Abstract:
An electrostatic discharge protection structure disposed in a peripheral area of a display panel is electrical connected to a wire of a display area of the display panel and a short ring of the peripheral area. The electrostatic discharge protection structure comprises a first path having a first resistance, and a second path having a second resistance. The first path and the second path are parallel connected between the wire and the short ring, wherein the first resistance is lower than the second resistance.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an electrostatic discharge (ESD) protection structure, and more particularly, to an electrostatic discharge protection structure for avoiding a feedback electrostatic discharge.  
         [0003]     2. Description of the Prior Art  
         [0004]     Please refer to  FIG. 1 .  FIG. 1  is a circuit diagram of an electrostatic discharge protection structure according to the prior art. A peripheral area  100  of an LCD panel has plural electrostatic discharge protection structures  110 ,  120 , and  150 . Each electrostatic discharge protection structure  110 ,  120 ,  150  is connected to a data line  102 ,  104 ,  106  respectively or a scan line (not shown) of a display area of the LCD panel. The structures of the electrostatic discharge protection structures  110 ,  120 ,  150  are the same. To take the electrostatic discharge protection structure  120  for example, the electrostatic discharge protection structure  120  has a wire  126  electrically connected to two TFTs (thin film transistor)  122 ,  124 . The TFTs  122 ,  124  are connected to a short ring  128 , and the TFT  122  has a gate  132 . The gate  132  shorts to its source (not shown) or drain (not shown). The TFT  124  has a gate  142 . The gate  142  shorts to its source (not shown) or drain (not shown).  
         [0005]     When the data line  104  of the display area accumulates electrostatic charge, the threshold voltage of the TFT  122  will be reached. The electrostatic charge in the data line  104  passes through the TFT  122  to the short ring  128  by a path  134 . When the electrostatic charge passes into the short ring  128 , it also passes into the peripheral electrostatic discharge protection structures e.g. electrostatic discharge protection structures  110 , and  150  by the paths  118 , and  158  respectively. This means the electrostatic charge passes into data lines  102 , and  106  from the wires  116 , and  156 , and the TFTs  114 , and  154  respectively. The electrostatic charge spreads in each data line of the display area, so the function of electrostatic discharge protection is achieved. If the electrostatic discharge protection structure  120  has the same voltage difference across the paths, the paths  134 ,  144  will have the same resistances. The electrostatic charge accumulated in the data line  104  passes into the short ring  128  by the path  134  of the electrostatic discharge protection structure  120 . Then, the electrostatic charge is fed back into the data line  104  through the path  144  of the electrostatic discharge protection structure  120 . This causes a feedback electrostatic discharge.  
         [0006]     Other patents, such as Japan patent JP10-123574, mention forming nonlinear resistance structures on the data line and the scan line to improve the electrostatic discharge. They do not mention any way to solve the problem of the feedback electrostatic discharge, however. Therefore, pursuing a more effective electrostatic discharge protection structure is important.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides an electrostatic discharge protection structure to solve the above-mentioned problems.  
         [0008]     The embodiment of the present invention provides an electrostatic discharge protection structure in a peripheral area of a display panel is electrical connected to a wire of a display area of the display panel and a short ring of the peripheral area. The electrostatic discharge protection structure comprises a first path having a first resistance, and a second path having a second resistance. The second path and the first path are parallel connection between the wire and the short ring, wherein the first resistance is lower than the second resistance.  
         [0009]     Another embodiment of the present invention provides an electrostatic discharge protection structure in a peripheral area of a TFT liquid crystal display panel. The electrostatic discharge protection structure is electrical connected to a wire of a display area of the TFT LCD and a short ring of the peripheral area. The electrostatic discharge protection structure comprises a first TFT having a first resistance, and a second TFT having a second resistance. And the second TFT and the first TFT are parallel connection between the wire and the short ring, wherein the first resistance is lower than the second resistance.  
         [0010]     Another embodiment of the present invention provides an thin film transistor liquid crystal display panel comprises a display area having a plurality of data lines and a plurality of scan lines, and the data lines and the scan lines are interlocking, and a peripheral area having a short ring and a plurality of electrostatic discharge protection structures. And the electrostatic discharge protection structure is electrical connected to the data line and the short ring and to the scan line and the short ring. And the electrostatic discharge protection structure comprises a first TFT having a first resistance, and a second TFT having a second resistance. And the second TFT and the first TFT are parallel connection, wherein the first resistance is lower than the second resistance.  
         [0011]     The resistance of the path passing the electrostatic charge from the data line or the scan line into the short ring is smaller than the resistance of the path passing the electrostatic charge from the short ring into the data line or the scan line in the electrostatic discharge protection structure of the present invention. Thus, the present invention makes the electrostatic charge unable to feed back into the data line or the scan line, avoiding the feedback electrostatic discharge, and thereby increasing the yield of the LCD panel.  
         [0012]     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a circuit diagram of an electrostatic discharge protection structure according to the prior art.  
         [0014]      FIG. 2  is a circuit diagram of an electrostatic discharge protection structure according to the present invention.  
         [0015]      FIG. 3  is an equivalent circuit diagram of an electrostatic discharge protection structure according to the present invention.  
         [0016]      FIG. 4  is a circuit diagram of an electrostatic discharge protection structure according to another embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0017]     Please refer to  FIG. 2 .  FIG. 2  is a circuit diagram of an electrostatic discharge protection structure according to the present invention. The electrostatic discharge protection structure of the present invention applies to the thin film transistor liquid crystal (TFT LCD) panel or the organic light emitting diodes (OLED) display panel. To take the TFT LCD for example, as  FIG. 2  shows, a peripheral area  200  of TFT LCD panel has many electrostatic discharge protection structures  210 ,  220 , and  250 . Each electrostatic discharge protection structure  210 ,  220 ,  250  is connected to a data line  202 ,  204 ,  206  or a scan line (not shown) of a display area of the TFT LCD panel. The structures of the electrostatic discharge protection structures  210 ,  220 ,  250  are the same. To take the electrostatic discharge protection structure  220  for example, the electrostatic discharge protection structure  220  has a wire  226  electrically connected to two TFTs (thin film transistor)  222 ,  224 . The TFTs  222 ,  224  are connected to a short ring  228 , and the TFT  222  has a gate  232 . The gate  232  shorts to its source (not shown) or drain (not shown). The TFT  224  has a gate  242 . The gate  242  shorts to its source (not shown) or drain (not shown). Therefore, the functions of the two TFTs are equal to the functions of two diodes.  
         [0018]     In other words, the TFTs  222 ,  224  can replace two diodes in other embodiment, as  FIG. 3  shows.  FIG. 3  is an equivalent circuit diagram of an electrostatic discharge protection structure according to the present invention. The TFTs  222 ,  224  in  FIG. 2  are equal to diodes  422 ,  424  in  FIG. 3 .  
         [0019]     Please continue to refer to  FIG. 2 . When each data line of the display area such as the data line  204  of the display area accumulates electrostatic charge, the threshold voltage of the TFT  222  is reached. The electrostatic charge in the data line  204  passes through the TFT  222  to the short ring  228  by a path  234 . When the electrostatic charge passes into the short ring  228 , the electrostatic charge further passes into the peripheral electrostatic discharge protection structures, e.g. into electrostatic discharge protection structures  210 ,  250  by the paths  218 ,  258  respectively. That means the electrostatic charge passes into the data lines  202 ,  206  from the wires  216 ,  256  through the TFTs  214 ,  254 . The electrostatic charge spreads in each data line of the display area, so the function of electrostatic discharge protection is achieved.  
         [0020]     Please pay attention to that when the electrostatic discharge protection structure applies to TFT LCD panel, the layout of the TFTs  222 ,  224  can be changed, and the resistance of the TFT  222  is lower than the TFT  224 . And the resistance of path  234  is lower than the resistance of path  244 . If the value of the transistor channel width/length of the TFT  222  is higher than the value of the transistor channel width/length of the TFT  224 , the resistance of the path  234  is lower than the path  244 . For example, the length of the TFTs  222 ,  224  are the same, but the channel width of the TFT  222  is bigger, for example the transistor channel width/length of the TFT  222  is 80/5, and the transistor channel width/length of the TFT  224  is 30/5. Similarly, the channel width of the TFTs  222 ,  224  are the same, but the channel length of the TFT  222  is lower, for example the transistor channel width/length of the TFT  222  is 50/4, and the transistor channel width/length of the TFT  224  is 50/7. All of them make the resistance of the TFT  222  is lower than the resistance of the TFT  224 .  
         [0021]     In this embodiment, the electrostatic discharge protection structures  210 ,  220 ,  250  are connected to the data lines  202 ,  204  of the LCD panel. In fact, the electrostatic discharge protection structure can also be connected to the scan line (not shown). The data line and the corresponding scan line can control a pixel unit to turn on or off. In this embodiment, the electrostatic charge from the data line  204  passes into the short ring  228  through the electrostatic discharge protection structure  220 , and the whole pixel unit in the data line  204  cannot be electrostatically discharged. Moreover, the electrostatic charge in the short ring  228  cannot be fed back to the data line  204 , so the electrostatic charge spreads to several electrostatic discharge protection structures surrounding the electrostatic discharge protection structure  220 . Please note that not only the electrostatic discharge protection structures  210 ,  250  in  FIG. 2  can spread the electrostatic charge. If the electrostatic charge can reach the threshold voltage of TFT in the electrostatic discharge protection structure, the electrostatic charge can pass into the data line through the electrostatic discharge protection structure and can be spread.  
         [0022]     Please refer to  FIG. 4 .  FIG. 4  is a circuit diagram of an electrostatic discharge protection structure according to another embodiment of the present invention. The principles of the embodiment in  FIG. 4  and the  FIG. 2  are the same. In  FIG. 4 , however, the electrostatic discharge protection structures  310 ,  320 ,  350  in  FIG. 4  are made by four TFTs. Take the electrostatic discharge protection structure  320  in  FIG. 4  for example. The electrostatic discharge protection structure  320  in the peripheral area  300  of the LCD is connected to a data line  304  by a wire  326 . It has four TFTs  322 ,  324 ,  332 , and  334 . The TFTs  322 ,  332  are connected in series, and the TFTs  324 ,  334  are connected in series, too. The TFTs  322 ,  332  and the TFTs  324 ,  334  are connected in parallel, and then connected to the short ring  328 . The resistance of the TFTs  322 ,  332  is lower than the resistance of the TFTs  324 ,  334 . When the electrostatic charge from the data line  304  passes into the short ring  328  through the path  334  of the electrostatic discharge protection structure  320 , the electrostatic charge cannot be fed back into the data line  304  by the path  344  of the electrostatic discharge protection structure  320 . The present invention not only utilizes a symmetric amount of TFTs in paths  334 ,  344 , but also utilizes a symmetric amount of TFTs in two paths. The resistance of the path passing the electrostatic charge from the data line into the short ring is lower than the resistance of the path passing the electrostatic charge from the short ring into the data line. This obeys the spirit of the present invention.  
         [0023]     Compare with the prior art. The resistance of the path passing the electrostatic charge from the data line or the scan line into the short ring is smaller than the resistance of the path passing the electrostatic charge from the short ring into the data line or the scan line in the electrostatic discharge protection structure of the present invention. The Japan patent JP10-123574 does not have different nonlinear resistances, so it cannot limit the feedback electrostatic discharge. In comparison, the present invention makes the electrostatic charge unable to be fed back into the data line or the scan line, avoiding the feedback electrostatic discharge, and thereby increasing the yield of the LCD. Moreover, the present invention only changes the channel width or length of the TFT, to change the resistance of the TFT. The present invention does not need to change the driver circuits, and does not need to add PEP. So, it can be easily utilized in current display panel manufacturing.  
         [0024]     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.