Patent Publication Number: US-2012040116-A1

Title: Device housing and method for making the same

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to device housings, particularly to a device housing having a photochromic property and a method for making the device housing. 
     2. Description of Related Art 
     Many electronic device housings are coated with a photochromic coating. These photochromic coatings are commonly printed with an ink or painted with a paint that contains photochromic compounds. However, the printed or painted coatings are thick (commonly 2 μm-4 μm) and not very effective. Furthermore, the paint or ink may not be environmentally friendly. 
     Therefore, there is room for improvement within the art. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURE 
       Many aspects of the 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 device housing. 
       The FIGURE is a cross-sectional view of an exemplary embodiment of a device housing. 
     
    
    
     DETAILED DESCRIPTION 
     The FIGURE shows a device housing  10  according to an exemplary embodiment. The device housing  10  includes a substrate  11 , a photochromic coating  13  formed on a surface of the substrate  11 , and a protective coating  15  formed on the photochromic coating  13 . 
     The substrate  11  may be made of metal or glass or under certain circumstances plastic. 
     The photochromic coating  13  includes at least one of a silver chloride-cuprous chloride (AgCl—CuCl) mixture, a silver bromide-cuprous bromide (AgBr—CuBr) mixture, and a AgCl—CuCl—AgBr—CuBr mixture. Each mixture has a property of reversible color change. The CuCl or CuBr may have a mass percentage of about 10%-20% in the mixture of AgCl—CuCl or AgBr—CuBr, or the CuCl and CuBr may have a mass percentage of about 10%-20% in the mixture of AgCl—CuCl—AgBr—CuBr. The photochromic coating  13  may be formed by vacuum evaporation. The photochromic coating  13  has a thickness of about 500 nm-1500 nm, which is lower than the printed or painted photochromic coatings. 
     When irradiated, the AgCl or AgBr within the photochromic coating  13  may break down and generate Ag crystal particles, and the Ag crystal particles then change the color of the photochromic coating  13  from white to black. When the irradiation lessens or stops, the CuCl or CuBr within the photochromic coating  13  may catalyze the Ag crystal particles back to AgCl or AgBr, causing the photochromic coating  13  to revert its color back from black to white. 
     As mentioned above, the CuCl or CuBr acts as a color changing catalyst in the photochromic coating  13 . The CuCl or CuBr contained in the photochromic coating  13  has a high photosensitivity, which makes the photochromic property of the photochromic coating  13  more effective. 
     The protective coating  15  may be a silica dioxide (SiO 2 ) optical coating formed by vacuum evaporation. The protective coating  15  is optically transparent and has a thickness of about 300 nm-500 nm. The protective coating  15  protects the photochromic coating  13  from abrasion. Since the protective coating  15  is an optically transparent coating, it does not affect the irradiation of the photochromic coating  13  or its photochromic property. 
     A method for making the device housing  10  may include the following steps: 
     The substrate  11  is provided for pre-treatment. The pre-treating process may include the step of cleaning the substrate  11  in an ultrasonic cleaning device (not shown) filled with ethanol or acetone. 
     The photochromic coating  13  is deposited on the pretreated substrate  11  by vacuum evaporation. Vacuum evaporation depositing the photochromic coating  13  is implemented in a plating chamber of a vacuum evaporative equipment (not shown). The substrate  11  is positioned in the plating chamber. The plating chamber is then evacuated to about 4.0×10 −3  Pa. Compounds of AgCl and CuCl, compounds of AgBr and CuBr, or compounds of AgCl, CuCl, AgBr, and CuBr may be used as an evaporation target for the deposition. The CuCl or CuBr may have a mass percentage of about 10%-20%  in the compounds of AgCl and CuCl or AgBr and CuBr, or the CuCl and CuBr may have a mass percentage of about 10%-20% in the compounds of AgCl, CuCl, AgBr, and CuBr. The evaporation target may be electron beam heated to evaporate and deposit on the substrate  11  to form the photochromic coating  13 . The depositing rate of the photochromic coating  13  may be about 3 angstrom per second (Å/S)-10 Å/S. The inside of the plating chamber may be heated to about 50° C.-150° C. during the depositing process. Additionally, during the depositing process, the substrate  11  may be bombarded by plasma at a power of about 900 W-1500 W to enhance the bond between the photochromic coating  13  and the substrate  11 . The plasma may be produced by a plasma producer. 
     It is to be understood that if the inside temperature of the plating chamber is lower than 100° C. during the depositing process, the substrate  11  can also be made of plastic. 
     The protective coating  15  is formed on the photochromic coating  13  by vacuum evaporation. The protective coating  15  is a transparent silica dioxide optical coating and has a thickness of about 300 nm-500 nm. 
     It is believed that the exemplary embodiment and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its advantages, the examples hereinbefore described merely being preferred or exemplary embodiment of the disclosure.