Patent Publication Number: US-7911141-B2

Title: Plasma display panel having dielectric layer providing improved discharge efficiency

Description:
This application claims the benefit of the Korean Patent Application No. 10-2007-0084022, filed in Korea on Aug. 21, 2007, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     This relates to a plasma display panel, and more particularly, to a plasma display panel capable of achieving improved discharge efficiency and reduced discharge voltage. 
     2. Background 
     Generally, a plasma display panel (hereinafter, referred to as a “PDP”) is a luminous device that displays an image using an electric discharge within a plurality of discharge cells. Such a PDP does not require that each cell be provided with an active device and therefore, such a PDP may have a relatively large-size screen produced by a simplified manufacturing process, an easily increased screen size, and rapid response time. 
     Referring to  FIG. 1 , a PDP is generally configured in such a manner that an upper panel  10  and a lower panel  20  are stacked one above another so that they face each other. The upper panel  10  includes a pair of sustain electrodes  12  arranged at an inner surface of a transparent substrate  11 . Normally, the sustain electrodes  12  are divided into a transparent electrode and a bus electrode. The sustain electrodes  12  are coated with a dielectric layer  13  for AC driving. A protective film  14  is formed at a surface of the dielectric layer  13 . 
     The lower panel  20  includes address electrodes  22  arranged on an inner surface of a lower substrate  21 , and a dielectric layer  23  is formed over the address electrodes  22 . A stripe type or well-type barrier rib  24  is formed over the dielectric layer  23  to partition the space between the upper panel  10  and the lower panel  20  into discharge cells  25 . Red, blue, and green fluorescent layers  26  for display of different colors are coated over the discharge cell space partitioned by the barrier rib  24  to define sub-pixels. A discharge cell  25  is partitioned, on a sub-pixel basis, by the barrier rib  24 , and is filled with a discharge gas. One pixel includes three sub-pixels. 
     The upper dielectric layer  13  covering the sustain electrodes  12  may be made of a material having a uniform specific dielectric constant. In this case, if the upper dielectric layer  13  is made of a material having a relatively low specific dielectric constant, it may cause an increase in discharge voltage upon driving of the PDP. 
     Moreover, if the upper dielectric layer  13  is made of the relatively low specific dielectric constant material, a capacitance between the sustain electrodes  12  may be increased, resulting in increased unavailable electric power. 
     SUMMARY OF THE INVENTION 
     Accordingly, embodiments as broadly described herein are directed to a plasma display panel that substantially obviates one or more problems due to such limitations and disadvantages. 
     An object is to provide a plasma display panel in which a dielectric layer has an improved configuration to achieve improved discharge efficiency and reduced discharge voltage, resulting in an improvement in reliability and durability of the plasma display panel. 
     Additional advantages, objects, and features will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice. The objectives and other advantages of embodiments as broadly described herein may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with a first embodiment as broadly described herein, a plasma display panel may include a substrate; a sustain electrode located on the substrate; a first dielectric layer located on the substrate formed with the sustain electrode; and a second dielectric layer located on the first dielectric layer and having a larger dielectric constant than a dielectric constant of the first dielectric layer. 
     In accordance with a second embodiment as broadly described herein, a plasma display panel may include a substrate; a sustain electrode located on the substrate; and a dielectric layer located on the substrate formed with the sustain electrode and consisting of a plurality of layers having a specific dielectric constant proportional to distance from the substrate. 
     In accordance with a third embodiment as broadly described herein, a plasma display panel may include a substrate; a sustain electrode located on the substrate; a dielectric layer located on the substrate formed with the sustain electrode; a protective film located on the dielectric layer; and a dielectric particle layer disposed on the protective film. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the embodiments as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG. 1  is a perspective view of an exemplary plasma display panel; 
         FIG. 2  is a sectional view of a plasma display panel in accordance with an embodiment as broadly described herein; 
         FIGS. 3 and 4  are schematic views illustrating equipotential line distribution based on the embodiment shown in  FIG. 2 ; 
         FIG. 5  is a sectional view of a plasma display panel in accordance with another embodiment as broadly described herein; 
         FIG. 6  is a schematic view illustrating equipotential line distribution based on the embodiment shown in  FIG. 5 ; 
         FIG. 7  is a sectional view of plasma display panel in accordance with another embodiment as broadly described herein; and 
         FIGS. 8 and 9  are sectional views of a plasma display panel in accordance with another embodiment as broadly described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. 
     The same reference numbers will be used throughout the drawings where possible to refer to the same or like parts. In the drawings, dimensions of layers and regions are exaggerated for clarity of description. In addition, the respective embodiments described herein include complementary aggressive embodiments. 
     It is well understood that, when an element such as a layer, region or substrate is referred to as being “on” another element, it may be directly on the other element or intervening elements may also be present. 
     It is well understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. 
     As shown in  FIG. 2 , a plasma display panel as embodied and broadly described herein may include a pair of sustain electrodes  110  located in a single discharge space, the sustain electrodes  110  being disposed on a substrate  100 . 
     An upper dielectric layer  200  is located on the substrate  100  such that the sustain electrodes  110  are coated with the dielectric layer  200 . The upper dielectric layer  200  has a multi-layer configuration having two or more layers. Specifically,  FIG. 2  illustrates a two-layer upper dielectric layer  200  having a first dielectric layer  210  and a second dielectric layer  220 . 
     The specific dielectric constants of the respective dielectric layers  210  and  220  may increase in proportion to distance from the substrate  100  (∈ 1 &lt;∈ 2 ). The specific dielectric constants of the dielectric layers  210  and  220  may be in a range of, for example, approximately 3 to 20. 
     In addition, in consideration of an entire thickness of the panel and a discharge space size, the respective dielectric layers  210  and  220  may have a thickness of, for example, approximately 5 μm to 30 μm. 
     In  FIG. 2 , a discharge space  300  is defined below the dielectric layer  200  and in turn, a lower dielectric layer  400  is located below the discharge space  300 . The panel includes a plurality of discharge spaces  300  partitioned by barrier ribs (not shown). Each discharge space  300  defines a single sub-pixel. 
     Through the adoption of the above-described multi-layered dielectric layer  200  having a dielectric constant proportional to distance from the substrate  100 , the discharge space  300  exhibits a wide electric field distribution therein, thereby achieving a lengthened discharge path and consequently, improved discharge efficiency. 
       FIGS. 3 and 4  illustrate equipotential distribution in the plasma display panel. More particularly,  FIG. 3  illustrates equipotential distribution based on a single-layered dielectric layer, and  FIG. 4  illustrates equipotential distribution based on the above-described multi-layered upper dielectric layer  200 . 
     As shown, if a specific dielectric constant of the first dielectric layer  210  is smaller than a specific dielectric constant of the second dielectric layer  220 , the discharge space  300  exhibits a wide electric field distribution and thus, can achieve a longer discharge path, as compared to  FIG. 3  in which the single-layered dielectric layer is made of a material having a uniform specific dielectric constant. 
     As will be appreciated from the above description, the length of the discharge path is proportional to a degree of freedom in the occurrence of an actual discharge and consequently, discharge efficiency can be increased. 
     In addition, in the case where the first dielectric layer  210 , which contributes greatly to a capacitance between the sustain electrodes  110 , has a smaller specific dielectric constant than a specific dielectric constant of the second dielectric layer  220 , this limits any increases in capacitance, resulting in a reduction in electric power consumption. 
     Alternatively, the above-described multi-layered dielectric layer  200  may include three or more layers. Even in this case, the respective layers of the dielectric layer  200  satisfy the above-described conditions, for example, the specific dielectric constant range of 3 to 20, the thickness range of 5 μm to 30 μm, and an increasing specific dielectric constant with increasing distance from the substrate  100  as set forth above. 
     Specifically, a third dielectric layer  230  may be located on the second dielectric layer  220  of the upper dielectric layer  200 . As shown in  FIG. 5 , the third dielectric layer  230  may include dielectric particles  231 . The dielectric particles  231  may have a specific dielectric constant of approximately 3 to 20, and have a spherical shape, an ellipsoidal shape, a polyhedral shape such as, for example, a tetrahedral shape and a hexahedral shape, or other shape as appropriate. At least two or more of the dielectric particles  231  may be located in a single sub-pixel, namely, in the single discharge space  300  of the plasma display panel. 
     In this case, the dielectric particles  231  may be sized such that a largest diameter portion of each dielectric particle has a diameter of approximately 0.2 μm to 10 μm. In the present embodiment, the term “diameter” may be applied to a polyhedral shape. For example, the diameter may be a longest length portion of the polyhedral dielectric particle, having a length of approximately 0.2 μm to 10 μm. 
     To form the third dielectric layer  230  including the dielectric particles  231 , in one example, a dielectric material may be coated over the second dielectric layer  220  under conditions of a predetermined temperature and pressure, so as to be crystallized on the second dielectric layer  220 . In another example, the dielectric particles  231  having a predetermined size may be attached to the second dielectric layer  220 . In the latter case, the dielectric particles  231  can remain permanently attached due to electrostatic attraction, without separate attachment means. 
       FIG. 6  illustrates equipotential line distribution based on the embodiment shown in  FIG. 5 . As can be appreciated from  FIG. 6 , the presence of the third dielectric layer  230  including the dielectric particles  231  can result in a denser equipotential line distribution. 
     Such a dense equipotential line distribution has the effect of further reducing a discharge voltage for driving of the plasma display panel. 
     More particularly, in the case where the upper dielectric layer  200 , which has the specific dielectric constant proportional to distance from the substrate  100 , includes the dielectric particles  231 , increasing an intensity of an electric field between the dielectric particles  231  distributed in the dielectric layer  200  is possible, and this can reduce a discharge voltage. 
     Alternatively, as shown in  FIG. 7 , in addition to the configuration of  FIG. 5 , a protective film  240  may be located between the second dielectric layer  220  and the third dielectric layer  230 . Alternatively, a fourth dielectric layer may be located between the second dielectric layer  220  and the third dielectric layer  230 , in the position of the protective film  240  shown in  FIG. 7 . 
     In this case, note that the first dielectric layer  210 , the second dielectric layer  220 , the third dielectric layer  230 , and the fourth dielectric layer may each have a specific dielectric constant established in proportion to its distance from the substrate  100 . 
     As shown in  FIG. 8 , a plasma display panel according to a second embodiment may include a pair of sustain electrodes  510  located in a single discharge space, the sustain electrodes  510  being disposed on a substrate  500 . 
     An upper dielectric layer  600  is located over the sustain electrodes  510  and the substrate  500 . The dielectric layer  600  may include a first dielectric layer  610  coated over the sustain electrodes  510 , and a second dielectric layer  620  located on the first dielectric layer  610 . 
     In the present embodiment, the second dielectric layer  620  may be a layer including dielectric particles  621 . The dielectric particles  621  may have a specific dielectric constant of approximately 3 to 20, and have a spherical shape, an ellipsoidal shape, a polyhedral shape such as, for example, a tetrahedral shape and a hexahedral shape, or other shape as appropriate. 
     A discharge space  700  and a lower dielectric layer  800  are located below the second dielectric layer  620 . The discharge space  700  is partitioned into a plurality of discharge spaces by barrier ribs (not shown), and each resulting discharge space  700  defines a single sub-pixel. 
     At least two or more of the dielectric particles  621  may be located in a single sub-pixel, namely, in the single discharge space  700  of the plasma display panel. 
     The dielectric particles  621  may be sized such that a largest diameter portion of each dielectric particle has a diameter of approximately 0.2 μm to 10 μm. 
     To form the second dielectric layer  620  including the dielectric particles  621 , in one example, a dielectric material may be coated over the first dielectric layer  610  under conditions of a predetermined temperature and pressure, so as to be crystallized on the first dielectric layer  610 . In another example, the dielectric particles  621  having a predetermined size may be attached to the first dielectric layer  610  by various methods such as for example electrostatic attraction or bonding. The dielectric particles  621  have the same features as those of the above-described first embodiment. 
     The second dielectric layer  620  including the dielectric particles  621  can result in a denser equipotential line distribution in the discharge space  700 . Such a dense equipotential line distribution has the effect of further reducing a discharge voltage for driving of the plasma display panel. 
     The second dielectric layer  620  may have a larger specific dielectric constant than a specific dielectric constant of the first dielectric layer  610 . In this case, assuming that the specific dielectric constant of the dielectric layer  600  is proportional to distance from the substrate  500 , increasing an intensity of an electric field between the dielectric particles  621  distributed in the second dielectric layer  620  is possible, and this can reduce a discharge voltage. 
     Alternatively, as shown in  FIG. 9 , in addition to the configuration of  FIG. 8 , a protective film  630  may be located between the first dielectric layer  610  and the second dielectric layer  620 . Alternatively a third dielectric layer may be located between the first dielectric layer  610  and the second dielectric layer  620 , in the position occupied by the protective film  630  shown in  FIG. 9 . 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” “certain embodiment,” “alternative embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment as broadly described herein. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     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 spirit and scope of the principles of this disclosure. More particularly, various numerous 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.