JPH0685472B2 - Radio wave absorber - Google Patents

Description

The present invention relates to a composite type electromagnetic wave absorber having good mechanical strength and rigidity.

[Conventional technology]

In recent years, the use of radio waves has been rapidly expanding mainly in the mobile communication field toward the realization of an advanced information society. In addition, various electronic devices have come into widespread use along with the innovative progress of today's microelectronics technology.

Against this background, electromagnetic interference due to unwanted radio waves generated by various wireless devices, electronic devices, etc. tends to increase year by year, and therefore good electromagnetic environment (EMC) in buildings There is an urgent need to develop a high-performance electromagnetic wave absorber that is necessary to maintain the environment.

It is important that the material used for the radio wave absorber is a material with large electric loss and magnetic loss that effectively attenuates electromagnetic energy. Conventionally, various ohmic loss materials, dielectric loss materials, magnetic loss materials that meet this requirement Materials etc. are developed,
It is provided.

As the most representative radio wave absorber, a material in which carbon is held by an insulating resin material such as urethane foam, or a material in which carbon is mixed with rubber or plastic is known.

[Problems to be Solved by the Invention]

However, the type that uses urethane foam as a holding material has a drawback that it requires skill in molding work such as demolding and processing because the material itself is soft and cannot hold a desired shape by itself. . Further, in the case of using rubber, plastic, etc. as a matrix, it is difficult to uniformly disperse carbon, and the strength and weather resistance of the forming structure are insufficient, and it cannot be applied as a building material. There is a point. For this reason, a method of mixing a fiber reinforcing material such as carbon fiber in order to reinforce the structure has been proposed, but it has not yet been achieved to impart uniform mechanical strength and rigidity.

The present inventors have carried out multifaceted test research on a holding material that is lightweight and has good moldability, and as a result, confirmed that wood chips meet this requirement, and led to the development of the present invention. . Therefore, an object of the present invention is to provide a radio wave absorber having a formed structure having mechanical strength and rigidity and an appropriate radio wave absorption performance.

[Means for Solving the Problems]

The radio wave absorber according to the present invention for achieving the above object comprises a molded product having a component composition in which a carbon paste obtained by mixing carbon powder and / or carbon fiber with a resin binder is mixed with wood chips, and The mixing is characterized in that the carbon powder and / or the carbon fiber is mixed with the wood chips in a compounding ratio of 10 to 20 g / l and is composed of a carbon-based molding and a metal-based mesh.

The wood chips constituting the holding material in the present invention refer to powder having a particle size of about 10 to 100 mesh obtained by crushing, crushing or cutting various kinds of wood. For the purpose of the present invention, those having a particle size of 30 to 60 mesh are effectively used.

The wood chips are mixed with carbon powder, carbon fibers or both together with a binder. As the carbon powder, finely pulverized graphite, coke or the like, carbon black or the like is used. When carbon black is applied, conductive carbon black is effective.
The carbon fiber may be polyacrylonitrile-based, rayon-based, or pitch-based, and is usually used as a chop cut into about 1 to 3 mm.

Carbon powders and / or carbon fibers are, for example, vinyl acetate / ethylene-based, vinyl acetate / ethylene / acrylic-based, styrene / vinyl chloride-based, styrene / butadiene-based, acrylic-based, styrene / acrylic-based, formalin-based (urea, melamine, It is mixed with wood chips in a state of being mixed with a resin binder such as phenol and resorcinol resin), but particularly good results are obtained when a commercially available carbon paste in which conductive carbon black is suspended in the above binder component is used in advance. Is obtained.

It is desirable that these carbon powders and / or carbon fibers are mixed with the wood chips in a mixing ratio of 10 to 20 g / l. If the carbon powder and / or carbon fibers deviate from this range, it becomes difficult to ensure proper radio wave absorption.

As described above, the wood chip is mixed with carbon powder and / or carbon fiber together with the binder, and the component composition is molded into a desired wedge shape, pyramid shape, plate shape or the like.

The metal-based net body combined with the radio wave absorbing carbon-based molded body functions to shield and attenuate radio waves, and copper,
The plane mesh made of aluminum or an alloy thereof, stainless steel, glass fiber coated with metal or the like can be mentioned.

The composite ratio of the carbon-based molded body and the metal-based mesh body is determined by embedding the metal-based mesh body inside the tissue in the above-described molding process of the carbon-based molded body or sandwiching the carbon-based molded body and the metal-based mesh body. It can be carried out by a method such as forming into layers.

The radio wave absorber of the present invention thus formed can be coated or impregnated with a material for the purpose of making it incombustible, or can be colored with a pigment in order to be used for the same purpose as other building materials. .

[Action]

ADVANTAGE OF THE INVENTION According to this invention, the dielectric loss characteristic by the carbon type | mold molded body which mixed and mixed carbon powder and / or carbon fiber into the wood chip, and the shielding attenuation characteristic by the metal type | system | group mesh | composite with this synergistically. It acts to exert a high degree of shielding effect. In addition, since the metal-based mesh further strengthens the structure of the carbon-based compact that is strongly formed by using wood chips that are lightweight and has good formability as a holding material, the material as a whole is an excellent machine. It presents a tissue having a desired strength and rigidity.

Therefore, the electromagnetic wave absorber is suitable as a building material.

〔Example〕

 Hereinafter, the present invention will be described in detail based on examples.

Example 1 10-18 mesh: 1.6%, 18-30 mesh: 9.2%, 30-40
Mesh: 17.0%, 40-60 mesh: 42.8%, 60 mesh or more: 29.4% particle size distribution on wood chips, carbon paste with conductive carbon black as a dispersant (Lion Co., Ltd., Lion paste W- 311N] are mixed so that the carbon content (C amount) is different, and this is mixed vertically and horizontally 40
It was preformed into a plate having a thickness of 3 mm and a thickness of 3 mm. This preform and a copper wire mesh were alternately laminated and molded to obtain a composite type electromagnetic wave absorber having a structure in which the carbon-based molding 1 and the wire mesh 2 were laminated in a sandwich shape as shown in the figure.

This composite type electromagnetic wave absorber has excellent mechanical strength and rigidity, and shows an electromagnetic wave absorption performance of 20 dB or more in the frequency range of 10 to 50 MHz.

Example 2 To the wood chips having the same particle size distribution as in Example 1, the same carbon paste and carbon fiber chop (length 0.7 mm) as in Example 1 were used, and the carbon content was 10 g / l. The mixture was mixed as described above, and one layer of brass wire mesh was embedded in the mixture to form a plate-shaped body having a length and width of 40 mm and a thickness of 7 mm. The obtained molded body has a high bending strength and elastic modulus, and shows a radio wave absorption performance of 20 dB or more in the frequency range of 10 to 50 MHz.

〔The invention's effect〕

As described above, according to the present invention, the wood chips having good moldability are used as the holding material, and the carbon-based molded product and the metal-based molded product in which the carbon paste obtained by mixing the carbon powder and / or the carbon fiber with the resin binder is mixed therein. By forming a composite with a net, it is possible to provide a radio wave absorber having appropriate radio wave absorption performance, light weight, and excellent mechanical strength and rigidity.

Therefore, it is extremely useful as a radio wave absorption wall for building materials.

[Brief description of drawings]

FIG. 1 is a sectional view of a radio wave absorber showing an embodiment of the present invention. 1 ... Carbon-based compact 2 ... Wire mesh

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tadahiro Shimazu 1-2-7 Moto-Akasaka, Minato-ku, Tokyo Within Kashima Construction Co., Ltd. (72) Eiji Matsushita 1-2-7 Moto-Akasaka, Minato-ku, Tokyo No. Kashima Construction Co., Ltd. (72) Inventor Shuichi Takasaka 2-19-1 Tobita-cho, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Norinori Yamada 1-2-7 Moto-Akasaka, Minato-ku, Tokyo No. Kashima Construction Co., Ltd. (72) Inventor Yoshinori Kasashima 2-19-1 Tobita, Chofu-shi, Tokyo Kashima Construction Co., Ltd. Technical Research Institute (72) Inventor Masaru Fujimoto 776-2, Kawaguchi City, Saitama Prefecture (72) ) Yoshinaga Katsuzawa 2-229, Suzuki-cho, Kodaira-shi, Tokyo (56) References JP-A-1-191500 (JP, A) JP-A 64-58502 (JP, A) JP-A 60-57700 ( JP A) Patent Akira 49-13698 (JP, A) JP Akira 59-47796 (JP, A)

Claims (1)

[Claims] 1. A molded product having a component composition in which a carbon paste prepared by mixing carbon powder and / or carbon fiber with a resin binder is mixed with wood chips, and the mixture is carbon powder and / or carbon for wood chips. An electromagnetic wave absorbing material composed of a composite of a carbon-based molded body and a metal-based mesh body having a fiber compounding ratio of 10 to 20 g / l.