Magnetic shield for wireless power transfer

Abstract

To provide a magnetic shield used in a wireless power supply system using an Fe-Si-Al alloy, capable of sufficiently shielding magnetism due to a complicated shape and high power.SOLUTION: A magnetic shield for a wireless power supply includes a thermoplastic resin (A) and soft magnetic particles (B), and the soft magnetic particles (B) include scaly soft magnetic particles (b1) made of Fe-Si-Al surface-treated with an inorganic compound, in which the ratio of the Fe element amount (t1) present on the particle surface before the surface treatment to the Fe element amount (t2) present on the particle surface after the surface treatment satisfies 0.05<t2 / t1<0.7, and has a thickness of 2 to 5 mm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a magnetic shielding body used in wireless power transfer systems. [Background technology]

[0002] In recent years, the development of wireless power supply systems utilizing magnetic resonance-based contactless power transmission has been actively pursued. Wireless power supply refers to the transmission of power without the use of metal contacts or connectors, and the technology behind it. It is also called wireless power transmission, wireless charging, or contactless power transmission. For example, Patent Document 1 proposes wireless charging for charging a vehicle battery, in which power is transmitted between a power supply (transmitting) coil on the road surface and a power receiving coil on the vehicle. In this method, the power supply coil and the power receiving coil are placed opposite each other at a predetermined distance, and power is transmitted by causing the power receiving coil to resonate with the magnetic field vibrations generated by the power supply coil. This method has the advantage of being able to transmit over longer distances compared to power transmission methods using electromagnetic induction between coils.

[0003] During power supply, multiple receiving coils are positioned near the top surface of the power supply coil to receive power from it. At this time, a magnetic shield is installed between the receiving coil and the equipment to be powered by the vehicle to prevent the magnetic flux from the power supply coil from causing malfunctions in electronic circuits and other equipment installed inside the vehicle. Patent Document 2 describes a technology that suppresses leakage of magnetic flux generated during power supply using this magnetic shield. As this magnetic shield, a sheet is known in which soft magnetic powder is kneaded into a sheet made of silicone or other rubber.

[0004] As such a magnetic shielding body, Patent Document 3 discloses a magnetic material comprising flattened magnetic powder dispersed in an insulating material, wherein the complex permeability and loss tangent are within a specific range. In the examples of the same document, a magnetic shielding body is disclosed in which permalloy, which is a flattened magnetic powder, is added to an epoxy resin with a solid content ratio of 40%, and the resulting mixture is formed into a film by the doctor blade method. Patent Document 4 discloses an electromagnetic wave absorbing material containing a specific graphite as a dielectric constant modifier along with a dielectric and / or magnetic material. Examples 7 to 9 of the same document disclose a 100 μm thick sheet-like electromagnetic wave absorbing material formed by a bar coater using a paint mixture containing hydrogenated acrylonitrile-butadiene rubber, a flattened soft magnetic material, graphite or carbon black, and a solvent. Furthermore, Patent Document 5 discloses a coating film containing a binder and a magnetic filler, with the objective of providing a coating film that can be formed by a simple process of painting and has excellent magnetic shielding properties. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-036389 [Patent Document 2] Japanese Patent Publication No. 2008-206234 [Patent Document 3] Japanese Patent Publication No. 2012-134463 [Patent Document 4] Japanese Patent Publication No. 2004-336028 [Patent Document 5] Japanese Patent Publication No. 2016-21490 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Conventional wireless power transfer systems have primarily been used for small, low-power devices such as communication equipment. However, in recent years, there has been a growing demand for high-power applications in large industrial machinery and electric vehicles. As wireless power transfer systems become larger, the coil shapes become more complex, and the magnetic shield shapes also become more complex. In the case of sheet-type systems like the one described in Patent Document 4, multiple sheets must be bonded together. This creates gaps between the sheet members, which weakens the magnetic shielding effect and prevents the system from functioning as intended.

[0007] In addition, a method of forming a coating film having magnetic shielding properties as described in Patent Document 5 on the surface can be considered. However, in a coating film formed of such a magnetic shielding paint, there is a problem that the film thickness is thin and it is difficult to sufficiently shield the magnetism generated by high power.

[0008] In order to improve the transmission efficiency in a wireless power supply system using magnetic resonance non-contact power transmission, it is essential to enhance the magnetic shielding effect of the magnetic material. At the same time, it is required to suppress the eddy current generated in the magnetic material and suppress the decrease in the transmission efficiency due to the decrease in the coil inductance caused by the heat generation of the coil.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide a magnetic shield for use in a wireless power supply system using an Fe-Si-Al alloy, which can sufficiently shield magnetism generated by a complex shape and high power.

Means for Solving the Problems

[0010] As a result of intensive studies by the present inventors, it has been found that the problems of the present invention can be solved in the following aspects, and the present invention has been completed. [1]: Containing a thermoplastic resin (A) and soft magnetic particles (B), The soft magnetic particles (B) include flaky soft magnetic particles (b1) made of an Fe-Si-Al alloy surface-treated with an inorganic compound, where the ratio of the amount of Fe element (t1) present on the particle surface before surface treatment to the amount of Fe element (t2) present on the particle surface after surface treatment is 0.05 < t2 / t1 < 0.7, A magnetic shield for wireless power supply, characterized in that the thickness is 1.5 to 5 mm. [2]: The flaky soft magnetic particles (b1) are an Fe-Si-Al alloy surface-treated with at least one of silica, alumina, zirconia, and titania. The magnetic shield for wireless power supply according to [1]. [3]: The thermal diffusivity in the in-plane direction is 1.5 [mm 2The magnetic shield body for wireless power supply according to [1] or [2], characterized in that it is as described above. [4]: Characterized in that the surface resistivity is 1 × 10 3 The magnetic shield body for wireless power supply according to any one of [1] to [3], characterized in that it is [Ω / □] or more. [5]: The magnetic shield body for wireless power supply according to any one of [1] to [4], characterized in that the thermoplastic resin (A) contains a polyamide resin. [Advantages of the Invention]

[0011] According to the present invention, it is possible to provide a magnetic shield body using an Fe—Si—Al alloy that can sufficiently shield magnetism due to a complex shape and high power in a wireless power supply system. [Embodiments for Carrying Out the Invention]

[0012] Hereinafter, an example of an embodiment to which the present invention is applied will be described. However, the present invention is not limited to the above-described embodiments and modified examples, and other embodiments may belong to the present invention as long as they conform to the gist of the present invention. Further, the embodiments and modified examples described below can be suitably combined with each other. Further, the numerical range “A to B” specified in the present invention means a range that satisfies a value greater than the numerical value A and a value less than the numerical value B. The numerical values specified in this specification are values obtained by the methods disclosed in the embodiments or examples. Further, the sheet in this specification is synonymous with a film or a plate. Unless otherwise noted, the various components appearing in this specification may each be used alone or in combination of two or more.

[0013] [Magnetic Shield Body for Wireless Power Supply] The magnetic shield body for wireless power supply in the present embodiment contains a thermoplastic resin (A) and soft magnetic particles (B), and has a thickness of 1.5 to 5 mm. Furthermore, the soft magnetic particles (B) include flaky soft magnetic particles (b1) made of an Fe-Si-Al alloy surface-treated with an inorganic compound, where the ratio of the amount of Fe element (t1) present on the particle surface before surface treatment to the amount of Fe element (t2) present on the particle surface after surface treatment is 0.02 < t2 / t1 < 0.7. As a result, in a wireless power supply system, it is possible to sufficiently shield magnetism caused by complex shapes and high power, and it can also be suitably used in a large-sized wireless power supply system for industrial machines, electric vehicles, etc.

[0014] When the thickness of the magnetic shield for wireless power supply is 1.5 to 5 mm, it is possible to achieve both high magnetic shielding performance and weight reduction in mounting on automobiles and industrial machines. The thickness is preferably 2 to 4 mm.

[0015] Due to the increase in the power of the wireless power supply system, there may be cases where the winding coating resin is dissolved due to the heat generation of the transmission and reception coils, or the transmission efficiency decreases due to the increase in the thermal resistance of the winding itself. Therefore, when installed on the back of the receiving coil, it is required to improve the heat dissipation effect of the magnetic shield for wireless power supply. Especially for a large-sized receiving coil, since heat spreads in the plane direction, the thermal diffusivity in the in-plane direction of the magnetic shield for wireless power supply is preferably 1.5 [mm 2 / s] or more, and more preferably 2.0 [mm 2 / s] or more. Preferably, it is 100 [mm 2 / s] or less.

[0016] Also, in a wireless power supply system, the magnetic shield receives a magnetic field resonated between the transmission coil and the receiving coil. If the filler in the magnetic shield has conductivity, eddy currents are generated with respect to the magnetic field, and the transmission efficiency of the entire wireless power supply system due to the magnetic loss of the magnetic field decreases. Therefore, it is necessary to suppress the generated eddy currents. For this reason, since it is required that the conductivity of the magnetic shield for wireless power supply itself in this embodiment is low, the surface resistivity of the magnetic shield for wireless power supply is preferably 1 × 10 3 [Ω / □] or more, and 1 × 105 It is more preferable that the value is [Ω / □] or greater. Preferably 10 17 It is less than or equal to [Ω / □].

[0017] <Thermoplastic resin (A)> Thermoplastic resins are resins that soften and become plastic when heated to a suitable temperature, and solidify when cooled. Examples include polyamide resins, polyurethane resins, polyester resins, polyimide resins, fluororesins, polystyrene resins, polycarbonate resins, polyethersulfone resins, polyolefin resins, (meth)acrylic resins, vinyl resins, acrylonitrile-styrene-butadiene resins, styrene-olefin resins, and vinyl chloride resins. Among these, polyamide resin, polyurethane resin, polyester resin, polystyrene resin, or polycarbonate resin are preferred due to their excellent processability, mechanical properties, electrical properties, and heat resistance. Polyamide resin is particularly preferred from the viewpoint of heat resistance and electrical properties.

[0018] The mass-average molecular weight of the thermoplastic resin (A) is not particularly limited, but is preferably 10,000 to 500,000 from the viewpoint of film-forming properties and durability. A mass-average molecular weight of 15,000 to 400,000 is more preferred, and 15,000 to 300,000 is even more preferred. The mass-average molecular weight can be calculated from the polystyrene equivalent value obtained by measuring the molecular weight distribution curve using gel permeation chromatography (GPC) with the Shimadzu Prominence GPC system.

[0019] <Soft magnetic particles (B)> The soft magnetic particles (B) include flaky soft magnetic particles (b1) made of an Fe-Si-Al alloy surface-treated with an inorganic compound. Furthermore, the ratio of the amount of Fe element present on the particle surface before surface treatment (t1) to the amount of Fe element present on the particle surface after surface treatment (t2) of the flaky soft magnetic particles (b1) is 0.05 <t2 / t1<0.7である。 By using the flaky soft magnetic particles (b1), it becomes possible to improve the compatibility with the thermoplastic resin (A) and suppress the generation of eddy currents due to the magnetic field emitted from the power supply coil, and high magnetic shielding performance can be exhibited. When t2 / t1 < 0.7, it becomes possible to improve the compatibility with the thermoplastic resin (A) and suppress the eddy currents generated by the magnetic field due to the increase in surface resistivity, and high magnetic shielding properties can be exhibited. Also, when 0.05 < t2 / t1, the surface treatment with the inorganic compound does not become excessive, and a decrease in the thermal diffusivity and a decrease in the magnetic permeability can be suppressed.

[0020] The flaky soft magnetic particles (b1) are flaky soft magnetic particles made of an Fe-Si-Al alloy surface-treated with an inorganic compound. Here, flaky particles refer to thin plate-like particles like scales, and mean flake-shaped or flat-shaped particles. The planar shape can include circular, elliptical, angular, irregular, etc., but preferably, it is circular or elliptical. The aspect ratio (average particle diameter D 50 / thickness) of the flaky particles is preferably 5 to 100 from the viewpoint of relative magnetic permeability, more preferably 10 to 90, and even more preferably 20 to 80. The average particle diameter D of the flaky soft magnetic particles 50 refers to the volume average particle diameter. For example, by using a commercially available particle size distribution measuring device (product name: "LA-300", manufactured by Horiba, Ltd., etc.), the particle diameters and volumes of 100 flaky particles are obtained, and based on this, an average value weighted by volume can be calculated.

[0021] From the viewpoint of relative magnetic permeability, the content of the flaky soft magnetic particles (b1) in 100% by mass of the soft magnetic particles (B) is preferably 50% by mass or more, more preferably 95 to 100% by mass, and even more preferably 98 to 100% by mass.

[0022] The average particle diameter of the flaky soft magnetic particles (b1) is preferably 15 to 100 μm, more preferably 15 to 80 μm, and even more preferably 4 to 80 μm in order to obtain excellent relative magnetic permeability. The average thickness of the flaky soft magnetic particles (b1) is preferably 0.5 to 20 μm, more preferably 1 to 10 μm, and even more preferably 1 to 5 μm from the viewpoint of preventing cracking and chipping. The average thickness of the flaky particles can be calculated by obtaining the thicknesses of 100 flaky particles respectively using a commercially available digital microscope, an electron scanning microscope, etc. for the cross-section of the flaky particles and then obtaining the average value of these.

[0023] The mass ratio (%) of the contained components of the Fe-Si-Al alloy can be arbitrary, but preferred ranges include 82 < Fe < 86.5, 9.0 < Si < 11.0, 4.5 < Al < 7.0, and preferably 83 < Fe < 85.6, 9.4 < Si < 10.6, 5.0 < Al < 6.4. Also, Sendust is cited as a preferred product of the Fe-Si-Al alloy.

[0024] The flaky soft magnetic particles (b1) need to be surface-treated with an inorganic compound to improve the compatibility with the thermoplastic resin (A) and to suppress the generation of eddy currents due to the magnetic field emitted from the power supply coil, thereby reducing the conductivity. Examples of the inorganic compound include compounds containing silicon, aluminum, zirconium, titanium, etc., and compounds containing silicon are more preferred due to the effect on the surface resistivity. The inorganic compound is preferably an inorganic oxide such as silica, alumina, zirconia, or titania, and silica is more preferred due to the effect on the surface resistivity.

[0025] Examples of the inorganic compound containing silicon can include the mode of depositing a silicon compound. The Fe-Si-Al alloy surface-treated with silicon can be easily formed using a silicon-based surface treatment agent. The silicon compound may be an organosilicon compound.

[0026] As the surface treatment with titania, zirconia, or alumina which are inorganic oxides, surface treatment with a known surface treatment agent such as a titanate, zirconate, or aluminate-based coupling agent is possible.

[0027] As the degree of surface treatment decreases the amount of exposed Fe element on the surface of the flaky soft magnetic particles (b1), the conductivity decreases. Therefore, the ratio of the amount of Fe element (t1) present on the particle surface before surface treatment to the amount of Fe element (t2) present on the particle surface after surface treatment is 0.02 < t2 / t1 < 0.7, preferably 0.05 < t2 / t1 < 0.65, and more preferably 0.05 < t2 / t1 < 0.5. By being greater than 0.02, it can have excellent magnetic permeability, and by being less than 0.7, it can be made into a magnetic shield body with excellent surface resistivity. The ratio of t2 / t1 can be controlled by the shape, average particle diameter, and aspect ratio of the flaky soft magnetic particles before surface treatment, as well as the type and blending amount of the surface treatment agent. The amount of elements can be measured using an X-ray photoelectron analyzer (K-alpha +, manufactured by Thermo Fisher Scientific).

[0028] By performing the surface modification treatment of the surface layer of the flaky soft magnetic particles so that 0.02 < t2 / t1 < 0.7, the following effects can be obtained. First, the compatibility with the thermoplastic resin (A) can be improved. Thereby, cracks and chips of the flaky soft magnetic particles when formed into a sheet can be effectively prevented. Also, the fluidity of the magnetic resin composition can be improved. As a result, the orientation of the flaky soft magnetic particles when formed into a sheet can be enhanced, and a sheet having excellent relative magnetic permeability can be obtained. Furthermore, by setting the exposure of the highly conductive Fe element within an appropriate range, the magnetic loss due to the generation of eddy currents can be effectively reduced. By increasing the addition amount of the surface treatment agent to the flaky soft magnetic particles, it is possible to reduce the exposure amount of the Fe element, but if excessive addition is performed, the amount of soft magnetic metal in the flaky soft magnetic particles relatively decreases, leading to a decrease in the relative magnetic permeability of the magnetic shield body. Therefore, the ratio of the amount of Fe element (t1) present on the particle surface before surface treatment to the amount of Fe element (t2) present on the particle surface after surface treatment needs to be 0.02 < t2 / t1 < 0.7. Furthermore, this provides the effect of suppressing the degradation of the resin in the magnetic resin composition, thereby improving heat resistance and heat aging resistance, and also effectively preventing rust on the flake-shaped soft magnetic particles. In addition, surface treatment of the particle surface of the flake-shaped soft magnetic particles improves the dispersibility of the flake-shaped soft magnetic particles by reducing the specific surface area.

[0029] Suitable silicon compounds include silane compounds such as alkoxysilanes and silazanes. Examples of alkoxysilanes include tetramethoxysilane, tetraethoxysilane (TEOS), tetraisopropoxysilane, tetrabutoxysilane, tetraoctylsilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, methyltriisopropoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, and dimethyldimethoxysilane. Examples of silazanes include hexamethyldisilazane, N-methyl-hexamethyldisilazane, N-ethyl-hexamethyldisilazane, hexamethyl-N-propyldisilazane, and perhydropolysilazane.

[0030] Furthermore, examples of silicon compounds include silicone compounds in which all or part of the side chains and / or terminals of polysiloxane are methyl groups, silicone compounds in which part of the side chain is a hydrogen atom, modified silicone compounds in which organic groups such as amino groups and epoxy groups are introduced to all or part of the side chains and / or terminals, and silicone resins having a branched structure. Note that the silicone compound may have either a linear or cyclic structure.

[0031] Silicone compounds in which all or part of the side chains and / or terminals of a polysiloxane are methyl groups include, for example, monomethylpolysiloxanes such as polymethylhydrosiloxane (hydrogen-terminated), polymethylhydrosiloxane (trimethylsiloxy-terminated), polymethylphenylsiloxane (hydrogen-terminated), and polymethylphenylsiloxane (trimethylsiloxy-terminated), and dimethylpolysiloxanes such as dimethylpolysiloxane (hydrogen-terminated), dimethylpolysiloxane (trimethylsiloxy-terminated), and cyclic dimethylpolysiloxane.

[0032] Examples of silicone compounds in which part of the side chain consists of hydrogen atoms include methylhydrosiloxane-dimethylsiloxane copolymer (trimethylsiloxy terminus), methylhydrosiloxane-dimethylsiloxane copolymer (hydrogen terminus), polymethylhydrosiloxane (hydrogen terminus), polymethylhydrosiloxane (trimethylsiloxy terminus), polyethylhydrosiloxane (triethylsiloxy terminus), polyphenyl-(dimethylhydrosiloxy)siloxane (hydrogen terminus), methylhydrosiloxane-phenylmethylsiloxane copolymer (hydrogen terminus), and methylhydrosiloxane-octylmethylsiloxane copolymer / terpolymer.

[0033] Furthermore, modified silicones with introduced organic groups include, for example, reactive silicones with introduced organic groups such as amino groups, epoxy groups, methoxy groups, (meth)acryloyl groups, phenol groups, carboxylic acid anhydride groups, hydroxyl groups, mercapto groups, carboxyl groups, and hydrogen atoms, as well as non-reactive silicones modified with, for example, polyethers, aralkyls, fluoroalkyls, long-chain alkyls, long-chain aralkyls, higher fatty acid esters, higher fatty acid amides, and polyether methoxysulfates.

[0034] The surface coating treatment of the flaky soft magnetic particles (b1) of the silicon compound can be carried out by a dry or wet method. A preferred example is a method in which a silicon-based surface treatment agent is added to a solution containing raw material particles, and the silicon compound such as silica (SiO2) is coated onto the surface of the flaky soft magnetic particles (b1) by a sol-gel method. A base may be added to the silicon compound to promote the hydrolysis of silane compounds such as alkoxysilanes and silazanes. Examples of bases include ammonia, sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0035] The silicon compound used for the deposition treatment of the surface layer of the flake-shaped soft magnetic particles (b1) is preferably a silane compound such as alkoxysilane or silazane, with alkoxysilane being more preferred, from the viewpoint of reaction rate with the flake-shaped soft magnetic particles (b1) and yield.

[0036] Specific examples of titanate-based coupling agents include isopropyltriisostearoyl titanate, isopropyltridodecylbenzenesulfonyl titanate, isopropyltris(dioctyl pyrophosphate) titanate, tetraisopropyl(dioctyl phosphite) titanate, tetraisopropylbis(dioctyl phosphite) titanate, tetraoctylbis(ditridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate, bis(dioctyl pyrophosphate)oxyacetate titanate, and bis(dioctyl pyrophosphate)ethylene titanate.

[0037] Specific examples of aluminate coupling agents include acetalkoxyaluminum diisopropylate, aluminum diisopropoxymonoethylacetoacetate, aluminum trisethylacetoacetate, and aluminum trisacetylacetonate.

[0038] Specific examples of zirconate coupling agents include isopropyltriisostearoyl zirconate, isopropyltridodecylbenzenesulfonyl zirconate, isopropyltris(dioctyl pyrophosphate) zirconate, tetraisopropylbis(dioctyl phosphate) zirconate, tetraoctylbis(ditridecyl phosphite) zirconate, tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl) phosphite zirconate, and bis(dioctyl pyrophosphate) oxyacetate. Examples include zirconate, bis(dioctyl pyrophosphate)ethylene zirconate, isopropyl trioctanoyl zirconate, isopropyl dimethacrylate isostearoyl zirconate, isopropyl isostearoyl diacrylic zirconate, isopropyl tri(dioctyl phosphate) zirconate, isopropyl tricumylphenyl zirconate, isopropyl tri(N-aminoethyl-aminoethyl) zirconate, dicumylphenyl oxyacetate zirconate, and diisostearoylethylene zirconate.

[0039] In surface treatment, the amount of surface treatment agent added is preferably 5 to 50 parts by mass of an inorganic compound, which is the surface treatment agent, per 500 parts by mass of flaky soft magnetic particles before surface treatment, and more preferably 15 to 40 parts by mass, from the viewpoint of controlling the change ratio t2 / t1 of the amount of Fe element before surface treatment.

[0040] The blending ratio of thermoplastic resin (A) and soft magnetic particles (B) is preferably thermoplastic resin (A) / soft magnetic particles (B) = 5 / 95 to 25 / 75, and more preferably 10 / 90 to 20 / 80, from the viewpoint of improving relative permeability and thermal diffusivity and controlling surface resistivity.

[0041] <Manufacturing of magnetic shields for wireless power transfer> The magnetic shield for wireless power transfer is molded using a magnetic resin composition containing a thermoplastic resin (A) and soft magnetic particles (B). The magnetic resin composition is a kneaded mixture that is solid at room temperature. As used herein, the magnetic resin composition refers to a resin composition obtained by kneading the components, and is the composition before molding. The composition before molding includes, for example, a lump, pellet, or granular magnetic resin composition.

[0042] The above magnetic resin composition is processed by any molding method to become a magnetic shield for wireless power transfer. One example is melt press molding, which makes it possible to produce a shield of any shape at a temperature above the melting point of the thermoplastic resin (A). Other methods such as injection molding and extrusion molding are also possible, but are not limited to these. [Examples]

[0043] The present invention will be further described in detail by the following examples, but these examples are not intended to limit the present invention in any way. In the examples, unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "percentage by mass". Furthermore, the amounts listed in the table are in parts by mass, and blank spaces indicate that an ingredient is not included.

[0044] <Measurement of average particle size> Average particle diameter D of soft magnetic particles (B) 50 This is the volume-average particle diameter, which was calculated by determining the particle diameter and volume of 100 flake-like particles using a particle diameter distribution analyzer (product name: "LA-300", manufactured by Horiba, Ltd., etc.), and then obtaining a volume-weighted average value based on this.

[0045] <Measurement of average particle thickness> The average particle thickness of the soft magnetic particles (B) was calculated by embedding the soft magnetic particles in a bisphenol A type liquid epoxy resin and a modified alicyclic polyamine by room-temperature curing, cutting the cross-section of the soft magnetic particles, measuring the thickness of 100 cross-sections of the soft magnetic particles using a digital microscope VHX-7000 (manufactured by Keyence), and obtaining the average value.

[0046] <Measurement of Fe element content on the surface of flake-shaped soft magnetic particles> The amount of Fe element in the planar portion of flaky soft magnetic particles was measured using an X-ray photoelectron analyzer (K-alpha+, Thermo Fisher Scientific). Monochromatic AlKαX-rays were used as the X-ray source, and the amount of Fe element was determined by quantitative analysis at an output of 72W.

[0047] <Measuring the melting point of thermoplastic resins> The melting point of the resin was calculated from the crystal melting endothermic peak temperature using the heating method of differential scanning calorimetry based on JIS K 7121, using a differential scanning calorimetry system (Seiko Instruments, DSC6200). The melting point of the resin was determined by heating from 40°C to 300°C at a heating rate of 10°C / min.

[0048] <Measurement of mass-average molecular weight of thermoplastic resins> The mass-average molecular weight was calculated from the polystyrene equivalent value obtained by measuring the molecular weight distribution curve using gel permeation chromatography (GPC) with a Shimadzu Prominence GPC system. For the polystyrene equivalent, VARIAN polystyrene was used as the standard polystyrene, the column was TSKgelGMH-HT manufactured by Tosoh Corporation, and orthodichlorobenzene was used as the carrier during measurement. The column temperature was 140°C and the carrier flow rate was 1.0 mL.

[0049] The raw materials used in the examples are as follows: <Thermoplastic resin> (A1) Polyamide resin: 6-nylon, Amilan CM-1007 (manufactured by Toray Industries, Inc., melting point: 225°C, mass-average molecular weight: 250,000) • (A2) Polycarbonate resin: PC, Yupiron E2000 (manufactured by MEP Corporation, melting point: 220°C, mass-average molecular weight: 60,000) • (A3) Styrene resin: GPPS, HF77 (manufactured by Nippon Polystyrene Co., Ltd., melting point: 240℃, mass-average molecular weight: 220,000) • (A4) Polyester resin: NEH-2050 (manufactured by Unitika Corporation, melting point: 166℃, mass-average molecular weight: 18,000)

[0050] <Soft magnetic particles (B)> • (b1-1) Sendust: Average particle size 50 μm, thickness 1 μm, flaky. Treated with a silane coupling agent. • (b1-2) Sendust: Average particle size 80 μm, thickness 1 μm, flaky. Treated with silane coupling agent. • (b1-3) Sendust: Average particle size 50 μm, thickness 1 μm, flaky. Treated with aluminate coupling agent. • (b1-4) Sendust: Average particle size 50 μm, thickness 1 μm, flaky. Treated with titanate-based coupling agent. • (b1-5) Sendust: Average particle size 50 μm, thickness 1 μm, flaky. Treated with silane coupling agent. • (b'-1) Sendust: Average particle size 50 μm, thickness 1 μm, flaky. Treated with silane coupling agent. (b'-2) Sendust: Average particle size 50 μm, thickness 1 μm, flaky. (b'-3) Sendust: Average particle size 80 μm, thickness 1 μm, flaky. • (b'-4) Sendust: Average particle size 50 μm, thickness 1 μm, scaly. Treated with silane coupling agent.

[0051] (Method for producing flake-shaped soft magnetic particles (b1-1)) 500 parts by mass of flake-shaped soft magnetic particles (b'-2), 15 parts by mass of tetraethoxysilane (TEOS), 500 parts by mass of isopropyl alcohol, and 65 parts by mass of water were mixed and stirred at 25°C for 3 hours. Then, 1 part by mass of 28% aqueous ammonia was added to adjust the pH to 9.5, and the mixture was stirred at 50°C for 5 hours, followed by drying at 120°C for 3 hours to obtain flake-shaped soft magnetic particles (b1-1) whose particle surface was coated with a silicon compound.

[0052] (Method for producing flake-shaped soft magnetic particles (b1-2)) 500 parts by mass of flake-shaped soft magnetic particles (b'-3), 15 parts by mass of tetraethoxysilane (TEOS), 500 parts by mass of isopropyl alcohol, and 65 parts by mass of water were mixed and stirred at 25°C for 3 hours. Then, 1 part by mass of 28% aqueous ammonia was added to adjust the pH to 9.5, and the mixture was stirred at 50°C for 5 hours, followed by drying at 120°C for 3 hours to obtain flake-shaped soft magnetic particles (b1-2) whose particle surfaces were coated with a silicon compound.

[0053] (Method for producing flake-shaped soft magnetic particles (b1-3)) 500 parts by mass of flake-shaped soft magnetic particles (b'-2), 15 parts by mass of acetalkoxyaluminum diisopropylate (PlenAct AL-M), and 500 parts by mass of isopropyl alcohol were mixed and stirred at 25°C for 3 hours. After that, the mixture was stirred at 70°C for 5 hours and then dried at 120°C for 3 hours to obtain flake-shaped soft magnetic particles (b1-3) whose particle surfaces were coated with an aluminate compound.

[0054] (Method for producing flake-shaped soft magnetic particles (b1-4)) 500 parts by mass of flake-shaped soft magnetic particles (b'-3), 15 parts by mass of isopropyl triisostearoyl titanate (PlenAct KR-TTS), and 500 parts by mass of isopropyl alcohol were mixed and stirred at 25°C for 3 hours. After that, the mixture was stirred at 70°C for 5 hours and then dried at 120°C for 3 hours to obtain flake-shaped soft magnetic particles (b1-4) whose particle surfaces were coated with the titanate compound.

[0055] (Method for producing flake-shaped soft magnetic particles (b1-5)) 500 parts by mass of flake-shaped soft magnetic particles (b'-2), 25 parts by mass of tetraethoxysilane (TEOS), 500 parts by mass of isopropyl alcohol, and 65 parts by mass of water were mixed and stirred at 25°C for 3 hours. Then, 1 part by mass of 28% aqueous ammonia was added to adjust the pH to 9.5, and the mixture was stirred at 50°C for 5 hours, followed by drying at 120°C for 3 hours to obtain flake-shaped soft magnetic particles (b1-5) whose particle surfaces were coated with a silicon compound.

[0056] (Method for producing flaky soft magnetic particles (b'-1)) 500 parts by mass of flake-shaped soft magnetic particles (b'-2), 1 part by mass of tetraethoxysilane (TEOS), 500 parts by mass of isopropyl alcohol, and 65 parts by mass of water were mixed and stirred at 25°C for 3 hours. Then, 1 part by mass of 28% aqueous ammonia was added to adjust the pH to 9.5, and the mixture was stirred at 50°C for 5 hours, followed by drying at 120°C for 3 hours to obtain flake-shaped soft magnetic particles (b'-1) whose particle surfaces were coated with a silicon compound.

[0057] (Method for producing flake-shaped soft magnetic particles (b'-4)) 500 parts by mass of flake-shaped soft magnetic particles (b'-2), 100 parts by mass of tetraethoxysilane (TEOS), 500 parts by mass of isopropyl alcohol, and 65 parts by mass of water were mixed and stirred at 25°C for 3 hours. Then, 1 part by mass of 28% aqueous ammonia was added to adjust the pH to 9.5, and the mixture was stirred at 50°C for 5 hours, followed by drying at 120°C for 3 hours to obtain flake-shaped soft magnetic particles (b'-4) whose particle surfaces were coated with a silicon compound.

[0058] The amount of Fe in the flake-shaped soft magnetic particles before surface treatment (t1) and the amount of Fe in the flake-shaped soft magnetic particles after surface treatment (t2) were used to determine t2 / t1. D of flake-shaped soft magnetic particles (B) 50 Table 1 shows the average particle diameter, thickness, shape, and t2 / t1.

[0059] [Table 1]

[0060] [Example 1] (Manufacturing of magnetic resin composition 1) A mixture of 15% polyamide resin (A1) and 85% Sendust (b1-1) was prepared and placed in an open kneader, where it was kneaded at 260°C for 10 minutes. Subsequently, the mixture was pelletized through a feeder to obtain pelletized magnetic resin composition 1.

[0061] (Fabrication of a magnetic shield for wireless power transfer (X-1)) The obtained pellet-shaped magnetic resin composition 1 was pressed into a sheet-like shape by applying a uniform pressure of 15 MPa from the direction of one of the main surfaces of the sheet at a temperature of 15°C + 15°C (240°C) above the melting point of the thermoplastic resin (A) for 1 minute, thereby producing a magnetic shield body (X-1) with dimensions of 200 mm in length, 200 mm in width, and 2.0 mm in thickness.

[0062] [Examples 2-11, Comparative Examples 1-6] Magnetic resin compositions 1 to 17 were prepared in the same manner as in Example 1, except that the thermoplastic resin (A) and soft magnetic particles (B) of Example 1 were changed to the raw materials and blending amounts listed in Tables 2 and 3. Press sheets were then prepared in the same manner as in Example 1 with the thicknesses listed in Tables 2 and 3 to obtain magnetic shields (X-2) to (X-17).

[0063] Evaluation of magnetic shielding materials The relative permeability, thermal diffusivity, surface resistivity, and magnetic field shielding performance of the magnetic shielding body of the present invention were evaluated by the following methods. The results are shown in Tables 2 and 3.

[0064] (Measurement of relative permeability) A magnetic shield was fabricated into a ring shape with an outer diameter of 11.0 mm, an inner diameter of 6.5 mm, and a thickness of 1.0 mm. An impedance analyzer (E4990A, manufactured by KEYSIGHT) was used to measure the inductance at a frequency f = 1 MHz, and the relative permeability was measured using the short-circuit coaxial tube method. [Evaluation Criteria] +++: 150 or more. ++: 100 or more, less than 150. +: 50 or more but less than 100. NG: Less than 50.

[0065] (Measurement of thermal diffusivity) A 500 μm thick section was cut from the magnetic shield body in a cross-sectional direction perpendicular to the main surface, and the thermal diffusivity in the in-plane direction was measured using the laser flash method. [Evaluation Criteria] +++:4.0[mm 2 / s] or more. ++:2.5[mm 2 / s] or more 4.0[mm 2Less than / s. +:1.5[mm 2 / s] or more 2.5[mm 2 Less than / s. NG: 1.5 [mm] 2 Less than / s.

[0066] (Measurement of surface resistivity) The electrical resistivity of the main surface of the obtained magnetic shield was measured using the four-probe method. The applied voltage was 10V. [Evaluation Criteria] +++: 1 × 10 7 [Ω / □] or more ++: 1 × 10 5 [Ω / □] or more 1×10 7 [Ω / □] less than +: 1 × 10 3 [Ω / □] or more 1×10 5 [Ω / □] less than NG: 1 x 10 3 [Ω / □] less than

[0067] (Measurement of magnetic field shielding performance) The measurement was performed using the KEC method. The state without a sample in the KEC method jig was set to 0 dB, and the magnetic shielding performance was measured after installing the magnetic shielding body. [Evaluation Criteria] +++: 30dB or higher. ++: 25dB or more and less than 30dB. +: 20dB or more, but less than 25dB. NG: Less than 20dB.

[0068] [Table 2]

[0069] [Table 3]

[0070] From the results in Tables 2 and 3, the ratio of the amount of Fe elements present on the particle surface before surface treatment (t1) to the amount of Fe elements present on the particle surface after surface treatment (t2) for thermoplastic resin (A) is 0.02

Claims

1. It contains a thermoplastic resin (A) and soft magnetic particles (B), The soft magnetic particles (B) include flake-shaped soft magnetic particles (b1) made of an Fe-Si-Al alloy surface-treated with an inorganic compound, wherein the ratio of the amount of Fe element present on the particle surface before surface treatment (t1) to the amount of Fe element present on the particle surface after surface treatment (t2) is 0.46 ≤ t2 / t1 ≤ 0.

62. The flaky soft magnetic particles (b1) are Fe-Si-Al alloy surface-treated with silica. A magnetic shield for wireless power transfer, characterized by having a thickness of 2 to 4 mm.

2. The thermal diffusivity in the in-plane direction is 1.5 [mm²] ２ A magnetic shield for wireless power supply according to claim 1, characterized in that it is ≥ / s.

3. Surface resistivity is 1 × 10⁻⁶ ３ A magnetic shield for wireless power supply according to claim 1 or 2, characterized in that it is [Ω / □] or greater.

4. A magnetic shield for wireless power supply according to any one of claims 1 to 3, characterized in that the thermoplastic resin (A) contains a polyamide resin.

5. A method for manufacturing a magnetic shield for wireless power supply according to any one of claims 1 to 4, The process includes kneading a thermoplastic resin (A) and soft magnetic particles (B), A method for manufacturing a magnetic shield for wireless power transfer with a thickness of 2 to 4 mm.

Images