Abstract:
A plasma display panel and a driving method thereof that are capable of improving the brightness and the discharge efficiency. In the plasma display panel, an auxiliary electrode pair causes an auxiliary discharge. An area of the auxiliary electrode at the periphery of a discharge cell is wider than that at the center of the discharge cell. A sustaining electrode pair is arranged at each side of the auxiliary electrode pair to cause a sustaining discharge by utilizing the auxiliary discharge. In the driving method, wall charges concentrate on the center portion of the discharge cell during an auxiliary discharge generated between the auxiliary electrode pair. Then, a sustaining discharge is generated between the sustaining electrode pair by utilizing the wall charges produced by the auxiliary discharge.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a flat panel display device, and more particularly to a plasma display panel that is capable of improving the discharge efficiency and the brightness. Also, the present invention is directed to a method of driving said plasma display panel. 
     2. Description of the Related Art 
     Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system. The DC-type PDP causes an opposite discharge between an anode and a cathode provided at a front substrate and a rear substrate, respectively to display a picture. On the other hand, the AC-type PDP allows an alternating voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Since such an AC-type PDP uses a dielectric material which allows a wall charge to be accumulated on the surface thereof upon discharge, it produces a memory effect. 
     Referring to FIG. 1, the AC-type PDP includes a front substrate  1  provided with a sustaining electrode pair  10 , and a rear substrate  2  provided with an address electrode  4 . The front substrate  1  and the rear substrate  2  are spaced in parallel to each other with having barrier ribs  3  therebetween. A mixture gas, such as Ne−Xe or He−Xe, etc., is injected into a discharge space defined by the front substrate  1 , the rear substrate  2  and the barrier ribs  3 . The sustaining electrode  10  makes a pair by two within a single of plasma discharge channel. Any one of the sustaining electrode pair  10  is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode  4  while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes  10 . Also, the remaining one of the sustaining electrode pair  10  is used as a common sustaining electrode to which a sustaining pulse is applied commonly. On the front substrate  1  provided with the sustaining electrodes  10 , a dielectric layer  8  and a protective layer  9  are disposed. The dielectric layer  8  is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film  9  prevents a damage of the dielectric layer  8  caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film  9  is usually made from MgO. The barrier ribs  3  for dividing the discharge space are extended perpendicularly at the rear substrate  2 . On the surfaces of the rear substrate  2  and the barrier ribs  3 , a fluorescent material  5  excited by a vacuum ultraviolet lay to generate a visible light is provided. 
     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 discharge pixel cells on which a data is to be displayed are selected by the address discharge in the address interval. The selected discharge pixel 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. However, the three-electrode, AC surface-discharge PDP has problems in that, since a voltage required for the sustaining discharge is high, the power consumption is large and that the discharge and light-emission efficiency upon sustaining-discharge between the sustaining electrode pair is low. 
     In order to solve these problems of the three-electrode, AC surface-discharge PDP, there has been suggested a PDP provided with four sustaining electrodes. 
     Referring to FIG.  2  and FIG. 3, the conventional five-electrode PDP includes a sustaining electrode pair  13  and  16  and a trigger electrode pair  30  and  36  formed on a front substrate  20 , and an address electrode  17  formed on a rear substrate  18 . The trigger electrode pair  30  and  36  is provided between the sustaining electrode pair  13  and  16  to cause a trigger discharge by a wall voltage produced upon address-discharge and an application voltage, thereby initiating a sustaining electrode. The sustaining electrode pair  13  and  16  forms a pair within a single plasma discharge channel. Any one of the sustaining electrode pair  13  and  16  is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode  17  while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrode  13  or  16 . Also, the remaining one of the sustaining electrode pair  13  and  16  is used as a common sustaining electrode to which a sustaining pulse is applied commonly. The sustaining electrode pair  13  and  16  causes a sustaining discharge by a wall voltage formed by the trigger discharge generated between the trigger electrode pair  30  and  36  and an application voltage. The sustaining electrode pair  13  and  16  and the trigger electrode pair  30  and  36  have a line width smaller than transparent electrodes  28  and  34  and includes metal bus electrodes  26  and  32  formed at one edge of the transparent electrodes  28  and  34 , respectively. A dielectric layer  23  and a protective layer  24  are disposed on the front substrate  20  to cover the sustaining electrode pair  13  and  16  and the trigger electrode pair  30  and  36 . Wall charges produced upon plasma display are accumulated in the dielectric layer  23 . The protective film  24  prevents a damage of the dielectric layer  23  caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. Barrier ribs  25  and a fluorescent material  22  are formed on the rear substrate  18  provided with the address electrode  17 . 
     When the sustaining electrode pair  13  and  16  of the five-electrode PDP is compared with the sustaining electrode pair  10  of the three-electrode PDP, a distance between the sustaining electrode pair  13  and  16  is longer than that between the electrode pair  10 . Thus, the five-electrode PDP has a better light-emission efficiency than the three-electrode PDP upon discharge. 
     However, as shown in FIG. 4, the five-electrode PDP concentrates the sustaining discharge upon the middle portion of the discharge cell. The PDP having such a structure has a problem in that only a portion of energy produced upon sustaining-discharge excites the fluorescent material. In other words, only a portion of energy produced during the sustaining discharge excites the fluorescent material while the remaining energy other than the energy exciting the fluorescent material emerges an excessive current flowing the electrodes. As a result, the PDP has a large power consumption and a low discharge and light-emission efficiency. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a plasma display panel and a driving method thereof that are capable of improving the discharge efficiency as well as the brightness. 
     In order to achieve these and other objects of the invention, a plasma display panel according to one aspect of the present invention includes an auxiliary electrode pair for causing an auxiliary discharge in which its area at the periphery of a discharge cell is wider than that at the center of the discharge cell; and a sustaining electrode pair arranged at each side of the auxiliary electrode pair to cause a sustaining discharge by utilizing the auxiliary discharge. 
     A plasma display panel according to another aspect of the present invention includes a transparent electrode formed at the sustaining electrode pair in such a manner to be separated within the discharge cell. 
     A method of driving a plasma display panel according to still another aspect of the present invention includes the steps of enlarging an area of an auxiliary electrode pair corresponding to the center portion of a discharge cell to concentrate wall charges on the center portion of the discharge cell during an auxiliary discharge generated between the auxiliary electrode pair; and causing a sustaining discharge between a sustaining electrode pair by utilizing the wall charges produced by the auxiliary discharge. 
     A method of driving a plasma display panel according to still another aspect of the present invention includes the steps of causing an auxiliary discharge between a trigger electrode pair; and simultaneously causing a plurality of sustaining discharge within a discharge cell using an auxiliary electrode pair. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic perspective view showing the structure of a conventional three-electrode plasma display panel; 
     FIG. 2 is a schematic perspective view showing the structure of a conventional five-electrode plasma display panel; 
     FIG.  3  and FIG. 4 are plan views showing a discharge cell structure of the conventional five-electrode plasma display panel; 
     FIG. 5 is a plan view showing a discharge cell structure of a plasma display panel according to a first embodiment of the present invention; 
     FIG. 6 is a plan view showing a discharge cell structure of a plasma display panel according to a second embodiment of the present invention; 
     FIG. 7 is a plan view showing a discharge cell structure of a plasma display panel according to a third embodiment of the present invention; and 
     FIG. 8 is a plan view showing a discharge cell structure of a plasma display panel according to a fourth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 5, there is shown a five-electrode plasma display panel (PDP) according to a first embodiment of the present invention. The five-electrode PDP includes a sustaining electrode pair  42  and  44  and a trigger electrode pair  46  and  48  formed on a front substrate (not shown). The sustaining electrode pair  42  and  44  forms a pair within a single plasma discharge channel. Any one of the sustaining electrode pair  42  and  44  is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with an address electrode (not shown) while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrode  42  or  44 . Also, the remaining one of the sustaining electrode pair  42  and  44  is used as a common sustaining electrode to which a sustaining pulse is applied commonly. The trigger electrode pair  46  and  48  has wings  46 A,  46 B and  48 A,  48 A formed symmetrically at each side of the center portion A′. The trigger electrode pair  46  and  48  are provided between the sustaining electrode pair  42  and  44  to cause a trigger discharge by a wall voltage produced by the address discharge and an application voltage, thereby initiating a sustaining discharge. The trigger electrode pair  46  and  48  receives an AC trigger pulse voltage in the sustaining interval to cause an auxiliary discharge. Just after the auxiliary discharge is generated, a sustaining pulse is applied to the sustaining electrode  42 . Then, the sustaining electrode pair  42  and  44  can generate a discharge by a priming effect caused by the auxiliary discharge, wall charges accumulated in the discharge cell and a voltage difference caused by the sustaining pulse. Such a sustaining discharge is continuously generated by the sustaining pulse and the trigger pulse. 
     Accordingly, in the PDP according to the first embodiment, the wings are formed at the center portions of the trigger electrodes such that the center portions of the trigger electrodes have a wide electrode area. Thus, since the wall charges are concentrated in the area around the wings of the trigger electrodes when the auxiliary discharge has been generated within the discharge cell, a voltage applied to the discharge cell becomes high even though a low voltage is applied to the trigger electrodes from the exterior. Therefore, the sustaining discharge can be maintained by an application of a low trigger voltage. 
     Referring to FIG. 6, there is shown a five-electrode PDP according to a second embodiment of the present invention. The five-electrode PDP includes a sustaining electrode pair  42  and  44  and a trigger electrode pair  50  and  52  formed on a front substrate (not shown). The sustaining electrode pair  42  and  44  forms a pair within a single plasma discharge channel. Any one of the sustaining electrode pair  42  and  44  is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with an address electrode (not shown) while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrode  42  or  44 . Also, the remaining one of the sustaining electrode pair  42  and  44  is used as a common sustaining electrode to which a sustaining pulse is applied commonly. The trigger electrode pair  50  and  52  have wings  50 A and  52 A formed symmetrically at the outside of the center portion B. The trigger electrode pair  50  and  52  are provided between the sustaining electrode pair  42  and  44  to cause a trigger discharge by a wall voltage produced by the address discharge and an application voltage, thereby initiating a sustaining discharge. The trigger electrode pair  46  and  48  receives an AC trigger pulse voltage in the sustaining interval to cause an auxiliary discharge. Just after the auxiliary discharge is generated, a sustaining pulse is applied to the sustaining electrode  42 . Then, the sustaining electrode pair  42  and  44  can generate a discharge by a priming effect caused by the auxiliary discharge, wall charges accumulated in the discharge cell and a voltage difference caused by the sustaining pulse. Such a sustaining discharge is continuously generated by the sustaining pulse and the trigger pulse. 
     Accordingly, in the PDP according to the second embodiment, the wings are formed at the center portions of the trigger electrodes such that the center portions of the trigger electrodes have a wide electrode area. Thus, since the wall charges are concentrated in the area around the wings of the trigger electrodes when the auxiliary discharge has been generated within the discharge cell, a voltage applied to the discharge cell becomes high even though a low voltage is applied to the trigger electrodes from the exterior. Therefore, the sustaining discharge can be maintained by an application of a low trigger voltage. 
     Referring to FIG. 7, there is shown a five-electrode PDP according to a third embodiment of the present invention. The five-electrode PDP includes a sustaining electrode pair  42  and  44  and a trigger electrode pair  54  and  56  formed on a front substrate (not shown). The sustaining electrode pair  42  and  44  forms a pair within a single plasma discharge channel. Any one of the sustaining electrode pair  42  and  44  is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with an address electrode (not shown) while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrode  42  or  44 . Also, the remaining one of the sustaining electrode pair  42  and  44  is used as a common sustaining electrode to which a sustaining pulse is applied commonly. The trigger electrode pair  54  and  56  has wings  54 A and  56 A formed oppositely at the inside of the center portion B′. The trigger electrode pair  54  and  56  are provided between the sustaining electrode pair  42  and  44  to cause a trigger discharge by a wall voltage produced by the address discharge and an application voltage, thereby initiating a sustaining discharge. The trigger electrode pair  46  and  48  receives an AC trigger pulse voltage in the sustaining interval to cause an auxiliary discharge. Just after the auxiliary discharge is generated, a sustaining pulse is applied to the sustaining electrode  42 . Then, the sustaining electrode pair  42  and  44  can generate a discharge by a priming effect caused by the auxiliary discharge, wall charges accumulated in the discharge cell and a voltage difference caused by the sustaining pulse. Such a sustaining discharge is continuously generated by the sustaining pulse and the trigger pulse. 
     Accordingly, in the PDP according to the third embodiment, the wings are formed at the center portions of the trigger electrodes such that the center portions of the trigger electrodes have a wide electrode area. Thus, since the wall charges are concentrated in the area around the wings of the trigger electrodes when the auxiliary discharge has been generated within the discharge cell, a voltage applied to the discharge cell becomes high even though a low voltage is applied to the trigger electrodes from the exterior. Therefore, the sustaining discharge can be maintained by an application of a low trigger voltage. 
     Referring to FIG. 8, there is shown a five-electrode PDP according to a fourth embodiment of the present invention. The five-electrode PDP includes a sustaining electrode pair  64  and  74  formed, in parallel to each other, at each boundary portion of a discharge cell and having transparent electrodes  60 ,  62 ,  70  and  72  and metal bus electrodes  66  and  76 , and a trigger electrode pair  82  and  88  formed, in parallel to each other, at a narrow distance between the sustaining electrode pair  64  and  74  and having transparent electrodes  80  and  86  and metal bus electrodes  78  and  84 . 
     The sustaining electrode pair  65  and  74  forms a pair within a single plasma discharge channel. Any one of the sustaining electrode pair  64  and  74  is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with an address electrode (not shown) while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrode  64  or  74 . Also, the remaining one of the sustaining electrode pair  64  and  74  is used as a common sustaining electrode to which a sustaining pulse is applied commonly. The transparent electrodes  60 ,  62 ,  70  and  72  formed on the metal bus electrodes  66  and  76  are separately patterned at each boundary portion of the discharge cell such that the sustaining discharge is generated at each edge of the discharge cell. Thus, a distance between the sustaining electrode pair  64  and  74  at the center portion of the discharge cell becomes different from that at the edge portion thereof. In other words, a distance between the sustaining electrode pair  64  and  74  is spaced with a wide distance at the center portion of the discharge cell while being spaced with a relatively narrow distance at each edge portion of the discharge cell. The transparent electrodes  80  and  86  of the trigger electrode pair  82  and  88  are arranged at each intersection between them and the address electrode to be formed only at the center portion of the discharge cell. Thus, since an area occupied by the transparent electrodes  80  and  86  of the trigger electrode pair  82  and  88  within the discharge cell is small, the trigger electrode pair  82  and  88  have a dielectric constant and a capacitance lower than the conventional trigger electrode pair. As a result, a leakage current caused by a high dielectric constant and a high capacitance of the trigger electrode pair  82  and  88  can be reduced, and a current value applied to the trigger electrode pair  82  and  88  can be reduced. Also, since the transparent electrodes  80  and  86  of the trigger electrode pair  82  and  88  are positioned only at the center portion of the discharge cell, the sustaining electrode pair  64  and  74  positioned at each edge of the discharge cell can effectively generate a sustaining discharge. 
     Accordingly, in the PDP according to the fourth embodiment, a reset pulse is applied to any one of the sustaining electrode pair  64  and  74  or the trigger electrode pair  82  and  88  arranged within all of the discharge cells so as to initialize all of the discharge cells of the panel, thereby causing a reset discharge. During the reset discharge, wall charges are produced for each discharge cell to lower a discharge voltage required for an address discharge. Then, a scanning pulse is applied to the sustaining electrode  74  and a data pulse is applied to the address electrode in synchronization with the scanning pulse, thereby generating an address discharge between two electrodes. Wall charges are formed at the dielectric layers of the upper and lower substrates by the address discharge. The wall charges formed in this manner lower a discharge voltage required for the sustaining discharge and the auxiliary discharge. In the discharge cells selected by the address discharge, the trigger electrode pair  82  and  88  provided between the sustaining electrode pair  64  and  74  are positioned at the center portion of the discharge cell to receive an AC trigger pulse voltage in the sustaining interval, thereby causing an auxiliary discharge. In such a discharge process, the wall charges are formed at the trigger electrode pair  82  and  88  and space charges are diffused into the entire space of the cell at which a discharge has been generated. The sustaining electrode pair  64  and  74  are arranged at a mutually wide distance at each outer side of the trigger electrode pair  82  and  88  to simultaneously receive a desired level of AC pulse voltage alternately with any one of the trigger electrode pair  82  and  88 . The sustaining electrode pair  64  and  74  supplied with the AC pulse voltage simultaneously generates a plurality of sustaining discharge at each edge of the discharge cell by utilizing the space charges formed by the auxiliary discharge and the wall charges at the trigger electrode pair  82  and  88 . Such a sustaining discharge is continuously generated by the sustaining pulse and the trigger pulse. 
     Accordingly, in the PDP according to the fourth embodiment, a plurality of sustaining discharge are simultaneously generated at each edge of the discharge cell with having the transparent electrodes of the trigger electrode pair therebetween. Thus, an energy produced upon sustaining-discharge is dispersed into each edge of the discharge cell to excite the fluorescent material, so that an excessive current emerging by an energy fed back to the electrodes can be minimized. As a result, the present PDP has advantages of a reduced power consumption and an enhanced discharge and light-emission efficiency. 
     As described above, according to the present invention, the wings are formed at the center portions of the trigger electrodes such that the center portions of the trigger electrode pair have a wide electrode area, and the transparent electrodes at the sustaining electrode pair are formed in such a manner to be spaced at the edge thereof. Thus, a plurality of sustaining discharge is simultaneously generated at each edge of the discharge cell with having the transparent electrodes of the trigger electrode pair therebetween. Thus, an energy produced upon sustaining-discharge is dispersed into each edge of the discharge cell to effectively excite the fluorescent material. Accordingly, the discharge and light-emission efficiency can be improved, and an excessive current emerging by an energy fed back to the electrodes can be minimized. As a result, the present PDP has a reduced power consumption and an improved brightness in comparison with the prior art. 
     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.