Adhesive sheets, articles, and methods for manufacturing articles.

Abstract

The present invention provides an adhesive sheet that can be expanded by heating, which before expansion has both temporary fixation properties at room temperature and ease of insertion when inserting one component into a gap in another component, and which after expansion maintains excellent adhesive strength even in a high-temperature environment and can firmly bond components together, as well as an article using the adhesive sheet and a method for manufacturing the same. [Solution] An adhesive sheet (10) having opposing first and second main surfaces (a1, a2), wherein the first main surface of the adhesive sheet is composed of a heat-expandable thermosetting adhesive layer (1) and a plurality of adhesive portions (2) arranged in a pattern on the first main surface of the heat-expandable thermosetting adhesive layer, and the second main surface of the adhesive sheet is composed of the heat-expandable thermosetting adhesive layer that constitutes the first main surface of the adhesive sheet or another heat-expandable thermosetting adhesive layer.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet having an adhesive layer that can expand by heating.

Background Art

[0002] A fixing method in which one member is inserted and fixed into a gap formed in another member or a gap formed between two or more other members is used in manufacturing scenes of various products such as automobiles and electric devices. For example, in a motor mounted in a hybrid vehicle or the like, a magnet is inserted and fixed in a gap provided at a predetermined position of a core portion (rotor core). Note that a member inserted into the gap is referred to as an inserted member, and a member in which the gap is formed or a set of two or more members constituting the gap is referred to as an inserted member.

[0003] In the above fixing method, in order to prevent the member inserted into the gap from falling, usually, after the inserted member is inserted into the gap of the inserted member, the gap is filled with a liquid adhesive to join the inserted member and the inserted member. However, in this method, positional displacement of the inserted member in the gap or dropping from the gap may occur before the adhesive is cured. In addition, since it is necessary to adjust the viscosity and filling amount of the liquid adhesive, etc., the process is complicated and the process time may be long. Furthermore, in the above method, the adhesive adheres outside the gap of the member and causes contamination.

[0004] Therefore, in recent years, instead of a liquid adhesive, a method of joining an inserted member and an inserted member using an adhesive sheet has been studied. Among them, a method of disposing an expandable adhesive sheet together with an inserted member in a gap of an inserted member, expanding the adhesive sheet to fill the gap, and joining the inserted member and the inserted member has been studied (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The adhesive sheet used to join an insertable member to an insertable member needs to be inserted into the gap between the members before it can be joined by heating and expansion. Therefore, to avoid hindering the insertability of the members, the adhesive sheet at room temperature before insertion must have low or no initial adhesion. On the other hand, after insertion, the insertable member and the insertable member cannot be joined immediately. Therefore, the adhesive sheet needs to have high initial adhesion at room temperature to prevent it from shifting from its predetermined bonding position on the adherend before it expands and bonds / fixes itself. Furthermore, when joining high-temperature components such as automotive motors, high heat resistance is required. Therefore, the adhesive sheet must exhibit excellent adhesive strength not only in room temperature environments but also in high-temperature environments, enabling a strong bond between the insertable member and the insertable member. However, conventional adhesive sheets used to join insertable members to insertable members have found it difficult to adequately balance room temperature temporary fixing, ease of insertion, and heat resistance.

[0007] The present invention has been made in view of the above circumstances, and provides an adhesive sheet that can be expanded by heating, which, before expansion, provides both temporary fixing at room temperature and ease of insertion when inserting one member into a void in another member, and after expansion, maintains excellent adhesive strength even in a high-temperature environment and can firmly bond members together, as well as an article using the adhesive sheet and a method for manufacturing the same. [Means for solving the problem]

[0008] Firstly, the present invention provides an adhesive sheet having a first main surface and a second main surface facing each other, wherein the first main surface of the adhesive sheet is composed of a heat-expandable thermosetting adhesive layer and a plurality of adhesive portions arranged in a pattern on the first main surface of the heat-expandable thermosetting adhesive layer, and the second main surface of the adhesive sheet is composed of the heat-expandable thermosetting adhesive layer constituting the first main surface of the adhesive sheet or another heat-expandable thermosetting adhesive layer.

[0009] Secondly, the present invention provides an article having a first adherend and a second adherend, wherein a void is formed in the second adherend, the first adherend is placed in the void of the second adherend, and the first adherend and the second adherend are bonded together in the void via the expanded adhesive sheet described above. To provide.

[0010] Furthermore, the present invention provides an article having a first adherend, a third adherend, and a fourth adherend, with a gap between the third adherend and the fourth adherend, the first adherend being positioned within the gap, and within the gap, the first adherend and the third adherend, and the first adherend and the fourth adherend, are each bonded together via the expanded adhesive sheet described above.

[0011] Thirdly, the present invention provides a method for manufacturing an article, comprising the steps of: [1A] bonding the first main surface of the adhesive sheet described above to the surface of a first adherend or the surface of a void formed in a second adherend; [2A] inserting the first adherend into the void; and [3A] heating the adhesive sheet to expand and harden the heat-expandable thermosetting adhesive layer, thereby bonding the first adherend and the second adherend via the expanded material of the adhesive sheet.

[0012] The present invention also provides a method for manufacturing an article, comprising the steps of: [1B] bonding a first major surface of the above-described adhesive sheet to a surface of a first adherend or a surface of a void formed by a third adherend and a fourth adherend; [2B] inserting the first adherend into the above-described void; and [3B] heating the adhesive sheet to expand and cure the thermally expandable thermosetting adhesive layer, thereby bonding the first adherend to the third adherend and the fourth adherend through the expanded material of the adhesive sheet.

Advantages of the Invention

[0013] According to the adhesive sheet of the present invention, it has heat-expandability, can achieve both temporary fixability at normal temperature before expansion and ease of insertion when inserting a member into a void, and can maintain excellent adhesive strength even in a high-temperature environment after expansion to firmly join members together.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic cross-sectional view showing an example of the adhesive sheet of the present invention. [Figure 2] It is a schematic cross-sectional view showing an example of the adhesive sheet of the present invention after expansion. [Figure 3] It is a schematic cross-sectional view showing an example of the adhesive sheet of the present invention. [Figure 4] It is a schematic cross-sectional view showing an example of the adhesive sheet of the present invention after expansion. [Figure 5] It is a schematic cross-sectional view showing an example of the adhesive sheet of the present invention after expansion. [Figure 6] It is a schematic cross-sectional view showing an example of the adhesive sheet of the present invention. [Figure 7] It is a schematic cross-sectional view showing an example of the method for manufacturing an article of the present invention. [Figure 8] It is a schematic cross-sectional view showing an example of the method for manufacturing an article of the present invention. [Figure 9] It is a schematic diagram showing a method for measuring the shear adhesive strength of the adhesive sheet after heating (after expansion).

Embodiments for Carrying Out the Invention

[0015] I. Adhesive Sheet The adhesive sheet of the present invention is an adhesive sheet having opposed first and second major surfaces, wherein the first major surface of the adhesive sheet is composed of a thermally expandable thermosetting adhesive layer and a plurality of adhesive portions provided in a pattern on the first major surface of the thermally expandable thermosetting adhesive layer, and the second major surface of the adhesive sheet is composed of the thermally expandable thermosetting adhesive layer constituting the first major surface of the adhesive sheet or another thermally expandable thermosetting adhesive layer.

[0016] For example, in the expandable adhesive sheets disclosed in Patent Documents 1 and 2, since the thermosetting expandable adhesive layer has low or no initial adhesiveness, it is difficult to temporarily fix it to an adherend easily at normal temperature. Also, there is a method of thermally laminating and temporarily fixing it to an adherend, but it may be difficult to sufficiently temporarily fix it by thermal lamination depending on the material of the adherend, or equipment for thermal lamination may be required and the process may become complicated. On the other hand, since the thermoplastic pressure-sensitive adhesive layer is inferior in heat resistance, the pressure-sensitive adhesive layer thermally deteriorates under a high-temperature environment and the adhesive force decreases or disappears, making it difficult to firmly join an insertion member and an insertion-receiving member. Further, since the surface on the opposite side of the bonding surface of the pressure-sensitive adhesive layer with a member also has initial adhesiveness, the insertion member may get caught when inserting into a gap, or misalignment may occur due to bonding at a position other than a predetermined position. Thus, in the conventional expandable adhesive sheets, it has been difficult to achieve both temporary fixability and insertability at normal temperature and heat resistance.

[0017] In contrast, the adhesive sheet of the present invention can achieve both good temporary fixation and insertability at room temperature, and furthermore, it has excellent heat resistance after expansion and can maintain excellent adhesive strength even in high-temperature environments. More specifically, the adhesive sheet of the present invention has a first main surface of the sheet surface which has a plurality of adhesive parts arranged in a pattern, so it can be temporarily fixed to the adherend at room temperature by utilizing the high initial adhesion of the adhesive parts, while the second main surface is composed of a heat-expandable thermosetting adhesive layer, so by utilizing the low initial adhesion of the heat-expandable thermosetting adhesive layer that constitutes the second main surface, it is possible to prevent other adherends from adhering to the second main surface of the adhesive sheet, and the insertion member can be easily inserted into the gap. In addition, the heat-expandable thermosetting adhesive layer expands when heated to fill the gap between the insertion member and the member to be inserted, and hardens when heated to exhibit high adhesive strength. At this time, on the first main surface of the adhesive sheet, the expansion of the heat-expandable thermosetting adhesive layer fills the gaps between the adhesive parts or embeds the adhesive parts, so that the expanded heat-expandable thermosetting adhesive layer can come into contact with one of the members and bond firmly. On the second main surface of the adhesive sheet, the expanded heat-expandable thermosetting adhesive layer can come into contact with the other member and bond firmly. In this way, the expanded adhesive sheet of the present invention adheres to the members on both sides of the sheet, exhibiting high adhesive strength even in high-temperature environments, and firmly fixing the members together.

[0018] The first main surface of the adhesive sheet of the present invention is composed of a heat-expandable thermosetting adhesive layer and a plurality of adhesive portions arranged in a pattern on the surface of the heat-expandable thermosetting adhesive layer. The first main surface of the adhesive sheet may be an uneven surface with convex adhesive portions provided on the surface of the heat-expandable thermosetting adhesive layer, or it may be a flat surface in which the surface of the heat-expandable thermosetting adhesive layer and the surface of the adhesive portions are on the same plane.

[0019] One preferred embodiment of the adhesive sheet of the present invention is such that the adhesive portion has a first surface and a second surface opposite to it, and before expansion, in the thickness direction of the adhesive sheet, the first surface of the adhesive portion is located outside the first main surface of the thermally expandable thermosetting adhesive layer on which the adhesive portion is provided, and the second surface of the adhesive portion is in contact with the first main surface of the thermally expandable thermosetting adhesive layer on which the adhesive portion is provided, or is located between the first main surface and the second main surface opposite to it of the thermally expandable thermosetting adhesive layer. In this embodiment of the adhesive sheet, after expansion, in the thickness direction of the adhesive sheet, the first surface of the adhesive portion is located at the same position as the first main surface of the expanded thermally expandable thermosetting adhesive layer on which the adhesive portion is provided, or between the first main surface and the second main surface opposite to it, and the second surface of the adhesive portion is located between the first main surface and the second main surface opposite to it of the expanded thermally expandable thermosetting adhesive layer on which the adhesive portion is provided. Hereinafter, the above-described embodiment may be referred to as the first embodiment of the adhesive sheet.

[0020] Figures 1 and 2 are schematic cross-sectional views showing an example of a first embodiment of the adhesive sheet of the present invention, with Figure 1 showing the sheet before expansion and Figure 2 showing the sheet after expansion. Of the surface of the adhesive sheet, the Z-side surface in the thickness direction Z-Z' is the first main surface of the adhesive sheet, and the Z'-side surface is the second surface. In the adhesive sheet 10 before expansion, as shown in Figures 1(a) and (b), in the thickness direction Z-Z' of the sheet, the first surface b1 of the adhesive portion 2 is located outside the first main surface a1 of the thermally expandable thermosetting adhesive layer 1 on which the adhesive portion 2 is provided (on the opposite side from the thermally expandable thermosetting adhesive layer 1 to the first main surface a1 of the thermally expandable thermosetting adhesive layer 1). Furthermore, as shown in Figure 1(a), the second surface b2 of the adhesive portion 2 is in contact with the first main surface a1 of the thermally expandable thermosetting adhesive layer 1 on which the adhesive portion 2 is provided, or as shown in Figure 1(b), it is located between the first main surface a1 and the second main surface a2 of the thermally expandable thermosetting adhesive layer 1 on which the adhesive portion 2 is provided. On the other hand, as shown in Figure 2, in the expanded adhesive sheet 10', the space between the adhesive portions 2, that is, the area on the first main surface of the adhesive sheet where the adhesive portion 2 is not provided (non-adhesive area), is filled by the expanded thermally expandable thermosetting adhesive layer 1'. As a result, in the thickness direction Z-Z' of the sheet, the first surface b1 of the adhesive portion 2 is located at the same position as the first main surface a1 of the expanded thermally expandable thermosetting adhesive layer 1' on which the adhesive portion 2 is provided, as shown in Figure 2(a), or between the first main surface a1 and the second main surface a2 on the opposite side, as shown in Figure 2(b). Furthermore, at this time, the second surface b2 of the adhesive portion 2 is located between the first main surface a1 and the second main surface a2 on the opposite side of the expanded thermally expandable thermosetting adhesive layer 1' on which the adhesive portion 2 is provided.

[0021] As shown in Figures 1 and 2, in the first embodiment of the adhesive sheet of the present invention, the adhesive portion is arranged on the first main surface of the heat-expandable thermosetting adhesive layer, or a part of the adhesive portion is within the heat-expandable thermosetting adhesive layer and the remainder protrudes from the first main surface of the heat-expandable thermosetting adhesive layer. That is, the first surface of the adhesive sheet is an uneven surface in which the adhesive portion is convex and the surface area of ​​the heat-expandable thermosetting adhesive layer where the adhesive portion is not provided (non-adhesive area) is concave. As a result, before expansion, the adhesive sheet can exhibit temporary fixing properties by the adhesive portion contacting either the insertion member or the member to be inserted on the first main surface. Furthermore, the second main surface of the adhesive sheet is a surface composed of the heat-expandable thermosetting adhesive layer and does not have an adhesive portion, thus enabling insertion of the insertion member. On the other hand, after expansion, the expansion of the heat-expandable thermosetting adhesive layer fills the spaces between the adhesive portions on the first surface of the sheet, and the adhesive portion becomes embedded in the heat-expandable thermosetting adhesive layer. Furthermore, the heat-expandable thermosetting adhesive layer expands and hardens upon heating, exhibiting high adhesive strength. As a result, after expansion, the heat-expandable thermosetting adhesive layer of the adhesive sheet can come into contact with the inserting member and the member to be inserted on the first and second main surfaces, enabling strong adhesion. In particular, the first embodiment of the adhesive sheet of the present invention is preferable because, when the adhesive sheet of the present invention is temporarily fixed to the adherend (the inserting member) at room temperature before expansion, air bubbles trapped at the interface with the adherend can be quickly released, preventing air bubbles from remaining at the interface and suppressing adhesion defects of the adhesive sheet.

[0022] Furthermore, in one preferred embodiment of the adhesive sheet of the present invention, the adhesive portion has a first surface and a second surface opposite to it, and before expansion, in the thickness direction of the adhesive sheet, the first surface of the adhesive portion is in the same position as the first main surface of the heat-expandable thermosetting adhesive layer on which the adhesive portion is provided, and the second surface of the adhesive portion is located between the first main surface and the second main surface opposite to it of the heat-expandable thermosetting adhesive layer on which the adhesive portion is provided. In this embodiment of the adhesive sheet, after expansion, in the thickness direction of the adhesive sheet, the first surface of the adhesive portion is in the same position as the first main surface of the heat-expandable thermosetting adhesive layer after expansion on which the adhesive portion is provided, or between the first main surface and the second main surface opposite to it, and the second surface of the adhesive portion is located between the first main surface and the second main surface opposite to it of the heat-expandable thermosetting adhesive layer after expansion on which the adhesive portion is provided. Hereinafter, the above embodiment may be referred to as the second embodiment of the adhesive sheet.

[0023] Figures 3 and 4 are schematic cross-sectional views showing an example of a second embodiment of the adhesive sheet of the present invention, with Figure 3 showing the sheet before expansion and Figure 4 showing the sheet after expansion. Of the surface of the adhesive sheet, the Z-side surface in the thickness direction Z-Z' is the first main surface of the adhesive sheet, and the Z'-side surface is the second surface. As shown in Figure 3, before expansion, in the thickness direction Z-Z' of the adhesive sheet 10 of the present invention, the first surface b1 of the adhesive portion 2 is in the same position as the first main surface a1 of the heat-expandable thermosetting adhesive layer 1 on which the adhesive portion 2 is provided, and the second surface b2 of the adhesive portion 2 is located between the first main surface a1 and the second main surface a2 on the opposite side of the heat-expandable thermosetting adhesive layer 1 on which the adhesive portion 2 is provided. On the other hand, as shown in Figure 4, in the expanded adhesive sheet 10', in the thickness direction Z-Z' of the sheet, the first surface b1 of the adhesive portion 2 is located at the same position as the first main surface a1 of the expanded thermal expandable thermosetting adhesive layer 1' on which the adhesive portion 2 is provided (Figure 4(a)) or between the first main surface a1 and the second main surface a2 on the opposite side (Figure 4(b)), and the second surface b2 of the adhesive portion 2 is located between the first main surface a1 and the second main surface a2 on the opposite side of the expanded thermal expandable thermosetting adhesive layer 1' on which the adhesive portion 2 is provided.

[0024] As illustrated in Figures 3 and 4, in a second embodiment of the adhesive sheet of the present invention, the adhesive portion is embedded in a heat-expandable thermosetting adhesive layer, and the first main surface of the adhesive sheet has the region of the first main surface of the heat-expandable thermosetting adhesive layer and the region of the first surface of the adhesive portion in the same plane. As a result, when the adhesive sheet is bonded to one member on its first main surface before expansion, the adhesive portion can come into contact with the member and exhibit temporary fixing properties. Furthermore, since the second main surface of the adhesive sheet is a surface composed of a heat-expandable thermosetting adhesive layer and does not have an adhesive portion, it can exhibit insertability for inserting members. On the other hand, in the adhesive sheet after expansion, the heat-expandable thermosetting adhesive layer expands and hardens upon heating, exhibiting high adhesive strength. Therefore, in the adhesive sheet after expansion, the expanded heat-expandable thermosetting adhesive layer can come into contact with the other member on both the first and second main surfaces of the adhesive sheet and be firmly bonded. In particular, the second aspect of the adhesive sheet of the present invention is preferable because, before expansion, the first main surface of the heat-expandable thermosetting adhesive layer is uniformly filled between the adhesive parts, making it less likely for the heat-expandable thermosetting adhesive layer to fail to fill the adhesive parts after heating, and allowing for more uniform adhesion to the adherend, which is an inserted member.

[0025] In the thickness direction of the adhesive sheet, the first surface of the adhesive portion being at the same position as the first main surface of the heat-expandable thermosetting adhesive layer on which the adhesive portion is provided means that the adhesive portion is embedded in the heat-expandable thermosetting adhesive layer and the first surface of the adhesive portion and the first main surface of the heat-expandable thermosetting adhesive layer are in the same plane. When the first surface of the adhesive portion and the first main surface of the heat-expandable thermosetting adhesive layer are at the same position, the first main surface of the adhesive sheet has a region of multiple adhesive portions arranged in a pattern (adhesive region) and a region where the surface of the heat-expandable thermosetting adhesive layer is exposed (non-adhesive region). Furthermore, in the thickness direction, the second surface of the adhesive portion being located between the first main surface and the second main surface on the opposite side of the heat-expandable thermosetting adhesive layer on which the adhesive portion is provided does not include the case where the second surface of the adhesive portion and the first or second main surface of the heat-expandable thermosetting adhesive layer are at the same position (in the same plane) in the thickness direction. Furthermore, in the thickness direction of the expanded adhesive sheet, the first surface of the adhesive portion being located between the first main surface and the second main surface of the expanded thermally expandable thermosetting adhesive layer means that, as shown in Figure 4(b), the first surface b1 of the adhesive portion 2 may be entirely covered by the expanded thermally expandable thermosetting adhesive layer 1', or, as shown in Figure 5, a part of the first surface b1 of the adhesive portion 2 may be exposed from the first main surface a1 of the expanded thermally expandable thermosetting adhesive layer 1'.

[0026] In the adhesive sheet of the present invention, when at least the second surface of the adhesive portion is located between the first main surface and the second main surface of the heat-expandable thermosetting adhesive layer, that is, when part or all of the adhesive portion is located within the heat-expandable thermosetting adhesive layer, part or all of the adhesive portion located within the heat-expandable thermosetting adhesive layer may or may not penetrate the heat-expandable thermosetting adhesive layer. When the adhesive portion is said to have penetrated the heat-expandable thermosetting adhesive layer, it means that, before expansion, the adhesive composition constituting the heat-expandable thermosetting adhesive layer is mixed within the adhesive portion, and after expansion, it means that at least the cured product of the thermosetting resin contained in the adhesive composition constituting the heat-expandable thermosetting adhesive layer is mixed within the adhesive portion.

[0027] The expanded adhesive sheet only needs to ensure that the expanded surface of the thermally expandable thermosetting adhesive layer and the adherends to be joined via the adhesive sheet are in close contact on both the first and second main surfaces, and the shape of the adhesive portion on the expanded adhesive sheet is not particularly limited. The shape of the adhesive portion on the expanded adhesive sheet may be the same as or different from the shape of the adhesive portion on the unexpanded adhesive sheet. If the first and / or second surfaces of the adhesive portion on the expanded adhesive sheet cannot be identified, the adhesive portion is embedded in the expanded thermally expandable thermosetting adhesive layer, and therefore the relationship between the first and second surfaces of the adhesive portion on the expanded adhesive sheet and the first and second main surfaces of the thermally expandable thermosetting adhesive layer, as described in the first and second embodiments above, is satisfied.

[0028] The adhesive sheet of the present invention typically has a shear adhesive strength greater on the first main surface than on the second main surface, so that it can exhibit temporary fixing properties on the first main surface and insertability on the second main surface. Specifically, the difference between the shear adhesive strength of the first main surface and the shear adhesive strength of the second main surface of the adhesive sheet is preferably 0.01 MPa or more, more preferably 0.1 MPa or more, more preferably 0.4 MPa or more, and even more preferably 0.5 MPa or more. This is because having the difference in shear adhesive strength between the first and second main surfaces of the adhesive sheet within the above range allows the first and second main surfaces to fully exhibit the functions described above, and prevents the function exhibited on one surface from impairing the function exhibited on the other surface. The difference between the shear adhesive strength of the first and second main surfaces of the adhesive sheet is preferably as large as possible, and is not particularly limited, but can be, for example, 2 MPa or less, or 1 MPa or less.

[0029] The first main surface of the adhesive sheet of the present invention only needs to have a shear adhesive strength that allows it to exhibit temporary fixing properties, and usually has a higher shear adhesive strength than the second main surface. The shear adhesive strength of the first main surface of the adhesive sheet can be such that the difference between it and the shear adhesive strength of the second main surface falls within the above range, and is preferably 0.2 MPa or more, more preferably 0.3 MPa or more, more preferably 0.5 MPa or more, and more preferably 1.0 MPa or more, as this allows the first main surface of the adhesive sheet to exhibit higher temporary fixing properties. Furthermore, the higher the shear adhesive strength of the first main surface of the adhesive sheet, the better, and there is no particular upper limit to the shear adhesive strength, but the upper limit can be, for example, 2 MPa or 1 MPa. The shear adhesive strength of the first surface of the adhesive sheet is mainly due to the shear adhesive strength of the adhesive portion and the thermally expandable thermosetting adhesive layer that constitute the first main surface, but it can be adjusted as appropriate depending on the layer structure of the adhesive sheet.

[0030] On the other hand, the second main surface of the adhesive sheet only needs to have a shear adhesive strength that allows it to exhibit insertability, and usually has a lower shear adhesive strength than the first main surface. The shear adhesive strength of the second main surface of the adhesive sheet can be set to a size that allows the difference from the shear adhesive strength of the first main surface to fall within the above range. Specifically, it is preferably less than 0.5 MPa, more preferably 0.3 MPa or less, even more preferably 0.2 MPa or less, and more preferably 0.1 MPa or less, as this prevents problems such as the second main surface of the adhesive sheet of the present invention sticking to a position other than the predetermined position, and improves insertability when inserting the insertion member into the gap. Furthermore, the lower the shear adhesive strength of the second main surface, the less initial adhesion there is, which is preferable as it improves insertability when inserting the insertion member into the gap. The lower limit is preferably 0 MPa, but may be 0.01 MPa or more. The shear bonding strength of the second main surface of the adhesive sheet is mainly due to the shear bonding strength of the thermally expandable thermosetting adhesive layer constituting the second main surface, but it can be adjusted according to the layer structure of the adhesive sheet, etc.

[0031] The shear bonding strength of each side of the adhesive sheet can be measured by the following method in accordance with the tensile shear test described in JIS Z 1541. First, the adhesive sheet is cut to a size of 10 mm x 10 mm. One side (the non-measurement surface) of the cut adhesive sheet is fixed to the surface of one aluminum plate A of two degreased, smooth-surfaced aluminum plates (width 15 mm x length 70 mm x thickness 0.5 mm) using strong adhesive, and the other side (measurement surface) of the adhesive sheet is brought into contact with the surface of the other aluminum plate B. The adhesive sheet is then sandwiched between the two aluminum plates A and B and pressed together for 10 seconds under a load of 0.5 MPa at 23°C to form a test specimen. Next, the test specimen is left in a 23°C environment for 5 minutes, then the ends of the two aluminum plates A and B are chucked, and a tensile test is performed at 10 mm / min in a 180-degree direction using a Tensilon tensile testing machine. The value obtained at this time can be used as the shear adhesive strength of the adhesive sheet surface (measurement target surface) on the aluminum B side. Furthermore, since the non-measurement surface of the adhesive sheet is firmly fixed to the aluminum plate A using a strong adhesive, delamination does not occur on the non-measurement surface side of the adhesive sheet during the tensile test, making it possible to measure the shear adhesive strength of the measurement surface.

[0032] The first and second surfaces of the adhesive sheet refer to the outermost surfaces of one and the other of the adhesive sheet, excluding the release liner. Unless otherwise specified, when describing the "adhesive sheet" and the "thermal-expandable thermosetting adhesive layer," they refer to the "adhesive sheet" and the "thermal-expandable thermosetting adhesive layer" before expansion. Furthermore, "expanded adhesive sheet" and "expanded thermal-expandable thermosetting adhesive layer" refer to the "adhesive sheet after expansion" and the "thermal-expandable thermosetting adhesive layer after expansion," respectively. "After expansion" refers to the expansion and curing of the thermal-expandable thermosetting adhesive layer, and unless otherwise specified, it refers to "after heating at 150°C for 60 minutes."

[0033] 1. Thermally expandable thermosetting adhesive layer The thermally expandable thermosetting adhesive layer in this invention is a layer that expands and hardens upon heating.

[0034] The adhesive sheet of the present invention may have one or more heat-expandable thermosetting adhesive layers. The two or more heat-expandable thermosetting adhesive layers may be directly laminated or laminated via an intermediate layer described later. When the adhesive sheet of the present invention has one heat-expandable thermosetting adhesive layer, the second main surface of the adhesive sheet is composed of the heat-expandable thermosetting adhesive layer that constitutes the first main surface of the adhesive sheet. That is, a plurality of adhesive portions are provided in a pattern on the first main surface of the single-layer heat-expandable thermosetting adhesive layer, and the second main surface becomes the second main surface of the adhesive sheet.

[0035] On the other hand, if the adhesive sheet of the present invention has two or more heat-expandable thermosetting adhesive layers, the second main surface of the adhesive sheet is composed of a different heat-expandable thermosetting adhesive layer from the heat-expandable thermosetting adhesive layer that constitutes the first main surface of the adhesive sheet. That is, of the two or more heat-expandable thermosetting adhesive layers, the first main surface of the adhesive sheet is composed of a heat-expandable thermosetting adhesive layer located at the outermost edge in the thickness direction of the adhesive sheet, with a plurality of adhesive portions provided on the outermost heat-expandable thermosetting adhesive layer, and the second main surface of the adhesive sheet is composed of the other heat-expandable thermosetting adhesive layer located at the outermost edge. If the adhesive sheet of the present invention has two or more heat-expandable thermosetting adhesive layers, each heat-expandable thermosetting adhesive layer may have the same or different composition and thickness.

[0036] At least the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet of the present invention should, in order to prevent problems such as the second main surface of the adhesive sheet adhering to a position other than the predetermined position and to improve insertability, typically have lower shear adhesive strength than the adhesive portion, and more preferably have low or no initial adhesion (tackiness).

[0037] The shear adhesive strength of the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet of the present invention is preferably less than 0.5 MPa, more preferably 0.3 MPa or less, more preferably 0.2 MPa or less, and even more preferably 0.1 MPa or less. By setting the shear strength to the above, when inserting the adhesive sheet of the present invention into the gap of the member to be inserted, it is possible to prevent problems such as sticking to a position other than the predetermined position and improve insertability. Furthermore, the lower the shear adhesive strength of the heat-expandable thermosetting adhesive layer, the less initial adhesion there is, which is preferable as it improves insertability when inserting the member into the gap. The lower limit is preferably 0 MPa, but may be 0.05 MPa or more.

[0038] Furthermore, if the adhesive sheet of the present invention has two or more heat-expandable thermosetting adhesive layers, it is sufficient that the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet has the above-described shear adhesive strength, while the other heat-expandable thermosetting adhesive layers may have shear adhesive strengths within the above range or greater. If the shear adhesive strength of the heat-expandable thermosetting adhesive layer with the adhesive portion is higher than the shear adhesive strength of the heat-expandable thermosetting adhesive layer constituting the second main surface, the temporary fixing properties on the first main surface of the adhesive sheet can be improved. In the above case, the preferred range for the shear adhesive strength of the heat-expandable thermosetting adhesive layer with the adhesive portion can be the same as the preferred range for the shear adhesive strength of the adhesive portion described later.

[0039] The shear bonding strength of the thermally expandable thermosetting adhesive layer can be adjusted as needed by, for example, the blending of resin components, inorganic fillers, slip agents, and other additives contained in the thermosetting adhesive composition described later.

[0040] The shear bonding strength of a heat-expandable thermosetting adhesive layer can be measured by the following method in accordance with the tensile shear test described in JIS Z 1541. First, a sheet is formed using an adhesive of the same composition to achieve the same thickness as the heat-expandable thermosetting adhesive layer in the adhesive sheet. The molded material is then cut to a size of 10 mm x 10 mm, and sandwiched between two degreased, smooth-surfaced aluminum plates (width 15 mm x length 70 mm x thickness 0.5 mm). The test specimen is then pressed together at 23°C and a load of 0.5 MPa for 10 seconds. After leaving the test specimen in a 23°C environment for 5 minutes, the ends of the two aluminum plates are chucked, and a tensile test is performed using a Tensilon tensile testing machine at 10 mm / min in a 180-degree direction. The value obtained at this time can be used as the shear bonding strength.

[0041] The thickness of the heat-expandable thermosetting adhesive layer is preferably 1 μm or more, more preferably in the range of 10 μm to 400 μm, even more preferably in the range of 15 μm to 250 μm, and particularly preferably in the range of 20 μm to 200 μm, in order to obtain even better adhesive strength. If there are two or more heat-expandable thermosetting adhesive layers, the thickness is determined as the thickness per layer.

[0042] Furthermore, the thickness of the heat-expandable thermosetting adhesive layer is preferably 10% or more, and more preferably 30% or more, of the total thickness of the adhesive sheet. This range makes it easier, for example, to fix one adherend (inserted member) into a void in one adherend (inserted member) or to fill the void with the adhesive sheet. When there are two or more heat-expandable thermosetting adhesive layers, it is preferable that the total thickness of the heat-expandable thermosetting adhesive layers relative to the total thickness of the adhesive sheet is within the above range.

[0043] A heat-expandable thermosetting adhesive layer is a layer that expands when heated, and preferably, after heating at 150°C for 60 minutes, the expansion rate in the thickness direction of the heat-expandable thermosetting adhesive layer is 150% or more, more preferably 175% or more, and even more preferably 200% or more. Furthermore, the above expansion rate is preferably 1000% or less, more preferably 800% or less, and even more preferably 500% or less. If the adhesive sheet exhibits the above expansion rate for the heat-expandable thermosetting adhesive layer, even if the height (thickness) of the void in the member to be inserted is large, the adhesive sheet can be expanded to suitably fix the other adherend within the void, or the void can be filled with the adhesive sheet. Furthermore, even if the surface of the adherend is rough or uneven, sufficient adhesion can be achieved, and the other adherend can be suitably fixed. In addition, if the expansion rate is too high, the density of the layer decreases and it is prone to deterioration due to exposure to high temperatures, but if the expansion rate is within the above range, thermal deterioration is less likely to occur and high adhesive strength can be maintained even in high-temperature environments. If there are two or more thermally expandable thermosetting adhesive layers, the expansion rate shall be that of each individual layer.

[0044] The expansion rate (%) in the thickness direction of the heat-expandable thermosetting adhesive layer after heating at 150°C for 60 minutes shall be the value calculated based on the following method and formula. First, the thickness of the heat-expandable thermosetting adhesive layer A on the adhesive sheet before heating (before expansion) is measured in a 23°C environment. Next, the adhesive sheet is heated by standing in a 150°C environment for 60 minutes, then the adhesive sheet is removed to a 23°C environment, and the thickness of the heat-expandable thermosetting adhesive layer on the adhesive sheet after heating (after expansion) is immediately measured. The expansion rate is calculated based on the above measurement results and the following formula. Expansion rate in the thickness direction of the heat-expandable thermosetting adhesive layer after heating (%) = [Thickness of the heat-expandable thermosetting adhesive layer after heating / Thickness of the heat-expandable thermosetting adhesive layer before heating] × 100 (%)

[0045] Alternatively, instead of using an adhesive sheet, a test sample may be prepared by forming a heat-expandable, thermosetting adhesive layer with the same composition and thickness as the heat-expandable, thermosetting adhesive layer in the adhesive sheet onto a release liner. The expansion rate may then be calculated based on the thickness of the test sample before and after heating it at 150°C for 60 minutes, and the above formula.

[0046] The thickness of the thermally expandable thermosetting adhesive layer after expansion, or in other words, the expanded adhesive layer formed by the expansion and curing of the thermally expandable thermosetting adhesive layer by heating, is preferably in the range of 20 μm to 2500 μm, and more preferably in the range of 40 μm to 1500 μm, in order to obtain even better adhesive strength. Furthermore, it is preferable that the thermally expandable thermosetting adhesive layer after expansion has a porous structure.

[0047] The glass transition temperature of the thermally expandable thermosetting adhesive layer after expansion is preferably 80°C or higher. This is because the expanded adhesive layer can exhibit excellent adhesive strength even when exposed to high-temperature environments, and can firmly hold the bond between the inserting member and the inserted member, especially in applications where high temperatures are likely to be reached. More specifically, the glass transition temperature of the thermally expandable thermosetting adhesive layer after expansion is preferably 80°C or higher, more preferably 100°C or higher, even more preferably 120°C or higher, and most preferably 150°C or higher. There is no particular upper limit to the glass transition temperature of the thermally expandable thermosetting adhesive layer after expansion, but for example, setting it to 300°C or lower allows the inserting member and the inserted member to be bonded without damage. If the adhesive sheet of the present invention has two or more thermally expandable thermosetting adhesive layers, it is preferable that at least the thermally expandable thermosetting adhesive layers constituting the first main surface and the second main surface of the adhesive sheet have a glass transition temperature within the above range after expansion (after curing), and it is preferable that all thermally expandable thermosetting adhesive layers have the above glass transition temperature after expansion (after curing).

[0048] The glass transition temperature of the thermally expandable thermosetting adhesive layer after expansion is determined using a dynamic viscoelasticity analyzer (Rheometrics, product name: RSA-II). The test specimen is chucking the specimen with the gripping device of the analyzer, and the storage modulus (E') and loss modulus (E") are measured at a frequency of 1 Hz. The peak temperature is determined by the loss tangent (tanδ) spectrum calculated from the value obtained by dividing the loss modulus (E") by the storage modulus (E') (E'' / E'). The test specimen used for the above measurement can be prepared by heating the thermally expandable thermosetting adhesive layer at 150°C for 60 minutes, and then punching out the expanded thermally expandable thermosetting adhesive layer into the shape of a JIS K 7127 test specimen type 5 using a dumbbell cutter.

[0049] It is preferable that the heat-expandable thermosetting adhesive layer, after expansion, has a curing rate of 80% or more. This curing rate allows for excellent adhesive strength even when exposed to high-temperature environments, and enables strong bonding of insertable members and inserted members, especially in applications where high temperatures are likely to occur. Furthermore, it is more preferable that the heat-expandable thermosetting adhesive layer, after expansion (heating), has a curing rate of 90% or more, and even more preferable that it has a curing rate of 99% or more.

[0050] The curing rate of the thermally expandable thermosetting adhesive layer after expansion is expressed as gel fraction and refers to the value calculated based on the following formula, obtained by heating the thermally expandable thermosetting adhesive layer at 150°C for 60 minutes, immersing the expanded thermally expandable thermosetting adhesive layer in a toluene solution adjusted to 23°C for 24 hours, and then drying the remaining thermally expandable thermosetting adhesive layer in the solvent.

[0051] Gel fraction (mass%) = {(mass of the heat-expandable thermosetting adhesive layer remaining undissolved in toluene) / (mass of the heat-expandable thermosetting adhesive layer before toluene immersion)} × 100

[0052] A heat-expandable thermosetting adhesive layer is a layer containing at least a thermosetting resin and an expander. In other words, a heat-expandable thermosetting adhesive layer is a layer formed by a heat-expandable thermosetting adhesive composition containing at least a thermosetting resin and an expander.

[0053] The above-mentioned heat-expandable thermosetting adhesive layer can be formed, for example, by applying an adhesive composition containing a thermosetting resin and an expander to a release liner or the like and drying it. Furthermore, the expanded thermally expandable thermosetting adhesive layer is an expanded adhesive layer whose volume has increased due to the expansion of the expander contained in the thermally expandable thermosetting adhesive composition upon heating, and is formed by the cured product of the thermally expandable thermosetting adhesive composition.

[0054] Furthermore, "in the (all resin components) of the heat-expandable thermosetting adhesive layer" can also be interpreted as "in the (all resin components) of the heat-expandable thermosetting adhesive composition that forms the heat-expandable thermosetting adhesive layer." The resin components refer to the resin components that make up the adhesive composition excluding the expander.

[0055] (thermosetting resin) The heat-expandable thermosetting adhesive layer contains at least a thermosetting resin as a resin component. As the thermosetting resin, one or more thermosetting resin species selected from, for example, urethane resin, phenolic resin, unsaturated polyester resin, epoxy resin, and acrylic resin can be used. In particular, as the thermosetting resin, the use of epoxy resin and / or phenolic resin is preferable in that it provides good adhesion to the adherend during heat curing, and the use of epoxy resin is even more preferable in that it ensures good heat curability and has high heat resistance.

[0056] As the epoxy resin mentioned above, compounds having one or more epoxy groups in one molecule can be used. Specifically, bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, and their modified resins, dicyclopentadiene type epoxy resins such as dicyclopentadiene-phenol addition reaction type epoxy resins, biphenyl type epoxy resins, tetramethylbiphenyl type epoxy resins, polyhydroxynaphthalene type epoxy resins, isocyanate modified epoxy resins, and 10-(2,5-dihydroxyphenyl)-9,10-dihydro 9-Oxa-10-phosphaphenanthrene-10-oxide modified epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, dicyclopentadiene-phenol addition reaction type epoxy resin, phenol aralkyl type epoxy resin, naphthol novolac type epoxy resin, hexanediol type epoxy resin, naphthol aralkyl type epoxy resin, naphthol-phenol co-condensed novolac type epoxy resin, naphthol-cresol co-condensed novolac type epoxy resin, aromatic hydrocarbon formaldehyde resin modified phenol resin type epoxy resin, biphenyl modified novolac type epoxy resin, trimethylolpropane type epoxy resin, alicyclic epoxy resin, acrylic resin having epoxy groups, polyurethane resin having epoxy groups, polyester resin having epoxy groups, flexible epoxy resin, etc. can be used.

[0057] The epoxy resin may be used alone or in combination of two or more types. Furthermore, the epoxy resin may be solid, semi-solid, or liquid. In particular, it is preferable to use a polyfunctional epoxy resin having two or more epoxy groups per molecule and / or a mixture thereof. Using the above epoxy resin allows for a higher glass transition temperature of the thermally expandable thermosetting adhesive layer after expansion, thereby suppressing a decrease in adhesive strength at high temperatures. Additionally, epoxy resins other than polyfunctional epoxy resins may be used in combination. By using the above epoxy resins in combination, the flexibility, softening point, melt viscosity, glass transition temperature, etc., of the thermally expandable thermosetting adhesive layer can be easily adjusted.

[0058] It is preferable to use a thermosetting resin in which the total epoxy equivalent is in the range of 2,000 g / eq. or less as the thermoexpandable thermosetting adhesive layer described above. This is preferable because it can raise the glass transition temperature of the thermoexpandable thermosetting adhesive layer after expansion, thereby suppressing the decrease in adhesive strength at high temperatures. The total epoxy equivalent is preferably 50 g / eq. to 1,500 g / eq., 100 g / eq. to 1,000 g / eq., or 150 g / eq. to 500 g / eq.

[0059] As the thermosetting resin mentioned above, it is preferable to include an epoxy resin with an epoxy equivalent of 500 g / eq. or less in the total resin components of the thermoexpandable thermosetting adhesive layer in an amount of 30% to 70% by mass, because this can raise the glass transition temperature of the thermoexpandable thermosetting adhesive layer after heat curing and suppress the decrease in adhesive strength at high temperatures. The epoxy equivalent is preferably 50 g / eq. to 450 g / eq., 100 g / eq. to 400 g / eq., or 150 g / eq. to 300 g / eq. Furthermore, the content of epoxy resin having an epoxy equivalent within the above range is preferably within the range of 35% to 65% by mass, 40% to 60% by mass, or 45% to 55% by mass in the total resin components of the thermoexpandable thermosetting adhesive layer. The content of epoxy resin having an epoxy equivalent within the above range refers to the total amount if two or more types of epoxy resins having an epoxy equivalent within the above range are included.

[0060] "Epoxy equivalent" is defined as the molecular weight of epoxy resin per epoxy group, and can be determined by methods such as the perchloric acid-tetraethylammonium bromide method described in JIS K7236, Method for Determining the Epoxy Equivalent of Epoxy Resin (2001).

[0061] The heat-expandable thermosetting adhesive layer preferably contains one or more solid thermosetting resins (hereinafter referred to as "solid resins") as the thermosetting resin. "Solid resin" refers to a resin with a high softening point or a resin that is semi-solid or solid at 25°C. The softening point of the solid resin is preferably 5°C or higher. Among the thermosetting resins, it is preferable to include a solid resin with a softening point of 30°C to 150°C, and more preferably a solid resin with a softening point of 50°C to 100°C.

[0062] The content of solid resin in the heat-expandable thermosetting adhesive layer can be appropriately set according to the required shear bonding strength and other factors for the heat-expandable thermosetting adhesive layer. At least in the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet of the present invention, the content of the solid resin is preferably 30% by mass or more of the total resin components of the heat-expandable thermosetting adhesive layer, more preferably 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 85% by mass or more, and 90% by mass or more. Furthermore, the above content is preferably 99% by mass or less of the total resin components of the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet, more preferably 97% by mass or 95% by mass. More specifically, the content of solid resin is preferably 30% by mass or more, more preferably 50% by mass or more and 99% by mass or less, and even more preferably 70% by mass or more and 95% by mass or less. By including solid resins within the above range, the initial adhesion (tackiness) of the heat-expandable thermosetting adhesive layer can be reduced, preventing problems such as misalignment of the adhesive sheet or adhesion to a position other than the intended position when inserting the insertable member into the gap of the member to be inserted, thereby improving insertability. If two or more types of solid resins are included, the solid resin content refers to the total amount of the two or more types of solid resins.

[0063] Specific examples of the solid resins mentioned above include phenol novolac type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, dicyclopentadiene-phenol addition reaction type epoxy resin, phenol aralkyl type epoxy resin, naphthol novolac type epoxy resin, naphthol aralkyl type epoxy resin, naphthol-phenol co-condensed novolac type epoxy resin, naphthol-cresol co-condensed novolac type epoxy resin, and the like. These resins may be used individually or in combination of two or more types.

[0064] Furthermore, the heat-expandable thermosetting adhesive layer may be used in combination with a thermosetting resin that is liquid at room temperature (hereinafter sometimes referred to as a liquid resin) as needed. This is because it is possible to adjust the shear bonding strength of the heat-expandable thermosetting adhesive layer to a desired level. The liquid resin preferably has a viscosity of 3 million mPa·sec or less at 25°C, more preferably 1,000 mPa·sec to 2 million mPa·sec, and even more preferably 10,000 mPa·sec to 1.5 million mPa·sec.

[0065] The liquid resin content in the heat-expandable thermosetting adhesive layer can be appropriately set according to the required shear bonding strength and other factors for the heat-expandable thermosetting adhesive layer. At least in the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet of the present invention, the liquid resin content is preferably 40% by mass or less of the total resin components of the heat-expandable thermosetting adhesive layer, more preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. Furthermore, the liquid resin content may be 0% by mass, greater than 0% by mass, 1% by mass or more, 3% by mass or more, or 5% by mass or more. More specifically, the content can be 40% by mass or less, 1% by mass or more and 30% by mass or less, 3% by mass or more and 20% by mass or less, or 5% by mass or more and 10% by mass or less. By setting the liquid resin content in the heat-expandable thermosetting adhesive layer constituting the second main surface within the above range, initial adhesion (tackiness) can be reduced, preventing problems such as misalignment of the adhesive sheet's bonding position or adhesion to a position different from the intended position when inserting the insertion member into the gap of the member to be inserted, thereby improving insertability. Furthermore, the flexibility of the heat-expandable thermosetting adhesive layer before expansion and its fluidity during heating can be optimized, allowing for optimal handling of the adhesive sheet of the present invention and optimal expansion rate of the adhesive sheet during heating. When two or more types of liquid resins are included, the liquid resin content refers to the total amount of the two or more types of liquid resins.

[0066] When the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet of the present invention contains a liquid resin, the liquid resin can be used in an appropriate combination of the viscosity range and content range described above. The liquid resin can be used in an appropriate combination of the viscosity range and content range described above. As one example of a preferred embodiment of the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet of the present invention, it is preferable to contain 20% by mass or less of a liquid resin with a viscosity of 3 million mPa·sec or less, it is preferable to contain 1% by mass to 15% by mass of a liquid resin with a viscosity in the range of 1,000 mPa·sec to 2 million mPa·sec, and it is preferable to contain 3% by mass to 10% by mass of a liquid resin with a viscosity in the range of 10,000 mPa·sec to 1,500,000 mPa·sec. This is because the shear adhesive strength of the second main surface of the adhesive sheet can be made sufficiently smaller than that of the first main surface, improving insertability.

[0067] Furthermore, with respect to thermally expandable thermosetting adhesive layers other than the thermally expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet, the liquid resin content is not particularly limited and can be adjusted as appropriate according to the required shear bonding strength.

[0068] Specific examples of the liquid resins mentioned above include bisphenol type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, modified resins thereof, trimethylolpropane type epoxy resin, and alicyclic epoxy resin. The liquid resin may be used individually or in combination of two or more types.

[0069] When the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet of the present invention contains the above-mentioned solid resin and liquid resin, the mixing ratio of the solid resin to the liquid resin (solid resin:liquid resin) should be such that the shear adhesive strength of the heat-expandable thermosetting adhesive layer can be set to a desired range. For example, a mass ratio of 99.9:0.1 to 60:40 is preferred, a range of 99:1 to 70:30 is preferred, and a range of 95:5 to 80:20 is preferred. This is because by setting the mixing ratio of the solid resin to the liquid resin within the above range, the shear adhesive strength of the second main surface of the adhesive sheet can be made sufficiently lower than that of the first main surface.

[0070] The thermosetting resin is preferably present in the total resin components of the heat-expandable thermosetting adhesive layer in an amount of 10% to 99% by mass, more preferably 20% to 90% by mass, more preferably 30% to 80% by mass, and even more preferably 40% to 70% by mass. By keeping the content of the thermosetting resin in the heat-expandable thermosetting adhesive layer within the above range, the flexibility of the heat-expandable thermosetting adhesive layer before expansion and its fluidity during heating can be optimized, and the handling properties of the adhesive sheet of the present invention and the expansion rate of the adhesive sheet during heating can be optimized.

[0071] (Hardening agent) The heat-expandable thermosetting adhesive layer and the heat-expandable thermosetting adhesive composition comprising it preferably contain a curing agent that can react with the thermosetting resin. This is because when the heat-expandable thermosetting adhesive layer is heated, the thermosetting resin hardens sufficiently, enabling it to exhibit high adhesive strength. The curing agent is preferably included before the heat-curing of the heat-expandable thermosetting adhesive layer, or before it is formed into a sheet-like heat-expandable thermosetting adhesive layer.

[0072] The curing agent described above can be appropriately selected and used according to the type of thermosetting resin, particularly the type of functional group the thermosetting resin possesses. For example, if epoxy resin is used as the thermosetting resin, it is preferable to use a curing agent that has functional groups that can react with the epoxy groups. Examples of curing agents include amine compounds, amide compounds, acid anhydride compounds, and phenolic compounds. It is preferable to use the curing agent in powder form.

[0073] For example, amine compounds such as diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, diaminodiphenylsulfone, isophoronediamine, imidazole derivatives, BF3-amine complexes, and guanidine derivatives can be used.

[0074] Examples of the above-mentioned amide compounds include dicyandiamide and polyamide resins synthesized from a linolenic acid dimer and ethylenediamine.

[0075] Examples of the above-mentioned acid anhydride compounds include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0076] Examples of the phenolic compounds mentioned above include polyhydric phenol compounds such as phenol novolac resins, cresol novolac resins, aromatic hydrocarbon formaldehyde resin-modified phenolic resins, dicyclopentadienephenol addition resins, phenol aralkyl resins (Zyloc resins), naphthol aralkyl resins, trimethylol methane resins, tetraphenyloleethane resins, naphthol novolac resins, naphthol-phenol co-condensed novolac resins, naphthol-cresol co-condensed novolac resins, biphenyl-modified phenolic resins (polyhydric phenolic compounds in which the phenol core is linked by a bismethylene group), biphenyl-modified naphthol resins (polyhydric naphthol compounds in which the phenol core is linked by a bismethylene group), aminotriazine-modified phenolic resins (compounds having a phenol skeleton, a triazine ring, and a primary amino group in their molecular structure), and alkoxy-group-containing aromatic ring-modified novolac resins (polyhydric phenolic compounds in which the phenol core and alkoxy-group-containing aromatic ring are linked by formaldehyde).

[0077] As for the curing agent, for example, when using epoxy resin as the thermosetting resin, the ratio of the functional group equivalents that can react with epoxy groups contained in the curing agent to the total epoxy equivalents of the thermosetting resin is preferably in the range of 0.3 to 2.0, more preferably in the range of 0.5 to 1.5, and even more preferably in the range of 0.7 to 1.0. By using it within the above range, the thermosetting resin can be sufficiently cured and the heat resistance of the adhesive sheet can be improved.

[0078] The curing temperature of the thermosetting material is preferably higher than or equal to the expansion temperature of the expander described later, and the curing time is preferably longer than or equal to the expansion time. This allows the expander to expand sufficiently in the thermosetting material softened by heating, making the sheet thickness after expansion uniform.

[0079] (Curing accelerator) Furthermore, the heat-expandable thermosetting adhesive layer and the heat-expandable thermosetting adhesive composition comprising it may contain a curing accelerator. The curing accelerator is preferably included before the heat-expandable thermosetting adhesive layer A is heat-cured, or before it is formed into a sheet-like thermosetting adhesive layer A.

[0080] Phosphorus compounds, amine compounds, imidazole derivatives, etc., can be used as the curing accelerator. When using the curing accelerator, the amount used is preferably 0.1 to 10 parts by mass, and more preferably in the range of 0.5 to 5 parts by mass, per 100 parts by mass of the total resin components contained in the thermally expandable thermosetting adhesive layer.

[0081] It is preferable to use a powdered curing accelerator. Compared to liquid curing accelerators, the powdered curing accelerator suppresses the thermosetting reaction at low temperatures, thereby further improving the storage stability of the thermosetting material at room temperature before heat curing.

[0082] (thermoplastic resin) Furthermore, the heat-expandable thermosetting adhesive layer and the heat-expandable thermosetting adhesive composition constituting it may contain a thermoplastic resin, to the extent that it does not impair the fixation of the joint even when used in an environment with large temperature changes after expansion and curing.

[0083] Examples of the above thermoplastic resins include: thermoplastic polyurethane (TPU); phenoxy resins such as polyhydroxypolyethers synthesized from bisphenols and epichlorohydrin; polycarbonate (PC); vinyl chloride resins such as polyvinyl chloride (PVC) and vinyl chloride-vinyl acetate copolymer resins; acrylic resins such as polyacrylic acid, polymethacrylic acid, polymethyl polyacrylate, polymethyl methacrylate (PMMA), and polyethyl methacrylate; polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate; polyamide resins such as nylon (registered trademark); polystyrene (PS), imide-modified polystyrene Polystyrene resins such as acrylonitrile-butadiene-styrene (ABS) resin, imide-modified ABS resin, styrene-acrylonitrile copolymer (SAN) resin, and acrylonitrile-ethylene-propylene-diene-styrene (AES) resin; olefin resins such as polyethylene (PE) resin, polypropylene (PP) resin, and cycloolefin resin; cellulose resins such as nitrocellulose and cellulose acetate; silicone resins; thermoplastic resins such as fluororesins; thermoplastic elastomers such as styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, urethane-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers can be used.

[0084] In particular, the heat-expandable thermosetting adhesive layer preferably contains one or more thermoplastic resins having reactive groups that react with the thermosetting resin (hereinafter sometimes referred to as reactive thermoplastic resins). This is because the reactive groups of the reactive thermoplastic resin react with the thermosetting resin, enabling the heat-expandable thermosetting adhesive layer to exhibit stronger adhesive strength after curing. Examples of reactive groups that react with the thermosetting resin include epoxy groups, hydroxyl groups, carboxyl groups, amino groups, and isocyanate groups. Examples of thermoplastic resins having such reactive groups include thermoplastic polyurethane (TPU), polyhydroxy polyether (phenoxy resin), and acrylic resin.

[0085] For the reasons stated above, the thermoplastic resin can be used in an amount of 1 to 200 parts by mass per 100 parts by mass of the thermosetting resin. In particular, it is preferable to use it in an amount of 10 to 150 parts by mass per 100 parts by mass of the thermosetting resin, and more preferably in an amount of 30 to 100 parts by mass, as this allows for the development of strong adhesive strength.

[0086] (Leavening agent) As the expanding agent contained in the heat-expandable thermosetting adhesive layer and the heat-expandable thermosetting adhesive composition that constitutes it, it is preferable to use one that allows the heat-expandable thermosetting adhesive layer to form a porous structure within the layer after expansion. Examples of such expanding agents include inorganic compounds such as ammonium carbonate, ammonium bicarbonate, ammonium nitrite, ammonium borohydride, and azides; fluorinated alkanes such as trichloromonofluoromethane; azo compounds such as azobisisobutyronitrile; hydrazine compounds such as p-toluenesulfonyl hydrazide; semicarbazide compounds such as p-toluenesulfonyl semicarbazide; triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; and N-nitroso compounds such as N,N'-dinitrosoterephthalamide.

[0087] Furthermore, as the above-mentioned expanding agent, for example, expandable capsules containing a hydrocarbon solvent in microencapsulation can be used. The above-mentioned expanding agent can be used alone or in combination of two or more types.

[0088] Among the above-mentioned expanding agents, it is more preferable to use expandable capsules containing hydrocarbon solvents in microencapsulated form, as this helps prevent deterioration of the thermally expandable thermosetting adhesive layer due to factors such as heat.

[0089] Furthermore, it is preferable to use an expanding agent that can expand at temperatures around the softening point of the heat-expandable thermosetting adhesive layer, as this allows the adhesive sheet to expand sufficiently.

[0090] Examples of commercially available expandable capsules include Expancel (manufactured by Nippon Philite Co., Ltd.), Matsumoto Microsphere (manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd.), and Microsphere (manufactured by Kureha Corporation). It is preferable to use expandable capsules in which the volume after expansion (volume expansion ratio) is 8 to 60 times the volume of the capsule before expansion.

[0091] The amount of the above-mentioned expander used, preferably the amount of the above-mentioned heat-expandable capsule, is preferably in the range of 0.3 to 30 parts by mass, more preferably in the range of 0.5 to 25 parts by mass, and even more preferably in the range of 1 to 20 parts by mass, per 100 parts by mass of the total resin components of the above-mentioned heat-expandable thermosetting adhesive layer. By using the amount of expander within the above range, the voids in the member to be inserted can be sufficiently filled, and an even better adhesive strength can be obtained, making it possible to firmly join the inserting member and the member to be inserted by maintaining a high adhesive strength to the inserting member or the member to be inserted, which is the adherend.

[0092] (Any component) Furthermore, in addition to those described above, the heat-expandable thermosetting adhesive layer and the heat-expandable thermosetting adhesive composition constituting it may also contain additives such as fillers, softeners, stabilizers, adhesion promoters, leveling agents, defoamers, plasticizers, tackifying resins, fibers, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, thickeners, colorants such as pigments, and other fillers, to the extent that they do not impair the effects of the present invention.

[0093] 2.Adhesive part In the present invention, the adhesive portion is provided in a patterned manner on the first main surface of the heat-expandable thermosetting adhesive layer that constitutes the first main surface of the adhesive sheet, and thus constitutes the first main surface of the adhesive sheet.

[0094] The first main surface of the adhesive sheet has multiple adhesive portions, which allows it to exhibit the desired shear adhesive strength through the initial adhesive force of at least the adhesive portions. This allows the adhesive sheet to be temporarily fixed in place so that it does not shift from its predetermined position after the insertion member is inserted into the gap of the member to be inserted, until the adhesive sheet is expanded to bond and fix the insertion member and the member to be inserted.

[0095] In order for the first main surface of the adhesive sheet of the present invention to have a higher shear adhesive strength than the second main surface and to exhibit a temporary fixing function, it is preferable that the shear adhesive strength of the multiple adhesive parts be 0.2 MPa or higher, more preferably 0.3 MPa or higher, more preferably 0.5 MPa or higher, and even more preferably 1.0 MPa or higher. By setting it within the above range, an adhesive sheet with higher temporary fixing properties can be obtained. The higher the shear adhesive strength of the multiple adhesive parts, the better, and there is no particular upper limit, but it can be, for example, 2 MPa or less, or even 1 MPa. The shear adhesive strength of the multiple adhesive parts can be adjusted by adjusting the adhesive components described later, the pattern and shape of the adhesive parts, the size of each part, and the ratio of the total area of ​​the multiple adhesive parts to the first main surface of the adhesive sheet. In other words, the shear adhesive strength of the multiple adhesive parts refers to the shear adhesive strength of the adhesive layer consisting of multiple adhesive parts and non-adhesive areas where no adhesive parts are provided.

[0096] The shear bonding strength of multiple adhesive sections can be measured in accordance with the tensile shear test described in JIS Z 1541. Similar to the multiple adhesive sections in an adhesive sheet, multiple adhesive sections are formed in a pattern on a release liner, the adhesive sections are transferred to one of two smooth adherends (aluminum plates), and then the two adherends are placed on top of each other so that the adhesive sections are in contact. The specimen is then pressed with a load of 0.5 MPa at 23°C for 10 seconds, and left to stand at 23°C for 30 minutes to be used as a test specimen. The ends of the two aluminum plates of the test specimen are chucked, and a tensile test is performed using a tensile testing machine at 10 mm / min in a 180-degree direction. The values ​​obtained from this test can be used.

[0097] The peak temperature of the loss tangent (tanδ) based on the dynamic viscoelastic spectrum measured at a frequency of 1 Hz in the adhesive area is not particularly limited, but is preferably -30°C to 20°C, more preferably -20°C to 10°C, and preferably -10°C to 5°C in order to maintain good adhesive strength.

[0098] The loss tangent based on the dynamic viscoelastic spectrum is calculated using a viscoelasticity tester (Rheometrics, product name: Ares 2KSTD). The test specimen is placed between the parallel discs that constitute the measurement section of the tester, and the storage modulus (G') and loss modulus (G") are measured at a frequency of 1 Hz. The loss tangent is then calculated using the formula tanδ = (G") / (G'). The peak temperature refers to the peak temperature confirmed in the tanδ spectrum for the measurement temperature range (-50°C to 150°C). As the test specimen, an adhesive layer with a thickness of 0.5 mm to 2.5 mm, formed using the adhesive used to form the adhesive portion, can be used.

[0099] In the present invention, multiple adhesive portions are provided in a patterned manner on the first main surface of the thermally expandable thermosetting adhesive layer, and there are non-adhesive regions between adjacent adhesive portions where components constituting the adhesive portion are absent.

[0100] Multiple adhesive sections are generally independent of each other, but there may be areas where two or more adhesive sections are partially connected. Examples of adhesive section patterns include dots (so-called island-like patterns), stripes (band-like patterns), and grid patterns.

[0101] The planar shape of the adhesive portion (the shape observed from the plane of the adhesive sheet) is preferably approximately circular, approximately square, or approximately hexagonal. The approximately circular shape is not particularly limited, but the ratio of the maximum diameter to the minimum diameter of any one adhesive portion [maximum diameter / minimum diameter] is preferably 1 to 4. The above [maximum diameter / minimum diameter] is more preferably 1 to 2, and most preferably 1 to 1.5.

[0102] Furthermore, examples of roughly square shapes include roughly square, roughly rectangular, roughly trapezoidal, and roughly rhombic shapes. The term "roughly" in each shape indicates that the corners of the square and hexagonal shapes may be rounded, or that straight sections may become curved, for example, due to pressure on the adhesive portion. The corners of the above roughly square shape are preferably roughly rhombic, with the angle of the corners facing the direction of the adhesive sheet flow being less than 90°, and a range of 45° to 70° is more preferable because it maintains good adhesive strength for achieving temporary fixation.

[0103] If the adhesive portion is dot-shaped (so-called island-shaped), the size of each adhesive portion (area in plan view) is preferably 0.02 mm. 2 ~0.50mm 2 It is within the range, more preferably 0.03 mm 2 ~0.30mm 2 It is within the range, and particularly preferably 0.05 mm 2 ~0.20mm 2 It is within the range described above. By setting the size of each adhesive portion within the above range, the adhesive sheet maintains good temporary fixation before expansion, and after expansion, the thermally expandable thermosetting adhesive layer can adhere more firmly to the adherend on the first main surface of the adhesive sheet after expansion without hindering the filling between adhesive portions or the embedding of adhesive portions due to the expansion of the thermally expandable thermosetting adhesive layer.

[0104] Furthermore, if the pattern of the adhesive portion is grid-like or striped, the planar shape of the adhesive portion can be, for example, linear, and the linear shape may be straight or wavy (serpentine, zigzag). If the pattern of the adhesive portion is grid-like or striped, the width of the adhesive portion is not particularly limited as long as the above-mentioned effects are achieved, and can be appropriately set according to the ratio of the total area of ​​the adhesive portion to the first main surface of the adhesive sheet described later.

[0105] The shapes and individual sizes of the multiple adhesive parts described above may be different or the same, but it is preferable that their shapes and individual sizes be substantially the same.

[0106] The shortest distance between any first adhesive portion selected from a plurality of adhesive portions and the second adhesive portion adjacent to (closest to) the first adhesive portion is preferably in the range of 0.05 mm to 0.60 mm, more preferably in the range of 0.10 mm to 0.40 mm, and more preferably in the range of 0.15 mm to 0.30 mm. By setting the shortest distance between two adjacent adhesive portions within the above range, the adhesive sheet maintains good temporary fixation before expansion, and after expansion, the thermally expandable thermosetting adhesive layer can adhere more firmly to the adherend on the first main surface of the sheet after expansion without hindering the filling between adhesive portions or the embedding of adhesive portions due to the expansion of the thermally expandable thermosetting adhesive layer. Furthermore, the distance between the first adhesive portion and the second adhesive portion adjacent to the first adhesive portion refers to the shortest distance between the first adhesive portion and the second adhesive portion adjacent to the first adhesive portion. Also, if the pattern of the adhesive portion is grid-like or strip-like, the shortest distance between any first adhesive portion and the second adhesive portion adjacent to the first adhesive portion (the closest one) refers to the distance between the first adhesive portion and the second adhesive portion that extends in the same direction as the first adhesive portion and is adjacent to the first adhesive portion.

[0107] In a plan view, the ratio of the total area of ​​the multiple adhesive parts to the first main surface of the adhesive sheet of the present invention before expansion is preferably 20% to 80%, more preferably 30% to 70%, and even more preferably 40% to 60%. By keeping the ratio of the area of ​​the adhesive parts to the first main surface of the adhesive sheet within the above range, the first main surface of the adhesive sheet maintains good temporary fixation before expansion, and after expansion, the thermally expandable thermosetting adhesive layer can adhere more firmly to the adherend on the first main surface of the sheet after expansion without hindering the filling between adhesive parts or the embedding of adhesive parts due to the expansion of the thermally expandable thermosetting adhesive layer. The ratio of the total area of ​​the multiple adhesive parts is also called the area occupancy rate of the adhesive parts to the area of ​​the first main surface of the adhesive sheet.

[0108] In a plan view, the ratio of the total area of ​​multiple adhesive portions to the first main surface of the adhesive sheet of the present invention before expansion is calculated using the following formula. The ratio of the total area of ​​multiple adhesive parts on the first main surface of the adhesive sheet before expansion = [Total area of ​​adhesive parts in a plan view of the adhesive sheet before expansion] / [Total area of ​​the first main surface of the adhesive sheet before expansion] × 100 (%)

[0109] The shape and size of the adhesive portion, the shortest distance between any first adhesive portion selected from multiple adhesive portions and the second adhesive portion adjacent to the first adhesive portion (the closest one), etc., can be determined, for example, by planar observation using an electron microscope.

[0110] The thickness of the adhesive portion is preferably 1 μm to 50 μm, preferably 2 μm to 30 μm, and more preferably 3 μm to 10 μm. By setting the thickness within the above range, for example, even if the surface of the adherend is rough or uneven, it conforms to the surface of the adherend, providing good temporary fixation. Furthermore, even after heating the adhesive sheet of the present invention to expand the heat-expandable thermosetting adhesive layer, filling voids and fixing it, excellent adhesive strength can be obtained, which is preferable.

[0111] The adhesive portion may or may not have thermal expansion properties, and can be appropriately set according to the composition of the adhesive constituting the adhesive portion. In particular, it is preferable that the adhesive portion does not have thermal expansion properties, from the viewpoint that the thermally expandable thermosetting adhesive layer can adhere more firmly to the adherend on the first main surface of the adhesive sheet after expansion, without hindering the filling between the adhesive portions or the embedding of the adhesive portions by the expansion of the thermally expandable thermosetting adhesive layer after the expansion of the adhesive sheet. It is preferable that the expansion rate in the thickness direction of the adhesive portion after heating at 150°C for 60 minutes is 120% or less, preferably 115% or less, and most preferably 100% (the adhesive portion does not expand substantially).

[0112] The expansion rate (%) in the thickness direction of the adhesive portion refers to the ratio of the thickness of the adhesive portion after heating to the thickness of the adhesive portion before heating, when the adhesive sheet of the present invention is heated at 150°C for 60 minutes. Specifically, it refers to the value calculated by the following method. First, the thickness of the adhesive portion of the adhesive sheet before heating (before expansion) is measured at 23°C. Next, the adhesive sheet is heated by standing at 150°C for 60 minutes, then the adhesive sheet is removed to 23°C, and the thickness of the adhesive portion of the adhesive sheet after heating (after expansion) is immediately measured. The expansion rate is calculated based on the above measurement results and the following formula. Expansion rate in the thickness direction of the adhesive part (%) = [Thickness of the adhesive part after heating / Thickness of the adhesive part before heating] × 100

[0113] The gel fraction of the adhesive portion is preferably 60% by mass or less, more preferably 10% to 55% by mass, and even more preferably 20% to 50% by mass. By keeping the gel fraction of the adhesive portion within the above range, the surface shape of the adhesive portion is easily maintained, thus preventing changes in shape over time, and it is possible to have sufficient initial adhesion to exhibit temporary fixation on the first main surface of the adhesive sheet.

[0114] The gel fraction of the adhesive portion can be calculated from the insoluble fraction when a patterned adhesive portion is formed on a release liner, similar to the adhesive sheet of the present invention, and immersed in toluene for 24 hours, using the following formula. Gel fraction (mass%) = {(mass of adhesive part after immersion in toluene) / (mass of adhesive part before immersion in toluene)} × 100

[0115] It is preferable to use an adhesive composition that constitutes the adhesive portion and has excellent initial adhesive strength (tackiness) at room temperature (23°C), and that can exhibit excellent adhesive strength even after the adhesive sheet of the present invention has been heated and expanded. Examples of such adhesive compositions include compositions that contain at least an adhesive resin.

[0116] Examples of adhesive resins that can be included in the adhesive composition include acrylic resins, rubber resins, polyurethane resins, polyester resins, and silicone resins. Among these, it is preferable that the adhesive composition contains acrylic resin as its main component. The main component refers to the component present in the greatest quantity in the adhesive composition.

[0117] As the above-mentioned acrylic resin, for example, one obtained by polymerizing monomers containing alkyl (meth)acrylate can be used, and one or more of the following can be used in combination: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. Among these, it is more preferable to use alkyl (meth)acrylate with 4 to 12 carbon atoms in the alkyl group in order to obtain an adhesive sheet that has excellent conformability and adhesion to substrates with uneven surfaces, as well as excellent workability for application.

[0118] In addition to those mentioned above, other monomers that can be used include acrylonitrile, (meth)acrylic acid, maleic anhydride, acrylamide, itaconic acid, styrene, vinyl acetate, and the like.

[0119] Examples of the rubber-based resins mentioned above include styrene-based AB-type diblock copolymers such as styrene-ethylene-butylene copolymer (SEB); styrene-based ABA-type triblock copolymers such as styrene-butadiene-styrene copolymer (SBS), hydrogenated SBS (styrene-ethylene-butylene-styrene copolymer (SEBS)), styrene-isoprene-styrene copolymer (SIS), hydrogenated SIS (styrene-ethylene-propylene-styrene copolymer (SEPS)), and styrene-isobutylene-styrene copolymer (SIBS); styrene-based ABAB-type tetrablock copolymers such as styrene-butadiene-styrene-butadiene (SBSB); styrene-based ABABA-type pentablock copolymers such as styrene-butadiene-styrene-butadiene-styrene (SBSBS); styrene-based multiblock copolymers having more than these AB repeating units; and hydrogenated styrene-based random copolymers such as styrene-butadiene rubber (SBR) with hydrogenated ethylenically double bonds. Commercially available styrene-based thermoplastic elastomers may also be used.

[0120] In addition to the resins mentioned above, the adhesive composition may optionally contain tackifying resins, crosslinking agents, and other additives.

[0121] As the tackifying resin mentioned above, for the purpose of adjusting the strong adhesion of the adhesive part, for example, rosin-based tackifying resins, polymerized rosin-based tackifying resins, polymerized rosin ester-based tackifying resins, rosin-phenol-based tackifying resins, stabilized rosin ester-based tackifying resins, disproportionated rosin ester-based tackifying resins, terpene-based tackifying resins, terpene-phenol-based tackifying resins, petroleum resin-based tackifying resins, etc., can be used.

[0122] As the crosslinking agent mentioned above, known isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, polyvalent metal salt-based crosslinking agents, metal chelate-based crosslinking agents, keto-hydrazide-based crosslinking agents, oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, silane-based crosslinking agents, glycidyl(alkoxy)epoxysilane-based crosslinking agents, etc., can be used for the purpose of improving the cohesive force of the adhesive portion.

[0123] As additives, known materials such as bases (such as aqueous ammonia) and acids for adjusting pH, foaming agents, plasticizers, softeners, antioxidants, fibrous, balloon-shaped, bead-shaped, or metal powder-shaped fillers made of glass or plastic, colorants such as pigments and dyes, pH adjusters, film-forming aids, leveling agents, thickeners, water repellents, defoamers, and leavening agents can be used as needed, within a range that does not hinder the desired effects of the present invention.

[0124] Examples of adhesive compositions include solvent-based adhesives, emulsion-type adhesives, water-based adhesives such as water-soluble adhesives, and solvent-free adhesives such as hot-melt adhesives, UV-curing adhesives, and EB-curing adhesives.

[0125] The adhesive composition may contain a solvent to maintain good coating properties. Examples of solvents include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and hexane. When using a water-based adhesive composition, water or a water-based aqueous solvent may be used as the solvent. Note that the amount of solvent is not included in the "total amount of the adhesive composition" when specifying the content of each component.

[0126] 3. Any configuration The adhesive sheet of the present invention has at least an adhesive portion and a heat-expandable thermosetting adhesive layer, but may have any configuration as needed. The adhesive sheet of the present invention, as illustrated for example in Figure 6, has a first heat-expandable thermosetting adhesive layer 1A having a first main surface a11 and a second main surface a21, a second heat-expandable thermosetting adhesive layer 1B having a first main surface a21 and a second main surface a22, and an intermediate layer 3 disposed between the first heat-expandable thermosetting adhesive layer 1A and the second heat-expandable thermosetting adhesive layer 1B and bonded to the second main surface a21 of the first heat-expandable thermosetting adhesive layer 1A and the first main surface a12 of the second heat-expandable thermosetting adhesive layer 1B, and may also have a plurality of adhesive portions 2 provided in a pattern on the first main surface a11 of the first heat-expandable thermosetting adhesive layer 1A. The adhesive sheet illustrated in Figure 6 has a first main surface composed of an adhesive portion 2 and a first heat-expandable thermosetting adhesive layer 1A, and a second main surface composed of a second heat-expandable thermosetting adhesive layer 1B. The adhesive sheet of the present invention has an intermediate layer 3, which gives it good rigidity and superior ease of application.

[0127] The intermediate layer is preferably a heat-resistant substrate. The level of heat resistance of the substrate varies depending on the application, but the melting point of the substrate is preferably 150°C or higher, more preferably 200°C or higher, and even more preferably 250°C or higher.

[0128] The melting point mentioned above refers to the temperature at which the maximum endothermic peak is observed when the intermediate layer (substrate) is heated from 30°C at a heating rate of 10°C / min using a differential scanning calorimetry (DSC).

[0129] Examples of heat-resistant substrates include polybutylene terephthalate, polyethylene naphthalate (PEN), polyamide, polyimide, polyetherimide, polysulfone, polyetherketone (PEEK), polyphenylene sulfide (PPS), and modified polyphenylene oxide.

[0130] The intermediate layer preferably has a thickness of 1 μm to 200 μm, more preferably 5 μm to 150 μm, and even more preferably 10 μm to 100 μm. By setting the thickness of the intermediate layer within the above range, when the adhesive side of the adhesive sheet of the present invention is attached to the adherend, even if the adherend surface is rough or uneven, the intermediate layer can sufficiently follow the surface shape of the adherend, resulting in excellent adhesion. The intermediate layer may consist of a single layer of the heat-resistant substrate, or it may be a laminate of two or more layers of the same or different heat-resistant substrates.

[0131] The adhesive sheet of the present invention may have a release liner on both the first main surface having an adhesive portion and the second main surface opposite to the side having the adhesive portion. A known release liner such as a resin film can be used.

[0132] 4. Others The adhesive sheet of the present invention preferably has a total thickness of 10 μm or more and 600 μm or less before expansion (before heating), more preferably 50 μm or more and 500 μm or less, and more preferably 100 μm or more and 400 μm or less. Furthermore, the total thickness after expansion (after heating) is preferably 20 μm or more and 2500 μm or less, more preferably 40 μm or more and 2000 μm or less, and more preferably 100 μm or more and 1000 μm or less. Note that the thickness of the release liner is not included in the total thickness of the adhesive sheet.

[0133] The adhesive sheet of the present invention preferably has a shear adhesive strength of 3 MPa or more after expansion at room temperature (23°C), more preferably 5 MPa or more, more preferably 6 MPa or more, and even more preferably 9 MPa or more. This is because it provides excellent adhesive retention performance to the inserting member and the inserted member. Furthermore, the shear adhesive strength after expansion preferably has a shear adhesive strength of 1 MPa or more at 150°C, more preferably 4 MPa or more, and even more preferably 7 MPa or more. This is because, by exhibiting the desired shear adhesive strength at the above temperature environments, the adhesive sheet of the present invention can exhibit excellent adhesive retention performance to the inserting member and the inserted member, and even higher retention performance, at room temperature and high temperature environments after expansion. The shear adhesive strength of the adhesive sheet of the present invention after expansion is measured by the method described in the examples below.

[0134] The adhesive sheet of the present invention can be manufactured by, for example, the steps of: forming a heat-expandable, thermosetting adhesive layer by applying a heat-expandable, thermosetting adhesive composition to a release film and drying it; forming a plurality of patterned adhesive portions by printing an adhesive composition in a desired pattern onto another release liner using a gravure coater or the like and drying it; and transferring the plurality of patterned adhesive portions to the first main surface of the heat-expandable, thermosetting adhesive layer and pressing them together. According to the above-described method for manufacturing adhesive sheets, in the step of transferring a plurality of patterned adhesive portions to the first main surface of the heat-expandable thermosetting adhesive layer and pressing them, by adjusting the pressing load and temperature in a timely manner, adhesive sheets can be manufactured in any of the following forms: one in which the adhesive portions are formed on the first main surface of the heat-expandable thermosetting adhesive layer (as shown in Figure 1(a)), one in which a portion of the adhesive portions protrudes from the surface of the heat-expandable thermosetting adhesive layer (as shown in Figure 1(b)), and one in which the adhesive portions are embedded in the heat-expandable thermosetting adhesive layer (as shown in Figure 3).

[0135] If the adhesive sheet of the present invention has an intermediate layer as illustrated in Figure 6, the manufacturing method can be as follows: for example, by taking the steps of forming a first heat-expandable, thermosetting adhesive layer by applying a heat-expandable, thermosetting adhesive composition to a release film and drying it; forming a second heat-expandable, thermosetting adhesive layer by applying a heat-expandable, thermosetting adhesive composition to another release liner and drying it; laminating an intermediate layer to the first heat-expandable, thermosetting adhesive layer; laminating the second heat-expandable, thermosetting adhesive layer to the side of the intermediate layer opposite to the first heat-expandable, thermosetting adhesive layer; forming a plurality of patterned adhesive parts by printing an adhesive composition in a desired pattern onto another release liner using a gravure coater or the like and drying it; and transferring the plurality of patterned adhesive parts to the first main surface of the first heat-expandable, thermosetting adhesive layer and pressing it into place.

[0136] The adhesive sheet of the present invention preferably expands in the thickness direction when heated, and preferably does not expand substantially in the surface direction (flow direction or width direction).

[0137] Furthermore, the adhesive sheet of the present invention is not limited to the application of bonding an insertion member to a member to be inserted, but can also be used simply to join two members together or to fill voids in an object to be adhered to. For example, it can be used when placing the adhesive sheet of the present invention in a void in an object to be adhered to and then expanding it to form a configuration in which two or more locations within the void are bonded by the adhesive sheet.

[0138] II. Goods One embodiment of the article of the present invention comprises a first adherend and a second adherend, wherein the second adherend has a void, the first adherend is placed within the void of the second adherend, and within the void, the first adherend and the second adherend are bonded together via an expanded adhesive sheet as described in section "I. Adhesive Sheet".

[0139] In the article of this embodiment, the expanded adhesive sheet described in section "I. Adhesive Sheet" above is filled between the first and second adherends within the void of the second adherend, and the first and second adherends are bonded to each other via the expanded adhesive sheet. At this time, the heat-expandable thermosetting adhesive layer in the expanded adhesive sheet hardens upon heating and exhibits adhesive strength. Furthermore, due to the expansion, the expanded heat-expandable thermosetting adhesive layer can adhere to the adherend not only on the second main surface of the adhesive sheet but also on the first main surface, allowing high adhesive strength to be maintained even in high-temperature environments. As a result, the first adherend is fixed with high positional accuracy within the void of the second adherend, and an article can be made that can maintain a strong bond between the first and second adherends even in high-temperature environments.

[0140] In the article of this embodiment, one of the first adherend and the second adherend is adhered to the first main surface of the expanded adhesive sheet, and the other is adhered to the second main surface of the expanded adhesive sheet. In particular, from the viewpoint of ease of manufacturing an article that can be easily manufactured regardless of the width or size of the gap by inserting the first adherend with the adhesive sheet attached into the gap, it is preferable that the first adherend is adhered to the first main surface of the expanded adhesive sheet and the second adherend is adhered to the second main surface of the expanded adhesive sheet.

[0141] Another embodiment of the article of the present invention has a first adherend, as well as a third adherend and a fourth adherend, with a gap between the third adherend and the fourth adherend, the first adherend being placed in the gap, and within the gap, the first adherend and the third adherend, and the first adherend and the fourth adherend, are bonded together via the expanded adhesive sheet described in section "I. Adhesive Sheet" above.

[0142] In the article of this embodiment, the expanded adhesive sheet described in section "I. Adhesive Sheet" above is filled in the gap between the third adherend and the fourth adherend, between the first adherend and the third adherend, and between the first adherend and the fourth adherend, respectively, and the first adherend and the third adherend, and the first adherend and the fourth adherend are bonded to each other via the expanded adhesive sheet. At this time, in the expanded adhesive sheet, the heat-expandable thermosetting adhesive layer hardens upon heating and exhibits adhesive strength, and further expansion allows the expanded heat-expandable thermosetting adhesive layer to adhere to the adherend not only on the second main surface of the adhesive sheet but also on the first main surface, thus maintaining high adhesive strength even in high-temperature environments. This allows the first adherend to be fixed with high positional accuracy within the gap between the third adherend and the fourth adherend, and also enables the creation of an article that can maintain a strong bond between the first adherend and the third and fourth adherends even in high-temperature environments.

[0143] In the article of this embodiment, it is preferable that the first adherend and the third and fourth adherends are bonded to the first main surface of the expanded adhesive sheet, and the third and fourth adherends are bonded to the second main surfaces of the expanded adhesive sheet, respectively. From the viewpoint of ease of manufacturing an article, in which an article can be easily manufactured regardless of the width or size of the gap by inserting the first adherend with the adhesive sheet bonded to it into the gap, it is preferable that the first adherend is bonded to the first main surface of the expanded adhesive sheet, and the third and fourth adherends are bonded to the second main surfaces of the expanded adhesive sheet, respectively.

[0144] In the article of the present invention, the "expanded adhesive sheet" is the adhesive sheet after heating and expansion, as described in section "I. Adhesive Sheet" above. Further details are omitted here, as they were explained in detail in the above section. Furthermore, the first to fourth adherends are not particularly limited and can be appropriately selected depending on the type of article.

[0145] The articles of the present invention are not particularly limited, as the type of substrate can be appropriately selected, but examples include motors used in automobiles, consumer electronics, robots, etc. This can be done. If the article of the present invention is a motor, for example, a combination in which a magnet is used as the first adherend and a rotor with slots formed thereon is used as the second adherend, or a combination in which insulating paper for insulating a stator with slots formed thereon and wires placed in the slots is used as the first adherend and the stator with slots formed thereon is used as the second adherend.

[0146] The articles of the present invention can be manufactured, for example, by the article manufacturing method described later.

[0147] 7. Method of manufacturing articles The present invention relates to a method for manufacturing an article, which involves bonding two members together via an expanded adhesive sheet as described in section "I. Adhesive Sheet" above. In particular, it relates to a method for bonding an insertion member having a void and an insertion member placed within the void via an expanded adhesive sheet as described in section "I. Adhesive Sheet" above.

[0148] One embodiment of the method for manufacturing an article of the present invention includes the steps of: [1A] bonding the first main surface of the adhesive sheet described in section "I. Adhesive Sheet" to the surface of a first adherend or a void formed in a second adherend; [2A] inserting the first adherend into the void; and [3A] heating the adhesive sheet to expand and harden the heat-expandable thermosetting adhesive layer, thereby bonding the first adherend and the second adherend via the expanded material of the adhesive sheet.

[0149] Figure 7 is a process diagram showing one example of a method for manufacturing an article according to the present invention. First, the first main surface (the surface having the adhesive portion 2) of the adhesive sheet 10 described in section "I. Adhesive Sheet" above is bonded to both sides of the first adherend 51 (Figure 7(a), step [1A]). Next, the first adherend 51 with the adhesive sheet 10 bonded to it is inserted into the void S formed in the second adherend 52 (Figure 7(b), step [2A]). Subsequently, the adhesive sheet 10 is heated to expand and harden the heat-expandable thermosetting adhesive layer (reference numeral 1 in Figure 7(c)), and the second main surface (the surface opposite to the surface having the adhesive portion 2) of the expanded adhesive sheet 10' is bonded to the second adherend 52 (Figure 7(c), step [3A]). At this time, the expanded thermally expandable thermosetting adhesive layer (reference numeral 1' in Figure 7(c)) fills the void S, and the side of the expanded thermally expandable thermosetting adhesive layer opposite to the side that adhered to the first adherend 51 adheres to the second adherend 52. As a result, an article 50 is obtained in which the first adherend 51 and the second adherend 52 are adhered to each other via the expanded adhesive sheet 10'.

[0150] Another embodiment of the method for manufacturing an article of the present invention includes the steps of: [1B] bonding the first main surface of the adhesive sheet described in section "I. Adhesive Sheet" to the surface of the first adherend or the surface of the gap formed by the third adherend and the fourth adherend; [2B] inserting the first adherend into the gap; and [3B] heating the adhesive sheet to expand and harden the heat-expandable thermosetting adhesive layer, thereby bonding the first adherend to the third adherend and the fourth adherend via the expanded material of the adhesive sheet.

[0151] Figure 8 is a process diagram showing another example of the method for manufacturing an article according to the present invention. First, the first main surface (the side having the adhesive portion 2) of the adhesive sheet 10 described in section "I. Adhesive Sheet" above is bonded to both sides of the first adherend 51 (Figure 8(a), step [1B]). Next, the first adherend 51 with the adhesive sheet 10 bonded to it is inserted into the gap S between the third adherend 53 and the fourth adherend 54 (Figure 8(b), step [2B]). Subsequently, the adhesive sheet 10 is heated to expand and harden the heat-expandable thermosetting adhesive layer (reference numeral 1 in Figure 8(c)), and the second main surface (the side opposite to the side having the adhesive portion 2) of the expanded adhesive sheet 10' is bonded to the third adherend 53 and the fourth adherend 54 (Figure 8(c), step [3B]). At this time, the expanded thermally expandable thermosetting adhesive layer (reference numeral 1' in Figure 8(c)) fills the void S, and the surface of the expanded thermally expandable thermosetting adhesive layer (reference numeral 1' in Figure 8(c)) adheres to the third adherend 53 and the fourth adherend 54. As a result, an article 50 is obtained in which one surface of the first adherend 51 is adhered to the third adherend 53, and the other surface of the first adherend 51 is adhered to the fourth adherend 54, each via the expanded adhesive sheet 10'.

[0152] The first adherend corresponds to an insertion member. The second adherend, which has a void formed in it, and the set of the third and fourth adherends that constitute the void, also correspond to an insertion member. The void in the second adherend can be, for example, a hole, groove, or opening formed in the adherend. The void between the third and fourth adherends can be, for example, a space between the third and fourth adherends when they are spaced apart, or a hole, groove, or opening formed between the third and fourth adherends.

[0153] In steps [1A] and [1B], the first main surface of the adhesive sheet is bonded to the surface of one of the adherends that will be the insertion member or the member to be inserted. In Figures 7 and 8, the first main surface of the adhesive sheet is bonded to both sides (two opposing surfaces) of the first adherend in steps [1A] and [1B], but the first main surface of the adhesive sheet may be bonded to at least one surface of the first adherend, or to three or more surfaces.

[0154] Furthermore, in steps [1A] and [1B], the first main surface of the adhesive sheet may be bonded to the first adherend, or in the case of step [1A], the first main surface of the adhesive sheet may be bonded to the surface of the void formed in the second adherend, while in the case of step [1B], it may be bonded to the surface of the void formed by the third adherend and the fourth adherend. In this case, the first main surface of the adhesive sheet may be bonded to one of the surfaces of the void, or the first main surface of the adhesive sheet may be bonded to two or more surfaces.

[0155] When the first main surface of an adhesive sheet is bonded to two or more surfaces of an object, a single adhesive sheet may be continuously bonded to multiple surfaces of the object, or an adhesive sheet may be bonded to each surface of the object individually. For example, when bonding an adhesive sheet to a first object, the first main surfaces of separate adhesive sheets may be bonded to two opposing surfaces of the first object, sandwiching the first object between the two adhesive sheets, or a single adhesive sheet may be bonded to cover multiple surfaces of the first object. Similarly, when bonding an adhesive sheet to a void formed in a second object or to the surface of a void formed by a third object and a fourth object (the surface of the object), the first main surfaces of separate adhesive sheets may be bonded to two opposing surfaces of the void, or a single adhesive sheet may be bonded to cover multiple surfaces of the void.

[0156] The conditions for bonding the first main surface of the adhesive sheet to the surface of the adherend are not particularly limited, but bonding is preferably done in the range of room temperature (23°C) to 40°C, and more preferably at room temperature (23°C). Bonding at room temperature (23°C) is preferable because it allows for easy bonding using the initial adhesiveness of the first main surface of the adhesive sheet, and also suppresses an increase in the initial adhesive strength of the second main surface of the adhesive sheet, thereby maintaining insertability.

[0157] In step [2A], the first adherend is inserted into the void formed in the second adherend. In step [2B], the first adherend is inserted into the void between the third adherend and the fourth adherend. In steps [2A] and [2B], since the second main surface of the adhesive sheet bonded to the adherend is located on the outermost surface, when the adhesive sheet is bonded to the first adherend, the adhesive sheet is less likely to adhere to the void surface, making insertion easy. Even if it does adhere, the force received during insertion makes it difficult for the adhesive sheet to peel off, thus maintaining temporary fixation and improving insertability. Similarly, when the adhesive sheet is bonded to the void surface, the adhesive sheet is less likely to adhere to the first adherend, making insertion easy. Even if it does adhere, the force received during insertion makes it difficult for the adhesive sheet to peel off, thus maintaining temporary fixation and improving insertability.

[0158] In steps [3A] and [3B], with the first adherend inserted into the void, the adhesive sheet is heated to expand and cure the heat-expandable thermosetting adhesive layer. Heating may be performed directly on the heat-expandable thermosetting adhesive layer of the adhesive sheet, or on the entire sheet including the adherend. The heating method may be non-contact or contact type, and may include hot air heating, heating by contact with an electric heater, heating by light irradiation such as an infrared heater or halogen heater, dielectric heating, induction heating, etc.

[0159] The heating temperature in steps [3A] and [3B] can be set to a temperature at which the thermally expandable thermosetting adhesive layer can expand and harden. Preferably, the temperature is one that corresponds to the hardening temperature of the thermally expandable thermosetting adhesive layer and the expansion temperature (expansion start temperature) of the expander, and preferably is higher than or equal to the expansion temperature of the expander. Specifically, it is preferably 80°C to 350°C, more preferably 100°C to 250°C, and even more preferably 150°C to 200°C.

[0160] Furthermore, the heating time in steps [3A] and [3B] can be set to a time that allows the thermally expandable thermosetting adhesive layer to expand and harden, and is preferably longer than the expansion time. Specifically, it is preferably 5 to 300 minutes, more preferably 10 to 200 minutes, and even more preferably 20 to 100 minutes. By setting the above heating time, thermal damage to the adherend can be suppressed and a strong bond between the members can be suitably achieved.

[0161] In steps [3A] and [3B], the void is filled by the expansion of the adhesive sheet due to heating, and in the case of step [3A], the first adherend and the second adherend are bonded together via the expanded adhesive sheet, while in the case of step [3B], the first adherend is bonded together with the third adherend and the fourth adherend. Within the void, the adhesive sheet expands due to heating, allowing the second main surface of the adhesive sheet to come into contact with the adherend that does not have the adhesive sheet. At this time, the expanded material of the heat-expandable thermosetting adhesive layer constituting the first and second main surfaces of the adhesive sheet exhibits adhesive strength through heat curing, thus enabling strong adhesion between the first adherend, which is the insertion member, and the second adherend, or the third and fourth adherends, which are the insertion members. Furthermore, since the expanded material of the heat-expandable thermosetting adhesive layer is a thermosetting material with high heat resistance, it is possible to maintain high adhesive strength in high-temperature environments.

[0162] The articles obtained by the article manufacturing method of the present invention are not particularly limited, but examples include motors used in hybrid automobiles and the like. Specifically, such motors can be manufactured by first bonding a first main surface of an adhesive sheet to a part of a component such as a magnet, inserting and placing the component to which the adhesive sheet is bonded into a void in a core member constituting the motor, and then heating the adhesive sheet to expand and harden the heat-expandable thermosetting adhesive layer. Therefore, the article manufacturing method of the present invention is useful as a method for manufacturing motors.

[0163] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0164] The present invention will be specifically described below with reference to examples.

[0165] (Preparation Example 1) <Preparation of a thermally expandable thermosetting adhesive composition (a-1)> 35 parts by mass of epoxy resin 1 (BPA type, epoxy equivalent 8,000 g / eq., solid (25°C), softening point 200°C or higher), 7 parts by mass of epoxy resin 2 (modified BPA type, epoxy equivalent 400 g / eq., 1,400,000 mPa·s (25°C)), 58 parts by mass of epoxy resin 3 (dicyclopentadiene type, epoxy equivalent 280 g / eq., solid (25°C), softening point 100°C), and curing agent 1 (di A thermo-expandable thermosetting adhesive composition (a-1) was prepared by dissolving 3.8 parts by mass of cyanidiamide (solid), 3 parts by mass of curing agent 2 (2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct (solid)), and 1 part by mass of expanding agent 1 (thermal expansion capsule, expansion start temperature 125°C, solid) in 60 parts by mass of methyl ethyl ketone.

[0166] (Preparation Example 2) <Preparation of a thermally expandable thermosetting adhesive composition (a-2)> A thermo-expandable thermosetting adhesive composition (a-2) was prepared in the same manner as in Preparation Example 1, except that epoxy resin 4 (BPA type, epoxy equivalent 188 g / eq., 11,000 mPa·s (25℃)) was used in place of epoxy resin 2 (7 parts by mass), epoxy resin 5 (modified novolac type, epoxy equivalent 160 g / eq., semi-solid (25℃)) was used in place of epoxy resin 3 (58 parts by mass), and the amount of curing agent 1 used was changed from 3.8 parts by mass to 6.7 parts by mass.

[0167] (Preparation Example 3) <Preparation of a thermally expandable thermosetting adhesive composition (a-3)> A thermo-expandable thermosetting adhesive composition (a-3) was prepared in the same manner as in Preparation Example 1, except that the amount of epoxy resin 1 used was changed from 35 parts by mass to 25 parts by mass, the amount of epoxy resin 2 used was changed from 7 parts by mass to 17 parts by mass, and the amount of curing agent 1 used was changed from 3.8 parts by mass to 4.1 parts by mass.

[0168] (Preparation Example 4) <Adjustment of adhesive (b-1)> An acrylic polymer with a weight-average molecular weight of 500,000 was obtained by solution polymerization of 97.98 parts by mass of n-butyl acrylate, 2 parts by mass of acrylic acid, and 0.02 parts by mass of 4-hydroxybutyl acrylate in an ethyl acetate solution at 90°C for 6 hours, with 0.3 parts by mass of azobisisobutyronitrile as a polymerization initiator.

[0169] To 100 parts by mass of the above acrylic polymer, 5 parts by mass of "D-135" (manufactured by Arakawa Chemical Industries, Ltd., polymerized rosin ester), 20 parts by mass of "KE-100" (manufactured by Arakawa Chemical Industries, Ltd., disproportionate rosin ester), and 25 parts by mass of "FTR6100" (manufactured by Mitsui Chemicals, Inc., petroleum resin) were mixed, and ethyl acetate was added to obtain an adhesive solution adjusted to a solid content of 40% by mass.

[0170] The above adhesive solution was mixed with 1.2 parts by mass of "NC40" (manufactured by DIC Corporation, an isocyanate-based crosslinking agent) and stirred to obtain adhesive (b-1).

[0171] The peak temperature of tanδ of the adhesive layer obtained using the above adhesive (b-1) was 0°C, and its gel fraction was 20% by mass.

[0172] (Example 1) The heat-expandable thermosetting adhesive composition (a-1) obtained in the above adjustment example 1 was applied to the surface of a release liner (a polyethylene terephthalate film with a thickness of 50 μm on one side, which had been peeled off with a silicone compound) using a rod-shaped metal applicator so that the thickness after drying would be 62 μm. The coated material was then placed in an 85°C dryer for 5 minutes to dry, thereby obtaining a sheet in which a 62 μm thick sheet-like heat-expandable thermosetting adhesive layer (A-1) was formed on one side of the release liner. Two such sheets were prepared.

[0173] Of the two sheets obtained above, a 25 μm thick polyimide film was placed on the surface of the heat-expandable thermosetting adhesive layer (A-1) of one of the sheets, and bonded with a linear pressure of 3 N / mm using a laminator preheated to 50°C, thereby laminating the polyimide film onto one side of the thermosetting expandable adhesive layer (A-1). Next, the heat-expandable thermosetting adhesive layer (A-1) of the other sheet was placed on the polyimide film side of the laminate, and bonded with a laminator preheated to 50°C at a linear pressure of 3 N / mm, thereby obtaining an adhesive sheet (x-1) with a thickness of 149 μm (excluding the thickness of the release liner; the same applies hereafter) in which the heat-expandable thermosetting adhesive layer (A-1) was laminated on both sides of the polyimide film.

[0174] Next, the adhesive (b-1) is dot-printed onto the surface of a release liner (a 25 μm thick polyethylene terephthalate film with one side treated with a silicone compound) using a gravure coater, and dried at 85°C for 2 minutes, resulting in a thickness of 3 μm and an area of ​​0.5 mm per dot. 2 Multiple approximately circular, island-shaped adhesive portions (B-1) were formed. The shortest distance between any adhesive portion (b1) selected from two or more adhesive portions (B-1) and an adhesive portion (b2) adjacent to the above adhesive portion (b1) was 0.2 mm.

[0175] Next, the release liner was peeled off one side of the adhesive sheet (x-1), and the heat-expandable thermosetting adhesive layer (A-1) and the adhesive portion (B-1) of the adhesive sheet (x-1) were placed on top of each other and bonded together in a laminator at 23°C with a linear pressure of 3 N / mm to obtain adhesive sheet (X-1).

[0176] The total thickness of the adhesive sheet (X-1) was 152 μm, and the adhesive portion (B-1) was laminated on one surface of the heat-expandable thermosetting adhesive layer (A-1). That is, as illustrated in Figure 1(a), in the thickness direction of the adhesive sheet (X-1), the first surface of the adhesive portion (B-1) was located outside the first main surface of one of the heat-expandable thermosetting adhesive layers (A-1), and the second surface of the adhesive portion (B-1) was in contact with the first main surface of one of the heat-expandable thermosetting adhesive layers (A-1). The ratio of the total area of ​​the adhesive portion (B-1) to the area of ​​the first main surface of the adhesive sheet (X-1) was 60%.

[0177] Furthermore, as illustrated in Figure 2(a), in the adhesive sheet (X-1) heated at 150°C for 60 minutes, the first surface of the adhesive portion (B-1) was in the same position as the first main surface of one of the thermally expandable thermosetting adhesive layers (A-1) in the thickness direction, and the second surface of the adhesive portion (B-1) was located between the first and second main surfaces of one of the thermally expandable thermosetting adhesive layers (A-1). After curing (expansion), the thermally expandable thermosetting adhesive layer (A-1) in the adhesive sheet (X-1) heated at 150°C for 60 minutes had an expansion coefficient of 390% and a glass transition temperature of 157°C. The expansion coefficient and glass transition temperature were measured by the method described in the "I. Adhesive Sheet" section above. The same method was used in the following examples and comparative examples.

[0178] (Example 2) An adhesive sheet (X-2) was obtained in the same manner as in Example 1, except that the thermally expandable thermosetting adhesive layer (A-1) of the adhesive sheet (x-1) and the adhesive portion (B-1) were overlapped and the lamination temperature during application was changed from 23°C to 50°C. The shortest distance between any adhesive portion (b1) selected from two or more adhesive portions (B-1) and the adhesive portion (b2) adjacent to the adhesive portion (b1) was 0.2 mm.

[0179] The total thickness of the adhesive sheet (X-2) was 149 μm, and the adhesive portion (B-1) was embedded in one surface of the heat-expandable thermosetting adhesive layer (A-1). That is, as illustrated in Figure 3, in the thickness direction of the adhesive sheet (X-2), the first surface of the adhesive portion (B-1) was in the same position as the first main surface of one of the heat-expandable thermosetting adhesive layers (A-1), and the second surface of the adhesive portion (B-1) was located between the first and second main surfaces of one of the heat-expandable thermosetting adhesive layers (A-1). The ratio of the total area of ​​the adhesive portion (B-1) to the area of ​​the first main surface of the adhesive sheet (X-2) was 60%.

[0180] Furthermore, as illustrated in Figure 2(a), in the adhesive sheet (X-2) after heating at 150°C for 60 minutes, the first surface of the adhesive portion (B-1) was in the same position as the first main surface of one of the thermally expandable thermosetting adhesive layers (A-1) in the thickness direction, and the second surface of the adhesive portion (B-1) was located between the first and second main surfaces of one of the thermally expandable thermosetting adhesive layers (A-1). After curing (expansion) in the adhesive sheet (X-2) after heating at 150°C for 60 minutes, the thermally expandable thermosetting adhesive layer (A-1) had an expansion coefficient of 390% and a glass transition temperature of 157°C.

[0181] (Example 3) Instead of the adhesive portion (B-1) on the release liner, a portion with a thickness of 3 μm and an area of ​​0.3 mm² per piece is used. 2An adhesive sheet (X-3) was obtained in the same manner as in Example 1, except that multiple approximately circular adhesive portions (B-2) were formed and the adhesive portions (B-2) were superimposed on one of the heat-expandable thermosetting adhesive layers (A-1) of the adhesive sheet (x-1). The shortest distance between any adhesive portion (b1) selected from the two or more adhesive portions (B-2) and the adhesive portion (b2) adjacent to the adhesive portion (b1) was 0.2 mm.

[0182] The total thickness of the adhesive sheet (X-3) was 152 μm, and the adhesive portion (B-2) was laminated on one surface of the heat-expandable thermosetting adhesive layer (A-1). That is, as illustrated in Figure 1(a), in the thickness direction of the adhesive sheet (X-3), the first surface of the adhesive portion (B-2) was located outside the first main surface of one of the heat-expandable thermosetting adhesive layers (A-1), and the second main surface of the adhesive portion (B-2) was in contact with the first main surface of one of the heat-expandable thermosetting adhesive layers (A-1). The ratio of the total area of ​​the adhesive portion (B-2) to the total area of ​​the first main surface of the adhesive sheet (X-3) was 37%.

[0183] Furthermore, as illustrated in Figure 2(a), in the adhesive sheet (X-3) after heating at 150°C for 60 minutes, the first surface of the adhesive portion (B-2) was in the same position as the first main surface of one of the thermally expandable thermosetting adhesive layers (A-1) in the thickness direction, and the second surface of the adhesive portion (B-2) was located between the first and second main surfaces of one of the thermally expandable thermosetting adhesive layers (A-1). After curing (expansion) in the adhesive sheet (X-3) after heating at 150°C for 60 minutes, the thermally expandable thermosetting adhesive layer (A-1) had an expansion coefficient of 390% and a glass transition temperature of 157°C.

[0184] (Example 4) Instead of the sheet-like heat-expandable thermosetting adhesive layer (A-1) described above, two sheets were prepared by forming a sheet-like heat-expandable thermosetting adhesive layer (A-2) with a thickness changed from 62 μm to 75 μm on one side of a release liner. The other heat-expandable thermosetting adhesive layer (A-2) was placed on the surface of one heat-expandable thermosetting adhesive layer (A-2), and the sheets were bonded at a linear pressure of 3 N / mm using a laminator preheated to 50°C, thereby obtaining an adhesive sheet (x-4) with a thickness of 150 μm by laminating the heat-expandable thermosetting adhesive layers (A-2). The adhesive sheet (X-4) was obtained in the same manner as in Example 1, except that adhesive sheet (x-4) was used instead of adhesive sheet (x-1).

[0185] The total thickness of the adhesive sheet (X-4) was 153 μm, and the adhesive portion (B-1) was laminated on one side of the heat-expandable thermosetting adhesive layer (A-2). That is, as illustrated in Figure 1(a), in the thickness direction of the adhesive sheet (X-4), the first surface of the adhesive portion (B-1) was located outside the first main surface of one of the heat-expandable thermosetting adhesive layers (A-2), and the second surface of the adhesive portion (B-1) was in contact with the first main surface of one of the heat-expandable thermosetting adhesive layers (A-2). The ratio of the total area of ​​the adhesive portion (B-1) to the area of ​​the first main surface of the adhesive sheet (X-4) was 60%.

[0186] Furthermore, as illustrated in Figure 2(a), in the adhesive sheet (X-4) after heating at 150°C for 60 minutes, the first surface of the adhesive portion (B-1) was in the same position as the first main surface of one of the thermally expandable thermosetting adhesive layers (A-2) in the thickness direction, and the second surface of the adhesive portion (B-1) was located between the first and second main surfaces of one of the thermally expandable thermosetting adhesive layers (A-2). After curing (expansion) in the adhesive sheet (X-4) after heating at 150°C for 60 minutes, the thermally expandable thermosetting adhesive layer (A-2) had an expansion coefficient of 390% and a glass transition temperature of 157°C.

[0187] (Example 5) Two sheets were prepared by using a heat-expandable thermosetting adhesive composition (a-2) instead of a heat-expandable thermosetting adhesive composition (a-1) to form a heat-expandable thermosetting adhesive layer (A-3) on one side of a release liner. An adhesive sheet (X-5) was obtained in the same manner as in Example 1, except that the heat-expandable thermosetting adhesive layer (A-3) was used on both sides of a polyimide film instead of a heat-expandable thermosetting adhesive layer (A-1).

[0188] The total thickness of the adhesive sheet (X-5) was 152 μm, and the adhesive portion (B-1) was laminated on one side of the heat-expandable thermosetting adhesive layer (A-3). That is, as illustrated in Figure 1(a), in the thickness direction of the adhesive sheet (X-5), the first surface of the adhesive portion (B-1) was located outside the first main surface of one of the heat-expandable thermosetting adhesive layers (A-3), and the second surface of the adhesive portion (B-1) was in contact with the first main surface of one of the heat-expandable thermosetting adhesive layers (A-3). The ratio of the total area of ​​the adhesive portion (B-1) to the area of ​​the first main surface of the adhesive sheet (X-5) was 60%.

[0189] Furthermore, as illustrated in Figure 2(a), in the adhesive sheet (X-5) after heating at 150°C for 60 minutes, the first surface of the adhesive portion (B-1) was in the same position as the first main surface of one of the thermally expandable thermosetting adhesive layers (A-3) in the thickness direction, and the second surface of the adhesive portion (B-1) was located between the first and second main surfaces of one of the thermally expandable thermosetting adhesive layers (A-3). After curing (expansion) in the adhesive sheet (X-5) after heating at 150°C for 60 minutes, the thermally expandable thermosetting adhesive layer (A-3) had an expansion coefficient of 415% and a glass transition temperature of 172°C.

[0190] (Example 6) An adhesive sheet (X-6) was obtained in the same manner as in Example 1, except that two sheets were prepared by forming a heat-expandable thermosetting adhesive layer (A-4) on one side of a release liner using a heat-expandable thermosetting adhesive composition (a-3) instead of a heat-expandable thermosetting adhesive composition (a-1), and then laminating the heat-expandable thermosetting adhesive layer (A-4) on both sides of a polyimide film using the heat-expandable thermosetting adhesive layer (A-4) instead of the heat-expandable thermosetting adhesive layer (A-1).

[0191] The total thickness of the adhesive sheet (X-6) was 152 μm, and the adhesive portion (B-1) was laminated on one side of the heat-expandable thermosetting adhesive layer (A-4). That is, as illustrated in Figure 1(a), in the thickness direction of the adhesive sheet (X-6), the first surface of the adhesive portion (B-1) was located outside the first main surface of one of the heat-expandable thermosetting adhesive layers (A-4), and the second surface of the adhesive portion (B-1) was in contact with the first main surface of one of the heat-expandable thermosetting adhesive layers (A-4). The ratio of the total area of ​​the adhesive portion (B-1) to the area of ​​the first main surface of the adhesive sheet (X-6) was 60%.

[0192] Furthermore, as illustrated in Figure 2(a), in the adhesive sheet (X-6) after heating at 150°C for 60 minutes, the first surface of the adhesive portion (B-1) was in the same position as the first main surface of one of the thermally expandable thermosetting adhesive layers (A-4) in the thickness direction, and the second surface of the adhesive portion (B-1) was located between the first and second main surfaces of one of the thermally expandable thermosetting adhesive layers (A-4). After curing (expansion) in the adhesive sheet (X-6) after heating at 150°C for 60 minutes, the thermally expandable thermosetting adhesive layer (A-4) had an expansion coefficient of 424% and a glass transition temperature of 145°C.

[0193] (Comparative Example 1) A sheet was obtained in which a 3 μm thick sheet-like adhesive layer (B'-1) was formed on one side of the release liner (a polyethylene terephthalate film with a thickness of 25 μm, one side of which was treated with a silicone compound) by applying the adhesive (b-1) to the entire surface using a gravure coater and then drying it at 85°C for 2 minutes. An adhesive sheet (X'-1) was obtained in the same manner as in Example 1, except that the adhesive layer (B'-1) was used instead of the adhesive portion (B-1).

[0194] The total thickness of the adhesive sheet (X'-1) was 152 μm, and the adhesive layer (B'-1) was laminated on one side of the heat-expandable thermosetting adhesive layer (A-1). Of the surfaces of the adhesive sheet (X'-1), the side with the adhesive layer (B'-1) was designated as the first main surface, and the side with the heat-expandable thermosetting adhesive layer (A-1) was designated as the second main surface.

[0195] Since the adhesive layer (B'-1) was non-patterned and provided on the entire surface of one side of the thermally expandable thermosetting adhesive layer (A-1), the ratio of the total area of ​​the adhesive layer (B'-1) to the area of ​​the first main surface of the adhesive sheet (X'-1) was 100%. Furthermore, the expansion rate and glass transition temperature of the thermally expandable thermosetting adhesive layer (A-1) after curing (expansion) in the adhesive sheet (X'-1) after heating at 150°C for 60 minutes were the same as the expansion rate and glass transition temperature of the thermally expandable thermosetting adhesive layer (A-1) in Example 1.

[0196] (Comparative Example 2) The adhesive sheet (x-1) obtained in Example 1 above was evaluated as adhesive sheet (X'-2).

[0197] The total thickness of the above adhesive sheet (X'-2) was 149 μm.

[0198] Since the above adhesive sheet (X'-2) does not have an adhesive portion, the ratio of the total area of ​​the adhesive portion to the area of ​​one side of the adhesive sheet (X'-2) was 0%. One side of the surface of the adhesive sheet (X'-2) facing the thermally expandable thermosetting adhesive layer (A-1) was designated as the first main surface, and the other side facing the thermally expandable thermosetting adhesive layer (A-1) was designated as the second main surface. After heating at 150°C for 60 minutes, the expansion rate and glass transition temperature of the thermally expandable thermosetting adhesive layer (A-1) in the adhesive sheet (X'-2) after curing (expansion) were the same as those of the thermally expandable thermosetting adhesive layer (A-1) in Example 1.

[0199] [Method for measuring the shear adhesion strength of a thermally expandable thermosetting adhesive layer before heating] Test samples were obtained by cutting the release liners, which were provided with the heat-expandable thermosetting adhesive layers (A-1) to (A-4) obtained in the above examples and comparative examples, into 10 mm x 10 mm pieces. Two smooth-surfaced aluminum plates, 15 mm wide x 70 mm long x 0.5 mm thick, were degreased, and the side of the test sample with the heat-expandable thermosetting adhesive layer was placed against the upper surface of one of the aluminum plates and pressed down at 23°C using a 2 kg hand roller.

[0200] Next, the release liner was peeled off the test sample that had been pressed onto the aluminum plate, and another aluminum plate with a degreased, smooth surface was placed on top of the test sample. The two plates were then pressed together under a load of 0.5 MPa for 10 seconds at 23°C. After being left in a 23°C environment for 30 minutes, the ends of the two aluminum plates were chucked, and the shear adhesive strength was measured when a tensile test was performed at 10 mm / min in a 180-degree direction using a Tensilon tensile testing machine [A&D Co., Ltd., model: RTM-100].

[0201] [Method for measuring the shear adhesive strength of the adhesive portion] The release liners with adhesive portions (B-1) to (B-2) formed in the above examples and comparative examples were cut into 10mm x 10mm pieces and used as test samples. Two smooth-surfaced aluminum plates measuring 15mm wide x 70mm long x 0.5mm thick were degreased, and the adhesive side of the test sample was placed on the upper surface of one of the aluminum plates and pressed down at 23°C using a 2kg hand roller.

[0202] Next, the release liner was peeled off the test sample that had been pressed onto the aluminum plate, and another aluminum plate with a degreased, smooth surface was placed on top of the test sample. The two plates were then pressed together under a load of 0.5 MPa for 10 seconds at 23°C. After being left in a 23°C environment for 30 minutes, the ends of the two aluminum plates were chucked, and the shear adhesive strength was measured when a tensile test was performed at 10 mm / min in a 180-degree direction using a Tensilon tensile testing machine [A&D Co., Ltd., model: RTM-100].

[0203] [Measurement of shear adhesion strength of one and two surfaces of the adhesive sheet before heating] The adhesive sheets from the above examples and comparative examples were cut to a size of 10 mm x 10 mm to serve as test samples. Two smooth-surfaced aluminum plates measuring 15 mm wide x 70 mm long x 0.5 mm thick were degreased. A two-component room-temperature curing acrylic adhesive (Metal Lock, manufactured by Cemedyne Co., Ltd.) was applied to the top surface of one of the aluminum plates as a strong adhesive for fixing the test sample. The release liner on the second main surface side of the test sample was peeled off, and the second main surface of the test sample was placed on the first aluminum plate via the strong adhesive. The sample was then pressed together at 23°C using a 2 kg hand roller. Next, the release liner on the first main surface side of the test sample pressed onto the aluminum plate was peeled off, and the other aluminum plate, which had a degreased smooth surface, was placed on top of the test sample. The sample was then pressed together at 23°C for 10 seconds with a load of 0.5 MPa. The two aluminum plates were left in a 23°C environment for 5 minutes, and their ends were chucked. A Tensilon tensile testing machine [A&D Co., Ltd., model: RTM-100] was used to measure the shear adhesive strength when a tensile test was performed at 10 mm / min in a 180-degree direction. This adhesive strength was defined as the shear adhesive strength of the first main surface of the adhesive sheet.

[0204] Furthermore, the shear adhesive strength was measured in the same manner as described above, except that the first main surface of the test sample from which the release liner had been removed was pressed against one aluminum plate via the strong adhesive, and the other aluminum plate was pressed against the second main surface of the test sample. At this time, the adhesive strength was defined as the shear adhesive strength of the second main surface of the adhesive sheet.

[0205] [Method for evaluating the temporary fixation of adhesive sheets to a component] The adhesive sheets (X-1) to (X-6) and (X'-1) to (X'-2) obtained in the above examples and comparative examples were cut to a size of 15 mm x 15 mm and used as test samples. Next, the release liner on the first main surface (the side with the adhesive part or adhesive layer) of the test sample was peeled off, and it was placed in the center of a degreased, smooth SUS plate measuring 40 mm wide x 50 mm long x 3 mm thick. The test sample was then fixed by applying pressure at 0.5 MPa for 10 seconds at 23°C. For the adhesive sheet (X'-2) prepared in Comparative Example 2, the release liner on one main surface was peeled off and it was pressed onto the SUS plate to fix it in place.

[0206] Subsequently, the SUS plate was placed upright at a 90°C angle to the floor at 23°C. The SUS plate was then lifted so that the test sample attached to it was 15 cm above the floor, and then dropped vertically. This was repeated 10 times. After that, the amount of displacement of the fixed test sample due to the drop was measured, and the temporary fixation to the material was evaluated according to the following criteria. (judgment criteria) ◎: The displacement of the test sample was 0 mm. ○: The displacement of the test sample was less than 1 mm. △: The displacement of the test sample was 1 mm or more. ×: The test sample peeled off the SUS plate.

[0207] [Method for evaluating the insertability of adhesive sheets into materials] The adhesive sheets (X-1) to (X-6) and (X'-1) to (X'-2) obtained in the above examples and comparative examples were each cut to a size of 15 mm x 15 mm. Next, the release liner on the first main surface (the side with the adhesive part or adhesive layer) of the adhesive sheet was peeled off, and it was placed in the center of a degreased, smooth SUS plate measuring 30 mm wide x 30 mm long x 1 mm thick. The adhesive sheet was then pressed down with a load of 0.5 MPa for 10 seconds at 23°C to fix it in place. For the adhesive sheet (X'-2) prepared in Comparative Example 2, the release liner on one main surface was peeled off and it was pressed down onto the SUS plate to fix it in place. After that, the other release liner of the adhesive sheet was removed and used as the test sample.

[0208] Next, two smooth glass plates measuring 70 mm wide x 50 mm long x 1.5 mm thick were prepared. Two spacers measuring 5 mm wide x 50 mm long were placed parallel to one of the glass plates (C1) with a 60 mm gap between them and glued in place. Then, the other glass plate (C2) was placed on top of the spacers and glued to them, thereby creating a gap consisting of the two glass plates and the two spacers.

[0209] Subsequently, the test sample was placed upright at a 90° angle to the floor and inserted perpendicularly into the gap consisting of two glass plates and two spacers. The thickness of the spacers through which the test sample could pass without adhering to the glass was measured, and the insertability of the test sample into the component was evaluated according to the following criteria. (judgment criteria) ◎: The test sample was able to pass through even when the spacer thickness was increased by 50 μm relative to the total thickness of the adhesive sheet and SUS plate. ○: The test sample could not pass through when the spacer thickness was increased by 50 μm relative to the total thickness of the adhesive sheet and SUS plate, but it could pass through when the thickness was increased by 75 μm. △: The test sample could not pass through when the spacer thickness was increased by 75 μm relative to the total thickness of the adhesive sheet and SUS plate, but it could pass through when the thickness was increased by 100 μm. ×: The test sample could not pass through even when the spacer thickness was increased by 100 μm relative to the total thickness of the adhesive sheet and the SUS plate, or the adhesive sheet peeled off from the SUS plate when it was passed through.

[0210] [Method for measuring the shear adhesive strength of adhesive sheets after heating (expansion)] Two smooth-surfaced aluminum plates 51 and 52, measuring 15 mm wide x 70 mm long x 0.5 mm thick, were degreased. As shown in Figure 9, two 5 mm wide spacers 53 were attached to the edge of the upper surface of one of the aluminum plates 51, parallel to each other with a 12 mm gap between them. The spacers 53 were prepared so that the total thickness of the spacers 53 and the adhesive tape used for bonding was 150 μm thicker than the total thickness of the adhesive sheet. Next, adhesive sheets (X-1) to (X-6) and (X'-1) to (X'-2) (reference numeral 10 in Figure 9), which had been pre-cut to a size of 10 mm x 10 mm, were attached to the upper surface of the aluminum plate 51 and between the two spacers 53, after peeling off the release liner from the first main surface (the side with the adhesive portion or adhesive layer) of the adhesive sheet, and then pressed down using a 2 kg hand roller. For the adhesive sheet (X'-2) prepared in Comparative Example 2 above, the release liner was peeled off one of the main surfaces and applied, and then pressed down using a 2kg hand roller.

[0211] Next, the release liner on the second main surface (thermally expandable thermosetting adhesive layer) side of the adhesive sheet 10 was peeled off, and another aluminum plate 52 (width 15 mm × length 70 mm × thickness 0.5 mm) with a degreased smooth surface was placed on the second main surface (upper surface of the thermally expandable thermosetting adhesive layer) of the adhesive sheet 10, and these were fixed together with clips. For the adhesive sheet (X'-2) prepared in Comparative Example 2, the release liner on the other main surface side was peeled off and placed on the other aluminum plate 52. The fixed assembly was heated at 150°C for 60 minutes, and then left to cool in a 23°C environment for 30 minutes. Next, the clips mentioned above were removed to form the test samples. The ends of the two aluminum plates 51 and 52 were chucked, and the shear adhesive strength was measured using a Tensilon tensile testing machine [manufactured by A&D Co., Ltd., model: RTM-100] at 23°C and 150°C at a 180-degree direction at 10 mm / min.

[0212] The evaluation results for each category are shown in the table below.

[0213] [Table 1]

[0214] [Table 2]

[0215] The adhesive sheets of Examples 1 to 6 exhibited good temporary fixation and insertability before expansion, and high adhesive strength at room temperature and high temperature after expansion. On the other hand, in Comparative Example 1, where the adhesive portion was not provided in a patterned manner on the first main surface of the adhesive sheet (the adhesive layer was provided on the entire surface of one side of the heat-expandable thermosetting adhesive layer), the temporary fixation and insertability before expansion were good, but the adhesive strength at room temperature and high temperature after expansion was lower than that of the adhesive sheets of the Examples, suggesting particularly poor high-temperature adhesion. Furthermore, in Comparative Example 2, where the adhesive portion was not provided on the surface of the heat-expandable thermosetting adhesive layer on the first main surface of the adhesive sheet, the adhesive strength at room temperature and high temperature after expansion was as high as that of the adhesive sheets of the Examples, but temporary fixation before expansion was not achieved. In addition, in the evaluation of insertability, the adhesive sheet peeled off when the test sample was passed through, hindering the insertion of the test sample, and thus insertability was not achieved. [Explanation of symbols]

[0216] 1, 1A, 1B … Thermally expandable thermosetting adhesive layer 1' ... Thermally expandable thermosetting adhesive layer after expansion (expanded material of the thermally expandable thermosetting adhesive layer) 2 … Adhesive part 3… Middle class 10… Adhesive sheet 10' ... Adhesive sheet after expansion (expanded adhesive sheet) Z-Z' ... thickness direction of the adhesive sheet a1, a11, a12... First main surface of the thermally expandable thermosetting adhesive layer a2, a21, a22... Second main surface of the thermally expandable thermosetting adhesive layer b1 ... First surface of the adhesive part b2 ... Second side of the adhesive part 50 … Goods

Claims

1. An adhesive sheet having opposing first main surface and second main surface, The first main surface of the adhesive sheet is composed of a heat-expandable thermosetting adhesive layer and a plurality of adhesive portions arranged in a pattern on the first main surface of the heat-expandable thermosetting adhesive layer. The second main surface of the adhesive sheet is composed of the thermally expandable thermosetting adhesive layer that constitutes the first main surface of the adhesive sheet or another thermally expandable thermosetting adhesive layer. The shortest distance between adhesive portions in the plurality of adhesive portions arranged in a pattern on the first main surface is 0.05 to 0.6 mm. The aforementioned heat-expandable thermosetting adhesive layer contains a solid epoxy resin and a liquid epoxy resin as resin components. The content of the solid epoxy resin is 70% by mass or more and 95% by mass or less of the total resin components of the heat-expandable thermosetting adhesive layer. The content of the liquid epoxy resin is 5% by mass or more and 10% by mass or less of the total resin components of the heat-expandable thermosetting adhesive layer. The aforementioned heat-expandable thermosetting adhesive layer further contains a curing agent and an expanding agent, The curing agent has a ratio of functional group equivalents that can react with epoxy groups contained in the curing agent to the total epoxy equivalents contained in the thermally expandable thermosetting adhesive layer of 0.7 or more and 1.0 or less. The amount of the expanding agent is 0.5 to 25 parts by mass per 100 parts by mass of the total resin components of the heat-expandable thermosetting adhesive layer. The adhesive portion is an adhesive sheet whose main component is at least one selected from the group consisting of acrylic resin, rubber resin, polyurethane resin, polyester resin, and silicone resin.

2. The adhesive sheet according to claim 1, wherein the shear adhesive strength of the first main surface of the adhesive sheet is higher than the shear adhesive strength of the second main surface.

3. The adhesive portion has a first surface and a second surface on the opposite side. Before expansion, in the thickness direction of the adhesive sheet, the first surface of the adhesive portion is located outside the first main surface of the heat-expandable thermosetting adhesive layer on which the adhesive portion is provided, and the second surface of the adhesive portion is in contact with the first main surface of the heat-expandable thermosetting adhesive layer on which the adhesive portion is provided, or is located between the first main surface of the heat-expandable thermosetting adhesive layer and the second main surface on the opposite side thereof. The adhesive sheet according to claim 1 or 2, wherein, after expansion, in the thickness direction of the adhesive sheet, the first surface of the adhesive portion is located at the same position as the first main surface of the expanded thermal expandable thermosetting adhesive layer on which the adhesive portion is provided, or between the first main surface and the second main surface on the opposite side thereof, and the second surface of the adhesive portion is located between the first main surface and the second main surface on the opposite side thereof of the expanded thermal expandable thermosetting adhesive layer on which the adhesive portion is provided.

4. An adhesive sheet according to any one of claims 1 to 3, wherein the total thickness is 10 μm or more and 600 μm or less, and in a plan view, the ratio of the total area of ​​the plurality of adhesive parts to the first main surface of the adhesive sheet before expansion is 20% or more and 80% or less, and the shear adhesive strength of the first main surface of the adhesive sheet before expansion is 0.2 MPa or more.

5. The adhesive sheet according to any one of claims 1 to 4, wherein the total thickness is 10 μm or more and 600 μm or less, and the shear adhesive strength of the second main surface of the adhesive sheet before expansion is less than 0.5 MPa.

6. The adhesive sheet according to any one of claims 1 to 5, wherein, in a plan view, the ratio of the total area of ​​the plurality of adhesive portions to the first main surface of the adhesive sheet before expansion is 20% or more and 80% or less.

7. The adhesive sheet according to any one of claims 1 to 6, wherein the gel fraction of the adhesive portion is 60% by mass or less.

8. The adhesive sheet according to any one of claims 1 to 7, wherein the plan view shape of the adhesive portion is substantially circular, substantially square, or substantially hexagonal.

9. The adhesive sheet according to any one of claims 1 to 8, wherein the heat-expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet contains a liquid thermosetting resin having a viscosity of 3 million mPa·sec or less at 25°C in an amount of 20% by mass or less of the total resin components of the heat-expandable thermosetting adhesive layer.

10. The adhesive sheet according to any one of claims 1 to 9, wherein the glass transition temperature after expansion of the thermally expandable thermosetting adhesive layer constituting the second main surface of the adhesive sheet is 80°C or higher.

11. It has a first adherend and a second adherend, The second adherend has a void formed therein. The first adherend is placed within the gap of the second adherend, An article in which, within the aforementioned void, the first adherend and the second adherend are bonded together via an expanded adhesive sheet according to any one of claims 1 to 10.

12. It has a first adherend, a third adherend, and a fourth adherend, There is a gap between the third adherend and the fourth adherend. The first object to be adhered to is placed within the gap, An article in which, within the aforementioned void, the first adherend and the third adherend, and the first adherend and the fourth adherend, are each bonded together via an expanded adhesive sheet according to any one of claims 1 to 10.

13. Step [1A] of bonding the first main surface of the adhesive sheet according to any one of claims 1 to 10 to the surface of the first adherend or the surface of a void formed in the second adherend, Step [2A] of inserting the first object to be attached into the gap, A method for manufacturing an article, comprising the step [3A] of heating the adhesive sheet to expand and harden the heat-expandable thermosetting adhesive layer, thereby bonding the first adherend and the second adherend via the expanded material of the adhesive sheet.

14. Step [1B] of bonding the first main surface of the adhesive sheet according to any one of claims 1 to 10 to the surface of the first adherend or the surface of the gap formed by the third adherend and the fourth adherend, The first adherend is inserted into the aforementioned void [2B], A method for manufacturing an article, comprising the step [3B] of heating the adhesive sheet to expand and harden the heat-expandable thermosetting adhesive layer, thereby bonding the first adherend, the third adherend, and the fourth adherend via the expanded material of the adhesive sheet.

Images