Abstract:
An electrode structure of a plasma display panel and a method of driving sustaining electrodes in the plasma display panel that are capable of improving the brightness. In the electrode structure, refractive electrodes are connected to a sustaining electrode pair and are bent to generate a sustaining discharge at at least two positions within a cell.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a plasma display panel, and more particularly to an electrode structure of a plasma display panel that is capable of improving the brightness. Also, the present invention is directed to a method of driving a sustaining electrode in the plasma display panel. 
     2. Description of the Related Art 
     Generally, a plasma display panel (PDP) is a light-emitting device which displays a picture using a gas discharge phenomenon within the cell. This PDP does not require providing an active device for each cell like a liquid crystal display (LCD). Accordingly, the PDP has a simple fabrication process and has the advantage of providing a large-dimension screen. 
     Such a PDP has a number of discharge cells arranged in a matrix type. The discharge cells are provided at each intersection between sustaining electrode lines for sustaining a discharge and address electrode lines for selecting the cells to be discharged. The PDP is largely classified into a direct current (DC) type panel and an alternating current (AC) type panel depending on whether or not a dielectric layer for accumulating a wall charge exists in the discharge cell. 
     Referring to FIG.  1  and FIG. 2, each cell of the AC-type, three-electrode PDP includes a front substrate  11  provided with a sustaining electrode pair  12 A and  12 B, and a rear substrate  18  provided with an address electrode  20 . The front substrate  10  and the rear substrate  18  are spaced in parallel to each other with having barrier ribs  24  therebetween and sealed with a fritz glass. A mixture gas, such as Ne—Xe or He—Xe, etc., is injected into a discharge space defined by the front substrate  11 , the rear substrate  18  and the barrier ribs  24 . The sustaining electrode pair  12 A and  12 B makes a pair by two within a single of plasma discharge channel. Any one electrode of the sustaining electrode pair  12 A and  12 B is used as a scanning electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode  20  while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge along with the other adjacent sustaining electrode. Also, the sustaining electrode  12 B or  12 A adjacent to the sustaining electrode  12 A or  12 B used as the scanning electrode is used as a common sustaining electrode to which a sustaining pulse is applied commonly. 
     The sustaining electrode pair  12 A and  12 B includes transparent electrodes  30 A and  30 B and metal electrodes  28 A and  28 B connected electrically to each other, respectively. The transparent electrodes  30 A and  30 B is formed by depositing indium thin oxide (ITO) on the front substrate  10  into an electrode width of about 300 m so as to prevent deterioration of an aperture ratio. The metal electrodes  28 A and  28 B are deposited on the front substrate  10  to have a three-layer structure of Ag or Cr—Cu—Cr. The metal electrodes  28 A and  28 B play a role to reduce a voltage drop caused by the transparent electrodes  30 A and  30 B. 
     On the front substrate  10  provided with the sustaining electrodes  12 A and  12 B, a dielectric layer  14  and a protective layer  16  are disposed. The dielectric layer  14  is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film  16  prevents a damage of the dielectric layer  14  caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film  16  is usually made from MgO. The rear substrate  18  is provided with a dielectric thick film  26  covering the address electrode  24 . The barrier ribs  24  for dividing the discharge space are extended perpendicularly at the rear substrate  18 . On the surfaces of the rear substrate  18  and the barrier ribs  24 , a fluorescent material  22  excited by a vacuum ultraviolet lay to generate a visible light is provided. 
     As shown in FIG. 3, such cells  1  of the PDP are arranged on a panel  30  in a matrix type. In each cell  1 , scanning/sustaining electrode lines S 1  to Sm, common sustaining electrode lines C 1  to Cm and address electrode lines D 1  to Dn cross each other. The scanning/sustaining electrode lines S 1  to Sm and the common sustaining electrodes C 1  to Cm consists of the sustaining electrode pair  12 A and  12 B in FIG. 1, respectively. The address electrode lines D 1  to Dn consist of the address electrodes  20 . 
     In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. The cells on which a data is to be displayed are selected by a writing discharge in the address interval. The selected cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2 n  depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 2 0 , 2 1 , 2 3 , 2 4 , 2 5 , 2 6  and 2 7 . To this end, the number of sustaining pulses generated in the sustaining interval also increases into 2 0 , 2 1 , 2 3 , 2 4 , 2 5 , 2 6  and 2 7  depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields. 
     An emission process of the PDP will be described below. First, a wall charge is uniformly accumulated within the cells of the entire screen by the reset discharge generated in the reset interval. In the address interval, a writing discharge is generated at the cells selected by an address discharge voltage applied to the scanning/sustaining electrode lines S 1  to Sm and the address electrode lines D 1  to Dn. Subsequently, when a sustaining pulse is alternately applied to the scanning/sustaining electrode lines S 1  to Sm and the common sustaining electrode lines C 1  to Cm, a discharge of the cells selected in the address interval is sustained. 
     When a plasma discharge is generated within the cell, a very small amount of electrons in discharge gases within the cell begin to be accelerated and continuously collide with neutral particles. By such an avalanche effect, the discharge gases within the cell is rapidly ionized into electrons and ions to be in a plasma state and, at the same time, generate a vacuum ultraviolet. This vacuum violet excites the fluorescent material  22  to generate a visible light. 
     However, the conventional PDP has a limit in improving the brightness into a satisfying level in view of its discharge structure. More specifically, the sustaining discharge of the PDP begins at one opposite surface between the scanning/sustaining electrode lines S 1  to Sm and the common sustaining electrode lines C 1  to Cm and is gradually diffused all over the cells. In such a discharge structure, since the discharge concentrates on only one surface between the scanning/sustaining electrode lines S 1  to Sm and the common sustaining electrodes C 1  to Cm, the brightness becomes low. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an electrode structure of a plasma display panel and a method of driving a sustaining electrode in the plasma display panel that are adaptive for improving the brightness. 
     In order to achieve these and other objects of the invention, an electrode structure of a plasma display panel according to one aspect of the present invention includes refractive electrodes connected to a sustaining electrode pair and bent to generate a sustaining discharge at at least two positions within a cell. 
     A method of driving sustaining electrodes in a plasma display panel according to another aspect of the present invention includes the steps of forming refractive electrodes at the sustaining electrode pair to generate a sustaining discharge at at least two positions within the cell. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG.  5  and FIG. 6, there is shown an electrode structure of a plasma display panel (PDP) according to a first embodiment of the present invention. In FIG.  5  and FIG. 6, elements of the PDP having the same structure and function as those in FIG. 1 are given the same reference numerals. A detailed explanation as to said elements will be omitted. 
     Referring to FIG. 5, the PDP includes a front substrate  40  provided with refractive electrodes  54 A and  54 B connected to a sustaining electrode pair  50 A and  50 B, respectively, and a rear substrate  18  provided with an address electrode  20 . Any one of the sustaining electrode pair  50 A and  50 B is used as a scanning electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode  20  while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge along with the other adjacent refractive electrode. The other sustaining electrode  50 A or  50 B is used as a common sustaining electrode supplied commonly with a sustaining pulse. The refractive electrodes  54 A and  54 B is discharged mutually or discharged along with the sustaining electrode pair  50 A and  50 B to cause a discharge at a plurality of positions within the cell. Each of the sustaining electrode pair  50 A and  50 B has a three-layer structure of Ag(or Cr)—Cu—Cr. 
     Each of the refractive electrodes  54 A and  54 B is a transparent electrode patterned into a “T” shape. A material of the transparent is selected from a transparent conductive electrode material (e.g., ITO or indium zinc oxide (IZO)) that has a high transmissivity and a high electrical conductivity with respect to a light emitted from a fluorescent material  22 . Alternately, the refractive electrodes  54 A and  54 B may be made from a metal electrode. The refractive electrodes  54 A and  54 B have first protrusions  52 A and  52 C connected to the sustaining electrode pair  50 A and  50 B, respectively, and second protrusions  52 B and  52 D bent in the longitudinal direction of the sustaining electrode pair  50 A and  50 B at the ends of the first protrusions  52 A and  52 C, respectively. Each of the first protrusions  52 A and  52 C are located at a position overlapping with a barrier rib  24 , that is, at a boundary between the cells. On the front substrate  40  provided with the refractive electrodes  54 A and  54 B and the sustaining electrode pair  50 A and  50 B, a dielectric layer and a protective layer (not shown) are disposed as shown in FIG.  1 . 
     In such a structure of the refractive electrodes  54 A and  54 B, as shown in FIG. 6, distances a and c between the sustaining electrode pair  50 A and  50 B and the second protrusions  52 B and  52 D are equal to a distance b between the second protrusions  52 B and  52 D. That is to say, a=b=c. Thus, if a sustaining voltage is applied to the sustaining electrode pair  50 A and  50 B, then a discharge is generated between the sustaining electrode pair  50 A and  50 B and the second protrusions  52 B and  52 D and, at the same time, a discharge is generated between the second protrusions  52 B and  52 D, and such a discharge is gradually diffused all over the cells. In other words, whenever a sustaining pulse is applied, a sustaining discharge is simultaneously initiated at three positions within the cell. If a sustaining discharge is simultaneously generated at various locations within the cell, then the brightness at a discharge initiation time is not only heightened to that extent, but also an emission efficiency and a utility factor of discharge space are improved. 
     On the other hand, if the distances a, b and C between the electrodes are not equal, then a discharge is first generated between the electrodes having the smallest distance between electrodes and thereafter a discharge is generated between the electrodes having a relatively larger distance between electrodes. 
     Referring to FIG.  7  and FIG. 8, there is shown an electrode structure of a plasma display panel (PDP) according to a second embodiment of the present invention. In FIG.  7  and FIG. 8, elements of the PDP having the same structure and function as those in FIG. 1 are given the same reference numerals. A detailed explanation as to said elements will be omitted. 
     Referring to FIG. 7, the PDP includes a sustaining electrode pair  56 A and  56 C having protrusions  56 B and  56 D extended in the width direction, and transparent electrodes  58 A and  58 B contacting the protrusions  56 B and  56 D and arranged in the longitudinal direction of the sustaining electrode pair  56 A and  56 C. The protrusions  56 B and  56 D of the sustaining electrode pair  56 A and  56 C play a role to reduce a voltage drop amount caused by the first protrusions  52 A and  52 C of the transparent electrodes  54 A and  54 B shown in FIG. 5 as well as to apply a voltage signal to the transparent electrodes  58 A and  58 B. These protrusions  56 B and  56 D are alternately formed at the opposite metal electrode pair  56 A and  56 C, and is vertically opposed to the barrier rib  24  to be positioned at a boundary between the cells. Thus, the protrusions  56 B and  56 D dose not interfere a visible light emitted from a fluorescent material  22  and progressing into the display screen. Such a sustaining electrode pair  56 A and  56 C has a three-layer structure of Ag(or Cr)—Cu—Cr. The transparent electrodes  54 A and  54 B is formed of a transparent conductive electrode material (e.g., ITO or IZO) in the longitudinal direction of the sustaining electrode pair  56 A and  56 C to simultaneously generate a sustaining discharge at a plurality of positions within the cell. 
     As shown in FIG. 8, distances a and c between the protrusions  56 B and  56 D of the sustaining electrode pair  56 A and  56 C are equal to a distance b between the transparent electrodes  58 A and  58 B. That is to say, a=b=c. Thus, if a sustaining voltage is applied to the sustaining electrode pair  56 A and  56 C, then a discharge is initiated simultaneously at the distances between the protrusions  56 B and  56 D and the transparent electrodes  58 A and  58 B and at the distance between the transparent electrodes  58 A and  58 B. 
     Referring to FIG.  9 A through FIG. 11C, there are shown electrode structures of a plasma display panel (PDP) according to other embodiments of the present invention. In FIG. 9A to FIG. 11C, elements of the PDP having the same structure and function as those in FIG. 1 are given the same reference numerals. A detailed explanation as to said elements will be omitted. 
     Referring to FIGS. 9A and 9B, a PDP according to a third embodiment of the present invention includes refractive electrodes  104 A and  104 B having a plurality of second protrusions  102 B and  102 D. Each of the refractive electrodes  104 A and  104 B is made from a transparent conductive electrode material or a metal. A sustaining electrode pair  100 A and  100 B are made from a metal and are connected to first protrusions  102 A and  102 C of the refractive electrodes  104 A and  104 B, respectively. The refractive electrodes  104 A and  104 B are patterned into a tree structure in such a manner that the first protrusions  102 A and  102 C are extended in the width direction of the sustaining electrode pair  100 A and  100 B and that the second protrusions  102 B and  102 D are extended in the longitudinal direction of the sustaining electrode pair  100 A and  100 B. The first protrusions  102 A and  102 C are located at a position overlapping with a barrier rib  24 , that is, at a boundary between the cells. On the front substrate  40  provided with the refractive electrodes  104 A and  104 B and the sustaining electrode pair  100 A and  100 B, a dielectric layer and a protective layer (not shown) are disposed. 
     In such a structure of the refractive electrodes  104 A and  104 B, distances between the sustaining electrode pair  100 A and  100 B and the second protrusions  102 B and  102 D are equal to a distance between the second protrusions  102 B and  102 D. Thus, if a sustaining voltage is applied to the sustaining electrode pair  100 A and  100 B, then a discharge is generated between the sustaining electrode pair  100 A and  100 B and the second protrusions  102 B and  102 D and, at the same time, a discharge is generated between the second protrusions  102 B and  102 D, and such a discharge is gradually diffused all over the cells. In other words, whenever a sustaining pulse is applied, a sustaining discharge is simultaneously initiated at a plurality of positions within the cell. Alternately, the distances between the sustaining electrode pair  100 A and  100 B and the second protrusions  102 B and  102 D may be different from the distance between the second protrusions  102 B and  102 D. In this case, a discharge is initiated between the electrodes having a narrow distance between electrodes and just thereafter a discharge is generated between the electrodes having a relatively wider distance between electrodes. 
     By the way, in the first embodiment as described earlier, distances between the second protrusions  52 B and  52 D of the refractive electrodes  54 A and  54 B or distances between the second protrusions  52 B and  52 D and the sustaining electrode pair  50 A and  50 B must be adjusted narrowly so that a stable discharge can be generated at a low voltage. In order to narrow the distance between electrodes, widths of the second protrusions  52 B and  52 D must be enlarged. However, if the second protrusions  52 B and  52 D are enlarged, then an aperture ratio is reduced to that extent. As compared with this, the refractive electrodes  104 A and  104 B shown in FIGS. 9A and 9B have a greater number of second protrusions  102 B and  102 D to narrow a distance between the electrodes, it is unnecessary to enlarge the second protrusions  102 B and  102 D. 
     Referring to FIG. 10, a PDP according to a fourth embodiment of the present invention includes refractive electrodes  114 A and  114 B having a plurality of second protrusions  112 B and  112 D extended at an incline of a certain angle from first protrusions  112 A and  112 C. Each of the refractive electrodes  114 A and  114 B is made from a transparent conductive electrode material or a metal. A sustaining electrode pair  110 A and  110 B is made from a metal and are connected to first protrusions  112 A and  112 C of the refractive electrodes  114 A and  114 B, respectively. The refractive electrodes  114 A and  114 B are patterned into a tree structure in such a manner that the first protrusions  112 A and  112 C are extended in the width direction of the sustaining electrode pair  110 A and  110 B and that the second protrusions  112 B and  112 D are inclined at a desired angle. The first protrusions  112 A and  112 C are located at a position overlapping with a barrier rib  24 , that is, at a boundary between the cells. On the front substrate  40  provided with the refractive electrodes  114 A and  114 B and the sustaining electrode pair  110 A and  110 B, a dielectric layer and a protective layer (not shown) are disposed. 
     In such a structure of the refractive electrodes  114 A and  114 B, distances between the second protrusions  112 B and  112 D are equal. Thus, if a sustaining voltage is applied to the sustaining electrode pair  110 A and  110 B, then a discharge is generated between the second protrusions  112 B and  112 D, and is gradually diffused all over the cells. 
     Such refractive electrodes  114 A and  114 B has a narrow distance between electrodes because the number of second protrusions  112 B and  112 D is large, so that it is easy to adjust a distance between electrodes and it is unnecessary to enlarge the second protrusions  112 B and  112 D. Alternatively, the distances between the second protrusions  112 B and  112 D may be different. 
     In such an electrode structure, since the second protrusions  112 B and  112 D are inclined at a desired angle, they have a larger length than the second protrusions extended in the horizontal direction in the earlier embodiments. Accordingly, a discharge path between the second protrusions  112 B and  112 D becomes longer and a discharge area becomes larger in comparison to the earlier embodiments. 
     Referring to FIGS. 11A to  11 C, a PDP according to a fifth embodiment of the present invention includes refractive electrodes  124 A and  124 B that have first protrusions  122 A and  122 D perpendicular to a sustaining electrode pair  120 A and  120 B, a plurality of second protrusions  122 B and  122 E extended at an incline of a certain angle from the first protrusions  122 A and  122 D, and third protrusions  122 C and  122 F opposed, in parallel, to the sustaining electrode pair  120 A and  120 B, respectively. Each of the refractive electrodes  124 A and  124 B is made from a transparent conductive electrode material or a metal. The sustaining electrode pair  120 A and  120 B are made from a metal and are connected to the first protrusions  122 A and  122 D of the refractive electrodes  124 A and  124 B, respectively. The first protrusions  122 A and  122 C are located at a position overlapping with a barrier rib  24 , that is, at a boundary between the cells. On a front substrate  40  provided with the refractive electrodes  124 A and  124 B and the sustaining electrode pair  120 A and  120 B, a dielectric layer and a protective layer (not shown) are disposed. 
     In such a structure of the refractive electrodes  124 A and  124 B, distances between the second protrusions  122 B and  122 E are equal to distances between the sustaining electrode pair  120 A and  120 B and the third protrusions  122 C and  122 F. Thus, if a sustaining voltage is applied to the sustaining electrode pair  120 A and  120 B, then a discharge is generated between the second protrusions  122 B and  122 E and, at the same time, a discharge is generated between the sustaining electrode pair  120 A and  120 B and the third protrusions  122 C and  122 F, and such a discharge is gradually diffused all over the cells. Alternately, the distances between the second protrusions  122 B and  122 E may be different from the distance between the sustaining electrode pair  120 A and  120 B and the third protrusions  122 C and  122 F. 
     As described above, according to the present invention, each of the sustaining electrodes has a refractive structure such that a discharge between the sustaining electrodes is generated at a plurality of positions, thereby simultaneously generating a sustaining discharge at a plurality of positions within the cell. Accordingly, the brightness can be improved. Furthermore, the transparent electrodes are reduced to lower a voltage drop amount caused by the transparent electrodes, so that the power consumption can be reduced. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.