Patent Publication Number: US-8125148-B2

Title: Plasma display panel with a defined relationship between an exhaust hole circumferential length and distances between main and separation barrier ribs and seal layer structures

Description:
This application claims the benefit of Korean Patent Application Nos. 10-2009-0025383 filed on Mar. 25, 2009 and 10-2010-0020958 filed on Mar. 9, 2010, the entire contents of which is incorporated herein by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     This document relates to a plasma display panel. 
     2. Related Art 
     A plasma display panel includes a phosphor layer formed inside discharge cells partitioned by barrier ribs and a plurality of electrodes. 
     When driving signals are applied to the electrodes of the plasma display panel, a discharge occurs inside the discharge cell due to the supplied driving signals. In other words, when the discharge occurs inside the discharge cell due to the supplied driving signals, a discharge gas filled in the discharge cell generates vacuum ultraviolet rays, which thereby cause a phosphor inside the discharge cell to emit light, thus producing visible light. An image is displayed on the screen of the plasma display panel due to the visible light. 
     SUMMARY 
     In one aspect, there is a plasma display panel comprising a front substrate, a rear substrate arranged to face the front substrate, barrier ribs for partitioning discharge cells between the front substrate and the rear substrate, and an exhaust hole formed on the rear substrate in an area between the barrier ribs and the seal layer, wherein a distance between the outermost barrier rib and the seal layer is less than a circumferential length of the exhaust hole. 
     In another aspect, there is a plasma display panel comprising a front substrate, a rear substrate arranged to face the front substrate, barrier ribs for partitioning discharge cells between the front substrate and the rear substrate, a separation barrier rib arranged between the barrier ribs and the seal layer and spaced apart from the seal layer and the barrier ribs, and an exhaust hole formed on the rear substrate in an area between the barrier ribs and the seal layer, wherein the sum of a distance between the outermost barrier rib and the separation barrier rib and a distance between the separation barrier rib and the seal layer is less than a circumferential length of the exhaust hole. 
     In another aspect, there is a plasma display panel comprising a front substrate on which first electrodes are arranged, a rear substrate on which second electrodes are arranged to cross the first electrodes, barrier ribs for partitioning discharge cells between the front substrate and the rear substrate, a seal layer for bonding the front substrate and the rear substrate together, and an exhaust hole formed on the rear substrate in an area between the barrier ribs and the seal layer, wherein a distance, parallel to the first electrodes, between the outermost barrier rib and the seal layer is less than a distance, parallel to the second electrodes, between the outermost barrier rib and the seal layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram for explaining a structure of a plasma display panel; 
         FIG. 2  is a diagram for schematically explaining a method of manufacturing a plasma display panel; 
         FIGS. 3 to 7  are diagrams for explaining a relationship between a distance between a seal layer and an outermost barrier rib and a circumferential length of an exhaust hole; 
         FIGS. 8 to 13  are diagrams for explaining another structure of a plasma display panel according to the present invention; 
         FIGS. 14 to 22  are diagrams for explaining the arrangement of open dummy barrier ribs; and 
         FIG. 23  is a diagram for explaining the shape of the exhaust hole. 
     
    
    
     DETAILED DESCRIPTION 
     Since the present invention may be modified in various ways and may have various forms, specific embodiments are illustrated in the drawings and are described in detail in the present specification. However, it should be understood that the present invention are not limited to specific disclosed embodiments, but include all modifications, equivalents and substitutes included within the spirit and technical scope of the present invention. In the description of each drawing, the same reference characters are used to designate the same or similar components. 
     The terms ‘first’, ‘second’, etc. may be used to describe various components, but the components are not limited by such terms. The terms are used only for the purpose of distinguishing one component from other components. For example, a first component may be designated as a second component without departing from the scope of the present invention. In the same manner, the second component may be designated as the first component. 
     The term “and/or” encompasses both combinations of the plurality of related items disclosed and any item from among the plurality of related items disclosed. 
     When an arbitrary component is described as “being connected to” or “being linked to” another component, this should be understood to mean that still another component may exist between them, although the arbitrary component may be directly connected to, or linked to, the second component. In contrast, when an arbitrary component is described as “being directly connected to” or “being directly linked to” another component, this should be understood to mean that no component exists between them. 
     The terms used in the present application are used to describe only specific embodiments, and are not intended to limit the present invention. A singular expression includes a plural expression as long as it does not have an apparently different meaning in context. 
     In the present application, the terms “include” and “have” should be understood to be intended to designate that illustrated features, numbers, steps, operations, components, parts or combinations thereof exist and not to preclude the existence of one or more different features, numbers, steps, operations, components, parts or combinations thereof, or the possibility of the addition thereof. 
     Unless otherwise specified, all of the terms which are used herein, including the technical or scientific terms, have the same meanings as those that are generally understood by a person having ordinary knowledge in the art to which the present invention pertains. The terms defined in a generally used dictionary must be understood to have meanings identical to those used in the context of a related art, and are not to be construed to have ideal or excessively formal meanings unless they are obviously specified in the present application. 
     The following exemplary embodiments of the present invention are provided to those skilled in the art in order to describe the present invention more completely. Accordingly, shapes and sizes of elements shown in the drawings may be exaggerated for clarity. 
       FIG. 1  is a diagram for explaining a structure of a plasma display panel. 
     Referring to  FIG. 1 , a plasma display panel  100  may comprise a front substrate  101 , on which a plurality of display electrodes  102  and  103  are positioned, and a rear substrate  111  on which an address electrode  113  (X) is positioned to intersect the display electrodes  111 . 
     The display electrodes  102  and  103  may be a scan electrode  102  (Y) and a sustain electrode  103  (Z). Also, the display electrodes  102  and  103  may be referred to as first electrodes. 
     An upper dielectric layer  104  may be positioned on the display electrodes  102  and  103 , i.e., the scan electrode  102  (Y) and the sustain electrode  103  (Z) to limit a discharge current of the scan electrode  102  (X) and the sustain electrode  103  (Z) and to provide electrical insulation between the scan electrode  102  (X) and the sustain electrode  103  (Z). 
     A protective layer  105  may be positioned on the upper dielectric layer  104  to facilitate discharge conditions. The protective layer  105  may include a material having a high secondary electron emission coefficient, for example, magnesium oxide (MgO). 
     The address electrode  113  (X) is formed on the rear substrate  111 , and a lower dielectric layer  115  may be positioned on the address electrode  113  (X) to provide electrical insulation of the address electrodes  113  (X). Also, the address electrodes  113  may be referred to as second electrodes. 
     Barrier ribs  112  of a stripe type, a well type, a delta type, a honeycomb type, and the like may be positioned on the lower dielectric layer  115  to partition discharge spaces (i.e., discharge cells). Hence, a first discharge cell emitting red (R) light, a second discharge cell emitting blue (B) light, and a third discharge cell emitting green (G) light, and the like, may be formed between the front substrate  101  and the rear substrate  111 . 
     The barrier rib  112  includes first and second barrier ribs  112   a  and  112   a  crossing each other. Heights of the first and second barrier ribs  112   a  and  112   b  may be different from each other. The first barrier rib  112   a  may be parallel to the scan electrode  102  and the sustain electrode  103 , and the second barrier rib  112   b  may be parallel to the address electrode  113 . 
     The height of the first barrier rib  112   a  may be less than the height of the second barrier rib  112   b . Hence, in an exhaust process and a process for injecting a discharge gas, an impurity gas in the panel may be efficiently exhausted to the outside of the panel, and the discharge gas may be uniformly injected. 
     Each of the discharge cells partitioned by the barrier ribs  112  may be filled with the discharge gas. 
     A phosphor layer  114  may be formed inside the discharge cells partitioned by the barrier ribs  112  to emit visible light for an image display during an address discharge. For example, first, second, and third phosphor layers that respectively generate red, blue, and green light may be formed inside the discharge cells. 
     Although the above description illustrates a case where the upper dielectric layer  104  and the lower dielectric layer  115  each are formed in the form of a single layer, at least one of the upper dielectric layer  104  and the lower dielectric layer  115  may be formed in the form of a plurality of layers. 
     While the address electrode  113  formed on the rear substrate  111  may have a substantially constant width or thickness, a width or thickness of the address electrode  113  inside the discharge cell may be different from a width or thickness of the address electrode  113  outside the discharge cell. For example, a width or thickness of the address electrode  113  inside the discharge cell may be greater than a width or thickness of the address electrode  113  outside the discharge cell. 
     When a predetermined signal is supplied to at least one of the scan electrode  102 , the sustain electrode  103 , and the address electrode  113 , a discharge may occur inside the discharge cell. The discharge may allow the discharge gas filled in the discharge cell to generate ultraviolet rays. The ultraviolet rays may be incident on phosphor particles of the phosphor layer  114 , and then the phosphor particles may emit visible light. Hence, an image may be displayed on the screen of the plasma display panel  100 . 
       FIG. 2  is a diagram for schematically explaining a method of manufacturing a plasma display panel. 
     Referring to  FIG. 2 , first, a seal layer  210  may be formed at an edge of at least one of the front substrate  101  and the rear substrate  111  having an exhaust hole  200  formed therethrough as shown in (a), and the front substrate  101  and the rear substrate  111  may be bonded together using the seal layer  210  as shown in (b). 
     Thereafter, as shown in (b), an exhaust tip  220  may be connected to the exhaust hole  200  and an exhaust pump  230  may be connected to the exhaust tip  220 . 
     Then, impurity gases remaining in the discharge space between the front substrate  101  and the rear substrate  111  may be exhausted outside using the exhaust pump  230 . Also, a discharge gas such as argon (Ar), neon (Ne), xenon (Xe), etc. may be injected into the discharge space. 
       FIGS. 3 to 7  are diagrams for explaining a relationship between a distance between a seal layer and an outermost barrier rib and a circumferential length of an exhaust hole. Although the exhaust hole  200  may be formed in the front substrate  101  as well and the exhaust hole  200  may be provided in plural number, the following description will be made with respect to a case where the exhaust hole  200  is formed in the rear substrate  111  and there is only one exhaust hole  200 . Alternatively, the exhaust hole  200  may be formed on the front substrate  101  and the rear substrate  111 , respectively. 
     First, referring to  FIG. 3 , a long side LS of the rear substrate  111  may have a length L 1 , and a short side SS thereof may have a length L 3  which is less than the length L 1 . 
     Moreover, a long side LS of the front substrate  101  has a length L 2  which is greater than the length L 1 , and a short side SS thereof has a length L 4  which is less than the length L 3 . 
     That is, the long side of the rear substrate  111  may protrude further than the long side of the front substrate  101 , and the short side of the front substrate  101  may protrude further than the short side of the rear substrate  111 . 
     In this way, the front substrate  101  and the rear substrate  111  are alternately arranged so that a driving device for supplying driving signals to the plasma display panel  100  is connected to the scan electrode (Y), the sustain electrode (Z), or the address electrode (X). 
     The exhaust hole  200  may be arranged in an area between the seal layer  210  and the barrier rib  112 . 
     The barrier rib  112  may be spaced apart from the seal layer  210  by d 1  on the short sides SS of the front substrate  101  and rear substrate  111 , and may be spaced apart from the seal layer  210  by d 2  on the long sides of the front substrate  101  and rear substrate  111 . That is, a distance between the outermost barrier rib  112  and the seal layer  210  on the short sides SS of the front substrate  101  and rear substrate  111  is d 1 , and a distance between the outermost barrier rib  112  and the seal layer  210  on the long sides LS of the front substrate  101  and rear substrate  111  is d 2 . 
     The distances d 1  and d 2  may be equal to or different from each other. 
     Also, the distance d 1  and d 2  between the outermost barrier rib  112  and the seal layer  210  may be less than or equal to a circumferential length of the exhaust hole  200 . 
     For example, the distance d 1  between the outermost barrier rib  112  and the seal layer  210  on the short sides SS of the front substrate  101  and rear substrate  111  may be less than the circumferential length of the exhaust hole  200 , and the distance d 2  between the outermost barrier rib  112  and the seal layer  210  on the long sides LS of the front substrate  101  and rear substrate  111  may be greater than the circumferential length of the exhaust hole  200 . As shown in  FIG. 4 , the first electrodes Y 1 -Yn and Z 1 -Zn may be arranged parallel to the long sides LS of the front substrate  101  and rear substrate  111 , and the second electrodes X 1 -Xn may be arranged parallel to the short sides SS of the front substrate  101  and rear substrate  111 . That is, the first electrodes are arranged transversely arranged on the panel, and the second electrodes are arranged longitudinally arranged on the panel. In view of this, the distance d 1 , parallel to the first electrodes, between the outermost barrier rib  112  and the seal layer  210  may be less than the circumferential length of the exhaust hole  200 , and the distance d 2 , parallel to the second electrodes, between the outermost barrier rib  112  and the seal layer  210  may be greater than the circumferential length of the exhaust hole  200 . 
     Alternatively, the distance d 1  between the outermost barrier rib  112  and the seal layer  210  on the short sides SS of the front substrate  101  and rear substrate  111  may be greater than the circumferential length of the exhaust hole  200 , and the distance d 2  between the outermost barrier rib  112  and the seal layer  210  on the long sides LS of the front substrate  101  and rear substrate  111  may be less than the circumferential length of the exhaust hole  200 . 
     Alternatively, the distance d 1  between the outermost barrier rib  112  and the seal layer  210  on the short sides SS of the front substrate  101  and rear substrate  111  and the distance d 2  between the outermost barrier rib  112  and the seal layer  210  on the long sides LS of the front substrate  101  and rear substrate  111  each may be less than the circumferential length of the exhaust hole  200 . If the exhaust hole  200  has a spherical shape with a radius of R, the circumferential length of the exhaust hole  200  is 2nR. 
     As above, if at least one of d 1  and d 2  is set smaller than the circumferential length of the exhaust hole  200 , the size of a bezel can be reduced. Also, an excessive increase in the processing time during the exhaust process or the gas injection process can be prevented. 
     Also, it may be preferable that at least one of d 1  and d 2  is greater than the radius 2R of the exhaust hole  200  even if at least one of d 1  and d 2  is less than the circumferential length of the exhaust hole  200 . 
     During the exhaust process in the manufacturing process of the plasma display panel, as shown in  FIG. 5 , the gas in the panel can be exhausted to the outside of the panel by being moved toward the exhaust hole  200  through a space between the barrier rib  112  and the seal layer  210 . 
     The gas moved toward the exhaust hole  200  can be exhausted outside in such a manner as to flow along the edge of the exhaust hole  200  as indicated in the arrows in  FIG. 5 . 
     As such, when the gas in the panel is exhausted to the outside of the panel, it flows along the edge of the exhaust hole  200 . Therefore, the exhaust characteristics may depend on the circumferential length of the exhaust hole  200 . 
     Also, the exhaust characteristics may depend on the size of a path through which the gas can pass, i.e., a space between the outermost barrier rib  112  and the seal layer  210 . 
     Meanwhile, if the distance between the outermost barrier rib  112  and the seal layer  210  is excessively large, with the circumferential length of the exhaust hole  200  being fixed, the size of an unnecessary area, i.e., the size of the bezel, becomes excessively large, thus increasing manufacturing costs. 
     For instance, as shown in (a) of  FIG. 6 , it is assumed that, in a first exemplary embodiment, the distance d 1  and d 2  between the outermost barrier rib  112  and the seal layer  210  is less than the circumferential length of the exhaust hole  200 . 
     Also, as shown in (b) of  FIG. 6 , it is assumed that, in a first comparative example, distance d 10  and d 20  between the outermost barrier rib  112  and the seal layer  210  is approximately twice as large as the circumferential length of the exhaust hole  200 . 
     The exhaust characteristics of the first exemplary embodiment and the first comparative example will be discussed below. 
     In comparing the first exemplary embodiment and the first comparative example, the time required to exhaust the gas in the panel to a vacuum pump and reduce the internal pressure to a critical degree of vacuum in the first exemplary embodiment according to the present invention may be substantially equal to that in the first comparative example. The reason for this is that, as explained above in  FIG. 5 , the exhaust characteristics may depend on the circumferential length of the exhaust hole  200  because the gas in the panel flows along the edge of the exhaust hole  200  when exhausted outside, and as a result, as shown in (b) of  FIG. 6 , the degree of improvement of the exhaust characteristics is small even if the distance d 10  and d 20  between the outermost barrier rib  112  and the seal layer  210  is greater than the circumferential length of the exhaust hole  200 . 
     Meanwhile, in the first exemplary embodiment according to the present invention of (a) of  FIG. 6 , the distance d 1  and/or d 2  between the outermost barrier rib  112  and the seal layer  210  can be set smaller than the distance d 10  and d 20  of the first exemplary embodiment of (b) of  FIG. 6 . 
     In comparing (a) and (b) of  FIG. 6 , in the first comparative example, an unconditional increase in the distance d 10  and/or d 20  between the outermost barrier rib  112  and the seal layer  210  may only lead to an increase in the size of the bezel area without significant improvement in the exhaust characteristics. 
     That is, as shown in (a) of  FIG. 6 , if the distance d 1  and/or di 2  between the outermost barrier rib  112  and the seal layer  210  is set substantially equal to or less than the circumferential length of the exhaust hole  200 , a degradation of the exhaust characteristics can be prevented and the size of the bezel area can be reduced. 
     Also, the exhaust characteristics may depend on the size of a path through which the gas can pass, i.e., a space between the outermost barrier rib  112  and the seal layer  210 . Hence, in order to prevent an excessive degradation of the exhaust characteristics, it may be preferable that the distances d 1  and d 2 , parallel to the first electrodes and the second electrodes, respectively, between the outermost barrier rib  112  and the seal layer  210  are larger than the diameter 2R of the exhaust hole  200 . 
     Also, it may be preferable that at least one of d 1  and d 2  is larger than the diameter 2R of the exhaust hole  200  even if the at least one of d 1  and d 2  is less than the circumferential length of the exhaust hole  200 . 
     Moreover, as shown in  FIG. 7 , dummy barrier ribs  710  may be arranged in a dummy area DA outside an active area AA. The active area AA may be an image display area. The description of the parts having been described above in detail will be omitted in  FIG. 7 . 
     For example, active barrier ribs for partitioning active discharge cells are arranged in the active area between the front substrate  101  and the rear substrate, and dummy barrier ribs  710  for partitioning dummy discharge cells are arranged in the dummy area DA outside the active area AA. 
     As such, when the dummy barrier ribs  710  are formed in the dummy area DA, a buffer zone can be provided between the active area AA and the seal layer  210 , thereby preventing damage of the active barrier ribs  112  formed in the active area AA and improving discharge characteristics of the discharge cells partitioned by the active barrier ribs  112 . 
     The barrier ribs arranged in the active area are referred to as the active barrier ribs and the barrier ribs arranged in the dummy area are referred to as the dummy barrier ribs  710  so as to differentiate the dummy area from the active area. The dummy barrier ribs  710  and the active barrier ribs may be formed of substantially the same material, and may have the same shape. Of course, the dummy barrier ribs  710  and the active barrier ribs may include different materials from each other or may have different shapes from each other. 
     As shown in  FIG. 7 , in the case where the dummy barrier ribs  710  are arranged in the dummy area DA, the outermost barrier rib is an outermost dummy barrier rib  710 . The arrangement of the dummy barrier ribs  710  may be substantially equal to that in  FIG. 3  except that the dummy barrier ribs  710  are added in the dummy area DA. For example, it may be preferable that the distance d 1  and/or d 2  between the outermost dummy barrier rib  710  and the seal layer  210  is less than the circumferential length of the exhaust hole  200 . 
       FIGS. 8 to 13  are diagrams for explaining another structure of a plasma display panel according to the present invention. The description of the parts having been described above in detail will be omitted below. 
     First, referring to  FIG. 8 , a separation barrier rib  1100  for preventing intrusion of the seal layer  210  into the active area AA may be further arranged between the active area AA and the seal layer  210 . 
     That is, the separation barrier rib  1100  is arranged between the barrier ribs  112  partitioning the discharge cells in the active area AA and the seal layer  210 . The separation barrier rib  1100  of this type may be referred to as a seal barrier rib SBR. 
     The separation barrier rib  1100  may be structurally spaced apart from the barrier ribs  112 . Also, the separation barrier rib  1100  may be spaced apart from the seal layer  210 . Alternatively, the separation barrier rib  1100  may be contacted with the seal layer  210 . 
     In this manner, once the separation barrier rib  1100  is formed, the distance between the front substrate  101  and the rear substrate  111  may be kept substantially constant, thus enabling reduction of noise. 
     Also, as shown in  FIG. 9 , in the case where the dummy barrier ribs  710  are arranged in the dummy area DA, the separation barrier rib  1100  may be arranged between the dummy barrier ribs  710  and the seal layer  210 . Moreover, the separation barrier rib  1100  may be spaced apart from the dummy barrier ribs  710 . 
     When the separation barrier rib  1100  is formed as explained above, the exhaust hole  200  may be arranged in an area between the seal layer  210  and the separation barrier rib  1100 . 
     Alternatively, the exhaust hole  200  may overlap with the separation barrier rib  1100  in a direction parallel to the long side LS of the rear substrate  111  and/or in a direction parallel to the short side SS of the rear substrate  111 . In other words, though not shown, the exhaust hole  200  may overlap with an extension line of the separation barrier rib  1100  in a direction parallel to the long side LS of the rear substrate  111  and/or in a direction parallel to the short side SS of the rear substrate  111 . 
     In this way, if the separation barrier rib  1100  is arranged, the sum d 130 +d 140  and/or d 110 +d 120  of the distance d 3   a  and d 4   a  between the outermost dummy barrier rib  710  and the separation barrier rib  1100  and the distance d 3   b  and d 4   b  between the separation barrier rib  1100  and the seal layer  210  may be less than the circumferential length of the exhaust hole  200 . Preferably, the distance d 1  and/or d 2  between the outermost barrier rib  112  (in  FIG. 9 , the outermost barrier rib is the outermost dummy barrier rib  710 ) and the seal layer  210  may be less than the circumferential length of the exhaust hole  200 . Here, unexplained reference numeral  1110  may be a second separation barrier rib, and unexplained reference numeral  1120  may be a first separation barrier rib. 
     In this case, too, it is possible to prevent a degradation of the exhaust characteristics and reduce the size of the bezel area. 
     Meanwhile, the position of the exhaust hole  200  may be changed. 
     For example, as shown in  FIG. 10 , the exhaust hole  200  may overlap with an extension line EL 1  and/or EL 2  of the outermost dummy barrier rib  710  arranged in the dummy area DA. 
     In this case, the distance d 1  and/or d 2  between the outermost dummy barrier rib  710  and the seal layer  210  can be decreased, thus enabling a further reduction of the size of the bezel area. For example, in  FIG. 10 , the exhaust hole  200  may overlap with the first extension line EL 1  of the outermost dummy barrier rib  710  in a direction parallel to the short side SS of the rear substrate  111 . In this case, it is possible to reduce the size of the distance d 1  between the seal layer  210  and the outermost barrier rib  112  in a direction parallel to the first electrodes, that is, in a direction parallel to the long side LS of the rear substrate  111 . 
     Meanwhile, the distance between the outermost barrier rib  112  (in the case where the outermost dummy barrier rib  710  is arranged) and the seal layer  210  may be varied according to position. 
     For example, as shown in  FIG. 11 , the distance d 1 , parallel to the first electrodes, i.e., the long side LS of the rear substrate  111 , between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) may be less than the distance d 2 , parallel to the second electrodes, i.e., the short side SS of the rear substrate  111 , between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ). 
     The transverse length (long side length) of the plasma display panel is larger than the longitudinal length (short side length) thereof. This is to provide screen ratios of 16:9, 4:3, 21:9, etc. 
     Hence, though human eyes are able to easily perceive an increase in the transverse length of the panel, they are very likely not to be able to perceive a slight increase in the longitudinal length thereof. 
     Considering this, it may be preferable that the distance d 1 , parallel to the first electrodes, between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) is set smaller than the distance d 2 , parallel to the second electrodes, between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) in terms of a visual effect that makes an image stand out. 
     Also, if the distance d 2 , parallel to the second electrodes, between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) is set larger than the distance d 1 , parallel to the first electrodes, between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ), this makes it easier to arranged the exhaust hole  200  in a manner as shown in  FIG. 10 . 
     Referring to  FIG. 11 , the distance d 1 , parallel to the first electrodes, between the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) and the seal layer  210  may be less than the circumferential length of the exhaust hole  200 , while the distance d 2 , parallel to the second electrodes, between the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) and the seal layer  210  may be greater than the circumferential length of the exhaust hole  200 . 
     In this case, too, the distances d 1  and d 2 , parallel to the first electrodes and the second electrodes, respectively, between the outermost barrier rib  112  and the seal layer  210  may be larger than the diameter of the exhaust hole  200 . 
     Meanwhile, even when the separation barrier rib  1100  is arranged, the exhaust hole  200  and an extension line of the outermost barrier rib  112  may overlap with each other. For example, as shown in  FIG. 12 , the first separation barrier rib  1110  parallel to the long side LS of the rear substrate  111  is arranged between the first dummy barrier rib  710   a  of the dummy barrier ribs  710  and the seal layer  210 , and the second separation barrier rib  1120  parallel to the short side SS of the rear substrate  111  may be arranged between the second dummy barrier rib  710   b  of the dummy barrier ribs  710  and the seal layer  210 . Here, the exhaust hole  200  may overlap with the first extension line EL 1  of the outermost dummy barrier rib  710  in a direction parallel to the short side SS of the rear substrate  111 . That is, the exhaust hole  220  may overlap with the dummy barrier ribs  710  in a direction parallel to the short side SS of the rear substrate  111 . 
     In the structure of  FIG. 12 , similarly to  FIG. 11 , if the distance d 1 , parallel to the first electrodes, i.e., the long side LS of the rear substrate  111 , between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) is less than the distance d 2 , parallel to the second electrodes, i.e., the short side SS of the rear substrate  111 , between the seal layer  210  and the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ), the sum of the distance d 131  between the outermost dummy barrier rib  710  and the second separation barrier rib  1120  and the distance d 141  between the second separation barrier rib  1120  and the seal layer  210 , which is measured parallel to the first electrodes, may be less than the circumferential length of the exhaust hole  200 . On the contrary, the sum of the distance d 121  between the outermost dummy barrier rib  710  and the first separation barrier rib  1120  and the distance d 131  between the first separation barrier rib  1110  and the seal layer  210 , which is measured parallel to the second electrodes, may be greater than the circumferential length of the exhaust hole  200 . 
     Meanwhile, the width of the seal layer  200  may be greater than the distance between the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) and the seal layer  210 . For example, as shown in  FIG. 13 , the width Ws of the seal layer  210  may be greater than the distance d 1 , parallel to the first electrodes, between the outermost dummy barrier rib  710  and the seal layer  210 . While the preceding drawings have illustrated that the width Ws of the seal layer  210  is relatively small for the convenience of explanation, the width Ws of the seal layer  210  may be sufficiently large as shown in  FIG. 13 . 
     As such, if the width Ws of the seal layer  200  is made larger than the distance between the outermost barrier rib  112  (or the outermost dummy barrier rib  710 ) and the seal layer  210 , the size of the bezel area can be reduced. 
       FIGS. 14 to 22  are diagrams for explaining the arrangement of open dummy barrier ribs. The description of the parts having been described above in detail will be omitted below. For instance, in the following discussion, the width of the seal layer  210  is illustrated to be relatively small for the convenience of explanation. 
     Referring to  FIG. 14 , at least one open barrier rib  700  may be arranged in a dummy area DA outside an active area AA. By arranging the open barrier rib  700  in the dummy area DA, the size of a bezel area can be reduced and exhaust characteristics can be further improved. That is, dummy barrier ribs have an open structure. 
     At least one open barrier rib  700  having a stripe shape may be arranged in the dummy area DA. 
     In this case, the outermost barrier rib is the open barrier rib  700  arranged in an outermost portion of the dummy area DA. 
     Barrier rib  112  formed in the active area may be closed barrier ribs. The closed barrier ribs  112  may comprise horizontal barrier ribs  112   a  and longitudinal barrier ribs  112   b  that cross each other. 
     When the open dummy barrier ribs  710  are formed in the dummy area DA, a buffer zone can be provided between the active area AA and the seal layer  210 , thereby preventing damage of the active barrier ribs  112  formed in the active area AA and improving discharge characteristics of the discharge cells partitioned by the active barrier ribs  112 . 
     Moreover, to increase the buffering effect of the open barrier ribs  700  to a sufficiently high level, it may be preferable that the distance d 33 , d 34 , d 43 , and d 44  between two adjacent open barrier ribs  700  is less than the distance d 3  and d 4  between the outermost open barrier rib  700  and the seal layer  210 . 
     Also, it may be preferable that the distance d 32  and d 42  between the outermost barrier rib  112  formed in the active area AA and the first open barrier rib  700  is less than the distance d 3  and d 4  between the outermost open barrier rib  700  and the seal layer  210 . 
     Moreover, the distance d 43  and d 44  between two open barrier ribs adjacent to each other in the dummy area of the long sides LS of the front substrate  101  and rear substrate  111  may be substantially equal to a longitudinal width (any one of W 4 , W 5 , and W 6 ) of at least one discharge cell formed in the active area AA, i.e., a width (any one of W 4 , W 5 , and W 6 ) of at least one discharge cell in a direction of the short sides SS of the front substrate  101  and rear substrate  111 . 
     Further, the distance d 33  and d 34  between two open barrier ribs adjacent to each other in the dummy area of the short sides SS of the front substrate  101  and rear substrate  111  may be substantially equal to a transverse width (any one of W 1 , W 2 , and W 3 ) of at least one discharge cell formed in the active area AA, i.e., a width (any one of W 1 , W 2 , and W 3 ) of at least one discharge cell in a direction of the long sides LS of the front substrate  101  and rear substrate  111 . 
     In this case, it is possible to form open barrier ribs  700  in the dummy area merely by a change of a photo mask pattern, thereby preventing an excessive increase of manufacturing costs. 
     As shown in  FIG. 14 , in the case where at least one open barrier rib  700  is arranged in the dummy area DA outside the active area AA, the distance d 3  and d 4  between the seal layer  210  and the outermost open barrier rib  700  may be less than the distance d 31  and/or d 41  between the outermost open barrier rib  700  and the outermost active barrier rib  112 . In this case, the size of the bezel area can be further reduced. Of course, the distance d 3  and d 4  between the seal layer  210  and the outermost open barrier rib  700  may be greater than the distance d 31  and/or d 41  between the outermost open barrier rib  700  and the outermost active barrier rib  112 . 
     Moreover, the distance d 3  and/or d 4  between the outermost barrier rib  700  and the seal layer  210  may be less than the circumferential length of the exhaust hole. 
     As above, if at least one of d 3  and d 4  is set smaller than the circumferential length of the exhaust hole  200 , the size of the bezel can be reduced. Also, an excessive increase in the processing time during the exhaust process or the gas injection process can be prevented. 
     Further, in the case where the open barrier ribs  700  are arranged in the dummy area DA, it may be preferable that the distance d 31  and/or d 41  between the outermost closed barrier rib  112  arranged in the active area AA and the outermost open barrier rib  700  arranged in the dummy area DA is set smaller than the circumferential length of the exhaust hole  22  in order to prevent an increase in the size of the bezel area. 
     In addition, the sum d 31 +d 3  and/or d 41 +d 4  of the distance d 3  and d 4  between the outermost open barrier rib  700  and the seal layer  210  and the distance d 31  and d 41  between the outermost closed barrier rib  112  arranged in the active area AA and the outermost open barrier rib  700  arranged in the dummy area DA may be greater than the circumferential length of the exhaust hole  200 . 
     That is, the total distance d 30  and/or d 40  from the active area AA to the seal layer  210  may be greater than the circumferential length of the exhaust hole  200 . 
     In this case, since a path through which the gas in the panel can pass can be secured sufficiently in the dummy area DA as well, the distance d 3  and/or d 4  between the outermost open barrier rib  700  and the seal layer  210  may be set smaller in order to reduce the size of the bezel area. Also, even if the distance d 3  and/or d 4  between the outermost open barrier rib  700  and the seal layer  210  is set substantially equal to or less than the circumferential length of the exhaust hole  200 , degradation of the exhaust characteristics can be prevented. 
     As above, a path through which gas can pass is provided between the open barrier ribs  700  and the closed barrier ribs  112 , thus improving the exhaust characteristics. 
     From the viewpoint of the path through which gas can pass, a width of the remaining portion, excluding the portion occupied by the open barrier ribs  700 , of the region d 30  and/or d 40  from the active area AA and the seal layer  210  may be greater than the circumferential length of the exhaust hole  200 . 
     For example, as shown in  FIG. 14 , in the case where a plurality of open barrier ribs  700  are arranged in the dummy area DA, the sum d 33 +d 34  and/or d 43 +d 44  of the distance between two adjacent open barrier ribs  700  and the sum d 32 +d 33 +d 34  and/or d 42 +d 43 +d 44  of the distance d 32  and/or d 42  between the outermost closed barrier rib  112  and an adjacent open barrier rib may be greater than the circumferential length of the exhaust hole  200 . 
     Alternatively, since the path through which gas can pass is formed by the open barrier ribs  700  in the dummy area DA, the distance d 3  and/or d 4  between the outermost open barrier rib  700  and the seal layer  210  may be set smaller, and, as a result, the sum d 33 +d 34  and/or d 43 +d 44  of the distance between the two adjacent open barrier ribs  700  and the sum d 32 +d 33 +d 34  and/or d 42 +d 43 +d 44  of the distance d 32  and/or d 42  between the outermost closed barrier rib  112  and the adjacent open barrier rib may be made smaller than the circumferential length of the exhaust hole  200 . 
     Moreover, the distance D 3  and/or D 4  between the outermost open barrier rib  700  and the seal layer  210  may be less than the distance D 31  and/or D 41  between the outermost closed barrier rib  112  and the outermost open barrier rib  700 . 
     As shown in  FIG. 14 , in the case where at least one open barrier rib  700  Is arranged in the dummy area DA, a path through which gas can pass is provided in the dummy area as well, thereby enabling a further decrease in the size of the bezel area by reducing the distance between the outermost open barrier rib  700  and the seal layer  210 . 
     Meanwhile, if the distance between the outermost open barrier rib  700  and the seal layer  210  is excessively large, with the circumferential length of the exhaust hole  200  being fixed, the size of an unnecessary area, i.e., the size of the bezel, becomes excessively large, thus increasing manufacturing costs. 
     For example, it is assumed that, as shown in  FIG. 14 , the distance d 3  and/or d 4  between the outermost open barrier rib  700  and the seal layer  210  is substantially equal to the circumferential length of the exhaust hole  200  in the second exemplary embodiment according to the present invention, and as shown in  FIG. 15 , the distance d 10  and/or d 20  between the outermost open barrier rib  700  and the seal layer  210  is approximately twice as large as the circumferential length of the exhaust hole  200  in a second comparative example. 
     The exhaust characteristics of the second exemplary embodiment and the second comparative example will be discussed with reference to  FIG. 16 . 
     Here, the times required to exhaust the gas in the panel to a vacuum pump and reduce the internal pressure to a critical degree of vacuum in the second exemplary embodiment and the second comparative example are measured. The critical degree of vacuum is set to approximately 2.1×10 −21 . 
     Referring to (a) of  FIG. 16 , it can be seen that, in the second comparative example, the time (t) required for the internal pressure of the panel to reach the critical degree of vacuum from a point of time when the vacuum pump is operated to start sucking impurity gases in the panel is approximately 220 minutes 
     Referring to (b) of  FIG. 16 , it can be seen that, in the second exemplary embodiment according to the present invention, the time (t) required for the internal pressure of the panel to reach the critical degree of vacuum from a point of time when the vacuum pump is operated to start sucking impurity gases in the panel is approximately 225 minutes, which is substantially at an equal level to that of the second comparative example. 
     In comparing (a) and (b) of  FIG. 16 , in the second comparative example, it can be seen that an unconditional increase in the distance d 10  and/or d 20  between the outermost barrier rib  112  and the seal layer  210  as shown in  FIG. 15  may only lead to an increase in the size of the bezel area without significant improvement in the exhaust characteristics. That is, as shown in  FIG. 14 , if the distance d 3  and/or d 4  between the outermost open barrier rib  700  and the seal layer  210  is substantially equal or less than the circumferential length of the exhaust hole  200 , the exhaust characteristics can be maintained at an equal level to those of the second comparative example and the size of the bezel area can be reduced. 
     The open barrier ribs  700  may be arranged on the long sides LS or short sides SS of the front substrate  101  and rear substrate  111 , or may be arranged on the long sides LS and short sides SS, respectively, of the front substrate  101  and rear substrate  111 . 
     For example, as shown in  FIG. 17 , the open barrier ribs  700  may be arranged in the dummy area DA on the short sides SS of the front substrate  101  and rear substrate  111 . 
     Alternatively, as shown in  FIG. 18 , the open barrier ribs  700  may be arranged in the dummy area DA on the long sides LS of the front substrate  101  and rear substrate  111 . 
     Referring to  FIG. 19 , even when the open barrier ribs  700  are arranged in the dummy area DA, the separation barrier rib  1100  may be arranged between the open barrier ribs  700  and the seal layer  210 . 
     Also, the separation barrier rib  1100  may be spaced apart from the open barrier ribs  700 . 
     In the case where the separation barrier rib  1100  is formed as above, the distance d 3  and/or d 4  between the outermost open barrier rib  700  and the seal layer  210  may be less than the circumferential length of the exhaust hole  200 . Moreover, the sum d 3   a +d 3   b  and/or d 4   a +d 4   b  of the distance d 3   a  and d 4   a  between the outermost open barrier rib  700  and the separation barrier rib  1100  and the distance d 3   b  and d 4   b  between the separation barrier rib  1100  and the seal layer  210  may be less than the circumferential length of the exhaust hole  200 . 
     Meanwhile, the closed barrier ribs and the open barrier ribs may be arranged together in the dummy area DA. Therefore, at least one dummy discharge cell may be formed. 
     To this end, as shown in  FIG. 20 , at least one of the dummy barrier ribs arranged in the dummy area DA may be a closed dummy barrier rib  1500 . 
     The closed dummy barrier rib  1500  may comprise a dummy transverse barrier rib  1510  and a dummy longitudinal barrier rib  1520 . 
     When a dummy discharge cell is formed in the dummy area DA as above, the stability of discharge in the active discharge cells partitioned, by the active barrier ribs  112  in the active area can be further improved. 
     Also, even when at least one dummy discharge cell is formed in the dummy area DA, it may be preferable that at least one open barrier rib  700  is arranged in the dummy area DA. 
     In this case, it may be preferable that the sum d 51 +d 52  and/or d 61 +d 62  of the distance d 51  and d 61  between the closed dummy barrier rib  1500  and the open barrier rib  700  and the distance d 52  and d 62  between the open barrier rib  700  and the seal layer  210  is greater than the circumferential length of the exhaust hole  200 . 
     Alternatively, as shown in  FIG. 21 , the closed dummy barrier rib  1500  for partitioning the dummy discharge cell in the dummy area DA may be spaced apart from the active barrier ribs  112  by a predetermined distance d 53  and d 63 . 
     In this case, it may be preferable that the sum d 51 +d 52 +d 53  and/or d 61 +d 62 +d 63  of the distance d 53  and d 63  between the active barrier ribs  112  and the closed dummy barrier rib  1500 , the distance d 51  and d 61  between the closed dummy barrier rib  1500  and the opened barrier rib  700 , and the distance d 52  and d 62  between the open barrier rib  700  and the seal layer  210  is greater than the circumferential length of the exhaust hole  200 . 
     Alternatively, as shown in  FIG. 22 , open barrier ribs  1720  arranged in the dummy area DA may comprise a first portion  1700  having a stripe shape and parallel to the long sides LS or short sides SS of the front substrate  101  and rear substrate  111  and a second portion  1710  projecting from the first portion  1700 . 
     Although  FIG. 22  shows the case where the open barrier ribs  1720  is arranged on the short sides SS of the front substrate  101  and rear substrate  111 , the open barrier ribs  1720  may be arranged on the long sides LS of the front substrate  101  and rear substrate  111 . 
     In the above-described structure, it may be preferable that the sum d 71 +d 72 +d 73  of the distance  70  between the active barrier ribs  112  and the open barrier ribs  1720 , the distance d 71  between the two open barrier ribs  1720 , and the distance d 72  between the outermost open barrier rib  1720  and the seal layer  210  is greater than the circumferential length of the exhaust hole  200 . 
       FIG. 23  is a diagram for explaining the shape of the exhaust hole. 
     Referring to  FIG. 23 , the exhaust hole  200  may have a spherical shape with a radius of R as shown in (a) or an elliptical shape whose transverse length L 2  and longitudinal length L 1  are different from each other as shown in (b). 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.