Abstract:
A plasma display panel may be provided having metal and auxiliary metal electrodes formed such that brightness and efficiency are improved. A plasma display panel may include transparent ITO electrodes and metal electrodes. The transparent ITO electrodes are spaced in parallel to each other at a predetermined distance within a discharge cell. The metal electrodes are formed on the transparent ITO electrodes and in parallel to the transparent ITO electrodes. Central portions of the metal electrodes are closer to a central portion of the discharge cell than central portions of the transparent ITO electrodes.

Description:
TECHNICAL FIELD 
     The present invention relates to a plasma display panel and more specifically to a plasma display panel in which metal and auxiliary metal electrodes are formed such that brightness and efficiency are improved. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  is a perspective view illustrating a discharge cell of a general AC plasma display panel arranged in matrix shape. 
     As shown in  FIG. 1 , a conventional PDP comprises a front substrate  10  and rear substrate  12 . A pair of sustain electrode  14 ,  16 , upper dielectric layer  18  and protective layer  20  are gradually formed on the front substrate  10 , and address electrodes  22 , lower dielectric layer  24  and barrier ribs  26  and phosphor layer  28  are gradually formed on the rear substrate  12 . The front substrate  10  and the rear substrate  12  are spaced in parallel to each other at a predetermined distance by barrier ribs  26 . 
     Wall charges occurred upon the plasma discharge is accumulated on the upper dielectric layer  18  and the lower dielectric layer  24 . The protection layer  20  serves to prevent damage of the upper dielectric layer  18  due to sputtering generated upon the plasma discharge and to increase emission efficiency of secondary electrons. The protection layer  20  is usually formed using magnesium oxide (MgO). 
     The address electrodes  22  are formed in the direction intersecting a pair of sustain electrodes  14 ,  16 . A data signal is supplied for the address electrodes  22  to select a cell that is displayed. 
     The barrier ribs  26  are formed in parallel to the address electrode  22  and serves to prevent ultraviolet rays and a visible ray generated due to the discharge from leaking toward neighboring discharge cells. The barrier ribs  26  may be existed or not a boundary line of sub-pixel. 
     The phosphor layer  28  is excited by ultraviolet rays generated upon the plasma discharge to generate a visible ray of one of red, green and blue. Inert mixed gases such as He+Xe, Ne+Xe and He+Ne+Xe for discharge are inserted into a discharge space of the discharge cell formed between the upper/lower substrates  10 ,  12 . 
     A pair of sustain electrode  14 ,  16  comprises scan electrodes  14  and sustain electrodes  16 . A scan signal for scanning of the panel is supplied for scan electrodes  14  and a sustain signal for maintaining discharge of a selected cell is supplied for sustain electrodes. 
     A pair of sustain electrode  14 ,  16  comprises transparent ITO electrodes  14 A,  16 A, which are stripe pattern, are made of transparent material in order to transmit a visible ray and have a wide width relatively, and metal electrodes  14 B,  16 B, which compensate a resistance of transparent ITO electrodes  14 A,  16 A and have a narrow width relatively. Each of the transparent ITO electrodes of a pair of sustain electrodes  14 ,  16  is opposite to each other at a predetermined distance. Further, metal electrodes  14 B,  16 B are formed in parallel to the transparent ITO electrodes  14 A,  16 A and formed on a verge of the transparent ITO electrodes  14 A,  16 A, respectively. Namely, metal electrodes  14 B,  16 B are formed on outside verge of the transparent ITO electrodes  14 A,  16 A. 
     A PDP cell of this structure sustains a discharge according to surface discharge between a pair of sustain electrodes  14 ,  16  after being selected by opposite discharge between the address electrode  22  and the scan electrode  14 . In the PDP cell, a visible ray is emitted to an outside of cell as radiating phosphors  28  by ultraviolet rays which are generated while the sustain discharge occurs. As a result, the PDP having cells displays an image. In this case, the PDP realizes a gray scale by controlling the discharge sustaining period, i.e. the number of sustain discharge according to a video data. 
     In the conventional PDP, Xe inert gas excites phosphors  28  using a vacuum ultraviolet generated by changing from excited state to ground state according to gas discharge. Therefore, as a content of Xe is much, a quantity of vacuum ultraviolet rays generated upon the gas discharge and the efficiency of the PDP increase. However, the increase of Xe is caused by rising discharge starting voltage and discharge sustaining voltage between sustain electrodes. 
     Furthermore, in the conventional PDP, the discharge starting voltage and the discharge sustaining voltage is raised because the metal electrodes  14 B,  16 B are formed on the outside verge of the transparent ITO electrodes  14 A,  16 A, respectively. Also, the brightness and efficiency of the conventional PDP are decreased. 
     That is, the conventional PDP structure has a difficulty in increasing brightness and efficiency without any problem such as the structure of electrodes within the discharge cell. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a plasma display panel for increasing brightness and efficiency and improving a stability of discharge. 
     A plasma display panel according to a first embodiment of the present invention comprises: transparent ITO electrodes which are spaced in parallel to each other at a predetermined distance within a discharge cell; metal electrodes which are formed on said transparent ITO electrodes and in parallel to said transparent ITO electrodes so that are positioned in the direction of opposite sides of said transparent ITO electrodes, respectively. 
     A plasma display panel according to a second embodiment of the present invention comprises: transparent ITO electrodes which are spaced in parallel to each other at a predetermined distance within a discharge cell and are patterned so that a part of said transparent ITO electrodes is different in width, respectively; and metal electrodes which are formed on said transparent ITO electrodes and in parallel to said transparent ITO electrodes so that are positioned in the direction of opposite sides of said transparent ITO electrodes, respectively. 
     A plasma display panel according to a third embodiment of the present invention comprises: transparent ITO electrodes which are spaced in parallel to each other at a predetermined distance within a discharge cell; metal electrodes which are formed on said transparent ITO electrodes and in parallel to said transparent ITO electrodes so that are positioned in the direction of opposite sides of said transparent ITO electrodes, respectively; and projecting metal electrodes which are jutted from said metal electrodes, respectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view illustrating a discharge cell of a plasma display panel of the prior art. 
         FIG. 2  is a plane view illustrating a pair of sustain electrodes shown in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating a discharge cell of a plasma display panel according to a first embodiment of the present invention. 
         FIG. 4  is a plane view illustrating a pair of sustain electrodes according to the first embodiment of the present invention shown in  FIG. 3 . 
         FIG. 5  is a graph showing comparison of brightness between the first embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 6  is a graph showing comparison of efficiency between the first embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 7  is a plane view illustrating a pair of sustain electrodes according to a modification of the first embodiment. 
         FIG. 8   a  is a plane view illustrating a pair of sustain electrodes according to another modification of a first embodiment. 
         FIG. 8   b  is a cross-sectional view of a pair of sustain electrodes of  FIG. 8   a  taken along a line A–A′. 
         FIG. 9  is a perspective view illustrating a discharge cell of a plasma display panel according to a second embodiment of the present invention. 
         FIG. 10  is a graph showing comparison of brightness between the second embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 11  is a graph showing comparison of efficiency between the second embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 12  is a plane view illustrating a pair of sustain electrodes according to a modification of the second embodiment. 
         FIG. 13  is a graph showing comparison of brightness between a modification of the second embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 14  is a graph showing comparison of efficiency between a modification of the second embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 15  is a plane view illustrating a pair of sustain electrodes according to another modification of the second embodiment. 
         FIG. 16  is a plane view illustrating a pair of sustain electrodes according to a third embodiment of the present invention. 
         FIG. 17  is a graph showing comparison of brightness between the third embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 18  is a graph showing comparison of efficiency between the third embodiment of the present invention and the prior art with respect to discharge voltage. 
         FIG. 19  is a plane view illustrating a pair of sustain electrodes according to a modification of the third embodiment. 
         FIG. 20  is a plane view illustrating a pair of sustain electrodes according to another modification of the third embodiment. 
         FIG. 21  is a plane view illustrating a pair of sustain electrodes according to the other modification of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     The First Embodiment 
       FIG. 3  is a perspective view illustrating a discharge cell of a plasma display panel according to a first embodiment of the present invention,  FIG. 4  is a plane view illustrating a pair of sustain electrodes according to the first embodiment of the present invention shown in  FIG. 3 . 
     As shown in  FIG. 3 , a plasma display panel according to the first embodiment of the present invention has a front substrate  110  and rear substrate  112 . A pair of sustain electrodes  114 ,  116 , upper dielectric layer  118  and protective layer  120  are gradually formed on the front substrate  110 , and address electrodes  122 , lower dielectric layer  124  and barrier ribs  126  and phosphor layer  128  are gradually formed on the rear substrate  112 . The front substrate  110  and the rear substrate  112  are spaced in parallel to each other at a predetermined distance by barrier ribs  126 . 
     A pair of sustain electrode  114 ,  116  is composed of scan electrodes  114  and sustain electrodes  116 . A scan signal for scanning of the panel is supplied for scan electrodes  114  and a sustain signal for maintaining discharge of a selected cell is supplied for sustain electrodes  116 . 
     According to the first embodiment of the present invention, the sustain electrodes  114 ,  116  are consisted of the transparent ITO electrodes  114 A,  116 A and the metal electrodes  114 B,  116 B. The transparent ITO electrodes  114 A,  116 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. The metal electrodes  114 B,  116 B have a stripe pattern of a narrow width relatively and are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  114 A,  116 A. 
     Each of the transparent ITO electrodes  114 A,  116 A of a pair of sustain electrodes  114 ,  116  are opposite to each other at a predetermined distance. 
     Preferably, the position of each of the metal electrodes  114 B,  116 B satisfies the following the equation 1.
 
d 2 &lt;d½  [Equation.1]
 
wherein d 1  represents a distance between a central portion of the transparent ITO electrodes  114 A,  116 A and a center line(Pc) of the discharge cell, d 2  represents a distance between a central portion of the metal electrodes  114 B,  116 B and a center line(Pc) of the discharge cell.
 
     In the PDP according to the first embodiment of the present invention, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at this time of the discharge, although the contents of Xe inert gas increases. 
     In the concrete, since the distance between the metal electrodes  114 B,  116 B is near, the strong electric field generates at the central portion of the discharge cell, at this time of the discharge. And, the discharge starting voltage and discharge sustaining voltage are decreased by the strong electric field generated at the central portion of the discharge cell. 
       FIG. 5  is a brightness graph which compares a first embodiment of the present invention with a prior art and  FIG. 6  is an efficiency graph which compares a first embodiment of the present invention with a prior art. 
     As shown in  FIG. 5  and  FIG. 6 , the brightness of the PDP according to the first embodiment of the present invention is improved approximately 40% to 60% as compared to the conventional PDP at the same discharge voltage, and the efficiency of the PDP according to the first embodiment of the present invention is improved approximately 40% to 60% as compared to the conventional PDP at the same discharge voltage. Further, as the discharge starting voltage and the discharge delay time are decreased, the stability of discharge can be improved. 
       FIG. 7  is a plane view illustrating a pair of sustain electrodes according to a modification of the first embodiment. 
     The description of the same elements with the first embodiment of the present invention shown in  FIG. 3  is omitted. 
     According to a modification of the first embodiment of the present invention, sustain electrodes  214 ,  216  are consisted of transparent ITO electrodes  214 A,  216 A and metal electrodes  214 B,  216 B on the transparent ITO electrodes  214 A,  216 A. 
     The transparent ITO electrodes  214 A,  216 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. 
     Each of the metal electrodes  214 B,  216 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  214 A,  216 A and is formed in the direction of a central portion of the transparent ITO electrodes  214 A,  216 A from a opposite sides of the transparent ITO electrodes  214 A,  216 A. Further, a position of the metal electrodes  214 B,  216 B satisfies the above equation 1 and the metal electrodes  214 B,  216 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  214 A,  216 A. 
     That is, a distance between the metal electrodes  214 B,  216 B according to a modification of the first embodiment is smaller than a distance between the metal electrodes  114 B,  116 B according to the first embodiment. Therefore, a strong electric field is induced at the central portion (Pc) of the discharge cell when the plasma discharge occurs. 
     A characteristic of the brightness and efficiency is similar to those of the first embodiment shown in  FIG. 5  and  FIG. 6 . 
       FIG. 8   a  is a plane view illustrating a pair of sustain electrodes according to another modification of a first embodiment, and  FIG. 8   b  is a cross-sectional view of a pair of sustain electrodes of  FIG. 8   a  taken along a line A–A′. 
     The description of the same elements with the first embodiment of the present invention shown in  FIG. 3  is omitted. A pair of sustain electrode  314 ,  316  are composed of scan electrodes  314  and sustain electrodes  316 . The sustain electrodes  314 ,  316  are consisted of the transparent ITO electrodes  314 A,  316 A, and the metal electrodes  314 B,  316 B. Each of the transparent ITO electrodes  314 A,  316 A of a pair of sustain electrodes  314 ,  316  is opposite to each other at a predetermined distance. 
     Transparent ITO electrodes  314 A,  316 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. 
     Each of the metal electrodes  314 B,  316 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  314 A,  316 A. A part of each of the metal electrodes  314 B,  316 B is formed on an opposite sides of the transparent ITO electrodes  314 A,  316 A. Further, a position of the metal electrodes  314 B,  316 B satisfies the above equation 1 and the metal electrodes  314 B,  316 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  314 A,  316 A. 
     That is, a distance between the metal electrodes  314 B,  316 B according to another modification of the first embodiment is smaller than a distance between the metal electrodes according to the first embodiment. Therefore, a strong electric field is induced at the central portion (Pc) of the discharge cell when the plasma discharge occurs. 
     Furthermore, a characteristic of the brightness and efficiency is similar to those of the first embodiment shown in  FIG. 5  and  FIG. 6 . 
     The Second Embodiment 
     The description of the same elements with the first embodiment of the present invention shown in  FIG. 3  is omitted. 
       FIG. 9  is a perspective view illustrating a discharge cell of a plasma display panel according to a second embodiment of the present invention. 
     Sustain electrodes  414 ,  416  are consisted of transparent ITO electrodes  414 A,  416 A and metal electrodes  414 B,  416 B on the transparent ITO electrodes  414 A,  416 A. The transparent ITO electrodes  414 A,  416 A are opposite to each other at a predetermined distance. 
     The transparent ITO electrodes  414 A,  416 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. And, each of the transparent ITO electrodes  414 A,  416 A is a“T” shape, namely both edges are patterned in a shape of quadrangle. Wherein the pattern is a part which an influence of brightness is little. 
     Preferably, the “T” shape of each of the transparent ITO electrodes  414 A,  416 A satisfies the following the equation 2 and 3.
 
0.2×W1&lt;W2&lt;0.8×W1  [Equation. 1]
 
     wherein W 1  represents a horizontal length of a discharge cell, W 2  represents a horizontal length of a part of a narrow area of the transparent ITO electrodes  414 A,  416 A, relatively.
 
0.2×D3&lt;D4&lt;0.8×D3  [Equation 3]
 
     wherein D 3  represents a width of the transparent ITO electrodes  414 A,  416 A, D 4  represents a width of a part of a narrow area of the transparent ITO electrodes  414 A,  416 A, relatively. 
     Each of the metal electrodes  414 B,  416 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  414 A,  416 A and is formed in the direction of a central portion of the transparent ITO electrodes  414 A,  416 A from an opposite sides of the transparent ITO electrodes  414 A,  416 A. Further, a position of the metal electrodes  414 B,  416 B satisfies the above equation I and the metal electrodes  414 B,  416 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  414 A,  416 A. 
     In the PDP according to the second embodiment of the present invention, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at this time of the discharge, although the contents of Xe inert gas increases. Further, as an area ratio of the transparent ITO electrodes  414 A,  416 A in comparison with a discharge cell is decreased, a consumption power is reduced and a radiation efficiency is improved. 
     Therefore, as shown in  FIG. 10 , a current density according to the second embodiment of the present invention is decreased approximately 20% to 25% in comparison with the conventional PDP and a reductive width of the current density is larger as a discharge voltage is high. 
     As shown in  FIG. 11 , the efficiency of the PDP according to the second embodiment of the present invention is improved as compared to the conventional PDP at the same discharge voltage. 
       FIG. 12  is a plane view illustrating a pair of sustain electrodes according to a modification of the second embodiment. 
     Sustain electrodes  514 ,  516  are consisted of transparent ITO electrodes  514 A,  516 A and metal electrodes  514 B,  516 B on the transparent ITO electrodes  514 A,  516 A. The transparent ITO electrodes  514 A,  516 A are opposite to each other at a predetermined distance. 
     The transparent ITO electrodes  514 A,  516 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. And, each of the transparent ITO electrodes  514 A,  516 A is consisted of an upper portion of a first width and a lower portion of a second width. Namely, both edges are patterned in a shape of triangle. Wherein the pattern is a part which an influence of brightness is little. In result, each of the transparent ITO electrodes  514 A,  516 A becomes a joined shape of quadrangle and trapezoid. 
     Each of the metal electrodes  514 B,  516 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  514 A,  516 A and is formed in the direction of a central portion of the transparent ITO electrodes  514 A,  516 A from a opposite sides of the transparent ITO electrodes  514 A,  516 A. Further, the metal electrodes  514 B,  516 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  514 A,  516 A. 
     In the PDP according to the transformation of second embodiment of the present invention, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at this time of the discharge, although the contents of Xe inert gas increases. Further, as an area ratio of the transparent ITO electrodes  514 A,  516 A in comparison with a discharge cell is decreased, a consumption power is reduced and a radiation efficiency is improved. 
     Therefore, as shown in  FIG. 13 , a brightness of PDP according to a modification of the second embodiment is improved approximately 77% in comparison with the conventional PDP at a same discharge voltage. And as shown in  FIG. 14 , a efficiency of PDP according to the transformation of second embodiment is improved approximately 57% in comparison with the conventional PDP at a same discharge voltage. 
       FIG. 15  is a plane view illustrating a pair of sustain electrodes according to another modification of the second embodiment. 
     Sustain electrodes  614 ,  616  are consisted of transparent ITO electrodes  614 A,  616 A and metal electrodes  614 B,  616 B on the transparent ITO electrodes  614 A,  616 A. The transparent ITO electrodes  614 A,  616 A are opposite to each other at a predetermined distance. 
     The transparent ITO electrodes  614 A,  616 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. And, each of the transparent ITO electrodes  614 A,  616 A is consisted of an upper portion of a first width and a lower portion of a second width. Namely, both edges are patterned in a shape of trapezoid. Wherein the pattern is a part which an influence of brightness is little. In result, each of the transparent ITO electrodes  614 A,  616 A becomes a joined shape of stripe and trapezoid. 
     Each of the metal electrodes  614 B,  616 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  614 A,  616 A and is formed in the direction of a central portion of the transparent ITO electrodes  614 A,  616 A from a opposite sides of the transparent ITO electrodes  614 A,  616 A. Further, the metal electrodes  614 B,  616 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  614 A,  616 A. 
     In the PDP according to another modification of second embodiment of the present invention, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at this time of the discharge, although the contents of Xe inert gas increases. Further, as an area ratio of the transparent ITO electrodes  614 A,  616 A in comparison with a discharge cell is decreased, a consumption power is reduced and a radiation efficiency is improved. 
     Therefore, a brightness and efficiency of PDP according to the other transformation of second embodiment is improved in comparison with the conventional PDP at a same discharge voltage. 
     The Third Embodiment 
     The description of the same elements with the first embodiment of the present invention shown in  FIG. 3  is omitted. 
       FIG. 16  is a plane view illustrating a pair of sustain electrodes according to a third embodiment of the present invention. 
     Sustain electrodes  714 ,  716  are consisted of transparent ITO electrodes  714 A,  716 A, metal electrodes  714 B,  716 B and projecting metal electrodes  714 C,  716 C on the transparent ITO electrodes  714 A,  716 A. The transparent ITO electrodes  714 A,  716 A are opposite to each other at a predetermined distance. 
     The transparent ITO electrodes  714 A,  716 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. 
     Each of the metal electrodes  714 B,  716 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  714 A,  716 A and is formed in the direction of a central portion of the transparent ITO electrodes  714 A,  716 A from a opposite sides of the transparent ITO electrodes  714 A,  716 A. Further, the metal electrodes  714 B,  716 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  714 A,  716 A. 
     Each of the projecting metal electrodes  714 C,  716 C is jutted in the direction of a verge of a discharge cell from a middle point of the metal electrodes  714 B,  716 B. Whereupon, the projecting metal electrodes  714 C,  716 C and the metal electrodes  714 B,  716 B become a “T” shape. The projecting metal electrodes  714 C,  716 C are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  714 A,  716 A, and are expanded in the direction of the outside sides of the discharge cell. 
     Preferably, the position of each of the metal electrodes  714 B,  716 B satisfies the following the equation 4.
 
D&lt;H/4  [Equation 4]
 
     wherein H represents a length of discharge cell, D represents a distance between a central portion of the metal electrodes  714 B,  716 B and a central portion of the discharge cell. 
     In the PDP according to the third embodiment of the present invention, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at this time of the discharge, although the contents of Xe inert gas increases. Further, as an area ratio of the transparent ITO electrodes  714 A,  716 A in comparison with a discharge cell is decreased, a consumption power is reduced and a radiation efficiency is improved. 
     That is, since the distance between the metal electrodes  714 B,  716 B is near, the strong electric field generates at the central portion of the discharge cell, at this time of the discharge, and then the discharge is expanded in the direction of the verge of the discharge cell. In this result, the discharge starting voltage and discharge sustaining voltage are decreased by the generated strong electric field at the central portion of the discharge cell and the brightness and efficiency are increased. Furthermore, since the discharge starting voltage and the discharge delay time are decreased, the stability of the discharge is improved. 
     Therefore, as shown in  FIG. 17 , a brightness of PDP according to the transformation of third embodiment is improved approximately 40% to 50% in comparison with the conventional PDP at a same discharge voltage. And as shown in  FIG. 18 , an efficiency of PDP according to the transformation of second embodiment is improved approximately 30% to 40% in comparison with the conventional PDP at a same discharge voltage. 
       FIG. 19  is a plane view illustrating a pair of sustain electrodes according to a modification of the third embodiment. 
     Sustain electrodes  814 ,  816  are consisted of transparent ITO electrodes  814 A,  816 A, metal electrodes  814 B,  816 B, projecting metal electrodes  814 C,  816 C and auxiliary metal electrodes  814 D,  816 D on the transparent ITO electrodes  814 A,  816 A. The transparent ITO electrodes  814 A,  816 A are opposite to each other at a predetermined distance. 
     The transparent ITO electrodes  814 A,  816 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. 
     Each of the metal electrodes  814 B,  816 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  814 A,  816 A and is formed in the direction of a central portion of the transparent ITO electrodes  814 A,  816 A from a opposite sides of the transparent ITO electrodes  814 A,  816 A. Further, a position of the metal electrodes  814 B,  816 B satisfies the above equation 4 and the metal electrodes  814 B,  816 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  814 A,  816 A. 
     Each of the projecting metal electrodes  814 C,  816 C is jutted in the direction of a verge of a discharge cell from a middle point of the metal electrodes  814 B,  816 B. Whereupon, the projecting metal electrodes  814 C,  816 C and the metal electrodes  814 B,  816 B become a “T” shape. The projecting metal electrodes  814 C,  816 C are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  814 A,  816 A, and are expanded in the direction of the outside sides of the discharge cell. 
     Each of the auxiliary metal electrodes  814 D,  816 D is formed at a tip of the projecting metal electrodes  814 C,  816 C and formed in parallel to the metal electrodes  814 B,  816 B and is short than a length of the metal electrodes  814 B,  816 B. Whereupon, the metal electrodes  814 B,  816 B, the projecting metal electrodes  814 C,  816 C and the auxiliary metal electrodes  814 D,  816 D become a “H” shape. The auxiliary metal electrodes  814 D,  816 D are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  814 A,  816 A, and are expanded in the direction of the outside sides of the discharge cell. 
     In the PDP according to a modification of third embodiment of the present invention, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at this time of the discharge, although the contents of Xe inert gas increases. Further, as an area ratio of the transparent ITO electrodes  814 A,  816 A in comparison with a discharge cell is decreased, a consumption power is reduced and a radiation efficiency is improved. 
       FIG. 20  is a plane view illustrating a pair of sustain electrodes according to another modification of the third embodiment. 
     Sustain electrodes  914 ,  916  are consisted of transparent ITO electrodes  914 A,  916 A, metal electrodes  914 B,  916 B, projecting metal electrodes  914 C,  916 C and auxiliary metal electrodes  914 D,  916 D on the transparent ITO electrodes  914 A,  916 A. The transparent ITO electrodes  914 A,  916 A are opposite to each other at a predetermined distance. 
     The transparent ITO electrodes  914 A,  916 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. 
     Each of the metal electrodes  914 B,  916 B has a stripe pattern which has a narrower width than the transparent ITO electrodes  914 A,  916 A and is formed in the direction of a central portion of the transparent ITO electrodes  914 A,  916 A from a opposite sides of the transparent ITO electrodes  914 A,  916 A. Further, a position of the metal electrodes  914 B,  916 B satisfies the above equation 4 and the metal electrodes  914 B,  916 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  914 A,  916 A. 
     Each of the projecting metal electrodes  914 C,  916 C is jutted in the direction of a verge of a discharge cell from a middle point of the metal electrodes  914 B,  916 B. Whereupon, the projecting metal electrodes  914 C,  916 C and the metal electrodes  914 B,  916 B become a “T” shape. The projecting metal electrodes  914 C,  916 C are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  914 A,  916 A, and are expanded in the direction of the outside sides of the discharge cell. 
     Each of the auxiliary metal electrodes  914 D,  916 D is formed at a middle portion of the projecting metal electrodes  914 C,  916 C and formed in parallel to the metal electrodes  914 B,  916 B and is short than a length of the metal electrodes  914 B,  916 B. Whereupon, the metal electrodes  914 B,  916 B, the projecting metal electrodes  914 C,  916 C and the auxiliary metal electrodes  914 D,  916 D become a “±” shape. The auxiliary metal electrodes  914 D,  916 D are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  914 A,  916 A, and are expanded in the direction of the outside sides of the discharge cell. 
       FIG. 21  is a plane view illustrating a pair of sustain electrodes according to the other modification of the third embodiment. 
     Sustain electrodes  1014 ,  1016  are consisted of transparent ITO electrodes  1014 A,  1016 A, metal electrodes  1014 B,  1016 B, projecting metal electrodes  1014 C,  1016 C and auxiliary metal electrodes  1014 D,  1016 D on the transparent ITO electrodes  1014 A,  1016 A. The transparent ITO electrodes  1014 A,  1016 A are opposite to each other at a predetermined distance. 
     The transparent ITO electrodes  1014 A,  1016 A have a stripe pattern of a wide width relatively and are made of transparent material in order to transmit a visible ray. 
     Each of the metal electrodes  1014 B,  1016 B has a stripe pattern has a narrower width than a wide of the transparent ITO electrodes  1014 A,  1016 A and is formed in the direction of a central portion of the transparent ITO electrodes  1014 A,  1016 A from an opposite sides of the transparent ITO electrodes  1014 A,  1016 A. Further, a position of the metal electrodes  1014 B,  1016 B satisfies the above equation 4 and the metal electrodes  1014 B,  1016 B are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  1014 A,  1016 A. 
     Each of the projecting metal electrodes  1014 C,  1016 C is jutted in the direction of a verge of a discharge cell from a middle point of the metal electrodes  1014 B,  1016 B. Whereupon, the projecting metal electrodes  1014 C,  1016 C and the metal electrodes  1014 B,  1016 B become a “T” shape. The projecting metal electrodes  1014 C,  1016 C are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  1014 A,  1016 A, and are expanded in the direction of the outside sides of the discharge cell. 
     Each of the auxiliary metal electrodes  1014 D,  1016 D has a first auxiliary metal electrode and a second auxiliary metal electrode. The first auxiliary metal electrodes is formed at a tip of the projecting metal electrodes  1014 C,  1016 C and formed in parallel to the metal electrodes  1014 B,  1016 B and is short than a length of the metal electrodes  1014 B,  1016 B. The second auxiliary metal electrodes is formed at a middle portion of the projecting metal electrodes  1014 C,  1016 C and formed in parallel to the metal electrodes  1014 B,  1016 B and is short than a length of the metal electrodes  1014 B,  1016 B. Whereupon, the metal electrodes  1014 B,  1016 B, the projecting metal electrodes  1014 C,  1016 C and the auxiliary metal electrodes  1014 D,  1016 D become a “           ∓” shape. The auxiliary metal electrodes  1014 D,  1016 D are made of material having a good conductivity in order to compensate a conductivity of transparent ITO electrodes  1014 A,  1016 A, and are expanded in the direction of the outside sides of the discharge cell.
     In a plasma display panel according to the first embodiment of the present invention, a auxiliary metal electrode induces a strong electric field in the central portion of discharge cell and the discharge starting voltage and the discharge sustaining voltage are decreased. Therefore, the present invention has an effect that it can increase the brightness and efficiency at the same discharge voltage. 
     In a plasma display panel according to the second embodiment of the present invention, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at this time of the discharge, although the contents of Xe inert gas increases. Further, as an area ratio of the transparent ITO electrodes in comparison with a discharge cell is decreased, a consumption power is reduced and a radiation efficiency is improved. 
     In a plasma display panel according to the third embodiment of the present invention, since a distance between metal electrodes is near, the strong electric field generates at the central portion of the discharge cell and the discharge is expanded in the direction of the verge of the discharge cell by a auxiliary metal electrode. Therefore, the discharge starting voltage and discharge sustaining voltage are decreased and the brightness and efficiency are increased at the same discharge voltage. Furthermore, as the discharge starting voltage and the discharge delay time are decreased, the stability of the discharge is improved.