Abstract:
A plasma display panel (PDP) has a front and a back substrate mounted together, with a gap between them. Barrier ribs are positioned within this space of this gap, and they define a series of discharge space groups. Each discharge space group has a first, second and third discharge space for red, green and blue emitting phosphors. Within these discharge spaces are traverse ribs. The lengths of these traverse ribs are adjusted to change the relative proportions of phosphor surface areas, and thus adjust the color temperature of the PDP.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the invention 
     The present invention relates to a full-color plasma display panel, and more particularly, to a full-color plasma display panel with a high color temperature that is achieved by adjusting the coverage of the phosphor materials within the plasma display panel. 
     2. Description of the Prior Art 
     A full-color plasma display panel (PDP) is composed of hundreds of thousands of tiny discharge cells arranged in a matrix formation. When a voltage is induced in one of these discharge cells, it causes a gas in the cell to discharge and generate ultra-violet radiation. This ultra-violet radiation falls on different phosphor materials and causes them respectively to emit one of three primary colors of light, i.e., red, green, or blue. Generally, the color of the emitted light depends on the composition of the phosphor materials. If the phosphor material is made of (Y,Gd)BO 3 , and Eu is added as a luminescent agent, the phosphor material will emit red light. If the phosphor material is made of Zn 2 SO 4 , and Mn is added as a luminescent agent, the phosphor material will emit green light. If the phosphor material is made of BaMgAl 14 O 23 , and Eu is added as a luminescent agent, the phosphor material will emit blue light. However, this blue light suffers from color degradation at higher temperatures. In order to improve the luminescence of the PDP, the discharge space for blue light is enlarged to increase the coverage of the associated phosphor materials. In this manner, the proportion of emitted red light, green light, and blue light of the PDP can be adjusted so as to promote color temperatures in the range of 7000K to 11000K. 
     Please refer to FIG.  1 . FIG. 1 is a schematic diagram of a full-color plasma display panel  10  according to the prior art. The prior art PDP  10  comprises a first substrate  12 , a second substrate  14  positioned in parallel to the first substrate  12 , a discharge gas filling the space between the first substrate  12  and the second substrate  14 , and a plurality of first electrodes  18 , second electrodes  20 , and address electrodes  22 . Each of the first electrodes  18  and the second electrodes  20  are. alternately positioned on the first substrate  12  in parallel to each other. Each of the address electrodes  22  is positioned on the second substrate  14  perpendicular to the first electrodes  18  and the second electrodes  20 . Each of the first electrodes  18  and the second electrodes  20  comprises a support electrode  181 ,  201  made of ITO, and a complementary electrode  182 ,  202  made of Cr/Cu/Cr, a sandwiched structure with three metallic layers. The support electrode  181 ,  201  is transparent to most visible light, but has great electrical resistance. The complementary electrode  182 ,  202  has better conductivity and thus enhances the conductivity of the first electrodes  18  and the second electrodes  20 . 
     The PDP  10  further comprises a dielectric layer  24  that covers the first substrate  12 , a protective layer  26  covering the dielectric layer  24 , a plurality of barrier ribs  28  positioned on the second substrate  14  in parallel to each other for isolating two adjacent address electrodes  22  and defining a plurality of line-shaped discharge spaces  30 , and a phosphor layer  32  coating the surfaces of the second substrate  14  and the walls of the barrier ribs  28  that surround each discharge space. The phosphor layer  32  emits red light, green light or blue light. Each of the discharge spaces  30  comprises a plurality of unit display elements  34  arranged in matrix formation between the first substrate  12  and the second substrate  14 . All of the discharge spaces  30  are divided into a plurality of discharge space groups. Each of the groups comprises a red discharge space  30 R coated with a red phosphor layer  32 R, a green discharge space  30 G coated with a green phosphor layer  32 G, and a blue discharge space  30 B coated with a blue phosphor layer  32 B. Consequently, a plurality of red unit display elements  34 R are formed within the red discharge spaces  30 R, a plurality of green unit display elements  34 G are formed within the green discharge spaces  30 G, and a plurality of blue unit display elements  34 B are formed within the blue discharge spaces  30 B. Generally, one red unit display element  34 R, one green unit display element  34 G, and one blue unit display element  34 B form a pixel. 
     In order to improve the luminescence of blue light emitted from the PDP  10 , the width of the red discharge space  30 R is designed to be the narrowest. The width of the green discharge space  30 G is designed to be 1.2 times as wide as the width of the red discharge space  30 R. The width of the blue discharge space  30 B is designed to be 1.6 times as wide as the width of the red discharge space  30 R. Therefore, the red unit display element  34 R has smallest space, and the blue unit display element  34 B has the largest space. Hence, the coverage of the red phosphor layer  32 R is the smallest, and the blue phosphor layer  32 B has the largest coverage. Under these size ratios, the red, green and blue light will combine to form white light with a color temperature of about 11000K. 
     However, the widths of the different discharge spaces  30  are designed according to specific proportions. When the size of all of the discharge spaces  30  needs to be reduced to increase the resolution of the PDP  10 , the width of the red discharge space  30 R can become quite small. This not only increases the difficulty of manufacturing the barrier ribs  28  and the red phosphor layer  32 R, but can also lead to contraposition when sealing the first substrate  12  to the second substrate  14 . Furthermore, the red discharge space  30 R with a much smaller width can easily cause the discharge gas to cross talk with the adjacent discharge spaces  30 . This interference damages the electrical performance of the PDP  10 . 
     SUMMARY OF THE INVENTION 
     It is therefore a primary objective of the present invention to provide a full-color PDP with a higher color temperature by adjusting the coverage of the phosphor layer, and thus avoid the above-mentioned problems of the prior art. 
     In a preferred embodiment, the present invention provides a plasma display panel that comprises a back substrate, a front substrate positioned on the back substrate, with a space between the facing surfaces of the front substrate and the back substrate. A plurality of barrier ribs are positioned in the space for defining a plurality of discharge space groups wherein each group comprises a first discharge space and a second discharge space. A first traverse rib is positioned in each first discharge space. A second traverse rib is positioned in each second discharge space wherein the transverse length of the second traverse rib is smaller than that of the first traverse rib. A first phosphor layer is coated on the surfaces of the back substrate, the first traverse ribs, and on the barrier ribs surrounding each first discharge space. A second phosphor layer is coated on the surfaces of the back substrate, the second traverse ribs, and on the barrier ribs surrounding each second discharge space. The coverage of the first phosphor layer is greater than that of the second phosphor layer. For a first discharge space and a second discharge space, a distance between the side of the first traverse rib and the center of the first discharge space is less than a distance between the side of the second traverse rib and the center of the second discharge space. Thus, the luminous intensity of the first phosphor layer is greater than that of the second phosphor layer. 
     It is an advantage of the present invention that the plurality of barrier ribs, cooperating with the traverse ribs of various size and placements, adjusts the coverage of the phosphor layers. This adjusts the coverage proportions of the phosphor layers coated within each discharge space to promote a color temperature of the PDP of up to 11000K. 
     These and other objectives of the present. invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a full-color plasma display panel according to the prior art. 
     FIG. 2 is a schematic diagram of a full-color PDP according to the first embodiment of the present invention. 
     FIG. 3 is a top view of the plurality of barrier ribs shown in FIG.  2 . 
     FIG. 4 is a top view of a plurality of barrier ribs according to the second embodiment of the present invention. 
     FIG. 5 is a top view of a plurality of barrier ribs according to the third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The First Embodiment 
     Please refer to FIG.  2  and FIG.  3 . FIG. 2 is a schematic diagram of a full-color PDP  40  according to the first embodiment of the present invention. FIG. 3 is a top view of the plurality of barrier ribs shown in FIG.  2 . According to the first embodiment of the present invention, a full-color PDP  40  comprises a back substrate  42 , a front substrate  44  positioned on and in parallel with the back substrate  42 , a discharge gas (not shown) that fills the space between the back substrate  42  and the front substrate  44 , a plurality of first electrodes  46 , second electrodes  48  and address electrodes  50 , a dielectric layer  52  that covers the front substrate  44 , and a protective layer  54  covering the dielectric layer  52 . Each of the first electrodes  46  and the second electrodes  48  are positioned in an alternating manner on the front substrate  44 , and are parallel to each other. Each of the address electrodes  50  is positioned on the back substrate  42  and is perpendicular to the first electrodes  46  and the second electrodes  48 . Each of the first electrodes  46  and second electrodes  48  comprises a wider line-width support electrode  461 ,  481 , and a narrower line-width complementary electrode  462 ,  482 . The support electrode  461 ,  481  is made of indium tin oxide (ITO) or tin oxide (SnO) for maintaining surface discharge. Transparent, the support electrode  461 ,  481  has a high electrical resistance. The complementary electrode  462 ,  482  is from a Cr/Cu/Cr sandwich of three metallic layers, or a Ag metal material. The complementary electrode  462 ,  482  increases the conductivity of the first electrode  46  and the second electrode  48 . 
     The full-color PDP  40  further comprises a plurality of barrier ribs  56  equidistantly positioned on the back substrate  42  and in parallel with each other. The barrier ribs  56  define a plurality of discharge space groups. The full-color PDP  40  also has a plurality of first traverse ribs  66 , a plurality of second traverse ribs  64 , and a plurality of phosphor layers coated within the discharge space groups. Each of the discharge space groups comprises a red discharge space  60 R, a green discharge space  60 G, and a blue discharge space  60 B. In the blue discharge. space  60 B, two of the first traverse ribs  66  are positioned on the walls of the barrier ribs  56  and each first traverse rib  66  is connected with two adjacent barrier ribs  56 . In the green discharge space  60 G, the four second traverse ribs  64  are not connected to each other, and each is positioned on the walls of the barrier ribs  56 . The plurality of phosphor layers comprises a red-emissive phosphor layer  58 R, a green-emissive phosphor layer  58 G, and a blue-emissive phosphor layer  58 B. The blue-emissive phosphor layer  58 B is coated on the surfaces of the back substrate  42 , the first traverse ribs  66  and the barrier ribs  56  that surround each blue discharge space  60 B. The green-emissive phosphor layer  58 G is coated on the surfaces of the back substrate  42 , the second traverse ribs  64  and the barrier ribs  56  that surround each green discharge space  60 G. The red-emissive phosphor layer  58 R is coated on the surfaces of the back substrate  42  and the barrier ribs  56  surrounding each red discharge space  60 R. 
     As shown in FIG. 3, the longitudinal length of the second traverse rib  64  is equal to that of the first-traverse rib  66 . The transverse length  64   a  of the second traverse rib  64  is smaller than that  66   a  of the first traverse rib  66 . Thus, the surface area of the barrier ribs  56  and the first traverse ribs  66  surrounding the blue discharge space  60 B is the greatest in size. The surface area of the barrier ribs  56  and the second traverse ribs  64  surrounding the green discharge space  60 G is the next greatest. The surface area of the barrier ribs  56  surrounding the red discharge space  60 R has the smallest size. In other words, the blue-emissive phosphor layer  58 B within the blue discharge space  60 B has the greatest coverage, while the red-emissive phosphor layer  58 R within the red discharge space  60 R has the smallest coverage. For the blue discharge space  60 B and the green discharge space  60 G, a distance between the side of the first traverse rib  66  and the center of the blue discharge space  60 B is less than a distance between the side of the second traverse rib  64  and the center of the green discharge space  60 G. Consequently, the luminous intensity of the blue-emissive phosphor layer  58 B is greater than that of the green-emissive phosphor layer  58 G. For the red discharge space  60 R without any traverse ribs, the luminous intensity of the red-emissive phosphor layer  58 R is the smallest. The proportion of emitted blue light is thus increased. Red, green and blue light will mix to form white light with a color temperature of about 11000K. 
     If all of the width of all of the discharge spaces needs to be reduced, the barrier ribs  56  remain equidistantly spaced, while the first traverse ribs  66  and second traverse ribs  64  can be adjusted to alter the coverage proportions of the phosphor layers. Therefore, it is unnecessary to over-reduce the space between two adjacent barrier ribs  56 . This helps to lower the manufacturing difficulty of the PDP 40 , and avoids degradation of the electrical performance caused by cross talking of the discharge gas. 
     The Second Embodiment 
     The coverage of the phosphor layers coated within the discharge spaces can be changed by the placement of traverse ribs with different sizes, shapes and positions. Please refer to FIG.  4 . FIG. 4 is a top. view of the plurality of barrier ribs  56  according to the second embodiment of the present invention. The full-color PDP comprises a plurality of barrier ribs  56  equidistantly positioned on the back substrate  42 . As before, the barrier. ribs  56  are all parallel to each other. Each of the discharge spaces comprises. a plurality of traverse ribs that are unconnected to each. This ensures that the discharge spaces are not completely closed after sealing the front substrate  44  to the back substrate  42 . Such a design is beneficial for a subsequent process that involves the extraction of gases from the discharge spaces. A plurality of first traverse ribs  70 , unconnected to each other, are positioned on the walls of two adjacent barrier ribs  56  surrounding each blue discharge space  60 B. A plurality of second traverse ribs  69 , also unconnected to each other, are positioned on the walls of two adjacent barrier ribs  56  surrounding each green discharge space  60 G. Similarly, a plurality of third traverse ribs  68 , unconnected to each other, are positioned on the walls of two adjacent barrier ribs  56  surrounding each red discharge space  60 R. 
     The longitudinal length of the first traverse ribs  70  is equal to that of the second traverse ribs  69  and to that of the third traverse rib  68 . The first traverse ribs  70  have the greatest transverse length  70   a.  The second traverse ribs  69  have the next greatest transverse length  69   a.  Finally, the third traverse ribs  68  have the shortest transverse length  68   a.  Thus, the barrier ribs  56  and the first traverse ribs  70  within the blue discharge space  60 B have the greatest surface area. The barrier ribs  56  and the third traverse ribs  68  within the red discharge space  60 R have the least surface area. Hence, the blue-emissive phosphor layer  58 B within the blue discharge space  60 B has the greatest coverage, whereas the red-emissive phosphor layer  58 R within the red discharge space  60 R has the smallest coverage. Note that the distance between the side of the first traverse rib  70  and the center of the blue discharge space  60 B is shorter than an equivalent distance in either the red or green discharge spaces. The green discharge space  60 G has the next shortest such distance. Generally, those portions of a phosphor layer close to the center of the discharge space where the plasma intensity is the highest receive more ultra-violet radiation. Consequently, the luminous intensity of the blue-emissive phosphor layer  58 B is the greatest, the luminous intensity of the green-emissive phosphor layer  58 G is second, and the red-emissive phosphor layer  58 R is the smallest luminous intensity. This increases the proportion of blue light, which boosts the color temperature of the PDP  40  up to about 11000K. 
     The Third Embodiment 
     Please refer to FIG.  5 . FIG. 5 is a top view of the plurality of barrier ribs  56  according to the third embodiment of the present invention. The full-color PDP comprises a plurality of barrier ribs  56  equidistantly positioned on the back substrate  42 . The barrier ribs  56  are in parallel with each other. A plurality of first traverse ribs  76 , unconnected to each other, are positioned on the walls of two adjacent barrier ribs  56  that surround each blue discharge space  60 B. A plurality of second traverse ribs  74 , unconnected to each other, are positioned on the walls of two adjacent barrier ribs  56  surrounding each green discharge space  60 G. A plurality of third traverse ribs  72 , unconnected to each other, are positioned on the walls of two adjacent barrier ribs  56  surrounding each red discharge space  60 R. The transverse length of the first traverse rib  76  is equal to that of the second traverse rib  74  and to that of the third traverse rib  72 . The longitudinal length  76   a  of the first traverse rib  76  is the greatest (about 320 μm), the longitudinal length  74   b  of the second traverse rib  74  is second (about 160 μm), and the longitudinal length  72   b  of the third traverse rib  72  is the smallest (about 80 μm). Consequently, the blue-emissive phosphor layer  58 B coated on the first traverse rib  76  is closest to the center of the blue discharge space  60 B, and thus receives the highest intensity of ultra-violet radiation. The red-emissive phosphor layer  58 R coated on the third traverse rib  72  is farthest from the center of the red discharge space  60 R, and thus receives the lowest intensity of ultra-violet radiation. Hence, the luminous intensity of the blue-emissive phosphor layer  58 B is the greatest., and the red-emissive phosphor layer  58 R has the weakest luminous intensity. This increases the proportion of blue light to boost the color temperature of the PDP to up to about 11000K. 
     Compared to the prior art full-color PDP  10 , the plurality of barrier ribs  56  of the present invention are arranged in equidistant cooperation with traverse ribs of various sizes and placements, which is used to adjust the coverage of the various phosphor layers. This is used to boost the color temperature of the present invention PDP to up to about 11000K. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.