Patent Publication Number: US-7906907-B2

Title: Plasma display panel (PDP)

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 24 Jan. 2007 and there duly assigned Serial No. 10-2007-0007639. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a Plasma Display Panel (PDP), and more particularly, the present invention relates to a PDP having a structure that minimizes regions that reduce a discharge space and brightness in a discharge cell. 
     2. Description of the Related Art 
     A PDP is a flat panel display device that displays desired numbers, letters, or graphics using visible light emitted from phosphor layers which are excited by ultraviolet rays generated during a gas discharge initiated by supplying a DC or AC voltage to a plurality of electrodes formed on a plurality of substrates after a discharge gas is sealed between the plurality of substrates. 
     Generally, Plasma Display Panels (PDPs) can be classified into Direct Current (DC) PDPs and Alternating Current (AC) PDPs according to the type of driving voltage supplied to discharge cells, i.e., according to their discharge type. PDPs can further be classified into face discharge PDPs and surface discharge PDPs according to the arrangement of their electrodes. 
     A conventional three-electrode surface discharge PDP includes: a first substrate, a second substrate facing the first substrate, sustain discharge electrode pairs each having an X electrode and a Y electrode formed on an inner surface of the first substrate, a first dielectric layer that buries the sustain discharge electrode pairs, a protective film layer formed on a surface of the first dielectric layer, a plurality of address electrodes formed on an inner surface of the second substrate in a direction crossing the sustain discharge electrode pairs, a second dielectric layer that buries the address electrodes, barrier ribs formed between the first and second substrates to define a plurality of discharge cells, and red, green, and blue phosphor layers formed in the discharge cells. A discharge gas is filled in a space formed by mating the first and second substrates to form discharge regions. 
     In the conventional three-electrode surface discharge PDP having the above structure, when an electrical signal is supplied to the address electrodes and the Y electrode, discharge cells for emitting light are selected, and electrical signals are alternately supplied to the X electrode and the Y electrode. Thus, a surface discharge is generated from a surface of the first substrate, and ultraviolet rays generated as a result of the surface discharge excite phosphor layers coated on the selected discharge cells. Accordingly, visible light is emitted from phosphor materials of the phosphor layers, and thus, a stationary or moving image can be displayed. 
     In the conventional three-electrode surface discharge PDP, the gas discharge in the discharge cells is generated by controlling a voltage supplied to the X electrode, the Y electrode, and the address electrodes, and as a result of the gas discharge, visible light is emitted. 
     Recently, research have been conducted on panel structures that can increase brightness by changing a discharge electrode structure and can increase discharge efficiency by increasing a discharge space. 
     SUMMARY OF THE INVENTION 
     To solve the above and/or other problems, the present invention provides a Plasma Display Panel (PDP) having increased brightness by improving a discharge aperture ratio through the modification of a structure of its discharge electrodes. 
     The present invention also provides a PDP having increased discharge efficiency by increasing a discharge space through the modification of locations of the discharge electrodes. 
     According to one aspect of the present invention, a Plasma Display Panel (PDP) is provided including: a first substrate and a second substrate; a plurality of barrier ribs disposed between the substrates to define discharge cells and including single walled barrier ribs and double walled barrier ribs; a plurality of discharge electrodes disposed on portions of the panel corresponding to the barrier ribs to supply a discharge voltage to the discharge cells; and phosphor layers formed in the discharge cells. 
     The discharge spaces of the discharge cells may be defined by the barrier ribs into discharge cells having different discharge spaces from each other. The discharge spaces of the discharge cells may have an asymmetrical structure. The discharge spaces of the discharge cells may be defined to have different areas corresponding to changes of the thickness of the barrier ribs. 
     The barrier ribs may include first barrier ribs arranged in a first direction of the PDP and second barrier ribs arranged in a second different direction of the PDP and connected to the first barrier ribs. 
     The first barrier ribs may include single walled barrier ribs, each single walled barrier rib arranged between adjacently disposed discharge cells, and double walled barrier ribs, each double walled barrier rib arranged between a pair of adjacently disposed discharge cells and another pair of neighbored discharge cells and including a plurality of barrier ribs having a gap therebetween. 
     The gaps in the double wall barrier ribs may be arranged in a direction of the PDP to be used as a path for discharging an exhaust gas. 
     The discharge electrodes may include X and Y electrodes, each of the X electrodes including an X transparent electrode and an X bus electrode electrically connected to the X transparent electrode, and each of the Y electrodes including a Y transparent electrode and a Y bus electrode electrically connected to the Y transparent electrode. 
     Each of the X bus electrodes may include an X bus electrode line and a plurality of X protrusion electrodes, the X bus electrode line is arranged on the single wall barrier rib, and the X protrusion electrode includes a first X protrusion electrode and a second X protrusion electrode respectively arranged on the second barrier ribs connected to both sides of a single wall barrier rib. 
     The X transparent electrodes may respectively protrude into the discharge spaces of the adjacent discharge cells from the both sides of the X bus electrode line. 
     Each of the Y bus electrodes may include a Y bus electrode line and a plurality of Y protrusion electrodes extending from the Y bus electrode line, the Y bus electrode line is arranged on the double wall barrier rib, and the Y protrusion electrodes are arranged on the second barrier ribs. 
     The Y transparent electrodes may respectively protrude into the discharge spaces of the discharge cells from a side of the Y bus electrode line. 
     The single wall barrier ribs may have different widths in different discharge cells corresponding to variations of widths of the X bus electrode in each of the discharge cells. 
     An area of the discharge space of the discharge cell in which the X bus electrode has a relatively wide width may be smaller than an area of the discharge space of the discharge cell in which the X bus electrode has a relatively narrow width. 
     The discharge electrode may have an X-YY structure in which the X electrodes that commonly relate to the discharge in the adjacent discharge cells are disposed on the single wall barrier ribs and the Y electrodes are disposed on the double wall barrier ribs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present invention, and many of the attendant advantages thereof, will be readily apparent as the present invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1  is a partial cut-away exploded perspective view of a three-electrode surface discharge PDP according to an embodiment of the present invention; 
         FIG. 2  is a cross-sectional view taken along line II-II of  FIG. 1 , according to an embodiment of the present invention; and 
         FIG. 3  is a plan view of discharge electrodes of the three-electrode surface discharge PDP of  FIG. 1 , according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is described more fully below with reference to the accompanying drawings in which exemplary embodiments of the present invention are shown. 
       FIG. 1  is a partial cut-away exploded perspective view of a three-electrode surface discharge PDP  100  according to an embodiment of the present invention.  FIG. 2  is a cross-sectional view taken along line II-II of  FIG. 1 , and  FIG. 3  is a plan view of discharge electrodes of the three-electrode surface discharge PDP  100  of  FIG. 1 , according to an embodiment of the present invention. 
     Referring to  FIGS. 1 through 3 , the three-electrode surface discharge PDP  100  includes a first substrate  101  and a second substrate  102  facing the first substrate  101 . Frit glass (not shown) is coated along edges of inner surfaces of the first substrate  101  and the second substrate  102  to seal the discharge cells. 
     The first substrate  101  is a transparent substrate formed of, for example, soda lime glass. Alternatively, the first substrate  101  can be a semi-transparent substrate, a colored substrate, or a reflection plate. 
     X electrodes  104  and Y electrodes  105 , which form sustain discharge electrode pairs  103 , are disposed on an inner surface of the first substrate  101  along an X direction of the three-electrode surface discharge PDP  100 . Each of the X electrodes  104  includes an X transparent electrode  106  and an X bus electrode  107  connected to the X transparent electrode  106 . Each of the Y electrodes  105  includes a Y transparent electrode  108  and a Y bus electrode  109  connected to the Y transparent electrode  108 . 
     The X electrodes  104  and the Y electrodes  105  are buried by a first dielectric layer  110 . The first dielectric layer  110  can be formed of a high dielectric material, for example, ZnO—B 2 O 3 —Bi 2 O 3 . The first dielectric layer  110  can be selectively formed in regions where the X electrodes  104  and the Y electrodes  105  are formed, or can be formed in all areas of an inner surface of the first substrate  101 . 
     A protective film layer  111  is deposited on a surface of the first dielectric layer  110  using, for example, MgO to prevent the first dielectric layer  110  from being damaged and to increase the emission of secondary electrons. 
     The second substrate  102  can be formed of substantially the same material as the first substrate  101 . A plurality of address electrodes  112  are disposed on an inner surface of the second substrate  102  in a direction crossing the sustain discharge electrode pairs  103 . The address electrodes  112  are buried in a second dielectric layer  113 . The second dielectric layer  113  is formed of a high dielectric material, for example, PbO—B 2 O 3 —SiO 2 . A barrier rib structure  114  that defines a plurality of discharge cells together with the first substrate  101  and the second substrate  102  is formed between the first and second substrates  101  and  102 . 
     The discharge cells defined by the combination of the first substrate  101 , the second substrate  102 , and the barrier rib structure  114  are filled with a discharge gas, such as Ne—Xe gas or He—Xe gas. 
     Also, red, green, and blue phosphor layers  119  for emitting visible light by being excited by ultraviolet rays generated by the discharge gas are formed in the discharge cells. The phosphor layers  119  can be coated in any region in the discharge cells. 
     The phosphor layers  119  include red, green, and blue phosphor materials, but are not limited thereto. That is, the phosphor layers  119  can be replaced by different color phosphor layers, or an additional different phosphor layer can be added. In the present embodiment, the red phosphor layer  119 R may be formed of (Y,Gd)BO 3 ;Eu +3 , the green phosphor layer  119 G may be formed of Zn 2 SiO 4 :Mn 2+ , and the blue phosphor layer  119 B may be formed of BaMgAl 10 O 17 :Eu 2+ . 
     The barrier rib structure  114  has a structure including single walled barrier ribs  117  and double walled barrier ribs  118 , and the X electrodes  104  and the Y electrodes  105  are disposed on portions of the first substrate  101  corresponding to the barrier rib structure  114 . A discharge space of the discharge cell is divided into spaces having areas different from each other. 
     Referring to  FIGS. 1 through 3 , the barrier rib structure  114  includes first barrier ribs  115  disposed in the X direction of the PDP  100  and second barrier ribs  116  disposed in the Y direction of the PDP  100 . The first barrier ribs  115  are disposed in a direction crossing the address electrodes  112 , and the second barrier ribs  116  are disposed parallel to the address electrodes  112 . 
     Both the first barrier ribs  115  and second barrier ribs  116  substrates have a stripe shape and define discharge cells by being connected to each other. For example, the discharge cells defined by the coupling of the first barrier ribs  115  and the second barrier ribs  116  have rectangular shape horizontal cross-sections. The structure of the barrier rib structure  114  according to the present embodiment is not limited to the above configuration, and can have various shapes as long as they can define discharge cells, such as a different rectangular shape, a circular shape, or an oval shape besides the rectangular shape. 
     The first barrier ribs  115  have a structure including the single walled barrier ribs  117  and the double walled barrier ribs  118 . 
     That is, one single walled barrier rib  117  formed of one walled barrier rib is disposed between a first discharge cell  120 A and a second discharge cell  120 B adjacently disposed in the Y direction of the PDP  100 . 
     Unlike the single walled barrier rib  117 , the double walled barrier ribs  118  including a plurality of barrier ribs  118   a  and  118   b  is disposed between a pair of the first discharge cell  120 A and the second discharge cell  120 B, and another pair of the first discharge cell  120 A and the second discharge cell  120 B. 
     A gap g is formed between the plurality of barrier ribs  118   a  and  118   b . The gap g is formed along the X direction of the PDP  100 , and is used for an exhaust gas path when the discharge cells are vacuumed. 
     Alternatively, instead of forming the gap g in the double walled barrier rib  118 , a single layer can be divided into a double walled barrier rib by forming a groove having a predetermined size in the single walled barrier rib. The double walled barrier rib having the groove may have a total width identical to the total width of the plurality of barrier ribs  118   a  and  118   b  with the gap g. 
     The first barrier ribs  115  include the single walled barrier ribs  117  and the double walled barrier ribs  118  are alternately disposed in the Y direction of the PDP  100 . That is, the single walled barrier rib  117  is disposed in the center between the first and second discharge cells  120 A and  120 B which are adjacently disposed in the Y direction of the PDP  100 , and the double walled barrier ribs  118  is disposed with a gap g between a pair of the first and second discharge cells  120 A and  120 B and an adjacent pair of the first and second discharge cells  120 A and  120 B. 
     The X and Y electrodes  104  and  105  are alternately disposed on the first barrier ribs  115 . 
     That is, X bus electrode lines  107   a  are formed on the single walled barrier ribs  117 . The X bus electrode lines  107   a  are disposed in a stripe shape on corresponding regions of upper parts of the single walled barrier ribs  117  in a direction in which the single walled barrier ribs  117  are disposed. 
     A first X protrusion electrode  107   b  and a second X protrusion electrode  107   c  protrude from both sides of each of the X bus electrode lines  107   a . The first X protrusion electrode  107   b  extends a predetermined length on a portion of the second barrier rib  116   a  in a direction corresponding to the direction in which the first discharge cell  120 A is disposed. The second X protrusion electrode  107   c  extends a predetermined length on a portion of the second barrier rib  116   b  in a direction corresponding to the direction in which the second discharge cell  120 B is disposed. 
     Accordingly, the X bus electrode  107  includes the X bus electrode lines  107   a  disposed on the single walled barrier rib  117  and the first X protrusion electrode  107   b  and the second X protrusion electrode  107   c  extend from the side of the X bus electrode lines  107   a  and disposed on the second barrier ribs  116   a  and  116   b . The X bus electrode  107  is formed of a highly conductive material, such as an Ag paste. 
     The X bus electrode lines  107   a  are disposed in each of the discharge cells with different widths. For example, a portion of a X bus electrode line  107   d  disposed on the single walled barrier rib  117  that defines the discharge cell in which a red phosphor layer  119 R is coated has a relatively wide width, and portions of the X bus electrode lines  107   e  and  107   f  disposed on the single walled barrier ribs  117  that define the discharge cells in which a green phosphor layer  119 G and a blue phosphor layer  119 B are coated have a relatively narrow width. 
     Furthermore, the line width of the X bus electrode line  107   e  disposed on the single walled barrier rib  117  that defines the discharge cell in which the green phosphor layer  119 G is coated and the line width of the X bus electrode line  107   f  disposed on the single walled barrier rib  117  that defines the discharge cell in which the blue phosphor layer  119 B is coated can be identical or different. 
     The line widths of the X bus electrode lines  107  formed in each discharge cells are different from each other along the lengthwise direction of the single walled barrier rib  117  are different. Accordingly, the widths of the single walled barrier ribs  117  are also different from each other corresponding to the widths of the X bus electrode lines  107 . 
     Also, a first X transparent electrode  106   a  and a second X transparent electrode  106   b  that respectively extend towards the first discharge cell  120 A and the second discharge cell  120 B from the X bus electrode line  107   a  are electrically connected to the X bus electrode  107 . 
     That is, the first X transparent electrode  106   a  and the second X transparent electrode  106   b  are respectively formed in the center of the first discharge cell  120 A and the second discharge cell  120 B. The arrangement of the first X transparent electrode  106   a  and the second X transparent electrode  106   b  is not limited to the above configuration. For example, the first X transparent electrode  106   a  and the second X transparent electrode  106   b  can be connected to each other in one unit, or can respectively extend from both sides of the X bus electrode line  107   a . The first X transparent electrode  106   a  and the second X transparent electrode  106   b  are formed of a transparent conductive film, such as an ITO film, in order to increase an aperture ratio of the PDP  100 . 
     Since the X bus electrode line  107  is disposed on the single walled barrier rib  117 , the first X transparent electrode  106   a  is disposed in the first discharge cell  120 A, and the second X transparent electrode  106   b  is disposed in the second discharge cell  120 B, the X electrode  104  commonly relates to the discharges of the first discharge cell  120 A and the second discharge cell  120 B. 
     A Y bus electrode line  109   a  is disposed on the double walled barrier rib  118 . The Y bus electrode line  109   a  is formed in a stripe shape in a corresponding region of the double walled barrier rib  118  along the direction of the double walled barrier rib  118 . 
     Y protrusion electrodes  109   b  protrude from a side of the Y bus electrode line  109   a  and are formed on the second barrier ribs  116 . The Y protrusion electrodes  109   b  extend a predetermined length on the second barrier ribs  116  in a direction in which the first discharge cell  120 A or the second discharge cell  120 B is disposed. 
     Thus, the Y bus electrode  109  includes the Y bus electrode lines  109   a  disposed on the double walled barrier ribs  118  and the Y protrusion electrodes  109   b  extend from the Y bus electrode line  109   a  and are disposed on the second barrier ribs  116 . The Y bus electrode  109  is formed of a highly conductive material, such as an Ag paste. 
     The Y transparent electrodes  108  disposed towards the first discharge cell  120 A or the second discharge cell  120 B are electrically connected to the Y bus electrode line  109   a . The Y transparent electrodes  108  are disposed in the center of the first discharge cell  120 A or the second discharge cell  120 B. The Y transparent electrodes  108  can be formed of a transparent conductive film, such as an ITO film, to increase an aperture ratio of the PDP  100 . 
     Since the Y bus electrode line  109   a  is disposed on the double walled barrier rib  118 , the Y protrusion electrodes  109   b  are formed in the first discharge cell  120 A and the second discharge cell  120 B, and the Y electrode  105  independently relate to the discharges in the first discharge cell  120 A and the second discharge cell  120 B. 
     As described above, the PDP  100  has a structure, a so called X-YY electrode structure, in which, when the structure is viewed based on the first discharge cells  120 A and the second discharge cells  120 B adjacently disposed in a direction of the PDP  100 , the X bus electrode line  107   a  is disposed on the single walled barrier rib  117  located between the first discharge cells  120 A and the second discharge cells  120 B, the first X transparent electrode  106   a  and the second X transparent electrode  106   b  which are electrically connected to the X bus electrode lines  107   a  respectively protrude in the first discharge cells  120 A and the second discharge cells  120 B, Y bus electrode lines  109   a  are respectively disposed on the barrier ribs  118   a  and  118   b  of the double walled barrier rib  118 , and the Y transparent electrodes  108  which are electrically connected to the Y bus electrode line  109   a  respectively protrude towards the first discharge cells  120 A and the second discharge cells  120 B. 
     Also, the first X transparent electrode  106   a  and the Y transparent electrodes  108  maintain a predetermined discharge gap in the first discharge cells  120 A, and the second X transparent electrode  106   b  and the Y transparent electrodes  108  maintain a discharge gap in the second discharge cells  120 B. Therefore, a discharge can primarily be initiated from the discharge gaps. 
     Furthermore, the first X protrusion electrode  107   b  and the second X protrusion electrode  107   c  extend from the X bus electrode lines  107   a  and are disposed on the second barrier ribs  116   a  and  116   b , and the Y protrusion electrodes  109   b  extend from the Y bus electrode line  109   a  and is disposed on the second barrier ribs  116 . 
     Also, the first X protrusion electrode  107   b  and the Y protrusion electrodes  109   b  maintain a predetermined gap, and the second X protrusion electrode  107   c  and the Y protrusion electrodes  109   b  also maintain a predetermined gap. Accordingly, the generation of a surface discharge and a facing discharge is possible in the discharge cells. 
     In order to increase the aperture ratio of the PDP  100 , the widths of the single walled barrier ribs  117  in the discharge cells are different from each other since the widths of the X bus electrode lines  107   a  in the discharge cells are different from each other. 
     Accordingly, the discharge spaces of the discharge cells in which the red phosphor layer  119 R, the green phosphor layer  119 G, and the blue phosphor layer  119 B are coated are defined with different areas. That is, the widths of the discharge cells in the X direction of the PDP  100  are the same. However, the widths of the discharge cells in the Y direction are different from each other. 
     For example, a gap d 1  of the discharge space of the discharge cell in which the red phosphor layer  119 R is coated is relatively small. However, a gap d 2  of the discharge space of the discharge cell in which the green phosphor layer  119 R is coated or a gap d 3  of the discharge space of the discharge cell in which the green phosphor layer  119 G is coated is relatively large. The gaps d 2  and d 3  of the discharge spaces of the discharge cells in which the green phosphor layer  119 G and the blue phosphor layer  119 B are coated can be the same or different. 
     Accordingly, the PDP  100  has an asymmetrical discharge cell structure in which the discharge space of the discharge cell in which the red phosphor layer  119 R is coated is relatively small and the discharge spaces of the discharge cells in which the green phosphor layer  119 G and the blue phosphor layer  119 B are coated are relatively large. 
     The operation of the PDP  100  having the above structure according to the present invention is described below with reference to  FIGS. 1 through 3 . 
     First, when a predetermined pulse voltage is supplied between the Y electrodes  105  and the address electrodes  112 , discharge cells which will be lit are selected and wall charges are accumulated on inner walls of the selected discharge cells. 
     Next, when a “+” voltage is supplied to the X electrodes  104  and a voltage relatively higher than the “+” voltage is supplied to the Y electrodes  105 , the wall charges move due to a voltage difference between the X electrodes  104  and the Y electrodes  105 . 
     Due to the movement of the wall charges, the wall charges collide with discharge gas atoms in the discharge cells to cause a discharge. As a result of the discharge, a plasma is generated, and the discharge expands from the discharge gaps between the X transparent electrodes  106  and the Y transparent electrodes  108  where strong electric fields are formed towards edges of the discharge cells. 
     After the discharge is generated as described above, the voltage difference between the X electrodes  104  and the Y electrodes  105  is reduced below a discharge voltage. Thus, a further discharge is not generated, but space charges and wall charges are accumulated in the discharge cells. 
     When the polarities of the voltages supplied to the X electrodes  104  and the Y electrodes  105  are reversed, the discharge is re-generated with the aid of the wall charges. In this way, if the polarities of the X electrodes  104  and the Y electrodes  105  are reversed, the discharge process is repeated. In this manner, the discharge is stably generated by repeating the above process. 
     Ultraviolet rays generated by the discharge excite the red, green, and blue phosphor layers  119  coated in each of the discharge cells. The excited phosphor layers  119  generate visible light which realizes a stationary or moving image by being emitted from the discharge cells. 
     Since the PDP  100  employs the X-YY structure, the X bus electrode  107  is disposed on the single walled barrier rib  117  disposed between the first discharge cell  120 A and the second discharge cell  120 B which are adjacently disposed in the Y direction of the PDP  100 . Therefore, the X bus electrode  107  commonly relates to the discharge in the first discharge cell  120 A and the second discharge cell  120 B. 
     Also, the first X protrusion electrode  107   b  and the second X protrusion electrode  107   c  protrude from the X bus electrode lines  107   a  on the second barrier rib  116  towards the first discharge cell  120 A and the second discharge cell  120 B, and the Y protrusion electrodes  109   b  extend from the Y bus electrode line  109   a  on the second barrier ribs  116  towards the first discharge cell  120 A and the second discharge cell  120 B. Therefore, a surface discharge and a face discharge are possible in the discharge cells. 
     As described above, the PDP according to the present invention has the following advantages. 
     First, a barrier rib structure includes single walled barrier ribs and double walled barrier ribs, and discharge electrodes disposed on the single walled barrier ribs can commonly be related to adjacent discharge cells, thereby increasing the discharge areas. 
     Second, since the discharge areas are extended, the efficiency of generating ultraviolet rays that excite phosphor materials and the discharge aperture ratio can be increased. 
     Third, since the discharge spaces of the discharge cells are asymmetrically formed, the brightness of discharge cells having relatively low brightness can be increased. 
     Fourth, when discharge electrode lines are disposed on the barrier ribs, line widths of the electrodes can be formed to be different from each other. Accordingly, the problem of the asymmetrical discharge spaces of the discharge cells can be resolved. 
     Fifth, since protrusion electrodes extending from the discharge electrode lines are disposed on the barrier ribs, reflection brightness caused by external light can be reduced, thereby increasing the bright room contrast of the PDP. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various modifications in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.