Electromagnetic wave absorption material and an associated device

Abstract

The purpose of the present invention is to provide an easy-to-manufacture electromagnetic wave absorption material usable from submillimeter wave region to millimeter wave region with an excellent radio wave absorbing performance and a variety of usage thereof. The present invention is characterized by an electromagnetic wave absorption material comprised of a dispersions of at least one of the materials: a multi-layer hollow globule of carbon, a schungite carbon, and the schungite ore; mixed into a matter having a high electrical resistivity. The invention is further characterized by an electronic device, an optical transmission module, an optical reception module, a high frequency telecommunication equipment, and a stop-free automated tollgate system, wherein at least a part of their board, electronic element, and circuit wiring are covered with said electromagnetic wave absorption material.

What is claimed is:  
     
         1 . Electromagnetic wave absorption material comprising a multi-layer hollow globule of carbon.  
     
     
         2 . Electromagnetic wave absorption material comprising a multi-layer hollow globule of carbon, wherein said globule contains at least one of a carbon nanotube formed therein, metallic constituent, and free water.  
     
     
         3 . Electromagnetic wave absorption material comprising a schungite carbon.  
     
     
         4 . Electromagnetic wave absorption material comprising a schungite carbon, wherein said schungite carbon contains at least one of a carbon nanotube formed therein, metallic constituent, and free water.  
     
     
         5 . Electromagnetic wave absorption material according to  claim 4 , wherein said metallic constituent is comprised of one or more materials selected from the group of materials consisting of metals, metallic silicates, metallic sulfides, and metallic oxides.  
     
     
         6 . Electromagnetic wave absorption material according to  claim 4  or  claim 5 , wherein said metallic constituent is comprised of one or more materials selected from the group of materials consisting of Cu, Ni, V, Cr, Co, Mn, and Ti.  
     
     
         7 . Electromagnetic wave absorption material comprising a schungite ore.  
     
     
         8 . Electromagnetic wave absorption material according to any one of  claims 1  to  7 , wherein said electromagnetic wave absorption material is further comprised of a substance that has an electrical resistivity higher than that of said multi-layer hollow globule or said schungite carbon and said electromagnetic wave absorption material is a composite of said substance.  
     
     
         9 . Electromagnetic wave absorption material comprising a particulate of electromagnetic wave absorbing matter and a substance that has an electrical resistivity higher than that of said particulate of electromagnetic wave absorbing matter, wherein said electromagnetic wave absorption material has the radio wave return loss of not less than −3.5 dB per 1 GHz of frequency.  
     
     
         10 . Electromagnetic wave absorption material comprising a particulate of electromagnetic wave absorbing matter and a substance that has an electrical resistivity higher than that of said particulate of electromagnetic wave absorbing matter, wherein said electromagnetic wave absorption material has the radio wave return loss of not less than −20 dB at a frequency of 6 GHz.  
     
     
         11 . Electromagnetic wave absorption material according to any one of  claims 8  to  10 , wherein said high electrical resistivity substance contains at least one of rubber, insulating polymeric material, and inorganic insulating material.  
     
     
         12 . Electromagnetic wave absorption material according to any one of  claims 8  to  11 , wherein the content of said multi-layer hollow globule, said schungite carbon, a schungite carbon included in said schungite ore, and said particulate of electromagnetic wave absorbing matter is 5 to 50 weight-% of the whole weight of said electromagnetic wave absorption material.  
     
     
         13 . Electromagnetic wave absorption material according to any one of  claims 8  to  12 , wherein content of said multi-layer hollow globule, said schungite carbon, and said particulate of electromagnetic wave absorbing matter are graded to plural degrees so that characteristic impedance may reduce toward inside from the incident plane of electromagnetic wave.  
     
     
         14 . Electromagnetic wave absorption material according to any one of  claims 8  to  13 , wherein said absorption material further includes any one of: a magnetic metal of which main constituent is at least one of Fe, Co, and Ni; a compound selected from the group consisting of an oxide, a nitride, and a carbide, in which their main constituent is at least one of Fe, Co, Ni, Al, Si, Ti, Ba, Mn, Zn, and Mg; or a carbon-based substance which contains at least one of carbon black, graphite, coke, and carbon micro-coil.  
     
     
         15 . A printed wiring board comprising an insulated board having a circuit wiring thereon, said circuit wiring being at least partly covered with an insulating layer, wherein at least one of surfaces of said insulated board, one surface having said wiring circuit thereon and the other the reverse surface thereof, has a layer comprised of an electromagnetic wave absorption material, which is the electromagnetic wave absorption material described in any one of  claims 1  to  14 .  
     
     
         16 . An electronic device comprising an electronic element mounted on a printed wiring board, said electronic element being covered with a metal cap, wherein at least a part of internal surface of said metal cap is provided with an electromagnetic wave absorption material, which is the electromagnetic wave absorption material described in any one of  claims 1  to  14 .  
     
     
         17 . An electronic device comprising a printed wiring board, an electronic device mounted on said printed wiring board, said printed wiring board and said electronic device being covered with a metal casing, wherein at least a part of internal surface of said metal casing is provided with an electromagnetic wave absorption material, which is the electromagnetic wave absorption material described in any one of  claims 1  to  14 .  
     
     
         18 . A metal casing having an opening, wherein at least a part of internal surface of said metal casing is provided with the electromagnetic wave absorption material described in any one of  claims 1  to  14 .  
     
     
         19 . A module of optical transmission or of optical reception comprising a circuit board having at least either a light emitting element or a photo acceptance element and having at least either a transmission circuitry or a reception circuitry thereon, wherein at least a part of said circuit board, said element, and said circuitry are covered with the electromagnetic absorption material described in any one of  claims 1  to  14 .  
     
     
         20 . A module of optical transmission or of optical reception comprising a circuit board having at least either a light emitting element or a photo acceptance element and having at least either a transmission circuitry or a reception circuitry thereon, wherein at least a part of said circuit board, said elements, and said circuitry are covered with a metal cap, and at least a part of internal surface of said metal cap is formed by an element having the electromagnetic absorption material described in any one of  claims 1  to  14 .  
     
     
         21 . A module of optical transmission or of optical reception comprising a circuit board having at least either a light emitting element or a photo acceptance element and having at least either a transmission circuitry or a reception circuitry thereon, wherein at least a part of said circuit board, said elements, and said circuitry are covered with an element having the electromagnetic absorption material described in any one of  claims 1  to  14 , and external surface of said element is covered with a metal cap.  
     
     
         22 . A module of optical transmission or of optical reception according to any one of  claims 18  to  20 , wherein at least a part of said circuit board, said elements, and said circuitry are covered with an insulating resin, the surface of said insulating resin is provided with said electromagnetic absorption material.  
     
     
         23 . An automated tollgate comprising a roofed tolling gate, an entrance antenna arranged at the entrance of said tolling gate and faced to a transit vehicle approaching said tolling gate, an exit antenna arranged at the exit of said tolling gate and faced to a transit vehicle leaving said tolling gate, and an automated toll collection system that exchanges information between a roadside communication equipment and an on-vehicle equipment carried by said transit vehicle, 
 wherein the surface of a structural member in said tolling gate and its vicinity which reflects electromagnetic wave, the surface of facing-to-vehicle side of the roof of said tolling gate, and at least a part of the surface of a supporting column for said entrance antenna and said exit antenna are provided with the electromagnetic wave absorption material described in any one of  claims 1  to  14 .    
     
     
         24 . A high frequency communication equipment comprising a high frequency circuit element mounted and accommodated inside a casing, wherein at least the inner wall of said casing and at least a part of said inner wall are provided with the electromagnetic wave absorption material described in any one of  claims 1  to  14 .