Abstract:
A plasma display panel and a method for manufacturing the same. The plasma display panel includes: a first substrate; sustain electrodes on the first substrate, each being composed of an X electrode and a Y electrode; a first dielectric layer covering the sustain electrodes; a protective layer on the first dielectric layer; a second substrate facing the first substrate; address electrodes on the second substrate and crossing the sustain electrodes; a second dielectric layer covering the address electrodes; and barrier ribs for partitioning discharge spaces between the first substrate and the second substrate; and a phosphor layer at sides of the barrier ribs. Here, the protective layer is a single deposition layer having a non-uniform thickness, the sustain electrodes are located to correspond to a first region of the protective layer, and the first region of the protective layer is thicker than a second region of the protective layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2007-0007974, filed on Jan. 25, 2007, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a plasma display panel. 
     2. Discussion of Related Art 
     Plasma display panels (PDPs) refer to flat display panels that display images using a gas discharge phenomenon. Such display panels may provide excellent display capabilities, e.g., large-capacity display, high brightness, high contrast, low image sticking, a wide-range of viewing angle, and so forth, and a thin/large screen, as compared to conventional cathode ray tube (CRT) displays. 
     With reference to  FIG. 1 , a conventional plasma display panel (PDP)  100  includes a first substrate  101 , a second substrate  102 , sustain electrodes  120 , a first dielectric layer  105 , a protective layer  106 , address electrodes  107 , a second dielectric layer  108 , barrier ribs  109 , and red, green, and blue phosphor layers  110 . Each of the sustain electrodes  120  includes an X electrode  103  and a Y electrode  104  arranged in a pair, which are alternately arranged at a surface of the first substrate  101 . The first dielectric layer  105  covers (or encases) the X electrode  103  and the Y electrode  104 . The protective layer  106  is formed on a surface of the first dielectric layer  105 . A corresponding one of the address electrodes  107  is arranged at a surface of the second substrate  102  to cross the X electrode  103  and the Y electrode  104 . The second dielectric layer  108  covers (or encases) the address electrode  107 . The barrier ribs  109  are installed between the first substrate  101  and the second substrate  102  and define a discharge space. The red, green, and blue phosphor layers  110  are coated on sides of the barrier ribs  109  and on a surface of the second dielectric layer  108 . 
     The first substrate  101  and the second substrate  102  are formed to face each other with a gap therebetween. The gap formed between the first substrate  101  and the second substrate  102  is filled with a mixture of Ne+Xe gas or a mixture of He+Ne+Xe gas at a pressure level that may be predetermined (for example, 450 Torr). 
     In the PDP  100  having the construction as described above, when an electric signal is applied to the Y electrode  104  and the corresponding one of the address electrodes  107 , a discharge cell is for an emission. When the electric signal is alternately applied to the X and Y electrodes  103  and  104 , a visible ray is emitted from the phosphor layers  110  coated in the selected discharge (or emission) cell to display a static image and/or a moving image. 
     The X and Y electrodes  103  and  104  and the address electrodes  107  are driven by a circuit. 
     The protective layer  106  in the PDP  100  has three functions. 
     First, the protective layer  106  functions to protect an electrode and a dielectric material. That is, a discharge may be generated in an electrode only structure or in a dielectric material and electrode only structure. Here, when the discharge is generated in the electrode only structure, it may be difficult to control a discharge current. When the discharge is generated in the dielectric material and electrode only structure, because the dielectric material can be damaged due to a sputtering etch, the dielectric material should be coated with a protective layer, which is resistant to plasma ions. 
     Second, the protective layer  106  functions to reduce a discharge start voltage. A physical quantity directly related to the discharge start voltage is a secondary electron emission coefficient of a material that is used to form the protective layer  106  for plasma ion resistance. The more the secondary electron coefficient of the protective layer is, the less the discharge start voltage is. Accordingly, the greater the secondary electron emission coefficient of a material forming a protective layer is, the better a characteristic thereof is. 
     Finally, the protective layer  106  functions to reduce a discharge delay time. The discharge delay time is a physical quantity that refers to a time after which a discharge occurs from an applied voltage, and may be derived from a sum of a formation delay time and a statistical delay time. As the discharge delay time is reduced, the addressing speed is increased, thereby allowing for the use of a single scan, reducing a scan driver cost, and/or increasing the number of available sub fields. Also, the reduction of the discharge delay time can also provide the PDP  100  with improved luminance and/or image quality. 
     When the PDP  100  is driven, a voltage is applied into the panel and discharge gas injected therein is electrolyzed to form plasma. 
     However, when the plasma is generated, positive ions in the plasma periodically collide with the first substrate  101  by an alternating current voltage applied to the X and Y electrodes  103  and  104  of the first substrate  101 . 
     The protective layer  106  may be etched (or damaged) by the ion shock, which is positioned at a peripheral part of the X and Y electrodes  103  and  104  of the first substrate  101 . 
     When the protective layer  106  is etched, it interrupts a normal discharge in the panel, thereby reducing the lifespan of the PDP  100 . 
       FIG. 2  is a picture showing an etching of a protective layer in a conventional plasma display panel. As shown in  FIG. 2 , an etch  130  of the protective layer  106  due to an ion shock mainly occurs at regions near an ITO electrode  103   b  and a bus electrode  104   a  of the X and Y electrodes  103  and  104 . 
     SUMMARY OF THE INVENTION 
     An aspect of an embodiment of the present invention is directed to a plasma display panel that includes a protective layer for an electrode part on a substrate of the plasma display panel, the protective layer being thickly formed (e.g., without an additional and/or special process) to have a thickness capable of improving quality and/or lifespan of the plasma display panel. 
     An aspect of an embodiment of the present invention is directed to a plasma display panel and a method for manufacturing the same, which partially and/or thickly form a protective layer (e.g., without an additional and/or special process) to improve a lifespan of the plasma display panel. 
     In an embodiment of the present invention, a plasma display panel is provided. The plasma display panel includes: a first substrate; a plurality of sustain electrodes on the first substrate, each of the sustain electrodes being composed of an X electrode and a Y electrode; a first dielectric layer covering the sustain electrodes; a protective layer on the first dielectric layer; a second substrate facing the first substrate; a plurality of address electrodes on the second substrate and crossing the sustain electrodes; a second dielectric layer covering the address electrodes; and a plurality of barrier ribs for partitioning red, green, and blue discharge spaces between the first substrate and the second substrate; and a phosphor layer at a side of each of the barrier ribs, wherein the protective layer is a single deposition layer having a non-uniform thickness, wherein the sustain electrodes are located to correspond to a first region of the protective layer, and wherein a thickness portion of the first region of the protective layer is greater in thickness than a thickness portion of a second region of the protective layer. 
     In one embodiment, the second region of the protective layer is any region of the protective layer other than the first region of the protective layer. 
     In one embodiment, the thickness portion of the first region of the protective layer is set to be greater in thickness than the thickness portion of the second region of the protective layer by applying a negative bias voltage to the sustain electrodes. The protective layer may include a magnesium oxide (MgO). The protective layer may include a magnesium oxide that includes aluminum (Al) and/or calcium (Ca). 
     In one embodiment, the thickness portion of the first region of the protective layer is negative bias voltage thickened to be greater in thickness than the thickness portion of the second region of the protective layer. 
     In one embodiment, a thickness portion of the protective layer at a Y electrode part of the sustain electrodes is set to be greater in thickness than a thickness portion of the protective layer at an X electrode part of the sustain electrodes. The thickness portion of the first region of the protective layer may be set to be greater in thickness than the thickness portion of the second region of the protective layer by applying a negative bias voltage to the sustain electrodes, and the thickness portion of the protective layer at the Y electrode part of the sustain electrode may be set to be greater in thickness than the thickness portion of the protective layer at the X electrode part of the sustain electrode by applying a voltage to the Y electrodes of the sustain electrodes to be greater in intensity than that applied to the X electrodes of the sustain electrodes. Alternatively, the thickness portion of the first region of the protective layer may be set to be greater in thickness than the thickness portion of the second region of the protective layer by applying a negative bias voltage to the sustain electrodes, and the thickness portion of the protective layer at the Y electrode part of the sustain electrode may be set to be greater in thickness than the thickness portion of the protective layer at the X electrode part of the sustain electrode by applying a voltage to the Y electrodes of the sustain electrodes to be greater in time period than that applied to the X electrodes of the sustain electrodes. 
     According to another embodiment of the present invention, a method for manufacturing a plasma display panel is provided. The method includes: forming a sustain electrode on a first substrate; forming a first dielectric layer to cover the sustain electrode; and forming a protective layer of a non-uniform thickness on the first dielectric layer by a single deposition so that a first region of the protective layer is located to correspond to the sustain electrode and a thickness portion of the first region of the protective layer is formed to be greater in thickness than a thickness portion of a second region of the protective layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
         FIG. 1  is a cross-sectional view showing an unit cell structure of a conventional plasma display panel (PDP); 
         FIG. 2  is a picture showing an etching of a protective layer in the conventional plasma display panel; 
         FIG. 3  is a cross-sectional view showing an upper substrate structure of a conventional PDP; 
         FIG. 4  is a cross-sectional view showing an upper substrate structure of a plasma display panel (PDP) according to an embodiment of the present invention; 
         FIGS. 5A ,  5 B, and  5 C are cross-sectional views of an upper substrate structure of a PDP for illustrating a method for manufacturing the upper substrate structure of the PDP according to an embodiment of the present invention; and 
         FIG. 6  is a cross-sectional view showing a cross-sectional view of an upper substrate structure of a PDP according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, exemplary embodiments according to the present invention will be described with reference to the accompanying drawings. Here, when one element is described as being connected to another element, one element may be not only directly connected to another element but instead may be indirectly connected to another element via one or more other elements. Also, in the context of the present application, when an element is referred to as being “on” another element, it can be directly on the another element or be indirectly on the another element with one or more intervening elements interposed therebetween. Further, some of the elements that are not essential to the complete description of the invention have been omitted for clarity. Also, like reference numerals refer to like elements throughout. 
     Referring to  FIG. 3 , in the PDP  100  of  FIG. 1 , the protective layer  106  is uniformly deposited on the first substrate  101  to have a uniform thickness. 
       FIG. 3  is a cross-sectional view showing an upper substrate structure of the PDP  100 . The X electrode  103  and the Y electrode  104  are disposed on a second surface (upper surface in  FIG. 3 ) of the first substrate  101 . The dielectric layer  105  covers the X electrode  103  and the Y electrode  104 . The protective layer  106  is formed on the dielectric layer  105  with an uniform thickness. The X electrode  103  and the Y electrode  104  include ITO electrodes  103   b  and  104   b  and bus electrodes  103   a  and  104   a , respectively. 
     As such, in the conventional plasma display panel in which the protective layer  106  is formed with the uniform thickness, the protective layer  106  is etched by an ion shock when the panel is driven, thereby reducing a lifespan of the panel. Thus, there is a need to increase (or partially increase) a thickness of the protective layer  106 . 
       FIG. 4  is a cross-sectional view showing a substrate (or an upper substrate) structure of a plasma display panel (PDP) according to an embodiment of the present invention. 
     As shown, in the upper substrate structure of the PDP, a sustain electrode  220  is provided at a second surface (upper surface in  FIG. 4 ) of a substrate (or a first substrate)  101 ′. The sustain electrode  220  is composed of an X electrode  203  and a Y electrode  204 . A dielectric layer  105 ′ covers (or encases) the sustain electrode  220 . A protective layer  210  is formed on the dielectric layer  105 ′. The X electrode  203  and the Y electrode  204  include ITO electrodes  203   b  and  204   b  and bus electrodes  203   a  and  204   a , respectively. 
     Here, the protective layer  210  is a single deposition layer. However, the protective layer  210  is not deposited with the same thickness. A thickness of the protective layer  210  is partially and non-uniformly formed. In more detail, in the protective layer  210 , a first thickness portion  208  of the protective layer  210  at a region A formed on the sustain electrode  220  is formed to be greater than that of a second thickness portion  206  of the protective layer  210  at a region B corresponding to regions of the protective layer  210  other than regions of the protective layer  210  corresponding to the sustain electrode  220 . 
     As described earlier, so as to form a thickness of the first thickness portion  208  of the protective layer  210  at the region A to be greater than that of a thickness of the second thickness portion  206  of the protective layer  210  at the region B, in an embodiment of the present invention, a negative bias voltage is applied to the sustain electrode  220  as a bias during a formation of the protective layer  210 . 
     When the negative bias voltage is applied to the sustain electrode  220  of the upper substrate structure during a deposition, more positive ions separated from an oxide are accumulated at the sustain electrode  220  region (or side) to which a negative bias voltage is applied during a deposition of the protective layer  210 , thereby relatively increasing the thickness of the first thickness portion  208  of the protective layer  210 . 
     Accordingly, the thickness of the first thickness portion  208  of the protective layer  210  can be increased on the desired ITO electrodes  203   b  and  204   b  and bus electrodes  203   a  and  204   a.    
     In one embodiment, the protective layer  210  is formed by magnesium oxide (MgO) in the form of an oxide film. Further, the protective layer  210  can be formed by magnesium oxide that includes a material selected from the group consisting of aluminum Al calcium Ca, and combinations thereof. 
     In addition, a formation method of the protective layer  210  can be formed by various suitable protective layer formation methods. For example, the protective layer  210  can be formed by a sputtering method and/or an ion plating method. However, the present invention is not limited thereto. 
     As described above, the thickness of the first thickness portion  208  of the protective layer  210  at the region A on which the sustain electrode  220  is formed is set to be greater than that of the second thickness portion  206  of the protective layer  210  at the region B other than the region A. Accordingly, although the first thickness portion  208  of the protective layer  210  present at a peripheral part of the X and Y electrodes  203  and  204 , being a sustain electrode of the first substrate  101 , may experience an ion shock due to positive plasma ions when the panel is driven, since the thickness of the protective layer  210  is not thinly formed at the first thickness portion  208 , this thickness portion  208  can more easily withstand the ion shock than the protective layer  206  formed at a region (region B) other than the sustain electrode, thereby increasing a lifespan of the plasma display panel due to etching of the protective layer  210 . 
       FIGS. 5A ,  5 B, and  5 C are cross-sectional views of an upper substrate structure of a PDP for illustrating a method for manufacturing the upper substrate structure of the PDP according to an embodiment of the present invention. 
     The method for manufacturing the upper substrate structure of the plasma display panel of the present invention includes the steps of: forming the sustain electrode  220  on the first substrate  101 ′ ( FIG. 5A ); forming the first dielectric layer  105 ′ to cover the sustain electrode  220  ( FIG. 5C ); and forming the protective layer  210  with an non-uniform thickness on the first dielectric layer  105 ′ by a single deposition ( FIG. 5C ). 
     The formation step of the protective layer  210  forms the first thickness region  208  of the protective layer  210  on the sustain electrode  220  to be greater than that of the second thickness region  206  of the protective layer  210  at a part other than a part corresponding to the sustain electrode  220  by applying a negative bias voltage to the sustain electrode  220 . 
     The formation method of the protective layer  210  is not limited to the above described method and can be formed by various suitable formation methods. A sputtering method and an ion plating method are examples of the formation methods of the protective layer  210 . However, the present invention is not limited thereto. 
     In one embodiment, for example, when the protective layer  210  is deposited with magnesium oxide MgO, the magnesium oxide is divided into magnesium positive ion Mg 2+  and oxide negative ion O 2   − . In an upper substrate of a plasma display panel on which a magnesium deposition material is formed, more magnesium positive ion Mg 2+  is accumulated in a sustain electrode  220  part to which a negative bias voltage is applied in comparison with a part to which a voltage is not applied so that a thickness of MgO film is relatively thicker. 
     Accordingly, the first thickness portion  208  of the protective layer  210  on the sustain electrode  220  is formed to be thicker than the second thickness portion  206  of the protective layer  210  on the part other than the part corresponding to the sustain electrode  220 . 
     In the method for manufacturing the plasma display panel of the present invention, a thickness of a protective layer is differently formed according to its position during a formation thereof in order to enhance a lifespan of the plasma display panel. 
       FIG. 6  is a cross-sectional view showing a cross-sectional view of an upper substrate structure of a PDP according to another embodiment of the present invention. When the plasma display panel is driven, an electric signal is applied to an address electrode and a Y electrode  204  to select a discharge cell for an emission. Further, since the electric signal is alternately applied to the X and Y electrodes  203  and  204 , the Y electrode is etched deeper than the X electrode. 
     In consideration of this, the embodiment of  FIG. 6  of the present invention forms a first thickness region  309  of the protective layer  310  at a region corresponding to a Y electrode  204  part of the sustain electrode  220  that is thicker than that of a second thickness region  308  of protective layer  310  at a region corresponding to an X electrode  203  part of the sustain electrode  220 . In addition, the second thickness region  308  of the protective layer  310  at the region corresponding to the X electrode  203  part of the sustain electrode  220  is thicker than that of a thick thickness region  306  of protective layer  310  at a region not corresponding to the X electrode  203  part of the sustain electrode  220  and the Y electrode part  204  part of the sustain electrode  220 . 
     In one embodiment for forming the protective layer  310 , an intensity of a voltage applied to the Y electrode  204  of the sustain electrode  220  is adjusted to be greater than that applied to the X electrode  203  thereof. Alternatively, in another embodiment, a time period of a voltage applied to the Y electrode  204  of the sustain electrode  220  is adjusted to be greater than that applied to the X electrode  203  thereof. 
     In a method for manufacturing a plasma display panel according to an embodiment of the present invention, a first thickness portion (e.g.,  309 ) of a protective layer (e.g.,  310 ) of a Y electrode part is formed to be greater than that of a second thickness portion (e.g.,  308 ) of the protective layer of an X electrode part so that a lifespan of the plasma display panel can be enhanced. 
     In view of the foregoing, in a plasma display panel according to an embodiment of the present invention, a thickness of a protective layer of an electrode part on a first substrate is thickly formed (e.g., is thickly formed without an additional and/or special process) to improve the quality and lifespan of a product. 
     While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.