Patent Publication Number: US-2007097053-A1

Title: Plasma display apparatus with differing-size protrusion electrodes

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application is a divisional application of U.S. patent application Ser. No. 10/803,380, filed on Mar. 18, 2004 which claims priority to and the benefit of Korea Patent Application No. 2003-16855 filed on Mar. 18, 2003 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      (a) Field of the Invention  
      The present invention relates to a plasma display panel (PDP) apparatus and a driving method thereof.  
      (b) Description of the Related Art  
      The PDP is a flat panel display that uses plasma generated by gas discharge to display characters or images and includes, according to its size, more than several scores to millions of pixels arranged in a matrix pattern.  
      Scan electrodes and sustain electrodes are formed in parallel on one side of the PDP, and address electrodes crossing them are formed on another side thereof. The sustain electrodes are formed corresponding to the respective scan electrodes, and ends of the sustain electrodes are coupled in common.  
      The method for driving the AC PDP includes a reset period, an addressing period, a sustain period, and an erase period, in temporal sequence.  
      The reset period is for initiating the status of each cell so as to facilitate the addressing operation. The addressing period is for selecting turn-on/off cells and applying an address voltage to the turn-on cells (i.e., addressed cells) to accumulate wall charges. The sustain period is for applying sustain pulses and causing a sustain for displaying an image on the addressed cells. The erase period is for reducing the wall charges of the cells to terminate the sustain.  
      A general PDP pixel has red (R), green (G), and blue (B) discharge cells. An address electrode is provided in a single discharge cell, and protrusions of the scan electrode and the sustain electrode face each other with a predetermined protrusion gap therebetween. A discharge cell is selected by an address pulse applied to an address electrode and a scan pulse applied to a scan pulse in an address interval. A discharge cell selected in the address interval is discharged by sustain pulses respectively applied to a scan electrode and a sustain electrode in a sustain interval.  
      Regarding a discharge phenomenon in the sustain interval light emission at cathodes of scan and sustain electrodes is greater that at anodes thereof as shown in  FIG. 1 . Since the size of the cathode that manifests ⅔ of the total emission is the same as that of the anode in the prior art, an area for diffusing a discharge at a cathode is reduced, and the luminance is accordingly lost.  
     SUMMARY OF THE INVENTION  
      In one exemplary embodiment of the present invention, there is provided a PDP apparatus for diffusing a discharge of a cathode that substantially manifests ⅔ of the total light emission.  
      In an exemplary embodiment of the present invention is provided a PDP apparatus which includes a first substrate. A plurality of first electrodes is provided in the row direction on the first substrate. A plurality of second electrodes is provided in the row direction on the first substrate, formed between two adjacent first electrodes. The first electrode and the second electrode face each other with a predetermined electrode gap therebetween. A sustain discharge is generated by a potential difference between the first electrode and the second electrode. An area of the first electrode is larger than that of the second electrode.  
      In another exemplary embodiment, the first electrode has a first protrusion formed in the column direction. The second electrode has a second protrusion formed in the column direction. The first protrusion and the second protrusion face each other with the predetermined protrusion gap therebetween. An area of the first protrusion is larger than that of the second protrusion.  
      In yet another exemplary embodiment, a column-directional length of the first protrusion is longer than a column-directional length of the second protrusion.  
      In still another exemplary embodiment, a row-directional width of the first protrusion is greater than a row-directional width of the second protrusion.  
      In a further exemplary embodiment, the PDP further includes a second substrate facing the first substrate with a substrate gap therebetween. A plurality of third electrodes is provided in the column direction on the second substrate, wherein an address discharge is generated by a potential difference between the third and first electrodes.  
      In a yet further exemplary embodiment, a first sustain pulse is applied to the first electrode and a second sustain pulse is applied to the second electrode in the sustain interval. A voltage of the first sustain pulse is less than a voltage of the second sustain pulse in a first interval. A voltage of the first sustain pulse is greater than a voltage of the second sustain pulse in a first interval. A voltage of the second sustain pulse in the second interval is less than a voltage obtained by subtracting a minimum voltage for generating a sustain from the voltage of the first sustain pulse.  
      In another exemplary embodiment of the present invention is provided a method for driving a PDP apparatus. A first electrode and a second electrode are formed in parallel on a first substrate. An address electrode crossing the first and second electrodes is formed on a second substrate. The PDP apparatus generates an address according to a potential difference between the first electrode and the address electrode. The method includes, in a sustain interval, applying a first sustain pulse with a first voltage to the first electrode. A second sustain pulse is applied with a second voltage less than the first voltage to the second electrode to generate a sustain. A first sustain pulse is applied with a third voltage to the first electrode. A second sustain pulse is applied with a fourth voltage greater than the third voltage to the second electrode to generate a sustain, wherein the first and second electrodes face each other with a predetermined electrode gap therebetween. The first electrode has an area greater than that of the second electrode.  
      In yet another exemplary embodiment, the second voltage is less than a voltage obtained by subtracting a minimum voltage for generating a sustain from the first voltage.  
      In still another exemplary embodiment, an interval during which the first sustain pulse has the third voltage is longer than an interval during which the first sustain pulse has the first voltage.  
      In a further exemplary embodiment, the first and second electrodes respectively have protrusions, and the protrusion of the first electrode has an area wider than that of the protrusion of the second electrode. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a discharge phenomenon at scan and sustain electrodes of a PDP.  
       FIG. 2  shows a simplified perspective view of a PDP apparatus according to an exemplary embodiment of the present invention.  
       FIGS. 3A and 3B  show a configuration of an electrode of a PDP according to an exemplary embodiments of the present invention shows a configuration of an electrode of a PDP according to an exemplary embodiment of the present invention.  
       FIGS. 4 through 7  show PDP drive waveforms according to first through fourth exemplary embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION  
      As shown in  FIGS. 2, 3A  and  3 B, the PDP includes two substrates  1  and  2  facing each other with a predetermined substrate gap  100  therebetween. A plurality of scan electrodes (Y electrodes)  10  and a plurality of sustain electrodes (X electrodes)  20  are alternately provided in the row direction on substrate  1 . Protrusions  11  ( 11   a  and  11   b ) are respectively formed on the top and the bottom of scan electrode  10 , and protrusions  21  ( 21   a  and  21   b ) are respectively formed on the top and the bottom of sustain electrode  20 . Protrusions  11  and  21  of scan and sustain electrodes  10  and  20  operate for a discharge. Top protrusion  11   a  of scan electrode  10  and bottom protrusion  21   b  of sustain electrode  20  face each other with a predetermined protrusion gap  51  therebetween, and bottom protrusion  11   b  of scan electrode  10  and top protrusion  21   a  of sustain electrode  20  face each other with a predetermined protrusion gap  52  therebetween. Protrusions  11  and  21  are made of a transparent dielectric material including ITO (indium tin oxide). Transparent dielectric layer  30  and protection layer  40  are formed on scan and sustain electrodes  10  and  20  and protrusions  11  and  21  to cover substrate  1 .  
      A plurality of address electrodes  110  covered with dielectric layer  120  is formed in the column direction on substrate  2 . A space determined by address electrode  110  and adjacent scan and sustain electrodes  10  and  20  forms a discharge cell. Address electrodes  110  formed at protrusions  11  and  21  of scan electrodes  10  and  20  can have a wide width for easy discharge.  
      A barrier rib (not illustrated) can be formed on dielectric layer  120  to partition the discharge cell, which is referred to as a closed structure. Further, the barrier rib may not be formed, or part of the barrier rib in the closed structure can be removed.  
      Referring to  FIGS. 2, 3A  and  3 B, top and bottom protrusions  11   a  and  11   b  of scan electrode  10  are alternately formed, and top and bottom protrusions  21   a  and  21   b  of sustain electrode  20  are alternately formed. R, G, and B phosphors are applied to three discharge cells that are adjacent in a triangular format, and R, G, and B discharge cells  140 R,  140 G, and  140 B form single pixel  140 , which is referred to as a delta structure. In addition, top protrusions  11   a  and  21   a  and bottom protrusions  11   b  and  21   b  can be provided in the column direction and in parallel. R, G, and B phosphors are applied to three discharge cells that are adjacent in the row direction, and the R, G, and B discharge cells form a single pixel, which is referred to as a stripe structure.  
      As shown in  FIGS. 2 and 3 A, a column-directional length of protrusion  11  formed at scan electrode  10  is longer than a column-directional length of protrusion  21  formed at sustain electrode  20 . Address discharges occur between address electrodes  110  and scan electrodes  10  in the address interval. In the first exemplary embodiment, an area where address and scan electrodes  110  and  10  face each other increases to stably generate an address discharge. As shown in  FIG. 1 , substantially ⅔ of the total light emission is generated at the cathode in the sustain interval. Therefore, when a voltage applied to scan electrode  10  is less than a voltage applied to sustain electrode  20  in the sustain interval, that is, when scan electrode  10  operates as a cathode with respect to sustain electrode  20 , light emission is more effectively performed because the length of protrusion  11  of scan electrode  10  is long.  
      The column-directional length of protrusion  11  of scan electrode  10  is increased in the exemplary embodiment, and further, a width of protrusion  11  can be greater than that of protrusion  22  of sustain electrode  20  ( FIG. 3B ), and an area of protrusion  11  can be greater than that of protrusion  21 .  
      In addition, when scan electrode  10  operates as a cathode, a sustain pulse, such as that depicted in  FIG. 4 , can be applied to scan electrodes  10  and sustain electrodes  20  so as to maintain a sufficient discharge time. Referring still to  FIG. 4 , a PDP apparatus drive method according to the first exemplary embodiment of the present invention will now be described. In the first embodiment, it is assumed that a sustain pulse alternately having voltages Vs/2 and −Vs/2 is applied to scan electrodes  10  and sustain electrodes  10   20  so that a potential difference of two electrodes  10  and  20  may be voltage Vs in the sustain interval, voltage Vs being a voltage for allowing the generation of a sustain discharge. It is also possible to apply another type of a pulse that causes the potential difference of two electrodes  10  and  20  to be voltage Vs, which will be applicable to the first through fourth exemplary embodiments.  
       FIG. 4  shows a PDP apparatus drive waveform according to the first exemplary embodiment of the present invention. Negative voltage Vy 2  is applied to scan electrode  10  and positive voltage Vx 1  is applied to sustain electrode  20  in interval T 1  of a single sustain pulse in the sustain interval. Since scan electrode  10  with a long protrusion compared to that of sustain electrode  20  in interval T 1  operates as a cathode, a discharge diffusion time at protrusion  11  of scan electrode  10  increases to increase the luminance. In this instance, interval T 1  for applying a negative voltage to scan electrode  10  is lengthened so as to maintain voltages Vy 2  and Vx 1  applied to scan electrodes  10  and sustain electrodes  20  while maintaining the discharge. Interval T 2  for applying negative voltage Vx 2  t 6  sustain electrode  20  is reduced by the increment of interval T 1  so as to maintain a total number of sustain pulses in the sustain interval.  
      In the first embodiment, the length of protrusion  11  of scan electrode  10  is established to be longer than that of protrusion  21  of sustain electrode  20 , and the interval for applying a negative voltage to scan electrode  10  is set to be longer than that for applying a negative voltage to sustain electrode  20 . As a result, the area of protrusion  11  of scan electrode  10  becomes greater to improve address discharge efficiency during the address interval, and an interval for applying a negative voltage to scan electrode  10  increases to increase the luminance.  
      However, since the length of protrusion  21  is short in interval T 2  during which sustain electrode  20  operates as a cathode, the discharge diffusion time shortens, and hence, the luminance can be reduced in interval T 2 . With reference to  FIGS. 5 through 7 , methods for compensating for the luminance in interval T 2  during which sustain electrode  20  operates as a cathode will now be described.  
       FIGS. 5 through 7  show PDP drive waveforms according to second through fourth exemplary embodiments of the present invention.  
      Referring to  FIG. 5 , levels of negative voltages Vx 2  and Vy 2  are lowered in the sustain pulse according to the second embodiment compared to the sustain pulse of  FIG. 4 . That is, intensities of negative voltages Vx 2  and Vy 2  are made greater than those of positive voltages Vx 1  and Vy 1 , and are applied to sustain and scan electrodes  20  and  10 . Accordingly, when negative voltage Vx 2  is applied to sustain electrode  20  in interval T 2 , a potential difference between sustain electrode  20  and scan electrode  10  and a potential difference between address electrode  110  and sustain electrode  20  are increased to improve the luminance. That is, when sustain electrode  20  operates as a cathode in interval T 2 , shortened protrusion  21  of sustain electrode  20  can be compensated by increasing the potential difference between scan electrode  10  and sustain electrode  20 , and since the intensity of negative voltage Vy 1  of scan electrode  10  is also Increased, the luminance is further improved when scan electrode  10  operates as a cathode.  
      The intensity of the negative voltage applied to scan electrode  10  is increased in the second embodiment, and differing from this, a pulse (i.e., a pulse shown as a dotted line in  FIG. 5 ) corresponding to the existing sustain pulse can be applied to scan electrode  10 .  
      In the sustain pulse according to the third embodiment, referring to  FIG. 6 , levels of negative voltages Vx 2  and Vy 2  of the sustain pulse of  FIG. 4  are lowered in the like manner of the second embodiment. Interval T 1  for applying a negative voltage to scan electrode  10  is lengthened, and interval T 2  for applying a negative voltage to sustain electrode  20  is shortened. As a result, the discharge diffusion time is lengthened by the length of protrusion  11  of scan electrode  10  in interval T 1  during which scan electrode  10  is a cathode to thereby increase the luminance, and since interval T 1  is long, the applied voltage is maintained during the discharge diffusion time. In interval T 2  during which sustain electrode  20  is a cathode, since negative voltage Vx 2  applied to sustain electrode  20  has been greatly increased, the potential difference between sustain electrode  20  and scan electrode  10  and the potential difference between sustain electrode  20  and address electrode  110  increase to activate the discharge and improve the luminance.  
      Referring to  FIG. 7 , in the sustain pulse according to the fourth embodiment, the negative voltage applied to scan electrode  10  corresponds to the existing sustain pulse, differing from the third embodiment. That is, a time for applying negative voltage Vy 2  is increased to maintain the discharge when scan electrode  10  becomes a cathode, and negative voltage Vx 2  is increased to compensate for the luminance reduction when sustain electrode  20  becomes a cathode.  
      According to the present invention, an address discharge can be effectively generated because of the large size of the protrusion of the scan electrode. The discharge is maintained for a long time since the time for applying a negative voltage to the scan electrode is long. Also, the size of the protrusion of the sustain electrode is decreased to compensate for the reduced luminance since the negative voltage applied to the sustain electrode is large.  
      While this invention has been described in connection with what is presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.