JPH0661679A - Thin radio wave absorbent - Google Patents

Abstract

PURPOSE:To provide flexibility by providing a flexible radio wave absorbing sheet layer produced by mixing an electromagnetic wave energy loss material and a holding material, and a radio wave reflection layer produced by subjecting an organic fiber cloth to electroless plating of highly conductive metal material and laminated on the rear of the radio wave absorbing sheet layer, thereby integrating a radio wave reflector. CONSTITUTION:A flexible radio wave absorbing sheet layer 10 is provided by admixing powder of magnetic loss material, i.e., ferrite, with a holding material, i.e., rubber. A radio wave reflective layer 11 is laminated integrally on the rear of the radio wave absorbing layer 10. The radio wave reflective layer 11 is provided by subjecting a polyester fiber cloth to electroless plating of nickel and copper. Accuracy is not required in the bonding thickness of the radio wave absorbent and a body to be applied because of the integrated radio wave reflector and workability is enhanced, especially at the time of mounting onto a curved face, because of the flexibility. The radio wave absorbing layer 10 may employ an ohmic loss material such as carbon or other loss material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin electromagnetic wave absorber used for preventing radar ghosts (preventing false images) and for preventing reflection of electromagnetic waves scattered from structures.

[0002]

2. Description of the Related Art In recent years, as the use of radio waves has advanced, problems such as radio wave interference and malfunction due to radio waves have often occurred. As a measure to solve such a problem, a thin electromagnetic wave absorber is mounted on a structure having a large reflection and scattering of electromagnetic waves, which suppresses the scattering of the electromagnetic waves from the structure. It has an effect.

The thin electromagnetic wave absorber is generally a electromagnetic wave absorbing material formed by mixing a magnetic loss material such as ferrite or an ohmic loss material such as carbon with a holding material such as rubber and resin, and a metal disposed on the back surface thereof. And a radio wave reflector of. When such a thin electromagnetic wave absorber is attached to a structure, since the structure has various shapes, it is required to use a flexible electromagnetic wave absorber so as to conform to the shape.

As a method of mounting the thin wave absorber on a structure (generally a metal body), a flexible wave absorber without a wave reflector is directly attached to the structure (metal body) with an adhesive or the like. There is a method of using the structure as a radio wave reflector, and a method of mounting a flexible radio wave absorber on which a radio wave reflector such as a metal foil is lined in advance.

[0005]

However, in the method of directly bonding the electromagnetic wave absorber to the structure, the thickness of the adhesive layer between the electromagnetic wave absorber and the structure affects the electromagnetic wave absorption performance. Since it is necessary to control the thickness of the adhesive layer to mount it, the work of mounting the electromagnetic wave absorber is not easy.

Further, in the prior art in which the radio wave absorber and the radio wave reflector are integrated in advance, as a radio wave reflector,
Metal foil, metal deposition film, metal fiber cloth, carbon fiber cloth,
Alternatively, there is a method using a metal-plated glass fiber cloth or the like.

However, when a metal foil is used, since it hardly expands or contracts, wrinkles or cracks are formed in the metal foil when it is integrated with the electromagnetic wave absorber and bent, and this is damaged.

When a metal vapor deposition film is used, the vapor deposition film is easily damaged by bending or the like, and when it is integrated with a radio wave absorber, the film does not have stretchability, resulting in deterioration of flexibility.

When a metal fiber cloth is used, since the fiber is metal, it is difficult to restore it when it is bent, and there is a problem in workability. Moreover, when it is bent, wrinkles are formed as in the case of the metal foil.

When a carbon fiber cloth or a metal-plated glass fiber cloth is used, if the electromagnetic wave absorber and the fiber cloth are heated and integrally molded, the coefficient of thermal expansion of the fiber cloth is smaller than that of the electromagnetic wave absorber, so that the electromagnetic wave There is a problem that the absorber is deformed.

Therefore, the present invention has been made to solve the above-mentioned problems of the prior art, and provides a thin wave absorber having flexibility by integrating a wave reflector.

[0012]

According to the present invention, a flexible sheet-shaped electromagnetic wave absorbing layer formed by mixing an electromagnetic wave energy loss material and a holding material is laminated on the back surface of the sheet-shaped electromagnetic wave absorbing layer. Accordingly, a thin wave absorber provided with a radio wave reflection layer formed by electrolessly plating a highly conductive metal material on an organic fiber cloth is provided.

It is preferable to further include an organic protective film such as an organic polymer film or an organic coating film deposited on the front surface of the sheet-shaped electromagnetic wave absorbing layer.

The surface resistance of the radio wave reflection layer is preferably 0.5Ω / □ or less.

The highly conductive metal material preferably contains nickel, copper, or silver.

[0016]

[Function] As a radio wave reflection layer, a conductive organic fiber cloth is electrolessly plated with a highly conductive metal material such as nickel, copper or silver to realize a high conductivity of 0.5Ω / □ or less. Therefore, since it has a sufficient radio wave reflection property and uses a base material such as an organic fiber cloth, it is highly stretchable, resistant to bending and easily integrated with a radio wave absorber. Therefore, by forming a radio wave absorber using such a radio wave reflection layer, it is possible to obtain a thin radio wave absorber which is flexible and easy to mount on a curved surface portion.

[0017]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a perspective view of a thin electromagnetic wave absorber which is an embodiment of the present invention.

In the figure, 10 is a flexible sheet-shaped electromagnetic wave absorbing layer formed by mixing ferrite powder, which is a magnetic loss material, with rubber, which is a holding material. The radio wave absorption layer 10 is formed to have a thickness of 2.5 mm, and a radio wave reflection layer 11 is integrally laminated on the back surface thereof.
The radio wave reflection layer 11 is formed by electrolessly plating a polyester fiber cloth with nickel and copper, and its surface resistance is set to 0.1 Ω / □ or less in this embodiment.

FIG. 2 shows the frequency-reflection coefficient characteristic of the thin electromagnetic wave absorber of the embodiment shown in FIG. As is clear from the figure, the thin electromagnetic wave absorber of this embodiment has excellent electromagnetic wave absorption characteristics with a large amount of attenuation, especially at around 10 GHz.

As shown in FIG. 3, the thin electromagnetic wave absorber was wound around a cylindrical rod 12 having a diameter of 30 mm (30φ) and bent, and the characteristics and appearance were evaluated again. It didn't change.

On the other hand, the radio wave absorption layer 1 in the embodiment of FIG.
A radio wave absorber formed by integrally laminating a 25 μm thick aluminum foil on a radio wave absorption layer similar to that of No. 0 was wound around this cylindrical rod 12 and bent, and then the characteristics and appearance were evaluated. A crack was formed in the aluminum foil.

FIG. 4 is a perspective view of a thin electromagnetic wave absorber according to another embodiment of the present invention.

In this embodiment, a radio wave reflection layer 11 is integrally laminated on the back surface of the radio wave absorption layer 10 as in the embodiment of FIG. 1, and an organic protective film 13 is further laminated on the front surface of the radio wave absorption layer 10. It is a thing. In this embodiment, the organic protective film 13 is made of a fluorine-based resin having a thickness of 50 μm and protects the surface of the radio wave absorption layer 10.

FIG. 5 shows the frequency-reflection coefficient characteristic of the thin electromagnetic wave absorber of the embodiment shown in FIG. As is clear from the figure, the thin electromagnetic wave absorber of this embodiment has excellent electromagnetic wave absorption characteristics with a large amount of attenuation, especially at around 10 GHz.

The operation and effect of this embodiment are almost the same as those of the embodiment of FIG.

In the above-mentioned embodiments, the electromagnetic wave absorbing layer 10 is made of ferrite which is a magnetic loss material. However, it is obvious that ohmic loss material such as carbon or other loss material may be used. is there. The holding material may be any material as long as the radio wave absorption layer is flexible.

As the radio wave reflection layer 11, an organic fiber cloth different from polyester fiber cloth may be used, or silver may be electroless plated in addition to nickel and copper.

Further, as the organic protective film 13, an organic polymer film or an organic coating film different from fluorine resin may be used.

[0030]

As described in detail above, according to the present invention,
A flexible sheet-shaped electromagnetic wave absorption layer formed by mixing an electromagnetic energy loss material and a holding material, and laminated on the back side of this sheet-shaped electromagnetic wave absorption layer. And a radio wave reflection layer formed by plating. In this way, since the radio wave reflector is integrated, the accuracy of the adhesive thickness between the radio wave absorber and the adherend is not required, and since it has flexibility, it can be easily installed and mounted on a curved surface. Becomes very easy.

[Brief description of drawings]

FIG. 1 is a perspective view of a thin electromagnetic wave absorber that is an embodiment of the present invention.

2 is a characteristic diagram of frequency vs. reflection coefficient in the embodiment of FIG.

FIG. 3 is a perspective view showing a state where the thin electromagnetic wave absorber of the embodiment of FIG. 1 is wound around a cylindrical rod and bent.

FIG. 4 is a perspective view of a thin electromagnetic wave absorber that is another embodiment of the present invention.

5 is a characteristic diagram of frequency vs. reflection coefficient in the embodiment of FIG.

[Explanation of symbols]

 10 Radio wave absorption layer 11 Radio wave reflection layer 12 Cylindrical rod 13 Organic protective film

Claims (8)

[Claims] 1. A flexible sheet-shaped electromagnetic wave absorption layer formed by mixing an electromagnetic wave energy loss material and a holding material, and laminated on the back surface of the sheet-shaped electromagnetic wave absorption layer, and made of an organic fiber cloth with high conductivity. A thin radio wave absorber comprising a radio wave reflection layer formed by electrolessly plating a metal material. 2. The thin electromagnetic wave absorber according to claim 1, further comprising an organic protective film deposited on the front surface of the sheet-shaped electromagnetic wave absorbing layer. 3. The thin electromagnetic wave absorber according to claim 2, wherein the organic protective film is an organic polymer film. 4. The thin electromagnetic wave absorber according to claim 2, wherein the organic protective film is an organic coating film. 5. The surface resistance of the radio wave reflection layer is 0.5 Ω /
□ The following is a thin electromagnetic wave absorber according to any one of claims 1 to 4. 6. The thin electromagnetic wave absorber according to claim 1, wherein the highly conductive metal material contains nickel. 7. The thin electromagnetic wave absorber according to claim 1, wherein the highly conductive metal material contains copper. 8. The thin electromagnetic wave absorber according to claim 1, wherein the highly conductive metal material contains silver.