Patent Publication Number: US-2013240350-A1

Title: Electronic device housing and method for making the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. Ser. No. 12/949934, filed Nov. 19, 2010, the contents of which are hereby incorporated by reference. The patent application Ser. No. 12/949934 in turn claims the benefit of priority under 35 USC 119 from Chinese Patent Application 200910312423.6, filed on Dec. 28, 2009. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to electronic device housings, particularly to an electronic device housing having self-cleaning property and a method for making the electronic device housing. 
     2. Description of Related Art 
     Decorative metallic coatings are often formed on housings of electronic devices. The metallic coatings are typically formed by vacuum deposition to present an aesthetic metallic appearance. Metallic coatings formed by vacuum deposition can be nonconductive so as not to block electromagnetic waves. However, the metallic coatings are not self-cleaning, and cannot repel dust and sweat that collects on the electronic device housings. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURE 
       Many aspects of the electronic device housing can be better understood with reference to the following FIGURE. The components in the FIGURE are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the electronic device housing. 
       The FIGURE is a cross-section of an exemplary embodiment of an electronic device housing. 
     
    
    
     DETAILED DESCRIPTION 
     The FIGURE shows an electronic device housing  10  according to an exemplary embodiment. The electronic device housing  10  includes a substrate  11 , a base paint coating  13  formed on a surface of the substrate  11 , and a nano titanium dioxide coating  15  formed on the base paint coating  13 . The electronic device housing  10  may be a housing of mobile phone, PDA, note book computer, MP3, MP4, GPS navigator, or digital camera. 
     The substrate  11  may be formed by molding one or more plastic materials selected from a group consisting of polycarbonate (PC), polyethylene (PE), polymethyl methacrylate (PMMA), and a mixture of polycarbonate and acrylonitrile-butadiene-styrene plastics (PC+ABS). The substrate  11  may also be made of glass or ceramic. 
     The base paint coating  13  may be an acrylic resin paint coating, an epoxy resin paint coating, a polyurethane resin paint coating, or a phenolic resin paint coating. The base paint coating  13  may have a thickness of about 1 μm to about 30 μm. The base paint coating  13  can be colored or transparent. The base paint coating  13  enhances the bonding between the substrate  11  and the nano titanium dioxide coating  15 . 
     The nano titanium dioxide coating  15  may be formed on the base paint coating  13  by vacuum sputtering. The nano titanium dioxide coating  15  is formed of rutile crystals, or composite crystals formed of rutile and anatase. The thickness of the nano titanium dioxide coating  15  may be in a range of about 10-100 nm. The thickness of the nano titanium dioxide coating  15  is controlled to present a metallic appearance for the electronic device housing  10  without interfering with radio transmission capabilities. The nano titanium dioxide coating  15  further has a self-cleaning property. Specifically, dust and sweat may attach on the surface of the nano titanium dioxide coating  15 . However, during irradiation under visible light or ultraviolet light, the nano titanium dioxide coating  15  can oxygenize and clean off dust and sweat. 
     The base coating  13  is used as a bonding agent between the nano titanium dioxide coating  15  and the substrate  11  but may be omitted in applications that allows a bond to be formed by directly applying the nano titanium dioxide coating  15  on the substrate  11 . 
     A method for making the electronic device housing  10  may include the following steps. 
     The substrate  11  is provided. The substrate  11  may be made of plastic material, glass, or ceramic. 
     The base paint coating  13  is sprayed on the substrate  11 . The paint for forming the base paint coating  13  may be acrylic resin paint, epoxy resin paint, polyurethane resin paint, or phenolic resin paint. Before forming the base paint coating  13 , the surface of the substrate  11  may be cleaned by plasma. 
     The nano titanium dioxide coating  15  is formed on the base paint coating  13  by vacuum sputtering. Vacuum sputtering of the nano titanium dioxide coating  15  may be implemented by a vacuum depositing machine. The vacuum depositing machine may be vacuum pumped to about 1×10 −3  Pa and receives the substrate  11 . Then the vacuum depositing machine continues to be vacuum pumped to about 5×10 −4 ˜9×10 −4  Pa. Oxygen gas (O 2 , having a purity of about 99.99%) and argon gas (Ar) are introduced into the vacuum depositing machine to get a pressure of about 0.05˜0.29 Pa with the pressure of the O 2  being in a range of about 0.01˜0.225 Pa. The target material for vacuum sputtering the nano titanium dioxide coating  15  may be titanium. The output power of the target may be 3000˜4000 watt (W). During the vacuum sputtering process, the argon gas converts into plasma and strikes the titanium target to make the titanium target generate titanium atoms. These titanium atoms then immediately react with the oxygen gas to form the nano titanium dioxide coating  15  on the base paint coating  13 . The deposition rate of the nano titanium dioxide coating  15  is about 0.3-0.5 nm/s. 
     It is to be understood that before forming the nano titanium dioxide coating  15 , the base paint coating  13  may undergo plasma cleaning. 
     It should be understood, however, that though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.