Molded ferrite sheet, sintered ferrite substrate and antenna module

Abstract

The present invention relates to a molded ferrite sheet having opposing surfaces and a thickness in a range of 30 μm to 430 μm, at least one surface of said opposing surfaces having the following surface roughness characteristics (a) to (c): (a) a center line average roughness is in a range of 170 nm to 800 nm, (b) a maximum height is in a range of 3 μm to 10 μm, and (c) an area occupancy rate of cross-sectional area taken along a horizontal plane at a depth of 50% of the maximum height in a square of side 100 μm is in a range of 10 to 80%.

1 . A molded ferrite sheet having opposing surfaces and a thickness in a range of 30 μm to 430 μm, at least one surface of said opposing surfaces having the following surface roughness characteristics (a) to (c):
 (a) a center line average roughness is in a range of 170 nm to 800 nm, 
 (b) a maximum height is in a range of 3 μm to 10 μm, and 
 (c) an area occupancy rate of cross-sectional area taken along a horizontal plane at a depth of 50% of the maximum height in a square of side 100 μm is in a range of 10 to 80%. 
 
     
     
         2 . A molded ferrite sheet as recited in  claim 1 , wherein said at least one surface is roughened by sandblasting. 
     
     
         3 . A molded ferrite sheet as recited in  claim 1 , wherein said molded ferrite sheet is prepared by molding under pressure using a mold or calender roll having a roughened surface so that the roughness of the roughened surface of said mold or calender roll is transferred to a surface of said molded ferrite sheet in contact with the roughened surface of said mold or calender roll. 
     
     
         4 . A molded ferrite sheet as recited in  claim 1 , wherein said molded ferrite sheet is prepared by a method which comprises applying a coating of a ferrite-dispersed coating liquid to a surface of a plastic film, and drying the applied coating, and wherein said surface of said plastic film has been roughened by sandblasting so that the roughness of said plastic film is transferred to a surface of the dried coating in contact with the roughened surface of said plastic film. 
     
     
         5 . A molded ferrite sheet as recited in  claim 1 , wherein said molded ferrite sheet is prepared by a method which comprises applying a coating of a ferrite-dispersed coating liquid to a support and drying the applied coating, and wherein the ferrite has been obtained by adjusting a particle size of a ferrite powder having an average particle diameter of 0.1 to 10 μm so that said surface roughness characteristics (a) to (c) are imparted to a surface of the dried coating in contact with said support. 
     
     
         6 . A molded ferrite sheet as recited in  claim 1 , wherein the ferrite is Ni—Zn—Cu-based spinel ferrite or Mg—Zn—Cu-based spinel ferrite. 
     
     
         7 .- 18 . (canceled)