Insulating sheet and motor

Abstract

Provided is an insulating sheet provided with two outer layers disposed so as to face each other, two adhesive layers disposed so as to face each other between the two outer layers, and a base layer disposed between the two adhesive layers, the two adhesive layers each containing an inorganic filler.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to Japanese Patent Application No. 2023-107332, which is incorporated by reference into the specification of this application. TECHNICAL FIELD

[0003] The present application relates to an insulating sheet, for example, as a component of an electric machine, and an electric machine provided with the insulating sheet. BACKGROUND

[0004] In the past, an insulating sheet has been known which is provided with a base material layer, two outer layers disposed so as to respectively face one face and the other face of the base material layer, and two adhesive layers disposed between the one and the other outer layers and the base material layer, respectively.

[0005] As such an insulating sheet, for example, an insulating sheet for an electric machine has been known. As such an insulating sheet for an electric machine, for example, an insulating sheet of a 5-layer structure has been known in which a base material layer is formed of a polyester film, and one outer layer and the other outer layer are adhered to the base material layer by two adhesive layers formed of an acrylic adhesive (for example, Patent Literature 1).

[0006] In the insulating sheet described in Patent Literature 1, the outer layer is adhered to the adhesive layer.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Patent Application Publication No. 2006-262687 SUMMARY

[0010] PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] However, the insulating sheet described in Patent Literature 1 does not necessarily have good thermal conductivity. Therefore, an insulating sheet having good thermal conductivity and good adhesiveness between the outer layer and the adhesive layer is desired.

[0012] In view of the above problems and desires, an object of the present application is to provide an insulating sheet having good thermal conductivity and good adhesiveness between the outer layer and the adhesive layer.

[0013] In addition, an object of the present application is to provide an electric machine provided with the above-described insulating sheet.

[0014] SOLUTION TO PROBLEM

[0015] In order to solve the above problems, the insulating sheet according to the present application is provided with:

[0016] Two outer layers disposed in opposition to each other, two adhesive layers disposed in opposition to each other between the aforementioned two outer layers, and a base material layer disposed between the aforementioned two adhesive layers, the aforementioned two adhesive layers each containing an inorganic filler.

[0017] The motor according to the present application includes the aforementioned insulating sheet. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a schematic cross-sectional view of the insulating sheet of the present embodiment, cut along the thickness direction.

[0019] Figure 2 is a perspective view of a stator that drives a motor. DETAILED DESCRIPTION

[0020] Hereinafter, one embodiment of the insulating sheet of the present application will be described with reference to the drawings.

[0021] As shown in Figure 1 the insulating sheet 10 of the present embodiment includes two outer layers 13 disposed in opposition to each other, two adhesive layers 12 disposed in opposition to each other between the aforementioned two outer layers 13, and a base material layer 11 disposed between the aforementioned two adhesive layers 12.

[0022] In other words, the insulating sheet 10 of the present embodiment includes one base material layer 11, two adhesive layers 12 disposed in a manner to sandwich the base material layer 11 in the thickness direction, and two outer layers 13 disposed in a manner to sandwich the two adhesive layers 12 in the thickness direction.

[0023] In the present embodiment, the base material layer 11 is in direct contact with one adhesive layer 12, and the base material layer 11 is in direct contact with the other adhesive layer 12. In addition, on one side of the base material layer 11, the adhesive layer 12 is in direct contact with the outer layer 13, and on the other side, the adhesive layer 12 is also in direct contact with the outer layer 13.

[0024] Each outer layer 13 can also be the outermost layer of the insulating sheet 10.

[0025] The thickness of the aforementioned insulating sheet 10 is, for example, 50 μm or more and 500 μm or less. The thickness of the insulating sheet 10 can be 100 μm or more, or 150 μm or more. In addition, the thickness of the insulating sheet 10 can be 450 μm or less, or 400 μm or less.

[0026] From the aspect of further improving the operability when inserting into the slots of the stator (described later), the thickness of the aforementioned insulating sheet 10 is preferably 150 μm or more, and more preferably 200 μm or more.

[0027] The thickness of the substrate layer 11 can be, for example, 25 μm or more and 200 μm or less. The thickness of the substrate layer 11 is preferably 100 μm or less.

[0028] The thickness of the adhesive layer 12 (per 1 layer) can be, for example, 1 μm or more and 150 μm or less. The thickness of the adhesive layer 12 is preferably 5 μm or more and 100 μm or less, and more preferably 25 μm or more and 80 μm or less.

[0029] In the two adhesive layers 12, the thickness of one adhesive layer 12 is preferably small in comparison with the thickness of the other adhesive layer 12. For example, the thickness of the other adhesive layer 12 can be 0.9 times or more and 1.1 times or less in comparison with the thickness of one adhesive layer 12.

[0030] The thickness of the outer layer 13 (per 1 layer) can be, for example, 10 μm or more and 200 μm or less. The thickness of the outer layer 13 is preferably 20 μm or more and 125 μm or less, and more preferably 25 μm or more and 75 μm or less.

[0031] In the two outer layers 13, the thickness of one outer layer 13 is preferably small in comparison with the thickness of the other outer layer 13. For example, the thickness of the other outer layer 13 can be 0.9 times or more and 1.1 times or less in comparison with the thickness of one outer layer 13.

[0032] In addition, the thickness of each layer described above refers to an average thickness. The thickness of each layer is obtained by averaging the thicknesses of at least 5 randomly selected points. The thickness of any layer is the same.

[0033] The thickness of each layer can be measured, for example, by observing the side surface or cross section of the insulation sheet 10 with a digital microscope.

[0034] The ratio of the thickness of the substrate layer 11 to the total thickness of the insulation sheet 10 can be 0.10 or more, or 0.15 or more. Note that the ratio of the thickness can be 0.50 or less, or 0.40 or less. By making the ratio 0.15 or more, the insulation sheet 10 has the advantage that the electrical insulation is further improved.

[0035] The ratio of the total thickness of the adhesive layers 12 (the thickness of 2 layers) to the total thickness of the insulation sheet 10 can be 0.10 or more, 0.15 or more, 0.20 or more, or 0.30 or more. In addition, the ratio can be 0.70 or less, or 0.60 or less. By making the ratio 0.30 or more, the insulation sheet 10 has the advantage that the thermal conductivity is further improved.

[0036] The ratio of the total thickness of the outer layer 13 (the thickness of 2 layers) to the total thickness of the insulation sheet 10 is preferably 0.10 or more. Note that the ratio can be 0.70 or less, or 0.50 or less. By making the ratio 0.50 or less, the insulation sheet 10 has the advantage that the thermal conductivity is further improved.

[0037] Note that the above-described numerical range related to the ratio of the thickness of each of the adhesive layers 12 to the thickness of each of the outer layers 13 is preferably satisfied in at least either one of the one-side or the other-side of the base material layer 11. More preferably, in both the one-side and the other-side of the base material layer 11, the ratio of the thickness of each of the adhesive layers 12 to the thickness of each of the outer layers 13 is within the above-described numerical range.

[0038] The base material layer 11 in the present embodiment is a resin film. As the resin film, a heat-resistant resin film such as a polyimide resin film or a polyester resin film, or the like can be given. The resin film is preferably a polyester resin film.

[0039] As the above-described polyester resin film, a film formed of a polymer of a dicarboxylic acid such as terephthalic acid or 2,6-naphthalene dicarboxylic acid and a diol such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, or 1,4-cyclohexane dimethanol, or the like can be given.

[0040] Specifically, as the polyester resin film, a polyethylene terephthalate resin (PET) film or a polyethylene naphthalate resin (PEN) film, or the like can be given.

[0041] The base material layer 11 is more preferably a polyethylene naphthalate resin film.

[0042] The base material layer 11 can be a single layer as in the present embodiment, or can be a laminated film in which a plurality of resin films are laminated.

[0043] As the above-described base material layer 11, a commercially available product such as the product name "TEONEX" series (manufactured by Toyobo Co., Ltd.), or the like can be given.

[0044] Both of the adhesive layers 12 constituting the insulation sheet 10 of the present embodiment contain an inorganic filler, and further contain a polymer component (adhesive component), a crosslinking agent, and a tackifier, or the like.

[0045] The adhesive layer 12 can contain 20% by volume or more and 60% by volume or less of an inorganic filler. The content ratio of the inorganic filler in the adhesive layer 12 is preferably 25% by volume or more. Thereby, the adhesive layer 12 has the advantage that the thermal conductivity is further improved. The content ratio of the inorganic filler is preferably 50% by volume or less, and more preferably 45% by volume or less. Thereby, the adhesive layer 12 has the advantage that the adhesive layer 12 and the outer layer 13 can be more sufficiently adhered.

[0046] Note that the above volume value is calculated from the mass and specific gravity of each material. Specifically, the calculation is performed in accordance with the following calculation formula.

[0047] Inorganic filler content [vol%] = 100 x (A / A') / [(A / A') + (B / B')]

[0048] A: mass of inorganic filler, A': specific gravity of inorganic filler,

[0049] B: mass of polymer component, B': specific gravity of polymer component

[0050] As the inorganic filler, a magnesium carbonate filler or an alumina filler, or the like can be given. The inorganic filler preferably contains at least a magnesium carbonate filler.

[0051] The shape of each particle of the inorganic filler is not particularly limited. The shape of each particle is, for example, spherical, needle-like, plate-like, or amorphous (a shape that cannot be determined), or the like. Note that the spherical shape includes a regular spherical shape and an oblate spherical shape.

[0052] As the polymer component, for example, an acrylic polymer, or the like can be given.

[0053] The above acrylic polymer is preferably a polymer polymerized from at least an alkyl (meth)acrylate.

[0054] The above acrylic polymer can be, for example, a polymer of an alkyl (meth)acrylate, or a copolymer of an alkyl (meth)acrylate and another polymerizable monomer. Note that in the present specification, the expression "(meth)acrylic acid" means both "acrylic acid" and "methacrylic acid".

[0055] As the alkyl (meth)acrylate, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate [for example, n-propyl (meth)acrylate, isopropyl (meth)acrylate, or the like], butyl (meth)acrylate [for example, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, or the like], 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, or isononyl (meth)acrylate, or the like can be given.

[0056] As the other polymerizable monomer, for example, ethylene, styrene, vinyl chloride, acrylic acid, butadiene, or acrylonitrile, or the like can be given.

[0057] As the copolymer, for example, ethylene-(meth)alkyl acrylate copolymer, ethylene-(meth)alkyl acrylate-acrylic acid copolymer, styrene-(meth)alkyl acrylate-acrylic acid copolymer, (meth)alkyl acrylate-vinyl chloride copolymer, (meth)alkyl acrylate-acrylic acid copolymer, (meth)alkyl acrylate-vinyl chloride copolymer, styrene-(meth)alkyl acrylate-butadiene copolymer, and (meth)alkyl acrylate-acrylonitrile copolymer, and the like can be exemplified.

[0058] As the above-described acrylic polymer, polybutyl acrylate (PAB) which is a polymer of at least butyl (meth)acrylate is preferable. The polybutyl acrylate (PAB) can have a carboxyl group or a hydroxyl group, or the like in the molecule.

[0059] The above-described acrylic polymer can be used alone as one kind or in combination as two or more kinds.

[0060] As the above-described crosslinking agent, for example, isocyanate compounds, and the like can be exemplified.

[0061] The isocyanate compound is preferably a polyfunctional isocyanate compound. The polyfunctional isocyanate compound is a compound having a plurality of isocyanate groups in the molecule.

[0062] As the polyfunctional isocyanate compound, for example, diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and the like can be exemplified.

[0063] The polyfunctional isocyanate compound can be an adduct of a trimer of toluene diisocyanate added to trimethylolpropane.

[0064] As the above-described tackifier, for example, petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, or alicyclic copolymers, coumarone-indene resins, terpene resins, terpene phenol resins, rosin resins such as polymerized rosin, alkylphenol resins, xylene resins, or hydrogenated products thereof, and the like can be exemplified.

[0065] The tackifier can be used alone as one kind or in combination as two or more kinds.

[0066] The adhesive layer 12 preferably contains a high molecular compound which is a crosslinking reaction product of the above-described polybutyl acrylate (PAB) as a polymer component and the above-described isocyanate compound as a crosslinking agent.

[0067] The adhesive layer 12 more preferably contains a cross-linking reactant of polybutyl acrylate (PAB) and an isocyanate compound and an alkylphenol resin as an adhesion promoter. Thereby, the adhesion of the adhesive layer 12 to the outer layer 13, particularly the aromatic polyamide paper, becomes more favorable. The addition amount of the alkylphenol resin is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 30 parts by mass or less, with respect to 100 parts by mass of polybutyl acrylate (PAB).

[0068] Note that the polybutyl acrylate (PAB) can have a carboxyl group in the molecule.

[0069] The unit area weight of the adhesive layer 12 can be, for example, 20 g / m 2 240 g / m 2 or more.

[0070] The adhesive layer 12 described above can be formed of a commercially available polymer, for example. The adhesive layer 12 described above can be formed of a polymer composition in which a plurality of polymers are subjected to a cross-linking reaction, for example.

[0071] Both of the outer layers 13 constituting the insulation sheet 10 of the present embodiment are preferably aromatic polyamide papers. By the outer layers 13 being aromatic polyamide papers, the insulation sheet 10 of the present embodiment can have favorable heat resistance. In addition, for example, after the insulation sheet 10 is disposed in the slots of a motor stator, favorable slidability can be imparted when a coil wire is inserted.

[0072] As the aromatic polyamide paper, for example, a wholly aromatic polyamide paper in which at least one of short fibers composed of a wholly aromatic polyamide and synthetic pulp composed of a wholly aromatic polyamide is paper-made, a sheet containing at least one of short fibers composed of an aromatic polyamide or synthetic pulp composed of an aromatic polyamide and mica powder (mica sheet), or a sheet subjected to a calendering process treatment at high temperature / high pressure, or the like can be used.

[0073] As the aromatic polyamide paper, from the aspect of the insulation sheet 10 being able to have more favorable heat resistance, a wholly aromatic polyamide paper is preferable.

[0074] As the wholly aromatic polyamide constituting the short fibers or the synthetic pulp described above, for example, a condensate of m-phenylenediamine and isophthalic acid, a condensate of p-phenylenediamine and terephthalic acid, or the like can be exemplified.

[0075] The outer layer 13 described above can be subjected to a lamination process or a surface treatment, or the like. The surface treatment can be performed using a coating agent containing a polyamide resin (for example, a methoxymethylated polyamide resin in which an amido group is methoxymethylated) or the like. Note that, as the outer layer 13 described above, for example, a commercially available product (product name "Nomex", manufactured by DuPont, or the like) can be used.

[0076] The insulation sheet 10 of the present embodiment has a volume resistivity of 1 x 10 13 Ω-cm or more. The volume resistivity of the insulation sheet 10 is preferably 1 x 10 14 Ω-cm or more.

[0077] The insulation sheet 10 of the present embodiment has good thermal conductivity and high adhesion between the outer layer 13 and the adhesive layer 12.

[0078] The adhesive layer 12 can further improve the adhesion described above by containing the acrylic polymer described above. The adhesive layer 12 can more sufficiently impart thermal conductivity to the insulation sheet 10 by containing magnesium carbonate filler as an inorganic filler.

[0079] Next, a manufacturing method of the insulation sheet 10 of the present embodiment will be described.

[0080] In the manufacturing method of the insulation sheet 10 of the present embodiment, for example, a mixture containing each component constituting the adhesive layer 12 described above and an organic solvent (as needed) is prepared, the mixture is applied to both surfaces of the base material layer 11, and the organic solvent contained in the applied mixture is volatilized (as needed) to produce two adhesive layers 12. Further, by adhering the outer layer 13 to each adhesive layer 12, the insulation sheet 10 can be manufactured.

[0081] Note that, as the application device, for example, a roll coater or the like can be used.

[0082] As the organic solvent described above, for example, ethyl acetate, methyl ethyl ketone (MEK), toluene, or the like can be used.

[0083] When the mixture containing the organic solvent is applied to the outer layer 13, a conventional application method such as die coating or reverse coating can be used. The temperature during application is, for example, room temperature (15 to 25°C).

[0084] The insulation sheet 10 manufactured as described above is used, for example, for a component constituting a motor. The insulation sheet 10 can also be used, for example, as an insulation sheet for a drive motor of an automobile. Specifically, it can be used for a slot insulation paper for a motor stator. The insulation sheet 10 can be used, for example, in a heated state.

[0085] As the automobile, for example, a hybrid electric vehicle (HEV) or an electric vehicle (EV) or the like can be given. As the drive motor, for example, an HV motor, a motor generator, an alternator, a 4WD motor, an oil pump motor, an EPS motor, a compressor motor, or a hub motor or the like can be given.

[0086] Next, one embodiment of a motor of the present application will be described with reference to the drawings.

[0087] The motor of the present embodiment has the above-described insulating sheet 10. The insulating sheet 10 is, for example, an insulating sheet for a motor.

[0088] The motor is, for example, a driving motor mounted on a hybrid automobile or an electric automobile, or the like.

[0089] The driving motor of the automobile has a rotor having a permanent magnet and a stator 20 that generates a force for rotating the rotor. As shown in FIG. 1, the stator 20 has a coil 21 and a stator core 22. The stator 20 rotates the rotor by causing the coil 21 to generate a magnetic field. Figure 2

[0090] In the driving motor described above, the coil 21 is composed of a plurality of segment conductors connected to each other, for example. In the driving motor described above, a core such as the stator core 22 or a rotor core has a plurality of slot grooves in which the respective coils 21 are housed.

[0091] In the driving motor described above, in order to ensure insulation between the coil 21 and the inner wall surface of the slot groove, an insulating sheet for a motor is used. The insulating sheet for a motor and the coil 21 are housed in the slot groove. In detail, the insulating sheet for a motor is housed in the slot groove in a state of being disposed around the coil 21.

[0092] Further, the coil 21 wound by the insulating sheet for a motor is fixed in the slot groove by an insulating resin (for example, an epoxy varnish) impregnated in the slot groove.

[0093] The insulating sheet and the motor of the present embodiment are as exemplified above, but the present application is not limited to the above-described exemplified insulating sheet or motor.

[0094] That is, various modes used in general insulating sheets or motors can be employed within a range that does not impair the effects of the present application.

[0095] The matters disclosed in the present specification include the following matters. (1)

[0097] An insulating sheet having: two outer layers disposed in a manner facing each other, two adhesive layers disposed in a manner facing each other between the two outer layers, and a base material layer disposed between the two adhesive layers,

[0098] Each of the two adhesive layers contains an inorganic filler.

[0099] The insulating sheet configured as described above has good thermal conductivity and has relatively large adhesive force between the outer layers and the adhesive layers. (2)

[0101] ​The insulation sheet according to any one of the above (1) to (3), wherein each of the two outer layers is an aromatic polyamide paper. (3)

[0103] The insulation sheet according to any one of the above (1) or (2), wherein the particle shape of the inorganic filler is spherical. (4)

[0105] The insulation sheet according to any one of the above (1) to (3), wherein each of the two outer layers is an aromatic polyamide paper. (5)

[0107] The insulation sheet according to any one of the above (1) to (4), wherein each of the two adhesive layers contains an acrylic polymer. (6)

[0109] The insulation sheet according to the above (5), wherein the acrylic polymer is an acrylic polymer obtained by polymerization of at least an alkyl (meth)acrylate. (7)

[0111] The insulation sheet according to the above (6), wherein the adhesive layer contains a high molecular compound which is a crosslinking reaction product of butyl (meth)acrylate which is a (meth)acrylate of the above (1) to (7) and an isocyanate compound which is a crosslinking agent, and an alkylphenol resin which is a tackifier. (8)

[0113] The insulation sheet according to any one of the above (1) to (7), wherein the base material layer is a polyethylene naphthalate resin film. (9)

[0115] A motor provided with the insulation sheet according to any one of the above (1) to (8).

[0116] Examples

[0117] Next, the present application will be described in more detail by way of experimental examples, but the present application is not limited thereto.

[0118] The following shows the materials or raw materials for each of the outer layer, the adhesive layer, and the base material layer of the insulation sheet.

[0119] [Material of the outer layer]

[0120] [Para-aramid paper (PA paper)]

[0121] Thickness: 40 μm for one layer Commercially available product

[0122] <Raw materials of the adhesive layer>

[0123] [Inorganic filler]

[0124] • Anhydrous magnesium carbonate filler (particle shape: amorphous)

[0125] Product name "MAG Thermo" MS-S (manufactured by Kaneka Corporation)

[0126] • Alumina filler (particle shape: spherical)

[0127] A mixture of 70:30 (mass ratio) of product name "AW-17-25" and product name "AX3-32" (both manufactured by MICRON)

[0128] [Polymer component]

[0129] Polybutyl acrylate (PAB) (commercial product) 100 parts by mass

[0130] [Crosslinking agent]

[0131] Polyisocyanate compound (commercial product) 5 parts by mass

[0132] [Adhesion promoter]

[0133] Alkylphenol resin (commercial product) 20 parts by mass

[0134] <Materials of the substrate layer>

[0135] • Polyethylene naphthalate resin film (PEN)

[0136] Product name "TEONEX Q51" (manufactured by Toyobo Co., Ltd.) Thickness: 50 μm

[0137] (Examples 1 to 9, Comparative Examples 1 to 3)

[0138] The constitution of the insulating sheet of each example and each comparative example (thickness, material, etc. of each layer) is shown in Table 1 and Table 2. Note that any of the insulating sheets of the examples and the comparative examples has a 5-layer laminated structure as shown in Table 1 and Table 2. Figure 1

[0139] Note that each of Reference Examples 1 to 3 has a structure of one resin film.

[0140] <Manufacture of the insulating sheet>

[0141] ​A mixture containing each of the above-mentioned components constituting the adhesive layer and an organic solvent (methyl ethyl ketone (MEK)) was prepared. The mixture was applied to one face of the base material layer using a bar coater, respectively, so that the thickness of the dried adhesive layer would be a prescribed thickness. The organic solvent contained in the applied mixture was volatilized (dried) by drying treatment at 110°C for 3 minutes, and the adhesive layer was produced on the single face side of the base material layer. Further, a 3-layered laminate was produced by attaching the outer layer on the adhesive layer. Subsequently, the adhesive layer and the outer layer were produced on the other face of the base material layer in the same manner as described above. As described above, each of the insulating sheets having a 5-layered structure was manufactured.

[0142] [Table 1]

[0143]

[0144] [Table 2]

[0145]

[0146] The thermal conductivity and the adhesive force of the outer layer to the adhesive layer were evaluated for each of the insulating sheets manufactured in each of the examples and each of the comparative examples as described below.

[0147] <Thermal conductivity of the insulating sheet>

[0148] The thermal conductivity at 62.5°C was measured for each of the insulating sheets by the guarded hot plate method (steady state method) in accordance with ASTM E1530.

[0149] <Adhesive force (peeling force) of the outer layer to the adhesive layer of the insulating sheet>

[0150] The peeling force (peeling strength) between the outer layer and the adhesive layer was measured for each of the insulating sheets by the following operation.

[0151] Specifically, the peeling force was measured when the outer layer was stretched at a peeling angle of 180° at a peeling speed of 100 mm / minute using a tensile testing machine. The temperature at the time of measurement was 23°C.

[0152] The test results are shown in Table 1 and Table 2, respectively.

[0153] As is apparent from Table 1 and Table 2, the insulating sheet of the example has a higher thermal conductivity and a higher adhesive force of the outer layer to the adhesive layer than the insulating sheet of the comparative example.

[0154] As is apparent from the results of Example 1, Examples 4 to 8, and Comparative Example 1, by making the content of the anhydrous magnesium carbonate filler in the adhesive layer less than 50% by volume, cohesive failure of the aromatic polyamide paper (the outer layer) occurred in the peeling strength test, and a more favorable peeling strength was exerted. It can be said that the content of the anhydrous magnesium carbonate filler in the adhesive layer is particularly preferably 25% by volume or more and 45% by volume or less.

[0155] From the results of Example 1 and Example 9, in the case where the adhesive layer contains 50% by volume of inorganic filler, in the peeling strength test, peeling occurred at the interface between the outer layer and the adhesive layer in Example 1, but cohesive failure of the outer layer occurred in Example 9. It is considered that the reason is the particle shape of the inorganic filler. It is considered that by making the particle shape spherical, the specific surface area of the filler particles decreases, the polymer component (adhesive component) adhering to the surface of the particles decreases, and accordingly the adhesion between the outer layer and the adhesive layer increases, as compared with the case where the particle shape is amorphous. It can be said that the particle shape of the inorganic filler is preferably spherical.

[0156] From the results of Example 2, 3, 6, 8, and Comparative Examples 1 to 3, if the adhesive layer does not contain inorganic filler, the thermal conductivity does not depend on the thickness of the adhesive layer (Comparative Examples 1 to 3). On the other hand, in the adhesive layer containing inorganic filler, even if the content rate of inorganic filler is reduced, by thickening the thickness of the adhesive layer, approximately the same thermal conductivity can be exerted (Example 2 and 6, Example 3 and 8). By adjusting the content rate of inorganic filler and the thickness of the adhesive layer, respectively, it is possible to maintain the thermal conductivity at a desired high value.

[0157] In recent years, for example in the automobile industry, the electrification of automobiles is accelerating. Along with this, development of high-output and downsized (lightweight) motors is being continuously made. However, with the development of high-output of the motor, the heat generation amount of the motor also increases. If the heat generation amount increases, higher heat resistance performance is required for each component of the motor. If the heat resistance limit is exceeded, the resistance increases, and a decrease in energy efficiency of the motor, a decrease in output, and the like can occur. In the stator constituting the motor, the heat generation amount from the coil wire will also increase in the future, and therefore performance of efficiently transferring the generated heat to the core with the insulation sheet arranged in the slot is required. That is, it is desired that the insulation sheet has good thermal conductivity.

[0158] Industrial applicability

[0159] The insulation sheet of the present application is, for example, used for the purpose of constituting a component of a motor. The insulation sheet of the present application is, for example, included in a motor and used appropriately.

[0160] Explanation of reference numerals

[0161] 11: base material layer, 12: adhesive layer, 13: outer layer, 10: insulation sheet.

Claims

1. An insulating sheet comprising: two outer layers arranged opposite to each other; two adhesive layers arranged opposite to each other between the two outer layers; and a substrate layer disposed between the two adhesive layers. Both adhesive layers contain inorganic fillers.

2. The insulating sheet according to claim 1, wherein, The two adhesive layers each contain more than 20% by volume and less than 50% by volume of the inorganic filler.

3. The insulating sheet according to claim 1 or 2, wherein, The inorganic filler particles are spherical in shape.

4. An electric motor having the insulating sheet as described in claim 1 or 2.

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