesive composition (x-1) may contain, in addition to the additives described above, a pressure-sensitive adhesive additive used in a general pressure-sensitive adhesive, as long as the effect of the present invention is not impaired. Examples of such adhesive additives include antioxidants, softeners (plasticizers), rust inhibitors, pigments, dyes, retarders, reaction accelerators (catalysts), ultraviolet absorbers, energy ray-curable compounds and photopolymerization initiators, which will be described later. These adhesive additives may be used alone or in combination of two or more.

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

[0072] (Adhesive strength of pressure-sensitive adhesive layer (X1) before thermal expansion of heat-expandable base layer (Y1)) The adhesive strength of the pressure-sensitive adhesive layer (X1) before thermally expanding the heat-expandable base layer (Y1) is preferably 0.1 to 12.0 N / 25 mm, more preferably 0.5 to 9.0 N / 25 mm, even more preferably 1.0 to 8.0 N / 25 mm, and still more preferably 1.2 to 7.5 N / 25 mm. If the adhesive strength of the pressure-sensitive adhesive layer (X1) before thermally expanding the heat-expandable base layer (Y1) is 0.1 N / 25 mm or more, unintended peeling from the adherend during temporary fixation, misalignment of the adherend, etc. can be more effectively suppressed. On the other hand, if the adhesive strength is 12.0 N / 25 mm or less, releasability during heat peeling can be further improved. The adhesive strength of the pressure-sensitive adhesive layer (X1) at 23° C. before thermal expansion can be measured by the method described above.

[0073] (Adhesive strength of pressure-sensitive adhesive layer (X1) at 23°C after thermally expanding heat-expandable base layer (Y1)) The adhesive strength of the pressure-sensitive adhesive layer (X1) at 23°C after thermally expanding the heat-expandable base layer (Y1) is preferably 1.5 N / 25 mm or less, more preferably 0.05 N / 25 mm or less, even more preferably 0.01 N / 25 mm or less, and even more preferably 0 N / 25 mm. Note that an adhesive strength of 0 N / 25 mm means an adhesive strength below the measurement limit in the method for measuring adhesive strength after thermal expansion described below, and also includes cases where the adhesive strength is too small when fixing the pressure-sensitive adhesive sheet for measurement, resulting in unintentional peeling. The adhesive strength of the pressure-sensitive adhesive layer (X1) at 23°C after thermally expanding the heat-expandable base layer (Y1) can be measured by the above-mentioned method using a pressure-sensitive adhesive sheet heated for 1 minute at the expansion starting temperature of the heat-expandable particles contained in the heat-expandable base layer (Y1) + 22°C.

[0074] (Thickness of adhesive layer (X1)) The thickness of the pressure-sensitive adhesive layer (X1) in the pressure-sensitive adhesive sheet of the first embodiment 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 heat-expandable particles are expanded by heating. By adjusting the thickness of the pressure-sensitive adhesive layer (X1) to fall within the above range, the pressure-sensitive adhesive layer (X1) can be easily formed, and good unevenness can be easily formed on the adhesive surface of the pressure-sensitive adhesive layer (X1).

[0075] <Thermal Expandable Base Layer (Y1)> The heat-expandable base layer (Y1) of the pressure-sensitive adhesive sheet of the first embodiment is a heat-expandable layer containing heat-expandable particles in a resin material, and is a layer provided between the pressure-sensitive adhesive layer (X1) and the non-heat-expandable base layer (Y2).

[0076] The thermally expandable substrate layer (Y1) is preferably a non-adhesive substrate. The probe tack value on the surface of the thermally expandable base 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 can be 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 applied 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.

[0077] In order to improve the interlayer adhesion between the thermally expandable base layer (Y1) and other layers to be laminated thereto, 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 oxidation methods include corona discharge treatment, plasma discharge treatment, chromic acid treatment (wet), hot air treatment, ozone treatment, and ultraviolet irradiation treatment, and examples of roughening methods include sandblasting and solvent treatment.

[0078] The thermally expandable base 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, with the preferred embodiment of the thermally expandable particles being as described above.

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

[0080] The mass average molecular weight (Mw) of the resin contained in the resin composition (y-1) is preferably 1,000 to 1,000,000, more preferably 1,000 to 700,000, and even more preferably 1,000 to 500,000. Furthermore, when the resin is a copolymer 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.

[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%, relative to 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 one or more resins 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 pressure-sensitive adhesive layer (X1) and improving the sheet shape retention after thermal expansion. That is, the thermally expandable base layer (Y1) preferably contains one or more resins selected from the group consisting of acrylic urethane resins and olefin resins. As the acrylic urethane resin, the following resin (U1) is preferred. · An acrylic urethane resin (U1) obtained by polymerizing a 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) that forms 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. 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 even more preferably an ester-type diol or a carbonate-type diol.

[0085] Examples of ester-type diols include condensation polymers of one or more diols selected from alkanediols such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol; and alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; and one or more dicarboxylic acids selected from 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 anhydrides thereof. Specific examples 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 alkanediols 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 raw materials 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 polyvalent isocyanates may be trimethylolpropane adduct-type modified products, biuret-type modified products reacted 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-isocyanatomethyl-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 forms the main chain of the acrylic urethane resin (U1) is preferably a linear 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 that forms 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 blending 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 still more preferably 1.5 to 10 parts by mass.

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

[0096] In addition, examples of the hydroxyalkyl (meth)acrylate include the same hydroxyalkyl (meth)acrylates as those used to introduce 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 vinyltoluene; 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 alkyl (meth)acrylate and 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%, relative to the total amount (100 mass%) of the vinyl compound.

[0100] The acrylic urethane resin (U1) used in one embodiment of the present invention is 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 in the presence of 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 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 by mass.

[0102] [Olefin Resin] The olefin resin suitable for use as the resin contained in the resin composition (y-1) is a polymer having at least a structural unit derived from an olefin monomer. The olefin monomer is preferably an α-olefin having 2 to 8 carbon atoms, and specific examples thereof include ethylene, propylene, butylene, isobutylene, and 1-hexene. Of these, ethylene and propylene are preferred.

[0103] Specific examples of olefin resins include ultra-low density polyethylene (VLDPE, density: 880 kg / m 3 More than 910kg / m 3 less than 910 kg / m 3 More than 915kg / m 3less than 915 kg / m 3 More than 942kg / m 3 less than 942 kg / m 3 Examples of suitable olefin terpolymers include 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), and olefin terpolymers such as ethylene-propylene-(5-ethylidene-2-norbornene).

[0104] In one embodiment of the present invention, the olefin resin may be a modified olefin resin that has been further 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 olefin resins to acid modification include modified polymers obtained by graft polymerizing unsaturated carboxylic acids or anhydrides thereof onto the above-mentioned unmodified olefin resins. 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 acids or anhydrides thereof may be used alone or in combination of two or more.

[0106] Examples of acrylic-modified olefin resins obtained by acrylic modification of olefin resins include modified polymers obtained by graft polymerizing alkyl (meth)acrylate as a side chain to the above-mentioned unmodified olefin resin as a main chain. The alkyl group in the alkyl (meth)acrylate preferably has 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and even more preferably 1 to 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 group-modified olefin resins obtained by subjecting olefin resins to hydroxyl group modification include modified polymers obtained by graft polymerizing a hydroxyl group-containing compound onto the above-mentioned unmodified olefin resin main chain. Examples of the hydroxyl group-containing compound include the same 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 that do not fall under the category of acrylic urethane resins; polysulfone; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide resins such as polyetherimide and polyimide; polyamide resins; acrylic resins; and fluorine-based resins.

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

[0110] (Additives for substrates) The resin composition (y-1) may contain additives for substrates as needed, as long as the effects of the present invention are not impaired. 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. When these base material additives are contained, the content of each base material additive is preferably 0.0001 to 20 parts by mass, more preferably 0.001 to 10 parts by mass, based on 100 parts by mass of the resin.

[0111] (Solvent-free resin composition (y-1a)) One embodiment of the resin composition (y-1) used in one aspect of the present invention is a solvent-free resin composition (y-1a) that is obtained by blending an oligomer having an ethylenically unsaturated group and having a mass average molecular weight (Mw) of 50,000 or less, an energy ray-polymerizable monomer, and the above-mentioned thermally expandable particles, and does not contain a solvent. In the solventless resin composition (y-1a), no solvent is blended, but the energy ray polymerizable monomer contributes to improving the plasticity of the oligomer. By irradiating the solventless resin composition (y-1a) with energy rays, the oligomer having an ethylenically unsaturated group, the energy ray polymerizable monomer, etc. are polymerized to form the thermally expandable base layer (Y1).

[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 resin composition (y-1) described above, as long as it has an ethylenically unsaturated group with a mass average molecular weight of 50,000 or less. The urethane prepolymer (UP) described above 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%, relative to the total amount (100 mass%) of the solventless resin composition (y-1a).

[0115] Examples of the energy beam polymerizable monomer 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. Among these, isobornyl (meth)acrylate and phenylhydroxypropyl acrylate are preferred. These energy ray polymerizable monomers may be used alone or in combination of two or more.

[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] is preferably 20 / 80 to 90 / 10, more preferably 30 / 70 to 85 / 15, and even more preferably 35 / 65 to 80 / 20, in mass ratio.

[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. Examples of photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, diacetyl, β-chloroanthraquinone, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. These photopolymerization initiators may be used alone or in combination of two or more. The amount of the photopolymerization initiator to be 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.

[0118] The resin composition (y-1) can be produced by mixing the above-mentioned components. The method for mixing the components is not particularly limited, and may be appropriately selected from known mixing methods depending on the types of components used, the viscosity of the resin composition, and the like. Since the resin composition (y-1) contains thermally expandable particles, it may be subjected to a dispersion treatment to improve the dispersibility of the thermally expandable particles. By improving the dispersibility of the thermally expandable particles in the resin composition (y-1), the surface of the thermally expandable base layer (Y1) becomes even smoother, and the surface (S x1 ) can be made smaller. Examples of dispersion treatment methods for thermally expandable particles include stirring treatments that apply shear using a high-speed stirrer such as a homomixer, homogenizer, planetary mixer, or ball mill; ultrasonic treatment; and filtration treatments that remove aggregates using a filter. Among these, it is preferable to appropriately determine a method and conditions that can improve dispersibility while maintaining the functionality of the thermally expandable particles. The dispersion treatment of the thermally expandable particles may be carried out after the thermally expandable particles are mixed with other components, or may be carried out in a dispersion medium before the particles are mixed with other components.

[0119] (Thickness of the thermally expandable base layer (Y1)) In one embodiment of the present invention, the thickness of the thermally expandable base layer (Y1) before thermal expansion is preferably 30 to 300 μm, more preferably 40 to 270 μm, even more preferably 50 to 240 μm, and still more preferably 55 to 220 μm. When the thickness of the heat-expandable base layer (Y1) before thermal expansion is 30 μm or more, the occurrence of irregularities due to the heat-expandable particles before thermal expansion is suppressed, and the surface (S x1 ) can be further reduced, and the adhesiveness tends to be improved. Furthermore, when the thickness of the thermally expandable base layer (Y1) before thermal expansion is 300 μm or less, the pressure-sensitive adhesive sheet tends to be easier to handle.

[0120] <Non-thermally expandable base layer (Y2)> The non-thermally expandable base layer (Y2) of the pressure-sensitive adhesive sheet of the first embodiment is provided on the surface of the heat-expandable base layer (Y1) opposite to the surface on which the pressure-sensitive adhesive layer (X1) is laminated.

[0121] The non-thermally expandable base layer (Y2) is preferably a non-adhesive base material. The probe tack value on the surface of the non-thermally expandable base 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 even more preferably less than 5 mN / 5 mmφ.

[0122] Examples of materials for forming the non-thermally expandable base layer (Y2) include resins, metals, and paper materials, and can be appropriately selected depending on the application of the pressure-sensitive adhesive sheet.

[0123] 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.

[0124] 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 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 metal using a general adhesive.

[0125] In addition, in order to improve the interlayer adhesion between the non-thermally expandable base layer (Y2) and other layers to be laminated thereto, 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).

[0126] When the non-thermally expandable base layer (Y2) contains a resin, it may contain, together with the resin, the above-mentioned base additives which may also be contained in the resin composition (y-1).

[0127] 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%, preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and even more preferably less than 0.01%.

[0128] 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 thermally expandable particles are contained. 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 still more preferably less than 0.001 mass%, relative to the total mass (100 mass%) of the non-thermally expandable base layer (Y2).It is even more preferable that the layer does not contain any thermally expandable particles.

[0129] (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 9 Pa, 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 If the elastic modulus is 0.05 Pa or less, the handleability of the pressure-sensitive adhesive sheet can be 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.

[0130] (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.

[0131] <Adhesive layer (X2)> The pressure-sensitive adhesive sheet of the first embodiment may have 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. That is, the pressure-sensitive adhesive sheet of the first embodiment may be a pressure-sensitive adhesive sheet having a laminate structure in which the pressure-sensitive adhesive layer (X1), the heat-expandable base layer (Y1), the non-thermally expandable base layer (Y2), and the pressure-sensitive adhesive layer (X2) are arranged in this order.

[0132] The pressure-sensitive adhesive layer (X2) is preferably a non-thermally 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 still more preferably less than 0.01%. The pressure-sensitive adhesive layer (X2) preferably does not contain any heat-expanding particles, but may contain heat-expanding 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 %, still 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).

[0133] The adhesive layer (X2) is preferably an energy ray-curable adhesive layer that is cured by irradiation with energy rays and thereby reduces its adhesive strength. By making the adhesive layer (X2) an energy ray-curable adhesive layer, the adhesive surface of the adhesive layer (X1) can be configured to have its adhesive strength reduced by heating, and the adhesive surface of the adhesive layer (X2) can be configured to have its adhesive strength reduced by irradiation with energy rays, making it possible to make the mechanisms of action for reducing the adhesive strength of each adhesive layer different. This makes it possible to avoid unintentionally reducing the adhesive strength of one adhesive layer when performing a treatment to reduce the adhesive strength of the other adhesive layer.

[0134] 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.

[0135] 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 components.

[0136] (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).

[0137] The adhesive resin may be the same as the adhesive resin contained in the adhesive composition (x-1). These adhesive resins may be used alone or in combination of two or more. Furthermore, when these adhesive resins are copolymers having two or more types of constitutional units, the copolymer may be in the form of a block copolymer, a random copolymer, or a graft copolymer.

[0138] The adhesive resin contained in the adhesive composition (x-2) is preferably an adhesive resin having an energy ray-polymerizable functional group in the side chain, from the viewpoint of making the resulting adhesive layer (X2) 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.

[0139] The adhesive resin preferably contains an acrylic resin from the viewpoint of exhibiting excellent adhesive strength. 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).

[0140] 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).

[0141] (energy ray curable compound) The pressure-sensitive adhesive composition (x-2) may contain, together with the pressure-sensitive adhesive resin, a monomer or oligomer that can be polymerized and cured by energy ray irradiation as an energy ray-curable compound. Examples of such energy ray-curable compounds include polyvalent (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 that they have a relatively high molecular weight and are less likely to reduce the elastic modulus of the pressure-sensitive adhesive layer (X2). The molecular weight of the energy ray-curable compound (mass average molecular weight (Mw) in the case of an oligomer) 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.

[0142] (Photopolymerization initiator) The pressure-sensitive adhesive composition (x-2) preferably further contains a photopolymerization initiator. By including a photopolymerization initiator, the polymerization of the energy ray-polymerizable component can be more efficiently promoted. Examples of the photopolymerization initiator include the same ones as those exemplified in the description of the solvent-free resin composition (y-1a), and among these, 1-hydroxycyclohexyl phenyl ketone is preferred. 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, relative to 100 parts by mass of the total amount of the adhesive resin having an energy ray-polymerizable functional group.

[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, the pressure-sensitive adhesive composition (x-2) preferably further contains a crosslinking agent. The crosslinking agent reacts with the 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 or equivalent crosslinking agents as the crosslinking agents that may be contained in the pressure-sensitive adhesive composition (x-1). However, from the viewpoints of increasing the cohesive strength and improving the adhesive strength, ease of availability, etc., an isocyanate-based crosslinking agent is preferred.

[0145] The content of the crosslinking agent is adjusted appropriately 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 per 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. The tackifier that may be contained in the pressure-sensitive adhesive composition (x-2) may be the same as or equivalent to the tackifier that may be contained in the pressure-sensitive adhesive composition (x-1).

[0147] (adhesive additives) Examples of the additives for pressure-sensitive adhesives include the same additives for pressure-sensitive adhesives 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, a pressure-sensitive adhesive additive, and the like.

[0149] (Adhesive strength of adhesive layer (X2) before energy ray irradiation) The adhesive strength of the adhesive layer (X2) before irradiation with energy rays is preferably 1.1 to 30.0 N / 25 mm, more preferably 3.0 to 25.0 N / 25 mm, and even more preferably 5.0 to 20.0 N / 25 mm. If the adhesive strength of the pressure-sensitive adhesive layer (X2) before energy ray irradiation is 1.1 N / 25 mm or more, unintended peeling from the adherend, misalignment of the adherend, etc. can be more effectively suppressed. On the other hand, if the adhesive strength is 30.0 N / 25 mm or less, the releasability after energy ray irradiation can be further improved. The adhesive strength of the pressure-sensitive adhesive layer (X2) before irradiation with energy rays can be measured by the method described above.

[0150] (Adhesive strength of adhesive layer (X2) after energy ray irradiation) The adhesive strength of the pressure-sensitive adhesive layer (X2) after energy ray irradiation is preferably 1.0 N / 25 mm or less, more preferably 0.9 N / 25 mm or less, even more preferably 0.8 N / 25 mm or less, and still more preferably 0.7 N / 25 mm or less. There is no particular restriction on the lower limit of the adhesive strength of the pressure-sensitive adhesive layer (X2) after energy ray irradiation, and it may be 0 N / 25 mm or more. If the adhesive strength of the pressure-sensitive adhesive layer (X2) after irradiation with energy rays is 1.0 N / 25 mm or less, the peelability from the adherend will be superior. The adhesive strength of the adhesive layer (X2) after irradiation with energy rays was measured at an illuminance of 230 mW / cm 2 , light intensity 90mJ / cm 2 The measurement can be performed by the above-mentioned method using a pressure-sensitive adhesive sheet irradiated with ultraviolet light.

[0151] (Thickness of adhesive layer (X2)) The thickness of the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet of the first embodiment is preferably 5 to 150 μm, more preferably 8 to 100 μm, even more preferably 12 to 70 μm, and even more preferably 15 to 50 μm. If the thickness of the pressure-sensitive adhesive layer (X2) is 5 μm or more, sufficient adhesive strength is likely to be obtained, and unintended peeling from the adherend during temporary fixation, displacement of the adherend, etc., tend to be suppressed. On the other hand, if the thickness of the pressure-sensitive adhesive layer (X2) is 150 μm or less, handling of the pressure-sensitive adhesive sheet tends to be easier.

[0152] <Method for producing pressure-sensitive adhesive sheet according to first embodiment> The method for producing the pressure-sensitive adhesive sheet of the first embodiment 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 the release-treated surface of a release liner to form a pressure-sensitive adhesive layer (X1). Step (2a): A step of applying a resin composition (y-1) to one surface 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. Step (3a): A step of bonding the adhesive surface of the adhesive layer (X1) formed in step (1a) to the surface of the thermally expandable base layer (Y1) of the base laminate formed in step (2a) to obtain a pressure-sensitive adhesive sheet.

[0153] Furthermore, when the pressure-sensitive adhesive sheet of the first aspect has a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are arranged in this order, the pressure-sensitive adhesive sheet can be produced by a method further comprising the following steps (4a) and (5a): Step (4a): A step of applying a pressure-sensitive adhesive composition (x-2) onto the release-treated surface of the release liner 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 adhesive sheet formed in step (3a) on the side of the non-thermally expandable base layer (Y2).

[0154] In the method for producing the 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.

[0155] 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.

[0156] [Adhesive sheet of the second embodiment] The pressure-sensitive adhesive sheet of the second embodiment is a pressure-sensitive adhesive sheet having a laminated structure including a pressure-sensitive adhesive layer (X1) that is a heat-expandable layer, and a substrate layer (Y). The pressure-sensitive adhesive sheet of the second embodiment may have a pressure-sensitive adhesive layer (X2) on the surface of the base layer (Y) opposite to the surface on which the pressure-sensitive adhesive layer (X1) is laminated. That is, the pressure-sensitive adhesive sheet of the second embodiment may be a pressure-sensitive adhesive sheet having a laminated structure in which the pressure-sensitive adhesive layer (X1) as a heat-expandable layer, the base layer (Y), and the pressure-sensitive adhesive layer (X2) are arranged in this order.

[0157] The explanation for the base layer (Y) in the pressure-sensitive adhesive sheet of the second embodiment is the same as the explanation for the non-thermally expandable base layer (Y2) in the pressure-sensitive adhesive sheet of the first embodiment. The explanation for the pressure-sensitive adhesive layer (X2) that the pressure-sensitive adhesive sheet of the second embodiment may have is the same as the explanation for the pressure-sensitive adhesive layer (X2) that the pressure-sensitive adhesive sheet of the first embodiment may have.

[0158] <Adhesive layer (X1)> The pressure-sensitive adhesive layer (X1) of the second embodiment is a heat-expandable layer containing heat-expandable particles, and preferably contains a polymer of an energy ray-polymerizable component and heat-expandable particles. The above polymer is a polymer obtained by irradiating a polymerizable composition (hereinafter also referred to as "polymerizable composition (x-1')") containing, as the energy ray-polymerizable components, a monomer (b1) (hereinafter also referred to as "component (b1)") having an energy ray-polymerizable functional group and a prepolymer (b2) (hereinafter also referred to as "component (b2)") having an energy ray-polymerizable functional group. In this specification, a prepolymer refers to a compound obtained by polymerizing a monomer, which can be further polymerized to form a polymer.

[0159] The energy ray-polymerizable component contained in the polymerizable composition (x-1') is a component that polymerizes upon irradiation with energy rays and has an energy ray-polymerizable functional group. 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, an allyl group, etc. In the following description, functional groups containing a vinyl group or a substituted vinyl group as a part thereof, such as a (meth)acryloyl group or an allyl group, and the vinyl group or substituted vinyl group itself may be collectively referred to as a "vinyl group-containing group." Each component contained in the polymerizable composition (x-1') will be described below.

[0160] (Monomer (b1) having an energy ray-polymerizable functional group) The monomer (b1) having an energy ray-polymerizable functional group may be any monomer having an energy ray-polymerizable functional group, and may have, in addition to the energy ray-polymerizable functional group, a hydrocarbon group, a functional group other than the energy ray-polymerizable functional group, etc.

[0161] Examples of the hydrocarbon group contained in the component (b1) include aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and groups that combine these groups. The aliphatic hydrocarbon group may be a straight-chain or branched-chain aliphatic hydrocarbon group, or may be an alicyclic hydrocarbon group. Examples of the linear or branched aliphatic hydrocarbon group include aliphatic hydrocarbon groups having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, a sec-butyl group, an n-pentyl group, an n-hexyl group, a 2-ethylhexyl group, an n-octyl group, an isooctyl group, an n-decyl group, an n-dodecyl group, an n-myristyl group, an n-palmityl group, and an n-stearyl group. Examples of the alicyclic hydrocarbon group include alicyclic hydrocarbon groups having 3 to 20 carbon atoms, such as a cyclopentyl group, a cyclohexyl group, and an isobornyl group. An example of the aromatic hydrocarbon group is a phenyl group. Examples of the group combining an aliphatic hydrocarbon group and an aromatic hydrocarbon group include a phenoxyethyl group and a benzyl group. Among these, from the viewpoint of further improving the adhesive strength of the pressure-sensitive adhesive layer (X1), it is preferable that the (b1) component contains a monomer (b1-1) having an energy ray-polymerizable functional group and a linear or branched aliphatic hydrocarbon group (hereinafter also referred to as "component (b1-1)"), a monomer (b1-2) having an energy ray-polymerizable functional group and an alicyclic hydrocarbon group (hereinafter also referred to as "component (b1-2)"), or the like.

[0162] When the (b1) component contains the (b1-1) component, the content thereof is preferably 20 to 80 mass %, more preferably 40 to 70 mass %, and even more preferably 50 to 60 mass %, relative to the total (100 mass %) of the (b1) component. When the (b1) component contains the (b1-2) component, the content thereof is preferably 5 to 60 mass %, more preferably 10 to 40 mass %, and even more preferably 20 to 30 mass %, relative to the total (100 mass %) of the (b1) component.

[0163] Examples of the monomer having an energy ray-polymerizable functional group and a functional group other than the energy ray-polymerizable functional group include monomers having, as the functional group other than the energy ray-polymerizable functional group, for example, a hydroxy group, a carboxy group, a thiol group, a primary or secondary amino group, etc. Among these, from the viewpoint of further improving the formability of the pressure-sensitive adhesive layer (X1), it is preferable that the (b1) component contains a monomer (b1-3) having an energy ray-polymerizable functional group and a hydroxy group (hereinafter also referred to as "component (b1-3)"). When the (b1) component contains the (b1-3) component, the content thereof is preferably 1 to 60 mass %, more preferably 5 to 30 mass %, and even more preferably 10 to 20 mass %, relative to the total (100 mass %) of the (b1) component.

[0164] The number of energy ray-polymerizable functional groups contained in the component (b1) may be 1 or 2 or more. From the viewpoint of further improving the releasability of the pressure-sensitive adhesive layer (X1), the component (b1) preferably contains a monomer (b1-4) having 3 or more energy ray-polymerizable functional groups (hereinafter also referred to as "component (b1-4)"). When the (b1) component contains the (b1-4) component, the content thereof is preferably 1 to 20 mass %, more preferably 2 to 15 mass %, and even more preferably 3 to 10 mass %, relative to the total (100 mass %) of the (b1) component.

[0165] As the monomer having one energy ray-polymerizable functional group, a monomer having one vinyl group-containing group (hereinafter also referred to as "polymerizable vinyl monomer") is preferred. As the monomer having two or more energy ray-polymerizable functional groups, a monomer having two or more (meth)acryloyl groups (hereinafter also referred to as "polyfunctional (meth)acrylate monomer") is preferred. When component (b1) contains the above compound, the cohesive strength of the pressure-sensitive adhesive obtained by polymerizing these compounds is improved, and a pressure-sensitive adhesive layer (X1) can be formed that causes less contamination of the adherend after peeling.

[0166] [Polymerizable vinyl monomer] The polymerizable vinyl monomer is not particularly limited as long as it has a vinyl group-containing group, and any conventionally known polymerizable vinyl monomer can be used as appropriate. The polymerizable vinyl monomers may be used alone or in combination of two or more.

[0167] Examples of the polymerizable vinyl monomer include compounds corresponding to the above component (b1-1), such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate; compounds corresponding to the above component (b1-2), such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; and (meth)acrylates that do not have functional groups other than vinyl group-containing groups in the molecule, such as phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and polyoxyalkylene-modified (meth)acrylates. Of these, 2-ethylhexyl acrylate and isobornyl acrylate are preferred.

[0168] The polymerizable vinyl monomer may further contain a functional group other than the vinyl group-containing group in the molecule. Examples of such functional groups include a hydroxy group, a carboxy group, a thiol group, and a primary or secondary amino group. Among these, a polymerizable vinyl monomer having a hydroxy group corresponding to the above component (b1-3) is preferred. Examples of polymerizable vinyl monomers having a hydroxy group 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 hydroxy group-containing acrylamides such as N-methylol acrylamide and N-methylol methacrylamide. Examples of polymerizable vinyl monomers having a carboxy group include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferred.

[0169] Other polymerizable vinyl monomers include, for example, vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene-based monomers such as styrene and α-methylstyrene; diene-based monomers such as butadiene, isoprene, and chloroprene; nitrile-based monomers such as acrylonitrile and methacrylonitrile; amide-based monomers such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N-vinylpyrrolidone; and tertiary amino group-containing monomers such as N,N-diethylaminoethyl (meth)acrylate and N-(meth)acryloylmorpholine.

[0170] [Polyfunctional (meth)acrylate monomer] The polyfunctional (meth)acrylate monomer is not particularly limited as long as it is a monomer having two or more (meth)acryloyl groups in one molecule, and any conventionally known monomer can be used as appropriate. The polyfunctional (meth)acrylate monomers may be used alone or in combination of two or more.

[0171] Examples of polyfunctional (meth)acrylate monomers include bifunctional (meth)acrylate monomers such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl) isocyanurate, allylated cyclohexyl di(meth)acrylate, and isocyanuric acid ethylene oxide-modified diacrylate; trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and the like. Examples of polyfunctional (meth)acrylate monomers that fall under the above component (b1-4) include acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl)isocyanurate, bis(acryloxyethyl)hydroxyethyl isocyanurate, ethylene oxide isocyanurate-modified triacrylate, ε-caprolactone-modified tris(acryloxyethyl)isocyanurate, diglycerin tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, propionic acid-modified dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0172] (b1) Component Content The total content of polymerizable vinyl monomers in the polymerizable composition (x-1') is preferably 10 to 80 mass %, more preferably 30 to 75 mass %, and even more preferably 50 to 70 mass %, relative to the total amount (100 mass %) of the active ingredients of the polymerizable composition (x-1'). The total content of the polyfunctional (meth)acrylate monomers in the polymerizable composition (x-1') is preferably 0.5 to 15 mass%, more preferably 1 to 10 mass%, and even more preferably 2 to 5 mass%, relative to the total amount (100 mass%) of the active ingredients of the polymerizable composition (x-1'). The total content of the (b1) component in the polymerizable composition (x-1') is preferably 15 to 90 mass%, more preferably 35 to 80 mass%, and even more preferably 55 to 75 mass%, relative to the total amount (100 mass%) of the active ingredients of the polymerizable composition (x-1').

[0173] (Prepolymer (b2) having an energy ray-polymerizable functional group) Examples of the prepolymer (b2) having an energy ray-polymerizable functional group include a prepolymer having one energy ray-polymerizable functional group, a prepolymer having two or more energy ray-polymerizable functional groups, etc. Among these, from the viewpoint of forming a pressure-sensitive adhesive layer that is excellent in releasability and causes little contamination of the adherend after peeling, the component (b2) preferably contains a prepolymer having two or more energy ray-polymerizable functional groups, more preferably contains a prepolymer having two energy ray-polymerizable functional groups, and even more preferably contains a prepolymer having two energy ray-polymerizable functional groups and having the energy ray-polymerizable functional groups at both ends.

[0174] The component (b2) preferably contains a prepolymer having two or more (meth)acryloyl groups as energy ray-polymerizable functional groups (hereinafter also referred to as a "polyfunctional (meth)acrylate prepolymer"). When the component (b2) contains the above compound, the cohesive strength of the pressure-sensitive adhesive obtained by polymerizing these is improved, and a pressure-sensitive adhesive layer (X1) can be formed that has excellent releasability and reduces contamination of the adherend after peeling.

[0175] [Multifunctional (meth)acrylate prepolymer] The polyfunctional (meth)acrylate prepolymer is not particularly limited as long as it is a prepolymer having two or more (meth)acryloyl groups in one molecule, and any conventionally known prepolymer can be used as appropriate. The polyfunctional (meth)acrylate prepolymers may be used alone or in combination of two or more.

[0176] Examples of polyfunctional (meth)acrylate prepolymers include urethane acrylate prepolymers, polyester acrylate prepolymers, epoxy acrylate prepolymers, polyether acrylate prepolymers, polybutadiene acrylate prepolymers, silicone acrylate prepolymers, and polyacryl acrylate prepolymers.

[0177] Urethane acrylate prepolymers can be obtained, for example, by reacting a compound such as polyalkylene polyol, polyether polyol, polyester polyol, hydrogenated isoprene having a hydroxyl group terminal, or hydrogenated butadiene having a hydroxyl group terminal with polyisocyanate to obtain a polyurethane prepolymer, and then esterifying the polyurethane prepolymer with (meth)acrylic acid or a (meth)acrylic acid derivative.

[0178] Examples of polyalkylene polyols used in producing urethane acrylate prepolymers include polypropylene glycol, polyethylene glycol, polybutylene glycol, polyhexylene glycol, etc., and among these, polypropylene glycol is preferred. Note that, when the number of functional groups of the obtained urethane acrylate prepolymer is to be 3 or more, for example, glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, diethylenetriamine, sorbitol, sucrose, etc. may be appropriately combined.

[0179] Examples of polyisocyanates used in the production of urethane acrylate prepolymers include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate and diphenyl diisocyanate; and alicyclic diisocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate. Among these, aliphatic diisocyanates are preferred, and hexamethylene diisocyanate is more preferred. Note that the polyisocyanate is not limited to bifunctional ones, and trifunctional or higher functional ones can also be used.

[0180] Examples of (meth)acrylic acid derivatives used in the production of urethane acrylate prepolymers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, and 1,1-bis(acryloxymethyl)ethyl isocyanate; and among these, 2-isocyanate ethyl acrylate is preferred.

[0181] Another method for producing a urethane acrylate prepolymer is to react a hydroxy group contained in a compound such as polyalkylene polyol, polyether polyol, polyester polyol, hydrogenated isoprene having a hydroxy group terminal, or hydrogenated butadiene having a hydroxy group terminal with an -N=C=O moiety contained in an isocyanate alkyl (meth)acrylate. In this case, the isocyanate alkyl (meth)acrylate may be, for example, the above-mentioned 2-isocyanate ethyl acrylate, 2-isocyanate ethyl methacrylate, or 1,1-bis(acryloxymethyl)ethyl isocyanate.

[0182] The polyester acrylate prepolymer can be obtained, for example, by esterifying with (meth)acrylic acid the hydroxy groups of a polyester prepolymer having hydroxy groups at both ends, which is obtained by condensation of a polycarboxylic acid with a polyhydric alcohol. Alternatively, the polyester acrylate prepolymer can be obtained by adding an alkylene oxide to a polycarboxylic acid and esterifying with (meth)acrylic acid the hydroxy groups at the ends of a prepolymer.

[0183] Epoxy acrylate prepolymers can be obtained, for example, by esterifying the oxirane ring of a relatively low-molecular-weight bisphenol epoxy resin, novolac epoxy resin, etc. with (meth)acrylic acid. Also, carboxy-modified epoxy acrylate prepolymers, which are obtained by partially modifying an epoxy acrylate prepolymer with a dibasic carboxylic acid anhydride, can be used.

[0184] The polyether acrylate prepolymer can be obtained, for example, by esterifying the hydroxy group of a polyether polyol with (meth)acrylic acid.

[0185] The polyacrylacrylate prepolymer may have an acryloyl group in a side chain, or may have an acryloyl group at both ends or one end. A polyacrylacrylate prepolymer having an acryloyl group in a side chain can be obtained, for example, by adding glycidyl methacrylate to the carboxy group of polyacrylic acid. Furthermore, a polyacrylacrylate prepolymer having acryloyl groups at both ends can be obtained, for example, by introducing acryloyl groups to both ends by utilizing the polymerization growth end structure of a polyacrylate prepolymer synthesized by ATRP (Atom Transfer Radical Polymerization).

[0186] The mass average molecular weight (Mw) of the component (b2) is preferably 10,000 to 350,000, more preferably 15,000 to 200,000, and even more preferably 20,000 to 50,000.

[0187] (b2) Component Content The total content of the polyfunctional (meth)acrylate prepolymers in the polymerizable composition (x-1') is preferably 10 to 60 mass%, more preferably 15 to 55 mass%, and even more preferably 20 to 30 mass%, relative to the total amount (100 mass%) of the active ingredients of the polymerizable composition (x-1'). The total content of the (b2) component in the polymerizable composition (x-1') is preferably 10 to 60 mass%, more preferably 15 to 55 mass%, and even more preferably 20 to 30 mass%, relative to the total amount (100 mass%) of the active ingredients of the polymerizable composition (x-1').

[0188] The content ratio of the (b2) component to the (b1) component in the polymerizable composition (x-1') [(b2) / (b1)] is preferably 10 / 90 to 70 / 30, more preferably 20 / 80 to 50 / 50, and even more preferably 25 / 75 to 40 / 60, on a mass basis.

[0189] Among the above energy ray-polymerizable components, the polymerizable composition (x-1') preferably contains a polymerizable vinyl monomer, a polyfunctional (meth)acrylate monomer, and a polyfunctional (meth)acrylate prepolymer. The total content of the polymerizable vinyl monomer, polyfunctional (meth)acrylate monomer, and polyfunctional (meth)acrylate prepolymer in the energy ray-polymerizable component contained in the polymerizable composition (x-1') is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 99% by mass or more, relative to the total amount (100% by mass) of the energy ray-polymerizable component, and may be 100% by mass.

[0190] The total content of the energy ray-polymerizable components in the polymerizable composition (x-1') is preferably 70 to 98 mass%, more preferably 75 to 97 mass%, even more preferably 80 to 96 mass%, and still more preferably 82 to 95 mass%, relative to the total amount (100 mass%) of the active ingredients of the polymerizable composition (x-1').

[0191] (Other ingredients) The polymerizable composition (x-1') may contain other components in addition to the energy ray-polymerizable component and the thermally expandable particles. Examples of the other components include a photopolymerization initiator, a tackifier, and adhesive additives other than the above components that are used in general adhesives. These components include the same as those described for the pressure-sensitive adhesive sheet of the first embodiment.

[0192] The polymerizable composition (x-1') may contain a solvent such as a diluent within the scope of the present invention, but preferably does not contain a solvent. That is, the polymerizable composition (x-1') is preferably a solvent-free polymerizable composition. Since the polymerizable composition (x-1') is a solventless polymerizable composition, the step of drying the solvent by heating can be omitted when forming the adhesive layer (X1), thereby suppressing the expansion of the heat-expandable particles during heating and drying. When the polymerizable composition (x-1') contains a solvent, the smaller the content, the better. The content is preferably 10% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and still more preferably 0.01% by mass or less, relative to the total amount (100% by mass) of the active ingredients of the polymerizable composition (x-1').

[0193] The polymerizable composition (x-1') can be produced by mixing an energy ray-polymerizable component, thermally expandable particles, and other components that may be contained as needed. The method for mixing the components is not particularly limited, and may be appropriately selected from known mixing methods depending on the types of components used, the viscosity of the resin composition, and the like. Since the polymerizable composition (x-1') contains thermally expandable particles, it may be subjected to a dispersion treatment to improve the dispersibility of the thermally expandable particles in the polymerizable composition (x-1'). By improving the dispersibility of the thermally expandable particles, the surface of the pressure-sensitive adhesive layer (X1) becomes even smoother, and the surface (S x1) can be made smaller. The method for dispersing the thermally expandable particles may be the same as the method for dispersing the thermally expandable particles described above in the "Resin composition (y-1)" section of the "Pressure-sensitive adhesive sheet of the first embodiment."

[0194] Since the polymerizable composition (x-1') is subsequently polymerized by energy ray polymerization, when forming a layer, the viscosity can be adjusted to an appropriate level by adding a low-molecular-weight energy ray-polymerizable component. Therefore, the polymerizable composition (x-1') can be used as a coating solution to form the pressure-sensitive adhesive layer (X1) without adding a solvent such as a diluent. The adhesive layer (X1) formed by irradiating the polymerizable composition (x-1') with energy rays contains a wide variety of polymers formed by polymerization of energy ray-polymerizable components and thermally expandable particles dispersed in the polymers, but there are circumstances in which it is impossible or almost impractical to directly identify these by their structure and physical properties.

[0195] (Adhesive strength of adhesive layer (X1)) The explanation of the adhesive strength of the adhesive layer (X1) in the adhesive sheet of the second embodiment before thermal expansion and after thermal expansion is the same as the explanation of the adhesive strength of the adhesive layer (X1) before thermally expanding the heat-expandable base layer (Y1) and after thermally expanding the heat-expandable base layer (Y1) in the explanation of the adhesive sheet of the first embodiment.

[0196] (Thickness of adhesive layer (X1)) The thickness of the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of the second embodiment before thermal expansion is preferably 20 to 270 μm, more preferably 30 to 240 μm, even more preferably 40 to 220 μm, and even more preferably 50 to 200 μm. When the thickness of the pressure-sensitive adhesive layer (X1) before thermal expansion is 20 μm or more, the occurrence of irregularities due to the heat-expanding particles before thermal expansion is suppressed, and the surface (S x1) can be further reduced, and the adhesiveness tends to be improved. Furthermore, when the thickness of the pressure-sensitive adhesive layer (X1) before thermal expansion is 270 μm or less, the pressure-sensitive adhesive sheet tends to be easier to handle.

[0197] <Method for producing pressure-sensitive adhesive sheet according to second embodiment> The method for producing a pressure-sensitive adhesive sheet of the second embodiment is preferably a method for producing a pressure-sensitive adhesive sheet in which the method for forming the pressure-sensitive adhesive layer (X1) comprises a step of irradiating a polymerizable composition (x-1') containing the energy ray-polymerizable component and the thermally expandable particles with energy rays to form a polymer of the energy ray-polymerizable component, and more preferably a production method comprising the following steps (1b) and (2b): Step (1b): A step of forming a polymerizable composition layer made of a polymerizable composition (x-1′) on one surface of a substrate (Y). Step (2b): A step of irradiating the polymerizable composition layer with energy rays to form a polymer of the energy ray-polymerizable component, and forming a pressure-sensitive adhesive layer (X1) containing the polymer and the thermally expandable particles, thereby obtaining a pressure-sensitive adhesive sheet.

[0198] Furthermore, when the pressure-sensitive adhesive sheet of the second embodiment has a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are arranged in this order, the pressure-sensitive adhesive sheet can be produced by a method further comprising the following step (3b): Step (3b): A step of forming a pressure-sensitive adhesive layer (X2) on the surface of the base layer (Y) of the pressure-sensitive adhesive sheet formed in step (2b) opposite to the surface on which the pressure-sensitive adhesive layer (X1) is laminated.

[0199] An example of step (1b) is a method in which a polymerizable composition (x-1') is applied to the release-treated surface of a release material to form a polymerizable composition layer, the polymerizable composition layer is irradiated with a first energy ray to prepolymerize the energy ray-polymerizable component in the polymerizable composition layer, and then a substrate (Y) is attached to the prepolymerized polymerizable composition layer. As described above, the polymerizable composition (x-1') is preferably a solventless polymerizable composition. When the polymerizable composition (x-1') is a solventless polymerizable composition, the solvent does not need to be dried by heating in this step, and the expansion of the thermally expandable particles can be suppressed.

[0200] Step (2b) is a step of irradiating the polymerizable composition layer formed in step (1b) with energy rays to form a polymer of the energy ray-polymerizable component, and forming a pressure-sensitive adhesive layer (X1) containing the polymer and thermally expandable particles. Here, when the first energy ray irradiation is carried out in the step (1b), the energy ray irradiation in the step (2b) is the second energy ray irradiation carried out on the polymerizable composition layer after prepolymerization. Unlike the first energy ray irradiation, the energy ray irradiation in step (2b) is preferably carried out to an extent that further irradiation with energy rays does not substantially cause polymerization of the energy ray-polymerizable component to proceed. The energy ray irradiation in step (2b) causes polymerization of the energy ray-polymerizable component to proceed, and a polymer of the energy ray-polymerizable component that constitutes the pressure-sensitive adhesive layer (X1) is formed.

[0201] An example of step (3b) is a method in which a pressure-sensitive adhesive composition (x-2) is applied to one side of a release material to form a pressure-sensitive adhesive layer (X2), and the pressure-sensitive adhesive layer (X2) is then attached to the other side of the substrate (Y).

[0202] In any of the above steps, it is preferable that the step of heating the polymerizable composition is not included, from the viewpoint of suppressing expansion of the thermally expandable particles. The term "heating" as used herein means intentional heating, for example, during drying, lamination, etc., and does not include temperature increases due to heat imparted to the polymerizable composition by energy ray irradiation, polymerization heat generated by polymerization of the energy ray-polymerizable composition, etc.

[0203] <Removal material> Examples of release materials that may be included in the pressure-sensitive adhesive sheet of one embodiment of the present invention include release sheets that have been treated for release on both sides and release sheets that have been treated for release on one side, and examples include those in which a release agent is applied to a substrate for the release material. Examples of substrates for release materials include plastic films, papers, etc. Examples of plastic films include polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin; and olefin resin films such as polypropylene resin and polyethylene resin. Examples of papers include fine paper, glassine paper, and kraft paper.

[0204] Examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins; long-chain alkyl resins, alkyd resins, and fluorine-containing resins. One type of release agent may be used alone, or two or more types may be used in combination.

[0205] The thickness of the release material is preferably 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 35 to 80 μm.

[0206] [Uses and methods of use of adhesive sheets] The pressure-sensitive adhesive sheet of one embodiment of the present invention can easily peel off a temporarily fixed adherend by heating, and is therefore applicable to a variety of uses. Specifically, the pressure-sensitive adhesive sheet 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 expandable tape used to expand the distance between adherends such as semiconductor chips that have been individualized by dicing, a transfer tape used to turn over an adherend such as a semiconductor chip, and a temporary fixing sheet for temporarily fixing an object to be inspected for inspection.

[0207] 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 one embodiment of the pressure-sensitive adhesive sheet of the present invention, when the expansion initiation temperature (t) of the heat-expandable particles is set to less than 125°C, thermal 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 one embodiment of the pressure-sensitive adhesive sheet of the present invention, if 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 when grinding an adherend, for example, can be suppressed, making the sheet suitable for use as a backgrinding sheet in the process of grinding an adherend.

[0208] The heating temperature when the pressure-sensitive adhesive sheet of one embodiment of the present invention is heat-peeled from an adherend is equal to or higher than the expansion start temperature (t) of the heat-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 conservation 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 thermal peeling 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, within the range of the expansion starting temperature (t) or more.

[0209] 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 examples of the heating method that can be used include electric heaters, dielectric heating, magnetic heating, and heating by electromagnetic waves such as near-infrared, mid-infrared, and far-infrared rays. The heating method may be any of contact heating methods such as a heating roller or a heating press, and non-contact heating methods such as an atmospheric heating device or infrared irradiation.

[0210] [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 term "semiconductor device" refers to any device that can function by utilizing semiconductor properties, such as a wafer having an integrated circuit, a thinned wafer having an integrated circuit, a chip having an integrated circuit, a thinned chip having an integrated circuit, an electronic component including such a chip, and electronic equipment including such an electronic component.

[0211] <First embodiment of the method for manufacturing the semiconductor device> A more specific embodiment of the first embodiment of the method for manufacturing a semiconductor device includes a step of attaching an object to be processed and inspected to an adhesive sheet of one embodiment of the present invention, subjecting the 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 starting temperature (t). Examples of the processed and inspected objects include semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, LED elements, sapphire substrates, displays, and panel substrates. The processing performed on the inspection object is not particularly limited, but examples thereof include grinding and singulation. Inspections performed on processed inspection objects are not particularly limited, but examples include defect inspection using an optical microscope or laser (e.g., dust inspection, surface scratch inspection, wiring pattern inspection, etc.), and visual surface inspection.

[0212] In the first embodiment of the method for manufacturing a semiconductor device, the adhesive layer of the adhesive sheet to which the processing and inspection object is attached may be the adhesive layer (X1), or if the adhesive sheet is a double-sided adhesive sheet, it may be the adhesive layer (X2). When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable to attach the processing test object to one pressure-sensitive adhesive layer and attach a support to the other pressure-sensitive adhesive layer. Fixing the processing test object to the support via the pressure-sensitive adhesive sheet suppresses vibration, misalignment, and damage to fragile processing test objects during processing, thereby improving processing accuracy and processing speed. Furthermore, the pressure-sensitive adhesive sheet of one embodiment of the present invention has excellent adhesive properties, so it can more effectively suppress vibration, misalignment, and damage to the processing object caused by air pockets at the adhesive interface between the pressure-sensitive adhesive sheet and the adherend. In this case, the support may be attached to the pressure-sensitive adhesive layer (X1) and the processing test object may be attached to the pressure-sensitive adhesive layer (X2), or the processing test object may be attached to the pressure-sensitive adhesive layer (X1) and the support may be attached to the pressure-sensitive adhesive layer (X2). In the case where the support is attached to the adhesive layer (X1) and the processed 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 thermally peeled off without bending. Furthermore, the composition of the adhesive layer (X2) can be selected appropriately depending on the type of processed test object, etc. For example, if the adhesive layer (X2) is an adhesive layer whose adhesive strength decreases when irradiated with energy rays, it can be peeled off without contaminating the processed test object with residues derived from the heat-expanding particles. On the other hand, in a case where the processed inspection object is attached to the adhesive layer (X1) and the support is attached to the adhesive layer (X2), the processed inspection object is attached to the adhesive layer (X1) which has excellent peelability after heat treatment, so that the processed inspection object can be easily peeled off from the adhesive sheet after processing, thereby reducing damage to the processed inspection object.

[0213] <Second embodiment of semiconductor device manufacturing method> The second embodiment of the method for producing a semiconductor device includes a production method (hereinafter also referred to as "production method A") that uses an adhesive sheet having a laminated structure in which an adhesive layer (X1), a base layer (Y), and an adhesive layer (X2) are arranged in this order as the adhesive sheet of one embodiment of the present invention, and includes the following steps 1A, 2A, 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) 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. 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) of the heat-expanding particles 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

[0214] Manufacturing method A will be described below with reference to the drawings. Note that the following description will mainly focus on an example in which a semiconductor wafer is used as the workpiece, but the same applies to other workpieces. Examples of other workpieces include the same ones listed above as the workpieces to be processed and inspected.

[0215] (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). 3(a) and (b), a semiconductor wafer W is attached to the adhesive layer (X2) of the adhesive sheet 2a, and the surface (S) of the adhesive layer (X1) is x1) on the surface of the support 3 (S s ) is shown in a cross-sectional view illustrating the process of attaching the film. The semiconductor wafer W is attached so that the 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 etching or lift-off.

[0216] The material of the support 3 may be appropriately selected in consideration of the required properties 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 wafer; resin materials such as epoxy resin, ABS resin, acrylic resin, engineering plastic, super engineering plastic, polyimide resin, and polyamide-imide resin; and composite materials such as glass epoxy resin. Of these, SUS, glass, and silicon wafer 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).

[0217] The support 3 is preferably attached to the entire adhesive surface of the pressure-sensitive adhesive layer (X1). Therefore, the surface area of ​​the support 3 on the side attached to the adhesive surface of the pressure-sensitive adhesive layer (X1) is preferably equal to or larger than the surface area of ​​the adhesive surface of the pressure-sensitive adhesive layer (X1). In addition, the surface of the support 3 on the side attached to the adhesive surface of the pressure-sensitive adhesive layer (X1) is preferably flat. The shape of the support 3 is not particularly limited, but is preferably plate-like. The thickness of the support 3 may be appropriately selected in consideration of the required properties, but is preferably 20 μm or more and 50 mm or less, and more preferably 60 μm or more and 20 mm or less.

[0218] In step 1A, the step of attaching the support 3 to the adhesive layer (X1) of the adhesive sheet 2a is performed by bonding the surface (S X1 ) and the surface of the support 3 to which the adhesive sheet 2a is attached (S s ) is maintained in a substantially parallel state, and the surface (S X1 ) on the surface of the support 3 (S s ) (hereinafter also referred to as "surface pasting step A"). The pressure-sensitive adhesive sheet of one embodiment of the present invention has excellent adhesion properties, and therefore, even when the surface-attaching step A is carried out, the occurrence of air pockets at the adhesive interface between the pressure-sensitive adhesive sheet 2a and the support 3 can be suppressed. In the surface pasting step A, for example, an object to be processed is pasted on the adhesive layer (X2) of the adhesive sheet 2a, and then the surface (S X1 ) and the surface of the support 3 to which the adhesive sheet 2a is attached (S s ) is maintained in a substantially parallel state, and the surface (S X1 ) on the surface of the support 3 (S s ) is attached. In this specification, "substantially parallel" means a state where the angle is less than 0 degrees ±10 degrees from the parallel direction, preferably within 0 degrees ±5 degrees, and more preferably within 0 degrees ±1 degree.

[0219] The attachment in step 1A may be carried out while applying pressure, heating, decompression, or the like, as necessary. From the viewpoints of application properties and productivity, the bonding pressure is preferably 0.12 to 1.0 MPa, more preferably 0.15 to 0.7 MPa, and even more preferably 0.17 to 0.5 MPa. When the bonding pressure is 0.12 MPa or more, better application properties tend to be obtained. Furthermore, when the bonding pressure is 1.0 MPa or less, better productivity tends to be obtained. The bonding may be performed by pressing with a flat surface, or by applying linear pressure with a roll. The bonding pressure here refers to the pressure applied to the object to be applied. For example, when both a pressure applied by a pressure mechanism of the device and atmospheric pressure are applied to the object to be applied, the bonding pressure is the sum of the pressure applied by the pressure mechanism of the device and the atmospheric pressure. From the viewpoint of application properties and productivity, the heating temperature is preferably 40 to 88°C, more preferably 45 to 80°C, and even more preferably 50 to 70°C. When the heating temperature is 40°C or higher, better application properties tend to be obtained. On the other hand, when the heating temperature is 88°C or lower, better productivity tends to be obtained. From the viewpoint of adhesiveness and productivity, the above-mentioned pressure-bonding or heating time is preferably 5 to 120 seconds, more preferably 10 to 60 seconds, and even more preferably 20 to 40 seconds. When the pressure-bonding time is 5 seconds or more, better adhesiveness tends to be obtained. Furthermore, when the pressure-bonding time is 120 seconds or less, better productivity tends to be obtained. When the atmospheric pressure is reduced during application, from the viewpoints of application property and productivity, the atmospheric pressure is preferably 50 hPa or less, more preferably 10 hPa or less, and even more preferably 5 hPa or less. There is no particular restriction on the lower limit of the atmospheric pressure, and it may be 0 hPa.

[0220] (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 using a blade dicing method, a laser dicing method, or a stealth dicing (registered trademark) method; grinding processes and dicing processes using a blade tip dicing method or a stealth tip dicing method; and the like. Among these, the dicing process using the stealth dicing method, the grinding process and dicing process using the blade tip dicing method, and the grinding process and dicing process using the stealth tip dicing method are preferred, and the grinding process and dicing process using the blade tip dicing method and the grinding process and dicing process using the stealth tip dicing method are more preferred.

[0221] The stealth dicing method forms a modified region inside a semiconductor wafer by irradiating it with laser light, and then separates the semiconductor wafer using the modified region as the starting point for division. The modified region formed in the semiconductor wafer is a portion embrittled by multiphoton absorption, and when the semiconductor wafer is expanded, stress is applied parallel to the wafer surface and in the direction of the wafer expansion, causing cracks to propagate from the modified region toward the front and back surfaces of the semiconductor wafer, resulting in the semiconductor wafer being separated into individual semiconductor chips. In other words, the modified region is formed along the dividing line during division. The modified region is formed inside the semiconductor wafer by irradiating the semiconductor wafer with laser light focused on the inside of the semiconductor wafer. The incident surface of the laser light may be the front or back surface of the semiconductor wafer. The incident surface of the laser light may also be the surface to which an adhesive sheet is attached. In this case, the laser light is irradiated onto the semiconductor wafer through the adhesive sheet.

[0222] The blade tip dicing method is also called the DBG method (Dicing Before Grinding). The blade tip dicing method involves forming grooves in a semiconductor wafer along the intended dividing lines, with a depth shallower than the wafer's thickness, and then thinning and dicing the semiconductor wafer by back-grinding until the grinding surface reaches at least the groove. The grooves reached by the grinding surface become cuts that penetrate the semiconductor wafer, and the semiconductor wafer is divided by the cuts into individual semiconductor chips. The pre-formed grooves are typically provided on the front 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.

[0223] The stealth dicing method is also called the SDBG method (Stealth Dicing Before Grinding). Like the stealth dicing method, the stealth dicing method is a method of forming a modified region inside a semiconductor wafer by irradiating it with laser light and dividing the semiconductor wafer using the modified region as the dividing starting point. However, the stealth dicing method differs from the stealth dicing method in that the semiconductor wafer is divided into semiconductor chips while being thinned by a grinding process. Specifically, a semiconductor wafer having a modified region is thinned by back-grinding, and the pressure applied to the semiconductor wafer during this process causes cracks to extend from the modified region toward the adhesive surface of the semiconductor wafer, thereby dividing the semiconductor wafer 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 reach the modified region strictly, it may be ground to a position close to the modified region and then fractured using the processing pressure of a grinding wheel or the like.

[0224] 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 that is 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 using a stealth 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.

[0225] FIG. 4 shows a cross-sectional view illustrating a process of forming a plurality of modified regions 5 using a laser beam irradiation device 4 on a semiconductor wafer W attached to an adhesive layer (X2). The laser light is irradiated onto the back surface W2 side of the semiconductor wafer W, and a plurality of modified regions 5 are formed inside the semiconductor wafer W at approximately equal intervals.

[0226] 5(a) and 5(b) show cross-sectional views illustrating the process of thinning the semiconductor wafer W and singulating 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 the semiconductor wafer W to be fractured 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 having the modified region 5 formed thereon has its back surface W2 ground, for example, while the support 3 supporting the semiconductor wafer W is fixed on a fixed table such as a chuck table.

[0227] 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, preferably 2 Less than 300 mm, more preferably 2The plan view refers to a view in the thickness direction. The shape of the semiconductor chips CP after separation in a plan view may be square or an elongated shape such as a rectangle.

[0228] (Process 3A) Preferably, production method A further includes the following step 3A. Step 3A: A step of attaching a thermosetting film to the surface of the object to be processed that has been subjected to the treatment, opposite to the pressure-sensitive adhesive layer (X2). However, in production method A, step 3A is an optional step, and an embodiment may not include step 3A. When step 3A is performed, the expansion initiation temperature (t) of the heat-expanding particles contained in the pressure-sensitive adhesive sheet used in production method A is preferably 50° C. or higher and lower than 125° C. This makes it possible to prevent the thermosetting film from unintentionally curing when the first separation step described below is performed.

[0229] Figure 6 shows a cross-sectional view illustrating the process of attaching a thermosetting film 7 with a support sheet 8 to the side opposite the adhesive layer (X2) of multiple semiconductor chips CP obtained by the above-mentioned processing.

[0230] The thermosetting film 7 is a thermosetting film obtained by forming a film from 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 a curing agent for the thermosetting resin, a thermoplastic resin, an inorganic filler, a curing accelerator, etc., as necessary. As the thermosetting film 7, for example, a thermosetting film that is 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 material capable of supporting the thermosetting film 7, and examples thereof include the resins, metals, paper materials, etc. listed as examples of the non-thermally expandable base layer (Y2) of the pressure-sensitive adhesive sheet of one embodiment of the present invention.

[0231] The thermosetting film 7 may be attached to the semiconductor chips CP by lamination, for example. The lamination may be performed with or without heating. When the lamination is performed with heating, the heating temperature is preferably "a temperature lower than the expansion start temperature (t)", more preferably "expansion start temperature (t) - 5°C" or less, even more preferably "expansion start temperature (t) - 10°C" or less, and still more preferably "expansion start temperature (t) - 15°C" or less, from the viewpoint of suppressing the expansion of the thermally expandable particles and suppressing thermal changes in the adherend.

[0232] (First separation step) 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) of the heat-expanding particles to separate the pressure-sensitive adhesive layer (X1) from the support. FIG. 7 shows a cross-sectional view illustrating the step of heating the adhesive sheet 2a to separate the adhesive layer (X1) from the support 3.

[0233] The heating temperature in the first separation step 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 viewpoints of energy conservation and suppressing thermal changes in the adherend during thermal peeling, the heating temperature in the first separation step 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, within a range of less than 125°C. From the viewpoint of suppressing thermal changes in the adherend, the heating temperature in the first separation step is within the range of the expansion starting 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. In particular, if the heating temperature in the first separation step is less than 125°C, unintended curing of the thermosetting film can be suppressed when the above-mentioned step 3A is carried out.

[0234] (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 the step of separating the adhesive layer (X2) from the plurality of 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, if 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 its adhesive strength before separation.

[0235] Through the above steps, a plurality of semiconductor chips CP attached to the thermosetting film 7 are obtained. Next, it is preferable to divide the thermosetting film 7 to which the plurality of semiconductor chips CP are attached into pieces of 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, methods such as laser dicing using a laser beam, expanding, and melt-cutting can be applied. FIG. 9 shows semiconductor chips CP with thermosetting films 7 that have been divided into the same shapes as the semiconductor chips CP.

[0236] The semiconductor chips CP with the thermosetting film 7 are 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 turning the semiconductor chips CP upside down, etc. as needed, and then attached (die-attached) to a substrate from the side of the thermosetting film 7. The thermosetting film is then thermally cured to bond the semiconductor chips to the substrate.

[0237] The second embodiment of the method for producing a semiconductor device may be a production method (hereinafter also referred to as "production method B") that uses a pressure-sensitive adhesive sheet having a laminated structure in which a pressure-sensitive adhesive layer (X1), a base layer (Y), and a pressure-sensitive adhesive layer (X2) are arranged in this order as the pressure-sensitive adhesive sheet of one embodiment of the present invention, and includes the following steps 1B to 2B, a first separation step, and a second separation step 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: A step of subjecting the object to one or more treatments selected from a grinding treatment and a singulation 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) of the heat-expanding particles 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

[0238] Preferably, production method B further includes the following step 3B. Step 3B: A step of attaching a thermosetting film to the surface of the object that has been subjected to the treatment, opposite to the pressure-sensitive adhesive layer (X1). However, in Production Method B, Step 3B is an optional step, and an embodiment may not include Step 3B. When step 3B is performed, the expansion initiation temperature (t) of the heat-expanding particles contained in the pressure-sensitive adhesive sheet used in production method B is preferably 50° C. or higher and lower than 125° C. This makes it possible to prevent the thermosetting film from unintentionally curing when the first separation step described below is performed.

[0239] In the step 1B, the step of attaching the object to the adhesive layer (X1) of the adhesive sheet 2a is performed by applying pressure to the surface (S X1 ) and the surface (S w ) is maintained in a substantially parallel state, and the surface (S X1 ) to the surface of the workpiece (S w ) (hereinafter also referred to as "surface pasting step B"). In the surface-attaching step B, for example, a support 3 is attached to the adhesive layer (X2) of the adhesive sheet 2a, and then the surface (S X1 ) and the surface (S w ) is maintained in a substantially parallel state, and the surface (S X1 ) to the surface of the workpiece (S w ) is attached. The pressure-sensitive adhesive sheet of one embodiment of the present invention has excellent adhesion properties, and therefore, even when the surface-attaching step B is carried out, it is possible to prevent air pockets from forming at the adhesive interface between the pressure-sensitive adhesive sheet 2a and the object to be processed.

[0240] The application in step 1B may be carried out while applying pressure, heat, vacuum, etc., as necessary, and the suitable conditions therefor are the same as the suitable conditions explained in step 1A above.

[0241] Steps 1B to 3B are explained by substituting 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).

[0242] The first separation step is a step of heating the pressure-sensitive adhesive sheet to the expansion starting temperature (t) or higher 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 explained in production method A. In particular, when step 3B is performed, the first separation step is preferably 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 first separation step yields a plurality of semiconductor chips attached to the thermosetting film. Thereafter, the thermosetting film is divided in the same manner as in the above-described manufacturing method A, to obtain semiconductor chips with the thermosetting film.

[0243] 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 pressure-sensitive adhesive layer (X2). For example, when the pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer whose adhesive strength decreases when irradiated with energy rays, the pressure-sensitive adhesive layer (X2) may be irradiated with energy rays to decrease its adhesive strength, and then the pressure-sensitive adhesive layer (X2) may be separated from the support. It should be noted that production method B may not include the second separation step.

[0244] <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.

[0245] Another 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 other sheet using a pressure-sensitive adhesive sheet of one embodiment of the present invention. For example, multiple semiconductor chips spaced apart on an 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 embodiment of the present invention, the adhesive layer (X1) of the adhesive sheet of one embodiment of the present invention is attached to the exposed surfaces of multiple semiconductor chips attached to the expanding tape, and then the expanding tape is peeled off from the multiple semiconductor chips, thereby allowing the multiple semiconductor chips to be separated all at once from the expanding tape. Through the above steps, a plurality of semiconductor chips attached to the pressure-sensitive adhesive sheet of one embodiment of the present invention are obtained, and the plurality of semiconductor chips can be easily separated by subsequently heating the pressure-sensitive adhesive layer (X1) to a temperature equal to or higher than the expansion initiation temperature (t) of the thermally expandable particles. 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. [Example]

[0246] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The physical properties in each example were measured by the following methods.

[0247] [Mass average molecular weight (Mw)] Measurement was carried out using a gel permeation chromatograph (manufactured by Tosoh Corporation, product name "HLC-8020") under the conditions below, and the values ​​measured were converted into standard polystyrene equivalents. (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

[0248] [Thickness of each layer] Measurements were taken at 23°C using a constant pressure thickness measuring instrument manufactured by Teclock Corporation (model number: "PG-02J", standard specifications: compliant with JIS K6783, Z1702, Z1709).

[0249] [Average particle diameter of thermal expansion particles (D 50 ), 90% particle size (D 90 )] The particle size distribution of the thermoexpandable particles before expansion at 23° C. was measured using a laser diffraction particle size distribution measuring device (for example, manufactured by Malvern, product name "Mastersizer 3000"). 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 thermally expandable particles (D 50 ) and "90% particle diameter of thermal expansion particles (D 90 )"

[0250] [Method for measuring arithmetic mean waviness (Wa)] The arithmetic mean waviness (Wa) was measured in accordance with JIS B0601:2013 using a scanning white light interference microscope (Hitachi High-Tech Corporation, product name "VS-1550") under the conditions of measurement mode PSI and 10x objective lens. X1 ) was observed, and a total of 100 images (with an overlap rate of 10% with adjacent images) were obtained in a grid of 10 vertical x 10 horizontal. Next, each image was combined with the adjacent image to form a composite, and the height data of the resulting composite image was processed with a Gaussian filter with a cutoff value of 100 μm and an amplitude transmission rate of 50% to obtain the arithmetic mean waviness (Wa).

[0251] In the following examples, the details of the materials used to form each layer are as follows:

[0252] <Adhesive resin> Acrylic copolymer (A1): A solution containing an acrylic copolymer with a molecular weight of 600,000, which has 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, solids concentration: 40 mass%

[0253] <Crosslinking agent> Isocyanate-based crosslinking agent (i): Tosoh Corporation, product name "Coronate L", solution containing trimethylolpropane-modified tolylene diisocyanate, solid content: 75% by mass

[0254] <Photopolymerization initiator> Photopolymerization initiator (i): 1-hydroxycyclohexyl phenyl ketone

[0255] <Additives> Phthalocyanine pigments

[0256] <Thermal expansion particles> Thermally expandable particles: Nouryon, 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

[0257] <Removal material> Heavy-duty release film: Lintec Corporation, product name "SP-PET382150", polyethylene terephthalate (PET) film with a release layer formed from a silicone-based release agent on one side, thickness: 38 μm

[0258] Examples 1 to 10 and Comparative Examples 1 to 10: Formation of adhesive sheets (1) Formation of adhesive layer (X1) 100 parts by mass of the solid content of the acrylic copolymer (A1) was mixed with 1.38 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 adhesive composition (x-1) was then applied to 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 an adhesive layer (X1) with a thickness of 5 μm.

[0259] (2) Preparation of Solventless Resin Composition (y-1a) An isocyanate-terminated urethane prepolymer obtained by reacting an ester-type diol with isophorone diisocyanate (IPDI) was reacted with 2-hydroxyethyl acrylate to obtain a linear urethane prepolymer having ethylenically unsaturated groups at both ends, which is an oligomer with a mass average molecular weight (Mw) of 5,000. Then, 40 parts by mass (solid content ratio) of the urethane prepolymer synthesized above was blended with 40 parts by mass (solid content ratio) of isobornyl acrylate (IBXA) and 20 parts by mass (solid content ratio) of phenylhydroxypropyl acrylate (HPPA) as energy ray polymerizable monomers, and 2.0 parts by mass (solid content ratio) of photopolymerization initiator (i) and 0.2 parts by mass (solid content ratio) of a phthalocyanine pigment and 20 parts by mass of cyclohexyl acrylate (CHA) as additives were further blended with respect to the total amount (100 parts by mass) of the urethane prepolymer and energy ray polymerizable monomer to prepare an energy ray curable composition. Then, thermally expandable particles were blended into the energy ray-curable composition so that the content of the thermally expandable particles relative to the total mass (100 mass%) of the resulting thermally expandable base layer (Y1) was the content shown in Table 1. Thereafter, one of the dispersion treatments shown in Table 1 was carried out to prepare a solventless resin composition (y-1a) that did not contain a solvent. Details of the dispersion treatment shown in Table 1 are as follows. (Distributed processing) Stirring treatment: Stirring was carried out at 200 rpm for 5 minutes using a cylindrical stirring rod (manufactured by Engineering Test Service Co., Ltd., product name "PE05", 30 mmΦ×300 mm). Filtration treatment: Filtration was carried out using a Tetron mesh (#200). High-speed stirring treatment: Using a stirring device (manufactured by Primix Corporation, product name "Labo-Lution") equipped with a stirring blade (manufactured by Primix Corporation, product name "Homomixer MARK II"), stirring was carried out at 10,000 rpm for 20 minutes while cooling with 10°C water.

[0260] (3) Formation of a base laminate by laminating a thermally expandable base layer (Y1) and a non-thermally expandable base layer (Y2) As the non-thermally expandable base layer (Y2), a PET film (manufactured by Toyobo Co., Ltd., product name "Cosmoshine A4300", thickness: 50 μm) was prepared. Next, a solventless resin composition (y-1a) was applied to one side of the PET film so that the thickness of the thermally expandable base layer (Y1) formed would be the thickness shown in Table 1 to form a coating film. Then, an ultraviolet irradiation device (manufactured by Eye Graphics Co., Ltd., product name "ECS-401GX") and a high-pressure mercury lamp (manufactured by Eye Graphics Co., Ltd., product name "H04-L41") were used to irradiate the sample with an illuminance of 160 mW / cm. 2 , light intensity 500mJ / cm 2 The coating film was cured by irradiating it with ultraviolet light under the conditions shown in Table 1, thereby obtaining a substrate laminate in which a thermally expandable substrate layer (Y1) having a thickness shown in Table 1 was formed on a PET film as a non-thermally expandable substrate layer (Y2). The illuminance and light amount during ultraviolet irradiation were measured using an illuminance / actinometer (manufactured by EIT, product name "UV Power Puck II").

[0261] (4) Formation of adhesive sheet The adhesive surface of the pressure-sensitive adhesive layer (X1) formed in the above (1) was bonded to the surface of the thermally expandable base layer (Y1) of the base laminate formed in the above (2), thereby producing a pressure-sensitive adhesive sheet having the following configuration. <Heavy release film> / <Adhesive layer (X1), thickness: 5 μm> / <Thermal-expandable base layer (Y1), thickness: thickness listed in Table 1> / <Non-thermal-expandable base layer (Y2), thickness: 50 μm>

[0262] FIG. 10 shows the surface (S X1 10 and 11 show three-dimensional surface shape images of a sample. Both Fig. 10 and Fig. 11 show an area of ​​approximately 16 mm in the x-axis direction and approximately 12 mm in the y-axis direction, and the scale in the z-axis direction is the same in Fig. 10 and Fig. 11. 10 and 11, the surface (S X1 ) is the surface (S X1 ) shows that there are swells larger than those in the figure.

[0263] [Storage modulus E'(23) of non-thermally expandable base layer (Y2) at 23°C] The non-thermally expandable base layer (Y2) cut into 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 serving as the non-thermally expandable base layer (Y2) was 2.27 x 10 9 It was Pa.

[0264] [Evaluation of adhesiveness] The pressure-sensitive adhesive sheet obtained in each example was cut into a piece with a diameter of 300 mm, the heavy release film was removed, and the surface of the exposed pressure-sensitive adhesive layer (X1) (S x1 The wafer was placed on a flat surface with the adhesive layer (X1) facing upward. A silicon mirror wafer with a diameter of 300 mm was placed on top of the wafer with the mirror surface facing the adhesive layer (X2) side (S x1 ) and place the surface (S x1The test sample was prepared by placing the laminated sheet on the mirror surface while maintaining the mirror surface approximately parallel to the laminated sheet, and pressing the laminated sheet for 30 seconds using a vacuum laminator (manufactured by Nikko Materials Co., Ltd., product name "V-130") at a pressure of 0.2 MPa set by the pressure mechanism of the device, while reducing the atmospheric pressure to 2 hPa or less. Note that with the vacuum laminator, the total pressure of 0.3 MPa was the pressure of 0.2 MPa applied by the pressure mechanism of the device and atmospheric pressure of 0.1 MPa. The test samples obtained in each example were visually observed from the non-thermally expandable base layer (Y2) side, and samples in which no air pockets were found at the adhesive interface between the pressure-sensitive adhesive layer (X1) and the silicon mirror wafer were rated "A," while samples in which air pockets were found were rated "F." Note that, because transparent materials are used for the heat-expandable base layer (Y1) and the non-thermally expandable base layer (Y2), it is possible to visually check the condition of the adhesive interface between the silicon mirror wafer and the pressure-sensitive adhesive layer (X1) from the non-thermally expandable base layer (Y2) side. The evaluation results for each example are shown in Table 1. Examples of external appearance photographs of test samples that received an "A" rating are shown in Figures 12(a) and (b), and examples of external appearance photographs of test samples that received an "F" rating are shown in Figures 13(a) and (b). 12 and 13, (b) is an enlarged photograph of the area enclosed by the black dotted line in (a). In Fig. 12, no air pockets are observed, but in Fig. 13, it can be seen that there are multiple island-shaped air pockets (relatively lighter areas).

[0265] [Table 1]

[0266] From Table 1, the pressure-sensitive adhesive sheets of Examples 1 to 10 have a surface (S X1 ) was 0.090 μm or less, which indicates that the adhesiveness was excellent. In contrast, the pressure-sensitive adhesive sheets of Comparative Examples 1 to 10 had a surface (S X1 ) exceeded 0.090 μm, indicating poor adhesion. [Explanation of symbols]

[0267] 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 Backside of semiconductor wafer CP semiconductor chip (X1) Adhesive layer (X1) (X2) Adhesive layer (X2) (Y) Base material layer (Y) (S x1 ) Surface of adhesive layer (X1) (S x1 ) (S s ) The surface of the support to which the adhesive sheet is attached (S s )

Claims

1. It has a laminated structure including a pressure-sensitive adhesive layer (X1) and a base layer (Y), the substrate layer (Y) is a substrate laminate in which a thermally expandable substrate layer (Y1) containing thermally expandable particles and a non-thermally expandable substrate layer (Y2) are laminated together, a laminated structure in which the pressure-sensitive adhesive layer (X1), the heat-expandable base layer (Y1), and the non-heat-expandable base layer (Y2) are arranged in this order, the pressure-sensitive adhesive layer (X1) does not contain the heat-expandable particles, or if it contains the heat-expandable particles, the content of the heat-expandable particles is less than 3 mass% relative to the total mass (100 mass%) of the pressure-sensitive adhesive layer (X1); The surface (S) of the pressure-sensitive adhesive layer (X1) opposite to the surface facing the base material layer (Y) Ｘ１ ) the arithmetic mean waviness (Wa) is 0.090 μm or less.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the thickness of the thermally expandable base layer (Y1) before thermal expansion is 30 to 300 μm.

3. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the content of the thermally expandable particles in the thermally expandable base layer (Y1) is 1 to 25 mass% relative to the total mass (100 mass%) of the thermally expandable base layer (Y1).

4. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the expansion starting temperature (t) of the heat-expanding particles is 50°C or higher and lower than 125°C.

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the average particle size of the heat-expanding particles before expansion at 23°C is 3 to 50 µm.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, further comprising a pressure-sensitive adhesive layer (X2), and having a laminate structure in which the pressure-sensitive adhesive layer (X1), the base material layer (Y), and the pressure-sensitive adhesive layer (X2) are arranged in this order.

7. The pressure-sensitive adhesive sheet according to claim 6 , wherein the pressure-sensitive adhesive layer (X2) is an energy ray-curable pressure-sensitive adhesive layer that is cured by irradiation with energy rays and has a reduced adhesive strength.

8. A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to claim 6 or 7, comprising the following steps 1A, 2A, 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. 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) of the heat-expandable particles 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

9. The expansion starting temperature (t) of the thermally expandable particles is 50°C or higher and lower than 125°C, After the step 2A, a step 3A is included in which a thermosetting film is attached to a surface of the object that has been subjected to the treatment, the surface being opposite to the pressure-sensitive adhesive layer (X2), the first separation step is a step of heating the PSA sheet to a temperature equal to or higher than the expansion initiation temperature (t) and lower than 125°C to separate the PSA layer (X1) from the support; The method for manufacturing a semiconductor device according to claim 8 .

10. In the step 1A, the step of attaching the support to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet is carried out by applying a pressure-sensitive adhesive layer (X1) to the surface (S Ｘ１ ) and the surface of the support to which the adhesive sheet is attached (S ｓ ) is maintained in a substantially parallel state, the surface (S Ｘ１ ) on the surface (S ｓ 10. The method for manufacturing a semiconductor device according to claim 8, wherein the step of attaching a substrate to the semiconductor device is a step of attaching a substrate to the semiconductor device.

11. A method for manufacturing a semiconductor device using the pressure-sensitive adhesive sheet according to claim 6 or 7, comprising the following steps 1B, 2B, 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. 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) of the heat-expanding particles, to separate the pressure-sensitive adhesive layer (X1) from the object to be processed. Second separation step: step of separating the pressure-sensitive adhesive layer (X2) from the support

12. The expansion starting temperature (t) of the thermally expandable particles is 50°C or higher and lower than 125°C, After the step 2B, a step 3B of attaching a thermosetting film to a surface of the object that has been subjected to the treatment, opposite to the pressure-sensitive adhesive layer (X1), the first separation step is a step of heating the PSA sheet to a temperature equal to or higher than the expansion initiation temperature (t) and lower than 125°C to separate the PSA layer (X1) from the object to be processed; The method for manufacturing a semiconductor device according to claim 11 .

13. In the step 1B, the step of attaching the object to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet is carried out by applying pressure-sensitive adhesive layer (X1) to the surface (S Ｘ１ ) and the surface (S ｗ ) is maintained in a substantially parallel state, the surface (S Ｘ１ ) to the surface (S ｗ 13. The method for manufacturing a semiconductor device according to claim 11, wherein the step of attaching a protective film is performed by attaching a protective film to the protective film.

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