Electromagnetic-wave absorber, and process for its production

Abstract

An electromagnetic-wave absorber comprising a base material and an electromagnetic-wave absorption layer provided on the base material. The electromagnetic-wave absorption layer contains at least i) a polymeric material having a glass transition temperature (Tg) of from −15° C. to 110° C. and a number-average molecular weight (Mn) of from 3,000 to 1,000,000 and ii) an inorganic material. Also provided is a process for producing the absorber.

What is claimed is:  
     
         1 . An electromagnetic-wave absorber comprising an electromagnetic-wave absorption layer, wherein; 
 said electromagnetic-wave absorption layer contains at least i) a polymeric material having a glass transition temperature Tg of from −15° C. to 110° C. and a number-average molecular weight Mn of from 3,000 to 1,000,000 and ii) an inorganic material.    
     
     
         2 . The electromagnetic-wave absorber according to  claim 1 , wherein said inorganic material is a material selected from the group consisting of a carbon material, a magnetic material, an inorganic oxide, a composite metal oxide, silicon carbide and silicon nitride.  
     
     
         3 . The electromagnetic-wave absorber according to  claim 1 , wherein said polymeric material has a glass transition temperature Tg of from 0° C. to 70° C.  
     
     
         4 . The electromagnetic-wave absorber according to  claim 1 , wherein said electromagnetic-wave absorption layer is provided on a base material.  
     
     
         5 . The electromagnetic-wave absorber according to  claim 4 , wherein said base material has an electrically conductive layer on its surface, and said electromagnetic-wave absorption layer is provided on the electrically conductive layer of the base material.  
     
     
         6 . The electromagnetic-wave absorber according to  claim 1 , wherein said electromagnetic-wave absorption layer has a weight per unit area of 1.0 mg/cm 2  or more.  
     
     
         7 . The electromagnetic-wave absorber according to  claim 1 , wherein said electromagnetic-wave absorption layer has a weight per unit area of from 1.0 mg/cm 2  to 20,000 mg/cm 2 .  
     
     
         8 . The electromagnetic-wave absorber according to  claim 4 , wherein said base material is formed of a material selected from the group consisting of paper, cloth, plastic and metal.  
     
     
         9 . The electromagnetic-wave absorber according to  claim 4 , wherein said base material has an adhesive portion at least partly on its surface.  
     
     
         10 . The electromagnetic-wave absorber according to  claim 4 , wherein said base material has the electromagnetic-wave absorption layer at least partly on its each side.  
     
     
         11 . The electromagnetic-wave absorber according to  claim 4 , wherein said electromagnetic-wave absorption layer comprises different two or more types of electromagnetic-wave absorption layers superposed on said base material.  
     
     
         12 . An electromagnetic-wave absorber comprising a base material and an electromagnetic-wave absorption layer provided on the base material, wherein; 
 said electromagnetic-wave absorption layer is a layer formed by:    causing electromagnetic-wave absorption particles to adhere to the base material by the aid of static electricity; the particles containing at least a polymeric material and an inorganic material; and    heating the electromagnetic-wave absorption particles to fix them to the base material.    
     
     
         13 . The electromagnetic-wave absorber according to  claim 12 , wherein said polymeric material has a glass transition temperature Tg of from −15° C. to 110° C. and a number-average molecular weight Mn of from 3,000 to 1,000,000.  
     
     
         14 . The electromagnetic-wave absorber according to  claim 13 , wherein said polymeric material has a glass transition temperature Tg of from 0° C. to 70° C.  
     
     
         15 . The electromagnetic-wave absorber according to  claim 12 , wherein said electromagnetic-wave absorption particles are fixed to said base material by heating the electromagnetic-wave absorption particles to a temperature not lower than the glass transition temperature Tg of the polymeric material the electromagnetic-wave absorption particles contain.  
     
     
         16 . The electromagnetic-wave absorber according to  claim 12 , wherein said electromagnetic-wave absorption particles has an average particle diameter of from 2 μm to 15 μm.  
     
     
         17 . A process for producing an electromagnetic-wave absorber comprising: 
 an adhesion step of causing electromagnetic-wave absorption particles to adhere to a base material by the aid of static electricity; the particles containing at least a polymeric material and an inorganic material; and    a fixing step of fixing the electromagnetic-wave absorption particles to the base material by heating, to form an electromagnetic-wave absorption layer.    
     
     
         18 . The process for producing an electromagnetic-wave absorber according to  claim 17 , wherein said polymeric material has a glass transition temperature Tg of from −15° C. to 110° C. and a number-average molecular weight Mn of from 3,000 to 1,000,000.  
     
     
         19 . The process for producing an electromagnetic-wave absorber according to  claim 18 , wherein said polymeric material has a glass transition temperature Tg of from 0° C. to 70° C.