Patent Publication Number: US-7218043-B2

Title: Plasma display panel with light guides for improving contrast

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2004-0029176, filed on Apr. 27, 2004, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma display panel. More particularly, the present invention relates to a plasma display panel with an improved structure that can enhance brightness and bright room contrast. 
     2. Description of the Related Art 
     A plasma display panel (PDP) is an apparatus that forms an image using an electrical discharge, and has superior display performances in brightness and viewing angle. In such a PDP, a DC or AC voltage applied to electrodes causes a gas discharge between the electrodes, and ultraviolet rays generated during the gas discharge excites phosphors, so that visible light is emitted from the excited fluorescent material. 
     The PDP can be classified into either a DC type PDP or an AC type PDP according to the type of gas discharge. The DC type PDP has a structure in which all electrodes are exposed to a discharge space and charges move directly between the electrodes. The AC type PDP has a structure in which at least one electrode is covered with a dielectric layer, and charges do not move directly between the corresponding electrodes but discharge is performed by wall charges. 
     Alternatively, the PDP may be classified into either a facing discharge type PDP or a surface discharge type PDP according to the arrangement structure of the electrodes. The facing discharge type PDP has a structure in which two sustaining electrodes forming a pair are formed respectively on a lower substrate and an upper substrate, and a discharge occurs in a direction perpendicular to the substrate. The surface discharge type PDP has a structure in which two sustaining electrodes forming a pair are respectively formed on the same substrate, and a discharge occurs in a direction parallel to the substrate. 
     The facing discharge type PDP has a high luminous efficiency, but it has also a disadvantage in that the fluorescent phosphor layer is easily degenerated. To this end, at present, the surface discharge type PDP is mainly used. 
       FIGS. 1 and 2  show a construction of a general surface discharge type PDP. Particularly,  FIG. 2  shows that only an upper substrate of the surface discharge type PDP is rotated by 90 degrees for easier understanding of an inner structure of the PDP. 
     Referring to  FIGS. 1 and 2 , the conventional PDP includes a lower substrate  10  and an upper substrate  20  facing each other. 
     On an upper surface of the lower substrate  10 , a plurality of address electrodes  11  are arranged in a stripe configuration. The address electrodes  11  are buried by a first dielectric layer  12 . On the first dielectric layer  12 , a plurality of barrier ribs  13  are formed spaced away by a predetermined distance from one another so as to prevent electrical and optical cross-talk between discharge cells  14 . The inner surfaces of discharge cells  14  are partitioned by the barrier ribs  13  and are coated with a predetermined thickness of a red (R), green (G) and blue (B) fluorescent layer  15 . Inside the discharge cells  14 , a discharge gas is filled. The discharge gas is a mixture gas of neon (Ne) gas and a small amount of xenon (Xe) gas, which is generally used for a plasma discharge. 
     The upper substrate  20  is a transparent substrate through which visible light passes, and is formed mainly of glass. The upper substrate  20  is coupled with the lower substrate  10  having the barrier ribs  13 . On a lower surface of the upper substrate  20 , sustaining electrodes  21   a  and  21   b  forming pairs and perpendicularly crossing the address electrodes  11  are arranged in a stripe configuration. The sustaining electrodes  21   a  and  21   b  are formed of a transparent conductive material such as indium tin oxide (ITO) such that the visible light can pass through the sustaining electrodes  21   a  and  21   b . In order to reduce a line resistance of the sustaining electrodes  21   a  and  21   b , bus electrodes  22   a  and  22   b  formed of a metal are formed beneath the respective sustaining electrodes  21   a  and  21   b  at a width less than that of the sustaining electrodes  21   a  and  21   b . These sustaining electrodes  21   a  and  21   b  and the bus electrodes  22   a  and  22   b  are covered with a second dielectric layer  23 . Beneath the second dielectric layer  23 , a protective layer  24  is formed. The protective layer  24  prevents the second dielectric layer  23  from being damaged due to a sputtering of plasma particles and emits secondary electrons, thereby lowering the discharge voltage. The protective layer  24  is generally formed of magnesium oxide (MgO). Meanwhile, a plurality of black stripes  30  are formed spaced away by a predetermined distance from one another in parallel with the sustaining electrodes  21   a  and  21   b  on an upper surface of the upper substrate  20  so as to prevent light from being introduced into the panel from the exterior. 
     The operation of the conventional PDP constructed as above is generally classified into an operation for an address discharge and an operation for the sustaining discharge. The address discharge occurs between the address electrodes  11  and any one of the sustaining electrodes  21   a  and  21   b , and during the address discharge, wall charges are formed. The sustaining discharge occurs due to a potential difference between the sustaining electrodes  21   a  and  21   b  positioned at the discharge cells  14  in which the wall charges are formed. During the sustaining discharge, the fluorescent layer  15  of the corresponding discharge cell is excited by ultraviolet rays generated from the discharge gas, so that visible light is emitted. When this visible light passes through the upper substrate  20 , an image that is conceivable by a user is formed. 
     However, in the conventional PDP constructed as above, when the exterior is in a bright condition, namely, in a bright room condition, exterior light is introduced into the discharge cells  14 , so that the introduced light overlaps the light generated from the discharge cells  14 . As a result, the bright room contrast is lowered and thus the image display performance of the PDP is deteriorated. 
     SUMMARY OF THE INVENTION 
     The present invention provides a PDP that can enhance brightness and bright room contrast by improving a structure of an upper substrate. 
     According to an aspect of the present invention, there is provided a plasma display panel. The plasma display panel comprises a lower substrate and an upper substrate, which are spaced apart by a predetermined distance from each other to define a plurality of discharge cells therebetween; a plurality of barrier ribs disposed between the lower substrate and the upper substrate; a plurality of address electrodes formed in parallel with one another on an upper surface of the lower substrate; a plurality of discharge electrodes formed in a direction crossing the address electrodes on a lower surface of the upper substrate; and a fluorescent layer formed on an inner wall of the discharge cells, wherein the upper substrate comprises a plurality of light guides, which are formed in parallel with the plurality of address electrodes to focus and output visible light generated from the discharge cells by a discharge, the light guides having a light incident surface, which is larger in area than a light emitting surface thereof. 
     Each of the light guides may be formed corresponding to each of the discharge cells. Alternatively, the light guides may be at least two, which are formed corresponding to each of the discharge cells. Each of the light guides is formed corresponding to the two or more of the discharge cells. At this point, it is preferable that each of the light guides is formed corresponding to three of the discharge cells, the three discharge cells forming a unit pixel. 
     It is preferable that the upper substrate comprises an external light shielding member formed between the light guides, for preventing external light from being introduced into the discharge cells. The external light shielding member may comprise a conductive film for shielding Electro magnetic interference (EMI). 
     Also, it is preferable that the light emitting surfaces of the light guides be treated with a non-glare material. 
     The barrier ribs may be formed in parallel with the address electrodes. 
     Alternatively, a plurality of bus electrodes may be formed on lower surfaces of the discharge electrodes. 
     A first dielectric layer may be formed on an upper surface of the lower substrate to cover the address electrodes. A second dielectric layer may be formed on a lower surface of the upper substrate to cover the discharge electrodes. At this point, it is preferable that a protective layer be formed on a lower surface of the second dielectric layer. 
     According to another aspect of the present invention, there is provided a plasma display panel. The plasma display panel comprises a lower substrate and an upper substrate, which are spaced apart by a predetermined distance from each other to define a plurality of discharge cells therebetween; a plurality of barrier ribs disposed between the lower substrate and the upper substrate; a plurality of address electrodes formed in parallel with one another on an upper surface of the lower substrate; a plurality of discharge electrodes formed in a direction crossing the address electrodes on a lower surface of the upper substrate; and a fluorescent layer formed on an inner wall of the discharge cells, wherein the upper substrate includes a plurality of light guides, which are formed in a direction perpendicular to the plurality of address electrodes to focus and output visible light generated from the discharge cells by a discharge, the light guides having a light incident surface, which is larger in area than a light emitting surface thereof. 
     Each of the light guides may be formed corresponding to each of the discharge cells. Alternatively, the light guides may be at least two, which are formed corresponding to each of the discharge cells. 
     According to another aspect of the present invention, there is provided a plasma display panel. The plasma display panel comprises a lower substrate and an upper substrate, which are spaced apart by a predetermined distance from each other to define a plurality of discharge cells therebetween; a plurality of barrier ribs disposed between the lower substrate and the upper substrate; a plurality of address electrodes formed in parallel with one another on an upper surface of the lower substrate; a plurality of discharge electrodes formed in a direction crossing the address electrodes on a lower surface of the upper substrate; and a florescent layer formed on an inner wall of the discharge cells, wherein the upper substrate comprises a plurality of light guides, which are formed corresponding to the respective discharge cells to focus and output visible light generated from the discharge cells by a discharge, the light guides having a light incident surface, which is larger in area than a light emitting surface thereof. 
     The light guides may have a conical shape or a pyramidal shape. Also, it is preferable that the upper substrate comprises an external light shielding member formed between the light guides, for preventing an external light from being introduced into the discharge cells. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a partial cut-away perspective view of a conventional PDP; 
         FIG. 2  is a cross-sectional view illustrating an inner structure of the PDP of  FIG. 1 ; 
         FIG. 3  is a partial cut-away perspective view of a PDP according to an embodiment of the present invention; 
         FIG. 4  is a cross-sectional view illustrating an inner structure of the PDP of  FIG. 3 ; 
         FIG. 5  is a cross-sectional view illustrating a modification of the PDP of  FIG. 3 ; 
         FIG. 6  is a cross-sectional view illustrating another modification of the PDP of  FIG. 3 ; 
         FIG. 7  is a partial cut-away perspective view of a PDP according to another embodiment of the present invention; 
         FIG. 8  is a cross-sectional view illustrating an inner structure of the PDP of  FIG. 7 ; 
         FIG. 9  is a cross-sectional view illustrating a modification of the PDP of  FIG. 7 ; 
         FIG. 10  is a partial cut-away perspective view of a PDP according to yet another embodiment of the present invention; and 
         FIGS. 11 and 12  are cross-sectional views illustrating an inner structure of the PDP of  FIG. 10 . 
     
    
    
     It should be understood that like reference numerals refer to like features, structures, and elements through out the drawings. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The present invention will now be described more filly with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. 
       FIG. 3  is a partial cut-away perspective view of a PDP according to an embodiment of the present invention, and  FIG. 4  is a sectional view illustrating an inner structure of the PDP of  FIG. 3 . 
     Referring to  FIGS. 3 and 4 , the PDP comprises a lower substrate  10  and an upper substrate  130 , which are spaced apart by a predetermined distance from each other. A plurality of discharge cells where plasma discharge occurs are formed between the lower substrate  110  and the upper substrate  130 . 
     The lower substrate  110  is preferably formed of a glass substrate. A plurality of address electrodes are formed in parallel with one another in a stripe configuration on an upper surface of the lower substrate  110 . A first dielectric layer  112  is formed to cover the address electrodes  111  and the lower substrate  110 . The first dielectric layer  112  can be formed by depositing a preferably white dielectric material to a predetermined thickness. 
     A plurality of barrier ribs  113  are formed in parallel with the address electrodes  111  and spaced apart by a predetermined distance from the address electrodes  111  on an upper surface of the first dielectric layer  112 . The barrier ribs  113  partition the discharge space between the lower substrate  110  and the upper substrate  130 , thereby defining discharge cells  114 . Also, the barrier ribs  113  function to prevent electrical and optical cross-talk between the adjacent discharge cells  1   14 , thereby enhancing color purity. A red (R), green (G) and blue (B) fluorescent layer  115  is formed to a predetermined thickness on an upper surface of the first dielectric layer  112 , and side surfaces of the barrier ribs  113  forming inner walls of the discharge cells  114 . The fluorescent layer  115  is preferably excited by ultraviolet rays generated by a plasma discharge, thereby emitting visible light having a predetermined color. A discharge gas is filled inside the discharge cells  114 . The discharge gas is preferably a mixture of neon (Ne) gas and a small amount of xenon (Xe) gas, which is typically used for plasma discharge. 
     The upper substrate  130  comprises a plurality of light guides  131 , which are formed in parallel with the plurality of address electrodes  111  to focus and output visible light generated by a discharge. Each of the light guides  131  is formed corresponding to each of the discharge cells  114 . Each of the light guides  131  is designed to reflect light from a surface thereof and to induce the light incident into a light incident surface  131  a to be emitted through a light emitting surface  131   b . The light guides  131  have the light incident surface  131   a , which is preferably larger in area than the light emitting surface  131   b . An internal surface extends between the light incident surface  131   a  and the light emitting surface  131   b  to internally reflect light so as to focus and output the visible light generated in the discharge cells  114 . By providing the light guides  131  having the above construction on the upper substrate  130 , loss of visible light generated by the discharge can be reduced, thereby enhancing the brightness of the panel. Also, since the light guides  131  can be made at a width less than a few tens of jim, they can be employed in the resolution of XGA or SXGA level, thereby being capable of realizing a high definition image. 
     The light emitting surfaces  131   b  of the light guides  131  are preferably non-glare treated to prevent a dazzling phenomenon generated when external light is reflected by the light emitting surface  131   b  of the light guides  131 . 
     The upper substrate comprises an external light shielding member  132  formed in parallel with the address electrodes  111  between the light guides  131 , and prevents external light from being introduced into the discharge cells  114 . Since the external light shielding member  132  is formed on a region of the upper substrate  130  other than a region through which visible light is emitted, the external light can be more effectively prevented from being introduced into the discharge cells  114  compared to the conventional art, thereby being capable of enhancing the bright room contrast. The external light shielding member  132  may comprise a conductive film for shielding electromagnetic interference (EMI). 
     First and second discharge electrodes  121   a  and  121   b  for sustaining a discharge are formed on a lower surface of the upper substrate  130  in a direction perpendicular to the address electrodes  111 . The first and second discharge electrodes  121   a  and  121   b  are preferably made of a transparent conductive material, such as indium tin oxide (ITO), such that the visible light generated in the discharge cells  114  can be transmitted. First and second bus electrodes  122   a  and  122   b  are preferably formed of a metal material on lower surfaces of the first and second discharge electrodes  121   a  and  121   b . The first and second bus electrodes  122   a  and  122   b  are used for reducing the line resistance of the first and second discharge electrodes  121   a  and  121   b , and are preferably formed with a width narrower than that of the first and second discharge electrodes  121   a  and  121   b.    
     A second dielectric layer  123  is formed on a lower surface of the upper substrate  130  so as to cover the first and second discharge electrodes  121   a  and  121   b  and the first and second bus electrodes  122   a  and  122   b . The second dielectric layer  123  can preferably be formed by depositing a transparent dielectric material on the lower surface of the upper substrate  130  to a predetermined thickness. 
     A protective layer  124  is formed on a lower surface of the second dielectric layer  123 . The protective layer  124  functions to prevent the second dielectric layer  123  and the first and second discharge electrodes  121   a  and  121   b  from being damaged due to sputtering of the plasma particles and from emitting secondary electrons, thereby lowering a discharge voltage. The protective layer  124  can preferably be formed by depositing a dielectric material, such as magnesium oxide (MgO), on a lower surface of the second dielectric layer  123  to a predetermined thickness. 
     In the PDP constructed as above, when an address discharge occurs between the address electrodes  111  and any one of the electrodes of the first and second discharge electrodes  121   a  and  121   b , wall charges are formed. Thereafter, when an AC voltage is applied to the first and second discharge electrodes  121   a  and  121   b , a sustaining discharge occurs inside the discharge cells  114  where the wall discharges are formed. The sustaining discharge generates ultraviolet rays from the discharge gases, and the generated ultraviolet rays excite the fluorescent layer  115 , thereby generating visible light. 
     The visible light generated in each of the discharge cells  114  are focused onto the upper surface of the upper substrate  130  by the light guides  131 , and are then diffused and emitted to the outside. Accordingly, loss of the visible light generated in the discharge cells  114  can be reduced, so that the brightness of the PDP is enhanced. 
     Also, since the external light shielding member  132  is provided between the light guides  131 , external light can be effectively prevented from being introduced into the discharge cells  114 , so that the bright room contrast is enhanced. 
       FIG. 5  is a cross-sectional view illustrating a modification of the PDP of  FIGS. 3 and 4 . Referring to  FIG. 5 , two light guides  231 ′ and  231 ″ for focusing and outputting the visible light generated in the discharge cells  114  are formed corresponding to one discharge cell  114  in parallel with the address electrodes  111 . The respective light guides  231 ′ and  231 ″ have light incident surfaces  231 ′ a  and  231 ″ a , which are larger in area than light emitting surfaces  231 ′ b  and  231 ″ b . Internal surfaces extend between the light incident surfaces  231 ′ a  and  231 ″ a  and light emitting surfaces  231 ′ b  and  231 ″ b  to internally reflect light. Although  FIG. 5  shows and describes that two light guides  231 ′ and  231 ″ corresponding to one discharge cell  114  are formed, three or more light guides may be formed corresponding to one discharge cell  114 . Preferably, the light emitting surfaces  231 ′ b  and  231 ″ b  of the light guides  231 ′ and  231 ″ are non-glare treated. Thus, if two or more light guides are formed corresponding to one discharge cell, loss of visible light generated in the discharge cells can be reduced and light integrity can be enhanced, thereby further enhancing the brightness of the panel. 
     An external light shielding member  232 , which prevents external light from being introduced into the discharge cells  114 , is formed between the light guides  231 ′ and  231 ″. Hence, the external light shielding member  232  can be formed on a wider area on the upper substrate  230  than that in the previous embodiment, so that the bright room contrast of the panel is further enhanced. The external light shielding member  232  can include a conductive film for shielding electromagnetic interference (EMI). 
       FIG. 6  is a cross-sectional view illustrating another embodiment of the PDP of  FIGS. 3 and 4 . Referring to  FIG. 6 , each of light guides  331  is formed corresponding to two or more discharge cells  114  on an upper substrate  330 . Each of the light guides  331  has a light incident surface  331   a , which is larger in area than a light emitting surface  331   b . An internal surface extends between the light incident surface  331   a  and the light emitting surface  331   b  to internally reflect light. It is preferable that each of the light guides  331  is formed corresponding to one pixel. In other words, it is preferable that each of the light guides  331  is formed corresponding to three discharge cells  114  in which red (R), green (G) and blue (B) fluorescent layers  115 R,  115 G,  115 B are formed. Each of the light guides  331  focuses and outputs visible light generated from three discharge cells  114  in which red (R), green (G) and blue (B) fluorescent layers  115 R,  115 G,  115 B are formed. The light emitting surfaces  331   b  of the light guides  331  are preferably non-glare treated. Thus, if each of the light guides  331  is formed corresponding to one pixel, brightness of the panel can be enhanced and processing of the light guides  331  is also enhanced, so that low price panels can be manufactured. 
     Additionally, an external light shielding member  332  for preventing external light from being introduced into the discharge cells  114  is formed between the light guides  331 . Hence, the external light shielding member  332  can include a conductive film for shielding electromagnetic interference (EMI). 
       FIG. 7  is a partial cut-away perspective view of a PDP according to another embodiment of the present invention, and  FIG. 8  is a sectional view illustrating an inner structure of the PDP of  FIG. 7 . 
     Referring to  FIGS. 7 and 8 , a lower substrate  210  and an upper substrate  430  are spaced apart by a predetermined distance from each other, and a plurality of discharge cells  214  are formed between the lower substrate  210  and the upper substrate  430 . A plurality of address electrodes  211  and a first dielectric layer  212  are preferably sequentially formed on an upper surface of the lower substrate  210 . A plurality of barrier ribs  213  are formed in parallel with and spaced apart by a predetermined distance from the address electrodes  211  on an upper surface of the first dielectric layer  212 . A fluorescent layer  215  is deposited on an upper surface of the first dielectric layer  212 , and side surfaces of the barrier ribs  213  forming inner walls of the discharge cells  214 . The discharge cells  214  are filled with a discharge gas. 
     Unlike in the above described embodiment, the upper substrate  430  comprises a plurality of light guides  431 , which are formed in a direction perpendicular to the address electrodes  211  to focus and output visible light generated by a discharge. Each of the light guides  431  is formed corresponding to each of the discharge cells  214 . Each of the light guides  431  is designed to reflect light from a surface thereof and to induce the light incident into a light incident surface  431   a  to be emitted through a light emitting surface  431   b . The light guides  431  have the light incident surface  431   a , which is larger in area than the light emitting surface  431   b . An internal surface extends between the light incident surface  131   a  and the light emitting surface  131   b  to internally reflect light so as to focus and output the visible light generated in the discharge cells  214 . By providing the light guides  431  having the above construction on the upper substrate  430 , loss of the visible light generated by the discharge can be reduced, thereby enhancing the brightness of the panel. 
     The light emitting surfaces  431   b  of the light guides  431  are preferably non-glare treated to prevent a dazzling phenomenon from being generated when external light is reflected by the light emitting surface  431   b  of the light guides  431 . 
     The upper substrate  430  comprises an external light shielding member  432  formed in a direction perpendicular to the address electrodes  211  between the light guides  431 , for preventing external light from being introduced into the discharge cells  214 . Due to the external light shielding member  432 , external light can be more effectively prevented from being introduced into the discharge cells  214 , thereby capable of enhancing the bright room contrast. The external light shielding member  432  may include a conductive film for shielding electromagnetic interference (EMI). 
     First and second discharge electrodes  221   a  and  221   b  for sustaining a discharge are formed in the direction perpendicular to the address electrodes  211 . Also, first and second bus electrodes  222   a  and  222   b  are formed of a metal material on lower surfaces of the first and second discharge electrodes  221   a  and  221   b.    
     A second dielectric layer  223  is formed on a lower surface of the upper substrate  430  so as to cover the first and second discharge electrodes  221   a  and  221   b  and the first and second bus electrodes  222   a  and  222   b . A protective layer  224  is formed on a lower surface of the second dielectric layer  223 . 
       FIG. 9  is a cross-sectional view illustrating a modification of the PDP of  FIGS. 7 and 8 . Referring to  FIG. 9 , two light guides  531 ′ and  531 ″ for focusing and outputting visible light generated in discharge cells  214  are formed corresponding to one discharge cell  214  in a direction perpendicular to the address electrodes  211 . The respective light guides  531 ′ and  531 ″ have light incident surfaces  531 ′ a  and  531 ″ a , which are larger in area than light emitting surfaces  531 ′ b  and  531 ″ b . Internal surfaces extend between the light incident surfaces  531 ′ a  and  531 ″ a  and light emitting surfaces  531 ′ b  and  531 ″ b  to internally reflect light. Although  FIG. 9  shows two light guides  531 ′ and  531 ″ corresponding to one discharge cell  214  being formed, three or more light guides may be formed corresponding to one discharge cell  214  unlike in  FIG. 9 . Preferably, the light emitting surfaces  531 ′ b  and  531 ″ b  of the light guides  531 ′ and  531 ″ are non-glare treated. Thus, if two or more light guides are formed corresponding to one discharge cell, loss of the visible light generated in the discharge cells can be reduced and the light integrity can also be enhanced, thereby further enhancing the brightness of the panel. 
     Additionally, an external light shielding member  532  for preventing external light from being introduced into the discharge cells  214  is formed between the light guides  531 ′ and  531 ″. Accordingly, the bright room contrast of the panel is further enhanced. The external light shielding member  532  may include a conductive film for shielding electromagnetic interference (EMI). 
       FIG. 10  is a partial cutaway perspective view of a PDP according to another embodiment of the present invention, and  FIGS. 11 and 12  are sectional views illustrating an inner structure of the PDP of  FIG. 10 . 
     Referring to  FIGS. 10 through 12 , a lower substrate  310  and an upper substrate  630  are spaced apart from each other, and a plurality of discharge cells  314  are formed between the lower substrate  310  and the upper substrate  630 . A plurality of address electrodes  311  and a first dielectric layer  312  are sequentially formed on an upper surface of the lower substrate  310 . A plurality of barrier ribs  313  are formed in parallel with the address electrodes  311  on an upper surface of the first dielectric layer  312 . A fluorescent layer  315  is deposited on an upper surface of the first dielectric layer  312 , and side surfaces of the barrier ribs  313  forming inner walls of the discharge cells  314 . A discharge gas is filled inside the discharge cells  314 . 
     The upper substrate  630  comprises a plurality of light guides  631 , which are formed corresponding to the respective discharge cells  314  to focus and output visible light generated by a discharge. Each of the light guides  631  is designed to reflect light from a surface thereof and to induce the light to a light incident surface  631   a  to be emitted through a light emitting surface  631   b . Also, each of the light guides  631  has the light incident surface  631   a , which is larger in area than the light emitting surface  631   b . An internal surface extends between the light incident surface  331   a  and the light emitting surface  331   b  to internally reflect light. At this point, each of the light guides  631  may be formed in a conical shape, a pyramidal shape or other various shapes. The light guides  631  focus visible light generated in the discharge cells  314  and outputs the focused visible light to the outside, so that loss of visible light is reduced, thereby enhancing the brightness of the panel. Preferably, the light emitting surfaces  631   b  of the light guides  631  are non-glare treated. 
     The upper substrate  630  further comprises an external light shielding member  632 , which is formed between the light guides  631 , prevents external light from being introduced into the discharge cells  314 . In the present embodiment, since the external light shielding member  632  can be formed on a wider area on the upper substrate  630  than that in the previous embodiment, the bright room contrast of the panel is further enhanced. The external light shielding member  632  can include a conductive film for shielding electromagnetic interference (EMI). 
     First and second discharge electrodes  321   a  and  321   b  for sustaining a discharge are preferably formed on a lower surface of the upper substrate  630  in the direction perpendicular to the address electrodes  311 . Also, first and second bus electrodes  322   a  and  322   b  are formed of a metal material on lower surfaces of the first and second discharge electrodes  321   a  and  321   b.    
     A second dielectric layer  323  is formed on a lower surface of the upper substrate  630  so as to cover the first and second discharge electrodes  321   a  and  321   b  and the first and second bus electrodes  322   a  and  322   b . A protective layer  324  is formed on a lower surface of the second dielectric layer  323 . 
     As described above, the PDP according to an embodiment of the present invention has the following effects: 
     First, light guides each having a light incident surface, which is larger in area than a light emitting surface, are formed on an upper surface, so that loss of visible light generated by a discharge can be reduced, thereby enhancing the brightness of the panel. 
     Second, since an external light shielding member is formed between light guides, so that external light can be prevented from being introduced into discharge cells, thereby enhancing the bright room contrast. 
     Third, since light guides can be made at a width less than a few tens of μm, they can be employed in the resolution of XGA or SXGA level, thereby being capable of realizing a high definition image. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.