Article, manufacturing method of article, foamable adhesive sheet and adhesive composition

Abstract

To provide an article excellent in adhesive properties, a manufacturing method of an article capable of improving adhesive properties, a foamable adhesive sheet and an adhesive composition.SOLUTION: An article 100 includes: a first member 20a; a second member 20b; and an adhesive member 30 disposed between the first member and the second member. The adhesive member at least includes a curing adhesion layer 11. The curing adhesion layer is a foam layer 15 including a formed cured product of an adhesive composition including a curable adhesive agent and a gas generating agent. The curable adhesive agent is a thermo-setting adhesive agent. The gas generating agent is heat-expandable microcapsules. In a cross section parallel to a thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is a value -6 μm the thickness of the foam layer, or more is less than 7 pieces per a length 4 mm in a direction vertical to the thickness direction of the foam layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an article and a method for producing the same, as well as a foamable adhesive sheet and adhesive composition used therein. [Background technology]

[0002] Adhesives for bonding members together are used in a variety of fields, and many bonding methods are known.

[0003] For example, Patent Documents 1 to 3 disclose adhesive sheets containing a foaming agent (foamable adhesive sheets). A method of using a foamable adhesive sheet is known in which the foamable adhesive sheet is placed between components, and then the foamable adhesive sheet is heated to foam and harden, thereby bonding the components together.

[0004] In such a foamable adhesive sheet, it is desirable that the adhesiveness after foaming and curing is good. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-53944 A [Patent Document 2] Patent No. 6223477 [Patent Document 3] JP 2019-214729 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide an article with excellent adhesiveness, as well as a manufacturing method for an article that can improve adhesiveness, a foamable adhesive sheet, and an adhesive composition. [Means for solving the problem]

[0007] One embodiment of the present disclosure provides an article having a first member, a second member, and an adhesive member disposed between the first member and the second member, wherein the adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a blowing agent, the curable adhesive is a thermosetting adhesive, and the blowing agent is a thermally expandable microcapsule, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0008] Another embodiment of the present disclosure provides an article having a first member, a second member, and an adhesive member disposed between the first member and the second member, wherein the adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a blowing agent, the curable adhesive is a thermosetting adhesive, and the blowing agent is a thermally expandable microcapsule, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer.

[0009] Another embodiment of the present disclosure provides a method for manufacturing an article using a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, the method comprising: a positioning step of positioning the foamable adhesive sheet between a first member and a second member; and a bonding step of foaming and curing the foaming-agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer and bonding the first member and the second member, the foaming and curing conditions in the bonding step being set such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer minus 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0010] Another embodiment of the present disclosure provides a method for manufacturing an article using a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, the method comprising: a positioning step of positioning the foamable adhesive sheet between a first member and the second member; and a bonding step of foaming and curing the foaming-agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer and bonding the first member and the second member, the foaming and curing conditions in the bonding step being set such that in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

[0011] Another embodiment of the present disclosure provides a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, the foaming agent being a thermally expandable microcapsule, and when the foamable adhesive sheet is heated at a maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the foaming-agent-containing adhesive layer to form a foam layer, the number of bubbles in a cross section parallel to the thickness direction of the foam layer whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0012] Another embodiment of the present disclosure provides a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, the foaming agent being a thermally expandable microcapsule, and when the foamable adhesive sheet is heated at a maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the foaming-agent-containing adhesive layer to form a foam layer, the foamable adhesive sheet has a cross section parallel to the thickness direction of the foam layer, in which the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

[0013] Another embodiment of the present disclosure provides an adhesive composition comprising a curable adhesive and a foaming agent, wherein the curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; when the adhesive composition is applied to one side of a support to a thickness of 45 μm and the coating of the adhesive composition is heated at a maximum foaming temperature of the foaming agent ±20° C. for 15 minutes to foam and cure the coating to form a foam layer, the number of bubbles in a cross section parallel to the thickness direction of the foam layer, the length of which in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer −6 μm, is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0014] Another embodiment of the present disclosure provides an adhesive composition comprising a curable adhesive and a foaming agent, wherein the curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; the adhesive composition is applied to one side of a support to a thickness of 45 μm, and the coating of the adhesive composition is heated at a maximum foaming temperature of the foaming agent ±20° C. for 15 minutes to foam and cure the coating to form a foam layer; and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer. Effect of the Invention

[0015] The present disclosure can provide an article with excellent adhesiveness, as well as a method for producing an article that can improve adhesiveness, a foamable adhesive sheet, and an adhesive composition. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic cross-sectional view illustrating an article according to the present disclosure. [Diagram 2] 1 is a schematic cross-sectional view illustrating an article according to the present disclosure. [Diagram 3] 1 is a schematic cross-sectional view illustrating an article according to the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating an article according to the present disclosure. [Diagram 5] 1 is a process diagram illustrating a method for manufacturing an article according to the present disclosure. [Figure 6] 1 is a process diagram illustrating a method for manufacturing an article according to the present disclosure. [Figure 7] 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet according to the present disclosure. [Figure 8] 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet according to the present disclosure. [Figure 9] 1 is a schematic cross-sectional view illustrating a foamable adhesive sheet according to the present disclosure. [Figure 10]1 is a schematic cross-sectional view illustrating a foamable adhesive sheet according to the present disclosure. [Figure 11] 1 is a graph illustrating a TMA curve for a foamable adhesive sheet. [Figure 12] FIG. 2 is a schematic cross-sectional view illustrating the state of the foamable adhesive sheet according to the present disclosure after foaming and curing. [Figure 13] FIG. 2 is a schematic cross-sectional view illustrating the state of the foamable adhesive sheet according to the present disclosure after foaming and curing. [Figure 14] FIG. 2 is a schematic cross-sectional view illustrating a method for testing the adhesiveness of a foamable adhesive sheet after foaming and curing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The following describes the embodiments of the present disclosure with reference to the drawings. However, the present disclosure can be implemented in many different forms, and is not to be construed as being limited to the description of the embodiments exemplified below. In addition, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual form in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of the present disclosure. In addition, in this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same reference numerals, and detailed explanations may be omitted as appropriate.

[0018] In this specification, when describing a mode in which another component is disposed on a certain component, the term "above" or "below" includes both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component with another component interposed therebetween, unless otherwise specified. In addition, in this specification, when describing a mode in which another component is disposed on the surface of a certain component, the term "on the surface side" or "on the surface" includes both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component with another component interposed therebetween, unless otherwise specified.

[0019] In this specification, the term "sheet" also includes members called "films." In addition, the term "films" also includes members called "sheets." In addition, the numerical ranges in this specification are average value ranges.

[0020] In the thermally expandable microcapsule, a thermal expansion agent such as hydrocarbon is encapsulated inside a shell made of resin. When the thermally expandable microcapsule is heated, the resin constituting the shell softens and the pressure of the thermal expansion agent such as hydrocarbon increases, causing the thermally expandable microcapsule to expand. Since the shell becomes thinner due to the expansion, if heating is continued, the thermal expansion agent escapes from the thermally expandable microcapsule, causing the thermally expandable microcapsule to shrink. The inventors of the present disclosure have found that the thermal expansion agent (gas) that escapes from the thermally expandable microcapsule becomes air bubbles, and these air bubbles can gather to become large air bubbles. Furthermore, the inventors of the present disclosure have also found that when a foamable adhesive sheet is attached to a first member or a second member during the manufacture of an article, air bubbles may be mixed between the first member or the second member and the foamable adhesive sheet, and these air bubbles can gather to become large air bubbles.

[0021] In addition, in the case of a thermosetting adhesive, the resin component of the thermosetting adhesive softens and becomes more fluid during the foaming and curing process of the adhesive composition. The inventors of the present disclosure have also found that when there are bubbles in a layer, when the resin component of the thermosetting adhesive softens and becomes more fluid, the bubbles become more mobile and may gather together to form larger bubbles.

[0022] Thus, the inventors of the present disclosure have found a new problem that when the curable adhesive is a thermosetting adhesive and the foaming agent is a thermally expandable microcapsule, large air bubbles may be generated, and such large air bubbles become a cause of reduced adhesiveness. The present disclosure is intended to solve such a new problem.

[0023] The article, method for producing the article, foamable adhesive sheet, and adhesive composition of the present disclosure will be described in detail below.

[0024] A.Goods The article of the present disclosure has two embodiments, each of which will be described below.

[0025] I. First embodiment of the article A first embodiment of an article in the present disclosure is an article having a first member, a second member, and an adhesive member disposed between the first member and the second member, wherein the adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, the curable adhesive is a thermosetting adhesive, the foaming agent is a thermally expandable microcapsule, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0026] FIG. 1 is a schematic cross-sectional view showing an example of an article of this embodiment. As shown in FIG. 1, the article 100 has a first member 20a, a second member 20b, and an adhesive member 30 arranged between the first member 20a and the second member 20b. The adhesive member 30 has a cured adhesive layer 11. The cured adhesive layer 11 is a foam layer 15 containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and contains air bubbles 31 inside. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule. In a cross section parallel to the thickness direction D1 of the foam layer 15 constituting the cured adhesive layer 11, the number of air bubbles whose length s in the thickness direction D1 of the foam layer 15 is within a predetermined range with respect to the thickness t of the foam layer 15 is less than a predetermined value per predetermined length L in the direction d2 perpendicular to the thickness direction d1 of the foam layer 15.

[0027] In the case where the adhesive member has one cured adhesive layer, and the cured adhesive layer is a foam layer, if there are large bubbles whose size is about the thickness of the foam layer, the cured adhesive layer is not in contact with the first member and the second member in the region where such bubbles exist, or the contact area between the cured adhesive layer and the first member and the contact area between the cured adhesive layer and the second member become very small. Therefore, it is considered that the cured adhesive layer is likely to peel off, float, crack, or other adhesion defects starting from the above bubbles.

[0028] In contrast, in the article of this embodiment, when the adhesive member has one cured adhesive layer, and the cured adhesive layer is a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is a predetermined value or less per predetermined length in the direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion, and thus improving adhesion.

[0029] FIG. 2 is a schematic cross-sectional view showing another example of the article of this embodiment. In the article of this embodiment, as shown in FIG. 2, the adhesive member 30 can have a first cured adhesive layer 11a and a second cured adhesive layer 11b. The first cured adhesive layer 11a and the second cured adhesive layer 11b are foam layers 15a and 15b containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, respectively, and contain bubbles 31 inside. In the cross section of the thickness direction D1 of the foam layer 15a constituting the first cured adhesive layer 11a, the number of bubbles 31 whose length s in the thickness direction D1 of the foam layer 15a is within a predetermined range with respect to the thickness t1 of the foam layer 15a is less than a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15a. In addition, in the cross section of the thickness direction D1 of the foam layer 15b constituting the second cured adhesive layer 11b, the number of bubbles 31 whose length s in the thickness direction D1 of the foam layer 15b is within a predetermined range with respect to the thickness t2 of the foam layer 15b is less than a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15b.

[0030] In FIG. 2, both the first cured adhesive layer 11a and the second cured adhesive layer 11b are foam layers 15a, 15b containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, but only one of the first cured adhesive layer 11a and the second cured adhesive layer 11b may be a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent.

[0031] In the case where the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and the first cured adhesive layer and the second cured adhesive layer are foam layers, if there are large bubbles whose size is about the thickness of the foam layer, the first cured adhesive layer does not contact the first member, the second cured adhesive layer does not contact the second member, or the contact area between the first cured adhesive layer and the first member becomes very small, or the contact area between the second cured adhesive layer and the second member becomes very small, in the region where such bubbles exist. Therefore, it is considered that the first cured adhesive layer and the second cured adhesive layer are likely to have poor adhesion such as peeling, lifting, and cracking starting from the above bubbles.

[0032] In contrast, in the article of this embodiment, when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and when the first cured adhesive layer and the second cured adhesive layer are foam layers, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer in a cross section parallel to the thickness direction of the foam layer is a predetermined value or less per predetermined length in a direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0033] In addition, when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, it is also possible to suppress poor adhesion and improve adhesion when either the first cured adhesive layer or the second cured adhesive layer is a foam layer.

[0034] Fig. 3 is a schematic cross-sectional view showing another example of the article of this embodiment. In the article of this embodiment, as shown in Fig. 3, the adhesive member 30 can have a first cured adhesive layer 11a, a substrate 12, and a second cured adhesive layer 11b in this order. Note that Fig. 3 is the same as Fig. 2 above, except that the substrate 12 is disposed between the first cured adhesive layer 11a and the second cured adhesive layer 11b.

[0035] In FIG. 3, both the first cured adhesive layer 11a and the second cured adhesive layer 11b are foam layers 15a, 15b containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, but only one of the first cured adhesive layer 11a and the second cured adhesive layer 11b may be a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent.

[0036] In the case where the adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer in this order, and the first cured adhesive layer and the second cured adhesive layer are foam layers, if there are large bubbles whose size is about the thickness of the foam layer, the first cured adhesive layer does not contact the first member and the substrate, the second cured adhesive layer does not contact the second member and the substrate, or the contact area between the first cured adhesive layer and the first member and the substrate becomes very small, or the contact area between the second cured adhesive layer and the second member and the substrate becomes very small. Therefore, it is considered that the above-mentioned bubbles are likely to cause adhesion defects such as peeling, lifting, and cracking of the first cured adhesive layer and the second cured adhesive layer.

[0037] In contrast, in the article of this embodiment, when the adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer in this order, and when the first cured adhesive layer and the second cured adhesive layer are foam layers, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer in a cross section parallel to the thickness direction of the foam layer is a predetermined value or less per predetermined length in a direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0038] In addition, when an adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer, it is also possible to suppress poor adhesion and improve adhesion when either the first cured adhesive layer or the second cured adhesive layer is a foam layer.

[0039] Therefore, in the article of this embodiment, the reliability and durability can be improved.

[0040] Each component of the article of this embodiment will be described below.

[0041] 1. Adhesive material The adhesive member according to the present disclosure is disposed between a first member and a second member and has at least a cured adhesive layer. The cured adhesive layer is a foam layer containing a foamed and cured product of an adhesive composition containing a curable adhesive and a foaming agent, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is equal to or less than a predetermined value per predetermined length in a direction perpendicular to the thickness direction of the foam layer.

[0042] Furthermore, the adhesive member only needs to have at least a cured adhesive layer, and may, for example, have one cured adhesive layer, or may have a first cured adhesive layer and a second cured adhesive layer, or may have a first cured adhesive layer, a substrate, and a second cured adhesive layer in that order.

[0043] When the adhesive member has a first cured adhesive layer and a second cured adhesive layer, or has a first cured adhesive layer, a substrate, and a second cured adhesive layer in this order, at least one of the first cured adhesive layer and the second cured adhesive layer is the above-mentioned foam layer.

[0044] In this specification, for convenience, the cured adhesive layer located on the first member side of the adhesive member is referred to as the first cured adhesive layer, and the cured adhesive layer located on the second member side is referred to as the second cured adhesive layer.

[0045] Each component of the adhesive member will be described below.

[0046] (1) Cured adhesive layer The cured adhesive layer in this embodiment is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is a predetermined value or less per predetermined length in a direction perpendicular to the thickness direction of the foam layer.

[0047] (a) Air bubbles The cured adhesive layer in this embodiment is a foam layer containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and has bubbles inside. In a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer minus 6 μm is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer. In particular, the number of bubbles is preferably 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0048] In addition, "cells whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer minus 6 μm" refers to cells whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer minus 6 μm. For example, when the thickness of the foam layer is 200 μm, the number of cells whose length in the thickness direction of the foam layer is equal to or greater than 200-6=194 (μm) falls within the above range. Also, for example, when the thickness of the foam layer is 00 μm, the number of cells whose length in the thickness direction of the foam layer is equal to or greater than 300-6=294 (μm) falls within the above range.

[0049] Here, the length of the bubbles in the thickness direction of the foam layer and the number of bubbles in the cross section parallel to the thickness direction of the foam layer can be obtained, for example, from an image obtained by optical microscope or scanning electron microscope (SEM) observation, or from a tomographic image obtained by X-ray CT scanning. X-ray CT scanning allows the bubbles in the cross section of the foam layer to be observed non-destructively and non-contact. Therefore, it is possible to prevent the bubbles from being crushed when the article is cut to expose the cross section of the foam layer. Therefore, the length of the bubbles in the thickness direction of the foam layer and the number of bubbles can be accurately obtained. Among them, for example, when the first member and the second member are metal members, optical microscope or scanning electron microscope (SEM) observation is preferable.

[0050] The number of bubbles in a cross section parallel to the thickness direction of the foam layer is taken as the average value of the numbers of bubbles in three randomly selected locations.

[0051] The thickness of the foam layer is the value measured from the cross section of the foamable adhesive sheet in the thickness direction observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM), and is the average value of the thicknesses at 10 randomly selected points. The same method is used for measuring the thickness of each layer.

[0052] In addition, for the article, the thickness direction of the foam layer is the direction perpendicular to the planar direction of the first member or the second member. The direction perpendicular to the thickness direction of the foam layer is the planar direction of the first member or the second member. The planar direction of the first member and the second member refers to the planar direction of the first member and the second member when viewed macroscopically.

[0053] In the foam layer, means for suppressing bubbles whose length in the thickness direction of the foam layer is within a predetermined range include, for example, a method of adjusting the composition of the adhesive composition, and a method of adjusting the foaming and curing conditions of the adhesive composition.

[0054] Methods for adjusting the composition of the adhesive composition include, for example, adjusting the fluidity of the resin component of the curable adhesive, adjusting the maximum foaming temperature of the foaming agent, adjusting the foaming ratio at the maximum foaming temperature of the foaming agent, adjusting the content of the foaming agent, and, when the foaming agent is a thermally expandable microcapsule, adjusting the structure of the thermally expandable microcapsule.

[0055] Methods for adjusting the fluidity of the resin component of the curable adhesive include, for example, adjusting the molecular weight of the resin component that is the main agent of the curable adhesive, adjusting the state of the resin component that is the main agent of the curable adhesive, and adjusting the content of the resin component that is liquid at room temperature.

[0056] In the method of adjusting the molecular weight of the resin component, which is the main component of the curable adhesive, for example, a thermosetting adhesive is used as the curable adhesive. In this case, the resin component softens and becomes more fluid during the foaming and curing process of the adhesive composition. At this time, when the molecular weight of the resin component is large, the fluidity of the resin component is low compared to when the molecular weight of the resin component is small. Therefore, the bubbles are less likely to become large and the bubbles are less likely to connect with each other, so that the generation of the above-mentioned large bubbles tends to be suppressed. Therefore, by including a high molecular weight resin component as the main component of the curable adhesive, the generation of the above-mentioned large bubbles can be suppressed.

[0057] As described above, in the case of a thermosetting adhesive, the resin component softens and becomes more fluid during the foaming and curing process of the adhesive composition. A resin component that is solid at room temperature tends to have lower fluidity than a resin component that is liquid at room temperature. Therefore, the bubbles are less likely to grow large and are less likely to connect with each other, so that the generation of large bubbles as described above tends to be suppressed. Therefore, in the method of adjusting the state of the resin component that is the main component of the curable adhesive, the resin component that is solid at room temperature is contained as the main component of the curable adhesive, so that the generation of large bubbles as described above can be suppressed. Note that room temperature refers to 23°C.

[0058] When the curable adhesive contains a resin component that is liquid at room temperature as the resin component that is the main component of the curable adhesive, the resin component tends to have high fluidity when it softens during the foaming and curing process of the adhesive composition. On the other hand, by relatively reducing the content of the resin component that is liquid at room temperature, the fluidity of the resin component can be relatively reduced. Therefore, by reducing the content of the resin component that is liquid at room temperature among the resin components that are the main component of the curable adhesive, the generation of large bubbles as described above can be suppressed.

[0059] In the method of adjusting the maximum foaming temperature of the foaming agent, a thermally expandable microcapsule is used as the foaming agent. In the thermally expandable microcapsule, a thermally expandable agent such as a hydrocarbon is encapsulated inside a shell made of a resin. Here, when the thermally expandable microcapsule is heated, the resin constituting the shell softens and the pressure of the thermally expandable agent such as a hydrocarbon increases, causing the thermally expandable microcapsule to expand. Since the shell becomes thinner due to the expansion, if heating is continued, the thermally expandable microcapsule will lose the thermally expandable agent and shrink. Therefore, for example, if the maximum foaming temperature of the foaming agent is high, the foaming agent shrinks during the foaming and curing process of the adhesive composition, and the thickness of the foam layer (cured adhesive layer) can be suppressed from becoming thin. This can suppress the size of the bubbles from becoming relatively large with respect to the thickness of the foam layer (cured adhesive layer). Therefore, the size of the bubbles can be made relatively small with respect to the thickness of the foam layer (cured adhesive layer), and the above-mentioned large bubbles can be suppressed.

[0060] In the method of adjusting the expansion ratio at the maximum expansion temperature of the foaming agent, for example, if the expansion ratio at the maximum expansion temperature of the foaming agent is large, the thickness of the foam layer (cured adhesive layer) tends to be large. Therefore, the size of the bubbles can be made small relative to the thickness of the foam layer (cured adhesive layer). Therefore, the above-mentioned large bubbles can be suppressed.

[0061] In the method of adjusting the content of the foaming agent, for example, if the content of the foaming agent is high, the thickness of the foam layer (cured adhesive layer) tends to be thick. Therefore, the size of the bubbles can be made relatively small with respect to the thickness of the foam layer (cured adhesive layer). Therefore, the above-mentioned large bubbles can be suppressed.

[0062] In the case where the foaming agent is a thermally expandable microcapsule, in the method of adjusting the structure of the thermally expandable microcapsule, for example, if the shell of the thermally expandable microcapsule is thick, the gas permeability tends to decrease and the size of the bubbles tends to decrease. Also, for example, if the shell of the thermally expandable microcapsule is crosslinked, the gas permeability tends to decrease and the size of the bubbles tends to decrease.

[0063] As a method for adjusting the foaming and curing conditions of the adhesive composition, for example, when the foaming agent is a thermally expandable microcapsule, a method for adjusting the heating temperature can be mentioned. For example, by setting the heating temperature within a predetermined range with respect to the maximum foaming temperature of the foaming agent, the generation of the above-mentioned large bubbles can be suppressed. In addition, for example, by setting the heating temperature within a predetermined range with respect to the maximum displacement extrapolation temperature of the foamable adhesive sheet, the generation of the above-mentioned large bubbles can be suppressed. Specific heating temperatures are described in the section "B. Method for manufacturing an article" below.

[0064] (b) Material of the cured adhesive layer The cured adhesive layer in this embodiment contains a foamed, cured product of an adhesive composition that contains a curable adhesive and a blowing agent.

[0065] (i) Curable adhesive The curable adhesive used in the cured adhesive layer in this embodiment can be a curable adhesive generally used in the adhesive layer of a foamable adhesive sheet. Examples of the curable adhesive include a thermosetting adhesive and a photocurable adhesive. Among them, a thermosetting adhesive is preferred. A thermosetting adhesive can be applied even when the first member or the second member does not have transparency, such as a metal member.

[0066] Examples of the curable adhesive include epoxy resin adhesives, acrylic resin adhesives, phenol resin adhesives, unsaturated polyester resin adhesives, alkyd resin adhesives, urethane resin adhesives, and thermosetting polyimide resin adhesives.

[0067] Among them, the curable adhesive is preferably an epoxy resin adhesive. That is, the curable adhesive preferably contains an epoxy resin and a curing agent. In general, epoxy resin adhesives are excellent in mechanical strength, heat resistance, insulating properties, chemical resistance, etc., have small shrinkage upon curing, and can be used in a wide range of applications.

[0068] Hereinafter, an example will be described in which the curable adhesive is an epoxy resin adhesive.

[0069] (i-1) Epoxy resin The epoxy resin in this embodiment is a compound that has at least one epoxy group or glycidyl group and is cured by a crosslinking polymerization reaction in combination with a curing agent. The epoxy resin also includes a monomer having at least one epoxy group or glycidyl group.

[0070] As the epoxy resin, an epoxy resin generally used in an epoxy resin-based adhesive can be used.

[0071] Among them, the curable adhesive preferably contains an epoxy resin having a weight average molecular weight of 900 or more and 100,000 or less as the epoxy resin. As described above, in the foaming and curing process of the adhesive composition, the epoxy resin softens and becomes more fluid. At this time, when the molecular weight of the epoxy resin is large, the fluidity of the epoxy resin is low compared to when the molecular weight of the epoxy resin is small. Therefore, the bubbles are less likely to become large and the bubbles are less likely to be connected to each other, so the generation of large bubbles tends to be suppressed. Therefore, the generation of large bubbles can be suppressed by containing a high molecular weight epoxy resin.

[0072] In this case, the weight average molecular weight of the epoxy resin is, for example, 900 or more and 100,000 or less, alternatively 1,650 or more and 80,000 or less, or 3,800 or more and 60,000 or less.

[0073] The weight average molecular weight of the resin component is a value calculated in terms of polystyrene as measured by gel permeation chromatography (GPC).

[0074] In addition, the curable adhesive preferably contains an epoxy resin that is solid at room temperature as the epoxy resin. As described above, in the foaming and curing process of the adhesive composition, the epoxy resin softens and becomes more fluid. At this time, the epoxy resin that is solid at room temperature tends to have lower fluidity than the epoxy resin that is liquid at room temperature. Therefore, the bubbles are less likely to grow large and the bubbles are less likely to connect with each other, so the generation of large bubbles tends to be suppressed. Therefore, by containing an epoxy resin that is solid at room temperature, the generation of large bubbles can be suppressed.

[0075] It is also preferable that the curable adhesive contains an epoxy resin that is solid at room temperature and an epoxy resin that is liquid at room temperature as the epoxy resin. When the curable adhesive contains an epoxy resin that is liquid at room temperature, the fluidity is likely to increase when the resin component softens during the foaming and curing process of the adhesive composition. Therefore, the bubbles are likely to be connected to each other and the bubbles are likely to become large. Therefore, the article of this embodiment is useful when the curable adhesive contains an epoxy resin that is liquid at room temperature. When the adhesive member has a first cured adhesive layer and a second cured adhesive layer, it is preferable that at least one of the adhesive compositions used in the first cured adhesive layer and the second cured adhesive layer contains an epoxy resin that is liquid at room temperature, and it is more preferable that only one of the adhesive compositions contains an epoxy resin that is liquid at room temperature. As described above, the article of this embodiment is useful in such a case.

[0076] The content of the epoxy resin that is liquid at room temperature in the adhesive composition is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and even more preferably 50 parts by mass or less, relative to 100 parts by mass of the resin component in the adhesive composition. When the curable adhesive contains an epoxy resin that is liquid at room temperature, the fluidity of the resin component tends to increase during the foaming and curing process of the adhesive composition, but the fluidity of the resin component can be relatively low by relatively reducing the content of the epoxy resin that is liquid at room temperature. Therefore, by having the content of the epoxy resin that is liquid at room temperature in the above range, the generation of large bubbles can be suppressed. On the other hand, the content of the epoxy resin that is liquid at room temperature in the adhesive composition may be, for example, 5 parts by mass or more, or 10 parts by mass or more, relative to 100 parts by mass of the resin component in the adhesive composition. In addition, when the epoxy resin that is liquid at room temperature is an optional component, the lower limit of the content of the epoxy resin that is liquid at room temperature in the adhesive composition is not particularly limited.

[0077] In the case of an epoxy resin adhesive, the resin components in the adhesive composition refer to epoxy resin and acrylic resin. The resin components in the adhesive composition also include optional components such as urethane resin. In addition, when the curing agent is a phenolic resin, the resin components in the adhesive composition also include the phenolic resin that is the curing agent.

[0078] The curable adhesive preferably contains, as the epoxy resin, a first epoxy resin having a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g / eq or lower, and a second epoxy resin having a softening temperature higher than that of the first epoxy resin and a weight average molecular weight of 20,000 or higher. By using the first epoxy resin and the second epoxy resin in combination, the adhesive layer made of the adhesive composition can be reduced in tackiness and can be made to have good slip properties. Furthermore, the blocking resistance and the adhesiveness after foaming and curing can be made good.

[0079] For example, when only improving the adhesiveness after foaming and curing, it is more effective to use an epoxy resin with a low molecular weight (low epoxy equivalent) than an epoxy resin with a high molecular weight (high epoxy equivalent). However, when an epoxy resin with a low molecular weight (low epoxy equivalent) is used, blocking is more likely to occur.

[0080] In contrast, when a first epoxy resin having a relatively low softening temperature (relatively high crystallinity) and a low molecular weight (low epoxy equivalent) is used, the first epoxy resin melts rapidly and changes to a low-viscosity liquid when the temperature reaches or exceeds the softening temperature. Therefore, it is easy to improve the adhesiveness after foaming and curing. On the other hand, since the first epoxy resin has a relatively high crystallinity, it can suppress the occurrence of blocking compared to an epoxy resin having a relatively low crystallinity or an epoxy resin having no crystallinity. However, when only the first epoxy resin is used, there is a possibility that the effect of suppressing the occurrence of blocking is insufficient, or the adhesiveness (tackiness) of the adhesive layer composed of the adhesive composition becomes too high. Therefore, by further using a second epoxy resin having a relatively high softening temperature (relatively low crystallinity) and a high molecular weight, it is possible to improve the effect of suppressing the occurrence of blocking and to suppress the adhesiveness (tackiness) of the adhesive layer composed of the adhesive composition to a low level.

[0081] (i-1-1) First epoxy resin The first epoxy resin has a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g / eq or lower. The first epoxy resin has a relatively low softening temperature (relatively high crystallinity) compared to the second epoxy resin described below. The first epoxy resin has relatively high crystallinity and a low molecular weight, which makes it easy to improve adhesion and blocking resistance after foaming and curing. In addition, the first epoxy resin has a low molecular weight, which makes it possible to increase the crosslink density, and to obtain an adhesive layer with good mechanical strength, chemical resistance, and curing properties. In addition, the first epoxy resin is preferably an epoxy resin that is solid at room temperature (23° C.).

[0082] The softening temperature of the first epoxy resin is usually 50° C. or higher, and may be 55° C. or higher, or may be 60° C. or higher. On the other hand, the softening temperature of the first epoxy resin is, for example, 150° C. or lower. The softening temperature is measured by the ring and ball method in accordance with JIS K7234:1986.

[0083] The epoxy equivalent of the first epoxy resin is, for example, 5000 g / eq or less, may be 3000 g / eq or less, may be 1000 g / eq or less, or may be 600 g / eq or less. On the other hand, the epoxy equivalent of the first epoxy resin is, for example, 90 g / eq or more, may be 100 g / eq or more, or may be 110 g / eq or more. The epoxy equivalent is the number of grams of a resin containing 1 gram equivalent of an epoxy group. The epoxy equivalent is measured by a method conforming to JIS K7236:2009, which corresponds to ISO 3001 (Plastics Epoxy compounds-Determination of epoxy equivalent).

[0084] The first epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin.

[0085] The weight average molecular weight (Mw) of the first epoxy resin is usually smaller than the weight average molecular weight (Mw) of the second epoxy resin described below. The Mw of the first epoxy resin is, for example, 6,000 or less, may be 4,000 or less, or may be 3,000 or less. On the other hand, the Mw of the first epoxy resin is, for example, 400 or more.

[0086] The melt viscosity of the first epoxy resin at 150°C is, for example, 0.005 Pa·s or more, may be 0.015 Pa·s or more, may be 0.03 Pa·s or more, may be 0.05 Pa·s or more, or may be 0.1 Pa·s or more. If the melt viscosity is too low, good foaming properties may not be obtained. In addition, if the melt viscosity of the first epoxy resin is too low (if the crystallinity of the first epoxy resin is too high), the adhesive layer composed of the adhesive composition may have high tackiness. The reason for this is presumably that if the melt viscosity of the first epoxy resin is too low (if the crystallinity of the first epoxy resin is too high), when it is compatible with the second epoxy resin or the acrylic resin, its crystallinity is greatly reduced, and the Tg of the adhesive layer is reduced. On the other hand, the melt viscosity of the first epoxy resin at 150°C is, for example, 10 Pa·s or less, may be 5 Pa·s or less, or may be 2 Pa·s or less. If the melt viscosity is too high, the uniformity of the adhesive layer composed of the adhesive composition may be reduced. The melt viscosity is measured in accordance with JIS K6862:1984, which corresponds to ISO 2555 (Determination of Brookfield RV viscosity of Resins in the liquid state or as emulsions or dispersions), using a Brookfield type single cylinder rotational viscometer and a thermocell for heating the solution.

[0087] Next, the constitution of the first epoxy resin will be described. Examples of the first epoxy resin include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Specific examples of the first epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resins and bisphenol F type epoxy resins, novolac type epoxy resins such as bisphenol A novolac type epoxy resins and cresol novolac type epoxy resins, and modified epoxy resins such as urethane modified epoxy resins and rubber modified epoxy resins. Other specific examples include biphenyl type epoxy resins, stilbene type epoxy resins, triphenol methane type epoxy resins, alkyl modified triphenol methane type epoxy resins, triazine nucleus-containing epoxy resins, dicyclopentadiene modified phenol type epoxy resins, naphthalene type epoxy resins, glycol type epoxy resins, and pentaerythritol type epoxy resins. The first epoxy resin may be one type or two or more types.

[0088] Bisphenol A type epoxy resins can exist in a liquid state at room temperature or in a solid state at room temperature depending on the number of repeating units of the bisphenol skeleton. Bisphenol A type epoxy resins having, for example, 2 to 10 bisphenol skeletons in the main chain are solid at room temperature. In particular, bisphenol A type epoxy resins are preferred in that they can improve heat resistance.

[0089] In particular, the first epoxy resin is preferably a bisphenol A novolac type epoxy resin represented by the following general formula (1).

[0090] [ka]

[0091] In the general formula (1), R 1 is C m H 2m (m is 1 or more and 3 or less), 2 and R 3are each independently p H 2p+1 (p is 1 or more and 3 or less), and n is 0 or more and 10 or less.

[0092] In the general formula (1), R 1 m in is 1, that is, R 1 is preferably -CH2-. Similarly, R 2 and R 3 p in is 1, that is, R 2 and R 3 is preferably -CH3. Furthermore, the hydrogen bonded to the benzene ring in general formula (1) may be substituted with other elements or other groups.

[0093] (i-1-2) Second epoxy resin The second epoxy resin has a higher softening temperature than the first epoxy resin and a weight average molecular weight of 20,000 or more. The second epoxy resin has a relatively high softening temperature (relatively low crystallinity) compared to the above-mentioned first epoxy resin. The second epoxy resin has relatively low crystallinity and high molecular weight, so that it is easy to improve blocking resistance. Furthermore, the second epoxy resin has relatively low crystallinity and high molecular weight, so that it is possible to suppress an increase in adhesion (tackiness) caused by the first epoxy resin. Moreover, it is preferable that the second epoxy resin is an epoxy resin that is solid at room temperature (23°C).

[0094] The weight average molecular weight (Mw) of the second epoxy resin is usually larger than the weight average molecular weight (Mw) of the first epoxy resin. The Mw of the second epoxy resin is usually 20,000 or more, may be 30,000 or more, or may be 35,000 or more. On the other hand, the Mw of the second epoxy resin is, for example, 100,000 or less.

[0095] The epoxy equivalent of the second epoxy resin may be larger, smaller, or the same as that of the first epoxy resin. The epoxy equivalent of the second epoxy resin is, for example, 4000 g / eq or more, 5000 g / eq or more, or 6000 g / eq or more. On the other hand, the epoxy equivalent of the second epoxy resin is, for example, 20000 g / eq or less.

[0096] The second epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher functional epoxy resin.

[0097] The softening temperature of the second epoxy resin is usually higher than that of the first epoxy resin. The difference between the two is, for example, 10° C. or more, and may be 20° C. or more, or may be 30° C. or more. The softening temperature of the second epoxy resin is, for example, 80° C. or more, and may be 90° C. or more. On the other hand, the softening temperature of the second epoxy resin is, for example, 180° C. or less.

[0098] The composition of the second epoxy resin is the same as that of the first epoxy resin described above, and therefore the description thereof will be omitted here.

[0099] (i-2) Acrylic resin When the curable adhesive is an epoxy resin adhesive, the adhesive composition may further contain an acrylic resin compatible with the epoxy resin. The acrylic resin is a resin compatible with the epoxy resin. Since the acrylic resin is compatible with the epoxy resin, it is easy to improve the toughness of the adhesive layer composed of the adhesive composition. As a result, the adhesiveness after foaming and curing can be improved. Furthermore, it is considered that the acrylic resin acts as a compatibilizer for the foaming agent (for example, a foaming agent whose shell part is a resin of acrylonitrile copolymer), and uniformly disperses and foams, thereby improving the adhesiveness after foaming and curing. In addition, the flexibility of the acrylic resin is exerted, and the adhesion to the substrate after foaming and curing and the crack resistance after foaming and curing can be improved. In addition, the compatibility of the acrylic resin with the epoxy resin allows the hardness of the adhesive layer surface to be kept high. On the other hand, if the acrylic resin is incompatible with the epoxy resin, a soft portion is formed on the surface of the adhesive layer, so that the interface with the first member and the second member becomes difficult to slip, and the workability may be reduced.

[0100] The acrylic resin in this embodiment is compatible with the epoxy resin. Here, the compatibility of the acrylic resin with the epoxy resin can be confirmed, for example, by observing the cross section of the adhesive layer made of the adhesive composition with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and finding that no micron-sized islands are generated. More specifically, the average particle size of the islands is preferably 1 μm or less. In particular, the average particle size of the islands may be 0.5 μm or less, or may be 0.3 μm or less. It is preferable that the number of samples is large, for example, 100 or more. The area to be observed is in the range of 100 μm × 100 μm, or in the case where the thickness of the adhesive layer is 100 μm or less, in the range of the thickness × 100 μm.

[0101] The weight average molecular weight (Mw) of the acrylic resin is, for example, 50,000 or more, may be 70,000 or more, or may be 100,000 or more. The first epoxy resin has a relatively high crystallinity, and the melt viscosity (or dynamic viscoelasticity) during heating becomes too low, which may cause shrinkage during hardening after foaming (between the end of foaming of the foaming agent and the hardening of the adhesive composition). However, by using an acrylic resin having a certain molecular weight, it is possible to prevent the melt viscosity from becoming too low, and shrinkage is less likely to occur during hardening after foaming. On the other hand, the Mw of the acrylic resin is, for example, 1,500,000 or less. The weight average molecular weight of the acrylic resin is measured by GPC (eluent: THF, standard substance: PS, sample: 20 μL, flow rate: 1 mL / min, column temperature: 40° C.).

[0102] The glass transition temperature (Tg) of the acrylic resin is, for example, 90° C. or higher, and may be 100° C. or higher. On the other hand, the Tg of the acrylic resin is, for example, 180° C. or lower. Tg is measured by a differential scanning calorimeter (DSC) in accordance with JIS K7121:2012, which corresponds to ISO 3146.

[0103] Acrylic resin has a storage modulus (E') of 1 x 10 at the foaming start temperature. 6 Pa or less. When E' at the foaming start temperature is low, the fluidity is improved and good foaming properties can be obtained. On the other hand, E' at the foaming start temperature may be, for example, 1×10 5 The foaming initiation temperature is a temperature that differs depending on the type of foaming agent. When two or more foaming agents are used, the foaming initiation temperature is the initiation temperature of the main foaming reaction.

[0104] Acrylic resin has a storage modulus (E') of 1 x 10 at the curing start temperature. 5Pa or more. As described above, shrinkage may occur during curing after foaming (from the end of foaming of the foaming agent to the curing of the adhesive composition), but by having a large E' at the curing start temperature, shrinkage can be suppressed and good shape retention can be obtained. The curing start temperature is a temperature that differs depending on the type of curing agent. In addition, when two or more types of curing agents are used as the curing agent, the start temperature of the main curing reaction is taken as the curing start temperature.

[0105] In addition, the average storage modulus (E') of acrylic resin at temperatures between 0°C and 100°C is 1×10 6 The storage modulus (E') before foaming may be high, which provides good non-adhesiveness and blocking resistance. On the other hand, the storage modulus (E') at temperatures between 0°C and 100°C may be, for example, 1×10 8 Pa or less.

[0106] The acrylic resin may have a polar group, such as an epoxy group, a hydroxyl group, a carboxyl group, a nitrile group, or an amide group.

[0107] The acrylic resin may be a homopolymer of an acrylic acid ester monomer, a mixed component containing two or more of the above homopolymers, or a copolymer of two or more of the acrylic acid ester monomers, a component containing one or more copolymers. The acrylic resin may also be a mixed component of the above homopolymer and the above copolymer. The "acrylic acid" of the acrylic acid ester monomer also includes the concept of methacrylic acid. Specifically, the acrylic resin may be a mixture of a methacrylate polymer and an acrylate polymer, or an acrylic acid ester polymer such as acrylate-acrylate, methacrylate-methacrylate, or methacrylate-acrylate. Among them, the acrylic resin preferably contains a copolymer of two or more of the acrylic acid ester monomers ((meth)acrylic acid ester copolymer).

[0108] Examples of the monomer components constituting the (meth)acrylic acid ester copolymer include the monomer components described in JP 2014-065889 A. The monomer components may have the above-mentioned polar group. Examples of the (meth)acrylic acid ester copolymer include ethyl acrylate-butyl acrylate-acrylonitrile copolymer, ethyl acrylate-acrylonitrile copolymer, and butyl acrylate-acrylonitrile copolymer. Note that "acrylic acid" such as methyl acrylate and ethyl acrylate also includes "methacrylic acid" such as methyl methacrylate and ethyl methacrylate.

[0109] The (meth)acrylic acid ester copolymer is preferably a block copolymer, and more preferably an acrylic block copolymer such as a methacrylate-acrylate copolymer. Examples of (meth)acrylates constituting the acrylic block copolymer include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and benzidyl acrylate. These "acrylic acids" also include "methacrylic acid."

[0110] Specific examples of methacrylate-acrylate copolymers include acrylic copolymers such as methyl methacrylate-butyl acrylate-methyl methacrylate (MMA-BA-MMA) copolymers. MMA-BA-MMA copolymers also include block copolymers of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate (PMMA-PBA-PMMA).

[0111] The acrylic copolymer may not have a polar group, or may be a modified product having the above-mentioned polar group partially introduced therein. The modified product is easily compatible with the epoxy resin, and therefore the adhesiveness is further improved.

[0112] Among them, the acrylic resin is preferably a (meth)acrylic acid ester copolymer having a first polymer portion having a glass transition temperature (Tg) of 10° C. or lower and a second polymer portion having a glass transition temperature (Tg) of 20° C. or higher. Such a (meth)acrylic acid ester copolymer has the first polymer portion that becomes a soft segment and the second polymer portion that becomes a hard segment.

[0113] The manifestation of the above-mentioned effect can be presumed as follows: By using an acrylic resin having both a soft segment and a hard segment, such as the above-mentioned (meth)acrylic acid ester copolymer, the hard segment contributes to heat resistance, and the soft segment contributes to toughness or flexibility, so that an adhesive layer having good heat resistance, toughness, and flexibility can be obtained.

[0114] At least one of the first polymer portion and the second polymer portion contained in the (meth)acrylic acid ester copolymer has compatibility with epoxy resins. When the first polymer portion has compatibility with epoxy resins, flexibility can be increased. When the second polymer portion has compatibility with epoxy resins, cohesion and toughness can be increased.

[0115] When either the first polymer portion or the second polymer portion is incompatible with the epoxy resin, the (meth)acrylic acid ester copolymer has a compatible portion, which is a polymer portion compatible with the epoxy resin, and an incompatible portion, which is a polymer portion incompatible with the epoxy resin. In this case, when the (meth)acrylic acid ester copolymer is added, the compatible portion is compatible with the epoxy resin, and the incompatible portion is incompatible with the epoxy resin, so that fine phase separation occurs. As a result, a fine sea-island structure is developed. The sea-island structure varies depending on the type of (meth)acrylic acid ester copolymer, the compatibility of the first polymer portion and the second polymer portion contained in the (meth)acrylic acid ester copolymer, and the presence or absence of modification by introduction of a polar group, and examples thereof include a sea-island structure in which the compatible portion of the cured epoxy resin and the (meth)acrylic acid ester copolymer is a sea, and the incompatible portion of the (meth)acrylic acid ester copolymer is an island, a sea-island structure in which the incompatible portion of the (meth)acrylic acid ester copolymer is a sea, and the compatible portion of the cured epoxy resin and the (meth)acrylic acid ester copolymer is an island, and a sea-island structure in which the (meth)acrylic acid ester copolymer is a sea, and the cured epoxy resin is an island. By having such a sea-island structure, stress can be easily dispersed, so that interfacial destruction can be avoided, and excellent adhesion can be obtained after foaming and curing.

[0116] The (meth)acrylic acid ester copolymer is preferably a block copolymer, and more preferably an ABA block copolymer in which the compatible portion is polymer block A and the incompatible portion is polymer block B. Furthermore, it is preferable that the ABA block copolymer is an ABA block copolymer in which the first polymer portion is an incompatible portion, the second polymer portion is an compatible portion, the first polymer portion is polymer block B, and the second polymer portion is polymer block A. By using such an ABA block copolymer as the acrylic resin, in the case of a sea-island structure in which the compatible portion of the cured epoxy resin and the (meth)acrylic acid ester copolymer is the sea, and the incompatible portion of the (meth)acrylic acid ester copolymer is the island, the island portion can be made small. In addition, in the case of a sea-island structure in which the incompatible portion of the (meth)acrylic acid ester copolymer is the sea, and the compatible portion of the cured epoxy resin and the (meth)acrylic acid ester copolymer is the island, or in the case of a sea-island structure in which the (meth)acrylic acid ester copolymer is the sea, and the cured epoxy resin is the island, the sea portion can be made small.

[0117] The (meth)acrylic acid ester copolymer may be a modified product in which the above-mentioned polar group is introduced into a part of the first polymer segment or the second polymer segment.

[0118] The Tg of the first polymer portion contained in the above (meth)acrylic acid ester copolymer is 10°C or lower, and can be within the range of -150°C or higher and 10°C or lower, particularly within the range of -130°C or higher and 0°C or lower, and particularly within the range of -110°C or higher and -10°C or lower.

[0119] The Tg of the first polymer portion can be calculated using the following formula based on the Tg(K) of each homopolymer described in "POLYMERHANDBOOK, Third Edition" (published by John Wiley & Sons, Inc.). 1 / Tg(K)=W1 / Tg1+W2 / Tg2+····+W n / Tg n W n : Mass fraction of each monomer Tgn : Tg(K) of the homopolymer of each monomer, and publicly available values ​​such as those in the Polymer Handbook (3rd Ed., J. Brandrup and EH Immergut, WILEY INTERSCIENCE) may be used. The same applies to the Tg of the second polymer portion described below.

[0120] The first polymer portion contained in the (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but is preferably a homopolymer. The monomer component and polymer component constituting the first polymer portion may be a monomer component and polymer component capable of obtaining a first polymer portion having a Tg in a predetermined range, and examples thereof include acrylate monomers such as butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and methyl acrylate, other monomers such as vinyl acetate, acetal, and urethane, polar group-containing monomers containing the above-mentioned polar groups, and copolymers such as EVA.

[0121] The Tg of the second polymer portion contained in the above (meth)acrylic acid ester copolymer is 20°C or higher, and can be within the range of 20°C or higher and 150°C or lower, particularly within the range of 30°C or higher and 150°C or lower, and particularly within the range of 40°C or higher and 150°C or lower.

[0122] The second polymer portion contained in the (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but is preferably a homopolymer. The monomer component constituting the second polymer portion may be any monomer component capable of obtaining a second polymer portion having a Tg in a predetermined range, and examples thereof include acrylic acid ester monomers such as methyl methacrylate, other monomers such as acrylamide, styrene, vinyl chloride, amide, acrylonitrile, cellulose acetate, phenol, urethane, vinylidene chloride, methylene chloride, and methacrylonitrile, and polar group-containing monomers containing the above-mentioned polar groups.

[0123] A specific example of the (meth)acrylic acid ester copolymer having the above-mentioned first polymer portion and second polymer portion is the above-mentioned MMA-BA-MMA copolymer.

[0124] (i-3) Hardener As the curing agent in this embodiment, a curing agent generally used in an epoxy resin adhesive can be used. The curing agent is preferably solid at room temperature (23°C). A curing agent that is solid at room temperature can have a longer storage stability (pot life) than a curing agent that is liquid at room temperature. The curing agent may be a latent curing agent. The curing agent may be a curing agent that undergoes a curing reaction by heat, or may be a curing agent that undergoes a curing reaction by light. The curing agent may be used alone or in combination of two or more kinds.

[0125] The reaction initiation temperature of the curing agent is, for example, 110°C or higher, and may be 130°C or higher. If the reaction initiation temperature is too low, the reaction starts early, and curing occurs in a state where the flexibility and fluidity of the resin component is low, and uniform curing may be difficult to occur. On the other hand, the reaction initiation temperature of the curing agent is, for example, 200°C or lower. If the reaction initiation temperature is too high, the resin component may deteriorate. In addition to the epoxy resin, when a resin with high heat resistance, such as a phenolic resin, is used, the resin component is less deteriorated, so the reaction initiation temperature of the curing agent may be, for example, 300°C or lower. The reaction initiation temperature of the curing agent is determined by differential scanning calorimetry (DSC).

[0126] Specific examples of the curing agent include imidazole-based curing agents, phenol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, isocyanate-based curing agents, and thiol-based curing agents.

[0127] Examples of imidazole-based curing agents include imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, carboxylates of imidazole compounds, and adducts with epoxy compounds. It is also preferable that the imidazole-based curing agent has a hydroxyl group. Since crystallization occurs due to hydrogen bonds between hydroxyl groups, the reaction initiation temperature tends to be high.

[0128] Examples of phenol-based curing agents include phenol resins. Examples of phenol resins include resol-type phenol resins and novolac-type phenol resins. From the viewpoint of adhesion to the substrate after foaming and curing and crack resistance after foaming and curing, phenol-type novolac resins having a Tg of 110° C. or less are particularly preferred. Also, phenol-based curing agents and imidazole-based curing agents may be used in combination. In this case, it is preferable to use an imidazole-based curing agent as a curing catalyst.

[0129] Examples of the amine-based curing agent include aliphatic amines, aromatic amines, alicyclic amines, and polyamidoamines. Examples of the aliphatic amines include diethylenetriamine (DETA), triethylenetetramine (TETA), and metaxylylenediamine (MXDA). Examples of the aromatic amines include diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diaminodiphenylsulfone (DDS). Examples of the amine-based curing agent include dicyandiamide-based curing agents such as dicyandiamide (DICY), organic acid dihydrazide-based curing agents, amine adduct-based curing agents, and ketimine-based curing agents.

[0130] Examples of the acid anhydride-based hardener include alicyclic acid anhydrides (liquid acid anhydrides) and aromatic acid anhydrides. Examples of the alicyclic acid anhydrides include hexahydrophthalic anhydride (HHPA), methyltetrahydrophthalic anhydride (MTHPA), etc. Examples of the aromatic acid anhydrides include trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), benzophenonetetracarboxylic acid (BTDA), etc.

[0131] The isocyanate-based curing agent may, for example, be a blocked isocyanate.

[0132] Examples of the thiol-based curing agent include ester-bonded thiol compounds, aliphatic ether-bonded thiol compounds, and aromatic ether-bonded thiol compounds.

[0133] (ii) Foaming agent The foaming agent used in the cured adhesive layer in this embodiment may be a foaming agent generally used in the adhesive layer of a foamable adhesive sheet. The foaming agent may be a foaming agent that undergoes a foaming reaction due to heat or a foaming agent that undergoes a foaming reaction due to light.

[0134] The foaming agent may be, for example, a thermally expandable microcapsule, which preferably has a thermal expansion agent such as a hydrocarbon as a core and a resin such as an acrylonitrile copolymer as a shell.

[0135] In addition, for example, organic or inorganic foaming agents may be used as the foaming agent. Examples of organic foaming agents include azo foaming agents such as azodicarbonamide (ADCA), azobisformamide, and azobisisobutyronitrile, fluorinated alkane foaming agents such as trichloromonofluoromethane, hydrazine foaming agents such as paratoluenesulfonylhydrazide, semicarbazide foaming agents such as p-toluenesulfonylsemicarbazide, triazole foaming agents such as 5-morpholyl-1,2,3,4-thiatriazole, and N-nitroso foaming agents such as N,N-dinitrosoterephthalamide. On the other hand, examples of inorganic foaming agents include ammonium carbonate, ammonium hydrogen carbonate, ammonium nitrite, ammonium borohydride, and azides.

[0136] The foaming start temperature of the foaming agent is preferably equal to or higher than the softening temperature of the base of the curable adhesive such as epoxy resin, and equal to or lower than the activation temperature of the curing reaction of the base of the curable adhesive such as epoxy resin. The foaming start temperature of the foaming agent is, for example, 70°C or higher, and may be 100°C or higher. If the reaction start temperature is too low, foaming starts early, and foaming occurs in a state where the flexibility and fluidity of the resin component are low, and it may be difficult to generate uniform foaming. On the other hand, the foaming start temperature of the foaming agent is, for example, 210°C or lower. If the foaming start temperature is too high, the resin component may deteriorate.

[0137] The softening temperature of the base material of a curable adhesive such as an epoxy resin is measured using the ring and ball softening temperature test method specified in JIS K7234:1986.

[0138] In addition, as described later, when the foaming agent is a thermally expandable microcapsule, the maximum foaming temperature of the foaming agent is preferably higher than the glass transition temperature of the main agent of the curable adhesive such as an epoxy resin. The maximum foaming temperature of the foaming agent is, for example, preferably 140°C or higher, more preferably 150°C or higher, even more preferably 160°C or higher, and particularly preferably 175°C or higher. As described above, when the maximum foaming temperature of the foaming agent is high, the foaming agent shrinks during the foaming and curing process of the adhesive composition, and the thickness of the foam layer (cured adhesive layer) can be suppressed from becoming thin. This can suppress the size of the bubbles from becoming relatively large with respect to the thickness of the foam layer (cured adhesive layer). Therefore, by setting the maximum foaming temperature of the foaming agent within the above range, large bubbles can be suppressed. In addition, if the maximum foaming temperature is too low, the foaming agent shrinks, making it impossible to maintain the thickness of the cured adhesive layer, and there is a possibility that the adhesive strength will decrease. On the other hand, the maximum foaming temperature of the foaming agent is, for example, preferably 230°C or lower, more preferably 220°C or lower, and even more preferably 210°C or lower. If the maximum foaming temperature is too high, the foaming agent may not expand sufficiently, and the adhesive strength may decrease. Specifically, the maximum foaming temperature of the foaming agent is preferably 140°C or higher and 230°C or lower, more preferably 150°C or higher and 220°C or lower, and even more preferably 160°C or higher and 210°C or lower. The maximum foaming temperature of the foaming agent is also preferably 175°C or higher and 220°C or lower.

[0139] Here, the foaming initiation temperature and maximum foaming temperature of the foaming agent are determined by thermomechanical analysis (TMA). Specifically, when measuring by thermomechanical analysis (TMA) at a heating rate of 20°C / min and a load force of 0.06 N, the temperature is plotted on the x-axis and the displacement on the y-axis, and the temperature showing the maximum displacement is the maximum foaming temperature, and the temperature at which the displacement is 3% of the maximum displacement is the foaming initiation temperature.

[0140] The average particle size of the foaming agent may be, for example, 10 μm or more, 13 μm or more, or 17 μm or more. The average particle size of the foaming agent is preferably equal to or less than the thickness of the adhesive layer of the foamable adhesive sheet, and may be, for example, 44 μm or less, 30 μm or less, or 24 μm or less.

[0141] The average particle size of the foaming agent is the particle size at 50% of the cumulative value in the particle size distribution obtained by the laser diffraction scattering method. In addition, when measuring the average particle size of the foaming agent, the adhesive composition is dissolved in a solvent to separate the foaming agent. The solvent is not particularly limited as long as it can dissolve components other than the foaming agent contained in the adhesive composition, and is appropriately selected depending on the type of curable adhesive, and for example, a solvent used in the adhesive composition can be used. Specifically, methyl ethyl ketone, ethyl acetate, toluene, etc. can be used.

[0142] The expansion ratio of the foaming agent at the maximum foaming temperature is, for example, 1.5 times or more, and may be 2 times or more. On the other hand, the expansion ratio of the foaming agent at the maximum foaming temperature is, for example, 15 times or less, and may be 10 times or less. The expansion ratio of the foaming agent is the ratio of the diameter of the foaming agent after foaming to the diameter of the foaming agent before foaming.

[0143] The content of the foaming agent in the adhesive composition used in the cured adhesive layer is the same as the content of the foaming agent in the adhesive layer in the foamable adhesive sheet described below.

[0144] (iii) Other ingredients In the present embodiment, when the curable adhesive is an epoxy resin adhesive, the adhesive composition used in the cured adhesive layer may contain only epoxy resin and acrylic resin as resin components, or may further contain other resins, such as urethane resin.

[0145] The adhesive composition may contain additives such as a silane coupling agent, a filler, an antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a plasticizer, an antistatic agent, a crosslinking agent, and a colorant, as necessary. Examples of the silane coupling agent include an epoxy-based silane coupling agent. Examples of the filler include inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, a molybdenum compound, and titanium dioxide. Examples of the antioxidant include a phenol-based antioxidant and a sulfur-based antioxidant.

[0146] (c) Other points on the cured adhesive layer The thickness of the cured adhesive layer is not particularly limited and is appropriately set according to the application. The thickness of the cured adhesive layer is, for example, 30 μm or more and 1000 μm or less, and may be 40 μm or more and 900 μm or less, or 50 μm or more and 800 μm or less. If the cured adhesive layer is too thin, sufficient adhesion may not be obtained. Also, if the cured adhesive layer is too thick, the surface quality may be deteriorated.

[0147] The cured adhesive layer may be a continuous or discontinuous layer.

[0148] The cured adhesive layer contains a foamed and cured product of the adhesive composition. Examples of methods for foaming and curing the adhesive composition include heating and light irradiation. Among them, it is preferable to foam and cure the adhesive composition by heating. The method using heating can be applied even when the first member and the second member do not have transparency, such as when the first member and the second member are made of metal.

[0149] (d) a first cured adhesive layer and a second cured adhesive layer In this embodiment, when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, or when the adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer in this order, at least one of the first cured adhesive layer and the second cured adhesive layer may contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent. For example, one of the first cured adhesive layer and the second cured adhesive layer may contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the other may contain a cured product of an adhesive composition containing a curable adhesive and no foaming agent, and both the first cured adhesive layer and the second cured adhesive layer may contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent. Among them, it is preferable that both the first cured adhesive layer and the second cured adhesive layer contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent. The adhesiveness can be improved. In addition, when an article is manufactured using a foaming adhesive sheet, the insertability of the foaming adhesive sheet can be improved.

[0150] (2) Base material The adhesive member in this embodiment may have a substrate between the first cured adhesive layer and the second cured adhesive layer. When a substrate is disposed between the first cured adhesive layer and the second cured adhesive layer, the foamable adhesive sheet can be easily handled and worked when used to manufacture an article. On the other hand, when no substrate is disposed between the first cured adhesive layer and the second cured adhesive layer, the foamable adhesive sheet can be made thinner overall when used to manufacture an article, and the foamable adhesive sheet can be inserted into a narrow gap.

[0151] The substrate is preferably insulating. The substrate is preferably in the form of a sheet. The substrate may have a single layer structure or a multi-layer structure. The substrate may or may not have a porous structure inside.

[0152] Examples of the substrate include a resin substrate and a nonwoven fabric.

[0153] Examples of the resin contained in the resin substrate include polyester resin, polycarbonate, polyarylate, polyurethane, polyamide resin, polyimide resin, polysulfone resin, polyether ketone resin, polyphenylene sulfide (PPS), and modified polyphenylene oxide. Examples of the polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyester. Examples of the polyamide resin include polyamide and polyether amide. Examples of the polyimide resin include polyimide, polyether imide, and polyamide imide. Examples of the polysulfone resin include polysulfone and polyether sulfone. Examples of the polyether ketone resin include polyether ketone and polyether ether ketone. In addition, liquid crystal polymer (LCP) may be used as the resin. The glass transition temperature of the resin is, for example, 80°C or higher, may be 140°C or higher, or may be 200°C or higher.

[0154] Examples of the nonwoven fabric include nonwoven fabrics containing fibers such as cellulose fibers, polyester fibers, nylon fibers, aramid fibers, polyphenylene sulfide fibers, liquid crystal polymer fibers, glass fibers, metal fibers, and carbon fibers.

[0155] The substrate may be subjected to a surface treatment to enhance adhesion to the first cured adhesive layer and the second cured adhesive layer.

[0156] The thickness of the substrate is not particularly limited, but is, for example, from 2 μm to 200 μm, optionally from 5 μm to 100 μm, and optionally from 9 μm to 50 μm.

[0157] (3) Other configurations The adhesive member in this embodiment may have a first intermediate layer between the substrate and the first cured adhesive layer. The adhesive member in this embodiment may have a second intermediate layer between the substrate and the second cured adhesive layer. By arranging the first intermediate layer or the second intermediate layer, the adhesion of the first cured adhesive layer or the second cured adhesive layer to the substrate can be improved. Furthermore, when an article is manufactured using a foamable adhesive sheet, by arranging the first intermediate layer or the second intermediate layer, for example, the stress applied to the bent portion when the foamable adhesive sheet is folded, or the stress applied to the cut portion when the foamable adhesive sheet is cut can be alleviated. As a result, lifting or peeling of the first adhesive layer or the second adhesive layer from the substrate can be suppressed when the foamable adhesive sheet is bent or cut.

[0158] For example, in the article 100 shown in Fig. 4, in the adhesive member 30, a first intermediate layer 13a is disposed between the substrate 12 and the first cured adhesive layer 11a, and a second intermediate layer 13b is disposed between the substrate 12 and the second cured adhesive layer 11b. Note that, although the adhesive member 30 in Fig. 4 has both the first intermediate layer 13a and the second intermediate layer 13b, it may have only one of them.

[0159] The adhesive member may have at least one of a first intermediate layer and a second intermediate layer, and may, for example, have only the first intermediate layer arranged between the substrate and the first cured adhesive layer, may have only the second intermediate layer arranged between the substrate and the second cured adhesive layer, or may have both the first intermediate layer arranged between the substrate and the first cured adhesive layer and the second intermediate layer arranged between the substrate and the second cured adhesive layer. Among these, it is preferable that the first intermediate layer is arranged between the substrate and the first cured adhesive layer, and the second intermediate layer is arranged between the substrate and the second cured adhesive layer.

[0160] The materials contained in the first intermediate layer and the second intermediate layer are not particularly limited as long as they can increase the adhesion between the substrate and the first cured adhesive layer or the second cured adhesive layer and can relieve stress, and are appropriately selected depending on the materials of the substrate, the first cured adhesive layer, and the second cured adhesive layer, etc. Examples of the materials include polyester, polyvinyl chloride, polyvinyl acetate, polyurethane, polymers obtained by copolymerizing at least two or more of these, crosslinked products thereof, and mixtures thereof.

[0161] The crosslinked body is a crosslinked body obtained by crosslinking the above-mentioned resin with a curing agent. Examples of the curing agent include isocyanate-based curing agents. In addition, for example, when the reactive group / NCO equivalent is 1, it is preferable to add the isocyanate-based curing agent in a ratio of 0.5% by mass or more and 20% by mass or less to the resin.

[0162] In particular, the first intermediate layer and the second intermediate layer preferably contain a crosslinked resin. The crosslinked resin is one that does not melt even at high temperatures. This can improve the adhesive strength at high temperatures, i.e., heat resistance.

[0163] The thickness of the first intermediate layer and the second intermediate layer is not particularly limited, but may be, for example, 0.1 μm or more, may be 0.5 μm or more, or may be 1 μm or more. If the first intermediate layer or the second intermediate layer is too thin, when an article is manufactured using the foamable adhesive sheet, the effect of suppressing peeling of the first adhesive layer or the second adhesive layer from the substrate when the foamable adhesive sheet is bent or cut may not be sufficiently obtained. On the other hand, the thickness of the first intermediate layer and the second intermediate layer may be, for example, 4 μm or less, or may be 3.5 μm or less. Since the first intermediate layer and the second intermediate layer themselves usually do not have high heat resistance, if the first intermediate layer and the second intermediate layer are too thick, the heat resistance (adhesive strength at high temperatures) may decrease.

[0164] The first intermediate layer and the second intermediate layer can be formed, for example, by applying a resin composition and removing the solvent. Examples of the application method include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, and dip coating.

[0165] 2. First member and second member The first and second members in this embodiment are appropriately selected depending on the application of the article. The first and second members are preferably members that require adhesion and insulation. For example, they include parts of electric and electronic devices, specifically, stator cores and coils of stators for rotating electric machines, cores and permanent magnets of embedded magnet motors, etc.

[0166] 3. Manufacturing method of the article The method for manufacturing the article of this embodiment is described in the section "B. Method for Manufacturing the Article" below.

[0167] II. Second Embodiment of the Article A second embodiment of an article in the present disclosure is an article having a first member, a second member, and an adhesive member disposed between the first member and the second member, wherein the adhesive member has at least a cured adhesive layer, and the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer is less than 7 per length of 4 mm in a direction perpendicular to the thickness direction of the foam layer.

[0168] 1 to 3 are schematic cross-sectional views showing one example of the article of this embodiment. Note that since Figs. 1 to 3 have been described in the section on the first embodiment above, a description thereof will be omitted here.

[0169] In the article, when the first member and the second member are, for example, parts of an electric / electronic device, specifically, a stator core and coil of a stator for a rotating electric machine, or a core and permanent magnet of an embedded magnet type motor, the distance of the gap between the first member and the second member is, for example, about several hundred μm. In this case, the thickness of the adhesive member is, for example, about several hundred μm, and the thickness of the cured adhesive layer of the adhesive member is also, for example, about several hundred μm.

[0170] In the above-mentioned article, when the adhesive member has one cured adhesive layer and the cured adhesive layer is a foam layer, if there are large bubbles with a size of 100 μm or more, the cured adhesive layer does not contact the first member and the second member in the region where such bubbles exist, or the contact area between the cured adhesive layer and the first member and the contact area between the cured adhesive layer and the second member become very small. Therefore, it is considered that the cured adhesive layer is likely to peel off, float, crack, or other adhesion defects starting from the above-mentioned bubbles.

[0171] In contrast, in the article of this embodiment, when the adhesive member has one cured adhesive layer, and the cured adhesive layer is a foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or less in a cross section parallel to the thickness direction of the foam layer is a predetermined value or less per predetermined length in a direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion, and thus improving adhesion.

[0172] In addition, in the above-mentioned article, when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and the first cured adhesive layer and the second cured adhesive layer are foam layers, if there are large bubbles with a size of 100 μm or more, the first cured adhesive layer does not contact the first member, the second cured adhesive layer does not contact the second member, or the contact area between the first cured adhesive layer and the first member becomes very small, or the contact area between the second cured adhesive layer and the second member becomes very small. Therefore, it is considered that the above-mentioned bubbles are likely to cause adhesion defects such as peeling, lifting, and cracking of the first cured adhesive layer and the second cured adhesive layer.

[0173] In contrast, in the article of this embodiment, when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and the first cured adhesive layer and the second cured adhesive layer are foam layers, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is a predetermined value or less per predetermined length in a direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion, and thus improving adhesion.

[0174] In addition, when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and one of the first cured adhesive layer and the second cured adhesive layer is a foam layer, it is also possible to suppress poor adhesion and improve adhesion.

[0175] In addition, in the above-mentioned article, when the adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer in this order, and the first cured adhesive layer and the second cured adhesive layer are foam layers, if there are large bubbles whose size is about the thickness of the foam layer, the first cured adhesive layer does not contact the first member and the substrate, the second cured adhesive layer does not contact the second member and the substrate, or the contact area between the first cured adhesive layer and the first member and the substrate becomes very small, or the contact area between the second cured adhesive layer and the second member and the substrate becomes very small. Therefore, it is considered that the above-mentioned bubbles are likely to cause adhesion defects such as peeling, lifting, and cracking of the first cured adhesive layer and the second cured adhesive layer.

[0176] In contrast, in the article of this embodiment, when the adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer in this order, and the first cured adhesive layer and the second cured adhesive layer are foam layers, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is a predetermined value or less per predetermined length in the direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0177] In addition, when an adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer, it is also possible to suppress poor adhesion and improve adhesion when either the first cured adhesive layer or the second cured adhesive layer is a foam layer.

[0178] Therefore, in the article of this embodiment, the reliability and durability can be improved.

[0179] In the article of this embodiment, the adhesive member, the first member, and the second member can be the same as those in the first embodiment.

[0180] The method for manufacturing the article of this embodiment will be described later in the section "B. Method for manufacturing the article."

[0181] The cured adhesive layer in this embodiment is a foam layer containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and has bubbles inside. In a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer. In particular, the number of bubbles is preferably 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0182] In particular, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 150 μm or more per 4 mm in a direction perpendicular to the thickness direction of the foam layer is preferably less than 7, more preferably 3 or less, even more preferably 2 or less, particularly preferably 1 or less, and most preferably 0.

[0183] In addition, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more and having a distance of 3 μm or less between the bubble and the interface between the foam layer and other members adjacent to the foam layer is preferably less than 7, more preferably 3 or less, even more preferably 2 or less, particularly preferably 1 or less, and most preferably 0, per 4 mm length perpendicular to the thickness direction of the foam layer. In the region where the above-mentioned bubbles are present, the cured adhesive layer is not in contact with other members adjacent to the cured adhesive layer, or the contact area between the cured adhesive layer and other members adjacent to the cured adhesive layer becomes very small. Therefore, it is considered that the above-mentioned bubbles are the starting point for adhesion defects such as peeling, lifting, and cracking of the cured adhesive layer.

[0184] The distance between the air bubble and the interface between the foam layer and another member adjacent to the foam layer refers to, for example, the distance u1 from the end of the air bubble 31 to the interface between the foam layer 15a and another member (e.g., first member 20a) adjacent to one side of the foam layer 15a, and the distance u2 from the end of the air bubble 31 to the interface between the foam layer 15a and another member (e.g., substrate 12) adjacent to the other side of the foam layer 15a, as shown in Figure 3.

[0185] B. Method of Manufacturing the Article The method for producing an article according to the present disclosure has two embodiments. Each embodiment will be described below.

[0186] I. First embodiment of the method for manufacturing an article A first embodiment of the method for manufacturing an article in the present disclosure is a method for manufacturing an article using a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the method comprising: an arrangement step of arranging the foamable adhesive sheet between a first member and a second member; and an adhesion step of foaming and curing the foaming-agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer and adhering the first member and the second member, the foaming and curing conditions in the adhesion step being set such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0187] 5(a)-(b) are process diagrams illustrating a method for manufacturing an article according to this embodiment. First, as shown in FIG. 5(a), a foamable adhesive sheet 10 is disposed between a first member 20a and a second member 20b. The foamable adhesive sheet 10 has an adhesive layer 1, and the adhesive layer 11 is a foaming agent-containing adhesive layer 5 that contains a curable adhesive and a foaming agent. Next, as shown in FIG. 5(b), the foaming agent-containing adhesive layer 5 (adhesive layer 1) of the foamable adhesive sheet 10 is foamed and cured to form a cured adhesive layer 11, which is a foam layer 15, and the first member 20a and the second member 20b are bonded together by an adhesive member 30 having the cured adhesive layer 11. 1, the foaming and curing conditions are set so that, in a cross section parallel to the thickness direction D1 of the foam layer 15, the number of bubbles 31 whose length s in the thickness direction D1 of the foam layer 15 is within a predetermined range relative to the thickness t of the foam layer 15 is below a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15. In this way, the article 100 is obtained.

[0188] 6(a)-(c) are process diagrams illustrating a method for manufacturing an article according to this embodiment. First, as shown in FIG. 6(a), a foamable adhesive sheet 10 is attached to a second member 20b. The foamable adhesive sheet 10 has a first adhesive layer 1a and a second adhesive layer 1b, and the first adhesive layer 1a and the second adhesive layer 1b are foaming agent-containing adhesive layers 5a and 5b that contain a curable adhesive and a foaming agent, respectively. At this time, the surface of the second adhesive layer 11b of the foamable adhesive sheet 10 is attached to the second member 20b. Next, as shown in FIG. 6(b), the second member 20b on which the foamable adhesive sheet 10 is arranged is inserted into the hole in the first member 20a. Next, as shown in Fig. 6(c), the foaming agent-containing adhesive layers 5a, 5b (first adhesive layer 1a, second adhesive layer 1b) of the foamable adhesive sheet 10 are foamed and cured to form the first cured adhesive layer 11a and the second cured adhesive layer 11b, which are the foam layers 15a, 15b, respectively, and the first member 20a and the second member 20b are bonded by the adhesive member 30 having the first cured adhesive layer 11a and the second cured adhesive layer 11b. At this time, the foaming and curing conditions are set so that, for example, as shown in Fig. 2, in each cross section parallel to the thickness direction D1 of the foam layers 15a, 15b, the number of bubbles 31 whose length s in the thickness direction D1 of the foam layers 15a, 15b is within a predetermined range relative to the thicknesses t1, t2 of the foam layers 15a, 15b is below a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layers 15a, 15b. In this way, the article 100 is obtained.

[0189] In Figures 6(a) to (c), both the first adhesive layer 1a and the second adhesive layer 1b are foaming agent-containing adhesive layers 5a, 5b containing a curable adhesive and a foaming agent, but either one of the first adhesive layer or the second adhesive layer may be a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent.

[0190] In addition, in Figs. 6(a) to (c), the foamable adhesive sheet 10 is attached to both sides of the second member 20b, but the foamable adhesive sheet may be attached to one side of the second member.

[0191] In the method for producing the article of this embodiment, as described in the first embodiment of the article above, the foaming and curing conditions in the adhesion step are set so that the number of bubbles whose length in the thickness direction of the foam is within a predetermined range relative to the thickness of the foam layer in a cross section parallel to the thickness direction of the foam layer is less than a predetermined value per predetermined length in a direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion and improving adhesion. Therefore, an article with high reliability and durability can be obtained.

[0192] In this specification, for convenience, the adhesive layer located on the first member side of the foamable adhesive sheet is referred to as the first adhesive layer, and the adhesive layer located on the second member side is referred to as the second adhesive layer.

[0193] The foamable adhesive sheet used in the method for producing an article of this embodiment and each step of the method for producing an article of this embodiment will be described below.

[0194] 1. Foam adhesive sheet The foamable adhesive sheet in this embodiment has at least an adhesive layer, and the adhesive layer is a foaming agent-containing adhesive layer that contains a curable adhesive and a foaming agent.

[0195] The foamable adhesive sheet may have at least an adhesive layer. For example, as shown in FIG. 7, the foamable adhesive sheet 10 may have one adhesive layer 1. In this case, the adhesive layer 1 is a foaming agent-containing adhesive layer 5 containing a curable adhesive and a foaming agent. Also, as shown in FIG. 8, the foamable adhesive sheet 10 may have a first adhesive layer 1a and a second adhesive layer 1b. In this case, as shown in FIG. 8, both the first adhesive layer 1a and the second adhesive layer 1b may be foaming agent-containing adhesive layers 5a, 5b containing a curable adhesive and a foaming agent, and although not shown, either the first adhesive layer or the second adhesive layer may be a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent. Also, as shown in FIG. 9, the foamable adhesive sheet 10 may have a first adhesive layer 1a, a substrate 12, and a second adhesive layer 1b in this order. In this case, for example, as shown in FIG. 9, both the first adhesive layer 1a and the second adhesive layer 1b may be foaming agent-containing adhesive layers 5a, 5b containing a curable adhesive and a foaming agent, or, although not shown, either the first adhesive layer or the second adhesive layer may be a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent.

[0196] Each component of the foamable adhesive sheet will be described below.

[0197] (1) Adhesive layer In this embodiment, the adhesive layer is a foaming agent-containing adhesive layer that contains a curable adhesive and a foaming agent.

[0198] (a) Characteristics of the adhesive layer In the case where the foamable adhesive sheet in this embodiment has one adhesive layer, the adhesive layer is preferably substantially non-adhesive (tack-free). By making the adhesive layer substantially non-adhesive (tack-free), the foamable adhesive sheet can have good sliding properties and blocking resistance. Therefore, the handleability and workability of the foamable adhesive sheet can be improved. Specifically, in the arrangement step, the foamable adhesive sheet can be smoothly inserted into the gap between the first member and the second member, and when the first member has a hole or groove, the second member can be smoothly inserted into the gap after the foamable adhesive sheet is arranged in the hole or groove of the first member.

[0199] Here, non-tacky is generally used mainly to mean low adhesive strength, and in this specification, "non-tacky" refers to a state in which the foamable adhesive sheet can be wound into a roll and then easily unwound without resistance.

[0200] When the adhesive layer is substantially non-adhesive, specifically, the tack of the adhesive layer is preferably 0 gf or more and less than 10 gf, and may be 5 gf or less, or may be 2 gf or less. By having the tack of the adhesive layer within the above range, the adhesive layer can be made substantially non-adhesive, and a foamable adhesive sheet with good sliding properties and blocking resistance can be obtained.

[0201] Furthermore, when the foamable adhesive sheet of this embodiment has a first adhesive layer and a second adhesive layer, or has a first adhesive layer, a substrate, and a second adhesive layer in that order, both the first adhesive layer and the second adhesive layer may be substantially non-adhesive (tack-free), or one of the first adhesive layer and the second adhesive layer may be substantially non-adhesive (tack-free) and the other may be adhesive (tacky).

[0202] When both the first adhesive layer and the second adhesive layer are substantially non-tacky (tack-free), the same effect can be obtained as when the foamable adhesive sheet has one adhesive layer and the adhesive layer is non-tacky (tack-free).

[0203] On the other hand, when one of the first adhesive layer and the second adhesive layer is substantially non-adhesive (tack-free) and the other is adhesive (tacky), for example, when the first adhesive layer is substantially non-adhesive (tack-free) and the second adhesive layer is adhesive (tacky), the second adhesive layer can have good adhesion to the second member. Specifically, in the arrangement step, when the surface of the second adhesive layer of the foamable adhesive sheet is attached to the second member and the second member to which the foamable adhesive sheet is attached is inserted into a hole or groove of the first member, the second adhesive layer has adhesiveness, so that the surface of the second adhesive layer of the foamable adhesive sheet can be attached to the second member by utilizing the adhesiveness of the second adhesive layer, and the adhesiveness of the second adhesive layer to the second member can be increased. This makes it possible to suppress peeling or displacement of the foamable adhesive sheet when inserting the second member to which the foamable adhesive sheet is attached into a hole or groove of the first member.

[0204] In the above case, the second adhesive layer has adhesiveness, so that the second adhesive layer has good reworkability, and therefore, for example, when the surface of the second adhesive layer of the foamable adhesive sheet is attached to the second member by utilizing the adhesiveness of the second adhesive layer as described above, the positional deviation of the foamable adhesive sheet can be corrected.

[0205] In the above case, the first adhesive layer is non-adhesive, so that the first adhesive layer has good slipperiness. Therefore, for example, when inserting the second member to which the foamable adhesive sheet is attached into the hole or groove of the first member as described above, the second member to which the foamable adhesive sheet is attached can be smoothly inserted, and the insertability can be improved. This can suppress peeling or misalignment of the foamable adhesive sheet. In addition, when moving the second member relative to the first member to align the first member and the second member, the second member can be smoothly moved relative to the first member while the second member is inserted into the hole or groove of the first member, and alignment can be easily performed.

[0206] In the above case, as described above, the second adhesive layer has excellent adhesion to the second member, and the first adhesive layer has excellent slipperiness, so that peeling or misalignment of the foamable adhesive sheet can be suppressed. Therefore, a decrease in the adhesiveness of the foamable adhesive sheet after foaming and curing due to peeling or misalignment of the foamable adhesive sheet can be suppressed, and the variation in adhesive strength of the foamable adhesive sheet after foaming and curing due to peeling or misalignment of the foamable adhesive sheet can be reduced.

[0207] In the above case, the second adhesive layer has adhesiveness, and thus, for example, when the second adhesive layer is formed by a transfer method, the second adhesive layer can be prevented from lifting. Furthermore, as described below, when a second separator is disposed on the side of the second adhesive layer opposite to the first adhesive layer, the second adhesive layer has adhesiveness, and thus, the second separator can be easily peeled off, and workability can be improved.

[0208] In addition, when the adhesive layer has adhesiveness, for example, since it contains a relatively large amount of low molecular weight resin components, the resin components tend to become more fluid when they soften during the foaming and curing process of the adhesive layer. Therefore, when the adhesive layer (foaming agent-containing adhesive layer) is foamed and cured to form a foam layer, the bubbles tend to connect with each other and the bubbles tend to become larger. Therefore, when one of the first adhesive layer and the second adhesive layer is substantially non-adhesive (tack-free) and the other is adhesive (tacky), the manufacturing method of the article of this embodiment is useful.

[0209] When both the first adhesive layer and the second adhesive layer are substantially non-tacky, specifically, the tackiness of each of the first adhesive layer and the second adhesive layer is preferably 0 gf or more and less than 10 gf, and may be 5 gf or less, or may be 2 gf or less. By having the tackiness of the first adhesive layer and the second adhesive layer within the above range, the first adhesive layer and the second adhesive layer can be made substantially non-tacky, and a foamable adhesive sheet with good sliding properties and blocking resistance can be obtained.

[0210] Furthermore, when the first adhesive layer is substantially non-adhesive (tack-free) and the second adhesive layer is adhesive (tacky), specifically, it is preferable that the tack of the first adhesive layer is 0 gf or more and less than 10 gf, and the tack of the second adhesive layer is 10 gf or more and 400 gf or less.

[0211] In the above case, the tack of the first adhesive layer is preferably 0 gf or more and less than 10 gf, and may be 5 gf or less, or may be 2 gf or less. By having the tack of the first adhesive layer within the above range, the first adhesive layer can be made substantially non-sticky, and a foamable adhesive sheet with good sliding properties and blocking resistance can be obtained.

[0212] In the above case, the tack of the second adhesive layer is preferably 10 gf or more, may be 30 gf or more, or may be 50 gf or more. If the tack of the second adhesive layer is too low, for example, when the surface of the second adhesive layer of the foamable adhesive sheet is attached to the second member using the tack of the second adhesive layer, the adhesion between the second adhesive layer and the second member may be reduced, or when the second member to which the foamable adhesive sheet is attached is inserted into a hole or groove of the first member, the adhesion between the second adhesive layer and the second member may be poor, causing the foamable adhesive sheet to peel off or the position of the foamable adhesive sheet to shift, etc., which may reduce the adhesion of the first adhesive layer and the second adhesive layer after foaming and curing, or cause variations in the adhesive strength. In addition, the tack of the second adhesive layer is preferably 400 gf or less, may be 300 gf or less, or may be 200 gf or less. If the tack of the second adhesive layer is too high, reworkability will be reduced, and for example, when using the tack of the second adhesive layer to attach the second adhesive layer surface of the foamable adhesive sheet to a second component, it may become difficult to correct misalignment of the foamable adhesive sheet.

[0213] Here, the tack of the adhesive layer is measured by a probe tack test. Specifically, a cylindrical stainless steel probe with a diameter of 5 mm is pressed against the surface of the adhesive layer of the foamable adhesive sheet at a temperature of 25° C. with a load of 10.0 gf and a speed of 30 mm / min, and after holding for 1.0 second, it is peeled off at a speed of 30 mm / min, and the load at the time of peeling is measured. This measurement is performed five times, and the average value is taken as the tack. For example, a tack tester "TAC-II" manufactured by RHESCA can be used as the probe tack tester.

[0214] As a means for controlling the tack of the adhesive layer, for example, a method of adjusting the composition of the adhesive layer can be mentioned. Specifically, in an adhesive layer containing an epoxy resin and a curing agent, the adhesive layer can be made less sticky by using an epoxy resin that is solid at room temperature or a curing agent that is solid at room temperature. On the other hand, in an adhesive layer containing an epoxy resin and a curing agent, the adhesive layer tends to become more sticky when an epoxy resin that is liquid at room temperature or a curing agent that is liquid at room temperature is used. In addition, in an adhesive layer containing an epoxy resin and a curing agent, the adhesive layer can be made less sticky by including an epoxy resin with a high softening temperature or an epoxy resin with a large weight average molecular weight. For example, the adhesive layer can be made to include multiple types of epoxy resins with different softening temperatures, that is, the adhesive layer can be made to include one epoxy resin and another epoxy resin whose softening temperature is 25°C or higher and 10°C or higher than the softening temperature of the one epoxy resin, thereby making it possible to make the adhesive layer less sticky. Also, for example, the adhesive layer can be made to contain multiple types of epoxy resins with different weight average molecular weights, that is, the adhesive layer can be made to contain one epoxy resin and another epoxy resin with a weight average molecular weight of 370 or more and 300 or more greater than the weight average molecular weight of the one epoxy resin, thereby reducing the adhesiveness of the adhesive layer. More specifically, in an adhesive layer containing an epoxy resin and a curing agent, as described above, the adhesive layer can be made to contain a first epoxy resin with a low softening temperature and a low molecular weight, and a second epoxy resin with a high softening temperature and a high molecular weight, thereby reducing the adhesiveness of the adhesive layer. On the other hand, in an adhesive layer containing an epoxy resin and a curing agent, when an epoxy resin with a low softening temperature or an epoxy resin with a small weight average molecular weight is contained, the adhesiveness of the adhesive layer tends to increase. In an adhesive layer containing an epoxy resin and a curing agent, as described above, the adhesiveness of the adhesive layer can be reduced by containing an acrylic resin compatible with the epoxy resin. In addition, when a tackifier resin is added to the adhesive layer, the adhesiveness of the adhesive layer tends to increase.In addition, when a curing agent that is liquid at room temperature is used, the adhesiveness tends to be high, but there is a possibility that the storage stability may be reduced. Therefore, it is preferable to adjust the tack of the adhesive layer by adjusting the properties and type of components other than the curing agent, such as the epoxy resin.

[0215] Here, "adhesion" is a concept that is included in "bonding." The two are sometimes distinguished in that "adhesion" is used to mean a temporary adhesive phenomenon, whereas "bonding" is used to mean a substantially permanent adhesive phenomenon (Iwanami Shoten Physics and Chemistry Dictionary, 5th Edition). "Adhesiveness" and "adhesive strength" refer to the property of adhesion through pressure and the adhesive strength at that time.

[0216] In this specification, the "adhesiveness of the adhesive layer" and the "adhesive strength of the adhesive layer" refer to the adhesiveness and adhesive strength of the adhesive layer before curing, unless otherwise specified. In addition, in this specification, the "adhesiveness of the adhesive layer" and the "adhesive strength of the adhesive layer" refer to the adhesiveness and adhesive strength of the adhesive layer after curing, unless otherwise specified.

[0217] (b) Adhesive layer material The adhesive layer in this embodiment contains a curable adhesive and a foaming agent.

[0218] The material for the adhesive layer is the same as that described in the above section "A. Article," and therefore a description thereof will be omitted here.

[0219] When the curable adhesive is an epoxy resin adhesive, as described above, the curable adhesive preferably contains an epoxy resin that is liquid at room temperature as the epoxy resin. When the curable adhesive contains an epoxy resin that is liquid at room temperature, the method for manufacturing an article of this embodiment is useful. When the foamable adhesive sheet of this embodiment has a first adhesive layer and a second adhesive layer, it is preferable that at least one of the first adhesive layer and the second adhesive layer contains an epoxy resin that is liquid at room temperature, and it is more preferable that only one of the first adhesive layer and the second adhesive layer contains an epoxy resin that is liquid at room temperature. As described above, the method for manufacturing an article of this embodiment is useful in such cases.

[0220] The content of the epoxy resin that is liquid at room temperature in the adhesive layer is similar to the content of the epoxy resin that is liquid at room temperature in the adhesive composition used in the cured adhesive layer in the above-mentioned article.

[0221] In the case of an epoxy resin adhesive, the resin components in the adhesive layer refer to epoxy resin and acrylic resin. The resin components in the adhesive layer also include optional components such as urethane resin. In addition, in the case where the curing agent is a phenolic resin, the resin components in the adhesive layer also include the phenolic resin that is the curing agent.

[0222] In the case where the curable adhesive is an epoxy resin adhesive, and the curable adhesive contains a first epoxy resin having a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g / eq or lower, and a second epoxy resin having a softening temperature higher than that of the first epoxy resin and a weight average molecular weight of 20,000 or higher, as described above, the content of the first epoxy resin may be, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, or 25 parts by mass or more, based on 100 parts by mass of the resin component contained in the adhesive layer. If the content of the first epoxy resin is too low, the adhesiveness and blocking resistance after foaming and curing may be reduced. On the other hand, the content of the first epoxy resin may be, for example, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less, based on 100 parts by mass of the resin component contained in the adhesive layer. If the content of the first epoxy resin is too high, the contents of the second epoxy resin and the acrylic resin will be relatively low, and it may not be possible to achieve a balance between non-stickiness, blocking resistance, adhesion to substrates after foaming and curing, cracking resistance after foaming and curing, and adhesiveness after foaming and curing.

[0223] In the above case, the content of the second epoxy resin may be, for example, 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 35 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more, when the resin component contained in the adhesive layer is 100 parts by mass. If the content of the second epoxy resin is too small, the adhesion may be high and the blocking resistance may be reduced. On the other hand, the content of the second epoxy resin may be, for example, 90 parts by mass or less, 85 parts by mass or less, 80 parts by mass or less, or 75 parts by mass or less, when the resin component contained in the adhesive layer is 100 parts by mass. If the content of the second epoxy resin is too high, the content of the first epoxy resin and the acrylic resin becomes relatively low, and it may not be possible to balance the non-stickiness, blocking resistance, adhesion to the substrate after foaming and curing, cracking resistance after foaming and curing, and adhesion after foaming and curing.

[0224] The ratio of the first epoxy resin to the total of the first epoxy resin and the second epoxy resin is, for example, 5 mass% or more, optionally 10 mass% or more, optionally 15 mass% or more, or optionally 20 mass% or more, whereas the ratio of the first epoxy resin is, for example, 80 mass% or less, optionally 75 mass% or less, or optionally 60 mass% or less.

[0225] Furthermore, the total proportion of the first epoxy resin and the second epoxy resin to all epoxy resins contained in the adhesive layer is, for example, 50 mass% or more, optionally 70 mass% or more, optionally 90 mass% or more, or optionally 100 mass%.

[0226] In the case where the first adhesive layer is substantially non-adhesive and the second adhesive layer is adhesive, and the curable adhesive is an epoxy resin adhesive, the first adhesive layer preferably contains a first epoxy resin having a softening temperature of 50° C. or higher and an epoxy equivalent of 5000 g / eq or less, and a second epoxy resin having a softening temperature higher than that of the first epoxy resin and a weight average molecular weight of 20,000 or more, as described above. On the other hand, in the second adhesive layer, it is preferable to use an epoxy resin that is liquid at room temperature, such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin, and an epoxy resin with a low softening point. This is because the tack of the second adhesive layer can be easily adjusted within a predetermined range by using these epoxy resins.

[0227] When the curable adhesive is an epoxy resin adhesive and the adhesive layer further contains an acrylic resin compatible with the epoxy resin, the content of the acrylic resin may be, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more, based on 100 parts by mass of the resin component contained in the adhesive layer. If the content of the acrylic resin is too small, the adhesion to the substrate after foaming and curing, the crack resistance after foaming and curing, and the adhesiveness after foaming and curing may be reduced. On the other hand, the content of the acrylic resin may be, for example, 60 parts by mass or less, 50 parts by mass or less, 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less, based on 100 parts by mass of the resin component contained in the adhesive layer. If the content of the acrylic resin is too high, the content of the first epoxy resin and the second epoxy resin will be relatively low, and it may not be possible to balance the non-stickiness, blocking resistance, adhesion to the substrate after foaming and curing, the crack resistance after foaming and curing, and the adhesiveness after foaming and curing. Moreover, if the content of the acrylic resin is too high, the strength of the film may decrease.

[0228] The content of the curing agent is, for example, 1 part by mass or more and 40 parts by mass or less when the resin component contained in the adhesive layer is 100 parts by mass. For example, when an imidazole-based curing agent is used as the main component as the curing agent, the content of the curing agent is, for example, 1 part by mass or more and 15 parts by mass or less when the resin component contained in the adhesive layer is 100 parts by mass. On the other hand, when a phenol-based curing agent is used as the main component as the curing agent, the content of the curing agent is, for example, 5 parts by mass or more and 40 parts by mass or less when the resin component contained in the adhesive layer is 100 parts by mass. Note that using an imidazole-based curing agent or a phenol-based curing agent as the main component as the curing agent means that the mass ratio of the imidazole-based curing agent or the phenol-based curing agent is the highest in the curing agent.

[0229] The content of the foaming agent in the adhesive layer is, for example, 0.5 parts by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, 13 parts by mass or more, or 15 parts by mass or more, relative to 100 parts by mass of the resin component in the adhesive layer. As described above, when the content of the foaming agent is large, the thickness of the adhesive layer after foaming and curing, that is, the thickness of the foam layer (cured adhesive layer), tends to be large. Therefore, the size of the bubbles can be relatively small relative to the thickness of the foam layer (cured adhesive layer). Therefore, by having the content of the foaming agent in the above range, large bubbles can be suppressed. On the other hand, the content of the foaming agent in the adhesive layer is, for example, 30 parts by mass or less, 25 parts by mass or less, or 20 parts by mass or less, relative to 100 parts by mass of the resin component in the adhesive layer. If the content of the foaming agent is too high, the content of the curable adhesive becomes relatively small, so that the adhesiveness after foaming and curing may decrease.

[0230] At least one of the first adhesive layer and the second adhesive layer may contain a foaming agent. In particular, when the first adhesive layer is substantially non-adhesive and the second adhesive layer is adhesive, it is preferable that the first adhesive layer contains a foaming agent. This is because the inclusion of a foaming agent increases the surface roughness, reduces the friction coefficient, and improves the slipperiness. In particular, it is preferable that both the first adhesive layer and the second adhesive layer contain a foaming agent. By including a foaming agent in both the first adhesive layer and the second adhesive layer, the adhesion of the first adhesive layer and the second adhesive layer after foaming and curing can be increased.

[0231] The total proportion of epoxy resin and acrylic resin to the resin components contained in the adhesive layer is, for example, 70 mass% or more, optionally 80 mass% or more, optionally 90 mass% or more, or optionally 100 mass%.

[0232] The content of the resin component in the adhesive layer is, for example, 60% by mass or more, optionally 70% by mass or more, optionally 80% by mass or more, or optionally 90% by mass or more.

[0233] (c) Structure of adhesive layer The adhesive layer can be foamed at an expansion ratio of, for example, 1.5 times or more and 15 times or less. The expansion ratio may be, for example, 3.5 times or more, 4 times or more, or 4.5 times or more. The expansion ratio may be, for example, 9 times or less, 8.5 times or less, or 8 times or less. If the expansion ratio is too small or too large, the adhesiveness after foaming and curing may decrease.

[0234] Here, the expansion ratio can be calculated by the following formula. Expansion ratio (times) = thickness of adhesive layer after foaming and hardening / thickness of adhesive layer before foaming and hardening

[0235] The thickness of the adhesive layer is not particularly limited, but is preferably equal to or greater than the average particle size of the foaming agent, for example, 10 μm or more, may be 15 μm or more, or may be 20 μm or more. If the adhesive layer is too thin, there is a possibility that the adhesion to the substrate and the adhesiveness after foaming and curing cannot be sufficiently obtained. On the other hand, the thickness of the adhesive layer is, for example, 200 μm or less, may be 150 μm or less, or may be 100 μm or less. If the adhesive layer is too thick, there is a possibility that the surface quality will deteriorate.

[0236] The adhesive layer may be a continuous layer or a discontinuous layer. Examples of discontinuous layers include stripes, dots, and other patterns. The surface of the adhesive layer may have an uneven shape such as an embossed shape.

[0237] The adhesive layer can be formed, for example, by applying an adhesive composition containing the above-mentioned curable adhesive and a foaming agent, etc., and then removing the solvent. Examples of the application method include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, dip coating, etc.

[0238] The adhesive composition may or may not contain a solvent. In this specification, the solvent is used in a broad sense including not only a strict solvent (a solvent that dissolves a solute) but also a dispersion medium. The solvent contained in the adhesive composition is volatilized and removed when the adhesive composition is applied and dried to form an adhesive layer.

[0239] The adhesive composition can be obtained by mixing the above-mentioned components and kneading and dispersing them as necessary.As a mixing and dispersing method, a general kneading and dispersing machine, for example, a two-roll mill, a three-roll mill, a pebble mill, a tron ​​mill, a Szegvari attritor, a high-speed impeller dispersing machine, a high-speed stone mill, a high-speed impact mill, a disperser, a high-speed mixer, a ribbon blender, a co-kneader, an intensive mixer, a tumbler, a blender, a disperser, a homogenizer, or an ultrasonic dispersing machine can be used.

[0240] (2) Base material The foamable adhesive sheet in this embodiment may have a substrate between the first adhesive layer and the second adhesive layer. The substrate is the same as that described in the above section "A. Articles," and therefore will not be described here.

[0241] (3) Other configurations (a) The first and second intermediate layers The foamable adhesive sheet in this embodiment may have a first intermediate layer between the substrate and the first adhesive layer. The foamable adhesive sheet in this embodiment may have a second intermediate layer between the substrate and the second adhesive layer. The first intermediate layer and the second intermediate layer are the same as those described in the above section "A. Articles", so the description here is omitted.

[0242] For example, in the foamable adhesive sheet 10 shown in Fig. 10, a first intermediate layer 13a is disposed between the substrate 12 and the first adhesive layer 1a, and a second intermediate layer 13b is disposed between the substrate 12 and the second adhesive layer 1b. Note that, although the foamable adhesive sheet 10 in Fig. 10 has both the first intermediate layer 13a and the second intermediate layer 13b, it may have only one of them.

[0243] (b) Separator In the present embodiment, when the foamable adhesive sheet has one adhesive layer, it may have a separator on one or both sides of the adhesive layer. In addition, in the present embodiment, when the foamable adhesive sheet has a first adhesive layer and a second adhesive layer, or when the foamable adhesive sheet has a first adhesive layer, a substrate, and a second adhesive layer in this order, it may have a first separator on the side of the first adhesive layer opposite to the second adhesive layer, or a second separator on the side of the second adhesive layer opposite to the first adhesive layer.

[0244] When the foamable adhesive sheet has a separator, the separator is peeled off from the foamable adhesive sheet when the foamable adhesive sheet is disposed between the first member and the second member.

[0245] The separator is not particularly limited as long as it can be peeled off from the adhesive layer, and can have a strength sufficient to protect the adhesive layer. Examples of such separators include release films and release papers. The separator may have a single-layer structure or a multi-layer structure.

[0246] An example of a separator having a single layer structure is a fluororesin film.

[0247] In addition, examples of the separator having a multi-layer structure include laminates having a release layer on one or both sides of a substrate layer. Examples of the substrate layer include resin films such as polypropylene, polyethylene, and polyethylene terephthalate, and papers such as fine paper, coated paper, and impregnated paper. Materials for the release layer are not particularly limited as long as they have releasability, and examples include silicone compounds, organic compound-modified silicone compounds, fluorine compounds, aminoalkyd compounds, melamine compounds, acrylic compounds, polyester compounds, and long-chain alkyl compounds. These compounds can be any of emulsion type, solvent type, and solventless type.

[0248] The first separator and the second separator may be the same or different. In particular, when the first adhesive layer is substantially non-adhesive and the second adhesive layer is adhesive, it is preferable that the first separator has heavy releasability and the second separator has light releasability. For example, when inserting the second member on which the foamable adhesive sheet is arranged into the hole of the first member after arranging the foamable adhesive sheet on the second member, the surface of the second adhesive layer of the foamable adhesive sheet is attached to the second member and the surface of the first adhesive layer of the foamable adhesive sheet is placed on the front side, thereby improving the adhesion between the second member and the foamable adhesive sheet during insertion and the insertability of the second member on which the foamable adhesive sheet is arranged. In this case, the first separator and the second separator are peeled off from the second separator, so that the first separator has heavy releasability and the second separator has light releasability, making it easier to peel off the second separator than the first separator.

[0249] In addition, light peeling and heavy peeling refer to the degree of force required to peel the first separator and the second separator from the first adhesive layer and the second adhesive layer, and light peeling means that the peeling force is smaller than that of heavy peeling.

[0250] (4) Foamable adhesive sheet The thickness of the foamable adhesive sheet in this embodiment is, for example, 10 μm or more, and may be 20 μm or more, whereas the thickness of the foamable adhesive sheet is, for example, 1000 μm or less, and may be 200 μm or less.

[0251] The foamable adhesive sheet in this embodiment preferably has good shape retention. The foamable adhesive sheet preferably has good shape retention. The bending moment based on JIS P8125-2:2017 corresponding to ISO 2493 is, for example, 0.1 gf·cm or more, and may be 1 gf·cm or more. On the other hand, the bending moment may be, for example, less than 40 gf·cm, and may be less than 30 gf·cm. Conventionally, in foamable adhesive sheets, a method of increasing the bending moment to improve shape retention and insertion into narrow gaps is common. In contrast, the inventors of the present disclosure have found that shape retention can be guaranteed by devising the shape, and that a high bending moment has other problems, so that the bending moment is preferably within the above range in consideration of other characteristics. If the bending moment is smaller than the above range, it may be difficult to maintain the shape even by devising folding or the like. In addition, if the bending moment is larger than the above range, the shape will return to its original state after folding, so it is necessary to heat the sheet during folding or to make a crease at the fold. Heating reduces the sheet life, and streaks may reduce the insulation of those areas. In addition, the foamable adhesive sheet of this embodiment has a high surface hardness so that the surface is not damaged even when inserted at high speed.

[0252] The foamable adhesive sheet in this embodiment preferably has high adhesiveness after foaming and curing. The shear strength (adhesive strength) based on JIS K6850:1999 corresponding to ISO 4587:1995 may be, for example, 1.50 MPa or more, 1.80 MPa or more, or 2.10 MPa or more at 23°C. The shear strength (adhesive strength) may be, for example, 0.50 MPa or more, 0.75 MPa or more, or 1.00 MPa or more at 130°C. For example, in a high-strength acrylic foam adhesive tape that does not require heating, the shear strength (adhesive strength) is about 1 MPa or more and 2 MPa or less at room temperature, and does not have heat resistance at 200°C. Therefore, if the shear strength (adhesive strength) is within the above range at 23°C, it has an advantage in terms of strength. If the shear strength (adhesive strength) is within the above range at 130°C, it can be applied to applications that require heat resistance around an automobile engine or similar.

[0253] The foamable adhesive sheet in this embodiment preferably has high electrical insulation after foaming and curing. After foaming and curing of the foamable adhesive sheet, the dielectric breakdown voltage based on JIS C2107:2011 corresponding to IEC 60454-2 is, for example, preferably 3 kV or more, more preferably 5 kV or more. When the dielectric breakdown voltage is within the above range, it becomes possible to apply it to rust prevention and around copper wires. In addition, after foaming and curing of the foamable adhesive sheet, the thermal conductivity is, for example, preferably 0.1 W / mK or more, more preferably 0.15 W / mK or more. When the thermal conductivity is within the above range, it is possible to miniaturize the parts and promote the curing reaction during heating.

[0254] The method for producing the foamable adhesive sheet in this embodiment is not particularly limited, and may be appropriately selected depending on the layer structure of the foamable adhesive sheet.

[0255] 2.Placement process In the placing step in this embodiment, a foamable adhesive sheet is placed between the first member and the second member.

[0256] The method for disposing the foamable adhesive sheet between the first member and the second member is appropriately selected depending on the types of the first member and the second member, etc.

[0257] For example, a method of inserting a foamable adhesive sheet between a first member and a second member, a method of placing a foamable adhesive sheet in a hole or groove of a first member, and then inserting a second member into the gap after placing a foamable adhesive sheet in the hole or groove of the first member, etc. Also, for example, when the first member has a hole or groove and the second member is placed in the hole or groove of the first member, in a case where the first member and the second member are fixed by adhesion, a method of attaching the surface of the second adhesive layer of the foamable adhesive sheet to the second member by utilizing the tack of the second adhesive layer of the foamable adhesive sheet, and then arranging the second member to which the foamable adhesive sheet is attached in the hole or groove of the first member, a method of placing a foamable adhesive sheet in the hole or groove of the first member, attaching the surface of the second adhesive layer of the foamable adhesive sheet to the hole or groove of the first member by utilizing the tack of the second adhesive layer of the foamable adhesive sheet, and then arranging the second member in the hole or groove of the first member to which the foamable adhesive sheet is attached, etc. can be mentioned.

[0258] 3.Gluing process In the bonding step in this embodiment, the foaming agent-containing adhesive layer of the foamable adhesive sheet is foamed and cured to form a foam layer, which bonds the first member and the second member.

[0259] In the bonding step of this embodiment, the foaming and curing conditions are set so that the number of bubbles having a length in the thickness direction of the foam layer of at least the value of (the thickness of the foam layer - 6 μm) in a cross section parallel to the thickness direction of the foam layer is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer. In particular, the foaming and curing conditions are preferably set so that the number of bubbles is 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0260] The method of foaming and curing the foamable adhesive sheet can be, for example, heating or light irradiation. Among them, it is preferable to foam and cure the foaming agent-containing adhesive layer of the foamable adhesive sheet by heating. The method of heating can be applied even when the first member and the second member do not have transparency, such as a metal member.

[0261] The heating conditions are set so as to satisfy the foaming and curing conditions described above. The heating conditions can be appropriately set depending on, for example, the types of the curable adhesive and foaming agent contained in the adhesive layer.

[0262] The heating temperature is, for example, preferably within ±40°C of the maximum foaming temperature of the foaming agent, more preferably within ±30°C of the maximum foaming temperature of the foaming agent, and even more preferably within ±20°C of the maximum foaming temperature of the foaming agent. If the heating temperature is higher than the above range, even if the resin component is cured, the foaming agent shrinks, making it impossible to maintain the thickness of the adhesive layer at the time of foaming, and the size of the bubbles tends to become relatively large relative to the thickness of the foam layer (cured adhesive layer). Therefore, the adhesive strength may decrease. On the other hand, if the heating temperature is lower than the above range, the expansion of the foaming agent becomes insufficient, and the adhesive strength may decrease. In this case, there is a possibility that interface failure may easily occur between the cured adhesive layer and the first member or the second member.

[0263] In addition, when the adhesive layer contains multiple foaming agents, the heating temperature may be within the above range for at least one of the foaming agents. In particular, it is preferable that the heating temperature of the foaming agent with the largest content among the multiple foaming agents is within the above range. In particular, it is preferable that the heating temperature of all of the multiple foaming agents is within the above range.

[0264] In addition, the heating temperature is preferably, for example, the maximum displacement extrapolation temperature of the foamable adhesive sheet -7 ° C or more and the maximum displacement extrapolation temperature of the foamable adhesive sheet + 83 ° C or less, more preferably the maximum displacement extrapolation temperature of the foamable adhesive sheet + 15 ° C or more and the maximum displacement extrapolation temperature of the foamable adhesive sheet + 63 ° C or less, and even more preferably the maximum displacement extrapolation temperature of the foamable adhesive sheet + 23 ° C or more and the maximum displacement extrapolation temperature of the foamable adhesive sheet + 43 ° C or less. If the heating temperature is higher than the above range, even if the resin component is cured, the foaming agent shrinks, so that the thickness of the adhesive layer at the time of foaming cannot be maintained, and the size of the air bubbles tends to become relatively large with respect to the thickness of the foam layer (cured adhesive layer). Therefore, the adhesive strength may decrease. On the other hand, if the heating temperature is lower than the above range, the expansion of the foaming agent becomes insufficient, and the adhesive strength may decrease. In this case, there is a possibility that the interface destruction is easily caused between the cured adhesive layer and the first member or the second member.

[0265] 11 is a graph showing an example of a TMA curve in which a compressive load is applied to a foamable adhesive sheet, the temperature is increased at a predetermined heating rate, and the displacement is measured by thermomechanical analysis (TMA), with the temperature on the horizontal axis and the displacement on the vertical axis. A TMA curve for a foamable adhesive sheet containing thermally expandable microcapsules as a foaming agent usually has a peak associated with expansion (foaming). In the TMA curve for a foamable adhesive sheet as shown in FIG. 11, the temperature at the intersection of the tangent at the temperature showing the maximum displacement and the tangent at the minimum temperature when the curve of the portion of the TMA curve showing expansion behavior associated with the start of expansion (foaming) is differentiated is defined as the maximum displacement extrapolation temperature T max1 In the above case, the heating temperature is the maximum displacement extrapolation temperature T max1 It is preferable that the value is within a predetermined range.

[0266] Here, the thermomechanical analysis of the foamable adhesive sheet is performed by the following method. First, the foamable adhesive sheet is punched out to a size of φ4 mm to prepare a sample. Next, the sample is placed in an aluminum container of φ5 mm so that the surface of the second adhesive layer of the foamable adhesive sheet is on the bottom side. Next, an aluminum plate of φ4 mm is placed on the sample. Next, using a thermomechanical analyzer, the temperature is increased from 25° C. to 250° C. at a rate of 20° C. / min, and measurements are performed in compression mode under the condition of a load of 10 mN. The thermomechanical analyzer can be a thermomechanical analyzer TMA7100 manufactured by Hitachi High-Tech Science Corporation.

[0267] The above maximum displacement amount is the maximum value of the displacement amount in the TMA curve for the foamable adhesive sheet.

[0268] The maximum displacement extrapolation temperature is the intersection of the tangent at the temperature showing the maximum displacement in the TMA curve for the foamable adhesive sheet and the tangent at the minimum temperature when the curve of the portion of the TMA curve that shows expansion behavior associated with the onset of expansion (foaming) is differentiated.

[0269] Specifically, the heating temperature can be set to 130°C or higher and 200°C or lower.

[0270] The heating time can be, for example, from 3 minutes to 3 hours.

[0271] II. Second embodiment of the method for manufacturing an article A second embodiment of the method for manufacturing an article in the present disclosure is a method for manufacturing an article using a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the method comprising: an arrangement step of arranging the foamable adhesive sheet between a first member and the second member; and an adhesion step of foaming and curing the foaming-agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer and adhering the first member and the second member, the foaming and curing conditions in the adhesion step being set such that in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

[0272] Figures 5(a)-(b) and 6(a)-(c) are process diagrams illustrating the method for manufacturing the article of this embodiment. Note that Figures 5(a)-(b) and 6(a)-(c) are described in the first embodiment above, so their description will be omitted here.

[0273] In the method for producing the article of this embodiment, as described in the section of the second embodiment of the article above, the foaming and curing conditions in the adhesion step are set so that the number of bubbles having a length in the thickness direction of the foam of 100 μm or more in a cross section parallel to the thickness direction of the foam layer is a predetermined value or less per predetermined length in a direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion and improving adhesion. Therefore, an article with high reliability and durability can be obtained.

[0274] The foamable adhesive sheet used in the method for producing an article of this embodiment and the arrangement step in the method for producing an article of this embodiment can be the same as in the first embodiment.

[0275] In the adhesion step of this embodiment, the foaming and curing conditions are set so that the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer in a cross section parallel to the thickness direction of the foam layer is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer. Among these, the foaming and curing conditions are preferably set so that the number of bubbles is 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0276] The method for foaming and curing the foamable adhesive sheet and the heating conditions can be the same as those in the first embodiment.

[0277] C. Foam adhesive sheet The foamable adhesive sheet according to the present disclosure has two embodiments, each of which will be described below.

[0278] I. First embodiment of the foamable adhesive sheet A first embodiment of a foamable adhesive sheet in the present disclosure is a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, the foaming agent being a thermally expandable microcapsule, and when the foamable adhesive sheet is heated at a maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the foaming-agent-containing adhesive layer to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0279] FIG. 7 is a schematic cross-sectional view showing an example of the foamable adhesive sheet of this embodiment. The foamable adhesive sheet 10 in FIG. 7 has an adhesive layer 1. The adhesive layer 1 is a foaming agent-containing adhesive layer 5 containing a curable adhesive and a foaming agent. The curable adhesive contained in the foaming agent-containing adhesive layer 5 (adhesive layer 1) is a thermosetting adhesive, and the foaming agent contained in the foaming agent-containing adhesive layer 5 (adhesive layer 1) is a thermally expandable microcapsule. When the foamable adhesive sheet 10 is heated at a predetermined temperature for a predetermined time to foam and cure the foaming agent-containing adhesive layer 5 (adhesive layer 1) to form a foam layer 15, as shown in FIG. 12, for example, in a cross section parallel to the thickness direction D1 of the foam layer 15, the number of bubbles 31 whose length s in the thickness direction D1 of the foam layer 15 is within a predetermined range relative to the thickness t of the foam layer 15 is a predetermined value or less per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15.

[0280] Fig. 8 is a schematic cross-sectional view showing another example of the foamable adhesive sheet of this embodiment. The foamable adhesive sheet 10 in Fig. 9 has a first adhesive layer 1a and a second adhesive layer 1b. The first adhesive layer 1a and the second adhesive layer 1b are foaming agent-containing adhesive layers 5a, 5b containing a curable adhesive and a foaming agent. The curable adhesive contained in the foaming agent-containing adhesive layers 5a, 5b (first adhesive layer 1a, second adhesive layer 1b) is a thermosetting adhesive, and the foaming agent contained in the foaming agent-containing adhesive layers 5a, 5b (first adhesive layer 1a, second adhesive layer 1b) is a thermally expandable microcapsule. When the foamable adhesive sheet 10 is heated at a predetermined temperature for a predetermined time to foam and cure the foaming agent-containing adhesive layers 5a, 5b (first adhesive layer 1a, second adhesive layer 1b), the number of bubbles 31 whose length s in the thickness direction D1 of the foam layer 15a is within a predetermined range relative to the thickness t1 of the foam layer 15a is less than a predetermined value per a predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15a, as shown in Fig. 13. In addition, in a cross section parallel to the thickness direction D1 of the foam layer 15b, the number of bubbles 31 whose length s in the thickness direction D1 of the foam layer 15b is within a predetermined range relative to the thickness t2 of the foam layer 15b is less than a predetermined value per a predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15b.

[0281] Fig. 9 is a schematic cross-sectional view showing another example of the foamable adhesive sheet of this embodiment. The foamable adhesive sheet 10 in Fig. 9 has a first adhesive layer 1a, a substrate 12, and a second adhesive layer 1b in this order. Fig. 9 is the same as Fig. 8 above, except that the substrate 12 is disposed between the first adhesive layer 1a and the second adhesive layer 1b.

[0282] In Figures 8 and 9, both the first adhesive layer 1a and the second adhesive layer 1b are foaming agent-containing adhesive layers 5a, 5b containing a curable adhesive and a foaming agent, but only one of the first adhesive layer and the second adhesive layer may be a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent.

[0283] In the foamable adhesive sheet of this embodiment, as described in the first embodiment of the above-mentioned article, when the adhesive layer is a foaming agent-containing adhesive layer, the foamable adhesive sheet is heated at a predetermined temperature for a predetermined time to foam and harden the foaming agent-containing adhesive layer to form a foam layer, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is a predetermined value or less per predetermined length in the direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0284] The components of the foamable adhesive sheet of this embodiment are similar to those described above in the sections "A. Article" and "B. Method for manufacturing article," and therefore will not be described here.

[0285] In this embodiment, when the foamable adhesive sheet is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the foaming agent-containing adhesive layer to form a foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer minus 6 μm in a cross section parallel to the thickness direction of the foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer. The number of bubbles is preferably 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0286] When the foamable adhesive sheet is heated, a support having a smooth surface is used, and the foamable adhesive sheet is placed on the smooth surface of the support before heating. The support is not particularly limited as long as it has a smooth surface and is heat resistant, and for example, a glass substrate, a resin substrate, etc. can be used.

[0287] For a foamable adhesive sheet, the thickness direction of the foam layer is the direction perpendicular to the planar direction of the support, and the direction perpendicular to the thickness direction of the foam layer is the planar direction of the support.

[0288] The use of the foamable adhesive sheet of this embodiment is not particularly limited. The foamable adhesive sheet of this embodiment can be used, for example, in the manufacture of the above-mentioned articles.

[0289] II. Second embodiment of the foamable adhesive sheet A second embodiment of the foamable adhesive sheet of the present disclosure is a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming-agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, the foaming agent being a thermally expandable microcapsule, and when the foamable adhesive sheet is heated at a maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the foaming-agent-containing adhesive layer to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

[0290] Figures 7 to 9 are schematic cross-sectional views showing one example of the foamable adhesive sheet of this embodiment. Note that since Figures 7 to 9 were described in the section on the first embodiment above, a description thereof will be omitted here.

[0291] In the foamable adhesive sheet of this embodiment, as described in the section of the second embodiment of the above-mentioned article, when the adhesive layer is a foaming agent-containing adhesive layer, the foamable adhesive sheet is heated at a predetermined temperature for a predetermined time to foam and harden the foaming agent-containing adhesive layer to form a foam layer, and in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more per predetermined length in the direction perpendicular to the thickness direction of the foam layer is a predetermined value or less, so that poor adhesion can be suppressed. Therefore, it is possible to improve adhesion.

[0292] The components of the foamable adhesive sheet of this embodiment are similar to those described above in the sections "A. Article" and "B. Method for manufacturing article," and therefore will not be described here.

[0293] In this embodiment, when the foamable adhesive sheet is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and cure the foaming agent-containing adhesive layer to form a foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer in a cross section parallel to the thickness direction of the foam layer is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer. The number of bubbles is preferably 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0294] When the foamable adhesive sheet is heated, the foamable adhesive sheet may be placed on one side of a support and then heated. The support may be the same as in the first embodiment.

[0295] D. Adhesive Composition The adhesive composition according to the present disclosure has two embodiments. Each embodiment will be described below.

[0296] I. First embodiment of the adhesive composition A first embodiment of the adhesive composition in the present disclosure is an adhesive composition containing a curable adhesive and a foaming agent, wherein the curable adhesive is a thermosetting adhesive and the foaming agent is a thermally expandable microcapsule. When the adhesive composition is applied to one side of a support to a thickness of 45 μm and the coating of the adhesive composition is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the coating to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[0297] In the adhesive composition of this embodiment, as described in the section of the first embodiment of the above-mentioned article, when the adhesive composition is applied to one side of a support in a predetermined thickness and the coating of the adhesive composition is heated at a predetermined temperature for a predetermined time to foam and harden the coating to form a foam layer, the number of bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer in a cross section parallel to the thickness direction of the foam layer is a predetermined value or less per predetermined length in a direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0298] The components of the adhesive composition of this embodiment are the same as those described above in the sections "A. Article" and "B. Method for producing article," and therefore will not be described here.

[0299] In this embodiment, when the adhesive composition is applied to one side of the support to a thickness of 45 μm and the coating of the adhesive composition is heated at the maximum foaming temperature of the foaming agent ±20° C. for 15 minutes to foam and harden the coating to form a foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer minus 6 μm in a cross section parallel to the thickness direction of the foam layer is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer. The number of bubbles is preferably 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0300] When applying the adhesive composition to one side of the support, a support having a smooth surface is used, and the adhesive composition is applied to the smooth surface of the support. The support is not particularly limited as long as it has a smooth surface and is heat resistant, and for example, a glass substrate, a resin substrate, etc. can be used.

[0301] For the adhesive composition, the thickness direction of the foam layer is the direction perpendicular to the planar direction of the support, and the direction perpendicular to the thickness direction of the foam layer is the planar direction of the support.

[0302] II. Second embodiment of the adhesive composition A second embodiment of the adhesive composition of the present disclosure is an adhesive composition containing a curable adhesive and a foaming agent, wherein the curable adhesive is a thermosetting adhesive and the foaming agent is a thermally expandable microcapsule. When the adhesive composition is applied to one side of a support to a thickness of 45 μm and the coating of the adhesive composition is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the coating to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer.

[0303] In the adhesive composition of this embodiment, as described in the section of the second embodiment of the above-mentioned article, when the adhesive composition is applied to one side of a support in a predetermined thickness and the coating of the adhesive composition is heated at a predetermined temperature for a predetermined time to foam and harden the coating to form a foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more in the cross section parallel to the thickness direction of the foam layer is a predetermined value or less per predetermined length in the direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0304] The components of the adhesive composition of this embodiment are the same as those described above in the sections "A. Article" and "B. Method for producing article," and therefore will not be described here.

[0305] In this embodiment, when the adhesive composition is applied to one side of the support to a thickness of 45 μm and the coating of the adhesive composition is heated at the maximum foaming temperature of the foaming agent ±20° C. for 15 minutes to foam and harden the coating to form a foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer in a cross section parallel to the thickness direction of the foam layer is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer. The number of bubbles is preferably 3 or less, more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0.

[0306] The support may be the same as in the first embodiment.

[0307] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0308] [Examples 1 to 5 and Comparative Examples 1 to 2] First adhesive compositions 1 to 7 and second adhesive compositions 1 to 7 having the compositions shown in Table 1 below were prepared using the materials listed below.

[0309] Acrylic resin: PMMA-PBuA-PMMA (partially acrylamide groups), Tg: -20℃, 120℃, Mw: 150,000 Epoxy resin A: Bisphenol A novolac type, solid at room temperature, softening temperature: 70°C, epoxy equivalent: 210g / eq, Mw: 1300, melt viscosity at 150°C: 0.5Pa s Epoxy resin B: BPA phenoxy type, solid at room temperature, softening temperature: 110℃, epoxy equivalent: 8000g / eq, Mw: 50,000 Epoxy resin C: Bisphenol A type, liquid at room temperature, epoxy equivalent: 184~194g / eq Epoxy resin D: Diaminodiphenylmethane type, highly viscous liquid, epoxy equivalent: 110~130g / eq Epoxy resin E: Silicone modified, solid at room temperature, epoxy equivalent: 1200g / mol Epoxy resins A, B, and E are solids at room temperature, and epoxy resins C and D are liquids at room temperature.

[0310] Hardener A: Phenol-formaldehyde polycondensate, softening point 80°C, hydroxyl equivalent 104g / mol Hardener B: α-(hydroxy(or dihydroxy)phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene(hydroxy(or dihydroxy)phenylenemethylene)] Curing catalyst: 2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230°C, reaction start temperature: 145°C to 155°C, active region: 155°C to 173°C (Shikoku Chemical Industry Co., Ltd., 2PHZ-PW) Silane coupling agent: 3-glycidoxypropyltrimethoxysilane

[0311] Foaming agent A: Thermally expandable microcapsules, average particle size 10μm~16μm, expansion start temperature 123℃~133℃, maximum expansion temperature 168℃~178℃, core: hydrocarbon, shell: thermoplastic polymer Foaming agent B: Thermally expandable microcapsules, average particle size 18μm~24μm, expansion start temperature 120℃~130℃, maximum expansion temperature 175℃~190℃, core: hydrocarbon, shell: thermoplastic polymer Foaming agent C: Thermally expandable microcapsules, average particle size 18μm~24μm, expansion start temperature 123℃~133℃, maximum expansion temperature 180℃~195℃, core: hydrocarbon, shell: thermoplastic polymer Solvent: Methyl ethyl ketone

[0312] [Table 1]

[0313] A release film (PET separator, manufactured by Nippa Corporation, PET50x1-J2, thickness 50 μm) was used as a separator, and the second adhesive composition was applied to the release-treated surface of the release film using an applicator so that the thickness after coating and drying would be 45 μm. Then, it was dried in an oven at 100° C. for 3 minutes to form a second adhesive layer.

[0314] Polyethylene naphthalate (PEN film, Toyobo Film Solutions Co., Ltd., Teonex Q51, thickness 25 μm) was used as the substrate. The first adhesive composition was applied using an applicator so that the thickness after coating and drying was 45 μm. Thereafter, it was dried in an oven at 100° C. for 3 minutes to form a first adhesive layer.

[0315] Next, the surface of the second adhesive layer of the laminate having the separator and the second adhesive layer was laminated onto the surface of the substrate of the laminate having the substrate and the first adhesive layer, thereby obtaining a foamable adhesive sheet in which the first adhesive layer, substrate, second adhesive layer, and separator were arranged in this order.

[0316] [evaluation] (1) Adhesiveness As shown in Fig. 14(a) and (b), two metal plates 41 (cold-rolled steel plate SPCC-SD) with a thickness of 1.6 mm, width of 25 mm, and length of 100 mm were prepared. A spacer 42 was placed at a predetermined interval on one tip of one of the metal plates 41. The thickness of the spacer 42 was about 370 µm (the thickness of two sheets of Kapton tape P-221 manufactured by Nitto Denko Corporation and one sheet of fluororesin adhesive tape 8410 manufactured by Teraoka Seisakusho). In addition, the foamable adhesive sheet was cut into a size of 12.5 mm x 25 mm. When the foamable adhesive sheet had a separator, the separator was peeled off. Next, the foamable adhesive sheet 10 was placed between the spacers 42, and the other metal plate 41 was placed so that one tip of the metal plate 41 overlapped, and fixed with a clip to obtain a test piece. The test piece was then placed in a heat oven, heated from room temperature to a predetermined temperature in 13 minutes, and held for 20 minutes to foam and cure the first adhesive layer and the second adhesive layer of the foamable adhesive sheet 10. The heating temperatures were 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C.

[0317] The shear strength (adhesive strength) of the heated test pieces was measured using a tensile tester Tensilon RTF1350 (manufactured by A&D Co., Ltd.) in accordance with JIS K6850:1999. The measurement conditions were a tensile speed of 10 mm / min and a temperature of 23° C. Tables 2 and 3 show the heating temperature and adhesive strength at which the adhesive strength was the highest among the adhesive strengths at each heating temperature.

[0318] (2) Observation of bubbles A test piece was prepared by attaching the surface of the first adhesive layer of the foamable adhesive sheet to a glass substrate in such a way that it protruded about 1 mm. The test piece was placed in a heat oven, heated from room temperature to a predetermined temperature in 13 minutes, and held for 15 minutes to foam and cure the first adhesive layer and the second adhesive layer of the foamable adhesive sheet 10, thereby obtaining an adhesive sheet having the first cured adhesive layer, the substrate, and the second cured adhesive layer in this order. In this case, the heating temperature was the heating temperature at which the adhesive strength was the highest among the adhesive strengths at each heating temperature in the above-mentioned adhesive strength measurement.

[0319] In order to observe the cross section clearly, the part of the adhesive sheet protruding from the edge of the glass substrate was cut along the edge of the glass substrate with a trimming blade. The cut cross section was fixed so that it could be observed vertically, and air bubbles were observed with an optical microscope (Keyence Corporation, digital microscope VHX-2000). Then, for each cured adhesive layer, the number of air bubbles whose length was equal to or greater than the thickness of the cured adhesive layer (foam layer) minus 6 μm was counted in a 4 mm square field of view. The number of air bubbles was determined as the average number of air bubbles at three randomly selected locations.

[0320] [Table 2]

[0321] [Table 3]

[0322] In Examples 1 to 5, when the first and second adhesive layers of the foamable adhesive sheet were foamed and cured to form the first and second cured adhesive layers, respectively, the number of predetermined bubbles per predetermined length in the first and second cured adhesive layers was less than 7, particularly 3 or less, and the adhesiveness was good. In contrast, in Comparative Examples 1 to 3, when the first and second adhesive layers of the foamable adhesive sheet were foamed and cured to form the first and second cured adhesive layers, respectively, the number of predetermined bubbles per predetermined length in the first and second cured adhesive layers was large, and the adhesiveness was poor.

[0323] In the present disclosure, for example, the following inventions are provided. [1] An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; An article in which, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer minus 6 μm is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer. [2] An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; An article in which, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer. [3] The adhesive member has a first cured adhesive layer and a second cured adhesive layer, The article described in [1] or [2], wherein at least one of the first cured adhesive layer and the second cured adhesive layer is the foam layer. [4] The article described in [3], wherein the first cured adhesive layer and the second cured adhesive layer are the foam layer. [5] The article according to any one of [1] to [4], wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the content of the epoxy resin that is liquid at room temperature in the adhesive composition is 60 parts by mass or less per 100 parts by mass of the resin component in the adhesive composition. [6] The article according to any one of [1] to [5], wherein the content of the foaming agent in the adhesive composition is 13 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the resin component in the adhesive composition. [7] The article according to any one of [1] to [6], wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower. [8] A method for producing an article using a foamable adhesive sheet having at least an adhesive layer, comprising the steps of: the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; a step of disposing the foamable adhesive sheet between a first member and a second member; a bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer, and bonding the first member and the second member to each other; and setting foaming and curing conditions in the bonding step such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of equal to or greater than the thickness of the foam layer minus 6 μm is less than 7 bubbles per 4 mm length in a direction perpendicular to the thickness direction of the foam layer. [9] A method for producing an article using a foamable adhesive sheet having at least an adhesive layer, comprising the steps of: the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; a positioning step of positioning the foamable adhesive sheet between a first member and the second member; a bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer, and bonding the first member and the second member to each other; and setting foaming and curing conditions in the bonding step such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

[10] The foamable adhesive sheet has a first adhesive layer and a second adhesive layer, The method for manufacturing an article described in [8] or [9], wherein at least one of the first adhesive layer and the second adhesive layer is the foaming agent-containing adhesive layer.

[11] The method for producing an article according to any one of [8] to

[10] , wherein the heating temperature in the bonding step is within ±20°C of the maximum foaming temperature of the foaming agent.

[12] The method for manufacturing an article described in any of [8] to

[11] , wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the content of the epoxy resin that is liquid at room temperature in the adhesive layer is 60 parts by mass or less per 100 parts by mass of the resin component in the adhesive layer. {13} The method for producing an article according to any one of [8] to

[12] , wherein the content of the foaming agent in the adhesive layer is 13 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the resin component in the adhesive layer.

[14] The method for producing an article according to any one of [8] to

[13] , wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower.

[15] A foamable adhesive sheet having at least an adhesive layer, the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; A foamable adhesive sheet in which, when the foamable adhesive sheet is heated for 15 minutes at a maximum foaming temperature of the foaming agent ±20°C to foam and harden the foaming agent-containing adhesive layer to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer.

[16] A foamable adhesive sheet having at least an adhesive layer, the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; A foamable adhesive sheet in which, when the foamable adhesive sheet is heated for 15 minutes at a maximum foaming temperature of the foaming agent ±20°C to foam and harden the foaming agent-containing adhesive layer to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer.

[17] A first adhesive layer and a second adhesive layer, The foamable adhesive sheet according to

[15] or

[16] , wherein at least one of the first adhesive layer and the second adhesive layer is the foaming agent-containing adhesive layer.

[18] The foamable adhesive sheet according to

[17] , wherein the first adhesive layer and the second adhesive layer are the foaming agent-containing adhesive layers.

[19] The foamable adhesive sheet according to

[17] or

[18] , wherein the tack of the first adhesive layer is 0 gf or more and less than 10 gf, and the tack of the second adhesive layer is 10 gf or more and 400 gf or less.

[20] The foamable adhesive sheet according to any of

[15] to

[19] , wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the content of the epoxy resin that is liquid at room temperature in the adhesive layer is 60 parts by mass or less per 100 parts by mass of the resin component in the adhesive layer.

[21] The foamable adhesive sheet according to any one of

[15] to

[20] , wherein the content of the foaming agent in the adhesive layer is 13 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the resin component in the adhesive layer.

[22] The foamable adhesive sheet according to any one of

[15] to

[21] , wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower.

[23] An adhesive composition comprising a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; The adhesive composition is applied to one side of a support to a thickness of 45 μm, and the coating of the adhesive composition is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the coating to form a foam layer, wherein, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 per 4 mm length perpendicular to the thickness direction of the foam layer.

[24] An adhesive composition comprising a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; The adhesive composition is applied to one surface of a support to a thickness of 45 μm, and the coating of the adhesive composition is heated at a maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the coating to form a foam layer. In this adhesive composition, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer is less than 7 per length of 4 mm in the direction perpendicular to the thickness direction of the foam layer.

[25] The adhesive composition according to

[23] or

[24] , wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the content of the epoxy resin that is liquid at room temperature in the adhesive composition is 60 parts by mass or less per 100 parts by mass of the resin component in the adhesive composition.

[26] The adhesive composition according to any one of

[23] to

[25] , wherein the content of the foaming agent in the adhesive composition is 13 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the resin component in the adhesive composition.

[27] The adhesive composition according to any one of

[23] to

[26] , wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower. [Explanation of symbols]

[0324] 1 … Adhesive layer 1a … First adhesive layer 1b…Second adhesive layer 5, 5a, 5b, 15, 15a, 15b…foam layer 11 … Cured adhesive layer 11a...First cured adhesive layer 11b…Second cured adhesive layer 12 … Base material 13a … First intermediate layer 13b…Second intermediate layer 10... Foam adhesive sheet 20a … First member 20b … second member 30... Adhesive material 100 … Goods

Claims

1. An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; In a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the value of (the thickness of the foam layer) - 6 μm is less than 7 bubbles per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

2. An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foam layer containing a foamed, cured product of an adhesive composition containing a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; An article, in which, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer.

3. the adhesive member has a first cured adhesive layer and a second cured adhesive layer, 3. The article of claim 1 or claim 2, wherein at least one of the first cured adhesive layer and the second cured adhesive layer is the foam layer.

4. The article of claim 3 , wherein the first cured adhesive layer and the second cured adhesive layer are the foam layers.

5. 3. The article according to claim 1 or 2, wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and a content of the epoxy resin that is liquid at room temperature in the adhesive composition is 60 parts by mass or less per 100 parts by mass of a resin component in the adhesive composition.

6. 3. The article according to claim 1, wherein the content of the foaming agent in the adhesive composition is 13 parts by mass or more and 30 parts by mass or less per 100 parts by mass of a resin component in the adhesive composition.

7. The article according to claim 1 or 2, wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower.

8. A method for producing an article using a foamable adhesive sheet having at least an adhesive layer, comprising: the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; a positioning step of positioning the foamable adhesive sheet between a first member and a second member; a bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer, and bonding the first member and the second member to each other; and setting foaming and curing conditions in the bonding step such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of equal to or greater than the value of (the thickness of the foam layer) - 6 µm is less than 7 bubbles per length of 4 mm in a direction perpendicular to the thickness direction of the foam layer.

9. A method for producing an article using a foamable adhesive sheet having at least an adhesive layer, comprising: the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; a positioning step of positioning the foamable adhesive sheet between a first member and the second member; a bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamable adhesive sheet to form a foam layer, and bonding the first member and the second member to each other; and setting foaming and curing conditions in the bonding step such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per length of 4 mm in a direction perpendicular to the thickness direction of the foam layer.

10. the foamable adhesive sheet has a first adhesive layer and a second adhesive layer, The method for producing an article according to claim 8 or claim 9, wherein at least one of the first adhesive layer and the second adhesive layer is the foaming agent-containing adhesive layer.

11. The method for producing an article according to claim 8 or 9, wherein the heating temperature in the bonding step is within ±20° C. of the maximum foaming temperature of the foaming agent.

12. 10. The method for manufacturing an article according to claim 8 or claim 9, wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and a content of the epoxy resin that is liquid at room temperature in the adhesive layer is 60 parts by mass or less per 100 parts by mass of a resin component in the adhesive layer.

13. The method for producing an article according to claim 8 or 9, wherein a content of the foaming agent in the adhesive layer is 13 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of a resin component in the adhesive layer.

14. The method for producing an article according to claim 8 or 9, wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower.

15. A foamable adhesive sheet having at least an adhesive layer, the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; A foamable adhesive sheet, in which, when the foamable adhesive sheet is heated at a maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the foaming agent-containing adhesive layer to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the thickness of the foam layer - 6 μm is less than 7 bubbles per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

16. A foamable adhesive sheet having at least an adhesive layer, the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent; The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; A foamable adhesive sheet, in which, when the foamable adhesive sheet is heated at a maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam and harden the foaming agent-containing adhesive layer to form a foam layer, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length in the thickness direction of the foam layer of 100 μm or more is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

17. A first adhesive layer and a second adhesive layer are included, The foamable adhesive sheet according to claim 15 or 16, wherein at least one of the first adhesive layer and the second adhesive layer is the foaming agent-containing adhesive layer.

18. The foamable adhesive sheet according to claim 11 , wherein the first adhesive layer and the second adhesive layer are foaming agent-containing adhesive layers.

19. The foamable adhesive sheet according to claim 18 , wherein the tack of the first adhesive layer is 0 gf or more and less than 10 gf, and the tack of the second adhesive layer is 10 gf or more and 400 gf or less.

20. 17. The foamable adhesive sheet according to claim 15 or 16, wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the content of the epoxy resin that is liquid at room temperature in the adhesive layer is 60 parts by mass or less per 100 parts by mass of the resin component in the adhesive layer.

21. 17. The foamable adhesive sheet according to claim 15, wherein the content of the foaming agent in the adhesive layer is 13 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the resin component in the adhesive layer.

22. 17. The foamable adhesive sheet according to claim 15, wherein the foaming agent has a maximum foaming temperature of 175°C or higher and 220°C or lower.

23. An adhesive composition comprising a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; The adhesive composition is applied to one surface of a support to a thickness of 45 μm, and the coating of the adhesive composition is heated at a maximum foaming temperature of the foaming agent ±20° C. for 15 minutes to foam and harden the coating to form a foam layer. In this adhesive composition, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles whose length in the thickness direction of the foam layer is equal to or greater than the value of the thickness of the foam layer - 6 μm is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer.

24. An adhesive composition comprising a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule; The adhesive composition is applied to one side of a support to a thickness of 45 μm, and the coating of the adhesive composition is heated at the maximum foaming temperature of the foaming agent ±20° C. for 15 minutes to foam and harden the coating to form a foam layer. In this adhesive composition, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foam layer is less than 7 per length of 4 mm in the direction perpendicular to the thickness direction of the foam layer.

25. 25. The adhesive composition according to claim 23 or 24, wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and a content of the epoxy resin that is liquid at room temperature in the adhesive composition is 60 parts by mass or less per 100 parts by mass of a resin component in the adhesive composition.

26. The adhesive composition according to claim 23 or 24, wherein a content of the foaming agent in the adhesive composition is 13 parts by mass or more and 30 parts by mass or less per 100 parts by mass of a resin component in the adhesive composition.

27. The adhesive composition according to claim 23 or 24, wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower.

Images