Abstract:
A plasma display panel (PDP) with improved bright room contrast while achieving a high opening ratio and high luminance. The PDP includes display electrodes that includes auxiliary electrodes that suppress reflection of incident light off the discharge cells. With address electrodes formed on the rear substrate and the display electrodes formed on the front substrate, auxiliary electrodes connect pairs of display electrodes together. The auxiliary electrodes and the main bus electrodes extend into the discharge cells and reflect the external light. The opaque main bus and auxiliary electrodes are combined with a transparent electrode portion that overlies the main bus and the auxiliary portions to form the display electrodes.

Description:
CLAIM OF PRIORITY 
   This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for PLASMA DISPLAY PANEL earlier filed in the Korean Intellectual Property Office on 23 Jun. 2004 and there duly assigned Serial No. 10-2004-0047039. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention pertains to a plasma display panel (PDP), and in particular, to a design for a PDP design that results in improved bright room contrast while maintaining a high opening ratio and a high luminance. 
   2. Description of the Related Art 
   In general, a PDP is a display device where ultraviolet rays generated during gas discharge excite phosphors to produce a visible image. PDPs have received a lot of attention recently as next generation display devices because of their large screen size, thin depth, and high resolution. 
   PDPs are classified into direct current (DC) types and alternating current (AC) types based on the driving power. One type of AC PDP that has become very popular recently is the three-electrode type AC PDP that has an address electrode and a pair of display electrodes. 
   PDPs can be further classified according to the layout of the discharge cells where an independent discharge takes place. For example, the PDP can be classified as a stripe-type (or in-line type), where three red (R), green (G), blue (B) discharge cells are arranged in a stripe pattern, or a delta-type where discharge cells have a triangular shape. 
   In both the stripe-type and delta-type PDPs, address electrode, barrier ribs, and a phosphor layers are formed on the rear substrate and correspond to each discharge cell bounded by the barrier ribs, and display electrodes that include of scan electrodes and sustain electrodes are formed on the front substrate. A dielectric layer is formed on the rear substrate and on the front substrate to cover the display electrodes and the address electrodes. A discharge gas, being a Ne—Xe gas mixture, fills the discharge cells at locations where the address electrodes cross the display electrodes. 
   A discharge cell for light emission is selected by an address discharge that occurs when an address voltage is applied between the address electrode and the scan electrode. Then, a plasma discharge takes place inside selected discharge cells by applying a sustain voltage between the sustain electrode and the scan electrode, generating a plasma that emits vacuum ultraviolet rays that excites the phosphor layer in the discharge cell to emit visible light to form an image. 
   In an AC PDP, the sustain electrodes and the scan electrodes are made of a transparent material, such as indium-tin oxide (ITO), so that visible rays can be transmitted through them. The poor conductance of the transparent material is compensated by an additional bus electrode that is made of a highly conductive and opaque metal and is located outside the discharge area. 
   As described above, a higher opening ratio can be achieved by having the scan and the sustain electrodes made of a transparent material and also by having bus electrodes located outside the discharge area. However, such a design results in poor bright room contrast of the PDP operating under in bright room conditions because of a low absorption efficiency of outside light. Therefore, what is needed is a design for an AC PDP that provides for improved bright room contrast while also having a high opening ratio and high luminance characteristics. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an improved design for a PDP. 
   It is also an object of the present invention to provide a design for a PDP that has improved bright room contrast while having a high opening ratio. 
   It is further an object of the present invention to provide a design for a PDP that is easy to manufacture. 
   It is still an object of the present invention to provide a design for a PDP that has superior luminance characteristics. 
   These and other objects can be achieved by a PDP that includes a first substrate, a second substrate arranged facing the first substrate, address electrodes extending in a first direction on the first substrate, barrier ribs located between the first substrate and the second substrate and dividing a space between the first and the second substrates into a plurality of discharge cells, a phosphor layer formed inside the discharge cells, and display electrodes that include a first display electrode and a second display electrode formed at certain locations on the second substrate, the certain locations corresponding to the discharge cells. The first display electrode and the second display electrode include a first main bus electrode and a second main bus electrode, respectively. Each main bus electrode extends in a second direction and crosses the address electrodes at locations corresponding to sides of the discharge cells. The first display electrode and the second display electrode also include a first auxiliary bus electrode and a second auxiliary bus electrode, respectively, each extending in the first direction. Each of the first auxiliary bus electrode and the second auxiliary bus electrode connect a first main bus electrode of one discharge cell to a second main bus electrode of a neighboring discharge cell. 
   The first display electrode and the second display electrode can include first and second transparent electrodes, respectively, that are both superposed partially on the first and the second main bus electrodes, respectively. Each transparent electrode extends towards the center of corresponding discharge cells and is arranged to face a neighboring transparent electrode. The first and the second main bus electrodes and the first and the second auxiliary bus electrodes are preferably made of a highly conductive and opaque metallic material that supresses the reflection of incident light off the discharge cells. 
   Furthermore, the first and the second main bus electrodes, and the first and the second auxiliary bus electrodes each form a stripe pattern. The first and the second display electrodes are located, respectively, at a location near second and first display electrodes respectively of the neighboring discharge cells in the first direction. The first and the second main bus electrodes are located near the edges of the discharge cells, and the first and the second auxiliary bus electrodes are located near the center of the discharge cells. 
   Each of the first and the second auxiliary bus electrodes can be connected to both the first and the second main bus electrodes at the ends of the first and the second auxiliary bus electrodes. Also, both ends of the first and the second auxiliary bus electrodes can extend beyond the first and the second main bus electrodes, respectively, by a small amount, extending towards the center of the discharge cells. Furthermore, both ends of the first and the second auxiliary bus electrodes can also be connected to protrusions at the ends of the auxiliary electrodes, the protrusions extending in the second direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein: 
       FIG. 1  is a partial perspective view of a disassembled PDP according to a first embodiment of the present invention; 
       FIG. 2  is a partial plan view illustrating electrodes positioned on the second substrate of the PDP of  FIG. 1  according to the first embodiment of the present invention; 
       FIG. 3  is a partial plan view illustrating electrodes positioned on the second substrate of a PDP according to a second embodiment of the present invention that can be used in the PDP design of  FIG. 1 ; and 
       FIG. 4  is a partial plan view illustrating electrodes positioned on the second substrate of a PDP according to a third embodiment of the present invention that can be used in the PDP design of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   As illustrated in  FIG. 1 , a PDP according to the present invention includes a first substrate  10 , a second substrate  20  facing the first substrate  10  and spaced apart from the first substrate  10  by a certain distance, and discharge cells  14 R,  14 G,  14 B surrounded by barrier ribs  13 , the barrier ribs  13  having a height corresponding to the certain distance between the first substrate  10  and the second substrate  20 . 
   The barrier ribs  13  include first barrier rib members  13   a  extending in a first direction (y-direction of the figures) and second barrier rib members  13   b  extending in a second direction (x-direction of the figures). The barrier ribs  13  are formed in a lattice pattern and independently define the discharge cells  14 R,  14 G,  14 B, the discharge cells  14 R,  14 G,  14 B being filled with a discharge gas. R, G, B (red, green, blue) phosphor layers  15 R,  15 G,  15 B are formed on four sides of the barrier ribs  13  and on the floor (−z end) of the discharge cells  14 R,  14 G,  14 B. 
   On the first substrate  10 , address electrodes  11  are formed in a stripe pattern and extend in the first direction. Each address electrode  11  corresponds to one of  14 R,  14 G,  14 B discharge cells. Each address electrode  11  is spaced apart from each other. A dielectric layer  12  covers the address electrodes  11  on the inside side (+z side) of the first substrate  10 . 
   On the inside side (−z side) of the second substrate  20  facing the first substrate  10  are formed display electrodes  24  that consist of a first display electrodes  21  (or a scan electrode) and a second display electrodes  22  (or sustain electrode), both extending in the second direction. A dielectric layer  25  and an MgO protective layer  26  cover the display electrodes  24  on the inside side of the second substrate  20 . 
   The first display electrodes  21  and the second display electrodes  22  are located corresponding to the discharge cells  14 R,  14 G,  14 B and are positioned near the second and first display electrodes  22 ,  21  respectively of neighboring discharge cells  14 R,  14 G,  14 B in the first direction. Therefore, the first display electrodes  21  and the second display electrodes  22  are paired with each other and located alternately. 
   The first display electrodes  21  and the second display electrodes  22  includes first and second transparent electrodes  21   a ,  22   a  respectively and facing each other and spaced apart by a discharge gap and extending toward the center of the discharge cells  14 R,  14 G,  14 B. First display electrodes  21  and second display electrodes  22  also include first and second main bus electrodes  21   b ,  22   b  respectively, where each main bus electrode extends in the second direction and has a stripe pattern and is positioned corresponding to each side of the discharge cells  14 R,  14 G,  14 B. The first display electrodes  21  and the second display electrodes  22  further includes first and second auxiliary bus electrodes  21   c ,  22   c  respectively. Each the first auxiliary bus electrodes  21   c  extend in the first direction and connects the first main bus electrode  21   b  of a discharge cell  14 R,  14 G,  14 B to the second main bus electrode  22   b  of a neighboring discharge cell. The first auxiliary bus electrodes  21   c  have a stripe pattern. The second auxiliary bus electrodes  22   c  also extend in the first direction and connect the second main bus electrode  22   b  of the discharge cells  14 R,  14 G,  14 B to the first main bus electrode  21   b  of the other neighboring discharge cell. The second auxiliary bus electrodes  22   c  have a stripe pattern. 
   The first and the second transparent electrodes  21   a ,  22   a  are preferably made of indium tin oxide (ITO). The first and the second main bus electrodes  21   b ,  22   b  and the first and the second auxiliary bus electrodes  21   c ,  22   c  are preferably made of a highly conductive opaque metal. 
   The first and the second main bus electrodes  21   b ,  22   b  and the first and the second auxiliary bus electrodes  21   c ,  22   c  are located in the discharge cells  14 R,  14 G,  14 B and absorb outside light so that a bright room contrast of the PDP can be improved by suppressing the reflection of light incident onto the discharge cells  14 R,  14 G,  14 B. 
   Even when the first and the second auxiliary bus electrodes  21   c ,  22   c  are formed to have a small width in order to achieve a high luminance characteristics, the first and the second auxiliary bus electrodes  21   c ,  22   c  rarely break during the etching process used to make the first and the second main bus electrodes  21   b ,  22   b  and the first and the second auxiliary bus electrodes  21   c ,  22   c  from a metallic material. This is because the first and the second auxiliary bus electrodes  21   c ,  22   c  are in direct connection with both of the first and the second main bus electrodes  21   b ,  22   b.    
   In the first embodiment of the present invention as illustrated in  FIG. 2 , the first auxiliary bus electrodes  21   c  are connected to the first main bus electrodes  21   b  at ends  23   a ,  23   b  thereof. Similarly for the first embodiment of the present invention, the second auxiliary bus electrodes  22   c  are connected to the second main bus electrodes  22   b  at ends  23   a ′,  23   b ′ thereof. In the second embodiment of the present invention as illustrated in  FIG. 3 , both ends  23   a ,  23   b  of the first auxiliary bus electrodes  21   c  can extend past the first main bus electrodes  21   b  by a small amount so that they extend towards centers of the discharge cells  14 R,  14 G,  14 B, respectively. Similarly for the second embodiment of the present invention, both ends  23   a ′,  23   b ′ of the second auxiliary bus electrodes  22   c  can extend past the second main bus electrodes  22   b  by a small amount so that they extend towards centers of the discharge cells  14 R,  14 G,  14 B, respectively. In the third embodiment of the present invention as illustrated in  FIG. 4 , in addition to that of the second embodiment, the first auxiliary bus electrodes  21   c  each further include protrusions  23   c ,  23   d  at ends  23   a ,  23   b  respectively. Protrusions  23   c ,  23   d  extend in the second direction from ends  23   a ,  23   b  respectively. Likewise, in the third embodiment of the present invention, the second auxiliary bus electrodes  22   c  each further include protrusions  23   c ′,  23   d ′ at ends  23   a ′,  23   b ′ respectively. Protrusions  23   c ′,  23   d ′ also extend in the second direction from ends  23   a ′,  23   b ′ respectively. The designs for the display electrodes  21 ,  22  illustrated in  FIGS. 3 and 4  can be incorporated into the PDP design of  FIG. 1  to achieve superior bright room contrast characteristics, superior opening ratio characteristics, superior luminance and easy manufacturing according to the second and third embodiments of the present invention respectively. 
   As explained above, the PDPs according to the embodiments of the present invention can improve bright room contrast by suppressing the reflection of incident light off the discharge cells  14 R,  14 G,  14 B because outside light is absorbed by the first and the second main bus electrodes  21   b ,  22   b  and by the first and the second auxiliary bus electrodes  21   c ,  22   c  located in the discharge cells  14 R,  14 G,  14 B. Also, the PDPs of the present invention can be efficiently manufactured despite the fact that the auxiliary bus electrodes  21   c ,  22   c  are formed to have a small width. The auxiliary bus electrodes  21   c ,  22   c  are in direct connection with the main bus electrodes  21   b ,  22   b  and thus rarely break during the etching process used to make the main bus electrodes  21   b ,  22   b  and the auxiliary bus electrodes  21   c ,  22   c  from a metallic material. 
   Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and/or modifications of the basic inventive concept taught therein will still fall within the spirit and scope of the present invention, as defined in the appended claims.