Abstract:
A plasma display panel is provided that reduces reflective brightness and increases the black area. The plasma display panel includes: a front substrate and a rear substrate facing each other at a distance; an address electrode which is formed on the rear substrate and extends in a first direction; a display electrode which is formed on the front substrate and extends in a second direction crossing the first direction; a barrier rib which is disposed between the front and rear substrates to define a plurality of discharge cells; and a phosphor layer which is formed on each of the discharge cells, wherein the display electrode comprises: a transparent electrode which has a curved portion on a second surface that is an opposite surface of a first surface facing the front substrate; and a bus electrode which is attached to the second surface of the transparent electrode where the curved portion is formed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Application No. 2006-115224, filed Nov. 21, 2006 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Aspects of the present invention relate to a plasma display panel, and more particularly, to a plasma display panel that reduces reflective brightness and increases the black area. 
         [0004]    2. Description of the Related Art 
         [0005]    A plasma display panel generates plasma by using a discharge phenomenon. An ultraviolet (UV) ray is irradiated from the plasma. The UV excites a phosphor layer. The phosphor layer generates red (R), green (G), and blue (B) visible light beams. The visible light beams are combined to form an image. 
         [0006]    With a plasma display panel having this structure, a large screen display can easily be designed and manufactured. Further, since a plasma display panel is a self-emitting display element, for example a cathode ray tube (CRT), a plasma display panel provides not only a color reproduction capability but also a wide viewing angle, resulting in an excellent image display capability. Furthermore, a plasma display panel can be manufactured in a simpler process than the process for manufacturing a liquid crystal display (LCD). Therefore, there are advantages in terms of productivity and cost to a plasma display panel over an LCD. 
         [0007]    A typical AC-type plasma display panel has a structure in which address electrodes are formed on a rear substrate, and a dielectric layer covers the address electrodes. Further, a barrier rib is formed in a grid shape on the dielectric layer so as to define discharge cells. Phosphor layers are formed on the inner surfaces of the discharge cells. Display electrodes are formed on one surface of a front substrate, which is spaced apart from the rear substrate at a distance. The display electrodes extend orthogonally in the direction crossing the address electrodes. 
         [0008]    If the external environment is bright, for example, a bright room condition, the contrast of the plasma display panel is lowered. As a result, the image display capability of the plasma display panel also is lower. Various attempts have been made to improve the image display capability of the plasma display panel. There are methods in which the bright room contrast is increased by increasing the black area and reducing reflective brightness and methods in which brightness is improved by increasing emission efficiency. 
       SUMMARY OF THE INVENTION 
       [0009]    Aspects of the present invention solve the above-mentioned and/or other problems by providing a plasma display panel in which the structure of a display electrode (or front substrate) is improved so that the adhesive force between a bus electrode and the display electrode (i.e., the front substrate) is enhanced while increasing the black area and increasing the bright room contrast. 
         [0010]    An aspect of the present invention provides a plasma display panel comprising: a front substrate and a rear substrate facing each other at a distance; an address electrode which is formed on the rear substrate and extends in a first direction; a display electrode which is formed on the front substrate and extends in a second direction crossing the first direction; a barrier rib which is disposed between the front and rear substrates to define a plurality of discharge cells; and a phosphor layer which is formed on each of the discharge cells. The display electrode comprises: a transparent electrode which has a curved portion on a second surface that is an opposite surface to the first surface facing the front substrate; and a bus electrode which is attached to the second surface of the transparent electrode where the curved portion is formed. 
         [0011]    In the aforementioned aspect of the present invention, the bus electrode may comprise: a black layer in contact with the second surface of the transparent electrode; and a white layer formed on the black layer. Further, the black layer may include one or more metals selected from the group consisting of ruthenium (Ru), cobalt (Co), and manganese (Mn). Further, the white layer may include one or more metals selected from the group consisting of silver (Ag), gold (Au), and aluminum (Al). 
         [0012]    In addition, the curved portion of the transparent electrode may be formed as a depression in the electrode, and that depression may have a hemispheric cross-section. Further, the depressed portion may be constructed with a plurality of long channels adjacent to one another in one direction, and a part of the bus electrode may be inserted into the depressed portion. In addition, the curved portion of the transparent electrode may be formed in the shape of a protrusion. 
         [0013]    Another aspect of the present invention provides a plasma display panel comprising a bus electrode which is formed along a region where the depressions are formed on the surface of the front substrate that faces the rear substrate at a distance and in which the depressions are formed on the surface thereof facing the rear substrate. 
         [0014]    In the aforementioned aspect of the present invention, the bus electrode may comprise: a black layer in contact with the surface where the depressions of the front substrate are formed; and a white layer formed on the black layer. In addition, the plasma display panel may further comprise a colored layer which is formed along the region where the depressions are formed and is spaced apart from the bus electrode. 
         [0015]    The plasma display panel of this aspect of the present invention, and the actual surface area of the black layer are large, wherein the black layer is formed along the depressions or protrusions formed on the transparent electrode. Thus, there is an advantage in that the black area of the panel increases, whereas the reflective brightness decreases. 
         [0016]    In addition, the actual surface area of a black layer is large, wherein the black layer is formed along the depressions or protrusions formed on the front substrate. Therefore, there is an advantage in that the black area of the panel increases, whereas the reflective brightness decreases. 
         [0017]    In addition, the actual surface area of the colored layer is large, wherein the colored layer is formed along the depressions or protrusions formed on the front substrate. Therefore, there is an advantage in that the black area of the panel increases, whereas the reflective brightness decreases. 
         [0018]    In addition, since a bus electrode is formed along the depressions or protrusions formed on the transparent electrode, there is an advantage in that the assembled structure between the transparent electrode and the bus electrode can be strengthened. 
         [0019]    In addition, since a bus electrode (or a colored layer) is formed along depressions or protrusions formed on the front substrate, there is an advantage in that the assembled structure between the front substrate and the bus electrode (or the colored layer) can be strengthened. 
         [0020]    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  
         [0021]    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: 
           [0022]      FIG. 1  is a partial perspective view of a plasma display panel according to a first embodiment of the present invention; 
           [0023]      FIG. 2  is a cross-sectional view of the plasma display panel taken along line II-II of  FIG. 1 ; 
           [0024]      FIG. 3  is a detailed view of portion A of  FIG. 2 ; 
           [0025]      FIG. 4  is a partial perspective view illustrating a transparent electrode of the plasma display panel according to the first embodiment of the present invention; 
           [0026]      FIG. 5  is a plan view schematically illustrating an image display area of the plasma display panel according to the first embodiment of the present invention; 
           [0027]      FIG. 6  is a partial perspective view illustrating a transparent electrode of the plasma display panel according to a second embodiment of the present invention; 
           [0028]      FIG. 7  is a partial perspective view of the transparent electrode of the plasma display panel according to a third embodiment of the present invention; 
           [0029]      FIG. 8  is a partial perspective view of the transparent electrode of the plasma display panel according to a fourth embodiment of the present invention; 
           [0030]      FIG. 9  is a partial perspective view of the transparent electrode of the plasma display panel according to a fifth embodiment of the present invention; 
           [0031]      FIG. 10  is a partial cross-sectional view of the plasma display panel according to a sixth embodiment of the present invention; and 
           [0032]      FIGS. 11A to 11D  are plan views illustrating various patterns of depressions formed on the front substrate of the plasma display panel according to a sixth embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0033]    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. 
         [0034]      FIG. 1  is a partial perspective view of a plasma display panel according to a first embodiment of the present invention.  FIG. 2  is a cross-sectional view of the plasma display panel taken along line II-II of  FIG. 1 . 
         [0035]    Referring to the drawings, the plasma display panel includes a rear substrate  10 , an address electrode  11 , a rear dielectric layer  12 , a barrier rib  13 , and a phosphor layer  14 . Further, the plasma display panel includes a front dielectric layer  17 , a display electrode  16 , and a protective layer  18 . 
         [0036]    The rear substrate  10  and the front substrate  15  face each other at a distance. The address electrode  11  extends in a second direction (y-axis direction in the drawing) on the upper surface of the rear substrate  10 . Address electrodes  11  are formed in parallel with each other with distances between them. Further, the rear dielectric layer  12  is formed on the upper surface of the rear substrate  10 . The rear dielectric layer  12  covers the address electrode  11 . 
         [0037]    The display electrode  16  extends in a second direction (x-axis direction in the drawing) on the lower surface of the front substrate  15 . Adjacent display electrodes  16  are formed in parallel with each other with distances between them. 
         [0038]    As shown in the drawings, the display electrode  16  includes a sustain electrode  161  and a scan electrode  162 . The sustain electrode  161  and the scan electrode  162  respectively include transparent electrodes  161   a  and  162   a  and bus electrodes  161   b  and  162   b . The bus electrodes  161   b  and  162   b  are formed on the lower surface of the transparent electrodes  161   a  and  162   a . The transparent electrodes  161   a  and  162   a  are spaced apart from each other so as to form a discharge gap. 
         [0039]    The transparent electrodes  161   a  and  162   a  are made of a transparent material such as indium tin oxide (ITO), thereby easily transmitting visible light. However, the conductivity of the transparent material is poor due to its high electrical resistance. On the other hand, the bus electrodes  161   b  and  162   b  are made of a metal material having a good conductivity such as silver (Ag), so that voltage can be easily supplied to the transparent electrodes  161   a  and  162   a.    
         [0040]    When widths BW of the bus electrodes  161   b  and  162   b  increase, the black area increases, whereas the reflective brightness decreases. However, when that is done, visible light generated from the discharge cells  19  is blocked, and that leads to a reduction in emission efficiency. In order to solve the problem, in this embodiment of the present invention, the black area is increased by altering the structures of the bus electrodes  161   b  and  162   b , and the reflective brightness is therefore decreased. Details of this alteration will be further described later with reference to  FIG. 3 . 
         [0041]    The front dielectric layer  17  is formed on the lower surface of the front substrate  15 . The front dielectric layer  17  covers the display electrode  16 . Thus, the front dielectric layer  17  protects the display electrodes  16  against a discharge phenomenon. Further, the front dielectric layer  17  accumulates wall charges to produce a discharge. 
         [0042]    The front dielectric layer  17  is covered with a protective layer  18 . The protective layer  18  is made of a transparent material. Thus, the protective layer  18  not only easily transmits visible light emitted from the phosphor layer  14 , but also protects the front dielectric layer  17  against the discharge phenomenon. Further, the protective layer  18  serves to decrease the discharge ignition voltage by increasing the secondary electron emission coefficient. 
         [0043]    As shown in  FIGS. 1 and 2 , the barrier rib  13  is formed between the protective layer  18  and the rear dielectric layer  12 . The barrier rib  13  includes a horizontal barrier member  13   a  and a vertical barrier member  13   b . That is, the horizontal barrier member  13   a  extends in the second direction (x-axis direction in the drawing). The vertical barrier member  13   b  extends in the first direction (y-axis direction in the drawing). The horizontal barrier member  13   a  crosses the vertical barrier member  13   b . In this embodiment of the present invention, the horizontal and vertical barrier members  13   a  and  13   b  define the discharge cells  19  in a rectangular grid. 
         [0044]    The discharge cells  19  according to this embodiment of the present invention may be formed in various shapes such as rectangular or triangular. In whatever shape, the barrier rib  13  prevents cross-talk between the discharge cells  19  and provides a surface on which the phosphor layer  14  is applied. 
         [0045]    A discharge gas that is inert (e.g., a mixture of Ne and Xe) fills the discharge cells  19 . The discharge gas generates a gas discharge between the sustain electrode  161  and the scan electrode  162 . Visible light beams are generated from the phosphor layer  14  by the gas discharge. The visible light beams are combined to form an image. 
         [0046]      FIG. 3  is a detailed view of a portion A of  FIG. 2 , and  FIG. 4  is a partial perspective view illustrating the transparent electrode of the plasma display panel according to the first embodiment of the present invention. 
         [0047]    Referring to  FIG. 3 , the bus electrode  161   b  is formed below the transparent electrode  161   a . The bus electrode  161   b  has a width BW. Further, the bus electrode  161   b  includes a black layer  161   bb  and a white layer  161   ba . The black layer  161   bb  comes in contact with the transparent electrode  161   a . The white layer  161   ba  is formed on the lower surface of the black layer  161   bb.    
         [0048]    The black layer  161   bb  has a dark color close to black. The dark color easily absorbs light. Therefore, light externally irradiated toward the plasma display panel can be absorbed so as to reduce the reflective brightness and to increase the black area. Accordingly, the bright room contrast is improved. 
         [0049]    Depressions  30  are formed on the lower surface of the transparent electrode  161   a  (see  FIG. 4 ). The black layer  161   bb  is formed along the depressions  30 . In other words, the depressions  30  are formed on the lower surface of the transparent electrode  161   a  that is in contact with the bus electrode  161   b . In particular, a part of the black layer  161   bb  is inserted into the depressions  30  of the transparent electrode  161   a . Accordingly, the adhesive force between the transparent electrode  161   a  and the bus electrode  161   b  can be further enhanced. 
         [0050]    In addition, since the black layer  161   bb  is formed along the depressions  30  of the transparent electrode  161   a , there is an advantage in that the actual surface area of the black layer  161   bb  increases. As a result, the black layer  161   bb  appears even darker, thereby increasing the black area of the panel. Therefore, the light-absorption ratio for externally irradiated light increases, resulting in a decrease in the reflective brightness of the panel. 
         [0051]    The black layer  161   bb  contains ruthenium (Ru), cobalt (Co), or manganese (Mn). Hence, the black layer  161   bb  has a dark color, i.e., close to black, and the conductivity of the black layer  161   bb  is low. On the other hand, the white layer  161   ba  contains silver (Ag), gold (Au), or aluminum (Al). Hence, the white layer  161   ba  has a bright color, i.e., close to white, and the conductivity of the white layer  161   ba  is excellent. 
         [0052]    Referring to FIG., the depressions  30  are formed on the transparent electrode  161   a . The depressions  30  have a hemispheric shape and are arranged in the first direction (y-axis direction in the drawing) and the second direction (x-axis direction in the drawing), spaced apart from one another at a distance. 
         [0053]      FIG. 5  is a plan view schematically illustrating an image display area of the plasma display panel according to the first embodiment of the present invention. Referring to  FIG. 5 , the discharge cells  19  are defined by the barrier rib  13 . The sustain electrode  161  and the scan electrode  162  are formed in a pair and extend in the second direction (x-axis direction in the drawing) along the discharge cells  19 . The bus electrodes  161   b  and  162   b  are linearly formed on the lower surfaces of the transparent electrodes  161   a  and  162   a . As described with reference to  FIG. 3 , the bus electrode  161   b  includes the black layer  161   bb  and the white layer  161   ba.    
         [0054]    As shown in  FIG. 5 , the plasma display panel has an image display area  40 . For convenience, only a part of the image display area  40  is depicted. The image display area  40  includes a first area  40   a , a second area  40   b , and a third area  40   c . The first area  40   a  is an area in which the phosphor layer  14  is visible through the front substrate  15 . The second area  40   b  is an area in which the barrier rib  13  is visible through the front substrate  15 . The third area  40   c  is an area in which the bus electrodes  161   b  and  162   b  are visible through the front substrate  15 . In this embodiment of the present invention, the third area  40   c  has a black color due to the black layer  161   bb  (shown in  FIG. 3 ). That is, the actual surface area of the black layer  161   bb  increases, thereby increasing the black area and the external light absorption ratio. 
         [0055]      FIG. 6  is a partial perspective view illustrating the transparent electrode of the plasma display panel according to a second embodiment of the present invention. Referring to  FIG. 6 , depressions  60  are formed in the transparent electrode  161   a . The depressions  60  are formed in the shape of channels extending in a second direction (x-axis direction in the drawing). The depressions  60  are arranged in a first direction (y-axis direction in the drawing). Specifically, the channels formed in the depressions  60  have a concave shape in which a plurality of the channels are adjacent to one another in that first (y-axis) direction. 
         [0056]      FIG. 7  is a partial perspective view of the transparent electrode of the plasma display panel according to a third embodiment of the present invention. Referring to  FIG. 7 , depressions  70  are formed in the shape of channels extending in a first direction (y-axis direction in the drawing) and are arranged in a second direction (x-axis direction in the drawing). Specifically, the channels formed in the depressions  70  have a concave shape in which a plurality of the channels are adjacent to one another in that second (x-axis) direction. 
         [0057]      FIG. 8  is a partial perspective view of the transparent electrode of the plasma display panel according to a fourth embodiment of the present invention. Referring to  FIG. 8 , protrusions  80  are formed on a surface of the transparent electrode  161   a . The bus electrode  161   b  and the black layer  161   bb  are formed along the protrusion  80 . Although the protrusions  80  have a hemispheric shape in this embodiment of the present invention, the protrusions  80  may have another shape such as a pyramid shape or a cuboid shape. 
         [0058]      FIG. 9  is a partial perspective view of the transparent electrode of the plasma display panel according to a fifth embodiment of the present invention. Referring to  FIG. 9 , depressions  90  are formed in the transparent electrode  161   a . The depressions  90  are arranged in a zigzag shape. 
         [0059]    In several embodiments of the present invention, the protrusion portions  80  ( FIG. 8 ) or the depressions  30  ( FIG. 4 ),  60  ( FIG. 6 ), and  90  ( FIG. 9 ) may be formed on the transparent electrodes  161   a  and  162   a . With the resulting increase in contact area between the black layer  161   bb  and the transparent electrodes  161   a  and  162 , there is an advantage in that an assembled structure of the transparent electrode and the bus electrode is strengthened. 
         [0060]      FIG. 10  is a partial cross-sectional view of the plasma display panel according to a sixth embodiment of the present invention.  FIGS. 11A to 11D  are plan views illustrating various patterns of depressions formed in the front substrate of the plasma display panel according to the sixth embodiment of the present invention. Descriptions will be given with reference to  FIG. 10  and  FIGS. 11A to 11D  according to the sixth embodiment of the present invention. The same or like parts of  FIGS. 1 to 9  will be referenced with the same reference numerals. The descriptions thereof will be omitted. 
         [0061]    Referring to  FIG. 10 , the bus electrode  161   b  and a colored layer  100  are formed on the lower surface of the front substrate  15 . As described above, the bus electrode  161   b  includes the black layer  161   bb  and the white layer  161   ba . The colored layer  100  is formed above the barrier rib  13  formed between the discharge cells  19 . 
         [0062]    The sixth embodiment of the present invention is characterized in that curved portions are formed in the front substrate  15 , and the bus electrodes  161   b  are formed in regions where the curved portions are formed. As shown in the drawing, the black layer  161   bb  is formed along the curved portions of the front substrate  15 . The white layer  161   ba  is additionally formed on the black layer  161   bb . Similarly to the bus electrode  161   b , the colored layers  100  are also formed in regions where the curved portions of the front substrate  15  are formed. The curved portions are formed in the shape of depressions or protrusions. 
         [0063]    In this embodiment of the present invention, the contact area between the black layer  161   bb  and the front substrate  15  increases. Thus, there is an advantage in that the structure of the black layer and the front substrate is strengthened. 
         [0064]    The colored layer  100  is made of the same material as the black layer  161   bb  of the bus electrode  161   b . That is, the colored layer  100  contains ruthenium (Ru), cobalt (Co), or manganese (Mn). Hence, the colored layer  100  has a dark color, i.e., close to black, that increases the black area of the panel, and improves the bright room contrast. The colored layer  100  may be formed on a non-discharge area, for example, an upper surface of the barrier rib  13 , so as not to adversely affect the discharge efficiency. 
         [0065]    As shown in  FIGS. 11A to 11D  as examples, various shapes of depressions  110 ,  112 ,  114 , and  116  can be formed in the front substrate  15 . Referring to  FIG. 11A , the half-ellipsoidal depressions  110  and the hemispherical depressions  112  are formed in the front substrate  15 . The bus electrode  161   b  is formed along the half-ellispoidal depressions  110 . The colored layer  100  is formed along the hemispherical depressions  112 . 
         [0066]    Referring to  FIG. 11B , the bus electrode  161   b  is formed on one side of the hemispherical depressions  112 . The colored layer  100  is formed on the other side of the hemispherical depressions  112 . 
         [0067]    Referring to  FIG. 11C , cuboid depressions  114  are formed in the front substrate  15 . The bus electrode  161   b  and the colored layer  110  are formed on a region where the cuboid depressions  114  are formed. 
         [0068]    Referring to  FIG. 11D , rhomboid depressions  116  are formed in the front substrate  15 . The bus electrode  161   b  and the colored layer  110  are formed on a region where the rhomboid depressions  116  are formed. 
         [0069]    It should be noted that  FIGS. 11A through 11D  show different shapes only for depressions and only this embodiment in which the black layers of the bus electrodes are disposed in the front substrate. However, the depressions and protrusions in the embodiment comprising a bus electrode with the depressions or protrusions disposed in the transparent electrodes ( FIGS. 4 ,  8  and  9 ) can also have varying shapes. In both embodiments, and for depressions and protrusions, the shapes can be hemispheres, half-ellipsoids, cuboids, rhomboids, and pyramids, but are not limited thereto. 
         [0070]    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.