Foamed adhesive sheets, articles, stators and rotors for rotating electric machines

Abstract

This disclosure provides a foaming adhesive sheet having, in this order, a first adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, wherein the first adhesive layer contains a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

Description

[Technical Field]

[0001] This disclosure relates to foamed adhesive sheets, articles using the same, stators for rotating electric machines, and rotors for rotating electric machines. [Background technology]

[0002] Adhesives used to bond components together are used in a variety of fields, and many bonding methods are known.

[0003] For example, Patent Documents 1 and 2 disclose adhesive sheets containing a foaming agent (foaming adhesive sheets). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-203114 [Patent Document 2] International Publication No. 2016 / 163514 [Overview of the project] [Problems that the invention aims to solve]

[0005] One known method of using foamed adhesive sheets involves placing the sheet between two components and then allowing the sheet to foam and harden to bond the two components. Since such foamed adhesive sheets contain a curable adhesive in the bonding layer, high storage stability is desirable. However, storing foamed adhesive sheets under high temperature and high humidity conditions can sometimes lead to a decrease in foaming properties. In this case, depending on the size of the gap between the two components, the foamed adhesive sheet may not be able to fill the gap after foaming and hardening, resulting in reduced adhesion. Furthermore, since the environment in which two components are bonded using a foamed adhesive sheet may be high-temperature, high adhesive durability is also desirable.

[0006] This disclosure is made in view of the above circumstances, and its main purpose is to provide a foamed adhesive sheet that is excellent in foaming properties and adhesive durability. [Means for solving the problem]

[0007] One embodiment of the present disclosure provides a foaming adhesive sheet having, in this order, a first adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, wherein the first adhesive layer contains a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[0008] Another embodiment of the present disclosure provides an article having a first member, a second member, and an adhesive member disposed between the first member and the second member, wherein the adhesive member comprises, in this order, a first curable adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, the first curable adhesive layer containing a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent, and the foaming agent being a thermally expandable microcapsule.

[0009] Another embodiment of the present disclosure provides a stator for a rotating electric machine, comprising a stator core, coils arranged in slots of the stator core, and an adhesive member disposed between the stator core and the coils, wherein the adhesive member comprises, in this order, a first curable adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, and the first curable adhesive layer contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[0010] Other embodiments of the present disclosure provide a rotor for a rotating electric machine, comprising a rotor core, a permanent magnet or a coil disposed in a slot of the rotor core, and an adhesive member disposed between the rotor core and the permanent magnet or the coil. The adhesive member has, in this order, a first cured adhesive layer, a first gas barrier layer, a base material, and a second gas barrier layer. The first cured adhesive layer contains a foam-cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

Advantages of the Invention

[0011] The foaming adhesive sheet in the present disclosure has the effect of being excellent in foaming characteristics and adhesion durability.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic cross-sectional view illustrating the foaming adhesive sheet in the present disclosure. [Figure 2] It is a schematic perspective view illustrating the foaming adhesive sheet in the present disclosure. [Figure 3] It is a schematic cross-sectional view illustrating the foaming adhesive sheet in the present disclosure. [Figure 4] It is a schematic cross-sectional view illustrating the foaming adhesive sheet in the present disclosure. [Figure 5] It is a schematic cross-sectional view illustrating the foaming adhesive sheet in the present disclosure. [Figure 6] It is a schematic cross-sectional view illustrating an article in the present disclosure. [Figure 7] It is a schematic cross-sectional view illustrating a stator for a rotating electric machine in the present disclosure. [Figure 8] It is a schematic cross-sectional view illustrating a rotor for a rotating electric machine in the present disclosure. [Figure 9] It is a schematic cross-sectional view illustrating a rotor for a rotating electric machine in the present disclosure.

Embodiments for Carrying Out the Invention

[0013] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, the drawings may be schematically represented in terms of width, thickness, shape, etc. of each part compared to the actual form in order to make the explanation clearer, but these are merely examples and should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0014] In this specification, when describing a configuration in which one member is placed on top of another member, unless otherwise specified, the terms "on top" or "below" include both cases: when the other member is placed directly above or below the other member so as to be in contact with it, and when the other member is placed above or below the other member via yet another member. Similarly, when describing a configuration in this specification in which one member is placed on the surface of another member, unless otherwise specified, the terms "on the surface" or "on the surface" include both cases: when the other member is placed directly above or below the other member so as to be in contact with it, and when the other member is placed above or below the other member via yet another member.

[0015] Furthermore, in this specification, the term "sheet" also includes a component called "film."

[0016] Furthermore, the numerical ranges used in this specification represent the range of average values.

[0017] The foamed adhesive sheet, articles using the same, stators for rotating electric machines, and rotors for rotating electric machines described herein will be explained in detail below.

[0018] A. Foamed adhesive sheet The foamed adhesive sheet in this disclosure comprises, in this order, a first adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, wherein the first adhesive layer contains a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[0019] Figure 1 is a schematic cross-sectional view showing an example of a foamed adhesive sheet in this disclosure. The foamed adhesive sheet 10 in Figure 1 comprises a first adhesive layer 1, a first gas barrier layer 2, a substrate 3, and a second gas barrier layer 4, with the thickness direction D T The components are arranged in this order. The first adhesive layer 1 contains a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[0020] In this disclosure, the foaming agent is a thermally expandable microcapsule, in which a thermally expandable agent such as a hydrocarbon is encapsulated inside a resin shell. The inventors of this application have diligently studied the storage environment for foamed adhesive sheets and have found that storing foamed adhesive sheets under high humidity conditions reduces the foaming ratio. This is thought to be because, under high humidity conditions, the thermally expandable agent escapes from the thermally expandable microcapsules. When bonding a first member and a second member using a foamed adhesive sheet, if the foaming ratio decreases, the gap between the first member and the second member cannot be sufficiently filled with the foamed adhesive sheet after foaming and curing, resulting in reduced adhesion after foaming and curing. Therefore, it is necessary to prevent moisture when storing foamed adhesive sheets.

[0021] In this context, foamed adhesive sheets are sometimes manufactured using a roll-to-roll production line, which offers productivity advantages. In this roll-to-roll production line, the foamed adhesive sheets are wound onto a core and stored in roll form. Therefore, to prevent moisture damage, it is necessary to store the rolled foamed adhesive sheets in moisture-proof bags or in a low-humidity environment.

[0022] In contrast, in this disclosure, as shown in Figure 2, when the foamed adhesive sheet 10 is wound into a roll, as shown in Figure 3(a), if the foamed adhesive sheet 10 is wound into a roll so that the side of the second gas barrier layer 4 of the foamed adhesive sheet 10 is on the outside and the side of the first adhesive layer 1 is on the inside, the first adhesive layer 1 is located inside the first gas barrier layer 2 and the second gas barrier layer 4, so that the intrusion of moisture from the outside into the first adhesive layer 1 can be suppressed. Also, as shown in Figure 3(b), if the foamed adhesive sheet 10 is wound into a roll so that the side of the first adhesive layer 1 of the foamed adhesive sheet 100 is on the outside and the side of the second gas barrier layer 4 is on the inside, in the foamed adhesive sheet 10B which is located inside the outermost foamed adhesive sheet 10A, the first adhesive layer 1 of the foamed adhesive sheet 10B is located inside the first gas barrier layer 2 and the second gas barrier layer 4 of the foamed adhesive sheet 10A, so that the intrusion of moisture from the outside into the first adhesive layer 1 can be suppressed. The relationship between foamed adhesive sheet 10B and foamed adhesive sheet 10C is the same as the relationship between foamed adhesive sheet 10A and foamed adhesive sheet 10B described above.

[0023] Therefore, in this disclosure, the first adhesive layer can be protected from moisture by winding the foamed adhesive sheet into a roll. This suppresses the decrease in the foaming ratio of the first adhesive layer due to moisture, thereby obtaining stable foaming characteristics and improving adhesion after foaming and curing. In addition, precise humidity control is not required for the foamed adhesive sheet, making it easier to handle.

[0024] Furthermore, the inventors of this application have diligently investigated the usage environment of the foamed adhesive sheet after foaming and curing, and have found that when the foamed adhesive sheet is used at high temperatures after foaming and curing, the thickness of the foamed adhesive sheet decreases. This is thought to be partly due to the fact that at high temperatures, the substrate is oxidatively decomposed, and the thickness of the substrate tends to decrease. When a first member and a second member are bonded using a foamed adhesive sheet, if the thickness of the foamed adhesive sheet decreases after foaming and curing, the gap between the first member and the second member cannot be sufficiently filled with the foamed adhesive sheet after foaming and curing, resulting in a decrease in adhesion. In addition, if the substrate has insulating properties, it hardens when the substrate is oxidatively decomposed, making it prone to cracking. As a result, the adhesion decreases, and the insulating properties of the substrate also decrease.

[0025] Here, when a foamed adhesive sheet is used to bond the first and second components, a portion of the foamed adhesive sheet may be exposed. For example, when bonding a stator core and a coil in a rotating electric machine stator, it is preferable to position the foamed adhesive sheet between the stator core and the coil so that the foamed adhesive sheet protrudes from the edge of the stator core in order to suppress surface discharge. In a rotating electric machine, heat is generated when current flows through the coil. In this case, a portion of the foamed adhesive sheet is exposed after foaming and curing, and the foamed adhesive sheet is exposed to high temperatures, raising concerns about oxidative decomposition of the substrate. Also, depending on the material of the first or second component, such as when the first or second component contains thermoplastic resin or rubber, the oxygen permeability of the first or second component may increase at high temperatures. In this case as well, oxidative decomposition of the substrate is a concern.

[0026] In contrast, in the foamed adhesive sheet of this disclosure, a first gas barrier layer and a second gas barrier layer are arranged on both sides of the substrate, respectively, so that the intrusion of oxygen into the substrate from the outside can be suppressed. Therefore, oxidative decomposition of the substrate can be suppressed. As a result, when a first member and a second member are bonded using the foamed adhesive sheet, the thickness of the foamed adhesive sheet after foaming and curing can be maintained, and the adhesive properties can be maintained. Furthermore, the decrease in adhesive properties due to the substrate hardening due to oxidative decomposition can be suppressed. Therefore, when a first member and a second member are bonded using the foamed adhesive sheet, the durability of the bond can be improved. In addition, if the substrate has insulating properties, the decrease in the insulating properties of the substrate due to oxidative decomposition of the substrate can be suppressed. Therefore, when a foamed adhesive sheet is used in the manufacture of electrical products such as rotating electric machines, the durability of the insulation of the electrical products can be improved.

[0027] Figure 4 is a schematic cross-sectional view showing another example of a foamed adhesive sheet in this disclosure. The foamed adhesive sheet 10 in Figure 4 comprises a first adhesive layer 1, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second adhesive layer 5, with the thickness direction D T The layers are present in this order. The first adhesive layer 1 contains a curable adhesive and a foaming agent, the foaming agent being a thermally expandable microcapsule. The second adhesive layer 5 also contains a curable adhesive and may further contain a foaming agent, the foaming agent being a thermally expandable microcapsule.

[0028] As shown in Figure 2, when the foamed adhesive sheet 10 is wound into a roll, as shown in Figure 5, if the foamed adhesive sheet 10 is wound into a roll so that the side of the second adhesive layer 5 of the foamed adhesive sheet 10 is on the outside and the side of the first adhesive layer 1 is on the inside, the first adhesive layer 1 is located inside the first gas barrier layer 2 and the second gas barrier layer 4, so that the intrusion of moisture from the outside into the first adhesive layer 1 can be suppressed. Also, in the foamed adhesive sheet 10B, which is located inside the outermost foamed adhesive sheet 10A, the second adhesive layer 5 of the foamed adhesive sheet 10B is located inside the first gas barrier layer 2 and the second gas barrier layer 4 of the foamed adhesive sheet 10A, so that the intrusion of moisture from the outside into the second adhesive layer 5 can be suppressed. The relationship between the foamed adhesive sheet 10B and the foamed adhesive sheet 10C is the same as the relationship between the foamed adhesive sheet 10A and the foamed adhesive sheet 10B described above. Furthermore, although not shown in the diagram, if the foamed adhesive sheet 10 is wound into a roll with the first adhesive layer 1 facing outwards and the second adhesive layer 5 facing inwards, it will produce the same effect as if the foamed adhesive sheet 10 were wound into a roll with the second adhesive layer 5 facing outwards and the first adhesive layer 1 facing inwards.

[0029] Therefore, by winding the foamed adhesive sheet into a roll, the first and second adhesive layers can be protected from moisture. This suppresses the decrease in the foaming ratio of the first and second adhesive layers due to moisture, thereby achieving stable foaming characteristics and improving adhesion after foaming and curing. In addition, precise humidity control is not required for the foamed adhesive sheet, making it easier to handle.

[0030] Furthermore, in the foamed adhesive sheet shown in Figure 2, a first gas barrier layer and a second gas barrier layer are arranged on both sides of the substrate, similar to the foamed adhesive sheet shown in Figure 1. Therefore, it achieves the same effects as the foamed adhesive sheet shown in Figure 1.

[0031] Thus, as shown in Figure 1, the same effect can be obtained whether the foamed adhesive sheet 10 has a first adhesive layer 1, a first gas barrier layer 2, a substrate 3, and a second gas barrier layer 4 in that order, or as shown in Figure 2, whether the foamed adhesive sheet 10 has a first adhesive layer 1, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second adhesive layer 5 in that order.

[0032] The following describes the various components of the foamed adhesive sheet in this disclosure.

[0033] 1. First gas barrier layer and second gas barrier layer In this disclosure, the first gas barrier layer is positioned on the first surface side of the substrate and between the substrate and the first adhesive layer. The second gas barrier layer is positioned on the second surface side of the substrate.

[0034] The first gas barrier layer and the second gas barrier layer have gas barrier properties. Specifically, as described later, it is preferable that the oxygen permeability and water vapor permeability of the foamed adhesive sheet are within a predetermined range. The first gas barrier layer and the second gas barrier layer may or may not be transparent.

[0035] The first and second gas barrier layers are not particularly limited as long as they have the desired gas barrier properties, and examples include inorganic films and organic-inorganic composite films. Furthermore, the first and second gas barrier layers may have multiple inorganic films, multiple organic-inorganic composite films, or both an inorganic film and an organic-inorganic composite film. Among these, the first and second gas barrier layers are preferably inorganic films. Since inorganic films can be formed by vapor deposition, their thickness can be reduced while maintaining gas barrier properties. Therefore, the overall thickness of the foamed adhesive sheet can be reduced, and the foamed adhesive sheet can be applied even when the gap between the first and second members is narrow.

[0036] (1) Inorganic film Examples of inorganic materials constituting an inorganic film include metals and inorganic compounds. Examples of metals include aluminum, stainless steel, titanium, nickel, iron, copper, and alloys containing these metals. Examples of inorganic compounds include one or more inorganic compounds selected from inorganic oxides, inorganic oxidized nitrides, inorganic nitrides, inorganic oxidized carbides, inorganic oxidized carbidides, and zinc oxide. Specifically, examples include inorganic compounds containing one or more atoms selected from silicon, aluminum, magnesium, calcium, potassium, tin, sodium, titanium, boron, yttrium, zirconium, cerium, and zinc. More specifically, examples include silicon oxide, aluminum oxide, magnesium oxide, titanium oxide, tin oxide, silicon-zinc alloy oxide, indium alloy oxide, silicon nitride, aluminum nitride, titanium nitride, and silicon oxidized nitride. Aluminum oxide (alumina) and silicon oxide (silica) are particularly preferred. Inorganic compounds may be used individually or in mixtures of two or more. Among these, aluminum, aluminum oxide, or silicon oxide are preferred, with aluminum being more preferred.

[0037] The inorganic film may be a vapor-deposited film formed by a vapor deposition method, or a coated film formed by a coating method. Among these, vapor-deposited films are preferred from the viewpoint of good adhesion to the substrate and high gas barrier properties. The vapor-deposited film may be formed by a single vapor deposition or by multiple vapor depositions. That is, a single inorganic film may be a single film formed by a single vapor deposition, or it may have a layered structure formed by multiple vapor depositions.

[0038] (2) Organic-inorganic composite film Examples of organic-inorganic composite films include a layer containing a resin and an inorganic layered compound, a layer containing a reaction product of a polycarboxylic acid polymer and a polyvalent metal compound, a layer containing a reaction product of a metal oxide and a phosphorus compound, and a layer containing a sol-gel compound.

[0039] In the layer containing the resin and the inorganic layered compound, examples of resins include polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyvinylidene chloride (PVDC), polyacrylonitrile (PAN), polysaccharides, polyacrylic acid and its esters. Examples of inorganic layered compounds include clay minerals such as smectite, kaolin, mica, hydrotalcite, and chlorite.

[0040] The layer containing the reaction product of a polycarboxylic acid polymer and a polyvalent metal compound has crosslinking bonds between the carboxyl groups of the polycarboxylic acid polymer due to polyvalent metal ions. The reaction product is a polyvalent metal salt of the polycarboxylic acid polymer. Examples of polyvalent metal salts of polycarboxylic acid polymers include zinc acrylate. The layer containing the reaction product of a polycarboxylic acid polymer and a polyvalent metal compound can be formed, for example, by reacting a carboxylic acid resin film such as polyacrylic acid with a coating film in which fine particles of a polyvalent metal compound such as zinc oxide are dispersed.

[0041] The layer containing the reaction product of the metal oxide and the phosphorus compound has MOP bonds. M represents a metal atom, O represents an oxygen atom, and P represents a phosphorus atom. Examples of metal oxides include oxides of metals with a valence of 2 or higher, specifically metal oxides of Group 2 metals such as magnesium and calcium, Group 12 metals such as zinc, Group 13 metals such as aluminum, Group 14 metals such as silicon, and transition metals such as titanium and zirconium. Among these, aluminum oxide (alumina) is preferred. Examples of phosphorus compounds include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, and their derivatives. Specific reaction products of metal oxides and phosphorus compounds are similar to those disclosed in, for example, Japanese Patent Application Publication No. 2011-226644.

[0042] The layer containing the sol-gel compound is, for example, a compound of the general formula R 1 n M(OR 2 ) mIt contains one or more alkoxides represented by and a hydrophilic group-containing resin, and can be formed from a raw material liquid obtained by polycondensation by the sol-gel method. In the above general formula, R 1 , R 2 The formula represents an organic group with 1 to 8 carbon atoms, M represents a metal atom, n represents an integer of 0 or more, m represents an integer of 1 or more, and n+m represents the valence of M. Examples of metal atoms M in the alkoxide represented by the above general formula include silicon, zirconium, titanium, and aluminum. Among these, silicon is preferred. Tetraethyl orthosilicate (TEOS) is preferred as the silicon alkoxide. Examples of hydrophilic group-containing resins include resins containing hydrophilic groups, specifically polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacrylic acid, methylcellulose, carboxymethylcellulose, cellulose nanofiber, and polysaccharides. Among these, polyvinyl alcohol is preferred.

[0043] The above sol-gel compound is a mixed compound containing a metal element, an oxygen element, and a hydrophilic group-containing resin, and has a COM bond via oxygen (O) between the carbon atom (C) in the hydrophilic group-containing resin and the metal atom (M) in the metal alkoxide. In particular, the above sol-gel compound is preferably a polycondensate of tetraethyl orthosilicate (TEOS) and polyvinyl alcohol. The polycondensate of tetraethyl orthosilicate (TEOS) and polyvinyl alcohol is similar to that disclosed in, for example, Japanese Patent No. 5568897.

[0044] One method for forming organic-inorganic composite films is, for example, a coating method.

[0045] (3) Thickness The thickness of the first gas barrier layer and the thickness of the second gas barrier layer are, for example, 1 nm or more, but may also be 5 nm or more, or 10 nm or more. Depending on the materials of the first and second gas barrier layers, if the above thicknesses are within the above range, the desired gas barrier properties are easily obtained. On the other hand, the thickness of the first gas barrier layer and the thickness of the second gas barrier layer are, for example, preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. If the above thicknesses are within the above range, the thickness of the foamed adhesive sheet can be reduced. Therefore, even if the gap between the first and second members is narrow, the foamed adhesive sheet can be applied. Specifically, the thickness of the first gas barrier layer and the thickness of the second gas barrier layer are, for example, 1 nm or more and 10 μm or less, but may also be 5 nm or more and 5 μm or less, or 10 nm or more and 3 μm or less. Note that if the first gas barrier layer has multiple layers, the above thickness is the total thickness of the first gas barrier layer. Similarly, if the second gas barrier layer has multiple layers, the above thickness is the total thickness of the second gas barrier layer.

[0046] 2.First adhesive layer In this disclosure, the first adhesive layer is positioned on the side opposite to the substrate of the first gas barrier layer and contains a curable adhesive and a foaming agent.

[0047] (1) Material of the first adhesive layer (a) Curing adhesive The curable adhesive included in the first adhesive layer in this disclosure can be any curable adhesive that is generally used for adhesive layers. The curable adhesive is not particularly limited, but a thermosetting adhesive is preferably used. A thermosetting adhesive can be applied even when the component is not transparent, such as a metal component.

[0048] The curable adhesive is preferably an epoxy resin-based adhesive. That is, the curable adhesive preferably contains an epoxy resin and a curing agent. Generally, epoxy resin-based adhesives have a hard and tough cured film and are suitable for bonding hard materials such as metal and glass components. Furthermore, epoxy resin-based adhesives generally have excellent heat resistance, insulation properties, and chemical resistance, and have low curing shrinkage, making them suitable for a wide range of applications.

[0049] Furthermore, if the curable adhesive is an epoxy resin-based adhesive, it is preferable that the curable adhesive further contains an acrylic resin that is compatible with the epoxy resin. By further using an acrylic resin that is compatible with the epoxy resin, the toughness of the first adhesive layer can be increased, and the adhesion of the first adhesive layer to the first gas barrier layer can be improved.

[0050] (i) epoxy resin The epoxy resins in this disclosure are compounds having at least one epoxy group or glycidyl group, which undergo a crosslinking polymerization reaction and harden when used in combination with a curing agent. The epoxy resins also include monomers having at least one epoxy group or glycidyl group.

[0051] As the epoxy resin, epoxy resins commonly used for adhesive layers can be used. In particular, the curable adhesive preferably contains a primary epoxy resin having a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or less, and a secondary epoxy resin having a softening temperature higher than the primary epoxy resin and a weight-average molecular weight of 20,000 or more. By using a combination of the primary and secondary epoxy resins, a foamed adhesive sheet with good blocking resistance and adhesion after foam curing can be obtained. Furthermore, the tackiness of the primary adhesive layer can be reduced, and a foamed adhesive sheet with good slipperiness can be obtained.

[0052] For example, if the goal is solely to improve adhesion after foam curing, it is more effective to use a low molecular weight (low epoxy equivalent) epoxy resin than a high molecular weight (high epoxy equivalent) epoxy resin. However, when using a low molecular weight (low epoxy equivalent) epoxy resin, for example, when the foamed adhesive sheet is wound into a roll, the low molecular weight (low epoxy equivalent) epoxy resins tend to assimilate with each other, making blocking more likely.

[0053] In contrast, when using a primary epoxy resin with a relatively low softening temperature (relatively high crystallinity) and low molecular weight (low epoxy equivalent), the primary epoxy resin rapidly melts and changes into a low-viscosity liquid when the temperature exceeds the softening temperature. Therefore, it is easier to improve adhesion after foaming and curing. On the other hand, because the primary epoxy resin has relatively high crystallinity, it can suppress the occurrence of blocking compared to epoxy resins with relatively low crystallinity or epoxy resins that do not have crystallinity. However, if only the primary epoxy resin is used, the blocking suppression effect may be insufficient, or the tackiness of the first adhesive layer may become too high. Therefore, by further using a secondary epoxy resin with a relatively high softening temperature (relatively low crystallinity) and high molecular weight, the blocking suppression effect can be improved, and the tackiness of the first adhesive layer can be kept low.

[0054] (i-1) Primary epoxy resin The first epoxy resin has a softening temperature of 50°C or higher and an epoxy equivalent of 5000 g / eq or less. Compared to the second epoxy resin described later, the first epoxy resin has a relatively lower softening temperature (relatively higher crystallinity). Because the first epoxy resin has relatively high crystallinity and a low molecular weight, it is easy to improve the adhesion and blocking resistance after foam curing. In addition, because the first epoxy resin has a low molecular weight, a high crosslinking density can be achieved, resulting in a first adhesive layer with good mechanical strength, chemical resistance, and curability. Furthermore, it is preferable that the first epoxy resin is an epoxy resin that is solid at room temperature (23°C).

[0055] The softening temperature of primary epoxy resin is typically 50°C or higher, but may also be 55°C or higher, or even 60°C or higher. On the other hand, the softening temperature of primary epoxy resin is, for example, 150°C or lower. The softening temperature is measured by the ring-and-ball method in accordance with JIS K7234:1986.

[0056] The epoxy equivalent of the primary epoxy resin is, for example, 5000 g / eq or less, but may also be 3000 g / eq or less, 1000 g / eq or less, or 600 g / eq or less. On the other hand, the epoxy equivalent of the primary epoxy resin is, for example, 90 g / eq or more, but may also be 100 g / eq or more, or 110 g / eq or more. The epoxy equivalent is measured by a method in accordance with JIS K7236, which corresponds to ISO 3001 (Plastics - Epoxy compounds - Determination of epoxy equivalent). The epoxy equivalent is the number of grams of resin containing 1 gram equivalent of epoxy groups.

[0057] The first epoxy resin may be a monofunctional epoxy resin, a bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or more functional epoxy resin.

[0058] Furthermore, the weight-average molecular weight (Mw) of the primary epoxy resin is usually smaller than the weight-average molecular weight (Mw) of the secondary epoxy resin, which will be discussed later. The Mw of the primary epoxy resin is, for example, 6,000 or less, may be 4,000 or less, or 3,000 or less. On the other hand, the Mw of the primary epoxy resin is, for example, 400 or more. Mw is the polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0059] The first epoxy resin has a melt viscosity at 150°C of, for example, 0.005 Pa·s or more, but may also be 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 within the above range, good foaming properties can be obtained. Furthermore, if the melt viscosity is within the above range, it is possible to suppress the tackiness of the first adhesive layer from becoming too high. This is presumed to be because 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 acrylic resin, its crystallinity decreases significantly, and the Tg of the entire adhesive composition decreases. On the other hand, the first epoxy resin has a melt viscosity at 150°C of, for example, 10 Pa·s or less, but may also be 5 Pa·s or less, or 2 Pa·s or less. If the melt viscosity is within the above range, the uniformity of the first adhesive layer tends to be good. The melt viscosity is measured in accordance with JIS K6862:1984, which corresponds to ISO 2555 (Resins in the liquid state or as emulsions or dispersions - Determination of Brookfield RV viscosity), using a Brookfield-type single-cylinder rotational viscometer and a thermocell for heating the solution.

[0060] Next, the composition of the first epoxy resin will be described. Examples of the first epoxy resin include aromatic epoxy resins, aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins. Specific examples of the first epoxy resin include bisphenol-type epoxy resins such as bisphenol A-type epoxy resin and bisphenol F-type epoxy resin, novolak-type epoxy resins such as bisphenol A novolak-type epoxy resin and cresol novolak-type epoxy resin, and modified epoxy resins such as urethane-modified epoxy resin and rubber-modified epoxy resin. Other specific examples include biphenyl-type epoxy resin, stilbene-type epoxy resin, triphenolmethane-type epoxy resin, alkyl-modified triphenolmethane-type epoxy resin, triazine nucleus-containing epoxy resin, dicyclopentadiene-modified phenol-type epoxy resin, naphthalene-type epoxy resin, glycol-type epoxy resin, and pentaerythritol-type epoxy resin. The first epoxy resin may be one type or two or more types.

[0061] Bisphenol A-type epoxy resin can exist in a liquid state at room temperature or a solid state at room temperature depending on the number of repeating units of the bisphenol skeleton. Bisphenol A-type epoxy resin having a bisphenol skeleton in the main chain of, for example, 2 or more and 10 or less is solid at room temperature. In particular, bisphenol A-type epoxy resin is preferable in terms of improving heat resistance.

[0062] In particular, the first epoxy resin is preferably a bisphenol A novolak-type epoxy resin represented by the following general formula (1).

[0063] [Chemical formula]

[0064] In general formula (1), R 1 is a group represented by C m H 2m (where m is 1 or more and 3 or less), and R 2 and R 3Each of them is independent of C p H 2p+1 The base is represented by (p is between 1 and 3), and n is between 0 and 10.

[0065] In general formula (1), R 1 In this case, m is 1, that is, R 1 It is preferable that R is -CH2-. Similarly, 2 and R 3 In R, p is 1, that is, 2 and R 3 It is preferable that the group is -CH3. Furthermore, the hydrogen atoms bonded to the benzene ring of general formula (1) may be substituted with other elements or other groups.

[0066] The content of the first epoxy resin may be, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 10 parts by mass or more, 15 parts by mass or more, or 25 parts by mass or more, when the total resin components in the first adhesive layer are considered to be 100 parts by mass. If the content of the first epoxy resin is within the above range, good adhesion and blocking resistance after foam curing are likely to be achieved. On the other hand, the content of the first epoxy resin may be, for example, 90 parts by mass or less, 80 parts by mass or less, 70 parts by mass or less, 60 parts by mass or less, 50 parts by mass or less, or 40 parts by mass or less, when the total resin components in the first adhesive layer are considered to be 100 parts by mass. If the content of the first epoxy resin is within the above range, it is possible to suppress the relatively low content of the second epoxy resin and acrylic resin, and to balance blocking resistance and adhesion after foam curing.

[0067] (i-2) Second epoxy resin The second epoxy resin has a higher softening temperature than the first epoxy resin and a weight-average molecular weight of 20,000 or more. Compared to the first epoxy resin mentioned above, the second epoxy resin has a relatively higher softening temperature (relatively lower crystallinity). Because the second epoxy resin has relatively low crystallinity and high molecular weight, it is easier to improve blocking resistance. Furthermore, because the second epoxy resin has relatively low crystallinity and high molecular weight, it can suppress the increase in tackiness caused by the first epoxy resin. In addition, it is preferable that the second epoxy resin is a solid epoxy resin at room temperature (23°C).

[0068] The weight-average molecular weight (Mw) of the secondary epoxy resin is usually greater than that of the primary epoxy resin. The Mw of the secondary epoxy resin is typically 20,000 or more, but may be 30,000 or more, or even 35,000 or more. On the other hand, the Mw of the secondary epoxy resin may be, for example, 100,000 or less.

[0069] The epoxy equivalent of the second epoxy resin may be greater than, less than, or the same as the epoxy equivalent of the first epoxy resin. For example, the epoxy equivalent of the second epoxy resin may be 4000 g / eq or more, 5000 g / eq or more, or 6000 g / eq or more. On the other hand, for example, the epoxy equivalent of the second epoxy resin may be 20000 g / eq or less.

[0070] The second epoxy resin may be a monofunctional epoxy resin, a bifunctional epoxy resin, a trifunctional epoxy resin, or a tetrafunctional or more functional epoxy resin.

[0071] The softening temperature of the second epoxy resin is usually higher than that of the first epoxy resin. The difference between the two is, for example, 10°C or more, may be 20°C or more, or may be 30°C or more. The softening temperature of the second epoxy resin is, for example, 80°C or more, and may be 90°C or more. On the other hand, the softening temperature of the second epoxy resin is, for example, 180°C or less.

[0072] The composition of the second epoxy resin is the same as that of the first epoxy resin described above, so it will not be described here.

[0073] The content of the second epoxy resin may be, for example, 10 parts by mass or more, 15 parts by mass or more, 20 parts by mass or more, 25 parts by mass or more, 30 parts by mass or more, 35 parts by mass or more, 40 parts by mass or more, or 45 parts by mass or more, when the resin component contained in the first adhesive layer is considered to be 100 parts by mass. If the content of the second epoxy resin is within the above range, good blocking resistance is likely to be achieved. On the other hand, the content of the second epoxy resin may be, for example, 90 parts by mass or less, 85 parts by mass or less, 80 parts by mass or less, or 75 parts by mass or less, when the resin component contained in the first adhesive layer is considered to be 100 parts by mass. If the content of the second epoxy resin is within the above range, it is possible to suppress the relatively low content of the first epoxy resin and acrylic resin, and to balance blocking resistance and adhesion after foam curing.

[0074] The proportion of the first epoxy resin to the total of the first and second epoxy resins is, for example, 5% by mass or more, may be 10% by mass or more, may be 15% by mass or more, or may be 20% by mass or more. On the other hand, the above proportion of the first epoxy resin is, for example, 80% by mass or less, may be 75% by mass or less, or may be 60% by mass or less.

[0075] Furthermore, the total ratio of the first epoxy resin and the second epoxy resin to all epoxy resins contained in the first adhesive layer is, for example, 50% by mass or more, may be 70% by mass or more, may be 90% by mass or more, or may be 100% by mass.

[0076] (ii) Acrylic resin The acrylic resin in this disclosure is a resin that is compatible with epoxy resin. Because the acrylic resin is compatible with epoxy resin, it is easy to improve the toughness of the first adhesive layer. As a result, the adhesion of the first adhesive layer can be improved. Furthermore, by improving the toughness of the first adhesive layer, the adhesion after foam curing can be improved. In addition, it is thought that the acrylic resin acts as a compatibilizer for the foaming agent (for example, a foaming agent whose shell portion is a resin of acrylonitrile copolymer), and by uniformly dispersing and foaming, the adhesion after foam curing is improved. Moreover, because the acrylic resin is compatible with epoxy resin, the hardness of the surface of the first adhesive layer can be maintained at a high level. On the other hand, if the acrylic resin is incompatible with epoxy resin, flexible areas will be formed on the surface of the first adhesive layer, which may make the interface with the adherend less slippery and reduce workability.

[0077] The acrylic resin in this disclosure is compatible with epoxy resin. This compatibility can be confirmed, for example, by observing a cross-section of the first adhesive layer of a foamed adhesive sheet with a scanning electron microscope (SEM) or transmission electron microscope (TEM) and observing the absence of micron-sized islands. More specifically, the average island particle size is preferably 1 μm or less. In particular, the average island particle size may be 0.5 μm or less, or 0.3 μm or less. A large sample size is preferred, for example, 100 or more. The observation area is a range of 100 μm × 100 μm, or, if the thickness of the first adhesive layer is 100 μm or less, a range of thickness × 100 μm.

[0078] The weight-average molecular weight (Mw) of the acrylic resin is, for example, 50,000 or more, but may also be 70,000 or more, or 100,000 or more. Primary epoxy resins have relatively high crystallinity, which can lead to excessively low melt viscosity (or dynamic viscoelasticity) during heating, potentially causing shrinkage during curing after foaming (the period from when the foaming of the foaming agent is finished until the adhesive composition hardens). However, by using an acrylic resin with a certain molecular weight, it is possible to suppress the melt viscosity from becoming too low, making shrinkage during curing after foaming less likely. On the other hand, the Mw of the acrylic resin is, for example, 1,500,000 or less. The weight-average molecular weight of the acrylic resin is measured by GPC (eluent: THF, standard substance: PS, sample: 20 μL, flow rate: 1 mL / min, column temperature: 40°C).

[0079] The glass transition temperature (Tg) of acrylic resin is, for example, 90°C or higher, and may also be 100°C or higher. On the other hand, the Tg of acrylic resin is, for example, 180°C or lower. The Tg is measured by differential scanning calorimeter (DSC) in accordance with JIS K7121:2012, which corresponds to ISO 3146.

[0080] Acrylic resin has a storage modulus (E') of 1 × 10⁻¹⁰ at the foaming initiation temperature. 6 It may be less than Pa. A low E' at the start of foaming improves fluidity and allows for good foaming. On the other hand, E' at the foaming start temperature is, for example, 1 × 10⁻⁶. 5 The temperature must be above Pa. Note that the foaming initiation temperature varies depending on the type of foaming agent. Furthermore, if two or more foaming agents are used, the foaming initiation temperature shall be the temperature at which the primary foaming reaction begins.

[0081] Acrylic resin has a storage modulus (E') of 1 × 10⁻¹⁰ at the curing start temperature. 5It may be Pa or higher. As mentioned above, shrinkage may occur during curing after foaming (from the time the foaming of the foaming agent is finished until the adhesive composition hardens), but a large E' at the curing start temperature can suppress shrinkage and obtain good shape retention. Note that the curing start temperature is different depending on the type of curing agent. Also, when two or more curing agents are used, the curing start temperature is the temperature at which the main curing reaction starts.

[0082] Furthermore, the average storage modulus (E') of acrylic resin at temperatures between 0°C and 100°C is 1 × 10⁻⁶ 6 It may be Pa or higher. A high average value of E' before foaming allows for good blocking resistance. On the other hand, the average value of the storage modulus (E') between 0°C and 100°C is, for example, 1 × 10⁻⁶. 8 It is below Pa.

[0083] Acrylic resins may have polar groups. Examples of polar groups include epoxy groups, hydroxyl groups, carboxyl groups, nitrile groups, and amide groups.

[0084] The acrylic resin is a homopolymer of acrylic acid ester monomers, and may be a mixed component containing two or more of the above homopolymers, or a copolymer of two or more acrylic acid ester monomers, and may be a component containing one or more copolymers. Furthermore, the acrylic resin may be a mixed component of the above homopolymer and the above copolymer. The term "acrylic acid" in acrylic acid ester monomers also includes the concept of methacrylic acid. Specifically, the acrylic resin may be a mixture of a polymer of methacrylate and a polymer of acrylate, or it may be an acrylic acid ester polymer such as acrylate-acrylate, methacrylate-methacrylate, or methacrylate-acrylate. In particular, it is preferable that the acrylic resin contains a copolymer of two or more acrylic acid ester monomers ((meth)acrylic acid ester copolymer).

[0085] Examples of monomer components constituting the (meth)acrylic acid ester copolymer include the monomer component described in Japanese Patent Publication No. 2014-065889. The above monomer component may have the polar group described above. Examples of the above (meth)acrylic acid ester copolymer include ethyl acrylate-butyl acrylate-acrylonitrile copolymer, ethyl acrylate-acrylonitrile copolymer, and butyl acrylate-acrylonitrile copolymer. Note that "acrylic acid" such as methyl acrylate and ethyl acrylate also includes "methacrylic acid" such as methyl methacrylate and ethyl methacrylate.

[0086] As the (meth)acrylic acid ester copolymer mentioned above, block copolymers are preferred, and acrylic block copolymers such as methacrylate-acrylate copolymers are even more preferred. Examples of (meth)acrylates that constitute 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 acid."

[0087] 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).

[0088] The acrylic copolymer does not necessarily have polar groups, or it may be a modified product in which the aforementioned polar groups are partially introduced. Since the above modified product is easily compatible with epoxy resin, its adhesive properties are further improved.

[0089] In particular, the acrylic resin is preferably a (meth)acrylic acid ester copolymer having a first polymer portion with a glass transition temperature (Tg) of 10°C or less and a second polymer portion with a glass transition temperature (Tg) of 20°C or more. Such a (meth)acrylic acid ester copolymer has a first polymer portion that becomes a soft segment and a second polymer portion that becomes a hard segment.

[0090] The manifestation of the above effects can be estimated as follows: By using an acrylic resin that has both soft and hard segments, such as the (meth)acrylic acid ester copolymer described above, the hard segments contribute to heat resistance, and the soft segments contribute to toughness or flexibility, thus resulting in a first adhesive layer with good heat resistance, toughness, and flexibility.

[0091] At least one of the first polymer portion and the second polymer portion contained in the above (meth)acrylic acid ester copolymer is compatible with epoxy resin. When the first polymer portion is compatible with epoxy resin, flexibility can be increased. Furthermore, when the second polymer portion is compatible with epoxy resin, cohesiveness and toughness can be increased.

[0092] If either the first or second polymer portion is incompatible with the epoxy resin, the (meth)acrylic acid ester copolymer will have a compatible portion that is compatible with the epoxy resin and an incompatible portion that is incompatible with the epoxy resin. In this case, when the (meth)acrylic acid ester copolymer is added to the adhesive composition, the compatible portion becomes compatible with the epoxy resin, while the incompatible portion does not, resulting in fine phase separation. As a result, a fine sea-island structure is formed. The sea-island structure varies depending on the type of (meth)acrylic acid ester copolymer, the compatibility of the primary and secondary polymer portions contained in the (meth)acrylic acid ester copolymer, and whether or not it is modified by the introduction of polar groups. For example, there are sea-island structures in which the compatible parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the sea and the incompatible parts of the (meth)acrylic acid ester copolymer are the islands, or in which the incompatible parts of the (meth)acrylic acid ester copolymer are the sea and the compatible parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the islands, or in which the (meth)acrylic acid ester copolymer is the sea and the cured epoxy resin is the islands. Having such a sea-island structure makes it easier to distribute stress, thus avoiding interfacial fracture and resulting in excellent adhesion after foam curing.

[0093] The above-mentioned (meth)acrylic acid ester copolymer is preferably a block copolymer, and more preferably an ABA block copolymer in which the compatible parts are polymer block A and the incompatible parts are polymer block B. Furthermore, it is preferable that the first polymer portion is the incompatible part and the second polymer portion is the compatible part, with the first polymer portion being polymer block B and the second polymer portion being polymer block A. By using such an ABA block copolymer as the acrylic resin, in the case of a sea-island structure in which the compatible parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the sea and the incompatible parts of the (meth)acrylic acid ester copolymer are the islands, the island portion can be reduced. Also, in the case of a sea-island structure in which the incompatible parts of the (meth)acrylic acid ester copolymer are the sea and the compatible parts of the cured epoxy resin and the (meth)acrylic acid ester copolymer are the islands, or in the case of a sea-island structure in which the (meth)acrylic acid ester copolymer is the sea and the cured epoxy resin is the islands, the sea portion can be reduced.

[0094] Furthermore, the (meth)acrylic acid ester copolymer may be a modified product in which the above-mentioned polar group is introduced into a part of the first polymer portion or the second polymer portion.

[0095] The Tg of the first polymer portion contained in the above (meth)acrylic acid ester copolymer is 10°C or lower, and can be in the range of -150°C or higher and 10°C or lower, more particularly in the range of -130°C or higher and 0°C or lower, and especially in the range of -110°C or higher and -10°C or lower.

[0096] Furthermore, the Tg of the first polymer portion can be calculated using the following formula, based on the Tg(K) of each homopolymer listed in "POLYMERHANDBOOK Third Edition" (published by John Wiley & Sons, Inc.). 1 / Tg(K)=W1 / Tg1+W2 / Tg2+····+W n / Tg n W n : Mass fraction of each monomer Tgn :This is the Tg(K) of the homopolymer of each monomer, and you can use publicly available values ​​such as those found in the Polymer Handbook (3rd Ed., J. Brandrup and E. Himmergut, WILEY INTERSCIENCE). The same applies to the Tg of the second polymer portion, which will be discussed later.

[0097] The first polymer portion included in the above (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but a homopolymer is preferred. The monomer and polymer components constituting the first polymer portion may be any monomer and polymer components that can obtain a first polymer portion with a predetermined Tg, and examples include acrylic acid ester monomers such as butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and methyl acrylate, other monomers such as vinyl acetate, acetal, and urethane, polar group-containing monomers including the polar group mentioned above, and copolymers such as EVA.

[0098] The Tg of the second polymer portion contained in the above (meth)acrylic acid ester copolymer is 20°C or higher, and can be within the range of 20°C to 150°C, more particularly within the range of 30°C to 150°C, and especially within the range of 40°C to 150°C.

[0099] Furthermore, the second polymer portion included in the (meth)acrylic acid ester copolymer may be a homopolymer or a copolymer, but a homopolymer is preferred. The monomer component constituting the second polymer portion may be any monomer component that can obtain a second polymer portion with a predetermined Tg, and examples include acrylic acid ester monomers such as methyl methacrylate, other monomers such as acrylamide, styrene, vinyl chloride, amide, acrylonitrile, cellulose acetate, phenol, urethane, vinylidene chloride, methylene chloride, methacrylonitrile, and polar group-containing monomers including the polar group mentioned above.

[0100] A specific example of a (meth)acrylic acid ester copolymer having the above-mentioned first polymer portion and second polymer portion is the above-mentioned MMA-BA-MMA copolymer.

[0101] The acrylic resin content is, for example, 1 part by mass or more, 3 parts by mass or more, 5 parts by mass or more, 7 parts by mass or more, or 10 parts by mass or more, when the total resin components in the first adhesive layer are considered to be 100 parts by mass. If the acrylic resin content is within the above range, good adhesion after foam curing is likely to be achieved. On the other hand, the acrylic resin content is, for example, 60 parts by mass or less, when the total resin components in the first adhesive layer are considered to be 100 parts by mass, 50 parts by mass or less, 40 parts by mass or less, 35 parts by mass or less, or 30 parts by mass or less. If the acrylic resin content is within the above range, it is possible to suppress the relatively low content of the first epoxy resin and the second epoxy resin, and to balance blocking resistance and adhesion after foam curing.

[0102] (iii) Hardener The curing agent in this disclosure is appropriately selected depending on the type of curable adhesive. If the curable adhesive is, for example, an epoxy resin adhesive, then a curing agent commonly used for epoxy resin adhesives can be used. The curing agent is preferably solid at 23°C. A curing agent that is solid at 23°C has a longer storage stability (pot life) compared to a curing agent that is liquid at 23°C. The curing agent may also be a latent curing agent. Furthermore, the curing agent may be one that undergoes a curing reaction by heat, or one that undergoes a curing reaction by light. In addition, the curing agent may be used alone or two or more types may be used.

[0103] The reaction initiation temperature of the curing agent is, for example, 110°C or higher, and may also be 130°C or higher. If the reaction initiation temperature is within the above range, it is possible to suppress the early initiation of the reaction and the occurrence of curing while the resin components are still flexible and fluid, thereby making it easier to obtain uniform curing. On the other hand, the reaction initiation temperature of the curing agent is, for example, 200°C or lower. If the reaction initiation temperature is within the above range, the degradation of the resin components can be suppressed. In addition to epoxy resin, if a resin with high heat resistance such as phenolic resin is used, the degradation of the resin components is less, so the reaction initiation temperature of the curing agent may be, for example, 300°C or lower. The reaction initiation temperature of the curing agent is determined by differential scanning calorimetry (DSC).

[0104] Specific examples of curing agents include imidazole-based curing agents, phenol-based curing agents, amine-based curing agents, acid anhydride-based curing agents, isocyanate-based curing agents, and thiol-based curing agents.

[0105] Examples of imidazole-based curing agents include imidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-isopropylimidazole, 2-phenylimidazole, carboxylate salts of imidazole compounds, and adducts with epoxy compounds. Furthermore, it is preferable that the imidazole-based curing agent has hydroxyl groups. Because crystallization occurs through hydrogen bonding between hydroxyl groups, the reaction initiation temperature tends to be high.

[0106] Examples of phenolic curing agents include phenolic resins. Examples of phenolic resins include resol-type phenolic resins and novolac-type phenolic resins. From the viewpoint of adhesion of the first adhesive layer, phenolic novolac resins with a Tg of 110°C or lower are particularly preferred. A phenolic curing agent and an imidazole-type curing agent may also be used in combination. In this case, it is preferable to use an imidazole-type curing agent as a curing catalyst. Biphenyl-type phenolic resins are preferred from the viewpoint of heat resistance. Furthermore, the phenolic resin may be a resin in which the phenol nucleus has been modified. By modifying the phenol nucleus, for example, heat resistance can be further improved.

[0107] Examples of amine-based curing agents include aliphatic amines such as diethylenetriamine (DETA), triethylenetetramine (TETA), and metaxylylenediamine (MXDA); aromatic amines such as diaminodiphenylmethane (DDM), m-phenylenediamine (MPDA), and diaminodiphenylsulfone (DDS); alicyclic amines; and polyamidoamines. In addition, dicyandiamide-based curing agents such as dicyandiamide (DICY), organic acid dihydrazide-based curing agents, amine adduct-based curing agents, and ketimine-based curing agents can be used as amine-based curing agents.

[0108] Examples of acid anhydride-based curing agents 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 anhydride (BTDA).

[0109] Examples of isocyanate-based curing agents include blocked isocyanates.

[0110] Examples of thiol-based curing agents include ester-bonded thiol compounds, aliphatic ether-bonded thiol compounds, and aromatic ether-bonded thiol compounds.

[0111] The curing agent content is, for example, 1 part by mass or more and 40 parts by mass or less, when the resin component contained in the first adhesive layer is considered to be 100 parts by mass. For example, when an imidazole-based curing agent is used as the main component of the curing agent, the curing agent content is preferably, for example, 1 part by mass or more and 15 parts by mass or less, when the resin component contained in the first adhesive layer is considered to be 100 parts by mass. On the other hand, when a phenol-based curing agent is used as the main component of the curing agent, the curing agent content is preferably, for example, 5 parts by mass or more and 40 parts by mass or less, when the resin component contained in the first adhesive layer is considered to be 100 parts by mass. Note that using an imidazole-based curing agent or a phenol-based curing agent as the main component of the curing agent means that the mass proportion of the imidazole-based curing agent or the phenol-based curing agent is the largest in the curing agent.

[0112] (b) foaming agent The foaming agent in this disclosure is a thermally expandable microcapsule.

[0113] The thermally expandable microcapsules preferably have a thermally expandable agent such as a hydrocarbon as the core and a resin such as an acrylonitrile copolymer as the shell.

[0114] The foaming initiation temperature of the foaming agent is preferably above the softening temperature of the main component of the curable adhesive, such as epoxy resin, and below the activation temperature of the curing reaction of the main component of the curable adhesive, such as epoxy resin. The foaming initiation temperature of the foaming agent is, for example, 70°C or higher, and may also be 100°C or higher. If the foaming initiation temperature is within the above range, the reaction will start early, suppressing foaming that occurs when the flexibility and fluidity of the resin component are low, and making it easier to obtain uniform foam. On the other hand, the foaming initiation temperature of the foaming agent is, for example, 210°C or lower. If the foaming initiation temperature is within the above range, degradation of the resin component can be suppressed.

[0115] The softening temperature of the main component of curing adhesives such as epoxy resins is measured by the ring-and-ball method in accordance with JIS K7234:1986.

[0116] The average particle size of the foaming agent may be, for example, 10 μm or more, 13 μm or more, or 17 μm or more. Furthermore, the average particle size of the foaming agent is preferably less than or equal to the thickness of the first adhesive layer of the foamed adhesive sheet, for example, 44 μm or less, 30 μm or less, or 24 μm or less.

[0117] The average particle size of the foaming agent is the particle size at 50% of the integrated particle size distribution determined by laser diffraction scattering. Furthermore, when measuring the average particle size of the foaming agent, the first adhesive layer is dissolved in a solvent to separate the foaming agent. The solvent is not particularly limited as long as it can dissolve components other than the foaming agent contained in the first adhesive layer, and can be appropriately selected depending on the type of curable adhesive contained in the first adhesive layer. For example, a solvent used in the adhesive composition used to form the first adhesive layer can be used. Specifically, methyl ethyl ketone, ethyl acetate, toluene, etc., can be used.

[0118] The foaming agent content is, for example, 0.5 parts by mass or more per 100 parts by mass of resin component in the first adhesive layer, and may be 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, 13 parts by mass or more, or 15 parts by mass or more. If the foaming agent content is within the above range, sufficient adhesion of the first adhesive layer after foam curing can be obtained. On the other hand, the foaming agent content is, for example, 30 parts by mass or less per 100 parts by mass of resin component in the first adhesive layer, and may be 25 parts by mass or less, or 20 parts by mass or less. If the foaming agent content is within the above range, the relatively low content of thermosetting resin can be suppressed, and sufficient adhesion of the first adhesive layer after foam curing can be obtained. Specifically, the foaming agent content is, for example, 0.5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of resin component in the first adhesive layer, but may also be 2 parts by mass or more and 30 parts by mass or less, 3 parts by mass or more and 25 parts by mass or less, 4 parts by mass or more and 25 parts by mass or less, 5 parts by mass or more and 25 parts by mass or less, 13 parts by mass or more and 20 parts by mass or less, or 15 parts by mass or more and 20 parts by mass or less.

[0119] (c) Other ingredients In this disclosure, the first adhesive layer may contain only epoxy resin and acrylic resin as resin components, or it may further contain other resins, for example, when the curable adhesive is an epoxy resin-based adhesive.

[0120] The total ratio of the primary epoxy resin, secondary epoxy resin, and acrylic resin to the resin component contained in the first adhesive layer is, for example, 70% by mass or more, may be 80% by mass or more, may be 90% by mass or more, or may be 100% by mass.

[0121] The resin component content in the first adhesive layer is, for example, 60% by mass or more, may be 70% by mass or more, may be 80% by mass or more, or may be 90% by mass or more.

[0122] The first adhesive layer may optionally 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, or a colorant. Examples of silane coupling agents include epoxy-based silane coupling agents. Examples of fillers include inorganic fillers such as calcium carbonate, aluminum hydroxide, magnesium hydroxide, antimony trioxide, zinc borate, molybdenum compounds, and titanium dioxide. Examples of antioxidants include phenolic antioxidants and sulfur-based antioxidants.

[0123] (2) Morphology of the first adhesive layer The first adhesive layer can be foamed at a foaming ratio of, for example, 1.5 times or more and 15 times or less. The foaming ratio may also be, for example, 3.5 times or more, 4 times or more, or 4.5 times or more. Alternatively, the foaming ratio may also be, for example, 9 times or less, 8.5 times or less, or 8 times or less. If the foaming ratio is too low or too high, the adhesive strength after foaming and curing may decrease.

[0124] Here, the expansion ratio can be calculated using the following formula. Foaming ratio (times) = Thickness of the first adhesive layer after foaming and curing / Thickness of the first adhesive layer before foaming and curing

[0125] The thickness of the first adhesive layer is not particularly limited, but is preferably greater than or equal to the average particle size of the foaming agent, for example, 10 μm or more, but may be 15 μm or more, or 20 μm or more. If the thickness of the first adhesive layer is within the above range, sufficient adhesion and adhesion after foam curing can be obtained. On the other hand, the thickness of the first adhesive layer is, for example, 200 μm or less, but may be 150 μm or less, or 100 μm or less. If the thickness of the first adhesive layer is within the above range, deterioration of the surface quality can be suppressed. Specifically, the thickness of the first adhesive layer is 10 μm or more and 200 μm or less, may be 15 μm or more and 150 μm or less, or 20 μm or more and 100 μm or less.

[0126] The thickness of the first adhesive layer is measured from a cross-section in the thickness direction of the foamed adhesive sheet observed by a scanning electron microscope (SEM), and is the average of the thicknesses of 10 randomly selected locations. The same method is used to measure the thickness of each layer.

[0127] The first adhesive layer may be a continuous layer or a discontinuous layer. Examples of discontinuous layers include patterns such as stripes and dots. The surface of the first adhesive layer may also have an uneven shape such as an embossed surface.

[0128] The first adhesive layer can be formed, for example, by applying an adhesive composition containing the above-mentioned curable adhesive and foaming agent, and then removing the solvent. Examples of application methods include roll coating, reverse roll coating, transfer roll coating, gravure coating, gravure reverse coating, comma coating, rod coating, blade coating, bar coating, wire bar coating, die coating, lip coating, dip coating, and the like.

[0129] The adhesive composition may or may not contain a solvent. In this specification, "solvent" has a broad meaning, including not only a strict solvent (a solvent that dissolves the solute) but also a dispersion medium. Furthermore, any solvent contained in the adhesive composition is removed by volatilization when the adhesive composition is applied and dried to form the first adhesive layer.

[0130] Adhesive compositions can be obtained by mixing the above-mentioned components and kneading and dispersing them as necessary. Suitable mixing and dispersion methods include general kneading and dispersing machines such as two-roll mills, three-roll mills, pebble mills, thron mills, Szegvari attritors, high-speed impeller dispersers, high-speed stone mills, high-speed impact mills, despersers, high-speed mixers, ribbon blenders, conespers, intensive mixers, tumblers, blenders, despersers, homogenizers, and ultrasonic dispersers.

[0131] 3.Second adhesive layer In the foamed adhesive sheet of this disclosure, it is preferable that the second adhesive layer is positioned on the side opposite to the substrate of the second gas barrier layer. The second adhesive layer can protect the second gas barrier layer. Therefore, for example, when the foamed adhesive sheet is placed between the first member and the second member, peeling of the second gas barrier layer can be suppressed.

[0132] The second adhesive layer contains a curable adhesive. The curable adhesive is the same as the curable adhesive described in section "2. First Adhesive Layer" above. The curable adhesive contained in the first adhesive layer and the curable adhesive contained in the second adhesive layer may be the same or different.

[0133] The second adhesive layer may further contain a foaming agent. If both the first and second adhesive layers contain a curable adhesive and a foaming agent, the adhesion of the first adhesive layer after foaming and curing and the adhesion of the second adhesive layer after foaming and curing can be improved. The foaming agent is the same as the foaming agent described in section "2. First Adhesive Layer" above. The foaming agent contained in the first adhesive layer and the foaming agent contained in the second adhesive layer may be the same or different.

[0134] Other components contained in the second adhesive layer, the foaming ratio of the second adhesive layer, the thickness of the second adhesive layer, and the method of forming the second adhesive layer are the same as those described in section "2. First Adhesive Layer" above.

[0135] 4.Base material The substrate in this disclosure is preferably in the form of a sheet. The substrate may have a single-layer structure or a multi-layer structure. Furthermore, the substrate may or may not have a porous structure inside.

[0136] Examples of substrates include resin substrates and nonwoven fabrics.

[0137] Examples of resins included in the resin substrate include polyester resin, polycarbonate, polyarylate, polyurethane, polyamide resin, polyimide resin, polysulfone resin, polyetherketone resin, polyolefin resin, polyphenylene sulfide (PPS), and modified polyphenylene oxide. Examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyester. Examples of polyamide resins include polyamide and polyetheramide. Examples of polyimide resins include polyimide, polyetherimide, and polyamideimide. Examples of polysulfone resins include polysulfone and polyethersulfone. Examples of polyetherketone resins include polyetherketone and polyetheretherketone. Examples of polyolefin resins include polyethylene and polypropylene. Liquid crystal polymer (LCP) may also be used as the resin. The glass transition temperature of the resin is, for example, 80°C or higher, may be 140°C or higher, or may be 200°C or higher.

[0138] Examples of nonwoven fabrics include those containing fibers such as cellulose fibers, polyester fibers, nylon fibers, aramid fibers, polyphenylene sulfide fibers, liquid crystal polymer fibers, glass fibers, metal fibers, and carbon fibers.

[0139] In particular, the substrate is preferably heat-resistant and insulating, and more preferably has good adhesion to the first and second gas barrier layers. Good adhesion between the substrate and the first and second gas barrier layers eliminates the need to place a primer layer to improve adhesion, as will be described later, and allows for a thinner overall thickness of the foamed adhesive sheet. As such a substrate, a substrate containing at least one selected from the group consisting of polyester resin, polyamide resin, polyimide resin, polypropylene, and polyethylene is preferably used. In particular, the substrate is preferably polyester resin, and more preferably polyethylene naphthalate (PEN).

[0140] The substrate may be surface-treated to improve adhesion with the first or second gas barrier layer.

[0141] The thickness of the substrate is not particularly limited and may be, for example, 2 μm or more and 200 μm or less, 5 μm or more and 100 μm or less, or 9 μm or more and 50 μm or less.

[0142] 5. Other configurations (1) Primer layer A primer layer may be placed between the substrate and the first gas barrier layer, between the substrate and the second gas barrier layer, between the first gas barrier layer and the first adhesive layer, or between the second gas barrier layer and the second adhesive layer to improve adhesion.

[0143] (2) Separator The foamed adhesive sheet in this disclosure may have a first separator on the side of the first adhesive layer opposite to the substrate, and may have a second separator on the side of the second adhesive layer opposite to the substrate.

[0144] If the foamed adhesive sheet has a separator, the separator should be peeled off the foamed adhesive sheet before placing it between the first and second members.

[0145] The separator is not particularly limited as long as it can be peeled off from the adhesive layer, and it can have sufficient strength to protect the adhesive layer. Examples of such separators include release films and release paper. The separator may have a single-layer structure or a multi-layer structure.

[0146] Examples of single-layer separators include fluororesin-based films.

[0147] Furthermore, examples of multilayer separators include laminates having release layers on one or both sides of a base layer. Examples of base layers include resin films such as polypropylene, polyethylene, and polyethylene terephthalate, and papers such as fine paper, coated paper, and impregnated paper. The material of the release layer is not particularly limited as long as it has release properties, and examples include silicone compounds, organic compound-modified silicone compounds, fluorine compounds, amino alkyd compounds, melamine compounds, acrylic compounds, polyester compounds, and long-chain alkyl compounds. These compounds can be used in emulsion, solvent, or solvent-free forms.

[0148] The first separator and the second separator may be the same or different. In particular, when the first adhesive layer is substantially non-adhesive and the second adhesive layer is adhesive, it is preferable that the first separator has heavy peelability and the second separator has light peelability. For example, when inserting the second member with the foamed adhesive sheet into the hole of the first member after placing the foamed adhesive sheet on the second member, the adhesion between the second adhesive layer of the foamed adhesive sheet and the first adhesive layer of the foamed adhesive sheet can be improved during insertion, as can the adhesion between the second member and the foamed adhesive sheet and the insertability of the second member with the foamed adhesive sheet. In this case, since the second separator will be the first to peel off, having the first separator have heavy peelability and the second separator has light peelability makes it easier to peel off the second separator than the first separator.

[0149] Furthermore, "light peeling" and "heavy peeling" refer to the degree of force required to separate the first and second separators from the first and second adhesive layers, respectively. Light peeling means that the peeling force is less than that of heavy peeling.

[0150] (3) Protective layer As shown in Figure 1, if the foamed adhesive sheet 10 has a first adhesive layer 1, a first gas barrier layer 2, a substrate 3, and a second gas barrier layer 4 in this order, and does not have a second adhesive layer 5, then, although not shown, a protective layer to protect the second gas barrier layer may be placed on the side of the second gas barrier layer 4 opposite to the substrate 3.

[0151] 6. Physical properties of foamed adhesive sheets (1) Oxygen permeability In the foamed adhesive sheet described herein, the oxygen permeability is 2 cc / (m²). 2 (day·atm) or less is preferable, and 1.5cc / (m 2 (day·atm) or less is more preferable, 1cc / (m 2 A value of less than or equal to (day·atm) is even more preferable. If the oxygen permeability is within the above range, the oxidative decomposition of the substrate at high temperatures can be further suppressed.

[0152] Oxygen permeability shall be measured in accordance with JIS K7126:2006, using an oxygen permeability measuring device under measurement conditions of 23°C and 90% RH. The "OX-TRAN" oxygen permeability measuring device manufactured by Mocon Corporation may be used. When measuring oxygen permeability, if the foamed adhesive sheet has a separator, the separator shall be removed before measurement.

[0153] (2) Water vapor transmission In the foamed adhesive sheet described herein, the water vapor transmission rate is 1.6 g / (m²). 2 • day) or less is preferable, and 1.3 g / (m 2 • day) or less is more preferable, 1.0 g / (m 2 A value of less than or equal to the following is even more preferable. If the water vapor permeability is within the above range, the first and second adhesive layers can be protected from moisture by winding the foamed adhesive sheet into a roll, and the deterioration of the foaming properties can be further suppressed.

[0154] Water vapor transmission rate shall be measured in accordance with JIS K7129-2:2019, using a water vapor transmission rate measuring device under measurement conditions of 40°C and 100% RH. The "Permatran" water vapor transmission rate measuring device manufactured by Mocon Corporation can be used. When measuring water vapor transmission rate, if the foamed adhesive sheet has a separator, the separator should be removed before measurement.

[0155] (3) Tuck In the foamed adhesive sheet of this disclosure, it is preferable that both the first adhesive layer and the second adhesive layer are substantially non-tack-free, or that one of the first adhesive layer and the second adhesive layer is substantially non-tack-free and the other is tacky.

[0156] When both the first and second adhesive layers are substantially non-tack-free, a foamed adhesive sheet with good slipperiness and blocking resistance can be obtained. Therefore, the handling and workability of the foamed adhesive sheet can be improved. Specifically, the foamed adhesive sheet can be smoothly inserted into the gap between the first and second members, or, if the first member has holes or grooves, the second member can be smoothly inserted into the gap after the foamed adhesive sheet has been placed in the holes or grooves of the first member.

[0157] On the other hand, if one of the first adhesive layer and the second adhesive layer is substantially non-adhesive (tack-free) and the other is adhesive (tacky), for example, if the first adhesive layer is substantially non-adhesive (tack-free) and the second adhesive layer is adhesive (tacky), then the second adhesive layer can be made to have good adhesion to the second member. Specifically, when the surface of the second adhesive layer of the foamed adhesive sheet is attached to the second member and the second member with the foamed adhesive sheet attached is inserted into a hole or groove of the first member, the adhesiveness of the second adhesive layer allows the surface of the second adhesive layer of the foamed adhesive sheet to be attached to the second member by utilizing the adhesiveness of the second adhesive layer, thereby improving the adhesion of the second adhesive layer to the second member. As a result, when inserting the second member with the foamed adhesive sheet attached into a hole or groove of the first member, peeling or displacement of the foamed adhesive sheet can be suppressed.

[0158] Furthermore, in the above case, the second adhesive layer has adhesive properties, which allows for a second adhesive layer with good reworkability. Therefore, for example, when attaching the surface of the second adhesive layer of a foamed adhesive sheet to a second member by utilizing the adhesive properties of the second adhesive layer as described above, the misalignment of the foamed adhesive sheet can be corrected.

[0159] Furthermore, in the above case, the non-adhesive nature of the first adhesive layer allows for a first adhesive layer with good sliding properties. Therefore, for example, when inserting a second member with a foamed adhesive sheet attached into a hole or groove of the first member as described above, the second member with the foamed adhesive sheet attached can be inserted smoothly, improving insertability. This suppresses peeling and displacement of the foamed adhesive sheet. Also, when aligning the first and second members by moving the second member relative to the first member, the second member can be moved smoothly relative to the first member while it is inserted into a hole or groove of the first member, making alignment easier.

[0160] Furthermore, in the above case, as described above, the second adhesive layer has excellent adhesion to the second member, and the first adhesive layer has excellent slipperiness, which can suppress peeling and displacement of the foamed adhesive sheet. Therefore, it is possible to suppress the decrease in adhesiveness of the foamed adhesive sheet after foaming and curing due to peeling and displacement of the foamed adhesive sheet, and to reduce the variation in adhesive strength of the foamed adhesive sheet after foaming and curing due to peeling and displacement of the foamed adhesive sheet.

[0161] Furthermore, in the above case, because the second adhesive layer is tacky, for example, when the second adhesive layer is formed by a transfer method, lifting of the second adhesive layer can be suppressed. Moreover, as will be described later, if the second separator is placed on the side of the second adhesive layer opposite to the first adhesive layer, the tackiness of the second adhesive layer allows the second separator to be easily peeled off, improving workability.

[0162] When both the first and second adhesive layers are substantially non-adhesive, specifically, the tack of the first and second adhesive layers is preferably less than 0.1 N, may be 0.05 N or less, or 0.02 N or less. By having the tack of the first and second adhesive layers within the above range, the first and second adhesive layers can be made substantially non-adhesive, resulting in a foamed adhesive sheet with good slipperiness and blocking resistance. The lower limits of the tack of the first and second adhesive layers are not particularly limited and may be 0 N.

[0163] Furthermore, if the first adhesive layer is substantially non-tack-free and the second adhesive layer is tacky, specifically, the tack of the first adhesive layer is preferably less than 0.1N, and the tack of the second adhesive layer is preferably 0.1N or more and 5N or less.

[0164] In the above case, the tack of the first adhesive layer is preferably less than 0.1 N, may be 0.05 N or less, or 0.02 N or less. By having the tack of the first adhesive layer within the above range, the first adhesive layer can be made substantially non-adhesive, resulting in a foamed adhesive sheet with good slipperiness and blocking resistance. The lower limit of the tack of the first adhesive layer is not particularly limited and may be 0 N.

[0165] Furthermore, in the above case, the tack of the second adhesive layer is preferably 0.1N or higher, may be 0.3N or higher, or 0.5N or higher. Also, the tack of the second adhesive layer is preferably 5N or lower, may be 4N or lower, or 3N or lower. By having the tack of the second adhesive layer within the above range, when the surface of the second adhesive layer of the foamed adhesive sheet is attached to the second member using the tack of the second adhesive layer, the adhesion between the second adhesive layer and the second member can be improved. This prevents the foamed adhesive sheet from peeling off or shifting due to poor adhesion between the second adhesive layer and the second member when inserting the second member with the foamed adhesive sheet attached into a hole or groove in the first member. As a result, it is possible to prevent a decrease in the adhesion of the first and second adhesive layers after foam curing, and to prevent variations in adhesive strength. In addition, having the tack of the second adhesive layer within the above range improves the reworkability of the second adhesive layer.

[0166] Here, the tack of the adhesive layer is measured by a probe tack test. Specifically, a cylindrical stainless steel probe with a diameter of 5 mm is pressed onto the surface of the adhesive layer of the foamed adhesive sheet at a temperature of 25°C, with a load of 10.0 gf and a speed of 30 mm / min. After holding for 1.0 second, it is peeled off at a speed of 30 mm / min, and the load at which it is peeled off is measured. This measurement is performed five times, and the average value is taken as the tack. For example, the RHESCA tacking tester "TAC-II" can be used as a probe tack tester.

[0167] One way to control the tack of an adhesive layer is to adjust its composition. Specifically, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer can be reduced by using an epoxy resin that is solid at room temperature or a curing agent that is solid at room temperature. On the other hand, in an adhesive layer containing epoxy resin and a curing agent, using an epoxy resin that is liquid at room temperature or a curing agent that is liquid at room temperature tends to increase the tackiness of the adhesive layer. Furthermore, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer can be reduced by including an epoxy resin with a high softening temperature or an epoxy resin with a large weight-average molecular weight. For example, the tackiness of the adhesive layer can be reduced by including multiple types of epoxy resins with different softening temperatures in the adhesive layer, that is, by including one epoxy resin and another epoxy resin whose softening temperature is 25°C or higher and at least 10°C higher than the softening temperature of the first epoxy resin. Furthermore, the tackiness of the adhesive layer can be reduced by, for example, including multiple epoxy resins with different weight-average molecular weights in the adhesive layer; that is, by including one epoxy resin and another epoxy resin having a weight-average molecular weight of 370 or more and being at least 300 greater than the weight-average molecular weight of the first epoxy resin. More specifically, in an adhesive layer containing epoxy resin and a curing agent, as described above, the tackiness of the adhesive layer can be reduced by including a primary epoxy resin with a low softening temperature and low molecular weight, and a secondary epoxy resin with a high softening temperature and high molecular weight. On the other hand, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer tends to increase when an epoxy resin with a low softening temperature or an epoxy resin with a small weight-average molecular weight is included. Also, in an adhesive layer containing epoxy resin and a curing agent, the tackiness of the adhesive layer can be reduced by including an acrylic resin that is compatible with the epoxy resin, as described above. In addition, the tackiness of the adhesive layer tends to increase when a tackifier is added to the adhesive layer.While using a liquid curing agent at room temperature tends to increase tackiness, it may reduce storage stability. Therefore, it is preferable to adjust the tack of the adhesive layer by adjusting the properties and type of components other than the curing agent, such as epoxy resin.

[0168] Here, "adhesion" is a concept included in "bonding." Adhesion is sometimes used to mean a temporary bonding phenomenon, while bonding is sometimes used to mean a substantially permanent bonding phenomenon (Iwanami Shoten Dictionary of Physics and Chemistry, 5th Edition). "Adhesion" and "adhesion force" refer to the property of bonding upon pressure and the adhesive force at that time.

[0169] In this specification, "adhesion of the adhesive layer" and "adhesion strength of the adhesive layer" refer to the tackiness and adhesion strength of the adhesive layer before curing, unless otherwise specified. Furthermore, in this specification, "adhesion of the adhesive layer" and "adhesion strength of the adhesive layer" refer to the tackiness and adhesion strength of the adhesive layer after curing, unless otherwise specified.

[0170] (4) Shape retention The foamed adhesive sheet in this disclosure preferably has good shape retention. The bending moment according to JIS P8125-2:2017 corresponding to ISO 2493 is, for example, 0.1 gf·cm or more, and may be 1 gf·cm or more. On the other hand, the above bending moment may be, for example, less than 40 gf·cm, and may be less than 30 gf·cm. Conventionally, in foamed adhesive sheets, it is common to increase the bending moment to improve shape retention and insertability into narrow gaps. In contrast, the inventors of this disclosure have found that shape retention can be ensured by designing the shape, and that a high bending moment has other disadvantages, and that, considering other characteristics, it is preferable for the bending moment to be within the above range. If the bending moment is smaller than the above range, it may be difficult to maintain the shape even with techniques such as folding. Also, if the bending moment is larger than the above range, the shape will return to its original state after bending, so it is necessary to heat the sheet or make creases at the folds during bending. Heating can reduce the sheet life, and creating streaks may decrease the insulation properties in those areas.

[0171] (5) Adhesiveness The foamed adhesive sheet in this disclosure preferably has high adhesiveness after foaming and curing. The tensile shear adhesive strength (adhesive strength) according to JIS K6850:1999, which corresponds to ISO 4587:1995, may be, for example, 1.50 MPa or more, 1.80 MPa or more, or 2.10 MPa or more at 23°C. Furthermore, the above tensile shear adhesive strength (adhesive strength) may be, for example, 0.50 MPa or more, 0.75 MPa or more, or 1.00 MPa or more at 130°C. For example, in the case of high-strength acrylic foam adhesive tape that does not require heating, the tensile shear adhesive strength (adhesive strength) is about 1 MPa to 2 MPa at room temperature and has no heat resistance at 200°C. Therefore, if the above tensile shear adhesive strength (adhesive strength) is within the above range at 23°C, there is an advantage in terms of strength. Furthermore, if the tensile shear adhesive strength (adhesive strength) is within the above range at 130°C, it can be applied to applications requiring heat resistance around automobile engines and similar applications.

[0172] (6) Insulation The foamed adhesive sheet in this disclosure preferably has high electrical insulation properties after foaming and curing. After foaming and curing of the foamed adhesive sheet, the dielectric breakdown voltage according to JIS C2107:2011 corresponding to IEC 60454-2 is preferably, for example, 3kV or higher, and more preferably 5kV or higher. Having the dielectric breakdown voltage within the above range makes it possible to apply it for rust prevention and around copper wires. Furthermore, after foaming and curing of the foamed adhesive sheet, the thermal conductivity is preferably, for example, 0.1W / mK or higher, and more preferably 0.15W / mK or higher. Having the thermal conductivity within the above range makes it possible to miniaturize the components and accelerate the curing reaction during heating.

[0173] 7. Other aspects of foamed adhesive sheets The thickness of the foamed adhesive sheet in this disclosure is, for example, 10 μm or more and 1000 μm or less, and may be 20 μm or more and 200 μm or less.

[0174] The applications of the foamed adhesive sheet in this disclosure are not particularly limited. The foamed adhesive sheet in this disclosure can be used, for example, to bond two members by placing the foamed adhesive sheet between them and then heating and curing the foamed adhesive sheet. In particular, the foamed adhesive sheet in this disclosure is preferably used to bond metal members together.

[0175] B.Goods The article in this disclosure is an article having a first member, a second member, and an adhesive member disposed between the first member and the second member, wherein the adhesive member has, in this order, a first curable adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, and the first curable adhesive layer contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[0176] Figure 6(a) is a process diagram showing an example of an article in this disclosure. The article 20 shown in Figure 6(a) has a first member 21, a second member 21, and an adhesive member 23 positioned between the first member 21 and the second member 22. The adhesive member 23 has, in this order, a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, and a second gas barrier layer 4. The first cured adhesive layer 11 contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, the foaming agent being a thermally expandable microcapsule.

[0177] Figure 6(b) is a process diagram illustrating another example of an article in the present disclosure. The article 20 shown in Figure 6(a) comprises a first member 21, a second member 21, and an adhesive member 23 positioned between the first member 21 and the second member 22. The adhesive member 23 comprises, in this order, a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second cured adhesive layer 15. The first cured adhesive layer 11 and the second cured adhesive layer 15 each contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, the foaming agent being a thermally expandable microcapsule.

[0178] The articles in this disclosure can be manufactured using the foamed adhesive sheet described above. The articles in this disclosure will have the same effects as the foamed adhesive sheet described above.

[0179] The articles in this disclosure are described below.

[0180] 1. Adhesive material The adhesive member in this disclosure is positioned between a first member and a second member and has a first cured adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer in this order. Alternatively, the adhesive member may have a first cured adhesive layer, a first gas barrier layer, a substrate, a second gas barrier layer, and a second adhesive layer in this order.

[0181] In an adhesive member, the adhesive layer located on the first member side may be either the first adhesive layer or the second adhesive layer. Similarly, in an adhesive member, the adhesive layer located on the second member side may be either the first adhesive layer or the second adhesive layer.

[0182] (1) Base material The base material is the same as described in section "A. Foamed Adhesive Sheet 4. Base Material" above.

[0183] (2) First gas barrier layer and second gas barrier layer The first and second gas barrier layers are the same as those described in section A. Foamed Adhesive Sheet 1. First and Second Gas Barrier Layers above.

[0184] (3) First cured adhesive layer The first cured adhesive layer is positioned on the side opposite to the substrate of the first gas barrier layer and contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent. The materials included in the adhesive composition are the same as those of the first adhesive layer described in section "A. Foamed Adhesive Sheet 2. First Adhesive Layer" above.

[0185] The thickness of the first cured adhesive layer is not particularly limited and is set appropriately according to the application. For example, the thickness of the first cured adhesive layer may be 10 μm or more and 1000 μm or less, 20 μm or more and 900 μm or less, or 30 μm or more and 800 μm or less. Sufficient adhesion can be obtained if the thickness of the first cured adhesive layer is within the above range.

[0186] The first curing adhesive layer may be a continuous layer or a discontinuous layer.

[0187] (4) Second cured adhesive layer The adhesive member may have a second cured adhesive layer on the side opposite to the substrate of the second gas barrier layer. The second cured adhesive layer contains a cured product of an adhesive composition containing a curable adhesive. The second cured adhesive layer may also contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent. The materials included in the adhesive composition are the same as the materials for the second adhesive layer described in section "A. Foamed Adhesive Sheet 3. Second Adhesive Layer" above.

[0188] Other aspects of the second cured adhesive layer are the same as those of the first adhesive layer described above.

[0189] If the adhesive composition used for the second curing adhesive layer does not contain a foaming agent, the thickness of the second curing adhesive layer is not particularly limited and is set appropriately according to the application. For example, it may be 10 μm or more and 200 μm or less, 15 μm or more and 150 μm or less, or 20 μm or more and 100 μm or less.

[0190] (5) Other configurations In addition to the above-mentioned substrate, first gas barrier layer, second gas barrier layer, first cured adhesive layer, and second cured adhesive layer, the adhesive member may have other components as needed. The other components are the same as those described in section A. Foamed Adhesive Sheet 5. Other Components above.

[0191] 2. First member and second member The first and second members in this disclosure are appropriately selected according to the application of the article. The material and shape of the first and second members are not particularly limited. Examples of the first and second members include metal members, resin members, and ceramic members. In particular, the first and second members are preferably members that require bonding and insulation. Examples include components of electrical and electronic equipment, specifically the stator core and coil of a stator for a rotating electric machine, the rotor core and coil of a rotor for a rotating electric machine, and the rotor core and permanent magnet of a rotor for a rotating electric machine.

[0192] 3. Method of manufacturing articles The method for manufacturing an article in this disclosure includes, for example, a placement step of placing the above-mentioned foaming adhesive sheet between a first member and a second member, and an bonding step of foaming and curing the foaming adhesive sheet to bond the first member and the second member.

[0193] The method for placing the foam adhesive sheet between the first and second members can be appropriately selected depending on the types of the first and second members. For example, one method is to insert the foam adhesive sheet into the gap between the first and second members, or to place the foam adhesive sheet in a hole or groove of the first member, and then insert the second member into the gap left after placing the foam adhesive sheet in the hole or groove of the first member. Also, for example, if the first member has a hole or groove and the second member is to be placed in the hole or groove of the first member, one method is to use the tack of the second adhesive layer of the foam adhesive sheet to attach the surface of the second adhesive layer of the foam adhesive sheet to the second member, and then place the second member with the foam adhesive sheet attached into the hole or groove of the first member, or to place the foam adhesive sheet in the hole or groove of the first member, use the tack of the second adhesive layer of the foam adhesive sheet to attach the surface of the second adhesive layer of the foam adhesive sheet to the hole or groove of the first member, and then place the second member into the hole or groove of the first member with the foam adhesive sheet attached.

[0194] Heating is preferred as a method for foaming and curing foamed adhesive sheets. The heating method is applicable even when the first and second components are not transparent, such as in metal components. The heating conditions are set appropriately depending on the type of curable adhesive and foaming agent used to form the first and second cured adhesive layers, the type of substrate, etc. The heating temperature is, for example, 130°C or higher and 200°C or lower. The heating time is, for example, 3 minutes or more and 3 hours or less.

[0195] C. Stator for rotating electric machine The stator for a rotating electric machine in this disclosure comprises a stator core, coils arranged in slots of the stator core, and an adhesive member arranged between the stator core and the coils, wherein the adhesive member comprises, in this order, a first curable adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, the first curable adhesive layer contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[0196] Figure 7(a) is a schematic plan view illustrating a stator for a rotating electric machine in this disclosure, and Figures 7(b) and 7(c) are enlarged views of Figure 7(a). As shown in Figures 7(a) to 7(c), the stator 30 for a rotating electric machine includes a stator core 31, coils 33 arranged in slots 32 of the stator core 31, and an adhesive member 34 arranged between the stator core 31 and the coils 33. The adhesive member 34 includes, in this order, a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second cured adhesive layer 15. The first cured adhesive layer 11 and the second cured adhesive layer 15 each contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule. In Figure 7(c), the adhesive member 34 has a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second cured adhesive layer 15 in this order. However, although not shown, the adhesive member 34 may also have the first cured adhesive layer 11, the first gas barrier layer 2, the substrate 3, and the second gas barrier layer 4 in this order.

[0197] The stator for a rotating electric machine in this disclosure can be manufactured using the foamed adhesive sheet described above. The article in this disclosure will have the same effects as the foamed adhesive sheet described above.

[0198] The configuration of the stator for a rotating electric machine in this disclosure will be described below.

[0199] 1. Adhesive material The adhesive members are the same as those described in section B. Articles 1. Adhesive Members above.

[0200] 2. Stator Core The stator core has slots into which the coils are inserted. Since the stator core is similar to a typical stator core, a detailed explanation is omitted here.

[0201] 3. Coil The coil is the same as a typical coil, so we will omit its explanation here.

[0202] 4. Other aspects of stators for rotating electric machines The method for manufacturing a stator for a rotating electric machine in this disclosure includes, for example, a placement step of placing a foamed adhesive sheet between a stator core and coils, and an bonding step of foaming and curing the foamed adhesive sheet and bonding the coils to the stator core.

[0203] Methods for placing a foam adhesive sheet between the stator core and the coil include placing the foam adhesive sheet around the coil and then inserting the coil and foam adhesive sheet into the slots of the stator core; inserting the foam adhesive sheet into the slots of the stator core and then inserting the coil into the slots of the stator core; and inserting the foam adhesive sheet into the slots of the stator core and then inserting the foam adhesive sheet into the slots of the stator core.

[0204] One method for foaming and curing foamed adhesive sheets is heating. The heating conditions are the same as those described in section B. Articles 3. Method for Manufacturing Articles above.

[0205] D. Rotors for rotating electric machines The rotor for a rotating electric machine in this disclosure comprises a rotor core, permanent magnets or coils arranged in slots of the rotor core, and an adhesive member arranged between the rotor core and the permanent magnets or coils, wherein the adhesive member comprises, in this order, a first curing adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer, the first curing adhesive layer contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[0206] Figure 8(a) is a schematic plan view illustrating a rotor for a rotating electric machine in this disclosure, and Figures 8(b) and (c) are enlarged partial views of Figure 8(a). As shown in Figures 8(a) to 8(c), the rotor 40 for a rotating electric machine includes a rotor core 41, permanent magnets 43 arranged in slots 42 of the rotor core 41, and an adhesive member 45 arranged between the rotor core 41 and the permanent magnets 43. The adhesive member 45 includes, in this order, a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second cured adhesive layer 15. The first cured adhesive layer 11 and the second cured adhesive layer 15 each contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule. In Figure 8(c), the adhesive member 45 has a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second cured adhesive layer 15 in this order. However, although not shown, the adhesive member 45 may also have the first cured adhesive layer 11, the first gas barrier layer 2, the substrate 3, and the second gas barrier layer 4 in this order.

[0207] Figure 9(a) is a schematic plan view illustrating a rotor for a rotating electric machine in this disclosure, and Figures 9(b) and (c) are enlarged partial views of Figure 9(a). As shown in Figures 9(a) to 9(c), the rotor 40 for a rotating electric machine includes a rotor core 41, coils 44 arranged in slots 42 of the rotor core 41, and an adhesive member 45 arranged between the rotor core 41 and the coils 44. The adhesive member 45 includes, in this order, a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second cured adhesive layer 15. The first cured adhesive layer 11 and the second cured adhesive layer 15 each contain a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule. In Figure 9(c), the adhesive member 45 has a first cured adhesive layer 11, a first gas barrier layer 2, a substrate 3, a second gas barrier layer 4, and a second cured adhesive layer 15 in this order. However, although not shown, the adhesive member 45 may also have the first cured adhesive layer 11, the first gas barrier layer 2, the substrate 3, and the second gas barrier layer 4 in this order.

[0208] The rotor for a rotating electric machine in this disclosure can be manufactured using the foamed adhesive sheet described above. The article in this disclosure will have the same effects as the foamed adhesive sheet described above.

[0209] The configuration of the rotor for the rotating electric machine in this disclosure will be described below.

[0210] 1. Adhesive material The adhesive members are the same as those described in section B. Articles 1. Adhesive Members above.

[0211] 2. Rotor core The rotor core has slots into which the coils are inserted. The rotor is similar to the rotor core generally used in wound-field motors, so its explanation is omitted here.

[0212] 3. Coil The coil is the same as a typical coil, so we will omit its explanation here.

[0213] 4. Other aspects of rotors for rotating electric machines The rotors for rotating electric machines in this disclosure are, for example, rotors for rotating electric machines used in permanent magnet embedded motors, or rotors for rotating electric machines used in wound field motors.

[0214] The present disclosure provides a method for manufacturing a rotor for a rotating electric machine, comprising: an arrangement step of placing a foamed adhesive sheet between a rotor core and a coil; and an adhesion step of foaming and curing the foamed adhesive sheet to bond the coil to the rotor core.

[0215] Each step in the manufacturing method of the rotor for a rotating electric machine is the same as the steps in the manufacturing method of the stator for a rotating electric machine described above.

[0216] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0217] [Reference example 1] Polyethylene naphthalate (PEN film, manufactured by Toyobo Film Solutions Co., Ltd., Teonex Q51, 100 μm thick) was used as the substrate. A 10 nm thick alumina vapor-deposited film was formed on both sides of the substrate as the first and second gas barrier layers, respectively. This resulted in a barrier film having the first gas barrier layer, the substrate, and the second gas barrier layer in that order.

[0218] [Reference example 2] The substrate used was the same as in Reference Example 1 above.

[0219] [Rating 1] For the barrier film of Reference Example 1 and the substrate of Reference Example 2, dumbbell-shaped test specimens of type 3 as described in JIS K6251:2017 were prepared. The following durability tests were performed on the test specimens. The following tensile tests were performed on the test specimens before and after the durability tests, and the tensile strength and elongation were measured. Five test specimens were used for each test, and the average value of the tensile test results was calculated.

[0220] <Durability Test> • Test environment: 200℃, 500 hours • Equipment: Yamato Scientific Co., Ltd. "DN610"

[0221] <Tensile Test> • Equipment: A&D Corporation tensile testing machine (Tensilon RTF1150-H), contact extensometer (U-4310D) • Tensile speed: 15 mm / min • Distance between gauge marks (distance between extensometer clamps): 20mm • Chuck spacing: 60mm

[0222] [Table 1]

[0223] As shown in Reference Example 2, when gas barrier layers were not placed on both sides of the substrate, the elongation of the substrate after the durability test was very small. This is because the substrate was oxidatively decomposed and hardened at high temperatures. When the elongation of the substrate after the durability test is very small, cracks are more likely to occur. Cracks can lead to a decrease in the insulating properties of the substrate and a decrease in the adhesive properties of the foamed adhesive sheet. In contrast, as shown in Reference Example 1, when gas barrier layers were placed on both sides of the substrate, the elongation of the substrate after the durability test was small, but not as small as in Reference Example 2. Specifically, the elongation of the substrate in Reference Example 1 after the durability test was approximately 1.8 times that of the substrate in Reference Example 2 after the durability test. This is thought to be because the oxidative decomposition of the substrate was suppressed by the gas barrier layer.

[0224] [Example 1] First, an adhesive composition with the following composition was prepared. <Composition of adhesive composition> • Acrylic resin: PMMA-PBuA-PMMA (partially containing acrylamide groups), Tg: -20℃, 120℃, Mw: 150,000 13 parts by mass • Epoxy resin A: Bisphenol A novolac type, solid at room temperature, softening temperature: 70°C, epoxy equivalent: 210 g / eq, Mw: 1300, melt viscosity at 150°C: 0.5 Pa·s, 40 parts by mass Epoxy resin B: BPA phenoxy type, solid at room temperature, softening temperature: 110°C, epoxy equivalent: 8000 g / eq, Mw: 50,000 42 parts by mass • Hardening agent A: α-(hydroxy(or dihydroxy)phenylmethyl)-ω-hydropoly[biphenyl-4,4'-diylmethylene(hydroxy(or dihydroxy)phenylenemethylene)] 6 parts by mass • Curing catalyst: 2-phenyl-4,5-dihydroxymethylimidazole, average particle size: 3 μm, melting point: 230°C, reaction initiation temperature: 145°C to 155°C, active range: 155°C to 173°C (manufactured by Shikoku Chemicals, Inc., 2PHZ-PW) 8 parts by mass • Foaming agent: Thermally expandable microcapsules, average particle size 10 μm to 16 μm, expansion start temperature 123°C to 133°C, maximum expansion temperature 168°C to 178°C, core: hydrocarbon, shell: thermoplastic polymer 13.5 parts by mass • Solvent: Methyl ethyl ketone 150 parts by mass

[0225] Polyethylene naphthalate (PEN film, manufactured by Toyobo Film Solutions Co., Ltd., Teonex Q51, 100 μm thick) was used as the substrate. A 10 nm thick alumina vapor-deposited film was formed on both sides of the substrate as the first and second gas barrier layers, respectively. Next, the adhesive composition was applied to the first gas barrier layer using an applicator to a thickness of 45 μm after coating. Then, it was dried in an oven at 100°C for 3 minutes to form the first adhesive layer. Next, the adhesive composition was applied to the second gas barrier layer using an applicator to a thickness of 45 μm after coating. Then, it was dried in an oven at 100°C for 3 minutes to form the second adhesive layer. As a result, a foamed adhesive sheet was obtained in which the first adhesive layer, first gas barrier layer, substrate, second gas barrier layer, and second adhesive layer were arranged in this order.

[0226] This disclosure provides, for example, the following inventions. [1] It comprises a first adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer in this order. The above first adhesive layer contains a curable adhesive and a foaming agent, The foaming agent is a thermally expandable microcapsule, resulting in a foamed adhesive sheet. [2] The foamed adhesive sheet according to [1], wherein the second adhesive layer has a second adhesive layer on the side of the second gas barrier layer opposite to the substrate, and the second adhesive layer contains a curable adhesive. [3] The foaming adhesive sheet according to [2], wherein the second adhesive layer contains a foaming agent, and the foaming agent is a heat-expandable microcapsule. [4] The oxygen permeability of the above foamed adhesive sheet is 2 cc / (m²). 2 A foamed adhesive sheet as described in any of [1] to [3] below (day·atm). [5] The water vapor permeability of the above foamed adhesive sheet is 1.6 g / (m²). 2 A foamed adhesive sheet as described in any of [1] to [4], which is less than or equal to [day]. [6] A foamed adhesive sheet according to any one of [1] to [5], wherein the thickness of the first gas barrier layer and the thickness of the second gas barrier layer are each 1 nm or more and 10 μm or less. [7] The foamed adhesive sheet described in any of [1] to [6], wherein the foamed adhesive sheet described above is wound into a roll. [8] An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The above adhesive member comprises, in this order, a first curing adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The above-mentioned first cured adhesive layer contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent, An article wherein the foaming agent is a thermally expandable microcapsule. [9] The article according to [8], wherein the adhesive member has a second curing adhesive layer on the side of the second gas barrier layer opposite to the substrate, and the second curing adhesive layer contains a cured product of an adhesive composition containing a curable adhesive.

[10] The article according to [9], wherein the second curing adhesive layer contains a foamed cured product of an adhesive composition comprising the curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[11] The article according to [8] or [9], wherein the thickness of the first gas barrier layer and the thickness of the second gas barrier layer are each 1 nm or more and 10 μm or less.

[12] A stator for a rotating electric machine having a stator core, coils arranged in slots of the stator core, and adhesive members arranged between the stator core and the coils, The above adhesive member comprises, in this order, a first curing adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The above-mentioned first cured adhesive layer contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent, The above-mentioned foaming agent is a thermally expandable microcapsule, used in a stator for a rotating electric machine.

[13] The stator for a rotating electric machine according to

[12] , wherein the adhesive member has a second curing adhesive layer on the side of the second gas barrier layer opposite to the substrate, and the second curing adhesive layer contains a cured product of an adhesive composition containing a curable adhesive.

[14] The stator for a rotating electric machine according to

[13] , wherein the second curing adhesive layer contains a foamed cured product of an adhesive composition comprising the curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

[15] A rotor for a rotating electric machine, comprising a rotor core, permanent magnets or coils arranged in slots of the rotor core, and adhesive members arranged between the rotor core and the permanent magnets or coils, The above adhesive member comprises, in this order, a first curing adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The above-mentioned first cured adhesive layer contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, The above-mentioned foaming agent is a thermally expandable microcapsule, and the rotor is for a rotating electric machine.

[16] The rotor for a rotating electric machine according to

[15] , wherein the adhesive member has a second curing adhesive layer on the side of the second gas barrier layer opposite to the substrate, and the second curing adhesive layer contains a cured product of an adhesive composition containing a curable adhesive.

[17] The rotor for a rotating electric machine according to

[16] , wherein the second curing adhesive layer contains a foamed cured product of an adhesive composition comprising the curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule. [Explanation of Symbols]

[0227] 1 … First adhesive layer 2… First gas barrier layer 3 … Base material 4. Second gas barrier layer 5…Second adhesive layer 10 … Foaming adhesive sheet 11 … First cured adhesive layer 15 … Second cured adhesive layer 20 … Article 21 … First member 22 … Second member 23 … Adhesive member 30 … Stator for rotating electric machine 31 … Stator core 32 … Slot 33 … Coil 34 … Adhesive member 40 … Rotor for rotating electric machine 41 … Rotor core 42 … Slot 43 … Permanent magnet 44 … Coil 45 … Adhesive member

Claims

1. It comprises a first adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer in this order. The first adhesive layer contains a curable adhesive and a foaming agent, The blowing agent is a thermally expandable microcapsule, A foamed adhesive sheet having an oxygen permeability of 2 cc / (m²·day·atm) or less.

2. Having a first adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer in this order, The first adhesive layer contains a curable adhesive and a foaming agent, The blowing agent is a thermally expandable microcapsule, A foamed adhesive sheet having a water vapor permeability of 1.6 g / (m²·day) or less.

3. The foamed adhesive sheet according to claim 1 or 2, wherein the second gas barrier layer has a second adhesive layer on the side opposite to the substrate, and the second adhesive layer contains a curable adhesive.

4. The foaming adhesive sheet according to claim 3, wherein the second adhesive layer contains a foaming agent, and the foaming agent is a heat-expandable microcapsule.

5. The water vapor permeability of the foamed adhesive sheet is 1.6 g / (m²). ２ The foamed adhesive sheet according to claim 1, wherein the number of days is less than or equal to the number of days.

6. The foamed adhesive sheet according to claim 1 or claim 2, wherein the thickness of the first gas barrier layer and the thickness of the second gas barrier layer are each 1 nm or more and 10 μm or less.

7. The foamed adhesive sheet according to claim 1 or claim 2, wherein the foamed adhesive sheet is wound into a roll.

8. An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The adhesive member comprises, in this order, a first cured adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The first cured adhesive layer contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. The blowing agent is a thermally expandable microcapsule, An article having an oxygen permeability of 2 cc / (m²·day·atm) or less for the adhesive member.

9. An article having a first member, a second member, and an adhesive member disposed between the first member and the second member, The adhesive member comprises, in this order, a first cured adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The first cured adhesive layer contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. The blowing agent is a thermally expandable microcapsule, An article having a water vapor permeability of the adhesive member of 1.6 g / (m²·day) or less.

10. The article according to claim 8 or 9, wherein the adhesive member has a second cured adhesive layer on the side of the second gas barrier layer opposite to the substrate, and the second cured adhesive layer contains a cured product of an adhesive composition containing a curable adhesive.

11. The article according to claim 10, wherein the second curing adhesive layer contains a foamed cured product of an adhesive composition comprising the curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

12. The article according to claim 8 or claim 9, wherein the thickness of the first gas barrier layer and the thickness of the second gas barrier layer are each 1 nm or more and 10 μm or less.

13. A stator for a rotating electric machine having a stator core, coils arranged in slots of the stator core, and adhesive members arranged between the stator core and the coils, The adhesive member comprises, in this order, a first cured adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The first cured adhesive layer contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. The blowing agent is a thermally expandable microcapsule, A stator for a rotating electric machine, wherein the oxygen permeability of the adhesive member is 2 cc / (m²·day·atm) or less.

14. A stator for a rotating electric machine, comprising a stator core, coils arranged in slots of the stator core, and adhesive members arranged between the stator core and the coils, The adhesive member comprises, in this order, a first cured adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The first cured adhesive layer contains a foamed cured product of an adhesive composition comprising a curable adhesive and a foaming agent. The blowing agent is a thermally expandable microcapsule, A stator for a rotating electric machine, wherein the water vapor permeability of the adhesive member is 1.6 g / (m²·day) or less.

15. The stator for a rotating electric machine according to claim 13 or claim 14, wherein the adhesive member has a second curing adhesive layer on the side of the second gas barrier layer opposite to the substrate, and the second curing adhesive layer contains a cured product of an adhesive composition containing a curable adhesive.

16. The stator for a rotating electric machine according to claim 15, wherein the second curing adhesive layer contains a foamed cured product of an adhesive composition comprising the curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

17. A rotor for a rotating electric machine, comprising a rotor core, permanent magnets or coils arranged in slots of the rotor core, and adhesive members arranged between the rotor core and the permanent magnets or coils, The adhesive member comprises, in this order, a first cured adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The first cured adhesive layer contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, The blowing agent is a thermally expandable microcapsule, A rotor for a rotating electric machine, wherein the oxygen permeability of the adhesive member is 2 cc / (m²·day·atm) or less.

18. A rotor for a rotating electric machine, comprising a rotor core, permanent magnets or coils disposed in slots of the rotor core, and an adhesive member disposed between the rotor core and the permanent magnets or coils, The adhesive member comprises, in this order, a first cured adhesive layer, a first gas barrier layer, a substrate, and a second gas barrier layer. The first cured adhesive layer contains a foamed cured product of an adhesive composition containing a curable adhesive and a foaming agent, The blowing agent is a thermally expandable microcapsule, A rotor for a rotating electric machine, wherein the water vapor permeability of the adhesive member is 1.6 g / (m²·day) or less.

19. Rotor for a rotating electric machine according to claim 17 or 18, wherein the adhesive member has a second curing adhesive layer on the side of the second gas barrier layer opposite to the substrate, and the second curing adhesive layer contains a cured product of an adhesive composition containing a curable adhesive.

20. The rotor for a rotating electric machine according to claim 19, wherein the second curing adhesive layer contains a foamed cured product of an adhesive composition comprising the curable adhesive and a foaming agent, and the foaming agent is a thermally expandable microcapsule.

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