Patent Publication Number: US-2012043222-A1

Title: Coating method for forming pattern on workpiece

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to coating methods, and particularly to a coating method for forming a pattern on a workpiece, for example, an outer shell of a mobile phone. 
     2. Description of Related Art 
     Metal or metal oxide coatings can be applied to a predetermined area of a workpiece by physical vapor deposition (PVD) methods or chemical vapor deposition (CVD) methods. A shielding sheet covers the non-predetermined area so that the metal or metal oxide materials will be only coated on the predetermined area. However, the disadvantage of using PVD or CVD methods only is that the shielding sheet is usually too thick; some metal or metal oxide coatings may be deposited on the edges of the shielding sheet and on the edges of the predetermined area. Therefore, the edges of the predetermined area may be blurred, and the thickness of the coat may not be uniform. 
     What is needed, therefore, is a coating method for forming pattern on workpiece, which can overcome the above shortcomings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present coating method for forming pattern on workpiece can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present coating method for forming patterns. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is a schematic view of a workpiece coated with a coating layer. 
         FIG. 2  is a schematic view of the workpiece shown in  FIG. 1  covered by a mask and coated with a shielding layer through a through hole of the mask. 
         FIG. 3  is a schematic view of the workpiece shown in  FIG. 2  with the coating layer except a part protected by the shielding layer removed. 
         FIG. 4  is a schematic view of the workpiece shown in  FIG. 3  with a pattern. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the  FIG. 1 , a workpiece  10  constituting an external surface  101  is subjected to a coating step. The workpiece  10  is made of ferromagnetic materials, for example iron, nickel, or cobalt. The surface  101  is flat. A predetermined pattern  50  (shown in  FIG. 4 ) will be formed on the surface  101 . The area of the predetermined pattern  50  is smaller than that of the surface  101 . The predetermined pattern  50  in this embodiment is a circular shape. 
     In a first step, a coating layer  20  is deposited over the entire surface  101 . The predetermined pattern  50  may be a logo, or a trademark. The coating layer  20  may be coated on the surface  101  by PVD method. The coating layer  20  may include a single film or a multi-layer film. The material of the coating layer  20  may be metal, metal oxide, or plastic. 
     In a second step, referring to the  FIG. 2 , a mask  30  is applied to the coating layer  20 . The mask  30  shields the coating layer  20  except the area of the predetermined pattern  50 . The mask  30  is made of magnetic materials, for example magnet, or permanent magnet. The mask  30  includes a through hole  300  that has a shape conforming to the predetermined pattern  50 . The area of predetermined pattern  50  is exposed due to the through hole  300 . Because the workpiece  10  is made of ferromagnetic materials, it is easy to attach the mask  30  to the workpiece  10  firmly. The mask  30  is required to shield the surface  101  as much as possible except the area of the predetermined pattern  50 . Thus, the coating layer  20  consists of the exposed portion and unwanted portion surrounding the exposed portion. The form of the mask  30  is not limited to the form shown in  FIG. 2 . 
     In a third step, a shielding layer  40  is deposited on the exposed portion of the coating layer  20  in the through hole  300 . That is, the shielding layer  40  has the same pattern as the predetermined pattern  50 . The material of the shielding layer  40  may be ink or photoresist. 
     In a fourth step, referring to the  FIG. 3 , the mask  30  is removed after the shielding layer  40  is deposited on the surface  101 . The unwanted portion of the coating layer  20  is removed by electrochemical machining method. Because the shielding layer  40  is made of the ink or photoresist that does not react with materials used in the electrochemical machining method, the shielding layer  40  thus protects the coating layer  20  under the shielding layer  40 . 
     Next, referring to the  FIG. 4 , after the unwanted portion of the coating layer  20  is removed, the shielding layer  40  is removed according to the properties of the material. If the shielding layer  40  is made of an ink, alkaline solution, for example sodium hydroxide (NaOH) solution, may be used to remove the shielding layer  40 . The shielding layer  40  made of photoresist may be removed using a photoresist developer. Because the alkaline solution or photoresist developer does not act on the material of the coating layer  20 , the coating layer  20  under the shielding layer  40  is kept; therefore, a predetermined pattern  50  is shown. 
     The predetermined pattern  50  is formed actually in the first step of coating the coating layer  20 . Because the coating layer  20  is coated on the entire surface  101 , the thickness of the coating layer  20  is uniform. The area of the predetermined pattern  50  is kept protecting by the shielding layer  40 , so the predetermined pattern  50  will not be destroyed or blurred by the other procedures. 
     It is understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the disclosure.