Foamable adhesive sheet and method for producing article

Abstract

The present invention provides a foamable adhesive sheet comprising a substrate and an adhesive layer disposed on at least one surface side of the substrate, the adhesive layer containing a curable adhesive and a foaming agent, the adhesive layer being disposed on the outermost surface, the adhesive force of the adhesive layer being 0 N / 25 mm or more and 0.1 N / 25 mm or less, the static friction coefficient of the surface of the adhesive layer opposite to the substrate being 0.30 or less, and the pencil hardness of the surface of the adhesive layer opposite to the substrate being F or more.

Description

Technical Field

[0001] The present invention relates to a foamable adhesive sheet and a method for producing an article using the foamable adhesive sheet. Background Art

[0002] Adhesives for bonding members to each other are used in various fields, and various bonding methods are known.

[0003] For example, adhesive sheets containing foaming agents (foamable adhesive sheets) are disclosed in Patent Documents 1 and 2. Patent Document 1 discloses an adhesive sheet having expandable adhesive layers on both sides or one side of a substrate, the expandable adhesive layers containing epoxy resins including multifunctional epoxy resins, phenolic resins as curing agents, imidazole compounds as curing catalysts, and thermosensitive foaming agents, and a release agent is applied on the surface of at least one expandable adhesive layer. In addition, Patent Document 2 discloses an adhesive sheet having a substrate, heat-expandable adhesive layers disposed on both sides of the substrate, and adhesive permeable layers disposed on the surfaces of each adhesive layer and through which the adhesive can permeate when the adhesive thermally expands.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: International Publication No. 2016 / 163514

[0007] Patent Document 2: Japanese Patent Application Publication No. 2019-203062 Summary of the invention

[0008] Problems to be solved by the invention

[0009] As a method of using a foamable adhesive sheet, for example, a method of placing the foamable adhesive sheet between members and then foaming and curing the foamable adhesive sheet to bond the members to each other is known.

[0010] Such a foamable adhesive sheet is expected to have easy insertion when, for example, the foamable adhesive sheet is inserted into a gap between components or a gap between components, or when the foamable adhesive sheet is placed in a component and inserted into a gap of another component.

[0011] In addition, it is desired that such a foamable adhesive sheet has good adhesiveness after foaming and curing. However, when the gap between the members is relatively wide, the adhesiveness may be reduced.

[0012] The present invention is made in view of the above actual situation, and the first object is to provide a foaming adhesive sheet with good insertability and component insertability. In addition, the second object of the present invention is to provide a foaming adhesive sheet with good adhesiveness even when the gap between components is relatively wide.

[0013] Means for solving problems

[0014] One embodiment of the present invention provides a foamable adhesive sheet, which has a substrate and an adhesive layer arranged on at least one side of the substrate, the adhesive layer contains a curable adhesive and a foaming agent, the adhesive layer is arranged on the outermost surface, the adhesive force of the adhesive layer is greater than 0N / 25mm and less than 0.1N / 25mm, the static friction coefficient of the surface of the adhesive layer opposite to the substrate is less than 0.30, and the pencil hardness of the surface of the adhesive layer opposite to the substrate is greater than F.

[0015] Another embodiment of the present invention provides a foamable adhesive sheet having a substrate and an adhesive layer disposed on at least one surface of the substrate, wherein the adhesive layer contains a curable adhesive and a foaming agent, and the foaming agent has an average particle size of 10 μm to 24 μm.

[0016] Another embodiment of the present invention provides a method for manufacturing an article, comprising: a placement step of placing the foamable adhesive sheet between a first member and a second member; and a bonding step of foaming and curing the foamable adhesive sheet to bond the first member to the second member.

[0017] Effects of the Invention

[0018] The foamable adhesive sheet of the present invention has the effect of good insertability of the foamable adhesive sheet and good insertability of the member. In addition, the foamable adhesive sheet of the present invention can have the effect of good adhesiveness even when the gap between the members is relatively wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic cross-sectional view showing an example of the foamable adhesive sheet in the present invention.

[0020] Figure 2 This is a schematic cross-sectional view showing another example of the foamable adhesive sheet in the present invention.

[0021] Figure 3 This is a schematic cross-sectional view showing another example of the foamable adhesive sheet in the present invention.

[0022] Figure 4 It is a schematic perspective view showing another example of the foamable adhesive sheet in the present invention.

[0023] Figure 5 This is a schematic cross-sectional view showing an example of a method for producing an article in the present invention.

[0024] Figure 6 It is a schematic cross-sectional view for explaining the test method of adhesion. DETAILED DESCRIPTION

[0025] Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings, etc. However, the present invention can be implemented in a variety of different ways and should not be construed as being limited to the contents of the embodiments described below. In addition, in order to make the description clearer, the drawings sometimes schematically show the width, thickness, shape, etc. of each part compared to the actual method, but this is only an example and does not limit the interpretation of the present invention. In addition, in this specification and each figure, the same elements as those described previously with respect to the figures that have already appeared are sometimes marked with the same figure numbers, and the detailed description is appropriately omitted.

[0026] In this specification, when expressing the manner of arranging other members on a certain member, if it is simply expressed as "above" or "below", unless otherwise specified, it is assumed that the following two situations are included: the situation where other members are arranged directly above or directly below in a manner of contacting with a certain member, and the situation where other members are arranged above or below a certain member with another member further interposed therebetween. In addition, in this specification, when expressing the manner of arranging other members on the surface of a certain member, if it is simply expressed as "on the surface side" or "on the surface", unless otherwise specified, it includes the situation where other members are arranged directly above or directly below in a manner of contacting with a certain member, and the situation where other members are arranged above or below a certain member with another member further interposed therebetween.

[0027] In this 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 this specification is a range of average values.

[0028] Hereinafter, the foamable adhesive sheet and the method for producing an article using the foamable adhesive sheet in the present invention will be described in detail.

[0029] A. Foam adhesive sheet

[0030] The foamable adhesive sheet of the present invention will be described by being divided into a first embodiment and a second embodiment.

[0031] I. First Embodiment

[0032] The first embodiment of the foamable adhesive sheet of the present invention will be described in detail.

[0033] The foamable adhesive sheet in this embodiment comprises a substrate and an adhesive layer arranged on at least one side of the substrate, the adhesive layer contains a curable adhesive and a foaming agent, the adhesive layer is arranged on the outermost surface, the adhesive force of the adhesive layer is greater than or equal to 0N / 25mm and less than or equal to 0.1N / 25mm, the static friction coefficient of the surface of the adhesive layer opposite to the substrate is less than or equal to 0.30, and the pencil hardness of the surface of the adhesive layer opposite to the substrate is greater than or equal to F.

[0034] Figure 1 and Figure 2 This is a schematic cross-sectional view illustrating the foamable adhesive sheet in this embodiment. Figure 1 The foamable adhesive sheet 10 in the embodiment includes a substrate 2 and an adhesive layer 1 disposed on one surface side of the substrate 2 . Figure 2 The foamable adhesive sheet 10 in the embodiment includes a substrate 2, a first adhesive layer 1a disposed on one surface side of the substrate 2, and a second adhesive layer 1b disposed on the other surface side of the substrate 2. The adhesive layer 1, the first adhesive layer 1a, and the second adhesive layer 1b contain a curable adhesive and a foaming agent, and are disposed on the outermost surface of the foamable adhesive sheet 10. Figure 1 In the foamable adhesive sheet 10, the adhesive force of the adhesive layer 1 is within a predetermined range, and the static friction coefficient and pencil hardness of the surface of the adhesive layer 1 opposite to the substrate 2 are within a predetermined range. Figure 2 In the foamable adhesive sheet 10, the adhesive force of the first adhesive layer 1a and the second adhesive layer 1b is within a predetermined range, and the static friction coefficient and pencil hardness of the surfaces of the first adhesive layer 1a and the second adhesive layer 1b opposite to the substrate 2 are within a predetermined range.

[0035] It should be noted that, when the foamable adhesive sheet has adhesive layers on both sides, it is preferred that the adhesive strength of the two adhesive layers is within a specified range, and the static friction coefficient and pencil hardness of the surfaces of the two adhesive layers opposite to the substrate are within a specified range. However, the foamable adhesive sheet in this embodiment can sometimes be used by paying attention to the direction in which the surfaces face. Therefore, it is sufficient as long as the adhesive strength of any one of the adhesive layers is within a specified range, and the static friction coefficient and pencil hardness of any one of the adhesive layers opposite to the substrate are within a specified range.

[0036] In the present embodiment, the adhesive force of the adhesive layer is below the specified value, and the adhesive layer is substantially non-adhesive (non-viscous). In addition, the static friction coefficient of the face opposite to the substrate of the adhesive layer is below the specified value, and the adhesive layer shows low friction. In addition, the pencil hardness of the face opposite to the substrate of the adhesive layer is more than the specified value, and the adhesive layer shows high hardness. And the adhesive layer is configured on the outermost surface. Therefore, it is possible to make the foamable adhesive sheet with good sliding and insertability. Specifically, because the adhesive force of the adhesive layer is below the specified value, the static friction coefficient of the face opposite to the substrate of the adhesive layer is below the specified value, so when the foamable adhesive sheet is configured between the components and the components are bonded to each other, the foamable adhesive sheet can be smoothly inserted in the gap between the components, the gap between the components, or another component can be smoothly inserted in the gap after the foamable adhesive sheet is configured in a component. In addition, since the pencil hardness of the surface of the adhesive layer opposite to the substrate is greater than a specified value, when inserting the foam adhesive sheet into the gap between components or the gap between components, or inserting another component into the gap after the foam adhesive sheet is arranged in one component, it is possible to suppress the end face of the component from sinking into the adhesive layer, and in particular, when there are burrs on the end face of the component, the adhesive layer can be prevented from being caught by the burrs on the end face of the component. In addition, since the pencil hardness of the surface of the adhesive layer opposite to the substrate is greater than a specified value, when inserting the foam adhesive sheet into the gap between components or the gap between components, or inserting another component into the gap after the foam adhesive sheet is arranged in one component, it is possible to suppress the end face and surface wear of the adhesive layer. Therefore, the insertability of the foam adhesive sheet when inserting the foam adhesive sheet into the gap between components or the gap between components, or the insertability of the component when inserting another component into the gap after the foam adhesive sheet is arranged in one component can be improved.

[0037] In addition, as mentioned above, the foamable adhesive sheet in this embodiment has good sliding property and insertability. In addition, the adhesive force of the adhesive layer of the foamable adhesive sheet in this embodiment is below the specified value, and the adhesive layer is substantially non-adhesive (non-adhesive), so the anti-blocking property is also good. Therefore, the operability and workability of the foamable adhesive sheet can be improved.

[0038] Furthermore, in the present embodiment, since the adhesive force of the adhesive layer is below a prescribed value, the static friction coefficient of the surface of the adhesive layer opposite to the substrate is below a prescribed value, and the non-adhesiveness and sliding properties of the adhesive layer are particularly excellent, when a foaming adhesive sheet is arranged between the components to bond the components to each other, when one component is moved relative to another component to align the components to each other, the other component can be smoothly moved relative to one component while the components are overlapped with each other.

[0039] In addition, for example, Patent Document 1 discloses that a release layer is provided on the surface of an expandable adhesive layer. However, if a release layer is provided on the surface of an adhesive layer, the adhesion of the adhesive layer after foaming and curing may be reduced. In contrast, the foamable adhesive sheet having an adhesive force of the adhesive layer within a specified range does not need to be provided with a release layer or a release sheet for the purpose of imparting anti-blocking properties and sliding properties, and the adhesive layer can be provided on the outermost surface. Therefore, a foamable adhesive sheet having good adhesion of the adhesive layer after foaming and curing can be made.

[0040] Here, "adhesion" is a concept included in "bonding". Sometimes there is a distinction in that adhesion is used to mean a temporary bonding phenomenon, while bonding is used to mean a substantially permanent bonding phenomenon (Iwanami Shoten Physical and Chemical Dictionary 5th edition). "Adhesion" and "adhesive strength" refer to the properties of bonding by pressure sensitivity and the adhesive strength at that time.

[0041] It should be noted that, in this specification, unless otherwise specified, "the adhesiveness of the adhesive layer" and "the adhesive strength of the adhesive layer" refer to the adhesiveness and adhesive strength of the adhesive layer before foaming and curing. In addition, in this specification, unless otherwise specified, "the adhesiveness of the adhesive layer" and "the adhesive strength of the adhesive layer" refer to the adhesiveness and adhesive strength of the adhesive layer after foaming and curing.

[0042] Hereinafter, each structure of the foamable adhesive sheet in this embodiment will be described.

[0043] 1. Characteristics of foam adhesive sheets

[0044] In the foamable adhesive sheet of the present embodiment, the adhesive force of the adhesive layer is 0 N / 25 mm or more and 0.1 N / 25 mm or less, and can be 0.05 N / 25 mm or less, or 0.02 N / 25 mm or less. By making the adhesive force of the adhesive layer within the above range, the adhesive layer can be made substantially non-adhesive (non-sticky), and a foamable adhesive sheet with good sliding properties, insertion properties, and anti-blocking properties can be made.

[0045] In the case where adhesive layers are arranged on both sides of the substrate, the adhesive force of at least one adhesive layer can be within the above range. For example, when a foamable adhesive sheet is arranged between components to bond the components to each other, sometimes the foamable adhesive sheet is first arranged on one component, and then another component is inserted into the gap after the foamable adhesive sheet is arranged on one component. In such a case, when another component is inserted into the gap after the foamable adhesive sheet is arranged on one component, as long as the sliding property of the surface of the foamable adhesive sheet on one side in contact with the other component is good. Therefore, as long as the adhesive force of at least one adhesive layer is within the above range.

[0046] When adhesive layers are disposed on both surfaces of the substrate, for example, the adhesive strength of either adhesive layer or both adhesive layers may be within the above range, and preferably, the adhesive strength of both adhesive layers is within the above range.

[0047] The adhesive strength of the adhesive layer can be measured according to JIS Z0237:2009 (test method for adhesive tapes and adhesive sheets) based on ISO 29862 and method 1 of the test method for adhesive strength (a test method in which the tape and sheet are peeled off at 180° from a stainless steel test plate at a temperature of 23°C and a humidity of 50%). It should be noted that the details of the method for measuring the adhesive strength of the adhesive layer are described in the section of the Examples described later.

[0048] In the present embodiment, the adhesive force of the adhesive layer can be set to a value below a predetermined value by, for example, adjusting the composition of the adhesive layer. Specifically, in an adhesive layer containing an epoxy resin and a curing agent, the adhesiveness of the adhesive layer can be reduced by using an epoxy resin that is solid at room temperature, or by using a curing agent that is solid at room temperature. In addition, by containing an epoxy resin with a high softening temperature, or containing an epoxy resin with a large weight-average molecular weight in the adhesive layer containing an epoxy resin and a curing agent, the adhesiveness of the adhesive layer can be reduced. For example, by making the adhesive layer contain a plurality of epoxy resins with different softening temperatures, that is, when the adhesive layer contains one epoxy resin, it further contains other epoxy resins with a softening temperature of 25°C or more and 10°C or more higher than the softening temperature of the above-mentioned one epoxy resin, the adhesiveness of the adhesive layer can be reduced. In addition, for example, by making the adhesive layer contain a plurality of epoxy resins with different weight average molecular weights, that is, when the adhesive layer contains one epoxy resin, it further contains another epoxy resin with a weight average molecular weight of 370 or more and 300 or more greater than the weight average molecular weight of the above-mentioned one epoxy resin, the adhesiveness of the adhesive layer can be reduced. More specifically, in an adhesive layer containing an epoxy resin and a curing agent, as described later, by containing a first epoxy resin with a low softening temperature and a low molecular weight and a second epoxy resin with a high softening temperature and a high molecular weight as epoxy resins, the adhesiveness of the adhesive layer can be reduced. In addition, in an adhesive layer containing an epoxy resin and a curing agent, as described later, by containing an acrylic resin compatible with the epoxy resin, the adhesiveness of the adhesive layer can be reduced.

[0049] In the foamable adhesive sheet in the present embodiment, the pencil hardness of the face opposite to the base material of the adhesive layer is more than F. By making the pencil hardness on the surface of the adhesive layer be the above-mentioned scope, the foamable adhesive sheet with good slidability and insertability can be made. Specifically, if the pencil hardness on the surface of the adhesive layer is the above-mentioned scope, there is a trend that friction resistance tapers off. In addition, the above-mentioned pencil hardness, for example, can be below 2H. If the above-mentioned pencil hardness is too high, then the adhesive layer sometimes reduces the adhesion of the base material.

[0050] When adhesive layers are disposed on both sides of the substrate, the pencil hardness of the surface opposite to the substrate of at least one adhesive layer may be within the above range. For example, the pencil hardness of the surface opposite to the substrate of any one adhesive layer may be within the above range, or the pencil hardness of the surfaces opposite to the substrate of both adhesive layers may be within the above range. Among them, it is preferred that the pencil hardness of the surfaces opposite to the substrate of both adhesive layers be within the above range.

[0051] The pencil hardness can be determined in accordance with JIS K5600 corresponding to ISO 15184. The details of the method for measuring the pencil hardness are described in the section of Examples described later.

[0052] In the present embodiment, the pencil hardness of the surface of the adhesive layer can be controlled, for example, by the composition of the adhesive layer. Specifically, the pencil hardness can be controlled by the average particle size and content of the foaming agent contained in the adhesive layer. More specifically, the pencil hardness can be increased by increasing the average particle size of the foaming agent. In addition, the pencil hardness can be increased by increasing the content of the foaming agent. In addition, for example, by making the adhesive layer contain an inorganic filler, the pencil hardness can be increased. In addition, for example, by making the adhesive layer contain a component having a rigid structure, the pencil hardness can be increased. Specifically, in the adhesive layer containing an epoxy resin and a curing agent, a phenolic resin can be cited as a component having a rigid structure.

[0053] In the foamable adhesive sheet of the present embodiment, the static friction coefficient of the surface of the adhesive layer opposite to the substrate is below 0.30, and can be below 0.26. By making the static friction coefficient of the surface of the adhesive layer within the above range, a foamable adhesive sheet with good sliding properties and insertability can be made. In addition, the above-mentioned static friction coefficient can be, for example, above 0.16.

[0054] When adhesive layers are disposed on both sides of the substrate, it is sufficient as long as the static friction coefficient of the surface opposite to the substrate of at least one adhesive layer is within the above range. For example, the static friction coefficient of the surface opposite to the substrate of any one adhesive layer may be within the above range, or the static friction coefficient of the surface opposite to the substrate of both adhesive layers may be within the above range. Among them, it is preferred that the static friction coefficient of the surface opposite to the substrate of both adhesive layers is within the above range.

[0055] The static friction coefficient can be determined in accordance with JIS K7125 corresponding to ISO 8295. The details of the method for measuring the static friction coefficient are described in the section of Examples described later.

[0056] In the present embodiment, the static friction coefficient of the surface of the adhesive layer can be controlled by, for example, adjusting the composition of the adhesive layer or adjusting the pencil hardness of the surface of the adhesive layer. Specifically, the static friction coefficient can be controlled by the average particle size and content of the foaming agent contained in the adhesive layer. More specifically, if the average particle size of the foaming agent becomes larger, there is a tendency for the static friction coefficient of the surface of the adhesive layer to become smaller. In addition, if the content of the foaming agent becomes more, there is a tendency for the static friction coefficient of the surface of the adhesive layer to become smaller.

[0057] The foamable adhesive sheet in this embodiment preferably has good shape retention. The bending moment based on JISP8125 corresponding to ISO 2493 is, for example, 3gf·cm or more, and can be 5gf·cm or more. On the other hand, the above bending moment is, for example, less than 40gf·cm, and can also be less than 30gf·cm. In the past, for foamable adhesive sheets, a method of increasing the bending moment to improve shape retention and insertability into narrow gaps was usually adopted. In contrast, the inventors of the present invention found that by thinking about the shape, shape retention can be ensured, and high bending moment will have other undesirable conditions, so in view of other characteristics, the bending moment is preferably within the above range. If the bending moment is less than the above range, it may be difficult to maintain the shape even by folding back. In addition, if the bending moment is greater than the above range, the shape will return to its original state after the bending process, so it is necessary to heat it during the bending process or form an indentation at the fold line. If heating is performed, the life of the sheet is reduced, and if an indentation is formed, the insulation of the part may be reduced. Furthermore, in the foamable adhesive sheet of the present embodiment, the surface hardness is increased, so that the surface is not damaged even when high-speed insertion is performed.

[0058] The foamable adhesive sheet in the present embodiment preferably has high adhesion after foaming and curing. The shear strength (bonding strength) based on JIS K6850 corresponding to ISO 4587 can be, for example, 2.10MPa or more, 2.40MPa or more, or 3.0MPa or more at 23°C. In addition, the above-mentioned shear strength (bonding strength) can be, for example, 0.27MPa or more, 0.55MPa or more, or 0.58MPa or more at 200°C. For example, in a high-strength acrylic foam adhesive tape that does not require heating, the shear strength (bonding strength) is 1MPa or more and 2MPa or less at room temperature, and has no heat resistance at 200°C. Therefore, if the above-mentioned shear strength (bonding strength) is the above-mentioned range at 23°C, it has an advantage in strength. In addition, if the above-mentioned shear strength (bonding strength) is the above-mentioned range at 200°C, it can be applied to the engine surrounding of the automobile and the use of heat resistance close to it.

[0059] The foamable adhesive sheet in this embodiment preferably has high electrical insulation after foaming and curing. The insulation breakdown voltage based on JIS C2107 corresponding to IEC 60454-2 is preferably 3kV or more, and more preferably 5kV or more. By making the above-mentioned insulation breakdown voltage into the above-mentioned range, it can be rust-proof and applied around copper wires. In addition, the thermal conductivity of the adhesive sheet after foaming and curing is preferably 0.1W / mK or more, and more preferably 0.15W / mK or more. By making the above-mentioned thermal conductivity into the above-mentioned range, the miniaturization of the components can be sought, and the curing reaction during heating can be promoted.

[0060] 2. Adhesive layer

[0061] The adhesive layer in the present embodiment is disposed on at least one surface side of the substrate, and contains a curable adhesive and a foaming agent.

[0062] (1) Adhesive layer material

[0063] (a) Curable adhesive

[0064] As the curable adhesive included in the adhesive layer in the present embodiment, a curable adhesive commonly used in the adhesive layer of the foamable adhesive sheet can be used. As the curable adhesive, for example, heat-curable adhesives and light-curable adhesives can be cited. Among them, heat-curable adhesives are preferred. Heat-curable adhesives can also be used when the components are not transparent, such as metal components.

[0065] The curable adhesive is preferably an epoxy resin adhesive. That is, the curable adhesive preferably contains an epoxy resin and a curing agent. Generally, epoxy resin adhesives are excellent in mechanical strength, heat resistance, insulation, chemical resistance, etc., have little shrinkage upon curing, and can be used for a wide range of purposes.

[0066] Hereinafter, an example will be described in which the curable adhesive is an epoxy resin adhesive.

[0067] (i) Epoxy resin

[0068] The epoxy resin in the present embodiment is a compound having at least one epoxy group or glycidyl group, and curing by cross-linking polymerization reaction when used in combination with a curing agent. The epoxy resin also includes a monomer having at least one epoxy group or glycidyl group.

[0069] As the epoxy resin, an epoxy resin commonly used in the adhesive layer of a foamable adhesive sheet can be used. Among them, the curable adhesive preferably contains a first epoxy resin having a softening temperature of 50°C or more and an epoxy equivalent of 5000g / eq or less, and a second epoxy resin having a softening temperature higher than the first epoxy resin and a weight average molecular weight of 20,000 or more as the epoxy resin. By using the first epoxy resin and the second epoxy resin in combination, the adhesion (tackiness) of the adhesive layer can be reduced, and a foamable adhesive sheet with good sliding properties can be obtained. In addition, a foamable adhesive sheet with good anti-blocking properties and adhesion after foaming and curing can be obtained.

[0070] For example, when only seeking to improve the adhesiveness after foaming and curing, it is effective to use low molecular weight (low epoxy equivalent) epoxy resins compared to high molecular weight (high epoxy equivalent) epoxy resins. However, when using low molecular weight (low epoxy equivalent) epoxy resins, for example, when the foamable adhesive sheet is wound into a roll, the low molecular weight (low epoxy equivalent) epoxy resins assimilate each other and are prone to adhesion.

[0071] In contrast, when using the first epoxy resin with a relatively low softening temperature (relatively high crystallinity) and low molecular weight (low epoxy equivalent), if the first epoxy resin becomes a temperature above the softening temperature, it rapidly melts and changes into a low-viscosity liquid state. Therefore, it is easy to improve the adhesion after foaming and curing. On the other hand, the first epoxy resin is relatively high in crystallinity, so compared with the epoxy resin with relatively low crystallinity or the epoxy resin without crystallinity, it is possible to suppress the generation of adhesion. However, when only using the first epoxy resin, there is the possibility that the generation inhibition effect of adhesion is insufficient, and the adhesion (viscosity) of the adhesive layer becomes too high. Therefore, by further using the second epoxy resin with a relatively high softening temperature (relatively low crystallinity) and high molecular weight, it is possible to improve the generation inhibition effect of adhesion, and the adhesion (viscosity) of the adhesive layer is suppressed to be low.

[0072] (i-1) First epoxy resin

[0073] The softening temperature of the first epoxy resin is above 50°C, and the epoxy equivalent is below 5000g / eq. Compared with the second epoxy resin described later, the first epoxy resin has a relatively low softening temperature (relatively high crystallinity). Since the first epoxy resin has relatively high crystallinity and low molecular weight, it is easy to improve the adhesion and anti-blocking properties after foaming and curing. In addition, since the first epoxy resin has a low molecular weight, it is possible to increase the crosslinking density, and an adhesive layer with good mechanical strength, chemical resistance, and curability can be obtained. In addition, the first epoxy resin is preferably an epoxy resin that is solid at room temperature (23°C).

[0074] The softening temperature of the first epoxy resin is usually 50° C. or higher, and may be 55° C. or higher, or 60° C. or higher. On the other hand, the softening temperature of the first epoxy resin is, for example, 150° C. or lower. The softening temperature can be measured by a ring and ball method in accordance with JIS K7234.

[0075] The epoxy equivalent of the first epoxy resin is, for example, less than 5000 g / eq, less than 3000 g / eq, less than 1000 g / eq, or less than 600 g / eq. On the other hand, the epoxy equivalent of the first epoxy resin is, for example, greater than 90 g / eq, greater than 100 g / eq, or greater than 110 g / eq. The epoxy equivalent can be measured by a method according to JIS K7236 corresponding to ISO 3001 (Plastics-Epoxy compounds-Determination of epoxy equivalent), and is the number of grams of resin containing 1 gram equivalent of epoxy groups.

[0076] The first epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher-functional epoxy resin.

[0077] In addition, the weight average molecular weight (Mw) of the first epoxy resin is usually less than the weight average molecular weight (Mw) of the second epoxy resin described later. The Mw of the first epoxy resin is, for example, 6,000 or less, 4,000 or less, or 3,000 or less. On the other hand, the Mw of the first epoxy resin is, for example, 400 or more. Mw is a value converted to polystyrene when measured by gel permeation chromatography (GPC).

[0078] The melt viscosity of the first epoxy resin at 150°C is, for example, 0.005 Pa·s or more, 0.015 Pa·s or more, 0.03 Pa·s or more, 0.05 Pa·s or more, or 0.1 Pa·s or more. If the melt viscosity is too low, good foaming may not be obtained. In addition, if the melt viscosity of the first epoxy resin is too low (if the crystallinity of the first epoxy resin is too high), there is a possibility that the adhesion (viscosity) of the resulting adhesive layer becomes higher. It is speculated that the reason is that if the melt viscosity of the first epoxy resin is too low (if the crystallinity of the first epoxy resin is too high), when it is compatible with the second epoxy resin or the acrylic resin, its crystallinity is greatly reduced, and the Tg of the adhesive composition as a whole is reduced. On the other hand, the melt viscosity of the first epoxy resin at 150°C is, for example, 10 Pa·s or less, 5 Pa·s or less, or 2 Pa·s or less. If the melt viscosity is too high, there is a possibility that the uniformity of the resulting adhesive layer is reduced. The melt viscosity can be determined by measuring in accordance with JIS K6862 corresponding 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 thermocouple for heating the solution.

[0079] Next, the composition of the first epoxy resin is described. As the first epoxy resin, for example, aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins can be cited. As specific examples of the first epoxy resin, bisphenol-type epoxy resins such as bisphenol A epoxy resin and bisphenol F epoxy resin; linear phenolic epoxy resins such as bisphenol A linear novolac epoxy resin and cresol linear novolac epoxy resin; modified epoxy resins such as urethane modified epoxy resins and rubber modified epoxy resins can be cited. In addition, as other specific examples, biphenyl epoxy resins, stilbene epoxy resins, trisphenol methane epoxy resins, alkyl-modified trisphenol methane epoxy resins, epoxy resins containing triazine cores, dicyclopentadiene-modified novolac epoxy resins, naphthalene epoxy resins, glycol epoxy resins, and pentaerythritol epoxy resins can be cited. The first epoxy resin can be one kind or two or more kinds.

[0080] Depending on the number of repeating units of the bisphenol skeleton, the bisphenol A type epoxy resin may exist in a liquid state at room temperature, or may exist in a solid state at room temperature. A bisphenol A type epoxy resin having a main chain bisphenol skeleton of, for example, 2 or more and 10 or less is solid at room temperature. In particular, bisphenol A type epoxy resin is preferred in that it can improve heat resistance.

[0081] In particular, the first epoxy resin is preferably a bisphenol A novolac type epoxy resin represented by the following general formula (1).

[0082] [Chemical formula 1]

[0083]

[0084] In the general formula (1), R 1 C m H 2m (m is 1 or more and 3 or less), R 2 and R 3 Each independently is C p H 2p+1 In the group represented by (p is 1 to 3), n is 0 to 10.

[0085] In the general formula (1), preferably R 1 The m in is 1, that is, R 1 is -CH2-. Similarly, R 2 and R 3 p in is 1, that is, R 2 and R 3 In addition, the hydrogen bonded to the benzene ring of the general formula (1) may be substituted by other elements or other groups.

[0086] When the resin component contained in the adhesive layer is set to 100 mass parts, the content of the first epoxy resin is, for example, more than 1 mass part, can be more than 3 mass parts, can also be more than 5 mass parts, can also be more than 10 mass parts, can also be more than 15 mass parts, can also be more than 25 mass parts.If the content of the first epoxy resin is too little, there is the possibility that the adhesiveness and anti-blocking after foaming and curing are reduced.On the other hand, when the resin component contained in the adhesive layer is set to 100 mass parts, the content of the first epoxy resin is, for example, less than 90 mass parts, can be less than 80 mass parts, can also be less than 70 mass parts, can also be less than 60 mass parts, can also be less than 50 mass parts, can also be less than 40 mass parts.If the content of the first epoxy resin is too much, the content of the second epoxy resin and acrylic resin decreases relatively, and it is possible not to balance the adhesion of non-adhesiveness, adhesive layer to substrate, anti-blocking and the adhesiveness after foaming and curing.

[0087] (i-2) Second epoxy resin

[0088] The softening temperature of the second epoxy resin is higher than that of the first epoxy resin, and the weight average molecular weight is greater than 20,000. Compared with the above-mentioned first epoxy resin, the second epoxy resin has a relatively high softening temperature (relatively low crystallinity). Since the second epoxy resin has relatively low crystallinity and high molecular weight, it is easy to improve anti-blocking properties. In addition, since the second epoxy resin has relatively low crystallinity and high molecular weight, it is possible to suppress the increase in adhesion (tack) caused by the first epoxy resin. In addition, the second epoxy resin is preferably an epoxy resin that is solid at room temperature (23°C).

[0089] The weight average molecular weight (Mw) of the second epoxy resin is usually greater than the weight average molecular weight (Mw) of the first epoxy resin. The Mw of the second epoxy resin is usually 20,000 or more, and may be 30,000 or more, or 35,000 or more. On the other hand, the Mw of the second epoxy resin is, for example, 100,000 or less.

[0090] The epoxy equivalent of the second epoxy resin may be larger, smaller, or the same as that of the first epoxy resin. The epoxy equivalent of the second epoxy resin is, for example, 4000 g / eq or more, 5000 g / eq or more, or 6000 g / eq or more. On the other hand, the epoxy equivalent of the second epoxy resin is, for example, 20000 g / eq or less.

[0091] The second epoxy resin may be a monofunctional epoxy resin, a difunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or higher-functional epoxy resin.

[0092] The softening temperature of the second epoxy resin is usually higher than the softening temperature of the first epoxy resin. The difference between the two is, for example, 10°C or more, 20°C or more, or 30°C or more. The softening temperature of the second epoxy resin is, for example, 80°C or more, or 90°C or more. On the other hand, the softening temperature of the second epoxy resin is, for example, 180°C or less.

[0093] The configuration of the second epoxy resin is the same as that of the first epoxy resin described above, and therefore description thereof is omitted here.

[0094] When the resin component contained in the adhesive layer is set to 100 mass parts, the content of the second epoxy resin is, for example, more than 10 mass parts, can be more than 15 mass parts, can also be more than 20 mass parts, can also be more than 25 mass parts, can also be more than 30 mass parts, can also be more than 35 mass parts, can also be more than 40 mass parts, can also be more than 45 mass parts.If the content of the second epoxy resin is too little, then the adhesiveness becomes high, and there is the possibility that the anti-blocking property reduces.On the other hand, when the resin component contained in the adhesive layer is set to 100 mass parts, the content of the second epoxy resin is, for example, less than 90 mass parts, can be less than 85 mass parts, can also be less than 80 mass parts, can also be less than 75 mass parts.If the content of the second epoxy resin is too much, then the content of the first epoxy resin and acrylic resin decreases relatively, and it is possible not to balance the adhesion of non-adhesiveness, the adhesive layer to the adhesion of the substrate, the anti-blocking property and the adhesiveness after foaming and curing.

[0095] The ratio of the first epoxy resin to the total of the first epoxy resin and the second epoxy resin is, for example, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more. On the other hand, the ratio of the first epoxy resin is, for example, 80% by mass or less, 75% by mass or less, or 60% by mass or less.

[0096] The ratio of the total of the first epoxy resin and the second epoxy resin to the total epoxy resin contained in the adhesive layer may be, for example, 50 mass % or more, 70 mass % or more, 90 mass % or more, or 100 mass %.

[0097] (ii) Acrylic resin

[0098] The acrylic resin in the present embodiment is a resin compatible with epoxy resin. Acrylic resin is compatible with epoxy resin, so it is easy to improve the toughness of bonding layer. As a result, the adhesion after foaming and curing can be improved. In addition, it is believed that acrylic resin plays a role as a compatibilizer of a foaming agent (for example, the foaming agent of the resin of the shell portion is acrylonitrile copolymer), and is evenly dispersed and foamed, so that the adhesion after foaming and curing improves. In addition, the flexibility brought by acrylic resin can be brought into play, and the improvement of the adhesion of bonding layer to substrate is sought. In addition, by acrylic resin and epoxy resin compatible, the hardness on the bonding layer surface can be kept high. On the other hand, if acrylic resin is incompatible with epoxy resin, soft position is formed on the bonding layer surface, so sometimes the interface with adherend becomes difficult to slide, and workability reduces.

[0099] The acrylic resin in the present embodiment is compatible with the epoxy resin. Here, the compatibility of the acrylic resin with the epoxy resin can be confirmed, for example, by observing the cross section of the adhesive layer of the foaming adhesive sheet with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) without producing micron-sized islands. More specifically, the average particle size of the island is preferably less than 1 μm. Among them, the average particle size of the island can be less than 0.5 μm, or less than 0.3 μm. The number of samples is preferably large, for example, more than 100. The area of ​​the observed region is carried out in the range of 100 μm × 100 μm, or, when the average thickness of the adhesive layer is less than 100 μm, it is carried out in the range of average thickness × 100 μm.

[0100] The weight average molecular weight (Mw) of the acrylic resin is, for example, 50,000 or more, 70,000 or more, or 100,000 or more. The first epoxy resin has relatively high crystallinity, and the melt viscosity (or dynamic viscoelasticity) when heated may become too low, and shrinkage may occur during curing after foaming (from the end of foaming of the foaming agent to the curing of the adhesive composition). However, by using an acrylic resin with a certain molecular weight, the melt viscosity can be prevented from becoming too low, and shrinkage is less likely to occur during curing after foaming. On the other hand, the Mw of the acrylic resin is, for example, 1,500,000 or less. The weight average molecular weight of the acrylic resin can be measured by GPC (eluent: THF, standard substance: PS, sample: 20 μL, flow rate: 1 mL / min, column temperature: 40°C).

[0101] The glass transition temperature (Tg) of the acrylic resin is, for example, 90° C. or higher, or 100° C. or higher. On the other hand, the Tg of the acrylic resin is, for example, 180° C. or lower. Tg can be measured by thermal analysis such as differential scanning calorimetry (DSC) in accordance with JIS K7121 corresponding to ISO 3146.

[0102] The storage modulus (E') of acrylic resin at the foaming starting temperature can be 1×10 6 Pa or less. By lowering E' at the start of foaming, fluidity is improved, and good foaming properties can be obtained. On the other hand, E' at the foaming start temperature is, for example, 1×10 5 Pa or more. It should be noted that the foaming initiation temperature is a temperature that varies depending on the type of foaming agent. In addition, when two or more foaming agents are used as the foaming agent, the initiation temperature of the main foaming reaction is taken as the foaming initiation temperature.

[0103] The storage modulus (E') of acrylic resin at the curing starting temperature can be 1×10 5Pa or more. As mentioned above, sometimes shrinkage occurs during the curing after foaming (from the end of the foaming of the foaming agent to the curing of the adhesive composition), but by making E' at the curing start temperature large, shrinkage can be suppressed and good shape retention can be obtained. It should be noted that the curing start temperature is a temperature that varies according to the type of curing agent. In addition, when using two or more curing agents as curing agents, the starting temperature of the main curing reaction is used as the curing start temperature.

[0104] In addition, the average value of the storage modulus (E') of the acrylic resin at 0°C or higher and 100°C or lower can be 1×10 6 Pa or more. By making the average value of E' before foaming high, good non-adhesiveness and anti-blocking properties can be obtained. On the other hand, the average value of the storage modulus (E') at 0°C or higher and 100°C or lower is, for example, 1×10 8 Below Pa.

[0105] The acrylic resin may have a polar group. Examples of the polar group include an epoxy group, a hydroxyl group, a carboxyl group, a nitrile group, and an amide group.

[0106] The acrylic resin is a homopolymer of an acrylate monomer, and may be a mixed component containing two or more of the above homopolymers, or a copolymer of two or more acrylate monomers, or a component containing one or more copolymers. In addition, the acrylic resin may be a mixed component of the above homopolymer and the above copolymer. The "acrylic acid" of the acrylate monomer also includes the concept of methacrylic acid. Specifically, the acrylic resin may be a mixture of a methacrylate polymer and an acrylate polymer, or may be an acrylate polymer such as acrylate-acrylate, methacrylate-methacrylate, or methacrylate-acrylate. Among them, the acrylic resin preferably contains a copolymer of two or more acrylate monomers (a (meth)acrylate copolymer).

[0107] As the monomer components constituting the (meth)acrylate copolymer, for example, the monomer components described in Japanese Patent Publication No. 2014-065889 can be cited. The above-mentioned monomer components may have the above-mentioned polar groups. As the above-mentioned (meth)acrylate copolymer, for example, ethyl acrylate-butyl acrylate-acrylonitrile copolymer, ethyl acrylate-acrylonitrile copolymer, butyl acrylate-acrylonitrile copolymer can be cited. It should be noted that "acrylic acid" of methyl acrylate, ethyl acrylate, etc. also includes "methacrylic acid" of methyl methacrylate, ethyl methacrylate, etc.

[0108] As the above-mentioned (meth)acrylate copolymer, a block copolymer is preferred, and an acrylic block copolymer such as a methacrylate-acrylate copolymer is more preferred. Examples of the (meth)acrylate constituting the acrylic block copolymer include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, and benzyl acrylate. These "acrylic acids" also include "methacrylic acids".

[0109] Specific examples of methacrylate-acrylate copolymers include acrylic copolymers such as methyl methacrylate-butyl acrylate-methyl methacrylate (MMA-BA-MMA) copolymers. MMA-BA-MMA copolymers also include block copolymers of polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate (PMMA-PBA-PMMA).

[0110] The acrylic copolymer may not have a polar group, or may be a modified product in which the polar group is introduced partially. The modified product is easily compatible with the epoxy resin, and thus the adhesiveness is further improved.

[0111] Among them, 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 is a soft segment and a second polymer portion that is a hard segment.

[0112] The above effects can be inferred as follows: by using an acrylic resin having both soft segments and hard segments such as the (meth)acrylate copolymer, the hard segments contribute to heat resistance and the soft segments contribute to toughness or flexibility, thereby obtaining an adhesive layer having good heat resistance, toughness and flexibility.

[0113] At least one of the first polymer part and the second polymer part contained in the (meth)acrylate copolymer is compatible with the epoxy resin. When the first polymer part is compatible with the epoxy resin, the flexibility can be improved. In addition, when the second polymer part is compatible with the epoxy resin, the cohesion and toughness can be improved.

[0114] In the case where one of the first polymer part or the second polymer part is not compatible with the epoxy resin, the (meth)acrylate copolymer has a compatible part which is a polymer part compatible with the epoxy resin and an incompatible part which is a polymer part incompatible with the epoxy resin. In this case, if the (meth)acrylate copolymer is added to the adhesive composition, the compatible part is compatible with the epoxy resin and the incompatible part is incompatible with the epoxy resin, so fine phase separation occurs. As a result, a fine sea-island structure is formed. The sea-island structure varies depending on the type of (meth)acrylate copolymer, the compatibility of the first polymer part and the second polymer part contained in the (meth)acrylate copolymer, and the presence or absence of modification based on the introduction of polar groups. For example, there can be cited a sea-island structure in which the compatible parts of the cured epoxy resin and the (meth)acrylate copolymer are the sea and the incompatible parts of the (meth)acrylate copolymer are the islands; a sea-island structure in which the incompatible parts of the (meth)acrylate copolymer are the sea and the compatible parts of the cured epoxy resin and the (meth)acrylate copolymer are the islands; and a sea-island structure in which the (meth)acrylate copolymer is the sea and the cured epoxy resin is the islands. By having such a sea-island structure, stress can be easily dispersed, so that interface damage can be avoided, and excellent adhesion can be obtained after foaming and curing.

[0115] As for the above-mentioned (meth) acrylate copolymer, among them, block copolymers are preferred, and ABA block copolymers in which the compatible part is set as polymer block A and the incompatible part is set as polymer block B are particularly preferred. In addition, ABA block copolymers in which the first polymer part is the incompatible part, the second polymer part is the compatible part, the first polymer part is set as polymer block B, and the second polymer part is set as polymer block A are preferred. By using such an ABA block copolymer as an acrylic resin, in the case of a sea island structure in which the compatible part of the cured product of epoxy resin and the (meth) acrylate copolymer is the sea and the incompatible part of the (meth) acrylate copolymer is the island, the island part can be reduced. In addition, in the case of a sea island structure in which the incompatible part of the (meth) acrylate copolymer is the sea, the compatible part of the cured product of epoxy resin and the (meth) acrylate copolymer is the island, or in the case of a sea island structure in which the (meth) acrylate copolymer is the sea and the cured product of epoxy resin is the island, the sea part can be reduced.

[0116] The (meth)acrylate copolymer may be a modified product in which the polar group is introduced into a part of the first polymer portion or the second polymer portion.

[0117] The Tg of the first polymer part contained in the above-mentioned (meth)acrylate copolymer is below 10°C, and can be set in the range of -150°C to 10°C, especially in the range of -130°C to 0°C, and particularly in the range of -110°C to -10°C.

[0118] The Tg of the first polymer portion can be calculated by the following formula based on the Tg (K) of each homopolymer described in "POLYMER HANDBOOK 3rd Edition" (published by John Wiley & Sons, Ink.).

[0119] 1 / Tg(K)=W1 / Tg1+W2 / Tg2+····+W n / Tg n

[0120] W n ; Mass fraction of each monomer

[0121] Tg n ; The Tg (K) of the homopolymer of each monomer may be a value generally disclosed, such as the value in the Polymer Handbook (3rd Ed., J. Brandrup and E. H. Immergut, WILEY INTERSCIENCE). The same applies to the Tg of the second polymer portion described later.

[0122] The first polymer part contained in the above-mentioned (meth)acrylate copolymer may be a homopolymer or a copolymer, and preferably a homopolymer. The monomer components and polymer components constituting the first polymer part may be monomer components and polymer components that can obtain the first polymer part having a Tg within a predetermined range, and examples thereof include acrylate monomers such as butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and methyl acrylate, other monomers such as vinyl acetate, acetal, and urethane, polar group-containing monomers containing the above-mentioned polar groups, and copolymers such as EVA.

[0123] The Tg of the second polymer part contained in the above-mentioned (meth)acrylate copolymer is higher than 20°C, and can be set in the range of higher than 20°C and lower than 150°C, especially in the range of higher than 30°C and lower than 150°C, and particularly in the range of higher than 40°C and lower than 150°C.

[0124] The second polymer part contained in the (meth)acrylate copolymer may be a homopolymer or a copolymer, and preferably a homopolymer. The monomer component constituting the second polymer part may be any monomer component that can obtain a second polymer part having a Tg within a predetermined range, and examples thereof include acrylic acid ester monomers such as methyl methacrylate, acrylamide, styrene, vinyl chloride, amide, acrylonitrile, cellulose acetate, phenol, carbamate, vinylidene chloride, methylene chloride, methacrylonitrile and other monomers, and polar group-containing monomers containing the above-mentioned polar groups.

[0125] Specific examples of the (meth)acrylate copolymer having the first polymer part and the second polymer part include the above-mentioned MMA-BA-MMA copolymer.

[0126] When the resin component contained in the adhesive layer is set to 100 mass parts, the content of acrylic resin is, for example, more than 1 mass part, can be more than 3 mass parts, can also be more than 5 mass parts, can also be more than 7 mass parts, can also be more than 10 mass parts. If the content of acrylic resin is too little, there is the possibility that the adhesion of the adhesive layer to the base material and the adhesion after foaming and curing are reduced. On the other hand, when the resin component contained in the adhesive layer is set to 100 mass parts, the content of acrylic resin is, for example, less than 60 mass parts, can be less than 50 mass parts, can also be less than 40 mass parts, can also be less than 35 mass parts, can also be less than 30 mass parts. If the content of acrylic resin is too much, the content of the first epoxy resin and the second epoxy resin is relatively reduced, and it is possible not to balance the adhesion of non-adhesiveness, the adhesive layer to the base material, the anti-blocking and the adhesion after foaming and curing. In addition, if the content of acrylic resin is too much, there is the possibility that the film strength is reduced.

[0127] (iii) Curing agent

[0128] As the curing agent in the present embodiment, a curing agent commonly used in epoxy resin adhesives can be used. The curing agent is preferably solid at 23°C. A curing agent that is solid at 23°C can extend the storage stability (applicable life) compared to a curing agent that is liquid at 23°C. In addition, the curing agent may be a latent curing agent. In addition, the curing agent may be a curing agent that undergoes a curing reaction by heat, or a curing agent that undergoes a curing reaction by light. In addition, in the present invention, the curing agent may be used alone, or two or more types may be used.

[0129] The reaction starting temperature of the curing agent is, for example, above 110°C, and may be above 130°C. If the reaction starting temperature is too low, the reaction starts at an early stage, and curing occurs in a state where the softness and fluidity of the resin component are low, and it may be difficult to uniformly cure. On the other hand, the reaction starting temperature of the curing agent is, for example, below 200°C. If the reaction starting temperature is too high, there is a possibility that the resin component deteriorates. It should be noted that, in the case of using a resin with high heat resistance such as a phenolic resin in addition to an epoxy resin, the reaction starting temperature of the curing agent may be, for example, below 300°C due to the small deterioration of the resin component. The reaction starting temperature of the curing agent can be obtained by differential scanning calorimetry (DSC).

[0130] Specific examples of the curing agent include imidazole-based curing agents, phenol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, isocyanate-based curing agents, and thiol-based curing agents.

[0131] As imidazole curing agents, for example, imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, carboxylates of imidazole compounds, and adducts with epoxy compounds can be cited. In addition, the imidazole curing agent preferably has a hydroxyl group. Crystallization occurs through hydrogen bonding between hydroxyl groups, so there is a tendency for the reaction starting temperature to become higher.

[0132] As the phenolic curing agent, for example, phenolic resin can be mentioned. In addition, as the phenolic resin, for example, resol type phenolic resin and linear phenolic resin can be mentioned. From the viewpoint of the adhesion of the adhesive layer to the substrate, linear phenolic resin with a Tg of 110° C. or less is particularly preferred. In addition, a phenolic curing agent and an imidazole curing agent can also be used in combination. In this case, it is preferred to use an imidazole curing agent as a curing catalyst.

[0133] Examples of amine curing agents include aliphatic amines such as diethylenetriamine (DETA), triethylenetetramine (TETA), and meta-xylylenediamine (MXDA); aromatic amines such as diaminodiphenylmethane (DDM), meta-phenylenediamine (MPDA), and diaminodiphenylsulfone (DDS); alicyclic amines; and polyamide amines. In addition, amine curing agents that can be used include dicyandiamide curing agents such as dicyandiamide (DICY), organic acid dihydrazide curing agents, amine adduct curing agents, and ketimine curing agents.

[0134] Examples of the acid anhydride curing agent include alicyclic acid anhydrides (liquid acid anhydrides) such as hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalic anhydride (MTHPA); and aromatic acid anhydrides such as trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), and benzophenonetetracarboxylic dianhydride (BTDA).

[0135] As an isocyanate type curing agent, blocked isocyanate is mentioned, for example.

[0136] Examples of the thiol-based curing agent include ester bond type thiol compounds, aliphatic ether bond type thiol compounds, and aromatic ether bond type thiol compounds.

[0137] When the resin component contained in the adhesive layer is set to 100 parts by mass, the content of the curing agent is, for example, more than 1 part by mass and less than 40 parts by mass. For example, when an imidazole curing agent is used as a curing agent as the main component, when the resin component contained in the adhesive layer is set to 100 parts by mass, the content of the curing agent is, for example, preferably more than 1 part by mass and less than 15 parts by mass. On the other hand, when a phenol curing agent is used as a curing agent as the main component, when the resin component contained in the adhesive layer is set to 100 parts by mass, the content of the curing agent is, for example, preferably more than 5 parts by mass and less than 40 parts by mass. It should be noted that using an imidazole curing agent or a phenol curing agent as the main component as a curing agent means that the mass proportion of the imidazole curing agent or the phenol curing agent in the curing agent is the largest.

[0138] (b) Foaming agent

[0139] As the foaming agent in this embodiment, a foaming agent generally used for the adhesive layer of a foamable adhesive sheet can be used. In addition, the foaming agent may be a foaming agent that generates a foaming reaction by heat or a foaming agent that generates a foaming reaction by light.

[0140] The foaming starting temperature of the foaming agent is preferably above the softening temperature of the main agent of the curable adhesive such as epoxy resin and below the activation temperature of the curing reaction of the main agent of the curable adhesive such as epoxy resin. The foaming starting temperature of the foaming agent is, for example, above 70°C, and can be above 100°C. If the reaction starting temperature is too low, the reaction starts too early, and foaming occurs in a state where the softness and fluidity of the resin component are low, and it may be difficult to produce uniform foaming. On the other hand, the reaction starting temperature of the foaming agent is, for example, below 210°C. If the reaction starting temperature is too high, there is a possibility that the resin component will deteriorate.

[0141] The softening temperature of the main component of a curable adhesive such as an epoxy resin can be measured using the ring and ball softening temperature test method specified in JIS K7234.

[0142] Examples of the foaming agent include microcapsule-type foaming agents, which preferably have a thermal expansion agent such as hydrocarbon as a core and a resin such as an acrylonitrile copolymer as a shell.

[0143] In addition, as a foaming agent, for example, an organic foaming agent or an inorganic foaming agent can be used. As an organic foaming agent, for example, azo foaming agents such as azodicarbonamide (ADCA), azobiscarbonamide, and azobisisobutyronitrile, fluorinated alkane foaming agents such as trichloromonofluoromethane, hydrazine foaming agents such as p-toluenesulfonylhydrazide, semicarbazide foaming agents such as p-toluenesulfonylsemicarbazide, triazole foaming agents such as 5-morpholinyl-1,2,3,4-thiotriazole, and N-nitroso foaming agents such as N,N-dinitrosoterephthalamide can be mentioned. On the other hand, as an inorganic foaming agent, for example, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, ammonium borohydride, and azides can be mentioned.

[0144] 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. By making the average particle size of the foaming agent within the above range, the pencil hardness of the surface of the adhesive layer can be increased, and the static friction coefficient of the surface of the adhesive layer can be reduced, so that a foamable adhesive sheet with good sliding and insertability can be prepared. In addition, the average particle size of the foaming agent is preferably less than the average thickness of the adhesive layer, for example, 44 μm or less, 30 μm or less, or 24 μm or less.

[0145] It should be noted that the average particle size of the foaming agent is the particle size at the cumulative value of 50% in the particle size distribution obtained by laser diffraction scattering method. In addition, when measuring the average particle size of the foaming agent, the adhesive layer is dissolved in a solvent to separate the foaming agent. As a solvent, there is no particular limitation as long as it is a solvent that can dissolve the components other than the foaming agent contained in the adhesive layer. It can be appropriately selected according to the type of curable adhesive contained in the adhesive layer, for example, a solvent used in an adhesive composition for forming the adhesive layer can be used. Specifically, methyl ethyl ketone, ethyl acetate, toluene, etc. can be mentioned.

[0146] When the resin composition contained in the adhesive layer is set to 100 mass parts, the content of the whipping agent is, for example, more than 0.5 mass parts, can be more than 2 mass parts, can also be more than 3 mass parts, can also be more than 4 mass parts, can also be more than 5 mass parts. On the other hand, relative to 100 mass parts of resin composition contained in the adhesive layer, the content of the whipping agent is, for example, below 25 mass parts, can be below 20 mass parts, can also be below 15 mass parts. If the content of the whipping agent is too little, there is the possibility that the static friction coefficient on the surface of the adhesive layer becomes large or the pencil hardness on the surface of the adhesive layer decreases. In addition, if the content of the whipping agent is too much, the content of the curable adhesive decreases relatively, so there is the possibility that the adhesiveness after the foaming and curing reduces.

[0147] (c) Other ingredients

[0148] The adhesive layer in the present embodiment may contain only epoxy resin and acrylic resin as resin components, or may further contain other resins, for example, urethane resins, when the curable adhesive is an epoxy resin-based adhesive.

[0149] The total ratio of the first epoxy resin, the second epoxy resin and the acrylic resin to the resin component contained in the adhesive layer is, for example, 70 mass % or more, 80 mass % or more, 90 mass % or more, or 100 mass %.

[0150] The content of the resin component contained in the adhesive layer may be, for example, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0151] The adhesive layer may contain, for example, a silane coupling agent, a filler, an antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a plasticizer, an antistatic agent, a crosslinking agent, and a colorant as required. As the silane coupling agent, for example, an epoxy silane coupling agent may be mentioned. As the filler, for example, inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, molybdenum compounds, and titanium dioxide may be mentioned. As the antioxidant, for example, a phenolic antioxidant and a sulfur antioxidant may be mentioned.

[0152] (2) Composition of Adhesive Layer

[0153] The adhesive layer can be foamed at a foaming ratio of, for example, 1.5 times or more and 15 times or less. The above-mentioned foaming ratio can be, for example, 3.5 times or more, or 4 times or more, or 4.5 times or more. In addition, the above-mentioned foaming ratio can be, for example, 9 times or less, or 8.5 times or less, or 8 times or less. If the above-mentioned foaming ratio is too small or too large, there is a possibility that the adhesion after foaming and curing will be reduced.

[0154] Here, the expansion ratio can be calculated by the following formula.

[0155] Foaming ratio (times) = thickness of adhesive layer after foaming and curing / thickness of adhesive layer before foaming and curing

[0156] The average thickness of the adhesive layer is not particularly limited, and is preferably above the average particle size of the foaming agent, for example, above 10 μm, above 15 μm, or above 20 μm. If the adhesive layer is too thin, there is a possibility that the adhesion to the substrate and the adhesion after foaming and curing cannot be fully obtained. On the other hand, the average thickness of the adhesive layer is, for example, below 200 μm, below 150 μm, or below 100 μm. If the adhesive layer is too thick, there is a possibility that the surface quality deteriorates or the pencil hardness decreases.

[0157] Here, the average thickness of the adhesive layer is a value measured based on a cross section in the thickness direction of the foamable adhesive sheet observed using a transmission electron microscope (TEM), a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM), and can be set as the average value of the thicknesses at 10 randomly selected locations. It should be noted that the method for measuring the average thickness of other layers of the foamable adhesive sheet can also be set in the same manner.

[0158] The adhesive layer may be a continuous layer or a discontinuous layer. Examples of the discontinuous layer include patterns such as stripes and dots. In addition, the surface of the adhesive layer may have a concave-convex shape such as embossing.

[0159] The adhesive layer can be formed, for example, by applying an adhesive composition containing the above-mentioned curable adhesive and a foaming agent and removing the solvent. Examples of the coating method include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, rod coating, wire bar coating, die coating, die lip coating, and dip coating.

[0160] The adhesive composition may contain a solvent or may not contain a solvent. It should be noted that the solvent in this specification not only includes a strict solvent (a solvent that dissolves a solute), but also includes the broad meaning of a dispersion medium. In addition, the solvent contained in the adhesive composition evaporates and is removed when the adhesive composition is applied and dried to form an adhesive layer.

[0161] The adhesive composition can be obtained by mixing the above-mentioned components and kneading and dispersing as needed. As a mixing and dispersing method, a common kneading disperser can be used, such as a double-roll mill, a triple-roll mill, a gravel mill, a drum mill, a Szegvari grinder, a high-speed impeller disperser, a high-speed stone mill, a high-speed impact mill, a disperser, a high-speed mixer, a ribbon mixer, a bidirectional kneader, a strong mixer, a rotary drum, a stirrer, a dispensing machine, a homogenizer, and an ultrasonic disperser.

[0162] 3. Substrate

[0163] The substrate in the present embodiment may be, for example, a supporting substrate that supports the adhesive layer or a separator that protects the adhesive layer.

[0164] (1) Support substrate

[0165] The support substrate in this embodiment preferably has insulating properties. In addition, the support substrate is preferably in sheet form. The support substrate may have a single-layer structure or a multi-layer structure. In addition, the support substrate may have a porous structure inside or may not have a porous structure.

[0166] Examples of the supporting substrate include resin substrates and nonwoven fabrics.

[0167] As the resin contained in the resin substrate, for example, polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyesters; polycarbonate; polyarylate; polyurethane; polyamide resins such as polyamide and polyether amide; polyimide resins such as polyimide, polyetherimide, and polyamideimide; polysulfone resins such as polysulfone and polyethersulfone; polyetherketone resins such as polyetherketone and polyetheretherketone; polyphenylene sulfide (PPS); modified polyphenylene ether, etc. The glass transition temperature of the resin is, for example, above 80°C, above 140°C, or above 200°C. In addition, a liquid crystal polymer (LCP) can be used as the resin.

[0168] Examples of the nonwoven fabric include nonwoven fabrics composed of 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.

[0169] In order to improve the adhesion with the adhesive layer, the surface of the support base material on which the adhesive layer is to be disposed may be subjected to a surface treatment.

[0170] The average thickness of the support substrate is not particularly limited, and is, for example, 2 μm or more, 5 μm or more, or 9 μm or more. Also, the average thickness of the support substrate is, for example, 200 μm or less, 100 μm or less, or 50 μm or less.

[0171] (2) Spacer

[0172] The spacer in the present embodiment is not particularly limited as long as it can be peeled from the adhesive layer, and can have a strength that can protect the adhesive layer. As such a spacer, for example, a release film, a release paper, etc. can be cited. In addition, the spacer can have a single-layer structure or a multi-layer structure.

[0173] Examples of the single-layer separator include fluororesin films and the like.

[0174] In addition, as a spacer of a multilayer structure, for example, a laminate having a release layer on one side or both sides of a substrate layer can be cited. As the substrate layer, for example, resin films of polypropylene, polyethylene, polyethylene terephthalate, etc., high-quality paper, coated paper, impregnated paper and other papers can be cited. As the material of the release layer, as long as it is a material with demoulding properties, there is no particular limitation, for example, organosilicon compounds, organic compound-modified organosilicon compounds, fluorine compounds, aminoalkyd compounds, melamine compounds, acrylic compounds, polyester compounds, long-chain alkyl compounds, etc. can be cited. These compounds can use any of emulsion type, solvent type or solvent-free type.

[0175] 4. Other components

[0176] The foamable adhesive sheet in the present embodiment can have an intermediate layer between substrate and adhesive layer when the above-mentioned substrate is a supporting substrate. By configuring the intermediate layer, the adhesion of the adhesive layer to the substrate can be improved. In addition, by configuring the intermediate layer, for example, the stress applied to the bending portion when the foamable adhesive sheet is bent can be relaxed, or the stress applied to the cut portion when the foamable adhesive sheet is cut can be relaxed. As a result, when the foamable adhesive sheet is bent or cut, the adhesive layer can be suppressed from floating and peeling off the substrate.

[0177] For example, in Figure 3 In the foamable adhesive sheet 10 shown, the substrate 2, the intermediate layer 3 and the adhesive layer 1 are arranged in this order in the thickness direction. Figure 4 In the foamable adhesive sheet 10 shown, a first adhesive layer 1a is disposed on one side of a substrate 2, a second adhesive layer 1b is disposed on the other side of the substrate 2, a first intermediate layer 3a is disposed between the substrate 2 and the first adhesive layer 1a, and a second intermediate layer 3b is disposed between the substrate 2 and the second adhesive layer 1b. Figure 4 In the embodiment, the foamable adhesive sheet 10 includes both the first intermediate layer 3a and the second intermediate layer 3b, but may include only one of them.

[0178] When adhesive layers are disposed on both sides of the substrate, it is sufficient to dispose an intermediate layer between the substrate and at least one adhesive layer. For example, an intermediate layer may be disposed only between the substrate and one adhesive layer, or between the substrate and two adhesive layers. Preferably, an intermediate layer is disposed between the substrate and the two adhesive layers.

[0179] The material contained in the intermediate layer is not particularly limited as long as it can improve the adhesion between the substrate and the adhesive layer and can relax the stress, and can be appropriately selected according to the materials of the substrate and the adhesive layer, etc. For example, polyester, polyvinyl chloride, polyvinyl acetate, polyurethane, polymers obtained by copolymerizing at least two of them, crosslinked products thereof, and mixtures thereof, etc. can be cited.

[0180] The crosslinked product is a crosslinked product formed by crosslinking the above-mentioned resin using a curing agent. As the curing agent, for example, an isocyanate curing agent can be cited. In addition, for example, when the reactive group / NCO equivalent is set to 1, it is preferred to add the isocyanate curing agent in a ratio of 0.5 mass % or more and 20 mass % or less relative to the resin.

[0181] The intermediate layer preferably contains a cross-linked resin. It should be noted that the cross-linked resin refers to a resin that does not melt even when it is heated to a high temperature. This can improve the adhesive force at high temperatures, that is, the heat resistance.

[0182] The average thickness of the middle layer is not particularly limited, for example, more than 0.1 μm, can be more than 0.5 μm, can also be more than 1 μm. If the middle layer is too thin, then there is the possibility of the effect of the adhesive layer peeling off from the base material when the foaming adhesive sheet is bent and cut off that can't be fully obtained. On the other hand, the average thickness of the middle layer is, for example, below 4 μm, can be below 3.5 μm. The middle layer itself is usually not high in heat resistance, so if the middle layer is too thick, then there is the possibility of heat resistance (adhesive force under high temperature) reduction.

[0183] The intermediate layer can be formed, for example, by applying the resin composition and removing the solvent. Examples of the coating method include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, rod coating, wire bar coating, die coating, die lip coating, and dip coating.

[0184] 5. Foam adhesive sheet

[0185] The average thickness of the foamable adhesive sheet in the present embodiment is, for example, 10 μm or more, or 20 μm or more. On the other hand, the average thickness of the foamable adhesive sheet is, for example, 1000 μm or less, or 200 μm or less.

[0186] The use of the foamable adhesive sheet in the present embodiment is not particularly limited. The foamable adhesive sheet in the present embodiment can be used, for example, when the foamable adhesive sheet is placed between members and then foamed and cured to bond the members together.

[0187] 6. Method for manufacturing foamable adhesive sheet

[0188] The manufacturing method of the foamable adhesive sheet in the present embodiment is not particularly limited. For example, a method of forming an adhesive layer by applying the above-mentioned adhesive composition on one side of a substrate and drying it can be cited. In the case where a first adhesive layer is formed on one side of a substrate and a second adhesive layer is formed on the other side of the substrate, the first adhesive layer and the second adhesive layer can be formed sequentially or simultaneously.

[0189] II. Second Embodiment

[0190] The second embodiment of the foamable adhesive sheet of the present invention will be described in detail.

[0191] The inventors of the present invention have focused on the average particle size of the foaming agent contained in the adhesive layer in the foamable adhesive sheet, and have conducted in-depth research on the adhesion after foaming and curing. In addition, it is clear that when the average particle size of the foaming agent is relatively small, even if the adhesion is good when the gap between the components is relatively narrow, the adhesion is sometimes reduced when the gap between the components is relatively wide. In addition, it is clear that when the average particle size of the foaming agent is relatively large, the adhesion is sometimes reduced when the gap between the components is relatively narrow. In addition, it is surprisingly found that when the average particle size of the foaming agent is within a specified range, the adhesion becomes good not only when the gap between the components is relatively narrow, but also when the gap between the components is relatively wide. This embodiment is based on such cognition.

[0192] The foamable adhesive sheet in this embodiment includes a substrate and an adhesive layer disposed on at least one surface of the substrate, the adhesive layer contains a curable adhesive and a foaming agent, and the foaming agent has an average particle size of 10 μm to 24 μm.

[0193] Figure 1 and Figure 2 2 is a schematic cross-sectional view illustrating a foamable adhesive sheet in this embodiment. Figure 1 and Figure 2 The adhesive layer 1, the first adhesive layer 1a and the second adhesive layer 1b contain a curable adhesive and a foaming agent, and the average particle size of the foaming agent is within a predetermined range.

[0194] In the foamable adhesive sheet of the present embodiment, by making the average particle size of the foaming agent contained in the adhesive layer within the prescribed range, good adhesion can be obtained even when the gap between components is relatively wide. The reason is not clear, but it is inferred as follows. That is, if the average particle size of the foaming agent is too small, there is a trend that the expansion ratio of the adhesive layer becomes smaller, so even if good adhesion is obtained when the gap between components is narrow, the adhesion is sometimes reduced when the gap between components is wide. In addition, it is believed that when the average particle size of the foaming agent is small, the expansion ratio of the adhesive layer can be increased by increasing the content of the foaming agent, but if the content of the foaming agent is increased, the content of the curable adhesive is relatively reduced, so the wall between the bubbles in the adhesive layer after foaming and curing becomes thinner, and the cohesive force is reduced, and the adhesion under the condition of the wide gap between components is reduced. On the other hand, it is believed that if the average particle size of the foaming agent is too large, the foaming ratio of the adhesive layer becomes large, but the bubbles in the adhesive layer after foaming and curing become large, so the wall between the bubbles becomes thinner, and the cohesive force decreases, and the adhesiveness decreases regardless of whether the gap between the components is narrow or wide. In contrast, it is speculated that when the average particle size of the foaming agent is within a specified range, the foaming ratio of the adhesive layer will not be too small, so the gap between the components can be fully filled. In addition, the bubbles in the adhesive layer after foaming and curing will not be too large, so the wall between the bubbles becomes thicker, and the contact area between the wall between the bubbles in the adhesive layer after foaming and curing and the components can be increased. As a result, good adhesiveness can be obtained not only when the gap between the components is narrow, but also when the gap between the components is wide.

[0195] Therefore, when the foamable adhesive sheet is arranged between the components and the components are bonded to each other, for example, the gap between the components can be enlarged, the foamable adhesive sheet can be easily inserted into the gap between the components, or another component can be easily inserted into the gap after the foamable adhesive sheet is arranged on one component. In addition, by using the foamable adhesive sheet in this embodiment, for example, even if tolerance occurs in the components, the components can be well bonded to each other without being affected by the tolerance.

[0196] Hereinafter, each structure of the foamable adhesive sheet in this embodiment will be described.

[0197] 1. Adhesive layer

[0198] The adhesive layer in the present embodiment is disposed on at least one surface side of the substrate, and contains a curable adhesive and a foaming agent.

[0199] (1) Adhesive layer material

[0200] (a) Foaming agent

[0201] The average particle size of the foaming agent in this embodiment is, for example, 10 μm or more, 13 μm or more, or 17 μm or more. In addition, the average particle size of the foaming agent is, for example, 24 μm or less, 21 μm or less, or 20 μm or less. By making the average particle size of the foaming agent within the above range, good adhesion can be obtained in both the case where the gap between the components is relatively narrow and the case where the gap between the components is relatively wide.

[0202] In addition, the method of measuring the average particle diameter of the foaming agent is the same as that of the above-mentioned first embodiment.

[0203] The foaming agent is not particularly limited as long as it has a predetermined average particle size, and any foaming agent commonly used in the adhesive layer of a foamable adhesive sheet can be used. The type of the foaming agent and the foaming starting temperature may be the same as those described in the first embodiment.

[0204] When the resin component contained in the adhesive layer is set to 100 parts by mass, the content of the foaming agent is, for example, more than 3 parts by mass, more than 4 parts by mass, or more than 5 parts by mass. On the other hand, relative to 100 parts by mass of the resin component contained in the adhesive layer, the content of the foaming agent is, for example, less than 25 parts by mass, less than 20 parts by mass, or less than 15 parts by mass. If the content of the foaming agent is too little, the foaming ratio of the adhesive layer decreases, and there is a possibility that the adhesiveness decreases when the gap between the components is wide. In addition, if the content of the foaming agent is too much, the content of the curable adhesive decreases relatively, so the wall between the bubbles in the adhesive layer after foaming and curing becomes thinner, and the cohesive force decreases in addition, and there is a possibility that the adhesiveness decreases.

[0205] (b) Curable Adhesive

[0206] The curable adhesive may be the same as the curable adhesive described in the first embodiment. 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. Among them, the curable adhesive is preferably an epoxy resin adhesive.

[0207] Hereinafter, a case where the curable adhesive is an epoxy resin adhesive will be described as an example.

[0208] (i) Epoxy resin

[0209] The definition of the epoxy resin may be the same as the epoxy resin described in the first embodiment. Also, the type of the epoxy resin may be the same as the first epoxy resin described in the first embodiment.

[0210] (ii) Acrylic resin

[0211] When the curable adhesive is an epoxy adhesive, it may further contain an acrylic resin compatible with the epoxy resin. The acrylic resin may be the same as the acrylic resin described in the first embodiment.

[0212] (iii) Curing agent

[0213] The curing agent may be the same as the curing agent described in the first embodiment.

[0214] (c) Other ingredients

[0215] The adhesive layer in the present embodiment may further contain other resins other than the epoxy resin and acrylic resin as a resin component when the curable adhesive is an epoxy resin-based adhesive, for example, urethane resin.

[0216] The ratio of the total amount of the epoxy resin and the acrylic resin to the resin component contained in the adhesive layer may be, for example, 70 mass % or more, 80 mass % or more, 90 mass % or more, or 100 mass %.

[0217] The content of the resin component contained in the adhesive layer may be the same as that in the first embodiment described above.

[0218] The adhesive layer may contain additives as necessary. The additives may be the same as those described in the first embodiment.

[0219] (2) Composition of Adhesive Layer

[0220] The adhesive layer in the present embodiment can be foamed at a foaming ratio of, for example, 3.5 times or more and 9 times or less. The above-mentioned foaming ratio can be, for example, 4 times or more, or 4.5 times or more. In addition, the above-mentioned foaming ratio can be, for example, 8.5 times or less, or 8 times or less. By making the above-mentioned foaming ratio within the above-mentioned range, there is a tendency that the adhesion becomes higher when the gap between the components is wide. On the other hand, if the above-mentioned foaming ratio is too small, there is a possibility that the adhesion is reduced when the gap between the components is wide. In addition, if the above-mentioned foaming ratio is too large, sometimes the adhesion is reduced even when the gap between the components is narrow. It should be noted that the method for calculating the foaming ratio is the same as that of the above-mentioned first embodiment.

[0221] The adhesive layer in the present embodiment is preferably substantially non-adhesive (non-adhesive). By making the adhesive layer substantially non-adhesive (non-adhesive), a foamable adhesive sheet having good sliding properties and anti-adhesive properties can be made. Therefore, the operability and workability of the foamable adhesive sheet can be improved. Specifically, when the foamable adhesive sheet is configured between components and the components are bonded to each other, the foamable adhesive sheet can be smoothly inserted into the gap between the components or the gap between the components, or another component can be smoothly inserted into the gap after the foamable adhesive sheet is configured in one component.

[0222] Here, the term "non-adhesive" is generally used to mean low adhesive strength. In the present invention, "non-adhesive" means a state in which the foamable adhesive sheet is rolled up and then easily unrolled without resistance.

[0223] The adhesive strength of the adhesive layer when the adhesive layer is substantially non-adhesive may be the same as the adhesive strength of the adhesive layer described in the item of the first embodiment. In addition, the adhesive strength of the adhesive layer when the adhesive layer is disposed on both sides of the substrate may be the same as the content described in the item of the first embodiment. It should be noted that the method for measuring the adhesive strength of the adhesive layer is the same as that of the first embodiment.

[0224] The average thickness, form, and formation method of the adhesive layer may be the same as those described in the first embodiment.

[0225] 2. Substrate

[0226] The substrate may be the same as the substrate described in the first embodiment.

[0227] 3. Other components

[0228] The foamable adhesive sheet in this embodiment may have an intermediate layer between the substrate and the adhesive layer when the substrate is a supporting substrate. The intermediate layer may be the same as the intermediate layer described in the first embodiment.

[0229] 4. Foam adhesive sheet

[0230] The average thickness and application of the foamable adhesive sheet in this embodiment may be the same as those described in the above-mentioned first embodiment.

[0231] The foamable adhesive sheet in the present embodiment preferably has high adhesion after foaming and curing. The shear strength (bonding strength) based on JIS K6850 corresponding to ISO 4587 is preferably 2.10MPa or more at 23°C, more preferably 2.40MPa or more, and further preferably 3.0MPa or more. In addition, the above-mentioned shear strength (bonding strength) is preferably 0.55MPa or more at 200°C, more preferably 0.58MPa or more. As mentioned above, for example, in a high-strength acrylic foam adhesive tape that does not require heating, the shear strength (bonding strength) is 1MPa or more and 2MPa or less at room temperature, and there is no heat resistance at 200°C. Therefore, if the above-mentioned shear strength (bonding strength) is the above-mentioned range at 23°C, it has an advantage in strength. In addition, if the above-mentioned shear strength (bonding strength) is the above-mentioned range at 200°C, it can be applied to the engine surrounding of the automobile and the use of heat resistance close to it.

[0232] The foamable adhesive sheet in this embodiment preferably has good shape retention. The bending moment may be the same as in the first embodiment.

[0233] The foamable adhesive sheet in this embodiment preferably has high electrical insulation after foaming and curing. The dielectric breakdown voltage and thermal conductivity may be the same as those in the first embodiment.

[0234] B. How the item is made

[0235] The method for manufacturing an article in the present invention comprises a placement step of placing the foamable adhesive sheet between a first member and a second member, and a bonding step of foaming and curing the foamable adhesive sheet to bond the first member and the second member.

[0236] Figure 5 1 is a process diagram showing an example of a method for manufacturing an article of the present invention. Figure 5 As shown in (a), a foamable adhesive sheet 10 is disposed between the first member 20a and the second member 20b. Figure 5 As shown in (b), the foamable adhesive sheet 10 is foamed and cured by heating, for example. The first member 20a and the second member 20b are bonded (joined) by the foamed and cured adhesive sheet 11. Thus, the article 100 having the adhesive sheet 11 disposed between the first member 20a and the second member 20b is obtained.

[0237] In the manufacturing method of the article of the present invention, when the foamable adhesive sheet of the first embodiment is used, the foamable adhesive sheet can be smoothly inserted into the gap of one component, the gap between two components, or another component can be smoothly inserted into the gap after the foamable adhesive sheet is arranged on one component. In addition, since the foamable adhesive sheet is used, the two components can be aligned with good accuracy.

[0238] In addition, in the manufacturing method of the article in the present invention, when the foamable adhesive sheet of the second embodiment is used, good adhesion can be obtained in both the case where the gap between the components is narrow and the case where the gap between the components is wide. Therefore, an article with good adhesion between the first component and the second component can be obtained.

[0239] Hereinafter, the method for producing the article of the present invention will be described.

[0240] 1. Foam adhesive sheet

[0241] In the method for producing an article of the present invention, the above-mentioned foamable adhesive sheet can be used as the foamable adhesive sheet.

[0242] In the case where the base material in the foamable adhesive sheet is a supporting base material, as the foamable adhesive sheet, a foamable adhesive sheet in which an adhesive layer and a base material are sequentially arranged can be used. In this case, in the case where the foamable adhesive sheet is the foamable adhesive sheet of the first embodiment described above, as the foamable adhesive sheet, a foamable adhesive sheet in which the adhesive force of the adhesive layer is a specified range, the static friction coefficient of the adhesive layer on the opposite side of the base material and the pencil hardness are specified ranges can be used. In addition, as the foamable adhesive sheet, a foamable adhesive sheet having a first adhesive layer and a second adhesive layer as adhesive layers, in which the first adhesive layer, the base material and the second adhesive layer are sequentially arranged in the thickness direction can be used. In this case, in the case where the foamable adhesive sheet is the foamable adhesive sheet of the first embodiment described above, as long as the adhesive force of the adhesive layer of any one of the first adhesive layer and the second adhesive layer is a specified range, the static friction coefficient of the adhesive layer on the opposite side of the base material and the pencil hardness of any one of the adhesive layer is a specified range.

[0243] On the other hand, when the base material in the foamable adhesive sheet is a separator, when the foamable adhesive sheet is disposed between the first member and the second member, the base material is peeled off from the foamable adhesive sheet before use.

[0244] In addition, since the details of the foamable adhesive sheet are described in the above-mentioned section "A. Foamable adhesive sheet", the description here is omitted.

[0245] 2. Configuration process

[0246] In the configuration process of the present invention, there is no particular limitation on the method for configuring the foaming adhesive sheet between the first component and the second component. For example, there can be cited a method of inserting the foaming adhesive sheet into the gap between the first component and the second component, a method of configuring the foaming adhesive sheet in the first component and then inserting the second component into the gap after configuring the foaming adhesive sheet in the first component, etc.

[0247] 3. Bonding process

[0248] In the bonding process of the present invention, as a method for foaming and curing the foamable adhesive sheet, heating or light irradiation can be cited. Among them, it is preferred to foam and cure the foamable adhesive sheet by heating. The method based on heating can also be applied when the first member and the second member are not transparent, such as metal members.

[0249] The heating conditions are appropriately set according to the curable adhesive contained in the adhesive layer, the type of the foaming agent, the type of the substrate, etc. The heating temperature can be set to, for example, 130° C. to 200° C. The heating time can be set to, for example, 3 minutes to 3 hours.

[0250] It should be noted that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are for illustration only, and any technical solution having substantially the same structure and having the same function and effect as the technical solution described in the present invention is included in the technical scope of the present invention.

[0251] Example

[0252] [Examples 1-1 to 1-11, Comparative Examples 1-1 to 1-4]

[0253] The foamable adhesive sheet according to the first embodiment will be described with reference to Examples and Comparative Examples.

[0254] First, an adhesive composition having a composition (mass %) shown in the following Table 1 was prepared. In addition, the details of each material described in Table 1 are shown below.

[0255] Acrylic resin: PMMA-PBuA-PMMA (partially acrylamide), Tg: -20°C, 120°C, Mw: 150,000

[0256] ·Epoxy resin A: Bisphenol A linear phenolic type, solid at room temperature, softening temperature: 70°C, epoxy equivalent: 210g / eq, Mw: 1300, melt viscosity at 150°C: 0.5Pa·s

[0257] ·Epoxy resin B: BPA phenoxy type, solid at room temperature, softening temperature: 110°C, epoxy equivalent: 8000g / eq, Mw: 50,000

[0258] Curing agent 1: α-(hydroxy (or dihydroxy) phenylmethyl)-ω-hydrogen poly [biphenyl-4,4'-diylmethylene (hydroxy (or dihydroxy) phenylene methylene)]

[0259] Curing agent 2: 2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230°C, reaction starting temperature 145°C to 155°C, active area 155°C to 173°C (manufactured by Shikoku Chemical Industry Co., Ltd., 2PHZ-PW)

[0260] Curing agent 3: dicyandiamide, particle size: 10 μm or less, melting point: 209°C (manufactured by Evonik Degussa, DYHARD100SH)

[0261] Thermal foaming agent 1: thermally expandable microcapsules, average particle size 7 μm, expansion starting temperature 120-145°C, maximum expansion temperature 155-175°C, core: hydrocarbon, shell: thermoplastic polymer

[0262] Thermal foaming agent 2: thermally expandable microcapsules, average particle size 13 μm, expansion starting temperature 123-133°C, maximum expansion temperature 168-178°C, core: hydrocarbon, shell: thermoplastic polymer

[0263] Thermal foaming agent 3: thermally expandable microcapsules, average particle size 17 μm, expansion starting temperature 120-130°C, maximum expansion temperature 160-170°C, core: hydrocarbon, shell: acrylonitrile copolymer

[0264] Thermal foaming agent 4: thermally expandable microcapsules, average particle size 20 μm, expansion starting temperature 115-125°C, maximum expansion temperature 155-165°C, core: hydrocarbon, shell: thermoplastic polymer

[0265] Thermal foaming agent 5: thermally expandable microcapsules, average particle size 21 μm, expansion starting temperature 130-140°C, maximum expansion temperature 160-170°C, core: hydrocarbon, shell: acrylonitrile copolymer

[0266] Thermal foaming agent 6: thermally expandable microcapsules, average particle size 25 μm, expansion starting temperature 125-135°C, maximum expansion temperature 165-180°C, core: hydrocarbon, shell: thermoplastic polymer

[0267] Thermal foaming agent 7: thermally expandable microcapsules, average particle size 30 μm, expansion starting temperature 120-130°C, maximum expansion temperature 160-170°C, core: hydrocarbon, shell: acrylonitrile copolymer

[0268] Thermal foaming agent 8: thermally expandable microcapsules, average particle size 41 μm, expansion starting temperature 115-125°C, maximum expansion temperature 165-175°C, core: hydrocarbon, shell: acrylonitrile copolymer

[0269] Solvent: Methyl Ethyl Ketone

[0270] Next, as a substrate, a highly insulating polyphenylene sulfide film (PPS film, manufactured by Toray Industries, TORELINA115-3F00, thickness 115 μm) was used. In addition, with respect to 100 parts by mass of the polyester polymer, 15 parts by mass of a curing agent (polyisocyanate) and 0.3 parts by mass of a catalyst (tris(dimethylaminomethylphenol)) were mixed, and further diluted with methyl ethyl ketone (MEK) so that the solid content became 15% by mass to prepare a resin composition. On one side of the above-mentioned substrate, the above-mentioned resin composition was applied with a rod coater, and dried in an oven at 100°C for 1 minute to form a first intermediate layer with a thickness of 2 μm. In addition, on the other side of the substrate, the second intermediate layer was formed in the same manner as the above-mentioned first intermediate layer.

[0271] Next, the adhesive composition is applied to the surface of the first intermediate layer opposite to the substrate using an applicator in a manner that the thickness after application is 38 μm. Then, it is dried in an oven at 100° C. for 3 minutes to form a first adhesive layer. In addition, the surface of the second intermediate layer opposite to the substrate is operated in the same manner as the first adhesive layer to form a second adhesive layer. Thus, a foamable adhesive sheet having a first adhesive layer, a first intermediate layer, a substrate, a second intermediate layer, and a second adhesive layer arranged in sequence is obtained.

[0272] [Evaluation 1]

[0273] (Adhesion)

[0274] The foamable adhesive sheet was cut into a width of 24 mm and a length of 300 mm, and the surface of the first adhesive layer of the foamable adhesive sheet was attached to a stainless steel plate (SUS304) using a hand roller. Then, the adhesive strength (N / 25 mm) to the stainless steel plate surface was measured using a tensile tester (TensilonRTF1150, manufactured by A&D Co., Ltd.) under the conditions (tensile speed: 300 mm / min, peeling distance: 150 mm, peeling angle: 180°) according to JIS Z0237:2009 (test method for adhesive tapes and adhesive sheets) based on ISO 29862 and method 1 of the adhesive strength test method (test method of peeling the tape and sheet 180° from the stainless steel test plate at a temperature of 23°C and a humidity of 50%).

[0275] (Coefficient of friction)

[0276] The dynamic friction coefficient and static friction coefficient of the first adhesive layer of the foamable adhesive sheet and the metal plate are measured according to JIS K7125 corresponding to ISO 8295. First, the foamable adhesive sheet is cut into 80mm×200mm. Next, the foamable adhesive sheet is placed on a horizontal rectangular metal plate, and a sliding sheet (63mm×63mm, weight 200g, bottom surface: felt) is placed on the first adhesive layer of the foamable adhesive sheet. The friction force is measured under the conditions of test speed 100mm / min, test length 50mm, force sensor 10N, and temperature 23°C, and the dynamic friction coefficient and static friction coefficient are calculated. The device uses a friction measuring machine FRICTION TESTER TR-2 made by Toyo Seiki Co., Ltd. In addition, the material of the stainless steel plate used as the metal plate is SUS304, and the surface roughness Ra is 0.05μm.

[0277] (Pencil hardness)

[0278] Prepare an A4-sized foaming adhesive sheet and place it on a glass plate. According to JIS K5600 corresponding to ISO 15184, use a pencil hardness tester (with a level) to measure the pencil hardness of the first adhesive layer of the foaming adhesive sheet. The measurement conditions are set to an angle of 45° from the horizontal state of the pencil, a load of 750 g, a test speed of 1 mm / sec, a test length of 20 mm, and a temperature of 23°C. Then, the hardness of the largest pencil that does not cause damage to the first adhesive layer of the foaming adhesive sheet by visual inspection is taken as the pencil hardness. The pencil hardness tester uses KT-VF2378-12 made by TQC.

[0279] (Insert weight)

[0280] Prepare 2 foam adhesive sheets cut into 5.5cm×6.0cm, a hollow cylinder 1 with an outer diameter of 22mm, a thickness of 1.5mm, and a length of 60mm, and a hollow cylinder 2 with an outer diameter of 18mm, a thickness of 1.0mm, and a length of 80mm. The two foam adhesive sheets are overlapped and rolled up in a manner that the surface on the first adhesive layer side becomes the inner side, and are arranged inside the cylinder 1 in this state. Next, a cylinder 2 of about 1mm is pre-inserted into the gap on the inner side of the foam adhesive sheet in the cylinder 1. Then, a weight is placed on the cylinder 2, and the weight of the weight when the cylinder 2 is completely inserted into the gap on the inner side of the foam adhesive sheet in the cylinder 1 is measured. The weight of the weight at this time is used as the insertion weight. The smaller the insertion weight, the better the insertion property.

[0281] [Table 1]

[0282]

[0283] As shown in Table 1, in Example 1-3, compared with Comparative Examples 1-1, 1-2, and 1-4, the static friction coefficient and the dynamic friction coefficient are small, and the pencil hardness is high, so the insertion weight becomes small. Thus, it is suggested that the friction coefficient and hardness of the surface of the adhesive layer contribute to the insertion property. It should be noted that the evaluation results of the first adhesive layer of the foaming adhesive sheet are roughly the same as the evaluation results of the second adhesive layer.

[0284] [Examples 2-1 to 2-9, Comparative Examples 2-1 to 2-5]

[0285] The foamable adhesive sheet according to the second embodiment will be described with reference to Examples and Comparative Examples.

[0286] A foamable adhesive sheet was prepared in the same manner as in Example 1-1.

[0287] In addition, the details of the curing agents 4 and 5 described in the following Table 2 are shown below.

[0288] Curing agent 4: 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, average particle size: 2 μm, melting point: 260°C, reaction starting temperature 120°C to 130°C, active region 130°C to 146°C (manufactured by Shikoku Chemical Industry Co., Ltd., 2MAOK-PW)

[0289] Curing agent 5: aliphatic dimethyl urea compound, powder particles, melting point: 175°C (manufactured by San-Apro, UCAT-3513N)

[0290] [Evaluation 2]

[0291] (Foaming ratio)

[0292] The foamable adhesive sheet was cut into a size of 50 mm × 50 mm, hung in the vertical direction in a hot air dryer, foamed and cured at 180°C or 150°C for 30 minutes, and then cooled at room temperature for 2 hours to obtain a foamed and cured adhesive sheet. Then, the thickness of the foamed and cured adhesive sheet was measured using a thickness gauge according to the method of JIS Z0237. The foaming ratio was calculated by the following formula.

[0293] Foaming ratio (times) = {thickness of adhesive sheet after foaming and curing - (thickness of substrate + thickness of first intermediate layer + thickness of second intermediate layer)} / (total thickness of first adhesive layer and second adhesive layer of foamable adhesive sheet before foaming and curing)

[0294] (Adhesion)

[0295] like Figure 6As shown in (a) and (b), two metal plates 31 (cold-rolled steel plate SPCC-SD) with a thickness of 1.6 mm, a width of 25 mm, and a length of 100 mm are prepared. A separator 32 (Kapton tape) is arranged at a predetermined interval at one front end of one of the metal plates 31. The thickness of the separator is set to about 280 μm, about 350 μm, or about 420 μm (the thickness obtained by overlapping 4, 5, or 6 pieces of Kapton Tape P-221 manufactured by Nitto Denko Corporation). Next, a foaming adhesive sheet 10 cut into a size of 12.5 mm × 25 mm is arranged between the separators 32, and another metal plate 31 is arranged in an overlapping manner at one front end.

[0296] For some, such as Figure 6 As shown in (a), a support member 33 having the same thickness as the total thickness of the metal plate 31 and the spacer 32 is respectively arranged at the front end of the other of the two metal plates 31 to obtain a test piece. Then, the test piece is placed in a hot press and heated at 150° C. for 8 minutes with a pressing load of 500 kgf to cure the foamable adhesive sheet 10.

[0297] The remaining portion was fixed with a jig to obtain a test piece. The test piece was then placed in a hot oven and heated at 180° C. for 30 minutes to cure the foamable adhesive sheet 10 .

[0298] The heated test piece was measured for shear strength (adhesive strength) using a tensile tester Tensilon RTF1350 (manufactured by A&D Co.) in accordance with JIS K6850 corresponding to ISO 4587. The measurement conditions were a tensile speed of 10 mm / min and a temperature of 200°C.

[0299] [Table 2]

[0300]

[0301] As shown in Table 2, in Comparative Examples 2-1 to 2-2, the average particle size of the foaming agent is small, so the bonding strength is good when the gap is about 280 μm, but the bonding strength is reduced when the gap is about 350 μm. In addition, in Comparative Examples 2-3 to 2-5, the average particle size of the foaming agent is large, so the bonding strength is reduced when the gap is about 280 μm. In addition, in Comparative Examples 2-6 and 2-8, the average particle size of the foaming agent is small, so the bonding strength is good when the gap is about 280 μm and about 350 μm, but the bonding strength is reduced when the gap is about 420 μm. In addition, in Comparative Examples 2-7 and 2-9, the average particle size of the foaming agent is large, so the foaming ratio is large, and the bonding strength is reduced regardless of the width of the gap. In contrast, in Examples 2-1 to 2-9, the average particle size of the foaming agent is within the specified range, so the bonding strength is good when the gap is about 280 μm and when the gap is about 350 μm. In addition, in Examples 2-10 to 2-13, the average particle size of the foaming agent was within the specified range, so the bonding strength was good when the gap was about 280 μm, about 350 μm, and about 420 μm. This suggests that when the average particle size of the foaming agent is within the specified range, the bonding property is good not only when the gap between the components is relatively narrow, but also when the gap between the components is relatively wide.

[0302] Description of Reference Numerals

[0303] 1…adhesive layer;

[0304] 2…substrate;

[0305] 3…middle layer;

[0306] 10…Foaming adhesive sheet;

[0307] 11…adhesive sheet after foaming and curing;

[0308] 20a ... a first member;

[0309] 20b ... a second member;

[0310] 100…items.

Claims

1. A foamable adhesive sheet comprising a substrate and an adhesive layer disposed on at least one surface side of the substrate, The adhesive layer contains a curable adhesive and a foaming agent. The adhesive layer is disposed on the outermost surface. The adhesive force of the adhesive layer is 0 N / 25 mm or more and 0.1 N / 25 mm or less, The static friction coefficient of the surface of the adhesive layer opposite to the substrate is 0.30 or less, The pencil hardness of the surface of the adhesive layer opposite to the substrate is F or higher, The adhesive layer contains an epoxy resin and a curing agent, and the adhesive layer contains an epoxy resin that is solid at room temperature as the epoxy resin. The average particle size of the foaming agent is greater than or equal to 17 μm and less than or equal to 44 μm, and when the resin component contained in the adhesive layer is set to 100 parts by mass, the content of the foaming agent is greater than or equal to 3 parts by mass and less than or equal to 25 parts by mass; alternatively, the average particle size of the foaming agent is greater than or equal to 13 μm and less than or equal to 44 μm, and when the resin component contained in the adhesive layer is set to 100 parts by mass, the content of the foaming agent is greater than or equal to 15 parts by mass and less than or equal to 25 parts by mass.

2. A foamable adhesive sheet comprising a substrate and an adhesive layer disposed on at least one surface side of the substrate, The adhesive layer contains a curable adhesive and a foaming agent. The average particle size of the foaming agent is 10 μm or more and 24 μm or less. The adhesive layer is disposed on the outermost surface. The adhesive force of the adhesive layer is 0 N / 25 mm or more and 0.1 N / 25 mm or less, The adhesive layer contains an epoxy resin and a curing agent, wherein the adhesive layer contains an epoxy resin that is solid at room temperature as the epoxy resin, When the resin component contained in the adhesive layer is 100 parts by mass, the content of the foaming agent is 3 parts by mass or more and 25 parts by mass or less.

3. The foamable adhesive sheet according to claim 2, wherein: The average thickness of the adhesive layer is equal to or greater than the average particle size of the foaming agent.

4. The foamable adhesive sheet according to claim 2 or 3, wherein: The average thickness of the adhesive layer is 10 μm or more and 200 μm or less.

5. The foamable adhesive sheet according to claim 2 or 3, wherein The adhesive layer can be foamed at a foaming ratio of 3.5 times or more and 9 times or less.

6. The foamable adhesive sheet according to any one of claims 1 to 3, wherein The bending moment of the foamable adhesive sheet is greater than or equal to 3 gf·cm and less than 40 gf·cm.

7. A method for manufacturing an article, comprising: a disposing step of disposing the foamable adhesive sheet according to any one of claims 1 to 3 between the first member and the second member; and The bonding step is to foam and cure the foamable adhesive sheet to bond the first member and the second member.

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