Abstract:
An exemplary method of repairing gate lines ( 201 ) of TFT array substrate, wherein the TFT array substrate includes a plurality of gate lines ( 201, 202 ), a plurality of data lines ( 211, 212, 213 ) crossing with the gate lines, a plurality of pixel electrode ( 221, 231 ), and a plurality of thin film transistors ( 240, 250 ), and one of the gate lines has a defect point (II). The method includes: cutting off an electrical connection between the gate electrode of one of the TFTs adjacent one side of the defect point and the corresponding data line, and cutting off an electrical connection between the gate electrode of one of the TFTs adjacent an opposite side of the defect point and the corresponding data line; electrically connecting the gate line having the defect point to each of two corresponding pixel electrodes that correspond to the two TFTs; and electrically connecting the two pixel electrodes.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method of repairing broken lines or short lines on a thin film transistor (TFT) array substrate, and more particularly to a method of repairing a gate line on a TFT array substrate of a thin film transistor liquid crystal display (TFT-LCD) without the need for a repair line. 
     GENERAL BACKGROUND 
     A TFT-LCD has the advantages of portability, low power consumption, and low radiation, and has been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras and the like. Furthermore, the TFT-LCD is considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions. 
     A TFT-LCD generally includes a color filter substrate, a TFT array substrate, and a liquid crystal layer sandwiched between the two substrates. When a TFT-LCD works, an electric field is applied to the liquid crystal molecules of the liquid crystal layer. At least some of the liquid crystal molecules change their orientations, whereby the liquid crystal layer provides anisotropic transmittance of light therethrough. Thus the amount of the light penetrating the color filter substrate is adjusted by controlling the strength of the electric field. In this way, desired pixel colors are obtained at the color filter substrate, and the arrayed combination of the pixel colors provides an image viewed on a display screen of the TFT-LCD. 
     Normally, the TFT array substrate includes a plurality of gate lines that are parallel to each other and extend along a first direction, and a plurality of data lines that are parallel to each other and extend along a second direction orthogonal to the first direction. The smallest rectangular area formed by any two adjacent gate lines together with any two adjacent data lines defines a pixel unit thereat. Each pixel unit includes a TFT which functions as a switching element, and a pixel electrode connected to the TFT. 
     As described above, the TFT array substrate has wiring patterns such as the gate lines and data lines, which supply signals to drive the pixel electrodes. However, the wiring patterns are liable to easily disconnect during heat treatment or etching processes when the TFT array substrate is being fabricated. That is, open or short circuits are liable to occur in the wiring patterns. The size and the resolution of certain contemporary TFT-LCD devices continue to increase with each new product release. Thus, a modern TFT array substrate may be required to have large numbers of data lines and gate lines each with a very narrow line width. The difficulties in fabricating such kind of TFT array substrate are also increased, with a greater possibility of broken wiring patterns. Accordingly, various repairing methods have been devised, whereby the corresponding TFT-LCD can operate correctly despite having sustained broken wiring. 
       FIG. 5  is a schematic, top plan view illustrating aspects of a typical method of repairing disconnected gate lines. An LCD (not shown) includes a TFT array substrate  10 . The TFT array substrate  10  includes a display region  20 . The display region  20  has a plurality of horizontally extended gate lines  16 , and a plurality of vertically extended data lines  12 , thereby forming an array of rectangular pixel regions (not labeled). The TFT array substrate  10  also includes a plurality of repair lines  22 ,  23 ,  24 , which are formed to cross the data lines  12  and the gate lines  16  outside the display region  20 . 
     When a broken point “A” occurs at the gate line  16 , laser fusing or other known techniques can be used to connect points  26 A and  26 B, which are located where the broken gate line  16  meets the repair line  24 . Then, the repair line  24  is cut off at positions  28 A and  28 B. Thus, the broken gate line  16  is connected through the repair line  24 . 
     However, a capacitor exists between the repair line  24  and the repaired gate line  16 . When signals transmit through the repair line  24 , the signals are liable to be distorted at either or both of the crossing points  26 A and  26 B. In addition, if the number of gate lines  16  is very large, there may be numerous repaired gate lines  16  and numerous crossing points through which signals are passing. The relatively large number of capacitors means that the overall signal quality in the TFT array substrate  10  may be unsatisfactory. Furthermore, depending on the location of the broken data line  16 , a large delay may occur due to the resistance and capacitance of the repair line  24  between opposite ends of the broken gate line  16 . The increased delay may be unacceptable for large, high-resolution TFT-LCDs. Moreover, one single gate line  16  is generally repaired using one single repair line  24 , and the number of repair lines  22 ,  23 ,  24  is limited due to the size of the display region  20 . 
     What is needed, therefore, is a method of repairing broken gate lines without using repair lines, in order to overcome the above-described deficiencies. 
     SUMMARY 
     In one preferred embodiment, a method of repairing gate lines of a TFT array substrate of an LCD is provided. The TFT array substrate includes a plurality of gate lines, a plurality of data lines crossing the gate lines, a plurality of pixel electrode, and a plurality of thin film transistors. Each TFT includes a gate electrode, a source electrode, and a drain electrode connecting to a corresponding one of the gate lines, a corresponding one of the data lines, and a corresponding one of the pixel electrodes respectively. One of the gate lines has a defect point. The method includes: cutting off an electrical connection between the gate electrode of one of the TFTs adjacent one side of the defect point and the corresponding data line, and cutting off an electrical connection between the gate electrode of one of the TFTs adjacent an opposite side of the defect point and the corresponding data line; electrically connecting the gate line having the defect point to each of two pixel electrodes that correspond to the two TFTs at the two opposite sides of the defect point; and electrically connecting the two pixel electrodes. 
     Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. In the drawings, all the views are schematic. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top plan view of part of a thin film transistor substrate of a TFT-LCD having a disconnected gate line. 
         FIG. 2  is similar to  FIG. 1 , but showing aspects of a method of repairing the disconnected gate line according to a first embodiment of the present invention. 
         FIG. 3  is a top plan view of part of a thin film transistor substrate of a TFT-LCD having a short point at a crossing between a gate line and a data line. 
         FIG. 4  is similar to  FIG. 3 , but showing aspects of a method of repairing the short point according to a second embodiment of the present invention. 
         FIG. 5  is a top plan view of part of a thin film transistor array substrate having a disconnected gate line, showing aspects of a conventional method of repairing the disconnected gate line. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic, top plan view of part of a TFT substrate of a TFT-LCD. The TFT substrate includes a plurality of gate lines  101 ,  102 , and a plurality of data lines  111 ,  112 ,  113  crossing the gate lines  101 ,  102 . Two rectangular areas formed by the gate lines  101 ,  102  and the data lines  111 ,  112 ,  113  define two pixel units  120 ,  130 . 
     The pixel unit  120  includes a pixel electrode  121 , a storage capacitor electrode  122  configured under the pixel electrode  121  and parallel to the gate line  101 , and a TFT  140  that functions as a switching element. The TFT  140  is provided in the vicinity of a point of intersection of the gate line  101  and the data line  111 . A gate electrode  141 , a source electrode  142 , and a drain electrode  143  of the TFT  140  are connected to the gate line  101 , the data line  111 , and the pixel electrode  121  respectively. 
     The pixel unit  130  includes a pixel electrode  131 , a storage capacitor electrode  132  configured under the pixel electrode  131  and parallel to the gate line  101 , and a TFT  150  that functions as a switching element. The TFT  150  is provided in the vicinity of a point of intersection of the gate line  101  and the data line  112 . A gate electrode  151 , a source electrode  152 , and a drain electrode  153  of the TFT  150  are connected to the gate line  101 , the data line  112 , and the pixel electrode  131  respectively. The storage capacitor electrodes  122 ,  132  and other storage capacitor electrodes (not labeled) are arranged in a line and are connected in series to be parts of a conducting line  103 . 
     The gate line  101  has a defect point “II” between the TFT  140  and the TFT  150 . In the illustrated embodiment, the defect point “II” is a break in the gate line  101 . When the TFT-LCD works, all TFTs connected to the gate line  101  at one side of the broken point “II” are not activated because of the broken point “II”. Thus, a dark line is always displayed on a screen of the TFT-LCD. 
       FIG. 2  shows aspects of a method of repairing the disconnected data line  101  according to a first embodiment of the present invention. The method includes the following steps: cutting off the electrical connection between the source electrode  142  of the TFT  140  and the data line  111  at the left side of the defection point “II” by a laser cutting process; cutting off the electrical connection between the source electrode  152  of the TFT  150  and the data line  112  at the right side of the defection point “II” by a laser cutting process; cutting off the electrical connection between a left end of the storage capacitor electrode  122  and other storage capacitor electrodes (not labeled) at the left side of the storage capacitor electrode  122  by a laser cutting process; cutting off the electrical connection between a right end of the storage capacitor electrode  132  and other storage capacitor electrodes (not labeled) at the right side of the storage capacitor electrode  132  by a laser cutting process; welding the gate electrode  141  and the drain electrode  143  of the TFT  140  to electrically short the gate and drain electrodes  141 ,  143  by a laser melting process; welding the gate electrode  151  and the drain electrode  153  of the TFT  150  to electrically short the gate and drain electrodes  151 ,  153  by a laser melting process; welding the pixel electrode  121  and the storage capacitor electrode  122  to electrically short the pixel and storage capacitor electrodes  121 ,  122  by a laser melting process; and welding the pixel electrode  131  and the storage capacitor electrode  132  to electrically short the pixel and storage capacitor electrodes  131 ,  132  by a laser melting process. 
     By performing the method described above, the two portions of the gate line  101  at the two opposite sides of the defect point “II” are electrically reconnected through the gate electrode  141  of the TFT  140 , the drain electrode  143  of the TFT  140 , the pixel electrode  121 , the storage capacitor electrode  122 , the storage capacitor electrode  132 , the pixel electrode  131 , the drain electrode  153  of the TFT  150 , and gate electrode  151  of the TFT  150  in that order. Thus the disconnected gate line  101  is repaired. Even though the two pixel units  140 ,  150  are rendered inoperative by the repairing process, the other pixel units connected to the gate line  101  can operate normally. Thus, the dark line displayed on the screen of the TFT-LCD can be eliminated. 
     Because the above-described method does not need a repairing line to be fabricated at a periphery of the TFT substrate, the cost of repairing the disconnected gate line  101  is lower. 
       FIG. 3  is a schematic, top plan view of part of a TFT substrate of another TFT-LCD. The TFT substrate includes a plurality of gate lines  201 ,  202 , and a plurality of data lines  211 ,  212 ,  213  crossing the gate lines  201 ,  202 . Two rectangular areas formed by the gate lines  201 ,  202  and the data lines  211 ,  212 ,  213  define two pixel units  220 ,  230 . 
     The pixel unit  220  includes a pixel electrode  221 , a storage capacitor electrode  222  configured under the pixel electrode  221  and parallel to the gate line  201 , and a TFT  240  that functions as a switching element. The TFT  240  is provided in the vicinity of a point of intersection of the gate line  201  and the data line  211 . A gate electrode  241 , a source electrode  242 , and a drain electrode  243  of the TFT  240  are connected to the gate line  201 , the data line  211 , and the pixel electrode  221  respectively. 
     The pixel unit  230  includes a pixel electrode  231 , a storage capacitor electrode  232  configured under the pixel electrode  231  and parallel to the gate line  201 , and a TFT  250  that functions as a switching element. The TFT  250  is provided in the vicinity of a point of intersection of the gate line  201  and the data line  212 . A gate electrode  251 , a source electrode  252 , and a drain electrode  253  of the TFT  250  are connected to the gate line  201 , the data line  212 , and the pixel electrode  231  respectively. The storage capacitor electrodes  222 ,  232  and other storage capacitor electrodes (not labeled) are arranged in a line and are connected in series to be parts of a conducting line  203 . 
     The gate line  201  has a defect point “IV” at a crossing between the gate line  201  and the data line  212 . In the illustrated embodiment, the defect point “IV” is a short. Thus, pixel units connected to the gate line  201  and pixel units connected to the data line  212  cannot work. Therefore, a dark cross is always displayed on the screen of the TFT-LCD. 
       FIG. 4  shows aspects of a method of repairing the short point at the crossing between the gate line  201  and the data line  212  according to a second embodiment of the present invention. The method includes the following steps: cutting off two electrical connections on the gate line  201  at two opposite sides of the data line  212  respectively by a laser cutting process; cutting off the electrical connection between the source electrode  242  of the TFT  240  and the data line  211  at the left side of the defect point “IV” by a laser cutting process; cutting off the electrical connection between the source electrode  252  of the TFT  250  and the data line  212  at the right side of the defect point “IV” by a laser cutting process; cutting off the electrical connection between a left end of the storage capacitor electrode  222  and other storage capacitor electrodes (not labeled) at the left side of the storage capacitor electrode  222  by a laser cutting process; cutting off the electrical connection between a right end of the storage capacitor electrode  232  and other storage capacitor electrodes (not labeled) at the right side of the storage capacitor electrode  232  by a laser cutting process; welding the gate electrode  241  and the drain electrode  243  of the TFT  240  to electrically short the gate and drain electrodes  241 ,  243  by a laser melting process; welding the gate electrode  251  and the drain electrode  253  of the TFT  250  to electrically short the gate and drain electrodes  251 ,  253  by a laser melting process; welding the pixel electrode  221  and the storage capacitor electrode  222  to electrically short the pixel and storage capacitor electrodes  221 ,  222  by a laser melting process; and welding the pixel electrode  231  and the storage capacitor electrode  232  to electrically short the pixel and storage capacitor electrodes  231 ,  232  by a laser melting process. 
     By performing the method described above, the two portions of the gate line  201  at the two opposite sides of the defect point “IV” are electrically reconnected through the gate electrode  241  of the TFT  240 , the drain electrode  243  of the TFT  240 , the pixel electrode  221 , the storage capacitor electrode  222 , the storage capacitor electrode  232 , the pixel electrode  231 , the drain electrode  253  of the TFT  250 , and gate electrode  251  of the TFT  250  in that order. Thus, the short at the crossing between the gate line  201  and the data line  212  is repaired. Even though the two pixel units  240 ,  250  are rendered inoperative by the repairing process, the other pixel units connected to the gate line  201  and the data line  212  can operate normally. Thus, the dark cross displayed on the screen of the TFT-LCD can be eliminated. 
     Because the above-described method does not need a repairing line to be fabricated at a periphery of the TFT substrate, the cost of repairing the shorted gate and data lines  201 ,  212  is lower. Furthermore, the above-described method can also be used to repair the data line  212  having a disconnected point on the data line. 
     In an alternative embodiment, a metal film (not shown) can be formed between the pixel electrode  121  and the pixel electrode  131  by a plasma sputtering deposition process. The two pixel electrodes  121 ,  131  are thus electrically connected to each other via the metal film. Similarly, a metal film (not shown) can be formed between the pixel electrode  221  and the pixel electrode  231  by a plasma sputtering deposition process. The two pixel electrodes  221 ,  231  are thus electrically connected to each other via the metal film. Each of the metal films can for example be made from metal selected from the group consisting of aluminum, copper, tantalum, and titanium. 
     It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, including in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.