Patent Publication Number: US-2007120486-A1

Title: Plasma display panel

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims the priority of Korean Patent Application No. 10-2005-0115878, filed on Nov. 30, 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  
      The present embodiments relate to a plasma display panel (PDP), and more particularly, to a PDP in which sizes of electron emitting sources differ in each of discharge cells such that a discharge characteristic is improved.  
      2. Description of the Related Art  
      Generally, plasma display panels (PDP) are flat display devices in which a discharge gas is injected into a plurality of substrates and sealed between the substrates and, if a gas discharge occurs due to a voltage applied to a plurality of discharge electrodes, a phosphor layer is excited by ultraviolet rays generated in a discharge process and visible rays are emitted such that desired numbers, characters or graphics are realized.  
      A 3-electrode surface discharge type PDP that is often used includes a front substrate; a rear substrate opposing the front substrate; an X electrode and a Y electrode which are a sustain discharge electrode pair formed on an inner surface of the front substrate; a front dielectric layer burying the sustain discharge electrode pair; a protective layer coated on a surface of the front dielectric layer; an address electrode formed on an inner surface of the rear substrate and disposed to cross the sustain discharge electrode pair; a rear dielectric layer burying the address electrode; barrier ribs installed between the front and rear substrates; and red, green, and blue phosphor layers coated on insides of the barrier ribs and a surface of the rear dielectric layer. A discharge gas is injected into an inner space in which the front and rear substrates are combined with each other, thereby forming a discharge region.  
      In a conventional PDP having the above structure, electrons are continuously supplied and accelerated through a discharge; the accelerated electrons collide with neutral particles and excitation particles are generated by the collision, ultraviolet rays are emitted by the excitation particles, a phosphor layer is excited by the ultraviolet rays whereby visible rays are generated.  
      However, in this procedure, ions that do not increase luminous efficiency are generated, much energy is consumed in accelerating the ions such that discharge efficiency is very low due to an unnecessary energy loss.  
      In addition, due to a discharge characteristic, if discharge cells are made smaller, a problem with reliability occurs, in that discharge efficiency is further lowered and an unstable discharge occurs. Thus, for the present, PDPs have been mainly used in a video graphics array (VGA) (640×480) and a super VGA (SVGA) (800×600). However, high definition is needed for development of a PDP for high definition television (HDTV) (1920×1035).  
     SUMMARY OF THE INVENTION  
      The present embodiments provide a plasma display panel (PDP) in which the area or the number of discharge electrodes or electron emitting sources such as porous silicon oxidized on a dielectric layer differs such that brightness is controlled by discharge cells.  
      According to an aspect of the present embodiments, there is provided a plasma display panel comprising: a front substrate; a rear substrate opposing the front substrate; a plurality of discharge electrodes disposed inside the substrates; a plurality of light emitting layers formed inside discharge cells; and an electron emitting source disposed inside the discharge cells so as to supply electrons, an area of electron emitting source differing in each of the discharge cells.  
      The electron emitting source may include: a first electrode which becomes a source for emitting electrons; and an electron accelerating layer formed on the first electrode.  
      The electron accelerating layer may be one layer selected from the group consisting of an oxidized porous poly silicon (OPPS) layer and an oxidized porous amorphous silicon (OPAS) layer.  
      A second electrode may be further formed on the electron accelerating layer so that an electric field can be formed between the first electrode and the second electrode.  
      The light emitting layer may be formed on an inner surface of other substrate corresponding to a substrate on which the electron emitting source is installed.  
      An area of the electron emitting source disposed in discharge cells having lower brightness may be larger than an area of an electron emitting source disposed in discharge cells having higher brightness.  
      According to another aspect of the present embodiments, there is provide a plasma display panel comprising: a front substrate; a rear substrate opposing the front substrate; a plurality of discharge electrodes disposed inside the substrates; a plurality of light emitting layers applied inside discharge cells; and an electron emitting source disposed inside the discharge cells so as to supply electrons, the number of electron emitting source differing in each of the discharge cells.  
      The number of electron emitting sources disposed in discharge cells having a lower brightness may be larger than the number of electron emitting sources disposed in discharge cells having higher brightness.  
      A plurality of electron emitting sources disposed in discharge cells having lower brightness, respectively, may be disposed along both opposed edges of the discharge cells. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other aspects and advantages of the present embodiments will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:  
       FIG. 1  is a combined cross-sectional view of a plasma display panel (PDP) according embodiment;  
       FIG. 2  is a combined cross-sectional view of a PDP according to another embodiment;  
       FIG. 3  is a combined cross-sectional view of a PDP according to another embodiment;  
       FIG. 4  is a combined cross-sectional view of a PDP according to another embodiment;  
       FIG. 5  is a combined cross-sectional view of a PDP according to another embodiment; and  
       FIG. 6  is a combined cross-sectional view of a PDP according to another embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present embodiments will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments are shown.  
       FIG. 1  illustrates a plasma display panel (PDP)  100  according to an embodiment. Referring to  FIG. 1 , the PDP  100  includes a front substrate  101  and a rear substrate  102  parallel to the front substrate  101 . The front substrate  101  and the rear substrate  102  form a discharge space sealed by a frit glass coated along edges of opposed inner surfaces.  
      The front substrate  101  may be a transparent substrate such as, for example, a soda lime glass, a semi-transmitted type substrate, a reflective type substrate or a colored substrate. A sustain discharge electrode pair  103  is formed on an inner surface of the front substrate  101 . The sustain discharge electrode pair  103  includes an X electrode  104  and a Y electrode  105 . A pair of the X electrode  104  and the Y electrode  105  is disposed by discharge cells.  
      The X electrode  104  includes a first discharge electrode line  104   a  disposed along one direction of the PDP  100  and a first bus electrode line  104   b  disposed along one edge of the surface of the first discharge electrode line  104   a . The first discharge electrode line  104   a  and the first bus electrode line  104   b  have striped shapes.  
      The Y electrode  105  includes a second discharge electrode line  105   a  disposed along one direction of the PDP  100  and a second bus electrode line  105   b  disposed along one edge of the surface of the second discharge electrode line  105   a . The second discharge electrode line  105   a  and the second bus electrode line  105   b  have striped shapes. The Y electrode  105  opposes the X electrode  104  by discharge cells. It is advantageous that the Y electrode  105  and the X electrode  104  are symmetrical with each other so that a discharge is uniformly performed.  
      According to the current embodiment, the first discharge electrode line  104   a  and the second discharge electrode line  105   a  are formed of a transparent conductive film, and the first bus electrode line  104   b  and the second bus electrode line  105   b  may be formed of a silver paste having high conductivity or metal such as chrome-copper-chrome, in order to compensate for a line resistance of the first discharge electrode line  104   a  and the second discharge electrode line  105   a.    
      The X electrode  104  and the Y electrode  105  include the first and second discharge electrode lines  104   a  and  105   a  formed of an ITO film, respectively, and the first and second bus electrode lines  104   a  and  105   b  formed of metal and disposed along one edge of an upper surface of each of the X electrode  104  and the Y electrode  105 , respectively. However, the present embodiments are not limited to this.  
      The X electrode  104  and the Y electrode  105  are buried by the front dielectric layer  106 . The front dielectric layer  106  is formed of transparent dielectric such as a high dielectric material, for example, PbO—B 2 O 3 —SiO 2 .  
      A protective layer  107  made of, for example, magnesium oxide (MgO) is formed on the surface of the front dielectric layer  106 , so as to increase the amount of secondary electron emitted. The protective layer  107  is deposited on the surface of the front dielectric layer  106 .  
      The rear substrate  102  may be a transparent substrate, a semi-transmitted type substrate, a reflective type substrate or a colored substrate. An address electrode  108  is disposed on an inner surface of the rear substrate  102  to cross the X electrode  104  and the Y electrode  105 . The address electrode  108  has a striped shape and goes across adjacent discharge cells along other direction of the PDP  100 . The address electrode  108  is formed of metal having high conductivity, for example, a silver paste. The address electrode  108  is buried by the rear dielectric layer  109 . The rear dielectric layer  109  is formed of a high dielectric material, as is the front dielectric layer  106 .  
      Barrier ribs  110  are disposed between the front substrate  101  and the rear substrate  102 . The barrier ribs  110  are formed to define the discharge cells and to prevent crosstalk between the adjacent discharge cells.  
      The barrier ribs  110  have one of striped, meander, and matrix shapes that can partition a discharge space. A cross-section of the discharge space partitioned by the barrier ribs  110  may be, for example, polygonal, circular, or elliptical shaped.  
      A light emitting layer  111  is coated on an inner surface of the protective layer  107  by discharge cells. A light emission mechanism in which visible rays can be emitted by a discharge is present in the light emitting layer  111 . The light emitting layer  111  includes a red light emitting layer  111 R, a green light emitting layer  111 G, and a blue light emitting layer  111 B so that the PDP  100  can realize color images. The red light emitting layer  111 R, the green light emitting layer  111 G, and the blue light emitting layer  111 B are disposed inside each of discharge cells and respectively form a sub-pixel.  
      The light emitting layer  111  may be formed of a material in which atoms which were released by an energy generated in a ultraviolet region are stabilized and visible rays can be generated. A photo luminescence (PL) phosphor layer or a quantum dot may be used for the light emitting layer  111 .  
      Since quantum dots have no interference between atoms, if an energy is generated from the outside, atoms released at an atom energy level are stabilized and emit light. Thus, since excitation can be performed with a low voltage, luminous efficiency can be improved and a printing process is possible which is advantageous in making a PDP larger.  
      Here, the area or number of discharge cells differs so that an electron emitting source for generating a larger amount of electrons in large-area or a number of discharge cells is disposed, which will be described in greater details as follows.  
      The electron emitting source  115  is disposed in a discharge space defined by the barrier ribs  110 . The electron emitting source  115  includes a red electron emitting source  112 , a green electron emitting source  113 , and a blue electron emitting source  114 .  
      The red electron emitting source  112  includes a first electrode  112   a  formed on a upper surface of the rear dielectric layer  109  and a first electron accelerating layer  112   b  having the same width as the first electrode  112   a  and formed on the surface of the first electrode  112   a.    
      The green electron emitting source  113  includes a second electrode  113   a  formed on the upper surface of the rear dielectric layer  109  in other discharge cells adjacent to the discharge cells in which the red electron emitting source  112  is disposed and a second electron accelerating layer  113   b  having the same width as the second electrode  113   a  and formed on the surface of the second electrode  113   a.    
      The blue electron emitting source  114  includes a third electrode  114   a  formed on the upper surface of the rear dielectric layer  109  in other discharge cells adjacent to the discharge cells in which the green electron emitting source  113  is disposed and a third electron accelerating layer  114   b  having the same width as the third electrode  114   a  and formed on the surface of the second electrode  114   a.    
      If the width of the red electron emitting source  112  is W 1 , the width of the green electron emitting source  113  is W 2  and the width of the blue electron emitting source  114  is W 3 , the width W 3  of the blue electron emitting source  114  is larger than the width W 1  of the red electron emitting source  112  or the width W 2  of the green electron emitting source  113 .  
      As a result, even when the same power is applied to the red electron emitting source  112 , the green electron emitting source  113 , and the blue electron emitting source  114 , respectively, the amount of electrons supplied to the blue discharge cells in which the blue electron emitting source  114  is disposed is larger than the amount of electrons supplied to the red discharge cells in which the red electron emitting source  112  is disposed or the amount of electrons supplied to the green discharge cells in which the green electron emitting source  113  is disposed.  
      The first, second, and third electrodes  112   a ,  113   a , and  114   a  may be formed of a transparent conductive layer, such as an indium tin oxide (ITO) layer, or a metallic layer having high conductivity, such as Al or Ag. The first, second, and third electrodes  112   a ,  113   a , and  114   a  are coupled to ground and biased to 0 V.  
      The first, second, and third electron accelerating layers  112   b ,  113   b , and  114   b  may be formed of a material in which atoms are accelerated and electron beams can be generated, for example, an oxidized porous silicon (OPS) layer. OPS includes oxidized porous poly silicon (OPPS) or oxidized porous amorphous silicon (OPAS).  
      As an alternative, an electron emitting source including boron nitride bamboo shoot (BNBS) may be used. BNBS has a transparent property in a wavelength region of from about 380 to about 780 nanometers, which is a visible ray region, and BNBS has negative electron affinity and thus, the electron emission characteristic of BNBS is excellent.  
      Even when BNBS is used, the first, second, and third electrodes  112   a ,  113   a , and  114   a  are formed on the surface of the rear dielectric layer  109  in each of the red, green, and blue discharge cells, and a BNBS layer is formed on the surface of the first, second, and third electrodes  112   a ,  113   a , and  114   a  to have the same width as the widths thereof.  
      A discharge gas is injected in an internal space sealed by the front substrate  101  and the rear substrate  102  combined with each other. The discharge gas can be for example, xenon (Xe) gas, neon (Ne) gas, helium (He) gas, argon (Ar) gas or any mixture thereof.  
      In this case, the gas in which the electron beams emitted from the electron emitting source  115  are used may be a gas which is excited by an external energy generated by the electron beams and can generate ultraviolet (UV) rays. That is, various gases such as N 2 , heavy hydrogen, carbon dioxide, hydrogen gas, carbon monoxide, and krypton (Kr) or an atmospheric pressure air may also be used. In addition, a discharge gas that is usually used in a PDP may be used.  
      The operation of the PDP  100  having the above structure according to the present embodiments will now be described.  
      First, if an address voltage is applied between the Y electrode  105  and the address electrode  108 , an address discharge occurs. Discharge cells in which a sustain discharge will occur as a result of the address discharge are selected.  
      In this case, an electric field is formed between the Y electrode  105  and the address electrode  108 . Due to the electric field, electrons flow into the first, second, and third electron accelerating layers  112   b ,  113   b , and  114   b  from the first, second, and third electrodes  112   a ,  113   a , and  114   a , and the electrons pass through the first, second, and third electron accelerating layers  112   b ,  113   b , and  114   b  and are accelerated and then are emitted into the discharge cells.  
      If the electrons flow into the discharge cells, an address discharge can occur smoothly. Thus, an address driving voltage can be reduced and a sufficient address discharge can be performed.  
      Next, if a sustain discharge voltage is applied between the X electrode  104  and the Y electrode  105  in the selected discharge cells, due to movement of wall charges accumulated on the X electrode  104  and the Y electrode  105 , a sustain discharge in a surface discharge form occurs.  
      If the sustain discharge occurs, the energy level of the excited discharge gas during the sustain discharge is reduced and UV rays are emitted. The UV rays excite the red, green, and blue light emitting layers  111 R,  111 G, and  111 B applied in the discharge cells.  
      After that, the energy level of the excited red, green, and blue light emitting layers  111 R,  111 G, and  111 B is reduced, visible rays are emitted through the front substrate  101 , and the emitted visible rays constitute an image.  
      In this way, in the PDP  100  according to the present embodiments, the electron emitting source  115  is disposed above the address electrode  102  such that a characteristic of emitting electrons into the discharge cells during the address discharge is improved such that an address voltage to be applied during the address discharge can be reduced. Thus, a leakage current between the address electrodes  102  during the address discharge can be reduced, and crosstalk between the discharge cells is prevented such that the number of discharge errors can be reduced.  
      In addition, during the sustain discharge, an electric field is also formed between the X electrode  104  and the Y electrode  105 . Due to the electric field, electrons pass through the first, second, and third electron accelerating layers  112   b ,  113   b , and  114   b  and are accelerated and then are emitted into the discharge cells. Thus, since sufficient electrons are emitted into the discharge cells from the electron emitting source  115  during the sustain discharge as well as during the address discharge, a discharge sustain voltage to be applied during the sustain discharge is reduced and the sustain discharge can be performed such that discharge efficiency can be improved.  
      In particular, in order to improve discharge brightness in the blue discharge cells having lower discharge efficiency, the area of the blue electron emitting source  114  disposed in the blue discharge cells is larger than the area of the red electron emitting source  112  and the area of the green electron emitting source  113  disposed in the green discharge cells. As such, a larger amount of electrons are generated in the blue discharge cells, and a large amount of excitation species are formed in the discharge cells such that brightness is compensated for.  
       FIG. 2  illustrates a plasma display panel (PDP)  200  according to another embodiment. Referring to  FIG. 2 , the PDP  200  includes a front substrate  201  and a rear substrate  202  that opposes the front substrate  201 .  
      A pair of sustain discharge electrodes  203  having an X electrode  204  in which a sustaing discharge occurs and a Y electrode  205  are disposed on an inner surface of the front substrate  201 . The X electrode  204  includes a first discharge electrode line  204   a  and a first bus electrode line  204   b  disposed along one edge of the first discharge electrode line  204   a . The Y electrode  205  includes a second discharge electrode line  205   a  and a second bus electrode line  205   b  disposed along one edge of the second discharge electrode line  205   a . The sustain discharge electrode  203  is buried by a front dielectric layer  206 . A protective layer  207  is formed on an inner surface of the front dielectric layer  206 .  
      An address electrode  208  is disposed on an inner surface of the rear substrate  202  to across the pair of sustain discharge electrodes  203 . The address electrode  208  is buried by a rear dielectric layer  209 .  
      Barrier ribs  210  for partitioning a discharge space and preventing crosstalk are installed between the front substrate  201  and the rear substrate  202 . In addition, a light emitting layer  211  is formed on an inner surface of the protective layer  207 . The light emitting layer  211  includes a red light emitting layer  211 R, a green light emitting layer  211 G, and a blue light emitting layer  211 B in each of discharge cells so that color images can be realized.  
      In this case, an electron emitting source  215  is disposed in the discharge space defined by the barrier ribs  210 . The electron emitting source  215  includes a red electron emitting source  212 , a green electron emitting source  213 , and a blue electron emitting source  214 .  
      The red electron emitting source  212  includes a first electrode  212   a  formed on an upper surface of the rear dielectric layer  208 , a first electron accelerating layer  212   b  having the same width as the first electrode  212   a  and formed on the surface of the first electrode  212   a  and a second electrode  212   c  formed on an upper surface of the first electron accelerating layer  212   b.    
      The green electron emitting source  213  includes a third electrode  213   a  formed on the upper surface of the rear dielectric layer  209  in other discharge cells adjacent to the discharge cells in which the red electron emitting source  212  is disposed, a second electron accelerating layer  213   b  having the same width as the third electrode  213   a  and formed on the surface of the third electrode  213   a  and a fourth electrode  213   c  formed on an upper surface of the second electron accelerating layer  213   b.    
      The blue electron emitting source  214  includes a fifth electrode  214   a  formed on the upper surface of the rear dielectric layer  209  in other discharge cells adjacent to the discharge cells in which the green electron emitting source  213  is disposed, a third electron accelerating layer  214   b  having the same width as the fifth electrode  214   a  and formed on the surface of the fifth electrode  214   a  and a sixth electrode  214   c  formed on an upper surface of the third electron accelerating layer  214   b.    
      As such, the first, third, and fifth electrodes  212   a ,  213   a , and  214   a  are cathode electrodes, and the second, fourth, and sixth electrodes  212   c ,  213   c , and  214   c  are grid electrodes. The first, third, and fifth electrodes  212   a ,  213   a , and  214   a  are ground biased, and voltages are applied to the second, fourth, and sixth electrodes  212   c ,  213   c , and  214   c , respectively, such that an accelerating energy of emitted electrons can be controlled according to sizes of the voltages.  
      In addition, if a predetermined voltage is applied to the first, third, and fifth electrodes  212   a ,  213   a , and  214   a , respectively, and the second, fourth, and sixth electrodes  212   c ,  213   c , and  214   c , respectively, the first, second, and third electron accelerating layers  212   b ,  213   b , and  214   b  accelerate electrons flowing from the first, third, and fifth electrodes  212   a ,  213   a , and  214   a  so that electron beams can be emitted into the discharge cells through the second, fourth, and sixth electrodes  212   c ,  213   c , and  214   c.    
      In this case, the electron beams may be larger than an energy needed in exciting a gas and smaller than an energy needed in ionizing the gas. Thus, a predetermined voltage having an optimized electron energy in which electron beams can excite a discharge gas may be applied to the first, third, and fifth electrodes  212   a ,  213   a , and  214   a , respectively and the second, fourth, and sixth electrodes  212   c ,  213   c , and  214   c , respectively.  
      As another embodiment of the first, second, and third electron accelerating layers  212   b ,  213   b , and  214   b , a metal-insulator-metal (MIM) structure is also possible. That is, if a predetermined voltage is applied between a cathode electrode and a grid electrode, a thin insulating layer starting from the cathode electrode is tunneled and then passes through the grid electrode and is emitted in a space. In this case, materials and thicknesses of the insulating layer and the grid electrodes may be controlled so that electrons can be emitted in the space with as large an accelerating energy as possible without colliding with the insulating layer and the grid electrode.  
      In this case, the area of the blue electron emitting source  214  is larger than the area of the red electron emitting source  212  and the area of the green electron emitting source  213 . That is, if the width of the blue electron emitting source  214  is W 6 , the width of the red electron emitting source  212  is W 4  and the width of the green electron emitting source  213  is W 5 , the width W 6  of the blue electron emitting source  214  is larger than the width W 4  of the red electron emitting source  212  or the width W 5  of the green electron emitting source  213 .  
      This is because brightness in the blue discharge cells is lowered compared to other discharge cells due to a material characteristic of the blue light emitting layer  211 B and a larger amount of electrons is emitted so that lowering of brightness can be compensated for.  
      The first through sixth electrodes  212   a ,  212   c ,  213   a ,  213   c ,  214   a , and  214   c  are transparent conductive layers such as ITO layers and may be formed of metal having high conductivity, such as Al or Ag. In addition, the first, second, and third electron accelerating layers  212   b ,  213   b , and  214   b  may be formed of a material in which atoms are accelerated and electron beams can be generated, for example, an oxidized porous silicon (OPS) layer. OPS includes oxidized porous poly silicon (OPPS) or oxidized porous amorphous silicon (OPAS). Furthermore, an electron emitting source including boron nitride bamboo shoot (BNBS) may be used. A discharge gas is injected in a sealed discharge space, and the discharge gas can be, for example, xenon (Xe) gas, neon (Ne) gas, helium (He) gas, argon (Ar) gas or any mixture thereof. In this case, the gas in which the electron beams emitted from the electron emitting source  215  are used may be a gas which is excited by an external energy generated by the electron beams and can generated ultraviolet (UV) rays.  
      In the PDP  200  having the above structure according to the present embodiments, if a predetermined address voltage is applied between the Y electrode  205  and the address electrode  208 , an address discharge occurs. Discharge cells in which a sustain discharge will occur as a result of the address discharge are selected.  
      In this case, an electric field is formed between the Y electrode  205  and the address electrode  208 . Due to the electric field, electrons flow into the first, second, and third electron accelerating layers  212   b ,  213   b , and  214   b  from the first, second, and third electrodes  212   a ,  213   a , and  214   a , and the electrons pass through the first, second, and third electron accelerating layers  212   b ,  213   b , and  214   b  and are accelerated and then are emitted into the red, green, and blue discharge cells.  
      If the electrons flow into the discharge cells, an address discharge can occur smoothly. Thus, an address driving voltage can be reduced and a sufficient address discharge can be performed.  
      Next, if a sustain discharge voltage is applied between the X electrode  204  and the Y electrode  205  in the selected discharge cells, due to movement of wall charges accumulated on the X electrode  204  and the Y electrode  205 , a sustain discharge in a surface discharge form occurs.  
      If the sustain discharge occurs, an energy level of the excited discharge gas during the sustain discharge is reduced and UV rays are emitted. The UV rays excite the red, green, and blue light emitting layers  211 R,  211 G, and  211 B applied in the discharge cells. After that, the energy level of the excited red, green, and blue light emitting layers  211 R,  211 G, and  211 B is reduced, visible rays are emitted through the front substrate  201 , and the emitted visible rays constitute an image that can be recognized by a user.  
      In this case, the width of the blue electron emitting source  214  having lower brightness than brightness of the red electron emitting source  212  or the green electron emitting source  213  is larger than the other electron emitting sources  212  and  213  so that a larger amount of electrons are generated in the blue discharge cells and brightness can be improved.  
       FIG. 3  illustrates a plasma display panel (PDP)  300  according to another embodiment. Referring to  FIG. 3 , the PDP  300  includes a front substrate  301  and a rear substrate  302  that opposes the front substrate  301 . A frit glass is applied to an inner edge in which the front substrate  301  and the rear substrate  302  oppose each other so that a sealed inner space is formed.  
      A pair of sustain discharge electrodes  303  are disposed on an inner surface of the front substrate  301 . The pair of sustain discharge electrodes  303  include an X electrode  304  and a Y electrode  305  that crosses the X electrode  304 . The X electrode  304  includes a first discharge electrode line  304   a  and a first bus electrode line  304   b  disposed along one edge of the first discharge electrode line  304   a . The Y electrode  305  includes a second discharge electrode line  305   a  and a second bus electrode line  305   b  disposed along one edge of the second discharge electrode line  305   a . The pair of sustain discharge electrodes  303  are buried by a front dielectric layer  306 . A protective layer  307  is formed on an inner surface of the front dielectric layer  306 .  
      An address electrode  308  is disposed on an inner surface of the rear substrate  302  to cross the pair of sustain discharge electrodes  306 . The address electrode  308  is buried by a rear dielectric layer  309 .  
      Barrier ribs  310  for partitioning a discharge space are disposed between the front substrate  301  and the rear substrate  302 . A light emitting layer  311  is applied to discharge cells defined by the barrier ribs  310 . According to the current embodiment, a red lighting emitting layer  311 R, a green light emitting layer  311 G, and a blue light emitting layer  311 B, respectively, are applied to adjacent discharge cells along an inner surface of the protective layer  307 .  
      In this case, an electron emitting source  315  is disposed on an upper surface of the address electrode  308 . The electron emitting source  315  includes a red electron emitting source  312 , a green electron emitting source  313 , and a blue electron emitting source  314 .  
      The red electron emitting source  312  includes a first electron accelerating layer  312   a  that contacts the surface of the address electrode  308  and a first electrode  312   b  having the same width as the first electron accelerating layer  312   a . The address electrode  308  is an electrode for supplying electrons, as mentioned in  FIGS. 1 and 2 .  
      The green electron emitting source  313  includes a second electron accelerating layer  313   a  formed on the surface of the address electrode  308  in other discharge cells adjacent to the discharge cells in which the red electron emitting source  312  is disposed and a second electrode  313   b  having the same width as the second electron accelerating layer  313   a  and formed on the surface of the second electron accelerating layer  313   a.    
      The blue electron emitting source  314  includes a third electron accelerating layer  314   a  formed on the surface of the address electrode  308  in other discharge cells adjacent to the discharge cells in which the green electron emitting source  313  is disposed and a third electrode  314   b  having the same width as the third electron accelerating layer  314   a  and formed on the surface of the third electron accelerating layer  314   a.    
      In this case, an oxidized porous silicon (OPS) layer is used for the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a . The OPS layer includes an oxidized porous poly silicon (OPPS) or an oxidized porous amorphous silicon (OPAS) layer.  
      Furthermore, the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a  contact the surface of the address electrode  308  but the present embodiments are not limited to this. That is, an electron accelerating layer may contact the side of the address electrode and may be a structure in which the electron accelerating layer contacts the address electrode  308  and electrons can flow into the electron accelerating layer. Thus, there is no limitation in the arrangement shape of the electron accelerating layer.  
      The first, second, and third electrodes  312   b ,  313   b , and  314   b  may be formed in a mesh structure so that electrons accelerated by the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a  can be easily emitted. In addition, the first, second, and third electrodes  312   b ,  313   b , and  314   b  are installed inside the rear dielectric layer  309  together with the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a . The first, second, and third electrodes  312   b ,  313   b , and  314   b  are configured in a shape in which other portions of the address electrode  308  are buried, other than a portion in which the first,&#39;second, and third electrodes  312   b ,  313   b , and  314   b  are installed. However, the first, second, and third electrodes  312   b ,  313   b , and  314   b  are positioned on the rear dielectric layer  309  and may also be exposed in the discharge cells.  
      Here, the area of the blue electron emitting source  314  is larger than the area of the red electron emitting source  312  and the area of the green electron emitting source  313 .  
      That is, if the width of the blue electron emitting source  314  is W 9 , the width of the red electron emitting source  312  is W 7  and the width of the green electron emitting source  313  is W 8 , the width W 9  of the blue electron emitting source  314  is larger than the width W 7  of the red electron emitting source  312  or the width W 8  of the green electron emitting source  313 .  
      In this way, by making the area of the blue electron emitting source  314  larger than the areas of the red and green electron emitting sources  312  and  313 , lowering of brightness is compensated for in the blue discharge cells due to a material characteristic of the blue light emitting layer  311 B.  
      The operation of the PDP  300  having the above structure according to the present embodiments will now be described.  
      If a predetermined address voltage is applied between the Y electrode  305  and the address electrode  308 , an address discharge occurs. Discharge cells in which a sustain discharge will occur as a result of the address discharge are selected.  
      In this case, electrons flow into the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a  from the address electrode  308  and accelerated. The accelerated electrons are emitted into the discharge cells via the first, second, and third electrodes  312   b ,  313   b , and  314   b . Even in this case, an electric field is formed between the Y electrode  305  and the address electrode  308 . Due to the electric field, electrons more easily flow into the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a  from the address electrode  308  and accelerated and emitted into the discharge cells.  
      If the electrons flow into the discharge cells, an address discharge can occur smoothly. Thus, an address driving voltage can be reduced and a sufficient address discharge can be performed.  
      Next, if a sustain discharge voltage is applied between the X electrode  304  and the Y electrode  305  in the selected discharge cells, due to movement of wall charges accumulated on the X electrode  304  and the Y electrode  305 , a sustain discharge in a surface discharge form occurs.  
      Even in the sustain discharge, an electric field is formed between the X electrode  304  and the Y electrode  305 . If the electric field is generated, electrons flow into the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a  from the address electrode  308 . The electrons pass through the first, second, and third electron accelerating layers  312   a ,  313   a , and  314   a  and are accelerated and then are emitted into the discharge cells via the first, second, and third electrodes  312   b ,  313   b , and  314   b.    
      As such, a sustain discharge can be sufficiently performed even when a sustain discharge voltage is reduced such that discharge efficiency is improved. This case corresponds to the case where a voltage is not directly applied to the address electrode  308  during a sustain discharge. However, if a lower voltage than a voltage during an address discharge is applied to the address electrode  308  during the sustain discharge, electrons more briskly flow into the discharge cells such that discharge efficiency is further improved.  
      If the sustain discharge occurs, the energy level of the excited discharge gas during the sustain discharge is reduced and UV rays are emitted. The UV rays excite the red, green, and blue light emitting layers  311 R,  311 G, and  311 B applied in the discharge cells. After that, the energy level of the excited red, green, and blue light emitting layers  311 R,  311 G, and  311 B is reduced, visible rays are emitted and constitute an image  
      In particular, in order to improve discharge brightness in the blue discharge cells having lower discharge efficiency, the area of the blue electron emitting source  314  disposed in the blue discharge cells is larger than the area of the red electron emitting source  312  disposed in the red discharge cells and the area of the green electron emitting source  313  disposed in the green discharge cells. As such, a large amount of electrons is generated in the blue discharge cells, and a large amount of excitation species is formed in the discharge cells such that brightness is compensated for.  
       FIG. 4  illustrates a plasma display panel (PDP)  400  according to another embodiment. Referring to  FIG. 4 , the PDP  400  includes a front substrate  401  and a rear substrate  402  parallel to the front substrate  401 .  
      A pair of sustain discharge electrodes  403  are disposed on an inner surface of the front substrate  401 . The pair of sustain discharge electrodes  403  include an X electrode  404  and a Y electrode  405 . The X electrode  404  includes a first discharge electrode line  404   a  and a first bus electrode line  404   b  disposed along one edge of the first discharge electrode line  404   a . The Y electrode  405  includes a second discharge electrode line  405   a  and a second bus electrode line  405   b  disposed along one edge of the second discharge electrode line  405   a.    
      The pair of sustain discharge electrodes  403  are buried by a front dielectric layer  406 . A protective layer  407  is formed on the surface of the front dielectric layer  406 . An address electrode  408  is disposed on an inner surface of the rear substrate  402  to cross the pair of sustain discharge electrodes  403 . Barrier ribs  410  are disposed between the front substrate  401  and the rear substrate  402 .  
      In addition, a light emitting layer  411  is coated on an inner surface of the protective layer  407  in each of discharge cells. The light emitting layer  411  includes a red emitting layer  411 R, a green light emitting layer  411 G, and a blue light emitting layer  411 B. The red emitting layer  411 R, the green light emitting layer  411 G, and the blue light emitting layer  411 B, respectively, are disposed in each of the discharge cells and form a subpixel so that the PDP  400  can realize a color image.  
      In this case, an electron emitting source  416  is disposed in a discharge space defined by the barrier ribs  410 . The electron emitting source  416  includes a red electron emitting source  412 , a green electron emitting source  413 , and blue electron emitting sources  414  and  415 .  
      The red electron emitting source  412  includes a first electrode  412   a  formed on an upper surface of a rear dielectric layer  409  and a first electron accelerating layer  412   b  having the same width as the first electrode  412   a  and formed on the surface of the first electrode  412   a.    
      The green electron emitting source  413  includes a second electrode  413   a  formed on the upper surface of the rear dielectric layer  409  in other discharge cells adjacent to the discharge cells in which the red electron emitting source  412  is disposed and a second electron accelerating layer  413   b  having the same width as the second electrode  413   a  and formed on the surface of the second electrode  413   a.    
      The blue electron emitting sources  414  and  415  include a third electrode  414   a  formed on the upper surface of the rear dielectric layer  409  in other discharge cells adjacent to the discharge cells in which the green electron emitting source  413  is disposed, a third electron accelerating layer  414   b  having the same width as the third electrode  414   a  and formed on the surface of the third electrode  414   a , a fourth electrode  415   a , and a fourth electron accelerating layer  415   b  having the same width as the fourth electrode  415   a  and formed on the surface of the fourth electrode  415   a.    
      In this case, the third electrode  414   a  and the fourth electrode  415   a  are separated from each other to be adjacent to a pair or barrier ribs  410  adjacent in the blue discharge cells. In addition, the third electrode  414   a  and the fourth electrode  415   a  are disposed in a direction perpendicular to the X electrode  404  and the Y electrode  405 .  
      The plurality of third and fourth electrodes  414   a  and  415   a  are separated from each other and disposed along edges of the discharge cells because the amount of electrons to be supplied to edges of the discharge cells is increased so that the area of the blue discharge cells having lower brightness than the red and green discharge cells can be increased and the amount of electrons to be supplied can be increased.  
      As such, even when the same power is applied to the red electron emitting source  412 , the green electron emitting source  413 , and the blue electron emitting source  414 , respectively, the amount of electrons supplied to the blue discharge cells in which the blue electron emitting sources  414  and  415  are disposed is larger than the amount of electrons supplied to the red discharge cells in which the red electron emitting source  412  is disposed or the amount of electrons supplied to the green discharge cells in which the green electron emitting source  413  is disposed.  
      In this case, the first through fourth electron accelerating layers  412   b ,  413   b ,  414   b , and  415   b  may be formed of a material in which atoms are accelerated and electron beams can be generated, for example, oxidized porous silicon (OPS) or OPS including oxidized porous amorphous silicon.  
      A discharge gas is injected in an internal space sealed by the front substrate  401  and the rear substrate  402  combined with each other. The discharge gas can be, for example, xenon (Xe) gas, neon (Ne) gas, helium (He) gas, argon (Ar) gas or or any mixture thereof.  
      In the PDP  400  having the above structure according to the present embodiments, due to an electric field formed between the Y electrode  405  and the address electrode  408  during an address discharge, electrons flow into the first through fourth electron accelerating layers  412   b ,  413   b ,  414   b , and  415   b  from the first through fourth electrodes  412   a ,  413   a ,  414   a , and  415   a . The electrons pass through the first through fourth electron accelerating layers  412   b ,  413   b ,  414   b , and  415   b  and are accelerated and then are emitted into the discharge cells. If the electrons flow into the discharge cells in this way, the address discharge can occur smoothly. Thus, an address driving voltage can be reduced and a sufficient address discharge can be performed.  
      In addition, even in the sustain discharge, due to the electric field formed between the X electrode  404  and the Y electrode  405 , electrons pass through the first through fourth electron accelerating layers  412   b ,  413   b ,  414   b , and  415   b  from the first through fourth electrodes  412   a ,  413   a ,  414   a , and  415   a  and are accelerated and then are emitted into the discharge cells. Thus, a sustain discharge voltage to be applied during the sustain discharge is reduced so that a sustain discharge can be performed.  
      Furthermore, in order to improve discharge brightness in the blue discharge cells having lower discharge efficiency, the areas of the blue electron emitting sources  414  and  415  disposed in the blue discharge cells are larger than the area of the red electron emitting source  412  disposed in the red discharge cells and the area of the green electron emitting source  413  disposed in the green discharge cells. As such, a large amount of electrons is generated in the blue discharge cells, and a large amount of excitation species is formed in the discharge cells such that brightness is compensated for.  
       FIG. 5  illustrates a plasma display panel (PDP)  500  according to another embodiment. Referring to  FIG. 5 , the PDP  500  includes a front substrate  501  and a rear substrate  502  that opposes the front substrate  501 .  
      A pair of sustain discharge electrodes  503  are disposed on an inner surface of the front substrate  501 . The pair of sustain discharge electrodes  503  include an X electrode  504  and a Y electrode  505 . The X electrode  504  includes a first discharge electrode line  504   a  and a first bus electrode line  504   b  disposed along one edge of the first discharge electrode line  504   a . The Y electrode  505  includes a second discharge electrode line  505   a  and a second bus electrode line  505   b  disposed along one edge of the second discharge electrode line  505   a . The pair of sustain discharge electrodes  503  are buried by a front dielectric layer  506 . A protective layer  507  is formed on the surface of the front dielectric layer  506 .  
      An address electrode  508  is disposed on an inner surface of the rear substrate  502  to cross the pair of sustain discharge electrodes  503 . The address electrode  508  is buried by a rear dielectric layer  509 .  
      Barrier ribs  510  are disposed between the front substrate  501  and the rear substrate  502 . A light emitting layer  511  is coated on an inner surface of the protective layer  507  in each of discharge cells. The light emitting layer  511  includes a red emitting layer  511 R, a green light emitting layer  511 G, and a blue light emitting layer  511 B.  
      In this case, an electron emitting source  515  is disposed in a discharge space defined by the barrier ribs  510 . The electron emitting source  515  includes a red electron emitting source  512 , a green electron emitting source  513 , and blue electron emitting sources  514  and  515 .  
      The red electron emitting source  512  includes a first electrode  512   a  formed on an upper surface of the rear dielectric layer  509 , a first electron accelerating layer  512   b  formed on the surface of the first electrode  512   a , and a second electrode  512   c  formed on an upper surface of the first electron accelerating layer  512   b.    
      The green electron emitting source  513  includes a second electrode  513   a  formed on the upper surface of the rear dielectric layer  509  in other discharge cells adjacent to the discharge cells in which the red electron emitting source  512  is disposed, a second electron accelerating layer  513   b  formed on the surface of the second electrode  513   a , and a fourth electrode  513   c  formed on an upper surface of the second electron accelerating layer  513   b.    
      The blue electron emitting sources  514  and  515  are disposed not in the center of the discharge cells but on both edges of the discharge cells in which the pair of adjacent barrier ribs  510  are disposed. That is, a fifth electrode  514   a , a third electron accelerating layer  514   b  formed on the surface of the fifth electrode  514   a , and a sixth electrode  515   c  formed on an upper surface of the third electron accelerating layer  514   b  are disposed on one edge of the discharge cells. In addition, a seventh electrode  515   a , a fourth electron accelerating layer  515   b  formed on the surface of the seventh electrode  515   a , and an eighth electrode  515   c  formed on an upper surface of the fourth electron accelerating layer  515   b  are disposed on the other edge of the discharge cells.  
      As such, the first, third, fifth, and seventh electrodes  512   a ,  513   a ,  514   a , and  515   a  are cathode electrodes, and the second, fourth, sixth, and eighth electrodes  512   c ,  513   c ,  514   c , and  514   c  are grid electrodes. In addition, if a predetermined power is applied to the first, third, fifth, and seventh electrodes  512   a ,  513   a ,  514   a , and  515   a , respectively, and the second, fourth, sixth, and eighth electrodes  512   c ,  513   c ,  514   c , and  515   c , respectively, the first through fourth electron accelerating layers  512   b ,  513   b ,  514   b , and  515   b  accelerate electrons flowing from the first, third, fifth, and seventh electrodes  512   a ,  513   a ,  514   a , and  515   a  and can emit electron beams into the discharge cells via the second, fourth, sixth, and eighth electrodes  512   c ,  513   c ,  514   c , and  515   c.    
      In this case, the electron beams may be larger than an energy needed in exciting a gas and smaller than an energy needed in ionizing the gas. Thus, a predetermined voltage having an optimized electron energy in which electron beams can excite a discharge gas may be applied to the first, third, fifth, and seventh electrodes  512   a ,  513   a ,  514   a , and  515   a , respectively, and the second, fourth, sixth, and eighth electrodes  512   c ,  513   c ,  514   c , and  515   c , respectively.  
      In this way, since the areas of the blue electron emitting sources  514  and  515  disposed in the blue discharge cells are larger than the area of the red electron emitting source  512  disposed in the red discharge cells and the area of the green electron emitting source  513  disposed in the green discharge cells. As such, a large amount of electrons is generated in the blue discharge cells and brightness can be compensated for.  
       FIG. 6  illustrates a plasma display panel (PDP)  600  according to another embodiment. Referring to  FIG. 6 , the PDP  600  includes a front substrate  601  and a rear substrate  602  that opposes the front substrate  601 .  
      A pair of sustain discharge electrodes  603  are disposed on an inner surface of the front substrate  601 . The pair of sustain discharge electrodes  603  include an X electrode  604  and a Y electrode  605 . The X electrode  604  includes a first discharge electrode line  604   a  and a first bus electrode line  604   b  disposed on an upper surface of the first discharge electrode line  604   a . The Y electrode  605  includes a second discharge electrode line  605   a  and a second bus electrode line  605   b  disposed on an upper surface of the second discharge electrode line  605   a . The pair of sustain discharge electrodes  603  are buried by a front dielectric layer  606 . A protective layer  607  is formed on an inner surface of the front dielectric layer  606 .  
      An address electrode  608  is disposed on an inner surface of the rear substrate  602  to cross the pair of sustain discharge electrodes  603 . The address electrode  608  is buried by a rear dielectric layer  609 .  
      Barrier ribs  610  are disposed between the front substrate  601  and the rear substrate  602 . A light emitting layer  611  is applied to the discharge cells defined by the barrier ribs  610 . According to the current embodiment, the red, green, and blue light emitting layers  611 R,  611 G, and  611 R, respectively, are applied to adjacent discharge cells along an inner surface of the protective layer  607 .  
      In this case, an electron emitting source  616  is disposed on an upper surface of the address electrode  608 . The electron emitting source  616  includes a red electron emitting source  612 , a green electron emitting source  613 , and blue electron emitting sources  614  and  615 .  
      The red electron emitting source  612  includes a first electron accelerating layer  612   a  that contacts the surface of the address electrode  608  and a first electrode  612   b  having the same width as the first electron accelerating layer  612   a . The address electrode  608  is an electrode for supplying electrons, as mentioned in  FIGS. 4 and 5 .  
      The green electron emitting source  613  includes a second electron accelerating layer  613   a  formed on the surface of the address electrode  608  in other discharge cells adjacent to the discharge cells in which the red electron emitting source  612  is disposed and a second electrode  613   b  formed on the surface of the second electron accelerating layer  613   a.    
      The blue electron emitting sources  614  and  615  are disposed in other discharge cells adjacent to the discharge cells in which the green electron emitting source  613  is disposed. The blue electron emitting sources  614  and  615  are disposed along both edges of the discharge cells to be adjacent to a pair of adjacent barrier ribs  610 .  
      That is, a third electron accelerating layer  614   a  formed on the surface of the address electrode  608  and a third electrode  614   b  formed on the surface of the third electron accelerating layer  614   a  are formed on one edge of the discharge cells. In addition, a fourth electron accelerating layer  615   a  formed on the surface of the address electrode  608  and a fourth electrode  615   b  formed on the surface of the fourth electron accelerating layer  615   a  are formed on the other edge of the discharge cells.  
      In this case, the first through fourth electron accelerating layers  612   a  through  615   a  are oxidized porous silicon (OPS) layers. The OPS layer includes oxidized porous poly silicon (OPPS) or oxidized porous amorphous silicon (OPAS).  
      In addition, the first through fourth electron accelerating layers  612   a  through  615   a  contact the surface of the address electrode  608  but the present embodiments are not limited to this. That is, an electron accelerating layer may contact the side of the address electrode  608  and may be a structure in which the electron accelerating layer contacts the address electrode  608  and electrons flow into the electron accelerating layer. Thus, there is no limitation in the arrangement shape of the electron accelerating layer.  
      In particular, the areas of the blue electron emitting sources  614  and  615  are larger than the area of the red electron emitting source  612  and the area of the green electron emitting source  613 . By making the areas of the blue electron emitting sources  614  and  615  larger than the areas of the red and green electron emitting sources  612  and  613 , lowering of brightness is compensated for in the blue discharge cells due to a material characteristic of the blue light emitting layer  611  B.  
      As described above, the plasma display panel (PDP) according to the present embodiments has the following effects. [ 01491  Firstly, the electron emitting source is installed in the discharge cells such that an electron emission characteristic is improved and brightness and luminous efficiency of the PDP can be improved. Secondly, the driving voltage for firing a discharge can be reduced. Thirdly, the area of the electron emitting source or the number of electron emitting sources differs in each of the discharge cells such that a discharge characteristic in discharge cells having lower brightness can be improved. Fourthly, luminous efficiency can be improved.  
      While the present embodiments have 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 changes in form and details may be made therein without departing from the spirit and scope of the present embodiments as defined by the following claims.