Articles, methods for manufacturing articles, foamed adhesive sheets, and adhesive compositions

Abstract

The present invention provides articles with excellent adhesive properties, methods for manufacturing articles capable of improving adhesive properties, foamed adhesive sheets, and adhesive compositions. [Solution] The present invention provides an article comprising 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 foamed 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 foamed layer, the number of bubbles whose length in the thickness direction of the foamed layer is equal to or greater than the thickness of the foamed layer minus 6 μm is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

Description

[Technical Field]

[0001] This disclosure relates to articles and methods for manufacturing them, as well as foamed adhesive sheets and adhesive compositions used therein. [Background technology]

[0002] Adhesives used to bond components 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 (foaming adhesive sheets). As a method of using foaming adhesive sheets, for example, a method is known in which the foaming adhesive sheet is placed between members, and then the foaming adhesive sheet is heated to foam and harden, thereby bonding the members together.

[0004] In such foamed adhesive sheets, good adhesion after foaming and curing is desirable. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2000-53944 [Patent Document 2] Patent No. 6223477 [Patent Document 3] Japanese Patent Publication No. 2019-214729 [Overview of the project] [Problems that the invention aims to solve]

[0006] This disclosure has been made in view of the above circumstances, and its main purpose is to provide articles with excellent adhesive properties, methods for manufacturing articles capable of improving adhesive properties, foamed adhesive sheets, and adhesive compositions. [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 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 minus 6 μm is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer.

[0008] Other embodiments of the present disclosure provide 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 with a length of 100 μm or more in 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.

[0009] Other embodiments of the present disclosure provide a method for manufacturing an article using a foamed adhesive sheet having at least an adhesive layer, wherein 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, and the method comprises a placement step of placing the foamed adhesive sheet between a first member and a second member, and an bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foam layer and bonding the first member and the second member, wherein the foaming and curing conditions in the bonding step are 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 in the direction perpendicular to the thickness direction of the foam layer.

[0010] Other embodiments of the present disclosure provide a method for manufacturing an article using a foamed adhesive sheet having at least an adhesive layer, wherein 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, and the method comprises a placement step of placing the foamed adhesive sheet between a first member and a second member, and an bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foam layer and bonding the first member and the second member, wherein the foaming and curing conditions in the bonding step are set such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles with a length of 100 μm or more in 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.

[0011] Other embodiments of the present disclosure provide a foamed adhesive sheet having at least an adhesive layer, wherein 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, and when the foamed 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 foamed layer, the number of bubbles in a cross section parallel to the thickness direction of the foamed layer, where the length of the foamed layer in the thickness direction is equal to or greater than the thickness of the foamed layer - 6 μm, is less than 7 bubbles per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[0012] Other embodiments of the present disclosure provide a foamed adhesive sheet having at least an adhesive layer, wherein 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, the foaming agent is a thermally expandable microcapsule, and when the foamed 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 foamed layer, the number of bubbles in a cross section parallel to the thickness direction of the foamed layer, with a length of 100 μm or more in the thickness direction of the foamed layer, is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[0013] Other embodiments of the present disclosure provide 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, and when 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 the 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, where the length of the foam layer in the thickness direction is equal to or greater than the thickness of the foam layer - 6 μm, is less than 7 bubbles per 4 mm length in the direction perpendicular to the thickness direction of the foam layer.

[0014] Another embodiment of the present disclosure is an adhesive composition containing a curable adhesive and a foaming agent, wherein the curable adhesive is a thermosetting adhesive, the foaming agent is a thermally expandable microcapsule, the adhesive composition is applied to one surface of a support at a thickness of 45 μm, and the coating film of the adhesive composition is heated at the maximum foaming temperature of the foaming agent ±20 °C for 15 minutes to foam and cure the coating film to form a foam layer. When the foam layer is formed, 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. An adhesive composition is provided.

Advantages of the Invention

[0015] In the present disclosure, it is possible to provide an article having excellent adhesiveness, a method for manufacturing an article capable of improving adhesiveness, a foaming adhesive sheet, and an adhesive composition.

Brief Description of the Drawings

[0016] [Figure 1] It is a schematic cross-sectional view illustrating an article in the present disclosure. [Figure 2] It is a schematic cross-sectional view illustrating an article in the present disclosure. <​​​​​​​​​​​​​​​​​​​​​​This is a schematic cross-sectional view illustrating an example of a foamed adhesive sheet in this disclosure. [Figure 11] This graph illustrates the TMA curve for foamed adhesive sheets. [Figure 12] This is a schematic cross-sectional view illustrating the state of the foamed adhesive sheet after foaming and curing in this disclosure. [Figure 13] This is a schematic cross-sectional view illustrating the state of the foamed adhesive sheet after foaming and curing in this disclosure. [Figure 14] This is a schematic cross-sectional view illustrating a test method for the adhesive properties of a foamed adhesive sheet after foaming and curing. [Modes for carrying out the invention]

[0017] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, the drawings may be schematically represented in terms of 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 should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0018] In this specification, when describing a configuration in which one member is placed on top of another member, unless otherwise specified, the terms "on top" or "below" include both cases: when the other member is placed directly above or below the other member so as to be in contact with it, and when the other member is placed above or below the other member via yet another member. Similarly, when describing a configuration in this specification in which one member is placed on the surface of another member, unless otherwise specified, the terms "on the surface" or "on the surface" include both cases: when the other member is placed directly above or below the other member so as to be in contact with it, and when the other member is placed above or below the other member via yet another member.

[0019] Furthermore, in this specification, "sheet" also includes a component called "film." Also, "film" also includes a component called "sheet." Furthermore, the numerical ranges in this specification represent average ranges.

[0020] In a thermally expandable microcapsule, a thermal expansion agent such as a hydrocarbon is enclosed inside a resin shell. When heated, the resin constituting the shell softens, and the pressure of the thermal expansion agent such as a hydrocarbon increases, causing the thermally expandable microcapsule to expand. As the shell thins due to the expansion, if heating continues, the thermal expansion agent escapes from the thermally expandable microcapsule, causing it to contract. The inventors of this disclosure have found that the thermal expansion agent (gas) that escapes from the thermally expandable microcapsule forms bubbles, and these bubbles can aggregate to form larger bubbles. Furthermore, the inventors of this disclosure have also found that when a foamed adhesive sheet is attached to a first or second component during the manufacturing of an article, bubbles may be mixed between the first or second component and the foamed adhesive sheet, and these bubbles can aggregate to form larger bubbles.

[0021] Furthermore, in the case of thermosetting adhesives, during the foaming and curing process of the adhesive composition, the resin component of the thermosetting adhesive softens and becomes more fluid. The inventors of this disclosure have also found that when there are air bubbles in the layer, if the resin component of the thermosetting adhesive softens and becomes more fluid, the air bubbles become more mobile and can gather together to form larger bubbles.

[0022] Thus, the inventors of this disclosure have identified a new problem: when a curable adhesive is a thermosetting adhesive and the foaming agent is a thermally expandable microcapsule, large bubbles may be generated, and such large bubbles can cause a decrease in adhesiveness. This disclosure solves this new problem.

[0023] The articles, methods for manufacturing the articles, foamed adhesive sheets, and adhesive compositions described herein will be explained in detail below.

[0024] A.Goods The articles described herein have two embodiments. Each embodiment is described below.

[0025] I. First Embodiment of the Article A first embodiment of an article in this 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 foamed 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 foamed layer, the number of bubbles whose length in the thickness direction of the foamed layer is equal to or greater than the thickness of the foamed layer - 6 μm is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[0026] Figure 1 is a schematic cross-sectional view showing an example of an article according to this embodiment. As shown in Figure 1, the article 100 has a first member 20a, a second member 20b, and an adhesive member 30 disposed 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 foamed 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 foamed layer 15 constituting the cured adhesive layer 11, the number of air bubbles 31 whose length s in the thickness direction D1 of the foamed layer 15 is within a predetermined range with respect to the thickness t of the foamed layer 15 is less than or equal to a predetermined value per predetermined length L in the direction d2 perpendicular to the thickness direction d1 of the foamed layer 15.

[0027] When an adhesive member has a single cured adhesive layer, and the cured adhesive layer is a foam layer, if there are large air bubbles, approximately the thickness of the foam layer, then in the region where such air bubbles exist, the cured adhesive layer may not be in contact with the first and second members, 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 may become very small. Therefore, it is thought that adhesion defects such as peeling, lifting, and cracking of the cured adhesive layer are likely to occur, starting from the air 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, the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer, is less than or equal to a predetermined value 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.

[0029] Figure 2 is a schematic cross-sectional view showing another example of an article of this embodiment. In the article of this embodiment, as shown in Figure 2, the adhesive member 30 may 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, respectively, containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and each contains air bubbles 31 inside. In a cross-section of the foam layer 15a constituting the first cured adhesive layer 11a in the thickness direction D1, the number of air 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 or equal to a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15a. Furthermore, in the cross-section of the foam layer 15b constituting the second cured adhesive layer 11b in the thickness direction D1, 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 or equal to a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15b.

[0030] In Figure 2, both the first curing adhesive layer 11a and the second curing 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. However, it is also possible that only one of the first curing adhesive layer 11a or the second curing adhesive layer 11b is a foam layer containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent.

[0031] When an adhesive member has a first cured adhesive layer and a second cured adhesive layer, and both the first and second cured adhesive layers are foam layers, if there are large air bubbles, approximately the thickness of the foam layer, then in the regions where such air bubbles exist, the first cured adhesive layer may not be in contact with the first member, or the second cured adhesive layer may not be in contact with the second member, or the contact area between the first cured adhesive layer and the first member may become very small, or the contact area between the second cured adhesive layer and the second member may become very small. Therefore, it is thought that adhesive defects such as peeling, lifting, and cracking of the first and second cured adhesive layers are likely to occur, starting from the air 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 the first cured adhesive layer and the second cured adhesive layer are foam layers, adhesion defects can be suppressed by ensuring that the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer, is less than or equal to a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foam layer. Therefore, it is possible to improve adhesion.

[0033] Furthermore, even when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and either the first cured adhesive layer or the second cured adhesive layer is a foam layer, it is similarly possible to suppress adhesion defects and improve adhesion.

[0034] Figure 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 Figure 3, the adhesive member 30 may have a first curing adhesive layer 11a, a substrate 12, and a second curing adhesive layer 11b in this order. Figure 3 is the same as Figure 2 described above, except that the substrate 12 is placed between the first curing adhesive layer 11a and the second curing adhesive layer 11b.

[0035] In Figure 3, both the first curing adhesive layer 11a and the second curing 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. However, either the first curing adhesive layer 11a or the second curing 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] When an adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer in that order, and the first and second cured adhesive layers are foam layers, if there are large air bubbles, approximately the thickness of the foam layer, then in the regions where such air bubbles exist, the first cured adhesive layer may not be in contact with the first member and substrate, or the second cured adhesive layer may not be in contact with the second member and substrate, or the contact area between the first cured adhesive layer and the first member and substrate may become very small, or the contact area between the second cured adhesive layer and the second member and substrate may become very small. Therefore, it is thought that adhesion defects such as peeling, lifting, and cracking of the first and second cured adhesive layers are likely to occur, starting from the air bubbles.

[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 that order, and the first cured adhesive layer and the second cured adhesive layer are foam layers, adhesion defects can be suppressed by ensuring that the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer, is less than or equal to a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foam layer. Therefore, it is possible to improve adhesion.

[0038] Furthermore, even when an adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer, and either the first cured adhesive layer or the second cured adhesive layer is a foam layer, it is similarly possible to suppress adhesion defects and improve adhesion.

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

[0040] The following describes the various components of the article in this embodiment.

[0041] 1. Adhesive material The adhesive member in this 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 foamed 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 foamed layer, the number of bubbles whose length in the thickness direction of the foamed layer is within a predetermined range relative to the thickness of the foamed layer is less than or equal to a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foamed layer.

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

[0043] When the adhesive member has a first cured adhesive layer and a second cured adhesive layer, or when it has a first cured adhesive layer, a substrate, and a second cured adhesive layer in that order, at least one of the first cured adhesive layer and the second cured adhesive layer is the foam layer described above.

[0044] For convenience, in this specification, 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] The following describes the various components of the adhesive members.

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

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

[0048] Furthermore, "bubbles whose length in the thickness direction of the foam layer is equal to or greater than the foam layer thickness - 6 μm" refers to bubbles whose length in the thickness direction of the foam layer is equal to or greater than the foam layer thickness - 6 μm. For example, if the thickness of the foam layer is 200 μm, the number of bubbles whose length in the thickness direction of the foam layer is 200 - 6 = 194 μm or more falls within the above range. Also, for example, if the thickness of the foam layer is 00 μm, the number of bubbles whose length in the thickness direction of the foam layer is 300 - 6 = 294 μm or more 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 a cross-section parallel to the thickness direction of the foam layer can be determined, for example, from images obtained by observation with an optical microscope or scanning electron microscope (SEM), or from tomographic images obtained by an X-ray CT scan. With an X-ray CT scan, bubbles in the cross-section of the foam layer can be observed non-destructively and non-contact. Therefore, it is possible to prevent bubbles from collapsing when cutting the article to expose the cross-section of the foam layer. Thus, the length of the bubbles in the thickness direction of the foam layer and the number of bubbles can be accurately determined. In particular, when the first and second members are made of metal, observation with an optical microscope or scanning electron microscope (SEM) is preferred.

[0050] Furthermore, the number of bubbles in a cross-section parallel to the thickness direction of the foam layer is the average of the number of bubbles at three randomly selected locations.

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

[0052] Furthermore, for articles, the thickness direction of the foam layer shall be perpendicular to the planar direction of the first or second member. The direction perpendicular to the thickness direction of the foam layer shall be the planar direction of the first or second member. Note that the planar directions of the first and second members refer to the planar directions of the first and second members 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, adjusting the composition of the adhesive composition or adjusting the foam curing conditions of the adhesive composition.

[0054] Methods for adjusting the composition of an adhesive composition include, for example, adjusting the fluidity of the resin component of a 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 amount of foaming agent, and, if 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 a curable adhesive include, for example, adjusting the molecular weight of the resin component which is the main component of the curable adhesive, adjusting the state of the resin component which is the main component of the curable adhesive, and adjusting the content of the resin component which is liquid at room temperature.

[0056] In a method for adjusting the molecular weight of the resin component that is the main component of a curable adhesive, for example, a thermosetting adhesive is used as the curable adhesive. In this case, during the foaming and curing process of the adhesive composition, the resin component softens and its fluidity increases. When the molecular weight of the resin component is large, the fluidity of the resin component is lower compared to when the molecular weight of the resin component is small. Therefore, bubbles are less likely to become large and less likely to connect with each other, thus tending to suppress the generation of large bubbles as described above. Thus, by including a high molecular weight resin component as the main component of the curable adhesive, the generation of large bubbles as described above can be suppressed.

[0057] As mentioned above, in the case of thermosetting adhesives, the resin component softens and becomes more fluid during the foaming and curing process of the adhesive composition. Resin components that are solid at room temperature tend to have lower fluidity compared to resin components that are liquid at room temperature. Therefore, bubbles are less likely to become large and less likely to connect with each other, thus suppressing the generation of large bubbles as described above. Accordingly, in a method for adjusting the state of the resin component that is the main component of a curable adhesive, the generation of large bubbles as described above can be suppressed by including a resin component that is solid at room temperature as the main component of the curable adhesive. Room temperature refers to 23°C.

[0058] When a curable adhesive contains a resin component that is liquid at room temperature as its main component, the fluidity of the resin component tends to increase when it softens during the foaming curing process of the adhesive composition. On the other hand, by relatively reducing the amount of resin component that is liquid at room temperature, the fluidity of the resin component can be made relatively low. Therefore, by reducing the amount of resin component that is liquid at room temperature in the main component of a curable adhesive, the generation of large bubbles as described above can be suppressed.

[0059] In a method for adjusting the maximum foaming temperature of a foaming agent, thermally expandable microcapsules are used as the foaming agent. In thermally expandable microcapsules, a thermally expandable agent such as a hydrocarbon is enclosed inside a resin shell. When heated, the resin constituting the shell softens, and the pressure of the thermally expandable agent such as the hydrocarbon increases, causing the thermally expandable microcapsule to expand. As the shell thins due to expansion, if heating continues, the thermally expandable agent escapes from the thermally expandable microcapsule, causing it to contract. Therefore, for example, if the maximum foaming temperature of the foaming agent is high, it is possible to suppress the contraction of the foaming agent during the foaming and curing process of the adhesive composition, which would otherwise reduce the thickness of the foam layer (cured adhesive layer). This suppresses the relative size of bubbles to the thickness of the foam layer (cured adhesive layer). Thus, the relative size of bubbles to the thickness of the foam layer (cured adhesive layer) can be reduced, thereby suppressing the formation of large bubbles as described above.

[0060] In a method for adjusting the foaming ratio at the maximum foaming temperature of the foaming agent, for example, a higher foaming ratio at the maximum foaming temperature tends to result in a thicker foam layer (hardened adhesive layer). Therefore, the size of the bubbles can be made relatively smaller relative to the thickness of the foam layer (hardened adhesive layer). Thus, the large bubbles described above can be suppressed.

[0061] In methods for adjusting the foaming agent content, for example, a higher foaming agent content tends to result in a thicker foam layer (hardened adhesive layer). Therefore, the size of the bubbles can be made relatively smaller relative to the thickness of the foam layer (hardened adhesive layer). Thus, the large bubbles mentioned above can be suppressed.

[0062] When the blowing agent is a thermally expandable microcapsule, in methods for adjusting the structure of the thermally expandable microcapsule, for example, increasing the thickness of the shell of the thermally expandable microcapsule tends to decrease gas permeability and reduce the size of the bubbles. Also, for example, crosslinking the shell of the thermally expandable microcapsule tends to decrease gas permeability and reduce the size of the bubbles.

[0063] One method for adjusting the foaming and curing conditions of the adhesive composition is to adjust the heating temperature, for example, when the foaming agent is a thermally expandable microcapsule. For example, by setting the heating temperature within a predetermined range relative to the maximum foaming temperature of the foaming agent, the generation of large bubbles as described above can be suppressed. Alternatively, by setting the heating temperature within a predetermined range relative to the maximum displacement extrapolation temperature of the foaming adhesive sheet, the generation of large bubbles as described above can also be suppressed. Specific heating temperatures will be described in section B, "Method for Manufacturing Articles," 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 containing a curable adhesive and a foaming agent.

[0065] (i) Curing adhesives In this embodiment, a curable adhesive used in the cured adhesive layer can be a curable adhesive generally used for the adhesive layer of foamed adhesive sheets. Examples of curable adhesives include thermosetting adhesives and photocuring adhesives. Among these, thermosetting adhesives are preferred. Thermosetting adhesives can be applied even when the first and second members are not transparent, such as when they are made of metal.

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

[0067] In particular, the curable adhesive is preferably an epoxy resin-based adhesive. That is, the curable adhesive preferably contains epoxy resin and a curing agent. Generally, epoxy resin-based adhesives have excellent mechanical strength, heat resistance, insulation, and chemical resistance, and exhibit low curing shrinkage, making them suitable for a wide range of applications.

[0068] The following explanation will provide an example of a case where the curing adhesive is an epoxy resin-based adhesive.

[0069] (i-1) Epoxy resin The epoxy resin in this embodiment is a compound having at least one epoxy group or glycidyl group, which undergoes a crosslinking polymerization reaction and hardens when used in combination with a curing agent. The epoxy resin also includes monomers having at least one epoxy group or glycidyl group.

[0070] As the epoxy resin, epoxy resins commonly used in epoxy resin adhesives can be used.

[0071] In particular, curable adhesives preferably contain an epoxy resin having a weight-average molecular weight of 900 to 100,000. As mentioned above, during 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 high, the fluidity of the epoxy resin is lower compared to when the molecular weight of the epoxy resin is low. Therefore, bubbles are less likely to become large and less likely to connect with each other, so the generation of large bubbles tends to be suppressed. Thus, the inclusion of a high molecular weight epoxy resin can suppress the generation of large bubbles.

[0072] In this case, the weight-average molecular weight of the epoxy resin may be, for example, 900 to 100,000, 1,650 to 80,000, or 3,800 to 60,000.

[0073] The weight-average molecular weight of the resin component is the polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0074] Furthermore, it is preferable that the curable adhesive contains an epoxy resin that is solid at room temperature. As mentioned above, during the foaming and curing process of the adhesive composition, the epoxy resin softens and becomes more fluid. At this time, epoxy resins that are solid at room temperature tend to have lower fluidity compared to epoxy resins that are liquid at room temperature. Therefore, bubbles are less likely to become large and less likely to connect with each other, thus suppressing the generation of large bubbles. Thus, the inclusion of an epoxy resin that is solid at room temperature can suppress the generation of large bubbles.

[0075] Furthermore, it is preferable that the curable adhesive contains both an epoxy resin that is solid at room temperature and an epoxy resin that is liquid at room temperature. When the curable adhesive contains an epoxy resin that is liquid at room temperature, the fluidity tends to increase when the resin component softens during the foaming curing process of the adhesive composition. As a result, bubbles tend to connect with each other and become larger. 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 curable adhesive layer and a second curable adhesive layer, it is preferable that at least one of the adhesive compositions used for the first curable adhesive layer and the second curable adhesive layer contains an epoxy resin that is liquid at room temperature, and it is more preferable that only one contains an epoxy resin that is liquid at room temperature. As described above, the article of this embodiment is useful in such cases.

[0076] The content of 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, per 100 parts by mass of the resin component in the adhesive composition. When a curable adhesive contains 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. However, by keeping the content of epoxy resin that is liquid at room temperature relatively low, the fluidity of the resin component can be kept relatively low. Therefore, by keeping the content of epoxy resin that is liquid at room temperature within the above range, the generation of large bubbles can be suppressed. On the other hand, the content of 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, per 100 parts by mass of the resin component in the adhesive composition. When the epoxy resin that is liquid at room temperature is an optional component, the lower limit of the content of epoxy resin that is liquid at room temperature in the adhesive composition is not particularly limited.

[0077] In the case of epoxy resin adhesives, the resin components in the adhesive composition refer to epoxy resin and acrylic resin. The resin components in the adhesive composition may also include optional components such as urethane resin. Furthermore, if the curing agent is a phenolic resin, the resin components in the adhesive composition also include the phenolic resin curing agent.

[0078] Furthermore, the curable adhesive preferably contains, as epoxy resin, a primary epoxy resin having a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or less, and a secondary epoxy resin having a softening temperature higher than that of the primary epoxy resin and a weight-average molecular weight of 20,000 or higher. By using a combination of the primary and secondary epoxy resins, the tackiness of the adhesive layer formed from the adhesive composition can be reduced, and the slipperiness can be improved. Moreover, blocking resistance and adhesion after foam curing can be improved.

[0079] For example, if the sole objective is to improve adhesion after foam curing, it is more effective to use a low molecular weight (low epoxy equivalent) epoxy resin than a high molecular weight (high epoxy equivalent) epoxy resin. However, using a low molecular weight (low epoxy equivalent) epoxy resin makes blocking more likely to occur.

[0080] In contrast, when using a primary epoxy resin with a relatively low softening temperature (relatively high crystallinity) and low molecular weight (low epoxy equivalent), the primary epoxy resin rapidly melts and changes into a low-viscosity liquid when the temperature exceeds the softening temperature. Therefore, it is easier to improve adhesion after foaming and curing. On the other hand, because primary epoxy resins have relatively high crystallinity, they can suppress the occurrence of blocking compared to epoxy resins with relatively low crystallinity or epoxy resins that do not have crystallinity. However, if only primary epoxy resin is used, the blocking suppression effect may be insufficient, or the tackiness of the adhesive layer composed of the adhesive composition may become too high. Therefore, by further using a secondary epoxy resin with a relatively high softening temperature (relatively low crystallinity) and high molecular weight, the blocking suppression effect can be improved, and the tackiness of the adhesive layer composed of the adhesive composition can be kept low.

[0081] (i-1-1) Primary epoxy resin The first epoxy resin has a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or less. Compared to the second epoxy resin described later, the first epoxy resin has a relatively lower softening temperature (relatively higher crystallinity). Because the first epoxy resin has relatively high crystallinity and a low molecular weight, it is easy to improve the adhesion and blocking resistance after foam curing. In addition, because the first epoxy resin has a low molecular weight, a high crosslinking density can be achieved, resulting in an adhesive layer with good mechanical strength, chemical resistance, and curability. Furthermore, it is preferable that the first epoxy resin is a solid epoxy resin at room temperature (23°C).

[0082] The softening temperature of primary epoxy resin is typically 50°C or higher, but may also be 55°C or higher, or even 60°C or higher. On the other hand, the softening temperature of primary 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 primary epoxy resin is, for example, 5000 g / eq or less, but may also be 3000 g / eq or less, 1000 g / eq or less, or 600 g / eq or less. On the other hand, the epoxy equivalent of the primary epoxy resin is, for example, 90 g / eq or more, but may also be 100 g / eq or more, or 110 g / eq or more. The epoxy equivalent is the number of grams of resin containing 1 gram equivalent of epoxy groups. The epoxy equivalent is measured by a method in accordance with 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 bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or more functional epoxy resin.

[0085] Furthermore, the weight-average molecular weight (Mw) of the primary epoxy resin is usually smaller than the weight-average molecular weight (Mw) of the secondary epoxy resin, which will be discussed later. The Mw of the primary epoxy resin is, for example, 6,000 or less, may be 4,000 or less, or 3,000 or less. On the other hand, the Mw of the primary epoxy resin is, for example, 400 or more.

[0086] The primary epoxy resin has a melt viscosity at 150°C of, for example, 0.005 Pa·s or higher, but may also be 0.015 Pa·s or higher, 0.03 Pa·s or higher, 0.05 Pa·s or higher, or 0.1 Pa·s or higher. If the melt viscosity is too low, good foaming properties may not be obtained. Also, if the melt viscosity of the primary epoxy resin is too low (if the crystallinity of the primary epoxy resin is too high), the tackiness of the adhesive layer formed from the adhesive composition may increase. This is presumed to be because, if the melt viscosity of the primary epoxy resin is too low (if the crystallinity of the primary epoxy resin is too high), its crystallinity decreases significantly when it is compatible with the secondary epoxy resin or acrylic resin, and the Tg of the adhesive layer decreases. On the other hand, the primary epoxy resin has a melt viscosity at 150°C of, for example, 10 Pa·s or less, but may also be 5 Pa·s or less, or 2 Pa·s or less. If the melt viscosity is too high, the uniformity of the adhesive layer formed from the adhesive composition may decrease. The melt viscosity is measured in accordance with JIS K6862:1984, which corresponds to ISO 2555 (Resins in the liquid state or as emulsions or dispersions - Determination of Brookfield RV viscosity), using a Brookfield-type single-cylinder rotational viscometer and a thermocell for heating the solution.

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

[0088] Bisphenol A type epoxy resins can exist in a liquid or solid state at room temperature, depending on the number of repeating units in the bisphenol skeleton. Bisphenol A type epoxy resins in which the main chain of bisphenol skeletons is, for example, 2 to 10 are solid at room temperature. Bisphenol A type epoxy resins are particularly preferable because 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 general formula (1), R 1 C m H 2m It is a group represented by (m is between 1 and 3), and R 2 and R 3is, independently of each other, a group represented by C p H 2p+1 (where 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), m in R 1 is 1, that is, it is preferable that R 1 is -CH2-. Similarly, p in R 2 and R 3 is 1, that is, it is preferable that R 2 and R 3 are -CH3. Further, the hydrogen bonded to the benzene ring of the 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-described first epoxy resin. Since the second epoxy resin has relatively low crystallinity and a high molecular weight, it is easy to improve the blocking resistance. Further, since the second epoxy resin has relatively low crystallinity and a high molecular weight, it can suppress an increase in adhesiveness (tackiness) due to the first epoxy resin. Also, the second epoxy resin is preferably 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 3,5000 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 greater than, less than, or the same as the epoxy equivalent of the first epoxy resin. For example, the epoxy equivalent of the second epoxy resin may be 4000 g / eq or more, 5000 g / eq or more, or 6000 g / eq or more. On the other hand, for example, the epoxy equivalent of the second epoxy resin may be 20000 g / eq or less.

[0096] The second epoxy resin may be a monofunctional epoxy resin, a bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or more 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, 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, so it will not be described here.

[0099] (i-2) Acrylic resin When the curable adhesive is an epoxy resin-based adhesive, the adhesive composition may further contain an acrylic resin that is compatible with the epoxy resin. The acrylic resin is a resin that is compatible with the epoxy resin. Because the acrylic resin is compatible with the epoxy resin, it is easy to improve the toughness of the adhesive layer formed from the adhesive composition. As a result, the adhesion after foam curing can be improved. Furthermore, it is thought that the acrylic resin acts as a compatibilizer for the foaming agent (for example, a foaming agent whose shell is a resin of acrylonitrile copolymer), and by uniformly dispersing and foaming, the adhesion after foam curing is improved. In addition, the flexibility of the acrylic resin is exhibited, which can improve the adhesion to the substrate after foam curing and the crack resistance after foam curing. Also, because the acrylic resin is compatible with the epoxy resin, the hardness of the adhesive layer surface can be kept high. On the other hand, if the acrylic resin is incompatible with the epoxy resin, flexible parts are formed on the surface of the adhesive layer, which can make the interface with the first and second members less slippery and reduce workability.

[0100] In this embodiment, the acrylic resin is compatible with the epoxy resin. Compatibility of the acrylic resin with the epoxy resin can be confirmed, for example, by observing a cross-section of the adhesive layer composed of the adhesive composition using a scanning electron microscope (SEM) or transmission electron microscope (TEM), where no micron-sized islands are observed. 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 0.3 μm or less. A large number of samples is preferred, for example, 100 or more. The observation area is a range of 100 μm × 100 μm, or, if the thickness of the adhesive layer is 100 μm or less, a range of thickness × 100 μm.

[0101] The weight-average molecular weight (Mw) of the acrylic resin is, for example, 50,000 or more, but may also be 70,000 or more, or 100,000 or more. Primary epoxy resins have relatively high crystallinity, which can lead to excessively low melt viscosity (or dynamic viscoelasticity) during heating, potentially causing shrinkage during curing after foaming (the period from when the foaming of the foaming agent is finished until the adhesive composition hardens). However, by using an acrylic resin with a certain molecular weight, it is possible to suppress the melt viscosity from becoming too low, making shrinkage during curing after foaming less likely. 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 acrylic resin is, for example, 90°C or higher, and may also be 100°C or higher. On the other hand, the Tg of acrylic resin is, for example, 180°C or lower. The Tg is measured by 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 × 10⁻¹⁰ at the foaming initiation temperature. 6 It may be less than Pa. A low E' at the start of foaming improves fluidity and allows for good foaming. On the other hand, E' at the foaming start temperature is, for example, 1 × 10⁻⁶. 5 The temperature must be above Pa. Note that the foaming initiation temperature varies depending on the type of foaming agent. Furthermore, if two or more foaming agents are used, the foaming initiation temperature shall be the temperature at which the primary foaming reaction begins.

[0104] Acrylic resin has a storage modulus (E') of 1 × 10⁻¹⁰ at the curing start temperature. 5It may be Pa or higher. As mentioned above, shrinkage may occur during curing after foaming (from the time the foaming of the foaming agent is finished until the adhesive composition hardens), but a large E' at the curing start temperature can suppress shrinkage and obtain good shape retention. Note that the curing start temperature is different depending on the type of curing agent. Also, when two or more curing agents are used, the curing start temperature is the temperature at which the main curing reaction starts.

[0105] Furthermore, the average storage modulus (E') of acrylic resin at temperatures between 0°C and 100°C is 1 × 10⁻⁶ 6 It may be Pa or higher. A high average value of E' before foaming allows for good non-stick and blocking resistance. On the other hand, the average value of the storage modulus (E') between 0°C and 100°C is, for example, 1 × 10⁻⁶ 8 It is below Pa.

[0106] Acrylic resins may have polar groups. Examples of polar groups include epoxy groups, hydroxyl groups, carboxyl groups, nitrile groups, and amide groups.

[0107] The acrylic resin is a homopolymer of acrylic acid ester monomers, and may be a mixed component containing two or more of the above homopolymers, or a copolymer of two or more acrylic acid ester monomers, and may be a component containing one or more copolymers. Furthermore, the acrylic resin may be a mixed component of the above homopolymer and the above copolymer. The term "acrylic acid" in acrylic acid ester monomers also includes the concept of methacrylic acid. Specifically, the acrylic resin may be a mixture of a polymer of methacrylate and a polymer of acrylate, or it may be an acrylic acid ester polymer such as acrylate-acrylate, methacrylate-methacrylate, or methacrylate-acrylate. In particular, it is preferable that the acrylic resin contains a copolymer of two or more acrylic acid ester monomers ((meth)acrylic acid ester copolymer).

[0108] Examples of monomer components constituting the (meth)acrylic acid ester copolymer include the monomer component described in Japanese Patent Publication No. 2014-065889. The above monomer component may have the polar group described above. Examples of the above (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] As the above (meth)acrylic acid ester copolymer, block copolymers are preferred, and acrylic block copolymers such as methacrylate-acrylate copolymers are even more preferred. 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 does not necessarily have polar groups, or it may be a modified product in which the aforementioned polar groups are partially introduced. Since the above modified product is easily compatible with epoxy resin, its adhesive properties are further improved.

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

[0113] The manifestation of the above effects can be estimated as follows: By using an acrylic resin that has both soft and hard segments, such as the (meth)acrylic acid ester copolymer described above, the hard segments contribute to heat resistance, and the soft segments contribute to toughness or flexibility, thus resulting in an adhesive layer with good heat resistance, toughness, and flexibility.

[0114] At least one of the first polymer portion and the second polymer portion contained in the above (meth)acrylic acid ester copolymer is compatible with epoxy resin. When the first polymer portion is compatible with epoxy resin, flexibility can be increased. Furthermore, when the second polymer portion is compatible with epoxy resin, cohesiveness and toughness can be increased.

[0115] If either the first or second polymer portion is incompatible with the epoxy resin, the (meth)acrylic acid ester copolymer will have a compatible portion that is compatible with the epoxy resin and an incompatible portion that is incompatible with the epoxy resin. In this case, when the (meth)acrylic acid ester copolymer is added, the compatible portion becomes compatible with the epoxy resin, while the incompatible portion does not, resulting in fine phase separation. As a result, a fine sea-island structure is formed. The sea-island structure varies depending on the type of (meth)acrylic acid ester copolymer, the compatibility of the primary and secondary polymer portions contained in the (meth)acrylic acid ester copolymer, and whether or not it is modified by the introduction of polar groups. For example, there are sea-island structures in which the compatible parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the sea and the incompatible parts of the (meth)acrylic acid ester copolymer are the islands, or in which the incompatible parts of the (meth)acrylic acid ester copolymer are the sea and the compatible parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the islands, or in which the (meth)acrylic acid ester copolymer is the sea and the cured epoxy resin is the islands. Having such a sea-island structure makes it easier to distribute stress, thus avoiding interfacial fracture and resulting in excellent adhesion after foam curing.

[0116] The above-mentioned (meth)acrylic acid ester copolymer is preferably a block copolymer, and more preferably an ABA block copolymer in which the compatible parts are polymer block A and the incompatible parts are polymer block B. Furthermore, it is preferable that the first polymer portion is the incompatible part and the second polymer portion is the compatible part, with the first polymer portion being polymer block B and the second polymer portion being 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 parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the sea and the incompatible parts of the (meth)acrylic acid ester copolymer are the islands, the island portion can be reduced. Also, in the case of a sea-island structure in which the incompatible parts of the (meth)acrylic acid ester copolymer are the sea and the compatible parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the islands, 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 islands, the sea portion can be reduced.

[0117] Furthermore, 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 portion or the second polymer portion.

[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 in the range of -150°C or higher and 10°C or lower, more particularly in the range of -130°C or higher and 0°C or lower, and especially in the range of -110°C or higher and -10°C or lower.

[0119] Furthermore, the Tg of the first polymer portion can be calculated using the following formula, based on the Tg(K) of each homopolymer listed 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 :This is the Tg(K) of the homopolymer of each monomer, and you can use publicly available values ​​such as those found in the Polymer Handbook (3rd Ed., J. Brandrup and E. Himmergut, WILEY INTERSCIENCE). The same applies to the Tg of the second polymer portion, which will be discussed later.

[0120] The first polymer portion included in the above (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but a homopolymer is preferred. The monomer and polymer components constituting the first polymer portion may be any monomer and polymer components that can obtain a first polymer portion with a predetermined Tg, and examples include acrylic acid ester 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 including the polar group mentioned above, 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 to 150°C, more particularly within the range of 30°C to 150°C, and especially within the range of 40°C to 150°C.

[0122] Furthermore, the second polymer portion included in the (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but a homopolymer is preferred. The monomer component constituting the second polymer portion may be any monomer component that can obtain a second polymer portion with a predetermined Tg, and examples 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, methacrylonitrile, and polar group-containing monomers including the polar group mentioned above.

[0123] A specific example of a (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 In this embodiment, a curing agent commonly used in epoxy resin adhesives can be used. The curing agent is preferably solid at room temperature (23°C). A curing agent that is solid at room temperature has a longer storage stability (pot life) compared to a curing agent that is liquid at room temperature. The curing agent may also be a latent curing agent. Furthermore, the curing agent may be one that undergoes a curing reaction with heat, or one that undergoes a curing reaction with light. The curing agent may be used alone, or two or more types may be used.

[0125] The reaction initiation temperature of the curing agent is, for example, 110°C or higher, and may also be 130°C or higher. If the reaction initiation temperature is too low, the reaction will start too early, and curing may occur with low flexibility and fluidity of the resin components, making uniform curing difficult. 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 components may deteriorate. In addition to epoxy resin, if a heat-resistant resin such as phenolic resin is used, the deterioration of the resin components is less, 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 curing agents 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, carboxylate salts of imidazole compounds, and adducts with epoxy compounds. Furthermore, it is preferable that the imidazole-based curing agent has hydroxyl groups. Because crystallization occurs through hydrogen bonding between hydroxyl groups, the reaction initiation temperature tends to be high.

[0128] Examples of phenolic curing agents include phenolic resins. Examples of phenolic resins include resol-type phenolic resins and novolac-type phenolic resins. From the viewpoint of adhesion to the substrate after foam curing and crack resistance after foam curing, phenolic novolac resins with a Tg of 110°C or lower are particularly preferred. Furthermore, a phenolic curing agent and an imidazole-type curing agent may be used in combination. In that case, it is preferable to use an imidazole-type curing agent as a curing catalyst.

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

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

[0131] Examples of isocyanate-based curing agents include blocked isocyanates.

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

[0133] (ii) foaming agent In this embodiment, the foaming agent used in the cured adhesive layer can be a foaming agent that is generally used in the adhesive layer of foamed adhesive sheets. Furthermore, the foaming agent may be one that undergoes a foaming reaction upon heating, or one that undergoes a foaming reaction upon exposure to light.

[0134] Examples of foaming agents include thermally expandable microcapsules. It is preferable that thermally expandable microcapsules use a thermally expandable agent such as a hydrocarbon as the core and a resin such as an acrylonitrile copolymer as the shell.

[0135] Furthermore, as a blowing agent, for example, organic blowing agents or inorganic blowing agents may be used. Examples of organic blowing agents include azo blowing agents such as azodicarbonamide (ADCA), azobisformamide, and azobisisobutyronitrile; fluoride alkane blowing agents such as trichloromonofluoromethane; hydrazine blowing agents such as p-toluenesulfonyl hydrazide; semicarbazide blowing agents such as p-toluenesulfonyl semicarbazide; triazole blowing agents such as 5-morpholyl-1,2,3,4-thiatriazole; and N-nitroso blowing agents such as N,N-dinitrosoterephthalamide. On the other hand, examples of inorganic blowing agents include ammonium carbonate, ammonium bicarbonate, ammonium nitrite, ammonium borohydride, and azides.

[0136] The foaming initiation temperature of the foaming agent is preferably above the softening temperature of the main component of the curable adhesive, such as epoxy resin, and below the activation temperature of the curing reaction of the main component of the curable adhesive, such as epoxy resin. The foaming initiation temperature of the foaming agent is, for example, 70°C or higher, and may also be 100°C or higher. If the reaction initiation temperature is too low, foaming may start prematurely, and foaming may occur with low flexibility and fluidity of the resin component, making it difficult to achieve uniform foaming. On the other hand, the foaming initiation temperature of the foaming agent is, for example, 210°C or lower. If the foaming initiation temperature is too high, the resin component may deteriorate.

[0137] The softening temperature of the main component of curable adhesives such as epoxy resins is measured using the ring-spherical softening temperature test method specified in JIS K7234:1986.

[0138] Furthermore, as will be 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 component of the curable adhesive, such as epoxy resin. The maximum foaming temperature of the foaming agent is preferably, for example, 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 mentioned above, a high maximum foaming temperature of the foaming agent can suppress the shrinkage of the foaming agent during the foaming and curing process of the adhesive composition, which can reduce the thickness of the foam layer (cured adhesive layer). This can suppress the relative size of bubbles to the thickness of the foam layer (cured adhesive layer). Therefore, by having the maximum foaming temperature of the foaming agent within the above range, large bubbles can be suppressed. On the other hand, if the maximum foaming temperature is too low, the foaming agent may shrink, making it impossible to maintain the thickness of the cured adhesive layer, which may reduce the adhesive strength. On the other hand, the maximum foaming temperature of the foaming agent is preferably, for example, 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, potentially reducing the adhesive strength. Specifically, the maximum foaming temperature of the foaming agent is preferably between 140°C and 230°C, more preferably between 150°C and 220°C, and even more preferably between 160°C and 210°C. Furthermore, a maximum foaming temperature of 175°C to 220°C is also preferable.

[0139] Here, the foaming initiation temperature and maximum foaming temperature of the foaming agent are determined by thermomechanical analysis (TMA). Specifically, when measured by thermomechanical analysis (TMA) at a heating rate of 20°C / min and a load force of 0.06N, with the x-axis representing temperature and the y-axis representing displacement, the temperature at which the maximum displacement is observed is defined as the maximum foaming temperature, and the temperature at which the displacement reaches 3% relative to the maximum displacement is defined as 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. Furthermore, the average particle size of the foaming agent is preferably less than or equal to the thickness of the adhesive layer of the foamed adhesive sheet, 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 integrated particle size distribution determined by laser diffraction scattering. Furthermore, 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 in the adhesive composition, and can be appropriately selected depending on the type of curable adhesive, etc. For example, the solvent used in the adhesive composition can be used. Specifically, methyl ethyl ketone, ethyl acetate, toluene, etc., can be used.

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

[0143] The content of the foaming agent in the adhesive composition used for the cured adhesive layer shall be the same as the content of the foaming agent in the adhesive layer of the foamed adhesive sheet described later.

[0144] (iii) Other ingredients The adhesive composition used in the cured adhesive layer in this embodiment may, for example, contain only epoxy resin and acrylic resin as resin components when the curable adhesive is an epoxy resin-based adhesive, or it may further contain other resins. Examples of other resins include urethane resin.

[0145] The adhesive composition may optionally contain additives such as silane coupling agents, fillers, antioxidants, light stabilizers, UV absorbers, lubricants, plasticizers, antistatic agents, crosslinking agents, and colorants. Examples of silane coupling agents include epoxy-based silane coupling agents. Examples of fillers include inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, molybdenum compounds, and titanium dioxide. Examples of antioxidants include phenolic antioxidants and sulfur-based antioxidants.

[0146] (c) Other aspects of the cured adhesive layer The thickness of the cured adhesive layer is not particularly limited and is set appropriately according to the application. For example, the thickness of the cured adhesive layer may be 30 μm or more and 1000 μm or less, 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 deteriorate.

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

[0148] The cured adhesive layer contains a foamed and cured product of the adhesive composition. Methods for foaming and curing the adhesive composition include, for example, heating or light irradiation. Among these, foaming and curing the adhesive composition by heating is preferred. The heating method is applicable even when the first and second members are not transparent, such as in the case of metal members.

[0149] (d) First cured adhesive layer and second cured adhesive layer In this embodiment, if the adhesive member has a first cured adhesive layer and a second cured adhesive layer, or if it has a first cured adhesive layer, a substrate, and a second cured adhesive layer in that order, it is sufficient that at least one of the first cured adhesive layer and the second cured adhesive layer contains 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 but not a foaming agent, or 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. In particular, 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. This can improve adhesion. Furthermore, when manufacturing articles using a foamed adhesive sheet, the insertability of the foamed adhesive sheet can be improved.

[0150] (2) Base material In this embodiment, the adhesive member may have a substrate between the first cured adhesive layer and the second cured adhesive layer. When a substrate is placed between the first cured adhesive layer and the second cured adhesive layer, the handling and workability of the foamed adhesive sheet can be improved when manufacturing articles using the foamed adhesive sheet. On the other hand, when a substrate is not placed between the first cured adhesive layer and the second cured adhesive layer, the overall thickness of the foamed adhesive sheet can be reduced when manufacturing articles using the foamed adhesive sheet, and the foamed adhesive sheet can be inserted into narrow gaps.

[0151] The base material is preferably insulating. Furthermore, the base material is preferably in sheet form. The base material may have a single-layer structure or a multi-layer structure. The base material may or may not have a porous structure internally.

[0152] Examples of substrates include resin substrates and nonwoven fabrics.

[0153] Examples of resins included in the resin substrate include polyester resin, polycarbonate, polyarylate, polyurethane, polyamide resin, polyimide resin, polysulfone resin, polyetherketone resin, polyphenylene sulfide (PPS), and modified polyphenylene oxide. Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyester. Examples of polyamide resins include polyamide and polyetheramide. Examples of polyimide resins include polyimide, polyetherimide, and polyamideimide. Examples of polysulfone resins include polysulfone and polyethersulfone. Examples of polyetherketone resins include polyetherketone and polyetheretherketone. Liquid crystal polymer (LCP) may also 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 nonwoven fabrics include those 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 surface-treated to improve adhesion with the first and second curing adhesive layers.

[0156] The thickness of the substrate is not particularly limited, but for example, it may be 2 μm or more and 200 μm or less, 5 μm or more and 100 μm or less, or 9 μm or more and 50 μm or less.

[0157] (3) Other components The adhesive member in this embodiment may have a first intermediate layer between the substrate and the first cured adhesive layer. Alternatively, the adhesive member in this embodiment may have a second intermediate layer between the substrate and the second cured adhesive layer. The presence of the first and second intermediate layers improves the adhesion of the first and second cured adhesive layers to the substrate. Furthermore, when manufacturing articles using a foamed adhesive sheet, the presence of the first and second intermediate layers can, for example, alleviate stress on the bent portion when the foamed adhesive sheet is folded, or alleviate stress on the cut portion when the foamed adhesive sheet is cut. As a result, lifting and peeling of the first and second adhesive layers from the substrate can be suppressed when the foamed adhesive sheet is bent or cut.

[0158] For example, in the article 100 shown in Figure 4, the adhesive member 30 has a first intermediate layer 13a positioned between the base material 12 and the first cured adhesive layer 11a, and a second intermediate layer 13b positioned between the base material 12 and the second cured adhesive layer 11b. In Figure 4, the adhesive member 30 has both the first intermediate layer 13a and the second intermediate layer 13b, but 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. For example, it may have only a first intermediate layer disposed between the substrate and the first cured adhesive layer, or only a second intermediate layer disposed between the substrate and the second cured adhesive layer, or it may have both a first intermediate layer disposed between the substrate and the first cured adhesive layer and a second intermediate layer disposed between the substrate and the second cured adhesive layer. In particular, it is preferable that the first intermediate layer is disposed between the substrate and the first cured adhesive layer, and the second intermediate layer is disposed between the substrate and the second cured adhesive layer.

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

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

[0162] In particular, the first and second intermediate layers preferably contain a cross-linked resin. A cross-linked resin is one that does not melt even at high temperatures. This improves the adhesive strength at high temperatures, i.e., the heat resistance.

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

[0164] The first and second intermediate layers can be formed, for example, by applying a resin composition and removing the solvent. Examples of application methods 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 In this embodiment, the first and second members are appropriately selected according to the intended use of the article. Preferably, the first and second members are components that require bonding and insulation. Examples include components of electrical and electronic equipment, specifically the stator core and coil of a stator for a rotating electric machine, the core and permanent magnet of an embedded magnet type motor, and so on.

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

[0167] II. Second Embodiment of the Article A second embodiment of the article in this 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 foamed 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 foamed layer, the number of bubbles with a length of 100 μm or more in the thickness direction of the foamed layer is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[0168] Figures 1 to 3 are schematic cross-sectional views showing an example of an article according to this embodiment. Since Figures 1 to 3 were described in the section on the first embodiment above, their explanation is omitted here.

[0169] In articles, if the first and second members are, for example, components of electrical and electronic equipment, specifically, the stator core and coil of a stator for a rotating electric machine, or the core and permanent magnet of an embedded magnet type motor, the distance of the gap between the first and second members is, for example, about several hundred micrometers. In this case, the thickness of the adhesive member is, for example, about several hundred micrometers, and the thickness of the cured adhesive layer of the adhesive member is also, for example, about several hundred micrometers.

[0170] In the case of the above-described articles, if the adhesive member has one cured adhesive layer and the cured adhesive layer is a foam layer, and large bubbles of 100 μm or more are present, then in the region where such bubbles are present, the cured adhesive layer will not be in contact with the first and second members, 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 will be very small. Therefore, it is thought that adhesion defects such as peeling, lifting, and cracking of the cured adhesive layer are likely to occur, starting from the 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 in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is 100 μm or less, is less than or equal to a predetermined value 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.

[0172] Furthermore, in the case of the above-mentioned articles, if the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and both the first and second cured adhesive layers are foam layers, then if there are large bubbles, such as those 100 μm or larger in size, then in the regions where such bubbles exist, the first cured adhesive layer may not be in contact with the first member, or the second cured adhesive layer may not be in contact with the second member, or the contact area between the first cured adhesive layer and the first member may become very small, or the contact area between the second cured adhesive layer and the second member may become very small. Therefore, it is considered that adhesion defects such as peeling, lifting, and cracking of the first and second cured adhesive layers are likely to occur, starting from the bubbles.

[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, adhesion defects can be suppressed by ensuring that the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer, is less than or equal to a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foam layer. Therefore, it is possible to improve adhesion.

[0174] Furthermore, even when the adhesive member has a first cured adhesive layer and a second cured adhesive layer, and either the first cured adhesive layer or the second cured adhesive layer is a foam layer, it is similarly possible to suppress adhesion defects and improve adhesion.

[0175] Furthermore, in the case of the above-mentioned articles, if the adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer in that order, and the first and second cured adhesive layers are foam layers, then if there are large air bubbles, approximately the thickness of the foam layer, then in the regions where such air bubbles exist, the first cured adhesive layer may not be in contact with the first member and substrate, or the second cured adhesive layer may not be in contact with the second member and substrate, or the contact area between the first cured adhesive layer and the first member and substrate may become very small, or the contact area between the second cured adhesive layer and the second member and substrate may become very small. Therefore, it is considered that adhesion defects such as peeling, lifting, and cracking of the first and second cured adhesive layers are likely to occur, starting from the air bubbles.

[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 that order, and the first cured adhesive layer and the second cured adhesive layer are foam layers, adhesion defects can be suppressed by ensuring that the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer, is less than or equal to a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foam layer. Therefore, it is possible to improve adhesion.

[0177] Furthermore, even when an adhesive member has a first cured adhesive layer, a substrate, and a second cured adhesive layer, and either the first cured adhesive layer or the second cured adhesive layer is a foam layer, it is similarly possible to suppress adhesion defects and improve adhesion.

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

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

[0180] Furthermore, the method for manufacturing the article in this embodiment will be described in section B, "Method for Manufacturing the Article," below.

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

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

[0183] Furthermore, in a cross-section parallel to the thickness direction of the foam layer, the number of bubbles with a length of 100 μm or more in the thickness direction of the foam layer, where the distance between the bubble and the interface of the foam layer and other members adjacent to the foam layer is 3 μm or less, is preferably less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foam layer, more preferably 3 or less, even more preferably 2 or less, particularly preferably 1 or less, and most preferably 0. In regions where such bubbles exist, the cured adhesive layer does not contact 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 thought that adhesion defects such as peeling, lifting, and cracking of the cured adhesive layer are likely to occur starting from the bubbles.

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

[0185] B. Method of manufacturing articles The method for manufacturing an article described in this disclosure has two embodiments. Each embodiment will be described below.

[0186] I. First Embodiment of a Method for Manufacturing Articles A first embodiment of a method for manufacturing an article in this disclosure is a method for manufacturing an article using a foamed adhesive sheet having at least an adhesive layer, wherein the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent, and comprises a placement step of placing the foamed adhesive sheet between a first member and a second member, and an bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foam layer and bonding the first member and the second member, wherein the foaming and curing conditions in the bonding step are 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 in the direction perpendicular to the thickness direction of the foam layer.

[0187] Figures 5(a) and 5(b) are process diagrams illustrating the manufacturing method of the article according to this embodiment. First, as shown in Figure 5(a), a foamed adhesive sheet 10 is placed between the first member 20a and the second member 20b. The foamed adhesive sheet 10 has an adhesive layer 1, which is a foaming agent-containing adhesive layer 5 containing a curable adhesive and a foaming agent. Next, as shown in Figure 5(b), the foaming agent-containing adhesive layer 5 (adhesive layer 1) of the foamed adhesive sheet 10 is foamed and cured to form a cured adhesive layer 11 which is a foamed 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. In this process, the foaming and curing conditions are set, for example, as shown in Figure 1, such 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 less than a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15. This yields article 100.

[0188] Figures 6(a) to 6(c) are process diagrams illustrating the manufacturing method of the article according to this embodiment. First, as shown in Figure 6(a), the foamed adhesive sheet 10 is attached to the second member 20b. The foamed 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, respectively, containing a curable adhesive and a foaming agent. At this time, the surface of the second adhesive layer 1b of the foamed adhesive sheet 10 is attached to the second member 20b. Next, as shown in Figure 6(b), the second member 20b with the foamed adhesive sheet 10 placed on it is inserted into the hole in the first member 20a. Next, as shown in Figure 6(c), the foaming agent-containing adhesive layers 5a and 5b (first adhesive layer 1a and second adhesive layer 1b) of the foaming adhesive sheet 10 are foamed and cured to form the foam layers 15a and 15b, which are the first cured adhesive layer 11a and the second cured adhesive layer 11b. The first member 20a and the second member 20b are then bonded together by an 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, for example as shown in Figure 2, such that in each cross section parallel to the thickness direction D1 of the foam layers 15a and 15b, the number of bubbles 31 whose length s in the thickness direction D1 of the foam layers 15a and 15b is within a predetermined range relative to the thicknesses t1 and t2 of the foam layers 15a and 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 and 15b. This results in the production of article 100.

[0189] In Figures 6(a) to 6(c), both the first adhesive layer 1a and the second adhesive layer 1b are foaming agent-containing adhesive layers 5a and 5b, which contain a curable adhesive and a foaming agent. However, 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.

[0190] Furthermore, in Figures 6(a) to (c), the foam adhesive sheet 10 is attached to both sides of the second member 20b, but the foam adhesive sheet may be attached to only one side of the second member.

[0191] In the method for manufacturing the article of this embodiment, as described in the section on the first embodiment of the article above, the foam curing conditions in the bonding process are set such that the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length of the foam in the thickness direction is within a predetermined range relative to the thickness of the foam layer, is below a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foam layer. This suppresses bonding defects and improves adhesion. Therefore, a highly reliable and durable article can be obtained.

[0192] For convenience, in this specification, the adhesive layer located on the first member side of the foamed 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 foamed adhesive sheet used in the manufacturing method of the article of this embodiment and each step of the manufacturing method of the article of this embodiment will be described below.

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

[0195] A foamed adhesive sheet only needs to have at least an adhesive layer. For example, as shown in Figure 7, a foamed 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. Alternatively, as shown in Figure 8, for example, a foamed adhesive sheet 10 may have a first adhesive layer 1a and a second adhesive layer 1b. In this case, as shown in Figure 8, for example, both the first adhesive layer 1a and the second adhesive layer 1b may be foaming agent-containing adhesive layers 5a and 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. Alternatively, as shown in Figure 9, for example, a foamed adhesive sheet 10 may have the first adhesive layer 1a, the substrate 12, and the second adhesive layer 1b in this order. In this case, as shown in Figure 9, for example, both the first adhesive layer 1a and the second adhesive layer 1b may be foaming agent-containing adhesive layers 5a and 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.

[0196] The following describes the various components of the foamed adhesive sheet.

[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 this embodiment, if the foamed adhesive sheet has one adhesive layer, it is preferable that the adhesive layer is substantially non-tack-free. By having a substantially non-tack-free adhesive layer, a foamed adhesive sheet with good slipperiness and blocking resistance can be obtained. Therefore, the handling and workability of the foamed adhesive sheet can be improved. Specifically, in the placement process, the foamed adhesive sheet can be smoothly inserted into the gap between the first member and the second member, or, if the first member has holes or grooves, the second member can be smoothly inserted into the gap after the foamed adhesive sheet has been placed in the holes or grooves of the first member.

[0199] Here, "non-adhesive" is generally used to mean having low adhesive strength, and in this specification, "non-adhesive" means that the foam adhesive sheet can be rolled up and then easily unrolled 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, but may be 5 gf or less, or 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, resulting in a foamed adhesive sheet with good slipperiness and blocking resistance.

[0201] Furthermore, if the foamed adhesive sheet of this embodiment has a first adhesive layer and a second adhesive layer, or if it 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-tack-free, or one of the first adhesive layer and the second adhesive layer may be substantially non-tack-free and the other tack-sensitive.

[0202] If both the first and second adhesive layers are substantially non-tack-free, the same effect can be obtained as when the foamed adhesive sheet has one adhesive layer and the adhesive layer is non-tack-free.

[0203] On the other hand, if 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, if the first adhesive layer is substantially non-adhesive (tack-free) and the second adhesive layer is adhesive (tacky), then the second adhesive layer can be made to have good adhesion to the second member. Specifically, in the placement process, when the surface of the second adhesive layer of the foam adhesive sheet is attached to the second member and the second member with the foam adhesive sheet attached is inserted into a hole or groove of the first member, the adhesiveness of the second adhesive layer allows the surface of the second adhesive layer of the foam adhesive sheet to be attached to the second member by utilizing the adhesiveness of the second adhesive layer, thereby improving the adhesion of the second adhesive layer to the second member. As a result, when inserting the second member with the foam adhesive sheet attached into a hole or groove of the first member, peeling or displacement of the foam adhesive sheet can be suppressed.

[0204] Furthermore, in the above case, the second adhesive layer has adhesive properties, which allows for a second adhesive layer with good reworkability. Therefore, for example, when attaching the surface of the second adhesive layer of a foamed adhesive sheet to a second member by utilizing the adhesive properties of the second adhesive layer as described above, the misalignment of the foamed adhesive sheet can be corrected.

[0205] Furthermore, in the above case, the non-adhesive nature of the first adhesive layer allows for a first adhesive layer with good sliding properties. Therefore, for example, when inserting a second member with a foamed adhesive sheet attached into a hole or groove of the first member as described above, the second member with the foamed adhesive sheet attached can be inserted smoothly, improving insertability. This suppresses peeling and displacement of the foamed adhesive sheet. Also, when aligning the first and second members by moving the second member relative to the first member, the second member can be moved smoothly relative to the first member while it is inserted into a hole or groove of the first member, making alignment easier.

[0206] Furthermore, 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, which can suppress peeling and displacement of the foamed adhesive sheet. Therefore, it is possible to suppress the decrease in adhesiveness of the foamed adhesive sheet after foaming and curing due to peeling and displacement of the foamed adhesive sheet, and to reduce the variation in adhesive strength of the foamed adhesive sheet after foaming and curing due to peeling and displacement of the foamed adhesive sheet.

[0207] Furthermore, in the above case, because the second adhesive layer is tacky, for example, when the second adhesive layer is formed by a transfer method, lifting of the second adhesive layer can be suppressed. Moreover, as will be described later, if the second separator is placed on the side of the second adhesive layer opposite to the first adhesive layer, the tackiness of the second adhesive layer allows the second separator to be easily peeled off, improving workability.

[0208] Furthermore, when the adhesive layer is tacky, it contains a relatively large amount of low molecular weight resin components, for example, so when the resin components soften during the foaming and curing process of the adhesive layer, the fluidity tends to increase. 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 become larger. Thus, the method for manufacturing the article of this embodiment is useful when one of the first adhesive layer and the second adhesive layer is substantially non-tacky (tack-free) and the other is tacky (tacky).

[0209] When both the first and second adhesive layers are substantially non-adhesive, specifically, the tack of the first and second adhesive layers is preferably 0 gf or more and less than 10 gf, and may be 5 gf or less, or 2 gf or less. By having the tack of the first and second adhesive layers within the above range, the first and second adhesive layers can be made substantially non-adhesive, resulting in a foamed adhesive sheet with good slipperiness and blocking resistance.

[0210] Furthermore, if the first adhesive layer is substantially non-tack-free and the second adhesive layer is tacky, 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 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-adhesive, resulting in a foamed adhesive sheet with good slipperiness and blocking resistance.

[0212] Furthermore, in the above case, the tack of the second adhesive layer is preferably 10 gf or more, may be 30 gf or more, or 50 gf or more. If the tack of the second adhesive layer is too low, for example, when using the tack of the second adhesive layer to attach the surface of the second adhesive layer of the foamed adhesive sheet to the second member, there is a possibility that the adhesion between the second adhesive layer and the second member will decrease. Also, when inserting the second member to which the foamed adhesive sheet has been attached into a hole or groove of the first member, poor adhesion between the second adhesive layer and the second member may cause the foamed adhesive sheet to peel off or shift position, which may reduce the adhesion between the first adhesive layer and the second adhesive layer after foam curing, or cause variations in adhesive strength. Furthermore, the tack of the second adhesive layer is preferably 400 gf or less, may be 300 gf or less, or 200 gf or less. If the tack of the second adhesive layer is too high, the reworkability will decrease. For example, when using the tack of the second adhesive layer to attach the surface of the second adhesive layer of the foam adhesive sheet to the second component, it may become difficult to correct any misalignment of the foam 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 onto the surface of the adhesive layer of the foamed adhesive sheet at a temperature of 25°C, with a load of 10.0 gf and a speed of 30 mm / min. After holding for 1.0 second, it is peeled off at a speed of 30 mm / min, and the load at which it is peeled off is measured. This measurement is performed five times, and the average value is taken as the tack. For example, the RHESCA tacking tester "TAC-II" can be used as a probe tack tester.

[0214] One way to control the tack of an adhesive layer is to adjust its composition. Specifically, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer can be reduced 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 epoxy resin and a curing agent, using an epoxy resin that is liquid at room temperature or a curing agent that is liquid at room temperature tends to increase the tackiness of the adhesive layer. Furthermore, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer can be reduced by including an epoxy resin with a high softening temperature or an epoxy resin with a large weight-average molecular weight. For example, the tackiness of the adhesive layer can be reduced by including multiple types of epoxy resins with different softening temperatures in the adhesive layer, that is, by including one epoxy resin and another epoxy resin whose softening temperature is 25°C or higher and at least 10°C higher than the softening temperature of the first epoxy resin. Furthermore, the tackiness of the adhesive layer can be reduced by, for example, including multiple epoxy resins with different weight-average molecular weights in the adhesive layer; that is, by including one epoxy resin and another epoxy resin having a weight-average molecular weight of 370 or more and being at least 300 greater than the weight-average molecular weight of the first epoxy resin. More specifically, in an adhesive layer containing epoxy resin and a curing agent, as described above, the tackiness of the adhesive layer can be reduced by including a primary epoxy resin with a low softening temperature and low molecular weight, and a secondary epoxy resin with a high softening temperature and high molecular weight. On the other hand, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer tends to increase when an epoxy resin with a low softening temperature or an epoxy resin with a small weight-average molecular weight is included. Also, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer can be reduced by including an acrylic resin that is compatible with the epoxy resin, as described above. In addition, the tackiness of the adhesive layer tends to increase when a tackifier is added to the adhesive layer.While using a liquid curing agent at room temperature tends to increase tackiness, it may reduce storage stability. 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 epoxy resin.

[0215] Here, "adhesion" is a concept included in "bonding." Adhesion is sometimes used to mean a temporary bonding phenomenon, while bonding is sometimes used to mean a substantially permanent bonding phenomenon (Iwanami Shoten Dictionary of Physics and Chemistry, 5th Edition). "Adhesion" and "adhesion force" refer to the property of bonding upon pressure and the adhesive force at that time.

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

[0217] (b) Material of the adhesive layer The adhesive layer in this embodiment contains a curable adhesive and a foaming agent.

[0218] The materials for the adhesive layer are the same as those described in section "A. Articles" above, so we will omit further explanation here.

[0219] When the curable adhesive is an epoxy resin-based adhesive, as described above, it is preferable that the curable adhesive contains an epoxy resin that is liquid at room temperature. The method for manufacturing the article of this embodiment is useful when the curable adhesive contains an epoxy resin that is liquid at room temperature. When the foamed 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 them contains an epoxy resin that is liquid at room temperature. As described above, the method for manufacturing the article of this embodiment is useful in such cases.

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

[0221] In the case of epoxy resin adhesives, the resin components in the adhesive layer refer to epoxy resin and acrylic resin. The resin components in the adhesive layer may also include optional components such as urethane resin. Furthermore, if the curing agent is phenolic resin, the resin components in the adhesive layer also include the phenolic resin curing agent.

[0222] When the curable adhesive is an epoxy resin-based adhesive, and the curable adhesive contains, as described above, a primary epoxy resin having a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or less, and a secondary epoxy resin having a softening temperature higher than the primary epoxy resin and a weight-average molecular weight of 20,000 or more, the content of the primary 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, when the total resin components contained in the adhesive layer are 100 parts by mass. If the content of the primary epoxy resin is too low, the adhesiveness and blocking resistance after foam curing may decrease. On the other hand, when the total resin components contained in the adhesive layer are 100 parts by mass or less, the content of the primary 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. If the primary epoxy resin content is too high, the secondary epoxy resin and acrylic resin content will be relatively low, which may make it difficult to balance non-stick properties, blocking resistance, adhesion to the substrate after foam curing, crack resistance after foam curing, and adhesive properties after foam curing.

[0223] Furthermore, in the above case, the content of the secondary 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 total resin components contained in the adhesive layer are considered to be 100 parts by mass. If the content of the secondary epoxy resin is too low, the tackiness may increase and the blocking resistance may decrease. On the other hand, the content of the secondary 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 total resin components contained in the adhesive layer are considered to be 100 parts by mass. If the content of the secondary epoxy resin is too high, the content of the primary epoxy resin and acrylic resin will be relatively low, and it may not be possible to balance non-tackiness, blocking resistance, adhesion to the substrate after foam curing, crack resistance after foam curing, and adhesion after foam curing.

[0224] The proportion of the first epoxy resin to the total of the first and second epoxy resins is, for example, 5% by mass or more, may be 10% by mass or more, may be 15% by mass or more, or may be 20% by mass or more. On the other hand, the above proportion of the first epoxy resin is, for example, 80% by mass or less, may be 75% by mass or less, or may be 60% by mass or less.

[0225] Furthermore, the total ratio of the primary epoxy resin and the secondary epoxy resin to all epoxy resins contained in the adhesive layer is, for example, 50% by mass or more, may be 70% by mass or more, may be 90% by mass or more, or may be 100% by mass.

[0226] When 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, as described above, 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. On the other hand, for the second adhesive layer, it is preferable to use a liquid epoxy resin 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 using these epoxy resins makes it easier to adjust the tack of the second adhesive layer within a predetermined range.

[0227] When the curable adhesive is an epoxy resin-based adhesive, and the adhesive layer further contains an acrylic resin compatible with the epoxy resin, the acrylic resin content 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 components contained in the adhesive layer. If the acrylic resin content is too low, the adhesion to the substrate after foam curing, crack resistance after foam curing, and adhesiveness after foam curing may decrease. On the other hand, the acrylic resin content 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 components contained in the adhesive layer. If the acrylic resin content is too high, the content of the primary epoxy resin and secondary epoxy resin will be relatively low, and it may not be possible to balance non-stick properties, blocking resistance, adhesion to the substrate after foam curing, crack resistance after foam curing, and adhesiveness after foam curing. Furthermore, if the acrylic resin content is too high, the film strength may decrease.

[0228] Furthermore, the curing agent content is preferably, 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 considered to be 100 parts by mass. For example, when an imidazole-based curing agent is used as the main component of the curing agent, the curing agent content is preferably, 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 considered to be 100 parts by mass. On the other hand, when a phenol-based curing agent is used as the main component of the curing agent, the curing agent content is preferably, 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 considered to be 100 parts by mass. Note that using an imidazole-based curing agent or a phenol-based curing agent as the main component of the curing agent means that the mass proportion of the imidazole-based curing agent or the phenol-based curing agent is the largest in the curing agent.

[0229] The amount of foaming agent in the adhesive layer is, for example, 0.5 parts by mass or more per 100 parts by mass of resin component in the adhesive layer, but may be 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. As mentioned above, a higher amount of foaming agent tends to increase the thickness of the adhesive layer after foaming and curing, i.e., the thickness of the foam layer (cured adhesive layer). Therefore, the size of bubbles can be made relatively smaller relative to the thickness of the foam layer (cured adhesive layer). Thus, by keeping the amount of foaming agent within the above range, large bubbles can be suppressed. On the other hand, the amount of foaming agent in the adhesive layer is, for example, 30 parts by mass or less per 100 parts by mass of resin component in the adhesive layer, but may be 25 parts by mass or less, or 20 parts by mass or less. If the amount of foaming agent is too high, the amount of curable adhesive will be relatively low, which may reduce the adhesiveness after foaming and curing.

[0230] The first adhesive layer and the second adhesive layer may contain a foaming agent in at least one of them. In particular, if 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 surface roughness, decreases the coefficient of friction, and further improves slipperiness. It is especially preferable that both the first and second adhesive layers contain a foaming agent. By including a foaming agent in both the first and second adhesive layers, the adhesion between the first and second adhesive layers after foam curing can be improved.

[0231] The total ratio of epoxy resin and acrylic resin to the resin component contained in the adhesive layer is, for example, 70% by mass or more, may be 80% by mass or more, may be 90% by mass or more, or may be 100% by mass.

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

[0233] (c) Composition of the adhesive layer The adhesive layer can be foamed at a foaming ratio of, for example, 1.5 times or more and 15 times or less. The foaming ratio may also be, for example, 3.5 times or more, 4 times or more, or 4.5 times or more. Alternatively, the foaming ratio may also be, for example, 9 times or less, 8.5 times or less, or 8 times or less. If the foaming ratio is too low or too high, the adhesive strength after foaming and curing may decrease.

[0234] Here, the expansion ratio can be calculated using the following formula. Foaming ratio (times) = Thickness of adhesive layer after foaming and curing / Thickness of adhesive layer before foaming and curing

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

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

[0237] The adhesive layer can be formed, for example, by applying an adhesive composition containing the above-mentioned curable adhesive and foaming agent, and then removing the solvent. Examples of application methods 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, and the like.

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

[0239] Adhesive compositions can be obtained by mixing the above-mentioned components and kneading and dispersing them as necessary. Suitable mixing and dispersion methods include general kneading and dispersing machines such as two-roll mills, three-roll mills, pebble mills, thron mills, Szegvari attritors, high-speed impeller dispersers, high-speed stone mills, high-speed impact mills, despersers, high-speed mixers, ribbon blenders, conespers, intensive mixers, tumblers, blenders, despersers, homogenizers, and ultrasonic dispersers.

[0240] (2) Base material The foamed 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 described in section "A. Articles" above, so its explanation is omitted here.

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

[0242] For example, in the foamed adhesive sheet 10 shown in Figure 10, a first intermediate layer 13a is placed between the base material 12 and the first adhesive layer 1a, and a second intermediate layer 13b is placed between the base material 12 and the second adhesive layer 1b. In Figure 10, the foamed adhesive sheet 10 has both the first intermediate layer 13a and the second intermediate layer 13b, but it may have only one of them.

[0243] (b) Separator In this embodiment, if the foamed adhesive sheet has one adhesive layer, it may have separators on one or both sides of the adhesive layer. Also, in this embodiment, if the foamed adhesive sheet has a first adhesive layer and a second adhesive layer, or if it has a first adhesive layer, a substrate, and a second adhesive layer in that order, the first separator may be on the side of the first adhesive layer opposite to the second adhesive layer, and the second separator may be on the side of the second adhesive layer opposite to the first adhesive layer.

[0244] If the foamed adhesive sheet has a separator, the separator should be peeled off the foamed adhesive sheet before placing it between the first and second members.

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

[0246] Examples of single-layer separators include fluororesin-based films.

[0247] Furthermore, examples of multilayer separators include laminates having release layers on one or both sides of a base layer. Examples of base layers include resin films such as polypropylene, polyethylene, and polyethylene terephthalate, and papers such as fine paper, coated paper, and impregnated paper. The material of the release layer is not particularly limited as long as it has release properties, and examples include silicone compounds, organic compound-modified silicone compounds, fluorine compounds, amino alkyd compounds, melamine compounds, acrylic compounds, polyester compounds, and long-chain alkyl compounds. These compounds can be used in emulsion, solvent, or solvent-free forms.

[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 peelability and the second separator has light peelability. For example, when inserting the second member with the foamed adhesive sheet into the hole of the first member after placing the foamed adhesive sheet on the second member, the adhesion between the second adhesive layer of the foamed adhesive sheet and the first adhesive layer of the foamed adhesive sheet can be improved during insertion, as can the adhesion between the second member and the foamed adhesive sheet and the insertability of the second member with the foamed adhesive sheet. In this case, since the second separator will be the first to peel off, having the first separator have heavy peelability and the second separator has light peelability makes it easier to peel off the second separator than the first separator.

[0249] Furthermore, "light peeling" and "heavy peeling" refer to the degree of force required to separate the first and second separators from the first and second adhesive layers, respectively. Light peeling means that the peeling force is less than that of heavy peeling.

[0250] (4) Foamed adhesive sheet In this embodiment, the thickness of the foamed adhesive sheet is, for example, 10 μm or more, and may be 20 μm or more. On the other hand, the thickness of the foamed adhesive sheet is, for example, 1000 μm or less, and may be 200 μm or less.

[0251] In this embodiment, the foamed adhesive sheet preferably has good shape retention. The bending moment according to 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 above bending moment may be, for example, less than 40 gf·cm, and may be less than 30 gf·cm. Conventionally, in foamed adhesive sheets, it is common to increase the bending moment to improve shape retention and insertability into narrow gaps. In contrast, the inventors of this disclosure have found that shape retention can be ensured by designing the shape, and that a high bending moment has other disadvantages, and that, considering other characteristics, it is preferable for the bending moment to be within the above range. If the bending moment is smaller than the above range, it may be difficult to maintain the shape even with techniques such as folding. Also, if the bending moment is larger than the above range, the shape will return to its original state after bending, so it is necessary to heat the sheet or make creases at the folds during bending. Heating reduces the sheet life, and creating creases may reduce the insulation properties in those areas. In addition, in the foamed adhesive sheet of this embodiment, the surface hardness is increased so that the surface is not damaged even when inserted at high speed.

[0252] In this embodiment, it is preferable that the foamed adhesive sheet has high adhesive properties after foaming and curing. The shear strength (adhesive strength) according to JIS K6850:1999, which corresponds 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. Furthermore, the above 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 the case of high-strength acrylic foam adhesive tape that does not require heating, the shear strength (adhesive strength) is about 1 MPa to 2 MPa at room temperature and has no heat resistance at 200°C. Therefore, if the above shear strength (adhesive strength) is within the above range at 23°C, there is an advantage in terms of strength. Furthermore, if the above shear strength (adhesive strength) is within the above range at 130°C, it becomes possible to apply it to applications around automobile engines and other applications requiring similar heat resistance.

[0253] In this embodiment, the foamed adhesive sheet preferably has high electrical insulation properties after foaming and curing. After foaming and curing of the foamed adhesive sheet, the dielectric breakdown voltage according to JIS C2107:2011 corresponding to IEC 60454-2 is preferably, for example, 3kV or higher, and more preferably 5kV or higher. Having the dielectric breakdown voltage within the above range makes it possible to apply the sheet for rust prevention and around copper wires. Furthermore, after foaming and curing of the foamed adhesive sheet, the thermal conductivity is preferably, for example, 0.1W / mK or higher, and more preferably 0.15W / mK or higher. Having the thermal conductivity within the above range makes it possible to miniaturize the components and accelerate the curing reaction during heating.

[0254] The method for manufacturing the foamed adhesive sheet in this embodiment is not particularly limited and can be appropriately selected depending on the layer structure of the foamed adhesive sheet.

[0255] 2.Placement process In the arrangement step of this embodiment, a foamed adhesive sheet is placed between the first member and the second member.

[0256] The method of disposing the foaming adhesive sheet between the first member and the second member is appropriately selected according to the types of the first member and the second member and the like.

[0257] For example, there are a method of inserting a foaming adhesive sheet between the first member and the second member, a method of disposing the foaming adhesive sheet in a hole or groove of the first member and then inserting the second member into the gap after the foaming adhesive sheet is disposed in the hole or groove of the first member, and the like. Further, for example, when the first member has a hole or groove and the second member is disposed in the hole or groove of the first member, and when the first member and the second member are fixed by adhesion, in the case of using the tack of the second adhesive layer of the foaming adhesive sheet, after attaching the surface of the second adhesive layer of the foaming adhesive sheet to the second member, a method of disposing the second member attached with the foaming adhesive sheet in the hole or groove of the first member, a method of disposing the foaming adhesive sheet in the hole or groove of the first member, attaching the surface of the second adhesive layer of the foaming adhesive sheet to the hole or groove of the first member by using the tack of the second adhesive layer of the foaming adhesive sheet, and then disposing the second member in the hole or groove of the first member to which the foaming adhesive sheet is attached, and the like can be mentioned.

[0258] 3. Adhesion step In the adhesion step in this embodiment, the foaming agent-containing adhesive layer of the foaming adhesive sheet is foamed and cured to form a foam layer, and the first member and the second member are adhered.

[0259] [[ID=X]] Also, in the adhesion step in this embodiment, the foaming and curing conditions are set such that the number of bubbles having a length in the thickness direction of the foam layer of 6 μm or more than the thickness 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 them, it is preferable to set the foaming and curing conditions such that the number of the above-mentioned bubbles is 3 or less, more preferably 2 or less, still more preferably 1 or less, and particularly preferably 0.

[0260] Examples of methods for foaming and curing a foaming adhesive sheet include heating and light irradiation. Among these, it is preferable to foam and cure the foaming agent-containing adhesive layer of the foaming adhesive sheet by heating. The method by heating is applicable even when the first member and the second member do not have transparency, such as in the case of a member made of metal.

[0261] The heating conditions are set so as to be the above-mentioned foaming and curing conditions. The heating conditions can be appropriately set according to, for example, the type of the curable adhesive and the foaming agent contained in the adhesive layer.

[0262] The heating temperature is preferably, for example, 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, so that the thickness of the adhesive layer during foaming cannot be maintained, and the size of the bubbles tends to be 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, interfacial failure is likely to occur between the cured adhesive layer and the first member or the second member.

[0263] When the adhesive layer contains a plurality of foaming agents, it is sufficient that the heating temperature is within the above range for at least one foaming agent. Among these, for the foaming agent with a large content among the plurality of foaming agents, it is preferable that the heating temperature is within the above range. In particular, it is preferable that the heating temperature is within the above range for all of the plurality of foaming agents.

[0264] Furthermore, the heating temperature is preferably, for example, -7°C or higher and +83°C or lower than the maximum displacement extrapolation temperature of the foamed adhesive sheet; more preferably +15°C or higher and +63°C or lower; and even more preferably +23°C or higher and +43°C or lower. If the heating temperature is higher than the above range, even if the resin component has hardened, the foaming agent will shrink, making it impossible to maintain the thickness of the adhesive layer during foaming, and the size of the bubbles tends to become relatively larger relative to the thickness of the foam layer (hardened adhesive layer). As a result, 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 will be insufficient, and the adhesive strength may decrease. In this case, interfacial fracture may easily occur between the hardened adhesive layer and the first or second member.

[0265] Figure 11 is a graph illustrating a thermomechanical analysis (TMA) curve for a foamed adhesive sheet, where a compressive load is applied, the temperature is raised at a predetermined heating rate, and the displacement is measured. The curve has temperature on the x-axis and displacement on the y-axis. In the TMA curve for a foamed adhesive sheet containing thermally expandable microcapsules as a foaming agent, there is usually a peak associated with expansion (foaming). In the TMA curve for a foamed adhesive sheet as shown in Figure 11, the temperature at the intersection of the tangent at the temperature showing the maximum displacement and the tangent at the minimum temperature obtained by differentiating the curve of the portion of the TMA curve that shows expansion behavior as expansion (foaming) begins is called the maximum displacement extrapolation temperature T of the foamed adhesive sheet. max1 In the above case, the heating temperature is the maximum displacement extrapolation temperature T. max1 It is preferable that it be within a predetermined range.

[0266] Here, thermomechanical analysis of the foamed adhesive sheet is performed by the following method. First, a sample is prepared by punching out a φ4 mm diameter piece of the foamed adhesive sheet. Next, the sample is placed in a φ5 mm aluminum container with the second adhesive layer of the foamed adhesive sheet facing the bottom. Then, a φ4 mm aluminum plate is placed on top of the sample. Next, a thermomechanical analyzer is used to measure the sample in compression mode under a load of 10 mN, with the temperature raised from 25°C to 250°C at a rate of 20°C / min. The thermomechanical analyzer that can be used is the TMA7100 manufactured by Hitachi High-Tech Science Corporation.

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

[0268] Furthermore, the maximum displacement extrapolation temperature is defined as the intersection point of the tangent line at the temperature showing the maximum displacement in the TMA curve for the foamed adhesive sheet and the tangent line at the minimum temperature obtained by differentiating the curve of the portion of the TMA curve that shows expansion behavior as expansion (foaming) begins.

[0269] Specifically, the heating temperature can be between 130°C and 200°C.

[0270] The heating time can be, for example, 3 minutes or more and 3 hours or less.

[0271] II. Second Embodiment of a Method for Manufacturing Articles A second embodiment of the method for manufacturing an article in this disclosure is a method for manufacturing an article using a foamed adhesive sheet having at least an adhesive layer, wherein the adhesive layer is a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent, and comprises a placement step of placing the foamed adhesive sheet between a first member and a second member, and an bonding step of foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foam layer, thereby bonding the first member and the second member, wherein the foaming and curing conditions in the bonding step are set such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles with a length of 100 μm or more in 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.

[0272] Figures 5(a)-(b) and 6(a)-(c) are process diagrams illustrating the manufacturing method of the article according to this embodiment. Note that Figures 5(a)-(b) and 6(a)-(c) were described in the section on the first embodiment above, so their explanation is omitted here.

[0273] In the method for manufacturing the article of this embodiment, as described in the section on the second embodiment of the article above, the foam curing conditions in the bonding process are set such that the number of bubbles with 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 below a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foam layer. This suppresses bonding defects and improves adhesion. Therefore, a highly reliable and durable article can be obtained.

[0274] The foamed adhesive sheet used in the method for manufacturing the article of this embodiment, and the arrangement step in the method for manufacturing the article of this embodiment, can be the same as in the first embodiment described above.

[0275] Furthermore, in the bonding process in this embodiment, the foam curing conditions are set such that, in a cross section parallel to the thickness direction of the foam layer, the number of bubbles with a length of 100 μm or more in 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. In particular, it is preferable to set the foam curing conditions so that the number of bubbles is 3 or less, more preferably 2 or less, even more preferably 1 or less, and especially preferably 0.

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

[0277] C. Foamed adhesive sheet The foamed adhesive sheet described herein has two embodiments. Each embodiment will be described below.

[0278] I. First Embodiment of Foamed Adhesive Sheet The first embodiment of the foamed adhesive sheet in this disclosure is a foamed adhesive sheet having at least an adhesive layer, wherein 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, and when the foamed 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 foamed layer, the number of bubbles in a cross section parallel to the thickness direction of the foamed layer, where the length of the foamed layer in the thickness direction is equal to or greater than the thickness of the foamed layer - 6 μm, is less than 7 bubbles per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[0279] Figure 7 is a schematic cross-sectional view showing an example of a foamed adhesive sheet according to this embodiment. The foamed adhesive sheet 10 in Figure 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. Furthermore, when the foamed adhesive sheet 10 is heated at a predetermined temperature for a predetermined time to foam and harden the foaming agent-containing adhesive layer 5 (adhesive layer 1) to form a foamed layer 15, for example as shown in Figure 12, the number of bubbles 31 in a cross section parallel to the thickness direction D1 of the foamed layer 15, where the length s of the thickness direction D1 of the foamed layer 15 is within a predetermined range relative to the thickness t of the foamed layer 15, is less than or equal to a predetermined value per predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foamed layer 15.

[0280] FIG. 8 is a schematic cross-sectional view showing another example of the foaming adhesive sheet of the present embodiment. The foaming 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 (the first adhesive layer 1a and the second adhesive layer 1b) is a thermosetting adhesive, and the foaming agent contained in the foaming agent-containing adhesive layers 5a, 5b (the first adhesive layer 1a and the second adhesive layer 1b) is a thermally expandable microcapsule. When the foaming 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 (the first adhesive layer 1a and the second adhesive layer 1b) to form foam layers 15a, 15b, for example, as shown in FIG. 13, in a cross section parallel to the thickness direction D1 of the foam layer 15a, among the air bubbles 31, the number of air bubbles in which the 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 becomes a predetermined value or less per a predetermined length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15a. Further, in a cross section parallel to the thickness direction D1 of the foam layer 15b, among the air bubbles 31, the number of air bubbles in which the 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 becomes a predetermined value or less 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 foaming adhesive sheet of the present embodiment. The foaming adhesive sheet 10 in FIG. 9 has a first adhesive layer 1a, a base material 12, and a second adhesive layer 1b in this order. Note that FIG. 9 is the same as FIG. 8 described above except that the base material 12 is disposed between the first adhesive layer 1a and the second adhesive layer 1b.

[0282] Note that in FIGS. 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 foamed adhesive sheet of this embodiment, as described in the section on the first embodiment of the article described above, when the adhesive layer is a foaming agent-containing adhesive layer, the foamed adhesive sheet is heated at a predetermined temperature for a predetermined time to foam and harden the foaming agent-containing adhesive layer into a foamed layer. In a cross-section parallel to the thickness direction of the foamed layer, the number of bubbles whose length in the thickness direction of the foamed layer is within a predetermined range relative to the thickness of the foamed layer is less than or equal to a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foamed layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0284] The components of the foamed adhesive sheet in this embodiment are the same as those described in sections "A. Article" and "B. Method for Manufacturing the Article" above, so their explanation is omitted here.

[0285] In this embodiment, when a foaming 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 into a foam layer, the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is equal to or greater than the foam layer thickness - 6 μm, is less than 7 bubbles 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.

[0286] When heating the foamed adhesive sheet, a support with a smooth surface is used, and the foamed 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; for example, a glass substrate, a resin substrate, etc., can be used.

[0287] Furthermore, for foamed adhesive sheets, the thickness direction of the foam layer shall be perpendicular to the planar direction of the support.

[0288] The applications of the foamed adhesive sheet of this embodiment are not particularly limited. The foamed adhesive sheet of this embodiment can be used, for example, in the manufacture of the articles described above.

[0289] II. Second Embodiment of Foamed Adhesive Sheet A second embodiment of the foamed adhesive sheet in this disclosure is a foamed adhesive sheet having at least an adhesive layer, wherein 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, and when the foamed 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 foamed layer, the number of bubbles with a length of 100 μm or more in the thickness direction of the foamed layer in a cross section parallel to the thickness direction of the foamed layer is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[0290] Figures 7 to 9 are schematic cross-sectional views showing an example of the foamed adhesive sheet of this embodiment. Note that Figures 7 to 9 were described in the section on the first embodiment above, so their explanation is omitted here.

[0291] In the foamed adhesive sheet of this embodiment, as described in the section on the second embodiment of the article described above, when the adhesive layer is a foaming agent-containing adhesive layer, the foamed adhesive sheet is heated at a predetermined temperature for a predetermined time to foam and harden the foaming agent-containing adhesive layer into a foamed layer. In a cross-section parallel to the thickness direction of the foamed layer, the number of bubbles with a length of 100 μm or more in the thickness direction of the foamed layer is less than or equal to a predetermined value per predetermined length in the direction perpendicular to the thickness direction of the foamed layer, thereby suppressing poor adhesion. Therefore, it is possible to improve adhesion.

[0292] The components of the foamed adhesive sheet in this embodiment are the same as those described in sections "A. Article" and "B. Method for Manufacturing the Article" above, so their explanation is omitted here.

[0293] In this embodiment, when a foaming 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 into a foam layer, the number of bubbles with 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 heating the foamed adhesive sheet, the foamed adhesive sheet may be placed on one side of the support before heating. The support can be the same as that of the first embodiment described above.

[0295] D. Adhesive Compositions The adhesive composition described herein has two embodiments. Each embodiment is described below.

[0296] I. First Embodiment of an Adhesive Composition The first embodiment of the adhesive composition in this disclosure is 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, and when 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 the maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam-cur the coating and form a foam layer, the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length of the foam layer in the thickness direction is equal to or greater than the thickness of the foam layer - 6 μm, is less than 7 bubbles per 4 mm length in the direction perpendicular to the thickness direction of the foam layer.

[0297] In the adhesive composition of this embodiment, as described in the section on the first embodiment of the article described above, when the adhesive composition is applied to one side of a support to a predetermined thickness and the coating of the adhesive composition is heated at a predetermined temperature for a predetermined time to foam-cur the coating and form a foam layer, the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer, is less than or equal to a predetermined value 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.

[0298] The components of the adhesive composition in this embodiment are the same as those described in sections "A. Article" and "B. Method for Manufacturing the Article" above, so their explanation is omitted here.

[0299] In this embodiment, when an 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-cure and form a foam layer, the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the 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 bubbles 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.

[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; for example, a glass substrate, a resin substrate, etc., can be used.

[0301] Furthermore, with respect to the adhesive composition, the thickness direction of the foam layer is perpendicular to the planar direction of the support.

[0302] II. Second Embodiment of Adhesive Composition A second embodiment of the adhesive composition in this disclosure is 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, and when 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 the maximum foaming temperature of the foaming agent ±20°C for 15 minutes to foam-cur the coating and form a foam layer, the number of bubbles with 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.

[0303] In the adhesive composition of this embodiment, as described in the section on the second embodiment of the article described above, when the adhesive composition is applied to one side of a support to a predetermined thickness and the coating of the adhesive composition is heated at a predetermined temperature for a predetermined time to foam-cur the coating and form a foam layer, the number of bubbles with 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 or equal to a predetermined value 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 in this embodiment are the same as those described in sections "A. Article" and "B. Method for Manufacturing the Article" above, so their explanation is omitted here.

[0305] In this embodiment, when an 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 and form a foam layer, the number of bubbles with 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 can be the same as in the first embodiment described above.

[0307] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0308] [Examples 1-5 and Comparative Examples 1-2] Using the materials listed below, first adhesive compositions 1-7 and second adhesive compositions 1-7 were prepared with the compositions shown in Table 1.

[0309] • Acrylic resin: PMMA-PBuA-PMMA (partially containing 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: 210 g / eq, Mw: 1300, melt viscosity at 150°C: 0.5 Pa·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: 184-194 g / eq • Epoxy resin D: Diaminodiphenylmethane type, high viscosity liquid, epoxy equivalent: 110-130 g / eq • Epoxy resin E: Silicone-modified, solid at room temperature, epoxy equivalent: 1200 g / mol Epoxy resins A, B, and E are solid at room temperature, while epoxy resins C and D are liquid at room temperature.

[0310] • Hardening agent A: Phenol-formaldehyde polycondensate, softening point 80°C, hydroxyl group equivalent 104 g / 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 initiation temperature: 145°C to 155°C, active range: 155°C to 173°C (manufactured by Shikoku Chemicals, Inc., 2PHZ-PW) • Silane coupling agent: 3-glycidoxypropyltrimethoxysilane

[0311] • Foaming agent A: Thermally expandable microcapsules, average particle size 10 μm to 16 μm, expansion start temperature 123°C to 133°C, maximum expansion temperature 168°C to 178°C, 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 Co., Ltd., PET50×1-J2, 50 μm thick) was used as a separator. 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 was 45 μm. Then, it was dried in an oven at 100°C for 3 minutes to form the second adhesive layer.

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

[0315] Next, the surface of the second adhesive layer of a laminate having a separator and a second adhesive layer was laminated onto the surface of the substrate of a laminate having a substrate and a first adhesive layer. This resulted in a foamed 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 Figures 14(a) and (b), two metal plates 41 (cold-rolled steel sheet SPCC-SD) with a thickness of 1.6 mm, a width of 25 mm, and a length of 100 mm were prepared. A spacer 42 was placed at a predetermined interval on one end of one of the metal plates 41. The thickness of the spacer 42 was approximately 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, a foam adhesive sheet was cut to a size of 12.5 mm x 25 mm. If the foam adhesive sheet had a separator, the separator was removed. Next, the foam adhesive sheet 10 was placed between the spacers 42, and the other metal plate 41 was placed so that one end overlapped, and it was fixed with a clip to obtain a test specimen. Subsequently, the test specimens were placed in a heated oven and heated from room temperature to a predetermined temperature in 13 minutes, and held for 20 minutes to allow the first and second adhesive layers of the foamed adhesive sheet 10 to foam and harden. The heating temperatures used were 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C.

[0317] The shear strength (adhesive strength) of the heated test specimens was measured using a Tensilon RTF1350 tensile testing machine (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 highest among the adhesive strengths at each heating temperature.

[0318] (2) Observation of bubbles A test specimen was prepared by bonding the surface of the first adhesive layer of a foamed adhesive sheet to a glass substrate, with an overhang of approximately 1 mm. The test specimen was placed in a heated oven and heated from room temperature to a predetermined temperature in 13 minutes, then held for 15 minutes to foam and cure the first and second adhesive layers of the foamed adhesive sheet 10, obtaining an adhesive sheet having the first cured adhesive layer, substrate, and second cured adhesive layer in that order. In this case, the heating temperature was the temperature at which the adhesive strength was highest among the adhesive strengths measured at each heating temperature.

[0319] To allow for clear observation of the cross-section, the portion of the adhesive sheet protruding from the edge of the glass substrate was cut along the edge of the glass substrate using a trimming blade. The cut cross-section was fixed so that it could be observed perpendicularly, and air bubbles were observed using an optical microscope (Keyence Corporation, digital microscope VHX-2000). For each cured adhesive layer, the number of air bubbles whose length was greater than or equal to 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 taken as the average of the number of air bubbles in 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 foamed adhesive sheet were foamed and cured to form the first and second cured adhesive layers, the number of predetermined air bubbles per predetermined length in the first and second cured adhesive layers was less than 7, particularly 3 or less, indicating good adhesion. In contrast, in Comparative Examples 1 to 3, when the first and second adhesive layers of the foamed adhesive sheet were foamed and cured to form the first and second cured adhesive layers, the number of predetermined air bubbles per predetermined length in the first and second cured adhesive layers was high, resulting in poor adhesion.

[0323] This disclosure provides, for example, the following inventions. [1] An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The above adhesive member has at least a cured adhesive layer, The above-mentioned cured adhesive layer is a foamed layer containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent. The above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned 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 length in the 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 above adhesive member has at least a cured adhesive layer, The above-mentioned cured adhesive layer is a foamed layer containing a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent. The above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned 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 with a length of 100 μm or more in 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. [3] The adhesive member has a first cured adhesive layer and a second cured adhesive layer, The article according to [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 according to [3], wherein the first curing adhesive layer and the second curing adhesive layer are the foam layers. [5] The article according to any one of [1] to [4], wherein the curable adhesive is an epoxy resin adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the amount 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 amount 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] An 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 manufacturing an article using a foamed 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 above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned foaming agent is a thermally expandable microcapsule. A placement step involves placing the foamed adhesive sheet between the first member and the second member, The bonding process involves foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foamed layer, and then bonding the first member and the second member. A method for manufacturing an article, comprising setting the foam 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 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. [9] A method for manufacturing an article using a foamed 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 above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned foaming agent is a thermally expandable microcapsule. A placement step of placing the foamed adhesive sheet between the first member and the second member, The bonding process involves foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foamed layer, and then bonding the first member and the second member. A method for manufacturing an article, comprising setting the foam 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 with a length of 100 μm or more in 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.

[10] The foamed adhesive sheet has a first adhesive layer and a second adhesive layer, A method for manufacturing an article according to [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] A method for manufacturing 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] A method for manufacturing an article according to any one of [8] to

[11] , wherein the curable adhesive is an epoxy resin adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the amount 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} A method for manufacturing an article according to any one of [8] to

[12] , wherein the amount 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] A method for manufacturing 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 foamed 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 above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned foaming agent is a thermally expandable microcapsule. A foamed adhesive sheet in which, when the foamed 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 into a foamed layer, the number of bubbles in a cross section parallel to the thickness direction of the foamed layer, where the length in the thickness direction of the foamed layer is equal to or greater than the thickness of the foamed layer - 6 μm, is less than 7 bubbles per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[16] A foamed 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 above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned foaming agent is a thermally expandable microcapsule. A foamed adhesive sheet in which, when the foamed 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 into a foamed layer, the number of bubbles with a length of 100 μm or more in the thickness direction of the foamed layer in a cross section parallel to the thickness direction of the foamed layer is less than 7 per 4 mm length in the direction perpendicular to the thickness direction of the foamed layer.

[17] Having a first adhesive layer and a second adhesive layer, The foaming 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 foaming adhesive sheet according to

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

[19] The foamed 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 foaming adhesive sheet according to any one 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 amount 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 foaming adhesive sheet according to any one of

[15] to

[20] , wherein the amount 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 foaming 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 containing a curable adhesive and a foaming agent, The above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned foaming agent is a thermally expandable microcapsule. An adhesive composition in which, 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 ±20°C of the foaming agent for 15 minutes to foam and harden the coating and form a foam layer, the number of bubbles in a cross section parallel to the thickness direction of the foam layer, where the 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 bubbles per 4 mm length in the direction perpendicular to the thickness direction of the foam layer.

[24] An adhesive composition containing a curable adhesive and a foaming agent, The above-mentioned curable adhesive is a thermosetting adhesive, and the above-mentioned foaming agent is a thermally expandable microcapsule. An adhesive composition in which, 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 ±20°C of the foaming agent for 15 minutes to foam and harden the coating and form a foam layer, the number of bubbles with 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.

[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 amount 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 amount 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 more and 220°C or less. [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… Foamed adhesive sheet 20a ... First component 20b ... Second member 30… Adhesive material 100 … Goods

Claims

[Claim 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 length in the direction perpendicular to the thickness direction of the foam layer.

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