Abstract:
A plasma display device including a back surface glass plate equipped with discharge electrodes and having electronics connected to the back surface thereof, a front surface glass plate mounted on and opposing to the back surface glass plate via separation walls and having discharge electrodes, and luminescent pixels defined by the back surface glass plate the separation wall and the front surface glass plate. The back surface glass plate of the luminescent pixel opposite the display surface is formed as a reflection surface, and a fluorescent layer is formed on said reflection surface.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma display device. 
     2. Description of the Related Art 
     A plasma display device is a flat panel display capable of displaying color images by generating ultraviolet light through high-voltage gas discharge, and lighting fluorescent agents of various colors painted to each pixel within the panel. 
     The technology related to plasma display devices has advanced remarkably during the recent years, and the plasma display devices have now reached amass production state. There exists a competition in developing a large-size plasma display device that is bright, has a wide viewing angle, has an even luminance throughout the whole screen, and that is free from distortion, effusion or mismatch of colors. 
     However, according to the conventional plasma display devices, a beautiful image is provided only when viewed in a dark room. The image provided by the plasma display is not bright enough to be viewed at a bright place, for example, outdoors. 
     The structure of a plasma display device according to the prior art is explained with reference to FIG.  5 . 
     Electronics  3  are connected to a display module  10  through a flex lead  5 . Tempered glass  9  is mounted on the display surface of the display module  10  via space  7 . 
     The display module  10  defines discharge spaces  20  by a back surface glass  11  placed to the side of the electronics  3 , separation walls  15 , and a front glass  13  placed to the side of the tempered glass  9  and superposed to the back surface glass  11  through the separation walls. Data electrodes  12  are mounted on the back surface glass  11 , and scan electrodes  14  are mounted on the front surface glass  13 , which are covered with dielectric layers  18  and  19 . Fluorescent  17  of three colors (17R, 17G, 17B) are applied on each discharge space corresponding to each pixel. 
     High voltage is impressed to electrodes  12  and  14  of the plasma display device formed as explained above, and gas discharge is performed within the discharge space  20  filled with neon gas including argon. Ultraviolet light is generated in each discharge space  20 , and causes the fluorescent  17  of the corresponding pixel to glow. 
     One cause of insufficient brightness of the plasma display device is that not all of the visible radiation from the fluorescent caused by the ultraviolet light generated by the gas discharge is radiated toward the display surface or front glass  12 . Visible radiation is also radiated toward the back surface glass  11  and the side surfaces (separation walls  15 ), and perpendicular members (such as glass) absorb the visible radiation. 
     In order to improve the radiation efficiency toward the display surface, there are attempts to color the dielectric layer  18  mounted to the back surface glass  11  white, so that it may reflect the visible radiation. However, the effect is not satisfying. 
     Moreover, many electronics  3  are mounted to the back surface of the display module  10 . The heat generated form the display module  10  heats the electronics  3 , causing problems. 
     This is because the gas discharge and the fluorescent of the display module  10  generates electromagnetic wave energy having various wavelengths, such as ultraviolet, visible radiation, heat wavelength energy and radio wavelength energy. The white-colored dielectric layer  118  mounted to the back surface of the module improves the luminance of the display by reflecting the visible radiation (electromagnetic wave having a wavelength of 0.38-0.78 micron) generated from the fluorescent. However, the white dielectric layer does not reflect electromagnetic wave energy having a long wavelength (0.78-100 micron) classified as heat wave energy, or radio wave energy (electromagnetic wave energy having a wavelength of 100 micron or greater). 
     Even further, the electromagnetic wave energy that has not been reflected by the dielectric layer is absorbed by the fluorescent, the white-colored dielectric layer  18  formed on the back surface, and the back surface glass plate  11  of the display module  10 , and there, the electromagnetic wave energy is converted into heat energy. The heat energy causes the temperature of the back surface portion of the display module  10  to increase. 
     From the above reasons, there is a need to forcedly diffuse the heat of the display module, not only to protect the module but also to protect the electronics connected to the module. 
     SUMMARY OF THE INVENTION 
     The present invention provides a plasma display device having improved luminosity and bright image quality with low power consumption, and with reduced electromagnetic wave energy radiated toward the back surface of the display module equipped with electronics converting into heat energy. 
     The plasma display device according to the present invention comprises a display module equipped with an array of luminescent pixels, and electronics connected to the back surface of the display module wherein the front surface of the display module is a display surface, and the surface of the luminescent pixels opposite said display surface is a reflection surface. 
     The display module of the plasma display device according to the present invention comprises a back surface glass plate having discharge electrodes and to which are connected electronics; a front surface glass plate mounted on and opposing to the back surface glass plate via separation walls and having discharge electrodes; and luminescent pixels defined by the back surface glass plate, the separation walls and the front surface glass plate; wherein the luminescent pixels are formed so that at least the surface of the back surface glass plate opposite the display surface is a reflection surface. In another example, the luminescent pixels of the display module are formed so that all surfaces other than the surface of the front surface glass plate are reflection surfaces. 
     According to another aspect of the invention, the reflection surface is formed by metal plating, or by adhering metal leafs. In another example, the reflection surface opposing the display surface has a concave surface, and the light reflected from the reflection surface is condensed at the display surface. 
     A method for manufacturing a display module of a plasma display device according to the present invention comprises mounting electrodes covered with dielectric on a back surface glass plate and on a front surface glass plate; mounting separation walls on the back surface glass plate, thereby forming discharge space; forming a reflection surface on walls of each discharge space; and superposing the front surface glass plate functioning as a display surface on the separation walls opposite the back surface glass plate, thereby forming luminescent pixels. 
     According to the present invention, the shape of the discharge spaces (luminescent pixels) are changed, and reflection surfaces formed by metal plating and the like are provided to the areas that are expected to reflect the electromagnetic wave. Thereby, any electromagnetic wave energy regardless of its wavelength can be reflected toward the front direction of the pixel to improve the brightness of the display, and to minimize the radiation of energy toward the back surface of the, module. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an explanatory cross-sectional view showing the structure of a display module of the plasma display device according to the present invention; 
     FIG. 2 is a perspective view of a display module of the plasma display device according to the present invention; 
     FIG. 3 is an explanatory cross-sectional view showing another embodiment of the display module; 
     FIG. 4 is an explanatory cross-sectional view showing another embodiment of the display module; 
     FIG. 5 is an explanatory view of the structure of a plasma display device of the prior art; 
     FIG. 6 is an explanatory view of the structure of a display module according to the prior art; and 
     FIG. 7 is an explanatory view of luminescent pixels. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will now be explained with reference to the drawings. 
     Embodiment 1 
     FIG. 1 is an explanatory cross-sectional view of one pixel of the display module according to the present invention. FIG.  2  is an explanatory view showing the structure of the display module. 
     The display module  100  comprises discharges paces  110 , each defined by a front glass plate  50 , a back,glass plate  60 , and separation walls  70 . 
     Electrodes  120  are mounted on the front glass plate  50 , which are covered with a dielectric layer  52 . 
     Electrodes  130  are mounted on the back glass plate  60 , which are covered with a dielectric layer  62 . 
     Metal plating treatment is provided to the surface of the dielectric layer  62  covering the back glass plate  60  and the surface of the separation wall  70 , thereby forming a reflection surface  80 . Further, a fluorescent agent is applied to the reflection surface  80  to form a fluorescent layer  85 . In other words, the reflection surface  80  and the fluorescent layer  85  are provided to all inner surfaces of each discharge space  10  except for the display surface near the front glass plate  50 . 
     According to the display module  100  formed as explained above, high voltage impressed to the electrodes  120  and electrodes  130  causes discharge to occur within each discharge space  110 , and generates ultraviolet light. Ultraviolet light impinges upon the fluorescent surface  85 . The ultraviolet light is reflected by the reflection surface  80 , and the reflected ultraviolet light is radiated toward the front glass plate  50  having no reflection surface (in the direction of the display surface). 
     Next, the method for manufacturing the display module  10  equipped with a reflecting surface is explained. 
     First, electrodes  130  and  120  covered with dielectric  62  and  52  are formed on the back surface glass plate  60  and on the front surface glass plate  50 . Thereafter, separation walls  70  are mounted on the back surface glass plate  60 , thereby defining the ditch for forming the discharge space  110 . 
     Next, a metal plating treatment and the like is applied to each of the inner wall surfaces of the discharge space  110 , that is, on the surface of the dielectric  62  placed on the back surface glass plate  60  and on the wall surfaces of the separation wall  70 , in order to form the reflection surface  80 . Thereafter, a fluorescent layer  85  is formed on the reflection surface  80  by applying fluorescent paint thereto. 
     Further, the front surface glass plate  50  is superposed on the upper area of the separation walls  70 . The back surface glass plate  60 , the separation wall  70  and the front surface glass plate  50  define a closed discharge space  110 . 
     Discharge is performed within each of the discharge spaces (pixels)  110  of the display module  100  formed as above. Each luminescent pixel is lighted by the ultraviolet generated by the discharge performed within each pixel, and generates light according to the fluorescent paint. All of the generated light is reflected by the reflection surface  86  toward the front surface glass, plate  50 , without being absorbed by the separation walls  70  or the back surface glass plate  60 . The surface luminance of the display module  100  utilizing the front surface glass plate  50  as the display surface is improved by the reflected light, and the surface becomes brighter. 
     Moreover, the metal-plated reflection surface  80  not only reflects visible light and ultraviolet, but also reflects all electromagnetic wave energy regardless of its wavelength. Visible light energy, electromagnetic wave energy with a long wavelength, and radio wave energy are all reflected by the reflection surface  80 , and will not be absorbed by the back surface glass plate  60 . As a result, no energy causing a temperature rise will reach the electronics equipped to the back surface of the module. 
     Embodiment 2 
     Another embodiment for improving the luminance of the display surface of the module is explained with reference to FIG.  3 . 
     The display module  200  defines the discharge space  110  by the front surface glass plate  50 , the back surface glass plate  60  and the separation wall  70 . Electrodes  120  are mounted to the front surface glass plate  50  and electrodes  130  are mounted on the back surface glass plate  60 , which are covered with dielectric layers. Such structure is similar to the display module  100  of embodiment 1. 
     In the present embodiment, the dielectric layer  620  covering the back surface glass plate  60  comprises a concave surface  625  positioned at the center of each discharge space. Sandblasting is applied to the concave surface  625  to form a concave mirror-like surface. Thereafter, metal plating is applied to the concave surface  625  to form a reflection surface  800 . Then, a fluorescent agent is applied on the surface of the metal-plated reflection surface  800 , forming the fluorescent layer  850 . 
     The display module  200  according to the present embodiment is characterize in that the visible light generated by the fluorescent layer  850  is all reflected by the reflection surface  800  having a concave surface, and the light is collected toward the front surface glass plate  50  functioning as the display surface. Therefore, the surface luminance of the display module  200  is improved greatly. Moreover, because the reflection surface  800  having a concave surface reflects all electromagnetic wave energy regardless of its wavelength, so the back surface glass plate  60  will absorb no electromagnetic wave. As a result, the electromagnetic wave energy will not heat the electronics mounted to the back surface glass plate  60 . 
     Embodiment 3 
     Another embodiment of the present invention is explained with reference to FIG.  4 . 
     The present display module is similar to the display module  100  of embodiment  1  in that discharge spaces  110  are defined by the separation walls  70 , the front surface glass plate  50 , and the back surface glass plate  60 , and that electrodes  120  are mounted on the front surface glass plate  50  and electrodes  130  are mounted on the back surface glass plate  60 , which are covered by dielectric layers  52  and  62 . The display module  300  is further equipped with a reflection surface  870  formed on a back surface  60   b  of the back surface glass plate  60 . 
     The reflection surface  870  is either formed by metal plating, or by metal leafs adhered on the back surface  60   b.    
     The display module  300  reflects light by a front surface  60   a  of the back surface glass plate  60 . The light transmitted through the back surface glass plate  60  is reflected by the reflection surface  870  toward the display surface or front surface glass plate  50 . A portion of the electromagnetic wave energy absorbed by the back surface glass plate  60  may turn into energy and cause the temperature of the back surface  60   b  of the back surface glass plate  60  to rise. However, since most of the electromagnetic wave energy absorbed is reflected by the reflection surface  870 , the temperature rise is limited to a low level. Even further, the module of the present embodiment has a simple structure, and has high reflection efficiency. 
     As explained, the display module according to the present embodiment reflects all of the visible light generated by the fluorescent body by the reflection mirror toward the display surface, and improves the luminance of the display surface greatly. Even further, because the reflection surface of the module reflects all electromagnetic wave energy regardless of its wavelength, the temperature of the electronics mounted to the back surface of the module is prevented from rising. 
     The present invention provides a display module of a plasma display device that solves the problem of heat diffusion of electronics mounted to the back surface of the module, with improved surface luminance, and with a display surface that is bright and provides good image quality, without increasing consumption power.