JPH07120574B2 - Radio wave absorber - Google Patents
Radio wave absorberInfo
- Publication number
- JPH07120574B2 JPH07120574B2 JP61054611A JP5461186A JPH07120574B2 JP H07120574 B2 JPH07120574 B2 JP H07120574B2 JP 61054611 A JP61054611 A JP 61054611A JP 5461186 A JP5461186 A JP 5461186A JP H07120574 B2 JPH07120574 B2 JP H07120574B2
- Authority
- JP
- Japan
- Prior art keywords
- radio wave
- magnetic material
- wave absorber
- composite magnetic
- frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000006096 absorbing agent Substances 0.000 title claims description 22
- 239000002131 composite material Substances 0.000 claims description 24
- 239000000696 magnetic material Substances 0.000 claims description 23
- 238000010521 absorption reaction Methods 0.000 claims description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims description 10
- 229920001971 elastomer Polymers 0.000 claims description 8
- 239000005060 rubber Substances 0.000 claims description 8
- 229920005989 resin Polymers 0.000 claims description 7
- 239000011347 resin Substances 0.000 claims description 7
- 239000006247 magnetic powder Substances 0.000 claims description 6
- 239000000843 powder Substances 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 3
- 239000013078 crystal Substances 0.000 claims 1
- 230000006698 induction Effects 0.000 claims 1
- 239000000463 material Substances 0.000 description 14
- 239000010410 layer Substances 0.000 description 12
- 239000006185 dispersion Substances 0.000 description 9
- 238000010586 diagram Methods 0.000 description 8
- 230000035699 permeability Effects 0.000 description 7
- 239000002356 single layer Substances 0.000 description 6
- 239000000654 additive Substances 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229920001084 poly(chloroprene) Polymers 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229920002379 silicone rubber Polymers 0.000 description 1
- 239000004945 silicone rubber Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
Landscapes
- Hard Magnetic Materials (AREA)
- Soft Magnetic Materials (AREA)
- Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
- Aerials With Secondary Devices (AREA)
Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は電波吸収体に関し、特に電波吸収体に適用して
好適な複合磁性材料に関する。Description: TECHNICAL FIELD The present invention relates to a radio wave absorber, and more particularly to a composite magnetic material suitable for application to a radio wave absorber.
（従来の技術） 近年、レーダー等の不要輻射防止ないし為像防止等のた
めに薄型電波吸収体が利用されている。この薄型電波吸
収体を構成する材料としては、たとえばフェライト粉末
をゴム、樹脂等に混練した複合磁性材料が使用される。
複合磁性材料を用いた電波吸収体は薄い単層型のもので
良好な電波吸収特性が得られ、耐候性に富む利点があ
る。(Prior Art) In recent years, a thin electromagnetic wave absorber is used for preventing unnecessary radiation such as radar and for preventing an image. As a material forming this thin electromagnetic wave absorber, for example, a composite magnetic material in which ferrite powder is kneaded with rubber, resin or the like is used.
The electromagnetic wave absorber using the composite magnetic material is a thin single layer type, which has excellent electromagnetic wave absorption characteristics and is advantageous in that it is rich in weather resistance.
（発明が解決しようとする問題点） しかしながら、このような複合磁性材料を電波吸収体に
用いた場合、反射減衰量が20dB以上となる周波数帯域は
Ｘバンドで１〜2GHz程度であった。そこで広帯域化を図
るためには多層型（例えば２層型）の構成による等の工
夫がなされてきたが、このようにすると構成が複雑とな
り製造工数が増加するという問題点があった。(Invention Problems to be Solved) However, when using such a composite magnetic material in the radio wave absorber, a frequency band return loss is equal to or greater than 20dB was about 1～2GH z at X band. Therefore, in order to achieve a wider band, various measures have been taken, such as by using a multi-layer type (for example, two-layer type) structure, but this has a problem that the structure becomes complicated and the number of manufacturing steps increases.
本発明はこのような従来技術の問題点に鑑みてなされた
ものであって、本発明に係る複合磁性材料を好適に適用
して薄型化及び広帯域可能な単層型の電波吸収体を提供
することを目的とする。The present invention has been made in view of the above problems of the prior art, and provides a single-layer type electromagnetic wave absorber capable of being thinned and having a wide band by suitably applying the composite magnetic material according to the present invention. The purpose is to
（問題点を解決するための手段） 本発明は、磁性体粉末と、ゴムまたは樹脂との混合物か
らなる複合磁性材料を用いた電波吸収体において、 前記磁性体粉末はCo及びBaのうちの少なくとも１種類以
上の元素を含む六方晶系フェライト粉末であって、 前記複合磁性材料の複素比誘磁率を 複素比誘電率＝εｒ′−ｊεｒ″、周波数をｆ（GH
z）とし、 ｘ＝ｆ ｙ＝logμｒ″ とおき、 dy/dx＜０の領域のｘ−ｙ曲線のほぼ直線部分の延長線
とｙ＝０の交点を（fn,0）としたとき、動作周波数がほ
ぼfn（GHz）であり、かつ前記延長線の傾きの絶対値α
が 0.05≦α≦0.2 であって、かつ ３≦εｒ′≦20 となる関係を満足する複合磁性材料からなる電波吸収層
と、 該電波吸収層の一面に設けた反射体とを含むことによ
り、前記従来技術の問題点を解決するようにしたもので
ある。(Means for Solving Problems) The present invention provides a radio wave absorber using a composite magnetic material made of a mixture of magnetic powder and rubber or resin, wherein the magnetic powder is at least Co or Ba. A hexagonal ferrite powder containing one or more elements, comprising: Complex relative permittivity = ε r ′ −jε r ″, frequency is f (GH
z), and x = fy = logμr ″, and the intersection of y = 0 with the extended line of the substantially straight line part of the xy curve in the region of dy / dx <0 is (f n , 0), The operating frequency is approximately f n (GHz), and the absolute value α of the slope of the extension line
By including a radio wave absorbing layer made of a composite magnetic material satisfying the relationship of 0.05 ≦ α ≦ 0.2 and 3 ≦ ε r ′ ≦ 20, and a reflector provided on one surface of the radio wave absorbing layer. The problems of the prior art described above are solved.
（作用） 本発明では前記延長線の傾きの絶対値αが0.05≦α≦0.
2を満足することにより、材料の電波吸収特性の広帯域
化に作用し、一方、複素誘電率のεｒ′が３≦εｒ′≦
20を満足することにより、材料の薄型化に作用する。し
たがって本発明に好適の複合磁性材料な単層型電波吸収
体に適用すると、非常に広帯域な薄型電波吸収体を得る
ことができるようになり、前記従来技術の問題点を解決
される。(Operation) In the present invention, the absolute value α of the slope of the extension line is 0.05 ≦ α ≦ 0.
When 2 is satisfied, the electromagnetic absorption characteristics of the material are broadened, while the complex permittivity ε r ′ is 3 ≦ ε r ′ ≦
Satisfying 20 will make the material thinner. Therefore, when it is applied to the single-layer type electromagnetic wave absorber which is a composite magnetic material suitable for the present invention, it becomes possible to obtain a thin electromagnetic wave absorber having a very wide band, and the above-mentioned problems of the prior art are solved.
（実施例） 本発明に係る複合磁性材料は磁性体粉末をゴムまたは樹
脂に混合分配されて構成される。そして複合磁性材料の
複素比透磁率を 複素比誘電率＝εｒ′−ｊεｒ″、周波数をｆ（GH
z）とし、 ｘ＝ｆ ｙ＝logμｒ″ とおき、 dy/dx＜０の領域のｘ−ｙ曲線のほぼ直線部分の延長線
とｙ＝０の交点を（fn,0）としたとき、動作周波数がほ
ぼfn（GHz）であり、かつ延長線の傾きの絶対値αが 0.05≦α0.2 ……（１） であって、かつ ３≦εｒ′≦20 ……（２） なる関係を満足する複素透磁率及び複素誘電率を有す
る。このような複合磁性材料は電波吸収体に適用した場
合、広帯域で良好な電波吸収特性を呈するとともに、薄
型化を可能とする。(Example) The composite magnetic material according to the present invention is formed by mixing and distributing magnetic powder in rubber or resin. And the complex relative permeability of the composite magnetic material Complex relative permittivity = ε r ′ −jε r ″, frequency is f (GH
z), and x = fy = logμr ″, and the intersection of y = 0 with the extended line of the substantially straight line part of the xy curve in the region of dy / dx <0 is (f n , 0), The operating frequency is approximately f n (GHz), the absolute value α of the slope of the extension line is 0.05 ≦ α 0.2 (1), and 3 ≦ ε r ′ ≦ 20 (2) When such a composite magnetic material is applied to a radio wave absorber, such a composite magnetic material has a complex magnetic permeability and a complex dielectric constant that satisfy the relationship, and exhibits excellent radio wave absorption characteristics in a wide band and enables thinning.
本発明に好適の複合磁性材料においては種々のフェライ
ト磁性体粉末が使用され、特にCo及びBaのうちの少なく
とも１種類以上の元素を含む六方晶系のものが好まし
い。一方、本発明においてゴムとしてはクロロプレンゴ
ム、シリコーンゴム等種々のゴムが使用可能で、樹脂と
しては種々の熱可塑性樹脂及び熱硬化性樹脂が使用可能
である。Various ferrite magnetic substance powders are used in the composite magnetic material suitable for the present invention, and a hexagonal system containing at least one element of Co and Ba is particularly preferable. On the other hand, various rubbers such as chloroprene rubber and silicone rubber can be used as the rubber in the present invention, and various thermoplastic resins and thermosetting resins can be used as the resin.
αの値が0.05より小さいとき及び0.2より大きいときに
は20dB以上の反射減衰量が得られる帯域が狭くなり好ま
しくない。When the value of α is smaller than 0.05 or larger than 0.2, the band in which the return loss of 20 dB or more can be obtained becomes narrow, which is not preferable.
一方、εｒ′は、磁性体粉末とゴムないし樹脂を使用し
ているので３以上の値をとるようになる。またεｒ′が
20以上の値をとると、その複合磁性材料を電波吸収体に
適用したとき、表面からの反射が大きくなるとともに動
作帯域が狭くなってしまう。したがって、εｒ′の値は
３から20の範囲にあるのが好ましい。On the other hand, ε r ′ takes a value of 3 or more because magnetic powder and rubber or resin are used. Also, ε r ′ is
When the value is 20 or more, when the composite magnetic material is applied to a radio wave absorber, the reflection from the surface becomes large and the operating band becomes narrow. Therefore, the value of ε r ′ is preferably in the range 3 to 20.
次に本発明に係る複合磁性材料を適用した電波吸収体に
ついて説明する。Next, a radio wave absorber to which the composite magnetic material according to the present invention is applied will be described.
第１図は本発明の一実施例の電波吸収体１を示す構成図
である。この電波吸収体１は単層型であり、複合磁性材
料から成る電波吸収層２の一面に反射体３を設けて構成
される。電波吸収層２に使用される複合磁性材料0.05≦
α≦0.2を満足する複素透磁率及び３≦εｒ′≦20を満
足する複素誘電率を有する。FIG. 1 is a configuration diagram showing a radio wave absorber 1 according to an embodiment of the present invention. This radio wave absorber 1 is of a single layer type and is constructed by providing a reflector 3 on one surface of a radio wave absorption layer 2 made of a composite magnetic material. Composite magnetic material used for the radio wave absorption layer 2 0.05 ≦
It has a complex magnetic permeability satisfying α ≦ 0.2 and a complex permittivity satisfying 3 ≦ ε r ′ ≦ 20.
電波吸収層２の厚さをｄ、自由空間波長をλとすると、
電波吸収層２の前面での反射係数は（３）式で表わされ
る。If the thickness of the radio wave absorption layer 2 is d and the free space wavelength is λ,
The reflection coefficient on the front surface of the radio wave absorption layer 2 is expressed by the equation (3).
フェライトを用いた複合磁性材料の場合、６〜18GHzで
は透磁率が共鳴現象付近にあるためμｒ′はほとんど１
前後の値を示す。そこでμｒ″の周波数分散、特に
μｒ″曲線の傾きと帯域幅の関係を考えてみる。（３）
式で｜｜＝０の場合には完全整合となるが、ここでは
｜｜＝0.1すなわち反射減衰量が20dBとなる周波数範
囲を帯域として着目する。 When the composite magnetic material using the ferrite, for permeability in 6～18GH z is near resonance mu r 'most 1
Indicates the value before and after. Therefore, let us consider the frequency dispersion of μ r ″, particularly the relationship between the slope of the μ r ″ curve and the bandwidth. (3)
When || = 0 in the formula, perfect matching is achieved, but here, attention is focused on the frequency range where || = 0.1, that is, the return loss is 20 dB.
第２図は反射減衰量が20dB以上となる場合の周波数ｆ
（GH2）と電波吸収層２の厚さｄ（mm）の関係を示す図
である。図中斜線部分が反射減衰量20dB以上の領域であ
る。この図で、例えば、電波吸収層２の厚さがdiのとき
には帯域幅はWiとなる。Figure 2 shows the frequency f when the return loss is 20 dB or more.
It is a figure which shows the relationship between (GH 2 ) and the thickness d (mm) of the radio wave absorption layer 2. The shaded area in the figure is the area where the return loss is 20 dB or more. In this figure, for example, when the thickness of the radio wave absorption layer 2 is d i , the bandwidth is W i .
第３図はμｒ″の周波数分散曲線を示す図である。この
周波数分散曲線の直接的部分を直線で近似し、その直線
の傾きαと、その直線とμｒ′＝１との交点の周波数fn
とにより、前記直線的部分を表現する。FIG. 3 is a diagram showing a frequency dispersion curve of μ r ″. The direct part of this frequency dispersion curve is approximated by a straight line, and the inclination α of the straight line and the intersection of the straight line and μ r ′ = 1 Frequency f n
And represent the linear portion.
第４図はfn値をパラメータとしたときの傾きの絶対値α
と帯域幅との関係を示す図である。ここではμｒ″は典
型的な周波数分散曲線をとり、これを一定とし、εｒ′
＝６、εｒ″＝0.1と固定した。この図から、あるfn値
に対して最大帯域幅を有するμｒ″の傾きαが存在し、
６〜18GHzにおいてはα＝0.11前後でfn＝10GHz前後の
時、約11GHzの広い帯域幅を持つことわかる。各fn値の
ときの最大帯域幅とfn値の関係を第５図に示す。Fig. 4 shows the absolute value of the slope α when the f n value is used as a parameter.
It is a figure which shows the relationship between and bandwidth. Here, μ r ″ takes a typical frequency dispersion curve, and this is made constant, and ε r ′
= 6, and ε r ″ = 0.1. From this figure, there is a slope α of μ r ″ having the maximum bandwidth for a certain f n value,
When f n = 10GH z and forth alpha = 0.11 before and after the 6~18GH z, understood that have a wide bandwidth of about 11GH z. FIG. 5 shows the relationship between the maximum bandwidth and the f n value at each f n value.
次に、εｒ′について着目してみる。複合磁性材料にお
いて、電波吸収特性を劣化させずに厚さを薄くするため
には、εｒ′を大きく満足すれば良い。εｒ′の値は添
加物により比較的容易に調整することができる。μｒ″
の周波数分散がfn＝9.5GHzのとき、εｒ′を4,6,8と変
えた場合の傾きαと帯域幅との関係を第６図に示す。こ
の図によれば、εｒ′の値により最大帯域幅となるαの
値が異なっているが、εｒ′＝６前後でα＝0.11付近の
とき最も良い特性となることがわかる。Next, let us focus on ε r ′. In order to reduce the thickness of the composite magnetic material without deteriorating the electromagnetic wave absorption characteristics, it is sufficient to satisfy ε r ′. The value of ε r ′ can be adjusted relatively easily with additives. μ r ″
When the frequency dispersion of the f n = 9.5GH z of shows the relationship between the inclination α and bandwidth when changing the epsilon r 'and 4, 6, 8 in Figure 6. According to this figure, epsilon r 'the value the value of alpha becomes maximum bandwidth are different by a, ε r' = 6 it can be seen that the best characteristics when alpha = 0.11 vicinity before and after.
以上のことより、複合磁性材料による単層型電波吸収体
の場合、εｒ′が６前後でμｒ″の周波数分散曲線がfn
＝10GHz、α＝0.11程度となるときに広帯域特性が得ら
れるようになることが理解される。From the above, in the case of a single-layer type electromagnetic wave absorber made of a composite magnetic material, when ε r ′ is around 6, the frequency dispersion curve of μ r ″ is f n
It is understood that the wide band characteristic can be obtained when = 10 GHz and α = 0.11.
次に具体例について説明する。フェライト粉末及びゴム
との混合物を変化させてA,B,Cの３種類のフェライト複
合材料を準備し、これらの電波吸収特性について調べ
た。材料Ａは立方晶系Ni−Zn系フェライトを含み初透磁
率μｉ＝100である従来の材料、材料Ｂは立方晶系Ni−Z
n系フェライトを含み初透磁率μｉ＝50である従来の材
料、材料Ｃは六方晶系Co系フェライトを含み初透磁率μ
ｉ＝10である本発明による材料である。材料A,B,Cのμ
ｒ″の周波数分散特性を第７図に示し、電波吸収特性を
第８図に示す。また、帯域幅と厚さ、logμｒ″の傾き
α及びμｒ′の関係を第１表に示す。Next, a specific example will be described. Three types of ferrite composite materials A, B, and C were prepared by changing the mixture of ferrite powder and rubber, and the electromagnetic wave absorption characteristics of these were investigated. Material A cubic N i -Z n based conventional materials ferrite is initial permeability mu i = 100 comprises, material B cubic N i -Z
A conventional material containing n- type ferrite and having an initial magnetic permeability μ i = 50, material C is a hexagonal Co-based ferrite and having an initial magnetic permeability μ
A material according to the invention in which i = 10. Μ of materials A, B, C
r "The frequency dispersion characteristics of the shown in Figure 7, shows a wave absorption characteristics in FIG. 8. Moreover, the band width and thickness, Logmyu r" shows a relationship between the inclination α and mu r 'of the first table.
以上の結果より、本発明による材料Ｃは厚さが薄い状態
で約5GHzと帯域幅を得ることができ、これは従来の材料
に比べ３倍以上の良好な特性であり、２層型に比べても
良好である。 These results, the material C according to the invention can be obtained about 5GH z and bandwidth is thin state, which is 3 times more excellent characteristics than conventional materials, the two-layer type It is also good in comparison.
（発明の効果） 本発明によれば、従来のものに比べて非常に広帯域な電
波吸収特性を有する薄型化された電波吸収体を得ること
ができる。(Effects of the Invention) According to the present invention, it is possible to obtain a thin electromagnetic wave absorber having an electromagnetic wave absorption characteristic in a very wide band as compared with a conventional one.
第１図は本発明の一実施例の単層型電波吸収体の構成を
示す斜視図、第２図は電波吸収特性と周波数及び厚さと
の関係を示す図、第３図はμｒ″の周波数分散曲線を示
す図、第４図はfn値をパラメータとしたときの傾きαと
帯域幅との関係を示す図、第５図はfn値とその値のとき
の最大帯域幅との関係を示す図、第６図はεｒ′を変え
たときの傾きαと帯域幅の関係を示す図、第７図は材料
A,B,Cのμｒ″の周波数分散曲線を示す図、第８図は材
料A,B,Cの電波吸収特性を示す図である。 １……電波吸収体、 ２……電波吸収層 ３……反射体。FIG. 1 is a perspective view showing the structure of a single-layer type electromagnetic wave absorber of one embodiment of the present invention, FIG. 2 is a diagram showing the relationship between electromagnetic wave absorption characteristics and frequency and thickness, and FIG. 3 is a graph showing μ r ″. FIG. 4 is a diagram showing the frequency dispersion curve, FIG. 4 is a diagram showing the relationship between the slope α and the bandwidth when the f n value is a parameter, and FIG. 5 is a diagram showing the f n value and the maximum bandwidth at that value. FIG. 6 shows the relationship, FIG. 6 shows the relationship between the slope α and the bandwidth when ε r ′ is changed, and FIG. 7 shows the material.
Fig. 8 is a diagram showing the µ r ″ frequency dispersion curves of A, B, C, and Fig. 8 is a diagram showing the electromagnetic wave absorption characteristics of materials A, B, C. 1 ... Electromagnetic wave absorber, 2 ... Electromagnetic wave absorption layer 3 ... Reflector.
Claims (1)
からなる複合磁性材料を用いた電波吸収体において、 前記磁性体粉末はCo及びBaのうちの少なくとも１種類以
上の元素を含む六方晶系フェライト粉末であって、 前記複合磁性材料の複素比誘磁率を 複素比誘電率＝εｒ′−ｊεｒ″、周波数をｆ（GH
z）とし、 ｘ＝ｆ ｙ＝logμｒ″ とおき、 dy/dx＜０の領域のｘ−ｙ曲線のほぼ直線部分の延長線
とｙ＝０の交点を（fn,0）としたとき、動作周波数がほ
ぼfn（GHz）であり、かつ前記延長線の傾きの絶対値α
が 0.05≦α≦0.2 であって、かつ ３≦εｒ′≦20 となる関係を満足する複合磁性材料からなる電波吸収層
と、 該電波吸収層の一面に設けた反射体とを含むことを特徴
とする電波吸収体。1. A radio wave absorber using a composite magnetic material comprising a mixture of magnetic powder and rubber or resin, wherein the magnetic powder is a hexagonal crystal containing at least one element of Co and Ba. System ferrite powder, the complex magnetic induction of the composite magnetic material Complex relative permittivity = ε r ′ −jε r ″, frequency is f (GH
z), and x = fy = logμr ″, and the intersection of y = 0 with the extended line of the substantially straight line part of the xy curve in the region of dy / dx <0 is (f n , 0), The operating frequency is approximately f n (GHz), and the absolute value α of the slope of the extension line
Of 0.05 ≦ α ≦ 0.2 and a radio wave absorption layer made of a composite magnetic material satisfying the relation of 3 ≦ ε r ′ ≦ 20, and a reflector provided on one surface of the radio wave absorption layer. Characteristic radio wave absorber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61054611A JPH07120574B2 (en) | 1986-03-14 | 1986-03-14 | Radio wave absorber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61054611A JPH07120574B2 (en) | 1986-03-14 | 1986-03-14 | Radio wave absorber |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62213101A JPS62213101A (en) | 1987-09-19 |
| JPH07120574B2 true JPH07120574B2 (en) | 1995-12-20 |
Family
ID=12975534
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61054611A Expired - Lifetime JPH07120574B2 (en) | 1986-03-14 | 1986-03-14 | Radio wave absorber |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07120574B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002250089A (en) * | 2001-02-27 | 2002-09-06 | Takechi Kogyo Gomu Co Ltd | Radio wave absorber |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3812977B2 (en) * | 1996-09-30 | 2006-08-23 | Ｎｅｃトーキン株式会社 | Electromagnetic interference suppressor |
| JP2004221977A (en) * | 2003-01-15 | 2004-08-05 | Murata Mfg Co Ltd | Manufacturing method of magnetic resonance type irreversible circuit element, magnetic resonance type irreversible circuit element, high frequency module and communication equipment |
-
1986
- 1986-03-14 JP JP61054611A patent/JPH07120574B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002250089A (en) * | 2001-02-27 | 2002-09-06 | Takechi Kogyo Gomu Co Ltd | Radio wave absorber |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62213101A (en) | 1987-09-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |