Abstract:
A Plasma Display Panel (PDP) with an improved structure of electrodes that enhances discharge efficiency and luminous efficiency includes: front and rear substrates facing each other; barrier ribs partitioning a plurality of discharge cells in a space between the front and rear substrates; address electrodes extending along a first direction between the front and rear substrates; first and second electrodes extending along a second direction crossing the first direction corresponding to each of the discharge cells, and phosphor layers contained within the discharge cells. The first and second electrodes include metal electrodes extending in the second direction, protrusion electrodes projecting toward a center of each of the discharge cells from the metal electrodes, and fence electrodes surrounding the protrusion electrodes.

Description:
CLAIM OF PRIORITY  
       [0001]     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 9 Mar. 2005 and there duly assigned Ser. No. 10-2005-0019547.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a Plasma Display Panel (PDP), and more particularly to a PDP with an improved electrode structure, which enhances discharge efficiency and luminous efficiency.  
         [0004]     2. Description of the Related Art  
         [0005]     A Plasma Display Panel (hereinafter referred to as a PDP) is a display apparatus using plasma discharge. In other words, vacuum ultraviolet light emitted by the plasma discharge excites phosphor layers, which in turn emit visible rays. The PDP has been highlighted as a next generation large-sized flat display because it has characteristics of a large screen and high definition.  
         [0006]     A typical PDP has a three-electrode surface discharge structure. A pair of electrodes is formed on a front substrate while facing each other on the same plane. Address electrodes are formed on a rear substrate spaced apart from the front substrate. Thus, a plurality of discharge cells are formed at the location where the pair of electrodes and the address electrodes intersect each other. The plurality of discharge cells are defined by barrier ribs which are formed between the front and rear substrates. Phosphor layers are formed in the discharge cells, and a discharge gas is injected therein.  
         [0007]     Millions of unit discharge cells are arranged in a matrix within the PDP. The discharge cells arranged in a matrix are driven simultaneously using memory characteristics.  
         [0008]     In more detail, discharge cells to be turned on are selected using memory characteristics of wall charges, and sustain discharges are generated in the selected discharge cells.  
         [0009]     In other words, in the case of selecting the discharge cells, scan pulse voltages are supplied to scan electrodes of the pair of electrodes arranged on the front substrate, and predetermined voltages are supplied to address electrodes. Accordingly, a weak discharge occurs between the scan and address electrodes and wall charges are accumulated inside the discharge cells, thereby selecting the discharge cells to be turned on. Subsequently, a discharge firing voltage is supplied to the pair of electrodes arranged on the front substrate, thereby causing the sustain discharge to occur in the selected discharge cells.  
         [0010]     In the PDP structured and operated as described above, several steps are involved between when power is input to the PDP to when visible light rays are emitted therefrom. Therefore, there is a problem in that the luminous efficiency (the ratio of brightness to power consumption) is very low because the energy conversion efficiency in each step is very low.  
         [0011]     Furthermore, the pair of electrodes arranged on the front substrate includes a transparent electrode formed over the discharge cells and a metal electrode. The metal electrode compensates for a voltage drop due to the high resistance of the transparent electrode. However, because the transparent electrode has a low conductivity, the structure of the electrodes require a high discharge current. This results in an increase in the consumed power and a decrease in the luminous brightness.  
       SUMMARY OF THE INVENTION  
       [0012]     The present invention has been made in an effort to provide a PDP with an improved electrode structure that enhances the discharge efficiency and luminous efficiency thereof.  
         [0013]     An exemplary Plasma Display Panel (PDP) according to an embodiment of the present invention includes: front and rear substrates facing each other; barrier ribs partitioning a plurality of discharge cells in a space between the front and rear substrates phosphor layers contained within the discharge cells; address electrodes extending along a first direction between the front and rear substrates; and first and second electrodes extending along a second direction crossing the first direction and corresponding to each of the discharge cells, the first and second electrodes including: metal electrodes extending in the second direction; protrusion electrodes projecting toward a center of each of the discharge cells from the metal electrodes; and fence electrodes surrounding the protrusion electrodes.  
         [0014]     The fence electrodes preferably extend from the metal electrodes. The fence electrodes preferably include: first line portions extending in the first direction from the metal electrodes and arranged between adjacent protrusion electrodes in the second direction; and second line portions extending in the second direction, the second line portions connecting the first line portions to each other.  
         [0015]     The first line portions are preferably arranged at boundaries between adjacent discharge cells in the second direction. The second line portions of the first electrodes and the second line portions of the second electrodes are preferably arranged opposite to each other with the center of each of the discharge cells therebetween. A distance between the second line portions of the first electrodes and the second line portions of the second electrodes is preferably less than the distance between the protrusion electrodes of the first electrodes and the protrusion electrodes of the second electrodes.  
         [0016]     The barrier ribs preferably include longitudinal barrier ribs extending in the first direction, and the first line portions are preferably arranged along and over the longitudinal barrier ribs. The barrier ribs preferably include longitudinal barrier ribs extending in the first direction and transverse barrier ribs extending in the second direction, and the metal electrodes are preferably arranged adjacent to the transverse barrier ribs.  
         [0017]     The fence electrodes are preferably arranged apart from the protrusion electrodes. The protrusion electrodes and the fence electrodes each preferably include a transparent conductive material. The protrusion electrodes and the fence electrodes each alternatively preferably include an opaque metal material.  
         [0018]     Widths of the protrusion electrodes measured in the second direction are preferably equal to widths of the metal electrodes. The protrusion electrodes preferably each include an opaque metal material, and the fence electrodes preferably each include a transparent conductive material.  
         [0019]     The protrusion electrodes preferably include first protrusions projecting toward the center of each of the discharge cells from the metal electrodes, and second protrusions surrounding the first protrusions. The second protrusions are preferably arranged between the first protrusions and the fence electrodes. The second protrusions are preferably respectively arranged apart from the first protrusions and the fence electrodes.  
         [0020]     Widths of the protrusion electrodes adjacent to the metal electrodes are preferably less than widths of the protrusion electrodes adjacent to the center of each of the discharge cells, the widths being measured in the second direction.  
         [0021]     The PDP further preferably includes recesses arranged in the protrusion electrodes, the recesses being arranged adjacent to the metal electrodes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     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:  
         [0023]      FIG. 1  is a partially exploded perspective view of a Plasma Display Panel (PDP) according to the first exemplary embodiment of the present invention.  
         [0024]      FIG. 2  is a partial plan view of the PDP of  FIG. 1 .  
         [0025]      FIG. 3  is cross-sectional view taken along the line III-III of  FIG. 2 .  
         [0026]      FIG. 4  is a partially exploded perspective view of a scan electrode according to the first exemplary embodiment of the present invention.  
         [0027]      FIG. 5  is a partially exploded perspective view of a scan electrode according to the second exemplary embodiment of the present invention.  
         [0028]      FIG. 6  is a partially exploded perspective view of a scan electrode according to the third exemplary embodiment of the present invention.  
         [0029]      FIG. 7  is a partial plan view of a PDP according to the fourth exemplary embodiment of the present invention.  
         [0030]      FIG. 8  is a graph of the distribution of the brightness in a unit discharge cell. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]     Embodiments of the present invention are described hereinafter in detail with reference to the accompanying drawings. The present invention can, however, be embodied in different forms and should not be construed as being limited to the exemplary embodiments set forth herein.  
         [0032]      FIG. 1  is a partially exploded perspective view showing a Plasma Display Panel (hereinafter, referred to as a PDP) according to the first exemplary embodiment of the present invention.  
         [0033]     Referring to  FIG. 1 , in the PDP of the present exemplary embodiment, a rear substrate  10  and a front substrate  20  are arranged opposite to each other with a predetermined distance therebetween. Color-based discharge cells  18  ( 18 R,  18 G, and  18 B) are partitioned using barrier ribs  16 , at a space between the rear and front substrates I 0  and  20 . Furthermore, phosphor layers  19 , which are excited to emit visible light, are formed in each of the discharge cells  18 . In more detail, the phosphor layers  19  are formed on side surfaces of the barrier ribs, and on bottom surfaces of the discharge cells  18 . The discharge cells  18  are filled with a discharge gas to generate a plasma discharge, and the discharge gas includes a mixture of xenon (Xe) and neon (Ne).  
         [0034]     The front substrate  20  is formed of a transparent material such as glass. Accordingly, the front substrate  20  transmits the visible light to thereby display an image.  
         [0035]     Address electrodes  12  are formed to extend in a first direction (y axis direction in  FIG. 1 ) on the inner surface of the rear substrate  10  opposite to the front substrate  20 . The address electrodes  12  are arranged to be spaced apart from each other while corresponding to each of the discharge cells  18 . In addition, the address electrodes  12  are covered with dielectric layers  14 . The barrier ribs  16  have a predetermined pattern and are formed on the dielectric layers  14 .  
         [0036]     The barrier ribs  16  partition the discharge cells  18 , i.e., discharge spaces where the discharge is performed. This prevents cross-talk between adjacent discharge cells  18 . The barrier ribs  16  include longitudinal barrier ribs  16   a  and transverse barrier ribs  16   b.  The longitudinal barrier ribs  16   a  extend in a first direction (y-axis direction  FIG. 1 ) and are spaced apart from each other with the address electrodes  12  therebetween, and the transverse barrier ribs  16   b  are formed to extend in a second direction (x axis direction in  FIG. 1 ) crossing the first direction. The longitudinal barrier ribs  16   a  and the transverse barrier ribs  16   b  are in one plane. In this way, discharge cells  18  with a closed structure are formed.  
         [0037]     The aforementioned structure of the barrier ribs is a preferable exemplary embodiment, and accordingly it is possible that variously shaped barrier ribs such as stripe-type barrier ribs can be arranged to be in parallel with the address electrodes  12 .  
         [0038]     Ultraviolet light emitted by the plasma discharge excites the phosphor layers  19  that are formed inside the discharge cells  18 , thereby causing visible light to be emitted. As shown in  FIG. 1 , the phosphor layers  19  are formed on side surfaces of the barrier ribs  16 , and on bottom surfaces of the discharge cells  18  defined by the barrier ribs  16 . The phosphor layers  19  can each be formed using any one of red (R), green (G), and blue (B) phosphors to represent color. Accordingly, the phosphor layers  19  may be classified into red, green, and blue phosphor layers  18 R,  18 G, and  18 B. As described above, the discharge gas, such as the mixture of neon (Ne) and xenon (Xe), is injected into the discharge cells  18  where the phosphor layers  19  are formed.  
         [0039]     Display electrodes  25  are formed to extend in the second direction (x axis direction in  FIG. 1 ) on an inner surface of the front substrate  20  opposite to the rear substrate  10 , corresponding to each of the discharge cells  18 . Each display electrode  25  is functionally comprised of a first electrode (hereinafter referred to as a sustain electrode)  21  and a second electrode (hereinafter referred to as a scan electrode)  23 . The scan electrode  23  interacts with an address electrode  12  to select a discharge cell  18  to be turned on, and the sustain electrode  21  interacts with the scan electrode  23  to generate a sustain discharge at the selected discharge cell  18 .  
         [0040]     The display electrodes  25  that are comprised of the scan and sustain electrodes  23  and  21  each include metal, protrusion, and fence electrodes. A detailed description of the display electrodes  25  will be given later.  
         [0041]     The display electrodes  25  are covered with dielectric layers  28 , which are formed of dielectric materials such as PbO, B 2 O 3 , or SiO 2 . The dielectric layers  28  prevent charged particles from directly colliding with and damaging the display electrodes  25  during the discharge, and collect the charged particles.  
         [0042]     Protective layers  29 , which are formed of magnesium oxide (MgO), are formed on the dielectric layers  28 . The protective layers  29  prevent charged particles from directly colliding with and damaging the dielectric layers  28  during the discharge. Furthermore, when the charged particles collide with the protective layers  29 , secondary electrons are emitted, thereby improving discharge efficiency.  
         [0043]      FIG. 2  is a partial plan view of the PDP of  FIG. 1 ,  FIG. 3  is cross-sectional view taken along the line III-III of  FIG. 2 , and  FIG. 4  is a partially exploded perspective view of a scan electrode according to the first exemplary embodiment of the present invention.  
         [0044]     The structure of the discharge cells according to the present embodiment is explained below with reference to FIGS.  2  to  4 .  
         [0045]     Referring to  FIGS. 2 and 3 , a plurality of transverse barrier ribs  16   b  are formed to extend along the second direction (x axis direction in  FIG. 2 ). The transverse barrier ribs  16   b  are formed over the entire surface of the dielectric layers  14  of the rear substrate  14  while maintaining a constant interval between adjacent transverse barrier ribs  16   b.    
         [0046]     Furthermore, the longitudinal barrier ribs  16   a  are formed in the first direction crossing the transverse barrier ribs  16   b.  Accordingly, the discharge cells  18  are partitioned into a lattice shape.  
         [0047]     The discharge cells  18  are formed in a rectangular shape in which the longitudinal length is greater than the transverse length. A pixel is configured to have red, green, and blue discharge cells. A pixel is a base unit for displaying an image. Display electrodes  25  are formed on the inner surface of the front substrate  20  opposite to the rear substrate  10 . The display electrodes  25  extend in the second direction (x axis direction in  FIG. 2 ), and the scan and sustain electrodes  23  and  21  of the display electrodes  25  are arranged opposite to each other up and down inside the discharge cells.  
         [0048]     The scan electrodes  23  and the sustain electrodes  21  have the same shape in the present embodiment. Therefore, the present embodiment is explained below with respect to the scan electrodes  23  and not the sustain electrodes  21 .  
         [0049]     In the present embodiment, the scan electrodes  23  include metal electrodes  231 , protrusion electrodes  233 , and fence electrodes  235 .  
         [0050]     The metal electrodes  231  are formed to extend in the second direction. Specifically, the metal electrodes  231  are arranged adjacent to the transverse barrier ribs  16   b  within the discharge cells. The metal electrodes  231  are formed as a thin film. The metal electrodes  231  and  211  of the scan and sustain electrodes  23  and  21  are respectively formed adjacent to the edges (x axis direction in  FIG. 2 ) of each of the discharge cells. In addition, the metal electrodes  231  and  211  are formed of a highly conductive material (Ag, Cr, etc.) to compensate for the high resistance of the protrusion electrodes  233  and  213  and the fence electrodes  235  and  215 . The protrusion electrodes  233  are formed to project from the metal electrodes  231  toward the center of the discharge cells. Furthermore, because the protrusion electrodes  233  have a predetermined surface area, wall charges can be accumulated at locations corresponding to the protrusion electrodes  233 . Accordingly, the protrusion electrodes  233  play a substantial role in generating a main discharge within the discharge cells. The protrusion electrodes  233  are formed of a conductive transparent material such as Indium Tin Oxide (ITO) so as to obtain a suitable aperture ratio.  
         [0051]     The fence electrodes  235  are formed within the discharge cells  18  to surround the protrusion electrodes  233 . The fence electrodes  235  are arranged to be spaced apart from the protrusion electrodes  233 , and are formed of a conductive transparent material.  
         [0052]     Specifically, the fence electrodes include first line portions  235   a  and second line portions  235   b.  The first line portions  235   a  are formed to extend along the first direction from the metal electrodes  231  between the adjacent protrusion electrodes  233  in the second direction, and the second line portions  235   b  are formed to extend in the second direction while connecting the first line portions  235   a  to each other. More specifically, the first line portions  215   a  and  235   a  are arranged at the boundaries between adjacent discharge cells  18  in the second direction. Furthermore, the second line portions  235   b  of the scan electrodes  23  and the second line portions  215   b  of the sustain electrodes  21  are arranged opposite to each other with the center of each of the discharge cells  18  therebetween, thereby forming a discharge gap.  
         [0053]     In other words, a distance GI between the second line portions  235   b  of the scan electrodes  23  and the second line portions  215   b  of the sustain electrodes  21  is shorter than a distance G 2  between the protrusion electrodes  233  of the scan electrodes  23  and the protrusion electrodes  213  of the sustain electrodes  21 . Accordingly, an initial discharge occurs between the second line portions  235   b  and  215   b  in the initial stage of discharge. Subsequently, the initial discharge spreads to a long gap discharge between the protrusion electrodes  233  and  213  by the priming effect, and the long gap discharge diffuses into a surface discharge using the entire discharge space.  
         [0054]     The first line portions  235   a  are formed in thin films of strips, and are formed along and over the longitudinal barrier ribs  16   a.    FIG. 8  is a graph of the distribution of brightness in the unit discharge cell in a PDP. Referring to  FIG. 8 , the brightness has a peak value at the locations adjacent to the discharge gap between electrodes  101  and at the locations adjacent to the barrier ribs  201 . Accordingly, the brightness can be significantly enhanced because the first line portions  235   a  in the present embodiment are formed along and over the longitudinal barrier ribs  16   a.  In addition, the aperture ratio and the transmittance can be enhanced.  
         [0055]      FIG. 5  is a partially exploded perspective view of a scan electrode according to the second exemplary embodiment of the present invention.  
         [0056]     Referring to  FIG. 5 , protrusion electrodes  433  of scan electrodes  43  according to the present embodiment are formed of an opaque metal material. Furthermore, fence electrodes  435  surrounding the protrusion electrodes  433  of the scan electrodes  43  are formed of the opaque metal material. Accordingly, the power consumption can be lowered because the entirety of each scan electrode  43  is formed of the opaque metal materials.  
         [0057]     Furthermore, the widths of the protrusion electrodes  433  measured in the second direction are substantially the same as widths of the metal electrodes  431 . By this configuration, there is an advantage in that the aperture ratio does not decrease while lowering the power consumption.  
         [0058]      FIG. 6  is a partially exploded perspective view of a scan electrode according to the third exemplary embodiment of the present invention.  
         [0059]     Referring to  FIG.6 , scan electrodes  53  according to the present embodiment include metal electrodes  531 , protrusion electrodes  533  formed of an opaque metal material, and fence electrodes  535  formed of a transparent conductive material. Furthermore, the protrusion electrodes  533  include first protrusions  533   a  and second protrusions  533   b.  The first protrusions  533   a  are formed to project toward the center of each of the discharge cells from the metal electrodes  531 . The second protrusions  533   b  are formed to surround the first protrusions  533   a,  and are arranged between the first protrusions  533   a  and the fence electrodes  535 . Furthermore, the second protrusions  533   b  are spaced apart from the first protrusions  533   a  and the fence electrodes  535  by a predetermined distance.  
         [0060]     This configuration provides an advantage in that the transmittance does not decrease while lowering the power consumption.  
         [0061]      FIG. 7  is a partial plan view of a PDP according to the fourth exemplary embodiment of the present invention.  
         [0062]     Referring to  FIG. 7 , recesses S are formed in sustain electrodes  61  and scan electrodes  63  of the display electrodes  65  according to the present embodiment. Specifically, the widths W 1  of protrusion electrodes  633  adjacent to metal electrodes  631  are less than widths W 2  of the protrusion electrodes  633  adjacent to the center of each of the discharge cells near the fence electrodes  635 , the widths being measured in the second direction (x axis direction in  FIG.7 ). Basically, a weak discharge occurs at the location where the protrusion electrodes  633  meet the metal electrodes  631 . Accordingly, because the recesses S are formed in the protrusion electrodes  633  at locations where the protrusion electrodes  633  meet the metal electrodes  631 , the discharge efficiency can be enhanced while lowering the power consumption.  
         [0063]     The discharge efficiency and luminous efficiency of a PDP can be enhanced because the display electrodes according to the present invention have the protrusion electrodes and the fence electrodes surrounding the protrusion electrodes.  
         [0064]     Furthermore, according to the display electrodes of the present invention, the aperture ratio and transmittance can be enhanced even more because the area of transparent conductive electrodes is decreased.  
         [0065]     While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the present invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.