Abstract:
A coated article includes a metal layer coated on a substrate. The substrate is made of plastic with photosensitivity property, and has a plurality of free radicals —O. and —CO. a surface thereof. The metal layer is coated on the substrate. The free radicals link with metal atoms of the metal layer to connect the substrate and the metal layer.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    This disclosure relates to a coated article and a method of making the same. 
         [0003]    2. Description of Related Art 
         [0004]    Physical vapor deposition (PVD) is widely used to improve properties of substrates. A plastic substrate coated with a metal layer by PVD has a metallic appearance and good wear resistance. Forming a metal layer on a plastic substrate using PVD is popular in the industry. However, since properties of metal can be quite different from those of the plastic substrate, a binding force between the metal layer and the plastic substrates can be weak, and the metal layer can be easily worn away. One way to improve the binding force between the metal layer and the plastic substrates, is increasing roughness of the binding surface of the plastic substrate by sandblasting. However, sandblasting may not always create enough binding force. 
         [0005]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0006]    Many aspects of the coated article and method of making the same can be better understood with reference to the following drawing. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the coated article and method of making the same. 
           [0007]    FIGURE is a cross-section view of a coated article, in accordance with an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0008]    FIGURE shows an exemplary embodiment of a coated article  10 . The coated article  10  includes a metal layer  13  coated on a plastic substrate  11 . The substrate  11  is made of polyester or polycarbonate plastics. The metal layer  13  is made of one of magnesium, zirconium, aluminum and titanium. The plastic substrate  11  is treated to form a plurality of free radicals, e.g., —O. and —CO. on a surface of the substrate  11 . The free radicals can react with metal atoms in the metal layer  13  to form chemical bonds. These chemical bonds can increase the binding force between the substrate  11  and the metal layer  13 . 
         [0009]    A method of making the coated article  10  includes the following steps: 
         [0010]    A plastic substrate  11  is provided. The substrate  11  needs to be photosensitive and able to form a plurality of active free radicals, e.g., —O. and —CO. under ultraviolet light. In this exemplary embodiment, the substrate  11  is made of polyester or polycarbonate plastics. 
         [0011]    A surface pre-treatment is applied to the substrate  11 . The pre-treatment includes oil cleaning, paraffin removal, cleaning by plasma, and drying. In this embodiment, a sodium hydroxide solution or a potassium hydroxide solution is used to clean oil and paraffin off the substrate  11 . 
         [0012]    A metal layer  13  is formed on the substrate  11  by magnetron sputtering, by a process including a first sputtering process and a second sputtering process. The substrate  11  is set in a vacuum chamber (not shown) of a vacuum sputtering coating machine (not shown). 
         [0013]    Before the first sputtering process, the chamber is evacuated until the pressure in the chamber is from about 3.0*10 −3  pascals (Pa) to about 8.0*10 −3  Pa. Argon gas is then input into the chamber at a flow of about 300 sccm to about 500 sccm. The purity of the argon gas is 99.9999%. A metal target and an ultraviolet lamp are disposed in the vacuum chamber. The target may be made of one of magnesium, zirconium, aluminum and titanium. The target is activated to sputter metal atoms on a baffle plate positioned in front of the target for about 5 minutes (min) to about 10 min. Thus, impurities or pollutants, such as dust, on the target can be completely removed. 
         [0014]    During the first sputtering process, the target and the ultraviolet lamp are activated. Power of the target is adjusted to be in a range of about 1 kilowatt (kw) to about 12 kw. The ultraviolet lamp is configured for applying ultraviolet light. The ultraviolet intensity is in a range of about 10 mv/cm 2  to about 20 mv/cm 2 . Argon gas is input into the chamber at a flow of about 50 sccm to about 400 sccm. A bias voltage in a range of about −50 V to about −150 V is applied to the substrate  11 . A temperature of air in the chamber is in a range of about 50° C. to about 100° C. The ultraviolet light irradiates the substrate  11 , and active free radicals, e.g., —O. and —CO. are formed on the surface of the substrate  11  to link with the metal atoms sputtered on the substrate  11 . The ultraviolet lamp may be fixed above the chamber, and vertically illuminates the surface of the substrate  11 . The time of the first sputtering process is in a range of about 5 min to about 10 min. 
         [0015]    During the second sputtering process, the ultraviolet lamp is turned off and the power of the target is adjusted to be about 8 kw to about 12 kw. The other technological parameters remain the same. The time of the second sputtering process is in a range of 5 min to 10 min. The metal layer  13  is formed on the substrate  11  with a thickness about 50 nm to 200 nm. 
         [0016]    Free radicals, e.g., —O. and —CO. are very active and react with the active metal atoms, e.g., Mg, Zr, Al, Ti, on the substrate  11  to form chemical bonds. These chemical bonds greatly improve the binding force between the substrate  11  and the metal layer  13 . 
         [0017]    It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts 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.