Abstract:
A plasma display panel that is capable of minimizing a brightness difference. In the plasma display panel, a driving waveform supply applies a driving waveform to electrodes provided at an effective display part. Pads apply the driving waveform from the driving waveform supply to the electrodes and have a different length depending on their location. Connecting parts are provided between the pads and the electrodes to electrically connect the pads to the electrodes.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a plasma display panel, and more particularly to a plasma display panel that is capable of minimizing a brightness difference. 
     2. Description of the Related Art 
     Recently, a plasma display panel (PDP) feasible to a manufacturing of a large-dimension panel has been highlighted as a flat panel display device. The POP typically includes a three-electrode, alternating current (AC) surface discharge PDP that has three electrodes and is driven with an AC voltage as shown in FIG.  1 . 
     Referring to FIG. 1, a discharge cell of the three-electrode, AC surface discharge PDP includes a scanning/sustaining electrode  12 Y and a common sustaining electrode  12 Z formed on an upper substrate  10 , and an address electrode  20 X formed on a lower substrate  18 . On the upper substrate  10  in which the scanning/sustaining electrode  12 Y is formed in parallel to the common sustaining electrode  12 Z, an upper dielectric layer  14  and a protective film  16  are disposed. Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer  14 . The protective film  16  prevents a damage of the upper dielectric layer  14  caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film  16  is usually made from MgO. A lower dielectric layer  22  and barrier ribs  24  are formed on the lower substrate  18  provided with the address electrode  20 X, and a fluorescent material  26  is coated on the surfaces of the lower dielectric layer  22  and the barrier ribs  24 . The address electrode  20 X is formed in a direction crossing the scanning/sustaining electrode  12 Y and the common sustaining electrode  12 Z. The barrier ribs  24  is formed in parallel to the address electrode  20 X to prevent an ultraviolet ray and a visible light generated by the discharge from being leaked to the adjacent discharge cells. The fluorescent material  26  is excited by an ultraviolet ray generated upon plasma discharge to produce a red, green or blue color visible light ray. An active gas for a gas discharge is injected into a discharge space defined between the upper/lower substrate and the barrier rib. 
     As shown in FIG. 2, such a discharge cell is arranged in a matrix type. In FIG. 2, the discharge cell  1  is provided at each intersection among scanning/sustaining electrode lines Y 1  to Ym, common sustaining electrode lines Z 1  to Zm and address electrode lines X 1  to Xn. The scanning/sustaining electrode lines Y 1  to Ym are sequentially driven while the common sustaining electrode lines Z 1  to Zm are commonly driven. The address electrode lines X 1  to Xn are driven with being divided into odd-numbered lines and even-numbered lines. 
     Such a three-electrode, AC surface discharge PDP is driven with being separated into a number of sub-fields. In each sub-field interval, a light emission having a frequency proportional to a weighting value of a video data is conducted to provide a gray scale display. For instance, if a 8-bit video data is used to display a picture of 256 gray scales, then one frame display interval (e.g., 1/60 second=16.7 msec) in each discharge cell  1  is divided into 8 sub-fields SF 1  to SF 8 . Each sub-field is again divided into a reset interval, an address interval and a sustaining interval. A weighting value at a ratio of 1:2:4:8: . . . :128 is given in the sustaining interval. Herein, the reset interval is a period for initializing the discharge cell; the address interval is a period for generating a selective address discharge in accordance with a logical value of a video data; and the sustaining interval is a period for sustaining the discharge in a discharge cell in which the address discharge has been generated. The reset interval and the address interval are equally assigned in each sub-field interval. 
     The scanning/sustaining electrode lines Y and the common sustaining electrode lines Z of the plasma display panel receive a driving waveform via a pad portion  30  shown in FIG.  3 . Referring to FIG. 3, the pad portion  30  includes pads  31  for receiving a driving waveform from a driving waveform supply, and connecting parts  32  for applying the driving waveform inputted to the pads  31  to the scanning/sustaining electrode lines Y or the common sustaining electrode lines Z. Each pad  31  is connected to a connector  34  of the driving waveform supply as shown in FIG.  4 . The driving waveform supply applies the driving waveform inputted to the scanning/sustaining electrode lines Y or the common sustaining electrode lines Z to the connectors  34 . The driving waveform inputted to the connectors  34  is applied, via the pads  31  and the connecting parts  32 , to the scanning/sustaining electrode lines Y or the common sustaining electrode lines Z. In this case, a longitudinal width of each connector  34  is formed to be narrower than a width of an effective display part in which a picture is to be displayed in compliance with a trend toward a slim-type PDP. Thus, a width of the pad  31  set in correspondence with a longitudinal width of the connector  34  also is formed narrowly. Accordingly, a length of a connecting part  32  provided between the pads  31  and the electrodes Y and Z formed at the periphery of the effective display part becomes longer than that of a connecting part  32  provided between the pads  31  and the electrodes Y and Z formed at the center portion of the effective display part. More specifically, a length sum L 1 +L 2  of a pad  31  and a connecting part  32  for supplying a driving waveform to the electrodes Y and Z formed at the center portion of the effective display part is different from a length sum L 3 +L 4  of a pad  31  and a connecting part  32  for supplying a driving waveform to the electrodes Y and Z formed at the periphery of the effective display part. If the lengths of the pads  31  and the connecting parts  32  provided at the pad portion  30  are different depending on their position, then a voltage applied from the pad portion  30  to the electrodes Y and Z becomes different. In other words, the electrodes Y and Z receiving a driving waveform via L 3  and L 4  is supplied with a smaller voltage than the electrodes Y and Z receiving a driving waveform via L 1  and L 2  due to a voltage drop. More specifically, the electrodes Y and Z formed at the periphery of the effective display part generates a voltage drop because they receive a driving waveform via the long connecting part L 3 . Thus, a brightness difference is generated between the periphery and the center of the effective display part. Also, since the conventional pad portion  30  has a large angle at a portion in which the electrodes Y and Z formed at the periphery of the effective display part are connected to the connecting part  32 , a breakage may be generated in the course of a electrode fabricating process of the pad portion  30 . Furthermore, the conventional pad portion  30  has a problem in that, since the conventional pad portion  30  also has a large angle at a portion in which the connecting part  32  and the pad  31  formed at the periphery of the pad portion  30  are connected to each other also, a breakage is generated in the course of its electrode fabricating to cause a product badness or deteriorate the productivity. 
     Meanwhile, the pad portion may be arranged in correspondence with the periphery of the effective display part as shown in FIG. 5 in consideration of a location of the connector or the circuit arrangement, etc. Referring to FIG. 5, a pad portion  38  is arranged to correspond to a first periphery  40  of the effective display part. Each pad  36  is connected to each connector  44 . A driving waveform inputted from the connector  44  is applied, via a connecting part  34 , to the electrodes Y and Z provided within the effective display part. If the pad portion  38  is formed at the first periphery  40  of the effective display part, then a length sum L 7 +L 8  of the pad  36  and the connecting part  34  for applying a driving waveform to the electrodes Y and Z formed at the first periphery  40  becomes different from a length sum LS+L 6  of the pad  36  and the connecting part  34  for applying a driving waveform to the electrodes Y and Z formed at a second periphery  42 . Thus, a voltage supplied from the pad portion  38  to the electrodes Y and Z formed at the first periphery  40  becomes a voltage supplied from the pad portion  38  to the electrodes Y and Z formed at the second periphery  42 . In other words, the electrodes Y and Z receiving a driving waveform via L 5  and L 6  is supplied with a smaller voltage than the electrodes Y and Z receiving a driving waveform via L 7  and L 8  due to a voltage drop. Accordingly, a brightness difference is generated between the first periphery  40  and the second periphery  42  of the effective display part. Furthermore, the conventional pad portion  38  has a problem in that, since the connecting part  32  connected from the second periphery  42  to the pad  38  has a large angle, a breakage is generated in the course of a manufacturing and installation process of the pad portion  38  to cause a product badness or deteriorate the productivity. The above-mentioned problems also may be generated at a pad portion (not shown) for applying a driving waveform to the address electrode lines X. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a plasma display panel (PDP) that is capable of minimizing a difference, that is, a voltage drop applied to an effective display part to diminution the brightness difference. 
     A Further object of the present invention is to provide a PDP wherein an angle between an effective display part and a connecting part and an angle between a connecting part and a pad are slowly formed so as to minimize a breakage that may be generated in the course of a electrode fabricating process of a pad portion. 
     In order to achieve these and other objects of the invention, a plasma display panel according to an embodiment of the present invention includes driving waveform supplying means for applying a driving waveform to electrodes provided at the effective display part; a plurality of pads for applying the driving waveform inputted from the driving waveform supplying means to the electrodes, said pads having a different length depending on their location; and connecting means provided between the pads and the electrodes to electrically connect the pads to the electrodes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view showing a structure of a discharge cell of a conventional three-electrode, AC surface discharge plasma display panel; 
     FIG. 2 illustrates an entire electrode arrangement of a plasma display panel including the discharge cells shown in FIG. 1; 
     FIG. 3 is a schematic view showing a pad portion installed in correspondence with the center portion of the plasma display panel to apply a driving waveform to the electrodes in FIG. 2; 
     FIG. 4 is a schematic view showing the pad portion of FIG. 3 that is in contact with connectors for supplying a driving waveform; 
     FIG. 5 is a schematic view showing a pad portion installed in correspondence with one side periphery of the plasma display panel to apply a driving waveform to the electrodes in FIG. 2; 
     FIG.  6  and FIG. 7 are schematic views showing a pad portion according to an embodiment of the present invention; 
     FIG. 8 is a schematic view showing the pad portion of FIG. 6 that is in contact with connectors for supplying a driving waveform; and 
     FIG. 9 is a schematic view showing a pad portion according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     IS Referring to FIG.  6  and FIG. 7, there is shown a pad portion  46  according to an embodiment of the present invention. The pad portion  46  includes pads  50  having a different length, and connecting parts  48  provided between an effective display part in which a picture is to be displayed and each pad  50 . As shown in FIG. 8, each pad  50  is connected to a connector  52  so as to receives a driving waveform from a driving waveform supply (not shown). The driving waveform supply applies the driving waveform inputted to scanning/sustaining electrode lines Y or common sustaining electrode lines Z to the connectors  52 . The driving waveform inputted to the connectors  52  is applied, via the pads  50  and the connecting parts  48 , to the scanning/sustaining electrode lines Y or the common sustaining electrode lines Z. The pad  50  has a large length at the center portion thereof while having a smaller length as it goes from the center portion thereof into the periphery thereof so that it can minimize a voltage drop in a driving waveform applied from the connector  52  to the electrodes Y and Z. To the contrary, the connecting part  48  has a small length at the center portion thereof while having a larger length as it goes from the center portion thereof into the periphery thereof. Accordingly, a difference between a length sum L 1 +L 2  of the pad  50  and the connecting part  48  for applying a driving waveform to the electrodes Y and Z formed at the center portion of the effective display part and a length sum L 3 +L 4  of the of the pad  50  and the connecting part  48  for applying a driving waveform to the electrodes Y and Z formed at the periphery of the effective display part is minimized. In other words, a brightness difference between the periphery and the center of the PDP can be minimized. Also, the pad  50  formed at the periphery of the pad portion  46  has a small length and, therefore, a portion in which the connecting part  48  and the electrodes Y and Z formed at the periphery of the effective display part are connected to each other and a portion in which the pad  50  and the connecting part  48  formed at the periphery of the pad portion  46  are connected to each other have a small angle, so that it becomes possible to minimize a breakage that may be generated in the course of a electrode fabricating process of the pad portion  46 . 
     FIG. 9 is a schematic view of a pad portion of a plasma display panel according to another embodiment of the present invention, which shows a structure of a pad portion  56  when the pad portion  56  has been installed at a first periphery  62  of an effective display part. Referring to FIG. 9, pads  60  have a different length so as to minimize a voltage drop of a driving waveform applied form connectors  66  to electrodes Y and Z. More specifically, the pad  60  applying a driving waveform to the electrodes Y and Z provided at a first periphery  62  has a large length while having a smaller length as it goes from the first periphery  62  into the second periphery  64 . To the contrary, connecting parts  56  have a larger length as they go from the first periphery  62  into the second periphery  64 . Accordingly, a difference between a length sum L 7 +L 8  of the pad  60  and the connecting part  58  for applying a driving waveform to the electrodes Y and Z formed at the first periphery  62  of the effective display part and a length sum LS+L 6  of the of the pad  60  and the connecting part  58  for applying a driving waveform to the electrodes Y and Z formed at the second periphery  64  of the effective display part is minimized. In other words, a brightness difference between the first periphery  62  and the second periphery of the PDP can be minimized. Also, the pad  60  for applying a driving waveform to the second periphery  64  has a small length and, therefore, a portion in which the pad  60  and the connecting part  58  are connected to each other and a portion in which the connecting part  58  and the electrodes Y and Z formed at the second periphery  64  of the effective display part are connected to each other have a small angle, so that it becomes possible to minimize a breakage that may be generated in the course of a electrode fabricating process of the pad portion  46 . 
     The above-mentioned embodiments of the present invention are applicable to a pad portion for applying a driving waveform to address electrode lines X. 
     As described above, according to the present invention, the pads have a different length so as to minimize a voltage drop of a driving waveform applied from the pad portion to the electrodes. Accordingly, a brightness difference at the effective display part caused by a voltage drop in a driving waveform applied to the electrodes can be minimized. Furthermore, since the pads have a different length, an angle at each portion in which the pad and the electrodes at the effective display part are connected to each other can be minimized. Accordingly, it becomes possible to prevent a breakage that may be generated in the course of a electrode fabricating process of the pad portion. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.