Method of applying a transfer film to metal surfaces

Abstract

A method is provided for applying a transfer film to a metal surface. The method comprises electrochemically treating the metal to form an oxide layer, on to which a transfer film is applied.

1 . A method of applying a transfer film to a metal surface of a device casing, the method comprising:
 treating the metal surface with an electrochemical treatment to form a metal oxide layer having a dielectric breakdown potential, the electrochemical treatment comprising:
 applying a potential to the metal surface of the casing in an electrolytic solution, wherein the potential applied is greater than the dielectric breakdown potential of the metal oxide layer; and 
   applying a transfer film to the metal oxide layer.   
     
     
         2 . The method according to  claim 1 , wherein applying the potential to the metal surface of the casing includes applying the potential to the metal surface utilizing pulsed direct current. 
     
     
         3 . The method according to  claim 1 , wherein applying the potential to the metal surface of the casing includes a dilute alkali composition in the electrolytic solution. 
     
     
         4 . The method according to  claim 1 , wherein applying the potential to the metal surface of the casing includes an organic acid in the electrolytic solution. 
     
     
         5 . The method according to  claim 3 , wherein the dilute alkali composition includes potassium hydroxide. 
     
     
         6 . The method according to  claim 1 , wherein the transfer film is a polymer-based transfer film. 
     
     
         7 . The method according to  claim 1 , wherein the application of the transfer film includes applying a transfer film comprising polymer nano-particles, metallic nano-particles or a combination thereof. 
     
     
         8 . The method according to  claim 1 , wherein the metal oxide layer undergoes a pre-film treatment prior to applying the transfer film to the metal oxide layer. 
     
     
         9 . The method according to  claim 1 , wherein the transfer film comprises one of inorganic nano-particles, metallic nano-particles or a combination thereof. 
     
     
         10 . The method according to  claim 1 , wherein the metal comprises aluminium, magnesium or titanium, or alloys thereof. 
     
     
         11 . A method of applying a transfer film to a metal surface of a device casing, the method comprising:
 treating the metal surface with a plasma electrolytic oxidation treatment to form a metal oxide layer having a dielectric breakdown potential, the plasma electrolytic oxidation treatment comprising:
 applying a potential to the metal surface of the casing in an electrolytic solution, wherein the potential applied is greater than the dielectric breakdown potential of the metal oxide layer, and wherein the plasma electrolytic oxidation treatment forms a porous metal oxide layer; and 
   applying a polymer transfer film to the metal oxide layer.   
     
     
         12 . The method of  claim 11 , wherein the porous metal oxide layer is altered by varying a voltage applied to the metal surface during the plasma electrolytic oxidation treatment, and wherein the porous metal oxide layer is titanium dioxide. 
     
     
         13 . The method of  claim 11 , the method further comprising:
 treating the metal oxide layer with a pre-film treatment prior to applying the transfer film to the metal oxide layer, wherein the pre-film treatment is used to alter a tactual property of the device casing.   
     
     
         14 . An electrochemically treated casing for a device comprising:
 a metal layer treated with the electrochemical treatment to form a metal oxide layer   the metal oxide layer having a dielectric breakdown potential formed by micro-arc oxidation of the metal layer, wherein the metal oxide layer is porous; and   a polymer transfer film on the metal oxide layer.   
     
     
         15 . The casing of  claim 14 , wherein the metal layer comprises aluminium, magnesium or titanium, or alloys thereof.