Abstract:
A plasma display panel (PDP) includes: a front substrate facing a rear substrate; first and second discharge enhancement layers disposed between the front and rear substrates and arranged on both sides of a main discharge space; first and second barrier ribs respectively formed on the first and second discharge enhancement layers and defining first and second asymmetric stepped spaces along with the first and second discharge enhancement layers; a scan electrode and a common electrode inducing a mutual discharge in the main discharge space; an address electrode generating an address discharge along with the scan electrode and extending in a direction to intersect the scan electrode; a phosphor layer formed in at least the main discharge space; and a discharge gas filled in the main discharge space and the first and second stepped spaces. Accordingly, the PDP having high efficiency may operate with low power and obtain high luminous brightness.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2009-0104303, filed Oct. 30, 2009 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    One or more embodiments of the present invention relate to a plasma display panel (PDP), and more particularly, to a high efficiency PDP that may operate with low power and obtain high luminous brightness. 
         [0004]    2. Description of the Related Art 
         [0005]    In general, plasma display panels (PDPs) are flat panel displays that excite phosphors using ultraviolet (UV) rays generated by a plasma discharge and create an image using visible light generated from the excited phosphors. PDPs are generally configured in such a manner that barrier ribs define a plurality of discharge cells. The barrier ribs are interposed between an upper substrate on which discharge electrodes are arranged and a lower substrate on which address electrodes are arranged to enable the upper substrate and the lower substrate to face each other. A discharge gas is injected between the upper substrate and the lower substrate. A discharge voltage is applied between the discharge electrodes to excite phosphors coated in the discharge cells, and create an image using visible light generated by the excited phosphors. 
         [0006]    General PDPs have a problem when a large portion of a phosphor layer is attached to side surfaces of the barrier ribs. Since flowable phosphor paste sags and flows down from the side surfaces of the barrier ribs, the phosphor layer is not formed with a sufficiently large and uniform thickness. Such general PDPs have another problem in that since visible light generated by the excited phosphors is not output upward but output in a lateral direction from side surfaces of the barrier ribs, visible light extraction efficiency is low. Such general PDPs have another problem in that since bottom surfaces of the discharge cells on which the phosphors are concentrated are relatively far from the front substrate on which the discharge electrodes are arranged, a sufficient amount of UV light does not reach the phosphors, thereby failing to effectively excite the phosphors. Such general PDPs have another problem in that since an address discharge occurs along a long discharge path corresponding to the height of a discharge cell, an address driving voltage is high and a sufficient voltage margin is not obtained. 
       SUMMARY OF THE INVENTION 
       [0007]    One or more embodiments of the present invention include a high efficiency plasma display panel (PDP) that may operate with low power and obtain high luminous brightness. 
         [0008]    One or more embodiments of the present invention include a PDP that may reduce trapped air bubbles in a phosphor layer and improve ultraviolet (UV)-visible light conversion efficiency by forming the phosphor layer with uniform thickness. 
         [0009]    According to one or more embodiments of the present invention, a PDP includes: a front substrate and a rear substrate facing each other; first and second discharge enhancement layers disposed between the front substrate and the rear substrate and arranged on both sides of a main discharge space; first and second barrier ribs respectively formed on the first and second discharge enhancement layers and defining first and second stepped spaces, which are asymmetric, along with the first and second discharge enhancement layers; a scan electrode and a common electrode inducing a mutual discharge in the main discharge space; an address electrode generating an address discharge along with the scan electrode and extending in a direction to intersect the scan electrode; a phosphor layer formed in at least the main discharge space; and a discharge gas filled in the main discharge space and the first and second stepped spaces. 
         [0010]    According to an aspect of the invention, the first stepped space may be defined by the first discharge enhancement layer and the first barrier rib which are disposed on one side of the main discharge space, and the second stepped space may be defined by the second discharge enhancement layer and the second barrier rib which are disposed on the other side of the main discharge space. 
         [0011]    According to an aspect of the invention, the first width W 1  between the first barrier rib defining the first stepped space and an end of the first discharge enhancement layer and a second width W 2  between the second barrier rib defining the second stepped space and an end of the second discharge enhancement layer may satisfy a relationship of W 1 &gt;W 2 . 
         [0012]    According to an aspect of the invention, the first and second stepped spaces formed on both sides of the main discharge space may form one unit cell by being connected to the main discharge space. 
         [0013]    According to an aspect of the invention, the first stepped space, the main discharge space, and the second stepped space forming the one unit cell may be repeatedly formed in the same order from one end to the other end of the PDP. 
         [0014]    According to an aspect of the invention, a non-discharge space in which no discharge occurs may be formed between adjacent unit cells. 
         [0015]    According to an aspect of the invention, the PDP may further include an external-light absorbing layer formed over the non-discharge space. 
         [0016]    According to an aspect of the invention, the PDP may further include a third barrier rib disposed between the front substrate and the rear substrate and extending in a direction to cross the first and second barrier ribs. 
         [0017]    According to an aspect of the invention, the phosphor layer may be expanded from the main discharge space to the first and second stepped spaces. 
         [0018]    Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
         [0019]    According to one embodiment of the present invention, a plasma display panel includes: a plurality of first barrier ribs and a plurality of second barrier ribs; a plurality of unit cells configured to emit light, each of the unit cells being located between a corresponding one of the first barrier ribs and a corresponding one of the second barrier ribs, the unit cells being filled with a discharge gas; a plurality of pairs of scan and common electrodes, each of the pairs being configured to induce a discharge in corresponding ones of the unit cells; a plurality of discharge enhancement layers, wherein at least one of the discharge enhancement layers extends across a portion of at least one of the unit cells and forms a raised area which is raised above a lower area of the at least one of the unit cells; and a plurality of phosphor layers in the unit cells, the phosphor layers being configured to emit light in accordance with the induced discharge. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0021]      FIG. 1  is an exploded perspective view of a plasma display panel (PDP) according to an embodiment of the present invention; 
           [0022]      FIG. 2  is an exploded perspective view illustrating a part of the PDP of  FIG. 1 ; 
           [0023]      FIG. 3  is a vertical cross-sectional view taken along line III-III of  FIG. 1 ; 
           [0024]      FIG. 4  is a perspective view for explaining a process of applying phosphors; 
           [0025]      FIG. 5  is an exploded perspective view of a PDP according to an embodiment of the present invention; and 
           [0026]      FIG. 6  is a vertical cross-sectional view taken along line VI-VI of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. 
         [0028]      FIG. 1  is an exploded perspective view of a plasma display panel (PDP) according to an embodiment of the present invention.  FIG. 2  is an exploded perspective view illustrating a part of the PDP of  FIG. 1 . Referring to  FIGS. 1 and 2 , the PDP includes a front substrate  110  facing a rear substrate  120  facing. The front substrate  110  is spaced apart from the rear substrate  120  by an interval. First and second discharge enhancement layers  151  and  152  are disposed on the rear substrate  120  and extend in a Z 1  direction. First and second barrier ribs  153  and  154  are disposed on the rear substrate  120 . Common electrodes X and scan electrodes Y are disposed on the front substrate  110 . 
         [0029]      FIG. 3  is a vertical cross-sectional view taken along line III-III of  FIG. 1 . Referring to  FIG. 3 , the first and second discharge enhancement layers  151  and  152  have relatively large widths. Adjacent first and second discharge enhancement layers  151  and  152  form one pair with a main discharge space SP therebetween. The first and second barrier ribs  153  and  154  having relatively small widths are disposed on the first and second discharge enhancement layers  151  and  152 . Since the first barrier rib  153  having the small width is stacked on the first discharge enhancement layer  151  having the large width, a first stepped space  51  is defined by the first discharge enhancement layer  151  and the first barrier rib  153 . Likewise, since the second barrier rib  154  having the small width is stacked on the second discharge enhancement layer  152  having the large width, a second stepped space S 2  is defined by the second discharge enhancement layer  152  and the second barrier rib  154 . For example, the first and second stepped spaces  51  and S 2  formed on both sides of the main discharge space SP may form one unit cell S. However, it is understood that the unit cell S need not include two stepped spaces  51  and S 2 , and can include only one stepped space or other numbers of stepped spaces. 
         [0030]    As shown and while not required in all aspects, a non-discharge space  130  is formed between adjacent unit cells S. In detail, the non-discharge space  130  is shown formed between the first and second barrier ribs  153  and  154  defining adjacent unit cells S. The non-discharge space  130  acts as an impurity gas flow path and reduces flow resistance during a process of exhausting an impurity gas remaining in the PDP. An external-light absorbing layer  140  is shown formed over the non-discharge space  130 . The external-light absorbing layer  140  includes a black pigment and a black coloring material, and improves the visibility of an image by improving contrast characteristics. However, the external-light absorbing layer  140  is optional, not mandatory. 
         [0031]    The common electrodes X and the scan electrodes Y are disposed on the front substrate  110 . Adjacent pairs of common and scan electrodes X and Y form one pair, causing a display discharge in one unit cell S. The shown common electrode X and the scan electrode Y respectively include transparent electrodes Xa and Ya formed of light transmitting conductive materials, and bus electrodes Xb and Yb electrically contacting the transparent electrodes Xa and Ya and forming power supply lines. 
         [0032]    The common electrode X and the scan electrode Y are covered by a dielectric layer  114  so as to be protected from direct collisions with charged particles participating in a discharge. The shown dielectric layer  114  is covered and protected by a protective layer  115  formed of, for example, an MgO thin film. 
         [0033]    The address electrodes  122  are disposed on the rear substrate  120 . Each of the address electrodes  122  performs an address discharge along with the scan electrode Y. A voltage applied between the scan electrode Y and the address electrode  122  helps to form an electric field high enough to fire a discharge in a unit cell S through the dielectric layer  114  covering the scan electrode Y and the first discharge enhancement layer  151  disposed on the address electrode  122 . At this time, an address discharge may be generated when the dielectric layer  114  covering the scan electrode Y and the first discharge enhancement layer  151  disposed on the address electrode  122  form facing discharge surfaces. 
         [0034]    The bus electrode Yb of the scan electrode Y on which an electric field is concentrated is shown disposed over the first discharge enhancement layer  151  so as to form the facing discharge surfaces. That is, the bus electrode Yb faces a top surface  151   a  of the first discharge enhancement layer  151  with the first and second barrier ribs  153  and  154  therebetween. Also, as shown in  FIG. 3 , the bus electrode Yb may also be disposed over the first barrier rib  153  so as to prevent extraction of light from being inhibited by the bus electrode Yb, which usually is formed of an opaque metal material. 
         [0035]    While a general PDP performs a discharge between scan electrodes Y and address electrodes  122  through a long discharge path between a front substrate  110  and a rear substrate  120 , since the PDP of  FIG. 1  performs an address discharge using the first discharge enhancement layer  151  projecting toward the scan electrode Y to have a height h, an address discharge path is reduced to a length corresponding to a discharge gap g between the first discharge enhancement layer  151  and the dielectric layer  114 . This achieves a higher driving efficiency than the general PDP. 
         [0036]    While not required in all aspects, the shown address electrode  122  is covered by a dielectric layer  121  that is formed on the rear substrate  120 . The first and second discharge enhancement layers  151  and  152  are formed on a flat surface of the dielectric layer  121 . 
         [0037]    A phosphor layer  125  is formed in the main discharge space Sp. Specifically, the phosphor layer  125  is shown formed on the dielectric layer  125  between the first and second discharge enhancement layers  151  and  152 . A plurality of the phosphor layers  125  generate different colors of visible light, for example, red (R), green (G), and blue (B) visible light, by interacting with ultraviolet (UV) rays generated as a result of a display discharge. 
         [0038]    The phosphor layer  125  is not limited by the main discharge space Sp, and may be expanded to the first and second stepped spaces  51  and S 2  as shown. In detail, the phosphor layer  125  covers part of the first and second discharge enhancement layers  151  and  152  defining the first and second stepped spaces  51  and S 2 . Also, as shown in  FIG. 3 , the phosphor layer  125  may be expanded to top surfaces  151   a  and  152   a  of the first and second discharge enhancement layers  151  and  152 , and even to side surfaces of the first and second barrier ribs  153  and  154 . As such, the phosphor layer  125  need not only be in the main discharge space Sp. Further, while shown as being on both the first and second stepped spaces S 1  and S 2 , the phosphor layer  125  need not be on both of the first and second stepped spaces S 1  and S 2 . 
         [0039]    The phosphor layer  125  formed on the top surfaces  151   a  and  152   a  of the first and second discharge enhancement layers  151  and  152  may be effectively excited by the common electrode X and the scan electrode Y, which are near to the phosphor layer  125 , thereby causing a display discharge. Also, the phosphor layer  125  formed on the top surfaces  151   a  and  152   a  is disposed near to the front substrate  110  having a display surface  110   a  to face the front substrate  110  in a display direction (referred to as a Z 3  direction). Accordingly, the visible light VL output from the phosphor layer  125  disposed on the first and second discharge enhancement layers  151  and  152  may be readily emitted to the outside of the PDP, thereby improving visible light extraction efficiency. 
         [0040]    The first and second stepped spaces S 1  and S 2  are formed on left and right sides of the main discharge space Sp. The shown first stepped space S 1  formed on one side of the main discharge space SP and the second stepped space S 2  formed on the other side of the main discharge space SP are asymmetric. Specifically, a first width W 1  is between the first barrier rib  153  defining the first stepped space S 1  and an end of the first discharge enhancement layer  151 . A second width W 2  is between the second barrier rib  154  defining the second stepped space S 2  and an end of the second discharge enhancement layer  152 . W 1  and W 2  are different from each other and satisfy a relationship of W 1 &gt;W 2 . The first stepped space S 1 , the main discharge space Sp, and the second stepped space S 2  forming each unit cell S are repeatedly formed in the same order in one direction (referred to as a Z 2  direction) from one end to the other end of the PDP. This is because since a process of applying phosphors is performed in the Z 2  direction, air bubbles trapped in the phosphor layer  125  may be reduced and the phosphor layer  125  may be uniformly formed. 
         [0041]      FIG. 4  is a perspective view for explaining a process of applying phosphors  125 ′. Referring to  FIG. 4 , the phosphors  125 ′ are in a paste form and may be continuously applied to the first stepped space S 1 , the main discharge space Sp, and the second stepped space S 2  arranged in the Z 2  direction as a spray nozzle N travels from one end to the other end of the PDP. The phosphors  125 ′ are ejected downward from the spray nozzle N and are inclined to a side opposite to a side toward which the spray nozzle travels in the Z 2  direction. Accordingly, the phosphors  125 ′ are heavily accumulated on the first discharge enhancement layer  151 , which is a starting position Ls of a coating area CL of each unit cell S. The phosphors  125 ′ are subsequently subjected to a thermal process to flow toward the second discharge enhancement layer  152 , which is an ending position Lf of the coating area CL, thereby enabling the phosphors  125 ′ to be uniformly applied. That is, the phosphors  125 ′ may be stably accumulated on a portion of the first discharge enhancement layer  151  having the first width W 1  that is relatively large, and then may be expanded to a portion of the second discharge enhancement layer  152  having the second width W 2  that is relatively small through the thermal process. 
         [0042]    Air bubbles trapped in the phosphors  125 ′ or escaping from the phosphors  125 ′ that are being hardened are efficiently discharged by stably accumulating the phosphors  125 ′ on the portion of the first discharge enhancement layer  151  having the first width W 1 . The phosphors  125 ′ are then expanded to all other parts of the unit cell S, thereby reducing trapped air bubbles remaining in the phosphors  125 ′. Also, since the phosphors  125 ′ are expanded to the portion of the second discharge enhancement layer  152  having the second width W 2  that is relatively small through a thermal process after being applied to the portion of the first discharge enhancement layer  151  having the first width W 1 , the phosphor layer  125  may be uniformly formed. 
         [0043]    The shown PDP of  FIG. 1  further includes a third barrier rib  155  extending in the Z 2  direction to cross the first and second barrier ribs  153  and  154 . Each substantially rectangular unit cell S may be defined by the third barrier rib  155  and the first and second barrier ribs  153  and  154 . 
         [0044]    A discharge gas is injected into the unit cell S. The discharge gas may be a multi-element gas in which xenon (Xe), krypton (Kr), helium (He), neon (Ne), and the like capable of providing UV rays through discharge excitement are mixed in a given volumetric ratio. 
         [0045]      FIG. 5  is an exploded perspective view of a PDP according to another embodiment of the present invention.  FIG. 6  is a vertical cross-sectional view taken along line VI-VI of  FIG. 5 . Referring to  FIGS. 5 and 6 , the first and second stepped spaces S 1  and S 2  are formed on both sides of a main discharge space Sp. The first width W 1  is between a first barrier rib  253  defining the first stepped space  51  and an end of a first discharge enhancement layer  251 . The second width W 2  is between a second barrier rib  254  defining the second stepped space S 2  and an end of a second discharge enhancement layer  252 . The widths W 1  and W 2  satisfy a relationship of W 1 &gt;W 2 . Accordingly, the first and second stepped spaces  51  and S 2  are asymmetric about the center of the unit cell S. Unlike the PDP of  FIG. 1 , the PDP of  FIG. 5  has no non-discharge space disposed between adjacent unit cells S. A third barrier rib  255  extends in a Z 2  direction to cross the first and second barrier ribs  253  and  254  and define each substantially rectangular unit cell S along with the first and second barrier ribs  253  and  254 . 
         [0046]    The PDP according to the one or more embodiments of the present invention may effectively excite phosphors and improve visible light extraction efficiency by allowing support surfaces of phosphors to be formed near to discharge electrodes for performing a display discharge and also near to a display surface. Furthermore, the PDP according to the one or more embodiments of the present invention may perform an address discharge at a low voltage and obtain a sufficient voltage margin by reducing the length of an address discharge path. Moreover, the PDP according to the one or more embodiments of the present invention may reduce trapped air bubbles remaining in a phosphor layer by analyzing a process of applying phosphors and improving the structure of barrier ribs, and may improve UV-visible light conversion efficiency by uniformly forming the phosphor layer. 
         [0047]    Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.