Patent Publication Number: US-2007114937-A1

Title: Plasma display panel

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
      This application claims the benefit of Korean Application No. 2005-112938, filed Nov. 24, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Aspects of the present invention relate to a plasma display panel, and more particularly, to a plasma display panel in which discharge electrodes are disposed so as to perform a surface discharge between a plurality of substrates in a perpendicular direction.  
      2. Description of the Related Art  
      Conventionally, plasma display panels are flat display devices that display desired numbers, letters, or graphics by sealing a discharge gas filled between two substrates on which a plurality of electrodes are formed, applying a predetermined discharge voltage, if gas in discharge cells emits light due to the discharge voltage, applying a proper pulse voltage, and addressing a point where two electrodes cross each other.  
      Conventional 3-electrode surface discharge type plasma display panels include a first substrate, a second substrate, X and Y electrodes which are a pair of sustain discharge electrodes formed on the first substrate, a first dielectric layer burying the pair of sustain discharge electrodes, a protection layer formed on the first dielectric layer, address electrodes formed on the second substrate and disposed to cross the pair of sustain discharge electrodes, a second dielectric layer burying the address electrodes, barrier ribs disposed between the first substrate and the second substrate, and phosphor layers of red, green, and blue colors coating the surface of respective sidewalls of the barrier ribs and the second dielectric layer. A discharge gas is filled in a space between the first substrate and the second substrate to form a discharge region.  
      The operation of conventional plasma display panels will be briefly described.  
      An address voltage is applied between the Y electrodes and the address electrodes to select discharge cells for light-emission, a sustain discharge voltage is applied between the X electrodes and the Y electrodes to perform a surface discharge in the discharge regions of the first dielectric layer and the protection layer of the selected discharge cells, thereby generating ultraviolet rays, which excite a phosphor substance of the respective phosphor layers so that a still image or motion picture is displayed.  
      However, conventional plasma display panels have the following disadvantages.  
      First, the discharge starts in each selected discharge cell from a discharge gap between the X electrode and the Y electrode disposed on the inner surface of the first substrate so that the discharge diffuses outward from the X electrode and the Y electrode. That is, the discharge spreads in the plane of the first substrate. Therefore, an entire space of the discharge cell is not properly utilized.  
      Second, the address voltage is very high since the Y electrodes and the address electrodes are far away from each other.  
      Third, plasma etching occurs due to the discharge, which deteriorates lifetime of plasma display panels.  
      Fourth, the X electrodes, the Y electrodes, the first dielectric layer, and the protection layer are formed on the inner surface of the first substrate. Therefore, transmission of visible rays is less than 60%, which reduces brightness.  
      Fifth, when plasma display panels are driven for a long time, charge particles of a discharge gas produce ion sputtering on the phosphor layers due to an electric field, which causes afterimage.  
     SUMMARY OF THE INVENTION  
      Aspects of the present invention provide a plasma display panel with an improved structure in which a surface discharge is performed from the center of discharge cells to a perpendicular direction in order to use an entire space of respective discharge cells.  
      Aspects of the present invention also provide a plasma display panel that can reduce an addressing voltage by reducing distances between electrodes that perform an addressing discharge.  
      According to an aspect of the present invention, there is provided a plasma display panel comprising: a first substrate; a second substrate facing the first substrate; barrier ribs disposed between the first substrate and the second substrate and partitioning discharge spaces; pairs of discharge electrodes disposed between the first substrate and the second substrate perpendicular to a direction in which the first substrate and the second substrate are disposed; dielectric layers disposed between the pairs of discharge electrodes in discharge spaces; and phosphor layers coated in the discharge spaces.  
      According to an aspect of the present invention, the pairs of discharge electrodes may include first discharge electrodes disposed on the bottom surface of the first substrate, and second discharge electrodes disposed on the upper surface of the second substrate.  
      According to an aspect of the present invention, the first discharge electrodes and the second discharge electrodes may include respectively first discharge electrode lines and second discharge electrode lines, and first and second discharge extension portions extending areas from the first discharge electrode lines and second discharge electrode lines in each discharge cell.  
      According to an aspect of the present invention, the dielectric walls may be disposed in the center of each discharge cell so that the pairs of discharge electrodes perform a surface discharge perpendicularly, and the pairs of discharge electrodes are disposed on the upper surface and the bottom surface of the dielectric walls.  
      According to an aspect of the present invention, the second discharge electrodes may be disposed between the second substrate and the barrier ribs.  
      According to an aspect of the present invention, the dielectric walls may be disposed between the first discharge extension portions and the second discharge extension portions.  
      Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:  
       FIG. 1  is a partially cutaway exploded perspective view of a 3-electrode surface discharge type plasma display panel according to an embodiment of the present invention;  
       FIG. 2  is a cross-sectional view taken along the line I-I of the plasma display panel of  FIG. 1 , according to the shown embodiment of the present invention;  
       FIG. 3  is a plan view of a discharge electrode layout of the plasma display panel of  FIG. 1 , according to the shown embodiment of the present invention; and  
       FIG. 4  is a plan view of a discharge electrode layout according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
      Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.  
       FIG. 1  is a partially cutaway exploded perspective view of a 3-electrode surface discharge type plasma display panel  100  according to an embodiment of the present invention.  FIG. 2  is a cross-sectional view taken along the line I-I of the plasma display panel of  FIG. 1 .  FIG. 3  is a plan view of a discharge electrode layout of the plasma display panel of  FIG. 1 .  
      Referring to  FIGS. 1 through 3 , the plasma display panel  100  includes a first substrate  111 , and a second substrate  161  disposed parallel to the first substrate  111 . The first substrate  111  and the second substrate  161  form a discharge space sealed by a frit glass (not shown) coated along opposing inside edges thereof.  
      The first substrate  111  is a transparent substrate such as soda lime glass, a semi-transparent substrate, a reflective substrate, or a colored substrate. X electrodes  112  are disposed inside the first substrate  111 . The X electrodes  112  are disposed in each discharge cell in an X direction of the plasma display panel  100 .  
      The second substrate  161  is substantially formed of the same material as the first substrate  111 . Address electrodes  164  are disposed inside the second substrate  161 . The address electrodes  164  are disposed to cross the X electrodes  112  disposed in a Y direction of the plasma display panel  100 . The address electrodes  164  are buried by a third dielectric layer  165 .  
      Y electrodes  162  are disposed on the third dielectric layer  165 . The Y electrodes  162  are disposed in each discharge cell in an X direction of the plasma display panel  100 . The Y electrodes  162  are buried by the third dielectric layer  165  but the present invention is not limited thereto.  
      The X electrodes  112  and the Y electrodes  162  are formed of a transparent conductive film, a silver paste having excellent conductivity to reduce line resistance of the X electrodes  112  and the Y electrodes  162 , a metal material such as Cr—Cu—Cr, or a mixture thereof.  
      Barrier ribs  166  are disposed between the first substrate  111  and the second substrate  161 . The barrier ribs  166  define discharge cells and prevent cross-talk between adjacent discharge cells.  
      Phosphor layers  167  of red, green, and blue colors are coated on the sidewalls of the barrier ribs  166  in respective discharge cells. The phosphor layer  167  of red color may be formed of (YGd)BO 3 :Eu +3 , the phosphor layer  167  of green color may be formed of Zn 2 SiO 4 :Mn 2+ , and the phosphor layer  167  of blue color may be formed of BaMgAl 10 O 17 :Eu 2+ .  
      Dielectric walls  114  are disposed between the X electrodes  112  and the Y electrodes  162  in each discharge cell. Protection layers  115  formed of magnesium oxide (MgO) can be formed on the surface of the dielectric walls  114  in order to increase an amount of secondary electron exhaust.  
      The X electrodes  112  and the Y electrodes  162  are correspondingly disposed. The dielectric walls  114  are formed between the X electrodes and the Y electrodes in each discharge cell.  
      In more detail, the X electrodes  112  are disposed on the inner surface of the first substrate  111 . The X electrodes  112  extend across adjacent discharge cells in an X direction of the plasma display panel  100  and are spaced apart from each other by a predetermined gap in a Y direction of the plasma display panel  100 .  
      The X electrodes  112  include first electrode lines  112   a  and first discharge extension portions  112   b  integrally formed with the first electrode lines  112   a.  The first electrode lines  112   a  are stripe type but the present invention is not limited thereto.  
      The first discharge extension portions  112   b  are protruded from both sidewalls of the first electrode lines  112   a  and form a rectangular shape with the first electrode lines  112   a.  The first discharge extension portions  112   b  can form polygon shapes other than the rectangular shape, such as a rhombus, pentagon, hexagon, etc., a circle shape, an oval shape, etc., with the first electrode lines  112   a.  The first discharge extension portions  112   b  are disposed in the center of respective discharge cells.  
      The X electrodes  112  can be buried by the first dielectric layer  113 . The first dielectric layer  113  is selectively formed in regions where the X electrodes  112  are disposed or in entire regions on the inner surface of the first substrate  111 .  
      The Y electrodes  162  are disposed parallel to the X electrodes  112 . The Y electrodes  162  are disposed to correspond to the X electrodes  112  in a direction perpendicular to a direction in which the first substrate  111  and the second substrate  161  are disposed. Therefore, the Y electrodes  162  extend across adjacent discharge cells in an X direction of the plasma display panel  100 , and the Y electrodes  162  are spaced apart from each other by a predetermined gap in a Y direction of the plasma display panel  100 .  
      The Y electrodes  162  include second electrode lines  162   a  and second discharge extension portions  162   b  integrally formed with the second electrode lines  162   a.  The second electrode lines  162   a  form a stripe type pattern but the present invention is not limited thereto.  
      The second discharge extension portions  162   b  are protruded from both sidewalls of the second electrode lines  162   a  and form a rectangular shape with the second electrode lines  162   a.  The second discharge extension portions  162   b  are disposed in the center of respective discharge cells.  
      The Y electrodes  162  can be buried by the second dielectric layer  163 . The second dielectric layer  163  can be selectively formed in regions where the Y electrodes  162  are disposed. Alternatively, the second dielectric layer  163  can be disposed in entire regions on the inside surface of the second substrate  161 .  
      The dielectric walls  114  are formed between the X electrodes  112  and the Y electrodes  162 . The dielectric walls  114  are disposed inside the discharge cells where the first discharge extension portions  112   b  and the second discharge extension portions  162   b  are formed. The upper surface of the dielectric walls  114  contacts the bottom surface of the first discharge extension portions  112   b.  The bottom surface of the dielectric walls  114  contacts the upper surface of the second discharge extension portions 162 b.    
      The dielectric walls  114  are formed in a rectangular pillar shape in the center of each discharge cell. The protection layers  115  can be formed on the outer surface of the dielectric walls  114  in order to increase secondary electron emission. Alternatively, the dielectric walls  114  are not independently formed in each discharge cell but extend across adjacent discharge cells in an X direction of the plasma display panel  100  parallel to the X electrodes  112  and the Y electrodes  162 .  
      The plasma display panel  100  includes the dielectric walls  114  between the X electrodes  112  and the Y electrodes  162  in the center of each discharge cells so that the X electrodes  112  and the Y electrodes  162  perform a surface discharge perpendicularly. In a 2-electrode plasma display panel, the X electrodes  112  and the Y electrodes  162  are disposed to cross each other so as to perform a sustain discharge and an addressing discharge.  
      The address electrodes  164  are formed on the second substrate  161  across the Y electrodes  162 . The address electrodes  164  extend across adjacent discharge cells in a Y direction of the plasma display panel  100 .  
      The address electrodes  164  are buried by the third dielectric layer  165 . The third dielectric layer  165  is formed on entire regions of the second substrate  161  or can selectively bury a region where the address electrodes  164  are disposed but the present invention is not limited thereto.  
      The barrier ribs  166  defining discharge cells are disposed between the first substrate  111  and the second substrate  161 . The barrier ribs  166  include first barrier ribs  166   a  disposed to cross the address electrodes  164  and second barrier ribs  166   b  disposed parallel to the address electrodes  164 .  
      The barrier ribs  166  partition rectangular discharge spaces. Also, the discharge spaces defined by the barrier ribs  166  can have any shape other than the rectangular shape, such as a polygonal shape, a circle shape, or an oval shape, but the present invention is not limited thereto.  
      When the dielectric walls  114  are not formed in the rectangular pillar shape in the center of each discharge cell but in a stripe type pattern in an X direction of the plasma display panel  100 , a predetermined portion of the second barrier ribs  166   b  can be removed to avoid interference with the dielectric walls  114 .  
      The operation of the plasma display panel  100  having the above construction according to the current embodiment of the present invention will be described with reference to  FIGS. 1 through 3 .  
      When an address voltage is applied to the Y electrodes  162  and the address electrodes  164  from an external power source, a light-emitting discharge cell is selected. Wall charges are accumulated on the Y electrodes  162  of the selected discharge cells.  
      When a sustain discharge voltage is applied to the X electrodes  112  and the Y electrodes  162 , the wall charges move due to a difference between the voltage applied between the X electrodes  112  and the Y electrodes  162 .  
      In detail, the movement of the wall charges causes collisions of discharge gas atoms in the discharge spaces, which generate a discharge and plasma. The discharge starts by a discharge gap between respective X electrodes  112  and the Y electrodes  162  in which a relatively strong electric field is formed.  
      As time elapses, if a sufficient voltage difference between the respective X electrodes  112  and the Y electrodes  162  is sustained, an electric field formed between the respective X electrodes  112  and the Y electrodes  162  becomes more intensive so that the discharge spreads to the entire respective discharge spaces.  
      After the discharge is performed, when a voltage difference between the respective X electrodes  112  and the Y electrodes  162  is lower than a discharge voltage, no more discharge is performed and space charges and wall charges are formed in discharge spaces.  
      When the respective X electrodes  112  and the Y electrodes  162  exchange polarities, an initial discharge process repeats, thereby performing a stable discharge.  
      Ultraviolet rays generated by the discharge excite a phosphor substance of the phosphor layers  167  coated in each discharge space, which results in visible rays. The visible rays are emitted into respective discharge spaces to display an image.  
      The discharge starts by a discharge gap between the X electrodes  112  and the Y electrodes  162  which are perpendicularly disposed to a plane of the first and second substrates  111 ,  161  so that a plasma density is intensive around the discharge gap. The plasma spreads outward from respective X electrodes  112  and the Y electrodes  162  based on a high electron density and an ion density so that wall charges can be formed across the entire respective discharge regions.  
      During the sustain discharge, the first discharge extension portions  112   b  and the second discharge extension portions  162   b  are formed from both sidewalls of the first electrode lines  112   a  and both sidewalls of the second electrode lines  162   a  on the X electrodes  112  and the Y electrodes  162 , respectively. Therefore, it is easy to utilize wall charges during a surface discharge in a perpendicular direction, so that the discharge can be stably performed and overall power consumption can be reduced.  
       FIG. 4  is a plan view of a discharge electrode layout according to another embodiment of the present invention. The characterizing portion of the current embodiment of the present invention will be described except for the overlapping portions with the previous embodiment of the present invention.  
      Referring to  FIG. 4 , barrier ribs  466  include first barrier ribs  466   a  disposed in an X direction of a plasma display panel, and second barrier ribs  466   b  disposed in a Y direction of the plasma display panel across the first barrier ribs  466   a.  The second barrier ribs  466   b  extend to cross inside walls of the first barrier ribs  466   a  adjacent thereto, and partition rectangular shaped discharge cells.  
      X electrodes  412  are disposed parallel to the first barrier ribs  466   a  in each discharge cell. The X electrodes  412  include stripe shaped first electrode lines  412   a  and first discharge extension portions  412   b  integrally extending from the first electrode lines  412   a  to increase their area. The first discharge extension portions  412   b  are disposed in the center of respective discharge cells, and form a circle shape with the first electrode lines  412   a.    
      Y electrodes  462  are disposed parallel to the X electrodes  412  in the discharge cells. The Y electrodes  462  include stripe shaped second electrode lines  462   a  and second discharge extension portions  462   b  integrally extending from the second electrode lines  462   a  to increase their area. The second discharge extension portions  462   a  are disposed to correspond to the first discharge extension portions  412   a  and form a circle shape with the second discharge electrode lines  462   a.    
      The X electrodes  412  and the Y electrodes  462  perform a sustain discharge. Address electrodes  464  are disposed to cross the Y electrodes  462  and perform an addressing discharge.  
      Although not shown, the X electrodes  412  are disposed on an inside surface of a substrate, the Y electrodes  462  are disposed on an inside surface of another substrate, and dielectric walls in a cylinder shape are disposed between respective first discharge extension portions  412   a  and second discharge extension portions  462   a  in order to perform a surface discharge perpendicularly to the inside surfaces of the substrates.  
      The plasma display panel according to aspects of the present invention provide the following advantages.  
      First, a pair of sustain discharge electrodes can perform a surface discharge perpendicularly to the inside surfaces of the substrates in the center of each discharge cell, thereby easily diffusing a discharge to an entire region of the discharge cell.  
      Second, discharge extension portions are disposed in each discharge cell so that use of wall charges is increased. Therefore, a discharge is stably performed and overall power consumption is reduced.  
      Third, distances between respective Y electrodes and address electrodes are reduced so that an address voltage can be reduced.  
      Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.