Black Colored Steel Sheet Having Excellent Electromagnetic Shielding Property, Electromagnetic Shielding Member, and Electromagnetic Shielding Case

Abstract

A black colored steel sheet comprises a Zn—Ni-plated steel sheet having a blackening-treated layer and a coating film on the surface of the Zn—Ni-plated steel sheet. The blackening-treated layer has a thickness of 0.01 to 1.0 μm. The Zn—Ni-plated steel sheet having a blackening-treated layer has an arithmetical mean roughness Ra of 0.7 to 2.0 μm and the number of peaks per inch (PPI) of at least 180.

1 . A black colored steel sheet having an excellent electromagnetic shielding property, comprising a Zn—Ni-plated steel sheet having a blackening-treated layer; and a coating film formed on the Zn—Ni-plated steel sheet, wherein 
 the blackening-treated layer has a thickness of 0.01 to 1.0 μm;    the Zn—Ni-plated steel sheet having the blackening-treated layer has an arithmetical mean roughness Ra of 0.7 to 2.0 μm and the number of peaks per inch (PPI) of at least 180.    
   
   
       2 . The black colored steel sheet according to  claim 1 , wherein the number of peaks per inch (PPI) is 200 to 400.  
   
   
       3 . The black colored steel sheet according to  claim 1 , wherein the arithmetical mean roughness Ra, the number of peaks per inch (PPI), and a coating weight of coating film applied to one side of the black colored steel sheet satisfy the equation (1):  
         z≦ (0.010 x− 0.0077) y− 1.05 x+ 2.16  (1)  wherein x denotes the arithmetical mean roughness Ra (μm), y denotes the number of peaks per inch (PPI), and Z denotes the coating weight of coating film applied to one side of the black colored steel sheet (g/m 2 ).    
   
   
       4 . An electromagnetic shielding member, 
 wherein all or part of the member is formed of the black colored steel sheet according to  claim 1 .    
   
   
       5 . An electromagnetic shielding case formed of the black colored steel sheet according to  claim 1 .  
   
   
       6 . The black colored steel sheet according to  claim 2 , wherein the arithmetical mean roughness Ra, the number of peaks per inch (PPI), and a coating weight of coating film applied to one side of the black colored steel sheet satisfy the equation (1):  
         z≦ (0.010 x− 0.0077) y− 1.05 x+ 2.16  (1)  wherein x denotes the arithmetical mean roughness Ra (μm), y denotes the number of peaks per inch (PPI), and Z denotes the coating weight of coating film applied to one side of the black colored steel sheet (g/m 2 ).    
   
   
       7 . An electromagnetic shielding member, wherein all or part of the member is formed of the black colored steel sheet according to  claim 2 .  
   
   
       8 . An electromagnetic shielding member, wherein all or part of the member is formed of the black colored steel sheet according to  claim 3 .  
   
   
       9 . An electromagnetic shielding member, wherein all or part of the member is formed of the black colored steel sheet according to  claim 6 .  
   
   
       10 . An electromagnetic shielding case formed of the black colored steel sheet according to  claim 2 .  
   
   
       11 . An electromagnetic shielding case formed of the black colored steel sheet according to  claim 3 .  
   
   
       12 . An electromagnetic shielding case formed of the black colored steel sheet according to  claim 6.