Insulating sheet and motor

Abstract

Provided is an insulating sheet or the like comprising 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 material layer disposed between the two adhesive layers, each of the two adhesive layers containing an inorganic filler.

Description

Insulation sheet and motor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Japanese Patent Application No. 2023-107332, which is incorporated herein by reference.

[0002] The present invention relates to an insulating sheet that is a component of a motor, for example, and a motor that includes the insulating sheet.

[0003] Conventionally, an insulating sheet has been known that includes a base layer, two outer layers arranged to face one side and the other side of the base layer, respectively, and two adhesive layers arranged between one and the other outer layer and the base layer, respectively.

[0004] Known examples of this type of insulating sheet include an insulating sheet for use in a motor, such as an insulating sheet having a five-layer structure in which a base layer is formed of a polyester film and one outer layer and the other outer layer are bonded to the base layer by two adhesive layers formed of an acrylic adhesive (see, for example, Patent Document 1).

[0005] In the insulating sheet described in Patent Document 1, the outer layer is adhered to the adhesive layer.

[0006] Japanese Patent Application Publication No. 2006-262687

[0007] However, the insulating sheet described in Patent Document 1 does not necessarily have good thermal conductivity. Therefore, there is a demand for an insulating sheet that has good thermal conductivity and good adhesion between the outer layer and the adhesive layer.

[0008] In view of the above problems and demands, an object of the present invention is to provide an insulating sheet having good thermal conductivity and good adhesion between the outer layer and the adhesive layer, and to provide a motor including the insulating sheet.

[0009] In order to solve the above problems, the insulating sheet of the present invention comprises two outer layers arranged to face each other, two adhesive layers arranged to face each other between the two outer layers, and a base material layer arranged between the two adhesive layers, and both of the two adhesive layers contain an inorganic filler.

[0010] A motor according to the present invention includes the insulating sheet described above.

[0011] Fig. 1 is a schematic cross-sectional view of an insulating sheet according to this embodiment, cut in the thickness direction, and Fig. 2 is a perspective view of a stator of a drive motor.

[0012] Hereinafter, an embodiment of an insulating sheet according to the present invention will be described with reference to the drawings.

[0013] As shown in FIG. 1 , the insulating sheet 10 of this embodiment includes two outer layers 13 arranged to face each other, two adhesive layers 12 arranged to face each other between the two outer layers 13, and a base material layer 11 arranged between the two adhesive layers 12. In other words, the insulating sheet 10 of this embodiment includes one base material layer 11, two adhesive layers 12 arranged to sandwich the base material layer 11 in the thickness direction, and two outer layers 13 arranged to sandwich the two adhesive layers 12 in the thickness direction. In this embodiment, the base material layer 11 and one of the adhesive layers 12 are in direct contact with each other, and the base material layer 11 and the other adhesive layer 12 are in direct contact with each other. Furthermore, the adhesive layer 12 and the outer layer 13 are in direct contact with each other on one side of the base material layer 11, and the adhesive layer 12 and the outer layer 13 are also in direct contact with each other on the other side. Each outer layer 13 may be the outermost layer of the insulating sheet 10.

[0014] The thickness of the insulating sheet 10 is, for example, 50 μm or more and 500 μm or less. The thickness of the insulating sheet 10 may be 100 μm or more, or 150 μm or more. The thickness of the insulating sheet 10 may be 450 μm or less, or 400 μm or less. The thickness of the insulating sheet 10 is preferably 150 μm or more, and more preferably 200 μm or more, in order to further improve the workability when inserting the insulating sheet 10 into the slots of a stator (described in detail later).

[0015] The thickness of the base layer 11 may be, for example, 25 μm or more and 200 μm or less, and is preferably 100 μm or less.

[0016] The thickness of the adhesive layer 12 (per layer) may 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. Of the two adhesive layers 12, it is preferable that the difference in thickness between one adhesive layer 12 and the other adhesive layer 12 is small. For example, the thickness of the other adhesive layer 12 may be 0.9 times or more and 1.1 times or less the thickness of one adhesive layer 12.

[0017] The thickness of the outer layer 13 (per layer) may 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. Of the two outer layers 13, it is preferable that the difference in thickness between one outer layer 13 and the other outer layer 13 is small. For example, the thickness of one outer layer 13 may be 0.9 times or more and 1.1 times or less the thickness of the other outer layer 13.

[0018] The thickness of each layer mentioned above refers to the average thickness. The thickness of each layer is determined by averaging the thicknesses of at least five randomly selected locations. The thickness of each layer is the same. The thickness of each layer can be measured, for example, by observing the side or cross section of the insulating sheet 10 with a digital microscope.

[0019] The ratio of the thickness of the base layer 11 to the total thickness of the insulating sheet 10 may be 0.10 or more, or 0.15 or more. This thickness ratio may be 0.50 or less, or 0.40 or less. A ratio of 0.15 or more has the advantage of further improving the electrical insulation of the insulating sheet 10.

[0020] The ratio of the total thickness of the adhesive layers 12 (the thickness of two layers) to the total thickness of the insulating sheet 10 may be 0.10 or more, 0.15 or more, 0.20 or more, or 0.30 or more. Furthermore, this ratio may be 0.70 or less, or 0.60 or less. Having this ratio of 0.30 or more has the advantage of further improving the thermal conductivity of the insulating sheet 10.

[0021] The ratio of the total thickness of the outer layers 13 (the thickness of two layers) to the total thickness of the insulating sheet 10 is preferably 0.10 or more. However, this ratio may be 0.70 or less, or 0.50 or less. A ratio of 0.50 or less has the advantage of further improving the thermal conductivity of the insulating sheet 10.

[0022] It is preferable that the above-mentioned numerical ranges relating to the ratios of the thicknesses of the adhesive layer 12 to the thicknesses of the outer layer 13 are satisfied on at least one side or the other side of the base layer 11. It is more preferable that the ratios of the thicknesses of the adhesive layer 12 to the thicknesses of the outer layer 13 are within the above-mentioned numerical ranges on both sides of the base layer 11.

[0023] The base material layer 11 in this embodiment is a resin film. Examples of the resin film include a heat-resistant resin film such as a polyimide resin film, a polyester resin film, etc. The resin film is preferably a polyester resin film.

[0024] Examples of the polyester resin film include films formed from a polymer of a dicarboxylic acid such as terephthalic acid or 2,6-naphthalenedicarboxylic acid and a diol such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, or 1,4-cyclohexanedimethanol. Specific examples of the polyester resin film include polyethylene terephthalate resin (PET) film and polyethylene naphthalate resin (PEN) film.

[0025] The base layer 11 is more preferably a polyethylene naphthalate resin film.

[0026] The base material layer 11 may be a single layer as in this embodiment, or may be a laminate film in which a plurality of resin films are laminated.

[0027] As the base material layer 11, for example, a commercially available product such as the "Teonex" series (manufactured by Toyobo Co., Ltd.) can be used.

[0028] The two adhesive layers 12 constituting the insulating sheet 10 of this embodiment each contain an inorganic filler, and further contain a polymer component (adhesive component), a crosslinking agent, a tackifier, and the like.

[0029] The adhesive layer 12 may contain 20% by volume or more and 60% by volume or less of inorganic filler. The content of inorganic filler in the adhesive layer 12 is preferably 25% by volume or more. This has the advantage of further improving the thermal conductivity of the adhesive layer 12. The content of inorganic filler is preferably 50% by volume or less, and more preferably 45% by volume or less. This has the advantage of more sufficiently bonding the adhesive layer 12 and the outer layer 13. The above volume % values ​​are calculated from the mass and specific gravity of each material. Specifically, they are calculated according to the following formula: Inorganic filler content [vol %] = 100 x (A / A') / [(A / A') + (B / B')] A: mass of inorganic filler, A': specific gravity of inorganic filler, B: mass of polymer component, B': specific gravity of polymer component

[0030] Examples of the inorganic filler include magnesium carbonate filler and alumina filler. The inorganic filler preferably contains at least magnesium carbonate filler.

[0031] The shape of each particle of the inorganic filler is not particularly limited. The shape of each particle may be, for example, spherical, needle-like, plate-like, or irregular (unspecified shape). Note that spherical includes true spheres and ellipsoids.

[0032] The polymer component may be, for example, an acrylic polymer.

[0033] The acrylic polymer is preferably a polymer obtained by polymerizing at least a (meth)acrylic acid alkyl ester. The acrylic polymer may be, for example, a polymer of a (meth)acrylic acid alkyl ester, or a copolymer of a (meth)acrylic acid alkyl ester and another polymerizable monomer. In this specification, the term "(meth)acrylic" includes both "acrylic" and "methacrylic."

[0034] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate [e.g., normal propyl (meth)acrylate, isopropyl (meth)acrylate, etc.], butyl (meth)acrylate [e.g., normal butyl (meth)acrylate, isobutyl (meth)acrylate, secondary butyl (meth)acrylate, tertiary butyl (meth)acrylate, etc.], 2-ethylhexyl (meth)acrylate, normal octyl (meth)acrylate, normal nonyl (meth)acrylate, and isononyl (meth)acrylate.

[0035] Examples of other polymerizable monomers include ethylene, styrene, vinyl chloride, acrylic acid, butadiene, and acrylonitrile.

[0036] Examples of the copolymer include ethylene-(meth)acrylic acid alkyl ester copolymer, ethylene-(meth)acrylic acid alkyl ester-acrylic acid copolymer, styrene-(meth)acrylic acid alkyl ester-acrylic acid copolymer, (meth)acrylic acid alkyl ester-vinyl chloride copolymer, (meth)acrylic acid alkyl ester-acrylic acid copolymer, (meth)acrylic acid alkyl ester-vinyl chloride copolymer, styrene-(meth)acrylic acid alkyl ester-butadiene copolymer, (meth)acrylic acid alkyl ester-acrylonitrile copolymer, and the like.

[0037] The acrylic polymer is preferably polybutyl acrylate (PAB), which is a polymer of at least butyl (meth)acrylate. Such polybutyl acrylate (PAB) may have a carboxy group or a hydroxy group in the molecule.

[0038] The above acrylic polymers may be used alone or in combination of two or more.

[0039] Examples of the crosslinking agent include isocyanate compounds.

[0040] The isocyanate compound is preferably a polyfunctional isocyanate compound. Such a polyfunctional isocyanate compound is a compound having multiple isocyanate groups in the molecule. Examples of the polyfunctional isocyanate compound include diphenylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate. The polyfunctional isocyanate compound may be an adduct in which tolylene diisocyanate trimer is added to trimethylolpropane.

[0041] Examples of the tackifier include petroleum-based resins such as aliphatic copolymers, aromatic copolymers, aliphatic-aromatic copolymers, and alicyclic copolymers. Further examples include coumarone-indene resins, terpene resins, terpene phenol resins, rosin resins such as polymerized rosin, alkylphenol resins, xylene resins, and hydrogenated products thereof. One type of tackifier may be used alone, or two or more types may be used in combination.

[0042] The adhesive layer 12 preferably contains a polymeric compound that is a crosslinked reaction product of the polybutyl acrylate (PAB) as a polymer component and the isocyanate compound as a crosslinking agent. The adhesive layer 12 more preferably contains a crosslinked reaction product of the polybutyl acrylate (PAB) and the isocyanate compound, and an alkylphenol resin as a tackifier. This improves adhesion between the adhesive layer 12 and the outer layer 13 (especially aromatic polyamide paper). The amount of alkylphenol resin added is preferably 1 part by mass or more and 50 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the polybutyl acrylate (PAB). The polybutyl acrylate (PAB) may have a carboxyl group in its molecule.

[0043] The basis weight of the adhesive layer 12 is, for example, 20 g / m ２ 240g / m or more ２ It may be the following:

[0044] The adhesive layer 12 may be formed of, for example, a commercially available polymer. The adhesive layer 12 may be formed of, for example, a polymer composition in which a plurality of types of polymers are crosslinked.

[0045] Preferably, both of the two outer layers 13 constituting the insulating sheet 10 of this embodiment are made of aromatic polyamide paper. The outer layers 13 are made of aromatic polyamide paper, which allows the insulating sheet 10 of this embodiment to have good heat resistance. Furthermore, after the insulating sheet 10 is placed in a slot of a motor stator, for example, good slipperiness can be imparted when inserting a coil wire.

[0046] Examples of aromatic polyamide paper include fully aromatic polyamide paper made from at least one of short fibers made from fully aromatic polyamide and synthetic pulp made from fully aromatic polyamide; a sheet containing at least one of short fibers made from aromatic polyamide or synthetic pulp made from aromatic polyamide and mica powder (mica flakes); and sheets obtained by subjecting these papers or sheets to high-temperature, high-pressure calendering treatment. As aromatic polyamide paper, fully aromatic polyamide paper is preferred because it provides the insulating sheet 10 with better heat resistance. Examples of fully aromatic polyamides that make up the short fibers or synthetic pulp include a condensation polymer of m-phenylenediamine and isophthalic acid, and a condensation polymer of p-phenylenediamine and terephthalic acid.

[0047] The outer layer 13 may be laminated or surface-treated. The surface treatment may be performed using a coating agent containing a polyamide resin (e.g., a methoxymethylated polyamide resin in which amide groups are methoxymethylated). For example, a commercially available product (e.g., product name "Nomex" manufactured by DuPont) may be used as the outer layer 13.

[0048] The insulating sheet 10 of this embodiment is, for example, 1×10 １３ The insulating sheet 10 has a volume resistivity of 1×10 Ω·cm or more. １４ It is preferably Ω·cm or more.

[0049] The insulating sheet 10 of this embodiment has good thermal conductivity and a relatively high adhesive strength between the outer layer 13 and the adhesive layer 12. The adhesive strength can be further increased by including the acrylic polymer described above in the adhesive layer 12. The adhesive layer 12 can also include a magnesium carbonate filler as an inorganic filler, thereby imparting more sufficient thermal conductivity to the insulating sheet 10.

[0050] Next, a method for manufacturing the insulating sheet 10 of this embodiment will be described.

[0051] In the method for producing the insulating sheet 10 of this embodiment, for example, a mixture containing the components that will constitute the adhesive layer 12 and an organic solvent (if necessary) is prepared, and the mixture is applied to both sides of the base layer 11, and the organic solvent contained in the applied mixture is volatilized (if necessary) to produce two adhesive layers 12. Furthermore, the insulating sheet 10 can be produced by bonding the outer layer 13 to each adhesive layer 12. Note that, for example, a roll coater or the like can be used as the coating device.

[0052] Examples of the organic solvent that can be used include ethyl acetate, methyl ethyl ketone (MEK), and toluene.

[0053] A general coating method such as die coating or reverse coating can be used when applying the mixture containing an organic solvent to the outer layer 13. The temperature during application is, for example, room temperature (15 to 25° C.).

[0054] The insulating sheet 10 manufactured as described above is used, for example, as a component of a motor. The insulating sheet 10 may be used, for example, as an insulating sheet for a drive motor of an automobile. Specifically, it can be used as slot insulating paper for a motor stator. The insulating sheet 10 can be used, for example, in a heated state.

[0055] Examples of the automobile include a hybrid electric vehicle (HEV) and an electric vehicle (EV). Examples of the drive motor include an HV motor, a motor generator, an alternator, a 4WD motor, an oil pump motor, an EPS motor, a compressor motor, and an in-wheel motor.

[0056] Next, an embodiment of a motor according to the present invention will be described with reference to the drawings.

[0057] The motor of this embodiment includes the above-described insulating sheet 10. The insulating sheet 10 is, for example, an insulating sheet for a motor.

[0058] For example, the motor is a drive motor mounted on a hybrid vehicle or an electric vehicle.

[0059] An automobile drive motor includes a rotor equipped with a permanent magnet and a stator 20 that generates a force to rotate the rotor. As shown in Figure 2, 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.

[0060] In the above-described drive motor, the coil 21 is composed of, for example, a plurality of segment conductors connected to each other. In the above-described drive motor, a core such as a stator core 22 or a rotor core has a plurality of slot grooves, and each of the plurality of slot grooves accommodates a coil 21. In addition, in the above-described drive motor, a motor insulating sheet is used to ensure insulation between the coil 21 and the inner wall surfaces of the slot grooves. The motor insulating sheet and the coil 21 are accommodated in each slot groove. More specifically, the motor insulating sheet is accommodated in the slot groove while surrounding the coil 21. The coil 21 wound with the motor insulating sheet is fixed in the slot groove via an insulating resin (e.g., epoxy varnish) impregnated in the slot groove.

[0061] The insulating sheet and motor of this embodiment are as exemplified above, but the present invention is not limited to the insulating sheet or motor exemplified above. In other words, various forms used in general insulating sheets or motors can be adopted as long as they do not impair the effects of the present invention.

[0062] The present specification discloses the following: (1) An insulating sheet comprising two outer layers arranged to face each other, two adhesive layers arranged between the two outer layers to face each other, and a base layer arranged between the two adhesive layers, wherein both of the two adhesive layers contain an inorganic filler. An insulating sheet configured in this manner has good thermal conductivity and relatively high adhesive strength between the outer layers and the adhesive layers. (2) The insulating sheet according to (1) above, wherein each of the two adhesive layers contains 20% by volume or more and 50% by volume or less of the inorganic filler. (3) The insulating sheet according to (1) or (2) above, wherein the inorganic filler particles have a spherical shape. (4) The insulating sheet according to any of (1) to (3) above, wherein both of the two outer layers are aromatic polyamide paper. (5) The insulating sheet according to any of (1) to (4) above, wherein both of the two adhesive layers contain an acrylic polymer. (6) The insulating sheet according to (5) above, wherein the acrylic polymer is an acrylic polymer obtained by polymerizing at least a (meth)acrylic acid alkyl ester. (7) The insulating sheet according to (6) above, wherein the adhesive layer contains a polymer compound that is a crosslinking reaction product of polybutyl acrylate (PAB), which is a polymer of a (meth)acrylic acid butyl ester as the (meth)acrylic acid alkyl ester, with an isocyanate compound as a crosslinking agent, and an alkylphenol resin as a tackifier. (8) The insulating sheet according to any one of (1) to (7) above, wherein the base layer is a polyethylene naphthalate resin film. (9) A motor comprising the insulating sheet according to any one of (1) to (8) above.

[0063] The present invention will now be described in more detail with reference to experimental examples, but the present invention is not limited to these examples.

[0064] The materials or raw materials for the outer layer, adhesive layer, and base layer used to manufacture the insulating sheet are shown below.

[0065] <Outer layer materials> [Fully aromatic polyamide paper (PA paper)] Thickness: 40 μm per layer Commercially available product <Adhesive layer raw materials> [Inorganic filler] - Anhydrous magnesium carbonate filler (particle shape: irregular) Product name "Magthermo MS-S" (manufactured by Konoshima Chemical Co., Ltd.) - Alumina filler (particle shape: spherical) Product name "AW-17-25" and product name "AX3-32" (both manufactured by Micron Corporation) mixed raw material at a ratio of 70:30 (by mass) [Polymer component] Polybutyl acrylate (PAB) (commercially available) 100 parts by mass [Crosslinking agent] Polyisocyanate compound (commercially available) 5 parts by mass [Tackifier] Alkylphenol resin (commercially available) 20 parts by mass

[0066] <Material of base layer> Polyethylene naphthalate resin film (PEN) Product name "Teonex Q51" (manufactured by Toyobo Co., Ltd.) Thickness: 50 μm

[0067] (Examples 1 to 9, Comparative Examples 1 to 3) The configurations (thickness, material, etc. of each layer) of the insulating sheets of each Example and Comparative Example are shown in Table 1 and Table 2, respectively. Note that the insulating sheets of all Examples and Comparative Examples have a five-layer laminate structure as shown in Fig. 1. Note that each of Reference Examples 1 to 3 has a configuration of a single resin film layer.

[0068] <Production of insulating sheet> A mixture containing the above components that would form the adhesive layer and an organic solvent (methyl ethyl ketone (MEK)) was prepared. Each of these mixtures was applied to one side of a base layer using a bar coater so that the adhesive layer would have a predetermined thickness after drying. The organic solvent contained in the applied mixture was volatilized (dried) by drying at 110°C for 3 minutes, creating an adhesive layer on one side of the base layer. Furthermore, an outer layer was bonded to the adhesive layer to create a three-layer laminate sheet. Subsequently, an adhesive layer and an outer layer were created on the other side of the base layer in the same manner as above. In this manner, each insulating sheet with a five-layer structure was produced.

[0069]

[0070]

[0071] The insulating sheets produced in each of the examples and comparative examples were evaluated for thermal conductivity and adhesive strength between the outer layer and the adhesive layer as follows.

[0072] <Evaluation of Thermal Conductivity of Insulating Sheet> The thermal conductivity of each insulating sheet was measured at 62.5°C by the guarded heat flow method (steady state method) in accordance with ASTM E1530.

[0073] <Adhesion strength (peel strength) between outer layer and adhesive layer of insulating sheet> The peel strength (peel strength) between the outer layer and adhesive layer of each insulating sheet was measured as follows. Specifically, the peel strength was measured using a tensile tester when the outer layer was pulled at a peel angle of 180° at a peel rate of 100 mm / min. The temperature during measurement was 23°C.

[0074] The test results are shown in Tables 1 and 2. As can be seen from Tables 1 and 2, the insulating sheets of the examples had higher thermal conductivity and stronger adhesive strength between the outer layer and the adhesive layer than the insulating sheets of the comparative examples.

[0075] As can be seen from the results of Example 1, Examples 4 to 8, and Comparative Example 1, when the content of the anhydrous magnesium carbonate filler in the adhesive layer was less than 50% by volume, the aromatic polyamide paper (outer layer) underwent cohesive failure in the peel strength test, while exhibiting better peel strength. 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. As can be seen from the results of Example 1 and Example 9, when the adhesive layer contained 50% by volume of inorganic filler, peeling occurred at the interface between the outer layer and the adhesive layer in Example 1, but cohesive failure occurred in the outer layer in Example 9. This is thought to be due to the particle shape of the inorganic filler. By using a spherical particle shape rather than an amorphous one, the specific surface area of ​​the filler particles is reduced, and the polymer component (adhesive component) adhering to the particle surface is reduced, thereby improving the adhesive strength between the outer layer and the pressure-sensitive adhesive layer. It can be said that a spherical particle shape of the inorganic filler is preferable. As can be seen from the results of Examples 2, 3, 6, and 8 and Comparative Examples 1 to 3, when 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, when the adhesive layer contains inorganic filler, even if the inorganic filler content is reduced, by increasing the adhesive layer thickness, approximately the same thermal conductivity is exhibited (Examples 2 and 6, Examples 3 and 8). By adjusting the inorganic filler content and the adhesive layer thickness, respectively, the thermal conductivity can be maintained at a desired level.

[0076] In recent years, for example, the automotive industry has seen an acceleration in the electrification of automobiles. Accordingly, the development of high-power, compact (lightweight) motors is progressing. However, as motors become more powerful, the amount of heat generated by them also increases. As the amount of heat generated increases, each component of the motor is required to have higher heat resistance. Exceeding the heat resistance limit increases electrical resistance, which can lead to reduced energy efficiency and output in the motor. As the amount of heat generated by the coil wires in the stators that make up motors will also increase in the future, there is a demand for the ability to efficiently transfer the generated heat to the core via insulating sheets placed within the slots. In other words, insulating sheets are required to have good thermal conductivity.

[0077] The insulating sheet of the present invention is preferably used, for example, as a component of a motor.The insulating sheet of the present invention is preferably used, for example, by being provided in a motor.

[0078] 11: Base material layer, 12: Adhesive layer, 13: Outer layer, 10: Insulating sheet.

Claims

1. An insulating sheet comprising two outer layers arranged to face each other, two adhesive layers arranged to face each other between the two outer layers, and a base material layer arranged between the two adhesive layers, wherein both of the two adhesive layers contain inorganic filler.

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

3. The insulating sheet according to claim 1 or 2, wherein the inorganic filler particles have a spherical shape.

4. A motor comprising the insulating sheet according to claim 1 or 2.

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