Abstract:
A plasma display panel minimizing the presence of electrodes outside the display area. In forming the display electrodes across the display, the electrodes extend to only one of the right or left side of the display area. In forming the address electrodes, the electrodes extend to only one of a top or a bottom side of the display area. By so limiting the amount of electrodes outside the display area, less electrode paste is consumed thus reducing expenses and the size of the glass substrate is reduced thus resulting in a more compact display. All of this can be achieved without reducing the display area of the display.

Description:
CLAIM OF PRIORITY 
   This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for PLASMA DISPLAY PANEL PROVIDED WITH AN IMPROVED ELECTRODE earlier filed in the Korean Intellectual Property Office on 31 Oct. 2003 and there duly assigned Ser. No. 2003-76914. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a plasma display panel having an improved electrode design, and in particular, to a plasma display panel where the presence of electrodes that are outside the display area is minimized. 
   2. Description of the Related Art 
   A plasma display panel (referred to as a PDP hereinafter) is typically a display device where ultraviolet rays generated by the discharge of a gas excites phosphors to realize visible images. Two electrodes installed in the discharge cell of the PDP makes plasma discharge under a predetermined voltage applied thereto, and the ultraviolet rays generated by the plasma discharge excite a phosphor layer arranged in a predetermined pattern to form a visible image. The PDP is divided mainly into alternating current (AC), direct current (DC), and hybrid types. 
   Unfortunately, in a PDP design, electrodes must extend outside the display area to form a connection with a driver and/or a power supply. Excessive electrode presence outside the display area increases the expense in that more electrode paste needs to be consumed and also leads to increases in the size of the device as the glass substrates have to be made significantly larger than the display area. Therefore, what is needed is a design for the electrodes so that the amount of electrodes external to the display area is minimized. 
   SUMMARY OF THE INVENTION 
   It is therefore an object of the present invention to provide an improved design for a plasma display panel. 
   It is also an object of the present invention to provide an improved electrode design for a plasma display panel. 
   It is further an object of the present invention to provide a design for a PDP that less expensive to make without reducing the size of the display area. 
   It is further an object of the present invention to provide a design for a PDP that results in a more compact PDP without reducing the size of the display area. 
   It is still an object of the present invention to provide an electrode design for a plasma display panel that minimizes the amount of electrode material used outside the display area. 
   It is yet an object of the present invention to provide a design for a plasma display panel that reduces the consumption of electrode paste and reduces the size of the glass substrate itself without compromising on the size of the display area. 
   These and other objects may be achieved by a plasma display panel that has a first substrate and a second substrate facing the first substrate, address electrodes formed on the first substrate, barrier ribs arranged in a space between the first substrate and the second substrate, forming a plurality of discharge cells, a phosphor layer formed in each of said discharge cells, and display electrodes formed on the second substrate in the direction orthogonal to the address electrodes. The first and the second substrates have a sealing line formed along their edges of where the two substrates overlap each other. The first and the second substrates are joined to each other at the sealing line by frit spread along the sealing line. A display area resides inside the sealing line and a non display area resides outside the sealing line. The address electrode has two ends, one end being inside -the area with the sealing line. The other end of the address electrode extends outside the sealing line and outside the display area. This portion of the address electrode includes a slant part and a terminal reaching outside the area surrounded by the sealing line while extending from the effective part located inside the display area surrounded by the sealing line. 
   Thus, the area surrounded by the sealing line and the area outside the sealing line where the slant part and the terminal are located are where the electrode paste is applied during the fabrication of the address electrodes. The other end of the address electrodes are located inside the area surrounded by the sealing line, a paste void region is formed outside the area surrounded by the sealing line. Preferably, the paste void area is as wide as 5 to 30 mm. 
   The display electrode pair includes a scan electrode and a sustain electrode and are formed on the second substrate. The sustain electrode has an effective part which is positioned inside the area surrounded by the sealing line and a short circuit part at one end of the effective part. The short circuit part is a common part connected to all of the sustain electrodes. The paste deposition region for the sustain electrodes is formed in the region where the effective part and the short circuit part are placed. The electrode paste is applied on the area during the fabrication of the sustain electrodes. 
   The scan electrodes are also formed on the second substrate and have one end inside the sealing line and the other end extending outside the sealing line. The end of the scan electrodes that extend outside the sealing line include a slant part and a terminal part. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
       FIG. 1  is a perspective view of a plasma display panel, illustrating the discharge cells; 
       FIG. 2  is a plan view of the address electrodes of the plasma display panel according to the present invention; and 
       FIG. 3  is a plan view of the display electrodes of the plasma display panel according to the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Turning now to the figures,  FIG. 1  is a perspective view of discharge cells in an AC plasma display panel  100 . According to the drawing, the PDP  100  includes a rear substrate  104 , address electrodes  102  that are formed on the rear substrate  104 , a dielectric layer  106  formed on the rear substrate  104  covering the address electrodes  102 , a plurality of barrier ribs  105  formed on top of the dielectric layer  106  to maintain a discharge space and to prevent crosstalk between discharge cells, and a phosphor layer  101  formed on the surfaces of the barrier ribs  105 . 
   A sustain electrode  107  and a scan electrode  108  are on a bottom side or −z side of the front substrate  110  and together form a pair of display electrodes for each discharge cell while extending in a direction that is perpendicular to the direction of the address electrodes  102  formed on the rear substrate  104 . A dielectric layer  109  and a protective layer  103  cover the sustain electrodes  107  and the scan electrodes  108 . 
   In the PDP  100  of  FIG. 1 , the address electrode  102  and the scan electrode  108  generate an address discharge therebetween upon application of driving voltages to form wall charges on the dielectric layer  109 . This causes a discharge in a selected discharge cell by the address discharge, a sustain discharge between the sustain electrode  107  and the scan electrode  108  then occurs by an alternating voltage signal applied alternately to the sustain electrode  107  and the scan electrode  108 . Accordingly, a discharge gas filled in the discharge space of the discharge cell is excited and emits ultraviolet radiation in transit, and the ultraviolet radiation excites the phosphor layer in the PDP to emit visible light to realize the images. 
   The address electrodes of the AC PDP are mainly made of Ag paste. Since an address electrode requires a fine width of as small as 70˜80 μm, it is formed mainly by a screen print method and a photolithography method. Also, a lift-off method and a thin film method can be used. 
   Indium oxide (In 2 O 3 ) is used for the material of the scan electrodes and the sustain electrodes. The scan electrodes and the sustain electrodes are called ITO (indium tin oxide) electrodes because a small amount of tin dioxide (SnO 2 ), a chemically stable and hard compound that is added in order to reduce the resistivity of the thin film. In this way, the ITO electrode is made by first forming an ITO thin film by sputtering or electron beam deposition and then patterning an electrode by a photolithography process. The tin dioxide (SnO 2 ) layer is formed by spray method or a CVD (chemical vapor deposition) method, etc. The ITO electrode is essentially transparent to visible light and does not chemically react with or destroy neighboring material. Also, the uniform formation of the thin film can be possible on a large area panel. 
   In the manufacturing process of the PDP, an electrode paste is spread on a glass substrate to form the address electrodes, the scan electrodes, and the sustain electrodes. During the manufacturing process, however, the electrode paste is spread not only on the display area of the glass where the discharge occurs, but also on areas outside the display area to provide electrical connection thereto. This is very expensive, especially when all of the areas outside the display area where the paste is applied is not absolutely necessary. That causes a waste of material and also causes the size of the device to be even larger and hence be less compact. 
   Turning now to  FIG. 2 ,  FIG. 2  is a plan view of the plasma display panel  200  according to an embodiment of the present invention.  FIG. 2  schematically illustrates address electrodes  35  formed on a rear substrate (or first substrate)  20 . As a mere example of the present invention, address electrodes  35  are positioned in the single scan mode such that the address electrodes come out at only one edge of the substrate  20 . In  FIG. 2 , the dashed line represents a front substrate (or second substrate)  10  having display electrodes. 
   The plasma display panel  200  is formed by joining the front substrate  10  to the rear substrate  20  using glass frit. As illustrated in  FIG. 2 , the front substrate  10  and the rear substrate  20  may have differing sizes. The front substrate  10  is attached to the rear substrate  20  at sealing line  38  located along the edges of the overlapped area. The frit is spread along the sealing line  38 . The sealing line  38  usually also separates the display area  30  from non-display areas. In the drawing, the dot-dashed line represents the sealing line  38  where the frit is spread for joining the front substrate  10  to the rear substrate  20 . The-area surrounded by the sealing line  38  is a display area  30 , and the area outside the sealing line  38  is a non-display area. In  FIG. 2 , the non-display area is does not have a reference numeral because the non-display area is clearly distinguished from the display area  30 . 
   According to the embodiment of the present invention, the address electrodes  35  are divided into three parts, an address electrode effective part  31  located within the display area  30  on the rear substrate  20 , an address electrode slant part  32  located in the non-display area and an address electrode terminal  33  also located in the non-display area but further from display area  30  than the slant part  32 . The slant part  32  is between the effective part  31  and the terminal  33  and is connected at one end to the effective part  31  and at the other end to the terminal  33 . The address electrode terminal  33  is located outside the overlapped area between the front substrate  10  and the rear substrate  20 , being exposed to the outside for connection to an electrical signaling transfer mechanism such as a FPC (Flexible Printed Circuit). Thus, address electrode terminal  33  portion of the address electrodes  35  are located on a part of the rear substrate  20  that is not covered by the front substrate  10 . 
   On the opposite side of the display  200 , the end of the address electrodes  35  that is located within sealing line  38  and within display area  30  is covered by front substrate  10 . This +y end of the display does not have the slant part  32  or the terminal part  33  as at the −y side of the PDP  200 . 
   During the making of the address electrodes  35 , conductive paste is deposited in areas of rear substrate  20  within the display area  30  where the address electrode effective part  31  is formed and in the non display area on the −y side only where the address electrode slant part  32  and the address electrode terminal  33  are formed. On the +y side of the rear substrate outside the sealing line  38  is referred to as the paste void region  40 . In the present invention, the paste deposition region for forming the address electrodes is reduced by an area the size of the paste void region  40  because the present invention recognizes that it is not absolutely necessary to use the electrode paste in the paste void region  40 . The present invention recognizes that it is not necessary to extend the electrodes into non-display areas at both sides of the display. One of these two opposing sides can be absent from electrodes. Therefore, it is possible to reduce both the consumption of the electrode paste for the address electrodes and the size of the glass substrate by the area equal to the paste void region  40 . In addition to these benefits, the integrity of the sealing is improved because of the absence of address electrodes  35  perforating the sealing line on the +y side of the PDP  200 . 
   In summary, PDP  200  of  FIG. 2  is an embodiment where the terminals  33  of the address electrodes  35  are formed in a lower end (−y end) of the rear substrate  20  but not at an upper end (+y end) of the PDP  200 . Alternately, it is instead possible for the address electrode terminals to be formed in the upper end (+y end) of the rear substrate  20  but not in the lower end (−y end) of the substrate. What is important is that paste need not be deposited and electrodes need not be formed to both ends. The electrodes can extend outside of the display area on one end only and the other end of the electrodes can terminate within, but near the edge of the display area  30 . 
   Turning now to  FIG. 3 ,  FIG. 3  is a plan view of the plasma display panel  300  according to another embodiment of the present invention. In the PDP  300  of  FIG. 3 , the sustain electrodes  15  and the scan electrodes  25  on the front substrate  10  are illustrated. 
   As illustrated in  FIG. 3 , a plurality of display electrodes are formed in the x direction on the front substrate  10  of the plasma display panel  300  of the present invention. The display electrodes include sustain electrodes  15  and scan electrodes  25 , preferably formed along the same +x direction and formed in an alternating manner. The sustain electrodes  15  begins at the left (or −x) side and extend to the right (or +x) side along the +x direction. The scan electrode  25  begin at the right (or +x) side and extend to the left side in the −x direction. The sustain electrodes  15  and the scan electrodes  25  can be formed alternately on front substrate  10 . The extending directions of the sustain electrodes  15  and the scan electrodes  25  described above are merely examples for the present invention, and therefore these electrodes can instead be formed and extended in directions reversed or opposite to those directions described above. 
   At the top surface (or +z surface) of the rear substrate  20 , located below the front substrate  10 , a plurality of address electrodes (not illustrated in  FIG. 3 ) are formed perpendicular to the display electrodes. The regions where the display electrodes cross the address electrodes define the discharge cells for the discharging space, and the discharge cells are located in the display area  30 . 
   A plurality of barrier ribs (not illustrated in  FIG. 3 ) coated with the phosphor layer are arranged in a space between the front substrate  10  and the rear substrate  20  and form the discharge spaces corresponding to the discharge cells defined by the address electrodes  35  and the display electrodes  15 ,  25 . In the plasma display panels  200  and  300 , both the sustain electrodes  15  and the scan electrodes  25  are formed on the −z surface of the front substrate  10  facing the rear substrate  20 . In  FIG. 3 , these sustain electrodes  15  and scan electrodes on the backside (or −z side) of the front substrate  10  are illustrated for better understanding. 
   A driving voltage is applied at the right (or +x) side of the scan electrodes  25 , and an address discharge takes place between the scan electrodes  25  and the corresponding address electrodes (not illustrated in  FIG. 3 ). The address discharge starts a substantial discharge process. Under the driving voltage, a sustain discharge follows the address discharge, emitting the visible light to realize the required visible images. The scan electrodes  25  are made up of a scan electrode effective part  21  located in the display area  30  and a scan electrode slant part  22  connected to the scan electrode effective part  21 . The scan electrode slant part  22  has a spacing between adjacent electrodes that is smaller than between the effective portions  21  of the scan electrode  25 . The scan electrodes  25  also include a scan electrode terminal  23  portion for connection to the electrical signaling transfer device such as the FPC. The spacing between neighboring terminal portions  23  of the scan electrodes is smaller than in the scan electrode slant part  22 . Both the slant part  22  and the terminal part  23  of the scan electrodes  25  reside outside the display area  30 . Thus, in the formation of the scan electrodes  25  of PDP  300 , the electrode paste is applied to the display area  30  and to a portion outside the display area on the right hand side (+x side) but not to the left hand side (or −x side). As in the case of the address electrodes, it is recognized that it is not necessary to extend the scan electrodes  25  into the non display areas on both sides of the display. Extension into the non display area is needed only on one side to connect to a driver. The other ends of the scan electrodes  25  can terminate near the edge but within the display area  30 . 
   According to the embodiment of the present invention illustrated in  FIG. 3 , the sustain electrodes.  15  have a sustain electrode effective part  11  located inside the display area  30  and a sustain electrode shorted part  12  connected to each of the sustain electrode effective parts  11 . A voltage is applied to the sustain electrodes  15  at the sustain electrode shorted part  12  by a separate FPC. FPC may be connected to the sustain electrode shorted part  12  by a fetching terminal which is preferably in a non overlapping region and generally runs in an x direction (not illustrated in  FIG. 3 .). This voltage is then realized in each of the sustain electrode effective parts  11  connected thereto. 
   The sustain electrode shorted part  12  is formed at the left end (−x end) of the sustain electrode effective part  11  and is connected by a single line to each of the left ends (−x ends) of the sustain electrode effective parts  11 . Since the voltage applied to all the sustain electrodes  15  is the same, it is possible to form this single short-circuit line  12  connected to all of the sustain electrode effective parts  11 . Therefore, the display area  30  having the sustain electrode effective parts  11  and the sustain electrode shorted part  12  receives paste deposition for forming the sustain electrodes  15 , and the area outside the sealing line  38  to the left (or −x side) of display area  30  is a paste void region  50 . 
   By such a design for the display electrodes, the paste deposition region is reduced by the area of the paste void region  50  due to the lack of need to deposit electrode paste in the paste void region  50  since no electrodes reside in paste void region  50 . Accordingly, it is possible to reduce both the consumption of the electrode paste for the sustain electrodes  15  and the size of the glass substrate by the area of the paste void region  50 . 
   It is to be appreciated that ITO is generally used for the display electrodes. ITO material is used generally for the transparent portion of the display electrodes. This ITO film is made by sputtering or ion plating and then is patterned with photolithography processes. Because the transparent ITO portions of the display electrodes have a high resistivity, the display electrodes also include a more conductive bus electrode portion along an edge of the transparent ITO portion. These highly conductive bus portions can be made using a silver paste. This silver bus electrode portion of the display electrodes is formed by a printing method by photolithography using a photo-sensitive silver paste and frit glass. Thus, the display electrode that is located on the front substrate can include both ITO and bus metal electrode at the same time. 
   As described above, in the plasma display panels according to the present invention, by minimizing the formation of the unnecessary electrodes outside the display area  30 , the material cost for forming the electrodes can be reduced by approximately 6% and the glass size can also be reduced while keeping the size of the display area  30  constant. 
   It is also to be appreciated that the embodiment of  FIG. 2  can be combined with the embodiment of  FIG. 3  so that tow of the four edges of the display can be absent of electrode paste and absent of electrodes. Thus, tow of the four sides are for electrical connections and the other two of the four sides are paste void regions. 
   Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concept herein taught which may appear to those skilled in the art will still fall within the spirit and scope of the present invention, as defined in the appended claims.