Abstract:
A plasma display panel with an improved barrier rib design. The barrier ribs between the substrates are designed to have differing heights to compensate for the difference in the amount of phosphor layer material formed on the tops of the barrier ribs. By designing the barrier ribs so, gaps between the tops of the barrier ribs and the front substrate are reduced or eliminated thus improving image quality. At the same time, the deposition of the phosphor layers is made easier by jet nozzle ejection so that the novel plasma display panel is easy to make. Fluorescent phosphor layers are applied in neighboring discharge cells with the first barrier members interposed there between. A total height of the first barrier members and the phosphor layers applied thereon is substantially the same as the height of the second barrier ribs members. This may protect the plasma display panel from cross-talk phenomenon.

Description:
CLAIM OF PRIORITY  
       [0001]     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 Industrial Property Office on 31 Oct. 2003 and there duly assigned Serial No. 10-2003-0076984.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a plasma display panel (PDP), and more particularly, to a structure of barrier ribs that is suitable for applying phosphor along resulting in reduced cross-talk.  
         [0004]     2. Description of the Related Art  
         [0005]     Generally, a plasma display panel (referred to hereinafter simply as the “PDP”) is a display device that displays images based on plasma discharge. When voltages are applied to electrodes formed on substrates of the PDP, a plasma discharge occurs between the electrodes thus generating ultraviolet rays. The ultraviolet rays excite phosphor layers formed in a predetermined pattern, thus displaying the desired visible images.  
         [0006]     When manufacturing such a PDP, first, a plurality of barrier ribs are formed, and phosphor layers are then formed thereon. Presently, photolithography, screen-printing or like are used as a method for forming phosphor layers.  
         [0007]     Since the structure for the closed barrier ribs is complex, the photolithography, screen printing or the like are not suitable to form the phosphor layers between the closed barrier ribs with a given quality. Also, when using these methods for forming the phosphor layers, if the phosphor layers are formed along the direction of the first barrier rib members, a gap is formed between the tops of the second barrier rib members and a protective layer due to the accumulation of a height of a phosphor layer on the top of the first barrier rib members. In other words, when phosphor is deposited in the cells and on the first barrier rib members but not on the second barrier rib members, and the height of the first and the second barrier rib members are equal, a gap is formed above the tops of the second barrier rib members when the second substrate is combined to the first substrate. Therefore, what is needed is a design for a PDP that minimizes this gap thus preventing deterioration of the discharge characteristics by, for example, preventing cross-talk between neighboring discharge cells.  
       SUMMARY OF THE INVENTION  
       [0008]     It is therefore an object of the present invention to provide an improved design for a plasma display panel.  
         [0009]     It is further an object to provide a design for a PDP that prevents the formation of gaps above the tops of barrier rib members.  
         [0010]     It is further an object to provide a design for a plasma display panel that is easy to make and improves image quality by reducing cross talk between neighboring cells.  
         [0011]     It is further an object to provide a plasma display panel with an improved design for the barrier ribs.  
         [0012]     These and other objects can be achieved by a plasma display panel with barrier ribs of varying heights, so that when phosphor layers are applied to the barrier ribs, the resultant display has less gap and hence less cross-talk or similar interference between neighboring discharge cells than if all the barrier ribs were formed to have the same height.  
         [0013]     A plasma display panel according to one embodiment of the present invention includes a first substrate and a second substrate opposing each other, first electrodes formed on the first substrate, second electrodes formed on the second substrate and in a direction intersecting the first electrodes, barrier ribs arranged in the space between the first substrate and the second substrate to define a plurality of discharge cells, and phosphor layers formed in each of the discharge cells. The barrier ribs may include first barrier ribs formed parallel to the first electrodes and second barrier ribs formed parallel to the second electrodes while intersecting the first barrier ribs. The phosphor layers of the same color are applied in the discharge cells neighboring each other with the first barrier members interposed therebetween. At this time, the combined height of the first barrier members and the phosphor layers applied thereon is substantially the same as the height of the second barrier rib members. Other design conditions include the height of the phosphor layers may be formed to have a thickness on top of the first barrier rib members in the range of 3 μm through 7 μm. The phosphor layers may be formed by applying phosphor paste using a jet nozzle.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     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:  
         [0015]      FIG. 1  is an exploded perspective view of a PDP;  
         [0016]      FIG. 2  is an exploded perspective view of a plasma display panel according to an exemplary embodiment of the present invention; and  
         [0017]      FIG. 3  is a cross-sectional view of the PDP of  FIG. 2  taken along line III-III′. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     Turning now to the figures,  FIG. 1  is an exploded perspective view of discharge cells used in an AC PDP  100 . With reference to  FIG. 1 , an AC PDP  100  includes a rear substrate  103 , address electrodes  107  formed on the rear substrate  103 , a dielectric layer  111  formed on a top surface of the rear substrate  103  covering the address electrodes  107 , a plurality of barrier ribs  113  formed over the dielectric layer  111  to maintain a constant discharge distance between barrier ribs  113  and dielectric layer  111  and to protect the AC PDP  100  from the cross-talk among the discharge cells and phosphor layers  115  formed between each neighboring barrier ribs  113 .  
         [0019]     As illustrated in  FIG. 1 , display electrodes  105  are formed on front substrate  101  in pairs spaced with each display electrode  105  corresponding to one discharge cell and intersecting the address electrodes  107  formed on the rear substrate  103 . A dielectric layer  109  and a protective layer  117  are sequentially formed and covering the display electrodes  107  on a bottom side of front substrate  101 .  
         [0020]     In more detail, in the PDP  100  illustrated in  FIG. 1 , the barrier ribs  113  are made up of a plurality of first barrier rib members  1131  intersecting the address electrodes  107  and a plurality of second barrier rib members  1132  intersecting the first barrier rib members  1131 . Such a closed structure of the barrier ribs  113  enables discharge characteristics to be enhance when compared to a striped structure where a plurality of barrier ribs are arranged only along one direction and usually in parallel to the address electrodes.  
         [0021]     In the formation of the PDP  100  of  FIG. 1 , when a nozzle jet is used to deposit the phosphor layers  115  on the dielectric layer  111  and the barrier ribs  113 , phosphor layers  115  may accumulate on the tops of first barrier rib members  1131  but not on the second barrier rib members  1132 . This can be problematical when the first and the second barrier rib members  1131  and  1132  respectively are formed to have the same height. When combined to the front substrate  101 , the phosphor layer  115  on top of the first barrier rib members  1131  causes a gap to exist between the tops of the second barrier rib members  1132  and the protective layer on the bottom of the front substrate  101 . This gap causes cross talk between neighboring discharge cells.  
         [0022]     Turning now to  FIG. 2 ,  FIG. 2  is an exploded perspective view illustrating schematically a plasma display panel  200  according to an embodiment of the present invention. As illustrated in  FIG. 2 , PDP  200  has a front substrate  11  and rear substrate  13  facing the front substrate  11 . In  FIG. 2 , the front substrate  11  and the rear substrate  13  are illustrated as being spread apart in order to better emphasize the barrier ribs and the discharge cells between these two substrates.  
         [0023]     In  FIG. 2 , the front substrate  11  (or first substrate) is illustrated using broken lines, and first electrodes  15  on front substrate  11  are illustrated with solid lines. Although not illustrated, a dielectric layer and a protective layer may be formed sequentially on the lower side of front substrate  11  covering the first electrodes  15 . Also as illustrated in  FIG. 2 , a rear substrate  13  (or second substrate) has a plurality of second electrodes  17  arranged in parallel thereon. Over the second electrodes  17  is formed a dielectric layer  21  for protecting the second electrodes  17 . Then, the barrier ribs  23  are formed on the dielectric layer  21  and then phosphor layers  25  are applied to the resultant structure.  
         [0024]     In the PDP  200  of  FIG. 2  according to the present invention, the barrier ribs  23  are formed in a closed structure. Barrier ribs  23  are made out of a first barrier rib members  231  (illustrated in a broken line) intersecting the second electrodes  17  and second barrier rib members  232  intersecting the first barrier rib members  231  essentially orthogonally. Here, the first barrier rib members  231  may have a lower height than the second barrier rib members  232 . The discharge cells are bounded by pairs of the first and second barrier rib members  231 ,  232 . The shape of the second barrier rib members  232  are not limited to the shape illustrated in  FIG. 2 , various other shapes may be used. Meanwhile, the second barrier rib members  232  may be formed by means of etching or sandblasting.  
         [0025]     The barrier ribs may be made by a process called “firing” which is a high temperature manufacturing process where various materials mixed with glass frit are heated to make the barrier ribs. After firing the barrier ribs formed as above, a phosphor paste is applied between the neighboring barrier ribs to form phosphor layers  25 . In this embodiment, the phosphor layers of same color can be applied to neighboring discharge cells separated by first barrier members  231 .  
         [0026]     In the PDP  200  according to the present invention, driving voltages are applied between the first and second electrodes  15 ,  17  such that an address discharge between these two electrodes occurs, thus forming wall charges in the dielectric layers (not illustrated). When a sustain pulse signal is alternately applied to a pair of the first electrodes  15 , sustain discharge occurs between them in the discharge cell selected by the address discharge. As a result, discharge gas charged in the discharge space generates ultraviolet rays, these ultraviolet rays excite phosphors thus displaying the visible image.  
         [0027]     In this embodiment, since the phosphor paste is deposited on top of the first barrier rib members  231  illustrated as a broken line in  FIG. 2 , the height of the first barrier rib members  231  is preferably designed so that the combined height of the first barrier rib members  231  and phosphor layers  25  is approximately equal to the height of the second barrier rib members  232 . This is so there is no gap left between the tops of the second barrier rib members  232  and the protective layer on the bottom of front substrate  11  when the front substrate  11  is combined with the rear substrate  13 .  FIG. 3  will illustrate this concept more clearly.  
         [0028]     Turning now to  FIG. 3 ,  FIG. 3  illustrates a cross-sectional view of PDP  200  of  FIG. 2  taken along line III-III′ of  FIG. 2  and looking in the +x direction.  FIG. 3  clearly illustrates a cross section of the barrier ribs  23  used in plasma display panel  200  according to one embodiment of the present invention  
         [0029]     As illustrated in  FIG. 3 , an embodiment of the plasma display panel  200  may include barrier ribs  23  having a plurality of the first barrier rib members  231  and a plurality of the second barrier rib members  232  intersecting the plurality of first barrier rib members  231 . The first barrier rib members  231  on which phosphor paste is deposited are formed to have a smaller height than that of the second barrier rib members  232 . The height difference between the first and second barrier rib members  231 ,  232  may vary. In some embodiments, the combined height of the first barrier rib member  231  and the height of the phosphor layer  25  deposited on it may be approximately the same height as the second barrier rib members  232 .  
         [0030]     The firing may allow the phosphor layers  25  to be tightly fitted to the first barrier rib members  231 . In addition, use of the firing method also prevents the formation of a gap between the second barrier rib members  232  and the protective layer formed over them. Therefore, in this embodiment, the plasma display panel  200  is protected sufficiently from cross-talk phenomenon between neighboring discharge cells.  
         [0031]     In this embodiment, a nozzle jet apparatus with a plurality of nozzles is provided to discharge the phosphor paste between the first barrier rib members  231  to form the phosphor layers  25  on them. The phosphor paste may be applied through the jet nozzle of the nozzle injecting apparatus, through a firing process or similar techniques known in the art. The amount of the phosphor paste applied through the jet nozzle injecting apparatus is determined considering deformation on firing or the like so that the total, combined height of the first barrier rib members  231  and phosphor layers  25  deposited on them are approximately the same height as the second barrier rib members  232 . By designing the barrier ribs and the phosphor layer application in this way, a tight fit can be formed between the protective layer (not illustrated) on the bottom of the front substrate  11  and the tops of the second barrier rib members  232 . Such a tight fit prevents cross talk between neighboring discharge cells.  
         [0032]     Generally, in the present invention, the first and second barrier rib members  231 ,  232  are designed to have different heights. Accordingly, the phosphor layers  25  may be formed on the first barrier rib members  231  at a thickness of from about 3 μm to about 7 μm such that there is a difference in height between the first and second barrier rib members  231  and  232  respectively. The height difference is determined by the amount of phosphor paste applied. If the height difference is below 3 μm, cross-talk occurs in the same manner as in plasma display panel  100  of  FIG. 1 . If the height difference is greater than about 7 μm, it is difficult for the phosphor paste to be applied on the first barrier rib members because too much phosphor paste is applied on the first barrier rib members  231   
         [0033]     In the PDP  200  described above, the total height of the first barrier rib members  231  and phosphor layers  25  deposited on the first barrier rib members may be approximately the same as the height of the second barrier rib members  232 . Deposits on neighboring discharge cells may include the same color phosphor layers to minimize the amount of phosphor paste left on the barrier ribs, to reduce the usage of the phosphor paste, and also to protect the PDP from cross-talk phenomenon.  
         [0034]     The phosphor layers formed on the first barrier rib members  231  and can have a height of 3 μm through 7 μm thus reducing the cross-talk and making the process for forming the phosphor layers easy. Also, production efficiencies may be increased when the nozzle injecting method is used to manufacture large quantities of plasma display panels.  
         [0035]     Although embodiments of the present invention have been described in detail hereinabove in connection with certain embodiments, it should be understood that the invention is not limited to the disclosed embodiments, but, on the contrary is intended to cover various modifications and/or equivalent arrangements included within the spirit and scope of the present invention, as defined in the appended claims.