Abstract:
A plasma display panel design with improved discharge efficiency. The plasma display panel includes a front substrate, a rear substrate that faces the front substrate, a plurality of barrier ribs adapted to partition a space between the front substrate and the rear substrate and define a plurality of discharge cells, a plurality of display electrodes arranged to correspond to the plurality of discharge cells, a dielectric layer that covers the plurality of discharge electrodes and a plurality of address electrodes extending in a direction that crosses the plurality of display electrodes and the plurality of discharge cells, wherein a recess portion is arranged on side surfaces of ones of the plurality of barrier ribs. Empirically, it is shown that the luminescence efficiency is improved with a recess portion formed on the barrier rib.

Description:
[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 Intellectual Property Office on 8 May 2006 and there duly assigned Serial No. 10-2006-0041099.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a plasma display panel (PDP) having an improved discharge cell structure that enhances discharge efficiency.  
         [0004]     2. Description of the Related Art  
         [0005]     A PDP is a display element that realizes an image using visible light generated by exciting phosphors with vacuum ultraviolet (UV) light radiated by plasma obtained by the discharge of gas. Such a PDP can realize an extra-large screen of over 60 inches, thus the PDP has been spotlighted as a next-generation industrial flat panel display.  
         [0006]     The most common structure for the PDP is a three-electrode surface discharge structure. The three-electrode surface discharge PDP includes a front substrate, a pair of discharge electrodes arranged thereon and facing each other, and a rear substrate arranged apart from the front substrate and having address electrodes arranged thereon. Between the front substrate and the rear substrate are a plurality of discharge cells that are defined by a plurality of barrier ribs. The discharge cells are formed in an area where the pair of discharge electrodes and the address electrodes intersect each other. A phosphor layer is formed within the discharge cells and the discharge cells are filled with a discharge gas.  
         [0007]     More than millions of unit discharge cells are arranged in matrix within the PDP that is formed in the above-described way. Discharge cells to be turned on or turned off are chosen using memory characteristics of wall charges. The selected discharge cells are discharged to display images.  
         [0008]     Vacuum ultraviolet rays generated from a discharge gas excite the phosphor and images are displayed by radiating visible light of respective colors. Therefore, phosphor layers formed along respective discharge cells bear a close relationship with display capacity and discharge efficiency of the PDP.  
         [0009]     As the resolution of the PDP becomes higher, the size of the discharge cells becomes smaller. When the discharge spaces become smaller, the area of phosphor that is provided for discharge cells diminishes causing discharge efficiency to lower. Therefore, what is needed is an improved design for a PDP that increases the area that phosphor can be deposited on within the discharge cells so that discharge efficiency can be improved, even when the discharge spaces are small.  
       SUMMARY OF THE INVENTION  
       [0010]     The embodiments of the present invention provide a plasma display panel that is capable of enhancing discharge efficiency by improving a structure of a discharge cell.  
         [0011]     According to one aspect of the present invention, there is provided a plasma display panel that includes a front substrate, a rear substrate that faces the front substrate, a plurality of barrier ribs adapted to partition a space between the front substrate and the rear substrate and define a plurality of discharge cells, a plurality of display electrodes arranged to correspond to each of the plurality of discharge cells, a dielectric layer that covers the plurality of discharge electrodes and a plurality of address electrodes extending in a direction that crosses the plurality of display electrodes and the plurality of discharge cells, wherein a recess portion is arranged on side surfaces of the plurality of barrier ribs.  
         [0012]     Ones of the plurality of barrier ribs can include a top surface that faces the front substrate, wherein a distance between the top surface one of said plurality of barrier ribs and a center of the recess portion is the same as a width of the top surface. A depth of the recess portion can be measured from an extension line that extends from an edge of the top surface and is perpendicular to the rear substrate, and the depth is ⅕ the width of the top surface of ones of the plurality of barrier ribs. A depth of the recess portion can be measured from an extension line that extends from an edge of the top surface and is perpendicular to the rear substrate, and the depth is smaller than ⅕ a width of the top surface of ones of the plurality of barrier ribs. Ones of the plurality of barrier ribs can further include a bottom surface that faces the rear substrate, wherein the top surface is wider than the bottom surface. the recess portion can be arranged closer to the top surface than the bottom surface. A distance between the top surface and a center of the recess portion can be smaller than a width of the top surface. A depth of the recess portion is measured from an extension line that extends from the edge of the top surface and is perpendicular to the rear substrate, and the depth can be ⅕ a width of the top surface of the barrier ribs. The depth can be smaller than ⅕ the width of the top surface of the barrier ribs. The top surface can be narrower than the bottom surface. The recess portion can be arranged closer to the top surface than to the bottom surface. A lateral cross-section of the recess portion can be in the shape of an arc. Each of the plurality of barrier ribs can include an inclined surface that extends from the recess portion towards the rear substrate. Each of the plurality of display electrodes can include a first linear portion that is in the shape of a stripe and faces each other to form a discharge gap and a second linear portion that is in the shape of a stripe and arranged apart from the first linear portion. Each of the plurality of display electrodes can also include a third linear portion that is arranged between the first linear portion and the second linear portion, wherein the third linear portion is arranged apart both from the first linear portion and the second linear portion.  
         [0013]     According to another aspect of the present invention, there is provided a PDP that includes a front substrate, a rear substrate that faces the front substrate, a plurality of barrier ribs partitioning a space between the front substrate and the rear substrate into a plurality of discharge cells, wherein sidewalls of ones of the plurality of barrier ribs include a recess, a plurality of address electrodes arranged on the rear substrate and adapted to select ones of the plurality of discharge cells for discharge, a plurality of display electrodes arranged on the front substrate and extending in a direction orthogonal to the plurality of address electrodes and adapted to produce a sustain discharge within said selected ones of the plurality of discharge cells, a dielectric layer arranged on the address electrodes and on the rear substrate and a plurality of phosphor layers arranged on the dielectric layer and on sidewalls of ones of the plurality of barrier ribs.  
         [0014]     The recess can be adapted to provide a greater surface area within each of said plurality of discharge cells onto which the plurality of phosphor layers can be arranged. The sidewalls of the plurality of barrier ribs can also include an inclined surface extending from said recess to a bottom surface that faces the rear substrate. The plurality of display electrodes can also include a plurality of linear portions that are stripe-shaped and are parallel to each other and are spaced apart from each other. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     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:  
         [0016]      FIG. 1  is a partial perspective view for a plasma display panel according to an embodiment of the present invention;  
         [0017]      FIG. 2  is a top plan view showing the structural relationship between discharge electrodes and discharge cells of the PDP in  FIG. 1 ;  
         [0018]      FIG. 3  is a top plan view showing discharge electrodes including metallic line portions according to another embodiment of the present invention;  
         [0019]      FIG. 4  is a cross-sectional view along the line IV-IV in  FIG. 2 ; and  
         [0020]      FIG. 5  is a photograph showing a lateral cross-section of a barrier rib formed according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring now to  FIG. 1 , the plasma display panel (PDP) of an embodiment of the present invention includes a front substrate  20  and a rear substrate  10  facing each other. A space between the front substrate  20  and the rear substrate  10  is partitioned by barrier ribs  16  to form a plurality of discharge cells  18 . The discharge cells  18  include a sub-pixels that are the smallest unit displaying an image, and a plurality of sub-pixels form a pixel. Display electrodes  25  and address electrodes  12  are formed to correspond to each discharge cell  18 . The display electrodes  25  and the address electrode  12  intersect within the discharge cell  18 .  
         [0022]     The front substrate  20  is made of transparent material such as reinforced glass. An image generated by a discharge in the discharge cell is displayed through the front substrate  20 .  
         [0023]     The display electrodes  25  are formed on the front substrate  20 . The display electrodes  25  correspond to each discharge cell  18 . The display electrodes  25  can include first electrodes (hereinafter “scan electrodes”  21 ) and second electrodes (hereinafter “sustain electrodes”  23 ). The scan electrodes  21  and the sustain electrodes  23  can face each other and form a discharge gap g (refer to  FIG. 2 ).  
         [0024]     The scan electrode  21  interacts with the address electrode  12  and selects a discharge cell to be turned on. The sustain electrode  23  interacts with the scan electrodes  23  and causes sustain discharge within selected discharge cells  18 .  
         [0025]     The display electrodes  25  are covered with a dielectric layer  28  made of a dielectric material (for example PbO, B 2 O 3 , or SiO 2 ). The dielectric layer  28  prevents electrically charged particles from colliding with and damaging the display electrodes  25  during discharge. The dielectric layer  28  can be covered with a protective layer  29  (for example MgO). The protective layer  29  prevents electrically charged particles from colliding with and damaging the dielectric layer  28 . In addition, the protective layer  29  improves discharge efficiency by emitting secondary electrons upon collision with electrically charged particles.  
         [0026]     The address electrodes  12  are formed on a surface of the rear substrate  10  that faces the front substrate  20 . The address electrodes  12  intersect the display electrodes  25  and extend along a direction (y-axis direction) corresponding to each discharge cell  18 . The address electrodes  12  can be formed in stripe patterns on the rear substrate  10 . The address electrodes  12  interact with the scan electrodes  21  to select discharge cells  18  to be turned on. The address electrodes  12  are covered with and protected by a dielectric layer  14 . The barrier ribs  16  are formed on the dielectric layer  14 .  
         [0027]     The barrier ribs  16  protrude from the rear substrate  10  toward the front substrate  20  in predetermined patterns (for example, a stripe pattern, a matrix pattern, a delta pattern, etc.) and partition the space between the rear substrate  10  and the front substrate  20 . In the present embodiment, the barrier ribs  16  in a matrix pattern are exemplified.  
         [0028]     A recess portion  17  is formed on a side surface  161  (refer to  FIG. 4 ) of the barrier ribs  16 . The lateral cross-section of the recess portion  17  is in the shape of an arc. The recess portion  17  expands the area of the phosphor that is distributed over the side surface  161  of the barrier rib  16 .  
         [0029]     A phosphor layer  19  that radiates visible light of each color is formed within the discharge cells  18 . The respective phosphor layers  19  of red (R), green (G), and blue (B) are formed within the respective discharge cells  18 . Red ( 18 R), green ( 18 G), and blue ( 18 B) discharge cells form a pixel. Each discharge cell  18  is filled with a mixed discharge gas of neon (Ne) or Xenon (Xe).  
         [0030]     Referring now to  FIG. 2 , the barrier ribs  16  includes horizontal barrier ribs  16   a  and vertical barrier ribs  16   b . The horizontal barrier ribs  16   a  extend in a first direction (x-axis direction in the drawings) and the vertical barrier ribs  16   b  extend along a second direction (y-axis direction in the drawings). In other words, the horizontal barrier ribs  16   a  are formed in a direction crossing the address electrodes  12 , and the vertical barrier ribs  16   b  are formed in a direction parallel to the address electrodes  12 .  
         [0031]     The discharge cells  18  are partitioned in a matrix pattern by the barrier ribs  16 . Thus, discharge cells of different colors are arranged sequentially in the first direction, and discharge cells of the same colors are arranged in the second direction.  
         [0032]     The scan electrodes  21  and the sustain electrodes  23  that form display electrodes  25  extend in the first direction, and face each other and form a discharge gap g in the second direction. In addition, the scan electrodes  21  and the sustain electrodes  23  can include transparent electrodes  251  that are formed in the shape of a thin film on an inner surface  201  of the front substrate  20  that faces the rear substrate  10 . Metal electrodes  253  can be formed on the transparent electrodes  251 . In this case, the display electrodes  25  are arranged over the discharge cells  18  (refer to  FIG. 4 ).  
         [0033]     Alternatively, the display electrodes  45  can include a plurality of linear portions that are each in the shape of stripes and arranged with a certain distance therebetween. In this case, the linear portions are made of a highly conductive and opaque metal such as silver (Ag) or copper (Cu).  
         [0034]     Referring now to  FIG.3 , a scan electrode  41  and a sustain electrode  43  respectively include first linear portions  411  and  431  and second linear portions  412  and  432 . The first linear portions  411  and  431  extend in the first direction and face each other to form a discharge gap g in the second direction. The second linear portions  412  and  432  also extend in the first direction and are arranged at a certain distance from the first linear portions  411  and  431 . In one embodiment, there is no electrode between the first linear portions  411  and  431  and the second linear portions  412  and  432 , so that the aperture ratio of the discharge cell  18  can be improved. In an alternate embodiment, third liner portions  413  and  433  can be formed between the first linear portions  411  and  431  and the second linear portions  412  and  432 , and can be apart from the first and second linear portions  411 ,  431 ,  412 , and  432 .  
         [0035]     Referring now to  FIG.4 , the barrier ribs  16  stand straight from the rear substrate  10  toward the front substrate  20 . The bottom surface b and the top surface t of each barrier rib  16  face the rear substrate  10  and the front substrate  20 , respectively. The bottom surface b is in contact with the dielectric layer  14  that protects the address electrodes  12 , and the top surface t is in contact with the protective layer  29 .  
         [0036]     The width t 1  of the top surface t of the barrier rib  16  is formed to be narrower than the width b 1  of the bottom surface b to establish a stable structure. Therefore, the barrier rib  16  can have a stable structure even though the recess portion  17  is formed on the side surface  161 .  
         [0037]     The recess portion  17  is formed inwardly from the side surface  161  of the barrier rib  16 . The lateral cross-section of the recess portion  17  can be formed in the shape of an arc.  
         [0038]     The recess portion  17  is formed to be closer to the top surface t than to the bottom surface b of the barrier rib  16 . An inclined portion  171  is formed to extend from the recess portion  17  toward the rear substrate  10 . The shape of the inclined portion  171  is not limited to a straight line.  
         [0039]     A distance h between the top surface t and the center of the recess portion  17  is the same as or smaller than the width t 1  of the top surface t. That is, the following Formula 1 can be applied to the recess portion  17 .
 
h≦t1   (Formula 1)
 
         [0040]     If the distance h between the top surface t of the barrier rib  16  and the center of the recess portion  17  is greater than the width t 1  of the top surface t, the barrier rib  16  becomes too thin so that it breaks or collapses.  
         [0041]     The depth d of the recess portion  7  is measured from an extension line that extends from the edge of the top surface t and is perpendicular (i.e., normal) to the rear substrate, and the depth d is the same as or smaller than ⅕ the width t 1  of the top surface t of the barrier rib  16 . That is, the following Formula 2 can be applied to the recess portion  17 .
 
 d≦ 0.2* t 1  (Formula 2)
 
         [0042]     If the depth d of the recess portion  17  is deeper than defined in Formula 2, cracks can appear in the barrier rib  16  and further the barrier rib  16  can collapse.  
         [0043]     When the recess portion  17  is formed according to Formulas 1 and 2, stability of the process can be ensured while efficiency of luminescence of the discharge cell can be maximized as shown in the following experimental examples:  
       EXAMPLES  
       [0044]     Table 1 shows results of different luminescences measured in a 42-inch SD class PDP between an experimental example and a comparative example. The experimental example has a recess portion formed on the barrier rib and the comparative example has no recess portion.  
         [0045]     The experimental example and the comparative example are manufactured to be the same except for the recess portion. The experiment was carried out with four different signal intensities. The results of the experiment as recorded in Table 1 show that luminescence in the experimental example that has a recess portion was relatively higher. One of the reasons for this result is that the recess within the sidewalls of the barrier ribs allows more phosphors to be formed within the discharge cells due to surface tension by the recess portion.  
                                     TABLE 1                           Comparative Example   Experimental Example       Signal Intensity   (without recess)   (with recess)                                A   1104   1218       B   675   734       C   310   345       D   84   93                  
 
         [0046]     Although certain exemplary embodiments of the present invention have been shown and described, the present invention is not limited to the described embodiments, but can be modified in various forms without departing from the scope of the invention set forth in the detailed description, the accompanying drawings, the appended claims, and their equivalents.