Abstract:
A plasma display panel including: first and second substrates facing each other; a barrier rib defining a plurality of discharge cells, disposed between the first and second substrates; a plurality of address electrodes disposed on the first substrate, adjacent to the discharge cells; and a plurality of transparent electrodes disposed on the second substrate, facing the discharge cells; and bus electrode connecting the transparent electrodes. Each of the transparent electrodes defines an opening through which light is discharged from the discharge cells. The transparent electrodes can further include one or more protrusions that extend into the openings.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Application No. 2007-53285, filed May 31, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Aspects of the present invention relate to a plasma display panel (PDP). More particularly, aspects of the present invention relate to a PDP having display electrodes having a reduced surface area, which have aspects that enhance discharge diffusion. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a PDP generates plasma using a gas discharge, excites phosphors using ultra-violet rays emitted from the plasma in a vacuum, and realizes an image using red, green, and blue visible light, generated when the excited phosphors are stabilized. 
         [0006]    A PDP includes front and rear substrates and discharge cells formed between the front and rear substrates. A PDP displays an image using visible light emitted from the discharge cells, toward the front substrate. 
         [0007]    In an alternating current type PDP, address electrodes are formed on the rear substrate and a dielectric layer covers the address electrodes. Barrier ribs are disposed on the dielectric layer, between the address electrodes. The barrier ribs are formed in a striped pattern. Red, green, and blue phosphor layers are formed on the barrier ribs. 
         [0008]    In each cell, display electrodes are paired with sustain and scan electrodes, on the front substrate, facing the rear substrate. The display electrodes extend across the address electrodes. The display electrodes are covered by a dielectric layer and an MgO protective layer. 
         [0009]    The discharge cells are correspond to interesting regions, at which the address electrodes on the rear substrate intersect the pairs of sustain and scan electrodes. Millions of the discharge cells are arranged in a matrix pattern, in the PDP. 
         [0010]    The display electrodes include transparent electrodes that generate surface discharges in the discharge cells, and bus electrodes to apply a voltage to the transparent electrodes. For example, when the transparent electrodes are formed of segments extending across the discharge cells, the reactive consumption power increases, due to the size increase of the transparent electrodes. 
         [0011]    As another example, when the transparent electrodes are line members formed along outer blocks and central portions of the discharge cells, the reactive consumption power is reduced, due to the size reduction of the transparent electrodes. However, since the line members are arranged discontinuously, the discharge diffusion between the line members is weakened, and thus, the discharge efficiency is reduced. The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY OF THE INVENTION 
       [0012]    Exemplary embodiments of the present invention provide a PDP that can reduce reactive power consumption, by reducing the size of transparent electrodes, and can improve discharge efficiency, by enhancing discharge diffusion from the transparent electrodes. 
         [0013]    In an exemplary embodiment of the present invention, a plasma display panel includes: rear and front substrates that face each other; a barrier rib defining a plurality of discharge cells, disposed between the rear and front substrates; a plurality of address electrodes disposed on one of the rear or front substrates, and aligned in a first direction with the discharge cells; and a plurality of transparent electrodes extending on the other of the front or rear substrates, in a second direction that intersects the first direction. The transparent electrodes are paired at each of the discharge cells, and are spaced apart from each other in the first direction. The transparent electrodes are paired, with one electrode of each pair facing each end of the respective discharge cell. The plasma display panel includes bus electrodes connecting the transparent electrodes in the second direction. The transparent electrodes include: first and second line members that respectively extend from the bus electrode, which correspond to opposite ends of the discharge cells, and are spaced apart from each other in the first direction, toward a central portion of the discharge cell; a third line member connecting the first and second line members in the second direction, at the central portion of the discharge cell, and a protrusion extending from at least one of the bus electrode and the first, second, and third line members, toward the bus electrode and the first, second, and third line members. 
         [0014]    According to some exemplary embodiments, the protrusions may extend from the bus electrode toward the third line member. 
         [0015]    According to some exemplary embodiments, the transparent electrode may further include a fourth line member extending in the second direction, at one of end of the discharge cell. The bus electrodes may be formed on the fourth line members. 
         [0016]    According to some exemplary embodiments, the protrusions may extend from the fourth line members, toward the third line members. Each of the protrusions is formed in a hemispherical shape protruding toward the discharge cell. 
         [0017]    According to some exemplary embodiments, the protrusions may include first protrusions extending from the fourth line members toward the third line members and second protrusions extending from the fourth line members toward the third line members. The first protrusions may face the respective second protrusions. 
         [0018]    According to some exemplary embodiments, the protrusions may further include third protrusions extending from the first line members toward the second line members and fourth protrusions extending from the second line members toward the first line members. The third protrusions may face the respective fourth protrusions. 
         [0019]    According to some embodiments, each of the protrusions may be rectangular, semicircular, triangular, or T-shaped. 
         [0020]    According to some exemplary embodiments, each of the protrusions may be triangular, and may point toward the discharge cell. 
         [0021]    According to some exemplary embodiments, the barrier rib may include first barrier rib members extending in the first direction to define the opposite ends of the discharge cell, which are spaced apart from each other in the second direction, and second barrier rib members extending in the second direction between the first barrier members, to define opposite ends of the discharge cell, which are spaced apart from each other in the first direction. 
         [0022]    According to some exemplary embodiments, the barrier rib may include first barrier rib members extending in the first direction, to define opposite ends of the discharge cell, which are spaced apart from each other in the second direction, second barrier rib members extending in the second direction to define the opposite ends of the discharge cell, which are spaced apart from each other in the first direction, third barrier rib members provided to make a width of the discharge cell at the central portion of the discharge cell greater than widths of the discharge cell at the opposite ends of the discharge cell. The third barrier rib members connect the first barrier rib members to the second barrier rib members, in a direction crossing the first and second directions. 
         [0023]    In another exemplary embodiment of the present invention, a plasma display panel includes: first and second substrates facing each other; a barrier rib defining discharge cells, disposed between the first and second substrates; address electrodes disposed upon the first substrate adjacent to the discharge cells; transparent electrodes disposed on the second substrate, such that pairs of transparent electrode face opposing ends of one of the discharge cells; and bus electrodes disposed across the opposing ends of the discharge cells, to electrically connect the transparent electrodes. Each transparent electrode defines an opening, through which light generated in the discharge cells passes. 
         [0024]    Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which: 
           [0026]      FIG. 1  is a schematic exploded perspective view of a PDP, according to a first exemplary embodiment of the present invention; 
           [0027]      FIG. 2  is a sectional view taken along line II-II; 
           [0028]      FIG. 3  is a top plan view illustrating an arrangement of a barrier rib and electrodes; 
           [0029]      FIG. 4  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a second exemplary embodiment of the present invention; 
           [0030]      FIG. 5  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a third exemplary embodiment of the present invention; 
           [0031]      FIG. 6  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a fourth exemplary embodiment of the present invention; 
           [0032]      FIG. 7  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a fifth exemplary embodiment of the present invention; 
           [0033]      FIG. 8  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a sixth exemplary embodiment of the present invention; and 
           [0034]      FIG. 9  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a seventh exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0035]    Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the aspects of the present invention, by referring to the figures. 
         [0036]      FIG. 1  is a schematic exploded perspective view of a PDP  100 , according to a first exemplary embodiment of the present invention, and  FIG. 2  is a sectional view taken along line II-II, of  FIG. 1 . Referring to  FIGS. 1 and 2 , the PDP  100  includes rear and front substrates  10  and  20  that face each other, and a barrier rib  16  disposed therebetween. 
         [0037]    The barrier rib  16  has discharge cells  17  defined therein. The discharge cells  17  are filled with a discharge gas, for example, neon (Ne) and xenon (Xe). Phosphor layers  19  are disposed in the discharge cells  17 . The discharge gas generates ultraviolet rays, through a gas discharge. The phosphor layers  19  are excited by the ultraviolet rays, and emit visible light when stabilized. 
         [0038]    Address electrodes  11 , first electrodes (sustain electrodes)  31 , and second electrodes (scan electrodes)  32  are disposed between the rear and front substrates  10  and  20 , adjacent to the discharge cells  17 , to generate the gas discharge. For example, the address electrodes  11  are formed on an inner surface of the rear substrate  10 . The address electrodes  11  extend in parallel, in a first direction (y-direction in  FIG. 1 ), across the discharge cells  17 . The discharge cells  17  have a long axis that extends in the y-direction. The address electrodes  11  are spaced apart from each other in a second direction (x-direction in  FIG. 1 ). 
         [0039]    The first dielectric layer  13  is formed on the inner surface of the rear substrate  10 , and covers the address electrodes  11 . The first dielectric layer  13  prevents the address electrodes  11  from being damaged, and accumulates wall charges. That is, the first dielectric layer  13  prevents cations, and/or electrons, from directly colliding with the address electrodes  11 . 
         [0040]    The address electrodes  11  may be formed of a non-transparent material. For example, the address electrodes  11  may be formed of silver (Ag), or other metals that have excellent electrical conductivity. Since the address electrodes  11  are disposed on the rear substrate  10 , they do not interfere with the transmission of the visible light. For example, the barrier rib  16  is provided on the first dielectric layer  13 , which is formed on the rear substrate  10 . The barrier rib  16  includes first barrier rib members  16   a  and second barrier rib members  16   b,  which define the discharge cells  17 . The discharge cells can form a matrix pattern. 
         [0041]    The first barrier rib members  16   a  extend in the y-direction, and are spaced apart from each other in the x-direction. The second barrier rib members  16   b  extend in the x-direction, and are spaced apart from each other in the y-direction. The barrier rib may not include the second barrier rib members  16   b,  in some exemplary embodiments. That is, the barrier rib may be formed with only the first barrier rib members  16   a.  In this case, the first barrier rib members are disposed in parallel with each other, in the x-direction, to form the discharge cells  17  in a striped pattern (not shown). 
         [0042]    The phosphor layers  19  are generally formed by depositing phosphor paste on sidewalls of the barrier rib  16 , and on surfaces of the first dielectric layer  13  that are surrounded by the barrier rib  16 . The phosphor paste is dried to form the phosphor layers  19 . 
         [0043]    The phosphor layers  19  extend in the y-direction, and are formed of phosphors that emit visible light. The phosphor layers  19  are formed of different phosphors, which emit different wavelengths of visible light (i.e., red, green, and blue light). That is, the phosphor layers  19  formed of the phosphors emitting the red, green, and blue visible light, and are alternately arranged in the x-direction. 
         [0044]    The sustain electrodes  31  and the scan electrodes  32  are arranged on an inner surface of the front substrate  20 , adjacent to the discharge cells  17 . The sustain electrodes  31  and the scan electrodes  32  form a surface discharge structure, to generate gas discharges in each of the discharge cells  17 . 
         [0045]      FIG. 3  is a top plan view illustrating an arrangement of the barrier rib  16  and the electrodes  31 ,  32 . Referring to  FIG. 3 , the sustain electrodes  31  and the scan electrodes  32  extend in the x-direction, and intersect the address electrodes  11 . Each of the sustain electrodes  31  includes a transparent electrode  31   a  to generate discharges, and a bus electrode  31   b  to apply a voltage signal to the transparent electrode  31   a.  Likewise, each of the scan electrodes  32  includes a transparent electrode  32   a  to generate discharges, and a bus electrode  32   b  to apply a voltage signal to the bus electrode  23   a.    
         [0046]    The transparent electrodes  31   a  and  32   a  are disposed in the discharge cells  17 , and are formed of a transparent material, such as, indium tin oxide (ITO), to ensure sufficient aperture ratios of the discharge cells  17 . The bus electrodes  31   b  and  32   b  are formed of metal having excellent electrical conductivity, to effectively apply the voltage signal to the transparent electrodes  31   a  and  32   a.    
         [0047]    The transparent electrodes  31   a  and  32   a  extend in the y-direction, over the discharge cells  17 . The transparent electrodes  31   a  and  32   a  respectively have widths W 31  and W 32 . A discharge gap DG is formed between corresponding pairs of the transparent electrodes  31   a  and  32   a.    
         [0048]    The bus electrodes  31   b  and  32   b  extend in the x-direction across ends of the discharge cells  14 , and are connected to the transparent electrodes  31   a  and  32   a.  Accordingly, the voltage signals applied to the bus electrodes  31   b  and  32   b  are applied to the respective transparent electrodes  31   a  and  32   a.    
         [0049]    Referring again to  FIGS. 1 and 2 , a second dielectric layer  21  is formed on the inner surface of the front substrate  20 , to cover the sustain and scan electrodes  31 ,  32 . The second dielectric layer  21  protects the sustain and scan electrodes  31 ,  32  from the gas discharge, and accumulate wall charges during the discharge. 
         [0050]    A protective layer  23  is formed to cover the second dielectric layer  21 . For example, the protective layer  23  is formed of transparent MgO, to transmit visible light, and to protect the second dielectric layer  21 . The protective layer  23  increases a secondary electron emission coefficient, during the discharge. 
         [0051]    When the rear and front substrates  10  and  20  are adhered to each other, the barrier rib  16  on the rear substrate  10  contacts the protective layer  23  on the front substrate  20 . A fine passage (not shown), defined between the barrier rib  16  and the protective layer  23 , functions to allow air to be exhausted from of the discharge cells  17 , and the discharge gas to be filled in the discharge cells  17 . 
         [0052]    In the PDP  100 , discharge cells  17  are turned on, in accordance with address discharges generated by the address and scan electrodes  11 ,  32 . The selected discharge cells  17  are driven, in accordance with sustain discharges generated by the sustain and scan electrodes  31  and  32 , thereby displaying an image. 
         [0053]    The transparent electrodes  31   a,    32   a  will now be described in more detail, with reference to  FIGS. 2 and 3 . The transparent electrodes  31   a,    32   a  define openings  31   c,    32   c  that correspond to inner portions of the discharge cells  17 . Since the openings  31   c,    32   c  reduce the size of the transparent electrodes  31   a,    32   a,  the reactive power consumption of the transparent electrodes  31   a,    32   a  is reduced. The second dielectric layer  21  formed by dielectric material for covering the bus electrodes  31   b,    32   b  and the transparent electrodes  31   a,    32   a.  Therefore, the openings  31   c,    32   c  is filled with the dielectric material. 
         [0054]    The transparent electrodes  31   a,    32   a  include protrusions  31   d,    32   d  which extend toward central portions of the openings  31   c,    32   c.  The protrusions  31   d,    32   d  compensate for weakened discharge diffusion, due to the openings  31   c,    32   c.  The protrusions  31   d,    32   d  reduce a distance between opposite sides of the openings  31   c,    32   c,  of each of the transparent electrodes  31   a,    32   a,  to compensate for the weakened discharge diffusion. 
         [0055]    The openings  31   c,    32   c  minimize the blocking of visible light emitted toward the front substrate  20 , thereby improving luminance efficiency. The protrusions  32   d,    32   d  partly intercept the visible light passing through the openings  32   c,    32   c,  to reduce unit light, thereby improving the expression of low grayscales. In more detail, the transparent electrodes  31   a,    32   a  include first line members  311 ,  321 , second line members  312 ,  322 , and third line members  313 ,  323 , which at least partially define the openings  31   c,    32   c.    
         [0056]    The first line members  311 ,  321  extends in the y-direction, adjacent to first sides of the discharge cells  17 , and are spaced part from each other in the x-direction. That is, the first line members  311 ,  321  extend from the bus electrodes  31   b,    32   b,  toward a central portion of the discharge cell  17  (e.g., toward the discharge gap DG), in parallel with the first barrier members  16   a.    
         [0057]    The second line members  312 ,  322  extend in the y-direction at second sides of the discharge cell  17 . That is, the second line members  312 ,  322  extend from the bus electrodes  31   b,    32   b,  toward the center of the discharge cell  17  (e.g., toward the discharge gap DG), in parallel with the first barrier members  16   a.  The first line members  311 ,  321  and the second line members  312 ,  322  are arranged in parallel with each other, and in parallel with the first barrier members  16   a,  and are spaced apart from each other in the x-direction. 
         [0058]    The third line members  313 ,  323  connect the first line members  311 ,  321  and the second line members  312 ,  322 , in the x-direction, at central portions of the discharge cells  17 . That is, the third line members  313 ,  323  extend in the x-direction, to connect the first line members  311 ,  321  and the second line members  312 ,  322 . 
         [0059]    In the sustain and scan electrodes  31 ,  32 , the discharge gap DG is defined between the adjacent third line members  313 ,  323 . As described above, each of the transparent electrodes  31   a,    32   a  is formed by the first line members  311 ,  321 , the second line members  313 ,  323 , and the third line members  313 ,  323 . 
         [0060]    The bus electrodes  31   b,    32   b  extend in the x-direction, at opposing ends of the discharge cells  17 , to define ends of the opening  31   c,    32   c . The first line members  311 ,  321 , the second line members  312 ,  323 , and the bus electrodes  31   a,    32   a  at least partially define the openings  31   c,    32   c.    
         [0061]    One end of the openings  31   c,    32   c  may be defined by the bus electrodes  31   b,    32   b.  Alternatively, as shown in  FIGS. 1 to 3 , one end of the opening  32   c,    32   c  may be defined by both the bus electrodes  31   b,    32   b  and fourth line members  314 ,  324 . 
         [0062]    The fourth line members  314 ,  324  extend in the x-direction, at the opposite ends of the discharge cells  17 , and are spaced apart from each other in the y-direction. When the fourth line members  314 ,  324  are provided, the bus electrodes  31   b,    32   b  are formed on the fourth line members  314 ,  324  (see  FIG. 2 ). 
         [0063]    The protrusions  31   d,    32   d  extend from at least one of the bus electrodes  31   b,    32   b,  the first line members  311 ,  321 , the second line members  312 ,  322 , and the third line members  313 ,  323 , toward the centers of the openings  31   c,    32   c.  For example, the protrusions  31 ,  32   d  protrude from the bus electrodes  31   b,    32   b,  toward the third line members  313 ,  323  (see  FIG. 3 ). The protrusions  31   d,    32   d  protrude in the y-direction. 
         [0064]    The protrusions  31   d,    32   d  reduce distances between the bus electrodes  31   b,    32   b  and the third line members  313 ,  323 , to compensate for the weakened discharge diffusion, resulting from the third line members  313 ,  323  defining the discharge gap DG toward the bus electrodes  31   b,    32   b.  The protrusions  31   d,    32   d  enhance the discharge diffusion, in the y-axis direction. When the fourth line members  314 ,  324  are provided, the protrusions  31   d,    32   d  may be formed on the bus electrodes  31   b,    32   b,  or on the fourth line members  314 ,  324 . 
         [0065]    The protrusions  31   d  and  32   d  reduce a distance between the fourth line members  314 ,  324  and the third line members  313 ,  323 , to enhance the discharge diffusion from the third line members  313 ,  323  to the fourth line members  314 ,  324 . For example, the protrusions  31   d,    32   d  are semicircular shapes protruding from the fourth line members  314 ,  324 , toward the centers of the discharge cells  17 . The protrusions  31   d,    32   d  enhance the discharge diffusion radially, into the discharge cells  17 . 
         [0066]    In the following exemplary embodiments, parts identical to those of the first embodiment will not be described, as only different parts will be described.  FIG. 4  is a top plan view of an arrangement of a barrier rib and electrodes of a PDP, according to a second exemplary embodiment of the present invention. 
         [0067]    Unlike the first exemplary embodiment, protrusions  41   d,    42   d  of the second exemplary embodiment include first protrusions  41   e,    42   e  and second protrusions  41   f,    42   f.  The first protrusions  41   e,    42   e  protrude from fourth line members  314 ,  324 , toward third line members  313 ,  323 . The second protrusions  41   f,    42   f  protrude from the third line members  313 ,  323 , toward the fourth line members  314 ,  324 . The first protrusions  41   e,    42   e  face the second protrusions  41   f,    42   f,  in the y-direction. 
         [0068]    The first protrusions  41   e,    42   e  and the second protrusions  41   f,    42   f  further reduce the lengths of openings  41   c,    42   c,  in the y-direction. As compared with the openings  31   c,    32   c  of first exemplary embodiment, the discharge diffusion can be further enhanced. The first protrusions  41   e,    42   e  and the second protrusions  41   f,    42   f  further reduce unit light deterioration, as compared with the first exemplary embodiment, where only the protrusions  31   d,    32   d  extend into each of the openings  31   c,    32   c.    
         [0069]      FIG. 5  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a third exemplary embodiment of the present invention. Unlike the second exemplary embodiment, the third exemplary embodiment further includes third protrusions  51   g,    52   g  and fourth protrusions  51   h,    52   h,  in addition to first protrusions  51   e,    52   e  and second protrusions  51   f,    52   f.    
         [0070]    The third protrusions  51   g,    52   g  protrude from first lines member  311 ,  321 , toward second line members  312 ,  322 . The fourth protrusions  51   h,    52   h  protrude from the second line members  312 ,  322 , toward the first line members  311 ,  321 . The third protrusions  51   g,    52   g  and the fourth protrusions  51   h,    52   h  face each other in the x-direction. 
         [0071]    The third protrusions  51   g,    52   g  and the fourth protrusions  51   h,    52   h  reduce a length of openings  51   c,    52   c  in the x-direction, to enhance the discharge diffusion in the x-direction. The third protrusions  51   g,    52   g  and the second protrusions  51   h,    52   h  further reduce unit light deterioration, as compared with the second exemplary embodiment, where the first protrusions  41   e,    42   e  and the second protrusion  41   f,    42   f  extend into the openings  41   c,    42   c.    
         [0072]      FIG. 6  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a fourth exemplary embodiment of the present invention. Unlike the first exemplary embodiment, protrusions  61   d,    62   d  of this exemplary embodiment are formed in a rectangular shape. 
         [0073]    The protrusions  61   d,    62   d  enhance the discharge diffusion from the centers of the rectangular protrusions  61   d,    62   d,  toward an overall region of the openings  61   c,    62   c.  Angular points of the protrusions  61   d,    62   d  enhance the discharge diffusion toward corners of the discharge cells  17 . 
         [0074]      FIG. 7  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a fifth exemplary embodiment of the present invention. Unlike the fourth exemplary embodiment, protrusions  71   d,    72   d  of this exemplary embodiment have enlarged portions  71   e,    72   e.  In other words, the protrusions  71   d,    72   d  are T-shaped. The protrusions  71   d,    72   d  and the enlarge portions  71   e,    72   e  further reduce the lengths of openings  71   c,    72   c  in the y-direction, to enhance the discharge diffusion. The protrusions  71   d,    72   d  and the enlarged portions  72   e,    72   e  reduce unit light deterioration, as compared with the fourth exemplary embodiment, which includes only the protrusions  61   d,    62   d.    
         [0075]      FIG. 8  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a sixth exemplary embodiment of the present invention. Unlike the first and fourth exemplary embodiments, protrusions  81   d,    82   d  of this exemplary embodiment are triangular and point toward a center of openings  81   c,    82   c.  In the first, fourth, and sixth embodiments, a variety of shapes of the protrusions, which have similar effect, are shown by way of example. 
         [0076]      FIG. 9  is a top plan view illustrating an arrangement of a barrier rib and electrodes of a PDP, according to a seventh exemplary embodiment of the present invention. Unlike the first through sixth exemplary embodiments, a barrier rib  26  of this exemplary embodiment includes first barrier rib members  26   a,  second barrier rib members  26   b,  and third barrier rib members  26   c.  The transparent electrodes and protrusions of the first through sixth exemplary embodiments may be identically applied to this seventh exemplary embodiment. Therefore, a detailed description of these parts is omitted. 
         [0077]    The first barrier rib members  26   a  extend in the y-direction, to define opposite sides of discharge cells  27 , and are spaced apart from each other in the x-direction. The second barrier rib members  26   b  extend in the x-direction, to define opposite ends of the discharge cells  27 , and are spaced apart from each other in the y-direction. 
         [0078]    The third barrier rib members  26   c  are angled, such that the widths of the discharge cells  27  are greater at the centers of the discharge cells  27 , than at the opposite ends of the discharge cells  27 . That is, the third barrier rib members  26   c  connect the first barrier rib members  26   a  to the second barrier rib members  26   b,  in a direction crossing the X and y-directions. 
         [0079]    The discharge diffusion may not be effectively realized at the opposite ends of the discharge cells  27 , which have the relatively more narrow widths as compared at the central portion of the discharge cell  27 . However, the protrusions  31   d,    32   d  enhance the discharge diffusion at the opposite ends having the relatively narrow widths. 
         [0080]    According to the exemplary embodiments of the present invention, by forming the openings on transparent electrodes, the surface area of each of the transparent electrodes can be reduced. Therefore, the reactive power consumption can be reduced. In addition, since protrusions extending toward the center of the openings are formed on the transparent electrodes, the discharge can be effectively diffused in the openings. Therefore, the discharge efficiency can be improved. 
         [0081]    Since the protrusions extending toward the openings are formed at both ends of discharge cells, which have narrowed opposing ends, the discharge diffusion at the narrowed ends can be enhanced. Further, since the protrusions formed on the transparent electrodes partially block the visible light passing through the openings, unit light can be reduced. Therefore, the expression of low grayscales can be improved. 
         [0082]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments, without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.