Adhesive sheet

Abstract

Provided is an adhesive sheet including a base material layer and an adhesive layer that is bonded to an adherend and overlaps at least one face of the base material layer, the adhesive layer containing an epoxy resin and a polyurethane resin having no epoxy group in the molecule.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Japanese Patent Application No. 2024-027589, which is incorporated herein by reference. Technical Field

[0003] This invention relates, for example, to adhesive sheets used in the drive motors of automobiles. Background Technology

[0004] Traditionally, automobile drive motors consist of a rotor and a stator that generates a force to rotate the rotor. The stator has multiple coils, and a Lorentz force is generated by creating a magnetic field in these coils, which is then used to rotate the rotor.

[0005] In drive motors like those described above, the coils typically consist of multiple interconnected segmented conductors. The coils are usually mounted on a component made of laminated magnetic steel plates, known as the stator core or rotor core. The magnetic steel plates usually contain iron, which is highly magnetic, as the main component. The segmented conductors are typically made of enameled wire, which is copper wire acting as the conductor, covered with an insulating coating (e.g., a polyurethane resin coating).

[0006] In the aforementioned drive motor, multiple slots are formed in the stator core or rotor core, and coils are respectively housed in the multiple slots.

[0007] Furthermore, in the drive motor described above, an insulating sheet for ensuring insulation between the coil and the inner wall of the slot is housed together with the coil in each slot. More specifically, the insulating sheet is housed in the slot in a state where it is wound around the coil.

[0008] Furthermore, the coil wound with insulating sheet is fixed in the groove by insulating resin (such as epoxy varnish) in the groove.

[0009] The aforementioned insulating sheet, for example, has a five-layer structure comprising: a substrate film such as a polyester resin film; two insulating layers such as paper sheets disposed on both sides of the substrate film; and adhesive layers disposed between the substrate film and the two insulating layers.

[0010] As such an insulating sheet, it is known, for example, that the adhesive layer is composed of a resin composition comprising polyurethane resin, epoxy resin and isocyanate-based crosslinking agent, wherein the resin composition comprises at least one isocyanate-based crosslinking agent selected from the group consisting of aliphatic isocyanates and aromatic isocyanates (Patent Document 1).

[0011] The insulating sheet described in Patent Document 1 is used, for example, as a slot liner for an electric motor, and when wound around a coil, it can ensure electrical insulation between the coil and the inner wall of the slot of the stator core.

[0012] Existing technical documents

[0013] Patent documents

[0014] Patent Document 1: Japanese Patent Application Publication No. 2023-013729 Summary of the Invention

[0015] The technical problem that the invention aims to solve

[0016] The insulating sheet described in Patent Document 1 can suppress the detachment of the surface portion of the outermost insulating layer even when force is applied from the outside. However, since the outermost layer is not adhesive, it cannot be bonded to the objects to be bonded on both sides of the sheet (such as coils or the inner wall of the groove mentioned above).

[0017] In contrast, in the past, during motor manufacturing, the coil was fixed in place and prevented from detaching from the groove by curing the insulating varnish injected into it. However, the varnish has high viscosity, so the injection process takes a relatively long time, reducing manufacturing efficiency.

[0018] Therefore, it is desirable to have an adhesive sheet that can adhere to the object being bonded even without the use of the aforementioned varnish or the like, and that can prevent the surface portion from detaching even when external force is applied.

[0019] In view of the aforementioned desired points, the technical problem of the present invention is to provide an adhesive sheet that can adhere to the object to which it is to be bonded and prevent the surface portion from falling off even when force is applied from the outside.

[0020] Technical solutions for solving technical problems

[0021] To solve the above-mentioned technical problems, the adhesive sheet of the present invention comprises: Substrate layer; and An adhesive layer is bonded to the object to be bonded and overlaps at least one side of the aforementioned substrate layer. The adhesive layer comprises epoxy resin and polyurethane resin that does not have epoxy groups in its molecules. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of an example of the adhesive sheet involved in this embodiment, cut along the thickness direction.

[0023] Figure 2 This is a schematic cross-sectional view of another example of the adhesive sheet involved in this embodiment, cut along the thickness direction.

[0024] Figure 3 This is a schematic 3D diagram of the stator of a car's drive motor.

[0025] Figure 4This is a rough top view of the stator core.

[0026] Figure 5 yes Figure 4 Enlarged view of part A. Detailed Implementation

[0027] Hereinafter, an embodiment of the adhesive sheet according to the present invention will be described with reference to the accompanying drawings. The adhesive sheet of this embodiment is used, for example, as a component of an electric motor.

[0028] For example, Figure 1 As shown, a specific example of the adhesive sheet in this embodiment has a multi-layered substrate layer 11 and two adhesive layers 12 respectively overlapping on both sides of the substrate layer 11.

[0029] On the other hand, for example, Figure 2 As shown, another specific example of the adhesive sheet of this embodiment has a multilayer substrate layer 11 and an adhesive layer 12 that overlaps only one side of the substrate layer 11.

[0030] The following is about Figure 1 The adhesive sheet shown above is described in detail as a specific example.

[0031] The adhesive sheet 10 of this embodiment includes two adhesive layers 12 arranged opposite each other, and a substrate layer 11 disposed between the two adhesive layers 12. In other words, the adhesive sheet 10 of this embodiment includes a substrate layer 11 and two adhesive layers 12 arranged to hold the substrate layer 11 in the thickness direction.

[0032] In the adhesive sheet 10 of this embodiment, the substrate layer 11 is in direct contact with one adhesive layer 12, and the substrate layer 11 is in direct contact with the other adhesive layer 12.

[0033] The thickness of the adhesive sheet 10 described above is, for example, 10 μm or more and 500 μm or less. The thickness of the adhesive sheet 10 can be 50 μm or more, or 70 μm or more. In addition, the thickness of the adhesive sheet 10 can be 400 μm or less, or 300 μm or less.

[0034] From the perspective of further improving workability when inserting into the slot of the stator (described in detail below), the thickness of the adhesive sheet 10 is preferably 50 μm or more.

[0035] The thickness (total thickness) of the substrate layer 11 is preferably 10 μm or more and 300 μm or less.

[0036] The thickness of the adhesive layer 12 (per layer) can be, for example, 1 μm or more and 150 μm or less. Preferably, the thickness of the adhesive layer 12 is 5 μm or more and 100 μm or less.

[0037] Preferably, the difference in thickness between the adhesive layer 12 and the adhesive layer 12 of the two adhesive layers 12 is small. For example, the thickness of the adhesive layer 12 of the other adhesive layer 12 may be more than 0.8 times and less than 1.2 times the thickness of the adhesive layer 12 of the other adhesive layer 12.

[0038] Furthermore, the thickness of each layer mentioned above refers to the average thickness. The thickness of each layer is calculated by averaging the thickness at at least five randomly selected locations.

[0039] The thickness of each layer can be determined, for example, by observing the side or cross-section of the adhesive sheet 10 using a digital microscope.

[0040] The ratio of the thickness (total thickness) of the substrate layer 11 to the total thickness of the adhesive sheet 10 can be 0.10 or more, or 0.20 or more. Increasing this ratio has the advantage of further improving the electrical insulation of the adhesive sheet 10. Alternatively, this thickness ratio can be 0.80 or less, or 0.40 or less.

[0041] The ratio of the total thickness of the adhesive layer 12 (the thickness of the two layers) to the total thickness of the adhesive sheet 10 can be 0.10 or more, or 0.30 or more. Increasing this ratio has the advantage of further improving the adhesiveness of the adhesive sheet 10. Alternatively, this ratio can be 0.90 or less, or 0.80 or less.

[0042] The ratio of the thickness of each adhesive layer 12 (the thickness of one layer) to the total thickness of the adhesive sheet 10 can be 0.05 or more, or 0.15 or more. Alternatively, this ratio can be 0.45 or less, or 0.40 or less.

[0043] Furthermore, the numerical range described above, relating to the ratio of the thickness of each adhesive layer 12 to the thickness of the substrate layer 11, is preferably satisfied on at least one side of the substrate layer 11, either on one side or the other side. More preferably, the aforementioned thickness ratio is within the aforementioned numerical range on both one side and the other side of the substrate layer 11.

[0044] <Substrate Layer>

[0045] The substrate layer 11 is sheet-like. The substrate layer 11 preferably possesses insulation and heat resistance. The substrate layer 11 can have a single-layer structure or a multi-layer structure with multiple layers stacked together. For example, the substrate layer 11... Figure 1 and Figure 2 The structure shown has 5 layers, including a substrate film 11a, two paper-like sheets 11b disposed on both sides of the substrate film 11a, and two fixing layers 11c disposed between the substrate film 11a and the two paper-like sheets 11b.

[0046] As the substrate film 11a and paper sheet 11b, for example, resin film or insulating paper such as aramid paper can be used independently.

[0047] The fixing layer 11c contains, for example, a conventional adhesive.

[0048] For example, the substrate layer 11 may also have a structure in which heat-resistant resin fiber sheets (paper-like sheets) are bonded to both sides of the insulating resin film (substrate film) using an adhesive. The insulating resin film is preferably a polyethylene naphthalate resin film or a polyimide resin film with a thickness of 10 μm or more and 250 μm or less. The heat-resistant resin fiber sheet is preferably an aromatic polyamide fiber sheet or a polyethersulfone fiber sheet with a thickness of 10 μm or more and 100 μm or less.

[0049] Alternatively, instead of the aforementioned heat-resistant resin fiber sheet (paper-like sheet), a structure can be adopted in which an insulating resin film different from the substrate film is bonded together via an adhesive.

[0050] In addition, as described above, the substrate layer 11 can also be a single layer, and the single-layer substrate layer 11 can be an insulating paper sheet or a resin film, etc.

[0051] As the aforementioned resin film, an insulating resin film is preferred. Examples of insulating resin films include polyethylene terephthalate (PET) resin film, polyethylene naphthalate (PEN) resin film, polyimide (PI) resin film, polyphenylene sulfide (PPS) resin film, or polyether ether ketone (PEEK) resin film.

[0052] Examples of insulating paper sheets mentioned above include resin fiber sheets. Examples of resin fiber sheets include aromatic polyamide fiber sheets or polyethersulfone fiber sheets.

[0053] The substrate layer 11 can also be subjected to lamination, high-temperature and high-pressure calendering, or surface treatment. Surface treatments include, for example, roughening treatment or corona treatment to improve adhesion to the adhesive layer 12.

[0054] <Adhesive layer>

[0055] Next, the adhesive layer 12 will be described in detail. The adhesive layer 12 is bonded (fixed) to the bonding object, which will be described in detail later. In other words, the adhesive sheet 10 of this embodiment is used to bond to the bonding object by means of the adhesive layer 12. The adhesive layer 12 has relatively low adhesion at room temperature, but it can be firmly bonded to the bonding object by heat treatment.

[0056] Each adhesive layer 12 contains a polymer component (adhesive component). Specifically, each adhesive layer 12 contains at least epoxy resin and polyurethane resin without epoxy groups in its molecules as polymer components. The adhesive layer 12 may also contain epoxy resin curing agents, foaming agents, or fillers, etc.

[0057] The adhesive layer 12 preferably contains 40% or more by mass of the epoxy resin described above, more preferably 50% or more by mass. The adhesive layer 12 preferably contains 90% or less by mass of the epoxy resin described above, more preferably 70% or less by mass.

[0058] The adhesive layer 12 preferably contains 3% or more by mass of the aforementioned polyurethane resin, more preferably 5% or more by mass, even more preferably 10% or more by mass, and even more preferably 20% or more by mass. The adhesive layer 12 preferably contains 80% or less by mass of the aforementioned polyurethane resin, more preferably 40% or less by mass.

[0059] The adhesive layer 12 preferably contains more than 15% by mass and less than 15% by mass of epoxy resin curing agent 1.

[0060] The adhesive layer 12 may also contain more than 5% by mass and less than 15% by mass of foaming agent.

[0061] The epoxy resins described above have multiple epoxy groups in their molecules. Examples of epoxy resins include phenolic varnish-type epoxy resins such as phenolic varnish-type epoxy resins or cresol varnish-type epoxy resins, and bisphenol-type epoxy resins such as bisphenol A type epoxy resins (including modified bisphenol A type epoxy resins) or bisphenol F type epoxy resins (including modified bisphenol F type epoxy resins).

[0062] Furthermore, examples of epoxy resins include pyromethane-type (triphenylmethane-type) epoxy resins, biphenyl-type epoxy resins, and dicyclopentadiene-type epoxy resins.

[0063] These epoxy resins can be used alone, or in combination with two or more types.

[0064] The epoxy equivalent [g / eq] of epoxy resin can be above 100 and below 3000. The above-mentioned epoxy equivalent is determined according to JIS K7236-2001.

[0065] Commercially available products can be used as the epoxy resin mentioned above.

[0066] The polyurethane resin mentioned above is, for example, a product of the carbamate reaction between a polyol component (a) having multiple hydroxyl groups in its molecule and a polyisocyanate component (b) having multiple isocyanate groups in its molecule.

[0067] Preferably, the polyurethane resin is at least a diol having two hydroxyl groups and no carboxyl groups in its molecule, which is the polyol component (a) mentioned above, and a product of the carbamate reaction of a diol having two hydroxyl groups and carboxyl groups in its molecule with a diisocyanate having two isocyanate groups in its molecule, which is the polyisocyanate component (b) mentioned above.

[0068] The acid value of the aforementioned polyurethane resin is, for example, 0.1 [mgKOH / g] or more and 25.0 [mgKOH / g] or less. Preferably, the acid value of the aforementioned polyurethane resin is 2.0 [mgKOH / g] or more, more preferably 5.0 [mgKOH / g] or more, and even more preferably 7.0 [mgKOH / g] or more. Preferably, the acid value of the aforementioned polyurethane resin is 23.0 [mgKOH / g] or less.

[0069] The high acid value of the polyurethane resin results in a higher crosslinking density after the reaction between the polyurethane resin and the epoxy resin, leading to better heat resistance of the cured adhesive layer 12. On the other hand, the low acid value further suppresses further chemical reactions from functional groups within the adhesive layer 12 during storage of the adhesive sheet 10, thus improving the long-term stability of the adhesive sheet 10's performance.

[0070] The acid value of polyurethane resin is determined by solvating the polyurethane resin with methyl ethyl ketone (MEK) and other solvents, according to the method of JIS K1557-5:2007.

[0071] The polyurethane resins described above may also have carboxyl or hydroxyl groups in their molecules. For example, the acid value can be increased by synthesizing polyurethane resins with more carboxyl groups in the molecule.

[0072] On the other hand, the polyurethane resins mentioned above may also not have epoxy groups in their molecules.

[0073] As the polyol component (a), a general polyol used in the synthesis of polyurethane resins is adopted. Specific examples of polyols include polyester polyols, polyether polyols, polycarbonate polyols, or other polyols.

[0074] Examples of polyester polyols include condensation polymers of aliphatic dicarboxylic acids (e.g., succinic acid, adipic acid, sebacic acid, glutaric acid, azelaic acid, etc.) or aromatic dicarboxylic acids (e.g., isophthalic acid, terephthalic acid, etc.) with low molecular weight diols (e.g., ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-bis(hydroxymethyl)cyclohexane, etc.).

[0075] Specific examples of polyester polyols include polyethylene adipate diol, polybutylene adipate diol, polyhexane adipate diol, polypentylene adipate diol, polyethylene adipate / butylene adipate diol, polypentylene adipate / hexane adipate diol, poly-3-methylpentane adipate diol, polybutylene isophthalate diol, polycaprolactone diol, and poly-3-methylpentane adipate diol.

[0076] Specific examples of polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and their random / block copolymers.

[0077] Specific examples of polycarbonate polyols include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polypentyl carbonate diol, polyhexamethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, and their random / block copolymers.

[0078] Other specific examples of polyols include dimer diols or their hydrogenated derivatives, polybutadiene polyols or their hydrogenated derivatives, polyisoprene polyols or their hydrogenated derivatives, acrylic polyols, epoxy polyols, polyether ester polyols, siloxane-modified polyols, α,ω-polymethyl methacrylate diols, α,ω-polybutyl methacrylate diols, or siloxane-modified polyols.

[0079] The number-average molecular weight (Mn, based on the terminal functional group quantification method) of the above-mentioned polyols is not particularly limited, but is preferably 500 or more and 6,000 or less.

[0080] In addition to the polyols mentioned above, the polyol component (a) may include short-chain diols as needed.

[0081] Specific examples of short-chain diols include aliphatic diols or their low-molar adducts into alkylene oxides, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol. Additionally, examples include alicyclic diols or their low-molar adducts into alkylene oxides, such as 1,4-bis(hydroxymethyl)cyclohexane and 2-methyl-1,1-cyclohexanediol. Furthermore, examples include aromatic diols or their low-molar adducts into alkylene oxides, such as xylene-methyldiol, or bisphenols or their low-molar adducts into alkylene oxides, such as bisphenol A, thiobisphenol, and sulfone bisphenol.

[0082] In addition, polyols can also be used as raw materials for polyurethane resins. Specific examples of polyols include glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, tri-(2-hydroxyethyl)isocyanurate, 1,1,1-trimethylolethane, or 1,1,1-trimethylolpropane.

[0083] The aforementioned polyols can be used alone or in combination of two or more.

[0084] As the polyisocyanate component (b) mentioned above, a general polyisocyanate component used for synthesizing polyurethane resin is adopted.

[0085] Specific examples of polyisocyanate components (b) include, for instance, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, 4,4'-methylenebis(phenylene isocyanate) [also known as 4,4'-diphenylmethane diisocyanate] (MDI), crude MDI or polymeric MDI, durene diisocyanate, phenylenediamine diisocyanate (XDI), 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate, 4,4'-diisocyanate dibenzyl and other aromatic diisocyanates. In addition, aliphatic diisocyanates such as methylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 1,10-decamethylene diisocyanate can be cited. Alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl) isocyanate, 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate (IPDI), and hydrogenated XDI can also be cited. Furthermore, polyurethane prepolymers obtained by reacting these diisocyanates with low molecular weight polyols to form isocyanates at the ends can be cited.

[0086] The aforementioned polyisocyanate component (b) can be used alone or in combination of two or more.

[0087] The mass average molecular weight (Mw) of the aforementioned polyurethane resin is preferably 1,000 or more and 500,000 or less. With a mass average molecular weight (Mw) within this range, the polyurethane resin can exhibit better physical properties such as flexibility, adhesion, and heat resistance.

[0088] Furthermore, the above-mentioned mass average molecular weight was determined by gel permeation chromatography (GPC) under the following determination conditions.

[0089] (1) Equipment: For example, the device name is "HLC-8020" (manufactured by Tosoh Corporation).

[0090] (2) Chromatographic column: Trade names "TSKgel G2000HXL", "G3000HXL", "G4000GXL" (made by Tosoh Corporation) (3) Solvent: THF (4) Flow rate: 1.0 ml / min (5) Sample concentration: 2 g / L (6) Injection volume: 100 μL (7) Temperature: 40℃ (8) Detector: Model “RI-8020” (manufactured by Tosoh Corporation) (9) Standard material: TSK standard polystyrene (manufactured by Tosoh Corporation) The aforementioned polyurethane resin can be manufactured using conventional polyurethane resin synthesis methods.

[0091] Specifically, firstly, a polyol component (a) and a polyisocyanate component (b) are combined via a carbamate reaction in the presence or absence of an organic solvent that does not contain active hydrogen in the molecule. Generally, the reaction can be carried out in a range where the equivalence ratio of isocyanate groups to hydroxyl groups is 0.8 or more and 1.25 or less. The carbamate reaction can be carried out using a so-called one-step or multi-step method, for example, at a temperature of 20°C or higher and 150°C or lower, preferably 60°C or higher and 110°C or lower.

[0092] In the synthesis of polyurethane resins, catalysts can be used as needed. Examples of catalysts include metal salts with organic or inorganic acids such as dibutyltin dilaurate, dioctyltin dilaurate, stannous octoate, zinc octoate, and tetra-n-butyl titanate; organometallic derivatives; organic amines such as triethylamine; and diazabicycloundecene catalysts.

[0093] The catalyst described above promotes the synthesis of polyurethane resin. However, if an excessive amount of catalyst is used, there is a concern that it may induce decomposition reactions that decompose substances other than polyurethane resin. Therefore, it is preferable to use an appropriate amount of catalyst.

[0094] In the synthesis of polyurethane resins, organic solvents can be used as reaction solvents, or they can be used without organic solvents. As organic solvents, organic solvents that are inert to isocyanate groups can be used.

[0095] The polyurethane resin described above can be synthesized, for example, by the method described above. Alternatively, commercially available products can be used as the polyurethane resin described above.

[0096] Examples of curing agents for the aforementioned epoxy resins include polymerization addition curing agents, catalyst-type curing agents, or other curing agents that have active hydrogen in their molecules.

[0097] Examples of addition-polymer curing agents include amine compounds, acid compounds such as organic acids and anhydrides, thiol compounds, and phenolic compounds (e.g., phenolic resins). Examples of amine compounds include aliphatic polyamines and aromatic polyamines. Amine compounds can be tertiary or secondary amines.

[0098] Examples of catalyst-type curing agents include boron trifluoride-amine complexes.

[0099] Other curing agents include, for example, dicyandiamide (DICY, also known as cyanoguanidine), imidazole compounds, or ketoimine compounds.

[0100] Examples of tertiary amine compounds include 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), diazabicycloundecene (DBU) and its salts, diazabicyclononene (DBN) and its salts, or tris(dimethylaminomethyl)phenol.

[0101] The curing agent preferably contains phenolic resin, dicyandiamide, and imidazole compounds.

[0102] Examples of phenolic resins mentioned above include phenolic varnish-type phenolic resins, aralkyl-type phenolic resins, methyl-type phenolic resins, dicyclopentadiene-modified phenolic resins, naphthalene-type phenolic resins, or bisphenol-based phenolic resins.

[0103] Examples of phenolic resins that can be used as varnishes include phenolic resins, cresol resins, bisphenol A varnishes, and phenolic resins containing a triazine skeleton. Phenolic resins that can also be xylene-modified phenolic resins (phenol-modified) may also be examples of phenolic resins that also have a xylene structure.

[0104] Examples of aryl alkyl phenolic resins include biphenyl aryl phenolic resins.

[0105] In addition, the curing agent may also contain a variety of phenolic resins.

[0106] The phenolic hydroxyl equivalent of phenolic resin can be, for example, 100 g / eq or more and 300 g / eq or less. Furthermore, the "hydroxyl equivalent" of phenolic resin can be calculated based on the hydroxyl value obtained according to JIS K0070:1992 (in principle, neutralization titration, but potentiometric titration if necessary), using the following formula.

[0107] Hydroxyl equivalent = Molecular weight of potassium hydroxide ÷ Hydroxyl value

[0108] Examples of imidazole compounds include 2-methylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-phenylimidazolium, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, and 2,4-diamino-6-[2'-methylimidazolium] -(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, etc.

[0109] The imidazole compound preferably has a benzene ring structure and a hydroxyl group in its molecule. In addition, the molecular weight of the imidazole compound is preferably 100 or more and 250 or less.

[0110] Furthermore, commercially available products can be used as the aforementioned curing agent.

[0111] Examples of foaming agents mentioned above include physical foaming agents whose volume increases with heating, chemical foaming agents that produce gas through a chemical reaction of their components with heating, and thermally expanding capsules containing physical foaming agents.

[0112] Examples of physical foaming agents include n-pentane, isopentane, isobutane, petroleum ether, and other hydrocarbons or their halides.

[0113] Examples of chemical foaming agents include inorganic foaming agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, and ammonium nitrite, as well as organic foaming agents such as azodicarbonamide (ADCA), N,N'-dinitrospentamethylenetetramine, benzenesulfonyl hydrazine, and 4,4'-diphenyldisulfonyl azide.

[0114] Thermally expandable capsules, for example, comprise hollow capsules formed from thermoplastic resins and a physical foaming agent encapsulated within the hollow capsules. Thermally expandable capsules are preferred in terms of ease of controlling the foaming initiation temperature. The particle size of each thermally expandable capsule is, for example, 5 μm or more and 50 μm or less. More than half of the thermally expandable capsules have the aforementioned particle size.

[0115] As a foaming agent, one of the above-listed agents can be used alone or in combination of two or more.

[0116] The foaming start temperature of the foaming agent is preferably above 60°C and below 170°C, more preferably above 80°C and below 160°C.

[0117] Inorganic fillers can be cited as examples of the aforementioned fillers. Examples of inorganic fillers include inorganic nitrides such as boron nitride, aluminum nitride, or silicon nitride; inorganic oxides such as silicon oxide, aluminum oxide, titanium oxide, magnesium oxide, or zirconium oxide; clay minerals such as talc, montmorillonite, mica, bentonite, or kaolinite; diamond; silicon carbide (SiC); and calcium carbonate.

[0118] The adhesive layer 12 may also contain 2% by mass or more and 50% by mass or less of filler. By moderately including filler in the adhesive layer 12, the processability of the adhesive sheet 10 is improved.

[0119] Since the adhesive layer 12 contains the components described above, the adhesive sheet 10 can be well bonded to the bonding objects on both sides in the thickness direction, and prevents a portion of the surface portion (adhesive layer) from falling off due to externally applied force.

[0120] The adhesive layer 12 preferably comprises epoxy resin, polyurethane resin without epoxy groups in its molecule, dicyandiamide, and imidazole compounds. By including the aforementioned polyurethane resin in the adhesive layer 12, it is possible to prevent a portion of the surface portion (adhesive layer) from detaching due to externally applied forces.

[0121] The adhesive layer 12, relative to 100 parts by weight of the epoxy resin (when the amount of the epoxy resin is set to 100 parts by weight), preferably contains 25 parts by weight or more and 70 parts by weight or less of the polyurethane resin, more preferably 30 parts by weight or more, and even more preferably 40 parts by weight or more. The adhesive layer 12, relative to 100% of the epoxy equivalent of the epoxy resin, preferably contains 95% or more and 105% or less of dicyandiamide. The adhesive layer 12, relative to 100 parts by weight of the combined amount of the epoxy resin and polyurethane resin, preferably contains 0.5 parts by weight or more and 2.0 parts by weight or less of an imidazole compound.

[0122] The adhesive layer 12 preferably contains a foaming agent. In an electric motor equipped with an adhesive layer 12 containing a foaming agent, when the adhesive sheet 10 is housed in a relatively narrow space (such as a slot described later) while wound around a coil or the like, it is possible to achieve better adhesion to the object to be bonded to at least one side of the adhesive sheet 10. Such a method of use will be described in detail later.

[0123] Next, the manufacturing method of the adhesive sheet 10 according to the above embodiment will be described.

[0124] In the manufacturing method of the adhesive sheet 10 of this embodiment, for example, a mixture comprising each component constituting the adhesive layer 12 described above and an organic solvent (as needed) is prepared, and the mixture is coated on both sides of the substrate layer 11, and the organic solvent contained in the coated mixture is evaporated (as needed) to form two adhesive layers 12.

[0125] Furthermore, as a coating device, a roller coater can be used, for example.

[0126] As organic solvents mentioned above, ethyl acetate, methyl ethyl ketone (MEK), toluene, etc., can be used, for example.

[0127] When coating the mixture containing the organic solvent onto the substrate layer 11, conventional coating methods such as mold coating and reverse coating can be used. The coating temperature is, for example, room temperature (15~25°C).

[0128] The adhesive sheet 10 manufactured as described above is used, for example, as a component constituting an electric motor. The adhesive sheet 10 can also be used, for example, as an adhesive sheet for a drive motor in an automobile. Specifically, the adhesive sheet 10 can be used as a slot insulation sheet for an electric motor stator. The adhesive sheet 10 can be used, for example, in a heated state.

[0129] When using the adhesive sheet 10, one side of the adhesive layer 12 is exposed. In other words, the side of the adhesive layer 12 that does not contact the substrate layer 11 is exposed when using the adhesive sheet 10. Moreover, the adhesive layer 12 of the adhesive sheet 10 can be well bonded to the object to be bonded, for example, by heat treatment at a temperature above 140°C and below 200°C.

[0130] For example, an adhesive sheet 10 with an adhesive layer 12 overlapping only on one side of the substrate layer 11 (see reference). Figure 2 The adhesive layer 12 can be configured to face either the inner surface of the stator core or the coil. Alternatively, the adhesive sheet 10, which has two adhesive layers 12 overlapping on both sides of the substrate layer 11, can also be housed in the slot of the stator core, for example, in a coil-wound state, as detailed later, for bonding to the inner surface of the coil and the slot of the stator core.

[0131] The adhesive sheet 10 of this embodiment can be well bonded to the object to be bonded by heat treatment. Before heat treatment, the adhesive layer 12 of the adhesive sheet 10 has relatively low adhesion (pressure-sensitive adhesion). Therefore, the coil with the motor adhesive sheet wound on it is less likely to adhere to the inner surface of the slot and is easier to insert into the slot. Furthermore, if the motor adhesive sheet housed in the slot is heat-treated while wound with the coil, it can be well bonded to both the coil and the inner surface of the slot (the object to be bonded).

[0132] Therefore, even without relying on insulating resin (such as epoxy varnish) placed in the slot as in the past, it is possible to fix the coil with the motor adhesive sheet wound inside the slot.

[0133] In addition, the adhesive layer 12 also contains the aforementioned foaming agent, which expands the adhesive layer 12 through foaming. The adhesive layer 12 can adhere more fully to the object to be bonded, thus more reliably fixing the coil in the slot.

[0134] Examples of vehicles mentioned above include hybrid electric vehicles (HEVs) and electric vehicles (EVs). Examples of drive motors include HV motors, generators, alternators, 4WD motors, oil pump motors, EPS motors, compressor motors, and in-wheel motors.

[0135] Next, an example of a motor equipped with the adhesive sheet 10 described above will be described with reference to the accompanying drawings. This motor is equipped with the adhesive sheet 10 described above. The adhesive sheet 10 is, for example, an adhesive sheet for a motor.

[0136] For example, an electric motor is a drive motor installed in hybrid vehicles or electric vehicles.

[0137] The car's drive motor consists of a rotor, which has permanent magnets, and a stator, which generates the force to rotate the rotor. For example... Figure 3 As shown, the stator 20 has a coil 21 and a stator core 22. The stator 20 rotates the rotor by generating a magnetic field in the coil 21. Figure 4 This is a top view of the stator 20 viewed from one side of the rotor (not shown) along the direction of its rotation axis. Figure 5 This indicates the case where the coil 21 is housed in slot P of the stator core 22. Figure 4 A cross-sectional view of part A.

[0138] In the drive motor described above, the coil 21 is, for example, composed of a plurality of interconnected segmented conductors 21a. In the drive motor described above, a plurality of slots P are formed in the stator core 22, rotor core, etc., and each coil 21 is housed in a plurality of slots P.

[0139] In detail, in the stator 20, a plurality of slots P are formed on the inner circumferential side of the cylindrical stator core 22. The stator 20 has a stator core 22 and a plurality of coils 21 partially housed in the plurality of slots P formed in the stator core 22. The plurality of slots P are arranged along the circumference of the stator core 22 at a certain interval from each other. In the direction of the rotation axis of the stator core 22, the slots P are formed to be the same length as the stator core 22.

[0140] In the stator core 22, multiple slots P are arranged as described above, with adjacent slots P forming plate-like protrusions 22a. Each plate-like protrusion 22a extends radially from the outer periphery of the stator core 22. Figure 5 Extends inside the DD direction.

[0141] The coil 21 is composed of multiple interconnected segmented conductors 21a. For example... Figure 5 As shown, each slot P of the stator core 22 contains, for example, four segmented conductors 21a forming coils 21. A total of four segmented conductors 21a are arranged in a row from the inner circumferential surface to the outer circumferential surface of the stator core 22 in each slot P.

[0142] In the drive motor described above, an adhesive sheet for the motor is used to ensure insulation between the coil 21 and the inner wall of the slot P. In other words, as... Figure 5 As shown, the motor adhesive sheet 10 is sandwiched between the coil 21 and the wall surrounding the groove P, and is housed within the groove P in a state of being wound around the coil 21. More specifically, the motor adhesive sheet 10 is positioned within the groove P in a state of being wound around the coil 21 more than once, with its ends overlapping each other (see reference). Figure 5 The overlapping portion is located outside the radial direction DD of the stator 20. Furthermore, in the direction of the rotation axis of the stator core 22, both ends of the motor adhesive piece 10 extend outward from the stator core 22.

[0143] The coil 21 is fixed in the groove by the adhesive force of the heat-treated adhesive layer while the motor adhesive sheet is wound around it.

[0144] The adhesive sheet in this embodiment is as described in the example above, but the present invention is not limited to the adhesive sheet described in the example above.

[0145] That is, various methods used in general adhesive sheets can be employed without compromising the effects of the present invention.

[0146] The matters disclosed in this specification include the following.

[0147] (1) An adhesive sheet comprising a substrate layer and an adhesive layer, the adhesive layer being bonded to an object to be bonded and overlapping at least one side of the substrate layer. The adhesive layer described above comprises epoxy resin and polyurethane resin that does not have epoxy groups in its molecules.

[0148] The adhesive sheet with this structure can bond the adhesive layer to the object being bonded. Furthermore, it can prevent a portion of the adhesive layer from detaching due to externally applied force.

[0149] (2) According to the adhesive sheet described in (1) above, wherein, The adhesive layer comprises 3% by mass and 80% by mass of the aforementioned polyurethane resin.

[0150] (3) According to the adhesive sheet described in (1) or (2) above, wherein, The acid value of the above polyurethane resin is 0.1 [mgKOH / g] or higher and 15.0 [mgKOH / g] or lower.

[0151] (4) The adhesive sheet described in any one of (1) to (3) above, wherein, The adhesive layer also contains a foaming agent.

[0152] The invention will now be further described in detail through experimental examples, but the invention is not limited to these examples.

[0153] The materials or raw materials of the substrate layer and adhesive layer used to manufacture the adhesive sheet are as follows.

[0154] <Substrate Layer>

[0155] Polyethylene naphthalate (PEN) resin film

[0156] Product name: "Teonex" series (manufactured by Toyobo Co., Ltd.)

[0157] Thickness: 100μm

[0158] <Materials for the Adhesive Layer>

[0159] [Polymer Components]

[0160] • Epoxy resin (phenolic varnish type epoxy resin / o-cresol phenolic varnish type)

[0161] Epoxy equivalent: Approximately 208 (g / eq)

[0162] Product name "YDCN-704" (manufactured by Nippon Steel Chemicals & Materials Co., Ltd.)

[0163] Polyurethane resin

[0164] The following methods are used to synthesize (represented by PU1 / PU2 / PU3 / PU4 / PU5 respectively).

[0165] [Curing agent]

[0166] Dicyandiamide (commercially available)

[0167] ·Imidazole compounds

[0168] (2-Phenylacetyl-4-methyl-5-hydroxymethylimidazolium)

[0169] Product name "2P4MHZ-PW" (manufactured by Shikoku Chemical Industry Co., Ltd.)

[0170] [Foaming agent (expanding agent)]

[0171] Expandable capsules

[0172] Product name: "Matsumoto Microspheres FN" series (manufactured by Matsumoto Oils & Fats Pharmaceutical Co., Ltd.)

[0173] <Synthesis of Polyurethane Resins>

[0174] Five polyurethane resins were synthesized as follows.

[0175] (PU1)

[0176] A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet pipe, and manhole was prepared. While purging the interior of the reaction vessel with nitrogen, 200.0 g of polyhexamethylene carbonate diol (Duranol: T6002, manufactured by Asahi Kasei Chemicals, number-average molecular weight = 2,000 based on terminal functional group quantification), 15.0 g of 1,3-butanediol, and 16.0 g of dimethylolpropionic acid (DMPA) with hydroxyl groups at both ends were added. Next, 99.0 g of methyl ethyl ketone (MEK) was added as a solvent, and the system was stirred. After stirring, 96.3 g of 4,4'-diphenylmethane diisocyanate (MDI) was added at 50°C, and the reaction was carried out at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by diluting it with methyl ethyl ketone (MEK) as a solvent, and the reaction proceeded until the free isocyanate group pair reached 2,270 cm⁻¹ as determined by infrared absorption spectroscopy. -1 A resin solution of polyurethane resin PU1 was obtained by continuing absorption until the absorption disappeared. The viscosity of the obtained resin solution was 500 dPa·s / 20℃, the solid content was 30% by mass, and the acid value of polyurethane resin PU1 was 20.5 mgKOH / g. In addition, the mass-average molecular weight of polyurethane resin PU1, as determined by GPC, was 86,000.

[0177] (PU2)

[0178] A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet pipe, and manhole was prepared. While purging the interior of the reaction vessel with nitrogen, 200.0 g of polyhexamethylene carbonate diol (Duranol: T6002, manufactured by Asahi Kasei Chemicals, number-average molecular weight = 2,000 based on terminal functional group quantification), 25.3 g of neopentyl glycol (NPG), and 8.0 g of dimethylolpropionic acid (DMPA) with hydroxyl groups at both ends were added. Next, 100.0 g of methyl ethyl ketone (MEK) was added as a solvent, and the system was stirred. After stirring, 100.8 g of 4,4'-diphenylmethane diisocyanate (MDI) was added at 50°C, and the reaction was carried out at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by diluting it with methyl ethyl ketone (MEK) as a solvent, and the reaction proceeded until the free isocyanate group pair reached 2,270 cm⁻¹ as determined by infrared absorption spectroscopy. -1 A resin solution of polyurethane resin PU2 was obtained after the absorption disappeared. The viscosity of the obtained resin solution was 410 dPa·s / 20℃, the solid content was 30% by mass, and the acid value of polyurethane resin PU2 was 10.0 mgKOH / g. In addition, the mass-average molecular weight of polyurethane resin PU2, determined by GPC, was 79,000.

[0179] (PU3)

[0180] A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet pipe, and manhole was prepared. While purging the interior of the reaction vessel with nitrogen, 200.0 g of polyhexamethylene carbonate diol (Duranol: T6002, manufactured by Asahi Kasei Chemicals, number-average molecular weight = 2,000 based on terminal functional group quantification), 25.3 g of neopentyl glycol (NPG), and 4.0 g of dimethylolpropionic acid (DMPA) with hydroxyl groups at both ends were added. Next, 98.2 g of methyl ethyl ketone (MEK) was added as a solvent, and the system was stirred. After stirring, 93.2 g of 4,4'-diphenylmethane diisocyanate (MDI) was added at 50°C, and the reaction was carried out at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by diluting it with methyl ethyl ketone (MEK) as a solvent, and the reaction proceeded until the free isocyanate group pair reached 2,270 cm⁻¹ as determined by infrared absorption spectroscopy. -1 A resin solution of polyurethane resin PU3 was obtained by continuing absorption until the absorption disappeared. The viscosity of the obtained resin solution was 420 dPa·s / 20℃, the solid content was 30% by mass, and the acid value of polyurethane resin PU3 was 5.2 mgKOH / g. In addition, the mass-average molecular weight of polyurethane resin PU3, determined by GPC, was 83,000.

[0181] (PU4)

[0182] A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet pipe, and manhole was prepared. While purging the interior of the reaction vessel with nitrogen, 200.0 g of dihydroxyl-terminated polyhexamethylene carbonate diol (Duranol: T6002, manufactured by Asahi Kasei Chemicals, number-average molecular weight = 2,000 based on terminal functional group quantification), 25.3 g of neopentyl glycol (NPG), and 4.0 g of dimethylolpropionic acid (DMPA) were added. Next, 133.8 g of methyl ethyl ketone (MEK) was added as a solvent, and the system was stirred. After stirring, 82.8 g of isophorone diisocyanate (IPDI) was added at 50°C, and the reaction was carried out at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by diluting it with methyl ethyl ketone (MEK) as a solvent, and the reaction proceeded until the free isocyanate group pairs reached 2,270 cm⁻¹ as determined by infrared absorption spectroscopy. -1 A resin solution of polyurethane resin PU4 was obtained by continuing absorption until the absorption disappeared. The viscosity of the obtained resin solution was 260 dPa·s / 25℃, the solid content was 30% by mass, and the acid value of polyurethane resin PU4 was 5.4 mgKOH / g. In addition, the mass-average molecular weight of polyurethane resin PU4, determined by GPC, was 77,000.

[0183] (PU5)

[0184] A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet pipe, and manhole was prepared. While purging the interior of the reaction vessel with nitrogen, 200.0 g of dihydroxyl-terminated polyhexamethylene carbonate diol (Duranol: T6002, manufactured by Asahi Kasei Chemicals, number-average molecular weight = 2,000 based on terminal functional group quantification), 30.0 g of 1,4-bis(hydroxymethyl)-cyclohexane (1,4-CHDM), and 4.0 g of dimethylolpropionic acid (DMPA) were added. Next, 132.4 g of methyl ethyl ketone (MEK) was added as a solvent, and the system was stirred. After stirring, 75.0 g of isophorone diisocyanate (IPDI) was added at 50°C, and the reaction was carried out at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by diluting it with methyl ethyl ketone (MEK) as a solvent, and the reaction proceeded until the free isocyanate group pair reached 2,270 cm⁻¹ as determined by infrared absorption spectroscopy. -1 A resin solution of polyurethane resin PU5 was obtained by continuing absorption until the absorption disappeared. The viscosity of the obtained resin solution was 150 dPa·s / 25℃, the solid content was 30% by mass, and the acid value of polyurethane resin PU5 was 5.4 mgKOH / g. In addition, the mass-average molecular weight of polyurethane resin PU5, as determined by GPC, was 77,000.

[0185] <Manufacturing of Adhesive Sheets>

[0186] A mixture comprising the aforementioned components constituting the adhesive layer and an organic solvent (methyl ethyl ketone (MEK)) was prepared. Using a bar coater, the mixture was applied to one side of a substrate layer to form a 40 μm thick adhesive layer (one layer). The mixture was then dried at 110°C for 5 minutes to evaporate the organic solvent, thus creating an adhesive layer on one side of the substrate layer. Similarly, an adhesive layer was created on the other side of the substrate layer. This produced three-layer adhesive sheets.

[0187] (Examples 1-12, Comparative Examples 1 and 2)

[0188] The composition of the adhesive layers in the adhesive sheets of each embodiment and comparative example is shown in Tables 1 and 2, respectively. Furthermore, each adhesive sheet in the embodiments and comparative examples has a three-layer laminated structure (with one substrate layer).

[0189]

[0190] The wear resistance of the adhesive layer was evaluated for the adhesive sheets manufactured in each embodiment and comparative example.

[0191] <Evaluation of powder shedding based on friction (scratching) (scratching abrasion test)>

[0192] The test was conducted according to ISO 6722. Specifically, a scratch abrasion tester was used, and the tests were performed under the following conditions. Furthermore, as test samples, samples were prepared by cutting the adhesive sheets shown in the above-described embodiments and comparative examples into 1.5cm × 4cm pieces and winding them around a cylindrical rod (5mm in diameter). The amount of powder generated and falling due to friction from the piano wire was then measured.

[0193] Testing machine (model name: 5420-7N, manufactured by TVAB)

[0194] Piano cable (0.45mm diameter) travel distance: 20mm, 20 reciprocations.

[0195] Piano wire movement speed: 3m / minute

[0196] Piano wire pressing pressure: approximately 5 MPa

[0197] There are 5 points where the piano cable slides.

[0198] Temperature: 23℃

[0199] For each embodiment and comparative example, the results of the above-described scratch test are shown in Tables 1 and 2. Based on these results, it can be seen that, compared to the adhesive sheet of the comparative example, the adhesive sheet of the embodiments is able to prevent a portion of the adhesive layer from detaching due to externally applied force.

[0200] In the adhesive sheet of the embodiment, the outermost adhesive layer is flexible, and even when force is applied from the outside, it is easy to prevent a portion of the adhesive layer from falling off. Therefore, when the thickness of the substrate layer, which is the inner layer, is relatively thick, even when the adhesive sheet is bent, it is possible to prevent a portion of the adhesive layer from falling off at the bent portion.

[0201] In addition, for example, during manufacturing, even when an adhesive layer formed on one side of a release sheet or the like is pasted (i.e. transferred) to one side of a substrate layer, in the adhesive sheet of the embodiment, the adhesive layer is flexible and thus easily follows the unevenness of the surface of the substrate layer, so the adhesive layer has good adhesion to the substrate layer.

[0202] In addition, as follows, the shear adhesion force of the adhesive sheets manufactured in each embodiment and each comparative example was evaluated.

[0203] <Determination of Shear Adhesion>

[0204] (Preparation of test pieces for evaluating shear adhesion)

[0205] Two cold-rolled steel sheets (SPCC-SD) with a thickness of 1.0 mm, a width of 15 mm, and a length of 100 mm were prepared. Two spacers were placed at a predetermined interval along the length of one of the cold-rolled steel sheets at the front end. The thickness of the spacers was 370 μm. Next, the adhesive sheets from the above-described embodiments and comparative examples were cut into 10 mm × 15 mm pieces and placed between the two spacers. The front end of this cold-rolled steel sheet overlapped with the front end of one of the other cold-rolled steel sheets. Using a fixing clamp (clamps, etc.), the overlapping portion of the two cold-rolled steel sheets was pressurized and fixed, thereby creating a temporary test piece. Then, the temporary test piece was heated from room temperature to 170°C over 3 minutes and heated at 170°C for 15 minutes, thereby curing the adhesive sheet and obtaining a test piece for evaluating shear adhesion (initial stage before storage).

[0206] In addition, the adhesive sheets of each embodiment and each comparative example were stored at 40°C and 90%RH for 14 days. Using the stored adhesive sheets, test pieces for evaluating shear adhesion (after storage) were prepared in the same order as described above.

[0207] (Determination of shear adhesion)

[0208] The test specimens for evaluating shear adhesion were placed in a thermostatic bath set at 200°C or higher, and clamped in a tensile testing machine located within the thermostatic bath. Tensile tests were performed when the specimens reached 200°C. The tensile speed was set to 5 mm / min.

[0209] For each embodiment and comparative example, the results of the above-described shear adhesion test are shown in Table 1. Additionally, the results of the scratch abrasion test are shown in Tables 1 and 2. As understood from these results, the adhesive sheets of the embodiments, while possessing adhesiveness to the adhered objects, also suppress the detachment of a portion of the adhesive layer due to externally applied forces, compared to the adhesive sheets of the comparative examples. Furthermore, the adhesive sheets of the embodiments in Table 2 also possess the same adhesiveness as those of the embodiments shown in Table 1.

[0210] The adhesive sheet of the present invention is suitable for use, for example, in applications constituting components of an electric motor. The adhesive sheet of the present invention is also suitable for use, for example, in applications involving slot materials in electric motors.

[0211] Explanation of reference numerals in the attached figures

[0212] 11: Substrate layer; 12: Adhesive layer; 10: Adhesive sheet.

Claims

1. An adhesive sheet comprising: Substrate layer; and An adhesive layer is bonded to the object to be bonded and overlaps at least one side of the substrate layer. The adhesive layer comprises epoxy resin and polyurethane resin that does not have epoxy groups in its molecules.

2. The adhesive sheet according to claim 1, wherein, The adhesive layer comprises 3% by mass and less than 80% by mass of the polyurethane resin.

3. The adhesive sheet according to claim 1 or 2, wherein, The acid value of the polyurethane resin is above 0.1 mg KOH / g and below 15.0 mg KOH / g.

4. The adhesive sheet according to claim 1 or 2, wherein, The adhesive layer also contains a foaming agent.

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