Article, method for producing article, foamable adhesive sheet, and adhesive composition

Abstract

In the present disclosure, provided is 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 having at least a cured adhesive layer, the cured adhesive layer is a foam layer of a foam 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 thickness of the foam layer is greater than the thickness of the foam layer. The number of bubbles having a length in the thickness direction of the foam layer equal to or greater than-6 [mu] m of the thickness of the foam layer is less than 7 per 4 mm length in a direction perpendicular to the thickness direction of the foam layer.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an article and a manufacturing method thereof, and a foaming adhesive sheet and an adhesive composition used therein. BACKGROUND

[0002] An adhesive for bonding between members is used in a variety of fields, and various methods of bonding are known.

[0003] For example, an adhesive sheet containing a blowing agent (foaming adhesive sheet) is disclosed in Patent Documents 1 to 3. As a method of using the foaming adhesive sheet, for example, a method is known in which the foaming adhesive sheet is arranged between members, and then the foaming adhesive sheet is foamed and cured by heating, whereby the members are bonded.

[0004] In such a foaming adhesive sheet, it is desirable that the adhesion after foaming and curing be good.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2000-53944

[0008] Patent Document 2: Japanese Patent No. 6223477

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2019-214729 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The present disclosure was made in view of the above-described actual circumstances, and the main object is to provide an article having excellent adhesion, and a manufacturing method of an article capable of improving adhesion, a foaming adhesive sheet, and an adhesive composition.

[0012] MEANS FOR SOLVING THE PROBLEMS

[0013] One embodiment of the present disclosure provides an article having a first member, a second member, and a bonding member arranged between the first member and the second member, the bonding member having at least a cured adhesive layer, the cured adhesive layer being a foamed layer containing a foaming cured product of an adhesive composition containing a cured adhesive and a blowing agent, the cured adhesive being a thermosetting adhesive, the blowing agent being a thermally expandable microcapsule, in a cross section parallel to the thickness direction of the foamed layer, the number of bubbles having a value of the thickness of the foamed layer - 6 μm or more in the length in the thickness direction of the foamed layer is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed layer.

[0014] Another embodiment of the present disclosure provides an article having a first member, a second member, and an adhesive member disposed between the first member and the second member, the adhesive member having at least a cured adhesive layer, the cured adhesive layer being a foamed body layer of a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, the number of bubbles having a length in a thickness direction of the foamed body layer of 100 μm or more being less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer in a cross section parallel to the thickness direction of the foamed body layer.

[0015] Another embodiment of the present disclosure provides a method for manufacturing an article using a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, the method including: a disposing step of disposing the foamable adhesive sheet between a first member and a second member; and an adhesive step of foaming and curing the foaming agent-containing adhesive layer of the foamable adhesive sheet to form a foamed body layer, and adhering the first member and the second member, the foaming and curing conditions in the adhesive step being set such that the number of bubbles having a length in a thickness direction of the foamed body layer of 100 μm or more is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer in a cross section parallel to the thickness direction of the foamed body layer.

[0016] Another embodiment of the present disclosure provides a method for manufacturing an article using a foamable adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, the method including: a disposing step of disposing the foamable adhesive sheet between a first member and a second member; and an adhesive step of foaming and curing the foaming agent-containing adhesive layer of the foamable adhesive sheet to form a foamed body layer, and adhering the first member and the second member, the foaming and curing conditions in the adhesive step being set such that the number of bubbles having a length in a thickness direction of the foamed body layer of 100 μm or more is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer in a cross section parallel to the thickness direction of the foamed body layer.

[0017] Another embodiment of the present disclosure provides a foaming adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, wherein when the foaming adhesive sheet is heated at ±20°C of the maximum foaming temperature of the foaming agent for 15 minutes to cause the foaming agent-containing adhesive layer to foam and cure to form a foamed layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer in a cross section parallel to the thickness direction of the foamed layer.

[0018] Another embodiment of the present disclosure provides a foaming adhesive sheet having at least an adhesive layer, the adhesive layer being a foaming agent-containing adhesive layer containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, wherein when the foaming adhesive sheet is heated at ±20°C of the maximum foaming temperature of the foaming agent for 15 minutes to cause the foaming agent-containing adhesive layer to foam and cure to form a foamed layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer in a cross section parallel to the thickness direction of the foamed layer.

[0019] Another embodiment of the present disclosure provides an adhesive composition containing a curable adhesive and a foaming agent, the curable adhesive being a thermosetting adhesive, and the foaming agent being a thermally expandable microcapsule, wherein when the adhesive composition is applied to one face of a support body at a thickness of 45 μm and the coating film of the adhesive composition is heated at ±20°C of the maximum foaming temperature of the foaming agent for 15 minutes to cause the coating film to foam and cure to form a foamed layer, the number of bubbles having a length of 100 μm or more in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer in a cross section parallel to the thickness direction of the foamed layer.

[0020] Another embodiment of the present disclosure provides an adhesive composition containing a curable adhesive and a blowing agent, the curable adhesive being a thermosetting adhesive, the blowing agent being a thermally expandable microcapsule, when the adhesive composition is coated on one face of a support body in a thickness of 45 μm, the coated film of the adhesive composition is heated at the maximum foaming temperature of the blowing agent ± 20°C for 15 minutes, thereby causing the coated film to foam and cure to form a foamed layer, and when a cross section parallel to the thickness direction of the foamed layer is observed, the number of bubbles having a length of 100 μm or more in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer.

[0021] Effects of the Invention

[0022] In the present disclosure, an article having excellent adhesiveness and a manufacturing method of an article capable of improving adhesiveness, a foaming adhesive sheet, and an adhesive composition can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic cross-sectional view illustrating an article of the present disclosure.

[0024] Figure 2 is a schematic cross-sectional view illustrating an article of the present disclosure.

[0025] Figure 3 is a schematic cross-sectional view illustrating an article of the present disclosure.

[0026] Figure 4 is a schematic cross-sectional view illustrating an article of the present disclosure.

[0027] Figure 5 is a process diagram illustrating a manufacturing method of an article of the present disclosure.

[0028] Figure 6 is a process diagram illustrating a manufacturing method of an article of the present disclosure.

[0029] Figure 7 is a schematic cross-sectional view illustrating a foaming adhesive sheet of the present disclosure.

[0030] Figure 8 is a schematic cross-sectional view illustrating a foaming adhesive sheet of the present disclosure.

[0031] Figure 9 is a schematic cross-sectional view illustrating a foaming adhesive sheet of the present disclosure.

[0032] Figure 10 is a schematic cross-sectional view illustrating a foaming adhesive sheet of the present disclosure.

[0033] Figure 11 is a graph illustrating a TMA curve with respect to a foaming adhesive sheet.

[0034] Figure 12 is a schematic cross-sectional view illustrating a state after foaming and curing of the foaming adhesive sheet of the present disclosure.

[0035] Figure 13 is a schematic cross-sectional view illustrating a state after foaming and curing of the foaming adhesive sheet of the present disclosure.

[0036] Figure 14 is a schematic cross-sectional view illustrating a test method for adhesiveness after foaming and curing of the foaming adhesive sheet. DETAILED DESCRIPTION

[0037] Embodiments of the present disclosure will be described below while referring to the accompanying drawings and the like. However, the present disclosure can be implemented in a variety of different ways, and should not be interpreted as being limited to the contents described in the following embodiments. In addition, in order to make the description clearer, the width, thickness, shape, and the like of each part are schematically shown in the drawings compared to the actual ones, and are ultimately only one example, and do not limit the explanation of the present disclosure. In addition, in the present specification and each drawing, the same symbol is sometimes attached to the same element as that described above with respect to the already appeared drawing, and detailed description is appropriately omitted.

[0038] In the present specification, in the case of expressing a manner in which one member is disposed on another member, in the case of merely stating "on" or "under", as long as not particularly stated, both a case in which the one member is disposed immediately above or immediately below the other member in a manner in contact with the other member and a case in which the one member is disposed further above or below the other member with another member interposed are included. In addition, in the present specification, in the case of expressing a manner in which one member is disposed on a surface of another member, in the case of merely stating "on the surface side" or "on the surface", as long as not particularly stated, both a case in which the one member is disposed immediately above or immediately below the other member in a manner in contact with the other member and a case in which the one member is disposed further above or below the other member with another member interposed are included.

[0039] In addition, in the present specification, a "sheet" also includes a member called a "film". In addition, a "film" also includes a member called a "sheet". In addition, the numerical range in the present specification is a range of average values.

[0040] In the heat-expandable microcapsule, inside the shell formed of a resin, a heat-expanding agent such as a hydrocarbon is enclosed. In the heat-expandable microcapsule, if heating is performed, the resin constituting the shell softens, and at the same time, the pressure of the heat-expanding agent such as a hydrocarbon rises, and the heat-expandable microcapsule expands. Since the shell becomes thin due to the expansion, if further heating is continued, the heat-expanding agent leaks from the heat-expandable microcapsule, and the heat-expandable microcapsule shrinks. The present inventors have found that the heat-expanding agent (gas) that leaks from the heat-expandable microcapsule becomes a bubble, and a large bubble can be generated due to the aggregation of the bubble. In addition, the present inventors have also found that, at the time of manufacturing the article, when the foaming adhesive sheet is attached to the first member or the second member, there is a case where a bubble is mixed between the first member or the second member and the foaming adhesive sheet, and a large bubble can be generated due to the aggregation of the bubble.

[0041] In addition, in the case of the thermosetting adhesive, during the foaming and curing of the adhesive composition, the resin component of the thermosetting adhesive softens and the fluidity becomes high. The present inventors have also found that, in the case where a bubble is present in the layer, if the resin component of the thermosetting adhesive softens and the fluidity becomes high, the bubble easily moves, and the bubbles aggregate and can become a large bubble.

[0042] As described above, the present inventors have found a new problem that, in the case where the curable adhesive is a thermosetting adhesive and the foaming agent is a heat-expandable microcapsule, a large bubble can be generated, and such a large bubble becomes a factor of reducing the adhesiveness. The present disclosure is an invention that solves such a new problem.

[0043] Hereinafter, the article, the manufacturing method of the article, the foaming adhesive sheet, and the adhesive composition of the present disclosure will be described in detail.

[0044] A. Article

[0045] The article of the present disclosure has two embodiments. Hereinafter, each embodiment will be described.

[0046] I. First Embodiment of the Article

[0047] The first embodiment of the article of the present disclosure has a first member, a second member, and an adhesive member disposed between the first member and the second member, and the adhesive member has at least a cured adhesive layer, the cured adhesive layer is a foamed body layer containing a foamed and 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 heat-expandable microcapsule, and in a cross section parallel to the thickness direction of the foamed body layer, the number of bubbles having a value of the thickness of the foamed body layer - 6 μm or more in the length in the thickness direction of the foamed body layer is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed body layer.

[0048] Figure 1 This is a schematic cross-sectional view illustrating an example of the article according to this embodiment. For example... Figure 1 As shown, article 100 has a first component 20a, a second component 20b, and an adhesive component 30 disposed between the first component 20a and the second component 20b. The adhesive component 30 has a cured adhesive layer 11. The cured adhesive layer 11 is a foamed layer 15 containing a cured foam of an adhesive composition comprising a curable adhesive and a foaming agent, and contains air bubbles 31 internally. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule. In a cross-section of the foamed layer 15 constituting the cured adhesive layer 11 parallel to the thickness direction D1, the number of air bubbles 31 whose length s in 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 a predetermined value in each predetermined length L in a direction d2 perpendicular to the thickness direction d1 of the foamed layer 15.

[0049] When the bonded component has a single cured adhesive layer, and this layer is a foam layer, if large air bubbles, roughly the same size as the thickness of the foam layer, exist, the cured adhesive layer will detach from both the first and second components in the areas where these air bubbles are present. Alternatively, the contact area between the cured adhesive layer and the first component, and between the cured adhesive layer and the second component, will become extremely small. Therefore, it is believed that poor adhesion, such as peeling, lifting, and cracking of the cured adhesive layer, is easily caused by these air bubbles.

[0050] In contrast, in the article of this embodiment, when the adhesive member has one cured adhesive layer, and the cured adhesive layer is a foam layer, in a cross-section parallel to the thickness direction of the foam layer, the number of air bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is less than a predetermined value in each predetermined length in the direction perpendicular to the thickness direction of the foam layer. This suppresses poor adhesion and thus improves adhesion.

[0051] Figure 2 This is a schematic cross-sectional view illustrating another example of the article according to this embodiment. In the article of this embodiment, such as... Figure 2As shown, the adhesive member 30 can have a first cured adhesive layer 11a and a second cured adhesive layer 11b. The first cured adhesive layer 11a and the second cured adhesive layer 11b are each a foamed layer 15a, 15b of a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and contain bubbles 31 inside. In a cross section in the thickness direction D1 of the foamed layer 15a constituting the first cured adhesive layer 11a, the number of bubbles in a prescribed range, in which the length s in the thickness direction D1 of the foamed layer 15a with respect to the thickness t1 of the foamed layer 15a, among the bubbles 31, is a prescribed value or less, is prescribed in each prescribed length L in a direction D2 perpendicular to the thickness direction D1 of the foamed layer 15a. Also, in a cross section in the thickness direction D1 of the foamed layer 15b constituting the second cured adhesive layer 11b, the number of bubbles in a prescribed range, in which the length s in the thickness direction D1 of the foamed layer 15b with respect to the thickness t2 of the foamed layer 15b, among the bubbles 31, is a prescribed value or less, is prescribed in each prescribed length L in a direction D2 perpendicular to the thickness direction D1 of the foamed layer 15b.

[0052] Note that, in the above embodiment, Figure 2 In the above embodiment, both the first cured adhesive layer 11a and the second cured adhesive layer 11b are foamed layers 15a, 15b of foamed cured products of an adhesive composition containing a curable adhesive and a foaming agent, but only either one of the first cured adhesive layer 11a and the second cured adhesive layer 11b can be a foamed layer of a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent.

[0053] In the case where the adhesive member has a first cured adhesive layer and a second cured adhesive layer, when the first cured adhesive layer and the second cured adhesive layer are foamed layers, if there is a large bubble having a size comparable to the thickness of the foamed layer, in a region where such a bubble exists, the first cured adhesive layer is out of contact with the first member, or the second cured adhesive layer is out of contact with the second member, or the contact area of the first cured adhesive layer with the first member becomes very small, or the contact area of the second cured adhesive layer with the second member becomes very small. It is thus considered that the peeling, warping, cracking, or the like of the first cured adhesive layer and the second cured adhesive layer is likely to occur from the above-mentioned bubble as a starting point.

[0054] On the other hand, in the article of the present embodiment, in the case where the adhesive member has a first cured adhesive layer and a second cured adhesive layer, when the first cured adhesive layer and the second cured adhesive layer are foamed layers, in a cross section parallel to the thickness direction of the foamed layer, the number of bubbles in a prescribed range, in which the length in the thickness direction of the foamed layer with respect to the thickness of the foamed layer, among the bubbles 31, is a prescribed value or less, is prescribed in each prescribed length in a direction perpendicular to the thickness direction of the foamed layer, whereby the occurrence of the peeling, warping, cracking, or the like of the first cured adhesive layer and the second cured adhesive layer can be suppressed. Thus, the adhesion can be improved.

[0055] Note that, in the case where the adhesive member has the first cured adhesive layer and the second cured adhesive layer, even when either of the first cured adhesive layer and the second cured adhesive layer is the foamed layer, it is possible to similarly suppress the adhesion failure and improve the adhesion.

[0056] Figure 3 is a schematic cross-sectional view showing another example of the article of the present embodiment. In the article of the present embodiment, as shown in Figure 3 , the adhesive member 30 can have, in order, the first cured adhesive layer 11a, the base material 12, and the second cured adhesive layer 11b. Note that, regarding Figure 3 , the same as the above-described Figure 2 applies except that the base material 12 is disposed between the first cured adhesive layer 11a and the second cured adhesive layer 11b.

[0057] Note that, in the Figure 3 , both the first cured adhesive layer 11a and the second cured adhesive layer 11b are the foamed layers 15a, 15b containing the foamed cured product of the adhesive composition containing the cured adhesive and the foaming agent, however, only either of the first cured adhesive layer 11a and the second cured adhesive layer 11b can be the foamed layer containing the foamed cured product of the adhesive composition containing the cured adhesive and the foaming agent.

[0058] In the case where the adhesive member has, in order, the first cured adhesive layer, the base material, and the second cured adhesive layer, in the case where the first cured adhesive layer and the second cured adhesive layer are the foamed layers, if there is an air bubble having a size comparable to the thickness of the foamed layer, in the region where such a bubble exists, the first cured adhesive layer and the first member and the base material are out of contact, or the second cured adhesive layer and the second member and the base material are out of contact, or the contact area of the first cured adhesive layer and the first member and the base material becomes very small, or the contact area of the second cured adhesive layer and the second member and the base material becomes very small. It is thus considered that the adhesion failure such as peeling, warping, cracking, and the like of the first cured adhesive layer and the second cured adhesive layer is likely to occur from the above-described bubble as a starting point.

[0059] In contrast, in the article of the present embodiment, in the case where the adhesive member has, in order, the first cured adhesive layer, the base material, and the second cured adhesive layer, in the case where the first cured adhesive layer and the second cured adhesive layer are the foamed layers, in a cross section parallel to the thickness direction of the foamed layer, the number of bubbles having a length in the thickness direction of the foamed layer within a prescribed range with respect to the thickness of the foamed layer is prescribed value or less in each prescribed length in a direction perpendicular to the thickness direction of the foamed layer, whereby it is possible to suppress the adhesion failure. Thus, it is possible to improve the adhesion.

[0060] Note that, in the case where the adhesive member has the first cured adhesive layer, the base material, and the second cured adhesive layer, even when either of the first cured adhesive layer and the second cured adhesive layer is the foamed layer, it is possible to similarly suppress the poor adhesion and improve the adhesion.

[0061] Thus, in the article of the present embodiment, it is possible to improve the reliability and durability.

[0062] Hereinafter, each component of the article of the present embodiment will be described.

[0063] 1. Adhesive member

[0064] The adhesive member of the present disclosure is disposed between a first member and a second member, and has at least a cured adhesive layer. In addition, the cured adhesive layer is a foamed layer containing a foamed cured product of an adhesive composition containing a cured adhesive and a foaming agent, and in a cross section parallel to a thickness direction of the foamed layer, the number of bubbles in a prescribed range with respect to the thickness of the foamed layer is prescribed value or less in each prescribed length in a direction perpendicular to the thickness direction of the foamed layer.

[0065] In addition, the adhesive member can have at least the cured adhesive layer, and for example, can have one cured adhesive layer, can have a first cured adhesive layer and a second cured adhesive layer, or can have a first cured adhesive layer, a base material, and a second cured adhesive layer in this order.

[0066] In the case where the adhesive member has a first cured adhesive layer and a second cured adhesive layer, or has a first cured adhesive layer, a base material, and a second cured adhesive layer in this order, at least one of the first cured adhesive layer and the second cured adhesive layer is the foamed layer.

[0067] Note that, in the present specification, for convenience, in the adhesive member, the cured adhesive layer on the first member side is set as the first cured adhesive layer, and the cured adhesive layer on the second member side is set as the second cured adhesive layer.

[0068] Hereinafter, each component of the adhesive member will be described.

[0069] (1) Cured adhesive layer

[0070] The cured adhesive layer of the present embodiment is a foamed layer containing a foamed cured product of an adhesive composition containing a cured adhesive and a foaming agent, and in a cross section parallel to a thickness direction of the foamed layer, the number of bubbles in a prescribed range with respect to the thickness of the foamed layer is prescribed value or less in each prescribed length in a direction perpendicular to the thickness direction of the foamed layer.

[0071] (a) Bubble

[0072] The cured adhesive layer of this embodiment is a foamed layer containing an adhesive composition comprising 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 at least 6 μm equal to the thickness of the foamed layer in the thickness direction is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed layer. Preferably, the number of air bubbles is 3 or less, more preferably 2 or less, further preferably 1 or less, and particularly preferably 0.

[0073] It should be noted that the term "bubbles with a length in the thickness direction of the foam layer that is greater than or equal to the thickness of the foam layer - 6 μm" refers to bubbles with a length in the thickness direction of the foam layer that is greater than or equal to the thickness of the foam layer - 6 μm. For example, when the thickness of the foam layer is 200 μm, the number of bubbles with a length in the thickness direction of the foam layer that is 200 - 6 = 194 (μm) or greater falls within the aforementioned range. Similarly, when the thickness of the foam layer is 300 μm, the number of bubbles with a length in the thickness direction of the foam layer that is 300 - 6 = 294 (μm) or greater falls within the aforementioned range.

[0074] Here, the length and number of bubbles in the thickness direction of the foam layer in a cross-section parallel to the thickness direction of the foam layer can be determined, for example, from images obtained using an optical microscope or a scanning electron microscope (SEM), or from tomographic images obtained using an X-ray CT scan. In an X-ray CT scan, bubbles in the cross-section of the foam layer can be observed non-destructively and non-contactly. Therefore, it is possible to prevent bubble rupture when cutting the object to expose the cross-section of the foam layer. Thus, the length and number of bubbles in the thickness direction of the foam layer can be accurately determined. In the case where the first and second components are made of metal, observation using an optical microscope or a scanning electron microscope (SEM) is preferred.

[0075] In addition, the number of bubbles in the cross section parallel to the thickness direction of the foam layer is the average of the number of bubbles at three randomly selected locations.

[0076] Furthermore, the thickness of the foamed layer was determined based on the cross-section along the thickness direction of the foamed adhesive sheet observed using transmission electron microscopy (TEM), scanning electron microscopy (SEM), or scanning transmission electron microscopy (STEM), using the average thickness from 10 randomly selected locations. It should be noted that the method for measuring the thickness of each layer was also set to the same.

[0077] Furthermore, for the article, the thickness direction of the foam layer is set to be perpendicular to the planar direction of the first or second component. It should be noted that the planar direction of the first and second components refers to their planar direction when viewed from a macroscopic perspective.

[0078] In the foamed layer, methods for suppressing air bubbles with a length within a specified range in the thickness direction of the foamed layer can include, for example, adjusting the composition of the adhesive composition or adjusting the foaming and curing conditions of the adhesive composition.

[0079] Methods for adjusting the composition of an adhesive composition include, for example, adjusting the flowability of the resin component of a curable adhesive, adjusting the maximum foaming temperature of a foaming agent, adjusting the foaming ratio of a foaming agent at the maximum foaming temperature, adjusting the content of a foaming agent, and adjusting the structure of a thermally expandable microcapsule when the foaming agent is a thermally expandable microcapsule.

[0080] Methods for adjusting the flowability of resin components in a curable adhesive include, for example, adjusting the molecular weight of the resin component as the main agent of the curable adhesive, adjusting the state of the resin component as the main agent of the curable adhesive, and adjusting the content of resin components that are liquid at room temperature.

[0081] In methods for adjusting the molecular weight of the resin component as the main agent in a curable adhesive, a thermosetting adhesive is used, for example, as the curable adhesive. In this case, during the foaming and curing process of the adhesive composition, the resin component softens, increasing its fluidity. At this time, when the molecular weight of the resin component is large, its fluidity is low compared to when the molecular weight is small. Therefore, bubbles are less likely to grow large or to coalesce, thus suppressing the generation of large bubbles as described above. Therefore, by using a resin component containing a high molecular weight resin component as the main agent in a curable adhesive, the generation of large bubbles as described above can be suppressed.

[0082] As described above, in the case of thermosetting adhesives, during the foaming and curing process of the adhesive composition, the resin component softens, increasing its fluidity. 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 grow large or to coalesce, thus suppressing the formation of large bubbles as described above. Therefore, in methods for adjusting the state of the resin component as the main agent in a curable adhesive, by including a resin component that is solid at room temperature as the main agent in the curable adhesive, the formation of large bubbles as described above can be suppressed. It should be noted that room temperature refers to 23°C.

[0083] In curable adhesives, when the resin component used as the main agent contains a resin component that is liquid at room temperature, there is a tendency for the resin component to become more fluid as it softens during the foaming and curing process of the adhesive composition. On the other hand, by reducing the content of the resin component that is liquid at room temperature, the fluidity of the resin component can be reduced. Therefore, by reducing the content of the resin component that is liquid at room temperature in the resin component used as the main agent of the curable adhesive, the generation of large bubbles as described above can be suppressed.

[0084] In a method for adjusting the maximum foaming temperature of a foaming agent, thermally expandable microcapsules are used as the foaming agent. Within each thermally expandable microcapsule, a thermally expandable agent such as a hydrocarbon is encapsulated inside a shell formed of resin. When heated, the resin constituting the shell softens, and the pressure of the thermally expandable agent (such as the hydrocarbon) increases, causing the microcapsule to expand. Since the shell thins due to expansion, further heating causes leakage of the thermally expandable agent from the microcapsule, resulting in shrinkage. Therefore, for example, if the maximum foaming temperature of the foaming agent is high, the shrinkage of the foaming agent during the foaming and curing process of the adhesive composition can be suppressed, preventing the foam layer (cured adhesive layer) from becoming thinner. This suppresses the increase in bubble size relative to the thickness of the foam layer (cured adhesive layer). Consequently, the bubble size can be relatively reduced relative to the thickness of the foam layer (cured adhesive layer), thus suppressing large bubbles as described above.

[0085] In methods for adjusting the expansion ratio of a foaming agent at its maximum foaming temperature, for example, if the expansion ratio at the maximum foaming temperature is large, there is a tendency for the thickness of the foam layer (cured adhesive layer) to increase. Therefore, relative to the thickness of the foam layer (cured adhesive layer), the size of the air bubbles can be relatively reduced. As a result, large air bubbles as described above can be suppressed.

[0086] In methods that adjust the content of the foaming agent, for example, if the content of the foaming agent is high, there is a tendency for the thickness of the foam layer (cured adhesive layer) to increase. Therefore, relative to the thickness of the foam layer (cured adhesive layer), the size of the air bubbles can be relatively reduced. As a result, large air bubbles as described above can be suppressed.

[0087] When the foaming agent is a thermally expandable microcapsule, in methods of adjusting the structure of the thermally expandable microcapsule, for example, if the shell of the thermally expandable microcapsule is thick, there is a tendency for the air permeability to decrease and the bubble size to become smaller. Additionally, for example, if the shell of the thermally expandable microcapsule is cross-linked, there is a tendency for the air permeability to decrease and the bubble size to become smaller.

[0088] As a method for adjusting the foaming and curing conditions of the adhesive composition, for example when the foaming agent is a thermally expandable microcapsule, the method of adjusting the heating temperature can be cited. For example, the generation of large bubbles as described above can be suppressed by setting the heating temperature within a specified range relative to the maximum foaming temperature of the foaming agent. In addition, for example, the generation of large bubbles as described above can be suppressed by setting the heating temperature within a specified range relative to the maximum displacement extrapolation temperature of the foamed adhesive sheet. Specific heating temperatures are described in section "B. Method of Manufacturing the Article" described later.

[0089] (b) Material of the cured adhesive layer

[0090] The cured adhesive layer of this embodiment contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent.

[0091] (i) Curing adhesives

[0092] As the curable adhesive used in the cured adhesive layer of this embodiment, a curable adhesive commonly used in the adhesive layer of foamed adhesive sheets can be used. Examples of curable adhesives include thermosetting adhesives and light-curing adhesives. Among these, thermosetting adhesives are preferred. For example, thermosetting adhesives can be applied even when the first and second components, such as metal components, are not transparent.

[0093] In addition, 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.

[0094] Among these, the curable adhesive is preferably an epoxy resin-based adhesive. That is, the curable adhesive preferably contains epoxy resin and a curing agent. Generally speaking, epoxy resin-based adhesives have excellent mechanical strength, heat resistance, insulation, and chemical resistance, and low curing shrinkage, making them suitable for a wide range of applications.

[0095] The following examples illustrate the use of epoxy resin-based adhesives for curing.

[0096] (i-1) Epoxy resin

[0097] The epoxy resin of this embodiment is a compound having at least one epoxy group or glycidyl group and cured by undergoing a crosslinking polymerization reaction with a curing agent. The epoxy resin also contains monomers having at least one epoxy group or glycidyl group.

[0098] As the epoxy resin, the epoxy resin commonly used in epoxy resin-based adhesives can be used.

[0099] In this context, the curable adhesive preferably contains an epoxy resin with a weight-average molecular weight of 900 or more and 100,000 or less. As described above, during the foaming and curing process of the adhesive composition, the epoxy resin softens, increasing its fluidity. At this point, when the epoxy resin has a high molecular weight, its fluidity is lower compared to when it has a low molecular weight. Therefore, bubbles are less likely to grow large or coalesce, thus suppressing the formation of large bubbles. Therefore, by using an epoxy resin containing a high molecular weight, the formation of large bubbles can be suppressed.

[0100] In this case, the weight-average molecular weight of the epoxy resin can be, for example, 900 or more and less than 100,000, or 16.50 or more and less than 80,000, or 3800 or more and less than 60,000.

[0101] It should be noted that the weight-average molecular weight of the resin component is a value converted from polystyrene obtained by gel permeation chromatography (GPC).

[0102] Furthermore, the curable adhesive preferably contains an epoxy resin that is solid at room temperature. As described above, during the foaming and curing process of the adhesive composition, the epoxy resin softens, increasing its fluidity. At this time, the epoxy resin that is solid at room temperature tends to have lower fluidity compared to the epoxy resin that is liquid at room temperature. Therefore, bubbles are less likely to grow large and less likely to coalesce, thus suppressing the formation of large bubbles. Therefore, by containing an epoxy resin that is solid at room temperature, the formation of large bubbles can be suppressed.

[0103] Furthermore, the curable adhesive preferably contains both a solid epoxy resin at room temperature and a liquid epoxy resin at room temperature. When the curable adhesive contains a liquid epoxy resin at room temperature, the fluidity tends to increase as the resin softens during the foaming and curing process of the adhesive composition. Therefore, bubbles easily coalesce and grow larger. Thus, the article of this embodiment is useful when the curable adhesive contains a liquid epoxy resin at room temperature. When the adhesive member has a first cured adhesive layer and a second cured adhesive layer, it is preferable that at least one of the adhesive compositions used in the first and second cured adhesive layers contains a liquid epoxy resin at room temperature, and more preferably, only one contains a liquid epoxy resin at room temperature. As described above, the article of this embodiment is useful in such cases.

[0104] The content of epoxy resin, which is liquid at room temperature, in the adhesive composition is preferably 60 parts by weight or less, more preferably 55 parts by weight or less, and even more preferably 50 parts by weight or less, relative to 100 parts by weight 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 low, the fluidity of the resin component can be kept low. Therefore, by keeping the content of epoxy resin that is liquid at room temperature within the above-mentioned 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 can, for example, be 5 parts by weight or more, or 10 parts by weight or more, relative to 100 parts by weight of the resin component in the adhesive composition. It should be noted that when 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.

[0105] In the case of epoxy resin-based adhesives, the resin component in the adhesive composition refers to epoxy resin and acrylic resin. The resin component in the adhesive composition may also include, as an optional component, urethane resin. Furthermore, if the curing agent is a phenolic resin, the resin component in the adhesive composition also includes phenolic resin as a curing agent.

[0106] Furthermore, the curable adhesive preferably contains a first epoxy resin and a second epoxy resin as the 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. The second epoxy resin has a softening temperature higher than that of the first epoxy resin and a weight-average molecular weight of 20000 or higher. By using the first epoxy resin and the second epoxy resin in combination, the tackiness (initial tack) of the adhesive layer formed by the adhesive composition can be reduced, resulting in good sliding properties. In addition, it improves both anti-blocking properties and adhesion after foaming and curing.

[0107] For example, when the sole aim is to improve adhesion after foaming and curing, using a low molecular weight (low epoxy equivalent) epoxy resin is effective compared to a high molecular weight (high epoxy equivalent) epoxy resin. However, when using a low molecular weight (low epoxy equivalent) epoxy resin, adhesion is more likely to occur.

[0108] In contrast, when using a first epoxy resin with a low softening temperature (high crystallinity) and low molecular weight (low epoxy equivalent), the first epoxy resin will rapidly melt and become a low-viscosity liquid if it reaches a temperature above its softening temperature. Therefore, it is easier to improve the adhesion after foaming and curing. On the other hand, because the first epoxy resin has high crystallinity, it can suppress adhesion compared to epoxy resins with low or no crystallinity. However, when using only the first epoxy resin, the adhesion suppression effect may be insufficient, or the adhesiveness (initial tack) of the adhesive layer formed by the adhesive composition may be too high. Therefore, by further using a second epoxy resin with a higher softening temperature (lower crystallinity) and high molecular weight, the adhesion suppression effect can be improved, and the adhesiveness (initial tack) of the adhesive layer formed by the adhesive composition can be reduced.

[0109] (i-1-1) First epoxy resin

[0110] The first epoxy resin has a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or lower. Compared to the second epoxy resin described later, the first epoxy resin has a lower softening temperature (higher crystallinity). Due to its higher crystallinity and lower molecular weight, the first epoxy resin easily improves the adhesion and anti-blocking properties after foaming and curing. In addition, due to its lower molecular weight, the first epoxy resin can increase the crosslinking density, resulting in an adhesive layer with good mechanical strength, chemical resistance, and curing properties. Furthermore, it is preferable that the first epoxy resin is a solid epoxy resin at room temperature (23°C).

[0111] The softening temperature of the first epoxy resin is typically above 50°C, but can also be above 55°C or above 60°C. On the other hand, the softening temperature of the first epoxy resin is, for example, below 150°C. The softening temperature is determined using the ring and ball method according to JIS K7234:1986.

[0112] The epoxy equivalent of the first epoxy resin is, for example, 5000 g / eq or less, or 3000 g / eq or less, or 1000 g / eq or less, or 600 g / eq or less. On the other hand, the epoxy equivalent of the first epoxy resin is, for example, 90 g / eq or more, or 100 g / eq or more, or 110 g / eq or more. Epoxy equivalent is the number of grams of resin containing 1 gram equivalent of epoxy groups. The epoxy equivalent is determined according to the method of JIS K7236:2009, which corresponds to ISO 3001 (Plastics—Epoxy compounds—Determination of epoxy equivalent).

[0113] The first epoxy resin can be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or an epoxy resin with four or more functions.

[0114] Furthermore, the weight-average molecular weight (Mw) of the first epoxy resin is generally lower than that of the second epoxy resin described later. The Mw of the first epoxy resin is, for example, 6000 or less, or 4000 or less, or 3000 or less. On the other hand, the Mw of the first epoxy resin is, for example, 400 or more.

[0115] The melt viscosity of the first epoxy resin at 150°C is, for example, 0.005 Pa·s or more, or 0.015 Pa·s or more, or 0.03 Pa·s or more, or 0.05 Pa·s or more, or 0.1 Pa·s or more. If the melt viscosity is too low, good foaming properties may not be obtained. Furthermore, if the melt viscosity of the first epoxy resin is too low (the crystallinity of the first epoxy resin is too high), the adhesiveness (initial tack) of the adhesive layer formed by the adhesive composition may increase. This is presumably because if the melt viscosity of the first epoxy resin is too low (the crystallinity of the first epoxy resin is too high), its crystallinity decreases significantly when compatible with the second epoxy resin or acrylic resin, resulting in a lower Tg of the adhesive layer. On the other hand, the melt viscosity of the first epoxy resin at 150°C is, for example, 10 Pa·s or less, or 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 by the adhesive composition may decrease. Melt viscosity was determined according to 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 single-cylinder rotational viscometer and a constant-temperature metal bath for heating the solution.

[0116] The composition of the first epoxy resin will now be described. Examples of first epoxy resins include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Specific examples of the first epoxy resin include bisphenol-type epoxy resins such as bisphenol A type epoxy resin and bisphenol F type epoxy resin, linear phenolic epoxy resins such as bisphenol A linear phenolic epoxy resin and cresol linear phenolic epoxy resin, urethane-modified epoxy resins, and rubber-modified epoxy resins. Other specific examples include biphenyl-type epoxy resins, stilbene-type epoxy resins, pyrrolidone-methane-type epoxy resins, alkyl-modified pyrrolidone-methane-type epoxy resins, triazine-core-containing epoxy resins, dicyclopentadiene-modified phenolic epoxy resins, naphthalene-type epoxy resins, diol-type epoxy resins, and pentaerythritol-type epoxy resins. The first epoxy resin may be one type or two or more types.

[0117] Depending on the number of repeating units in the bisphenol backbone, bisphenol A type epoxy resins can exist in a liquid state or a solid state at room temperature. For example, bisphenol A type epoxy resins with a main chain bisphenol backbone of 2 or more but less than 10 are solid at room temperature. From the perspective of achieving improved heat resistance, bisphenol A type epoxy resins are particularly preferred.

[0118] The first epoxy resin is particularly preferred to be a bisphenol A linear phenolic epoxy resin represented by the following general formula (1).

[0119] [Chemistry 1]

[0120]

[0121] General formula (1)

[0122] In general formula (1), R 1 For C m H 2m (A group represented by m being 1 or more and 3 or less), R 2 and R 3 Each independently as C p H 2p＋1 (p is 1 or more and 3 or less) represents a group, and n is 0 or more and 10 or less.

[0123] In general formula (1), R is preferred. 1 In this case, m is 1, that is, R is preferred. 1 It is -CH2-. Similarly, R is preferred. 2 and R 3 In this case, p is 1, that is, R is preferred. 2 and R 3 The value is -CH3. In addition, the hydrogen atoms bonded to the benzene ring in general formula (1) can be replaced by other elements or other groups.

[0124] (i-1-2) Second epoxy resin

[0125] 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. Compared to the first epoxy resin, the second epoxy resin has a higher softening temperature (lower crystallinity). Due to its lower crystallinity and higher molecular weight, the second epoxy resin is better able to improve anti-blocking properties. Furthermore, because of its lower crystallinity and higher molecular weight, the second epoxy resin can suppress the increase in adhesion (initial tack) caused by the first epoxy resin. Preferably, the second epoxy resin is a solid epoxy resin at room temperature (23°C).

[0126] The weight-average molecular weight (Mw) of the second epoxy resin is typically greater than that of the first epoxy resin. The Mw of the second epoxy resin is typically 20,000 or more, but can also be 30,000 or more, or 35,000 or more. On the other hand, the Mw of the second epoxy resin can be, for example, 100,000 or less.

[0127] The epoxy equivalent of the second epoxy resin can be larger, smaller, or the same as that of the first epoxy resin. For example, the epoxy equivalent of the second epoxy resin can be 4000 g / eq or more, 5000 g / eq or more, or 6000 g / eq or more. On the other hand, the epoxy equivalent of the second epoxy resin can be, for example, 20000 g / eq or less.

[0128] The second epoxy resin can be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or an epoxy resin with four or more functions.

[0129] The softening temperature of the second epoxy resin is typically higher than that of the first epoxy resin. The difference may be, for example, 10°C or more, or 20°C or more, or 30°C or more. The softening temperature of the second epoxy resin may be, for example, 80°C or more, or 90°C or more. On the other hand, the softening temperature of the second epoxy resin may be, for example, 180°C or less.

[0130] The composition of the second epoxy resin is the same as that of the first epoxy resin described above, so it is omitted here.

[0131] (i-2) Acrylic resins

[0132] When the curable adhesive is an epoxy resin-based adhesive, the adhesive composition may further contain an acrylic resin compatible with the epoxy resin. Acrylic resins are resins compatible with epoxy resins. Because acrylic resins are compatible with epoxy resins, the toughness of the adhesive layer formed by the adhesive composition is easily improved. As a result, the adhesion after foaming and curing can be improved. Furthermore, it is believed that the acrylic resin acts as a compatibilizer for the foaming agent (e.g., a foaming agent with an acrylonitrile copolymer shell), enabling uniform dispersion and foaming, thereby improving the adhesion after foaming and curing. In addition, the flexibility provided by the acrylic resin can improve the adhesion to the foamed and cured substrate and the crack resistance after foaming and curing. Furthermore, by making the acrylic resin compatible with the epoxy resin, the high hardness of the adhesive layer surface can be maintained. On the other hand, if the acrylic resin is incompatible with the epoxy resin, soft areas will be formed on the adhesive layer surface, making it difficult to slip at the interface with the first and second components, resulting in reduced workability.

[0133] The acrylic resin in this embodiment is compatible with the epoxy resin. Here, compatibility between the acrylic resin and the epoxy resin can be confirmed, for example, by observing the cross-section of the adhesive layer formed by the adhesive composition using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), without the formation of micron-sized islands. More specifically, it is preferable that the average particle size of the islands is 1 μm or less. The average particle size of the islands may also be 0.5 μm or less, or 0.3 μm or less. It is preferable to have a large number of samples, for example, 100 or more. The observed area is in the range of 100 μm × 100 μm, or, if the thickness of the adhesive layer is 100 μm or less, in the range of thickness × 100 μm.

[0134] The weight-average molecular weight (Mw) of acrylic resins is, for example, 50,000 or more, or 70,000 or more, or 100,000 or more. Firstly, epoxy resins have relatively high crystallinity, which can lead to an excessively low melt viscosity (or dynamic viscoelasticity) upon heating, and shrinkage during curing after foaming (from the end of foaming by the blowing agent to the curing of the adhesive composition). However, by using acrylic resins with a certain molecular weight, the excessively low melt viscosity can be suppressed, and shrinkage during curing after foaming is less likely to occur. On the other hand, the Mw of acrylic resins is, for example, 1,500,000 or less. The weight-average molecular weight of acrylic resins is determined using GPC (elution: THF, standard: PS, sample: 20 μL, flow rate: 1 mL / min, column temperature: 40 °C).

[0135] The glass transition temperature (Tg) of acrylic resins is, for example, 90°C or higher, or 100°C or higher. On the other hand, the Tg of acrylic resins is, for example, 180°C or lower. Tg is determined using a differential scanning calorimeter (DSC) in accordance with JIS K7121:2012, which corresponds to ISO 3146.

[0136] The storage modulus (E') of acrylic resins at the foaming initiation temperature can be 1×10⁻⁶. 6 Below Pa. By keeping the E' at the start of foaming low, fluidity is improved, and good foaming properties can be obtained. On the other hand, the E' at the foaming start temperature is, for example, 1×10. 5 Above Pa. It should be noted that the foaming start temperature varies depending on the type of foaming agent. Furthermore, when using two or more foaming agents, the temperature at which the main foaming reaction begins should be set as the foaming start temperature.

[0137] The storage modulus (E') of acrylic resins at the curing start temperature can be 1×10⁻⁶. 5Pa or higher. As mentioned above, shrinkage occurs during curing after foaming (from the end of foaming by the foaming agent to the curing of the adhesive composition). However, by maximizing E' at the curing start temperature, shrinkage can be suppressed, resulting in good shape retention. It should be noted that the curing start temperature varies depending on the type of curing agent. Furthermore, when using two or more curing agents, the starting temperature of the primary curing reaction is set as the curing start temperature.

[0138] In addition, the average value of the storage modulus (E') of acrylic resins above 0°C and below 100°C can be 1×10⁻⁶. 6 Pa or higher. By increasing the average value of E' before foaming, good non-adhesive and anti-blocking properties can be obtained. On the other hand, the average value of the storage modulus (E') above 0°C and below 100°C is, for example, 1 × 10⁻⁶. 8 Below Pa.

[0139] Acrylic resins can have polar groups. Examples of polar groups include epoxy, hydroxyl, carboxyl, nitrile, and amide groups.

[0140] Acrylic resins can be homopolymers of acrylate monomers, mixtures containing two or more of the above homopolymers, or copolymers of two or more acrylate monomers, or components containing one or more copolymers. Alternatively, acrylic resins can be mixtures of the above homopolymers and copolymers. The term "acrylic acid" in acrylate monomers also includes the concept of methacrylic acid. Specifically, acrylic resins can be mixtures of polymers of methacrylates and polymers of acrylates, or acrylate-acrylate, methacrylate-methacrylate, methacrylate-acrylate, and other acrylate polymers. Preferably, the acrylic resin contains copolymers of two or more acrylate monomers ((meth)acrylate copolymers).

[0141] Examples of monomeric components constituting (meth)acrylate copolymers include those described in Japanese Patent Application Publication No. 2014-065889. These monomeric components may possess the aforementioned polar groups. Examples of the aforementioned (meth)acrylate copolymers include ethyl acrylate-butyl acrylate-acrylonitrile copolymers, ethyl acrylate-acrylonitrile copolymers, and butyl acrylate-acrylonitrile copolymers. It should be noted that "acrylic acid" in methyl acrylate, ethyl acrylate, etc., also includes "methacrylic acid" in methyl methacrylate, ethyl methacrylate, etc.

[0142] As for the aforementioned (meth)acrylate copolymers, block copolymers are preferred, and acrylic block copolymers such as methacrylate-acrylate copolymers are even more preferred. Examples of (meth)acrylates constituting acrylic block copolymers include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and benzyl acrylate. Their "acrylic acid" also includes "methacrylic acid".

[0143] Specific examples of methacrylate-acrylate copolymers include acrylic copolymers such as methyl methacrylate-butyl acrylate-methyl methacrylate (MMA-BA-MMA) copolymer. MMA-BA-MMA copolymers also include block copolymers of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate (PMMA-PBA-PMMA).

[0144] Acrylic copolymers may lack polar groups, or they may be modified by incorporating the aforementioned polar groups in a portion of the copolymer. Because these modified copolymers readily integrate with epoxy resins, their adhesive properties are further enhanced.

[0145] The acrylic resin is preferably a (meth)acrylate copolymer having a first polymer portion having a glass transition temperature (Tg) of 10°C or less and a second polymer portion having a glass transition temperature (Tg) of 20°C or more. Such a (meth)acrylate copolymer has a first polymer portion that forms flexible segments and a second polymer portion that forms rigid segments.

[0146] The aforementioned effects can be inferred as follows. By using acrylic resins such as the aforementioned (meth)acrylate copolymers, which possess both soft and hard segments, the hard segments contribute to heat resistance, while the soft segments contribute to toughness or flexibility, thus resulting in an adhesive layer with good heat resistance, toughness, and flexibility.

[0147] At least one of the first polymer portion and the second polymer portion contained in the above-mentioned (meth)acrylate copolymer is compatible with epoxy resin. When the first polymer portion is compatible with epoxy resin, flexibility can be improved. Furthermore, when the second polymer portion is compatible with epoxy resin, cohesiveness and toughness can be improved.

[0148] When either the first polymer portion or the second polymer portion is incompatible with the epoxy resin, the (meth)acrylate copolymer has compatible and incompatible portions. The compatible portions are polymer portions compatible with the epoxy resin, and the incompatible portions are polymer portions incompatible with the epoxy resin. In this case, if the (meth)acrylate copolymer is added, fine phase separation occurs because the compatible portions are compatible with the epoxy resin, while the incompatible portions are incompatible with the epoxy resin. As a result, a fine island-like structure is exhibited. As an island structure, it varies depending on the type of (meth)acrylate copolymer, the compatibility of the first and second polymer portions contained in the (meth)acrylate copolymer, and whether or not there is modification based on the introduction of polar groups. For example, examples include an island structure where the compatible sites of the cured epoxy resin and the (meth)acrylate copolymer are "seas" and the incompatible sites of the (meth)acrylate copolymer are "islands"; an island structure where the incompatible sites of the (meth)acrylate copolymer are "seas" and the compatible sites of the cured epoxy resin and the (meth)acrylate copolymer are "islands"; and an island structure where the (meth)acrylate copolymer is "sea" and the cured epoxy resin is "island". With such an island structure, stress can be easily dispersed, thus avoiding interfacial damage and achieving excellent adhesion after foaming and curing.

[0149] In the aforementioned (meth)acrylate copolymers, block copolymers are preferred, and ABA block copolymers, particularly those with compatible polymer blocks A and incompatible polymer blocks B, are particularly preferred. More preferably, ABA block copolymers have an incompatible first polymer portion, a compatible second polymer portion, and have polymer blocks B for the first polymer portion and polymer blocks A for the second polymer portion. By using such an ABA block copolymer as an acrylic resin, in the case of a sea-island structure where the cured epoxy resin and the compatible (meth)acrylate copolymer have seas and the incompatible (meth)acrylate copolymer has islands, the island portion can be reduced. Furthermore, in the case of a sea-island structure where the incompatible (meth)acrylate copolymer has seas and the cured epoxy resin and the compatible (meth)acrylate copolymer have islands, or in the case of a sea-island structure where the cured (meth)acrylate copolymer has seas and the cured epoxy resin has islands, the sea portion can be reduced.

[0150] In addition, the above-mentioned (meth)acrylate copolymer can also be a modified product in which the above-mentioned polar groups are introduced into a part of the first polymer portion or a part of the second polymer portion.

[0151] The Tg of the first polymer portion contained in the above (meth)acrylate copolymer is below 10°C, which can be set in the range of -150°C to 10°C, and can be set in the range of -130°C to 0°C, and particularly in the range of -110°C to 10°C.

[0152] It should be noted that the Tg of the first polymer component can be calculated using the following formula based on the Tg(K) of each homopolymer as recorded in "POLYMER HANDBOOK (Third Edition)" (published by John Wiley & Sons, Ink.).

[0153] 1 / Tg(K)=W1 / Tg1+W2 / Tg2+···+W n / Tg n

[0154] W n Mass percentage of each monomer

[0155] Tg n The Tg (K) of the homopolymers of each monomer can be obtained using commonly published values ​​such as those in the Polymer Handbook (3rd edition, J. Brandrup and E. Himmergut, WILEY INTERSCIENCE). The same applies to the Tg of the second polymer section, which will be discussed later.

[0156] The first polymer portion contained in the above-mentioned (meth)acrylate copolymer can be a homopolymer or a copolymer, but a homopolymer is preferred. The monomer and polymer components constituting the first polymer portion can be any monomer and polymer components that can achieve a Tg within a specified range. Examples include acrylate monomers such as butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and methyl acrylate; other monomers such as vinyl acetate, acetal, and carbamate; monomers containing the aforementioned polar groups; and copolymers such as EVA.

[0157] The Tg of the second polymer portion contained in the above-mentioned (meth)acrylate copolymer is above 20°C, which can be set in the range of above 20°C and below 150°C, and can be set in the range of above 30°C and below 150°C, and particularly can be set in the range of above 40°C and below 150°C.

[0158] Furthermore, the second polymer portion contained in the above-mentioned (meth)acrylate copolymer can be a homopolymer or a copolymer, but a homopolymer is preferred. The monomeric components constituting the second polymer portion can be any monomeric components that can produce a second polymer portion with a Tg within a specified range. Examples include acrylate monomers such as methyl methacrylate, acrylamide, styrene, vinyl chloride, amide, acrylonitrile, cellulose acetate, phenol, carbamate, vinylidene chloride, dichloromethane, methacrylonitrile, and other monomers containing polar groups as described above.

[0159] As a specific example of a (meth)acrylate copolymer having the first polymer portion and the second polymer portion described above, the MMA-BA-MMA copolymer described above can be cited.

[0160] (i-3) Curing agent

[0161] As the curing agent 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 provides longer shelf life (usable time) compared to a curing agent that is liquid at room temperature. Alternatively, the curing agent can be a latent curing agent. Furthermore, the curing agent can be a curing agent that cures due to heat or light. Additionally, the curing agent can be used alone or in combination with two or more types.

[0162] The reaction initiation temperature of the curing agent is, for example, 110°C or higher, or 130°C or higher. If the reaction initiation temperature is too low, the reaction will start prematurely, and curing will occur when the resin components are in a state of low flexibility and fluidity, which may make 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. It should be noted that when using resins with high heat resistance, such as phenolic resins, other than epoxy resins, the resin components deteriorate less, so the reaction initiation temperature of the curing agent can be, for example, 300°C or lower. The reaction initiation temperature of the curing agent is determined by differential scanning calorimetry (DSC).

[0163] 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.

[0164] Examples of imidazole-based curing agents include imidazole, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2-methylimidazolium, 2-ethylimidazolium, 2-ethyl-4-methylimidazolium, 2-isopropylimidazolium, 2-phenylimidazolium, carboxylates of imidazole compounds, and adducts with epoxy compounds. Furthermore, imidazole-based curing agents preferably possess hydroxyl groups. Since crystallization occurs through hydrogen bonds between hydroxyl groups, there is a tendency for the reaction initiation temperature to be higher.

[0165] Phenolic resins are examples of phenolic curing agents. Furthermore, cresol-type phenolic resins and linear phenolic resins are examples of phenolic resins. From the viewpoints of adhesion to the substrate after foaming and curing, and crack resistance after foaming and curing, linear phenolic resins with a Tg of 110°C or lower are particularly preferred. Alternatively, phenolic curing agents and imidazole-based curing agents can be used in combination. In this case, imidazole-based curing agents are preferred as curing catalysts.

[0166] Examples of amine-based curing agents include aliphatic amines, aromatic amines, alicyclic amines, and polyamide amines. Examples of aliphatic amines include diethylenetriamine (DETA), triethylenetetramine (TETA), and m-phenylenediamine (MXDA). Examples of aromatic amines include diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diaminodiphenyl sulfone (DDS). Additionally, 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 also be used as amine-based curing agents.

[0167] Examples of anhydride-based curing agents include alicyclic anhydrides (liquid anhydrides) and aromatic anhydrides. Examples of alicyclic anhydrides include hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA). Examples of aromatic anhydrides include trimellitic anhydride (TMA), pyromellitic terephthalic anhydride (PMDA), and benzophenone tetracarboxylic anhydride (BTDA).

[0168] Examples of isocyanate-based curing agents include blocked isocyanates.

[0169] Examples of thiol-based curing agents include ester-bonded thiols, aliphatic ether-bonded thiols, and aromatic ether-bonded thiols.

[0170] (ii) foaming agent

[0171] As the foaming agent used in the cured adhesive layer of this embodiment, a foaming agent commonly used in the adhesive layer of foamed adhesive sheets can be used. Alternatively, the foaming agent can be a foaming agent that foams due to heat or a foaming agent that foams due to light.

[0172] Examples of foaming agents include thermally expandable microcapsules. These microcapsules preferably have a core of a thermally expandable agent such as a hydrocarbon and a shell of a resin such as an acrylonitrile copolymer.

[0173] In addition, as a blowing agent, both organic and inorganic blowing agents can be used. Examples of organic blowing agents include azodicarbonamide (ADCA), azobisformamide, and azobisisobutyronitrile; fluoroalkane-based blowing agents such as trichloromonofluoromethane; hydrazine-based blowing agents such as p-toluenesulfonylhydrazine; aminourea-based blowing agents such as p-toluenesulfonylaminourea; triazole-based blowing agents such as 5-morpholino-1,2,3,4-thiotriazole; and N-nitroso-based blowing agents such as N,N-dinitrosterephthalamide. On the other hand, examples of inorganic blowing agents include ammonium carbonate, ammonium bicarbonate, ammonium nitrite, ammonium borohydride, and azides.

[0174] 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. For example, the foaming initiation temperature of the foaming agent is 70°C or higher, or even 100°C or higher. If the reaction initiation temperature is too low, foaming will begin prematurely, and foaming may occur when the resin component is in a state of low softness and fluidity, potentially making it difficult to produce 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.

[0175] It should be noted that the softening temperature of the main component of curable adhesives such as epoxy resin is determined using the ring and ball softening temperature test method specified in JIS K7234:1986.

[0176] Furthermore, as described later, when the foaming agent is a thermally expandable microcapsule, the maximum foaming temperature of the foaming agent is preferably higher than the glass transition temperature of the main component of a curable adhesive such as epoxy resin. The maximum foaming temperature of the foaming agent is preferably 140°C or higher, more preferably 150°C or higher, even more preferably 160°C or higher, and particularly preferably 175°C or higher. As described above, if the maximum foaming temperature of the foaming agent is high, the shrinkage of the foaming agent during the foaming and curing process of the adhesive composition can be suppressed, preventing the thickness of the foam layer (cured adhesive layer) from becoming thinner. This suppresses the situation where the size of the bubbles becomes relatively large relative to the thickness of the foam layer (cured adhesive layer). Therefore, by setting the maximum foaming temperature of the foaming agent to the above range, large bubbles can be suppressed. Furthermore, if the maximum foaming temperature is too low, the foaming agent shrinks, making it impossible to maintain the thickness of the cured adhesive layer, and the adhesive strength may decrease. On the other hand, the maximum foaming temperature of the foaming agent is preferably 230°C or lower, more preferably 220°C or lower, and even more preferably 210°C or lower. If the maximum foaming temperature is too high, the foaming agent will not expand sufficiently, and the adhesive strength may decrease. Specifically, the maximum foaming temperature of the foaming agent is preferably above 140°C and below 230°C, more preferably above 150°C and below 220°C, and even more preferably above 160°C and below 210°C. Furthermore, the maximum foaming temperature of the foaming agent is also preferably above 175°C and below 220°C.

[0177] Here, the foaming start temperature and maximum foaming temperature of the foaming agent are determined by thermomechanical analysis (TMA). Specifically, when the thermomechanical analysis (TMA) is performed at a heating rate of 20°C / min and a load of 0.06N, with the x-axis set to temperature and the y-axis set to displacement, the temperature showing the maximum displacement is defined as the maximum foaming temperature, and the temperature at which the displacement is 3% relative to the maximum displacement is defined as the foaming start temperature.

[0178] The average particle size of the foaming agent can 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, it can be less than 44 μm, less than 30 μm, or less than 24 μm.

[0179] It should be noted that the average particle size of the foaming agent is the particle size at the 50% cumulative value of the particle size distribution determined by laser diffraction scattering. Furthermore, when determining the average particle size of the foaming agent, the adhesive composition is dissolved in a solvent to separate the foaming agent. There are no particular limitations on the solvent, as long as it can dissolve the components in the adhesive composition other than the foaming agent. It can be appropriately selected according to the type of adhesive that cures, for example, the solvent used in the adhesive composition can be used. Specifically, methyl ethyl ketone, ethyl acetate, toluene, etc., can be used.

[0180] The foaming ratio of the foaming agent at its maximum foaming temperature is, for example, 1.5 times or more, or even 2 times or more. On the other hand, the foaming ratio of the foaming agent at its maximum foaming temperature is, for example, 15 times or less, or even 10 times or less. It should be noted that the foaming ratio of the foaming agent is the ratio of the diameter of the foamed agent to the diameter of the foamed agent before foaming.

[0181] The content of the foaming agent in the adhesive composition used in the cured adhesive layer is set to be the same as the content of the foaming agent in the adhesive layer of the foamed adhesive sheet described later.

[0182] (iii) Other ingredients

[0183] Regarding the adhesive composition used in the cured adhesive layer of this embodiment, for example, if the curable adhesive is an epoxy resin-based adhesive, the resin component may contain only epoxy resin and acrylic resin, or it may further contain other resins. Examples of other resins include urethane resins.

[0184] The adhesive composition may contain additives such as silane coupling agents, fillers, antioxidants, light stabilizers, UV absorbers, lubricants, plasticizers, antistatic agents, crosslinking agents, and colorants, as needed. 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.

[0185] (c) Other aspects of the cured adhesive layer

[0186] There is no particular limitation on the thickness of the cured adhesive layer, which can be appropriately set according to the application. For example, the thickness of the cured adhesive layer can 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 achieved. Conversely, if the cured adhesive layer is too thick, the surface quality may deteriorate.

[0187] The cured adhesive layer can be a continuous layer or a discontinuous layer.

[0188] The cured adhesive layer contains a foamed cured product of the adhesive composition. Methods for foaming and curing the adhesive composition include, for example, heating or light irradiation. Heating is preferred for foaming and curing the adhesive composition. Heating-based methods can also be applied, for example, when the first and second components, such as those made of metal, are not transparent.

[0189] (d) First cured adhesive layer and second cured adhesive layer

[0190] In this embodiment, 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 sequence, it is sufficient that at least one of the first and second cured adhesive layers contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. For example, one of the first and second cured adhesive layers may contain a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent, and the other may contain a cured product of an adhesive composition comprising a curable adhesive but not a foaming agent; or both the first and second cured adhesive layers may contain a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. Preferably, both the first and second cured adhesive layers contain a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. This improves adhesion. Furthermore, when manufacturing articles using foamed adhesive sheets, the insertion of the foamed adhesive sheets is improved.

[0191] (2) Substrate

[0192] The adhesive member of this embodiment may have a substrate between the first cured adhesive layer and the second cured adhesive layer. When a substrate is disposed between the first and second cured adhesive layers, the operability and workability of the foamed adhesive sheet are improved when manufacturing articles using the foamed adhesive sheet. On the other hand, when no substrate is disposed between the first and second cured adhesive layers, the overall thickness of the foamed adhesive sheet can be reduced when manufacturing articles using the foamed adhesive sheet, allowing the foamed adhesive sheet to be inserted even into narrow gaps.

[0193] The substrate preferably has insulating properties. Furthermore, the substrate is preferably in sheet form. The substrate can have a single-layer structure or a multi-layer structure. Additionally, the substrate may or may not have an internal porous structure.

[0194] Examples of substrates include resin substrates and nonwoven fabrics.

[0195] Examples of resins included in the resin matrix include polyester resins, polycarbonate, polyarylate, polyurethane, polyamide resins, polyimide resins, polysulfone resins, polyetherketone resins, polyphenylene sulfide (PPS), and modified polyphenylene ether. Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyesters. Examples of polyamide resins include polyamides and polyetheramides. Examples of polyimide resins include polyimides, polyetherimides, and polyamide-imides. Examples of polysulfone resins include polysulfones and polyethersulfones. Examples of polyetherketone resins include polyetherketones and polyetheretherketones. Liquid crystal polymers (LCPs) can also be used as resins. The glass transition temperature of the resin is, for example, 80°C or higher, 140°C or higher, or 200°C or higher.

[0196] 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.

[0197] The substrate may be surface treated to improve its adhesion to the first cured adhesive layer and the second cured adhesive layer.

[0198] There is no particular limitation on the thickness of the substrate. For example, it can be 2μm or more and 200μm or less, or 5μm or more and 100μm or less, or 9μm or more and 50μm or less.

[0199] (3) Other components

[0200] The adhesive member of this embodiment may have a first intermediate layer between the substrate and the first cured adhesive layer. Alternatively, the adhesive member of this embodiment may also have a second intermediate layer between the substrate and the second cured adhesive layer. By configuring the first and second intermediate layers, the adhesion of the first and second cured adhesive layers to the substrate can be improved. Furthermore, when manufacturing articles using foamed adhesive sheets, configuring the first and second intermediate layers can, for example, alleviate stress applied to the bending portion when bending the foamed adhesive sheet and alleviate stress applied to the cutting portion when cutting the foamed adhesive sheet. As a result, it is possible to prevent the first and second adhesive layers from lifting or peeling off from the substrate when bending or cutting the foamed adhesive sheet.

[0201] For example, in Figure 4 In the illustrated article 100, in the adhesive member 30, a first intermediate layer 13a is disposed between the substrate 12 and the first cured adhesive layer 11a, and a second intermediate layer 13b is disposed between the substrate 12 and the second cured adhesive layer 11b. It should be noted that... Figure 4In the process, the adhesive member 30 has both a first intermediate layer 13a and a second intermediate layer 13b, but it may also have only one of them.

[0202] The adhesive component only needs to have at least one of a first intermediate layer and a second intermediate layer. For example, it may only have a first intermediate layer disposed between the substrate and the first cured adhesive layer, or it may only have 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. Preferably, a first intermediate layer is disposed between the substrate and the first cured adhesive layer, and a second intermediate layer is disposed between the substrate and the second cured adhesive layer.

[0203] The materials contained 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 can relieve stress. They can be appropriately selected based 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 them, crosslinks thereof, and mixtures thereof.

[0204] The crosslinker is a crosslinked body obtained by crosslinking the above-mentioned resin using 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 an isocyanate-based curing agent at a ratio of 0.5% by mass or more and 20% by mass or less relative to the resin.

[0205] Preferably, the first and second intermediate layers contain cross-linked resin. It should be noted that cross-linked resin refers to resin that will not melt even at high temperatures. This improves adhesion at high temperatures, i.e., heat resistance.

[0206] The thickness of the first and second intermediate layers is not particularly limited; for example, it can be 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 foamed adhesive sheets, it may not be possible to sufficiently suppress the peeling of the first and second adhesive layers from the substrate when the foamed adhesive sheet is bent or cut. On the other hand, the thickness of the first and second intermediate layers can be, for example, 4 μm or less, or 3.5 μm or less. Since the first and second intermediate layers themselves generally have low heat resistance, if the first and second intermediate layers are too thick, the heat resistance (adhesive strength at high temperatures) may decrease.

[0207] The first and second intermediate layers can be formed, for example, by coating a resin composition and removing the solvent. Examples of coating methods include roller coating, reverse roller coating, transfer roller coating, gravure coating, gravure reverse coating, comma coating, bar coating, scraper coating, rod coating, wire rod coating, die coating, die lip coating, and dip coating.

[0208] 2. First component and second component

[0209] The first and second components of this embodiment can be appropriately selected according to the intended use of the article. Preferably, the first and second components are components that require bonding and insulation. Examples include components of electrical / electronic equipment; more specifically, examples include the stator core and coil of a rotating electric motor stator, and the core and permanent magnet of a motor with a built-in magnet.

[0210] 3. Methods of manufacturing items

[0211] The method for manufacturing the article according to this embodiment is described in section "B. Method for manufacturing the article" below.

[0212] II. Second Implementation of the Article

[0213] The second embodiment of the article disclosed herein includes a first component, a second component, and an adhesive component disposed between the first component and the second component. The adhesive component has at least a cured adhesive layer. The cured adhesive layer is a foamed layer containing a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. 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 in a direction perpendicular to the thickness direction of the foamed layer.

[0214] Figures 1-3 This is a schematic cross-sectional view showing an example of the article according to this embodiment. It should be noted that, regarding... Figures 1-3 Since it has been described in the first embodiment above, the description here is omitted.

[0215] In articles where the first and second components are, for example, parts of electrical / electronic equipment, specifically, stator cores and coils for a rotating electric motor, or cores and permanent magnets for a type of motor with built-in magnets, the distance between the first and second components is, for example, about several hundred μm. In this case, the thickness of the adhesive component is, for example, about several hundred μm, and the thickness of the cured adhesive layer of the adhesive component is also, for example, about several hundred μm.

[0216] In the article described above, if the adhesive component has a single cured adhesive layer that is a foam layer, and large air bubbles larger than 100 μm are present, the cured adhesive layer will detach from the first and second components in the areas where such air bubbles are present, or the contact area between the cured adhesive layer and the first and second components will become very small. Therefore, it is believed that poor adhesion, such as peeling, lifting, and cracking of the cured adhesive layer, is likely to occur starting from these air bubbles.

[0217] In contrast, in the article of this embodiment, when the adhesive member has a single cured adhesive layer, and the cured adhesive layer is a foam layer, in a cross-section parallel to the thickness direction of the foam layer, the number of air bubbles with a length of 100 μm or less in the thickness direction of the foam layer is a predetermined value or less in each predetermined length in the direction perpendicular to the thickness direction of the foam layer, thereby suppressing poor adhesion. Therefore, adhesion can be improved.

[0218] Furthermore, in the articles described above, where the adhesive component has a first cured adhesive layer and a second cured adhesive layer, and both the first and second cured adhesive layers are foamed layers, if large air bubbles larger than 100 μm are present, then in the areas where such air bubbles exist, the first cured adhesive layer or the second cured adhesive layer may detach from the first component, or the contact area between the first cured adhesive layer and the first component may become very small, or the contact area between the second cured adhesive layer and the second component may become very small. Therefore, it is believed that poor adhesion, such as peeling, lifting, and cracking of the first and second cured adhesive layers, is easily generated starting from the aforementioned air bubbles.

[0219] 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 both the first and second cured adhesive layers are foam layers, in a cross-section parallel to the thickness direction of the foam layer, the number of air bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is less than a predetermined value in each predetermined length in the direction perpendicular to the thickness direction of the foam layer. This suppresses poor adhesion and thus improves adhesion.

[0220] It should be noted that even when the adhesive component 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, poor adhesion and improved adhesion can still be suppressed.

[0221] Furthermore, in the article described above, where the adhesive component sequentially comprises a first cured adhesive layer, a substrate, and a second cured adhesive layer, and both the first and second cured adhesive layers are foam layers, if large air bubbles exist that are roughly the same size as the thickness of the foam layers, then in the areas where such air bubbles exist, the first cured adhesive layer may detach from the first component and the substrate, or the second cured adhesive layer may detach from the second component and the substrate; or the contact area between the first cured adhesive layer and the first component and the substrate may become very small, or the contact area between the second cured adhesive layer and the second component and the substrate may become very small. Therefore, it is believed that poor adhesion, such as peeling, lifting, and cracking of the first and second cured adhesive layers, is easily caused by these air bubbles.

[0222] In contrast, in the article of this embodiment, when the adhesive member sequentially comprises a first cured adhesive layer, a substrate, and a second cured adhesive layer, and both the first and second cured adhesive layers are foam layers, in a cross-section parallel to the thickness direction of the foam layer, the number of air bubbles whose length in the thickness direction of the foam layer is within a predetermined range relative to the thickness of the foam layer is less than a predetermined value in each predetermined length in the direction perpendicular to the thickness direction of the foam layer. This suppresses poor adhesion and thus improves adhesion.

[0223] It should be noted that when the adhesive component has a first cured adhesive layer, a substrate, and a second cured adhesive layer, even if either the first cured adhesive layer or the second cured adhesive layer is a foam layer, poor adhesion and improved adhesion can still be suppressed.

[0224] Therefore, the reliability and durability of the items in this embodiment can be improved.

[0225] In the article of this embodiment, the adhesive member, the first member, and the second member can be configured to be the same as in the first embodiment described above.

[0226] Furthermore, the method for manufacturing the article according to this embodiment is described in section "B. Method for Manufacturing the Article" below.

[0227] The cured adhesive layer of this embodiment is a foamed layer containing an adhesive composition comprising 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 in the direction perpendicular to the thickness direction of the foamed layer. Preferably, the number of air bubbles is 3 or less, more preferably 2 or less, further preferably 1 or less, and particularly preferably 0.

[0228] Furthermore, 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 in the direction perpendicular to the thickness direction of the foam layer, more preferably 3 or less, further preferably 2 or less, particularly preferably 1 or less, and most preferably 0.

[0229] Furthermore, in a cross-section parallel to the thickness direction of the foam layer, preferably, the number of bubbles with a length of 100 μm or more in the thickness direction of the foam layer and a distance of 3 μm or less from the bubble to the interface between the foam layer and other components adjacent to the foam layer is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the foam layer, more preferably 3 or less, further preferably 2 or less, particularly preferably 1 or less, and most preferably 0. In areas where bubbles as described above exist, the cured adhesive layer loses contact with other components adjacent to the cured adhesive layer, or the contact area between the cured adhesive layer and other components adjacent to the cured adhesive layer becomes very small. Therefore, it is believed that poor adhesion such as peeling, lifting, and cracking of the cured adhesive layer is easily generated starting from the aforementioned bubbles.

[0230] It should be noted that the distance from the bubble to the interface between the foam layer and other components adjacent to the foam layer is, for example, as shown in the figure. Figure 3 As shown, u1 refers to the distance from the end of bubble 31 to the interface between foam layer 15a and other components (e.g., first component 20a) adjacent to one side of foam layer 15a; and u2 refers to the distance from the end of bubble 31 to the interface between foam layer 15a and other components (e.g., substrate 12) adjacent to the other side of foam layer 15a.

[0231] B. Methods of manufacturing the items

[0232] The method for manufacturing the article disclosed herein has two embodiments. Each embodiment will be described below.

[0233] I. First Embodiment of the Method for Manufacturing the Article

[0234] The first embodiment of the method for manufacturing an article disclosed herein 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. The manufacturing method includes: a placement step in which the foamed adhesive sheet is placed between a first component and a second component; and a bonding step in which the foaming agent-containing adhesive layer of the foamed adhesive sheet is foamed and cured to form a foamed body layer, and the first component and the second component are bonded together. The foaming and curing conditions in the bonding step are set such that, in a cross section parallel to the thickness direction of the foamed body layer, the number of bubbles with a length of at least 6 μm equal to the thickness of the foamed body layer in the thickness direction of the foamed body layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer.

[0235] Figure 5 (a) to (b) are process diagrams illustrating the manufacturing method of the article according to this embodiment. First, as Figure 5 As shown in (a), a foamed adhesive sheet 10 is disposed between the first component 20a and the second component 20b. The foamed adhesive sheet 10 has an adhesive layer 11, which is an adhesive layer 5 containing a curable adhesive and a foaming agent. Then, as... Figure 5 As shown in (b), the adhesive layer 5 (adhesive layer 1) containing a foaming agent of the foamed adhesive sheet 10 is foamed and cured to form a cured adhesive layer 11 as a foam body layer 15. The first component 20a and the second component 20b are bonded together using an adhesive member 30 having the cured adhesive layer 11. At this time, the foaming and curing conditions are, for example... Figure 1 The configuration is set 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 specified range relative to the thickness t of the foam layer 15 is below a specified value in each specified length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15. Thus, article 100 is obtained.

[0236] Figure 6 (a) to (c) are process diagrams illustrating the manufacturing method of the article according to this embodiment. First, as Figure 6 As shown in (a), a foamed adhesive sheet 10 is adhered to the second component 20b. The foamed adhesive sheet 10 has a first adhesive layer 1a and a second adhesive layer 1b, wherein the first adhesive layer 1a and the second adhesive layer 1b are respectively foamed adhesive layers 5a and 5b containing a curable adhesive and a foaming agent. At this time, the second adhesive layer 11b of the foamed adhesive sheet 10 is adhered to the surface of the second component 20b. Then, as... Figure 6 As shown in (b), a second member 20b, to which the foamed adhesive sheet 10 is disposed, is inserted into the hole of the first member 20a. Then, as... Figure 6As shown in (c), the adhesive layers 5a and 5b (first adhesive layer 1a and second adhesive layer 1b) containing a foaming agent of the foamed adhesive sheet 10 are foamed and cured respectively to form a first cured adhesive layer 11a and a second cured adhesive layer 11b as foam body layers 15a and 15b. The first component 20a and the second component 20b are bonded together using 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, for example, as follows: Figure 2 The configuration is set 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 specified range relative to the thicknesses t1 and t2 of the foam layers 15a and 15b is below a specified value in each specified length L in the direction D2 perpendicular to the thickness direction D1 of the foam layers 15a and 15b. Thus, article 100 is obtained.

[0237] It should be noted that, in Figure 6 In (a) to (c), both the first adhesive layer 1a and the second adhesive layer 1b are adhesive layers 5a and 5b containing a curable adhesive and a foaming agent. However, either the first adhesive layer or the second adhesive layer may be an adhesive layer containing a curable adhesive and a foaming agent.

[0238] In addition, Figure 6 In (a) to (c), foamed adhesive sheets 10 are attached to both sides of the second member 20b; however, foamed adhesive sheets may also be attached to one side of the second member.

[0239] In the article manufacturing method of this embodiment, as described in the first embodiment of the article above, the foaming curing conditions in the bonding process are set such that, in a cross-section parallel to the thickness direction of the foam layer, the number of air bubbles whose length in the thickness direction of the foam is within a predetermined range relative to the thickness of the foam layer is less than a predetermined value in each predetermined length in a direction perpendicular to the thickness direction of the foam layer. This suppresses poor adhesion and improves adhesion. Therefore, articles with high reliability and durability can be obtained.

[0240] It should be noted that, for convenience, in this specification, the adhesive layer located on the first component side is defined as the first adhesive layer, and the adhesive layer located on the second component side is defined as the second adhesive layer.

[0241] The following describes the foamed adhesive sheet used in the manufacturing method of the article according to this embodiment and each step of the manufacturing method of the article according to this embodiment.

[0242] 1. Foamed adhesive sheet

[0243] The foamed adhesive sheet of this embodiment has at least an adhesive layer, which is an adhesive layer containing a curable adhesive and a foaming agent.

[0244] Foamed adhesive sheets only need to have at least one adhesive layer. For example, Figure 7 As shown, the foamed adhesive sheet 10 may have one adhesive layer 1. In this case, the adhesive layer 1 is an adhesive layer 5 containing a foaming agent, which contains a curable adhesive and a foaming agent. Alternatively, for example, it may be as follows: Figure 8 As shown, the foamed adhesive sheet 10 has a first adhesive layer 1a and a second adhesive layer 1b. In this case, for example, it can be as follows: Figure 8 As shown, both the first adhesive layer 1a and the second adhesive layer 1b are adhesive layers 5a and 5b containing a curable adhesive and a foaming agent. Although not shown, either the first adhesive layer or the second adhesive layer may be an adhesive layer containing a curable adhesive and a foaming agent. Alternatively, for example, it may be as follows... Figure 9 As shown, the foamed adhesive sheet 10 sequentially comprises a first adhesive layer 1a, a substrate 12, and a second adhesive layer 1b. In this case, for example, it can be as follows: Figure 9 As shown, both the first adhesive layer 1a and the second adhesive layer 1b are adhesive layers 5a and 5b containing a curable adhesive and a foaming agent. Although not shown, either the first adhesive layer or the second adhesive layer may be an adhesive layer containing a curable adhesive and a foaming agent.

[0245] The following describes the components of the foamed adhesive sheet.

[0246] (1) Adhesive layer

[0247] In this embodiment, the adhesive layer is an adhesive layer containing a curable adhesive and a foaming agent.

[0248] (a) Characteristics of the adhesive layer

[0249] In the case where the foamed adhesive sheet of this embodiment has one adhesive layer, it is preferable that the adhesive layer is substantially non-adhesive (without initial tack). By making the adhesive layer substantially non-adhesive (without initial tack), a foamed adhesive sheet with good sliding properties and anti-adhesion properties can be formed. This improves the operability and workability of the foamed adhesive sheet. Specifically, in the placement process, the foamed adhesive sheet can be smoothly inserted into the gap between the first and second components, or, if the first component has holes or grooves, the second component can be smoothly inserted into the gap after the foamed adhesive sheet is placed in the holes or grooves of the first component.

[0250] Here, "non-adhesive" is usually used to mean low adhesive strength. In this specification, "non-adhesive" means that the foamed adhesive sheet can be easily rolled out without resistance after being wound into a roll.

[0251] When the adhesive layer is substantially non-adhesive, specifically, the initial tack of the adhesive layer is preferably 0 gf or more and less than 10 gf, or it can be less than 5 gf or less, or it can be less than 2 gf. By making the initial tack of the adhesive layer within the above range, the adhesive layer can be substantially non-adhesive, and a foamed adhesive sheet with good sliding properties and anti-adhesion properties can be produced.

[0252] Furthermore, in the case where the foamed adhesive sheet of this embodiment has a first adhesive layer and a second adhesive layer, or in the case where it has a first adhesive layer, a substrate and a second adhesive layer in sequence, both the first adhesive layer and the second adhesive layer may be substantially non-adhesive (without initial tack), or one of the first adhesive layer and the second adhesive layer may be substantially non-adhesive (without initial tack), while the other has adhesiveness (initial tack).

[0253] When both the first and second adhesive layers are substantially non-adhesive (without initial tack), the same effect as when the foamed adhesive sheet has one adhesive layer and the adhesive layer is non-adhesive (without initial tack) can be obtained.

[0254] On the other hand, when one of the first adhesive layer and the second adhesive layer is substantially non-adhesive (no initial tack) and the other is adhesive (initial tack), for example, when the first adhesive layer is substantially non-adhesive (no initial tack) and the second adhesive layer is adhesive (initial tack), a second adhesive layer with good adhesion to the second member can be formed. Specifically, in the configuration process, when the second adhesive layer on which the foamed adhesive sheet is adhered is inserted into the holes or grooves of the first member, by making the second adhesive layer adhesive, the adhesion of the second adhesive layer to the second member can be improved by utilizing the adhesiveness of the second adhesive layer on the surface of the second adhesive layer on which the foamed adhesive sheet is adhered. Thus, when the second member on which the foamed adhesive sheet is adhered is inserted into the holes or grooves of the first member, peeling and displacement of the foamed adhesive sheet can be suppressed.

[0255] Furthermore, in the above-described case, by making the second adhesive layer adhesive, a second adhesive layer with good reprocessability can be produced. Therefore, for example, when the adhesiveness of the second adhesive layer is used to attach the second adhesive layer of the foamed adhesive sheet to the second component as described above, the positional misalignment of the foamed adhesive sheet can be corrected.

[0256] Furthermore, in the above-described case, by making the first adhesive layer non-adhesive, a first adhesive layer with good sliding properties can be produced. Therefore, for example, when inserting the second component with the foamed adhesive sheet adhered to it into the hole, groove, or the like of the first component as described above, the second component with the foamed adhesive sheet adhered to it can be inserted smoothly, improving insertion performance. This suppresses peeling and positional displacement of the foamed adhesive sheet. Additionally, when aligning the first and second components by moving the second component relative to the first component, the second component can be moved smoothly relative to the first component while it is inserted into the hole, groove, or the like of the first component, making positional alignment easy.

[0257] Furthermore, in the aforementioned situation, as described above, due to the excellent adhesion between the second adhesive layer and the second component, and the excellent sliding properties of the first adhesive layer, peeling and displacement of the foamed adhesive sheet can be suppressed. Therefore, while suppressing the decrease in adhesion of the foamed adhesive sheet after foaming and curing caused by peeling and displacement of the foamed adhesive sheet, the fluctuation of the adhesive strength of the foamed adhesive sheet after foaming and curing caused by peeling and displacement of the foamed adhesive sheet can be reduced.

[0258] Furthermore, in the above-described case, by making the second adhesive layer adhesive, for example, when the second adhesive layer is formed using a transfer method, it is possible to suppress the lifting of the second adhesive layer. Moreover, as described later, when the second spacer is disposed on the side of the second adhesive layer opposite to the first adhesive layer, by making the second adhesive layer adhesive, the second spacer can be easily peeled off, thereby improving workability.

[0259] Furthermore, when the adhesive layer has adhesive properties, for example, it contains a large amount of low molecular weight resin components. Therefore, during the foaming and curing process of the adhesive layer, the fluidity tends to increase as the resin components soften. Consequently, when the adhesive layer (the adhesive layer containing the foaming agent) is foamed and cured to form a foamed layer, the bubbles tend to connect easily and the bubbles tend to enlarge. Thus, the article manufacturing method of this embodiment is useful when one of the first and second adhesive layers is substantially non-adhesive (no initial tack) and the other is adhesive (initial tack).

[0260] When both the first adhesive layer and the second adhesive layer are substantially non-adhesive, specifically, the initial tack of the first adhesive layer and the second adhesive layer is preferably 0 gf or more and less than 10 gf, or it can be 5 gf or less, or it can be 2 gf or less. By making the initial tack of the first adhesive layer and the second adhesive layer within the above range, the first adhesive layer and the second adhesive layer can be substantially non-adhesive, and a foamed adhesive sheet with good sliding properties and anti-adhesion properties can be produced.

[0261] In addition, when the first adhesive layer is substantially non-adhesive (no initial tack) and the second adhesive layer is adhesive (initial tack), specifically, it is preferable that the initial tack of the first adhesive layer is 0 gf or more and less than 10 gf, and the initial tack of the second adhesive layer is 10 gf or more and less than 400 gf.

[0262] In the above-described case, the initial tack of the first adhesive layer is preferably 0 gf or more and less than 10 gf, or it may be 5 gf or less, or it may be 2 gf or less. By making the initial tack of the first adhesive layer within the above-described range, the first adhesive layer can be made substantially non-adhesive, and a foamed adhesive sheet with good sliding properties and anti-adhesion properties can be made.

[0263] Furthermore, in the above-described case, the initial tack of the second adhesive layer is preferably 10 gf or more, or it can be 30 gf or more, or it can be 50 gf or more. If the initial tack of the second adhesive layer is too low, for example, when using the initial tack of the second adhesive layer to adhere the surface of the second adhesive layer of the foamed adhesive sheet to the second component, the adhesion between the second adhesive layer and the second component may decrease, or when the second component with the foamed adhesive sheet is inserted into the holes or grooves of the first component, the foamed adhesive sheet may peel off or shift in position due to poor adhesion between the second adhesive layer and the second component. This may lead to a decrease in the adhesion between the first adhesive layer and the second adhesive layer after foaming and curing, or fluctuations in the adhesive strength. In addition, the initial tack of the second adhesive layer is preferably 400 gf or less, or it can be 300 gf or less, or it can be 200 gf or less. If the initial tack of the second adhesive layer is too high, the reprocessability will be reduced. For example, when using the initial tack of the second adhesive layer to attach the second adhesive layer of the foamed adhesive sheet to the second component, it may become difficult to correct the positional offset of the foamed adhesive sheet.

[0264] Here, the initial tack of the adhesive layer is determined by a probe initial tack test. Specifically, at a temperature of 25°C, 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 with a load of 10.0 gf and a speed of 30 mm / min and held for 1.0 second. Then, it is peeled off at a speed of 30 mm / min, and the load during peeling is measured. This test is performed 5 times, and the average value is defined as the initial tack. For example, the RHEESCA "TAC-II" initial tack tester can be used as the probe initial tack tester.

[0265] As a means of controlling the initial tack of the adhesive layer, one example is adjusting the composition of the adhesive layer. Specifically, in an adhesive layer containing epoxy resin and a curing agent, using an epoxy resin that is solid at room temperature or a curing agent that is solid at room temperature can reduce the adhesiveness of the adhesive layer. 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 adhesiveness of the adhesive layer. In addition, in an adhesive layer containing epoxy resin and a curing agent, containing an epoxy resin with a high softening temperature or containing an epoxy resin with a high weight-average molecular weight can reduce the adhesiveness of the adhesive layer. For example, by containing multiple epoxy resins with different softening temperatures in the adhesive layer, that is, by containing one epoxy resin and another epoxy resin with a softening temperature of 25°C or higher and a softening temperature 10°C or higher than that of the aforementioned epoxy resin, the adhesiveness of the adhesive layer can be reduced. Furthermore, for example, by 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 with a weight-average molecular weight of 370 or more and a weight-average molecular weight 300 or more greater than that of the aforementioned epoxy resin—the adhesiveness of the adhesive layer can be reduced. More specifically, in an adhesive layer containing epoxy resin and a curing agent, as described above, by including a first epoxy resin with a low softening temperature and low molecular weight, and a second epoxy resin with a high softening temperature and high molecular weight, the adhesiveness of the adhesive layer can be reduced. On the other hand, in an adhesive layer containing epoxy resin and a curing agent, if an epoxy resin with a low softening temperature or a low weight-average molecular weight is included, the adhesiveness of the adhesive layer tends to increase. Additionally, in an adhesive layer containing epoxy resin and a curing agent, as described above, by including an acrylic resin compatible with the epoxy resin, the adhesiveness of the adhesive layer can be reduced. Furthermore, by adding a tackifying resin (tackifier) ​​to the adhesive layer, the adhesiveness of the adhesive layer tends to increase. It should be noted that if a curing agent that is liquid at room temperature is used, although there is a tendency for the adhesion to increase, the storage stability may be reduced. Therefore, it is preferable to adjust the initial tack of the adhesive layer by adjusting the properties and types of components other than the curing agent, such as epoxy resin.

[0266] Here, the term "adhesion" is a concept encompassed within "bonding." Adhesion is used to refer to temporary bonding phenomena, while bonding refers to substantially permanent bonding phenomena; this is a distinction (Iwanami Shoten RIKEN Dictionary, 5th Edition). "Adhesiveness" and "adhesive force" refer to the property of bonding through pressure sensitivity and the adhesive force at that point.

[0267] It should be noted that, unless otherwise specified, the terms "adhesiveness of the adhesive layer" and "adhesive force of the adhesive layer" in this specification refer to the adhesiveness and adhesive force of the adhesive layer before curing. Furthermore, unless otherwise specified, the terms "adhesiveness of the adhesive layer" and "adhesive force of the adhesive layer" in this specification refer to the adhesiveness and adhesive force of the adhesive layer after curing.

[0268] (b) Material of the adhesive layer

[0269] The adhesive layer in this embodiment contains a curable adhesive and a foaming agent.

[0270] Regarding the material of the adhesive layer, since it is the same as that described in the "A. Article" section above, the description here is omitted.

[0271] 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 more preferably, 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.

[0272] The content of epoxy resin, which is liquid at room temperature, in the adhesive layer is the same as the content of epoxy resin, which is liquid at room temperature, in the adhesive composition used in the cured adhesive layer of the above-mentioned article.

[0273] In the case of epoxy resin-based adhesives, the resin component in the adhesive layer refers to epoxy resin and acrylic resin. The resin component in the adhesive layer may also include, optionally, urethane resins. Furthermore, if the curing agent is phenolic resin, the resin component in the adhesive layer also includes phenolic resin as the curing agent.

[0274] When the curable adhesive is an epoxy resin-based adhesive, and the curable adhesive contains a first epoxy resin and a second epoxy resin as described above, wherein the first epoxy resin has a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or lower, and the second epoxy resin has a softening temperature higher than that of the first epoxy resin and a weight-average molecular weight of 20000 or higher, the content of the first epoxy resin, when the resin component contained in the adhesive layer is set to 100 parts by weight, can be, for example, 1 part by weight or more, or 3 parts by weight or more, or 5 parts by weight or more, or 10 parts by weight or more, or 15 parts by weight or more, or 25 parts by weight or more. If the content of the first epoxy resin is too low, the adhesion and anti-blocking properties after foaming and curing may be reduced. On the other hand, regarding the content of the first epoxy resin, when the resin component contained in the adhesive layer is set to 100 parts by weight, it can be, for example, 90 parts by weight or less, or 80 parts by weight or less, or 70 parts by weight or less, or 60 parts by weight or less, or 50 parts by weight or less, or 40 parts by weight or less. If the content of the first epoxy resin is too high, the content of the second epoxy resin and acrylic resin will be relatively low, which may not be able to balance the non-adhesiveness, anti-blocking properties, adhesion to the substrate after foaming and curing, crack resistance after foaming and curing, and adhesion after foaming and curing.

[0275] Furthermore, regarding the content of the second epoxy resin, when the resin component in the adhesive layer is set to 100 parts by weight, it can be, for example, 10 parts by weight or more, or 15 parts by weight or more, or 20 parts by weight or more, or 25 parts by weight or more, or 30 parts by weight or more, or 35 parts by weight or more, or 40 parts by weight or more, or 45 parts by weight or more. If the content of the second epoxy resin is too low, the adhesion will be high, but the anti-blocking property may be low. On the other hand, regarding the content of the second epoxy resin, when the resin component in the adhesive layer is set to 100 parts by weight, it can be, for example, 90 parts by weight or less, or 85 parts by weight or less, or 80 parts by weight or less, or 75 parts by weight or less. If the content of the second epoxy resin is too high, the content of the first epoxy resin and acrylic resin will be relatively low, which may not be able to balance the non-adhesiveness, anti-blocking property, adhesion to the substrate after foaming and curing, crack resistance after foaming and curing, and adhesion after foaming and curing.

[0276] The proportion of the first epoxy resin relative to the total of the first epoxy resin and the second epoxy resin is, for example, 5% by mass or more, or 10% by mass or more, or 15% by mass or more, or 20% by mass or more. On the other hand, the above-mentioned proportion of the first epoxy resin is, for example, 80% by mass or less, or 75% by mass or less, or 60% by mass or less.

[0277] In addition, the total amount of the first epoxy resin and the second epoxy resin relative to the total amount of epoxy resin contained in the adhesive layer is, for example, 50% by mass or more, or 70% by mass or more, or 90% by mass or more, or 100% by mass.

[0278] When the first adhesive layer is substantially non-adhesive and the second adhesive layer is adhesive and curable, and the adhesive is an epoxy resin-based adhesive, the first adhesive layer preferably contains a first epoxy resin and a second epoxy resin as described above. The first epoxy resin has a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or lower, while the second epoxy resin has a softening temperature higher than that of the first epoxy resin and a weight-average molecular weight of 20000 or higher. On the other hand, in the second adhesive layer, it is preferable to use bisphenol A type epoxy resin, bisphenol F type epoxy resin, or other epoxy resins that are liquid at room temperature and have low softening points. This is because by using these epoxy resins, it is easy to adjust the initial tack of the second adhesive layer to a specified range.

[0279] 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 content of the acrylic resin, when the resin component in the adhesive layer is set to 100 parts by weight, can be, for example, 1 part by weight or more, or 3 parts by weight or more, or 5 parts by weight or more, or 7 parts by weight or more, or 10 parts by weight or more. If the content of the acrylic resin is too low, the adhesion to the substrate after foaming and curing, the crack resistance after foaming and curing, and the adhesion after foaming and curing may decrease. On the other hand, regarding the content of the acrylic resin, when the resin component in the adhesive layer is set to 100 parts by weight, it can be, for example, 60 parts by weight or less, or 50 parts by weight or less, or 40 parts by weight or less, or 35 parts by weight or less, or 30 parts by weight or less. If the acrylic resin content is too high, the content of the first and second epoxy resins will be relatively low, which may disrupt the balance of non-adhesiveness, anti-blocking properties, adhesion to the substrate after foaming and curing, crack resistance after foaming and curing, and adhesion after foaming and curing. Furthermore, if the acrylic resin content is too high, the film strength may decrease.

[0280] Furthermore, regarding the content of the curing agent, when the resin component contained in the adhesive layer is set to 100 parts by weight, it is, for example, 1 part by weight or more and 40 parts by weight or less. For example, when an imidazole-based curing agent is used as the main component as the curing agent, the content of the curing agent, when the resin component contained in the adhesive layer is set to 100 parts by weight, is preferably, for example, 1 part by weight or more and 15 parts by weight or less. On the other hand, when a phenolic curing agent is used as the main component as the curing agent, the content of the curing agent, when the resin component contained in the adhesive layer is set to 100 parts by weight, is preferably, for example, 5 parts by weight or more and 40 parts by weight or less. It should be noted that, when "using an imidazole-based curing agent or a phenolic curing agent as the main component as the curing agent" means that the imidazole-based curing agent or the phenolic curing agent has the highest mass proportion in the curing agent.

[0281] The content of the foaming agent in the adhesive layer, relative to 100 parts by mass of the resin component in the adhesive layer, is, for example, 0.5 parts by mass or more, or 2 parts by mass or more, or 3 parts by mass or more, or 4 parts by mass or more, or 5 parts by mass or more, or 13 parts by mass or more, or 15 parts by mass or more. As mentioned above, if the content of the foaming agent is high, there is a tendency for the thickness of the adhesive layer after foaming and curing, i.e., the thickness of the foam body layer (cured adhesive layer), to increase. Therefore, relative to the thickness of the foam body layer (cured adhesive layer), the size of the air bubbles can be relatively reduced. Thus, by keeping the content of the foaming agent within the above range, large air bubbles can be suppressed. On the other hand, the content of the foaming agent in the adhesive layer, relative to 100 parts by mass of the resin component in the adhesive layer, is, for example, 30 parts by mass or less, or 25 parts by mass or less, or 20 parts by mass or less. If the content of the foaming agent is too high, the content of the curable adhesive becomes relatively low, and therefore the adhesion after foaming and curing may decrease.

[0282] It is permissible for at least one of the first and second adhesive layers to contain a foaming agent. Where 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 presence of a foaming agent increases surface roughness, reduces the coefficient of friction, and improves sliding properties. It is particularly 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 of the first and second adhesive layers after foaming and curing can be improved.

[0283] The total amount of epoxy resin and acrylic resin relative to the resin content in the adhesive layer is, for example, 70% by mass or more, or 80% by mass or more, or 90% by mass or more, or 100% by mass.

[0284] The adhesive layer contains resin components of, for example, 60% by mass or more, or 70% by mass or more, or 80% by mass or more, or 90% by mass or more.

[0285] (c) Composition of the adhesive layer

[0286] The adhesive layer can be foamed at a foaming ratio of 1.5 times or more and 15 times or less. For example, the foaming ratio can be 3.5 times or more, 4 times or more, or 4.5 times or more. Alternatively, the foaming ratio can be 9 times or less, 8.5 times or less, or 8 times or less. Whether the foaming ratio is too small or too large, the adhesive properties after foaming and curing may decrease.

[0287] Here, the foaming ratio can be calculated using the following formula.

[0288] Foaming ratio (times) = Thickness of the adhesive layer after foaming and curing / Thickness of the adhesive layer before foaming and curing

[0289] The thickness of the adhesive layer is not particularly limited; however, it is preferably greater than or equal to the average particle size of the foaming agent, for example, 10 μm or more, or 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 achieved. On the other hand, the thickness of the adhesive layer is, for example, less than or equal to 200 μm, or less than or equal to 150 μm, or less than or equal to 100 μm. If the adhesive layer is too thick, the surface quality may deteriorate.

[0290] The adhesive layer can be a continuous layer or a discontinuous layer. Examples of discontinuous layers include patterns such as stripes and dots. Additionally, the surface of the adhesive layer can have embossed or other textured shapes.

[0291] The adhesive layer can be formed, for example, by applying an adhesive composition containing the aforementioned curable adhesive and foaming agent, and then removing the solvent. Examples of coating methods include roller coating, reverse roller coating, transfer roller coating, gravure coating, gravure reverse coating, comma coating, bar coating, doctor blade coating, rod coating, wire rod coating, die coating, die lip coating, and dip coating.

[0292] The adhesive composition may or may not contain a solvent. It should be noted that the term "solvent" in this specification includes not only solvents in the strict sense (solvents that dissolve the solute) but also, in a broader sense, the dispersion medium. Furthermore, the solvents contained in the adhesive composition evaporate and are removed when the adhesive composition is applied and dried to form an adhesive layer.

[0293] The adhesive composition can be obtained by mixing the above-mentioned components and kneading and dispersing them as needed. Common kneading and dispersing machines can be used as mixing and dispersing methods, such as two-roll mills, three-roll mills, pebble mills, tronmills, Szegvari mills, high-speed impeller dispersers, high-speed stone mills, high-speed impact mills, dispersers, high-speed mixers, ribbon mixers, co-kneaders, high-intensity kneaders, drum mixers, blenders, applicators, homogenizers, and ultrasonic dispersers.

[0294] (2) Substrate

[0295] The foamed adhesive sheet of this embodiment may have a substrate between the first adhesive layer and the second adhesive layer. Regarding the substrate, since it is the same as described in item "A. Article" above, its description is omitted here.

[0296] (3) Other components

[0297] (a) First intermediate layer and second intermediate layer

[0298] The foamed adhesive sheet of this embodiment may have a first intermediate layer between the substrate and the first adhesive layer. Additionally, the foamed adhesive sheet of this embodiment may have a second intermediate layer between the substrate and the second adhesive layer. Since the first and second intermediate layers are identical to those described in item "A. Article" above, their description here is omitted.

[0299] For example, in Figure 10 In the foamed adhesive sheet 10 shown, a first intermediate layer 13a is disposed between the substrate 12 and the first adhesive layer 1a, and a second intermediate layer 13b is disposed between the substrate 12 and the second adhesive layer 1b. It should be noted that... Figure 10 In the foamed adhesive sheet 10, there are both a first intermediate layer 13a and a second intermediate layer 13b, but it may also have only one of them.

[0300] (b) Spacer

[0301] In the case where the foamed adhesive sheet of this embodiment has one adhesive layer, spacers may be provided on one or both sides of the adhesive layer. Furthermore, in the case where the foamed adhesive sheet of this embodiment has a first adhesive layer and a second adhesive layer, or where a first adhesive layer, a substrate, and a second adhesive layer are provided sequentially, a first spacer may be provided on the side of the first adhesive layer opposite to the second adhesive layer, and a second spacer may be provided on the side of the second adhesive layer opposite to the first adhesive layer.

[0302] When the foamed adhesive sheet has a spacer, it is used after the spacer is peeled off from the foamed adhesive sheet when the foamed adhesive sheet is disposed between the first member and the second member.

[0303] There are no particular limitations on the spacer as long as it can be peeled off from the adhesive layer, and it can have the strength to protect the adhesive layer. Examples of such spacers include release films and release papers. In addition, the spacer can have a single-layer structure or a multi-layer structure.

[0304] As a spacer in a single-layer structure, examples include fluoropolymer membranes.

[0305] Furthermore, as spacers in multi-layered structures, examples include laminates having release layers on one or both sides of the substrate layer. Examples of substrate layers include resin films such as polypropylene, polyethylene, and polyethylene terephthalate, as well as high-quality paper, coated paper, and impregnated paper. The material for the release layer is not particularly limited as long as it possesses release properties; examples include silicone compounds, organic-modified silicone compounds, fluorinated compounds, amino alkyd compounds, melamine compounds, acrylic compounds, polyester compounds, and long-chain alkyl compounds. These compounds can be emulsion-type, solvent-type, or solvent-free.

[0306] The first spacer and the second spacer can be the same or different. Where the first adhesive layer is substantially non-adhesive and the second adhesive layer is adhesive, it is preferable that the first spacer has heavy peelability and the second spacer has light peelability. For example, when a foamed adhesive sheet is disposed on the second member, and the second member with the foamed adhesive sheet disposed thereon is inserted into the hole of the first member, by making the surface of the first adhesive layer of the foamed adhesive sheet the outer surface of the second member adhered to the second member, the tightness of the fit between the second member and the foamed adhesive sheet during insertion, and the insertionability of the second member with the foamed adhesive sheet, can be improved. In this case, since the second spacer is peeled from the first spacer and the second spacer, by making the first spacer heavy peelability and the second spacer light peelability, the second spacer can be peeled more easily than the first spacer.

[0307] It should be noted that the terms "light peel" and "heavy peel" refer to the degree of force required to peel the first spacer and the second spacer from the first adhesive layer and the second adhesive layer, respectively. Light peel means that the peeling force is smaller compared to heavy peel.

[0308] (4) Foamed adhesive sheet

[0309] The thickness of the foamed adhesive sheet in this embodiment is, for example, 10 μm or more, or 20 μm or more. On the other hand, the thickness of the foamed adhesive sheet is, for example, 1000 μm or less, or 200 μm or less.

[0310] The foamed adhesive sheet of this embodiment preferably exhibits good shape retention. Good shape retention is preferred. Based on JIS P8125-2:2017 corresponding to ISO 2493, the bending moment is, for example, 0.1 gf·cm or more, and may also be 1 gf·cm or more. On the other hand, the bending moment is, for example, less than 40 gf·cm, and may also be less than 30 gf·cm. Conventionally, in foamed adhesive sheets, methods are typically employed to increase the bending moment, enhance shape retention, and improve insertability into narrow gaps. In contrast, the inventors of this disclosure have discovered that shape retention can be ensured through shape design, and that high bending moments can lead to other undesirable conditions. Therefore, considering other characteristics, a bending moment within the aforementioned range is preferred. If the bending moment is below the aforementioned range, it may still be difficult to maintain the shape even with bending designs. Furthermore, if the bending moment is above the aforementioned range, the shape returns to its original state after bending, therefore heating and adding folds at the folds are necessary during bending. Heating can reduce the lifespan of the sheet, and adding wrinkles may reduce the insulation of that part. Furthermore, in the foamed adhesive sheet of this embodiment, by increasing surface hardness, the surface will not be damaged even with high-speed insertion.

[0311] The foamed adhesive sheet of this embodiment preferably exhibits high adhesiveness after foaming and curing. Based on the shear strength (adhesive strength) of JIS K6850:1999 corresponding to ISO 4587:1995, at 23°C, it can be, for example, 1.50 MPa or more, 1.80 MPa or more, or 2.10 MPa or more. Furthermore, at 130°C, the aforementioned shear strength (adhesive strength) can be, for example, 0.50 MPa or more, 0.75 MPa or more, or 1.00 MPa or more. For example, in high-strength acrylic foam tapes that do not require heating, the shear strength (adhesive strength) is approximately 1 MPa or more and 2 MPa or less at room temperature, and there is no heat resistance at 200°C. Therefore, if the shear strength (adhesive strength) is within the above range at 23°C, it has advantages in terms of strength. Furthermore, if the shear strength (adhesive strength) is within the above range at 130°C, it can be applied to the engine area of ​​automobiles or applications requiring similar heat resistance.

[0312] The foamed adhesive sheet of this embodiment preferably exhibits high electrical insulation after foaming and curing. After the foamed adhesive sheet has cured, the insulation breakdown voltage, based on JIS C2107:2011 corresponding to IEC 60454-2, is preferably 3kV or higher, more preferably 5kV or higher. By setting the insulation breakdown voltage within this range, the application requirements for rust prevention and copper wire perimeter protection can be met. Furthermore, after the foamed adhesive sheet has cured, the thermal conductivity is preferably 0.1W / mK or higher, more preferably 0.15W / mK or higher. By setting the thermal conductivity within this range, component miniaturization can be achieved, and the curing reaction during heating can be promoted.

[0313] The manufacturing method of the foamed adhesive sheet in this embodiment is not particularly limited, and can be appropriately selected according to the layer composition of the foamed adhesive sheet.

[0314] 2. Configuration process

[0315] In the configuration process of this embodiment, a foamed adhesive sheet is disposed between the first component and the second component.

[0316] The method of placing a foamed adhesive sheet between the first component and the second component can be appropriately selected according to the types of the first component and the second component.

[0317] For example, methods include inserting a foamed adhesive sheet between a first member and a second member; and inserting a second member into the gap after placing a foamed adhesive sheet in a hole or groove of the first member. Furthermore, when the first member has a hole or groove, and a second member is placed in the hole or groove of the first member, methods for fixing the first member and the second member by adhesive include: placing the second member with the foamed adhesive sheet attached in the hole or groove of the first member after the initial adhesive force of the second adhesive layer of the foamed adhesive sheet is used to attach the second adhesive layer of the foamed adhesive sheet to the surface of the second adhesive layer of the second member; and placing a foamed adhesive sheet in the hole or groove of the first member, and after the initial adhesive force of the second adhesive layer of the foamed adhesive sheet is used to attach the second adhesive layer of the foamed adhesive sheet to the surface of the hole or groove of the first member, placing the second member in the hole or groove of the first member with the foamed adhesive sheet attached.

[0318] 3. Bonding process

[0319] In the bonding process of this embodiment, the adhesive layer containing a foaming agent of the foamed adhesive sheet is foamed and cured to form a foamed layer, and the first component and the second component are bonded together.

[0320] Furthermore, in the bonding process of this embodiment, the foaming curing conditions are set as follows: in a cross-section parallel to the thickness direction of the foam layer, the number of bubbles with a length of 6 μm or more in the thickness direction of the foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer. Preferably, the foaming curing conditions are set to have 3 or fewer bubbles, more preferably 2 or fewer, even more preferably 1 or fewer, and particularly preferably 0.

[0321] Methods for foaming and curing foamed adhesive sheets include, for example, heating or light irradiation. Heating is preferred for foaming and curing the adhesive layer containing the foaming agent. Heating-based methods can also be applied when the first and second components are not transparent, such as in metal components.

[0322] The heating conditions are set to achieve the aforementioned foaming and curing conditions. The heating conditions can be appropriately set, for example, according to the type of curable adhesive and foaming agent contained in the adhesive layer.

[0323] The heating temperature is preferably within ±40°C of the maximum foaming temperature of the foaming agent, more preferably within ±30°C, and even more preferably within ±20°C. If the heating temperature is higher than the above range, even if the resin component cures, the thickness of the adhesive layer during foaming may not be maintained due to the shrinkage of the foaming agent, and the size of the bubbles tends to increase relative to the thickness of the foamed 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 is insufficient, and the adhesive strength may decrease. In this case, interface damage may easily occur between the cured adhesive layer and the first or second component.

[0324] It should be noted that when the adhesive layer contains multiple foaming agents, it is sufficient that the heating temperature of at least one foaming agent is within the aforementioned range. Preferably, the heating temperature of the foaming agent with the highest content among the multiple foaming agents is within the aforementioned range. Particularly preferred is that the heating temperatures of all the multiple foaming agents are within the aforementioned range.

[0325] Furthermore, the heating temperature is preferably 7°C or more below the maximum displacement extrapolation temperature of the foamed adhesive sheet and 83°C or less, more preferably 15°C or more above the maximum displacement extrapolation temperature of the foamed adhesive sheet and 63°C or less, and even more preferably 23°C or more above the maximum displacement extrapolation temperature of the foamed adhesive sheet and 43°C or less. If the heating temperature is higher than the above range, even if the resin component cures, the thickness of the adhesive layer during foaming may not be maintained due to the shrinkage of the foaming agent, and the size of the bubbles tends to increase relative to the thickness of the foamed 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 is insufficient, and the adhesive strength may decrease. In this case, interface damage may easily occur between the cured adhesive layer and the first or second component.

[0326] Figure 11 This is a graph illustrating the TMA curve of a foamed adhesive sheet. The TMA curve is obtained by applying a compressive load through thermomechanical analysis (TMA), heating at a specified rate, and measuring the displacement, with temperature on the horizontal axis and displacement on the vertical axis. In TMA curves of foamed adhesive sheets containing thermally expandable microcapsules as the blowing agent, there is typically a peak associated with expansion (foaming). For example... Figure 11 In the TMA curves obtained for the foamed adhesive sheet shown, the temperature at which the tangent line at the temperature showing the maximum displacement intersects with the tangent line at the minimum temperature when differentiating the portion of the TMA curve that begins to show expansion behavior accompanied by expansion (foaming) is defined as the extrapolated maximum displacement temperature T of the foamed adhesive sheet. max1 In the above case, it is preferable to use a heating temperature relative to the extrapolated temperature T of the maximum displacement. max1 Within the prescribed scope.

[0327] The thermomechanical analysis of the foamed adhesive sheet was performed using the following method. First, a sample was prepared by punching the foamed adhesive sheet to a size of φ4mm. Then, the sample was placed in a φ5mm aluminum container with the surface of the second adhesive layer of the foamed adhesive sheet as the bottom side. Next, a φ4mm aluminum plate was placed on the sample. Then, using a thermomechanical analysis apparatus, the temperature was increased from 25°C to 250°C at a rate of 20°C / min, and the measurement was performed in compression mode under a load of 10mN. The thermomechanical analysis apparatus can be a Hitachi Advanced Technology Corporation TMA7100 thermomechanical analysis apparatus.

[0328] It should be noted that the above-mentioned maximum displacement is the maximum value of the displacement in the TMA curve obtained for the foamed adhesive sheet.

[0329] In addition, the above-mentioned maximum displacement extrapolation temperature is set as the intersection of the tangent at the temperature showing the maximum displacement in the TMA curve obtained from the foamed adhesive sheet and the tangent at the minimum temperature when the portion of the TMA curve that begins to show expansion behavior accompanied by expansion (foaming) is differentiated.

[0330] Specifically, the heating temperature can be set to above 130℃ and below 200℃.

[0331] The heating time can be set to, for example, more than 3 minutes and less than 3 hours.

[0332] II. Second Embodiment of the Method for Manufacturing the Article

[0333] The second embodiment of the method for manufacturing an article disclosed herein 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. The manufacturing method includes: a placement step in which the foamed adhesive sheet is placed between a first component and a second component; and a bonding step in which the foaming agent-containing adhesive layer of the foamed adhesive sheet is foamed and cured to form a foamed body layer, and the first component and the second component are bonded together. The foaming and curing conditions in the bonding step are set such that, in a cross section parallel to the thickness direction of the foamed body layer, the number of air bubbles with a length of 100 μm or more in the thickness direction of the foamed body layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer.

[0334] Figure 5 (a) to (b) and Figure 6 (a) to (c) are process diagrams illustrating the manufacturing method of the article according to this embodiment. It should be noted that, regarding... Figure 5 (a) to (b) and Figure 6 (a) to (c), since they are described in the first embodiment above, are omitted here.

[0335] In the article manufacturing method of this embodiment, as described in the second embodiment of the article above, the foaming and curing conditions of 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 less than a predetermined value in each predetermined length in a direction perpendicular to the thickness direction of the foam layer. This suppresses poor adhesion and improves adhesion. Therefore, articles with high reliability and durability can be obtained.

[0336] The foamed adhesive sheet used in the article manufacturing method of this embodiment and the configuration steps of the article manufacturing method of this embodiment can be set to be the same as those in the first embodiment described above.

[0337] Furthermore, in the bonding process of this embodiment, the foaming curing conditions are set as follows: 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 in the direction perpendicular to the thickness direction of the foam layer. Preferably, the foaming curing conditions are set to have 3 or fewer bubbles, more preferably 2 or fewer, even more preferably 1 or fewer, and particularly preferably 0.

[0338] The method and heating conditions for foaming and curing the foamed adhesive sheet can be set to be the same as those in the first embodiment described above.

[0339] C. Foamed adhesive sheet

[0340] The foamed adhesive sheet disclosed herein has two embodiments. Each embodiment will be described below.

[0341] I. First embodiment of the foamed adhesive sheet

[0342] The first embodiment of the foamed adhesive sheet disclosed herein has at least an adhesive layer, which is an 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. When the foamed adhesive sheet is heated at the maximum foaming temperature ±20°C of the foaming agent for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed body layer, in a cross section parallel to the thickness direction of the foamed body layer, the number of air bubbles with a length of more than 6 μm in the thickness direction of the foamed body layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer.

[0343] Figure 7 This is a schematic cross-sectional view showing an example of the foamed adhesive sheet of this embodiment. Figure 7 The foamed adhesive sheet 10 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 specified temperature for a specified time, thereby causing the foaming agent-containing adhesive layer 5 (adhesive layer 1) to foam and cure to form a foamed layer 15, for example... Figure 12As shown, in a cross section parallel to the thickness direction D1 of the foam layer 15, the number of bubbles 31 with a length s in the thickness direction D1 of the foam layer 15 relative to the thickness t of the foam layer 15 within a specified range is below a specified value in each specified length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15.

[0344] Figure 8 This is a schematic cross-sectional view showing another example of the foamed adhesive sheet of this embodiment. Figure 9 The foamed adhesive sheet 10 has a first adhesive layer 1a and a second adhesive layer 1b. The first adhesive layer 1a and the second adhesive layer 1b are foamed adhesive layers 5a and 5b containing a curable adhesive and a foaming agent. The curable adhesive contained in the foamed adhesive layers 5a and 5b (first adhesive layer 1a and second adhesive layer 1b) is a thermosetting adhesive, and the foaming agent contained in the foamed adhesive layers 5a and 5b (first adhesive layer 1a and second adhesive layer 1b) is a thermally expandable microcapsule. When the foamed adhesive sheet 10 is heated at a specified temperature for a specified time, thereby causing the foamed adhesive layers 5a and 5b (first adhesive layer 1a and second adhesive layer 1b) to foam and cure respectively to form foamed layers 15a and 15b, for example... Figure 13 As shown, in a cross-section parallel to the thickness direction D1 of the foam layer 15a, the number of bubbles in bubble 31 whose length s in the thickness direction D1 of the foam layer 15a is within a specified range relative to the thickness t1 of the foam layer 15a is less than a specified value in each specified length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15a. Furthermore, in a cross-section parallel to the thickness direction D1 of the foam layer 15b, the number of bubbles in bubble 31 whose length s in the thickness direction D1 of the foam layer 15b is within a specified range relative to the thickness t2 of the foam layer 15b is less than a specified value in each specified length L in the direction D2 perpendicular to the thickness direction D1 of the foam layer 15b.

[0345] Figure 9 This is a schematic cross-sectional view showing another example of the foamed adhesive sheet of this embodiment. Figure 9 The foamed adhesive sheet 10 sequentially comprises a first adhesive layer 1a, a substrate 12, and a second adhesive layer 1b. It should be noted that, regarding... Figure 9 In addition to the substrate 12 disposed between the first adhesive layer 1a and the second adhesive layer 1b, it is similar to the above-mentioned Figure 8 same.

[0346] It should be noted that, in Figure 8 and Figure 9In this process, both the first adhesive layer 1a and the second adhesive layer 1b are adhesive layers 5a and 5b containing a curable adhesive and a foaming agent. However, it is also possible for only one of the first adhesive layer and the second adhesive layer to be an adhesive layer containing a curable adhesive and a foaming agent.

[0347] In the foamed adhesive sheet of this embodiment, when the adhesive layer is an adhesive layer containing a foaming agent, as described in the first embodiment of the above-described article, and the foamed adhesive sheet is heated at a predetermined temperature for a predetermined time, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed layer, 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 within a predetermined range relative to the thickness of the foamed layer is less than a predetermined value in each predetermined length in the direction perpendicular to the thickness direction of the foamed layer, thereby suppressing poor adhesion. Therefore, adhesion can be improved.

[0348] Since the components of the foamed adhesive sheet in this embodiment are the same as those described in "A. Article" and "B. Method of manufacturing the article" above, the description here is omitted.

[0349] In this embodiment, when the foamed adhesive sheet is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed layer, in a cross-section parallel to the thickness direction of the foamed layer, the number of bubbles with a length of at least 6 μm equal to the thickness of the foamed layer in the thickness direction is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed 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.

[0350] It should be noted that when heating the foamed adhesive sheet, a support with a smooth surface is used. The foamed adhesive sheet is placed on the smooth surface of the support before heating. As for the support, there are no particular limitations as long as it has a smooth surface and heat resistance; for example, a glass substrate or a resin substrate can be used.

[0351] Furthermore, regarding the foamed adhesive sheet, the thickness direction of the foam layer is set to be perpendicular to the plane direction of the support. Additionally, the direction perpendicular to the thickness direction of the foam layer is set to the plane direction of the support.

[0352] The application of the foamed adhesive sheet of this embodiment is not particularly limited. For example, the foamed adhesive sheet of this embodiment can be used in the manufacture of the above-described articles.

[0353] II. Second Embodiment of Foamed Adhesive Sheets

[0354] The second embodiment of the foamed adhesive sheet disclosed herein has at least an adhesive layer, which is an 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. When the foamed adhesive sheet is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed body layer, in a cross section parallel to the thickness direction of the foamed body layer, the number of air bubbles with a length of 100 μm or more in the thickness direction of the foamed body layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer.

[0355] Figures 7-9 This is a schematic cross-sectional view showing an example of the foamed adhesive sheet of this embodiment. It should be noted that, regarding... Figures 7-9 Since it is described in the first embodiment described above, the description here is omitted.

[0356] In the foamed adhesive sheet of this embodiment, when the adhesive layer is an adhesive layer containing a foaming agent, as described in the second embodiment of the above-described article, and the foamed adhesive sheet is heated at a predetermined temperature for a predetermined time, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed layer, 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 a predetermined value or less in each predetermined length in the direction perpendicular to the thickness direction of the foamed layer, thereby suppressing poor adhesion. Therefore, adhesion can be improved.

[0357] Since the components of the foamed adhesive sheet in this embodiment are the same as those described in "A. Article" and "B. Method of manufacturing the article" above, the description here is omitted.

[0358] In this embodiment, when the foamed adhesive sheet is heated at ±20°C of the maximum foaming temperature of the foaming agent for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form 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 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed layer. The number of bubbles is preferably 3 or less, more preferably 2 or less, further preferably 1 or less, and particularly preferably 0.

[0359] It should be noted that when heating the foamed adhesive sheet, the foamed adhesive sheet can also be placed on one side of the support body before heating. The support body can be the same as in the first embodiment described above.

[0360] D. Adhesive composition

[0361] The adhesive composition disclosed herein has two embodiments. Each embodiment will be described below.

[0362] I. First embodiment of the adhesive composition

[0363] The first embodiment of the adhesive composition disclosed herein contains a curable adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule. The adhesive composition is coated on one side of a support with a thickness of 45 μm. The coating of the adhesive composition is heated at the maximum foaming temperature ±20°C of the foaming agent for 15 minutes, thereby causing the coating to foam and cure to form a foamed layer. In a cross section parallel to the thickness direction of the foamed layer, the number of bubbles with a length of more than 6 μm in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer.

[0364] In the adhesive composition of this embodiment, as described in the first embodiment of the above-described article, when the adhesive composition is applied to one side of the support with a predetermined thickness, and the coating of the adhesive composition is heated at a predetermined temperature for a predetermined time to foam and cure the coating to form a foamed layer, 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 within a predetermined range relative to the thickness of the foamed layer is less than a predetermined value in each predetermined length in the direction perpendicular to the thickness direction of the foamed layer, thereby suppressing poor adhesion. Therefore, adhesion can be improved.

[0365] Since the components of the adhesive composition of this embodiment are the same as those described in "A. Article" and "B. Method of Manufacturing Article" above, the description here is omitted.

[0366] In this embodiment, an adhesive composition is applied to one surface of the support with a thickness of 45 μm. The adhesive composition film is heated at ±20°C (maximum foaming temperature of the foaming agent) for 15 minutes, thereby causing the film to foam and solidify to form a foamed layer. In a cross-section parallel to the thickness direction of the foamed layer, the number of bubbles with a length greater than or equal to the thickness of the foamed layer minus 6 μm in the thickness direction is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed layer. Preferably, the number of bubbles is 3 or less, more preferably 2 or less, further preferably 1 or less, and particularly preferably 0.

[0367] It should be noted that when applying the adhesive composition to one side of the support, a support with a smooth surface is used, and the adhesive composition is applied to the smooth surface of the support. There are no particular limitations on the support as long as it has a smooth surface and is heat-resistant; for example, a glass substrate, resin substrate, etc., can be used.

[0368] Furthermore, regarding the adhesive composition, the thickness direction of the foam layer is set to be perpendicular to the plane direction of the support.

[0369] II. Second embodiment of the adhesive composition

[0370] The second embodiment of the adhesive composition disclosed herein contains a curable adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expandable microcapsule. The adhesive composition is coated on one side of a support with a thickness of 45 μm. The coating of the adhesive composition is heated at the maximum foaming temperature ±20°C of the foaming agent for 15 minutes, thereby causing the coating to foam and cure to form 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 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer.

[0371] In the adhesive composition of this embodiment, as described in one of the second embodiments of the above-described article, when the adhesive composition is applied to one side of the support with a predetermined thickness, and the coating of the adhesive composition is heated at a predetermined temperature for a predetermined time to foam and cure the coating to form 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 a predetermined value or less in each predetermined length in the direction perpendicular to the thickness direction of the foamed layer, thereby suppressing poor adhesion. Therefore, adhesion can be improved.

[0372] Since the components of the adhesive composition of this embodiment are the same as those described in "A. Article" and "B. Method of Manufacturing Article" above, the description here is omitted.

[0373] In this embodiment, an adhesive composition is coated on one surface of the support with a thickness of 45 μm. The coating of the adhesive composition is heated at ±20°C (maximum foaming temperature of the foaming agent) for 15 minutes, thereby causing the coating to foam and solidify to form 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 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed layer. Preferably, the number of bubbles is 3 or less, more preferably 2 or less, further preferably 1 or less, and particularly preferably 0.

[0374] Regarding the support body, it can be configured to be the same as in the first embodiment described above.

[0375] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are exemplary, and any embodiment having a substantially the same structure and performing the same effect as the technical concept described in the claims of this disclosure is included in the technical scope of this disclosure, regardless of the specific embodiment.

[0376] Example

[0377] [Examples 1-5 and Comparative Examples 1-2]

[0378] Using the materials described below, first adhesive compositions 1 to 7 and second adhesive compositions 1 to 7 with the compositions shown in Table 1 below were prepared.

[0379] • Acrylic resin: PMMA-PBuA-PMMA (partially acrylamide group), Tg: -20℃, 120℃, Mw: 150000

[0380] • Epoxy Resin A: Bisphenol A linear phenolic resin, solid at room temperature, softening temperature: 70℃, epoxy equivalent: 210 g / eq, Mw: 1300, melt viscosity at 150℃: 0.5 Pa·s

[0381] • Epoxy Resin B: BPA phenoxy type, solid at room temperature, softening temperature: 110℃, epoxy equivalent: 8000g / eq, Mw: 50000

[0382] • Epoxy resin C: Bisphenol A type, liquid at room temperature, epoxy equivalent: 184~194g / eq

[0383] • Epoxy Resin D: Diaminodiphenylmethane type, high viscosity liquid, epoxy equivalent: 110~130g / eq

[0384] • Epoxy Resin E: Silicone modified, solid at room temperature, epoxy equivalent: 1200 g / mol

[0385] Epoxy resins A, B, and E are solids at room temperature, while epoxy resins C and D are liquids at room temperature.

[0386] • Curing agent A: Phenol-formaldehyde condensate, softening point 80℃, hydroxyl equivalent 104 g / mol

[0387] • Curing agent B: α-(hydroxy(or dihydroxy)phenylmethyl)-ω-hydrogen poly[biphenyl-4,4'-dimethylmethylene(hydroxy(or dihydroxy)phenylmethylene)]

[0388] • Curing catalyst: 2-Phenyl-4,5-dihydroxymethylimidazolium, average particle size: 3 μm, melting point: 230℃, reaction start temperature: 145℃~155℃, active region: 155℃~173℃ (manufactured by Shikoku Chemical Industry Co., Ltd., 2PHZ-PW)

[0389] • Silane coupling agent: 3-epoxypropoxypropyltrimethoxysilane

[0390] • Foaming agent A: Thermally expandable microcapsules, average particle size 10μm~16μm, expansion start temperature 123℃~133℃, maximum expansion temperature 168℃~178℃, core: hydrocarbon, shell: thermoplastic polymer

[0391] • 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

[0392] • 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

[0393] Solvent: Methyl ethyl ketone

[0394]

[0395] As a spacer, a release film (PET spacer, manufactured by Nippa Corporation, PET50×1-J2, 50μm thick) was used. A second adhesive composition was applied to the release-treated surface of the release film using an applicator, resulting in a dry thickness of 45μm. Subsequently, it was dried in an oven at 100°C for 3 minutes to form a second adhesive layer.

[0396] Polyethylene naphthalate (PEN film, manufactured by Toyobo Film Solution, Teonex Q51, 25 μm thickness) was used as the substrate. The first adhesive composition was applied using an applicator to achieve a dry thickness of 45 μm. Subsequently, it was dried in an oven at 100°C for 3 minutes to form the first adhesive layer.

[0397] Then, on the surface of the substrate of the laminate having a substrate and a first adhesive layer, the surface of the second adhesive layer of the laminate having a spacer and a second adhesive layer is laminated. Thus, a foamed adhesive sheet having a first adhesive layer, a substrate, a second adhesive layer and a spacer arranged sequentially is obtained.

[0398] [evaluate]

[0399] (1) Adhesion

[0400] like Figure 14 As shown in (a) and (b), two metal plates 41 (cold-rolled steel plate 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 at one end of one of the metal plates 41. The thickness of the spacer 42 was set to approximately 370 μm (the thickness of two pieces of Nitto Denko polyimide tape (Kapton Tape) P-221 and one piece of Teraoka fluoropolymer adhesive tape 8410 overlapped). Additionally, a foamed adhesive sheet was cut to a size of 12.5 mm × 25 mm. The spacers on the foamed adhesive sheet were removed. Then, a foamed adhesive sheet 10 was placed between the spacers 42, and another metal plate 41 was arranged so that one end overlapped. It was then fixed with a clip to obtain a test piece. Subsequently, the test piece was placed in a hot oven and heated from room temperature to the specified temperature over 13 minutes, and maintained for 20 minutes, thereby allowing the first and second adhesive layers of the foamed adhesive sheet 10 to foam and cure. At this time, the heating temperature was set to 150℃, 160℃, 170℃, 180℃, 190℃, and 200℃.

[0401] The shear strength (bond strength) of the heated test specimens was determined using a TENSILON RTF1350 tensile testing machine (manufactured by A&D) according to JIS K6850:1999. The test conditions were set as tensile speed 10 mm / min and temperature 23℃. Tables 2 and 3 show the heating temperature and bond strength at which the bond strength was highest for each heating temperature.

[0402] (2) Observation of bubbles

[0403] A test piece was fabricated on a glass substrate, with approximately 1 mm of the first adhesive layer of the foamed adhesive sheet exposed. The test piece was placed in an oven and heated from room temperature to a specified temperature over 13 minutes, then held for 15 minutes. This allowed the first and second adhesive layers of the foamed adhesive sheet 10 to foam and cure, resulting in an adhesive sheet having a first cured adhesive layer, a substrate, and a second cured adhesive layer sequentially. The heating temperature was set to the temperature at which the adhesive strength was highest among the various heating temperatures used in the above adhesive strength determination.

[0404] To obtain a clear cross-section, a trimming tool was used to cut off the portion of the adhesive sheet protruding from the end face of the glass substrate. The cut section was fixed for vertical observation, and bubbles were observed using an optical microscope (Keyence VHX-2000 digital microscope). Furthermore, for each cured adhesive layer, the number of bubbles with a length greater than or equal to the thickness of the cured adhesive layer (foam layer) minus 6 μm was counted within a 4 mm square field of view. The bubble count was set as the average of the bubble counts at three randomly selected locations.

[0405]

[0406]

[0407] In Examples 1-5, when the first and second adhesive layers of the foamed adhesive sheet are foamed and cured to form a first cured adhesive layer and a second cured adhesive layer, respectively, the number of specified air bubbles per specified length in each of the first and second cured adhesive layers is less than 7, particularly less than 3, resulting in good adhesion. In contrast, in Comparative Examples 1-3, when the first and second adhesive layers of the foamed adhesive sheet are foamed and cured to form a first cured adhesive layer and a second cured adhesive layer, respectively, the number of specified air bubbles per specified length in each of the first and second cured adhesive layers is large, resulting in poor adhesion.

[0408] In this disclosure, for example, the following invention is provided.

[0409] [1] An article having a first component, a second component, and an adhesive component disposed between the first component and the second component.

[0410] The aforementioned adhesive components have at least a cured adhesive layer.

[0411] The aforementioned cured adhesive layer is a foamed layer containing an adhesive composition comprising a curable adhesive and a foaming agent.

[0412] The aforementioned curable adhesive is a thermosetting adhesive, and the aforementioned foaming agent is a thermally expanding microcapsule.

[0413] In a cross section parallel to the thickness direction of the aforementioned foam layer, the number of bubbles with a length greater than or equal to the thickness of the aforementioned foam layer minus 6 μm in the thickness direction of the aforementioned foam layer is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the aforementioned foam layer.

[0414] [2] An article having a first component, a second component, and an adhesive component disposed between the first component and the second component.

[0415] The aforementioned adhesive components have at least a cured adhesive layer.

[0416] The aforementioned cured adhesive layer is a foamed layer containing an adhesive composition comprising a curable adhesive and a foaming agent.

[0417] The aforementioned curable adhesive is a thermosetting adhesive, and the aforementioned foaming agent is a thermally expanding microcapsule.

[0418] In a cross section parallel to the thickness direction of the aforementioned foam layer, the number of bubbles with a length of 100 μm or more in the thickness direction of the aforementioned foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the aforementioned foam layer.

[0419] [3] According to the article described in [1] or [2], wherein the adhesive member has a first cured adhesive layer and a second cured adhesive layer,

[0420] At least one of the first cured adhesive layer and the second cured adhesive layer is the foam layer.

[0421] [4] According to the article described in [3], the first cured adhesive layer and the second cured adhesive layer are the foamed layers.

[0422] [5] The article according to any one of [1] to [4], wherein the curable adhesive is an epoxy resin-based adhesive, the curable adhesive contains an epoxy resin that is liquid at room temperature, and the content of the epoxy resin that is liquid at room temperature in the adhesive composition is 60 parts by mass or less relative to 100 parts by mass of the resin component in the adhesive composition.

[0423] [6] The article according to any one of [1] to [5], wherein the content of the foaming agent in the adhesive composition is 13 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the resin component in the adhesive composition.

[0424] [7] The article according to any one of [1] to [6], wherein the maximum foaming temperature of the foaming agent is 175°C or higher and 220°C or lower.

[0425] [8] A method for manufacturing an article, comprising a method for manufacturing an article using a foamed adhesive sheet having at least an adhesive layer.

[0426] The adhesive layer is an adhesive layer containing a curing adhesive and a foaming agent.

[0427] The aforementioned curable adhesive is a thermosetting adhesive, the aforementioned foaming agent is a thermally expandable microcapsule, and the aforementioned manufacturing method comprises:

[0428] In the configuration process, the aforementioned foamed adhesive sheet is disposed between the first component and the second component; and

[0429] In the bonding process, the adhesive layer containing the foaming agent of the foamed adhesive sheet is foamed and cured to form a foamed layer, and the first component and the second component are bonded together.

[0430] The foaming curing conditions in the above bonding process are set as follows: in a cross section parallel to the thickness direction of the above foam layer, the number of bubbles with a length of more than 6 μm in the thickness direction of the above foam layer is less than 7 per 4 mm in the direction perpendicular to the thickness direction of the above foam layer.

[0431] [9] A method for manufacturing an article, comprising a method for manufacturing an article using a foamed adhesive sheet having at least an adhesive layer.

[0432] The adhesive layer is an adhesive layer containing a curing adhesive and a foaming agent.

[0433] The aforementioned curable adhesive is a thermosetting adhesive, the aforementioned foaming agent is a thermally expandable microcapsule, and the aforementioned manufacturing method comprises:

[0434] In the configuration process, the foamed adhesive sheet is disposed between the first component and the second component; and

[0435] In the bonding process, the adhesive layer containing the foaming agent of the foamed adhesive sheet is foamed and cured to form a foamed layer, and the first component and the second component are bonded together.

[0436] The foaming curing conditions in the above bonding process are set as follows: in a cross section parallel to the thickness direction of the above foam layer, the number of bubbles with a length of 100 μm or more in the thickness direction of the above foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the above foam layer.

[0437]

[10] According to the method of manufacturing the article described in [8] or [9], wherein the foamed adhesive sheet has a first adhesive layer and a second adhesive layer,

[0438] At least one of the first adhesive layer and the second adhesive layer is the adhesive layer containing the foaming agent.

[0439]

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

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

[0440]

[12] The method of manufacturing an article according to any one of [8] to

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

[0441]

[13] The method of manufacturing an article according to any one of [8] to

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

[0442]

[14] The method of 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.

[0443]

[15] A foamed adhesive sheet having at least an adhesive layer,

[0444] The adhesive layer is an adhesive layer containing a curing adhesive and a foaming agent.

[0445] The aforementioned curable adhesive is a thermosetting adhesive, and the aforementioned foaming agent is a thermally expanding microcapsule.

[0446] When the foamed adhesive sheet is heated at the maximum foaming temperature ±20°C of the foaming agent for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed layer, in a cross section parallel to the thickness direction of the foamed layer, the number of bubbles with a length of more than 6 μm in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer.

[0447]

[16] A foamed adhesive sheet having at least an adhesive layer,

[0448] The adhesive layer is an adhesive layer containing a curing adhesive and a foaming agent.

[0449] The aforementioned curable adhesive is a thermosetting adhesive, and the aforementioned foaming agent is a thermally expanding microcapsule.

[0450] When the foamed adhesive sheet is heated at the maximum foaming temperature ±20°C of the foaming agent for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed layer, 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 in a direction perpendicular to the thickness direction of the foamed layer.

[0451]

[17] The foamed adhesive sheet as described in

[15] or

[16] has a first adhesive layer and a second adhesive layer.

[0452] At least one of the first adhesive layer and the second adhesive layer is the adhesive layer containing the foaming agent.

[0453]

[18] According to the foamed adhesive sheet described in

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

[0454]

[19] According to the foamed adhesive sheet described in

[17] or

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

[0455]

[20] The foamed 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 content of the epoxy resin that is liquid at room temperature in the adhesive layer is 60 parts by mass or less relative to 100 parts by mass of the resin component in the adhesive layer.

[0456]

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

[15] to

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

[0457]

[22] The foamed 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.

[0458]

[23] An adhesive composition comprising a curable adhesive and a foaming agent,

[0459] The aforementioned curable adhesive is a thermosetting adhesive, and the aforementioned foaming agent is a thermally expanding microcapsule.

[0460] When the adhesive composition is applied to one side of the support with 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 solidify the coating to form a foamed layer, in a cross section parallel to the thickness direction of the foamed layer, the number of bubbles with a length of more than 6 μm in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer.

[0461]

[24] An adhesive composition comprising a curable adhesive and a foaming agent,

[0462] The aforementioned curable adhesive is a thermosetting adhesive, and the aforementioned foaming agent is a thermally expanding microcapsule.

[0463] When the adhesive composition is coated with the above adhesive composition to a thickness of 45 μm on one side of the support, 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 solidify the coating to form 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 7 per 4 mm in the direction perpendicular to the thickness direction of the foamed layer.

[0464]

[25] According to the adhesive composition described in

[23] or

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

[0465]

[26] An adhesive composition according to any one of

[23] to

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

[0466]

[27] The adhesive composition according to any one of

[23] to

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

[0467] Explanation of reference numerals in the attached figures

[0468] 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 Substrate, 13a First intermediate layer, 13b Second intermediate layer, 10 Foamed adhesive sheet, 20a First component, 20b Second component, 30 Adhesive component, 100 Article.

Claims

1. An article having a first component, a second component, and an adhesive component disposed between the first component and the second component. The adhesive component has at least a cured adhesive layer. The cured adhesive layer is a foamed layer containing a curable adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expanding microcapsule. In a cross section parallel to the thickness direction of the foam layer, the number of bubbles with a length greater than or equal to the thickness of the foam layer minus 6 μm in the thickness direction of the foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer.

2. An article having a first component, a second component, and an adhesive component disposed between the first component and the second component. The adhesive component has at least a cured adhesive layer. The cured adhesive layer is a foamed layer containing a curable adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expanding microcapsule. 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 in a direction perpendicular to the thickness direction of the foam layer.

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

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

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

6. The article according to claim 1 or 2, wherein, The content of the foaming agent in the adhesive composition is 13 parts by weight or more and 30 parts by weight or less per 100 parts by weight of the resin component in the adhesive composition.

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

8. A method for manufacturing an article, comprising using a foamed adhesive sheet having at least an adhesive layer. The adhesive layer is an adhesive layer containing a curing adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, the foaming agent is a thermally expandable microcapsule, and the manufacturing method comprises: In the configuration process, the foamed adhesive sheet is disposed between the first component and the second component; and The bonding process involves foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foamed layer, thereby bonding the first component to the second component. The foaming and curing conditions in the bonding process are set as follows: in a cross section parallel to the thickness direction of the foam layer, the number of bubbles with a length greater than or equal to the thickness of the foam layer minus 6 μm in the thickness direction of the foam layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foam layer.

9. A method for manufacturing an article, comprising using a foamed adhesive sheet having at least an adhesive layer. The adhesive layer is an adhesive layer containing a curing adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, the foaming agent is a thermally expandable microcapsule, and the manufacturing method comprises: In the configuration process, the foamed adhesive sheet is disposed between the first component and the second component; and The bonding process involves foaming and curing the foaming agent-containing adhesive layer of the foamed adhesive sheet to form a foamed layer, thereby bonding the first component to the second component. The foaming and curing conditions in the bonding process are set as follows: 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 in the direction perpendicular to the thickness direction of the foam layer.

10. The method of manufacturing the article according to claim 8 or 9, wherein, The foamed adhesive sheet has a first adhesive layer and a second adhesive layer. At least one of the first adhesive layer and the second adhesive layer is the adhesive layer containing the foaming agent.

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

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

13. The method of manufacturing the article according to claim 8 or 9, wherein, The content of the foaming agent in the adhesive layer is 13 parts by weight or more and 30 parts by weight or less per 100 parts by weight of the resin component in the adhesive layer.

14. The method of manufacturing the article according to claim 8 or 9, wherein, The maximum foaming temperature of the foaming agent is above 175°C and below 220°C.

15. A foamed adhesive sheet having at least an adhesive layer, The adhesive layer is an adhesive layer containing a curing adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expanding microcapsule. When the foamed adhesive sheet is heated to the maximum foaming temperature ±20°C of the foaming agent for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed layer, in a cross section parallel to the thickness direction of the foamed layer, the number of bubbles with a length greater than or equal to the thickness of the foamed layer - 6 μm in the thickness direction of the foamed layer is less than 7 per 4 mm in a 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 an adhesive layer containing a curing adhesive and a foaming agent. The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expanding microcapsule. When the foamed adhesive sheet is heated at the maximum foaming temperature of the foaming agent ±20°C for 15 minutes, thereby causing the adhesive layer containing the foaming agent to foam and solidify to form a foamed body layer, in a cross section parallel to the thickness direction of the foamed body layer, the number of air bubbles with a length of 100 μm or more in the thickness direction of the foamed body layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed body layer.

17. The foamed adhesive sheet according to claim 15 or 16, comprising a first adhesive layer and a second adhesive layer. At least one of the first adhesive layer and the second adhesive layer is the adhesive layer containing the foaming agent.

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

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

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

21. The foamed adhesive sheet according to claim 15 or 16, wherein, The content of the foaming agent in the adhesive layer is 13 parts by weight or more and 30 parts by weight or less per 100 parts by weight of the resin component in the adhesive layer.

22. The foamed adhesive sheet according to claim 15 or 16, wherein, The maximum foaming temperature of the foaming agent is above 175°C and below 220°C.

23. An adhesive composition comprising a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expanding microcapsule. The adhesive composition is applied to one side of the support with a thickness of 45 μm. The coating of the adhesive composition is heated to the maximum foaming temperature ±20°C of the foaming agent for 15 minutes, thereby causing the coating to foam and solidify to form a foamed layer. In a cross section parallel to the thickness direction of the foamed layer, the number of bubbles with a length greater than or equal to the thickness of the foamed layer minus 6 μm in the thickness direction of the foamed layer is less than 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer.

24. An adhesive composition comprising a curable adhesive and a foaming agent, The curable adhesive is a thermosetting adhesive, and the foaming agent is a thermally expanding microcapsule. When the adhesive composition is applied to one side of the support with a thickness of 45 μm, and the coating of the adhesive composition is heated to the maximum foaming temperature ±20°C of the foaming agent for 15 minutes to foam and cure the coating to form 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 7 per 4 mm in a direction perpendicular to the thickness direction of the foamed layer.

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

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

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

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