Abstract:
A metal conductive film is provided on the outer surface of the rear substrate of a display panel for both shielding EM fields and helping to dissipate heat generated by the panel.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma display panel (PDP), and more particularly to a means for shielding EM interference and facilitating heat dissipation. 
     2. Description of the Related Art 
     FIG. 1 is an exploded of a conventional PDP. It is generally comprised of a frame  11 , a driving circuit board  12 , a display panel  13  and a filter  14 . The circuit  12 , the display panel  13 , and the filter  14  are received in an opening  15  of the frame  11 . The filter is basically a glass plate coated with an electrically conductive film grounded to the frame so that electromagnetic (EM) fields generated from the panel and the circuit board are absorbed. However, such a conventional PDP has to use a rather thicker conductive film for better conductivity in order to completely shield the EM field. The downside is that increased thickness of a conductive film reduces brightness of an image displayed on the panel can not shield part of EM field that radiates toward the driving circuit board which is located at the rear of the panel, opposite to the filter. Though the casing covering the driving circuit board may prevent such backward EM radiation from escaping from the device, the circuits on the driving board are subjected to and thus can be affected by a strong EM field since it is right next to the source of the EM field. 
     A PDP displays an image when inert gas in selected cells defined by the front and rear substrates of the panel discharges in response to voltage signals applied to electrodes embedded in the substrates. When the PDP is in operation for a period of time, substantial heat is generated and should be dissipated outside the device so as not to cause the driving circuits to malfunction. Conventionally, an electrical fan has been provided between the driving board and the panel for circulation of air. Installing an electrical fan, however, requires a separate power source and complicates a PDP design by that much. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to protect electrical/electronic circuit components on the driving board of a PDP from both EM field and heat generated from the panel portion thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a conventional PDP; 
     FIG. 2 is a detailed view of a PDP according to the present invention; 
     FIG. 3 is an exploded view of the panel portion of a PDP display according to the present invention; and 
     FIG. 4 is a PDP frame having a metal chassis. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3 shows a plasma display panel according to the present invention. A front glass substrate  21  is spaced apart from a rear glass substrate  22 . The front substrate has a plurality of pairs of display electrodes  23   a  and bus electrodes  23   c  on a surface facing the rear substrate. 
     Likewise, the rear substrate has a plurality of address electrodes  23   b  on a surface facing the front substrate. The front and rear substrates are disposed such that their electrodes are orthogonal to each other. On top of the display, electrodes are a dielectric layer  24  and a protective layer  25 . A dielectric layer  24  is also provided on top of the address electrodes on the rear substrate. Further, a plurality of phosphor coated parallel walls  27  are erected thereupon to define cells  29 . An inert gas such as argon is injected into the cells after the substrates are sealed on their periphery and evacuated. The PDP displays images when the inert gas such as argon discharges to becomes plasma in response to a high voltage difference between the electrodes, over a threshold voltage, after charges are accumulated on the cell walls by what is called a trigger voltage. 
     Ultraviolet light emitted during the discharge collides with the phosphor material  28  coating the walls of the cells to cause visible light emission. The characteristic feature of the present invention lies in that a conductive film is formed on the surface of the rear substrate facing the driving circuit board by such methods as vacuum deposition. The conductive film is grounded to the frame in which the panel is disposed. 
     This conductive film serves to absorb electromagnetic energy that is generated just as much toward the back of the panel as toward the screen side. Alternatively, a separate conductive film may be adhered to the rear surface. The EM shield may take a mesh form rather than a film. 
     An embodiment of the present invention is illustrated in FIG.  2 . 
     A driving circuit board  32  is installed within an opening  36  of a frame  31 . A panel  33  is disposed over the driving circuit board  32  that is installed within the frame  31 . 
     Additionally, a second electrically conductive EM shield  35  is provided on the rear side of the panel  33  according to the present invention. Both shields are grounded to the frame  31 . 
     According to a second embodiment of the present invention, a thermally and electrically conductive material is preferably used. Referring to FIG. 4, reference numerals  40  and  50  indicate front and rear glass substrates of the PDP display. For example, copper, aluminum or carbon compounds such as a diamond-like carbon can coat the surface of a rear glass substrate  40  in the form of a film  49 . This embodiment has an additional benefit of facilitating uniform heat dissipation across the panel surface so that deformation of the front or rear glass substrate is prevented. In the embodiment shown in FIG. 4, rather than totally depending on the air as a means of heat transfer the coating layer may be connected to a metal sash  43  of the frame, which would speed up the heat transfer to outside. Furthermore, a cooling device  44  such as a water-circulating pipes or heat sinks between the conductive coating layer and the sash can be provided for better heat transfer.