Patent Abstract:
A closed type AC plasma display panel. A first substrate and a second substrate are provided with a predetermined gap therebetween. Barrier ribs are interposed between the first substrate and the second substrate. The barrier ribs define a plurality sets of a first, a second and a third discharge cell. A plurality of address electrodes is formed on the first substrate in the first, the second, and the third discharge cells along a first direction, and a plurality of sustain electrodes formed on the second substrate in the first, the second, and the third discharge cells along a second direction, wherein each area of the sustain electrodes are substantially equal and at least one area of the address electrodes is different from others area of the address electrodes in the first, the second, and the third discharge cells.

Full Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a plasma display panel. More particularly, the present invention relates to a closed cell type alternating current (AC) plasma display panel capable of improving the address margin.  
       BACKGROUND OF THE INVENTION  
       [0002]     Plasma display panels (PDPs) are classified depending on how the discharge cells thereof are arranged. Two main types of PDPs are strip PDPs, in which gas discharge spaces are arranged in a strip pattern, and closed cell PDPs, in which individual cells are defined by enclosed partition barrier ribs.  
         [0003]     Referring to  FIG. 1A , the conventional AC plasma display panel  80  is provided with a front substrate  82  and a rear substrate  83  opposing each other and separated by a discharge space. A plurality of pairs of strip scanning electrodes  86  and sustaining electrodes  87  are arranged substantially in parallel and covered with a dielectric layer  84  and a protective coating  85  on the front substrate  82 . A plurality of strip address electrodes  88  are formed substantially in parallel on the rear substrate  83  in the direction perpendicular to the scanning electrode  86  and the sustaining electrode  87 . Strip barriers  89  are arranged between the address electrodes  88 . Phosphors  90  are formed between the barriers  89  and on the sidewalls of the barriers so as to cover the address electrodes  88 . Spaces surrounded by the surface substrate  82 , the rear substrate  83  and the barriers  89  form discharge cells  91 . The spaces in the discharge cells  91  are filled with gases radiating ultraviolet light due to discharge.  
         [0004]     Referring to  FIG. 1B , the phosphor  90  comprises a blue phosphor  90   b , a green phosphor  90   g  and a red phosphor  90   r , one of which is formed in each discharge cell. Thus, the discharge cell provided with the blue phosphor  90   b  constitutes a blue discharge cell  91   b , the discharge cell provided with the green phosphor  90   g  constitutes a green discharge cell  91   g , and the discharge cell provided with the red phosphor  90   r  constitutes a red discharge cell  91   r.    
         [0005]     The above-described configuration, however, has a problem in that the discharge starting voltage of the green discharge cell  91   g  is different from that of the other two discharge cells  91   b  and  91   r .  FIG. 1C  shows write voltages necessary to perform a write discharge in a stable manner when a constant voltage is applied to the scanning electrodes  86  in the write operation in the address period (complete lighting write voltages) with respect to the discharge cells of respective colors. As described above, in the conventional panel, the discharge cells have write voltages that differ from color to color. As a result, as is clearly shown in  FIG. 1C , the discharge cells have complete lighting write voltages that are considerably different depending on their colors. Thus, applying the same write voltage to all the discharge cells can cause unstable write discharge, erroneous discharge or discharge flicker, leading to improper display.  
         [0006]     In order to perform a stable write operation, the write voltage applied to the address electrodes  88  must change depending on the colors of the discharge cells in accordance with the complete lighting write voltage of the discharge cells of respective colors. This complicates the voltage control, however, and increase the cost of the apparatus.  
       SUMMARY OF THE INVENTION  
       [0007]     Embodiments of the invention provide a cell structure for an AC plasma display panel with equivalent complete lighting write voltages of the R, G, and B discharge cells to improve the address margin of the panel.  
         [0008]     Embodiments of the present invention further provide different addressing electrode areas of respective colors for an AC plasma display panel with equivalent complete lighting write voltages of the discharge cells to improve the address margin of the panel.  
         [0009]     To achieve these and other advantages, embodiments of the invention provide a closed cell type AC plasma display panel, comprising a first substrate and a second substrate opposing the first substrate. The first substrate and the second substrate are provided with a predetermined gap therebetween. Barrier ribs are interposed between the first substrate and the second substrate. The barrier ribs define a plurality sets of a first, a second and a third discharge cell. A plurality of address electrodes are formed on the first substrate in the first, the second, and the third discharge cells along a first direction. A plurality of sustain electrodes are formed on the second substrate in the first, the second, and the third discharge cells along a second direction, wherein each area of the sustain electrodes in the first, the second, and the third discharge cells are substantially equal, and at least one area of the address electrodes in the first, the second, and the third discharge cells is different from other areas of the address electrodes in the first, the second, and the third discharge cells.  
         [0010]     It is understood that the first, the second and the third discharge cell sets corresponding to the first color, the second color, and the third color, and the discharge cells sets can be arranged in triangular shape. Each of the present individual discharge spaces is formed in a quadrangular shape or hexagonal shape. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
         [0012]      FIG. 1A  is a partially cutaway perspective view illustrating a schematic configuration of a conventional AC type plasma display panel;  
         [0013]      FIG. 1B  is a cross section of  FIG. 1A  taken along the line B-B in the direction indicated by the arrow;  
         [0014]      FIG. 1C  shows write voltages necessary to perform a write discharge in a stable manner;  
         [0015]      FIG. 2A  is a schematic front view of rear substrate of an AC type plasma display panel according to the first embodiment of the present invention;  
         [0016]      FIG. 2B  is a cross section of  FIG. 2A  taken along the line V-V in the direction indicated by the arrow;  
         [0017]      FIGS. 2C and 2D  show the shape of large electrode portions of address electrode according to the first embodiment of the present invention;  
         [0018]      FIG. 3  is schematic front view of the second substrate of an AC plasma display panel according to the second embodiment of the present invention; and  
         [0019]      FIG. 4  is a schematic front view of rear substrate of an AC plasma display panel according to the third embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
     First Embodiment  
       [0020]     The embodiment of the invention provides a closed cell type AC plasma display panel.  FIGS. 2A  to  2 D illustrate the first embodiment of the closed cell type AC plasma display panel. In a plasma display panel (PDP) according to a first embodiment of the present invention, a plurality of discharge cell sets comprising R, G, and B colors are defined by barrier ribs partition, each set a substantially along the first direction (X) to forming a closed type PDP. Each discharge cell is independently controlled to display predetermined images.  
         [0021]     Referring to  FIG. 2A , the PDP  100  includes a first substrate  102  (also known as a rear substrate) and a second substrate  101  (also known as a front substrate). Rear substrate  102  and front substrate  101  are disposed substantially in parallel with a predetermined gap therebetween.  
         [0022]     Barrier ribs  130  are disposed at a predetermined height between rear substrate  102  and front substrate  101  in a ladder-shaped pattern along the first direction (X). Barrier ribs  130  define a plurality of discharge spaces  140 R,  140 G, and  140 B. In the present embodiment of the invention, each set of discharge spaces  140 R,  140 G, and  140 B is arranged substantially in a first direction, while each of the individual discharge spaces  140 R,  140 G, and  140 B is formed in a quadrangular shape.  
         [0023]     A plurality of address electrodes  110  is formed on rear substrate  102  along the second direction (Y). Address electrodes  110  are formed both within and outside of discharge spaces  140 R,  140 G, and  140 B. Also, a first dielectric layer  106  is formed over the surface of rear substrate  102  covering address electrodes  110 .  
         [0024]     The address electrodes  110  include small electrode portions  110   a  in Y direction, and large electrode portions  110   b  formed within discharge spaces  140 R,  140 G, and  140 B. The widths of the large electrode portions  10   b  vary with different discharge spaces  140 R,  140 G, and  140 B and denote as W R , W G , W B , respectively.  
         [0025]     A plurality of sustain electrodes  120  are formed on front substrate  101  along direction X. Sustain electrodes  120  include main electrode portions  120 , which are positioned corresponding to portions of barrier ribs  130  extending along direction X, and branch electrode portions  124 , extending from main electrode portions  120  into areas corresponding to formation of discharge spaces  140 R,  140 G, and  140 B. Two branch electrode portions  124  extend from two main electrode portions  120  of different sustain electrodes in each discharge space  140 R,  140 G, and  140 B. Branch electrode portions  124  include first electrode portion  124   a  that extends perpendicularly from main electrode portions  120 , and second electrode portion  124   b  that enlarges on a distal end of first electrode portion  124   a  extending parallel to the main electrode portions  120 . Within one discharge space, a gap G P  is formed between two second electrode portions  124   b  extending into discharge space from opposite directions, that is, from two different main electrode portions  120 .  
         [0026]     In the present embodiment, a bus electrode can be formed on the main electrode portions  120 . The bus electrode comprises an opaque material, such as Ag metal or like, and the sustain electrodes  120  comprise a transparent material, such as indium tin oxide (ITO) or like. Referring to  FIG. 2B , transparent second dielectric layer  104  is formed over front substrate  101  covering sustain electrodes  120 . Additionally, protective layer  105  comprising MgO or like is formed over second dielectric layer  104 .  
         [0027]     Phosphor layers  108 R,  108 G, and  108 B are formed in discharge spaces  140 R,  140 G, and  140 B, respectively. Phosphor layers  108 R,  108 G, and  108 B cover first dielectric layer  106  and are formed extending up the side-walls of barrier ribs  130 . In present embodiment, BaMgAl 10 O 17 :Eu is used as the blue phosphor  108 B, Zn 2 SO 4 :Mn is used as the green phosphor  108 G, and (Y 2 Gd)BO 3 :Eu is used as the blue phosphor  108 B.  
         [0028]     In  FIG. 2A , address electrodes  110  include large electrode portions  110   b  positioned in discharge spaces  140 R,  140 G, and  140 B, and small electrode portions  110   a  are positioned under barrier ribs  130  between discharge spaces  140 R,  140 G, and  140 B. Large electrode portions  110   b  have widths W R , W G , and W B  that are greater than widths of the small electrode portions  110   a.    
         [0029]     The widths W R , W G , and W B  are made different depending on the material properties of the R, G, and B phosphor layers  140 R,  140 G, and  140 B. In present embodiment of the invention, widths W R , W G , and W B  of large electrode portions  110   b  for the R. G, and B pixels, respectively, satisfy the following condition. 
 
 W   B   ≦W   R   ≦W   G . 
 
         [0030]     The width W G  of the large electrode portion  110   b  for the G pixel is made larger than the widths W R  and W B  of large electrode portions  10   b  for the R pixel and the G pixel, respectively, due to the creation of wall discharges on the phosphor layers by application of the write voltage during an address period. The creation of wall charges determines lighting of discharge cells in a sustaining period. As such, the write voltage of G phosphor layer  108 G exceeds the write voltages of R and B phosphor layers  108 R and  108 B. More specifically, by varying the widths W R , W G , and W B  of large electrode portions  10   b , the address margins of the R, G, and B pixels can be improved.  
         [0031]     The shape of large electrode portions  10   b  of address electrodes  110  is not limited to a quadrangular shape and can be formed in a circular shape  110   b   C  as shown in  FIG. 2C , and various polygonal shapes such as a hexagonal shape  110   b   H  as shown in  FIG. 2D .  
         [0032]     In the present embodiment, since discharge cells of all colors have substantially the same complete lighting write voltages, with increased address margins, write operations among the discharge cells of all colors during sustaining period are uniform, thus preventing display flickering, erroneous write operations and improving the address margins and voltage margins during the sustaining period in the panel. This indicates that a stable write operation (address operation) can be achieved as shown in  FIG. 1C  (dotted line II). Furthermore, the minimum voltage necessary for writing to the discharge cells of respective colors is considerably lower compared with that necessary for the conventional panel. Thus, a low-cost integrated circuit (IC) can be used for a write pulse generating circuit.  
         [0033]     The configurations of discharge cells R, G, and B of present embodiments of the invention are not limited to a linear sequence and can be formed in triangular arrangement, while each of the individual discharge spaces R, G, and B is formed in a quadrangular shape as shown in  FIG. 3 , and various polygonal shapes such as a hexagonal shape in an overall structure of a honeycomb as shown in  FIG. 4 .  
       Second Embodiment  
       [0034]     A plurality of discharge cells  240 R,  240 G,  240 B are defined by sets of barrier ribs, each set forming a substantially triangular arrangement (i.e., delta-nabla structure) sequence to realize a closed type PDP. Each discharge cell is independently controlled to display predetermined images, and each discharge cell is quadrangular shape.  
         [0035]     Referring to  FIG. 3 , address electrodes  210  include large electrode portions  210   b  that are positioned in discharge spaces  240 R,  240 G, and  240 B, and small electrode portions  210   a  positioned under barrier ribs  130  between discharge spaces  240 R,  240 G, and  240 B. Large electrode portions  210   b  have widths W R , W G , and W B  greater than widths W R , W G , and W B  of small electrode portions  210   a.    
         [0036]     Branch electrode portions  224  include first electrode portion  224   a  that extends perpendicularly from main electrode portions  220 , and second electrode portion  224   b  that enlarges on a distal end of first electrode portion  224   a  to extend parallel to main electrode portions  220 . Within one discharge space, a gap G P  is formed between two second electrode portions  224   b  extending into the discharge space from opposite directions, that is, from two different main electrode portions  220 .  
         [0037]     The widths W R , W G , and W B  are made different depending on the material properties of the R, G, B phosphor layers  240 R,  240 G, and  240 B. In the present embodiment of the invention, the widths W R , W G , and W B  of large electrode portions  210   b  for the R, G, and B pixels, respectively, satisfy the following condition. 
 
 W   B   ≦W   R   ≦W   G . 
 
         [0038]     The width W G  of the large electrode portion  210   b  for the G pixel is made larger than widths W R  and W B  of large electrode portions  210   b  for the R pixel and the B pixel, respectively, due to the creation of wall discharges on the phosphor layers by application of the write voltage during the address period. The creation of wall charges determines the lighting of discharge cells in the sustaining period. As such, the write voltage of G phosphor layer exceeds the write voltages of R and B phosphor layers. More specifically, by varying the widths W R , W G , and W B  of large electrode portions  110   b , the address margins of the R, G, and B pixels can be improved.  
         [0039]     The shape of large electrode portions  110   b  of address electrodes  110  is not limited to a quadrangular shape and can be formed in a circular shape  110   b   C  as shown in  FIG. 2C , and various polygonal shapes such as a hexagonal shape  110   b   H  as shown in  FIG. 2D .  
         [0040]     In the present embodiment, since discharge cells of all colors have substantially the same complete lighting write voltages, with increased address margins, write operations among the discharge cells of all colors during the sustaining period are uniformed, thus preventing display flickering, erroneous write operations, and improving address margins and voltage margins during the sustaining period in the panel. This indicates that a stable write operation (address operation) can be achieved as shown in  FIG. 1C  (dotted line II). Furthermore, the minimum voltage necessary for writing to the discharge cells of respective colors is considerably lower compared with that necessary for the conventional panel. Thus, a low-cost IC can be used for a write pulse generating circuit.  
       Third Embodiment  
       [0041]     A plurality of discharge cells  340 R,  340 G,  340 B are defined by sets of barrier ribs, each set forming a substantially hexagonal (i.e., honeycomb structure) sequence to realize a closed type PDP. Each discharge cell is independently controlled to display predetermined images.  
         [0042]     Referring to  FIG. 4 , address electrodes  310  include large electrode portions  310   b  that are positioned in discharge spaces  340 R,  340 G, and  340 B, and small electrode portions  310   a  positioned under barrier ribs  330  between discharge spaces  340 R,  340 G, and  340 B. Large electrode portions  310   b  have widths W R , W G , and W B  greater than widths of small electrode portions  310   a.    
         [0043]     Branch electrode portions  324  include first electrode portion  324   a  that extends perpendicularly from main electrode portions  320 , and second electrode portion  324   b  that enlarges on a distal end of first electrode portion  324   a  to extend parallel to main electrode portions  320 . Within one discharge space, a gap G P  is formed between two second electrode portions  324   b  extending into the discharge space from opposite directions, that is, from two different main electrode portions  320 .  
         [0044]     The widths W R , W G , and W B  are made different depending on the material properties of the red (R), green (G), and blue (B) phosphor layers  340 R,  340 G, and  340 B. In the present embodiment of the invention, the widths W R , W G , and W B  of the large electrode portions  310   b  for the R, G, and B pixels, respectively, satisfy the following condition. 
 
 W   B   ≦W   R   ≦W   G . 
 
         [0045]     The width W G  of the large electrode portion  310   b  for the G pixel is made larger than widths W R  and W B  of large electrode portions  310   b  for the R pixel and the B pixel, respectively, due to the creation of wall discharges on the phosphor layers by application of the write voltage during an address period. The creation of wall charges determines the lighting of discharge cells in the sustaining period. As such, the write voltage of G phosphor layer exceeds the write voltages of R and B phosphor layers. More specifically, by varying the widths W R , W G , and W B  of large electrode portions  310   b , the address margins of the R, G, and B pixels can be improved.  
         [0046]     The shape of large electrode portions.  110   b  of address electrodes  110  is not limited to a quadrangular shape and can be formed in a circular shape  110   b   C  as shown in  FIG. 2C , and various polygonal shapes such as a hexagonal shape  110   b   H  as shown in  FIG. 2D .  
         [0047]     In present embodiment, since discharge cells of all colors have substantially the same complete lighting write voltages, with increased address margins, write operations among the discharge cells of all colors during sustaining period are uniform, thus preventing display flickering, erroneous write operations, and improving the address margins and voltage margins during the sustaining period in the panel. This indicates that a stable write operation (address operation) can be achieved as shown in  FIG. 1C  (dotted line II). Furthermore, the minimum voltage necessary for writing to the discharge cells of respective colors is considerably lower compared with that necessary for the conventional panel. Thus, a low cost IC can be used for a write pulse generating circuit.  
         [0048]     While the invention has been particularly shown and described with reference to preferred embodiments, it will be readily appreciated by those of ordinary skill in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is intended that the claims be interpreted to cover the disclosed embodiment, those alternatives, which have been discussed above, and all equivalents thereto.

Technology Classification (CPC): 7