JP2002164689A - Radio wave absorbing body of high thermal conductivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio wave absorbing body of high thermal conductivity which provides a high thermal conductivity and radio wave absorbing characteristics. SOLUTION: The radio wave absorbing body of high thermal conductivity comprises a composite material where the powder comprising the metal soft- magnetic body in which an insulating film is formed on its surface and a thermally conductive filler are in diffusion phase while the polymer material is in matrix phase. The insulating film on the surface of powder is preferred to comprise a compound containing alkill radical of carbon-number 6 or higher. The particle size of the powder is preferred to be 1-20 μm while that of the thermally conductive filler to be 0.8-20 μm. The polymer material is preferred to be a silicon rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high thermal conductive radio wave absorber for absorbing electromagnetic waves in a frequency band of several tens of MHz to several tens of GHz.

[0002]

2. Description of the Related Art In recent years, electromagnetic interference caused by high-frequency electromagnetic noise generated from electronic devices such as personal computers has become a problem, and various electromagnetic wave absorbers have been proposed for the purpose of suppressing the electromagnetic noise. For example, a radio wave absorber using a composite material of a metal magnetic powder or a metal oxide magnetic powder or the like and a resin (Japanese Patent Application Laid-Open No. 50-155999), a metal soft magnetic material having an electrically insulating layer on the surface A radio wave absorber using a composite material of particles and a resin (Japanese Patent Laid-Open No. 11-45804), a radio wave absorber using a composite material of a conductive powder such as a dielectric powder, a non-magnetic metal, and carbon and a resin are disclosed. Have been.
These radio wave absorbers have a function of reflecting and absorbing a part of the radio wave to attenuate the radio wave.

On the other hand, in electronic devices, heat measures for effectively dissipating heat generated in various electronic components to the outside have also become an important issue, and various heat conductive sheets have been proposed. JP-A-2-166755, JP-A-2-
196453 and JP-A-6-155517).

[0004] For this reason, conventionally, in the case of suppressing electromagnetic wave noise and improving heat radiation performance in electronic equipment,
It was necessary to use the above-mentioned radio wave absorber and the heat conductive sheet together. However, if a radio wave absorber and a heat conductive sheet are used together, the number of parts increases and the cost rises. Therefore, it has been studied to solve the problem by adding heat conductivity to the radio wave absorber. I have.

[0005]

However, when the filling rate of, for example, a metallic soft magnetic material is increased in order to impart thermal conductivity to the radio wave absorber, the conductivity increases with the increasing filling rate. There is a problem that the radio wave absorption increases and the radio wave absorption decreases.

The present invention has been made by focusing on the problems existing in the prior art as described above. It is an object of the present invention to provide a high thermal conductivity radio wave absorber having both excellent heat conductivity and radio wave absorption.

[0007]

In order to achieve the above object, the invention according to claim 1 is characterized in that a powder made of a metal soft magnetic material having an insulating film formed on the surface thereof is filled with a heat conductive filler. And a composite material having a polymer as a matrix phase and a polymer material as a matrix phase.

According to a second aspect of the present invention, in the high thermal conductive radio wave absorber according to the first aspect, the insulating film is made of a compound containing at least one alkyl group having 6 or more carbon atoms. I do.

According to a third aspect of the present invention, in the high thermal conductive radio wave absorber according to the first or second aspect, the thermal conductive filler is made of aluminum oxide, magnesium oxide, aluminum nitride, aluminum nitride, boron nitride, or nitride. The gist consists of at least one selected from silicon, silicon carbide and aluminum hydroxide.

[0010] According to a fourth aspect of the present invention, in the high thermal conductive radio wave absorber according to any one of the first to third aspects, the insulating film is formed of a metal soft magnetic material having a surface formed thereon. The gist is that the particle diameter of the powder is 1 to 20 μm.

According to a fifth aspect of the present invention, there is provided the high thermal conductive radio wave absorber according to any one of the first to fourth aspects, wherein the thermally conductive filler has a particle size of 0.8 to 20 μm. The gist is that there is.

According to a sixth aspect of the present invention, in the high thermal conductive radio wave absorber according to any one of the first to fifth aspects, the polymer material is silicone rubber.

According to a seventh aspect of the present invention, there is provided the high thermal conductive radio wave absorber according to any one of the first to sixth aspects, wherein the composite material is formed into a sheet, and at least one surface or the inside thereof is formed. The gist is to provide a layer having a reinforcing function.

According to an eighth aspect of the present invention, in the high thermal conductive radio wave absorber according to the seventh aspect, the layer having a reinforcing function has conductivity.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail. The high-thermal-conductivity electromagnetic wave absorber (hereinafter, also simply referred to as an electromagnetic wave absorber) of the present embodiment is obtained by dispersing a powder made of a metal soft magnetic material having an insulating film formed on the surface and a heat-conductive filler. It is characterized by being composed of a composite material having a polymer phase as a matrix phase.

First, a powder made of a soft metal metal having an insulating film formed on the surface will be described. Specific examples of the metal soft magnetic material include simple metals such as iron, nickel and cobalt, alloys containing at least one selected from iron, nickel and cobalt, and carbides and nitrides thereof. These may be crystalline or amorphous.

The particle size of the powder is preferably in the range of 1 to 20 μm. When the particle size is less than 1 μm or more than 20 μm, the radio wave absorption tends to decrease, and when it exceeds 20 μm, it becomes more difficult to further fill the powder with high powder.

The shape of the powder may be spherical, massive, columnar, acicular,
Examples thereof include a plate shape and a scale shape, but are not particularly limited.
The insulating film on the surface of the powder is preferably made of a compound containing an alkyl group having 6 or more carbon atoms. Are preferable, and among them, a silane-based compound having a plurality of one-terminal silanol groups in one molecule is preferable.

The preferred range of the carbon number of the alkyl group is 6 or more, and the more preferred range is 10 to 25. 6 carbon atoms
If the amount is less than the above, the fluidity of the composite material may be reduced when the filling amount of the powder is increased, and the composite material may become powdery, and the obtained radio wave absorber tends to be inflexible and rigid. On the other hand, when the carbon number is large, high filling of the powder tends to be difficult. When a film is formed from a compound containing an alkyl group having 6 or more carbon atoms, the fluidity does not easily decrease even if the filling amount of the powder is increased, so that the kneading and dispersing operation is easy and the handling is easy. Moreover, the flexibility of the obtained radio wave absorber can be improved.
If the flexibility is good, for example, when a radio wave absorber is used as a heat transfer member by being interposed between a semiconductor element serving as a heat source and a heat radiating member in a semiconductor device, a gap between the radio wave absorber and the semiconductor element is obtained. Also, since a gap is hardly generated between the radio wave absorber and the heat radiating member, it is also advantageous in terms of thermal conductivity. Further, since the film is a low-polarity film, oxidation of the metal soft magnetic material by moisture can be suppressed, and the water resistance and moisture resistance of the radio wave absorber can be improved.

In the case of a film composed of a compound containing an alkyl group having 6 or more carbon atoms and having at least one functional group of a hydroxyl group, a carboxylic acid group, a phosphoric acid group and a silanol group at one end, Is more efficient. Also, in this case,
It is possible to form a film in which the alkyl group faces outward. Examples of the compound containing an alkyl group having 6 or more carbon atoms and further having any one of functional groups such as a hydroxyl group, a carboxylic acid group, a phosphoric acid group, and a silanol group at one end include stearic acid, oleic acid, and n-octanol. No.

In the case of a film composed of a silane compound containing an alkyl group having 6 or more carbon atoms and having a plurality of silanol groups at one end in one molecule, a strong film is formed by a crosslinking reaction between the silanol groups. Things. Examples of silane compounds containing an alkyl group having 6 or more carbon atoms and having a plurality of silanol groups at one end in one molecule include hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, and decyltriethoxysilane. Octadecyltrimethoxysilane, octadecylmethyldimethoxysilane, and the like. Other silane compounds containing an alkyl group having 6 or more carbon atoms include tetradecyltrichlorosilane, eicosyltrichlorosilane, and the like.

The thickness of the insulating film is 0.005 to 0.2
The range of μm is preferred. If the thickness is less than 0.005 μm, the film cannot exhibit electrical insulation,
If it is larger than this, high filling of the powder becomes difficult.

There is no particular limitation on the method for producing a powder made of a metal soft magnetic material. For example, in the case of a simple metal, the powder is produced by a reduction method, a carbonyl method, an electrolytic method, or the like. The granulation method is also not particularly limited, and the granulation is performed by a known granulation method such as a mechanical pulverization method, a hot water pulverization method, a reduction method, an electrolytic method, and a gas phase method.

Next, the heat conductive filler will be described.
The thermal conductive filler preferably has a thermal conductivity of 80 W / m · K or more. This is because the thermal conductivity of the powder made of a metal soft magnetic material is about 15 to 80 W / m · K, and the thermal conductivity of the polymer material is 1 W / m · K or less. This is because the use of a high material can surely improve the thermal conductivity of the radio wave absorber.

Specific examples of such a thermally conductive filler include those made of metal and ceramics, but those made of an electrically insulating material are preferred. Specific examples of the insulating heat conductive filler include metal oxides such as aluminum oxide and magnesium oxide, metal nitrides such as aluminum nitride, boron nitride, and silicon nitride; metal carbides such as silicon carbide; and aluminum hydroxide. And those composed of metal hydroxides. In the case of a non-insulating heat conductive filler, when the filling amount is increased, the electric wave absorber tends to be conductive, and the electric wave absorption tends to decrease.
However, even if it is non-insulating, the above problem can be solved by forming an insulating film on the surface, such as aluminum having an oxide film formed on the surface.

The preferred range of the particle size of the thermally conductive filler is as follows:
It depends on the intended use of the obtained radio wave absorber. First, in applications where thermal conductivity is prioritized, it is preferable that the particle size of the thermal conductive filler be relatively large, specifically, 10 to 5 particles.
A range of 0 μm is preferred. If the particle size is less than 10 μm, sufficient thermal conductivity may not be exhibited.
If it exceeds 0 μm, high filling becomes difficult. On the other hand, in applications where radio wave absorption is prioritized, it is preferable that the particle size is smaller than the particle size of the powder made of a metal soft magnetic material, and specifically, the range is 0.8 to 20 μm. 0.8μm particle size
When the particle size is less than 20 μm, the heat conductive filler becomes expensive and the cost increases. On the other hand, when the particle size exceeds 20 μm, there is a possibility that the filling rate of the powder is reduced and sufficient radio wave absorption is not exhibited.

Next, the polymer material will be described. Specific examples of the polymer material include a thermoplastic resin, a curable resin, a crosslinked rubber, and a thermoplastic elastomer.

Examples of the thermoplastic resin include ethylene-α-olefin copolymers such as polyethylene, polypropylene and ethylene-propylene copolymer, polymethylpentene,
Polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene vinyl acetate copolymer, polyvinyl alcohol, polyvinyl acetal, fluorine-based polymers such as polyvinylidene fluoride and polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate,
Polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene acrylonitrile copolymer, AB
S resin, polyphenylene ether (PPE), modified PP
E, aliphatic polyamides, aromatic polyamides, polyimides, polyamideimides, polymethacrylic acids (polymethacrylates such as polymethyl methacrylate), polyacrylic acids, polycarbonate, polyphenylene sulfide, polysulfone, polyether sulfone, poly Ether nitrile, polyether ketone, polyketone,
Examples include a liquid crystal polymer, a silicone resin, and an ionomer.

Examples of the curable resin include epoxy resin, phenol resin, acrylic resin, urethane resin, polyimide resin, unsaturated polyester resin, diallyl phthalate resin, dicyclopentadiene resin, and benzocyclobutene resin. In addition, the curable resin refers to a resin having a cured form such as a thermosetting property, a photocuring property, and a moisture curing property.

Examples of the crosslinked rubber include natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-propylene copolymer rubber, chlorinated polyethylene, and chlorosulfonated polyethylene. Butyl rubber, halogenated butyl rubber, fluorine rubber, urethane rubber, silicone rubber and the like.

Examples of the thermoplastic elastomer include styrene-butadiene copolymer and styrene-isoprene block copolymer and hydrogenated products thereof, styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyester -Based thermoplastic elastomer, polyurethane-based thermoplastic elastomer,
Polyamide-based thermoplastic elastomers and the like can be mentioned.

Among the above-listed polymer materials, polyolefin-based or silicone-based resins, rubbers, and elastomers are preferable because the temperature dependence and the frequency dependence of the dielectric constant are small. In applications requiring heat resistance, fluorine rubber and silicone rubber are preferred. When the insulating film on the surface of the powder is a silane-based compound, silicone rubber is most compatible and preferred. However, one or more polymer materials may be appropriately selected and used depending on the required performance of the radio wave absorber such as hardness, mechanical strength, heat resistance, electrical characteristics, durability, and reliability. Alternatively, a polymer alloy composed of two or more polymer materials may be used.

A composite material is formed by mixing and dispersing the powder and the thermally conductive filler in a polymer material, and the composite material is formed into a predetermined shape such as a sheet to form a composite material. The radio wave absorber of the embodiment is formed.

According to the above-described embodiment, the following effects are exhibited. The radio wave absorber of the present embodiment can exhibit excellent radio wave absorbability because it is formed of a composite material containing a powder made of a metal soft magnetic material. In addition, since the composite material also contains a thermally conductive filler, excellent thermal conductivity can be exhibited.

By forming an insulating film from a compound containing an alkyl group having 6 or more carbon atoms, it is possible to suppress a decrease in fluidity when the filling amount of the powder is increased.
For this reason, the kneading and dispersing operation can be facilitated, and the handleability can be improved. Further, since the obtained electromagnetic wave absorber has good flexibility, it can be deformed following irregularities of electronic components and the like even when used as a heat transfer member in a semiconductor device, for example. For this reason, the radio wave absorber can be mounted without any gap, and this is advantageous in terms of thermal conductivity.

By using a non-insulating thermally conductive filler such as aluminum oxide, magnesium oxide, aluminum nitride, boron nitride, silicon nitride, silicon carbide, aluminum hydroxide, etc., the amount of the thermally conductive filler can be increased. Increase in conductivity can be suppressed. For this reason, even if the filling amount of the heat conductive filler is increased, there is no possibility that the radio wave absorbing property of the radio wave absorber decreases.

The particle size of the powder made of the metal soft magnetic material is 1
When the thickness is in the range of 20 μm to 20 μm, the radio wave absorbability of the radio wave absorber can be improved. -By setting the particle size of the thermally conductive filler in the range of 0.8 to 20 µm, the obtained radio wave absorber can be suitably used in applications where radio wave absorption is prioritized. When the particle size is in the range of 10 to 50 μm,
The obtained radio wave absorber can be suitably used in applications where thermal conductivity is prioritized.

By using silicone rubber as the polymer material, the temperature dependence and frequency dependence of the dielectric constant can be suppressed, and the heat resistance can be improved. It is particularly preferable that the insulating film on the surface of the powder is made of a silane compound because the compatibility is good.

[0039]

Next, the embodiment will be described more specifically with reference to examples and comparative examples. (Example 1) Epoxy silane coupling agent (Toray
(SH6040 manufactured by Dow Corning Silicone Co., Ltd.)
Was added to toluene containing 20% by weight of carbonyl iron having an average particle diameter of 20 μm (manufactured by BASF) and mixed and stirred to obtain carbonyl iron particles having an insulating film formed on the surface. The carbonyl iron particles have an average particle size of 2
0 μm alumina particles (AS-2 manufactured by Showa Denko KK)
0) 20% by volume of a thermosetting liquid silicone rubber (SE174 manufactured by Dow Corning Toray Silicone Co., Ltd.)
0) to prepare a clay-like composite material, and heat molding of the composite material to obtain a sheet-like radio wave absorber. FIG. 1 shows the results of examining the return loss characteristics of the obtained radio wave absorber (2 mm thick). Table 1 shows the results of measuring the thermal conductivity and hardness of the radio wave absorber (1 mm thick).

(Example 2) Epoxy silane coupling agent (SH604 manufactured by Dow Corning Toray Co., Ltd.)
Carbonyl iron particles (manufactured by BASF) having an average particle size of 5 μm were added to toluene containing 20% by weight of (0), and mixed and stirred to obtain carbonyl iron particles having an insulating film formed on the surface. Alumina particles having an average particle diameter of 0.8 μm and 60% by volume of carbonyl iron particles (AL manufactured by Showa Denko KK)
-160SG-1) 1% by volume of a thermosetting liquid silicone rubber (manufactured by Dow Corning Toray Silicone Co., Ltd.)
SE1740) to prepare a powdery composite material,
The composite material was heated and molded to obtain a sheet-like radio wave absorber. FIG. 1 shows the results of examining the return loss characteristics of the obtained radio wave absorber (2 mm thick). In addition, radio wave absorber (1m
Table 1 shows the results of measuring the thermal conductivity and the hardness of the sample (thickness m).

(Example 3) Long-chain alkyl silane coupling agent (TSL81 manufactured by GE Toshiba Silicone Co., Ltd.)
85) having a mean particle size of 5 μm in toluene containing 20% by weight.
Was added and mixed and stirred to obtain carbonyl iron particles having an insulating film formed on the surface. Alumina particles having an average particle diameter of 0.8 μm and 60% by volume of carbonyl iron particles (AL manufactured by Showa Denko KK)
-160SG-1) 1% by volume of a thermosetting liquid silicone rubber (manufactured by Dow Corning Toray Silicone Co., Ltd.)
SE1740) to prepare a clay-like composite material,
The composite material was heated and molded to obtain a sheet-like radio wave absorber. FIG. 1 shows the results of examining the return loss characteristics of the obtained radio wave absorber (2 mm thick). In addition, radio wave absorber (1m
Table 1 shows the results of measuring the thermal conductivity and the hardness of the sample (thickness m).

(Example 4) Long-chain alkyl silane coupling agent (TSL81 manufactured by GE Toshiba Silicone Co., Ltd.)
85) in toluene containing 20% by weight and having an average particle size of 1 μm.
Was added and mixed and stirred to obtain carbonyl iron particles having an insulating film formed on the surface. Aluminum particles having an average particle diameter of 1 μm and 60% by volume of the carbonyl iron particles (A manufactured by Toyo Aluminum Co., Ltd.)
C-5005) 1% by volume of a thermosetting liquid silicone rubber (manufactured by Dow Corning Toray Silicone Co., Ltd. SE
1740) to prepare a clay-like composite material, and heat molding the composite material to obtain a sheet-like radio wave absorber.
FIG. 1 shows the results of examining the return loss characteristics of the obtained radio wave absorber (2 mm thick). In addition, radio wave absorber (1mm
Table 1 shows the results obtained by measuring the thermal conductivity and hardness of the film (thickness).

Example 5 An average particle size of 5 μm was contained in toluene containing 20% by weight of stearic acid (manufactured by Wako Pure Chemical Industries, Ltd.).
m permalloy particles (manufactured by Fukuda Metal Co., Ltd.) were added and mixed and stirred to obtain permalloy particles having an insulating film formed on the surface. Alumina particles having an average particle diameter of 0.8 μm and 60% by volume of the permalloy particles (A manufactured by Showa Denko KK)
L-160SG-1) with 1% by volume of thermosetting liquid urethane rubber (Takeda U-53 manufactured by Takeda Pharmaceutical Co., Ltd.)
And Takenate D-170N at a ratio of 10: 1) to prepare a clay-like composite material, and then heat-molded the composite material to obtain a sheet-like radio wave absorber. FIG. 1 shows the results of examining the return loss characteristics of the obtained radio wave absorber (2 mm thick). Table 1 shows the results of measuring the thermal conductivity and hardness of the radio wave absorber (1 mm thick).

(Comparative Example 1) Epoxy silane coupling agent (manufactured by Dow Corning Toray Silicone Co., Ltd.
H6040) was added to toluene containing 20% by weight of carbonyl iron particles having an average particle diameter of 20 μm (manufactured by BASF) and mixed and stirred to obtain carbonyl iron particles having an insulating film formed on the surface. 40% by volume of the carbonyl iron particles are mixed with a thermosetting liquid silicone rubber (SE1740, manufactured by Dow Corning Toray Silicone Co., Ltd.) to prepare a clay-like composite material, and the composite material is heated and formed into a sheet-like radio wave. An absorber was obtained. The obtained radio wave absorber (2 mm
FIG. 1 shows the result of examining the return loss characteristics of the (thickness).
Table 1 shows the results of measuring the thermal conductivity and hardness of the radio wave absorber (1 mm thick).

(Comparative Example 2) Epoxy silane coupling agent (manufactured by Dow Corning Toray Silicone Co., Ltd.
H6040) was added to toluene containing 20% by weight of carbonyl iron particles having an average particle diameter of 5 μm (manufactured by BASF) and mixed and stirred to obtain carbonyl iron particles having an insulating film formed on the surface. 60% by volume of these carbonyl iron particles are mixed with a thermosetting liquid silicone rubber (SE1740 manufactured by Dow Corning Toray Silicone Co., Ltd.) to prepare a clay-like composite material, and the composite material is heated and formed into a sheet-like radio wave. An absorber was obtained. Obtained radio wave absorber (2mm thickness)
FIG. 1 shows the result of examining the return loss characteristics of the sample. Table 1 shows the results of measuring the thermal conductivity and hardness of the radio wave absorber (1 mm thick).

Comparative Example 3 Long-chain alkyl silane coupling agent (TSL81 manufactured by GE Toshiba Silicone Co., Ltd.)
85) having a mean particle size of 5 μm in toluene containing 20% by weight.
Was added and mixed and stirred to obtain carbonyl iron particles having an insulating film formed on the surface. 60% by volume of these carbonyl iron particles are mixed with a thermosetting liquid silicone rubber (SE1740 manufactured by Dow Corning Toray Silicone Co., Ltd.) to prepare a clay-like composite material, and the composite material is heated and formed into a sheet-like radio wave. An absorber was obtained. FIG. 1 shows the results of examining the return loss characteristics of the obtained radio wave absorber (2 mm thick). Table 1 shows the results of measuring the thermal conductivity and hardness of the radio wave absorber (1 mm thick).

[0047]

[Table 1] In addition, the value of the thermal conductivity in Table 1 is a value measured by KTM-500 manufactured by Kyoto Electronics Industry Co., Ltd.
This is a value measured by an Asker C hardness tester according to RIS0101 (Japan Rubber Standards Association). However, Example 5
Is a value measured with a type A durometer according to JIS K7215.

As shown in Table 1, the radio wave absorbers of Examples 1 to 3 have larger thermal conductivity values than the radio wave absorbers of Comparative Examples 1 to 3, respectively. From this, it was shown that the thermal conductivity was improved by adding the thermal conductive filler. Further, regarding the hardness, when the amount of the thermally conductive filler added is small (1% by volume), there is no change, but when the amount added is large (20% by volume), the flexibility tends to decrease slightly. Indicated.

On the other hand, as shown in FIG. 1, no significant change was observed in the radio wave absorption characteristics even when the heat conductive filler was added. The above-described embodiment may be modified as follows.

Known additives such as a plasticizer, a filler, a stabilizer, and a coloring agent may be added to the composite material of the embodiment. Further, carbon fiber, glass fiber, aramid fiber, or the like may be added.

The composite material of the above embodiment may be used as an adhesive or a paint by adding an additive as appropriate. -The composite material of the above embodiment may be formed into a sheet, and a layer having a reinforcing function may be provided on one or both sides thereof. In this case, handleability after molding can be improved. The layer having a reinforcing function may be formed by attaching a plate-like reinforcing material or a cloth-like reinforcing material to one or both surfaces of the radio wave absorber, or a reinforcing material may be formed on one or both surface layers. It may be formed by adding or changing the type of the polymer material of the surface layer portion.

The layer having the reinforcing function is not always required to be located on the surface, and may be buried inside the sheet-like radio wave absorber. Further, the layer having the reinforcing function may be conductive. When the layer having the reinforcing function is conductive, various effects can be obtained depending on the position where the layer is provided. For example, when the layer having the reinforcing function is provided only on one surface, it has a shielding effect on electromagnetic waves incident from the side on which the layer having the reinforcing function is provided, and has a shielding effect on electromagnetic waves incident from the opposite side. This acts as a narrow band type radio wave absorber. Also,
When the layer having the reinforcing function is provided inside the radio wave absorber, the layer functions as a narrow band type radio wave absorber with respect to electromagnetic waves incident from either side. The method of imparting conductivity to the layer having the reinforcing function may be performed by forming the layer having the reinforcing function with a conductive material such as metal, carbon, or a conductive organic polymer, or plating, vapor deposition, Alternatively, a layer having a reinforcing function may be formed from a material having a surface on which a conductive layer is formed by a method such as sputtering.

The composite material of the above embodiment may be formed into a sheet, and one or both surfaces thereof may be provided with an adhesive layer. In this case, the usability can be improved because it can be fixed by sticking. This adhesive layer may be formed by laminating a double-sided adhesive tape on one or both surfaces of the radio wave absorber, or by forming a polymer material constituting a matrix phase of the composite material into a gel-like rubber. It may be formed.

Next, the technical ideas that can be grasped from the above embodiment will be described below. The high thermal conductive radio wave absorber according to any one of claims 1 to 8, wherein the metal soft magnetic material includes at least one selected from iron, nickel, and cobalt.

The high thermal conductive electromagnetic wave absorber according to any one of claims 1 to 6, wherein the composite material is formed into a sheet shape, and an adhesive layer is provided on at least one surface thereof. body. In this case, usability can be improved.

A composite material comprising a powder of a metal soft magnetic material having an insulating film formed on its surface and a thermally conductive filler as a dispersed phase and a polymer material as a matrix phase. Adhesive. In this case, excellent radio wave absorption and thermal conductivity can be exhibited.

A composite material comprising a powder of a metal soft magnetic material having an insulating film formed on its surface and a thermally conductive filler as a dispersed phase and a polymer material as a matrix phase. Paint. In this case, excellent radio wave absorption and thermal conductivity can be exhibited.

[0058]

Since the present invention is configured as described above, it has the following effects. According to the first aspect of the present invention, excellent radio wave absorption and heat conductivity can be exhibited.

According to the invention described in claim 2, according to claim 1
In addition to the effects of the invention described in the above, the kneading and dispersing work of the composite material can be facilitated and the handleability can be improved,
Further, the flexibility of the radio wave absorber can be improved.

According to the third aspect of the present invention, the first aspect
Or, in addition to the effect of the invention described in claim 2, even if the filling amount of the heat conductive filler is increased, there is no possibility that the radio wave absorbing property of the radio wave absorber decreases.

According to the fourth aspect of the present invention, the first aspect is provided.
Accordingly, in addition to the effects of the invention described in any one of the third to third aspects, the radio wave absorption can be improved. According to the invention described in claim 5, in addition to the effects of the invention described in any one of claims 1 to 4, it can be suitably used in applications where radio wave absorption is prioritized.

According to the invention of claim 6, according to claim 1,
In addition to the effects of the invention described in any one of the fifth to fifth aspects, the temperature dependency and the frequency dependency of the dielectric constant can be suppressed, and the heat resistance can be improved.

According to the invention of claim 7, according to claim 1,
In addition to the effects of the invention according to any one of claims 6 to 6, the handleability after molding can be improved. According to the invention of claim 8, in addition to the effect of the invention of claim 7, when the layer having the reinforcing function is provided only on one side, the side on which the layer having the reinforcing function is provided It has a shielding effect on electromagnetic waves incident from the opposite side, and can act as a narrow band type radio wave absorber on electromagnetic waves incident from the opposite side. Further, when the layer having the reinforcing function is provided inside the radio wave absorber, it is possible to act as a narrow band type radio wave absorber with respect to an electromagnetic wave incident from either side.

[Brief description of the drawings]

FIG. 1 is a graph showing the return loss characteristics of a high thermal conductive radio wave absorber.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // H01L 23/373 H01L 23/36 M

Claims (8)

[Claims] 1. A powder comprising a metal soft magnetic material having an insulating film formed on a surface thereof, and a thermally conductive filler as a dispersed phase,
A high-thermal-conductivity electromagnetic wave absorber comprising a composite material having a polymer material as a matrix phase. 2. The high thermal conductive radio wave absorber according to claim 1, wherein the insulating film is made of a compound containing at least one alkyl group having 6 or more carbon atoms. 3. The heat conductive filler is aluminum oxide,
3. The high thermal conductive radio wave absorber according to claim 1, wherein the radio wave absorber comprises at least one selected from magnesium oxide, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and aluminum hydroxide. 4. The powder according to claim 1, wherein the powder of the metal soft magnetic material having the insulating film formed on the surface has a particle size of 1 to 20 μm. High thermal conductivity radio wave absorber. 5. The heat conductive filler has a particle size of 0.8 to 20 μm.
The high thermal conductivity radio wave absorber according to any one of claims 1 to 4, wherein m is m. 6. The high thermal conductive radio wave absorber according to claim 1, wherein the polymer material is silicone rubber. 7. The high thermal conductivity according to claim 1, wherein the composite material is formed into a sheet, and a layer having a reinforcing function is provided on at least one surface or inside thereof. Radio wave absorber. 8. The high thermal conductive radio wave absorber according to claim 7, wherein the layer having a reinforcing function has conductivity.